US3414645A - Process for spinning wholly aromatic polyamide fibers - Google Patents

Description

Dec. 3, 1968 H. s. MORGAN, JR

PUOCESS FOR SPINNING WHOLLY AROMATIC POLYAMIDE FIBERS Filed June 19, 1964 R J M N 0 L 2% ER vO/M mM 5 MW E 2 5 H Y B ATTORNEY United States Patent 3,414,645 PROCESS FOR SPINNING WHOLLY AROMATIC POLYAMIDE FIBERS Herbert S. Morgan, Jr., Apex, N.C., assignor to Monsanto Company, St. Louis, Mo., a corporation of Delaware Filed June 19, 1964, Ser. No. 376,363 17 Claims. (Cl. 264-210) ABSTRACT OF THE DISCLOSURE The solution spinning of aromatic polyamides is improved by using a dry jet-wet spinning process wherein the polymer solution immediately after extrusion is led through a gaseous medium for a short distance, about A; to 1 /2 inches, before entering the coagulation bath.

This invention relates to a process for the preparation of high temperature resistant shaped and attenuated articles such as fibers, films, filaments, yarns and the like. More particularly, it relates to a process for the preparation of high strength thermally resistant fibers, filaments, films, and other shaped articles from Wholly aromatic polyamide compositions.

There has recently arisen a need for shaped articles of improved high temperature resistance. This need has 'been partially filled by the provision of wholly aromatic polyamide compositions such as those prepared and described in US. Patents 3,006,899 to Hill et al., 3,049,518 to Stephens et al., 3,068,188 to Beste et 2.1., 3,079,219 to King and 3,094,511 to Hill et al. Other wholly aromatic polyamide compositions of unique structure such as those in our copending applications Ser. No. 222,930 to Preston, now US. Patent 3,240,760, Ser. No. 222,932 to Preston et -al., now US. Patent 3,232,910, Ser. No. 298,467 to Smith et al., now US. Patent 3,354,125, Ser. No. 347,- 392 to Preston, now U.S. Patent 3,376,268 and Ser. No. 347,385 to Preston, now US. Patent 3,376,269, provide additional unique wholly aromatic polyamide structures and compositions of very high thermal stability. All such Wholly aromatic polyamides may be generally described as having no aliphatic linkages or segments in their regularly recurring structural units. Thus included are all resonance-stabilized ring systems whether benzene-aromatic or heteroaromatic. Examples of such polymers include:

poly (m-phenylene isophthalamide) {Zigiigil poly-N,N-m-phenylenebis (m-benzamide terephthalamide 3,414,645 Patented Dec. 3, 1968 poly-N,N'-m-phenylenebis(m benzamide)-2,6-naphthylene dicarbonamide poly-N,N'-m-phenylenebis (m-b enzamide) -4,4' -biphenyldicarbonamide poly-4,4- bis (p-aminophenyl -2,2'-bithiazole is ophthalamide n L its all @J poly-2,5 bis(p-aminophenyl)1,3,4oxadiazole isophthalamide l'i t i ii I @-t fiQ poly-3,4'-diaminobenzanilide isophthalamide iii n L l and poly-4,4-diaminobenzanilide terephthalamide i Q- Q- Q- l Because of the unique chemical structure of these wholly aromatic polyamide compositions they have proven very ditlicult to process into shaped articles. Their lack of any true melting point prevents satisfactory melt extrusion. Their low solu'bilities in most conventional polyamide solvents causes difficulty in dry or wet extrusion unless accessory solubilizing agents such as salts of alkali or alkaline earth metals are added to the solutions. This in turn requires exacting and extensive after treatments to remove the salts from the shaped articles and requires stringent conditions of heat and attenuation to yield satisfactory fine structure in the finished article.

Accordingly, it is an object of this invention to provide shaped articles of wholly aromatic polyamides.

Another object of the invention is to provide dense attenuated structures of unusually high crystallinity, orientation and thermal stability.

An additional object of the invention is to provide an improved modified Wet extrusion process for preparing wholly aromatic polyamide filaments, fibers, films and other shaped articles.

Yet another object is to provide a dry jet-wet spinning process for the production of wholly aromatic polyamides of improved zero strength temperatures, high birefringence thermal stability and tenacity.

A further object is to provide a process for spinning wholly aromatic polyamides which permits improved extraction of solvent and inorganic salts from the polymer solution.

Other objects and advantages of the invention will become apparent from the description of the invention.

In accordance with this invention outstanding improvements are provided in the extrusion of wholly aromatic polyamides by using a dry jet-wet spinning process wherein the polymer solution immediately after extrusion is led through a gaseous medium for a short distance, about A; to 1 /2 inches and preferably about from /4 to 1 inch before being led into the coagulating bath. The gaseous medium allows for instantaneous skin-core formation to begin before the fiber enters the coagulation bath. The expression dry jet-wet spinning refers to the fact that in the process of the invention the spinnerette or jet face is suspended above the coagulation bath liquid. After coagulation the fiber, depending on the type of polymer used, is either washed or advanced to the next step of the process. The remaining sequential steps are orientation, washing, a finish application if desired, drying, and an additional thermal stretching step referred to herein as a hot draw. Surprisingly, utilization of this technique leads to much improved extraction of inorganic salts from the polymer solution, improved structural properties of the shaped objects, and excellent thermal stability.

The patents and patent applications previously mentioned disclose methods for preparing the wholly aromatic polyamides of the invention. Generally the wholly aromatic polyamides of the invention may be prepared conveniently and preferably by combining an aromatic diacid chloride and an aromatic diamine in a lower alkylamide solvent to produce the desired polyamide and the byproduct, hydrogen chloride. The hydrogen chloride must be neutralized or removed to prevent its harmful effects to the resulting articles. Neutralization of the hydrogen chloride may be conveniently accomplished by adding an alkali, or alkaline earth, metal base to form a salt and water.

