US3506990A - Process for dyeing drawn filaments of aromatic polyamides with basic dye-stuffs in the presence of an organic dye carrier - Google Patents

Description

PROCESS FOR DYEING DRAWN FILAMENTS OF AROMATIC POLYAMIDES WITH BASIC DYE- STUFFS IN THE PRESENCE OF AN ORGANIC DYE CARRIER Arturo Jorge Richardson and Robert E. Walck, Jr., Waynesboro, Va., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Dec. 16, 1966, Ser. No. 602,144

Int. Cl. D06p /06 US. Cl. 8-172 2 Clafms ABSTRACT OF DISCLOSURE A process for dyeing a textile formed from an aromatic polyamide containing a dye-associable copolymeric unit wherein a drawn filament of the said polyamide, e.g., poly(m-phenyleneisophthalamide) and poly[N,N-m-phenylene bis(meta amino benzamide)isophthalamide], is heat-relaxed prior to dyeing the textile in a dye-bath containing (1) a dye to which the copolymeric unit is associable and (2) a dye carrier, e.g., an equal weight mixture of dimethyl terephthalate and benzilide.

BACKGROUND OF THE INVENTION Field of the invention Aromatic polyamides have been found well-suited for a broad range of utility where exposure to high temperatures is involved. Such polymers and shaped structures derived therefrom are shown, for example, in the Kwolek et al. US. Patent 3,063,966, which teaches process for their manufacture. Consistent with their excellent utility at high temperature there is a strong tendency for members of this class to crystallize or, by some mechanism not yet defined, to develop a highly consolidated, dense structure. The closely packed molecular configuration of shaped structures comprising aromatic polyamides known Description of the prior art While the various manipulative steps are individually known in the art, their combination in order to obtain the highly desirable result of the present invention is not known to be suggested by the art.

SUMMARY OF THE INVENTION In accordance with the present invention a process is provided for dyeing textiles formed from synthetic meta or para oriented, wholly aromatic polyamides containing from 2 to about 15 molar percentage of an aromatic dye associable copolymeric unit which comprises heating the drawn filaments of the said textile while the said filaments are free to relax to a temperature between about 150 to 280 C. for a period between about l'minute (at the upper temperature) and about 45 minutes (at the lower temperature) and thereafter dyeing the said textile in a dye-bath containing (1) a dye with which the said 00- polymeric unit is associable and (2) a dye assistant.

3,506,990 Patented Apr. 21, 1970 DEFINITIONS AND STANDARDS By a dye assistant is meant any organic substance which is substantially inert to the dyebath under the conditions employed and capable of being absorbed by the shaped aromatic polyamide structure to the indicated extent under the conditions of dyeing specified. The substance may be a pure compound or a mixture of compounds.

In the examples K/S refers to the ratio of absorbed light to scattered light as measured in the usual manner, using a photometer for measuring incident and reflected light. K/S values are related to apparent depth of dyeing attained; percent dye on fiber is no more complex than implied for the expression, being merely an indication of the quantity of dye in or on the fiber which is not removed by a simple scour. Dye yield is calculated as the ratio of K/S value to the percent dye-on-fiber and is an indication of the effectiveness of the dye taken up by the fiber in producing visible coloration. Dye yield and percent-exhaust are closely allied to economy of the dyeing operation and therefore of great practical importance. It will be obvious that a very high dye yield is of no commercial importance in a dyeing which gives unacceptably poor percent-exhaust, since the dye bath normally is discarded following a dyeing operation. Likewise, a high percent-exhaust can occur in a dyeing coincidentally with'a very low dye yield as, for example, in cases where the fiber has been delustered by taut annealing at high temperature. Thus, to be acceptable economically a dyeing process must be considered on the basis of all of the listed criteria and no single criterion may be used in determining adequacy of a dyeing operation.

The invention is illustrated by the following examples, which are not limitative. In the examples parts are by weight unless otherwise noted. Inherent viscosity is measured in the usual manner at 25 C., using dimethyl acetamide, containing 4% lithium chloride, as solvent.

