The visual appearance of silicon spots on the surface of the fabric is that oil spots appear from the tip to the size of the rice grain. Under extreme conditions, the area may be larger, and sometimes the oil spots have a certain color due to the floating color. The spot is like a small wet spot. Soft and grain-free, it is extremely difficult to find before drying, it is extremely difficult to remove. The reason is that the silicone oil demulsification and bleaching oil often occurs after finishing and washing the soft process.
1, the formation of silicon spots




The mystery of silicone oil and water repellent molecules






1. Molecular structure of common silicone oil














2. Waterproofing agent molecular structure














3. Effect diagram and schematic diagram of finishing agent on the surface of the fabric














2, the cause of the formation of silicon spots




1, alkaline problem


When pre-treatment of cotton fabrics, it is usually treated with a higher concentration of alkali to remove fabric impurities (especially the amount of mercerized alkali is larger). The alkali enters the inside of the fiber and is not easy to wash. When dyeing (active vat dye), alkali is added. The fabric may be alkaline when finishing.






The chemical fiber fabrics have to undergo reduction and cleaning after dyeing. At present, the printing and dyeing factory is still cleaning with insurance powder and caustic soda. If the cleaning is not clean afterwards, it will also cause alkali on the soft front cloth. Ordinary silicone oil is not alkali-resistant, and it will break under alkaline conditions, which is why the factory has a sticky roller after several kilometers of padding. Therefore, the soft front cloth must be washed with alkaline agent or acetic acid added to the working fluid to maintain the groove PH5-6.






2, cohesion problem


On fabrics containing short fibers (cotton, T/R cloth, velvet), some staple fibers will inevitably fall during processing, and the dropped staple fibers will accumulate in the groove. The silicone oil is cohesive, and as the finishing liquid is ascended to the roll, it is bonded to the extruded demulsified silicone oil to form a sticky roll or a silicon spot. When the water quality is relatively poor, it will also form a sticky roll with ordinary silicone oil. In addition, there will be similar situations in the pile fabric. Before the driving, do a good job of cleaning and find that the hair is cleaned at any time.






3, charge stability problem


Most of the dyes and brighteners used in cotton are anionic, and cotton whitening is basically done on a setting machine. In addition, the dyed cloth needs fine adjustment of the color when the color is wrong. The color correction usually adds a small amount of dye or paint to the soft finishing agent, and the factory generally uses ordinary silicone oil (weak cation) to generate an yin-yang charge attraction reaction, causing cohesion and sticking. However, the softness of the anionic silicone oil did not meet the requirements, which caused confusion in the factory. Charge consistency must be considered in processing.






4, temperature problems


The cloth dyed by the cotton long car is dried by a drying cylinder, and is wrapped or piled in a cloth box. If it is not sufficiently cooled, especially for a large package, the surface temperature of the fabric may be high when it is soft. The temperature of the working fluid in the groove is increased (especially in summer), sometimes it can reach above 60 °C, and the heat resistance of ordinary silicone oil is also bad, and the temperature in the groove does not exceed 40 °C.






5, fixed speed problem


When the factory is making some thin fabrics, the speed of the setting is very fast, and sometimes it can reach the speed of 60 m/min. The ordinary silicone oil has a poor permeability, causing the silicone oil to flow backward on the roller, resulting in a sticky roller. Pay attention to the replacement of the working fluid in the groove and wipe the rolls.






6, dilute cylinder problem


In many factories, when the impregnation is soft, the ordinary silicone oil will stick to the cylinder wall. After a long time, some black oil spots will form on the cylinder wall, and the silicone oil spots will be formed on the cloth surface. Strengthen cleaning work.






7, feel the problem


Due to the increasing demand for fabrics on the market, various fabrics need to exhibit a variety of different style requirements due to different seasons and different customer requirements, and are required to be slippery and sleek. Fluffy, soft, simple, and so on. A silicone oil generally only reflects one style. As a result, many factories use a variety of silicone oils, resulting in chaotic production, sometimes can not find silicone oil suitable for customer requirements, can only give up business and cause losses. We can control the molecular weight and molecular distribution by selecting different aminosilicon oil end groups with different ammonia values to synthesize amino acid viscosity and reaction difference amino silicone oil to meet the requirements of softness and smoothness of various fibers.






8, the cost problem


At present, the biggest problem for printing and dyeing factories is the cost problem. As the prices of water, electricity and steam are rising, the printing and dyeing processing fees are decreasing. Many printing and dyeing factories have been busy for one year, but the profits are basically not. Therefore, the cost control is printing and dyeing. The problem that the factory has to solve.






3, the removal of silicon spots




1. The fabric is not shaped by high temperature: 1 acetic acid washing; 2 solvent type degreasing agent is treated at high temperature.


2, the fabric has been set at high temperature: special fluorine and silicon stripping agent are treated under alkaline conditions.


The main principle is to hydrolyze the fluorosilicon chain by boiling under alkaline conditions, and then emulsify and disperse the hydrolyzed fluorosilicon segment in time by means of the emulsification and dispersing ability of the fluorosilicone stripping agent. Thereby the removal of the silicone oil spots and the waterproof spots is completed. Note that it is difficult to remove the method of adding deoiling and hydrogen peroxide on the basis of alkali and fluorine stripping agent. In addition, according to the severity of waterproof spots and silicone oil spots, the amount of stripping agent can be appropriately increased. Under the removal, the number of removal passes can be appropriately increased to complete the spot removal.






For regenerated cellulose fibers or protein fibers, it is recommended to use soda ash to adjust the pH of the treatment bath to 8.5-9.5 due to its poor alkali resistance to avoid strong damage or excessive protein loss.






4, silicone oil bleaching oil




When the amino silicone oil emulsion is used together with a fixing agent or a soft oil, silicon plaque sometimes occurs. When it is used alone, why?






Amino silicone oil is incompatible with additives such as fixing agent and soft oil, resulting in silicone oil.








Amino silicone oil emulsion is a cationic surfactant (or weak cation). Many chemicals used in the dyeing process are anionic surfactants, such as: dyes (some dyes are anionic), leveling agents, diffusing agents, fixing Agent...














After the dyeing and finishing of these chemicals, before the soft finishing, once the water washing is not thorough, when the cationic amino silicone oil softener reacts with the anionic substance in the dyeing bath, the aminosilicone oil cationic emulsion will be demulsified and the oil will appear soft. (Silicone spot), an effective method is to enhance the full washing before soft finishing, preferably not in the same dyeing machine for soft finishing.






After the dyeing is washed, the fabric is poured out and softly finished in the rolling cart. The special cylinder is too soft to effectively avoid or reduce the formation of soft spots (silicon spots).








At present, dyeing factories are mostly in the center of control, intelligent, technological development, employees are also operating in accordance with the factory process, careful and careful, it is inevitable that there will be problems, production is no small matter, each production step is very important.