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When silicone oil spots appear on the cloth, do you give up? Or insist on treatment? [printing and dyeing learning and exchange] just like being sick, our fabrics sometimes have very difficult diseases to deal with - such as silicon spots! The visual appearance of silicon spots on the fabric surface is that there are oil spots as small as the tip of the needle and as large as the size of the rice grain. Under extreme conditions, the area may be larger. Sometimes, the oil spots have certain color because of floating color. The spots are like small wet spots, soft and without particle feeling. It is very difficult to find and remove before drying. It is caused by the demulsification and bleaching oil of silicone oil, which often occurs after finishing and water washing. What should we do in the face of such a problem? Step by step, we need to find the source to solve the problem! Look at the following in-depth analysis!
Formation of silicon spots
Mysterious veil of silicone oil and water repellent
1. Molecular structure of common silicone oil
2. Molecular structure of waterproof agent
3. Effect drawing and schematic diagram of finishing agent on fabric surface
Causes of silicone oil spots
1. Alkaline problem:
In the pretreatment of cotton fabric, a higher concentration of alkali is usually used to remove the impurities (especially mercerizing alkali is used more). It is not easy to wash when alkali enters into the fiber, and alkali is added when dyeing (reactive vat dyes), so the cloth surface may be alkaline during the post finishing.
The chemical fiber fabric should be deoxidized and cleaned after dyeing. At present, the printing and dyeing factory still uses insurance powder and caustic soda for cleaning. If the back cleaning is not clean, it will also cause alkali on the soft front cloth. The common silicone oil is not alkali resistant, and will break the emulsion under alkaline conditions, which is the reason why the mill will stick the roll after thousands of meters in the process of making dip rolling soft. Therefore, before softening, the cloth surface must be cleaned with alkali agent or added with acetic acid in the working solution to keep the groove ph5-6.
2. Cohesion:
On the fabrics containing short fibers (cotton cloth, t / R cloth and velvet), it is inevitable that some short fibers will fall down during the processing. The short fibers falling down from the cloth will accumulate in the rolling groove, which will generate cohesion with the common silicone oil. As the finishing liquid goes up to the roll, it will bond with the extruded and demulsified silicone oil to form a sticking roll or silicon spot. When the water quality is poor, it will agglomerate with common silicone oil to produce sticky roller. In addition, there will be similar situation for fluffy fabric. Before driving, do a good job of cleaning, and clean the flower hair at any time.
3. Charge stability:
The dyes and whitening agents used in cotton cloth are mostly anionic, while the whitening of cotton is basically completed on the setting machine. In addition, when the color of the dyed cloth is not right, it needs to fine tune the color. Usually, a small amount of dye or coating is added when the color is modified with a soft finishing agent, while the common silicone oil (weak cation) is used in the factory, which will generate a negative and positive charge attraction reaction, resulting in condensation and roller sticking, while the hand feel softness of the anionic silicone oil fails to meet the requirements, causing confusion in the factory. Charge consistency must be considered in machining.
4. Temperature problem:
The cloth dyed by the long cotton cart must be dried by the drying cylinder. If it is not sufficiently cooled, especially the cloth in the large roll, the surface temperature of the fabric may be higher when it is soft, which may cause the temperature of the working liquid in the rolling groove to rise (especially in summer), sometimes to over 60 ℃, while the ordinary silicone oil with poor heat resistance may also cause roller sticking. It is better to keep the temperature within 40 ℃.
5. Fixed speed:
When the factory is making some thin fabrics, the setting speed is very fast, sometimes it can reach the speed of 60m / min. due to the poor permeability of common silicone oil, it causes the silicone oil to flow back on the roller, which results in roller sticking. Pay attention to change the working fluid in the rolling groove and wipe the roll frequently.
6. Problem of cylinder staining:
In many factories, ordinary silicone oil will stick to the cylinder wall when it is soaked and soft. After a long time, some black oil spots will form on the cylinder wall and the silicone oil spots will form on the cloth surface. Strengthen the cleaning work.
7. Hand feeling problems:
Due to the higher and higher hand feel requirements of fabrics in the market, and due to different seasons and customers' requirements, various fabrics need to show different style requirements, such as smooth and draping, smooth and flexible, fluffy and soft, pure elastic, etc. A silicone oil can only reflect one style.
As a result, many factories have to use many kinds of silicone oil, resulting in confusion in production. Sometimes, they can't find the silicone oil suitable for customers' requirements, so they can only give up business and cause losses. We can control molecular weight and molecular distribution by choosing different amino silicone oil end groups with different ammonia value to synthesize amino silicone oil with different viscosity and reaction to meet the requirements of flexibility and smoothness of various fibers.
8. Cost
At present, the most perplexing problem for the printing and dyeing factory is the cost problem. Because the price of water, electricity and steam is rising, while the printing and dyeing processing fee is decreasing, many printing and dyeing factories have been busy for a year, but the profit is basically not available, so the cost control is the problem to be solved by the printing and dyeing factory.
