Discussion on the production process of flax roving
As the level of consumption continues to increase, the demand for yarn-dyed fabrics is also heating up. China's flax fiber processing started relatively slowly, and it lags behind foreign countries in textile and dyeing and finishing technology. The products are only at the middle and low grades. In order to produce high-grade linen textiles, it is imperative to develop new linen textile technology. Row.
At present, the more popular dyeing process is: roving→acid washing→sub-bleaching→oxygen bleaching→water washing→dyeing→water washing→wet spinning yarn→drying→winding. The process not only has lower cost, saves energy, reduces pollution, but also has easy control of production process and stable product quality.
1 Characteristics of flax fiber
Flax is a kind of natural fiber, the fiber itself contains a lot of impurities, cellulose only accounts for about 70%, and pectin, lignin, fat wax, ash and other impurities account for about 30%. Due to the presence of the above impurities, the process of binding the reactive dye to the cellulose is severely hindered, so that the dyeing reaction cannot be diffused from the high position where the dye concentration is high to the low position where the dye concentration is low, thereby causing coloring, dyeing, and uneven dyeing. And so on. Because flax fiber is a bundle of fibers, it must be split to the number suitable for spinning, and impurities such as pectin and lignin affect the spinning performance so that the above impurities must be removed to increase the fiber count and the fiber root in the cross section of the spun yarn. The number is increased to achieve the purpose of improving the spinning performance of the fiber. As the impurities are removed, the fiber's hair effect and whiteness increase, making the color of the linen yarn more vivid and bright.
2 Design and control of roving and cooking and bleaching process
When the roving dyeing process, the process control of the pre-spinning roving process is as follows: the weight management is required between the pot and the pot, the net weight before the roving of each pot is controlled between 380kg-390kg, and the winding density is controlled at 0.37-0. .38, and the roving is screened before bleaching. First of all, it is necessary to control the forming defects as well as the bread, yarn, hair, soft and hard edges, etc., to ensure that the above-mentioned crepe is not used; secondly, strictly control the boiling loss rate within 10%, and the above measures can ensure The color difference between the pot and the pot, within one pot, and between the inner and outer layers of the roving is controlled to a minimum extent, and the roving dyeing color is uniform, uniform, colorless and chromatic. For the roving boiling and bleaching process, the roving boiling and bleaching process should be specifically adjusted according to the comprehensive factors such as the origin of the flax and the dyed color and the number of spun yarns.
2.1 cooking
The temperature is controlled at (14±0.1) mL, the fire 硷 is 5.8 g/L, the pure 硷 is 5.4 g/L, the temperature is 100 ° C, and the time is 60 min. The structure and chemical composition of flax fiber are under the action of strong sputum, pectin is hydrolyzed, and part of the lignin immobilized on the surface of the fiber is sulfonated and degraded, and its degradation product is cracked in decomposition.
2.2 Pickling
The purpose is to neutralize the residual residue on the roving and remove the impurities such as ash generated during the tanning process, while the hemicellulose and pectin polysaccharides are sensitive to acid, easy to hydrolyze to make it into a gel acid; remove iron and other metals in the fiber. The ions are degummed by the action of hydrazine, keeping the hydrogen peroxide stable and improving the bleaching effect. By appropriately controlling various influencing factors, the degree of reaction can be controlled. Flax fibers can be treated with concentrated sulfuric acid 2g/L, temperature 30 °C, and time 20 min, and the fiber strength is not significantly decreased.
2.3 Chlorination
Flax fiber contains a lot of impurities such as lignin. In order to remove lignin and damage the fiber, the fiber is bleached with sodium chlorite. Sodium chlorite selectively attacks flax fibers and oxidizes only the aldehyde groups to carboxyl groups, which achieves the purpose of bleaching and reduces the weight loss and damage of the fibers. If the controlled process conditions are improper, the fiber will be seriously damaged. Therefore, the process conditions are determined according to the origin of the raw materials and the coarseness of the hemp: acidity H2SO4 2.3g/L, penetrant Laonil2R 0.6g/L, NaClO2 2.7g/ L-3.4g/L, NaNO31.6g/L, and heat preservation at 50 °C for 40 min, controlled by the above process conditions, removes a part of fiber impurities, and makes the wet strength of the roving have certain control before dyeing.
2.4 Oxygen bleaching
Roving oxygen bleaching process: H2O2 concentration 1.8g / L, sputum 3.6g / L (its
Formula: sodium hydroxide: sodium carbonate = 1:2), pH between 11-11.5, sodium silicate 4.8g, and using silicon-free hydrogen peroxide stabilizer SOF 0.3g, can reduce silicic acid complexation Heavy metal ions prevent catalytic oxidation and premature decomposition of hydrogen peroxide to increase the utilization of hydrogen peroxide, reduce costs, maintain a certain degree of polymerization, and reduce fiber damage. After scouring and bleaching, the fiber has a high whiteness value, and impurities such as lignin, fat wax, and nitrogen-containing inorganic salt are largely removed, which improves the uniformity of dyeing and the inability to permeate.
3 dyeing
3.1 Selection of dyes
In the development of flax fiber dyeing, we have selected Swiss Clariant reactive dyes and auxiliaries, S-type dyes, which are excellent in dyeing rate, good transmissibility and excellent cost performance, namely vinyl type and salt, pure bismuth and fixing agent E. - 50 and other additives.
3.2 Dyeing equipment and process recipe
(1) Adopt CCA-140A Hong Kong Lixin Boiler.
(2) Process recipe:
3.3 Precautions in the dyeing process
(1) First, the dye is stirred and dissolved by the auxiliary cylinder and linearly metered in. At the same time, the salt is added linearly according to a preset procedure. For example, when the salt is first dyed, the one-time or several-time addition is not only greatly accelerated. The dyeing speed makes the dyeing uneven, and at the same time causes the dye to accumulate or even precipitate. After the second dyeing, the dyeing speed and the degree of fixation are controlled by the pH value in the dyeing bath. The pH value of the large amount of the tincture will increase rapidly, not only the hydrolysis dye is increased, but also a large amount of dye is fixed, which is difficult to transfer. It causes poor leveling and poor permeability. Therefore, the amount of salt and the way of adding salt are reasonable, so as to affect the dyeing (adsorption) stage and the fixing (reaction) stage to ensure the best dyeing effect and prevent dyeing, Transfection and color difference.
(2) The color yarn should be used as a soaping solution with detergent RSK with high efficiency of wetting and washing. This stage includes water washing temperature, water flow speed, pH value, etc., mainly to remove electrolysis.
Both quality and unreacted dyes require high temperature (90 ° C - 95 ° C), fast water flow and a strong cleansing detergent.
4 Conclusion
Pre-dye treatment of linen roving dyeing processing is the key and foundation, and the selection of reactive dyes plays a decisive role. It can reduce pot difference, batch difference, improve leveling, translucency and color fastness, and effectively control the impact. The unfavorable factors of dyeing ensure the quality of the product.
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