Polyester filament is widely used in clothing, decoration and other fields with its unique style. With the continuous improvement of spinning technology and people’s pursuit of the diversity of clothing requirements and personal delivery comfort, the demand for polyester filament The quality requirements are also getting higher and higher. Due to the limitations of DTY production process control and detection methods, some quality problems of DTY only become apparent during the weaving process. Tracking the after-sales service situation of a company in the past three years, the quality problems with more feedback from guest rooms mainly include color difference or horizontal stripes, stiff yarn, wool yarn, low weaving efficiency (unwinding), network and others. Their proportions are as shown in the figure 1.
These quality defects are not only caused by weaving, In addition to factors caused by dyeing and finishing processes or equipment, it is mainly caused by DTY raw materials. As users have more stringent requirements for weaving efficiency, yield and dyeing uniformity, especially with the increasingly fierce competition in the DTY market and the equipment advantages of new manufacturers, polyester DTY manufacturers are constantly improving the quality of DTY and increasing testing. Strengthen our efforts to provide products that satisfy customers.
Analysis and discussion
Color difference or Horizontal stripes
1 Defect phenomena and causes
As can be seen from Figure 1, cloth surface color difference or horizontal stripes are the most common quality defects of DTY in the weaving process, and they also cause losses. The biggest quality issue. It is the appearance of warp yarns with parallel axes that are an integral multiple of the color difference on the fabric, or the stripe color difference reflected in the weft direction, or the color difference in the warp and weft direction is inconsistent; in knitted fabrics, the width of one circle is produced at an interval equal to the total number of bobbins. (commonly known as a yarn loop), equidistant horizontal bars appear on it.
The phenomenon of color difference and horizontal stripes is mainly caused by the differences in the linear density, color absorption, curl shrinkage rate of certain spindles and the same batch number of silk spindles, resulting in the appearance of horizontal stripes or defects on the woven gray fabric. After dyeing and finishing, the cloth will have horizontal stripes of color difference. After finishing with glued sponge or sanding, the color difference will become more obvious. Differences in linear density will make the fabric rough or have abnormal light transmission and warp; differences in coloring will cause color differences; differences in curling and shrinkage rates will cause poor local dimensional stability of the fabric after dyeing and finishing high temperature treatment, and horizontal stripes will be caused by shrinkage differences.
2 Solutions
To solve the three problems that affect dyeing, namely linear density, color absorption and curl shrinkage, we must start with POY raw materials. Start full-process management. During the production process, the uniformity of linear density must be ensured, leaking slurry components and metering pumps must be dealt with promptly, and floating wires must be strictly diverted. Strengthen management to avoid the production of mixed batches and misaligned wires. Slice or melt quality, component cycle, and side-blowing cooling conditions must be stable; the pressure, pressure difference, temperature, and speed in the production process parameters must remain stable, and strict fluctuation diversion standards must be formulated. ; Strengthen spindle position management and reduce spindle position differences; replace expired DTY equipment components such as false twist discs, aprons, rollers, etc. in batches to keep the processing conditions of all spindle positions consistent; the wire path during DTY processing must be consistent; adopt More stringent color judgment standards. Practice has proved that it is increasingly difficult to meet the increasingly stringent dyeing needs of users using the gray card standard used by the national standard, often resulting in small color differences. At present, many manufacturers have adopted the 4.5 level standard and used it to increase the color judgment. The woven standard sample is used as a reference to subdivide the product color into dark, medium and light colors to further improve the dyeing uniformity of the product; in addition, it can be processed according to the characteristics of the customer’s fabric, such as weft knitted fabric, which can improve the curl shrinkage rate of DTY , so that DTY has good elasticity and fullness, and can cover up some slight streaks after the fabric is dyed and finished.
