Because the color spinning yarn is different from the original yarn, its evaluation index should try to reflect the overall appearance of the product quality, and pay attention to the physical quality and post-processing performance. In addition to the quality indexes such as the breaking strength and variation coefficient of single yarn, the variation coefficient of 100 meters weight and weight deviation, and the coefficient of variation of dry evenness, etc. of the yarn of the original color, the assessment of the obvious color knot, kilometer cotton knot, color fastness and color difference and the broken end of the bobbin winding yarn is increased according to the characteristics of the color spinning yarn and finished product.
Since the finished products of the yarn of the original color need to be processed in many processes, and the color light of the color spinning line is the color light required by the finished product, so the color light and color fastness of the yarn are strictly required.
The difference between the quality index level of color spinning and the yarn of the original color
Because the fiber of color spinning yarn is dyed, some indexes of fiber are lower than that of the original fiber, especially for varieties with color cotton ratio more than 50%, the breaking strength and evenness index of single yarn are lower than that of the yarn, while other quality indexes have different range improvement.
1. Breaking strength of single yarn and variation coefficient of single yarn strength
The standard of cotton yarn takes the yarn breaking strength as a secondary index, and only one stop level is used as the downtrend. However, the practice of color spinning yarn shows that the yarn fracture strength has a great influence on post-processing, the breaking strength is too low, and the number of weaving breaks increases, which not only reduces weaving efficiency but also increases defects. Therefore, the breaking strength of single yarn is taken as the grading index in the standard of color spinning line, and the requirements are tightened. According to the characteristics of color spinning, the ratio of color cotton is more than 50% and less than 50%, respectively.
The coefficient of variation of single yarn strength is a discrete index reflecting the strength difference of single yarn. The smaller the dispersion, the more uniform the strength of single yarn. The breaking head of weaving is less, the weaving property is good and the quality of the products is improved accordingly. Therefore, the user has higher requirements on the strength variation coefficient of single yarn than that of single yarn. In the standard formulation of color spinning yarn, the quality products are required to reach 25% of the statistical value of Uster in 2007.
2. Yarn evenness
The test method of the evenness of the yarn in the standard of the yarn is carried out by instrument or visual inspection, and it is selected by the enterprise at any time. Because of the particularity of yarn, it is difficult to operate the uniformity of eye detection strip. Therefore, the method of visual inspection of the dry of blackboard strip is cancelled in the standard, and the electronic strip evenness instrument is used to check it. But the index level is lower than that of the original yarn. Taking 18.5tex pure cotton yarn as an example, the superior quality of the yarn is 15.5% and the color spinning is 16.5%.
3. Variation coefficient of 100m weight
The variation coefficient of 100 meters weight reflects an important index of yarn length uniformity. Because the index value of the standard of the yarn is low, it has been greatly improved in the standard of color spinning yarn, such as 1.8% of the excellent pure cotton yarn, and close to 25% of the statistical value of the 2007 Uster Gazette. This data is mainly considered that many enterprises have self-adjusting device in the end lane and the enterprises equipped with self-adjusting device on the end Lane drawing machine generally can reach 25% of the statistical value of the 2007 Uster bulletin. Well managed enterprises can reach the level of 5-10% of the statistical value.
4. Clear color knot
Because the color spinning line has a certain proportion of color cotton mixed in the production process, the strength and elasticity of dyed fibers will be damaged, and the short cashmere will also increase. If the spinning process is unreasonable, it is very easy to cause color knot, especially the color knot with the coarseness greater than 2.5 times of the original yarn, which has great influence on the physical quality of knitted products. Therefore, it will be regarded as a separate evaluation index in the standard formulation.
5. Knot number per kilometer
Because many enterprises inspect the dry evenness of the yarn line of the color by visual inspection, the total number of black board neps and blackboard cotton miscellaneous particles is used as the evaluation index, and there is no one column of cotton knot per kilometer. From the effect of knitting factory, KM cotton knot is also a key index which seriously affects the physical quality. Therefore, after all the yarn yarn is made of electronic strip drying instrument, the index is included in the evaluation index, and the superior products are required to reach 25% of the statistical value of the 2007 Uster bulletin.
