When dyeing, silicone oil spots are formed on the cloth surface. How to break them?

The visual appearance of silicon spots on the fabric surface is oil spots ranging from the tip of a needle to the size of a grain of rice. Under extreme conditions, the area may be larger. Sometimes the oil spots may have a certain color due to floating color. The spots are like small wet spots, which feel soft and have no grain feeling. It is very difficult to find and remove them before drying. The reason is silicone oil demulsification and bleaching oil, which often occurs after finishing and washing.

1. Formation of silicon spots

The mystery of silicone oil and water repellent molecules

1. Molecular structure of common silicone oil

2. Molecular structure of waterproofing agent

3. Effect and sketch of finishing agent on fabric surface

2. The cause of silicon spot formation

1. Alkalinity problem

Cotton fabric is usually pretreated with high concentration of alkali to remove impurities (especially mercerizing alkali). Alkali entering into the fiber is not easy to clean, and alkali is also added during dyeing (reactive vat dyes). Therefore, the fabric surface may be alkaline during finishing.

At present, the printing and dyeing plants are still using sodium hydroxide and sodium hydroxide to clean the chemical fiber fabrics after dyeing. 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 to the roll after passing several thousand meters when it is making the dip mill soft. Therefore, the soft front cloth surface must be cleaned with alkali agent or acetic acid added into the working fluid to keep the rolling groove ph5-6.

2. Cohesion problem

On fabrics containing staple fibers (cotton cloth, t / R cloth and cashmere), it is inevitable that some staple fibers will fall down during processing. The staple fibers will accumulate in the rolling groove and agglomerate with ordinary silicone oil. With the finishing solution going up to the roller, they will bond with the silicone oil which is extruded and demulsified to form adhesive roller or silicon spot. When the water quality is poor, it will agglomerate with ordinary silicone oil to produce adhesive roll. In addition, there will be a similar situation in fluffy fabric. Do a good job in cleaning before driving, and clean up the fluffy at any time.

3. Charge stability problem

Most of the dyes and brighteners used in cotton fabric are anionic, and cotton whitening is basically completed on the setting machine. In addition, when the shade of dyed cloth is not right, it needs fine adjustment and color modification. Generally, a small amount of dye or coating is added when the softener is applied. However, the common silicone oil (weak cation) is generally used in the factory, which will produce the reaction of positive and negative charge attraction, resulting in condensation and sticking to the roller. However, the hand feel of anionic silicone oil can not meet the requirements, causing the confusion of the factory. Charge consistency must be considered in machining.

4. Temperature problem

If the cloth is not cooled sufficiently, especially the cloth in large package, the surface temperature of the fabric may be higher when it is soft, which may cause the temperature of the working fluid in the rolling groove to rise (especially in summer), sometimes to more than 60 ℃. When the heat resistance of common silicone oil is not good, it will also cause roll sticking, and the temperature in the rolling groove will not exceed 60 ℃ 40 ℃ is better.

5. Fixed speed problem

When the factory makes some thin fabrics, the setting speed is very fast, sometimes it can reach 60 m / min. due to the poor permeability of ordinary silicone oil, the silicone oil flows back on the roll, resulting in roll sticking. Pay attention to change the working fluid in the rolling groove and wipe the roll frequently.

6. Cylinder sticking problem

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

7. Handle problem

Due to the higher and higher requirements on the hand feel of fabrics in the market, various fabrics need to show a variety of different style requirements due to different seasons and customer requirements, such as smooth drape, smooth and flexible, fluffy and soft, simple elastic and so on. A kind of silicone oil can only reflect one style.

As a result, many factories have to use many kinds of silicone oil, resulting in production confusion. Sometimes they can't find the silicone oil suitable for customers' requirements, so they have to give up business and cause losses. We can synthesize amino silicone oil with different ammonia value and different end groups to control molecular weight and molecular distribution. Amino silicone oil with different ammonia value, viscosity and reaction can meet the requirements of softness, smoothness and elasticity of various fibers.

8. Cost problem

At present, the most perplexing problem for printing and dyeing plants is the cost problem. Due to the rising prices of water, electricity and steam, and the reduction of printing and dyeing processing fees, many printing and dyeing plants have been busy for a year, but the profits are basically not. Therefore, cost control is the problem to be solved by printing and dyeing plants.

3. Removal of silicon spots

1. Fabric without high temperature setting: ① acetic acid washing; ② solvent degreaser high temperature treatment.

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

The main principle is to hydrolyze the fluorosilicone chain by boiling under alkaline conditions, and then emulsify, disperse and seal the hydrolyzed fluorosilicone chain in time by virtue of the emulsifying and dispersing ability of fluorosilicone stripping agent. So as to complete the removal of silicone oil spots and waterproof spots.

In addition, according to the severity of waterproof spots and silicone oil spots, the amount of stripping agent can be appropriately increased. If one treatment can not completely remove the spots, the number of removal channels can be appropriately increased to complete the spot removal.

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

4. 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 not compatible with fixing agent, 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, fixing agents.

Once these chemicals are dyed and processed, once the water is not thoroughly washed, the cationic amino silicone oil softeners react with the anionic substances in the dye bath to produce the charge reaction. The amino silicone oil emulsion will be broken and the oil spots appear.

After dyeing and washing, the fabric is poured out and softened in the rolling mill. The special cylinder is too soft, which can effectively avoid or reduce the formation of soft spots (silicon spots).