Identification method for printing and dyeing textile cellulose fiber dyes

The color fastness is an important assessment index for printing and dyeing textiles. Different types of dyes have different evaluation indexes for color fastness. Different dyes have different molecular structures, chemical properties, etc. In the same way, some dyes chemically react with textile fiber molecules and bond to textiles in a chemical bond. Some dyes are fixed on textiles by means of physical reactions. Therefore, their color fastness indicators are reviewed. It is not the same. The types of dyes on textiles are difficult to distinguish with the naked eye and must be determined accurately by chemical methods. Our current general practice is to rely on the types of dyes provided by factories or applicants, together with the experience of inspectors and understanding of production plants. To judge. If we do not identify the type of dye in advance, it is very likely that the nonconforming product will be judged as a qualified product, which undoubtedly has a great disadvantage. There are many chemical methods to identify dyes, and the general procedures are complicated and time-consuming. Therefore, this article describes a simple identification method for dye types on cellulose fibers in textiles.

1 Determining the principle of the simple identification method According to the dyeing principle of dyes on textiles, the common types of dyes commonly used for textile components are as follows: Lun fiber - cationic dyes, nylon and protein fibers - acid dyes, polyesters and other chemical fibers - disperse dyes? Cellulose fibers - direct, reactive, reactive, reducing, naphthol, coatings and anthraquinone dyes. For blended or interwoven textiles, the type of dye is used for its composition, for example, for polyester and cotton blends, where The polyester component is a disperse dye, and the cotton component is performed using the above-mentioned corresponding dye species, such as dispersion/activity, dispersion/reduction process and the like. According to dyeing theory, the main factor affecting the color fastness of textiles depends on the type of dye used for cellulose fibers. Therefore, how to determine the dye type of cellulose fiber is the key.

2 Identification of dye types on cellulose fibers 2.1 Sampling and pre-treatment Identification of the types of dyes on cellulose fibers The key steps are sampling and sample preparation. When taking a sample, the same dye site should be taken. If the sample contains several shades, each shade should be taken. If fiber identification is required, fiber type should be confirmed according to FZ/TO1057 standard. If the test sample contains impurities, grease, and slurry that affect the test, it must be treated with hot detergent in 60-70°C hot water for 15 minutes, washed, and dried. If the sample is known to be resin-finished, it is treated with the following methods, respectively.

1) Urine formaldehyde resin is treated with 1% ** at 70-80°C for 15 minutes, washed and dried. 2) Acrylic resin The sample can be treated with 50-100 times of the two helium backflow for 2-3h, taken out for washing and drying. 3) The silicone resin can be washed and dried with 5g/L soap and 5g/L sodium carbonate 90cI= for 15 minutes.

2.2 Identification method of the direct dye The sample is added with a solution of 1 mL concentrated ** aqueous solution 5 ~ 10mL boiling, so that the dye is fully extracted.

The extracted sample was taken out, and 10-30 mg of white cotton cloth and 5-50 mg of sodium chloride were placed in the extract, boiled for 40-80 s, and allowed to cool and then washed with water. If the white cotton cloth is dyed to almost the same color as the sample, it can be concluded that the dye used for dyeing the sample is a direct dye.

2.3 Identification method of dyes 100-300mg sample was placed in a 35mL test tube, 2~3mL of water was added, 1-2mL of 10% sodium carbonate solution and 200-400mg* of sodium, heated and boiled for 1-2min, and the sample was taken out. -50mg white cotton cloth and 10-20mg sodium chloride in test tubes. Boil for 1-2min. Remove and place on filter paper to re-oxidize. If the resulting shades are similar to the original shades, only those with different shades may be regarded as oxidized or reduced vat dyes.

2.4 Identification method of vat dye Place 100-300mg sample in 35mL test tube, add 2-3mL water and 0.5-lmL 10% sodium hydroxide solution, heat and boil, then add 10-20mg of insurance powder, boil 0.5-lmin, Take out the sample into 25-50mg white cotton cloth and 0-20mg sodium chloride, continue to boil 40-80s, and then cooled to room temperature. Remove the cotton cloth and oxidize it on the filter paper. If the color after oxidation is similar to the original, it means that the vat dye is present.

2.5 Identification of Nafto dyes In 100 times the amount of 1% ** solution, the sample was boiled for 3min, fully washed, boiled with 1% ** 5-10mL 2min, such as the dye extraction does not come out or extraction is very small After dissolving or discoloring after sodium hydroxide, sodium hydroxide, sodium hydroxide, even if it is oxidized in air, it cannot be restored to its original color, and it cannot be confirmed that metal is present. At this time, the following 2.5.1 and 2.5.2 can be performed. Test, if the dye can be extracted in the test of 2.5.1, and the white cotton cloth is dyed yellow in the test of 2.5.2, and emits fluorescent light, it can be concluded that the dye used in the sample is a nalford dye.

1) Put the sample into a test tube, add 5mL pyridine and boil, observe whether the dye is extracted? 2) Put the sample in a test tube, add 2mL of 10% sodium hydroxide solution and 5mL of ethanol, boil and then add 5mL of water and even Dioxin sodium, boil it to restore. After cooling, the white cotton cloth and 20-30 mg of sodium chloride were added to the filtrate, and the mixture was boiled for 1-2 min. After cooling, the cotton cloth was taken out to observe whether the cotton cloth emitted fluorescence when irradiated with ultraviolet rays.

2.6 Identification method of reactive dyes The characteristic of reactive dyes is that they have relatively stable chemical bonds with fibers and are difficult to dissolve in water and solvents. At present, there is no specific test method. Coloring tests can be carried out first, respectively, with a 1 11 dimethyl ** aqueous solution and 100% dimethylformamide coloring test samples, non-colored dyes are reactive dyes.

2.7 Identification of Coatings Coatings, also known as pigments, have no affinity for fibers and need to be fixed to the fibers by a binder (typically a resin binder). Microscopy can be used to test the removal of starch or resin finishes that may be present on the sample to avoid interference with dye identification. A further drop of ethyl salicylate was added to the fibers treated above and the coverslipping was observed under a microscope. If the surface of the fiber is in the form of particles, it can be confirmed as a resin-bonded pigment (coating material).

2.8 Identification method of anthraquinone dye After the sample is dripping, the bright green is anthraquinone dye. In addition, it can also prove to be an anthraquinone dye by burning the sample in the flame to be obviously green.

3 Conclusions The above rapid identification methods are mainly for the rapid identification of dye types on cellulose fibers. Through the above identification steps, one can avoid the blindness caused by the type of dye provided by the person who submits the inspection, and ensure the accuracy of the inspection and determination. Second, by using this simple method of targeted verification, many unnecessary identifications can be reduced. Test procedure.