Among the above conditions, the consistency of DTY processing conditions is the most prone to problems. In the quality complaint statistics of the past three years, nearly 50% of color difference and horizontal stripe problems are due to the silk path of the texturing process. Ask about slippage or silk path problems. This problem requires the attention of DTY processing plants. Due to the characteristics of many spindles, many parts, and labor-intensive nature of DTY processing, the proportion of operating errors is high. According to the test comparison, the silk path between the first and second rollers is the most important in the texturing process. The POY yarn completes the lifting and false twisting process between these two components. The length of the silk path is the core of texturing. It must be accurate, otherwise any inconsistent conditions of stretching, heating, cooling, and twisting will lead to differences in fluffiness and shrinkage, which can easily cause large color differences and often cause large losses. Therefore, operators are required to do this after threading. A section of silk track is inspected and confirmed.
Stiff silk
1 Defect phenomena and causes
Stiff silk refers to the segmented, continuous and unfluffy tightly twisted silk on DTY. The shorter ones that are in the shape of points are called point stiffness. Under normal circumstances, stiff threads have little effect on the weaving process, but after dyeing gray fabrics, there will be spots of varying lengths, dotted (stiff spots) or intermittent strips (stiff threads). The color absorption is obviously darker than the surrounding ones and lacks elasticity. The main causes of stiff yarn include insufficient POY stretching, spindle failure, POY dryness and uneven oil content; excessive processing speed leads to yarn shaking and unstable processing; melt or slice quality problems and assembly.Not enough, but in the long-term user service process, we have concluded that these two factors are crucial indicators in determining the quality of product unwinding performance. Excessive residual torque increases the twisting performance of the yarn. Especially when warping, weft knitting, etc. start and stop, the tension of a section of DTY that has been unwound is relaxed, and kink is generated under the action of the residual torque, making the yarn unable to Through the yarn guide, steel reed teeth or knitting needles, the broken ends are formed.
Roll density is also a factor that has been ignored by many DTY manufacturers. Since this indicator has neither national standards nor contract regulations, it has not paid enough attention. However, in the study of unwinding breakage performance and roll In the process of examining the relationship between loading density, it was found that the two are closely linked. Especially for porous fine denier varieties such as 83dtex/144f, tests have found that ends will begin to appear when the package density is less than 0.66kg/cm3. When the density is as low as 0.61kg/cm3, the product base rate cannot be guaranteed to be unwound, especially In the area with the smallest density 5cm away from both ends of the silk cake, the tangled and broken ends of the silk ribbons are the most serious. The reason may be that the smaller the density, the looser the filaments and the easier they are to slide. Driven by the unwinding friction force, the upper layer of yarn gradually slips and loosens. After sliding to a certain extent, it becomes entangled with the lower layer of yarn under the action of residual torque, forming a broken end. Table 1 shows the end-break situation of unwinding 1kg of full roll DTY at the unwinding condition of 1500m/min under various package density conditions. It can be seen that as the package density increases, the unwinding performance becomes better and better. When the density reaches 0.68kg/cm3, the unwinding performance is better. Of course, due to the contradiction of the trip wire, the package density cannot be increased infinitely. During production, it was found that as long as the package density is controlled to above 0.67kg/cm3, user needs can be met.
2 Solution
The main reason for excessive residual torque is that the stability of the second hot box is not properly determined. One and two The temperature difference between the hot boxes is too high, so that the friction stress of the disc during the false twisting process is not fully released, and the yarn is not fully shaped. By appropriately increasing the temperature of the second hot box, the residual torque can be effectively reduced. Table 2 is a comparison of the unwinding and breakage conditions of a certain variety in the experiment under different second hot box temperature conditions (unwinding speed 1500m/min). It can be seen from Table 2 that an appropriate temperature setting of the second hot box can improve the unwinding breakage situation. Of course, considering that the temperature difference is too small, it is easy to cause color differences such as thickening and translucency in dyeing. After testing, generally for varieties with a linear density of 167dtex, it is more appropriate to set the temperature difference at 20 to 30°C.
