| With the development of new spinning technology,air-jet vortex spinning plays an important role in the field of spinning with the advantages of fast spinning speed,high spinning efficiency,small foot area and short spinning process.After several generations of technological innovation and process improvement,air-jet vortex spinning products on the requirements of raw materials gradually reduced,adapt to the continuous enrichment of fiber types,product varieties are also toward the direction of fine and coarse.Among them,the air-jet vortex spinning low count yarn is mainly used in industrial textiles.The requirements for raw materials are relatively low,and the selection of raw materials is more extensive.Combined with the advantages of air-jet vortex spinning,it shows a wide application prospect.However,there are still many problems in the production of low count yarn by air-jet vortex spinning.Compared with the medium count yarn by air-jet vortex spinning,the breaking strength of low count yarn by air-jet vortex spinning is still insufficient,and there are also problems such as frequent yarn breakage,uneven single yarn strength and uneven evenness caused by wrapping weak rings.Therefore,this paper takes polyester air-jet vortex spinning low count yarn as the object,studies its wrapping effect and evaluation method,analyzes the main factors affecting its yarn quality,and optimizes the yarn quality through the improvement of relevant process parameters to guide production.Specific research work includes:(1)Cause analysis of poor yarn quality of the low count yarn in air-jet vortex spinning.First,determine the general model configuration and process parameters of air-jet vortex spinning polyester yarn,and determine the key process parameters affecting yarn quality,and confirm the adjustable range.By observing the yarn structure of air-jet vortex spinning low count yarn,it is found that the yarn structure of low count yarn is poor,the wrapping is disordered,and most of the core fibers are exposed to the outer surface.According to the yarn formation mechanism of air-jet vortex spinning,it is analyzed that the wrapping effect is not as good as that of medium and fine count yarn,which may be the reason for the poor yarn performance of low count yarn.(2)Construction of the evaluation method for wrapping effect of the air jet vortex spinning and its influence on yarn properties.In order to quantify the wrapping effect,a super depth of field microscope is used to collect the image of air-jet vortex spinning yarn,and the ratio of the area of the wrapped yarn per unit length to the total area of the yarn was defined as the wrapping coefficient.The wrapping coefficient was used to characterize the wrapping effect,and the method of extracting and calculating the wrapping coefficient was established.The feasibility of using wrapping coefficient to characterize wrapping effect is verified.In order to further analyze the correlation between the breaking strength of single yarn and the wrapping effect,the wrapping coefficient and breaking strength of air-jet vortex spinning yarns with different linear densities were tested,and the relationship model between the breaking strength of single yarn and the wrapping coefficient was established and verified.(3)Post spinning process optimization aimed at improving the wrapping effect of air-jet vortex spinning polyester low count yarn.Based on the principle of air-jet vortex spinning,the key process parameters are analyzed.Combined with the influence of wrapping effect on yarn quality and the relationship model between wrapping coefficient and single yarn breaking strength,it is concluded that spinning speed and nozzle pressure are the main factors affecting the change of wrapping coefficient.Under this guidance,the full factor experiment within the parameter range is carried out for the nozzle pressure and spinning speed.Guided by the results of variance analysis,the optimum process parameters of air-jet vortex spinning polyester low count yarn were finally determined: spinning speed 430 m/min,nozzle pressure 0.57 MPa.It can be seen from the experimental results that further increasing the nozzle pressure of air-jet vortex spinning is expected to further improve the yarn performance.However,due to the limited supply of pressure in the enterprise where the experiment is located,the maximum nozzle pressure can only be opened to 0.57 MPa.It is concluded that,on the one hand,the method proposed in this paper can be used to optimize the process parameters in the actual production of enterprises,and the speed and yarn quality can be selected according to the comprehensive production efficiency.On the other hand,in order to improve the yarn quality of low count yarn,the process of air-jet vortex spinning machine in the future can be developed in the direction of improving nozzle pressure.(4)In order to improve the fore-spinning process optimization of air-jet vortex spinning polyester low count yarn wrapping effect.In order to further improve the performance of polyester low count yarn in air jet vortex spinning,combined with the front spinning process,the whole process spinning process was optimized for the weak ring structure of yarn.Since there is no roving process in air-jet vortex spinning,the cone yarn is directly formed by the sliver,so the quality of the sliver is also the key to ensure the yarn quality.Therefore,the drawing process was optimized,and the orthogonal experiment within the parameter range was carried out for the number of combined roots,the amount of cooked strips and the drafting ratio of the back zone.Using the response surface analysis technology,the optimal drawing process parameters of the air-jet vortex spinning coarse yarn were finally determined by the guidance of the constructed response surface model: Therefore,the final drawing process was optimized,and orthogonal experiments were carried out within the parameter range for the number of combined roots,the basis weight of the sliver and the draft multiple in the back zone.Using the response surface analysis technology,through the guidance of the constructed response surface model,the optimal drawing process parameters of the air-jet vortex low count yarn were finally optimized and determined: the number of combined roots was 6,the basis weight of the sliver was 24 g / 5 m,and the draft multiple in the back zone was 1.588,so the best wrapping coefficient is 0.535.From the experimental results,it can be seen that the weight of the sliver has a great influence on the breaking strength and elongation at break of the yarn,and the number of combined roots mainly affects the strength unevenness and evenness of the yarn.Therefore,this method can guide enterprises to improve the process of air-jet vortex spinning low count yarn and improve the performance of polyester low count yarn.In conclusion,the wrapping effect characterization method and the air-jet vortex spinning process optimization method based on the wrapping effect proposed in this paper can be used to guide the air-jet vortex spinning process optimization and help promote the development of air-jet vortex spinning low count yarn varieties. |
