Process For Dyeing Fibers Or Fabrics Of Aromatic Polyamides

Abstract

A process for dip dyeing aromatic polyamide fibers or fabrics with acid dyes with good dyeability and levelling properties, without modifying measures which may cause deterioration of the desirable properties of the aromatic polyamides, which comprises dip dyeing fibers or fabrics of an unmodified aromatic polyamide in a dye bath comprising an acid dye of the monosulfonic acid, monosulfonic acid-carboxylic acid, disulfonic acid, disulfonic acid-carboxylic acid, or carboxylic acid and at least 1 percent by weight (based on the weight of the solution) of a neutral or acidic inorganic salt, in the presence of a swelling agent having a phenolic hydroxyl group, and alkali metal salts thereof; and soaping the dyeing obtained.

Description

This invention relates to a process for dyeing fibers or fabrics of unmodified aromatic polyamides which are very difficult to dye with acid dyes. More specifically, the invention relates to a process for dip dyeing aromatic polyamide fibers or fabrics with acid dyes with good dyeability and levelling properties, without taking any modifying measures which may cause deterioration of the desirable properties of the aromatic polyamides.

According to the present invention, a process for dyeing fibers or fabrics of aromatic polyamides having an aromatic ring in the recurring units with acid dyes is provided, which comprises dip dyeing fibers or fabrics of an unmodified aromatic polyamide in which the recurring unit of the molecular chain is expressed by a recurring unit selected from the group consisting of:

I. NH-Ar.sub.1 -CO, wherein Ar.sub.1 is an aromatic ring, preferably phenyl,

Ii. NH-Ar.sub.1 -NHCO-Ar.sub.2 -CO, wherein Ar.sub.1 and Ar.sub.2 are the same or different, and represent an aromatic ring, preferably phenyl or naphthyl,

Iii. NH-R.sub.1 -Ar.sub.1 -CO, wherein Ar.sub.1 is an aromatic ring, preferably phenyl, and R.sub.1 is a lower alkyl group, preferably having 1 to 4 carbon atoms,

Iv. NH-R.sub.1 -Ar.sub.1 -R.sub.2 -NHCO-Ar.sub.2 -CO, wherein Ar.sub.1 and Ar.sub.2 may be the same or different, and represent an aromatic ring, preferably phenyl or naphthyl, and R.sub.1 and R.sub.2 may be the same or different and represent a lower alkyl group, preferably having 1 or 4 carbon atoms, and

V. combinations of two or more of the units (i) to (iv), in a dye bath comprising an acid dye of the monosulfonic acid, monosulfonic acid-carboxylic acid, disulfonic acid, disulfonic acid-carboxylic acid, or carboxylic acid type expressed by the formula

D----am).sub.p

Wherein D represents a dye molecule matrix, A represents --SO.sub.3 -- or --COO-- residue, M represents hydrogen or an alkali metal, and p is an integer of 1 to 3, with the proviso that when A is only --SO.sub.3 -- and when A contains both --SO.sub.3 -- and --COO--, the maximum number of --SO.sub.3 M is 2,

And at least 1 percent by weight (based on the weight of the solution) of a neutral or acidic inorganic salt, preferably alkali metal salts or ammonium salts of inorganic acids, especially alkali metal salts or ammonium salts of mineral acids in the presence of a swelling agent selected from compounds having a phenolic hydroxyl group expressed by the following formula

Ho - ar.sub.3 - R.sub.3

wherein Ar.sub.3 is a phenyl or naphthyl group, R.sub.3 is a member selected from the group consisting of hydrogen, lower alkyl groups, preferably those having 1 to 4 carbon atoms, especially a methyl group, halogen a nitro group, lower alkoxy groups, preferably those having 1 to 4 carbon atoms, especially a methoxy group, and a phenyl group, and when Ar.sub.3 is a naphthyl group, R.sub.3 is hydrogen or a lower alkyl group, preferably an alkyl group having 1 to 4 carbon atoms, especially a methyl group;

and alkali metal salts thereof; and soaping the dyeing obtained.

It is known that linear polyamides such as nylon 6, nylon 66, nylon 610, or nylon 11 can be dyed with acid dyes with practical dyeability. On the other hand, aromatic polyamides having an aromatic ring in the recurring units have better flameproofing properties, tenacity, elastic properties, and dimensional stability than the above-mentioned polyamides ordinarily used, but have higher hydrophobic properties and crystallinity. Therefore, dyeings having practical value cannot be obtained from such aromatic polyamides by dip dyeing with acid dyes in accordance with the procedure used for ordinary polyamides. They are either not dyed at all, or dyed only in very light colors.

This imposes serious restrictions in the application of fibers or fabrics made from such aromatic polyamides, and constitutes a setback in the utilization of the desirable properties of the aromatic polyamide fibers or fabrics mentioned above.

With a view to removing such a defect, it was proposed to modify aromatic polyamides to render them cationically dyeable, and dye them with basic dyes in the presence of a swelling agent (Textile Chemist and Colorist: Vol. 1, No. 18, pp. 388/27-319/30, 1969). It is also known to dye aromatic polyamide fibers modified with a tertiary amine-containing amide, sulfo-substituted amide, or a quaternary ammonium-containing amide with basic or acid dyes (see U. S. Pat. No. 3,506,990).

