Method for Dyeing of Natural Leathers Using Reactive Dyes

The present invention relates to a method for dyeing of natural leathers.

At present, natural leather materials are mainly dyed by acid dyestuffs, direct dyestuffs, basic dyestuffs, etc., however, the thus dyed leathers are not sufficient in alkaline fastness, wet fastness, etc., and a method for dyeing by using reactive dyestuffs has been also tried.

In the case of dyeing the natural leather materials with ordinary reactive dyestuffs having the reactive group(s) such as a monochlorotriazinyl group, a dichlorotriazinyl group, a monofluorotriazinyl group, a vinylsulfonyl group and the like, the acid-binder which is necessary for causing the reactive dyestuff to dye the leather material, or the substance which releases the acid-binder by heating, etc., for instance, sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, sodium metasilicate, trisodium phosphate, tripotassium phosphate, potassium pyrophosphate, sodium pyrophosphate, sodium hydrogencarbonate, sodium trichloroacetate and the like spoils the physical properties (the strength, the touch, etc.) of the natural leather material therefore a method for dyeing of the natural leather materials with ordinary reactive dyestuffs did not carried out commercially. Moreover, in the case of dyeing the natural leathers by acid dyestuffs, direct dyestuffs or basic dyestuffs, a use of a large amount of inorganic electrolytes such as sodium chloride, sodium sulfate and the like is required, and such an inorganic electrolyte not only gives detrimental effects on the physical properties of the leather but also the use thereof is not economically profitable.

Accordingly, the development of a method for obtaining the dyed natural leather which are excellent in fastness, particularly in light fastness, alkaline-sweat fastness, and wet fastness by using a dyestuff not using any acid-binder which spoils the physical properties of natural leather, any substance which releases an acid-binder by heating, etc. nor any inorganic electrolyte which is economically unprofitable has been eagerly required.

As a result of the present inventors' studies for finding a dyeing method which may give excellent dyed natural leather without using any acid-binder or any substance which releases the acid-binder nor any inorganic electrolyte, the present invention has been attained.

In an aspect of the present invention, there is provided a method for dyeing natural leathers, comprising dyeing the natural leather by an exhaustion method using a reactive dyestuff having at least one S-triazinyl group to which a substituent group having a quaternary nitrogen atom is bonded via the quarternary nitrogen atom in an aqueous dye bath.

The present invention relates to a method for dyeing natural leather materials by an exhaustion method using a reactive dyestuff having at least one S-triazinyl group to which a substituent group having a quarternary nitrogen atom is bonded via the nitrogen atom in an aqueous dye bath.

As the substituent group having a quarternary nitrogen atom ##STR1## according to the present invention, the following groups may be mentioned.

(1) A quarternary pyridinium group is represented by the formula (I): ##STR2## wherein R.sup.1 and R.sup.2 represent independently a hydrogen atom, a chlorine atom, a bromine atom, a methyl group, a sulfo group, a carboxyl group, a carbamoyl group, an alkoxy (C.sub.1 .about.C.sub.4) carbonyl group and a cyano group, and the concrete instances of the formula (I) may be mentioned as follows. ##STR3##

(2) A quarternary ammonium group is represented by the formula (II): ##STR4## wherein R.sup.3, R.sup.4 and R.sup.5 independently represent an alkyl (C.sub.1 .about.C.sub.4) group, a hydroxyalkyl (C.sub.1 .about.C.sub.4) group, a benzyl group, a sulfoalkyl (C.sub.1 .about.C.sub.4) group, a carboxyalkyl (C.sub.1 .about.C.sub.4) group and an alkoxy (C.sub.1 .about.C.sub.4) alkyl (C.sub.1 .about.C.sub.4) group, and the concrete instances of the formula (II) may be mentioned as follows. ##STR5##

In the present invention, the reactive dyestuffs having at least one S-triazinyl group to which a substituent group having a quarternary nitrogen atom is bonded via the nitrogen atom(s) are represented by the following formulae.

(1) The dyestuffs represented by the formula (III): ##STR6## wherein Y represents a group ##STR7## D represents a chromophore having at least one water-soluble group, and D is bonded to the triazinyl group via a group ##STR8## wherein R is a hydrogen atom or a C.sub.1 to C.sub.3 alkyl group, and A represents an unsubstituted or substituted amino group, an alkoxy group or a phenoxy group, which does not react with the chromophore.

