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July 23, w46. v_ l.. HANsLEY 244,74 POLYMER PRODUCTS Filed Nov. 4, v1944 IN VEN TOR. m4 ' j; " »gisant '2,404,716 roam/ma raonuc'rs f _ virgin r.. Hensley, Niagara raus, N. Y., assigner to iE. l. du Pont de Nemours & Company, Wil mington, Del.,a corporation of Delaware Application November 4, 1944, Serial No. 562,01€: V15.7 Claims. (Cl. 26o-_32) ß ' . This invention relates to a new composition of matter and shaped articles produced therefrom.' ' More particularly, this invention relates to an organic solvent solution of polyacrylonitrile, i. e. polymerized acrylonitrile or polymerized vinyl cyanide (CH2=CHCN):, and copolymers and in terpolymers of acrylonitrile vin which at least 85% by weight of the polymer is acrylonitrile, and the production of shaped articles from said organic solvent solution of said polymers of acrylonitrile. 2 resulting compositions in such-a manner. Their extrusion into coagulating baths of the type pro posed V(including such non-solvents for acrylo nitrile as water, dilute acid, dilute salt solutions, etc.) result in the formation of shaped articles that contain large amounts of the inorganic salt of the proposed> solvent. These salts‘are dis tributed throughout the structure and destroy the continuity ofthe polyarcylonitrile phase and the structure possesses poor physical properties. Removal of these“ salts, when possible, results in ' Polyacrylonitrile, and copolymers and inter- the formation of a porous, spongy, Weak, unde sirable structure that is very brittle and com l polymers of acrylonitrile with other polymeriz able substances, for example vinyl or` acrylic com pounds in which at least 85% by weight of the polymer is acrylonitrile have been known for ment yarn byv extruding, for example the pro some time and recognized as possessing desirable posed aqueous sodium sulfocyanide polyacrylo pletely unsuited for use as a yarn or film. More over, when it is attempted to form a multîiila physical and chemical properties including tough nitrile composition', into a dilute acid bath, it isness and insolubility in and insensitivity to com found that the individual filaments obtained mon organic solvents such as methyl or ethyl 20 stick together to form an essentially monoflla ment structure that is extremely brittle and can alcohol, acetone, ethyl ether, ethyl acetate, hydro not be bent or worked without breaking. carbon solvents, chlorinated hydrocarbons Iand U. S. Patent No. 2,167,537 to Tobls points out the like. Because of these facts, numerous at that certain copolymers of acrylonitrile and an tempts have been made to form these polymeric materials into yarns, films and other Vshaped articles. f ' acid ester (those copolymers containing v26 _acrylic not more than 65% of acrylonitrile) are soluble The copending application of George H. Latham, Serial No. 562,012, filed of even date . l in' mixtures of organic solvents such 'as dioxan,monochlorbenzene, cyclohexanone, etc, `How- herewith discloses solutions of polyacrylonitrile Y ever, these liquids are incapable of dissolving or in dimethyl carbamyl compounds and the pro 30 even swelling polyacrylonitrile or copolymers of acrylonitrile 'containing higher percentages of duction of extruded and otherwise shaped articles acrylonitrile, i. e. acrylonitrile polymers of the and structures from such solutions. The above type with which this invention is concerned. As said application of George H. Latham represents previously mentioned, polymers containing such the ñrst successful dissolution of polyacrylo' nitrile in a solvent to produce a solution which 35 high percentages (at least 85% by weight) of is suitable for the production'of commercially useful textile yarns 0r wrapping tissue films, and acrylonitrile are especially desirable for use be similar tough, ñexible structures. cellent chemical . resistance. The present application relates to a similarly cause of their good physical properties and ex It has also been proposed (Rein U. S. Patent satisfactory dissolution of polyacrylonitrile in an 40 No. 2,117,210) to dissolve polyacrylonitrile in -molten quatemary -»ammonium salts such as organic solvent taken from a different class of organic compounds and the polyacrylonitrile solutions produced thereby are similarly satis benzyl pyridinium chloride, an ionizable salt. Al- . though the resulting solution can allegedly be factory for the production of tough, flexible, ‘ used to form yarns or films of polyacrylonitrile, dense, colorless yarns andiilms which are suit able for vuse in practically all general commercial the solution itself is dark red to brown in color, indicating that some decomposition of the poly acrylonitrile or some reaction between the poly applications of such products. ' v acrylonitrile and the molten salt has probably taken place. Such solutions are not satisfactory as lithium bromide, zinc chloride and sodium 50 for the production of commercially useful, shaped articles of polyacrylonitrile. Here again, it has sulfocyanide will dissolve