IL45432A - Method for making acrylic fibers having good hot-wet characteristics - Google Patents

Description

Method for making acrylic Fibers having good hot-wet character ia tics mmo -Btn Bin mYuo ηη im π" ρκ pa'o niaiV v in C-14-53-0075A 4 METHOD FOR MAKING ACRYLIC FIBERS HAVING GOOD HOT-WET CHARACTERISTICS Background Of The Invention a. Field of the Invention The invention relates to polymers containing acrylonitrile and having enhanced dimensional stability. More particularly, it relates to fibers of acryloni tri le-conta1ning polymer blends having improved resistance to hot-wet deformation, especially under dyeing conditions. b. Description of the Prior Art It is well-known that polyacrylonl tri le and copolymers of acrylonitrile and other monoolefinic polymerizable monomers are excellent fiber-forming polymers. Polyacryloni tril e and copolymers having more than 75 percent and, preferably, more than 85 percent acrylonitrile and up to 15 percent of other polymerizable monomers produce fibers with very suitable tensile properties, desirable elongation, and excellent stabili under a wide range of physical and chemical conditions.

Although acrylic fibers possess a number of characteristic which render them of substantial value for a variety of textile and other purposes, fibers containing acrylonitrile are not as dimensional ly stable as other synthetic fibers under hot and wet conditions. Under such conditions there is thought to be chain distortion caused by molecular extension and slippage. The end result is that fibers containing acrylonitrile show a tendency to be easily stretched out of shape when subjected to hot, wet conditions. Accordingly, fabrics made of fibers containing acrylonitrile polymer compositions often show low C-14-53-0075A toughness, a low resilience, loss of bulk or crimp and poor crease resistance. Furthermore, loss of stitch definition and overstretching are often exhibited when a woven or knitted fabric thereof is subjected to tension under hot-wet conditions These tendencies are more pronounced 1n certain processing techniques, particularly in dyeing operations.

Crosslinking agents have been used to modify fiber characteristics. U. S. Patent 3,399,177 discloses a process for making a self-crimping fiber by copolymerizlng acrylonitrile with an N-substi tuted derivative of acrylamide or methacrylamid such as N-methylolacrylamide to provide a homogeneous fiber. French Patent 1,500,101 discloses a process for copolymeri zi ng acrylonitrile and N-methylolacrylamide. In both of these cases the crosslinking agent, N-methylolacrylamide, is apparently uniformly distributed throughout the fiber. The polymerization technique disclosed in French Patent 1,500,101 and 1n U. S.

Patent 3,399,177 involves a number of procedures designed to prevent crosslinking during polymer preparation and isolation. These procedures would be both difficult and costly 1f conducte in large-scale operations.

Various other methods have been employed to Improve the tensile properties of fibers and fabrics containing acrylonitri to combat distortion when such fibers are under hot-wet conditions. A number of known methods involve incorporating various chemical agents to modify the structural arrangement of the polymer itself. Certain coating and grafting compositions have been applied to the acrylic fibers and several methods hav been used to modify the fiber structure. These methods have C-14-53-0075A generally produced losses in other physical properties or have not been well suited to conventional operations. Accordingly, there 1s a need for a better method of Improving the hot-wet properties of fibers containing acryloni rile, without impairment of other desirable properties.

An object of this invention is to provide a process for making acrylon1trile-conta1ning fibers having improved modulus and distortion resistance under hot-wet conditions.

An object of this invention is to provide a process for making acryloni trile-containing fibers having improved modulus, distortion resistance and crimp retention under hot-wet conditions.

Another object of this invention is to provide a method for making acryloni trile-containing fibers having scattered areas of high crosslink density with little or no crosslinking in other portions of the fiber structure.

Summary Of The Invention In accordance with this invention it has been found that a fiber or filament having excellent hot-wet properties can be made by blending 98 to 70 percent of (A) an acryl oni tril e-containing polymer with 2 to 30 percent of (B) a copolymer of 50 to 90 percent acrylonitrile and 10 to 50 percent of a cross-linking agent, spinning fibers from the blend, washing and drying the fibers and then heating the fibers to effect cross-linking. The blending of the two components causes the crosslinking agent to be randomly dispersed through the fiber to give randomly located areas of high crosslink density, with the remainder of the fiber structure having little or no cross-linkin . Sur risin ly, this method roduces a fiber having C-14-53-0075A £ excellent hot-wet properties.