As a result of this neutralization reaction the polymers are further dissolved in the lower dialkylamide containing an amount of salt and water which is proportional to the amount of hydrogen chloride formed in the polymerization. This amount of salt ranges from about 1 to 8 percent based on the solution weight of alkali or alkaline earth metal chloride. These solutions may also be prepared by stirring previously washed salt-free polymer into a solvent consisting of a lower dialkylamide and from 1 to 8 percent of either an alkali or alkaline earth metal chloride or bromide at a temperature of 60 to 90 C. Although it is not absolutely essential it is preferred to add up to a total of 4 percent water to these dopes to improve their stability.

It is desirable and convenient to use the same solvent for polymerization and spinning. To this end lower alkylamides such as dimethylformamide and dimethylacetamide containing up to 10% by weight of dissolved metal salts such as lithium chloride, lithium bromide, calcium chloride, potassium chloride, zinc chloride and similar salts are especially useful. Calcium chloride and lithium chloride are preferred. Other solvents which may be used for spin solution preparation include trifiuoroacetic acid, dimethylsulfoxide, N-methyl-Z-pyrrolidone, and hexamethylphosphonic triamide. These solvents usually have their solvency power enhanced by adding the aforementioned salts to the spin solution. Additional solvents may be obtained by using mixtures of two or more of these solvents. Concentrated sulfuric acid may also be used.

The polymer solution may be extruded at temperatures of 30 to 120 C. The polymer concentration may be increased or decreased within the preferred limits of 10 to 30 percent to provide a suitable solution viscosity. Conversely, the viscosity of a given concentration may be adjusted by heating or cooling the solution briefly at a point just prior to the extrusion orifices. The spinnerette is preferably positioned with the face substantially parallel to the surface of the coagulation bath so that the extruded solution passes through a short gaseous space before entering the coagulation bath. It is normally a simple matter to adjust the jet to obtain the optimum distance and this distance will depend on the concentration, viscosity, temperature and other spinning solution conditions. Usually this distance will be from A; to 1 /2 inches, preferably about /2 an inch. However, this distance can be increased by taking precaution that adjacent polymer streams do not come in contact with and cohere to each other before entering the coagulation bath.

The temperature resistant wholly aromatic polyamides are conveniently spun from about 10 percent to about 30 percent solutions, preferably 12 to 20 percent solutions by weight, of the wholly aromatic polyamides having inherent viscosities of from about 0.6 to 3.0 or higher, and preferably above about 1.2 as measured at 30 C. as a 0.5% solution in dimethylacetamide containing 5% dissolved lithium chloride.

For best results the spinning variables should be correlated so that less than one percent, if any, of the solvent based on the weight of the solution is evaporated into the gaseous medium from the extruded stream.

It has been found that wholly aromatic polyamides with inherent viscosities of from about 0.6 to 3.0 or higher and preferably above about 2.0 may be spun according to the invention by variations in the coagulation bath and in the step immediately following coagulation. Where it is desirable to produce fibers for apparel and related end uses such fibers should range in denier from about 1.0 to around 3.0 d.p.f. and should have tenacities of from about 2.5 to 5.0 g.p.d. In order to produce fibers within these denier and tenacity ranges the inherent viscosity preferably should be about from 1.2 to about 2.0. When polymer within this inherent viscosity range is spun to fiber using a solvent and water coagulation bath, back diffusion of water into the fibers often occurs. In addition, excess swelling of the fiber results due to the salt content normally present in the solvent system. The product obtained in such cases is a delustered yarn having brittleness, poor tensile strength, large voids and granular structure. Instead of going to more expensive and often less eifective solvents which do not need an alkali or alkaline metal salt to enhance their solvency power a better approach is to change the composition of the coagulation bath to a solution of water and a polyalkylene glycol. Conversely, when it is desirable to produce fiber for tire cord and other heavy industrial uses having a tenacity of from about 5.5 to 8.5 g.p.d. and a denier of from about 6 to 8 d.p.f., the inherent viscosity should range from about 2.0 to 2.4 or higher. Fiber of higher deniers (9 to 15 d.p.f.) may be conveniently formed from the higher molecular weight polymers. At this level of inherent viscosity the polyalkylene glycol coagulation bath is less efiicient resulting in sticking or fusion of filaments. In such cases an aqueous coagulation bath is preferred.

The polyalkylene glycol coagulation bath comprises a mixture of from about to water by weight, and from about 30% to 5% of a polyalkylene glycol. The term polyalkylene glycol as used in the specification and claims refers to polyethers which may be derived from alkylene oxides or glycols and which may be rep esented by the formula HO(RO),,H in which R stands for an alkylene radical such as methylene, ethylene, propylene, and butylene, and n is an integer of at least 4. The polyglycol may contain inert substituents, for example methoxypolyethylene glycol, and may consist of a mixture of polyalkylene glycols. These glycols have molecular weights of from about 200 to 6000, preferably 600 to 2000. Although wide variations in the spin bath temperatures are permitted, it is preferred that the temperature range from about 5 C. to 60 C., preferably from about C. to C.

The coagulation bath, for polymers having an inherent viscosity of about 2.0 or higher, which is comprised of a mixture of from 0 to percent, preferably 0 to 10 percent of a dialkylamide in water, is highly effective even after a substantial concentration of metal salt builds up in the coagulation bath itself. It is convenient to provide fresh solvent-water mixture to the coagulation bath continuously while withdrawing continuously a portion of the bath containing solvent and metal salt concentrations thus maintaining an essentially constant environment for coagulation. In order to assure constant coagulating conditions in the bath, the solution is circulated and may be maintained at a preferred concentration by the continuous addition of fresh solution or water while continuously removing an equal proportion of the spent solution. The temperature of the coagulation bath may be from 10 C. to C., preferably 15 C. to 25 C., during coagulation. When coagulated in the spin bath described, the wholly aromatic polyamide fibers of this invention have properties which permit their conversion by further processing into useful fibers with unique and novel properties.

