US3402235A - Manufacture of shaped articles from acrylonitrile polymers by wet spinning - Google Patents

Description

P 17, 1968 w. B. HENDERSON ETAL 3,402,235

MANUFACTURE OF SHAPED'ARTICLES FROM ACRYLONITRILE POLYMERS BY WET SPINNING Filed April 8, 1964 2 Sheets-Sheet 1 FIG. 1. FIG. 2.

FIG. 3. FIG. 4.

INVENTORS GE RD R. BAUR BY WILLIAM B. HENDERSON AT TOR NEY 3,402,235 RILE Sept. 17, 1968 w. a. HENDERSON ETAL MANUFACTURE OF SHAPED ARTICLES FROM ACRYLONIT POLYMERS BY WET SPINNING 2 Sheets-Sheet 2 Filed April 8, 1964 FIG. 6.

FIG. 5.

FIG.

FIG. 7.

INVENTORS GERD R. BAUR WILLIAM B. HENDERSON ATTORNEY United States Patent ABSTRACT OF THE DISCLOSURE The Wet spinning of acrylonitrile polymer filaments by extruding a solution of polyacrylonitn'le into a spin bath which comprises at least 50 percent by weight of an amide or mixtures of amides having the formula on. H I

RCNR2 wherein R is an aliphatic hydrocarbon radical containing at least 5 carbon atoms and R and R are lower alkyl radicals.

Filaments composed of acrylonitrile polymers are produced commercially either by the dry spinning method or by the wet spinning method. In the latter method and with which the present invention is concerned, the poly mer is first dissolved in a suitable solvent. The resulting solution of polymer is extruded through a spinneret submerged in a solution capable of coagulating the polymer. The spinneret is provided with orifices, the diameter and number of which depend on the ultimate filament denier and the number of filaments produced. During their passage through the spin bath, the filaments may be given a stretch to diminish the diameter thereof. This stretch is called the spinning or jet stretch.

In many respects the coagulation of acrylonitrile polymer solutions is the most important step in the wet spinning process, for whatever structure that is established in the filaments during coagulation can only be modified during further processing into finished filaments. Initial Weaknesses or in homogeneities established during coagulation frequently persist as faults in the final product. Consequently, the composition of the spin bath influences considerably the mechanical properties and appearance of the ultimate filaments.

Ordinarily, in a wet spinning operation, coagulation is accomplished by extruding the polymer solution into an aqueous bath sometimes containing a percentage of solvent or dissolved salt. As used herein an aqueous or water bath refers to a composition having water as one of its major components. During coagulation there is an inward diffusion of bath liquid into the coagulating filaments and a corresponding outward movement of solvent into the spin bath. By employing a normal aqueous bath composition, the solvent and bath liquid interchange in such a manner that the resulting filament may contain voids along its length and may have a coarse, sponge-like structure that can be clearly seen with an optical phase microscope. Filaments containing these voids or unfilled spaces do not possess the requisite physical properties desired for some end uses. For example, such filaments may exhibit lower tenacity and lower abrasion resistance than filaments not containing voids.

To collapse the voids the filaments, during the aftertreatment thereof, are given a high degree of stretch and then dried at a rather high temperature under tension thereby forming a more dense, collapsed filamentary structure. Even by being subjected to this stretching and drying operation, filaments produced from acrylonitrile so that they are washed 3,402,235 Patented Sept. 17, 1968 polymers by the wet spinning process have a tendency to splinter or fibrillate and hence have a low abrasion resistance. Fibrillation is a phenomenon characterized by the splitting off from the parent filament or fiber of longitudinal sections of materials which are referred to as fibrils. The dimensions of the fibrils are small compared to those of the original filament or fiber. The aforesaid tendency to fibrillate may be attributed to void formation formed originally in the coagulating process. The abrasion resistance of the filaments may however be raised by subjecting them further to an annealing operation in which a series of elevated and reduced pressure treatments are applied to the filaments. More specifically, annealing consists of placing the acrylonitrile polymer filaments in a closed chamber, subjecting them to a high temperature and pressure in the presence of wet steam and then evacuating the chamber. This treating cycle is repeated as many times as needed. It will be appreciated that this annealing operation as just described is expensive and time consuming.

It is an object of this invention to provide a new and useful method of wet spinning acrylonitrile polymer filaments having improved physical properties, particularly in regard to tenacity, elongation, and the like, without the fibers having to be annealed.