More specifically, 1t has been found that a polymeric composition (A) selected from the group consisting of poly-acrylonitrile, a copolymer comprising from 35 to 98 weight percent of acryl oni tri le and 2 to 65 weight percent of at least one other monoolefinlc monomer copolymerizabl e therewith, and a polymer blend of a copolymer 30 to 98 weight percent acrylonitrile and 1 to 20 weight percent of another monoolefinic monomer and a copolymer of 50 to 80 weight percent acryl oni tri 1 and 20 to 50 percent of dye receptive monomers copolymerizable therewith, when mixed with (B) from 2 to 30 weight percent of a copolymer comprising from 50 to 90 weight percent acryloni tri and from 10 to 50 weight percent of an N-substi tuted derivative of an ethylenical ly unsaturated acid amide forms a polymer blend from which filaments having unusual hot-wet properties can be formed.

The N-subst1 tuted derivative, being only a minor part of the blend, will be widely dispersed through the filaments to provide areas of high crosslink density, while other portions of the filament structure will have little or no crosslinking.

Further 1n accordance with this invention it has been found that a fiber having excellent crimp retention properties can be made by blending 98 to 70 percent of (A) a polymeric material consisting of a major portion of acryloni trlle and a minor portion of monoolefinic monomers copolymeri zed with the acrylonitrile with 2 to 30 percent of (B) a copolymer of 50 to 90 percent acrylonitrile and 10 to 50 percent of an N-subst1 tut derivative of an ethylenically unsaturated acid amide, spinning C-14-53-0075A fibers from the blend, washing and drying the fibers and then crimping the fibers and thereafter heating the fibers to effect crossl Inking. The blending of the two components cause the crosslinking agent to be randomly dispersed through the fiber to give randomly located areas of high crosslink density with the remainder of the fiber structure having little or no crosslinking. Surprisingly, this method produces a fiber having excellent crimp retention properties.

More specifically, it has been found that a polymeric composition (A) selected from the group consisting of poly-acrylonltrile, a copolymer comprising from 35 to 98 weight percent of acryloni tri le and 2 to 65 weight percent of at leas one other monoolefinic monomer copolymer! zabl e therewith, and a polymer blend of another monoolefinic monomer and copolymer of 50 to 80 weight percent acrylonitrlle and 20 to 50 percent of dye receptive monomers copolymerizable therewith, when mixe with (B) from 2 to 30 weight percent of a copolymer comprising from 50 to 90 weight percent acrylonitrlle and from 10 to 50 weight percent of an N-substi tuted derivative of an ethylenica unsaturated acid amide forms a polymer blend from which filaments having unusual crimp retention properties can be formed.

The N-substi tuted derivative of an ethylenically unsatura acid amide is preferably derived from acrylamlde or methyl-acrylamlde. Generally, such derivatives must have the capacit of crosslinking with polymers containing acrylonitrlle. The N-substi tuted derivative is more preferably an N-methylol derivative, however, derivatives in which the hydrogen of the hydroxyl group of the N-methylol group is replaced by an alkyl C-14-53-0075A β group are also preferred. This latter class is known to interact to cause crossl i nki ng. The crosslinking may be achieved by various means, such as, by exposing spun filaments to temperatures above about 140°C. or by passing filaments through a bath containing acidic substances and heating of the filament to above about 140°C. for a period of 1 to 10 minutes.

The N-subst1 tuted derivatives used fn accordance with this invention include N-methylolacrylam de, N-methylolmethacrylamid N-methoxymethylacrylamide, N-methoxymethylmethacrylamide, and mixtures thereof.

It has been found that relatively small amounts, i.e., at least about 2 weight percent, of a copolymer containing an N-substituted derivative when blended with polymer of acryl oni tri unexpectedly impart dimensional stability to the entire fiber network. The proportions of the N-substi tuted derivative of an ethylenically unsaturated acid amide in the copolymer will generally depend upon the degree of crosslinking desired. In general, 1t is desirable to have from about 10 to 50 weight percent of the derivative in the copolymer. A number of other monomers such as methyl acrylate, vinyl acetate, vinyl bromide, styrene, etc., as well as various acid and basic dyeable monomers in amounts from about 2 to 20 weight percent may be incorporated with the N-substituted derivative-containing copolymer. The amount of copolymer containing the derivative to be blended with the polymeric composition may vary over a relatively wide range. Preferably, the amount of the copolymer to be blended may be from 2 to 30 weight percent. A very useful polymer for blending is one of about 70 percent acrylo- C-14-53-0075A £ of sodium p-sul fophenylmethal kyl ether.