These prior proposals require an additional step of modifying the polyamides, and suffer from other disadvantages including the adverse effect on the properties of the aromatic polyamides as a result of modification.

A method has also been proposed in which aromatic polyamides are dyed with basic dyes in the presence of benzaldehyde and sodium nitrate (Textile Chemist and Colorist: Vol 2, No. 15, pp. 25/262-28/265, 1970). According to this proposal, the modification of the polyamides is not required. But it has been pointed out that only basic dyes show practical dyeability, and acid dyes cannot give dyeings having practical sunlight fastness and crockfastness. As will be shown by a comparative example appearing later in this specification, the dyeing effect of the present invention cannot be produced even if the aromatic polyamides are dyed with acid dyes using benzaldehyde instead of the compound having a phenolic hydroxyl group as used in the process of the present invention. Furthermore, in this dyeing method, the dispersibility of benzaldehyde in the dye bath is poor, and it must be used in the form of an emulsion which is troublesome and difficult to control; frequently, the level dyeing properties are poor, and practical dyeings cannot be obtained.

It has now been found that fibers or fabrics composed of unmodified aromatic polyamides can be dyed with good results by a dye bath comprising the acid dye and at least 1 percent by weight of the neutral or acidic inorganic salt utilizing the compound having a phenolic hydroxyl group expressed by the above given formula and its alkali metal salts.

It is quite surprising that excellent dyeings of unmodified aromatic polyamides can be obtained by easy dyeing means using the acid dyes whose utilization proved unsatisfactory in the former proposal in which modified aromatic polyamides are dyed with basic or acid dyes, and was denied in the latter proposal in which unmodified polyamides are dyed with basic dyes.

Accordingly, an object of the present invention is to provide a process for dyeing fibers or fabrics composed of unmodified aromatic polyamides with good dyeability using an acid dye without adversely affecting the desirable properties of the polyamides.

Many other objects and advantages of the present invention will become apparent from the following description.

In the present specification and claims, the term "fibers" is meant to include all forms of fibers such as filaments, tows, yarns, or staples, and the term "fabrics" includes woven fabrics, knitted fabrics, felts, and nonwoven fabrics.

It is not clear what dyeing mechanism is responsible for the excellent dyeability obtained by the process of the present invention. It is assumed however that it is due to the ionic bond between the aromatic polyamide and the --SO.sub.3 -- or --COO-- group of the acid dye expressed by the formula given above. Some reasons given are that because the terminal amino group is a group derived from an aromatic amine and the polyamide is not modified at all, its basicity is not large enough to produce a sufficient dyeability by the ionic bond with the acid dye, and that when the polyamide is extracted with dimethyl formamide, a substantial amount of the dye is dissolved out.

It is assumed that in accordance with the present invention the excellent dyeability of the aromatic polyamide fibers or fabrics is obtained by the synergistic action of (a) the swelling agent having a phenolic hydroxyl group as expressed by the formula given above which has been applied to the aromatic polyamide fibers or fabrics in advance or is present in the dye bath, and (b) the neutral or acidic inorganic salt. In fact, when the aromatic polyamide fibers or fabrics are dyed with some acid dyes which are known to exhibit good dyeability towards ordinary polyamides but do not correspond to the general formula given above, the objects of the present invention cannot be achieved as shown in Comparative Examples set forth hereinafter. Furthermore, when benzaldehyde is used instead of the specific swelling agent used in the invention, the objects of the present invention cannot be achieved. Furthermore, if the use of the neutral or acidic inorganic salt is omitted in the process of the present invention, the objects of the present invention cannot be achieved as will be shown by the Comparative Examples given below.

Probably, a coated or permeated bayer of the swelling agent is formed on the surface or surface layer of the difficultly-dyeable aromatic polyamide fibers or fabrics, and the solubility of the acid dye having a certain range of water solubility in water is reduced by the copresence of the neutral or acidic inorganic salt, and the solubility of the swelling agent in water is reduced for the same reason. The dye molecules move into the coating or permeated layer of the swelling agent to increase the concentration of the dye at that portion, which in turn permits easy intrusion of the dye molecules by the swelling of the aromatic polyamide fibers or fabrics, and consequently, the aromatic polyamide fibers or fabrics are dyed with markedly improved dyeability.

The material to be dyed by the process of the present invention is fibers or fabrics of an aromatic polyamide in which the recurring unit (i) to (v) constitutes the main chain of the polyamide. Expecially, according to the process of the present invention, fibers or fabrics of aromatic polyamides having recurring units composed of (i), (ii) or a combination of these can be dyed with excellent dyeability.

Examples of the polyamide having the recurring unit (i) above include the aromatic polyamides disclosed in British Patent 901,159.

The polyamides having the recurring unit (ii) are disclosed, for instance, in U. S. Pat. Nos. 3,063,966 and 3,006,899.

As the polyamide having the recurring unit (iii), homopolymers of p-aminoalkylbenzoic acids produced by the same method as British Patent 901,159 are typical examples.

The polyamides having the recurring unit (iv) can be produced, for example, by the method disclosed in U. S. Pat. No. 3,232,910, and include, for example, aromatic polyamides derived from p- or m-xylylenediamine and iso- or tere-phthalic acid.

The polyamides having the recurring unit shown in (v) above can be produced by optional combinations of the polyamide-forming components above mentioned.

