After natural fibers such as cotton, linen, wool, silk, etc. have been bleached, dyed, printed, or functionally finished, the fibers will be damaged to a certain extent due to the removal of wax and oil stains, and the fabric will become rough and the luster will change. Darkness may even affect sewing performance, so soft finishing is required. The feel of synthetic fibers is worse than that of natural fibers such as cotton, wool, silk, and linen. After the synthetic fiber fabric is set at high temperature, the feel becomes very rough and hard. Only through soft finishing can the fabric be given the soft feel of natural fibers to improve its performance. .
1 Introduction
Silicone softeners can make fabrics soft, smooth, plump and elastic. The hand feel, anti-wrinkle, abrasion resistance, wash resistance and good sewing properties greatly increase the added value of the product, so it is favored by customers; however, during the soft finishing process, silicone oil spots often occur Defects bring great trouble to dyeing and finishing processing.
This article explains the causes, preventive measures and solutions to common defects during the use of softeners.
2 Classification of softeners
Softeners can be roughly divided into There are two major categories: fatty acid derivatives and silicones.
Fatty acid derivatives are traditionally widely used softeners, while silicones are a new type of softener. The development of silicone softeners is very fast, and new products with various properties and functions are constantly being developed and launched.
Because silicone softeners are not only more effective than fatty acid derivative softeners, but also have good durability, they have occupied a dominant position in the use of textile softening finishing. However, precisely because of its good durability, it also brings a certain degree of difficulty to its removal, making it difficult to repair or repair and dye it. If silicone oil spots occur, it will be even more troublesome and difficult to repair.
In terms of ionicity, most of the silicone softeners are cationic, weak cationic or non-ionic. Therefore, it is often processed in the same bath as the fixing agent during production and processing, and the processing bath temperature is generally 30 to 45°C. Do not wash after softening treatment. After baking, the film formed by the reaction will be stronger. If used improperly, silicone softeners can easily cause demulsification and oil bleaching problems. Some need to be processed on the dyeing machine, such as ready-made garments, yarns, loose fibers, softeners in the dye vat after dyeing, etc. After a long time, residues of silicone substances in the equipment are likely to occur. It is more difficult to remove and repair than fatty acid derivative softeners.
Organic silicone has poor water solubility and must be emulsified before it can be used during dyeing and finishing. In order to increase the water solubility of silicone oil, some self-emulsifying agents are added to some silicone oils to make them self-emulsifying in water. Therefore, if the properties and characteristics of silicone oil are not mastered during use, and the required process conditions are seriously violated, problems such as demulsification and bleaching of the oil and silicone oil spots will occur.
3 Characteristics of silicone softeners
Suitable working conditions and conditions of silicone softeners The physical and chemical characteristics can be summarized in the following three points:
1. The pH value of the working bath is relatively stable between 5 and 6.5;
2. The optimal temperature of the working bath is 30 to 45°C;
3. Ionicity, most varieties are cationic, followed by non-ionic; some varieties are anionic (comparing the softening effects of various varieties, cationic ones are generally dominant).
4 Common problems and solutions during application
1. The effect of PH value on silicone oil Influence
The stability of the softener is sensitive to the pH value. In general dyeing and finishing processes, cotton fabrics need to be pre-treated, and pre-treatment usually requires treatment with alkali or alkaline substances to remove impurities on the fabric. Some fabrics also need to be mercerized. The alkali used in these processes enters the interior of the fiber and is not easily washed. Alkali is also used when dyeing with reactive dyes or vat dyes, so the cloth surface may be alkaline during finishing.
Polyester fibers must also undergo reduction cleaning after dyeing with disperse dyes, especially those using insurance powder and caustic soda. If not cleaned thoroughly, the cloth surface will become alkaline. Ordinary silicone oil is generally not resistant to alkali and is easily demulsified under alkaline conditions. During padding and soft processing, roller sticking will occur after a period of time when the machine is turned on, resulting in silicone oil spots.
★Solution
1. Before softening, the cloth surface must be washed with alkali.
2． Add acetic acid to the working fluid to keep the rolling tank pH=5~6.
2. Influence of the speed of the setting machine
When the setting machine of the dyeing factory produces ultra-thin fabrics such as chiffon, imitation silk, and voile, The speed is very fast, sometimes reaching 60-80 meters/minute. However, due to the small amount of liquid carried by the thin fabric, the poor permeability of the fabric itself, the poor hydrophilicity of the silicone oil, and the poor shear resistance of ordinary silicone oil, the silicone oil brought up by the fabric will flow back on the roller and easily Causing roller sticking.
★Solution
1. Try to control your speed.
2. Improve cloth permeability.
3. During use, pay attention to changing the rolling groove working fluid and cleaning the rolls frequently.
4. Improve the shear resistance of silicone oil.
3. Problems that may occur when applying softener in the tank
In order to achieve a certain feel style and the actual production needs of the factory, some factories often have to add softener to the tank. Impregnated and softened. But ordinary siliconDue to structural factors and residues in the dyeing vat, some silicone oil and mixtures will stick to the vat wall. Over time, some black oily viscous matter will form on the vat wall. These things will form on the cloth. Formation of silicone oil spots.
★Solution
1. Increase cleaning efforts.
2. Try to use silicone oil in the cylinder with good stability.
3. Before passing silicone oil in the tank, the cloth surface should be washed and should not contain alkali; add some acid appropriately and adjust the pH value to about 6.
