The impact of workshop temperature and humidity on the production process of fine yarn was analyzed, the temperature and humidity control requirements in the production process of high-count fine yarn were introduced, and the technical parameters of temperature and humidity control in the production process were enumerated.
The quality of air temperature and humidity control and regulation in the workshop directly affects the output, quality, consumption of products and the physical and mental health of employees. The air conditioner should be able to meet the temperature and humidity requirements of textile fibers during processing. , ensure the normal progress of the production process of each process, and improve product quality and equipment utilization. Our company has made a lot of useful attempts on how to use air conditioning to meet the needs of the production of high-grade pure cotton yarn and reduce the impact of workshop air temperature and humidity on the production process.
1. Effect of temperature and humidity on cotton fiber spinning performance
There are many hydrophilic genes (-OH) in the macromolecules of cotton fiber and it has good hygroscopicity. The standard moisture regain rate of cotton fiber is 8.5%. The temperature and humidity of the air directly affects the moisture absorption and release state of cotton fibers. When the amount of moisture absorption is equal to the amount of moisture release, the moisture absorption equilibrium state is reached. Cotton fiber can reach the equilibrium state after 6-8 hours in a normal environment.
The relative humidity in the workshop has a great influence on the spinning performance of the fiber. When the relative humidity increases, it can promote and improve the alignment of long-chain molecules and increase the strength of the cotton fiber. Under standard temperature and humidity conditions, the strength of cotton fiber can be increased by 50% compared with that in a dry state. However, when the relative humidity exceeds 80%, the strength increase rate of cotton fiber decreases, and even tends to decrease. Temperature has little effect on fiber strength. Generally speaking, when the temperature is high, the motion energy of fiber molecules increases, which weakens the attraction between fiber molecules in certain areas, thus reducing the tensile strength. Some experiments have shown that when the temperature increases 1 ℃, the strength of the fiber is reduced by about 0.3%.
The cotton wax on the surface of cotton fiber has a protective effect on the fiber and is one of the reasons why cotton fiber has good spinning performance. The cotton wax in the fiber becomes hardened when the temperature is below 18.3°C, the lubrication effect is reduced during spinning, and the drafting resistance increases. When the ambient temperature exceeds 27°C, cotton wax begins to melt and become sticky, which also has a negative impact on spinning drafting. Only when the production environment temperature is between 18.3-27℃, the cotton wax will be in a softened state, the fiber will be lubricated and soft, and the spinnability will be optimal.
Temperature also affects the conductivity of fibers. Generally, as the temperature increases, the conductivity of fibers also increases accordingly. However, when the temperature is too high, the cotton wax melts, causing adverse consequences of winding the top roller and the roller. When the relative humidity increases from 20% to 60%, the conductive performance of cotton fiber can be increased four times; when the relative humidity is lower than 45%, a large amount of static electricity is easily generated and difficult to dissipate.
In the textile production process, high or low temperatures can easily lead to brittle breakage of cotton fibers, generate static electricity, and affect the drafting process. High or low relative humidity will also cause an increase in short lint fly and a decrease in yarn strength during the spinning process. Therefore, choosing the appropriate temperature and humidity based on the physical properties of cotton fiber is the prerequisite for spinning high-quality yarn products.
2. The impact of temperature and humidity on product quality during the production process
2.1 The influence of temperature and humidity on the blowroom and carding unit
Our company uses Xinjiang cotton and imported cotton, which have low moisture regain (generally below 6%) and are difficult to meet the cleaning process. The production process requires that the short staple increases more, so the raw cotton must be pre-bulked and humidified before production to increase the moisture regain of the raw cotton to more than 7.0%, which is beneficial to improving the fiber strength and reducing the impact of the fiber during the carding process. Production practice shows that (see Table 1), the moisture regain of raw cotton is too low, and the growth of raw cotton linters increases more. When the moisture regain of raw cotton reaches more than 7.5%, the growth of raw cotton linters basically stabilizes. Therefore, the relative humidity of cleaning cotton should generally be controlled at 60~65%, and that of carding should be controlled at 50~55%, so that the fiber is in a dehumidifying state of dry outside and wet inside during the production process, thereby enhancing the softness and impact resistance of the fiber. The moisture regain of raw cotton in the cleaning process is too small, the cotton fibers are fragile and easily broken, the waste increases, and the increase in short lint will directly affect the strength of the yarn. If the moisture regain is too high, it is not conducive to loosening and impurity removal, and the fibers are prone to bunching. If the relative humidity is too high during carding, carding will be difficult, neps will increase, impurity removal efficiency will decrease, and ends will break. If the relative humidity is too low, the fibers will be easily broken and noil will fly. The moisture regain rate of raw strips is generally controlled at (6.5±0.5)%.
Table 1 Card sliver short staple rate generated under different raw cotton moisture regain conditions
2.2 Effect of temperature and humidity on combing
Cotton fiber first moisturizes and then absorbs moisture during the drawing process. The moisture regain rate should be controlled at (6.8±0.5)%. The relative humidity of pre-drawing is required to be around 65~70%. At this time, the fiber is in a hygroscopic state, which can increase the friction coefficient of the fiber surface to ensure that the rollers hold the fiber and draw force during the drafting process, thereby improving the fiber’s strength. Parallel straightness, the straightening and parallel conditions of fibers under different temperature and humidity conditions are shown in Table 2. The combing process has high requirements on temperature and humidity. Generally, the moisture regain rate is required to be maintained between 63 and 68% to keep the fibers in a slightly dehumidified state of dry outside and moist inside, which is conducive to carding of the fibers by the carding element. If the relative humidity in the combing process is too high, it is easy to stick to the roll, top roller and roller, and the cotton net is easy to appear.By monitoring the temperature and humidity at the end of the workshop, we can accurately control the trend of temperature and humidity changes in the workshop, reasonably determine the adjustment range of the temperature and humidity meter, and ensure that the temperature and humidity of the spun yarn meets the production specification requirements.
With the deterioration of air quality, the number of haze weather is increasing, which has brought certain harm to textile production. If air conditioning measures are not effective, soot yarn will easily be produced. Therefore, we specially designed a fresh air supply channel and made use of the low resistance performance of needle-punched non-woven polypropylene fiber filter materials to make electret filter materials. This filter material uses the electrostatic effect to capture particulate matter (especially fine particles) based on the mechanical collection mechanism. It has high filtration efficiency without increasing the resistance. As a fresh air filter material, the filtration performance is improved and can Effectively prevent and control coal ash yarn and other phenomena. The workshop temperature and humidity control range is also shown in Table 4.
Table 4 Workshop temperature and humidity control range
Air conditioning management must be scientific, institutionalized and standardized. Controlling the moisture regain of semi-finished products and finished products in the production process, and reducing the fluctuation of moisture regain in each process by focusing on processes, equipment, operations, etc. is the basis for stabilizing product quality and ensuring stable production operations.