(2) The dyestuffs represented by the formula (IV): ##STR9## wherein both Y.sup.1 and Y.sup.2 are the group ##STR10## or one of Y.sup.1 and Y.sup.2 is the group ##STR11## and the other of Y.sup.1 and Y.sup.2 represents a chlorine atom, a fluorine atom or a bromine atom; X represents a diamino residual group bonded to the triazinyl group via the two amino groups (--NH--) and D and A are as defined above.

(3) The dyestuffs represented by the formula (V): ##STR12## wherein D, X, Y.sup.1 and Y.sup.2 are as defined above.

(4) The dyestuffs represented by the formula (VI): ##STR13## wherein D, A, Y.sup.1 and Y.sup.2 are as defined above.

As the chromophore represented by D in the formulae (III) to (VI), for instance, those chromophores such as azo dyestuffs, metal-containing azo dyestuffs, formazane dyestuffs, phthalocyanine dyestuffs, anthraquinone dyestuffs, etc. may be mentioned and they have at least one water-soluble group such as a sulfo group of a carboxyl group.

As the unsubstituted or substituted amino group, alkoxy (C.sub.1 .about.C.sub.4) group or phenoxy group which does not react with the dyestuff, and is represented by A, for instance, the following groups may be mentioned:

an amino group, alkylamino groups such as a methylamino group, an ethylamino group, a propylamino group, a butylamino group, a dimethylamino group, a diethylamino group, an N-methyl, N-ethyl amino group, an octylamino group and a cyclohexylamino group, hydroxyalkylamino groups such as a monoethanolamino group and a diethanolamino group, cyanoalkylamino groups such as a .beta.-cyanoethylamino group, and a di-.beta.-cyanoethylamino group, a .beta.-sulfoethylamino group, --NHC.sub.2 H.sub.4 SO.sub.3 H, --NHCH.sub.2 COOH, an anilino group, anilino groups substituted by a chlorine atom, a sulfo group, a lower alkyl group, a lower alkoxy group a nitro group or a carboxyl group such as an o-, m- or p-sulfoanilino group, a 2,5-disulfoanilino group, an o-, m- or p-toluidino group, an o-, m- or p-methoxyanilino group, an o-, m- or p-chloroanilino group, a 2-methyl-4-sulfoanilino group, a 2-methoxy-4-sulfoanilino group, a p-nitroanilino group, a 2-sulfo-4-methylanilino group, a 4-chloro-2-sulfoanilino group, an o-, m- or p-carboxyanilino group and a 2-carboxy-4-sulfoanilino group, an N-methylanilino group, an N-ethyl-4-chloroanilino group, alkoxy groups such as a methoxy group, an ethoxy group, a propoxy group and a butoxy group, alkoxyalkoxy groups such as a methoxyethoxy group, an ethoxyethoxy group and a methoxypropoxy group, a phenoxy group, substituted phenoxy groups by a chlorine atom, a nitro group, a methyl group, a sulfo group, a carboxyl group and the like such as an o-, m- or p-chlorophenoxy group, an o-, m- or p-nitrophenoxy group, an o-, m- or p-sulfophenoxy group and an o-, m- or p-carboxyphenoxy group, a morpholino group, a piperidino group and a piperadino group.

As the diamino residual group represented by X, for instance, the following groups may be mentioned:

alkylenediamino groups such as an ethylenediamino group, a 1,3-propylenediamino group, a 1,6-hexylenediamino group, a 2-hydroxy-1,3-propylenediamino group and --NHCH.sub.2 CH.sub.2 OCH.sub.2 CH.sub.2 NH--, arylenediamino groups such as a 1,4-phenylenediamino group, a 1-methyl-2,6-phenylenediamino group, a 1,3-phenylenediamono group, a 4-sulfo-1,3-phenylenediamono group, a 4,6-disulfo-1,3-phenylenediamino group, a 2-sulfo-1,4-phenylenediamino group, a 2,5-disulfo-1,4-phenylenediamino group, a 5-carboxy-1,3-phenylenediamino group, a 2,5-dimethoxy-1,4-phenylenediamino group, a 1-N-methylaminoanilino group, a 1,2-phenylenediamino group, a 2,4,6-trimethyl-5-sulfo-1,4-phenylenediamino group, ##STR14## a 2-methyl-5-sulfo-1,3-phenylenediamino group, a 4-methyl-1,2-phenylenediamino group, ##STR15##

The reactive dyestuff represented by the formulae (III) to (VI) can be produced byreacting a precursor represented by the formulae (III) to (VI) wherein Y, Y.sup.1 and Y.sup.2 are chlorine atoms, bromine atoms or fluorine atoms respectively with a tertiary amine or an alkali metal salt thereof, preferably in an aqueous solution of pH of from 5 to 9 at a temperature of from 45.degree. to 110.degree. C.