The swelling agent used in the present invention is selected from compounds having a phenolic hydroxyl group expressed by the following formula

Ho - ar.sub.3 - R.sub.3

wherein Ar.sub.3 is a phenyl or naphthyl group, R.sub.3 is a member selected from the group consisting of hydrogen, lower alkyl groups, preferably those having 1 to 4 carbon atoms, especially a methyl group, halogen, a nitro group, alkoxy groups, preferably those having 1 to 4 carbon atoms, especially a methoxy group, and a phenyl group, and when Ar.sub.3 is a naphthyl group, R.sub.3 is hydrogen or a lower alkyl group, preferably an alkyl group having 1 to 4 carbon atoms, especially a methyl group;

and alkali metal salts thereof.

Specific examples of such swelling agent include phenol, alphanaphthol, beta-naphthol, o-, m-, and p-cresols, o-phenylphenol, p-phenyl-phenol, nitro-phenol, chlorophenol, 4-methoxyphenol. The p-phenyl phenol gives most favorable results.

The acid dye that is used in the present invention is selected from acid dyes of the monosulfonic acid, monosulfonic acid-carboxylic acid, disulfonic acid, disulfonic acid-carboxylic acid, or carboxylic acid type expressed by the following formula

D--am).sub.p

wherein D represents a dye molecule matrix, A represents --SO.sub.3 -- or --COO-- residue, M represents hydrogen or an alkali metal, and p is an integer of 1 to 3, with the proviso that when A is only --SO.sub.3 -- and when A contains both --SO.sub.3 -- and --COO--, the maximum number of --SO.sub.3 M is 2.

Acid dyes of the monosulfonic acid and monosulfonic acid-carboxylic acid types are especially preferred. When p is 2 or 3, those dyes in which the structure of the dye molecule matrix D is large, for instance, those having at least 4 benzene rings, and which have low solubility in water are preferred.

Of these acid dyes, especially preferred for giving dyeings of aromatic polyamide fibers or fabrics having excellent light fastness are:

a. acid dyes in which the dye molecule matrix contains a structure expressed by the formula ##SPC1##

and which do not contain --NR'.sub.2, wherein R' is a hydrogen atom or an alkyl group, as an auxochrome;

b. acid dyes in which the dye molecule matrix contains a structure expressed by the formula ##SPC2##

c. acid dyes in which the dye molecule matrix contains a structure expressed by the formula ##SPC3##

Of these, acid dyes of the types (a) and (c) are especially preferred.

Specific examples of the acid dyes that are used in the present invention are the following:

1. monosulfonic acid type (m=1, A=--SO.sub.3 --)

c.i. 14675, 14680, 14690, 14695 14710, 15510, 15575, 15635, 15705, 18835, 18940 26660, 26665, 50120, 62045 44025, 45100, 50320, 50085

2. disulfonic acid type (m=2, A=--SO.sub.3 --)

c.i. 16240, 18130, 22910, 23635 24820, 24780

3. sulfonic acid-carboxylic acid mixed type (n=2 - 3, A=--SO.sub.2 -- and --COO--)

c.i. 14095, 17590, 18821, 26520 26560, 26695, 43825, 62120

4. carboxylic acid type (n=1 - 3, A=--COO--)

c.i. 13060, 14000, 14135, 16315 18710, 18885, 25100, 45305 43865, 43830

other examples are:

Acid dyes of the formula ##SPC4##

wherein R" is phenyl, alpha- or beta-naphthyl, 2-, 3-, or 4-halogenophenyls, 2-, 3-, or 4- tolyl, 2-, 3- or 4-nitrophenyl, 4-alkoxy-2-tolyl, 4-nitro-2-tolyl, 3-nitro-2-tolyl, 2-nitro-4-tolyl, 2-nitro-4-methoxyphenyl, 2-chloro-4-nitro phenyl, 2-methoxy-4-chlorophenyl, 2-methoxy-4-nitrophenyl, 2-methoxy-5-nitrophenyl, 2,5-dimethoxy-4-nitrophenyl, ##SPC5##

acid dye of the formula ##SPC6##

acid dye of the formula ##SPC7##

As the neutral or acidic inorganic salt to be present in the dye bath in the present invention, alkali metal salts of inorganic acids, or ammonium salts thereof are preferred, and especially preferred are the alkali metal salts or ammonium salts of mineral acids.

Specific examples of the salts include potassium chloride, sodium chloride, ammonium chloride, potassium bromide, sodium bromide, ammonium bromide, potassium nitrate, sodium nitrate, ammonium nitrate, potassium sulfate, sodium sulfate, ammonium sulfate, potassium pyrosulfate, sodium pyrosulfate, ammonium pyrosulfate, potassium phosphate, sodium phosphate, ammonium phosphate, potassium pyrophosphate, sodium pyrophosphate, and ammonium pyrophosphate. Of these, potassium sulfate, sodium sulfate, ammonium sulfate, potassium phosphate, sodium phosphate, ammonium phosphate, potassium pyrophosphate, sodium pyrophosphate, and ammonium pyrophosphate are preferred, and next come potassium nitrate, sodium nitrate, and ammonium nitrate. Ammonium sulfate gives especially good results. These salts are used either alone or in admixture.