It is another object of this invention to provide a new and useful method of wet spinning acrylonitrile polymer filaments that possess elongation and essentially void free construction and therefore high abrasion resistance without the need of subjecting the filaments to an annealing operation.

It is another object of this invention to provide a new and useful method of wet spinning acrylonitrile polymer filaments that possess excellent basic dye acceptance.

It is still another object of the present invention to provide a new spin bath composition useful in the production of acrylonitrile polymer filaments having improved physical properties.

Other objects and advantages of the invention will be come apparent from the following detailed description thereof.

In general, the objects of the present invention are accomplished by extruding an acrylonitrile polymer containing solution into a spin bath which comprises at least 50 percent by weight of a high molecular weight N,N-dialkylamide or mixtures of said amides. The spin bath may be composed entirely of high molecular weight amide or it may contain, in addition to the amide, up to 50 percent by weight of N,N-dimethylacetamide and/or up to 50 percent by weight of water, depending on the miscibility of the amides with water.

Filaments so spun have high tenacity, high elongation, and better abrasion resistance without the necessity of annealing than comparable filaments spun in a watersolvent spin bath. It has been found that the high molecular weight N,N-dialkylamide bath extracts a higher percentage of initial solvent from the yarn than does a water spin bath and yields a denser, more collapsed yarn at the point the filaments are withdrawn from the spin bath. The bath can be used at temperatures of up to C. and permits jet stretches of up to 2.0 times. After withdrawal from the spin bath the filaments of the present invention are washed with hot water to remove residual solvent and given an afterstretch to orient the polymer molecules. The afterstretching of the filaments can be accomplished by any suitable means which will effect the necessary extension, and it can be accomplished by passing the filaments between two driven thread advancing devices rotating at different predetermined peripheral speeds. The filaments during their passage between said devices are preferably passed through a hot water bath and stretched simultaneously. It

is noted that the conditions of the water bath where stretching is accomplished may be regulated so that it is possible to impart an afterstretch to the filaments to the extent of 8.0 times or more. Alternatively, the filaments may be dried prior to stretching and subsequently given a substantial stretch in either steam or dry heat.

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 photomicrograph at a magnification of about 820 times of a cross section of acrylonitrile polymer filaments that were spun into a coagulation bath comprised of about 55 percent of dimethylacetamide and about 45 percent of water and then dried and collapsed. FIGURE 2 is a photomicrograph at a magnification of about 410 times of a longitudinal view of the same acrylonitrile polymer filament.

FIGURE 3 is a photomicrograph at a magnification of about 820 times of a cross section of acrylonitrile polymer filaments that were spun into a coagulation bath comprised of about 95 percent of N,N,-dimethylmyristamide, about 3 percent of N,N-dimethylpalmitamide, and about 2 percent of N,N-dimethyllauramide and then dried and collapsed. FIGURE 4 is a photomicrograph at a magnification of about 410 times of a longitudinal view of the same acrylonitrile polymer filament.

FIGURE 5 is a photomicrograph at a magnification of about 820 times of a cross section of acrylonitrile polymer filaments that were spun into a coagulation bath comprised of about 85 percent of the amide mixture described above and about percent of dimethylacetamide and then dried and collapsed. FIGURE 6 is a photomicrograph at a magnification of about 410 times of a longitudinal view of the same acrylonitrile polymer filament.

FIGURE 7 is a photomicrograph at a magnification of about 820 times of a cross section of acrylonitrile polymer filaments that were spun into a coagulation bath comprised of about 72.5 percent of the amide mixture described above, about 15 percent of dimethylacetamide, and about 12.5 percent of water, and then dried and collapsed. FIGURE 8 is a photomicrograph at a magnification of about 410 times of a longitudinal view of the same acrylonitrile polymer filament.

It may be seen from FIGURES 1 and 2 that filament spun using a conventional coagulation bath contain undesirable voids whereas the filaments spun using coagulation baths of this invention (FIGURES 3 through 8) produce filament substantially free of undesirable voids.

Filaments produced according to the present invention pick up less water in the washing step, consequently carrying less water with them to the dryers, and therefore can be dried more rapidly or at lower temperatures than ordinary wet spun filaments, provided the excess coagulating N,N-dimethylamides are stripped from the filaments prior to the drying step.

