How to reduce the color difference between large and small samples when dyeing acrylic yarn is a very complicated problem. There are many reasons for the color difference between large and small samples. We can only produce large and small samples under normal circumstances. A brief analysis of the reasons for sample color difference is as follows:
① Be strict and precise when making small samples and color matching
Making small samples is the key to directly affecting the large-scale production of the workshop. Its importance must be fully understood to avoid large samples and small samples. difference. When making small samples, you should pay attention to the following issues: a: The water used for making small samples should be consistent with the water used for production of large samples to avoid water quality problems that will affect the color difference between large samples and small samples. b. The dyes and auxiliaries used for making small samples must be of the same batch number, same strength, and same brand. The concentration of dye absorbed by the sample should be appropriately selected using a straw. Try not to use a large straw to absorb a small volume of dye solution. The dyes and auxiliaries used in the sample must be current and ready for use. c. The acrylic yarn sample used in the small sample, including the pre-treatment method, must be consistent with the large sample. When color matching, you must choose a K value that is the same or similar to the K value of the dye, that is, the compatibility values of the dyes must be basically the same. At the same time, you must also choose a retarder that has the same K value as the dye or a difference of no more than 1, so as to ensure that each dye in the dye solution The proportional relationship between them is conducive to the stability and reproducibility of dyeing quality and color light. d. The pH value of the dye bath and the heating process for proofing should be the same as or close to those of mass production. e. Color matching should be strictly accurate.
② Errors in weighing dye additives for large and small samples
When weighing small samples, an analytical balance or an electronic balance should be used to weigh the dye. Avoid using a weight platform scale to minimize the error. When weighing dyes for large sample production, use weight scales as much as possible, and check the sensitivity of the balance and scales frequently.
③ Strictly control the pH value of the dye bath
In small sample production, the pH value is generally controlled more carefully. In large sample production, due to the cross-use of water quality and direct steam or indirect steam, the boiler steam is often alkaline and causes the problem. The pH of the dye bath is on the high side. When dyeing acrylic fiber, the pH value of the dye bath should be kept within the range of 4.5 to 5, otherwise the color light will change and produce color difference. If the pH value is high, the dye uptake rate and reproducibility of the dye will be affected, and the color difference between large and small samples will be greater. The measurement of pH value in the dye bath should be strengthened or buffers should be used, or an online pH value monitor should be installed.
④ Control the dye bath ratio
When making small samples, the bath ratio is generally larger (1:30), while the dyeing bath ratio for large samples is smaller (about 1:10). In order to avoid different bath ratios for large and small samples, Some cationic dyes are sensitive to the liquor ratio dependence. It must be emphasized that the sample making should be done in a package dyeing sample machine.
⑤ Strictly implement process operations
Practice has proved that different process operations are also one of the reasons for the color difference between large and small samples. Process operations including dissolution of dye, dosage of acetic acid, adding method of dye and additives, heating program, boiling dyeing time, etc. should be strictly operated according to process requirements and cannot be changed arbitrarily. The sampling personnel should be familiar with the process operation. After the color light of the small sample is determined, the sampling personnel should go into the workshop to conduct pioneer tests to ensure the consistency between the production of small samples and large samples.
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