The dye bath used in the present invention may contain various dyeing assistants conventionally utilized in dip dyeing with acid dyes, such as ultraviolet absorbants, pH adjusting agents, or surface active agents. Examples of the ultraviolet absorbants are 4,4'-dimethoxy-2,2'-dihydroxybenzophenone, 2,4-dihydroxybenzophenone, and 2-(2'-hydroxy-5'-methylphenyl)benzotriazole. Examples of the pH adjusting agents are sulfuric acid, formic acid, or succinic acid. As the surface active agent, anionic surfactants can be cited and nonionic surfactants.

The pretreatment of aromatic polyamide fibers or fabrics with the swelling agent may conveniently be carried out by immersing the fibers or fabrics in a solution, dispersion or emulsion containing the swelling agent or padding them with such solution, dispersion or emulsion, thereby bringing the fibers or fabrics into intimate contact with the swelling agent, preferably under heating, and thereby coating or permeating the swelling agent on or into at least the surface or surface layer of the fibers or fabrics. Where the boiling point of the swelling agent is very low, the fibers or fabrics may be contacted with a vapor of such swelling agent. If the swelling agent is a normally liquid compound, or a solid compound having a low melting point, the fibers or fabrics may be contacted with the liquid or a molten liquid of the swelling agent. In the case of using the swelling agent in the form of solution, dispersion or emulsion, not only water, but a solvent for the swelling agent can be used. Solvents or semi-solvents which dissolve or swell the aromatic polyamides can also be utilized. When acid mordant dyes are used, mordanting metal ions such as chromium, nickel, cobalt, and aluminum ions can be conjointly used at the time of the pretreatment.

When alkali metal salts of compounds having a phenolic hydroxyl group are used in the above-mentioned pre-treatment, organic or inorganic acids in amounts sufficient to at least neutralize the alkali salts are added to the dye bath in advance. Specific examples of such acids are those mentioned with respect to the pH adjusting agents.

The pretreatment can also be carried out in the copresence of the compound having a phenolic hydroxyl group and an alkali metal hydroxide or a salt of an alkali metal with a weak acid. In this case also, an acid in an amount at least sufficient to neutralize the alkali salt of the compound having a phenolic hydroxyl group picked up by the fibers or fabrics as a result of the pre-treatment should be added to the dye bath in advance.

In order to increase the solubility or dispersibility of the swelling agent, a small amount of a water-miscible organic solvent, such as alcohols or acetone, or an anionic surface active agent may be added to a solution of the swelling agent to be used for the pre-treatment.

The pre-treatment is conveniently performed by heating while the aromatic polyamide fibers or fabrics are brought into intimate contact with the swelling agent, and frequently, temperatures from 60.degree.C. to 160.degree.C., preferably from 80.degree.C. to 140.degree.C., are employed to this end.

When the pre-treatment is omitted in the process of the invention and the swelling agent is incorporated into the dye bath in advance, it is not necessary to pre-heat the fibers or fabrics to be dyed, but they may simply be dyed at the dyeing temperature.

The amount of the swelling agent can be optionally changed according to the type of swelling agent, the type of aromatic polyamide to be dyed, the type of acid dye used, or the shape of the fibers or fabrics. Generally, however, the preferred amount is 0.5 to 50 percent based on the weight of the fibers (o.w.f.), especially 4 to 40 percent o.w.f., more especially 5 to 30 percent o.w.f. At this time, the amount of the neutral or acidic inorganic salt is 1 to 40 percent o.w.s. (based on the weight of the solution), especially 3 to 30 percent o.w.s., and more especially 3 to 20 percent o.w.s.

The dyeing operation is not especially restrictive, and those operations which are used for conventional dip dyeing can be utilized. Since dyeings of deep color cannot be obtained when the amount of the neutral or acidic inorganic salt in the bath is not more than 1 percent by weight, the amount of this salt should be 1 percent by weight or more. The dyeing temperature is 80.degree.C. to 200.degree.C., preferably about 100.degree.C. to 150.degree.C.

In the dyeing process of the present invention, the goods-to-liquor ratio is important for dyeability. The preferred goods-to-liquor ratio is 1:5 to 1:100, more preferably 1:5 to 1:50.

After dyeing, the resulting dyeing is soaped by a customary method. The soaping is carried out with surface active agents, or alkalies. The soaping with alkalies is especially recommended. It is of course possible to soap the dyeing both with the surface active agent and alkalies. The compound having a phenolic hydroxyl group forms an alkali metal salt of phenol in an aqueous solution of an alkali metal hydroxide or an alkali metal weak acid salt, and thus, its affinity for the fibers is remarkably reduced, and on the other hand, its solubility in water is very much increased. Consequently, the compound having a phenolic hydroxyl group present in the dyeing can be readily removed, and the absorbed dye is hardly liberated. This is desirable for obtaining dyed aromatic polyamide fibers having excellent flame-proofing properties and thermal stability.

Examples of such alkaline compounds include hydroxides, carbonates, bicarbonates, borates, silicates, or acetates of alkali metals, for example, sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium acetate, potassium acetate, lithium acetate, sodium borate, potassium borate, sodium silicate, and potassium silicate.

The amount of alkaline compound is, for example, 0.5 to 10 percent by weight (o.w.s.), and it is used as an aqueous solution. The soaping is carried out by immersing the dyeing in an aqueous solution containing the alkaline compound at a temperature from 60.degree.C. to the boiling point, for 10 to 30 minutes.

