How to test vat dyes

1 Visual inspection 

Visually check whether the dye is dustproof. The outer packaging of vat dyes is generally an iron drum, and there is a tie-in plastic bag inside the drum. If the dye is treated with anti-dust, then the plastic paper outside the tie of the inner bag is relatively clean. If the plastic paper is stained with dye, depending on the degree of contamination, it can be judged that the dye is not qualified or not treated. After sampling, Can be further verified.

Is the size of the dye particles of the test sample uniform and consistent with the particle size of the standard sample?

2 Inspection of dye components

Take about 0.1 g of dye on the clean white paper on the side of the table, and then take a medium-speed qualitative filter paper, moisten it (without dripping), and blow the dye on the white paper onto the filter paper with a suction ball. At this time, the dye particles are on the filter paper. Disperse on the wet filter paper, and you can see that there are several colors of dye particles in the dye. Compare and test the standard sample and the sample at the same time. Generally, synthetic dyes contain dye particles of the same color. If the wet filter paper presents one or two particles of different colors in one main color, it may be that other dye dust flew in when the dye was in the can. Synthetic dyes; if there are a small amount of particles of different colors evenly distributed on the filter paper, it is a mixed dye, and the few colors are a few dyes. Common vat dyes are GN grass green, G brown, 2G brown, BG gray, M gray, and RB black. The shades and strengths of the products of these dyes from different manufacturers are very different, sometimes from the same manufacturer. The shades of different batches produced are also very different, and there is often a phenomenon of light jumping. Therefore, when the dye particle composition of the sample and the standard sample is different, the use is restricted.

3 Diffusion test

Fill the 1L graduated cylinder with water. Sprinkle about 0.5 g of the dye on the water and carefully observe the sinking of the dye particles: if the particles sink to the bottom of the measuring cylinder quickly, it is unqualified; if they are dispersed evenly like a mushroom cloud, it is better; if they are not floating on the water If it comes down or falls very slowly, there may be no dust-proof treatment or poor wettability. Sometimes the dyes with unqualified diffusibility due to inventory in the factory must not be used, and the large-scale production of chemical materials must be fully stirred and filtered before entering the rolling tank.

4 Inspection of Lifen Shade

The dyes to be tested and the standard dyes (approved) are subject to the following dyeing tests at the same time.

①Accurately weigh 1.000g of dye in a grinding bowl, measure 100mL of 2% anti-migration agent aqueous solution, first drop about 2mL of solution to fully grind the dye, then add all of it, stir well and pour it into the square pan. After dipping two 25cm×12cm cotton semi-bleached cloths with a padding solution, they are hung with iron clamps in a constant-temperature eight-basket oven at 100°C that rotates continuously. The cloths should be hung flat and pre-dried.

②Configuration of steaming reducing solution: Dissolve 30mL of 30% caustic soda in 500mL of water, add about 15g of 85% insurance powder, stir well, pour it into a square plate after it is completely dissolved, and set aside.

③ Configure hydrogen peroxide and oxygen liquid: Pour 500mL of hydrogen peroxide 6-8g/L into the square plate and set aside.

④Compare the shades of two pre-dried dyed semi-product samples, then quickly immerse them in the reducing solution, immediately pick up and place them on the flattened plastic film, close the other half of the film, and scrape off the film with a printing squeegee Move the film package on the partition screen of the high temperature oven at 150～160℃ (the two layers of gauze khaki have been spread on the partition screen). After the stick punctures the film, take out the cloth swatch, wash it thoroughly (without alkali oxidation), soak the cloth swatch flat in an oxidation pan for full oxidation, after it has completely changed color, take it out and wash it with water, soap and boil for 30 seconds, wash it with water, and dry it.

⑤After the cloth sample is completely cold (about 30min), compare the shade and strength of the sample cloth dyed with the standard dye and the sample cloth dyed with the standard dye. If the sample cloth dyed with the test dye is better than the sample cloth dyed with the standard dye If the shade is too light or the shade deviation is obvious, it is unqualified; if the shade of the semi-finished product dyed with the dye to be tested before reduction is very different from that of the semi-finished product dyed with the standard dye, the shade of the two fabric samples is not much different after reduction. The test dye is also unqualified; if the sample cloth dyed with the test dye is too deep, estimate the depth first, and weigh the test dye at a discount of 0.9000g/100mL, 0.9500g/100mL and standard dye 1.000g/100mL for further dyeing and proofing comparison. Get the strength of the dye to be tested.

5 Fastness test 

The sample cloth dyed with the dye to be tested and the sample cloth dyed with the standard dye are tested for the fastness of soaping, brushing and rubbing according to the national standard. The fastness is fully up to the standard and the fastness of the sample dyed with the dye to be tested is not inferior to the standard. For the fastness of the dyed sample cloth, the dye to be tested is qualified. For the three dyes of BG gray, M gray and RB black, the soaping time has a great influence on the shade. During the test, the soaping time of the two sample cloths must be controlled to be consistent, so that the test results can be accurate.