polyacrylonitrile and it been found practically impossible to obtain fila has been proposed (Rein U. ‘5. Patent No. mentary structures such as yarns from the com 2,140,921) to employ the resulting solutions in the position. Films or filaments, when obtainable, formation of yarns and ñlms. However, it has been found substantially impossible to use the 55 are extremely brittle; they are highly vcolored It has been known heretofore that concen trated aqueous solutions of inorganic salts‘such 2,404,716 3 4 and very weak, presumably because of the pres ence within them of residual quaternary am monium salt. Removal of this salt is difllcult and the resulting structures contain numerous the presence within the molecules of strong hy drogen-bonding forces and in order to dissolve one of these polymers, it is necessary to 11nd a material which will undergo hydrogen bonding and large voids that make the structures sub stantially useless for commercial purposes. with the active hydrogen-bonding groups of the polymer molecules and thus weaken the strong hydrogen bond within the polymer molecules and cause the hydrogen-bonding forces to be shared between molecules of the polymer and the sol It is therefore an object of this invention to dissolvel polyacrylonitrile or‘a copolymer or in terpolymer of acrylonitrile in which at least 85% by weight oi’ the polymer is acrylonitrile, in a y10 vent. In this mannenit is‘possible to form a solvent which does not react with or decompose molecular dispersion of the polymer within the the polymer and which may be substantially solvent and thus form a solution. However, the strength of the hydrogen-bond completely removed from the structures formed ing capacity cannot be taken as the sole crite of such a solution. It isanother object of this invention to pro rion as to whether or nota compound will func duce a solution of polyacrylonitrile or-a copoly ltion to dissolve an acrylonitrile polymer. It is mer or interpolymer of acrylonitrile in which at least 85% by weight of the polymer is acrylo , also necessary that, in order to function as a solvent for an'acrylonitrile polymer, the com pound contain certain groups which will be ca or decompose the polymer, the solution being 20 pable of satisfactorily sharing a hydrogen bond suitable for the formation of commercially use ing force with the particular active group of the ful, void free articles of polyacrylonitrile, for acrylonitrile polymer. In most , these groups require the presence of a hydrogen atom example yarns which are suitable as textile yarns and films which are suitable as wrapping tissue. on a carbon atom to which the group is'attached 'It is another object of this invention to pro 25 (designated as an alpha-hydrogen atom). Such groups as require the alpha-hydrogen atom are duce a solutionvof polyacrylonitrile, or a copoly ineffective to impart solvent power if the alpha mer or interpolymer of acrylonitrile in which at hydrogen atom ls missing. ' l least 85% by weight of the polymer is acrylo It has now been found that groups capable ot nitrile, in a volatile organic solvent, which so lution is stable over extended periods of time and 30 conferring solvent power include dimethyl car and is eminently suited for use in the manufac~ ture of shaped articles such as yarns, films, tubes, nitrile, in a solvent which does not react with straws, artiiicial horsehair, bristles and ribbons, or when highly concentrated, for use in the man ufacture of molded articles. 35 It is a still further object of this invention to produce shaped articles and structures of poly acrylonitrile, >or copolymers or intel-polymers of acrylonitrile in which at least 85% by weight of 40 the polymer is acrylonitrile. cyano (-CENL thiocyano (-S-CEN) and It is still another object of this invention to produce a shaped article or structure of poly acrylonitrile or copolymers or interpolymers of acrylonitrile in which at least 85% by Weight of the polymer is acrylonitrile, for example a yarn, film, tube, bristle or the like which is tough, flexible, tenacious and free from voids. Other objects of the invention will appear hereinafter. ’I‘he objects of the invention may be accom plished in general by dissolving polyacrylonitrile, or a copolymer or interpolymer of acrylonitrile in which at least 85% by weight of the polymer is acrylonitrile, in an organic compound which sulfoxy (no „EL lo- l...) f ,. rg. . ä groups, provided however that the cyano, thio cyano and sulfoxy groups require attachment 50 (through their respective unsatisfied carbon and sulfur valences) to a carbon atom which is in turn attached to at least one hydrogen atom (alpha-hydrogen) in order to render them effec tive. The dimethyl carbamyl and the form'yl limido groups are effective in the absence of the is not a salt and which contains at least _one di 55 alpha-hydrogen atom. (It is possible that they methyl carbamyl group and at least one cyano contain the equivalent of an alpha-hydrogen methylene group. If the solvent has a relatively atom within their own structures.) lThus, the