Style finishing refers to a process that improves the appearance and intrinsic quality of textiles, improves the wearability or other application properties of textiles, or certain special functions through physical, chemical, or combined physical and chemical methods, as well as biological methods.
The specific summary is:
1. Standardize the fabric: consistent width and size of the fabric Stablize.
2. Improve fabric feel: soft, stiff, plump.
3. Improve the appearance quality of fabrics: increase gloss, whiteness, velvet, and fluff.
4. Give fabrics new functions: perform special finishing such as waterproof, fireproof, antibacterial, anti-UV finishing, etc.
Knitted fabric finishing methods
1. According to principles
1. Physical and mechanical finishing: using moisture, heat energy, pressure and mechanical effects to achieve the purpose of finishing. The characteristic is to cause chemical changes in the fiber.
2. Chemical finishing: Reactive chemical finishing agents are used to chemically react with fabric fibers to change the physical and chemical properties of the fibers.
3. Comprehensive finishing: chemical finishing and mechanical and physical finishing are combined. The fabric will have both mechanical and chemical changes after finishing. For example, polyester-cotton fabrics can be polished for durability.
2. Classification according to finishing effect
1. Feel of finishing, soft or stiff.
2. Styling and finishing, stretching, fluffing or whitening.
3. Appearance finishing, raising, fluffing or whitening.
4. Special finishing, waterproof, fireproof, antibacterial and anti-UV finishing.
3. According to the durability of the finishing effect
1. Temporary,
2. Semi-durable,
3. Durable.
Style finishing method
After finishing, a certain form of stability (shape, size) is obtained, that is, the elimination of The accumulated stress and strain keep the fibers in the fabric in a more appropriate arrangement, thereby reducing fabric deformation factors.
Method:
1. Use mechanical methods to adjust the fabric structure. Such as tentering and pre-shrinking finishing.
2. Use powerful bulking agents to eliminate the inherent strain of fibers in the fabric. Such as mercerization and liquid ammonia treatment.
3. Use covalent cross-linking method to determine the fiber structure. Such as resin finishing. Theoretically, the shrinkage deformation phenomenon of fabrics can be improved by using any of the above methods, but in fact, two or more methods must be combined to achieve the goal.
Example
Tenter (shaping).
1. Principle: Utilize the certain plasticity of cotton fiber in hot and humid conditions to slowly widen the door width to the specified size (referring to the weft size) to meet the specifications of the finished printing and dyeing products. , eliminate existing wrinkles on the fabric and improve the dimensional stability of the fabric.
2. Equipment: pin chain tenter and heat setting machine.
3. Main functional components of the equipment: moisture supply, tenter drying and cooling.
1) Moisture supply, the general moisture content is 15 to 20%, and uniform moisture supply is required. Methods: Wetting in circles (intermittent), spraying water on a brush roller, steam spraying, high-pressure water spraying, steam, etc. You can also pad the fabric first, dry it until it is semi-dry, and then tenter it. . The latter is mostly used and is often organized with various functions. Use padding finishing agent to moisten.
2) Tenturing: Two strings of needle and clip chains are used to tie the edge of the fabric and gradually stretch it. There is an overfeeding device at the cloth feeding place, which can overfeed by -10~-50%. The unloading weight of the cloth can be controlled within a certain range by adjusting the overfeed. The length of the needle clip chain is 15~34M, usually 27M. The fabric enters the drying room as the needle clip chain runs. The width of the fabric increases due to the gradual increase in the distance between the needle clip chains on both sides. Later, the distance between the needle clip chain remains within a certain range so that the fabric maintains the required width. Finally The distance gradually decreases to facilitate the separation of the cloth from the needle clip chain. Generally, the finished fabric has upper and lower limits within the required dimensional tolerance range.
3) Heating method: Hot air is the most common method. A powerful blower is used to send the air to the heater for heating, and then it is sprayed onto the upper and lower sides of the fabric through the hot air duct. Since the fabric enters the drying room with a certain amount of moisture, the humid air in the front can be discharged from the outside, while the drier air in the rear can be used. Usually, the distance traveled by the fabric surface before it 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. Usually, the temperature and humidity of the setting area are controlled according to the fabric variety and requirements, mechanical equipment conditions, etc., usually within 20 to 60 seconds.
4) Cooling: After the fabric leaves the setting area, it must be forced to cool down by trying to keep it in the state it was in when it was set. The cooling method is to blow cold air on the fabric or use the fabric to pass through the cooling roller. Generally, the drop temperature is required to be below 50°C. Otherwise, after the fabric is piled into the cloth box or rolled into a roll, it will not only shrink due to the effect of heat, but also may cause difficulty. Eliminate wrinkles.
