In order to solve the problem of bleaching and removing the pre-treated linen in production, the cause of the above phenomenon needs to be clearly established, and then the targeted technological measures are studied. To achieve a process goal of reducing the weight loss rate of the linen fabric before processing, reducing the strength loss in the pretreatment process, and ensuring the linen fabric style.
1 Test
Three bleached pure linen fabrics, primary colored linen fabrics, and dry-spun linen/cotton fabrics were treated with the same bleaching bath to compare the residual degree of linen skins and to verify the analysis of bleaching and removal of linen and husks. Then the bleached roving flax fabric was cooked, bleached and pickled to remove the flax hemp skin test, trying to find out the best way to remove flax hemp skin.
1.1 The same bath pretreatment test for different linen fabrics
Test fabrics: Pure bleached pure linen fabrics; primary colored linen fabrics; dry-spun linen/cotton fabrics.
Test process: (after desizing) the linen fabric is scouring and bleaching, oxygen bleaching, dehydration and drying test prescriptions and conditions:
Sculpting:
NaOH 10 g/L
Na2C03 10 g/L
Na2SiO3 (40° Bé) 5 g/L
Na3PO4·12H20 2 g/L
Bath ratio 1:15
Sculpting temperature 98 ~ 100 °C
Scouring time 40 min
Chlorine Drift:
NaC10 (effective chlorine) 1.5 g/L
pH 8.5 to 9
Temperature at room temperature (20°C)
Time 30 min
Bath ratio 1:15
Oxygen drift:
H202 5 g/L
Na2Si03 (40 ° Bé) 5 g/L
pH 10.5
Temperature 90°C
Time 40 min
Bath ratio 1:15
Dehydration and drying: Centrifugal dehydration and drying at room temperature.
Test Index: Test the fabric whiteness, weight loss rate, the number of flax hemp skin in the 10cmX10cm cloth surface, the results are shown in Table 1.
1.2 Experiments for strengthening the scouring process of linen fabrics
Before the scouring of the 101# flax fabric pre-processing production process, the swatches were taken for 5 m and scouring was conducted 2 times. Other processes were still performed according to the normal production process.
Process: linen fabric preparation a singeing a desizing a scouring training (test process) chlorine bleaching oxygen bleaching water washing a rolling water, drying scouring test process: continuous padding, steaming method padding scouring Liquid (multiple impregnation and multiple rolling) steam-steaming (102°C, 40 min) one padding scouring liquid (multiple impregnation and multiple rolling) steam one steam (102°C, 40 min) one hot water wash one cold water wash (go to the next process: chlorine drift)
Test prescription:
Na0H 25g/L
Water glass 5g/L
Sodium sulfite 2g/L
Trisodium phosphate 1.5g/L
Test conditions:
Rolling margin 110%
Steam temperature 102°C
Steaming time 2 times X40 min
Test items: Determine the weight of the fabric before and after the scouring test to obtain the weight loss rate of the fabric in this process, as shown in Table 2; determine the strength index of the whole process before and after the process, and obtain the full-process fabric strength loss rate ,as shown in Table 3.
1.3 Linen fabric pickling process test
In the pre-processing production process of 101# flax fabrics, a 5m flax fabric after singeing was used for the pickling process test, and then the large-volume jiggers received normal production were produced according to the normal production process.
Linen fabric test process flow:
Process flow: Linen fabric preparation Singeing and pickling (test procedure) De-slurry simmering One chlorine bleaching One oxygen bleaching One water washing--Rolling water, drying Pickling process: Impregnation one pickling (2 x 15 Min) a water wash (received the next process: desizing)
Pickling equipment: pickling test conditions:
Oxalic acid 3.5 g/L
Pickling temperature 45°C
Pickling time 30 min
Bath ratio 1:l0
Test item: Determine the weight of the fabric before and after the fabric pickling process test to obtain the weight loss rate of the fabric in this process, as shown in Table 2. As shown in the figure, the strength index of the whole process before and after the processing is measured to obtain the fabric strength loss rate of the whole process, as shown in Table 3. As shown.
2 test results
2.1 Results of the same bath treatment of various linen fabrics
Through the same bath pretreatment process of different linen fabrics, the number of hemp skins remaining in the size range of 10 cm X 10 cm on the fabric, the weight loss rate of the fabric was measured, and the whiteness of the fabric was measured. The results are shown in Table 1.
From Table 1, it can be seen that after the three kinds of linen fabrics were treated in the same bath, the whiteness of the fabrics was basically the same; the weight loss rate of the fabrics was: the weight loss rate of dry-spun linen cotton fabrics was the highest, as high as 38.3%, and the full-bleached linen fabrics were The weight loss rate was the lowest, 33.1%, the weight loss rate of the primary color yarn linen was 35.0%, and the number of hemp skins remaining on the fabric was: Full bleached linen fabric and dry-spun linen cotton fabric were all 3 (each/dm 2) The primary yarn linen fabric is 2 (pieces/dm2).
2.2 Linen fabric Strengthen scouring, pickling process test weight loss rate Through the linen fabric pre-treatment to strengthen the scouring, pickling process test, measuring the process weight loss rate, the results are shown in Table 2.
It can be seen from Table 2 that the weight loss rate of the pickling process test is 13.84%; the weight loss rate of the intensified scouring process is 30.31%. The weight loss rate of the two processes is quite different.
2.3 Strengthen scouring and pickling process of linen fabrics
The scouring and pickling process tests were conducted through the pre-treatment of the linen fabric to determine the strength before and after the pre-processing process to obtain a strong loss rate. The results are shown in Table 3.