low boiling point (less than about 250° C.), the solution of the acrylonitrile polymer` may then be formed into a .shaped structure, for example groups dimethyl carbamyl CH; o a yarn or film, and the solvent removed from the shaped structure to coagulate the same. CH: When the solvent is relatively non-volatile and formyl - imido (HCON<), cyanomethylene has a boiling point of about 300° C. or more, shaped articles may be made from the solution 05 (>CHCN)., thiocyanomethylene (>CHSCN) and sulfoxymethylene (>CHSO---, ~>CîHSOz--, andl at least a portion of the solvent may be re >CHSOO-, and >CHSOzO-) shall hereinafter tained therein as a plasticizer for the articles. be referred to as solvogenic groups and com It has been recognized in recent years that pounds containing them are frequently capable under certain conditions, an atom of hydrogen is attracted by rather strong forces to two atoms 70 of dissolving an acrylonitrile polymer containing at least 85% by weight of acrylonitrile. instead of only one, so that it may be considered In the event that two or more groups requiring to be acting as a bond between them. This is the presence of an alpha-hydrogen atom in order called the hydrogen bond. . The difficulty of dissolving polymers containing to render them solvogenic are attached to the at least 85% by weight of acrylonitrile is due to 75 Same carbon atom and compete with each other amarre ' for an available alpha-hydrogen atom, the sulf C Ha . oxy group, the cyano group and the thiocyano group take preference over each other in the NC-CHzCHIê CHQCHICN order named to form the solvogenic group, the lower ranking group or groups present assuming merely'the nature of an inert substituent on the Gamma-methyl-gammaN N-dimethyl-oarbamyl l carbon atom. - ON(C _ the ` above-mentioned trile . Nc-onnrcomcm), , It has furthermore been found that compounds containing pimeio I ì N,N~dimethyl-alpha-bromo-alphacyenoacetamide solvogenic groups will be solvents for the above-mentioned polymers only if the carbon content of the com pound be within certain limits as given below. If the ratio of carbon to solvogenic groupings is maintained within the said limits, the com pounds Will retain solvent properties of the poly mer leven though the molecule be of considerable size and complexity. The solvent power of the compound for acrylonitrile polymers is increased if additional solvogenic groups are present in the molecular structure of the compound, the eñîect 20 of these groups being additive. It has now been found that dimethyl carbamyl cyanomethylene compounds which are fusible Without decomposition embraced by the follow ing formula and preferably having a boiling point below 250° C. will dissolve polyacrylonitrile, and copolymers and interpolymers of acrylo nitrile in which at least 85% by Weight of the polymer is acrylonitrile: CN (NC--CHaCHDzC C O_N(CH|): Gamma-(N,N-dimethylcarbamyl)~gamme-cyenopimelonitrile l N C-CEhCHC 0N(CHa)a 30 H2O 0N(C Ha) a N,N,N’N'-tetramethyl»alphacyano-methyl-suocinamide wherein m and q are integers equal to or greater 35 C Ha C N ` than l.; n and p are integers of such value that n/m is equal to or less than 1.5 and p/q is equal to or less than 1.5. These compounds are not salts but may be cyclic or acyclic in nature and may contain one 40 or more ethylenic or acetylenic linkages. Va lences other than those contained in the carbon to-carbon linkages and not shown as satisñed C HaJJH-èH-C oNmHm N,N-dimethyl-alpha-cyanoiso-valeramide CN CHsflJHC ON(CHu): N,N-dimethyl-alpha-cyano-propiona mide CN by the above formula must be satisfied by a sub stituent taken from the group consisting or 45 hydrogen, halogen, oxygen, bivalent sulfur atoms and hydroxyl, thiol, cyano, thiocyano and sulfoxy radicals; the total number of halogen, oxygen and> sulfur atoms and hydroxyl and thiol sub stituents not exceeding one-half the sum of m-l-q 50 and the number of cyano, thiocyano and sulfoxy radicals not exceeding the sum of m-i-q. The respective tolerances of one-half m-i-q and m-l-q c HaCHQCHfcHCÉC omonm i N, N»dimethyl~alpha,beta-dicyanocaproamide for the said two groups of substituents are inde pendent of each other and members of said 55 groups may be present in the molecule up to their group tolerances. substituent oxygen and sulfur N,N-dimethyl-delta-cyano«veleramide atoms may appear in the compound as bivalent groups either as a side group (carbonyl or thio carbonyl) or within the` chain (ether or thio 60 ether) as the case may be. ' CHaCHzCHaCHC ON(CBa)2 N ,N-dimethyl-alpha-cyano-valeramide _ y 0N CN CN emcHCmCoNwHm N,N-dimethyl-beta-oyano-butyramide N C-C HzCHnCHsCHqC 0N(CHu) a CN CHaCHCHaCHrC ON(CH»)2 g N,N-dimethyl-gamma-cyano-valeramide C Ha NC-~CH¢tlJ-C ON(CHa)| Representative compounds coming Within the scope of the above formula and suitable for use Ha as solvents for the above-mentioned acrylonitrile N ,N-alpha,alpha-tetramethyl-beta-cyanopropionamide polymers include: l C Hs CN , NC-CHnC ON(CI_Ia)2 NC-CHzèHCáCONwHsh N,N-dimethylcyanoacetamide N,N-dimethyl-alpha-gamma-dicyanoisovaleramide NC-CHiCHnC ON(CHs): 7@ C Hs ' NC-CHN‘JHCH’C ON (CHs): N,N»dimethyl-gamma-cyanoisovaleramide . 