The coagulation step in the process is followed by an orientation step in which the fiber may be relaxed or stretched from less than one to about four times its length in a conventional hot water or boiling water stretch bath at a temperature of from about 50 C. to 100 C. The orientation of the fiber may include washing the fiber on the take up roller or first godet which Withdraws the fiber from the coagulation bath and advances it toward the hot water stretch bath. This extra aqueous wash is desirable when very high salt concentrations are present such as occur when highly insoluble polymers are being spun from salt containing solvents.

After orientation the fiber is washed with water at a temperature of 15 C. to 65 C., with higher wash temperatures used when shorter washing time is desired and lower wash temperatures when longer washing periods are desired to remove substantially all traces of solvent and salts. The washed, oriented fiber is next passed through an optional aqueous finish bath where conventional lubricants and/or antistatic agents may be applied. Of the types of finishes applicable, an antistatic type to control the static electricity has been found the most valuable. Without an antistatic agent the dried fibers tend to repel one another and may be ditficult to handle in further processing steps.

The fiber is dried in the conventional manner on steamheated cylindrical rolls or by any other suitable drying means. The temperature is preferably maintained at from about 120 C. to 160 C.

Following the drying operation the fiber may be preheated by passing over a heated draw pin or through a heated enclosure such as an oven, furnace, or hot block slot where the fiber is continuously conditioned at about 300 C. to 500 C., preferably 400 C. to 450 C. The fiber is then drawn from one to four times over a heated surface such as a hot shoe type heater at about 300 C. to 450 C. Alternately the fiber after drying may be advanced directly to the heated surface when a continuous spinning system is employed. When it is desirable to reduce shrinkage and further stabilize the fiber at high temperatures, preferably at 350-450 C., the fiber may, after hot drawing, be passed over a heated surface several times by the use of small roller guides. The drawn (or drawn and heat stabilized) fiber is finally collected on bobbins using a conventional take-up device.

As a further spinning aid when spinning fibers from polymers of the general formula:

1.94-.. t1 LU U l such as poly N,N'-m-phenylenebis(m-benzamide) terephthalamide,

and poly N,N'-m-phenylenebis(m-benzamide) isophthalamide,

l 0 Q 0 (It it has been found desirable to include a dip bath with the first godet after the coagulation bath, containing a solvent extraction agent to improve the luster and other properties of the fiber. Suitable extraction agents which may be used include monohydroxy and polyhydroxy compounds such as methanol, ethanol, propanol, isopropanol, butanol, pentanol, ethylene glycol, propylene glycol, butylene glycol, glycerol, and mixtures of these compounds with up to 50 percent water. Other extraction agents are polyalkylene glycols of 600 to 2000 molecular weight such as polyethylene glycol of 1000 molecular weight. Amides such as dimethylacetamide, dimethylformamide, and urea mixed with 40 to 70% water may also be used. Other agents include acetonitrile (CH CN). These extraction agents are preferred when the polymer inherent viscosity is below about 1.90 and the desired denier is 6 d.p.f. or higher.

To further understand the invention reference will be made to the attached drawings that form part of the present application.

In the drawings, FIGURE 1 is a side elevational view partly in section showing schematically an apparatus arrangement of the type which can be used in carrying out the process of the present invention.

FIGURE 2 shows a drawing of a photomicrograph cross-sectional view of fibers obtained by the dry jet- Wet spinning technique.

FIGURE 3 shows a drawing of a photomicrograph cross-sectional view of fibers obtained by a conventional wet spinning technique.

Referring now to FIGURE 1, 1 is the polymer solution hold tank. Polymer solution is pumped via pump 2 through filter 3 composed of two layers of nylon, one layer of flannel, jet holder 4, and out of the spinnerette 5. The spinnerette is adjusted to the desired temperature by circulating a Warm fluid through the jet holder. The jet is normally of 10 to holes, each hole being 3-20 mils in diameter. The jet face is preferably positioned parallel to the surface of the coagulation bath 7. The polymer solution is extruded downward and enters the coagulation bath passing under spacer bar 6 positioned below the surface of the bath directly beneath the jet. The partially coagulated fiber continues an additional distance in the bath, emerges and passes over the first godet rolls 8. First godet rolls 8 may have a dip bath containing a solvent extraction agent through which the freshly coagulated yarn is further extracted before being drawn. The fiber is then fed through a hot or boiling water stretch bath 9 and over the draw wash rolls 10 where the fiber is washed with hot water. The fiber then passes through a finish bath 11 and on to drying rolls 12. After thorough drying is accomplished the fiber is fed directly over the hot pin 13 and is drawn by rolls 15 over shoe 14. The pin is normally set at a temperature about 50 C. above the shoe temperature to insure adequate preheating of the yarn. If an oven is used as the preheater, the temperature within the oven should be 50100 C. greater than the shoe temperature. Alternately the yarns may be preheated only with the drier rolls. The drawn yarn is collected on bobbin 16 using a conventional take-up device.

In FIGURES 2 and 3 the contrast of fiber cross-sections clearly shows the advantage of the process of the invention. The dry jet-wet spun fibers of FIGURE 2 have excellent clear internal structure, whereas those of FIGURE 3, of wet spun fibers, contain numerous voids.