The copolymer containing the amide derivative may be prepared in an aqueous medium in the presence of a water-solubl peroxide catalyst using conventional equipment. Polymerization may be conducted by batch processes, by continuous processes or by a combination of these processes. A preferred method of preparation involves batch procedure wherein the desired monomers are mixed and charged gradually throughout the polymerization. If desired, the polymerization reaction may be conducted in the presence of a redox agent, for example, sulfur dioxide, sodium bisulfite, sodium thiosulfate, or other sulfur compounds 1n which the sulfur is present in an oxidizable condition. Generally, the pH during polymerization is between about 3 and about 4. However, the pH should be adjusted to between 6 and about 8 prior to the isolation of the copolymer in order to retard any premature cross! inking. The presence of 2 to 10 weight percent of a soluble salt such as sodium sulfate 1s required to prevent premature crosslinking.

The procedure for preparing the polymeric compositions containing acryl oni tri 1 e for the blending polymer is substantially the same as that used in the preparation of the copolyme containing the amide derivative, except that pH adjustment and the presence of a soluble salt are not required. However, other known polymerization methods such as mass polymerization and solution polymerization can be used.

The polymeric compositions and the copolymer containing the amide derivative may be mixed in granular, solid state, and 1n solution in a suitable solvent. A most effective C-14-53-0075A technique Involves dissolving the polymers separately in a suitable solvent, for example, dimethyl formamide , and blending them shortly before extruding to form the filaments.

When mixtures are to be made 1n solid form the polymer mixture may be formed through the use of suitable conventional mechanical mixers, for example, roll mills or dough mixers, after which the polymer mixture is dissolved in a conventional solvent to form a spinning solution.

The blend compositions disclosed herein may be formed into fibers by conventional wet or dry spinning processes. After stretching the fibers to develop the necessary orientation, the fiber may be exposed to temperatures of about 140°C. to 180eC, 1n order to crosslink the polymeric composition with the copoly containing the amide derivative. Also, dilute acidic solutions (ca. pH 4 or lower) may be used to accelerate crosslinking of the composition hereindlsclosed. The filaments may be exposed to dilute solutions in baths of sulfuric or phosphoric acid ranging from about 0.0001 to 0.01N, and then heated to effect crosslinking. After the crosslinking step, the fibers are crimped in a conventional manner.

The polymeric materials, which may be employed 1n the practice of the present invention, are polyacrylonitrile, copolymers, including binary and ternary polymers containing at least 35 percent by weight of acrylonitrile in the polymer molecule, or a blend comprising polyacrylonitrile or copolymers comprising acrylonitrile with from 2 to 50 percent of another polymeric material, the blend having an overall polymerized acrylonitrile content of at least 35 percent by weight.

C-14-53-0075A £ Although the preferred polymers employed in the instant Invention are those containing about 80 percent of acrylo-nltrlle, generally recognized as the fiber-forming acrylonitril polymers, it will be understood that the invention 1s applicable to polymers containing between about 35 to about 98 weight percent acrylonitrile.

For example, the polymer may be a copolymer of from 80 to 98 weight percent acrylonitrile and fr percent of another monomer containing the and copolymeri zabl e with acrylonitrile. Suitable monoolefinic monomers include acrylic, alpha-chloroacrylic and methacrylic acids; the acrylates, such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, methoxymethyl methacrylate, beta-chloroethyl methacrylate, and the corresponding esters of acrylic and alpha-chloroacrylic acids; vinyl chloride, vinyl fluoride, vinyl bromide, vinyliden chloride, 1-chloro-l bromoethylene; methylacrylonitrile; acrylamide and methacrylamide; alpha-chloroacrylamide, or monoalkyl substitution products thereof, methyl vinyl ketone, vinyl carboxyl ates , such as vinyl acetate, vinyl chl oroacetate, vinyl propionate, and vinyl stearate; N-vinylimides, such as -vi nyl phthal imi de and N-vinylsuccinimide; methylene malonic esters; N-vi nyl carbazol e; vinyl furane; alkyl vinyl esters; styrene, vinyl naphthalene; vinyl-substituted tertiary heterocyclic amines, such as the vinylpyridines and al kyl -substi tuted vinyl-puridines, for example, 2-vinyl pyridine, 4-vinyl pyridi ne, 2-methyl-5-vinylpyridine, etc.; l-vinyl1midazole and alkyl-substituted 1 -vi nyl imldazol es , such as 2-, 4-, or 5-methyl-l-vin l imidazole and other C = C :ontainin ol meri zabl e C-14-53-0075A φ materials.