7@ NG-CHIC omemmn N,N,N'N’-tetramethyl-cyanomalonamide 2,404,716> 9 e . above room temperature. Shaped structures and articles can be produced by extruding many of such solutions into an evaporative or coagulative medium. By forming the structures in an evap orative medium, the solvent must be evaporated therefrom and by forming the structures in a coagulative medium, the solvent should be re moved by selective, solution in a non-solvent for the polymer. A The solutions are prepared by `dissolving the polyacrylonitrile, or copolymer or interpolymer , , i fractory in which is embedded an electrical heat ' ing coil I9. The spinning cell can thus be op erated at any desired temperature. A plurality of conduits 2| are provided adjacent thebottomV of the device vfor passing evaporative medium’ through- the cell so as to evaporate the solvent from the extruded filaments I5. The.evaporative medium is removed from the cell through loutlet openings '23.A The yarn comprising the plurality of filaments I5 is passed from the bottom of the spinning cell around guide roller 25 and is wound on a bobbin 21. of acrylonitrile with one or a mixture of the ' ’ Referring to Figure 2 of the drawing, the yarn l5 is removed from the bobbin package 2i and ` above-mentioned solvents. Some of these sol vents are solid at ordinary temperatures and dis solve or retain the polymer in clear solution only 15 passed about draw roller 29 and separating roller 3I. From draw roller 29, the yarn is passed to at elevated temperatures', for example at tem ` peratures of 100° C. or higher, below which tem ' a second draw roller 33 and separating roller 35. The yarn is passed around the two sets of >draw rollers including their separating rollers a sum of the above class, the resulting composition while 20 cient number of turns to prevent slippage of the yarn. Draw roller 33 is rotated at a greater hot has the appearance of a true solution. When speed, for example three to ten times the speed cooled to room temperature, the composition gen of draw ‘roller 29. In this manner, the yarn E5 erally takes on the appearance of a gel, which is stretched between _the two draw rollers. As gel may, on standing, undergo syneresis. Re heating of this gel or syneresed mass however 25 the yarn passes between the two draw rollers, a heating medium is brought into contact with the causes it to again return to solution form. yarn through blower nozzles 3i and 39. The In view `of the relatively high melting points yarn passing from the draw roller 33 is wound of some of the solvents of this invention, they on bobbin 0I. The-drawing or stretching of the would have comparatively little use in the -pro duction of a polyacrylonitrile spinning or casting 30 spun yarn as described is not claimed as part of the present invention, but is claimed in the solution. Such solvents are, however, excellent copending application of Daniel T. Meloon, Serial solvent plasticizers for polyacrylonitrile since perature the composition resembles a gel. In all cases when the polymer is dissolved in a solvent they are soluble in a wide range of proportions with the said acrylonitrile polymers. The pres ent invention therefore contemplates solid solu-- tions of acrylonitrile polymers containing at least 85% by weight of acrylonitrile as well as liquid solutions thereof. No. 496,397, filed July 28, 1943. . Figure 3 of the drawing illustrates a wet spin ning apparatus for the production of yarn. The acrylonitrile polymer solution is passed through conduit 5I and is extruded through spinneret 53 to form a multiiilament yarn Sli. The yarn 50 _ f is passed about guide roller 5l which is positioned Shaped articles obtained from solvent solutions of pols/acrylonitrile in accordance with the inven 40 within the coagulating liquid in tank 55. The yarn is then passed about guide roller 5S and is tion and from which the solvent is subsequently wound on bobbin 0I. removed are substantially free of foreign matter The organic solvent solution of polyacrylonitrile and voids and substantially undecomposed and may be cast in the form of a film as illustrated chemically unchanged from the simple polymer 45 in Figure 4. In accordance with this apparatus, prior to its solution. the polymer solution is passed from hopper l! The above-described organic solvent solutions on to the endless steel band 'i3 where it is of acrylonitrile polymer may be shaped in the smoothed by means of a doctor knife '85. The form of filaments, yarns, films, tubes and like band, together with the film, is passed under a structures by apparatus and processes generally known in the art, the detailed operating condi 50 means ‘Il for bringing a heated drying medium tions being suitably modiñed. , ' Suitable methods and apparatus for the pro duction of shaped articles of the polymers of this invention will be readily apparent by reference to ' the following detailed description when taken in 55 connection with