DYEING VEGETABLE LEATHERS BY EGEMEN

           1-OBJECTIVE

Practice 3:  We compare the leathers  with two system :  see the differences between a set of chrome dye skins and furs to vegetable tanning.We observe crossline  and watch changers charge different influence on the intensity, hue, equalization, the affinity for skin penetration power and the degree of fixation of the dye.

          2- TECHNICAL PART

         DYEING VEGETABLE LEATHERS

•          Our third process was ;  dyeing vegetable leathers.vegetable tannage, the isoelectric point of collagen is approximately at pH = 3.4 – 4. Therefore, the leather will show a propensity for combining with cationic or basic dyestuffs. These will grant full, bright dyeings with good covering power, but with poor levelling. In addition, their excessive use may result in bronzing (i.e. metallic reflexes).

•           Vegatable tannage leather when dyeing process completely that has poor fastness . especially with cationic dyestuffs (acid dyestuffs of low molecular weight).So that anionic dyestuffs are preferred, expect when a top dyeing is desired. Hence, improve fastness and showing better to leathers. Since vegetable tanned leather has a reduced reactive power against anionic dyestuffs, in most cases it is not necessary to add auxiliary products.The most suitable dyestuffs are sulphonated triphenylmethane.

•          These dyestuffs have an amphoterous character, give full and homogeneous dyes without stressing the defects of the leather and without precipitating with the tannins. Resinified tans have to be removed and replaced by new tans

•         3.MATERIAL AND PRODUCTS 

•          formic acid: Formic acid is a organic acid so that we usually use with 1/10 -  1/5 dilution rate  . this is formic acid formula   we use formic acid  a lot of processes. Fixation  to Dyestuffs , decrease ph in pickle .

This product reduces the pH below the pI value of the leather , so that the overall charge is cationic and has a greater capacity of reacting with the anionic products subsequently added. The density of reactive points increase since at acids pH, the carboxylic groups of the protein are not in dissociated form. A greater superficial performance is obtained.

•          Aluminium sulphate : resistant to water and with adequate hydrothermal stability aluminium gives strength for leathers and  relevant with  shrinkage  temperature and  developing appearance of dyeing on surface shortly, gives homogeneity dyeing on surface with slow penetration. we have bright tones.

This product is a strong cationic product.it is decrease in pH saused owing to the hydrolysis of basic sulphate and sulphuric acid, with resulting increase in total positive charge in the leather

In addition, complex between the collagen andaluminium sulphate can be formed.Although these are not as stable as basic chrome salts, they confer a quantitative leap in cationic  reactive points.

The basic aliminium sulphate used in a dyeing is usually an intermediate complex between:

İf a small amount of formic acid is added with aluminium sulphate  in order to decrease a little the basicity of the aluminium salt so that its reactionability with the leather surface is a little slower to improve the levelling out  of the intensity.

•          aluminium sulphate with different combinations with formic acid

•          cationic oil:  cationic lubricant are more resistant to change in pH . Also they attacking and fixation grain quickly.They can’t penetration very well.  

They consist of non-natural oxyethylated organic compounds and with anionic reactive groups.

The radicals of such products also have a certain fatliquoring effect, which will result in a surface which is less dry and coarge than when an inorganic or mineral charge changer is employed.

•          chrome salt with 33 % basicity  : most common using  basicity  chrome.  There are  only one OH  group İn its structure.so that  it occurred slowly  and deeply penetration. First , the salt is anionic; after dissolving ,its charge changes to zero , and finally it becomes cationic.

Once dissolved, the trivalent chrome salts present an acid  hydrolysis :

•          mimosa:  vegetable tanning substances ,gives tightness . they are connecting OH with amino groups.

•          Anionic polymer : this is retanning substance. Like as tanning material,gives plump structure.

•          Synthetic –phenolic  retanning substances:  gives plump structure well attitude.

•          aluminium chloride:

Common name AlCl3H2O compound with aluminum hydrochloride in the skin pores of thecompression feature. Shortly , it gives firmed leathers  gives light fastness and rubber effect

Commercially, the aluminium chloride employed  has a basicity of 60-65%  approximately.Thus, the basic complex will be most formed by

And  to lesser degree by

The basicity and hence reactionability of the complex can be reduced by adding  small amount of formic acid when dissolving the salt prior to adding it to the drum.