The polymer may be a ternary interpolymer, for example, products obtained by the interpolymerization of acrylonitrile and two or more of any of the monomers, other than acrylonitril enumerated above. More specifically and preferably, the ternary polymers may comprise acrylonitrile, vinyl acetate, and vinyl bromide. The ternary polymers preferably contain from 80 to 97 percent of acrylonitrile, from 1 to 10 percent of vinyl acetate or styrene, and from 1 to 18 percent of another substance, such as vinylidene chloride or vinyl bromide.

The polymer may also be a blend of polyacrylonitrile or of a binary interpolymer of from 80 to 99 percent acrylonitrile and from 1 to 20 percent of at least one other^ C = C containing substance with from 10 to 70 percent of acrylonitril and from 30 to 90 percent of at least one other^C = c ^ containing polymerizable monomer.

The polymer materials of this invention may readily have incorporated therein various acidic and basic monomers to increase their dyeability with various dyes; for example, sodium paramethacryl amidobenzenesul fonate, sodium styrenesul fon sodium methal lyl sul fonate , fumaric acid, itaconic acid, and various ^-al kyl and«^ % -dialkyl al lyl oxybenzenesul foni c acids and sulfonate salts thereof, such as sodium para-methal lyl benzenesulfonate; various tertiary amino alkyl ester monomers, such as dimethylaminoethyl methacrylate and various quaternary ammonium monomers, such as 2-methacryloylmethylammonium methyl sulfate and various -heterocycl 1c monomers, such as N-allyl-nicotlnamide and the like. Generally, such monomers may be em lo ed in amounts of about 0 C-14-53-0075A The following examples, which illustrate but do not limit the invention and in which parts, proportions and percentages are by weight unless otherwise specified, describe preferred modes of operating in accordance with the principles of this invention. In Examples 2 to 8 the fibers were spun, washed, dried and then passed over heated rolls to effect crossl inking prior to crimping.

EXAMPLE J, To a two liter flask provided with a stirring mechanism and containing 1 liter of water and 2.0 grams of sodium lauryl sulfate were charged 250 grams of water, 70 grams acryloni tri le, 25 grams N-methylolacryl amide (MAAm), 5.0 grams sodium p-sul-fophenyl methyllal ether (SPME), 1.5 grams potassium sulfate, 3.45 grams sulfur dioxide, 8.0 grams sodium sulfate, and 0.33 ppm ferrous sulfate. These substances were added over a period of about 2 hours while maintaining a temperature within the flask of about 50°C. The reactants were thoroughly stirred for an additional 30 minutes at 50°C. The contents of the flask in the form of a slurry had at the end of the reaction a pH of about 3.6 and was thereafter adjusted to a pH of 7.1 by an addition of about 5.5 ml of 1.0 N sodium hydroxide.

The resulting polymer was isolated by filtration and dried in an oven at about 50°C. The polymer conversion was approximately 88 percent. The specific viscosity (Nsp), was 0.29 (dimethyl-formamlde/lithium chloride, 25°C, 0.1 g/dl).

EXAMPLE_2_ A 25 percent total solids spinning dope was prepared by dissolving in dimethyl formamide a blend of 90 weight percent C-14-53-0075A £ of (A) a copolymer comprising 87.9 weight percent acryloni tri le, 7.1 weight percent vinyl acetate, and 5 weight percent vinyl bromide with (B) 10 weight percent of the polymer containing the N-methylolacrylamide prepared in Example 1. The spinning dope was mixed thoroughly at about 55°C, for about one hour and thereafter spun into filaments using an aqueous dimethyl-formamide (55/45) spin bath. The filaments were dried and then passed for two minutes over heated godets at 165°C. to effect crossl inki n , after which the fibers were annealed in an autoclave with steam at a gauge pressure of 0.35 kilogram per square centimeter (5 psi) for seven cycles as described in U. S. Patent 2,920,934. The filaments produced had a 12 percent extension under water at 100°C. at a load of 0.2 gpd. Young's modulus in water at 93°C. was 1.6 gpd. By way of comparison, the copolymer comprising 87.0 weight percent acrylonitrile, 7.1 weight percent vinyl acetate and 5 weight percent vinyl bromide was spun from a spinning dope composition with dimethyl formami de and resulted in filaments having greater than 150 percent extension in boiling water under a 0.2 gpd load and a Young's modulus of 0.6 gpd in water at 93°C.

