WO1995031506A1

WO1995031506A1 - Dyes for leather

Info

Publication number: WO1995031506A1
Application number: PCT/GB1995/001092
Authority: WO
Inventors: David Greenwood
Original assignee: Zeneca Limited
Priority date: 1994-05-17
Filing date: 1995-05-15
Publication date: 1995-11-23
Also published as: JPH10500162A; CA2189138A1; GB9409998D0; AU2451195A

Abstract

Dyes of formula (I), in which R1 is an alkyl or cycloalkyl group preferably having 1 to 6 and more preferably having 2 to 6 carbon atoms which is preferably in the 4(para) position relative to the diazo group; R2 is a lower alkyl group preferably having 1 to 4 carbon atoms or preferably a hydrogen atom; R?3 and R4¿ are independently hydrogen, SO¿3?H, OH, halogen preferably Cl, CH3, NO2 or COOH groups. R?5¿ is hydrogen OH, NH¿2? or NHCOCH3; R?6¿ is OH, NH¿2?, NR?8R9¿ (in which each group R?8 and R9¿ is independently hydrogen or an alkyl or cycloalkyl group, preferably a lower alkyl group having 1 to 6 carbon atoms or one of the groups R8 or R9 can be an amino alkyl group preferably having 1 to 6 carbon atoms for example an amino propyl group) or NHPh in which Ph represents a phenyl or substituted phenyl group; and R7 is hydrogen SO¿3?H, a halogen preferably Cl or CH3.

Description

DYES FOR LEATHER

THIS INVENTION relates to dyes for leather. In dyeing leather the skin to be dyed is usually brought into contact with an aqueous solution which comprises a dye. The leather does not take up the whole of the dye, and the solution is usually discarded after use. It is desirable therefore to use a dye which has a high affinity for leather so that as high a proportion as possible is incorporated into the leather and as low a proportion as possible is lost. A high affinity also tends to reduce losses of dye from the leather ("colour yield") on contact with water. This is beneficial if the leather is to come into contact with the skin, as it makes discoloration of human skin less. It is also beneficial for example in the case of footwear which is worn in wet conditions. It is necessary to incorporate considerable amounts of dye if dark coloured, especially black leather is to be obtained and it is difficult to achieve this end whilst attaining a satisfactory combination of other properties.

We have now discovered a group of dyes which have a beneficial combination of properties. In general they are black.

According to the invention there is provided a water soluble compound of formula (1) or a salt thereof

R¹ is an alkyl or cycloalkyl group preferably having 1 to 6 and more preferably having 2 to 6 carbon atoms which is preferably in the 4(para) position relative to the diazo group; R² is a lower alkyl group preferably having 1 to 4 carbon atoms or preferably a hydrogen atom;

R³ and R⁴ are independently hydrogen, S0₃H, OH, halogen preferably Cl, CH₃, N0₂ or COOH groups. R⁵ is hydrogen OH, NH₂ or NHCOCH₃; R⁶ is OH, NH₂, NR^aR⁹ (in which each group R⁸ and R⁹ is independently hydrogen or an alkyl or cycloalkyl group, preferably a lower alkyl group having 1 to 6 carbon atoms or one of the groups R⁸ and R⁹ can be an amino alkyl group preferably having 1 to 6 carbon atoms for example amino propyl group) or NHPh in which Ph represents a phenyl or substituted phenyl group; and R⁷ is hydrogen S0₃H, halogen for example, Cl or CH₃.

A particularly preferred compound is of formula

in which R¹⁰ is an alkyl group having 2 to 4 carbon atoms. It is preferred that there should be a total of three sulphonic acid groups as the only acidic groups present other than OH groups.

Compounds according to the invention may be made for example by the tetrazotisation of a 4,4^α dia inodiphenylamine substituted by the appropriate groups R³ and R* and coupling it with "H acid", i.e.

under acid conditions and subsequently reacting the product with a diazotised aniline having the appropriate R¹ and R² groups as substituents suitably under acidic conditions. The product may then be coupled with a compound having a benzene ring substituted by the groups R⁵, R⁶ and R⁷ under alkaline conditions. The product may be precipitated from aqueous solution by the addition of sodium chloride and filtered or centrifuged.

The dyes and compounds mentioned in this specification may be in the form of a salt with any cation, preferably and alkali metal cation, for example sodium, potassium, lithium or a mixture thereof.

According to a further aspect of the present invention there is provided a process for the coloration of a substrate by applying thereto a compound of Formula (1) as hereinbefore defined.

The dyes of the invention have been found to be particularly well suited for the coloration of leather due to their good dyeing properties, and notable light fastness. The present dyes can be applied to leather as an aqueous solution by spray, paddle, brush, tray or solvent dyeing, but are preferably applied by drum dyeing. It is preferred that dyeing is carried out at a temperature in the range of 35° to 70°C, more preferably 55 to 65°C, and at a weakly acid pH, e.g. Ph 3.8 to 6.5. The ratio of dye solution to leather (by weight) can be quite low, for example in the range 2:1 to 8:1. The aqueous solution preferably contains 0.1 to 20 grammes of a dye according to the invention per lOOg of water.

