Common problems and solutions for silicone oil softening and finishing

During the dyeing and finishing process, textiles are subjected to moist heat treatment with various chemical agents and mechanical tension, which not only deforms the tissue structure, but also causes stiffness and roughness in the hand. Softening is a process that compensates for this defect and makes the fabric feel soft. There are two methods of soft finishing, mechanical and chemical. The mechanical method uses techniques such as beating cloth to loosen the yarns or fibers to achieve a soft effect. The chemical method uses softeners to reduce the friction coefficient between fibers to obtain a soft effect. Chemical methods are more commonly used, sometimes supplemented by mechanical methods.

Common problems and solutions for silicone oil softening and finishing

  1. Alkaline problem

Cotton fabrics are usually pre-treated with a higher concentration of alkali to remove fabric impurities (especially mercerizing alkali, which uses a larger amount). It is not easy to clean the fiber when alkali enters the interior of the fiber. Alkali is also added when dyeing (reactive vat dyes), so the cloth surface may be alkaline during finishing. Chemical fiber fabrics must be restored and cleaned after dyeing. Printing and dyeing factories use insurance powder and caustic soda for cleaning. If the subsequent cleaning is not clean, it will also cause the cloth surface to be stained with alkali before softening. 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.

 

  1. Cohesion problem

On fabrics containing short fibers (cotton, T/R cloth, velvet), some short fibers will inevitably fall off during 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 dyeing, poor water quality will condense with ordinary silicone oil and cause sticky rollers. In addition, similar situations will also occur with velvet fabrics. Do a good job of cleaning before driving, and clean up any lint found.

 

  1. Charge stability problem

Most of the dyes and whitening agents used in cotton are anionic, and cotton whitening is basically done on the setting machine. In addition, dyed fabrics need fine-tuning and color correction when the shade is wrong. For color correction, a small amount of dye or paint is usually added when applying the softening agent. However, factories generally use ordinary silicone oil (weak cation), which will produce negative and positive charge attraction reactions, causing agglomeration and sticking to the roller. However, the softness of anionic silicone oil does not meet the requirements, causing confusion in the factory. Charge consistency must be considered during processing.

 

  1. Temperature problem

The cloth dyed by the long cotton machine must be dried in a drying drum and packed in large rolls or piled in cloth boxes. If it is not cooled sufficiently, especially for large rolls of cloth, the surface temperature of the fabric may be high when it is soft, causing the temperature of the rolling tank working fluid to rise (especially in summer), sometimes reaching more than 60°C. Ordinary silicone oil may also cause roller sticking if its heat resistance is not good. It is better that the temperature in the rolling groove does not exceed 40 ℃.

 

  1. Settingspeed problem

When the factory is making some thin fabrics, the setting speed is very fast, sometimes reaching a speed of 60 meters/minute. Due to the poor permeability of ordinary silicone oil, the silicone oil flows back on the roller, causing the roller to stick. Pay attention to changing the working fluid in the rolling groove and wiping the roll frequently.

 

  1. Cylinder sticking problem

When many factories are doing impregnation and softening, ordinary silicone oil will stick to the cylinder wall. Over time, some black oil spots will form on the cylinder wall and stick to the cloth to form silicone oil spots. Cleaning must be stepped up.

 

  1. Feeling problem

As the current market has increasingly higher requirements for the feel of fabrics, and various fabrics need to show a variety of different style requirements due to different seasons and different customer requirements. Some require the fabric to have a drapey feel, smooth and flexible, fluffy and soft, and high elasticity. But a kind of silicone oil can generally only reflect one style. Therefore, many factories have to use many kinds of silicone oil, causing production confusion. Sometimes they cannot find the silicone oil that suits the customer’s requirements, so they have to give up business and cause losses. We can control the molecular weight and molecular distribution by selecting amino silicone oil end groups with different ammonia values. In this way, amino silicone oils with different ammonia values, viscosity and reactions are synthesized to meet the soft, smooth and elastic requirements of various fibers.

 

  1. Cost problem

The biggest problem that puzzles printing and dyeing factories is the cost problem. Since the prices of water, electricity and gas are constantly rising, while the printing and dyeing processing fees are decreasing, many printing and dyeing factories have been busy for a year but have basically no profits. Therefore, cost control is a problem that printing and dyeing factories need to solve. The cost of finishing auxiliaries is a big part of the printing and dyeing factory, so reducing the cost of finishing auxiliaries is an urgent problem that printing and dyeing factories need to solve.

 

  1. Yellowing problem

Hot yellowing:

 

A long downtime during operation causes the fabric to remain and turn yellow, and the amino hydrogen of the aminosilicone oil is easily oxidized by air to form a chromophore, which causes yellowing. The product turns brown and the brown color makes the white fabric look like it has lost its essential whiteness or has simply turned yellow. The pH is too high and the temperature during drying is too high, causing the cotton fabric to turn yellow. Process control must be strengthened to reduce storage yellowing and pollution gases caused during storage.

 

  1. Fluorescence degradation

The interaction between the ions of the anionic whitening agent and the cationic softener causes agglomeration, which should be divided into two processes.

 

(1) Greenish:

If the whitening agent is acid-sensitive or excessive whitening agent is used, acid-resistant fluorescent whitening agent should be used.

 

(2) Light damage:

Fluorescent whitening agents have poor light fastness, and the light effect causes the fabric to turn brown. Therefore, choose the fluorescent whitening agent reasonably.

 

(3) Impact on water quality:

If the content of impurities such as microorganisms and seaweed is too high, it can be filtered and precipitated to remove impurities.

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