The natural leathers which are used according to the present invention are animal leathers, which are easily available for ornamental uses and clothing uses, and as the concrete instances thereof pigskin, calfskin, cow- and oxskin, horsehide, sheepskin, reptile-skin may be mentioned.

Although it is most desirable to use a leather tanned by chrome salts (chrome tanning) in the method according to the present invention, it is possible to use rawhide before subjecting to chrome tanning or leather tanned by tannin.

Various methods may be adopted in the case of carrying out the dyeing of the natural leather according to the present invention, however, an exhaustion dyeing method is desirable.

In the case of carrying out the exhaustion dyeing method, a chrome-tanned leather is dyed as follows.

A leather subjected to tanning by the use of sodium bichromate, etc. is treated in warm water, if chrome salts remain in the chrome-tanned leather, in warm water containing sodium bicarbonate, sodium formate, ammonia, etc., thereby subjecting to neutralization of the tanned leather. Then, the thus treated leather is dyed in the bath wherein neutralization were carried out or in an another bath.

Namely, the leather is at first treated in an aqueous dye bath containing the reactive dyestuff having at least one S-triazinyl group to which a substituent group having a quaternary nitrogen atom is bonded via the quaternary nitrogen atom for from 20 to 60 min at a temperature of from 20.degree. to 40.degree. C., thereby penetrating the dyestuff into the inner part of the leather. This step is so-called penetration of dyestuff.

Then, the thus treated leather is dyed for 20 to 60 min at a somewhat higher temperature than that of "penetration of a dyestuff" step, i.e. from 40.degree. to 60.degree. C., and after subjecting the thus dyed leather, if necessary, to neutralizing treatment and to fatting treatment by an ordinary method, the fatted leather is washed with water and dried.

On the other hand, in the case of carrying out the rapid dyeing method, the chrome tanned leather is, after being treated by sodium bicarbonate, sodium formate, etc. as neutralization step in accordance with the necessity, dyed in an aqueous dye bath containing the dyestuff having at least one s-triazinyl group to which a substituent group having a quaternary nitrogen atom is bonded via the quaternary nitrogen atom for from 15 to 60 min at a temperature of from 40.degree. to 60.degree. C. Then, the dyed leather is subjected to fatting treatment by an ordinary method, washed with water and dried.

In the case of carrying out the dyeing of the natural leather according to the present invention, the dyestuff defined as above is used in amount of till 10% by weight of the natural leather.

Also on the leather not yet subjected to tanning by chrome salts or the leather tanned by tannin, dyeing can be carried out according to the above-mentioned methods.

In addition, after dyeing, it is favorable to carry out neutralizing the dye bath and then fatting by adding a fatting agent to the dye bath.

In order to obtain a higher grade in alkaline-sweat fastness wet fastness of the dyed leather material, the dyed and fatted leather material may be subjected further to after-treatment by a fastening agent. As the fastening agent, those used for cellulosic fibers can be used and as the concrete instance, polymers of dimethyldiallylammonium chloride, polyethylenepolyamine and the like may be mentioned. Of them, polymers of organic- or inorganic acid salt of diallylamine are preferable. The treatment of the dyed leather by the fastening agent is ordinarily carried out as follows.

The dyed leather which has been subjected to fatting treatment is treated in an aqueous solution containing 0.1 to 50 g/liter, preferably 0.5 to 10 g/liter of a fastening agent for 5 to 20 min at a temperature of from 40.degree. to 60.degree. C., washed with water and dried.

In a method of dyeing natural leathers according to the present invention, by using a reactive dyestuff having at least one S-triazinyl group to which a substituent group having a quaternary nitrogen atom is bonded via the quaternary nitrogen atom the dyed natural leathers which are excellent in fastnesses, particularly in light fastness, alkaline-sweat fastness and wet fastness are obtained. Further, in a method according to the present invention, since any acid-binder, any substance releasing the acid-binder or any inorganic electrolyte is not used, the obtained, dyed natural leathers are excellent in physical properties such as touch, strength and as a result the method according to the present invention has great economic value.

The present invention will be explained more in detail while referring to Examples as follows.

For reference, the carboxyl group and the sulfo group are shown by the free form in Examples.

Into 20 liters of an aqueous dye bath containing 300 g of the dyestuff represented by the formula (VII): ##STR16## 10 kg of the pigskin which had been tanned by sodium bichromate and subjected to neutralization treatment were added, and the temperature of the dye bath was raised to 45.degree. C. in the coure of 30 minutes. Dyeing of the pigskin was carried out thus for 45 min at the same temperature, the pH of the dye bath being 5.3 at the finishing of dyeing.