The preferred and optimum spinning conditions for a 6 d.p.f. fiber are summarized in Table 1 as follows:

TABLE 1 Preferred Spinning condition operating Optimum ranges conditions Polymer inherent viscosity. 1. 70-2. 50 2. 20 Polymer solids, percent 15-22 20 Dope temperature at jet, C 40-130 70 Distance from jet fact to spin bath surface, inches 025-1. 50 0. 50 Spin bath comp., by volume:

Percent water 90-100 99 Percent solvent 10-0 1 Spin bath temp., C..." 10-30 25 First godet speed, f.p m 12-150 34 Orientation stretch 88-2. 80X 2.10X Wash water temp., 15- 60 Finish Finish concentration, percent by weight 0. -10 0 2.0 Washer to drier stretch 0.95-1.00 1. 0X Drier roll temp., C... 120-160 150 Drier speed, Lp 13-420 71. 2 Preheater oven temp 300-500 450 Shoe temp., C 300-450 375 Hot draw ratio 1. 0-4. 0X 1. 70X Final Speed, f.p.m 16. 3-714 121 1 An article and/or lubricant.

The maximum operable hot draw is dependent upon the orientation stretch ratio. The total draw from spinnerette or jet face to final takeup godet will vary from about 2.0x to 12.0 T

The invention is further illustrated by the following examples which are presented for illustrative purposes only and are not restrictive of the invention. In the examples all percentages are given on a total solution weight basis unless otherwise indicated. The examples employ five different wholly aromatic polymers comparing three different types of spinning systems.

EXAMPLE I Poly N, N-m-phenylenebis(m-benzamide)2,6-naphthylenedicarbonamide was polymerized as described in Ser. No. 222,930 to give a solution containing 20 percent polymer, 3 percent lithium chloride, 1 percent water and 76 percent dimethylacetamide with a viscosity of 17,280 poises at 23.5 C. The solution was heated to 102 C. and dry spun into hot air in a foot tower using a 5 mil 14-hole spinnerette with an inlet air temperature of 215 C., a spinning speed of 750 f.p.m. and a jet stretch of 7.82 The fiber was collected on a bobbin and then leached for two days with four changes of deionized water at room temperature and at approximately 12 hour intervals. The dried fiber at this point in the process contained about 4.5 percent dimethylacetamide. The fibers were then unwound from the bobbin onto advancing rolls and passed at 141 f.p.m. over a 12 inch hot shoe adjusted to 300 C., drawn 1.7 times and collected on bobbins. This fiber had the properties shown in Table 2, which follows Example IX.

EXAMPLE II The polymer-solvent system employed in Example I was heated to C. and used with a 10 hole, 5 mil spinnerette for wet spinning in to a 55 C. aqueous spin bath. After an immersion of 23 inches in the spin bath the fiber was advanced by drawing rolls which stretched the fiber 1.13 times in the spin bath. From the spin bath the fiber was subjected to an orientation stretch of 2.25 in a boiling water bath. The fiber was next advanced to a set of washer rolls and washed with 55 C. water. After washing a 5 percent antistatic finish dispersion was applied from an aqueous finish bath. After application of the finish the fiber was advanced over heated drier rolls, at a temperature of 135 C. where it was drawn an additional 1.16 times and simultaneously dried. After drying the fiber was passed over a 12 inch drawing shoe at 290 C. and drawn by advancing rolls an additional 1.5 times. The fiber was then collected on bobbins at a final spinning speed of 87.3 f.p.m. The properties of this fiber are shown in Table 2.

EXAMPLE III The polymer-solvent system employed in Example I was spun as shown in FIGURE 1 under the conditions prescribed in Table 1. The properties of the fiber are shown in Table 2.

EXAMPLE IV The conditions employed in Example III were followed in Example IV with the exception that the polymer employed was poly N,N-m-phenylenebis (m-benzamide) 4,4-biphenyldicarbonamide. The preparation of this polymer is described in Ser. No. 222,930 previously mentioned. The properties of the fiber obtained are shown in Table 2.

EXAMPLE V The conditions employed in Example III were followed in this example with the polymer used being poly N,N'- m phenylenebis(m benzamide) terephthala-mide. The preparation of this polymer is described in Ser. No. 222,932. The properties of the fiber obtained are shown in Table 2.

EXAMPLE VI The conditions employed in Example I were followed in Example VI with the following exceptions. The polymer, poly(m-phenylene isophthalamide), was prepared in accordance with U.S. 3,006,899 to give a dimethylacetamide solution containing 20 percent polymer and 3 percent lithium chloride with a viscosity of 5,760 poises at 25 C. The solution was heated to C. A 6 mil l4-hole spinnerette, and an inlet air temperature of 173 C. was used. The spinning speed was 132 f.p.m., jet stretch 4.58 and the fibers were drawn 5.62 times over a hot shoe adjusted to 325 C. The properties of this fiber are shown in Table 2.

EXAMPLE VII EXAMPLE VIII A solution containing 1 8 percent of poly-3,4'-diaminobenzanilide isophthalamide in dimethylacetamide containing 3 percent dissolved lithium chloride was prepared.

9 The solution was heated to 65 C. and dry spun in a 15 foot spinning tower using a mil-8 hole jet. A jet stretch of 3.7 times, a spinning speed of 225 f.p.m., an entrance air temperature of 190 C., and an exit air temperature of 165 C. were employed. Fiber was wound on a perforated bobbin and continuously leached for 24 hours with water at room temperature. After leaching the fiber was air dried at room temperature. The dried fiber was then unwound from the bobbin onto advancing rolls and passed at 123 f.p.m. through a 12 inch oven set at 425 C. and then immediately drawn 1.7 times over a 12 inch shoe adjusted to 425 C. After drawing the fiber was collected on bobbins. The properties of this fiber are recorded in Table 2.

EXAMPLE IX A solution containing 18 percent of poly-3,4'-diaminobenzanilide terephthalamide in dimethylacetamide containing 3 percent dissolved lithium chloride was prepared and spun as described in FIGURE 1 under the conditions prescribed in Table 1. The properties of this fiber are shown in Table 2 which follows:

jet stretch for the wet spinning technique was 1.38 For the dry jet-wet spinning method a jet stretch of 7.3x was obtainable. The ability to spin with this increased latitude in jet stretch makes the dry jet-wet spinning process more flexible and convenient to employ than the wet spinning system. It also facilitates a higher degree of orientation and crystallinity in the finish fiber, and enables a much wider range of fiber denier tobe spun conveniently.