The present dyes may be applied to all types of leather, and in particular to wet full chrome leather, retanned side leather, suede, mordant leather (e.g. nappa sheepskin full grain leather) and vegetable tanned leather.

According to further aspects of the present invention there is provided leather coloured with a dye according to the present invention or when coloured according to the present process.

In the following examples, which are not intended to limit the scope of the present invention, all parts and percentages are by weight unless stated otherwise.

EXAMPLE 1

4-4¹ Diaminodiphenylamine-2-sulphonic acid (ll.lβg 0.04 ) was stirred at ambient temperatures for one hour with water (113 ml) and hydrochloric acid (15.8 ml @ 35% str. 0.18 ). The suspension was cooled externally to

<5°C and a solution of sodium nitrite (5.65g, 0.082M) in water (25 ml) was added dropwise during 30 mins, a little ice being added to keep temperature <5°C. The suspension was stirred at 0-5°C for IV* hrs and the slight excess of nitrous acid destroyed with 10% aqueous sulphamic acid.

4N-sodium acetate was then added to adjust the pH to 3.2 forming a tetrazo suspension. H-acid, i.e.

(12.12g, 0.038M) was suspended in water (100 ml) and the pH adjusted to 6.0 with sodium hydroxide solution. (46% str.) This solution was added dropwise during 3 hours to the vigorously stirred tetrazo suspension whilst keeping temperature below 5°C. The pH was then adjusted to 2.2 with 4N-sodium acetace solution and stirring continued for several hours whilst the temperature was allowed to rise to 15°C, maintaining pH 2.2. Stirring was continued overnight at pH 2.2 and ambient temperature, thus forming a "diazo mono azo" compound.

2N-sodium nitrite solution (24.5 ml) was gradually added to a stirred ice-cold solution of 4-ethylaniline (5.8g, 0.048M) in water (100 ml) and hydrochloric acid (11.3 ml @ 35% str. 0.128M). The HN0₂ was substantially consumed in 10 minutes as checked with a sulphone indicator. The slight excess of nitrous acid was destroyed by addition of 10% aqueous sulphamic acid solution and the filtered diazo solution added 'all at once' to the stirred ice-cold suspension of "diazomonoazo" compound prepared above. The pH was adjusted to 8 with 20% sodium carbonate solution and stirring at pH 8.0-8.5 continued for 6 hours whilst permitting the temperature to rise to ambient temperature. Stirring at ambient temperature was continued for a further hour and a solution of 3- aminophenol (4.84g, 0.0444M) in water (100 ml) at pH 9 (NaOH) was then added "all at once' to the suspension. The pH was adjusted to 9 with 20% sodium carbonate solution and stirring at this pH and ambient temperature was continued for 18 hours.

Sodium chloride (20% w/w was added to precipitate the product at 80°C and this was repeated a further two times. The well pressed filter cake was milled in a Silverson mixer with acetone (1 litre) , the product was collected by filtration, and after being washed with acetone (500 ml) was dried at 70°C.

Yield, 16.5g of solid of which 64.8% was dye, the balance being largely sodium chloride. This dye is referred to as dye A.

The dye may be isolated as potassium salt using potassium chloride to precipitate the dye instead of sodium chloride.

Similar preparations using 4-N butyl aniline (dye B) and 4-isopropyl aniline (dye C) instead of 4-ethyl aniline were also carried using the above procedure, precipitation being carried out using potassium chloride. These dyes are referred to respectively as A, B and C.

EXAMPLE 2

The dyes from Example 1 and two known dyes for comparison "Coriacide" Black SB and "Daramene" Black 3B (respective formulas as follows) were applied to various leather substrates as described below.

(Coriacide Black SB)

(Daramene Black 3B) a) Dying on Wet Full Chrome Leather

A dyebath drum was prepared containing wet full chrome leather, water at 60°C ± 5°C (80 to 200 ml per piece of leather) and 0.3% Dye from Example 1 by weight based on the wet weight of the leather pieces. After 35 minutes emulsified anionic fat liquor (i.e. a water-oil emulsion, 1.5% of the anionic fat based on the wet weight of leather) was added, followed 15 minutes later by sufficient formic acid to adjust the pH to 3.5 to 4. After a further 15 minutes the dyed leather pieces were removed from the dyebath, rinsed for 5 minutes with cold, soft running water, sammed, (i.e. squeezed to remove liquid) dried at 55°C ± 5°C and staked (staked means that the leather was softened by working it over a blunt blade) . The leather was dyed black with dyes A and B showing a higher colour yield than both of the comparative dyes, good stability to acids in the dye bath and good fastness properties. b Dyeing of Retanned Side Leather Dyeing was carried out by running pieces of chrome retanned side leather in a drum containing 2% of dye by weight based on the wet weight of the leather from Example 1 in water, at 60°C over 30 minutes, followed by addition of fat liquor as above and 30 minutes later by 0.75% based on the weight of the dry leather of formic acid. After 30 minutes running the pieces were rinsed, horsed up for 24 hours (horsed up means the leather pieces were placed over a special stand called a "horse" to drain) . The dyes penetrated the leather pieces well and gave a black colour. Dyes A, B and C give much higher and higher colour yields respectively than the comparative dyes with higher light fastness. c) Dyeing on Dried Chrome Retanned Leather (Suede)

Pieces of chrome tanned leather retanned with synthetic tanning agents fat liquored as above, dried and buffed (suede) were cut along the spine to give pieces of approximately 18 cm x 24 cm.

