Anti-shrinking finishing refers to finishing clothes and the like for preventing shrinkage. The mechanical method is an effective way to solve the shrinkage of the warp direction, which is to make the potential shrinkage existing in the fabric and pre-retract it before it becomes a finished product. Mechanical shrinkage can be achieved with special equipment. In addition, there is a chemical shrink-proof method that seeks to reduce the hydrophilicity of the fiber so that it does not swell greatly in water, so that the fabric does not cause serious shrinkage.
Shrinkage
1. Shrinkage: When the dried fabric is wetted by water in a relaxed state, the size shrinks significantly. The shrinkage rate of the fabric is evaluated by the shrinkage rate in production. Shrinkage rate: The difference in length between the warp direction and the weft direction before and after washing according to the specified method, which is the percentage of the length before washing, which is the shrinkage rate in the warp direction or the weft direction.
2, felt shrinkage: some fabrics (such as wool fabrics), in addition to the general shrinkage phenomenon, in addition to the general shrinkage phenomenon, due to mechanical action, the fibers will undergo special creep and entanglement, and the fabric shrinks into a tight state, which Shrinkage is called felting and is generally expressed as a percentage change in area.
Shrinkproof finishing
Fabrics that are unstable in size (ie, have potential shrinkage) are shipped out as finished products, and it is difficult to make garments with stable shape (such as wrinkles at the seams, inaccurate flower shapes, poor forming effects, etc.), and the finishing effect during the taking process. Persistence is very poor. It is necessary to improve the shrinkage of the fabric by physical and chemical methods. The fiber shrinkage is different for different fabrics.
The wool fabric not only has serious initial shrinkage; but the subsequent shrinkage is also prominent. The initial shrinkage of the cotton fabric is larger, but the subsequent shrinkage is not high; the composite fabric shrinks less. In addition, the shrinkage of the fabric is also related to the structure of the yarn, the fabric, and the processing.
Shrinkage mechanism
1. Fibers with "dry setting" deformation cause shrinkage due to internal stress relaxation, but not the main reason.
2. The anisotropic swelling effect increases the diameter of the yarn, and the fiber winding of the yarn in the yarn increases, causing the yarn to shrink, but only 2 to 3.5% is still not the main reason.
3, the anisotropic swelling effect, the fabric shrinkage before and after wetting, is the main cause of shrinkage. Weaving: The length of the yarn after weaving is shortened (ie, the difference between the length of the yarn and the length of the fabric as a percentage of the length of the fabric). The above discussion is about the shrinkage mechanism of the cotton fabric, and the wool fabric has a similar phenomenon.
Anti-shrinking method
Mechanical pre-shrinking: an effective method to solve the warp shrinkage
Principle: The weft and warp woven shrinkage of the fabric is increased to a certain extent, so that the fabric has a slack structure. In effect, it is the potential shrinkage that originally exists in the fabric, which is pre-retracted before it becomes a finished product. The following equipment (pre-shrinking machine) is mainly used to achieve the pre-shrinking purpose.
1. Ultra-feeding needle-clamping tenter: The super-feeding device is used to stretch the fabric in a relaxed state, and the fabric can be retracted under the condition of constant-width drying to achieve the purpose of improving warp shrinkage.
2. Rubber blanket compression type anti-shrinking machine When the rubber blanket passes between the guide roller and the pressure-bearing roller, it is thinned and stretched. After leaving, the rubber shrinks back to its original shape, forcing the fabric to shrink synchronously. It consists of a feeding device, a wetting device, a short cloth tenter, a three-roll rubber blanket compression device and a blanket dryer.
Features: The shrinkage rate can be reduced to less than 1%, the equipment is simple in construction, and the fabric shrinks and sets more fully due to the pressure between the guide roller and the pressure roller.
3, blanket compression type anti-shrinking machine thick blanket bypassing the smaller diameter of the guide roller, the outer layer expands, return to the original, leaving the fabric close to the stretch surface of the blanket synchronous shrinkage, to eliminate potential shrinkage purpose. It consists of five parts: cloth feeding, wet feeding, full width, shrinking and drying (no tension). Features: The shrinkage rate can be reduced to less than 2%, the hand feels full, soft and has good taking performance.
chemical method
The pre-shrinked fabric structure becomes slack and the weaving is large. Although there is no shrinkage problem, it is easy to be elongated. Especially for viscose fabrics, chemical methods are required to achieve dimensional stability.
The basic principle of the chemical method: try to reduce the hydrophilicity of the fiber so that it does not swell greatly in the water, so that the fabric does not cause serious shrinkage. It is mainly treated by resin initial shrinkage or cross-linking agent, that is, the fabric has anti-shrinkage effect after anti-wrinkle finishing.
Fabric finishing
1. Strengthening the shaping effect in finishing
Drying on an overfeed pin tenter;
Try to reduce the warp tension when drying.
2, relaxation pre-shrink
The fabric is humidified to leave it in a relaxed state for a certain period of time and dried slowly.
Take a mandatory pre-shrinking method. The fabric is exposed to steam under tension and shaken or shaken, and then maintained under high tension without tension to obtain forced retraction.
Anti-felting finishing
1. The meaning and method of anti-shrinking
Eliminating the fluffing properties of wool fabrics is of great importance for pure wool fabrics and knitted fabrics, not only to achieve true dimensional stability of the fabric, but also to reduce pilling.
The reason for the felting: D, F, E due to the scale structure of the wool, and the high stretchability (elasticity) of the wool. The scales hold the displaced wool in a new position (braking factor), which causes the wool to move relative to each other (dynamic factor). As long as one of the factors is eliminated, the fluffing property is reduced.
The method to eliminate wool fluffing is:
A. Change the friction properties of wool
B. Changing the stretchability of wool Regardless of the method used, the reaction should be strictly controlled to a certain area of the fiber.
2, "subtraction" anti-felting process advantages: uniform processing, no yellowing, does not affect the fiber strength, the process is easier to control.
3. "Addition" anti-felting treatment: The polymer is deposited on the surface of the wool fiber, and the fibers are bonded together, and cannot be moved at will, thereby obtaining an anti-felting effect.
The resin should have the following conditions:
The resulting polycondensate should be soft and chemically compatible with the wool.
Can be attached to the surface, the amount is small and uniform.
It is best to combine with wool with a chemical bond.
4. Protease treatment method Chlorination method: Industrialized treatment is relatively mature, but labor protection is poor, environmental pollution is serious, affecting human health. With the enhancement of human health requirements and environmental awareness, the biodegradable protease method has attracted attention.
This method is a smoothing treatment (surface denaturation) of the wool surface. The principle is to use a protease to extract the inner layer of the scale which is easily digested by digestion. However, the middle layer above the inner layer of the scale has higher sulfur content and stronger anti-enzymatic ability. It must first oxidize the sulfur bridge with an oxidizing agent to reduce its anti-enzymatic ability, easy to digest and remove, in order to avoid enzymatic hydrolysis of the inner stratum corneum of the wool. Add enough neutral salt to the enzyme treatment.
The treated wool not only improves the anti-shrinking property, but also properly breaks the cross-linking of the wool due to the enzyme treatment, reduces the rigidity of the fiber, makes it easy to stretch, does not easily retract, feels relatively soft, and the wool becomes smooth and thin. Rich in cashmere.