Práctica 1: Tintura superficial

Pieles: curtidas al vegetal

% sobre peso seco

Remojo:          1000% Agua a 30ºC

                        0,1%    Humectante no iónico (1:10)

                                    Rodar 10 minutos. Reposar 8 horas, rodando 5 min/hora.

                                    Escurrir baño.

Tintura:            1000% Agua a 45ºC

                        2,5%    Colorante

                                    Rodar 20 minutos.

                        20%     Agua a 60ºC

                                    Rodar 30 minutos.

                        1,5%    Ácido fórmico (1:10)

                                    Rodar 20 minutos.

                                    Mirar pH.        

                                    Escurrir baño.

Práctica 2: Tintura atravesada

Pieles: curtidas al vegetal

% sobre peso seco

Remojo:          1000% Agua a 30ºC

                        0,1%    Humectante no iónico  (1:10)

                                    Rodar 10 minutos. Reposar 8 horas, rodando 5 min/hora.

                                    Escurrir baño.

Tintura:            300%   Agua a 30ºC

                        5%       Colorante

                                    Rodar 1 hora.

                        500%   Agua a 45ºC

                                    Rodar 10 minutos.

                        1%       Ácido fórmico (1:10)

                                    Rodar 15 minutos.

                        2,5%    Aceite catiónico

                                    Rodar 15 minutos.

                        2%       Colorante de superficie

                                    Rodar 30 minutos.

                        1,5%    Ácido fórmico (1:10)

                                    Rodar 30 minutos.

                                    Mirar pH.        

                                    Escurrir baño.

Práctica 3: Tintura atravesada

Pieles: curtidas al vegetal

% sobre peso seco

Remojo:          1000% Agua a 30ºC

                        0,1%    Humectante    (1:10)

                                    Rodar 10 minutos. Reposar 8 horas, rodando 5 min/hora.

                                    Escurrir baño.

Tintura:            300%   Agua a 30ºC

                        5%       Colorante

                                    Rodar 1 hora.

                        500%   Agua a 45ºC

                                    Rodar 10 minutos.

                        1%       Ácido fórmico (1:10)

                                    Rodar 15 minutos.

                        2,5%    Sulfato de aluminio

                                    Rodar 15 minutos.

                        2%       Colorante de superficie

                                    Rodar 30 minutos.

                        1,5%    Ácido fórmico (1:10)

                                    Rodar 30 minutos.

                                    Mirar pH.        

                                    Escurrir baño.

Práctica 4: Tintura atravesada

Pieles: curtidas al vegetal

% sobre peso seco

Remojo:          1000% Agua a 30ºC

                        0,1%    Humectante    (1:10)

                                    Rodar 10 minutos. Reposar 8 horas, rodando 5 min/hora.

                                    Escurrir baño.

Tintura:            300%   Agua a 30ºC

                        5%       Colorante

                                    Rodar 1 hora.

                        500%   Agua a 45ºC

                                    Rodar 10 minutos.

                        1%       Ácido fórmico (1:10)

                                    Rodar 15 minutos.

                        2,5%    Cloruro de aluminio

                                    Rodar 15 minutos.

                        2%       Colorante de superficie

                                    Rodar 30 minutos.

                        1,5%    Ácido fórmico (1:10)

                                    Rodar 30 minutos.

                                    Mirar pH.        

                                    Escurrir baño.

4 -  DISCUSSION AND CONCLUSION

Compare of darkness colour is difficult for crust learhers.Because  result of crusts very near . but if we should  make a sort , we can say : 5>1>2>3>4. They are softer than wet blue and vegetable leathers.We just use cationic oil in Formula 2 (leather 2) so that it is softer than all leathers.

 GENERAL DISCUSSION AND CONCLUSION  FOR WET-BLUE , CRUST AND VEGATABLE

We observe all leathers we can say vegetable leather has got darkest colour.Second is crust  and at last is wet-blue .