EXAMPLE_3 A 25 percent total solids spinning dope was prepared fromaa blend having (A) 83 weight percent of a copolymer comprising 87.9 weight percent acrylonitrile, 7.1 weight percent of vinyl acetate, and 5 weight percent vinyl bromide and (B) 17 weight percent of the polymer containing the N-methyl ol acryl amide prepared 1n Example 1 with dimethyl formamlde. The spinning dope was spun into aqueous dimethyl formamlde (55/45). After C-14-53-0075A 4 coagulation and stretching the filaments were passed through a bath containing 0.01 N sulfuric acid and then for two minutes over godets heated to 160°C. One batch of filaments was annealed in an autoclave with steam at a gauge pressure of abou 0.35 kilogram per square centimeter (5 psi) and one other batch was steam annealed at a gauge pressure of 1.054 kilogram per square centimeter (15 psi). The resulting filaments annealed at 5 psi had a 13 percent extension in boiling water (0.2 gpd load) and a Young's modulus of 1.8 gpd in water at 93°C. The filaments annealed at 15 psi had a 15 percent extension under 0.2 gpd load in boiling water and a Young's modulus of 1.4 gpd in water at 93°C.

EXAMPLE 4 A 25 percent total solids spinning dope was prepared from blend containing (A) 96 weight percent of a copolymer comprisin 87.9 weight percent acrylonitrile, 7.1 weight percent vinyl acetate, and 5 weight percent vinyl bromide and (B) 4 weight percent of a polymer containing the N-methylolacrylamide prepared in Example 1 with dimethyl formamide. The spinning dope was spun into an aqueous dimethylformamide (55/45) spin bath and thereafter passed through a bath containing 0.01 N sulfuric acid and then for two minutes over godets heated to 165°C. One batch of filaments was steam annealed in an autoclave at a gaug pressure of 0.35 kilogram per square centimeter (5 psi) and one other batch at 1.054 kilogram per square centimeter (15 psi) The filaments annealed at 5 psi had an 18 percent extension 1n boiling water (0.2 gpd load) and a Young's modulus of 1.3 gpd in water at 93°C. The filaments annealed at 15 psi had a 23 C-14-53-0075A 4| percent extension in boiling water (0.2 gpd load) and a Young's modulus of 1.1 gpd in water at 93°C.

EXAMPLE_5 A 25 percent total solids spinning dope was prepared from a blend of (A) 88 weight percent of copolymer comprising 87.9 weight percent acrylonitrile, 7.1 weight percent vinyl acetate, and 5 weight percent vinyl bromide and (B) 12 weight percent of a polymer containing the -methylolacrylamide prepared in Example 1 with dimethyl formamide. The spinning dope was divided and one batch was spun into aqueous di methyl formamide (55/45) and another batch was spun into an ethylene glycol spin bath at 30°C. The filaments were then dried and thereafter passed for two minutes over heated godets at 165°C. The filaments were steam annealed at 0.35 kilogram per square centimeter (gauge) (5 psi). The dope which was spun into an aqueous dimethyl formami de bath produced filaments having 11 percent extension in boiling water at 93°C. The filaments produced from spinning in ethylene glycol resulted in fibers having 14 percent extension in boiling water (0.2 gpd load) and a Young's modulus of 1.4 gpd in water at 93°C.

EXAMPLE_6 A 25 percent total solids spinning dope was prepared from a blend of (A) 96 weight percent of a copolymer comprising 87i9 weight percent acrylonitrile, 7.1 weight percent vinyl acetate, and 5 weight percent vinyl bromide and (B) 4 weight percent of the polymer containing the N-methylolacrylamlde prepared 1n Example 1 with dimethyl formamide. The spinning dope was spun Into aqueous dimethyl formamide (55/45) and thereafter assed throu h a bath containin 0 01 N sulfuric C-14-53-0075A 4 A 27 percent solids spinning dope was prepared from a copolymer described in this example with the exception that it contained none of the polymer containing the N-methylolacrylami The dope was spun as described 1n the above paragraph.

