US2975022A - Process for preparing acrylonitrile fibers - Google Patents

Description

R. D. EU LER March 14, 1961 PROCESS FOR PREPARING ACRYLONITRILE FIBERS Filed May 20, 1958 FIG. 3

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@QQQQQQQQQQQQ ATTORNEY 2,975,022 PROCESS non PREPARING ACRYLONITRILE This invention relates to the preparation of acrylonitrile fibers of modified cross-sectional shape. More particularly, this invention relates to a process for preparing fibers of a uniform,-round cross-sectionalshape from copolymers of acrylonitrile by a dry-spinningprocess.

Fibers arereadily prepared from acrylonitrile polymers by dissolving the polymer in -.a suitable organic solvent such-as dimethylforr'namide-and extruding the resultant solution into an evaporativeatmosphere. I Tlhe polymer used may be a homopolymer of acrylonitrile-or 'a copolymer of acrylonitrile containing up to 15% of one or more additional copolymerizable monomers to improve dye depth and dye uniformity, or tointroduee other desirable properties in the final yarnr;

Acrylonitrile fibers prepared by jknownprocesses have distinctive cross-sectional shape. -The cross-sections are in the form of dog-hones o r dumbbells. While filaments of this shape are suitable for many purposes, they are easily. bent in the direct-ion of the short axis of the cross-section. If increased stiffness is desired in such a filament, it is necessaryto increase thecross-sectional area.

.It is, therefore, an object of invention to provide a, process forpreparing fibers from acrylonitrile copolymersmwhich donot have a dog-bone or'dumbbell crosssectionaLshape. 'It is a further object of theinvention to produce acrylonitrile copolymer fibers having a uniform, round cross-sectional shape. Additional objects will appear hereinafter.

fl}hese:and other objects of the invention are accomplishedby extruding a solution of a polymer containing at least 85% acrylonitrile in a volatile organic solvent at awtemper'ature from about 130 C. to about 145 C. through-an orifice into a spinning cell which isfdivided into two-zones, the first zone containing an essentially static gaseous medium which issubstantially'saturated with a solvent for the polymer and is heated to a temperature from about 165 C. to about 205 C1, and the second zone-containing a gaseous mediumessentially free from solvent which is heated to a temperature'from about 50C.-to about 100 C. The flow of the gaseous medium in the second zone may be co-current or concurrent with the'direction of travel of the filaments. The filaments are removed from the spinning cell ata ratefro'm about 27540350 yards per minute. 7

The present invention will be more clearly understood by reference to the accompanyingdrawingsin which Figure l is a representative'drawingof theoross-sectional shape of a bundle of fibers of the present invention; Figure Z-i-llustrates the cross-sectionalshape of the filaments prepared by known prior art processes; and Figure 3 is a side elevation, partly in cross-section, of suitable apparatus for practicing this invention, 1 j

\ Referring to the drawings, in Figure 3 a solution of polymer is metered under pressure through inlet 1 to spinneret 2 which contains a plurality of small orifices, riotshown, to form filaments 3. As the filaments enter spinning cell 4; they pass into solvent-laden, jacketed Un ed 5% Patent 9 zone I. Suitable ba'fiiing, not shown, may be positioned which are relatively wet with solvent pass through zone- I into zone II of spinning cell 4 which is unheated where they are surrounded by a countercurrent flow of. an essentially solvent-free gaseous medium which is introduced through inlet 6 andremoved through outlet 7. The substantially dry'rfilaments are then converged near exit 8, passed out of the spinning cell, over guide roller 9', and then to a suitable collecting device not shown.

The apparatus shown in Figure 3 may, of course, be modified to include means for initially introducing a solvent laden' gaseous medium into zone I; however, aftertheprocs's is in operation, it has been found that the solvent removed from the spinning solution as the filaments coagulate is suflicient to maintain "a substantially solvent-saturated atmosphere. It has been found desirable to maintain fa'fsifiall neg'ative static pressure, e.g.-, in the order of "-0.l5 inch of water, throughout the spinning cell to prevent objectionable condensation of solvent 'nearexit'fl. V