the accompanying illustrations in which: ì Figure 1 is a diagrammatic vertical sectional , view showing a dry spinning cell suitable for use in accordance with the invention; - Figure 2 is a diagrammatic perspective view showing a lyarn drawing device for use in con nection with the invention; Figure 3 is a diagrammatic perspective view into contact with the film. The film 0I is pulled from the band 'I3 and collected on a mill roll 03. The polyacrylonitrile for use with the inven tion is preferably prepared by the ammonium persulfate catalyzed polymerization of monomeric acrylonitrile dissolvedor emulsifieddn water. It can, however, be preparedby any other suitable type of polymerization reaction such as, for exam ple, the emulsion type reaction disclosed by U. S. Patent No. 2,160,054 to Bauer et al. The poly mer preferably possesses a molecular weight within- the range of 15,000 to 250,000 or even higher, .as calculated from viscosity measure ments by the Staudinger equation: showing a wet spinning apparatus for use in the 65 . _'N., Molecular WeightKm0 invention; and Figure 4 is a diagrammatic side elevational view showing a suitable film casting apparatus for use in accordance with the invention. wherein: I ___ . . . _viscosity of solution Referring to Figure 1 of the drawing, reference 70 N” îd'spçclñc vlscoslty- viscosity of solvent 1 numeral I I designates a spinneret through whichv an a plurality of filaments I5 are formed by extrud C=concentration of the solution expressed as the ing a ñlament-forming solution supplied to the number _of moles of the monomer (calculated) per spinneret by means of conduit I3. The spinning liter of solution. cell is jacketed with a material I‘I., such as a re-` 2,404,716 1I - 12 . The molecular weight of the polymer obtained .is dependent on such factors as the concentra. tion of the monomer in the water, the amount and type of catalyst present, the temperature of the reaction, etc. For example, polyacrylcnitrile, having a molecular weight of approximately ‘ in the coating of wire and electrical parts where the high chemical and electrical< resistance of the polymer is important. For the purpose of definition, a solvent is a material which, when in the liquid state, is ca pable of forming solutions in which the polymer is present in a concentrationl by weight of 5% In most instances, the polymer is sol uble in almost all proportions although the mis 60,000 can be prepared as follows: To 94 pounds of distilled water heated to 40° C. _add 40 grams of ammonium persulfate-catalyst and 80 grams of sodium bisulilte activator. Then add 16 pounds -10 cibility may take place at elevated temperatures of acrylonitrile slowly with stirring over a period in the case of certaincompounds. of two hours.v The polyacrylonitrile having the As also shown, the solvents of the invention above said molecular weight will precipitate from are useful not only in connection with polyacryl the solution. Increasing or decreasing theonitrile, but also with copolymers and inter amount of the catalyst, while maintaining the polymers of acrylonitrile and with other poly other `conditions constant, decreases or increases the molecular'weight of the polymer. Acrylo- L nitrile copolymers and interpolymers containing e at least 85% by weight of acrylonitrile and like- ’ `merizable substances such as, for example, com pounds containing one or more ethylenic link ages including vinyl and acrylic compounds as ,Y Well as oleñnic or diolefinic hydrocarbons such as , wise preferably having a molecular weight of 20 isobutylene, butadiene, etc. They are eminently 15,000 to 250,000 or higher can be prepared in a satisfactory'for use with those polymers that con similar manner. tain an appreciablevamount of acrylonitrile, for The following examples in which parts, pro example, polymers, copolymers and interpoly portions Aand percentages are'by weight unless mers that contain at least 85% by weight of otherwise speciñed illustrate preferred methods 25 acrylonitrile and that have generally been re of preparing solutions of polymers in accordance garded by the art as being completely insoluble with the principles of this invention and of em ploying these solutions in the manufacture of commercially satisfactory shaped articles of the polymer. The invention is not to be limited b 30 the details set forth in the examples. Example I , - - >Fifteen (15) parts of an acrylonitrile polymer in all common organic solvents. Nor are these solvents limited to use with a polyacrylonitrile of any given molecular weight. They can be used with a polymer of' almost` any given molecular Weight and are especially satisfactory for use with those polymers having an average molecular weight within the range 15,000 to 250,000 as de termined by viscosity data using the Staudinger prepared by the polymerization of monomeric 35 equation and intended for. use in the manufac acrylonitrile in accordance with the disclosure of ture of yarns or iilms. _ U. S. Patent No. 2,160,054 to Bauer et al.