The pre-treatment of polyester yarn or fabric is generally based on oil removal, because spinning oil is added to polyester during spinning. So, what oils are generally used in polyester spinning oil?
There are many types of polyester filament oils, including POY and DTY oils, conventional spinning oils, drawn yarn oils, textured yarn oils and industrial silk oils, etc. They can all play a role in bundling, lubrication, reducing friction coefficient, antistatic, etc., but they have their own special functions and adaptability. Even for the same type of filament, due to different processing equipment and post-processing processes, the required oil agent The characteristics should also be different.
Polyester filament oils can be divided into two categories: spinning oils and finished oils. The basic properties of oils are the same, but the performance requirements for spinning oils are higher than those of finished oils.
Basic properties of oil
1. Smoothness Smoothness, or lubricity, is essentially the friction characteristic of oil.
The static friction coefficient (μs) and kinetic friction coefficient (μd) between wire and wire (F/F), wire and metal (F/M) and wire and rubber (F/R) after oiling are often measured )To represent. Generally speaking, after a better oil agent is applied to the wire, the static friction coefficient of F/F should be appropriately larger, so that the wire has good bundling, good winding shaping, and excellent unwinding properties. There are no special requirements for the dynamic friction coefficient of F/F, but during false twist deformation, if the wire slides, it will easily deform.
It is better that the static friction coefficient of F/M is smaller, and the smaller the kinetic friction coefficient is, the better. This can reduce the friction between the wire and the metal, reduce the hair and broken ends, and reduce the wire pairing. The wear and tear of metal can improve the processing and weaving performance of silk. The static and dynamic friction coefficients of F/R are appropriate. Because during the processing, rubber parts are used to increase the holding force of the wire. If the friction coefficient is too small, it will easily slip. Smoothness is determined by the properties of each component of the oil and has a certain relationship with the lubrication condition.
The lubrication when the oil content is high (0.5% ~ 1.0%) is fluid lubrication. In fluid lubrication, the friction coefficient increases with the increase in oil viscosity and oil content. The lubrication with the lowest oil content and the smallest friction coefficient is critical lubrication. At high speeds and high contact pressures, maintaining critical lubrication is of great significance. Under critical lubrication conditions, in addition to the viscosity of the oil agent affecting the friction coefficient, the oil film strength (interfacial adsorption force, intermolecular cohesion) also has a great influence on the friction coefficient. The oil film strength is high and the friction coefficient fluctuates little.
2. Antistatic polyester is a good insulator. When rubbed during processing and use, negative static electricity will be generated due to the accumulation of charges. Static electricity loosens the filaments and deteriorates processability. Therefore, oiled fibers should be antistatic. There are usually three antistatic mechanisms: enhancing the hygroscopicity of fibers; reducing friction; and neutralizing the generated charge. Three mechanisms can work simultaneously. The simplest method to measure the antistatic property of an oil is to measure the specific resistance of the wire after oiling. It can also measure the frictional charge of the wire.
3. Heat resistance For filaments that need to undergo thermal processing (drawing, false twisting, etc.), the heat resistance of the oil used is very important. Oils with poor heat resistance will be damaged at high temperatures. Decompose and the physical properties of the oil change. The volatilization of oil agents at high temperatures reduces the amount of oil applied and pollutes the environment. The tar or oil droplets produced will also affect the operation. The heat resistance of the oil agent can be measured by the volatilization loss method, that is, the oil agent is placed in an oven at 220°C for 8 hours, and its volatilization and decomposition loss are measured.
4. The interface characteristic oil must have certain emulsifying properties.
The oil emulsion is required to be stable and the emulsion has low surface tension and low viscosity. Can be evenly adhered to the fiber surface. If the interface characteristics are not good, even if other performance is good, it will not be able to meet the usage requirements.
Use of oil agent
1. According to the purpose of the yarn
Choose oil agent for woven yarn, which requires good sizing properties , after sizing, the serous film does not peel off or falls very little during weaving. This requires good compatibility between the oil agent and the slurry. The oil agent whose smoothing agent is mineral oil has better sizing properties. Because the viscosity of mineral oil is low, its emulsion oil film is not only compatible with the slurry, but also easy to be redispersed. The oil agent and slurry are replaced on the surface of the fiber. The oil film protects the serous membrane.
The knitting yarn will be directly put on the machine for warping and weaving, which will cause high-speed friction with the knitting needles. It has high requirements for smoothness, bundling and antistatic properties. The oil used should have low viscosity and The friction coefficient is small and the oiling amount is high.