Improving the package density requires appropriate molding parameters for the DTY silk cake. Otherwise, the upper limit will be reached by blindly increasing the winding tension to increase the package density. It is difficult to break through a certain critical value and prone to tripwires, convex shoulders and other phenomena. Especially for porous fine-denier varieties, due to the large number of single filaments, the bulkiness of the multifilament is increased. Compared with thicker denier filaments, the same weight requires more accumulation space, so the package density is smaller and the weaving process is more likely to occur. The phenomenon of wire breakage. Only by selecting appropriate forming parameters such as anti-bulging, anti-overlapping, end taper angle and intersection angle to make the density of the surface layer of the silk cake relatively uniform, can products with high packaging density and no trip wires be obtained.
Of course, DTY has a lot of filament and insufficient oil content, which will also have a certain impact on unwinding and end breakage, especially for porous and fine-denier varieties. Due to the large contact area between the filament and the yarn guide, A high number of frictions can easily generate static electricity, causing the filaments to tangle; the cohesion between the single filaments is not good and they twist around each other, resulting in a sudden change in the unwinding tension and breakage. Therefore, wool should be minimized during production and the appropriate oiling rate should be selected according to different varieties.
Poor network
1 Defect phenomena and causes
In order to meet the continuous improvement of weaving machinery processing speed and the requirements of some decorative fabric styles, polyester long Many varieties of silk are added with networks to increase the bundling of the threads, reduce the friction between the threads during weaving, and increase the processing speed. If the yarn network is poor, the warp yarns will frequently rub up and down against each other due to the shedding action in front of the reed of the loom, easily forming lint, tangles and breakage. At the same time, yarns with poor network will also have light-colored sunken defects on the fabric. The impact of poor network on the weaving process is somewhat similar to the serious analysis of wool yarn. The network problems reported by weaving users mainly include overall poor network and poor network of individual silk cakes.
2 Solutions
For overall network failure, improve the yarn tension by increasing the network air pressure, selecting the appropriate nozzle model, and adding 2BIS rollers Methods such as stability, adjusting the number of yarn holes and reducing the linear density of single filaments can effectively improve the overall fastness of the network, while also improving the overall level and reducing the chance of defective single-spindle networks. Table 3 shows the relationship between the network fastness of a company’s product 167dtex/47f heavy network products and the average user complaints per thousand tons. It can be seen that once the overall fastness of the product reaches a certain requirement, there will be a significant trend of individual or overall fastness problems. decline.
The main reasons for poor single-spindle network are clogged nozzles or equipment defects. Checking equipment defects through appearance self-inspection is the only way to reduce single-spindle network defects. , For example: the tension difference caused by the rust or looseness of the first and second rollers, the nozzle hole is blocked, the nozzle is not closed, etc.
Conclusion
To reduce the quality defects of polyester DTY in the weaving process, comprehensive quality management must be carried out in the production process. In addition to selecting the appropriate production In addition to the process, the focus is to ensure the quality of POY raw materials, maintain the stability of various process parameters in the production process, strengthen quality management of front and rear spindle positions, reduce differences between equipment spindle positions, improve product uniformity, strictly implement inspection standards, and understand customers Only by adjusting the needs and characteristics of the loom can we produce products that satisfy customers.
��, the only way to reduce equipment defects through visual self-inspection is to reduce single-spindle network defects, such as tension differences caused by rust or looseness of the first and second rollers, clogged nozzle holes, and unclosed nozzles.
Conclusion
To reduce the quality defects of polyester DTY in the weaving process, comprehensive quality management must be carried out in the production process. In addition to selecting the appropriate production In addition to the process, the focus is to ensure the quality of POY raw materials, maintain the stability of various process parameters in the production process, strengthen quality management of front and rear spindle positions, reduce differences between equipment spindle positions, improve product uniformity, strictly implement inspection standards, and understand customers Only by adjusting the needs and characteristics of the loom can we produce products that satisfy customers. </p