The filaments resulting from the blend had a 23 percent extension in boiling water (0.2 gpd load) and a Young's modulus of 1.1 gpd in water at 93°C. The filaments resulting from spinning the copolymer without the polymer containing N-methylo acrylamide had an extension greater than 150 percent in boiling water and a Young's modulus of 0.5 gpd in water at 93°C.

EXAMPLE_7 A 26 percent total solids spinning dope of a blend of (A) 96 percent of a copolymer comprising 87.9 weight percent -acrylonitri le, 7.1 weight percent vinyl acetate, and 5 weight percent vinyl bromide and (B) 4 weight percent of a copolymer containing 75 weight percent acryloni trile, 15 weight percent N-methylolacrylamide, and 10 weight percent 2-methacryl oyl oxy-ethyl trimethylammonium methyl sul fate in dimethyl formamide was prepared and spun into aqueous dimethylformamide (55/45) and the resulting filaments were passed through a bath containing 0.01 NH2S04 and thence for two minutes over godets heated to about 160°C. A 27 percent total solids spinning dope of the identical copolymer was prepared and spun under the same conditions with the exception that none of the polymer containing the N-methylolacrylamide was added thereto. The dope was spun as described in the above paragraph.

The filaments spun from the blend had about 23 percent extension in boiling water (0.2 gpd load) and a Young's modulus C-14-53-0075A of 1.1 gpd in water at 93°C. The filaments resulting from spinning the polymer containing no N-methylolacrylamide had an extension greater than 150 percent in boiling water and a Young's modulus of 0.5 gpd in water at 93°C.

EXAMPLE_8 A 26 percent total solids spinning dope was prepared from a blend of (A) 80 weight percent of a copolymer comprising 87.9 weight percent acrylonitrile, 7.1 weight percent vinyl acetate, and 5 weight percent vinyl bromide; (B) 10 weight percent of a copolymer comprising 70 weight percent acrylonitrile, 20 weight percent 2-methacryl oyl oxyethyl trimethyl ammonium methyl sul fate, and 10 weight percent dimethyl ami noethyl methacrylate; and (C) 10 weight percent of a polymer comprising 75 weight percent acrylonitrile and 25 weight percent N-methylolacrylamide with dimethylformamide. The spinning dope was spun into aqueous dimethylformamide (55/45) and the filaments thus formed were passed for two minutes over godets heated to 160°C.

The filaments from the blend had a 22 percent extension in boiling water (0.2 gpd load) and a Young's modulus of 1.2 gpd in water at 93°C.

In the following examples crosslinking was effected after the fibers had been crimped. The manner in which the fiber is crimped is not of importance. The fiber may be crimped in a stuffer box crimper or any other type of conventional crimper. The crimp in the fiber may be a result of a characteristic of the fiber rather than a crimp mechanically induced in the fiber. For example, the fiber may be a self-crimping bicom-ponent fiber.

C-14-53-0075A After spinning and prior to the heating step which follows crimping 1t 1s necessary that the fiber temperature be kept below a value of 130°C. to 140°C. in order to avoid premature crossl inking. If the fiber is passed through a dilute acid bath as described above it will be necessary to maintain the temperature of the fiber at a value no greater than about 120°C. subsequent to passage through the bath and prior to heat treatment.

EXAMPLE_9 A blend of 88 percent of (A) a terpolymer of 87.9 percent acryl oni tri 1 e , 7.1 percent vinyl acetate and 5 percent vinyl bromide and (B) 12 percent of a terpolymer of 70 percent acrylonitrile, 25 percent N-methylolacrylamide and 5 percent sodium p-siil f ophenylmethal lyl sul fonate was dissolved in dimethylformamide to give a 26 percent solids spinning solution. This spinning solution was extruded as fiber into a 60 percent dimethyl formami de/40 percent water bath at 35°C. The spun fiber was washed, stretched and dried at 130°C, after which it was crimped 1n a stuffer box crimper and then heat treated In an oven at a temperature of 165°C.

Samples of the fiber were heated under various conditions and then immersed in boiling water for 3 to 5 minutes. Crimp parameters were measured on the fibers before and after immersion 1n boiling water. The control fibers were spun from polymer (A) with no polymer (B). These results are shown in the following table.

