Set Up The Quality Problems And Control Methods!

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 or other application properties of textiles, or some special functions.

It can be concluded 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

I. 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 the 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 durability finishing.

II. According to the sorting 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.

Finalizing and 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 stretching and preshrinking.

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

3, the covalent chain method is used to determine fibrous structure. Such as resin finishing. Theoretically speaking, the shrinkage deformation of the fabric can be improved by any of the methods mentioned above, but in fact, two or more methods are often 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. The latter is mostly used, and often combined with various functions. Wet with finishing agent.

2) pull up: pull the edge of the cloth by two string needles and gradually pull it up. An overfeed device is arranged at the cloth feeding position, which can overfeed - 10 ~ - 50%. By adjusting overfeeding, the weight of cloth can be controlled in a certain range. The length of clip chain is 15-34m, generally 27m. The fabric enters the drying room with the clip chain running. The width of the fabric increases with the distance between the clip chains on both sides. Later, the distance between the clip chains keeps a certain range, so that the fabric maintains the required width, and the final distance decreases gradually, so as to facilitate the fabric to leave the clip chain. Generally, the upper and lower limits of finished fabrics are within the required dimensional 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 with a certain amount of moisture into the drying room, so the front of the more humid air can be excluded from the outdoor, the latter part of the more dry can be used. Generally speaking, the distance before the surface of the fabric reaches the required setting temperature is called the preheating zone, and the distance from the preheating zone to the heating zone is called the setting zone. Generally, the temperature and humidity in the setting area are controlled according to the variety and requirements of the fabric and the conditions of the mechanical equipment, generally within 20-60 seconds.

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 cooling method is to blow cold air to the fabric or use the fabric to pass through the cooling roller. Generally, the cloth dropping temperature is required to be below 50 ℃. Otherwise, after the fabric is piled into the cloth box or rolled, it will not only shrink due to the effect of heat, but also may produce wrinkles that are difficult to eliminate.

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 shape of synthetic fiber fabric mainly refers to the shrinkage and deformation of the fabric when it is heated, especially under high temperature. This reduces the use value of the fiber, so it is necessary to carry out heat setting processing.

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, it is due to the rearrangement of the macromolecular segments of the fiber, so as to eliminate the internal stress.

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 the size and shape stability in heat processing, reduce wrinkles that are difficult to eliminate, control door width and weight.

Two key points in the heat setting process of polyester knitted fabric are: controlling the setting temperature and 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 chromatic aberration.

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 a word, the technological conditions such as width, tension and overfeeding should be strictly controlled during operation.

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.