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.
01 Basic properties of oil
1. Smoothness
Smoothness, or lubricity, is essentially the friction characteristic of oil. It is often expressed by 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.
Generally speaking, after a better oil agent is applied to the yarn, the static friction coefficient of F/F should be appropriately larger, so that the yarn 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.
The smaller the static friction coefficient of F/M is, the better. The smaller the kinetic friction coefficient, the better. This can reduce the friction between the wire and the metal, reduce the hair and broken ends, reduce the wear of the wire on the metal, and improve the wire quality. processing and weaving properties. 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.
Lubrication when the oil content is high (0.5% to 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 property
Polyester is a good insulator. When it is 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 yarns that need to undergo thermal processing (drawing, false twisting, etc.), the heat resistance of the oil is very important. Oils with poor heat resistance will decompose at high temperatures and the physical properties of the oil will 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. Interface characteristics
The 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.
02 Use of oil
1. Select oil according to the purpose of the thread
Silk for woven fabrics requires good sizing properties. After sizing, the sizing film should not peel off or fall off 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, and will produce high-speed friction with the knitting needles. It has high requirements for smoothness, bundling and antistatic properties. The oil used should have low viscosity, small friction coefficient and high oiling amount. 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. The amount of oil used 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.
high speed spinning��The dosage of dispersant should be increased; if the dye bath is contaminated, the fabric should be fully washed before dyeing, and the cleaning and maintenance of the equipment should be strengthened.
6. Tangle
Knotting of fabric bundles can cause downtime, especially when using full-fill equipment and when dyeing light fabrics. Some full-fill machines are equipped with back-jet and control valves to control fabric stacking, but since it is impossible to see how the fabric is stacked, tangling is still possible. Reducing tangles can only rely on the experience and responsibility of the operator.
7. Dye spots and color spots
Causes: dye agglomeration; oligomers produced in the dye bath.
Prevention methods: See the relevant content on dye agglomeration and oligomer prevention.
8. Pilling and abrasions
Causes and prevention methods: The diameter of the nozzle is too small, so that the nozzle pressure is too high. A nozzle of appropriate diameter should be selected according to the weight of the dye to make the spray pressure moderate and not too large; the cloth speed and the rotation speed of the cloth guide wheel are out of proportion. , the two should be proportional; when handling gray cloth or semi-finished products, if there are scratches due to impact, handle the gray cloth or semi-finished products with care to prevent impact and scratches; when opening the width, if it is scratched, manual opening should be used.
9. Stretch
Causes and prevention methods: The cloth capacity is too low, which lengthens the transportation distance of the cloth and increases the tension. The cloth capacity should be controlled appropriately; the liquid level of the dye liquor is set too high, thus increasing the friction between the water and the cloth. Resistance should be kept to the lowest level possible.
07Repair technology for common defects
1. Severe uneven dyeing
In this case, you cannot use the migration property of the dye to repair it back and forth, you must strip it and then dye it. If it is a light or medium color, it can be dyed into a dark color.
Stripping methods include:
①Oxidation and color stripping.
Prescription example: 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.
② Restore and peel color.
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, raise the temperature, the temperature should be a few degrees higher than the original dyeing temperature, and then slowly cool down.
For lightly dyed uneven fabrics, the migration property of the dye is generally used for counterdying. The process flow is as follows: start dyeing at 60°C, raise the temperature to 90°C in 15 minutes, then raise the temperature to 130°C in 40 minutes, keep it warm for 60 minutes, and 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 to 3 g/L of degreaser and non-ionic detergent each, and treat it at 100°C for 20 minutes, or use 2 to 3 g/L of degreaser and non-ionic detergent, and 1 to 2 g/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 colors with better coverage such as deep sapphire blue or black.
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