In addition, the filaments show less tendency to fibrillate and can be used for textile purposes omitting the aforesaid annealing operation. Filaments may be spun which have a mirror smooth surface which is free from the pronounced crenulations which characterize normal wet spun filaments. Moreover, the filaments have a soft silky hand or feel even without a finish normally applied thereto.

Although it is not fully understood how the spin bath contributes to the formation of the improved fiber structure, it is believed that a rapid efflux of solvent out of as compared to bath inflow into a coagulating filament minimizes the formation of the aforedescribed porous structure. A denser and more compact filament is therefore attained.

The solutions to be spun in the spin bath composition of the present invention may be prepared by dissolving the acrylonitrile polymer in organic solvents conventionally used in the art. Suitable solvents include, for example,

N,N dimethylformamide; N,N dimethylacetamide; ethylene carbonate; dimethyl sulfoxide; tetramethylene sulfone; nitromethane and water; tris (dimethylamido) phosphate; N-nitropiperidine; mixtures of ethylene sulfite with N,N-dimethylacetamide, N,N-dimethylformamide, and nitromethane and water; tri(betacyanoethyl) nitromethane; trichloronitropropanol; dimethyl methane phosphonate; gamma-butyrolactone; and the like and give solutions of acrylonitrile polymer of high molecular weight without substantial modification by agitation at room temperature. It will be appreciated that a solution containing a higher percentage of acrylonitrile polymer may be prepared by using higher temperatures. The concentration of the acrylonitrile polymer varies with the particular solvent employed and for a given solvent varies inversely with the molecular weight of the polymer. In forming the solution, the polymer is best employed in the form of a dry powder and the solution or spinning dope may be made by combining the powder with the requisite quantity of solvent in a mixing device, preferably provided with means for controlling the temperature. The time required for mixing to obtain a useful solution is adjusted according to the ease of dissolution. The resulting dope is usually a clear, viscous liquid. Ordinarily, for spinning purposes, a solution containing at least 10 percent acrylonitrile polymer is desirable.

By acrylonitrile polymer used to define a polymer applicable to the present invention is meant polyacrylonitrile, copolymers and terpolymers of acrylonitrile, and blends of polyacrylonitrile and copolymers of acrylonitrile with other polymerizable mono-olefinic materials. In general, a polymer of monomeric mixture of which acrylonitrile is at least 50 percent by weight of the polymerizable content is useful in the practice of the present invention. Besides polyacrylonitrile, useful copolymers are those of 50 or more percent of acrylonitrile and one or more percent of other mono-olefinic monomers. Suitable other monomers include vinyl acetate and other vinyl esters of monocarboxylic acids, vinylidene chloride, vinyl chloride and other vinyl halides, dimethyl fumarate and other dialkyl esters of fumaric acid, dimethyl maleate and other dialkyl esters of maleic acid, methyl acrylate and other alkyl esters of acrylic acid, styrene and other vinyl substituted aromatic hydrocarbons, methyl methacrylate and other alkyl esters of methacrylic acid, meth acrylonitrile, alpha-vinylpyridine and other vinyl-substituted heterocyclic nitrogen ring compounds, such as the vinyl imidazoles, etc., the alkyl-substituted vinylpyridines, vinyl chloroacetate, allyl chloroacetate, methallyl chloroacetate, allyl glycidyl ether, methallyl glycidyl ether, allyl glycidyl phthalate, and the corresponding esters of other aliphatic and aromatic dicarboxylic acids, glycidyl acrylate, glycidyl methacrylate and other mono-olefinic monomers copolymerizable with acrylonitrile.

Many of the more readily available monomers for polymerization with acrylonitrile, form copolymers which are not reactive with the dyestuffs and may therefore be impossible or difiicult to dye by conventional techniques. Accordingly, these non-dyeable fiber-forming copolymers may be blended with polymers or copolymers which are in themselves more dye-receptive by reason of their physical structure or by reason of the presence of functional groups which are chemically reactive with the dyestuff, whereby the dyestutf is permanently bonded to the polymer in a manner which lends resistance to the usual laundering and dry cleaning procedures. Suitable blending polymers may be polyvinylpyridine, polyvinylpyrolidone, polymers of alkyl-substituted vinylpyridine, polymers of other vinyl-substituted N-heterocyclic compounds, the copolymers of the various vinyl-substituted N-heterocyclic compounds and other copolymerizable monomers, particularly acrylonitrile.