EXAMPLE XII TABLE 2.PROPERTIES OF FILAMENTS Example I II III IV V VI VII VIII IX Denier per filament" 2. 1 5. 0 10. 4 8. 2. 9 1. 5 1. 7 2. 5 2. 6 Tenacity (g./d.) 3. 2 2. 0 6.10 6.10 6.0 6. 50 4. 0 4.0 3.6 Elongation (percent) 19. 7 16. 5 15. 1 20. 8 23. 3 33. 0 1 16. 7 29 5. 6 Refractive index (parallel). 1. 785 1. 930 1. 855 1. 843 l. 792 1. 812 1. 820 Birefringence 0. 100 0. 274 0. 222 0. 184 0. 139 0. 154 0. 165 250 Zero strength temp. 0.)--. 302 320 515 500 500 470 515 325 500 Li content (p.p.m.) 85 0.5 3.4 38. 3 15.8 0. 24 2.4

1 Bundle breaks, elongation.

2 Refractive index (and birefringence) data are not reproducible due to the presence of large voids and a granular structure.

In the table birefringence data were obtained by measuring the parallel and perpendicular refractive indices in plane cross-polarized light using the Becke line technique. Birefringence is calculated from the refractive indices. Zero strength temperature test was determined by heating a yarn at 0.1 gram per denier load in a nitrogen atmosphere. The temperature was raised at a rate of 5 C. per minute until the sample broke. The temperature at which the sample broke was taken as the zero strength temperature.

The superiority of the dry jet-wet spinning technique over dry spinning is obvious on the basis of ease and completeness of salt removal, superior orientation, and crystallinity in the drawn fibers. In terms of wet spinning versus dry jet-wet spinning another distinction is readily demonstrable. The same polymer as described in Example III was dry jet-wet spun except that the jet stretch was retricted to 1.31 times. After collecting fiber under the stable dry jet-Wet spinning conditions, the spinnerette was lowered into the spin bath and the sample wet spun without changing any conditionother than submerging the spinnerette. The fiber cross section obtained by the dry jet-wet spinning technique is shown in FIGURE 2. The cross section obtained by the wet spinning technique is shown in FIGURE 3. The dry jet-wet spun fiber was void free and is much preferred over the highly voided structures shown in FIGURE 3. During the dry jet-wet spinning the distance from the face of the spinnerette to the point along the thread line where the fiber appeared to be coagulated or delustered was approximately 7 inches. This same point was observed only 0.5 inch from the spinnerette face with the fiber when wet spun.

EXAMPLE XI The spinning conditions employed in Example X were repeated with the exception that the maximum jet stretch was determined for both the dry jet-wet spinning and wet spinning techniques. The maximum jet stretch is defined as the maxi-mum stretch which may be applied between the spinerette face and the first advancing rolls without causing the breaking of filaments. The maximum EXAMPLE XIII TABLE 3 Dry heat Example shrinkage at (percent) 1 The dry heat shrinkage was obtained by measuring the decrease in a 20 cm. length of yarn after five minute contact with a heated metal surface. The percent shrinkage was calculated from the change in length.

EXAMPLE XIV A solution was prepared containing 20 percent of poly N,N-m-phenylenebis(m-benzamide) terephthalamide (with an inherent viscosity of 1.92), 3 percent lithium chloride, 1 percent water and 76 percent dimethylacetamide. Additional lithium chloride was added to increase the concentration to 6 percent lithium chloride. The solution was heated to 80 C. and spun as in Example III with the following exceptions. The coagulation bath was comprised of 80 percent water and 20 percent polyethylene glycol of 1000 average molecular weight at a temperature of 20 C. The fiber was given a preliminary wash on the first godet after emerging from the coagulation bath and prior to the orientation stretch. Spinning stability was good and a 5.1 d.p.f. fiber was obtained with a tenacity of 5.0 g.p.d., 29.1 percent elongation, modulus of 82 g./d. and a zero strength temperature of 511 C.

1 l EmMPLE xv A solution of poly N,N-m-phenylenebis(mbenzamide) 4,4-biphenyldicarbonamide was prepared and spun as in Example XIV. An 8.3 d.p.f. fiber having a tenacity of 6.1 g.p.d., elongation of 20.8 percent and a modulus of 82 g.p.d. was obtained.

EXAMPLE XVI A solution of poly N,N-m-phenylenebis(m-benzamide) 2,6-naphthylene dicarbonamide was prepared and spun as in Example XIV. A 2.2 d.p.f. fiber with a tenacity of 7.0 g.p.d., elongation of 16.6 percent, modulus of 118 g.p.d. and a zero strength temperature of 506 C. was obtained.

A study of these examples will Show that the process of the invention produces fibers of greatly improved properties over the prior art. The zero strength temperature of fibers produced by the dry jet-wet spinning process is consistently higher than that of fibers produced by alternate processes, ranging mostly from about 500 C. to around 525 C. The wholly aromatic fibers described in the prior art all have zero strength temperatures well below 500 C. and in most cases below 450 C. Dry heat shrinkage and the occurrence of voids are substantially improved. The dry heat shrinkage at 400 C., shown by Table 3, is especially noteworthy, showing an improvement for the same fiber in Examples VI and VII of from about 80 to about percent shrinkage. Birefringence values are also vastly improved with all fibers produced by the process of the invention having a birefringence greater than 0.150.

