how to dye suede fabric

With the improvement of living standards, people have higher and higher requirements for the bright colors and performance of leather products. As the primary material of casual shoes, cattle split suede requires a fine pile, even dyeing, and full and bright color. Still, it also emphasizes that the color of the leather incision should be the same as the surface.





To meet the market's needs, we have carried out experimental research on the problem of through-dyeing of cattle split suede leather, applied the obtained results to production, and achieved good results.

leather dyeing​

Leather dyeing is a complex physical and chemical process




Leather dyeing is a complex physical and chemical process, which is the process of penetration and binding of dye molecules to leather fibers and is the total effect of physical and chemical effects. In the whole dyeing process, adsorption, diffusion, penetration, and fixation are mutually influenced and alternated.





The leather dyeing process involves many factors, and there are many influencing factors. In addition to the mutual influence of various components that constitute the dye solution, the condition of the leather before dyeing, the control of pH value, temperature, and concentration during the dyeing process, the addition of auxiliaries, and Factors such as the coordination of the front and rear processes are critical.



We've discussed how to dye through split cattle suede for an even tone. To dye the leather thoroughly, the dye must fully penetrate the deep layer of the leather to color the deep fibers, which requires that the dyeing conditions be conducive to the penetration of the dye, and the state of the raw leather before dyeing is a crucial factor.





And the degree of control is the main factor determining the state of the leather. "Neutralization" can reduce the positive charge on the surface of chrome-tanned leather, conducive to the penetration of anionic dyes.



Neutralization and deep penetration




Neutralization and deep penetration so that the pH value of the deep layer of the leather is consistent with the surface, and the dye can be fully penetrated and slowly combined to meet the requirements of penetration. Therefore, we strengthened the neutralization, made the leather incision neutralized and fully penetrated, and controlled the neutralization pH not to exceed 5.5.



The uniform dispersion of suede fibers significantly influences the uniformity of dyeing. The fibrils in the buttocks and dorsal areas are relatively tight, and the fibers in the side and hem are relatively loose. Usually, the dyed surface is bound more in the tight fibers, and the color is dark; The use of simple fillers such as SCC acrylic filler resin for filling can not eliminate the poor position but instead causes the leather buttocks to produce "pockmarks" during sanding, which affects the quality of the product.





We switched to the auxiliary tanning acrylic resin retaining agent ART-I, which solved this problem very well because ART-I acrylic resin retaining agent has prominent selective filling properties, significantly reducing the difference between the leather parts. Make the fibers of the leather hem tight, the fibers of the natural leather are uniformly dispersed, and the dyeing is uniform. Moreover, ART-I is an anionic material that can slow down the combination of dyes and facilitate the penetration of dyes.



uniform color of the genuine leather


To achieve the uniform color of the genuine leather, and the color of the incision is the same as the surface, we have further done a lot of work in the dyeing process, referring to some foreign advanced technology, through continuous comparison and testing, we use the "dry dyeing method" dyeing to obtain the excellent effect. "Dry dyeing method" means that the dry skin and the evenly mixed dyes and auxiliaries are put into the drum without bathing thoroughly.





Then water is added to dye it after rotating evenly. Usually, the dry skin and the dye are rotated for about 20 minutes. Then a certain amount of normal temperature water and penetrating agent or auxiliary agent is added. The leather incision is entirely transparent (usually, it takes 30-60 minutes, depending on the color and thickness). Then add a Large liquid ratio, increase liquid temperature, carry out fatliquoring, and add acid to fix the color. This shortens the dyeing time and achieves the requirements of penetration.





The process technology breaks the traditional dyeing method of first re-wetting overnight and then the high temperature and sizeable liquid ratio. We use a low temperature and small liquid ratio to fully penetrate the dye, slowly combine it, and increase the liquid temperature later.





Dye speeds up the binding.


The high-concentration dye solution is fully contacted with the dry skin in this method. The strong hygroscopicity of the dry skin and the curled state of the solid molecular bonds of the dye are used to enhance the penetration of the dye.





And due to less water, the mechanical effect of the drum is enhanced, which promotes better penetration and uniform dyeing of the dye; At the same time, the temperature is low, the dyeing effect is moderate, and the binding speed of the fiber to the dye is small, the slower the coloring, the more uniform the color, and the more transparent.





Go deeper. In addition, the addition of penetrants or auxiliaries further increases the speed of dye penetration. When the incision of the leather has been dyed in the later stage, the liquid ratio and the liquid temperature are increased to weaken the penetration of the dye, accelerate the combination of the dye and the fiber, and make the surface color thick.



Suede leather is mainly used in combination with various dyes due to the needs of color plates, such as the combination of acid dyes and direct dyes or the simultaneous use of direct dyes with different properties.



Due to the inconsistent penetration speed of these dye molecules, the conventional dyeing method is likely to cause the leather cut to color to be very different from the surface color or "white heart," but the "dry dyeing method" completely avoids this phenomenon.





The reason may be that when the dye penetrates in the "dry dyeing method," the leather fibers are not completely wetted, and the binding force between the dye molecules and the fibers is minimal. In addition, the fiber gap is not entirely occupied by water molecules, and the gap is significant.



Dye molecules are easier to penetrate, and even direct dyes with larger molecules can penetrate, coloring the deep leather fibers. The color of the leather cuts is the same as the surface. Applying the "dry dyeing method," the absorption of dyes is also greatly improved because the concentration of dye liquor is high, and the penetration is good.





The dyes will not bind too much on the surface like the conventional method, affecting the penetration and making the residual dye in the residual liquid. Too much will cause pollution. Therefore, using the "dry dyeing method" can obtain ideal products and shorten working hours, save energy, and reduce pollution.





The "Dry dyeing method" has been tested and applied in production, and the product quality is stable.