The pieces were re-wetted over 2 hours in a bath containing water at 60°C ± 5°C (80-200 ml/piece) , ammonia (2% by weight) , and a wetting agent sold under the name "SUNAPTOL" MB, 0.5% by weight, rinsed and sammed.

The pieces were dyed over 50 minutes in a drum containing water at 60°C ± 5°C (80-200 ml/piece) and 8- 10% by weight of dye from Example 1. Formic acid (equivalent to half the weight of dye used) was then added to the liquor and after 30 minutes the pieces were rinsed, sammed, dried at 55°C ± 5°C and staked. The dye compositions dyed the leather pieces black with good light fastness dyes A and B showing much higher colour yield than the comparative dyes with acceptable fastness. d) Dyeing on Dried Chrome Retanned Leather (Nappa Sheepskin - Full Grain)

Pieces of Nappa sheepskin (full grain) were treated as described above for dried chrome retanned leather (suede) . The leather pieces were dyed black. Dye A showed a much higher colour yield and Dyes B and C a higher colour yield than the comparative dyes with acceptable fastness. e) Dyeing on Dried Vegetable Tanned Leather

Crust vegetable tanned leather (i.e. leather which had been converted to the crust state by drying in the tanned, but not finished, state) was cut along the spine into pieces of approximately 18cm x 24cm.

The pieces were rewetted in a bath containing 80 to 200ml of water per piece, at 45°C ± 5°C over 45 to 60 minutes, and sammed. Dying of the pieces was carried out over 45 minutes in a drum containing 50 to 70ml of water at 45°C ± 5°C per piece of leather and 4% by weight of dye from Example 1. The liquor was then acidified using formic acid (equivalent to half the weight of dye used) and after 30 minutes the dyed pieces of leather were rinsed for 5 minutes with cold, soft, running water, sammed and dried at 55°C ± 5°C. The leather pieces were dyed black. Dye B showed an exceptionally high colour yield and dye A a higher colour yield than the comparative dyes.

Claims

1 A water soluble compound of formula ( 1 )

in which

R¹ is an alkyl or cycloalkyl group preferably having

1 to 6 and more preferably having 2 to 6 carbon atoms which is preferably in the 4(para) position relative to the diazo group;

R² is a lower alkyl group preferably having 1 to 4 carbon atoms or preferably a hydrogen atom;

R³ and R⁴ are independently hydrogen, S0₃H, OH, halaogen preferably Cl, CH₃, N0₂ or COOH groups.

R⁵ is hydrogen OH, NH₂ or NHCOCH₃;

R⁶ is OH, NH₂, NR⁸R⁹ (in which each group R⁸ and R⁹ is independently hydrogen or an alkyl or cycloalkyl group, preferably a lower alkyl group having 1 to 6 carbon atoms or one of the groups R⁸ or R⁹ can be an amino alkyl group preferably having 1 to 6 carbon atoms for example an amino propyl group) or NHPh in which Ph represents a phenyl or substituted phenyl group; and

R⁷ is hydrogen S0₃H, a halogen preferably Cl or CH₃.

A compound of formula

SO,H Sθ,H in which R¹⁰is an alkyl group having 2 to 4 carbon atoms. A compound as claimed in Claim 1 or 2 which is in the form of a salt. A compound as claimed in any preceding claim in which the only acidic grops present are the three sulphonic acid grops shown and -OH groups. A process of making a compound according to any preceding claims which comprises tetrazotising a 4,4 diaminodiphenylamine substituted by the appropriate groups R³ and R⁴, coupling it with a compound of formula

OH NH₂

under acid conditions and subsequently reacting the product with a diazotised aniline having the appropriate R¹ and R² groups as substituents suitably under acidic conditions.

A process according to Claim 5 in which the product thereof is coupled with a compound having a benzene ring substituted by the groups R⁵, R⁶ and R⁷ under alkaline conditions.

A process of colouring a substrate which comprises contacting it with a compound according to any of claims 1 to 4 or produced by a process according to

Claim 5 or 6.

A process according to claim 7 in which the substrate is leather.

A process according to Claim 7 or 8 in which the compound in contacted with the substrate as an aqueous solution. A process as claimed in Claim 9 which is carried out at a temperature of 35 to 70°C and a pH of 3.8 to 6.5.