Of particular utility are the blends formed of polyacrylonitrile or a copolymer of more than percent acrylonitrile and up to 10 percent of vinyl acetate, and a copolymer of vinylpyridine or an alkyl-substituted vinylpyridine and acrylonitrile, the said acrylonitrile being present in substantial proportions, for example, 50 to 80 percent to provide heat and solvent resistance, and a substantial proportion of the vinylpyridine or derivative thereof to render the blend receptive to acid dyestuffs. Of particular utility are the blends of copolymers of 90 to 98 percent acrylonitrile and 2 to percent vinyl acetate and sufficient copolymer of 10 to 70 percent acrylonitrile and 30 to 90 percent vinylpyridine to produce a blended composition with a total of 3 to 8 percent by weight of vinylpyridine.

The acrylonitrile polymer preferably possesses a molecular weight of at least 10,000 and preferably between about 25,000 and 150,000, or even higher. This corresponds to a specific viscosity within the range of 0.1 to 0.4. The specific viscosity value, as employed herein, is represented by the formula N time of flow of polymer solutions in seeonds time of fiow of the solvent in seconds Viscosity determinations of the polymer solutions and solvent are made by allowing said solutions to flow by gravity at 25 C. through a capillary viscosity tube. In the determinations, a polymer solution containing 0.1 gram of the polymer dissolved in 100 ml. of N,N-dimethylformamide is employed. The most effective polymers for the preparation of filaments are those of uniform physical and chemical properties and of relatively high molecular weight.

The polymers just described may be prepared by any conventional polymerization procedure, such as mass polymerization methods, solution polymerizatiommethods, or aqueous emulsion methods. The polymerizat on is normally catalyzed by known catalysts and is carried out in equipment generally used in the art. However, the preferred practice utilizes suspension polymerization wherein the polymer is prepared in finely divided form for immediate use in the filament forming operations. The preferred suspension polymerization involves batch procedures, wherein monomers are charged with an aqueous medium containing the necessary catalyst and dispersing agents. A more desirable method involves the semi-continuous procedure in which the polymerization reactor containing the aqueous medium is charged with the desired monomers gradually throughout the course of the reaction. Entirely continuous methods involving the gradual addition of monomers and the continuous withdrawal of polymer can also be employed.

The polymerization is catalyzed by means of a watersoluble peroxy compound, for example, the potassium, ammonium and other Water-soluble salts of peroxy acids, sodium peroxide, hydrogen peroxide, sodium perborate, the sodium salts of other peroxy acids, and other watersoluble compounds containing the peroxy group. A wlde variation in quantity of peroxy compound is possible. For example, from 0.1 to 3.0 percent by weight of the polymerizable monomer may be used. The so-called redox catalyst system also may be used. Redox agents are generally compounds in a lower valent state which readily oxidized to the higher valent state under the conditions of reaction. Through the use of this reduction-oxidation system, it is possible to obtain polymerization to a substantial extent at lower temperatures than otherwise would be required, Suitable redox agents are sulfur dioxide, the alkali metal and ammonium bisulfites, and sodium formaldehyde sulfoxylate. The catalyst may be charged at the outset of the reaction, or it may be added continuously or in increments throughout the reaction for the purpose of maintaining a more uniform concentration of catalyst in the reaction mass. The latter method is preferred because it tends to make the resultant polymer more uniform in regard to its chemical and physical properties.

Although the uniform distribution of the reactants throughout the reaction mass can be achieved by a vigorous agitation, it is generally desirable to promote the uniform distribution of reagents by using inert wetting agents, or emulsion stabilizers. Suitable reagents for this purpose are the water-soluble salts of fatty acids, such as sodium oleate and potassium stearate, mixtures of Water-soluble fatty acid salts, such as common soaps prepared by the saponification of animal and vegetable oils, the amino soaps, such as salts of triethanolamine and dodecylmethylamine, salts of rosin acids and mixtures thereof, the water-soluble salts of half esters of sulfonic acids and long chain aliphatic alcohols, sulfonated hydrocarbons, such as alkyl aryl sulfonates and any other of a wide variety of Wetting agents, which are in general organic compounds containing both hydrophobic and hydrophilic radicals. The quantity of emulsifying agent will depend upon the particular agent selected, the ratio of the monomer to be used and the conditions of polymerization. In general, however, from 0.1 to 1.0 weight percent based on the weight of the monomers can be employed,

The emulsion polymerizations are preferably conducted in glass or glass-lined vessels provided with means for agitating the contents therein. Generally, rotary stirring devices are the most effective means for insuring the intimate contact of the reagents, but other methods may be successfully employed, for example, by rocking or rotating the reactors. The polymerization equipment generally used is conventional in the art and the adaptation of a particular type of apparatus to the reaction contemplated is within the providence of one skilled in the art.