The production or uniformly round a'crylonitrile fila ments is only possible by maintaining a "critical combination of con'ditions Within thespin'ning apparatus. The 5. temperature of the spinning solution must be'be't ween about 130 C. and 145 C. it the temperature falls'b'elovv the lower limit, the filaments tend to' coalesce and stick together. 'If the temperature goes above 145 C., the

dog-bone shaped'structures of" the zpxior'art are first o btained and then bubbles appear. The temperature of z lie I of the spinning cell must be maintainedbetween about 165 C. and 205 C. If th'e temperaturefalls'b elow-165 C.,the filaments stick together, and if it rises above 205 C., dog-bone shaped'filam'ents are obtained. The terriperature of the' gaseous medium which is introduced into zone II of the spinning cell rnustals'o be closely regulated.- At temperatures below about 5 0 "C.-, "the filaments coalesce and, at temperatures above C., the convert I tional d0g-bone shaped filaments are produced. The fil'aments must be removed at a rate of about 275, yards'per minute to prevent theformation of the dog-bone crosssectional shapes; however, the rate must not exceed about 350 yards per minute or the filaments "again'coalesce.

The invention will befurther illustrated but'is not inf tended to be limited by the following examples in which parts and percentages are given by weight unless other- 5 wise specified.

Example I p a A spinning solution was prepared by dissolving parts ofa-copolymer containing 94.0%acrylonitrileand I 6.0% methyl acrylate in 69'pa1ts'of dimethylformamide."

The viscosity of thissolution, as measured at JC;

was 52 poises. Apparatus similar to that shown in'Figure f a 3 was used in spinning the 'solutionintofilaments The solution was heated to and was forced' ati-th'e" rate of 38.8 grams per minute througha spinneret' hav ing 30 orifices 0.11 millimeter in diameter into a spin ning cell 8 inches in diameter and'16 feet long. Keinp gas, essentially a mixture of about 87% nitrogen and 13% carbon dioxide, was heated to a temperatureof 60 C. and passed into a zone at the bottom'of 'tlie s'piii ning cell through an inlet-located at a point about '5 inches from the exit point'for the yarn. This aspiration gas was removed from the cell at 'a'point about tfeet above the point of entrance. The zone at:the ,bottornidf' the spinning cell was unheated except for the heating ef-= fect of the Kemp gas. The 12-foot z onepf spinning jcell between the spinneret and thepoint at which tion gas was removed-was heatedto a tempe tur 2,975,022 I Patented Mar. 14,

180 C. This zone contained no openings for introduction of removal of aspiration gas. The yarn collected from the spinning cell was treated with an aqueous finish and was then wound onto a bobbin at a speed of 300 yards per minute. This yarn was found to contain 39.8% solvent. After removal of this solvent, the yarn was found to have a denier of 395. The filaments were found to be uniformly round in cross-sectional shape.

Bobbins of the spun yarn were extracted with water and dilute aqueous solutions of dimethylformamide at temperatures between 25 C. and 100 C. The resultant extracted yarns were then drawn to from 4 to 8 times their original length and were then relaxed 10% to The final relaxed yarns were all found to have the same cross-sectional shapes as the spun yarn.

Example II Example I was repeated except that the spinning solution was a terpolymer containing 93.7% acrylonitrile, 6.0% methyl acrylate, and 0.3% styrenesulfonic acid, and a spinneret having triangular holes measuring 0.18 millimeter on an edge was used. In spite of the shape of the spinneret holes, the filaments obtained were perfectly round as shown in Figure 1. This experiment demonstrates that it is the critical selection of spinning conditions and not the shape of the orifice which controls the shape of the filaments formed.

The process of this invention is not limited to the preparation of filaments from the copolymers specified in the examples but is equally applicable to producing round filaments from other copolymers of acrylonitrile containing at least 85% combined acrylonitrile in the polymer molecules. The polymer may contain from 2% to 15% of one or more ethylenically unsaturated monomers which are copolymerizable with acrylonitrile. For example, any of the monomers mentioned in U.S. 2,436,926 or U.S. 2,743,994 such as acrylic methacrylic, and alphachloracrylic acids, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, 2-nitro-2- methyl propyl methacrylate, methoxyethyl methacrylate, chloroethyl methacrylate, phenyl methacrylate, cyclohexyl methacrylate, dimethyl aminoethyl methacrylate, and the corresponding esters of acrylic or alpha-chloro acrylic acids; acryland methacryl-arnides or monoalkyl substitution products thereof; unsaturated ketones such as methyl vinyl ketone, phenyl vinyl ketone, and methyl isopropenyl ketone, vinylidene chloride, vinyl chloride, vinyl fluoride, vinyl carboxylates such as vinyl acetate, vinyl chloroacetate, vinyl propionate, vinyl butyrate, vinyl benzoate, vinyl thiolacetate, and vinyl stearate, ethylenealpha, beta-dicarboxylic acids, or their anhydrides or derivatives such as maleic anhydride, fumaric, maleic, citraconic, and mesaconie esters, N-alkyl maleimides; N- vinyl carbazole, N-vinyl succinimide, N-vinyl phthalimide, vinyl cthers, monoolefins, or substitution products thereof such as styrene, furyl ethylene, ethylene, and isobutylene may be used. In addition, the copolymers may contain from about 0.1% to about 10% of a copolymerizable monomer having sulfonic acid or sulfonate salt groups such as allyloxyethylsulfonic acid, allylthiopropanolsulfonic acid, vinyldichlorobenzenesulfonic acid, naphthylethylene sulfonic acid, methyl styrenesulfonic acid, as well as disulfonic and amino sulfonic acids.