4. Silicone oil agglomeration phenomenon
On fabrics containing short fibers such as cotton, T/R cloth, and brushed cloth , velvet, or woolen fabrics, etc., some short fibers will fall off during the processing. The short fibers falling off the cloth surface accumulate in the rolling groove, and are stained by silicone oil to produce cohesion. These cohesion It is easy for the material to be brought to the roller along with the working fluid, forming sticky roller or silicone oil spots. Also, if the water quality is relatively poor, ordinary silicone oil will also condense to cause roller sticking and silicone oil spots.
★Solution
1. Do a good job of cleaning before driving, and remove any lint found.
2. Try to wash the lint of the cloth as much as possible before applying silicone oil.
3. Choosing silicone oil with good hydrophilicity can reduce the problem of silicone oil aggregation.
5. The influence of temperature on silicone oil
Many silicone oils currently on the market are not resistant to high temperatures, especially in the summer. Many factories in the south have very high temperatures. The temperature of the upper cloth surface is too high, and sometimes the temperature of the rolling groove can reach 60°C, which seriously affects the stability of the silicone oil. Because the temperature of ordinary amino silicone oil is too high, the elasticity changes greatly, resulting in roller sticking, oil drift, demulsification, etc., resulting in silicone oil spots.
★Solution
1. Wait for the cloth to cool before passing it through the machine with silicone oil.
2. Use normal temperature hydration materials and lower the temperature of the silicone oil working fluid as much as possible.
3. Choose silicone oil with good high temperature resistance and stability. Generally, the temperature in the rolling groove should not exceed 40°C.
6. The influence of time on the stability of silicone oil
Because some silicone oils have poor shear resistance, if the silicone oil emulsion is used for too long, roller sticking will occur. Phenomenon, some poor quality silicone oil will also form skin on the roller and stick to the roller, causing silicone oil spots. Affects driving and quality.
★Solution
After working for a period of time, stop the machine for cleaning and replace the working fluid. Cleaning should be strengthened. Generally, degreasing agent and cleaning agent can be used, and the ratio should be adjusted before scrubbing on the roller.
7. Effect of concentration on silicone oil
If the concentration of silicone oil is too high during use and the viscosity of the working fluid is too high, it will easily cause roller sticking or Skinning will occur, resulting in silicone oil spots; if the high-concentration silicone oil liquid is directly in contact with the cloth surface, silicone oil spots will occur.
★Solution
Set the process reasonably, try to keep the concentration of the silicone oil working fluid from being too high, strengthen operation management, and do not get the silicone oil stock solution onto the cloth.
8. The influence of ionicity on the stability of silicone oil
Since the types of silicone oil or softeners include cationic, nonionic, and anionic, compare the various types. The cationic type generally dominates the softening effect of varieties. Therefore, many silicone oils used in factories are cationic, while some whitening agents or other additives are anionic. These two or more additives can be used in the same bath. There will be an attraction reaction between yin and yang charges, causing agglomeration and sticking to the roller.
★Solution
1. Ionic consistency must be considered during processing.
2. When softening and whitening are used in the same bath, try to use non-ionic whitening agents.
9. The effect of softeners on fabric yellowing
The amino groups of amino silicone oil are easily oxidized by air to form chromophores, which causes the fabric to turn yellow. The cloth surface contains a lot of alkali agents and has a high pH. Cotton fabrics tend to turn yellow when dried at high temperatures; pollutant gases during storage cause storage yellowing.
★Solution
1. Try to use linear block copolymer modified silicone softener.
2. Strengthen process control, control the drying temperature, and add some anti-heat yellowing finishing agents during processing to control high-temperature yellowing.
3. During processing, anti-phenol yellowing finishing agents should be added appropriately to control storage yellowing.
10. The impact of water quality on silicone softeners
Some factories use poor quality water, which is hard and contains more calcium and magnesium ions. , the use of ordinary silicone oil will react and produce aggregation or silicone oil spots; the water quality is not good, and the content of microorganisms, algae and other impurities in it is too high, which also has a certain impact on the use of softeners. Some factories use recycled water, which contains some untreated chemical components, which may affect the stable use of softeners.
★Solution
1. For impurities such as microorganisms and algae, the sediment can be filtered to remove impurities before use.
2. If the water quality is too hard, soften the water before use.
3. Try to use silicone oil with good stability.
4. For reused water, test the pH value of the water before use and adjust it to about 6 with acid before use.
5 Conclusion
There are many factors that affect the use of silicone oil, which can be summarized as follows:
1. The influence of PH value on silicone oil;
2. The influence of the speed of the setting machine;
3. The softener in the cylinder is prone to sticking to the cylinder;
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4. Silicone oil agglomeration phenomenon;
5. Effect of temperature on silicone oil;
6. Effect of time on silicone oil stability;
7. The effect of concentration on silicone oil;
8. The effect of ionicity on the stability of silicone oil;
9. The effect of water quality on silicone softener.
The preventive measures are to formulate a reasonable process, select silicone oil with good stability, and operate in strict accordance with the prescribed process conditions to avoid the occurrence of factors that affect the stability of silicone oil. The above are some of the experiences the author has summarized in production practice. Please forgive me for any inappropriateness!
Silicone oil with good stability must be operated strictly according to the specified process conditions to avoid factors that affect the stability of the silicone oil. The above are some of the experiences the author has summarized in production practice. Please forgive me for any inappropriateness! </p