The soaping of the dyeing can also be performed by utilizing a solvent (including a water-containing solvent) for the dye or compound having a phenolic hydroxyl group. Examples of such solvent include aliphatic lower alcohols such as methanol, ethanol, or propanol, aliphatic ketones such as acetone or methyl ethyl ketone, halogenated hydrocarbons such as trichloroethylene or perchloroethylene, and aliphatic amides sch as dimethyl acetamide, or dimethyl formamide.

The following Examples will illustrate the present invention in greater detail. In the Examples, the measurement of dyeability, removability of swelling agent, light fastness, and flame proofing properties was made as follows:

DYEABILITY

This is shown by the lightness (L value) of the dyeing which has been measured using a color differential meter. This value differs according to the dye used. When the same dye is used, larger L values show lighter dyeings, and smaller values, deeper dyeings.

REMOVABILITY OF SWELLING AGENT

The sample dyeing was soaped with N,N-dimethyl formamide at 100.degree.C. until the swelling agent on the sample was completely removed, and its weight (X) g was measured. Using this as a standard, the weight (Y gram) of a sample dyeing of the same size which was soaped was measured. The removability is calculated as follows:

(Y) -- (X)/(X) .times. 100 (%).

LIGHT FASTNESS

Measured using a fade-O-meter (JIS L-1044/59, carbn arc lamp method, A method).

FLAME-PROOFING PROPERTIES

Measured in accordance with JIS-L1091/71 (horizontal-type A.sub.3 method).

WASHING FASTNESS

Measured in accordance with JIS-L0844/70

DRYCLEANING FASTNESS

Measured in accordance with JIS-L0860/65

FASTNESS TO DRY AND WET RUBBING

Measured in accordance with JIS-L0849/67

EXAMPLE 1 AND COMPARATIVE EXAMPLE 1

Aromatic polyamide having an inherent visocisty of 1.7 obtained by the copolymerization of m-phenylene diamine and a 97:3 mixture of isophthaloyl chloride and terephthaloyl chloride was dry spun from its dimethyl acetamide solution containing calcium chloride, and then drawn 400 percent in boiling water and a hot plate to obtain a multifilament tow (1.8 denier per filament). The tow was crimped under wet heat, and then cut to a staple length of 3.8 cm. A staple fabric (250 g/m.sup.2) was prepared from the staples by spinning and weaving operations.

The fabric obtained was scoured for 30 minutes at 80.degree.C. in an aqueous solution containing 2 g/liter of sodium dodecylbenzenesulfonate, and then pre-set at 220.degree.C. for 30 seconds, followed by dyeing under the following dyeing conditions.

Dyeing conditions

Dye C.I. 15510 4% o.w.f. Swelling agent p-phenylphenol 7.5% o.w.f. Inorganic salt ammonium sulfate 150 g/liter pH adjusting agent acetic acid 20 g/liter Goods-to-liquor ratio 1:15 Temperature 130.degree.C. Time 90 minutes

After dyeing, the dyeing was thoroughly washed with water, and treated in an aqueous solution containing 3 g/liter of sodium carbonate (at a goods-to-liquor ratio of 1:30) at 85.degree.C. for 20 minutes to remove the swelling agent. The treated dyeing was washed with water, and then dried in air. The results are shown in Table 1 below.

For comparison, the foregoing procedure was repeated except that the dye bath did not contain ammonium sulfate (Comparative Example 1); the dye bath did not contain p-phenyl phenol (Comparative Example 2); Basic Orange 22, C.I. 48040 was used instead of the acid dye (Comparative Example 3); and benzaldehyde was used instead of p-phenyl phenol (Comparative Example 4).

TABLE 1

Properties of Dyeings Dyea- Remova- bility bility of (L- swelling Light Flame- value) agent fastness proofing Hand* properties Ex. 1 48.5 4.0% Class 3 4.1 cm Com. Ex. 1 59.2 3.8% Below class 1 4.1 cm Com. Ex. 2 67.4 3.6% Below class 1 4.3 cm Com. Ex. 3 49.3 0.5% Class 3 8.2 cm harsh Com. Ex. 4 59.6 0.2% Below class 1 7 cm * According to a functional test.

EXAMPLES 2 TO 5 AND COOPERATIVE EXAMPLES 5 TO 10

The staple woven fabric of Example 1 was dyed under the following dyeing conditions. The dyes used were acid dyes which could dye ordinary polyamides with only inferior light fastness but come within the acid dyes specified in the present invention. The results obtained are shown in Table 2.

Dye acid dye 6% o.w.f. Swelling agent p-phenyl phenol 20% o.w.f. Inorganic salt ammonium sulfate 75 g/liters pH adjusting agent acetic acid 20 g/liters Goods-to-liquor ratio 1:15 Temperature 130.degree.C. Time 90 minutes

For comparison, Table 2 also gives the results obtained when nylon 6 was dyed in a customary manner with the same dyes using a dye bath of a pH 4 at 95.degree.C. for 60 minutes. ##SPC8##

The staple fabrics of Example 1 were dyed in the same way as in Example 2 using acid dyes which dye ordinary polyamides with good fastness characteristics but are outside the scope of the acid dyes specified in the present invention. Using the same dyes, nylon 6 was dyed in the same way as set forth in Comparative Example 5. The results are given in Table 2' as Comparative Examples 9 and 10 and Controls 1 and 2. ##SPC9##

EXAMPLES 6 TO 17 AND COMPARATIVE EXAMPLES 11 TO 15

The same fabric as used in Example 1 was dyed under the following conditions using the swelling agent and inorganic salt shown in Tables 3 and 3' below. The results are given in Tables 3 and 3'.