The concentration of the polymer in the spinning solution should be between about 25% and 40%, and the solution should have a viscosity within the range of about 15 to 750 poises at the temperature of spinning with viscosities between about 50 and about 200 poises being preferred. The gaseous medium may be selected from any of a number of substantially inert compositions, e.g., Kemp gas, nitrogen, carbon dioxide, etc., as well as air may be used.

The various temperatures and flow conditions involved in the spinning will depend somewhat on the polymer being spun, the concentration of solution of that polymer in solvent, and the spinning speed being used. nowever, the solution temperature, the temperature in zones I and H of the spinning cell, the inlet gas temperature, and the spinning speed must be maintained within the critical limits previously set forth. The rate of flow of the gaseous medium introduced into zone 11 of the spinning cell should be from about 20 to about 60 pounds per hour. The flow is countercurrent to the direction of travel of the filaments. I prefer to use a solution temperature of 133 C. to 137 C. with a temperature of 170 C. to 200 C. in zone I and an inlet gas temperature of 55 C. to 70 C. in zone II, and to adjust the rate of aspiration within the range previously described to give a level of good spinning continuity and good yarn uniformity, according to the polymer and solution concentration employed.

The apparatus used in practicing the invention may be similar to that shown in Figure 3; however, many modifications as well as other suitable apparatus will be apparent to those skilled in the art. For example, the spinning apparatus described in U.S. 2,615,198 with certain modifications would be acceptable. A- spinneret of the type described in U.S. 1,883,423 is preferred.

The length of the zones in the spinning cell which is heated and the length which is unheated are not critical; however, I prefer to use a heated section from about eight to sixteen feet in length and a lower unheated section from about four to eight feet in length. It is not essential that the point of removal of the aspiration gas be immediately adjacent the lower end of the heated section of the cell. The gasmay be removed at a point several feet above or below the line of separation of the heated and unheated sections. However, steps must be taken to maintain the solvent-laden atmosphere and critical temperature range in the upper section. The gas is preferably removed at a point in the lower section of the spinning cell.

The products prepared by the process of this invention are particularly useful in the preparation of woven, knit, and pile fabrics for use in the apparel trade. The fabrics prepared from such fibers have improved crispness of hand without increasing the individual filament denier which would result, in some cases, in an over-all coarseness of fabric quality. Where the fibers are used in staple form and must be converted from staple to yarn by such spinning systems as the cotton system or woolen system, the fibers so prepared permit improve ments in hand without altering the fineness of the yarn count that may be spun. A further advantage of the fibers of my invention lies in the fact that fabrics prepared from these fibers do not show an undesirable shiny surface, which is frequently true of fabrics made from dogbone shaped filaments because of the tendency of those filaments to arrange themselves parallel to the surface of the fabric itself.

The chief advantage of the process of my invention is that it allows the preparation of filaments having a uniformly round cross-sectional shape from copolymers of acrylonitrile by a dry-spinning process which heretofore has not been possible. In addition, the process does not require complicated equipment and may be practiced using existing equipment with only minor changes being required.

It will be apparent that many widely different embodiments of this invention may be made without departing [from the spirit and scope thereof, and therefore it is not intended to be limited except as indicated in the appended claims.

' I claim:

, 1. A process for preparing acrylonitrile filaments having a uniform, round cross-sectional shape which comprises extruding a solution containing a polymer comprised of at least acrylonitrile and up to about 15% of an ethylenically unsaturated monomer copolymerizable with acrylonitrile in dimethylformamide at a temperature from about 130 C. to about 145 C. through a spinneret into an atmosphere containing a substantially solventsaturated static gaseous medium heated to a temperature from about 165 C. to about 205 C., and thereafter passing said filaments through an atmosphere containing a substantially solvent-free gaseous medium heated to a temperature from about 50 C. to about 100 C. and withdrawing said filaments at a rate from about 275 to about 350 yards per minute.