` and The solution of acrylonitrile polymer dissolved possessing an average molecular weight of 120,000 in an organic solvent in accordance with this as determined by the Staudinger equation from invention must be of such a concentration that viscosity data were ground to an average particle 40 its viscosity at the operating temperature is with size of 200 mesh and intimately mixed with 85 in a workable range. When it is to be employed parts of similarly ground dimethyl cyano acet in the spinning of yarn or the casting of ñlm, the amide. The mixture was heated to 120° C. to solution should preferably have a viscosity within form a clear, homogeneous dispersion or solu the range 25 to 750 poises. When the polymer tion. When cooled to room temperature, it set 45 has a molecular Weight of 250,000 or more, this to a clear, gel-like mass, which mass however requires that the maximum concentration _of again returned to solution form upon-heating to polymer in the spinning solution be of the o_rder ~ above 60° C. The solution heated to a tempera of 10%. Generally, it is preferred that the spin ture of 100° C. was extruded through a 10-hole ning solution contain at least 10% of the polymerv spinneret (hole diameter of 0.003 inch) into a 50 because of the diñiculty of rapidly- removing large bath comprising glycerol heated to a temperature amounts of solvent from the solution in the of 140° C. Y-The resulting multiñlament yarn of spinning operation. Moreover, it is economically acrylonitrile polymer was washed with water and` ' undesirable to use such large amounts of solvent dried. for the spinning of a >given amount of polymer Example II 55 although- it is true that the solvent can be com Forty (40) parts of the acrylonitrile polymer of Example I were mixed vwith 60 parts of gamma pletely recovered from the spinning operation and reused. For these reasons, itis preferred to employ a polymer having an` average molecular methyl-gamma-NN-dimethyl carbamyl pimelo -nitrile and heated to a temperature of 175° C. weight of lbetween 40,000 and 150,000 since such , to form a clear, homogeneous dispersionl or solu 00 la polymer forms a solution of the desired vis cosity in concentrations of the order „of 15% to tion. ’I'he solution was cooled to 25° C. to form 25% andat a desirable spinning temperature of a clear, solid mass which was ground to a iine the order of 100° to 150° C. OI course,- it is particle size f 20 mesh). This powdery mass was within the scope of the invention to heat the solu - molded at a temperature of 200° C. and a pres tion to a higher temperature, even to above the sure of 500 pounds to form a tough, durable, rod like structure, the structure being clear and free of haze. ' , normal boiling point of the solvent, for the actual spinning operation. Here again, the controlling factor with regard to the temperature of the> spinning solution is the viscosity of the solution. The evaporative medium employed in the-dry a solution of polyacrylonitrile, or a copolymer'or 70 spinning of filaments and yarns or the dry cast interpolymer of acrylonitrile which is eminently ing of films in accordance with this invention suited for use in the manufacture of shaped arti cles such as yarns, films, or molded articles. The may be any vapor inert to the film- or filament solutions are also suited for use as lacquers or forming solution such as air, nitrogen, steam, coating compositions. They are especially useful 76 etc., or any suitable mixture thereof. The tem As indicated in the above examples, it is pos sible by the practice of this invention to obtain 2,404,716 i4 - added in the desired amount to an already formed solution of the polymer in a lower boiling solvent, for example to a solution of the polymer perature of the evaporative medium is dependent on such factors as the dimensions of the spin ning cell, the composition and rate of extrusion of the spinning solution and the rate of flow of the Aevaporative medium. It is only necessary in dimethyl cyano acetamide. _ This invention is primarily concerned with' the steps of dissolving polyacrylonitrile in a suitable that these several factors be so correlated that solvent to form a stable solution adapted for> the yarn or other shaped article leaving the spin use in the manufacture of shaped articles of ning cell be sufficiently freed of the solvent so polyacrylonitrile. vIt is characteristic of the in that it is solidified and capable of being wound 10 vention that the solutions provided by it are sta into package form or otherwise collected. ble; the solvents do not cause a decomposition As indicated in Example I above, shaped arti or chemical alterationy of the dissolved acryloni- ` cles of acrylonitrile polymer can also be formed trile polymer. At the same time, it is also'char by extruding the spinning solution into a suitable acteristic that the solvents provided by the inven precipitating bath comprising a liquid that is tion are also useful in th'e dissolving of mixtures miscible with »the solvent but~ is a chemically of polyacrylonitrile and adjuvants such as dye inert