Dyeing conditions

(a) (b) Dye C.I. 14680 C.I. 15510 4% o.w.f. 6% o.w.f. p-phenylphenol Swelling agent 40% o.w.f. 11% o.w.f. Inorganic salt Ammonium sulfate 100 g/l. 75 g/l. Acetic acid 20 g/l. 20 g/l. Goods-to-liquor ratio 1:15 1:15 Temperature 130.degree.C. 130.degree.C. Time 90 minutes 90 minutes

After the dyeing operation, the resulting dyeing was washed thoroughly with water, and washed for 20 minutes at 80.degree.C. in an aqueous solution containing 2 g/liter each of sodium hydrosulfite, sodium hydroxide and polyoxyethylene (20 mols) stearylamine (the goods-to-liquor ratio being 1 : 100), followed by washing with water and air drying.

TABLE 3

[Dyeing under the conditions

(a)] Run Nos. Swelling agent Dyeability (L value)* Example 6 beta-naphthol 26.2 Example 7 alpha-naphthol 27.1 Example 8 p-phenylphenol 30.3 Example 9 m-cresol 36.4 Example 10 o-phenylphenol 37.5 Comparative Ex. 11 resorcinol 48.7 Comparative Ex. 12 chlorobenzene 50.8 Comparative Ex. 13 Methylnaphthalene 48.6 Comparative Ex. 14 Benzaldehyde 45.1 * With C.I. 14680 used in the dyeing under the conditions (a), dyeings having an L value of less than 45 are substantially dyed. If this value is below 35, the dyeings are of deep color.

TABLE 3'

[Dyeing under the conditions

(b)] Run Nos. Inorganic salts Dyeability (L value)* Example 11 ammonium sulfate 48.4 Example 12 ammonium phosphate 49.7 Example 13 sodium sulfate 50.5 Example 14 sodium phosphate 50.1 Example 15 sodium pyrophosphate 49.4 Example 16 sodium nitrate 52.5 Example 17 sodium chloride 53.2 Comparative Ex. 15 sodium bicarbonate 60.2 * With C.I. 15510 used in the dyeing under the conditions (b), dyeings having an L value more than 65 are not substantially dyed, but merely soiled. The dyeings having an L value of above 50 are of deep color.

EXAMPLE 18 AND COMPARATIVE EXAMPLES 16 TO 21

A fabric woven from staple fibers of polymetaphenylene isophthalamide terephthalamide was immersed in a homogeneous aqueous solution obtained by adding 20 parts of p-phenyl phenol and 6 parts of sodium hydroxide to 75 parts of water, and heating the mixture to 90.degree.C. Without cooling, the immersed fabric was uniformly squeezed by a mangle so that the aqueous solution of a sodium salt of p-phenyl phenol was uniformly impregnated in the fabric (pick up 80 percent). The fabric so treated was then put into a dye bath (goods-to-liquor ratio of 1 : 15) containing 6 percent o.w.f. of each of the dyes shown in Table 3, 75 g/liter of ammonium sulfate, and 20 g/liter of acetic acid at 80.degree.C., and dyed at 140.degree.C. for 90 minutes. After dyeing, the dyed fabric was washed with the same aqueous solution as used in Example 6, followed by washing with water and air drying. The L value and fastness to light of the dyed fabric were measured, and the results are shown in Tables 4-a to 4-c. ##SPC10## ##SPC11##

TABLE 4c

Color Dyeability Light fastness Run index of (L value) (class) No. dyes 1 15620 23.5 3-4 2 15635 32.1 4 3 15510 45.0 3 4 15575 43.0 3-4 5 18835 71.9 3-4 6 18130 37.2 3 7 22910 67.3 3-4 8 24820 69.7 3 9 50315 24.3 4 10 50320 19.6 4 11 18940 35.1 3 12 26520 41.1 3 13 17055 19.5 3

EXAMPLE 19

In accordance with the method of producing a regular copolyamide which is disclosed in Example 5 of U. S. Pat. No. 3,232,910, N,N'-metaphenylene bis-(metaaminobenzamide) was polycondensed with isophthaloyl chloride to form an aromatic polyamide having an inherent viscosity of 1.2. A staple fabric was prepared from the aromatic polyamide in the same way as set forth in Example 1. The woven fabric was scoured and pre-set in the same way as set forth in Example 1, and then dyed under the following conditions.

The woven fabric was immersed in a homogeneous aqueous solution prepared by adding 25 parts of the sodium salt of para-phenyl phenol to 75 parts of water, and heating the mixture to 85.degree.C. Without cooling, the immersed fabric was uniformly squeezed by a mangle (pick up 80 percent), and then put into a dye bath (goods-to-liquor ratio 1:10) containing 5 percent o.w.f. of dye C.I. 18835, 75 g/liter of ammonium sulfate, and 15 g/liter of formic acid. The dyeing was performed at 130.degree.C. for 2 hours.