EXAMPLES Example 1 A series of aromatic copolyamides is prepared by a process as taught in the Kwolek et al. US. Patent 3,063,-'

966 to comprise as the major constituent metaphenylene isophthalamide (MPD-I) and as copolymeric constituent instances, the tow is exposed for about one second to rolls.

heated to the indicated temperature while beingrestrained from shrinking (indicated'in Table I as taut). In oth-.

ers, it is heated at 260 C. for 20 or 30 minutes (as indicated in Table I) under no restraint (indicated in TableI as ,relaxed). l

The tows. are then cut to about a 2-inch staple length, and hand-carded pads are prepared from each lot for dyeing. The pads are dyed individually under a pressure of 20 p.s.i.g. in 40 times their weight of a dye-bathof the following parts by weight composition:

C.I. Basic Blue 22 0.l6 Dye assistant (where used) 0.8

Wetting agent 0.1 Acetic acid (to pH 2.9).

Water (to parts total).

Parts 3 4 Yarn identity and treatment history are reported in also extracts the residual solvent and salt, and dried for Table I. 5.7 seconds over rolls heated to 100 C.

TABLE I v Heating Denier Mole percent Polymer Percent conditions per NaSMPD-I inh. Visc. drawn min. 0.5 filament 1. 57 43s 'Iaut, (320)... 2 0 1. 57 43s Relaxed, 20 (260).- 2.6 2.5 1.71 438 Tent, 20 (320) 2.1 2.5 1.62 450 Relaxed, 20 (260).- 2.4 6.0 1.68 450 Tent, 20 (320) 1.3 0.0 1.68 450 Relaxed, (200 2.2 10.0 1. 43 447 Relaxed, 20 (260).- 2.7

A total of 13 dyeings is made, six without a dye assistant The yarn is knitted on a stoll-knitting machine and the and seven with an equal weight mixture of dimethyl ter- 15 resulting knitted fabric is relaxed at 240 C. for 30 minephthalate and benzanilide as a dye assistant. The dyeing utes under conditions of no restraint. The relaxed fabric periods and results obtained are summarized in Table II. is dyed with an acid dye under a pressure of 15 p.s.i.g. The a items each were dyed with the dye assistant, the for two hours, the dye bath having the following compob items contained no dye assistant. sition and the ratio of bath to tubing being 50/ 1.

TABLE II 2 hours 3 hours Percent Percent Dye Percent Percent Dye K/S on fiber exhaust yield /S on fiber exhaust yield As can be seen from Table II (comparing the various Pt. a and b items) use of the dye assistant is critical. Further- .CI Index @8215 0.1 more, comparing the 3a versus the 4a and the 5a versus Dye Assistant as in Ex. 1 1.0 the 6a sample (each pair with identical and comparable Wetting agent 0.1 copolymeric modification) substantial improvement of the Sulfuric acid (to pH 1.6). relaxed versus the taut samples can be observed. Water.(to 100 pts.). (Note that although sample Shows a Ielatwely hlgh Dye exhaust is nearly quantitative. In a comparison dye exhaust it .Shows a P dye yield) Samples with an unmodified MPD-I polymer yarn, it is found that 2a and 2b which contained no copolymerlc modlfylng less than 50% of the dye was taken up by the fiber unit are very poor in dyeing performance.

Without use of superatmospheric pressure, dye pickup Example 3 by the Polymer P thls examPle 18 5 as to This example illustrates suitability of the process of pletely unattractive commerclally even Wlth the highest this invention for dyeing of ordqed copolymers such as level of modification by NaSMPD. It will be apparent disclosed i US. 3,232,910. from the tabulateddata that WhBIL HI addition to pres- NN' m phenylene bis meta amino benzamide), abbre sure both a dye asslstant and appreclable modlficatlon by viated MPBB hereinafter, is prepared by reacting two mol- N are efnployedr an attractive increase in dyeabil' parts of meta nitro benzoyl chloride with one mol-part of W ffisults only In those Y which 'f f not been heated MPD in DMAc and reduction of the resulting dinitro inf taut- U of 1 Part f Sa11Y1amhde for the dye termediate to the diamine by atmospheric pressure by hyslstant of this example provides 100% more dye exhaust drogenation, using Pd 0n carb0n as catalyst a at Yemg- Example 2 To the diamine 154 parts) and 11.4 parts of CaSMPD m 1420 parts of DMAc cooled to --20 C. is slowly This example illustrates application of the process of added 101 parts isophthaloyl chloride with good agitathis invention to the acid-dyeing of aromatic polyamide tion. The resulting viscous solution is neutralized by structures. addition of 37 parts dry lime slurried in an additional To a nitrogen-blanketed solution of 100 parts meta- 100 parts DMAc. After vacuum deaeration with eliminaphenylenediamine (MPD) in 985 parts DMAc which has tion of a portion of the DMAc and a small amount of been cooled to 2-0 C. is slowly added 189 parts of a water, the solution is found to contain a copolymer of .94/.06 molar mixture of isophthaloyl chloride/pyridine MPBB-I/CaSMPD-I in a molar ratio of 89/11, suit- 2,5-dicarbony1 chloride (I/2,5-Py). The resulting viscous able for dry-spinning to useful fibers. The solution is solution is neutralized by the addition of 69 parts dry dry spun in a manner equivalent to that of Example 1 lime slurried in an additional 117 parts of DMAc. The and the filaments so obtained are extraction-drawn to solution is vacuum-deaerated with elimination of 180 450% of their spun length in hot water. The filaments are parts of DMAc containing a small amount of water, after heated at 260 C. for 20-30 minutes under conditions which it contains'19.5% of a copolymer of MPD-I/MPD- 70 of no restraint.