Removal of silicone oil spots
1. The fabric has not been set at high temperature:
① Acetic acid washing
② High temperature treatment of solvent type degreaser.
2. The fabric has been shaped at high temperature:
Special fluorine and silicon stripper are treated in alkaline condition.
The main principle is to hydrolyze the fluorosilicone chain by boiling in alkaline condition, and then to emulsify and disperse the hydrolyzed fluorosilicone chain segment in time by the emulsification and dispersion ability of fluorosilicone remover. So as to complete the removal of silicone oil spots and waterproof spots.
It should be noted that deoiling and hydrogen peroxide can be added on the basis of alkali and fluorine remover for those that are hard to be removed. In addition, the amount of remover can be increased properly according to the severity of waterproof spots and silicone oil spots. If one treatment can not be completely removed, the number of removal can be increased properly to complete the removal of spots.
For regenerated cellulose fiber or protein fiber, due to its poor alkali resistance, it is recommended to use soda ash to adjust the pH value of the treatment bath to 8.5-9.5 to avoid strong damage or excessive loss of protein.
Silicone oil bleaching oil
When silicone oil emulsion is used in combination with fixative and soft oil, sometimes it appears what happens when it is used alone. Why not?
Amino silicone oil is incompatible with fixative, soft oil and other additives, resulting in silicone oil floating.
Amino silicone oil emulsion is a cationic surfactant (or weak cation). Many chemicals used in dyeing process are anionic surfactants, such as dyes (some dyes are anionic), leveling agents, diffusers and fixing agents. Once these chemicals are thoroughly dyed and processed, once the water is not thoroughly washed, charge reaction occurs when the anionic amino silicone oil softeners and the anionic substances in the dyed bath will cause the amino silicone oil emulsion to break down and the oil to appear soft spots. Li. After dyeing and washing, the fabric is poured out and soft finished in the rolling mill.
The special cylinder is too soft, which can effectively avoid or reduce the formation of soft spots (silicon spots).
Common soft problems in printing and dyeing production
1. Decrease of hydrophilicity of fabric
Generally, the film structure problems and the lack of water absorption genes after silicone oil film formation, as well as the sealing of such water absorption centers as the hydroxyl group of cellulose fiber, the carboxyl group and the amino group on wool, etc., cause the decrease of water absorption.
Treatment method: anionic, non-ionic film and hydrophilic silicone oil should be selected as far as possible.
2. deep stain
Causes:
① During the pretreatment, the oil stain was not removed, and the color of the oil stain was darker during dyeing.
(2) excessive foam in dyeing bath, foam and flower sweater, dyestuff and other mixture on fabric.
③ Defoamer floating oil causes dark oil spots.
④ The tars in the VAT stick to the fabric.
⑤ The dye agglomerates into dark spots under different conditions.
⑥ Water quality calcium and magnesium ions too much and dye combination in fabrics and other reasons.
Treatment method:
① Before treatment, add degreaser for refining.
② Dyeing auxiliaries are low foam and non foam auxiliaries.
③ Antifoaming agents should be selected to prevent floating oil, chelating agents should be added to improve water quality, and solubilizing dispersants should be added to prevent dye agglutination. Clean and wash the cylinder with cleaning agent in time.
3. light spots
Causes:
① The pretreatment is not uniform, and the hair effect of some parts is not good, resulting in a certain degree of dye repellency, with dye repellent substances. During the pretreatment, the cloth has calcium soap, magnesium soap or uneven mercerization.
② The drying of semi-finished products is uneven.
③ The cloth surface is stained with solid matters such as undissolved sodium hydroxide and soda ash.
④ Drips the dye before drying.
⑤ The auxiliary stains in the post-treatment such as dyeing soft treatment.
Treatment method: strengthen the pre-treatment, the pre-treatment additives must not be easy to form calcium magnesium soap, and the pre-treatment must be uniform and thorough (this is related to the selection of scouring agent, penetrant, chelating dispersant, mercerizing penetrant, etc.). The sodium hydroxide and sodium hydroxide must be put into the cylinder and the production management must be strengthened.
4. alkali stain
Causes: after pretreatment (such as bleaching, mercerizing), alkali removal is not clean or uneven, resulting in alkali spots.
Treatment method: it is necessary to strengthen the dealkalization process of the pre-treatment process.
5. Silicone oil stain
Causes:
The pH value of cloth surface is not neutral, especially with alkali, resulting in the demulsification of silicone oil and floating oil. The water quality of the treatment bath is too poor and the hardness is too high. The silicone oil is easy to float in the water with hardness of & gt; 150ppm. The quality problems of silicone oil include poor emulsification (poor selection of emulsifier, poor emulsification process, too large emulsified particles, etc.) and shear resistance. The silicone oil with shear resistance, electrolyte resistance and pH resistance shall be selected, but the use mode and environment of silicone oil shall be paid attention to, and the hydrophilic silicone oil can also be selected.
Think more about details
At present, most dyeing factories are developing towards central control, intelligence and technology. Employees are also operating according to the process of the factory. They are very careful. It is inevitable that there will still be problems. There is no small matter in production. Every production step is very important.
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