The resulting dyeing was washed for 20 minutes at 70.degree.C. with an aqueous solution (goods-to-liquor ratio 1:50) containing 2 g/liter of sodium hydroxide, and washed thoroughly with warm water. The alkali remaining on the fabric was neutralized with water containing a small amount of acetic acid, and then the fabric was dried. The dyeing exhibited a brilliant deep yellow, and had an L value of 70.3. It had a light fastness of class 3. In the flame-proofing test, the maximum flame diameter was 4.5 cm, showing satisfactory results. The fabric also had excellent fastness characteristics such as fastness to washing (class 4), fastness to drycleaning (class 5), and fastness to dry and wet rubbing (class 5).

EXAMPLE 20

Poly (m-benzamide) having an inherent viscosity of 1.3 prepared in accordance with the method disclosed in British Patent 901,159 was dry spun from its dimethyl acetamide solution containing lithium chloride, and a fabric was woven from the resulting multifilament tow in the same way as set forth in Example 1. The fabric was immersed in a solution of 10 parts of beta-naphthol in 9 parts of ethanol at 50.degree.C. Without cooling, the immersed fabric was squeezed uniformly to a pick up of 80 percent, dried, and dyed in a dye bath (goods-to-liquor ratio 1:6) containing 4 percent o.w.f. of C.I. 15575 dye, 50 g/liter of sodium sulfate, and 10 g/liter of acetic acid at 140.degree.C. for 90 minutes. After the dyeing operation, the dyed fabric was washed twice with an aqueous solution of 20 g/liter of sodium carbonate (goods-to-solution ratio 1:30) at 70.degree.C. for 20 minutes, then washed thoroughly with water, and air dried to give a brilliant deep orange dyeing having an L value of 43.0. The dyed fabric had fastness to light (class 3), washing (class 4), drycleaning (class 5), and dry and wet rubbing (class 4).

EXAMPLE 21

Staple fibers were obtained in the same way as set forth in Example 1 from polymetaphenylene isophthalamide having an inherent viscosity of 1.8 obtained by the polymerization of m-phenylene diamine and isophthaloyl chloride, and made into a knitted fabric (200 g/m.sup.2). The knitted fabric was scoured under the same conditions as set forth in Example 1. The fabric was then pre-treated with the swelling agent, washed with water, and then dyed under the following dyeing conditions.

Conditions for treating with the swelling agent

Chromizing agent K.sub.2 Cr.sub.2 O.sub.7 15% o.w.f. Swelling agent p-phenyl phenol 20% o.w.f. Acid acetic acid 8 g/l. Goods-to-liquor ratio 1:15 Temperature 150.degree.C. Time 60 minutes

Dyeing conditions

Dye C.I. 43830 6% o.w.f. Swelling agent p-phenyl phenol 20% o.w.f. Inorganic salt ammonium sulfate 75 g/l. pH adjusting agent acetic acid 20 g/l. Goods-to-liquor ratio 1 : 15 Temperature 130.degree.C. Time 60 minutes

After the dyeing operation, the dyed fabric was washed thoroughly with water, and treated with an aqueous solution containing ethanol (goods-to-solution ratio 1 : 30) at 80.degree.C. for 20 minutes to thereby remove the swelling agent remaining in the fabric, followed by washing with water and air drying. The resulting dyed fabric had deep color with an L value 18.6. The dyeing had fastness to light (class 3), washing (class 4), drycleaning (class 5), and dry and wet rubbing (class 5).

EXAMPLE 22

Monofilaments (30 count) composed of polymetaphenylene isophthalamide obtained in the same way as set forth in Example 1 were steamed at 100.degree.C. to set the twist, and scoured in the form of skein in the same way as set forth in Example 1. The skein was packed into a carrier of a cheese dyeing machine with a packing density of 0.28 g/cm.sup.3, and at 90.degree.C. 5% o.w.f. of dye (C.I. 15510), 25 percent o.w.f. of o-phenyl phenol, 50 g/l. of ammonium sulfate, and 10 g/l. of acetic acid were put into the machine in this order (goods-to-liquor ratio 1 : 15). The temperature was raised at a rate of 10.degree.C. per 5 minutes, and the dyeing was performed at 130.degree.C. for 90 minutes (in-out only). After the dyeing operation, the liquor was discharged at 90.degree.C., and the yarn was thoroughly washed with warm water. The swelling agent remaining in the yarn was removed by treatment with an aqueous solution containing 2 g/l. of polyoxyethylene (20 mols) stearylamine and 5 g/l. of sodium carbonate (goods-to-solution ratio 1 : 15) at 90.degree.C. for 30 minutes. The dyed yarn was washed with warm water, and then dried. There was no difference in the dyeing density between the inner and outer layers of the yarn, and uniform dyeing could be effected.