non-solvent for the acrylonitrile polymer. modifiers, linear- polyamides such as nylon, de As examples of such a liquid may be mentioned rivatives of cellulose including cellulose ethers water, glycerin, organic solvents such as alcohol, and esters, polymers of vinyl compounds such as ether, etc., or aqueous solutions of salts, alkalines i or acids. The copending application of William 20 ` W. Watkins, Serial No. 496,376, filed July 28, 1943, covers the use of glycerol and aqueous solutions of salts as baths, preferably at elevated tempera tures, for the wet spinning of acrylonitrile poly mer yarn, from solutions of the polymer, pref vinyl chloride, vinyl acetate, acrylic acid, etc., which adjuvants may be incorporated in the acrylonitrile polymer solution to modify the properties, both chemical and physical, of the re sulting shaped articles. This invention provides a class of solvents for erably with substantial tension and stretch being polyacrylonitrile, and copolymers and interpoly applied vduring spinning. mers of acrylonitrile which were heretofore con The article of acrylonitrile polymer thus ob sidered substantially insoluble. The solvents >are capable of forming with the polymer clear solu stretching operation of the type employed in the 30 tions that are stable for extended periods of time and are admirably suited for use as lacquers or above examples. This stretching is preferably coating compositions or in the manufacture of performed by passing the yarn between two posi -shaped articles of the polymer, for example by tively driven rollers,> the peripheral speeds of tained can advantageously be subjected to ya which are so adjusted that the article is stretched from two to ten times its original length, prefer ably approximately six times its original length. This stretching of the formed article may be performed at any suitable time. However, in the case of articles formed by the wet spinning or casting technique, it is preferably performed be fore the article has been completely dried. The orientation of the structure thus obtained im proves the physical properties of the structure including its tenacity, its resilience, etc. ` extrusion into an evaporative or coagulative me- ' dium, or bythe use of a molding technique. The invention also provides a class of mate rials that'is. eminently suited for use in plasticiz ing structures comprising the acrylonitrile poly mers. The materials provided by this invention 40 are apparently true solvents for the above-men tioned'acrylonitrile polymers. They do not tend to react with or decompose the polymer, the poly merio material obtained from the solution of this invention apparently being the same identical This stretching of the shaped article can also 45 chemical composition -as the initial polymer. be accomplished by causing the article, while passing between stretching rollers„to contact .a Yarns, films and similar articles of polyacrylo nitrile prepared from the solutions of this inven tion can be stretched to yield oriented structures heated stationary pin or to pass through an inert that possess a high tenacity. a desirable elonga medium such as air, water, glycerin, etc. heated to a high temperature.V Obviously, the article 50 tion and a high' elastic recovery that compares favorably with that of silk. The articles are not must not be exposed to this high temperature for contaminated with undesirable salts and they are a period suñiciently long Ito decompose the poly substantially free of void spaces. mer. In general however, the time of contact of Reference, throughout the speciñcation and the article with the heated medium is so short that temperatures up to 250° C. can be employed. 55 claims, to acrylonitrile polymers, polymers of acrylonitrile, and copolymers and inter-polymers Although it is generally preferred to heat the of acrylonitrile “containing at least 85% by article to a temperature of at least 100° C. during weight of acrylonitrile” signifies polymers con the stretching operation, this is not'essentlal. taining in their molecules at least 85% by weight Desirable results can be obtained by stretching the article without the application of heat, for 60 of the acrylonitrile unit which is considered to be present in the polymer molecule as the group >example by stretching at room temperature. In addition to acting as solvents for polyacrylo nitrile, or copolymers of acrylonitrile, the ali phatic or arylaliphatic nitrile compounds of this that is, at least 85% by weight or the reaetant invention, when present in small amounts, can material converted into and forming the poli' ' also be used as plasticizing agents for the poly is acrylonitrile. mer and the higher boiling compounds of the in Since it is obvious that m changes and `vention are especially suited for such use. At the modifications can be made in the above described same time, it is, of course, to be understood that details without departing from the nature and ¿Hr-(IJlEI-CN non-solvent softeners, such as glycerol, can also be incorporated in the solutions