The optimum methods of polymerization for preparing fiber-forming acrylonitrile polymers involve the use of polymerization regulators to prevent the formation of polymer units of excessive molecular weight. Suitable re ulators are the alkyl and aryl mercaptans, carbon tetrachloride, chloroform, dithioglycidol and alcohols. The regulators may be used in amounts varying from 0.001 to 2 percent, based on the weight of the monomer to be polymerized.

As pointed out above, the improvement herein is obtained by spinning the polymer solution into a bath comprising at least 50 percent by weight of a high molecular N,N-dia'lkylamide. These high molecular Weight dialkylamides are amides having the formula R I I-R2 wherein R is an aliphatic hydrocarbon radical containing at least 5 carbon atoms and R and R are lower alkyl radicals of up to 6 carbon atoms. Preferably, the amide will contain from 11 to 21 carbon atoms and R and R will be methyl radicals.

Illustrative of suitable saturated amides that may be used in the preparation of the compositions of this invention are N,N-dimethylcaprylamide, N,N-diethylcaprylamide, N,N-dimethylcapramide, N,N dimethylcaproamide, N,N-dimethyllauramide, N,N-dibutyllauramide, N,N-dimethylmyristamide, N methyl N-ethylmyristamide, N,N-dimethylpa1mitamide, N,N-dipropylheptadecamide, N,N-dimethylstearamide, N-methyl-N-ethyldocosamide, and the like. Illustrative of suitable unsaturated amides that may be used in the preparation of the compositions of this invention are N,N-dimethylpalmitoleamide, N,N-di methyloleamide, N,N-dibutyloleamide, N, N-dimethyllinoleamide, N,Ndiethyllinoleamide, N-methyl-N-ebutylpropyllinoleamide, N,N-dirnethyllinolenamide, and the like. Mixtures of the used. These compounds may be prepared by reacting an acid anhydride with [a dialkyl amine such as dimethyl amine.

The spin bath will comprise at least 50 percent of high molecular weight polyamide. Preferably, the spin bath will be composed of from about 70 to percent by weight of a high molecular weight polyamide, from about above amides may also be to 30 percent by weight of a solvent for the acrylonitrile polymer selected from the solvents disclosed above, preferably N,N-dimethy1acetamide, and from about 0 to 30 percent by weight of water. Although wide variations in the spin bath temperatures are permitted, it is preferred that the temperature be of the order of about 20 C. to 100 C.

During spinning the solvent concentration will build up in the spin bath. Fresh spin bath composition should be supplied to the spin bath when the solvent concentration therein becomes excessively high, with the spent composition being recovered by conventional methods. Up to 50 percent by weight of solvent may ordinarily be tolerated in the spin bath without adversely effecting the filament appearance or properties. The amount of solvent that can be tolerated is determined by the particular amide or amides used.

Additives such as delusterants, antioxidants, plasticizers, coloring pigments, stabilizers, and other like modifying agents may be incorporated in the polymer solution without departing from the scope of the present invention.

Although reference has been made herein mainly to the production of filaments from the acrylonitrile polymers, the process of this invention is generally applicable to the production of any shaped article from polymers of acrylonitrile such as fibers, filaments, bristles, tubings, films, pellicles, and the like.

The following examples in which parts and percentages are given by weight unless otherwise specified illustrate preferred methods of preparing solutions in accordance with the principles of this invention and of employing the spin bath composition in the manufacture of commercially satisfactory filaments. The invention is not to be limited by the details set forth in the examples.

The basic dye acceptance values given in the examples were obtained by dyeing the fiber at about 97 C. for 2 hours in a dye bath containing 20 percent by weight of Sevron Blue 26 dye (C.=I. Basic Blue 22). The exhausted dyebath was then analyzed spectrophotometrically to determine the amount of dye remaining and the percentage of dye uptake on the fiber.