After neutralizing the dye bath by adding a diluted aqueous ammonia, 1 kg of a synthetic fatting agent (made by Hoechst Co., comprising 30 parts by weight of DERMINOLLIQUOR.RTM. EMB, 40 parts by weight of DERMINOLLIQUOR.RTM. MF and 40 parts by weight of DERMINOLLIQUOR.RTM. DF) were added thereto, and after subjecting the dyed pigskin to fatting treatment for 1 hour at 40.degree. C., 100 g of formic acid were added thereto, thereby treating the pigskin for 10 min at 25.degree. C. therein.

By further treating the thus treated pigskin in a separate bath containing 100 g of formic acid at 25.degree. C. for 10 min, washing the pigskin with water and drying thereof, the pigskin dyed in yellow was obtained.

The thus dyed pigskin showed the rating 7 as a result of light fastness test according to Japanese Industrial Standards (JIS) L0842.

On treating the thus dyed pigskin with an aqueous 50% solution of dimethylformamide for 10 min at 95.degree. C., the falling off of the dyestuff was extremely small and alkaline-sweat fastness and wet fastness of the dyed pigskin were extremely favorable. In addition, the color tone of the dyed pigskin was very clear.

Into 20 liters of an aqueous dye bath containing 300 g of the dyestuff represented by the formula (VIII): ##STR17## 10 kg of cowskin which had been tanned by chrome salts and subjected to neutralization treatment were introduced, and the temperature of the dye bath was raised to 50.degree. C. in the course of 35 minutes. Dyeing of the chrome-tanned skin was carried out in the dye bath for 50 min at the same temperature. After neutralizing the dye bath by adding a dilute aqueous ammonia, the same neutralization treatment, fatting treatment and acid treatment as in Example 1 were carried out on the cowskin, and by washing the thus treated cowskin with water and drying the washed cowskin, the cowskin dyed in red was obtained. The thus dyed cowskin showed the rating 5 as a result of light fastness test according to JIS L0842. On treating the thus dyed skin with a 50% aqueous solution of dimethylformamide (DMF), the falling off of the dyestuff was extremely small and the wet fastness of the dyed skin was extremely favorable.

The dyestuff represented by the formula (VIII) used in Example 2 was produced as follows.

Namely, 22 kg of the dyestuff represented by the formula (IX): ##STR18## were dissolved in 300 kg of water, and into the thus prepared solution, 70 kg of water containing 2 kg of sodium hydroxide and 6 kg of nicotinic acid were added, and the whole mixture was heated to 80.degree. C. After stirring the mixture for 16 hours at the same temperature, the mixture was subjected to salting out to obtain the dyestuff represented by the formula (VIII).

Into 25 liters of an aqueous dye bath containing 400 g of the dyestuff represented by the formula (X): ##STR19## 10 kg of sheepskin which had been tanned by chrome salts and subjected to neutralization treatment were introduced, and the sheepskin was dyed therein for 60 min at 40.degree. C. After subjecting the thus dyed sheepskin to the same neutralization treatment, fatting treatment and acid treatment as in Example 1, the thus treated sheepskin was washed with water and dried to obtain a blue sheepskin. The light fastness of the thus obtained, dyed sheepskin was the rating 4 according to JIS L0842. The wet fastness of the dyed sheepskin was extremely favorable. The falling off of the dyestuff from the dyed sheepskin by treating with a 50% aqueous solution of DMF was extremely small, and the color tone of the dyed sheepskin was very clear.