ofthe invention. these materials remaining in the subsequently formed articles to impart a softening effect. If it is desired to use such plasticizing or 'softening agents with -polyacrylonitri1e, they are preferably a spirit of the invention, it is to be understoodthat the invention is not to bev limited to the details described herein except as set forth in the ap bonded-claims. _ l I claim: 1. As a new composition of matter, a 2,404,716 16 ~ cule at least 85% by weight of acrylonitrile dis solved in N,N-dimetliyl-beta-cyano propionamide. of acrylonitrile containing in the polymer mole cule at least 85% by weight of aorylonitrile dis 10. As a new composition of matter, a polymer solved in a dimethyl amide nitrile compound, said compound embraced within the formula: of acrylonitrile containing in the polymer mole cule at least 85% by Weight of acrylonitrile dis solved in beta-cyano-beta'(N,N-dimethylcarbamyl) diethyl ether, 11. As a new composition of matter, a polymer Cé; m H _ ¢ of acrylonitrile containing in the polymer mole cule at least 85% by weight of acrylonitrile and a dimethyl amide nitrile compound, said compound wherein m and q are integers at least; equal to l; n and p are integers of such value that n/m does not exceed 1.5 and p/q does not exceed 1.5; all valences of said compound other than those con embraced within the formula: v tol-t teal ' tained in carbon-to-carbon linkages and not shown as satisfied in the formula being satisiied by a substituent. taken from the group consisting of hydrogen, halogen, oxygen, bivalent sulfur, hy wherein m and q are integers at least equal to 1; droxyl, thiol, cyano, thiocyano and sulfoxy; the total number of halogen, oxygen, sulfur, hydrox yl and thiol substituents not exceeding one half n and p are integers of such value that 11,/ m does not exceed 1.5 and p/q does not exceed 1.5; all valences of said compound other than those con tained in carbon-to-carbon linkages and not shown as satisñed in the formula being -satisñed by a substituent taken from the group consisting thev sum oí 'm-i-q and the total number of cyano, thiocyano and sulfoxy radicals not exceeding the sum of m+q. , ' 2. A new composition of matter as defined in claim 1 in which the polymer of acrylonitrile is 25 3. A new composition of matter as deñned in claim 1 in which the polymer of acrylonitrile is non-reactive with said dimethyl amide nitrile polyacrylonitrile. compound. . - 4. A new composition of matter as deñned in claim 1, in which said polymer is non-reactive with said dimethyl amide nitrile compound, but is soluble in all proportions therewith, _ 5. A new composition of matter as deñned in claim 1, in which the polymer of acrylonitrile has a molecular weight of between 15,000 and 250,000. 30 of hydrogen, halogen, oxygen, bivalent sulfur, hy droxyl, thiol, cyano, thiocyano and sulfoxy; the total number of halogen, oxygen, sulfur, hydroxyl and thiol substituents‘not exceeding one half the sum of m+q and the total number of cyano, thiocyano and sulfoxy radicals not exceeding the sum of m-i-q. . 12. The composition of claim l in which the solution contains at least 10% of said polymer of acrylonitrile. ' ` I 13. The composition of claim 1 in which the polymer of acrylonitrile is polyacrylonitrile hav ' ing a molecular weight of between 15,000 and 250,000. l 6. A new composition of matter as deñned in 14. The composition of claim 1 in which the 'claim l, in which the polymer of acrylonitrile has polymer of acrylonìtrile is polyacrylonitrile hav a molecular weight of between 40,000 and 150,000. 40 ing a molecular weight of between 40,000 and '7. A new composition of matter as defined in claim 1,_ in which the polymer solution has a vis 150,000. cosity between 25 and 750 poises. . 8. lAs a new .composition of matter, a polymer which said polymer is polyacrylonitrile. - of acrylonitrile containing in the polymer` mole cule at least 85% by weight' of acrylonitrile dis which said polymer is polyacrylonitrile. solved Ain N,N-dimethylcyanoacetamide. which said polymer is polyacrylonitrile. _ 15. The composition as- deñned in claim 9 in 16. The composition as defined in claim 10 in 17.'The composition as deñned in claim 8 in 9. As a newv composition oi matter, a polymer of acrylonitrile containing in the polymer mole 'VIRGIL L. HANSLEY. -Certiñcate of» Correction ` Patent No. 2,404,716. July 23, 1946. viRoiL L. HÀNSLEY the above It is hereby certified that errors'appear in the printed specification of “polyarcylo 2, line 9, for numbered patent re airingl correction as follows: Column. line 7, claim l, and column niti'ile” read polyacry onitmie; column 5, line 32; column l5, “C” after the third bracket, i6, line 15, claim ll, for the indistinct subscript following formula reading read p; column 7, lines 66 to 68,_for that portion oi the "a,' re'ad im columny 13,` line 19, for “alkalines” read alkalies; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oíiice. Signed and sealed this 5th day of November, A. D. 1946. . ï LESLIE imma, First Assistant Oommîasíoner of Patents.