The test for color stability used in the examples consists of a measurement of purity and brightness as calculated from the tristimulus values determined on a GE spectrophotometer by the methods recommended by the Standard Observer and Coordinate System of the International Commission on Illumination, as fully set forth in the Handbook of Colorimetry, published by the Technology Press, Massachusetts Institute of Technology, in 1936.

The results given in the examples for dyelightfastness represent the degree of alteration of shade of the exposed fibers after an exposure of 80 standard Fade-O-meter hours (SFH) and were determined on a subjective visual scale as follows:

5 Negligible or no change. 4 Slightly changed.

3 Noticeably changed.

2 Considerably changed.

1 Markedly changed.

Light Sample maintains color shade but loses depth. White Sample color shade and depth lighten or change toward white.

Example 1 fibers were then annealed in saturated steam at 35 p.s.i.g. The annealed fiber was found to have a tenacity of 2.3 grams per denier, an elongation of 29 percent, and a basic dye acceptance of 5.5 percent. The dyed fibers were exposed for a total of standard hours in the fade-O- meter and the dyed light stability found to be 3.0 Light. The annealed undyed fiber was evaluated for color on the GE spectrophotometer and found to have a purity of 5 .9 units and a brightness of 84.5 units.

Example 2 A spinning dope composed of about 93 percent acrylonitrile and about 7 percent of vinyl acetate dissolved in a solvent comprising dimethylacetamide was wet spun according to conventional techniques using a coagulation bath comprised of 100 percent of an amide mixture comprising about 95 percent of N,N-dimethyllauramide, about 3 percent of N,N-dimethylmyristamide, and about 2 percent of N,N-dimethylcapramide to produce fiber. The fiber produced was found to have a tenacity of 2.7 grams per denier and an elongation of 35 percent. The fiber was evaluated for color on the GE spectrophotometer and found to have a purity of 5.9 units and a brightness of 87.0 units. The fibers were then dyed with basic dyes and their basic dye acceptance determined to be 7.6 percent. These dyed fibers were exposed for a total of 80 standard hours in the fade-O-meter and the dyed light stability found to be 3.5 Light. The fibers were then annealed in saturated steam at 35 p.s.i.g. The annealed fibers were found to have an elongation of 52 percent.

Example 3 A spinning dope composed of about 93 percent of acrylonitrile and about 7 percent of vinyl acetate dissolved in a solvent comprising dimethylacetamide was wet spun according to conventional techniques using a coagulation bath comprising about 85 percent of the amide mixture of Example 2 and about 15 percent of dimethylacetamide to produce fiber. These fibers were found to have a tenacity of 2.8 grams per denier and an elongation of 30 percent. The fiber was evaluated for color on the GE spectrophotometer and found to have a purity of 5.9 units and a brightness of 87.4 units. The basic dye acceptance of the fiber was determined to be 8.2 percent. The fiber had a dyed light stability rating of 3.0 Light after 80 hours exposure in the fade-O-meter. The fibers were then annealed in saturated steam at 35 p.s.i.g. The annealed fiber was found to have an elongation of 54 percent.

Example 4 A spinning dope composed of about 93 percent of acrylonitrile and about 7 percent of vinyl acetate dissolved in a solvent comprising dimethylacetamide was wet spun according to conventional techniques using a coagulation bath comprised of percent of an amide mixture comprising about 50 percent of N,N-dimethylcaprylamide, about 40 percent of N,N-dirnethylcapramide, about 5 percent of N,N-dimethyllauramide, and about 5 percent of N,N-dimethylcaproamide to produce fiber. These fibers were found to have a tenacity of 1.7 grams per denier and an elongation of 36 percent. The fiber was evaluated for color on the GE spectrophotometer and the purity found to be 4.4 units and the brightness 89.6 units. The fibers were then dyed with basic dyes and the basic dye acceptance determined to be 8.0 percent. The dyed fibers were exposed for 80 standard hours and the fade-O-meter and the dyed light stability determined to be 3.5 Light. The fibers were annealed in saturated steam at 35 p.s.i.g. The annealed fibers were found to have an elongation of 69 percent.

