When silicone oil spots appear on the cloth, do you give up? Or insist on treatment? Just like illness, our fabrics can sometimes develop conditions that are extremely difficult to deal with – like silicone plaque! The intuitive manifestation of silicon spots on the surface of fabrics is the appearance of oil spots as small as a pin tip or as large as a rice grain. Under extreme conditions, the area may be larger. Sometimes the oil spots have a certain color due to floating color. The spots are like small wet spots. It feels soft and non-grainy, extremely difficult to spot and extremely difficult to remove before drying. The reason is caused by the demulsification and bleaching of silicone oil, which often occurs after finishing and washing. What should we do when encountering such a problem? Let’s take it step by step. To solve the problem, we still need to find the source! Check out the in-depth analysis below!
The formation of silicon plaque
The mystery of silicone oil and waterproofing agent molecules
1. The molecular structure of ordinary silicone oil
2. Molecular structure of waterproofing agent
3. Effect drawing and schematic diagram of finishing agent on fabric surface
Causes of silicone oil spots
1. Alkaline problem:
Cotton fabrics usually need to be treated with a higher concentration of alkali to remove fabric impurities (especially The amount of alkali used in mercerization is larger). The alkali enters the inside of the fiber and is not easy to clean. When dyeing (reactive vat dye), alkali is also added, so the cloth surface may be alkaline during finishing.
Chemical fiber fabrics must be restored and cleaned after dyeing. Currently, printing and dyeing factories still use insurance powder and caustic soda for cleaning. If the back cleaning is not clean, it will also cause the front fabric to become soft. With alkali. Ordinary silicone oil is not resistant to alkali and will break emulsification under alkaline conditions. This is the reason why the factory will stick to the roll after several kilometers of padding. Therefore, before softening, the cloth surface must be washed with alkali or acetic acid added to the working fluid to keep the rolling groove pH 5-6.
2. Cohesion problem:
On fabrics containing short fibers (cotton, T/R cloth, velvet), some short fibers will inevitably fall off during the processing. The short fibers falling off the cloth accumulate in the rolling groove and cohere with ordinary silicone oil. As the finishing fluid moves up to the roller, they bond with the extruded and demulsified silicone oil to form sticky rollers or silicon spots. When the water quality is relatively poor, it will also condense with ordinary silicone oil to produce sticky rollers. In addition, similar situations will also occur with velvet fabrics. Do a good job of cleaning before driving, and clean them at any time if you find any lint.
3. Charge stability problem:
Most of the dyes and whitening agents used in cotton are anionic, and cotton whitening is basically completed on the setting machine. In addition, dyed fabrics need fine-tuning and color correction when the shade is wrong. Color correction usually involves adding a small amount of dye or paint when applying a softening agent. Factories generally use ordinary silicone oil (weak cations), which will produce negative and positive charge attraction reactions, causing agglomeration and sticky rollers. , and the softness of the anionic silicone oil did not meet the requirements, causing confusion in the factory. Charge consistency must be considered during processing.
4. Temperature problem:
The cloth dyed by the cotton long machine must be dried in a drying drum and packaged in large rolls or piled in cloth boxes.align=””>The special cylinder is too soft, which can effectively avoid or reduce the formation of soft spots (silicone spots).
Common softness problems in printing and dyeing production
1. Decreased hydrophilicity of fabrics
Generally, it is caused by structural problems of the soft film used, the lack of water-absorbing genes after the silicone oil film is formed, and the sealing of elephant fibers The water-absorbing centers such as the hydroxyl group of the plain fiber and the carboxyl group and amino group of the wool cause the water absorption to decrease.
Processing method: Anionic, non-ionic film and hydrophilic silicone oil should be used as much as possible.
2. Dark spots
Causes:
① The oil stain on the fabric was not removed during pre-treatment, and the oil stain was darker in color during dyeing.
② There is too much foam in the dyeing bath, and the mixture of foam, floral sweaters, dyes, etc. stains the fabric.
③ Oil drifting from the defoaming agent causes dark oil spots.
④ The tar-like substance in the dye vat is stained on the fabric.
⑤ The dye agglomerates under different circumstances to form dark stains.
⑥ Excessive calcium and magnesium ions in the water combine with dyes and stain the fabric.
Processing method:
① Add degreasing agent for refining during pre-treatment.
② The dyeing auxiliaries use low-foaming and non-foaming auxiliaries.
③ Choose a defoaming agent that is not easy to float oil, add a chelating agent to improve the water quality, and add a solubilizing and dispersing agent to prevent dye aggregation. Use tank cleaning agent to clean and wash the tank promptly.
3. Caused by light spots
Reasons:
① The pre-treatment is uneven, and the hair effect in some parts is not good, resulting in a certain dye repellency and containing dye repellent substances. During pre-treatment, the cloth contains calcium soap, magnesium soap, etc. or the mercerization is uneven.
② The semi-finished product is unevenly dried.
③ The cloth surface is stained with undissolved Yuanming powder, soda ash and other solids.
④ Add water to the dyed material before drying.
⑤ The stains caused by additives during finishing such as softening of dyed goods.
Treatment method: Strengthen pre-treatment. When selecting pre-treatment additives, it must be difficult to form calcium magnesium soap. Pre-treatment must be uniform and thorough (this is related to scouring agents, penetrants, chelating dispersants, Mercerized penetrant and other selection related). Yuanming powder, soda ash, etc. must be melted into the tank and production management must be strengthened.
4. Alkali spots
Cause: Alkali removal after pre-treatment (such as bleaching, mercerization) is not clean or uniform, resulting in alkali spots.
Treatment method: The de-alkali process of the pre-treatment process must be strengthened.
5. Silicone oil stains
Causes:
The PH value of the cloth surface is not neutral, especially with alkali, causing the silicone oil to break and float. Oil. The water quality of the treatment bath is too poor and the hardness is too high. Silicone oil can easily float in water with a hardness of >150PPM. Silicone oil quality problems include poor emulsification (poor emulsifier selection, poor emulsification process, too large emulsified particles, etc.) and intolerance to shearing. Choose silicone oil that is resistant to shear, electrolytes, and pH changes, but pay attention to the use method and environment of the silicone oil. You can also consider choosing hydrophilic silicone oil.
Consider more details
At present, most dyeing factories are developing towards centralized control, intelligence and technology. Employees also operate according to factory processes. Be careful, problems will inevitably occur. Production is no small matter, and every production step is important.
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