Shaping of polyester knitted fabrics
Polyester is a thermoplastic fiber. During a series of processing processes such as dyeing, due to multiple mechanical actions and multiple stretches, the original width and coil geometry of the fabric are changed, resulting in deformation and shrinkage. Even the horizontal and vertical strands are skewed, seriously affecting the quality of the product.
The main purpose of heat setting is to heat polyester knitted fabrics under tension and bake the fabrics at a specified temperature to make the secondary bonds between fiber molecules and molecular segments Thermal movement intensifies, which allows the molecules to recombine and arrange, and the internal stress is relatively stable.
Heat setting of polyester and other synthetic fibers
1. Polyester and other synthetic fibers are thermoplastic fibers , there are hydrophilic groups in their macromolecular structure, the fiber structure is tight, and the hygroscopicity is very low. The expansion of the fiber after being wetted is small, and the shrinkage phenomenon is not significant under normal conditions. The dimensional and morphological stability of synthetic fiber fabrics mainly refers to the shrinkage and deformation of the fabric when heated, especially under higher temperature conditions. This reduces the use value of the fiber, so heat setting processing is required. The processing principle is to use the thermoplasticity of synthetic fibers to maintain the fabric in a certain size and shape, heat it to the required temperature, and then cool it rapidly to fix the microstructure that has changed after heating, thereby stabilizing the size and shape of the fabric. . It is essentially due to the rearrangement of fiber macromolecule segments, thereby eliminating internal stress.
2. Spandex (stretch frame) is also a synthetic fiber and is a thermoplastic fiber. Therefore, elastic cotton fabrics containing spandex need to be pre-shaped and post-shaped like other synthetic fibers to improve the Its dimensional and morphological stability during thermal processing can prevent wrinkles that are difficult to eliminate and control the width and weight.
Two key points in the heat setting process of polyester knitted fabrics:
Control setting temperature
Setting time
If the heat setting temperature is too low, the time is too short. It can cause fabric surface defects such as unevenness, stiffness, and width shrinkage, and lose its shaping effect; if the setting temperature is too high or the setting time is too long, it will cause the fabric to become hard and brittle, with reduced strength, reduced elasticity, and some dispersion. The sublimation of the dye causes color difference, which can even cause the fiber to melt in severe cases.
Practice has proven:
The appropriate setting temperature for polyester knitted fabrics is 180-210℃, the setting time is 20-90s, and the cooling temperature is about 50℃.
It can be calculated according to the following formula (calculated according to different shaping machine structures):
Setting time (s) = shaping length (m )/fabric linear speed (m/min) × 60
All kinds of polyester knitted fabrics are on the Z921 needle plate tenter setting machine. When the setting temperature is 185-190°C, The linear speed is: polyester warp knitted mosquito net cloth 10-15m/min, polyester warp knitted shirt cloth 12-18m/min, polyester warp, weft and knitted outerwear cloth 12-20m/min, polyester yarn-dyed jacquard cloth 7-10m/min. min.
When setting the shape, the “tension” and “overfeed” of the fabric should not be ignored and should cooperate appropriately with each other.
If the width of the tenter exceeds the width of the fabric, it will cause an increase in shrinkage and a decrease in strength;
If the overfeed is too large or the tension is unequal, it will easily cause weft wavy shapes (commonly known as “fungus edges”), otherwise stripes will occur in the warp direction. In short, process conditions such as width, tension, and overfeeding must be strictly controlled during the operation.
Heat setting quality issues
Notes
1. In order to eliminate wrinkles formed at high temperatures, the tenter setting temperature is 30 higher than the maximum dyeing temperature. ~40℃.
2. When setting the tenter, you should pay attention to check the weft and skew conditions. In addition to the seam head being flush and the headband fabric being appropriately lengthened, you should also check the weft and skew when setting the tenter. , pay attention to even tension on both sides. During the operation, the weft inclination and pattern deformation should be checked frequently and corrected in time.
3. When stenter is being finalized, the width of the blank fabric falling machine should be measured frequently. If the width does not meet the process requirements, it should be adjusted and controlled at any time.
4. Stenter setting has a direct relationship with the quality of the finished fabric, such as shrinkage, weight, clear pattern, texture and other appearance quality. Therefore, the process conditions should be strictly controlled. </p
