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Stereotyped finishing refers to physical, chemical, or physical and chemical methods, and biological methods to improve the appearance and internal quality of textiles, improve the wearability of textiles or other applications, or some special functions of the processing process.

Specifically summarized as follows:

1. normalize fabric: uniform fabric size and stable shape.

2. improve fabric feel: soft, tough and plump.

3. improve fabric appearance quality: gloss, whiteness, fuzzing and fuzzing.

4. new functions of fabrics: special finishing, such as waterproofing, fire protection, antibacterial, anti ultraviolet finishing, etc.

Finishing methods of knitted fabrics

First, according to the principle.

1. physical mechanical finishing: use water, heat, pressure and mechanical functions to achieve the purpose of finishing. It is characterized by chemical changes in fibers.

2. chemical finishing: using reactive chemical finishing agents to react with fabric fibers to change the physical and chemical properties of fibers.

3. collate: combine chemical finishing with mechanical and physical finishing. After finishing, the fabric has both mechanical and chemical changes. Such as polyester cotton fabric durable finishing.

Two. According to finishing effect.

1. handle, soft or stiff.

2. setting, finishing, stretching, raising or whitening.

3. appearance finishing, raising, raising or whitening.

4. special finishing, waterproof, fire prevention, anti bacteria, anti ultraviolet finishing.

Three. Durability according to finishing effect.

1. temporary.

2. semi durability,

3. durability.

Stereotyped finishing method

After finishing, a certain form of stability (form and size) is obtained, that is to eliminate the accumulated stress and strain in the fabric, so that the fibers in the fabric are in a proper arrangement, thereby reducing the fabric deformation factors.

Method:

1, adjust the fabric structure with mechanical method. Such as drawing and shrink finishing.

2, use strong expansion agent to eliminate the inherent strain of fabric. Such as mercerizing and liquid ammonia treatment.

3, the covalent chain method is used to determine fibrous structure. Such as resin finishing. Theoretically speaking, any method can improve the shrinkage deformation of fabric, but in fact, two or more methods must be combined to achieve the goal.

Example:

Stretching (setting).

1, principle: using cotton fiber in a hygrothermal state, it has a certain plasticity, widen the door width to the specified size (refer to the size of the weft) to meet the specifications of printing and dyeing products, eliminate the wrinkles on the fabric and improve the dimensional stability of the fabric.

2, equipment: needle chain chain drawing machine and heat setting machine.

3. Main function parts of the equipment: wet and pull drying and cooling.

1) wet, generally moisture content of 15 to 20%, to be uniform. Methods: wet ring heating (intermittent), brush drum splashing water, steam spray to wet, high pressure water spatter to wet, steam to wet, etc., you can also first dip the fabric, drying to half dry, and then stretching. Later users are mostly used, and often cooperate with various functions. Use the finishing agent to wet.

2) pull up: pull the edge of the cloth by two string needles and gradually pull it up. The feeding device is equipped with over feeding device, which can exceed -10 to -50%. By adjusting the over feeding, the weight of the cloth can be controlled within a certain range. The length of pin chain is 15 ~ 34M, usually 27M. As the fabric enters the drying room with the needle chain, the width of the fabric increases with the distance between the needle and chain on both sides. The distance between the needle and chain is kept at a certain extent, so that the fabric needs to maintain the required width and the final distance gradually decreases, so as to facilitate the cloth to break away from the needle chain. Generally, the finished fabric is the upper and lower limit in the required dimension tolerance.

3) heating mode: hot air is used for many, and strong air blower is used to heat the air to the heater and spray on the fabric under the hot air pipe. As the fabric enters the drying room with a certain amount of moisture, the humid air in front can be excluded from the outdoors, while the latter is relatively dry. Usually the distance before the fabric surface reaches the desired temperature is called the preheating zone, and the distance from the preheating zone to the heating zone is called the setting area. It is usually controlled in 20~60 seconds according to the variety and requirement of the fabric and the condition of the machine.

4) cooling: when the fabric is away from the setting area, it must try to keep it in a state of cooling when forced to cool. The method of cooling is to blow cold air to the fabric or to use fabric through the cooling roller. Generally, the falling temperature is below 50 degrees. Otherwise, if the fabric is stacked in a cloth box or rolled into a coil, it will not only shrink due to thermal effect, but also produce wrinkles which are difficult to remove.