2,5-Py in a 94/6 molar ratio having an inherent viscosity The filaments are cut to about 2" (about 5 cm.) staple of 1.58. and hand carded pads made therefrom. The pads are The solution is dry-spun by means available in the art dyed at 15 p.s.i.g. for 2 hours at a pH 45, otherwise using to denier. l8-filament yarn which subsequently is the procedure and formulation of Example 1 The fiber drawn to 316% of its as-spun length in hot water, which 7 is found to dye satisfactorily to deep shades.

While the invention has been described with particlar reference to copolymers of MPD-I, it will be obvious that the process may be advantageously applied to any aromatic copolyamide (including terpolymers). The amides which may occur at the major constituent in the aromatic polyamides used in the process of this invention are exemplified by those disclosed in the Kwolek et al., US. Patent 3,063,966. Suitable as major con stituents are those based on aromatic diamines and aromatic diacyl compounds as well as those based on aromatic amino-acyl compounds. The former yield polymers having the repeating structure 0 H H NAr N( JAr-a while the latter yields polymers having the repeating structure H i Y R -N-Ano N-And' wherein Ar and Ar represent divalent aromatic residues and may be the same or different. Also useful in the practice of this invention are the various combinations, ordered or random, of both types of structures. Ordered copolymers are illustrated in the Preston US. Patent 3,232,910. The minor amide constituents are exemplified by those derived from and the like.

In addition to copolyamides, blends of polyamides where a minor component of the lend is a polyamide containing a dye associable substituent may be used in the process of the present invention, the minor component constituting from about 2 to about 15 weight percentage of the blend. A typical blend for such a purpose can be formed by mixing 2400 parts of an 18.4% MPD-I polymer solution in DMAc/calcium chloride with 272 parts of a 20% solution of a CaSMPD-I polymer in DMAc. The solution can then be dry spun toafilament.

As pointed out above, the process of this invention is generally applicable to aromatic polyamide structures. It is especially useful for aromatic polyamides which strongly tend to consolidate to highly dense structures at high temperature; these are characterized as those having a well-ordered molecular structure and/ or unsubstituted amide hydrogens. When highly consolidated by heat, structures of polyamides are not penetrated by dyes available in the trade to a useful extent. The utility of this invention in process for dyeing of such structures is subject only to three limitations: (1) the polymer must carry functional groups which tend to yield stable associations with a dyestuff, (2) high temperature exposure in the process for preparation of the shaped structure must be encountered only when the structure is free to relax, and not exceed 280 C., and (3) a dye assistant is required which is, under the conditions of dyeing, absorbed by the structure to the extent of at least 5%. Typical useful dye assistants are B-napthol; diphenyl sulfone; salicyl aldehyde; salicylic acid, salicylanilide; dimethyl isophthalate; benzyl alcohol; pelargonic acid; benzoic acid; o-phenyl phenol; dimethyl terephthalate; benzanilide; isopropylidene 4,4'-di-phenol; hexamethyl phosphorarnide; dimethyl acetamide; or other members of the homologous series, wherein the acyl residue comprises 1-10 carbon atoms, formic acid and the lower homologues thereof, methylene chloride, dimethyl cyanamide, tetramethylene sulfone, 2,4-dimethyltetramethylene sulfone, ethylene diamine, triethylene tetramine, pyrrolidine, pyridine, piperidine, cyclohexylamine, and the like, it being required only that the compound or mixture employed as a dye assistant must have sufiicient affinity for the aromatic polyamide structure that it is absorbed by said structure to the indicated extent despite the tendency of many of the materials to form a stable solution in water under the conditions employed. It is recognized that not all of the materials which are suitable for use as a dye-carrier of a shaped structure comprising a given aromatic polymer will be suitable for use as a dye carrier for structures of all other polymers. The requirements are less severe in selection of a carrier for dyeing of a structure comprising a highly modified polymer, and a broader range of carriers is found suitable.