Dyeing of pigskin tanned by chrome salts and subjected to neutralization treatment was carried out in the same manner as in Example 1 using each one of the dyestuffs shown in the following tables, and by subjecting the thus dyed pigskin to the fatting treatment and acid treatment, the dyed pigskin of the color shown in the following table was obtained. Every one of the thus obtained, dyed pigskins showed excellent grade in light fastness, alkaline-sweat fastness and wet fastness with a very clear color tone. Example No. Structure Hue 4 ##STR20## yellow 5 ##STR21## yellow 6 ##STR22## yellow 7 ##STR23## yellow 8 ##STR24## reddishyellow 9 ##STR25## yellow 10 ##STR26## yellow 11 ##STR27## orange 12 ##STR28## orange 13 ##STR29## scarlet 14 ##STR30## red 15 ##STR31## red 16 ##STR32## red 17 ##STR33## red 18 ##STR34## blue 19 ##STR35## blue 20 ##STR36## blue 21 ##STR37## blue 22 ##STR38## greenishblue (wherein Pc represents Cuphthalocyanine, x, y and z are 0, 1, 2, 3 or 4, respectively and x + y + z = 4) 23 ##STR39## greenishblue (wherein Pc, x, y and z are the same as defined above) 24 ##STR40## blue 25 ##STR41## brown 26 ##STR42## black 27 ##STR43## orange 28 ##STR44## blue 29 ##STR45## yellow 30 ##STR46## yellow 31 ##STR47## yellow 32 ##STR48## reddishyellow 33 ##STR49## reddishyellow 34 ##STR50## yellow 35 ##STR51## yellow 36 ##STR52## orange 37 ##STR53## orange 38 ##STR54## reddishorange 39 ##STR55## red Example No. Structure Hue 40 ##STR56## red 41 ##STR57## red 42 ##STR58## violet 43 ##STR59## blue 44 ##STR60## blue 45 ##STR61## navyblue 46 ##STR62## blue 47 ##STR63## blue (wherein Pc, x, y and z are the same as defined above) 48 ##STR64## blue (wehrein Pc, x, y and z are the same as defined above) 49 ##STR65## blue 50 ##STR66## brown 51 ##STR67## black 52 ##STR68## yellow 53 ##STR69## yellow 54 ##STR70## yellow 55 ##STR71## yellow 56 ##STR72## yellow 57 ##STR73## reddishyellow 58 ##STR74## yellow 59 ##STR75## red 60 ##STR76## red 61 ##STR77## blue 62 ##STR78## greenishblue (wherein Pc, x, y and z are the same as defined above) 63 ##STR79## brown 64 ##STR80## brown 65 ##STR81## blue 66 ##STR82## red 67 ##STR83## red 68 ##STR84## blue 69 ##STR85## blue 70 ##STR86## blue 71 ##STR87## blue (wherein Pc, x, y and z are the same as defined above) 72 ##STR88## yellow Example No. Structure Hue 73 ##STR89## yellow 74 ##STR90## reddishyellow 75 ##STR91## yellow 76 ##STR92## reddishyellow 77 ##STR93## yellow 78 ##STR94## yellow 79 ##STR95## blue (wherein Pc, x, y and z are the same as defined above) 80 ##STR96## brown 81 ##STR97## brown 82 ##STR98## brown 83 ##STR99## black 84 ##STR100## blue 85 ##STR101## black 86 ##STR102## red 87 ##STR103## yellow 88 ##STR104## orange 89 ##STR105## scarlet 90 ##STR106## yellow 91 ##STR107## yellow 92 ##STR108## yellow 93 ##STR109## red 94 ##STR110## red 95 ##STR111## yellow 96 ##STR112## orange 97 ##STR113## scarlet 98 ##STR114## yellow 99 ##STR115## yellow 100 ##STR116## yellow 101 ##STR117## reddishyellow 102 ##STR118## reddishyellow 103 ##STR119## reddishyellow 104 ##STR120## red 105 ##STR121## red Example No. Structure Hue 106 ##STR122## violet 107 ##STR123## violet 108 ##STR124## scarlet 109 ##STR125## red 110 ##STR126## red 111 ##STR127## red 112 ##STR128## red 113 ##STR129## blue 114 ##STR130## red 115 ##STR131## blue 116 ##STR132## blue 117 ##STR133## yellow 118 ##STR134## red 119 ##STR135## navyblue 120 ##STR136## greenishblue 121 ##STR137## navyblue 122 ##STR138## navyblue 123 ##STR139## yellow 124 ##STR140## red 125 ##STR141## blue 126 ##STR142## navyblue 127 ##STR143## green 128 ##STR144## navyblue 129 ##STR145## navyblue 130 ##STR146## navyblue 131 ##STR147## navyblue 132 ##STR148## yellow 133 ##STR149## yellow 134 ##STR150## brown 135 ##STR151## black 136 ##STR152## black

In the process of Example 1, after treating the dyed pigskin with formic acid, the pigskin was subjected to an after-treatment in a bath prepared by dissolving 100 g of a polymer of hydrochloric acid salt of diallylamine (average molecular weight of about 3,000) in 30 liters of warm water at 40.degree. C. for 10 min and dried to obtain an after-treated yellow pigskin.

The thus obtained pigskin showed the rating 7 as a result of light fastness test according to JIS L0842.

As a result of alkaline sweat fastness test according to JIS L0848, no color-change of the dyed pigskin was observed, and the dyed pigskin did not stain cotton and wool.