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The application of imported dyes in leather dyeing is restricted by the European market's non-carcinogenic aromatic amine dyeing, forcing domestic tanning technicians to use azo-free black dyes, but the dyeing is not black. This process technology overcomes this problem and has achieved good results when it is used to dye black suede leather from Shenzhen Ruihua and Luen Tai cows, Zhejiang Jiangshan black suede leather, Dalian Jinma black nubuck leather, and Henan Kuroda bright black goat glove leather. The results of large-scale production show that: The blackness is good, the color is full, and the residual liquid after dyeing is clear, reducing pollution. 1． Selection and use of dyes When selecting dyes in production, the impact of dye performance on product quality and price should generally be considered. ； For tanneries, how to ensure good dye penetration is a difficult problem to solve. Some dyes with good surface dyeing effects are difficult to penetrate ； On the other hand, some simple dyes penetrate easily into the skin but lack good color fastness. However, Black FT and Black GRN are acidic leather dyes without the above-mentioned defects and are more suitable for base dyeing because they have a small molecular weight, below 350, good permeability, and only one SO3H group. ； Based on top dyeing, the surface color is thick and full, and the dry and wet rubbing fastness is good. During operation, it is generally added directly from the drum door in powder form. 2. The methods and experience of dyeing black are different, and the dyeing methods are also different. Pigskin suede leather is dyed black. If it needs to be dyed through, as long as the surface is dark enough, no other filling and retanning agents are needed to avoid affecting the feel and color. Based on this characteristic, we use a secondary dyeing method (taking reddish black as an example). The recipe is as follows: First time base dyeing: Black FT2%, Black FH/C0.5%, Brown MSR0.08%. Second over-dyeing: Black FH/C1.8%, Black FT0. %, Brown MSR0.06%. The internal temperature of the drum is around 55°C. After the first dyeing, oiling, and acid addition, the pH is controlled at 3.8-4.0 ； The second coloring is carried out in the same bath, and the pH value at the end is 3.4-3.6. Add 0.8% chromium powder and turn for 20 minutes. The dyeing of cowhide and sheepskin requires thorough dyeing. In order to dye the leather through, the dye must fully penetrate into the inner layer of the leather. For this reason, the skin must be completely neutralized before dyeing. The incision must be completely yellow when measured with methyl red, and the pH value should be 5.5-6.0. The purpose of neutralization is to reduce the positive charge on the surface of chrome tanned leather, ease the combination of dye and leather surface, and facilitate the penetration of chromium-tanned dye. The dyeing method generally adopts the normal temperature and less bath method. This method also greatly improves the absorption of dyes. Because the dye concentration is high, and the skins are squeezed against each other, it is easier for the dye to penetrate. Unlike the conventional method, there will not be too much surface binding, which will affect the penetration, and avoid pollution caused by too much dye remaining in the residual liquid. However, care must be taken to prevent the leather from knotting. Generally, a little grease or a small amount of SY anti-knot agent is added to control it. When dyeing is required, we often use Black FT, which can easily penetrate into the inner layer of the leather and takes only 30 minutes to penetrate. For top dyeing, use Black FH/C. Due to the short rotation time during dyeing, the loose surface rate and leather tear rate of the finished leather are reduced, and the price is lower. 3. Process examples and discussion of sheepskin garment leather dyeing process: Neutralize: 200% water, temperature 30°C, sodium acetate 1.5%, ammonium bicarbonate 1%, PAK-N 0.5%, rotate for 90 minutes, use methyl red to test the incision to be fully transparent. Dye filling: 80% water, room temperature, 1% SF-100 fatliquor (made in Taiwan), 1.5% ammonia, Black FT 2.6%, AG (BASF) 2%, D (BASF) 1%, rotate for 60 minutes, after the incision is fully transparent, heat water to a liquid-to-liquid ratio of 2.5, temperature 55°C, rotate for 10 minutes. Fatliquor: SE (produced in Shanghai) 3%, Kezhi 1# (produced in Tingjiang) 3%, 94S (produced by Sima Company) 2%, SF-100 (produced in Taiwan) 4%, rotate for 50 minutes. solid color: Formic acid 1.5% was added in two batches, the total rotation time was 30 minutes, and the water was changed. Surface staining: 200% water, temperature 55℃, YU-ＴＯＲＦＣ (deepening agent) 0.8%, 氒钒terpene じ钿?〉傂 fine sweat 阒菔 Salvation Huo Malaria 锭锟斤拷鰇??ぞ吖愠∪?? Contact number: 020-8669 8192.16%, turn for 30 minutes. solid color: Formic acid 1.2%, rotate for 20 minutes. fixed: Chromium powder 1%, turn for 15 minutes. The black dyeing process of cowhide split suede and Nubuck leather is the same as that of sheepskin clothing leather, except that there are two more drying processes in the middle, followed by grinding and coloring. ； However, when wearing black sets, you must pay attention to the water return time not being too long. Generally, the time is controlled to 30 minutes for home use. ； Due to the long time and the leather has been fully rewetted, the penetration of the dye is greater than the surface binding, which easily results in insufficient blackness, the pile head of the cow second-layer suede leather becomes longer and thicker, and the sides of the cow buckle leather become loose. Secondly, when the cowhide cover is black, you can reasonably use cationic additives such as YUTOR-FC (deepening color fixing agent), AL tannin, etc. Proper use can increase the blackness and fastness. When adding dye, 2% synthetic fatliquor can be added together with the dye to increase its brightness and moist feeling. 4. Precautions when dyeing leather black. At the end of leather dyeing, it should be thoroughly washed to remove suspended matter on the surface to prevent color fading. ； 0.5% chromium powder can also be added, because Cr3+ can increase the chance of coordination and complexation between dyes and leather fibers, thereby further increasing the colorability of the fibers and achieving a color-fixing effect. Do not add too much acid when dyeing leather black, otherwise pigmentation will easily accumulate on the leather surface, forming powdery particles that appear bronze. ； When the leather is dyed black and top-dyed, the temperature is slightly higher, which can increase the speed of the combination of the dye and the leather surface. In terms of the use of chemical additives, use as little color-based grease and tannin additives as possible, such as SCF combined fatliquor, OS tannins, etc. When using cationic additives, be careful not to leave unabsorbed grease and other anionic auxiliary materials in the dye solution, otherwise the combination of anionic and cationic materials will easily produce a gel phenomenon. 5. Summary: Leather blackening involves a wide range of factors, including water quality, fatliquor, additives, temperature, water volume, the speed of feeding, the leather before dyeing, the pH value during the dyeing process, the particle size of the black dyeing powder and the coordination of the before and after processes, and the performance of the material itself will all affect the depth of leather blackening. someone said: It is difficult to dye leather black, and there are big changes in red light black, blue light black, and bald head. In fact, as long as you are familiar with the characteristics of black dye and use the process method properly, you can dye black leather of any depth and color with ease. This post was last edited by zxh6267 on 2009-4-6 17:50 ]