Crimp Amplitude (cm) Original Af er Immersion Sample Value In Boiling Water Un eated Fiber 0.086 0.053 Heated l60°C, 20 minutes 0.076 0.058 Heated 180°C, 5 minutes 0.066 0.058 Heated 180°C, 15 minutes 0.084 0.081 I I-1 Control CO 0.081 0.058 I C-1 -55-0075A It will be noted that the tendency for crimp parameters to change as a result of boiling water treatment is reduced in proportion to the severity of the fiber heat treatment (degree of crosslinking) . That is, while the treatment at 160°C. shows some improvement in crimp stability, the treatment at 180°C. shows substantial improvement.

EXAMPLE 10 Fibers were spun in accordance with Example 9 except that dimethylacetamide was substituted for dimethylformamide both in making the spinning solution and in the spin bath. The fibers were washed, dried at a temperature of 130°C. and then crimped in a stuffer box crimper.

The fiber was divided into two portions, samples A and B.

Sample A was passed through a Fleissner drier at l6o°C. to l k°c with a dwell time of 3.6 minutes and was then cut into staple.

Sample B was cut into staple and carpet samples were prepared from the two samples. The carpet samples were formed in a higher low pattern with a fiber weight of 35 oz/yd (0.115 grams per square centimeter) . Two control carpet samples were prepared using a fiber spun from polymer (A) of Example 9. Carpets from Sample B and one of the controls were back coated with a rubber latex and then passed through an oven at l65°C, with a dwell time of 8 minutes to cure the latex and effect crosslinking of the filaments. The other control was not heated.

All of the samples were then blank dyed at the boil in a small dye beck. The samples were removed from the dye beck and dried. A subjective evaluation of carpet aesthetics is summariz in the table below.

C-1 -53-0075A Yarn Bulk Cut- o-side Pile Overall Sample and Cover Contrast Resilience Apparent Value Unheated poor poor poor poor Control Heated poor poor fair poor Control Sample A fair-good good good fair-good Sample B fair- ood good good fair- ood While the crosslinking step may be carried out at l o°C. to 180°C, the preferred range is l6o°C. to 180°C.

Claims (7)

1. C-1A-53-0075A 4 What Is Claimed 1s t

1. A method for making acrylic filaments having good dimensional stability under hot-wet conditions, characterized by a. mixing (A) a polymeric material selected from the group consisting of polyacrylonitrile, a copolymer comprising from about 35 to 98 weight percent acrylonitrile and about 2 to 65 weight percent of at least one other monoolefinic monomer copolymerizable therewith, a polymer blend of a copolymer comprising about 80 to 98 weight percent acrylonitrile and about 2 to 20 weight percent of another monoolefinic monomer and a copolymer comprising about 50 to 80 weight percent acrylonitrile and about 20 to 50 percent of a dye receptive monomer copolymerizable therewith, (B) a copolymer comprising about 50 to 90 weight percent acrylonitrile and from about 10 to 50 weight percent of an N-substituted derivative of an ethylenically unsaturated acid amide, and (c) a solvent therefor, the amount of said (A) polymeric material being from 70 to 98 weight percent and th amount of said copolymer (B) being from about 2 to 30 weight percent, both percentages being based on the total weight of (A) and (B); the total weight of (A) and (B) being from about 5 to 3 percent by weight based on the weight of the mixture of (A), (Β) and (C) J b. heating the mixture to dissolve the polymer; C-14-55-0075A d. removing the solvent from the filaments by washing e. drying the filaments; f. heating the filaments to a temperature within the range of 140°C. to 180°C. for a period of 1 to 10 minutes to react said N-substituted derivative to effect crosslinking, said copolymer (B) being located in the mixture in randomly scattered areas in such a manner that said crosslinking results in randomly scattered areas within said filaments; g. and crimping the filaments prior to or subsequent to crosslinking. 2„ The method of Claim 1 wherein said N-substituted derivative is selected from the. group consisting of N-methylol-acrylamide, N-methylolmethacrylamide and K-methoxymethylacrylami .

The method of Claim 2 wherein said N-substituted derivative is N-methylolacrylamide.

4. The method of Claim 2 wherein the fibers are treated wi a dilute acidic solution prior to heat treatment.

5. The process of Claim 4 wherein the acidic solution is a 0.001N to COIN solution of an acid selected from the group consisting of sulfuric and phosphoric acids.

6. The process of Claim 1 wherein the filaments are crimpe prior to being heated to a crosslinking temperature between 140° and 180°C.

7. Crosslinked acrylonitrile filaments prepared in accordance with the process of P. O. Box 33116 , Tel- 1 viv