6. Color fastness and color difference
The two indexes are also not available in the yarn of the original color, which is included in the standard for the special nature of the yarn. It is required to achieve good color fastness, non fading, water washing, soap washing and other good fastness, small color difference between batches, to achieve uniform color difference. Because of the difference between the current color fastness and the international level, in order to keep the gap between the two countries being narrowed, it is necessary to be included in the standard.
The test method of yarn quality
The quality inspection method of color spinning is consistent with that of the yarn except for obvious color knot, color fastness and color difference. In daily production, the yarn can be checked according to the standard. However, when the user has any objection to the product quality, it shall be inspected by the cylinder yarn, and it must be carried out under the standard test conditions. Now, the test methods of apparent color junction and color fastness are as follows:
1. Obvious test
1.1 definition of color knot
The color knot is a kind of cotton knot formed by the immature cotton or stiff cotton which is dyed and the original color is formed by the improper processing during the process of ginning or spinning.
1.2 determination of obvious color knot
1) When the content of dark fiber in color spinning is 30% or more, the obvious color knot refers to the dark big cotton knot and the native color cotton knot. When the content of dark fiber is less than 30%, the obvious color knot refers to the big cotton knot and dark cotton knot of the original color.
2) The obvious color knot in the cotton knot refers to the color knot with the coarseness reaching 2.5 times of the original yarn.
3) When the content of dark fiber or the content of the intrinsic fiber of the color spinning is less than 15%, the color fiber or the dark bundle fiber are wrapped on the yarn, and the count is obvious color knot because of the color comparison.
1.3 calculation of obvious color junction
The obvious color knot (grain) is equal to the total number of 10 obvious color knots in 10 squares of positive and negative sides of the blackboard.
1.4 inspection method
1) Based on the bobbin yarn, 10 blackboards are taken in each batch.
2) Requirements for inspection place: North natural light source shall be used as far as possible. When normal inspection, there must be large windows, and windows shall not have obstacles to ensure that the light in the window is light and sufficient.
3) Requirements for inspection of light source: generally, it is carried out under the illumination of not less than 400lx (the maximum is not more than 800lx). When the illumination is lower than 400lx, the light inspection (with blue or white fluorescent tube) shall be added. The light shall be shot from the left rear, and the angle of the inspection surface shall be 45 ± 5 ° with the horizontal plane. The shadow of the inspector shall be avoided from projecting to the blackboard.
4) Inspection steps: first insert the light blue (or other color) base plate between the sample and the blackboard, and then press the original blackboard plate on the sample for the obvious color knot inspection in each grid of both sides.
(5) Note: yarn shall not be turned over during inspection, and the line of sight shall be vertical to the yarn strip. The distance shall be based on the principle that the inspection personnel's visual power is not difficult to identify defects.
1.5 requirements for color knot inspection
The obvious color knot of color spinning is different from that of the cotton knot of the original yarn, which is the main index of the quality of the shadow knitted fabric. Therefore, the obvious color knot inspection of color spinning should also be combined with the physical quality of the knitted fabric surface. Generally, the color spinning factory will increase the fabric sample inspection.
2. The test of color fastness and color difference
As the color light of color spinning is the color light required by the finished product, compared with the yarn of the original color, the color fastness test is an essential and important item. The specific inspection items include: wash resistance, sweat resistance, abrasion resistance, sun exposure, color fastness, color difference, etc., and the inspection shall be carried out according to the standards of gb/t3921-3, gb/ t3922, gb/t3920, gb250 and other standards.
Conclusion
All kinds of yarn spinning enterprises should strengthen their understanding of the standards. In the process of implementing the standards, they should formulate practical internal control standards within the framework of corresponding national standards, strengthen the quality control of production process, and take "meeting the requirements of users" as the ultimate goal, Improve the quality management level of the enterprise.