EXAMPLE XVII A solution of percent of 2.38 inherent viscosity poly N,N-m-phenylenebis(m-benzamide) 2,6-naphthalene dicarbonamide in dimethylacetamide containing 5 percent dissolved lithium chloride was spun under the conditions set forth in Table 1. The fiber was given a 3.14 jet stretch, 2.55 X orientation stretch and finally hot drawn 1.27 at 350 C. The tensile properties of the fiber were 11.6 d.p.f., 5.86 g.p.d. tenacity, 14.10 percent elongation and a modulus of 134.0 g.p.d.

EXAMPLE XVIII This example shows various dehydrating or solvent extraction agents which are useful in improving the spinning of polymers of the general formula IHN/\-E NH Na salt ill LU l l @1 Samples of poly-N,N'-m-phenylenebis(m-benzamide) terephthalamide of 1.90 inherent viscosity were spun under the conditions described in Table 1, except that the orientation bath temperature was lowered to about C. with the addition of a dip bath on the first godet using the following solvent extraction agents:

In each case the use of the extraction agent achieved a uniform fiber collapse, elimination of any tendency for fiber ccmentation, improved yarn drying rate on the dryer rolls, more lustrous yarns, and a broader range of spinning variables which could be used without causing borderline performance.

The advantages of wholly aromatic polyamide fibers prepared by the process of this invention over such fibers prepared by either dry or wet spinning processes are obvious. The process is outstanding and unusual on the basis of the simplicity, ease of operation, and economically attractive use of conventional fiber spinning equipment. The process avoids explosion hazards and flammability and, in some cases, hazardous and ineffective leaching operations characteristic of other processes reported in the prior art. The range of fiber orientation combinations available is an additional attractive feature of the process. The fibers produced according to the process of this invention have excellent strength, outstanding thermal stability and are highly lustrous.

Fibers with such properties are particularly useful in shaped articles which find applications in uses requiring exposure to elevated temperatures. In the form of fibers, filaments and other shaped articles they are useful in applications such as electrical insulations, industrial filters, conveyor belts tire cord, heat resistant parachutes, protective clothing and the like.

The foregoing detailed description has been given for clearness of understanding only, and unnecessary limitations are not to be construed therefrom. The invention is not to be limited to the exact details shown and described since obvious modifications will occur to those skilled in the art, and any departure from the description herein that conforms to the present invention is intended to be included within the scope of the claims.

I claim:

1. A process for the preparation of shaped articles from wholly aromatic polyamide solutions comprising the steps of:

(1) extruding the solution in a downward direction into a stream by forcing the solution through a shaped orifice at a temperature of from about 30 C. to 120 C. into a gaseous medium in which only a small amount of the solvent is evaporated from the stream;

(2) directing the stream through the medium for a short distance and into a coagulating bath comprising a liquid containing at least 60 percent water that is a precipitant for the polymer and an extractant for the solvent;

(3) withdrawing the thus-formed article from the coagulating bath;

(4) passing the article through a wash liquid while stretching same to orient the polymer molecules thereof;

(5) washing the article;

(6) drying the article;

(7) and passing the article through a heated environment under tension to produce a shaped article.

2. A process for the preparation of fibers from wholly aromatic polyamide solutions, containing from 10 to 30 percent polyamide by solution weight, comprising the steps of:

(1) extruding the solution in a downward direction into a stream by forcing said solution through a shaped orifice at a temperature of from about 30 C. to 100 C. into a gaseous medium in which only a small amount of the solvent is evaporated from the stream;

(2) directing the stream through the medium a distance of from inch to 1% inches and into a coagulating bath comprising a liquid containing at least 60 percent water that is a precipitant for the polymer and an extractant for the solvent at ambient tem peratures;

(3) withdrawing the thus-formed fiber from the coagulating bath;

(4) passing the fiber through a wash liquid comprising boiling water while stretching same from less than 1 to 4 times to orient the polymer molecules thereof;

(5 washing the fiber with water at a temperature of from 40 C. to C.;

(6) drying the fiber at a temperature of from 120 to (7) and passing the fiber through a pre-heated environment at a temperature of from 400 C. to 480 C. under sufiicient tension to elongate said fiber one to three times its length.

3. A process for the preparation of fibers from a wholly aromatic polyamide solution, containing from 10 to 30 percent polyamide by solution weight dissolved in a lower dialkylamide containing from 1 percent to 8 percent of a (6) Washing the fiber with a second wash liquid comprising water at a temperature of from about 50 C. to 65 C.;

(7) drying the fiber at a temperature of from about 120 C. to about 160 C.;

(8) and advancing the fiber through a heated environment under tension to produce a wholly aromatic polyamide fiber.

10. A process for the preparation of fibers from wholly aromatic polyamide solutions, containing from to 22 metal halide selected from the group consisting of alkali and alkaline earth metal halides, comprising the steps of:

(1) extruding the solution in a downward direction into 'a stream by forcing said solution through a shaped orifice at a temperature of from 40 C. to 100 C. into a gaseous evaporative medium in which only a small amount of the lower dialkylamide is evapo rated from the stream;

(2) directing the stream through the medium for a distance of from A of an inch to 1 inch and into a coagulating bath comprising from about 1 percent to 10 percent of a lower dialkylamide and from 90 percent to 99 percent of water at ambient temperatures;

(3) withdrawing the thus-formed fiber from the coagulating bath at a rate suflicient to impart a jet stretch of from about 2 to 7 times its length;

(4) passing the fiber through a wash liquid comprising boiling water while stretching same from less than 1 to 4 times its length to orient the polymer molecules thereof;

(5) washing the fiber with water at a temperature of from 40 C. to 80 C.;

(6) drying the fiber at a temperature of from 120 C.

to 160 C.;

(7) and passing the fiber through a pre-heated enclosure at a temperature of from 400 C. to 480 C.

under sufiicient tension to elongate said fiber 1 to 3 times its length.