Claims

What we claim is:

1. A process for dyeing fibers or fabrics of an aromatic polyamide having an aromatic ring in the recurring units with acid dyes, which comprises dip dyeing said fibers or fabrics of an unmodified aromatic polyamide in which the recurring unit of the molecular chain is expressed by a recurring unit selected from the group consisting of:

i. -- NH-Ar.sub.1 -CO -- , wherein Ar.sub.1 is an aromatic ring,

ii. -- NH-Ar.sub.1 -NHCO-Ar.sub.2 -CO -- , wherein Ar.sub.1 and Ar.sub.2 are the same or different, and represent an aromatic ring,

iii. -- NH-R.sub.1 -Ar.sub.1 -CO -- , wherein Ar.sub.1 is an aromatic ring, and R.sub.1 is a lower alkyl group,

iv. --NH-R.sub.1 -Ar.sub.1 -R.sub.2 -NHCO-Ar.sub.2 -Co -- , wherein Ar.sub.1 and Ar.sub.2 may be the same or different, and represent an aromatic ring, and R.sub.1 and R.sub.2 may be the same or different and represent a lower alkyl group, and

v. combinations of two or more of units (i) to (iv),

in an aqueous dye bath comprising an acid dye of the monosulfonic acid, monosulfonic acid-carboxylic acid, disulfonic acid, disulfonic acid-carboxylic acid, or carboxylic acid type expressed by the formula D----AM).sub.p

wherein D represents a dye molecule matrix, A represents --SO.sub.3 -- or --COO-- residue, M represents hydrogen or an alkali metal, and p is an integer of 1 to 3, with the proviso that A is only --SO.sub.3 -- and when A contains both --SO.sub.3 -- and --COO--, the maximum number of --SO.sub.3 M is 2,

and at least 1 percent by weight, based on the weight of the dye bath, of a neutral or acidic inorganic salt, in the presence of a swelling agent selected from compounds having a phenolic hydroxyl group expressed by the following formula HO--Ar.sub.3 --R.sub.3

wherein Ar.sub.3 is a phenyl or naphthyl group, R.sub.3 is a member selected from the group consisting of hydrogen, lower alkyl groups, halogen, a nitro group, lower alkoxy groups, and a phenyl group, and when Ar.sub.3 is a naphthyl group, R.sub.3 is hydrogen or a lower alkyl group,

and alkali metal salt thereof; and soaping the dyeing obtained.

2. The process of claim 1, wherein said phenolic hydroxyl-containing compound or alkali metal salt thereof is selected from the group consisting of phenol, alpha-naphthol, beta-naphthol, cresol, o-phenyl phenol, p-phenyl phenol, nitrophenol, chlorophenol, and 4-methoxyphenol.

3. The process of claim 1, wherein the amount of said swelling agent is 0.5 to 50 percent based on the weight of said fibers or fabrics (o.w.f.).

4. The process of claim 1, wherein the amount of said inorganic salt is 1 to 40 percent based on the weight of the dye bath (o.w.s.).

5. The process of claim 1 wherein said neutral or acidic inorganic salt is an alkali metal salt or ammonium salt of an inorganic acid.

6. A process for dyeing fibers or fabrics of an aromatic polyamide having an aromatic ring in the recurring units with acid dyes, which comprises dip dyeing said fibers or fabrics of an unmodified aromatic polyamide in which the recurring unit of the molecular chain is expressed by a recurring unit selected from the group consisting of:

i. -- NH-Ar.sub.1 -CO -- , wherein Ar.sub.1 is phenyl,

ii. -- NH-Ar.sub.1 -NHCO-Ar.sub.2 -CO -- , wherein Ar.sub.1 and Ar.sub.2 are the same or different, and represent phenyl or naphthyl,

iii. -- NH-R.sub.1 -Ar.sub.1 -CO -- , wherein Ar.sub.1 is phenyl and R.sub.1 is an alkyl group of 1 - 4 carbon atoms,

iv. -- NH-R.sub.1 -Ar.sub.1 -R.sub.2 -NHCO-Ar.sub.2 -CO--, wherein Ar.sub.1 and Ar.sub.2 may be the same or different, and represent phenyl or naphthyl, and R.sub.1 and R.sub.2 may be the same of different and represent an alkyl group of 1 - 4 carbon atoms, and

v. combinations of two or more of units (i) to (iv), in an aqueous dye bath comprising an acid dye of the monosulfonic acid, monosulfonic acid-carboxylic acid, disulfonic acid, disulfonic acid-carboxylic acid, or carboxyiic acid type expressed by the formula

D----am).sub.p

wherein D represents a dye molecule matrix, A represents --SO.sub.3 -- or --COO-- residue, M represents hydrogen or an alkali metal, and p is an integer of 1 to 3, with the proviso that A is only --SO.sub.3 -- and when A contains both --SO.sub.3 -- and --COO--, the maximum number of --SO.sub.3 M is 2,

and at least 1 percent by weight, based on the weight of the dye bath, of a neutral or acidic inorganic salt in the presence of a swelling agent selected from compounds having a phenolic hydroxyl group expressed by the following formula

Ho--ar.sub.3 --R.sub.3

wherein Ar.sub.3 is a phenyl or naphthyl group, R.sub.3 is a member selected from the group consisting of hydrogen, lower alkyl groups, halogen, a nitro group, lower alkoxy groups, and a phenyl group, and when Ar.sub.3 is a naphthyl group, R.sub.3 is hydrogen or a lower alkyl group,

and alkali metal salt thereof; and soaping the dyeing obtained.

7. The process of claim 6 wherein said neutral or acidic inorganic salt is an alkali metal salt or ammonium salt of an inorganic acid.