In the dyeing and finishing process of textiles, the moist heat treatment of various chemical agents is subjected to mechanical tension and other effects, which not only deforms the tissue structure, but also causes stiffness and roughness in the hand. There are two methods of soft finishing, mechanical method uses the process of pounding cloth to loosen the phase between yarns or fibers, so as to obtain the soft effect, and the chemical method uses the action of softener to reduce the friction coefficient between fibers to obtain the soft effect. Chemical methods are commonly used and are sometimes supplemented by mechanical methods. Let's learn together:
Silicone oil soft finishing common problems and solutions
1. Alkaline problem:
Cotton fabrics are usually treated with a higher concentration of alkali to remove fabric impurities (especially the amount of mercerized alkali is larger), and the alkali is not easy to wash when it enters the fiber, and alkali should also be added when dyeing (reactive vat dye), so the cloth surface may be alkaline during finishing. The chemical fiber fabric must be reduced and cleaned after the dyeing is completed, and the printing and dyeing factory is used in the use of insurance powder and caustic soda cleaning. Ordinary silicone oil is not alkali-resistant, and it will break the emulsion under alkaline conditions, which is why the factory sticks to the roller after passing several kilometers when doing dipping and softening. Therefore, before softening, the cloth surface must be washed with alkali or acetic acid added to the working solution, and the pH of the rolling groove must be kept at 5-6.
2. Cohesion issues:
On fabrics containing staple fibers (cotton, T/R cloth, velvet), it is inevitable that some staple fibers will fall off during processing, and the staple fibers that fall off the cloth will accumulate in the rolling groove, and will form sticking with ordinary silicone oil, and with the finishing liquid going up to the rolls, it will bond with the silicone oil that is squeezed and broken to form sticky rollers or silica spots. When the printing and dyeing information prompts that the water quality is relatively poor, it will also coalesce with ordinary silicone oil to produce sticky rollers, and there will be a similar situation in fluffy fabrics.
3. Charge stability issues
Most of the dyes and whitening agents used in cotton cloth are anionic type, and cotton whitening is basically completed on the setting machine. In addition, when the color light of the dyed cloth is not right, it needs to be fine-tuned and repaired, and the color repair is usually added with a small amount of dye or paint when applying the soft finishing agent, and the factory generally uses ordinary silicone oil (weak cation) to produce a positive and negative charge attraction reaction, resulting in condensation and sticky rollers, and the soft feel of anionic silicone oil does not meet the requirements, causing confusion in the factory. Charge consistency must be taken into account in machining.
4. Temperature issues
If it is not fully cooled, especially the cloth in large rolls, the surface temperature of the fabric may be higher when it is soft, resulting in an increase in the temperature of the working fluid of the rolling groove (especially in summer), sometimes it can reach more than 60 °C, and the heat resistance of ordinary silicone oil is not good, it will also cause sticky rollers. It is better to have a temperature in the rolling groove not exceeding 40 °C.
5. Stereotyped speed issues
When the factory makes some thin fabrics, the setting speed is very fast, sometimes it can reach a speed of 60 m/min, and the ordinary silicone oil is not permeable due to the poor permeability, which causes the silicone oil to flow backwards on the roller, resulting in sticky rollers. Pay attention to replace the working fluid in the groove and wipe the roll frequently.
6. Dipping problems
In many factories, when making impregnated softness, ordinary silicone oil will be stained on the cylinder wall, and after a long time, some black oil spots will be formed on the cylinder wall, which will be stained on the cloth surface to form silicone oil spots. Intensify cleaning efforts.
7. Hand feel problems
Due to the higher and higher requirements for the feel of fabrics in the market, and various fabrics need to show a variety of different style requirements due to different seasons and different customer requirements, including those that require smooth draping, slippery and lively, fluffy and soft, simple elastic and so on. A silicone oil can only reflect one style. As a result, many factories have to use a lot of silicone oil, resulting in chaotic production, and sometimes they can't find silicone oil that meets customer requirements, so they can only give up business, resulting in losses. We can synthesize amino silicone oils with different ammonia value, viscosity and reaction by selecting different amino silicone oils with different ammonia values, end groups, and controlling molecular weight and molecular distribution, so as to meet the requirements of various fibers in terms of resoftness, smoothness and elasticity.
8. Cost issues
The biggest problem in the confusion of printing and dyeing factories is the cost problem, because the prices of water, electricity and steam are rising, while the printing and dyeing processing costs are decreasing, resulting in many printing and dyeing factories busy for a year, but the profits are basically nothing, so cost control is a problem to be solved by printing and dyeing factories. The cost of finishing auxiliaries is a large part of the printing and dyeing factory, so the reduction of the cost of finishing auxiliaries is an urgent problem for printing and dyeing factories.
9. Yellowing problem
(1) Thermal yellowing: The long-term shutdown during operation causes the fabric to remain yellowed, and the amino hydrogen of the amino silicone oil is easy to be oxidized by the air to form a chromophore, and the yellowing.
(2) The pH is too high, the temperature is too high when drying, and the accompanying substances of cotton fabrics turn yellow.
(3) Yellowing of storage. Caused by polluting gases during storage.
10. Fluorescence degradation
The interaction between the anionic brightener/cationic softener ions is condensed and should be divided into two processes.
(1) Greening: The brightener is sensitive to acid or the brightener is excessive, so the acid-resistant fluorescent whitening agent should be selected.
(2) Light damage: the light fastness of the fluorescent brightener is poor, and the light effect makes the fabric turn brown, so the fluorescent brightener is reasonably selected.
(3) Water quality impact: the content of impurities such as microorganisms and seaweed is too high, which can be filtered and precipitated to remove impurities.