2. The process of claim 1 wherein said solution is at a temperature from about 133 C. to about 137 C., said solvent-saturated gaseous medium is at a temperature from about 170 C. to about 200 C. and said solventfree gaseous medium is at a temperature from about 55 C. to about 70 C.

3. A process for preparing acrylonitrile filaments having a uniform, round cross-sectional shape which comprises extruding a solution containing a'polymer comprised of at least 85% acrylonitrile and up to about 15% of an ethylenically unsaturated monomer copolymerizable with acrylonitrile in dimethylformamide at a temperature from about 130 C. to about 145 C. through a spinneret into a first zone of a spinning cell containing a substantially solvent-saturated static gaseous medium at a temperature from about 165 C. to about 205 C., passing said filaments without cooling into a second zone of said spinning cell while simultaneously introducing a fiow from about 20 to about 60 pounds per hour of a solvent-free gaseous medium at a temperature from about 50 C. to about 100 C. in said second zone, and subsequently removing said filaments from said second zone at a rate from about 275 to about 350 yards per minute.

4. The process of claim 3 in which the flow of said solvent-free gaseous medium is counter-current to the direction of travel of the filaments.

5. A process for preparing acrylonitrile filaments having a uniform, round cross-sectional shape which comprises extruding a solution containing a polymer comprised of at least acrylonitrile and from about 2% to about 15% of a copolymerizable ethylenically unsaturated monomer in dimethylformamide' at a temperature from about 130 C. to about 145 C. and Withdrawing said filaments at a rate from about275 to about 350 yards per minute through a spinneret into an atmos phere containing a substantially solvent-saturated static gaseous medium heated to a temperature from about 165 C. to about 205 C., and thereafter passing said filaments through an atmosphere containing a substantially solvent-free gaseous medium heated to a temperature from, about 50 C. to about C. and withdrawing said filaments at a. rate from about 275 to about 350 yards per minute.

6. A process for preparing acrylonitrile filaments having a uniform, round cross-sectional shape which comprises extruding a solution containing a polymer comprised of at least 85 acrylonitrile, from about 2% to about 15% of a copolymerizable ethylenically unsaturated monomer, and from about 0.1% to about 10% of a eopolymerizable sulfonate monomer in dimethylformamide at a temperature from about C. to about C. through a spinneret into an atmosphere contain ing a substantially solvent-saturated static gaseous medium heated to a temperature from about C. to about 205 C., and thereafter passing said filaments through an atmosphere containing a substantially solvent-free gaseous medium heated to a temperature from about 50 C. to about 100 C. and withdrawing said filaments at a rate from about 275 to about 350 yards .per minute.

References Cited in the file of this patent UNITED STATES PATENTS 2,068,538 Dreyfus et al. Jan. 19, 1937 2,341,615 Hoifman Feb. 15, 1944 2,761,754 Jones Sept. 4, 1956 2,811,409 Clapp et a1. Oct. 29, 1957 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,975,022 March 14, 1961 Robert D. Euler It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent. should read as corrected below.

Column 6, lines 4, 5 and 6 strike out "and withdrawing sald fllaments at a rate from about 275 to about 350 yards per minute".

Signed and sealed this 26th day of December 1961,,

( SEA L). Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents USCOMM-DC-

Claims (1)

1. A PROCESS FOR PREPARING ACRYLONITRILE FILAMENTS HAVING A UNIFORM, ROUND CROSS-SECTIONAL SHAPE WHICH COMPRISES EXTRUDING A SOULTION CONTAINING A POLYMER COMPRISED OF AT LEAST 85% ACRYLONITRILE AND UP TO ABOUT 15% OF AN ETHYLENICALLY INSATURATED MONOMER COPOLYMERIZABLE WITH ACRYLONITRILE IN DIMETHYLFORMAMIDE AT A TEMPERATURE FROM ABOUT 130*C. TO ABOUT 145*C. THROUGH A SPINNERET INTO AN ATMOSPHERE CONTAINING A SUBSTANTIALLY SOLVENTSATURATED STATIC GASEOUS MEDIUM HEATED TO A TEMPERATURE

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