The use of autogenous superatmospheric pressure (5-30 p.s.i.g.) with its attendant higher temperature is of distinct advantage to this process. In addition, the presence of up to about 15 molar percentage of a second copolymeric constituent in addition to the one bearing the dye sensitive substituent will tend to break up the well ordered structure of the main polyamide chain and further enhance its susceptibility to dyeing. Use of such terpolymers in the copolymeric structure and/or presence of a larger quantity of carrier therein may permit dyeing to a practical degree without use of superatmospheric pressure.

In processing the fibers of the present invention it is important that they not be exposed to temperatures as high as about 200 C. while taut prior to high-temperature relaxation. Heating of the drawn filaments while relaxed for as little as 1 min. at the upper range of tempeature treatment is usually adequate for purposes of the present invention. Longer periods are required if lower temperatures are used. Generally a draw of about 4 /2 times extruded length is used to develop good textile properties in the yarn, and relaxed heating is provided until an effective draw of about 3 /2 times is reached due to shrinkage in the heat treatment step. The heat relaxation step can be performed upon the yarn, staple or fabric. It is often advantageous to steam the drawn yarn (or staple or fabric) prior to heat relaxation in order to reduce residual shrinkage in boiling water in the final structure. Such steaming does not affect dyeability.

Although only the sodium and calcium salts of the anionic-active minor constituent of the copolymeric structure have been exemplified, other neutralizing cations may conveniently and advantageously be employed. Among these are the magnesium, manganese, bismuth, triethyl ammonium, aluminum zinc, ammonium, cadmium, potassium and lithium salts.

The invention is not limited to the exemplified anionicactive or cationic-active copolymeric constituents. It will be apparent to one skilled in this art that the only criterion of such a constituent is that it comprise an aromatic-ring substituent of the desired functionality in combination with bifunctional, polyamide-forming capability. Such a compound may comprise one or more aromatic rings and where two or more are involved may comprise additionally alkylene, cycloalkylene or heterocyclic groups therebetween with the limitation that the chain-extending, amide-precursive groups must, in each case, be directly attached to carbon of aromatic rings.

Other bifunctional radicals which may bridge between aromatic moieties of the starting materials are x0; sulfide, disulfide, methylene, propylene, dimethyl methylene, carbonyl, sulfo, hexafluoroisopropylidene and the like. It is within the scope of this invention to employ an amino carbonyl halide bearing a functional group capable of stable association with a dyestuif, as exemplified by 3- amino chlorobenzoyl 5-sulfonic acid.

Since many departures from the specifically exemplified embodiments may be made which are within the spirit and scope of this invention, limitations are to be regarded only as set out in the claims which follow.

What is claimed is:

1. A process for dyeing drawn filaments of a copolymer of repeat units selected from the group consisting of mphenyleneisophthalamide and N,N'-m-phenylene bis (meta amino benzamide)isophthalamide, and from 2 to 15 molar percent of repeat units consisting of the isophthalamide of a metallic salt of 2,4-diaminobenzene sulfonic acid, said process comprising heating said drawn filaments, while they are free to relax, at a temperature between about 150 to 280 C. for a period of from about 1 minute at the upper temperature to about minutes at the lower temperature and thereafter dyeing said filaments under superatmospheric pressure in an aqueous dyebath containing a basic dye and an organic dye carrier which is substantially inert to the dyebath under the conditions employed and is capable of being absorbed by said filaments to the extent of at least 5% by weight of said filaments under the conditions employed.

2. The process of claim 1 wherein said organic dye carrier is an equal weight mixture of dimethyl terephthalate and benzilide.

References Cited UNITED STATES PATENTS 3,184,436 5/1965 Magat 26078 GEORGE F. LESMES, Primary Examiner T. I. HERBERT, JR., Assistant Examiner U.S. Cl. X.R.