4. The process of claim 3 wherein the lower dialkylamide is dimethylacetamide.

5. The process of claim 3 wherein the lower dialkylamide is dimethylformamide.

6. The process of claim 3 wherein the alkali metal halide is lithium chloride.

7. The process of claim 3 wherein the alkaline earth metal halide is calcium chloride.

8. The process of claim 3 wherein the alkali metal is lithium bromide.

9. A process for the preparation of fibers from wholly aromatic polyamide solutions containing from 10 to 30 percent polyamide by solution weight and having an inherent viscosity of from about 1.2 to 2.0 comprising the steps of:

(1) extruding the wholly aromatic polyamide solution in a downward direction into a stream by forcing the solution through a shaped orifice at a temperature of from about 30 to 120 C. into a gaseous medium in which only a small amount of the solvent is evaporated from the stream;

(2) directing the stream through the medium a distance of from Ms inch to 1 /2 inches and into a coagulating bath maintained at a temperature of from about 10 C. to 30 C., comprising a mixture of from about 70% to 95% water by weight, and from about 30% to 5% of a polyalkylene glycol;

(3) withdrawing the thus-formed fiber from the coagulating bath;

(4) moving the fiber through a wash liquid comprising water at a temperature of from about 15 C. to 60 C.;

(5) passing the fiber through a hot aqueous bath while stretching same to orient the polymer molecules thereof;

percent polyamide by weight dissolved in a solvent and having an inherent viscosity of from about"2.0 to 3.0, comprising the steps of:

(1) extruding the wholly aromatic polyamide solution in a downward direction into a stream by forcing the solution through a shaped orifice at a temperature of from about 30 to 120 C. into a gaseous evaporative medium in which only a small amount of the solution preparation solvent is evaporated from the stream as a gas;

(2) directing the stream through the medium for a short distance and into a coagulating bath comprising from about 1 percent to 10 percent of the solvent and from 90 percent to 99 percent of water at ambient temperatures;

(3) withdrawing the thus-formed fiber from the coagulating bath;

(4) passing the fiber through a boiling water bath while stretching same to orient the polymer molecules thereof;

(5) washing the fiber with water at a temperature of from about 15 C. to 65 C.;'

( 6) drying the fiber;

(7) and advancing the fiber through a heated environment under tension to produce a wholly aromatic polyamide fiber.

11. A process for the preparation of poly N,N'-mphenylenebis (m-benzamide) 2,6 naphthylenedicarbonamide fibers comprising the steps of:

(1) extruding a solution of 15 to 22 percent by solution weight of poly N,N'-m-phenylenebis (m-benzamide)-2,6-naphthylenedicarbonamide, dissolved in a solvent comprising 70 to percent dimethylacetamide. 1 to 10 percent lithium chloride and 1 to 5 percent water, in a downward direction into a stream by forcing the solution through a shaped orifice at a temperature of from about 30 C to 120 C. into a gaseous evaporative medium comprising air in which only a small amount of the solvent is evaporated from the stream as a gas;

(2) directing the stream through the air for a distance of inch to 1 inch and into a coagulating bath comprising percent to 99 percent of water and 1 percent to 10 percent of the solvent;

(3) withdrawing the thus-formed fiber from the coagulating bath;

(4) passing the fiber through a wash liquid comprising boiling water while stretching same from 0.88 to 2.80 times its length to orient the polymer molecules thereof;

(5 washing the fiber with water at a temperature of from 40 C. to 80 C.;

(6) drying the fiber at a temperature of from about C. to about C.

(7 and subjecting the fiber to a hot draw by advancing the fiber through a preheater oven at a temperature of from 300 C. to 450 C., then over a shoe heated to a temperature of from 300 C. to 450 C. while stretching the fiber from 1 to 4 times its length.

12. A- process for the preparation of poly-N,N'-mphenylenebis(m-benzamide)terephthalamide fibers comprising the steps of:

(1) extruding a solution of from 15 to 22 percent by solution weight of poly-N,N-m-phenylenebis(m- 15 benzamide)terephthalamide, dissolved in a solvent comprising 85 to 98 percent dimethylacetamide, 1 to 10 percent lithium chloride and 1 to percent water, in a downward direction into a stream by forcing the solution through a shaped orifice at a temperature of from about 30 C. to 120 C. into a gaseous evaporative medium comprising air in which only a small amount of the solvent is evaporative from the stream as a gas;

(2) directing the stream through the air for a distance (5 washing the fiber with water at a temperature of 1 6 prising 90 percent to 99 percent of water and 1 percent to percent of the solvent;

(3) withdrawing the thus-formed fiber from the coagulating bath;

(4) passing the fiber through a wash liquid comprising boiling water while stretching same from 0.88 to 2.80 times its length to orient the polymer molecules thereof;

(5) washing the fiber with water at a temperature of from 40C. to 80C.;

Of 1A inch t0 1 inch and into a coagulating bath COm- 10 (6) drying the fiber at a temperature of from about prising 90 percent to 99 percent of water and 1 per- 120 C. to about 160 C.

cent to 10 percent of the solvent; (7) and subjecting the fiber to a hot draw by advancing (3) withdrawing the thus-formed fiber from the cothe fiber through a preheater oven at a temperature agulating bath; of from 200 C. to 450 C. then over a shoe heated (4) passing the fiber through a wash liquid comprising to a temperature of from 300 C. to 450 C. while boiling water while stretching same from 0.88 to stretching the fiber from 1 to 4 times its length.