Example 5 A spinning dope composed of about 93 percent of acrylonitrile and about 7 percent of vinyl acetate dissolved in a solvent comprising dimethylacetamide was wet spun according to conventional techniques using a coagulating bath comprised of 100 percent of an amide mixture comprising about 95 percent of N,N-dimethylmyristamide, about 3 percent of N,Nrdimethylpalmitamide, and about 2 percent of N,N-dimethyllauramide to produce fiber. These fibers were found to have a tenacity of 3.5 grams per denier and an elongation of 33 percent. The fiber was evaluated for color on the GE spectrophotometer and the purity found to be 7.0 units and the brightness 84.8 units. The fibers were then dyed and the basic dye acceptance determined to be 6.2.percent. The. dyed fibers were exposed for 80 standard hours in the fade-O- meter and the dyed light stability determined to be 3.5 White. The fibers were annealed in saturated steam at 35 p.s.i.g. The annealed fibers were found to have an elongation of 46 percent.

Example 6 Avspinning dope composed of about 93 percent of acrylonitrile and about 7 percent of vinylacetate was wet spun according to conventional techniques using a coagulation bath comprised of about 12.5 percent of dimethylacetamide, about 15 percent of water, and about 72.5 percent of the amide mixture of Example 5 to produce fiber. These fibers were found to have a tenacity of 2.0 grams per denier and an elongation of 27 percent. The fibers were evaluated for col-or on the GE spectrophotometer and the purity found to be 7.0 units and the brightness 85.4 units.The fibers were then dyed with basic dyes and the basic dye acceptance determined to be 6.7 percent. The dyed fibers were exposed for 80 standard hours in the fade-O-meter and the dyed light stability determined to be 3.0 White. The fibers were annealed in saturated steam at 35 p.s.i.g. The annealed fibers were found to have an elongation of 45 percent.

As many variations within the spirit and scope of this invention will occur to those skilled in the art, it is to be understood that the invention is not limited to the specific embodiments thereof except as set forth in the appended claims.

What is claimed is:

1. A process for wet spinning of shaped objects of an acrylonitrile polymer containing at least 50 percent by,

weight polymerized acrylonitrile which comprises extruding a solution of said polymer into a spin bath comprising at least 50 percent by weight of an amide selected from the group consisting of amides having the formula.

R1 R-i-lL-Rz wherein R is an aliphatic hydrocarbon radical containing at least carbon atoms and R and R are lower alkyl radicals and mixtures of said amides.

2. A process for wet spinning of shaped objects of an acrylonitrile polymer containing at least 50 percent by weight polymerized acrylonitrile and at most 50 percent by weight of another mono-olefinic monomer copolymerized therein which comprises extruding a solution of said polymer into a spin bath comprising at least 50 percent by weight of an amide selected from the group consisting of amides having the formula 0 R1 R-(IJI-I1IR2 wherein R is an aliphatic hydrocarbon radical containing at least 5 carbon atoms and R and R are lower alkyl radicals and mixtures of said amides, up to about 50 percent by weight of N,N-dimethylacetamide and up to about 50 percent by weight of water.

3. A process for wet spinning of shaped objects of acrylonitrile polymer containing at least 50 percent by weight of polymerized acrylonitrile and at most 50 percent by weight of another mono-olefinic monomer copolymerized therewith which comprises extruding a solu tion of said polymer into a spin bath comprising from about 70 to about 100 percent by weight of an amide 10 selected from the group consisting of amides having the formula 2 r R-( J-N-R,

wherein R is an aliphatic hydrocarbon radical containing from about 11 to 21 carbon atoms and R and R are methyl groups and mixtures of said amides, from about 0 to 30 percent by weight of N,N-dimethylacetamide and from about 0 to 30 percent by weight of water and maintained at a temperature of 20 to C.

4. The process as defined in claim 3 wherein the spin bath consists essentially of an amide selected from the group consisting of amides having the formula wherein R is an aliphatic hydrocarbon radical containing from about 11 to 21 carbon atoms and R and R are methyl groups and mixtures of said amides.

5. A process for wet spinning of shaped objects of an acrylonitrile polymer containing at least 50 percent by weight polymerized acrylonitrile which comprises extruding a solution of said polymer through a shaped orifice submerged in a spin bath comprising at least 50 percent by weight of an amide selected from the group consisting of amides having the formula OR "I RON-Rz wherein R is an aliphatic hydrocarbon radical containing at least 5 carbon atoms and R and R are lower alkyl radicals and mixtures of said amides.