Setting of polyester knitted fabric

Polyester is a thermoplastic fiber, in dyeing and a series of processing, due to repeated mechanical action and multiple stretch, so that the original fabric door and coil geometry changes, resulting in deformation and shrinkage, or even straight wire skew, seriously affecting the quality of products.

The purpose of heat setting is to make the polyester knitted fabric heated under tension. The fabric is baked at the prescribed temperature, which increases the thermal movement between the secondary bond and the molecular segment of the fiber molecules, so that the molecules can be reassembled and arranged, and the internal stress is relatively stable.

Heat setting of polyester and other synthetic fibers

1. polyester and other synthetic fibers belong to thermoplastic fibers. In their macromolecular structure, the hydrophilic group has close fiber structure and low moisture absorption, and the swelling degree of the fibers after wetting is small. The stability of the size and morphology of synthetic fabrics mainly refers to shrinkage and deformation of fabrics when heated, especially at higher temperatures. This reduces the use value of fiber, so heat setting is necessary. The processing principle is to use the thermoplasticity of synthetic fibers to keep the fabric in a certain size and shape, heat it to the required temperature, and then rapidly cool down, so that the changed micro structure is fixed, so that the size and shape of the fabric can be stabilized. In essence, the internal stress is eliminated by rearrangement of fiber macromolecular segments.

2. spandex (Draft) is also synthetic fiber, which belongs to thermoplastic fiber. Therefore, spandex elastic cotton fabric and other synthetic fibers have to be pre processed and post processed to improve their size and shape stability during hot working, and to produce wrinkles which are difficult to eliminate and control door width and weight.

Two key points in the heat setting process of polyester knitted fabric:

Control setting temperature

Setting time

If the heat setting temperature is too low and the time is too short, it will cause defects such as uneven surface, uneven opening, shrinkage of the door and so on. It will lose the shaping effect. If the setting temperature is too high or the time is too long, it will cause the fabric to become hard and brittle, the strength will decrease, the elasticity will decrease, and some disperse dyes will sublimate to produce a color difference, which can even make the fiber melt.

Practice has proved that:

The suitable setting temperature of polyester knitted fabric is 180-210 C, the setting time is 20-90s, and the cooling temperature is about 50 C.

It can be calculated by pressing mode (according to different setting mechanisms):

Setting time (s) = setting length (m) / fabric linear velocity (m/min) * 60

For all kinds of polyester knitted fabrics, when the setting temperature is 185-190 degrees, the line speed is: polyester warp knitted mosquito net cloth 10-15m / min, polyester warp knitted shirting cloth 12-18m / min, polyester warp knitted fabric, weft knitted fabric 12-20m / min, polyester yarn dyed jacquard fabric 7-lOm / min, when setting temperature is at Z921.

When setting the shape, the tension and overfeed of the fabric should not be neglected.

If the width of the drawing is larger than that of the fabric, the shrinkage will increase and the strength will decrease.

If the overfeeding is too large or the tension is different in size, it is easy to cause the zonal wave shape (commonly known as "auricular edge"), otherwise it will generate streaks in meridional direction. In short, in the operation process, we must strictly control the width, tension, over feeding and other process conditions.

Heat setting quality problem

　　 Matters needing attention

1. in order to eliminate wrinkles formed in high temperature, the setting temperature is 30~40 degrees higher than that of the highest dyeing temperature.

2. when the drawing is fixed, attention should be paid to checking the skew of the weft. Apart from the seam should be flush and the cloth should be lengthened properly, it is necessary to pay attention to the tension on both sides when the machine is put on the head. In the process of operation, we should check the deformation of the skew and flower shape regularly and correct it in time.

3. when the drawing is fixed, the width of the embryo spreading machine should be measured regularly. If the width does not meet the technological requirements, it should be adjusted and controlled at any time.

4. the type of drawing is directly related to the quality of finished cloth, such as shrinkage, weight, pattern and texture. Therefore, the control of technological conditions should be strictly controlled.