2.80 times its length to orient the polymer molecules 15. A process for the preparation of poly-N,N'-mthereof; phenylenebis (m-benzamide) 4,4'-biphenyldicarbonamide (5) washing the fiber with water at a temperature of fib r comprising th steps of;

from 40 C. to 80 C.; (1) extruding a solution of 15 to 22 percent by solu- (6) drying the fiber at a temperature of from about tio weight of poly N,N-m-phenylenebis (tn-benz- 120 C. to about 150 C.; amide) 4,4-biphenyldicarbonamide, dissolved in a (7) and subjecting the fiber to a hot draw by advancsolvent comprising 85 to 98 percent dimethylacetaing the fiber through a preheater oven at a temp ra- 5 mide, 1 to 10 percent lithium chloride and 1 to 5 perture of from 300 C. to 450 C., then over a shoe cent water, in a downward direction into a stream heated to a temperature of from 300 C. to 450 C. by forcing the solution through a shaped orifice at a while stretching the fiber from 1 to 4 times its length. temperature of from about to 120 C. into a 13. A process for the preparation of poly(m-phenylgaseous evaporative medium comprising air in which eneisophthalamide) fibers comprising the steps of: 3 only a small amount of the solvent is evaporated (1) extruding a solution of 15 to 22 percent by solufrom th tr a as a gas;

tion weight of poly(rn-phenyleneisophthalamide) (2) directing the stream through the air for a distance dissolved in a solvent comprising 85 to 98 percent (11- of 1A inch to 1 inch and into a, coagulating bath cornmethylacetamide, 1 to 10 percent lithium chloride prising 90 percent to 99 percent of water and 1 perand 1 to 5 percent water in a downward direction cent to 10 percent of the solvent;

intO a Stream y forcing the Solution through a (3) withdrawing the thus-formed fiber from the coagshaped orifice at a temperature of from about 30 C. ulating b th;

to 120 C. into a gaseous evaporative med m C m- (4) passing the fiber through a wash liquid comprising p g air in which y a Small amount of the boiling water while stretching same from 0.88 to vent is evap rat d fr m th stream as a g 2.80 times'its length to orient the polymer molecules (2) directing the stream through the air for a distance th f;

Of 141 inch to 1 inch and into coagulating bath (5) washing the fiber with water at a temperature of prising 90 percent to 99 percent of water and 1 perf 40C to 80C.;

cent to 10 percent of the solvent; (6) drying the fiber at a temperature of from about (3) withdrawing the thus-formed fiber from the co- 120 C, t b t 160 C,

agulating bath; (7) and subjecting the fiber to a hot draw by advanc- P s g th r through a wash liquid comprising the fiber through a preheater oven at a temperaing boiling water while stretching same from 0.88 t e of fro 300 C t 450 c h over a h to 2.80 times its length to orient the polymer moleheated to a temperature of from 300 C. to 450 C.

cules thereof; while stretching the fiber from 1 to 4 times its length.

16. A wholly aromatic polyamide fiber produced acfrom 40 C. to 80 C.;

(6) drying the fiber at a temperature of from about 120 C. to about 160 C.;

(7) and subjecting the fiber to a hot draw by advancing the fiber through a preheater oven at a tempera ture of from 200 C. to 450 C. then over a shoe cording to the process of claim 1, having a birefringence of at least 0.150 and a Zero strength temperature of at least 500 C.

17. A process for the preparation of p0ly-N,N-rnphenylenebis (m-benzamide) terephthalamide, fibers of at least 6 d.p.f. comprising the steps of:

heated to a temperature of from 300 C. to 450 C. while stretching the fiber from 1 to 4 times its length.

C to 120 C. into a gaseous evaporative medium comprising air in which only a small amount of the solvent is evaporated from the stream as a gas; (2) directing the stream through the air for a distance of A inch to 1 inch and into a coagulating bath com- (1) extruding a solution of from 15 to 22 percent by solution weight of poly-N,N-m-phenylenebis (mbenzamide) terephthalamide having an inherent vis- 14. A process for the preparation of poly-3,4'-diamino- 6O benzanilide isophthalamide fibers comprising the steps coslty above about dls solved m a f of: comprising to percent dimethylacetamide, 1

(1) extruding a solution of 15 to 22 percent by solu- 33 g? gi s ggxgg g ggggis fi to tion weight of poly-3,4'-diaminobenzanilide isophthalr forcing the Solution through a p i i g Z amide dissolved in a solvent comprising to 98 temperature of from about C to C into percent dimethylacetamide, 1 to 10 percent lithium a gaseous medium comprising air'in which o'nly a chloride and 1 to 5 percent water, In a d wn small amount of the solvent is evaporated from the direction into a stream by forcing the solution through Stream as a a shapfid Oflfice at a temperature of from about 70 (2) directing the stream through the air for a distance of 4 inch to 1 inch and into a coagulating bath comprising percent to 99 percent of water and 1 percent to 10 percent of the solvent;

(3) withdrawing the thus-formed fiber from the coagulating bath;

l 7 1 8 (4) passing the fiber through a dip bath containing a ing the fiber over a shoe heated to a temperature of solvent extraction agent selected from the group confrom 300 C. to 450 C., while stretching the fiber sisting of hydroxy compounds containing one to three from 1 to 4 times its length.

hydroxy] groups and up to 6 carbon atoms, polyalkylene glycols of 600 to 2000 molecular Weight, mix- References Cited tures of amides with from to percent water, UNITED STATES PATENTS and mixtures of the hydroxy compounds with up to 3 210 452 10/1965 Howard 264 205 50 percent water, then through a wash liquid com- 3068188 12/1962 Beste at 26O 30 2 prising water at 50 C. While stretching the fiber 3:079:219 2/1963 King from 1.10 to 2.80 times lts length to orlent the 10 3,080,210 3/1963 Ucci 264 182 polymer molecules thereof,

(5) washing the fiber with water at a temperature of FOREIGN PATENTS from 40C. to C.; 240,201 8/1962 Australia.

t 5 2 iggi z f 3; gtemperature from abou JULIUS FROME, Primary Examiner.

1o (7) and subjecting the fiber to a hot draw by advanc- H. H. MINTZ, Assistant Examiner.

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