6. A process for wet spinning of shaped objects of an acrylonitrile polymer containing at least 50 percent by weight polymerized acrylonitrile and at most 50 percent by weight of another mono-olefinic monomer copolymerized therewith which comprises extruding a solution of said polymer through a shaped orifice submerged in a spin bath comprising at least 50 percent by weight of an amide selected from the group consisting of amides having the formula wherein R is an aliphtic hydrocarbon radical containing at least 5 carbon atoms and R and R are lower alkyl radicals and mixtures of said amides, up to about 50 percent by weight of N,N-dimethylacetamide, and up to about 50 percent by weight of water.

7. A process for wet spinning of shaped objects of an acrylonitrile polymer containing at least 50 percent by weight polymerized acrylonitrile and at most 50 percent by weight of another mono-olefinic monomer copolymerized therewith which comprises extruding a solution of said polymer through a shaped orifice submerged in a spin bath composed of from about 70 to 100 percent by weight of an amide selected from the group consisting of amides having the formula wherein R is an aliphatic hydrocarbon radical containing from about 11 to 21 carbon atoms and R and R are methyl groups and mixtures of said amides, from about 0 to 30 percent by weight of N,N-dimethylacetamide, and from about 0 to 30 percent by weight of water, said spin bath being maintained at a temperature of 20 to 100 C. 8. The process as defined in claim 7 wherein the spin bath consists essentially of an amide selected from the group consisting of amides having the formula wherein R is an aliphatic hydrocarbon radical containing from about 11 to 21 carbon atoms and R and R are methyl groups and mixtures of said amides.

9. A process for wet spinning of filaments of an acrylonitrile polymer containing at least 50 percent by weight polymerized acrylonitrile which comprises extruding a solution of said polymer through a shaped orifice submerged in a spin bath comprising at least 50 percent by weight of an amide selected from the group consisting of amides having the formula Ill wherein R is an aliphatic hydrocarbon radical containing at least 5 carbon atoms and R and R are lower alkyl radicals and mixtures of said amides, thereby precipitating said polymer from its solution into the form of a filament, withdrawing said filament from said spin bath, passing said filament through a boiling water bath wherein said filament is given a substantial stretch, and drying said filament, whereby a dense filament having a smooth surface substantially free from crenulations is .formed.

10. A process for wet spinning of filaments of acrylonitrile polymer containing at least 50 percent by weight acrylonitrile and at most 50 percent by weight of another mono-olefinic monomer copolymerized therewith, which comprises extruding a solution of said polymer through a shaped orifice submerged in a spin bath comprising at least 50 percent of an amide selected from the group consisting of amides having the formula wherein R is an aliphatic hydrocarbon radical containing at least 5 carbon atoms and R and R are lower alkyl radicals and mixtures of said amides, up to 50 percent by weight of N,N-dimethylacetamide and up to 50 percent by weight of water, thereby precipitating said polymer from its solution into the form of a filament, withdrawing said filament from said spin bath, passing said filament through a boiling water bath wherein said filament is given a substantial stretch, and drying said filament, whereby a dense filament having a smooth surface substantially free from crenulations is formed.

11. A process for wet spinning of filaments of acrylonitrile polymer containing at least percent by weight acrylonitrile and at most 50 percent by weight of another mono-olefinic monomer copolymerized therewith, which comprises extruding a solution of said polymer through a shaped orifice submerged in a spin bath consisting of from about to percent by weight of an amide selected from the group consisting of amides having the formula wherein R is an aliphatic hydrocarbon radical containing from about 11 to 21 carbon atoms and R and R are methyl groups and mixtures of said amides, from about 0 to 30 percent by weight of N,N-dimethylacetamide and from about 0 to 30 percent by weight of water and maintained at a temperature of 20 to 100 0., thereby precipitating said polymer from its solution into the form of a filament, withdrawing said filament from said spin bath, passing said filament through a boiling water bath wherein said filament is given a substantial stretch, and drying said filament, whereby a dense filament having a smooth surface substantially free from crenulations is formed.

12. The process as defined in claim 11 wherein the spin bath consists essentially of an amide selected from the group consisting of amides having the-formula from about 11 to 21 carbon atoms and R and R are methyl groups and mixtures of said amides.

References Cited UNITED STATES PATENTS 2,728,631 12/1955 Drisch et al. 18-54 JAMES A. SEIDLECK, Primary Examiner.

H. H. MINTZ, Assistant Examiner.

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