High temperature resistance should be the main feature of the oil for false twist deformation, and its smoothness should be moderate. If it is too large or too small, it will cause tension changes and make the twist uneven. In addition, the oil agent is required to produce less white powder and adhere evenly. Uneven adhesion affects the dyeing performance of the silk.
There are many brands of oil agents. When a certain oil agent is newly used, it is best to conduct a small test before officially using it in production. Improper use will affect production and product quality.
2. Oil dosage
The oil dosage is calculated based on the oil content (OPU) of the yarn. The OPU of conventional spinning and weaving yarns is 0.6% to 0.7%, knitting yarns are 0.7% to 0.9%, and texturing yarns are 0.5% to 0.6%. The amount of oiling in conventional spinning also depends on whether lint and breakage occur during stretching, because some oils with high content will increase the tension of the thread, causing lint and breakage.
The OPU of high-speed spinning varies with the processing speed of the DTY machine. The higher the processing speed, the lower the OPU should be (see Table 1). If high-speed spinning POY is used to draw drawn yarn, the amount of oil should be appropriately increased.
The relationship between the processing speed of the DTY machine and the amount of oil applied
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8. Pilling and scratches
Causes and prevention methods: The diameter of the nozzle is too small, so that the nozzle pressure is too large. Re-select a nozzle with a suitable diameter so that the spray pressure is moderate and should not be too high; the cloth speed and the rotation speed of the cloth guide wheel are out of proportion and the two should be proportional; scratches due to impact when transporting gray cloth or semi-finished products should be avoided when transporting gray cloth or semi-finished products. The product should be handled with care to prevent impact and scratches; if it is scratched when opening, it should be opened manually.
9. Elongation
Causes and prevention methods: The cloth capacity is too low, which lengthens the transportation distance of the cloth and increases the tension. Control the moderate fabric volume;
The liquid level of the dye liquor is set too high, thus increasing the resistance between the water and the cloth. The liquid level should be kept as low as possible.
Common repair techniques
1. Severe uneven dyeing
This situation cannot be used The migration of dyes is subject to repair and must be stripped before dyeing. If it is a light or medium color, it can be dyed into a dark color.
The peeling methods are:
① Oxidation peeling.
Prescription examples: sodium chlorite 2~5g/L, acetic acid (98%) 2~3g/L, methylnaphthalene or chlorobenzene 3~5g/L. The process is: start treatment at 30°C, raise the temperature to 98°C in 30 minutes, boil for 60 minutes, and wash with water. If necessary, use bleaching powder and acetic acid to bleach at boiling temperature.
②Restore color stripping.
Prescription example: caustic soda (flakes) 1g/L, insurance powder 5g/L, chlorobenzene 5g/L. Nonionic surfactant 2g/L. The process is: start treatment at 30°C, raise the temperature to boiling for 30 minutes, boil for 60 minutes, then wash with cold water and hot water. If the stripping is not sufficient, process it again, or use the oxidation stripping method again. Using the above methods may damage the feel of the fabric, so try to avoid it.
2. Wrinkles and mild uneven dyeing
Wrinkle treatment method: Put the fabric back into the jet dyeing machine and raise the temperature. The temperature should be The original dyeing temperature is a few degrees higher and then slowly cooled.
For lightly dyed uneven fabrics, the migration property of dyes is generally used for counterdying. The process flow is as follows: start dyeing at 60℃, raise the temperature to 90℃ in 15 minutes, then raise the temperature to 130℃ in 40 minutes, and keep the temperature for 60 minutes. , then cool. The repair formula is: disperse dye (determined after testing), leveling agent 1~2g/L, and adjust the pH value to 5~6. When using dyes with poor dye migration, the dyeing temperature should be increased to 135~140°C, but this must be done on the premise that the mechanical properties are acceptable and the hand feel of the fabric is not affected. The dispersion leveling agent includes a carrier (or repair agent).
3. Dyeing oil spots
①Removal of local oil spots or dead oil spots in small batches. Usually non-ionic detergent, carbon tetrachloride, gasoline and other organic solvents are used, sprayed with a spray gun, washed manually, and then the fabric is washed.
②Removal of large-area oil spots. Use 2~3g/L of degreaser and non-ionic detergent each, and treat it at 100°C for 20 minutes, or use 2~3g/L of degreaser and non-ionic detergent, and 1~2g/L of high-temperature dispersant at 130°C. Process for 20 minutes.
③ Oil spots that are difficult to remove. If the oil spots are serious and difficult to remove, you can consider dyeing them into dark sapphire blue, black and other colors with better coverage. </p