From Table 3, it can be seen that the strength loss of the linen fabrics in the scouring test process is the largest, 38.51% in the direction of the warp, 39.89% in the latitudinal direction; the strength loss in the pickling process test is low, and the warp direction is 35.15% in the weft direction. 37%, close to the normal processing technology indicators (34.20% warp, 36.75% weft).
3 Conclusion
According to the test results, the factors affecting the bleaching or removal of the flax fabrics, the applicability of the scouring process of the flax fabrics, and the bleaching or removal measures of the flax fabric husks can be obtained.
3.1 Factors affecting the bleaching or removal of flax fabrics The main factors for the bleaching or removal of flax fabrics include: the chemical processing experience during the formation of flax fabrics, the degree of impurity in fibers, and the processing methods. (See Table 1)
3.2 The method of strengthening fabric scouring should not be promoted
The process of strengthening the scouring of linen fabrics can solve some of the problems of bleaching or removal of linen husks, but it often results in weight loss of the linen fabric (as shown in Table 2), and the weight loss is related to the strength loss of the fabric. By comparing Table 3 of Table 25H, it can be seen that the weight loss and strength loss of the test data for the enhanced scouring test are the greatest and should not be used in normal production.
3.3 Bleaching or removal of flax hemp pre-treatment process measures
According to the pickling process test data (Table 2, Table 3), the weight loss and weight loss of the flax fabrics after pickling are all within an acceptable range, and the bleaching or removing effect of flax hemp is better. The process method is currently Many companies often adopt technological measures.
4 Discussion
The bleaching and removal of flax fabrics are related to the chemical treatment process during fabric formation, but the deeper the fabric is, the more the fabric is easier to bleach or remove hemp. Linen fabrics can be used to solve this problem by pickling or strengthening the scouring process of the linen fabric, but a more suitable process is to increase the pickling process.
4.1 The effect of various types of linen fabrics on the bleaching or removal of linen husks
The characteristics of the three flax fabrics vary and have different effects on the degree of fabric treatment. The first is that the residue of the process forms a barrier to chemical processing. Yarn (roving) forming a linen fabric undergoes degumming and bleaching of the fibers during chemical processing. However, the degumming of the flax rovings is semi-degumming, and the flax hemp skin in the fibers is not bleached or removed. The rovings are spun into yarns and dried. Afterwards, the hemp skin is coated inside the spun ply, resulting in the difficulty of bleaching and removing the hemp skin. Secondly, it is related to the degree of impurities in the fibers. Primary color yarn linen fabrics are generally made of dew-wool, which has a low lignin content and a relatively low hemp content. The lignin content of the flax boiled and dyed fabrics was relatively high, and the flax and cotton fabrics were dry-spun with the second flax fiber, and the lignin content was the highest.
(1) The effect of chemical processing of linen fabrics on the bleaching or removal of linen fabrics The chemical processing experience of linen fabrics refers to the roving boiled, fiber degumming, etc. The primary color linen fabrics are lighter in scouring and bleaching, and the hemp is covered more Light, so it's the easiest to deal with. The order in which the three kinds of linen fabrics are easily bleached or removed is that the primary colored yarn linen fabric is better than the full floating yarn linen fabric and the dry spinning linen/cotton fabric.
(2) The effect of the degree of linen inclusion on the bleaching or removal of linen flax The degree of impurity in flax fibers refers to the weight percentage of impurities including lignin, pectin, etc. prior to the formation of fabrics. The primary yarn linen fabric contains less impurities and is easily bleached. Or remove. The bleached linen fabric contains less impurities and the linen cotton fabric has higher impurity content. However, the results are quite the same, and may be related to the chemical processing experience of the fabric.
(3) Different linen fabrics should adopt different processing methods to effectively bleach or remove flax hemp. Through the treatment of the three kinds of linen fabrics in the same bath, the effects are not the same. Different pretreatment methods should be adopted according to the characteristics of the linen fabric.
4.2 The role of pickling
The pickling process preferably satisfies the bleaching of linen husks. The pickling process can be arranged after the singeing and before the desizing step, and can also be arranged after the chlorine bleaching step and before the oxygen bleaching step. The effect of the two pickling processes before and after is not exactly the same.
The pickling step after the singeing step and before the desizing step functions mainly to degumme the linen fabric and to bleach or remove the hemp skin. Pickling can achieve the degumming of flax fibers, providing bleaching agent access problems for the bleaching of the jute skin. Through this process, the flax hemp skin is exposed to chemicals.
The role of the pickling process after the chlorine bleaching process and before the oxygen bleaching process is firstly the same as the chlorine bleaching effect of the cotton fabric—dechlorination, which improves the chlorine bleaching effect and reduces subsequent processing problems. Another important role of the pickling process after the chlorine bleaching of the linen fabric is to remove the lignin in the flaxseed exposed to the process liquor, providing the best process for bleaching or removing the flax hemp. Therefore, the pickling and dechlorination after the chlorine bleaching process of the cotton fabric pre-treatment can be replaced by other methods. The chlorine bleaching process of the cotton fabric can also be replaced by the oxygen bleaching method, but the pretreatment of the linen fabric may not be without the chlorine bleaching process after the chlorine bleaching process. Pickling cannot be replaced by other processes. Only paying attention to the pickling process of the linen fabric can bleach or remove the flax hemp while ensuring the strength of the linen fabric.
4.3 The chemical composition of flax hemp
Linen husks are generally considered to be composed of cellulose, lignin, pectin, etc. The presence of lignin causes the linen husk to be bleached or removed more difficult. The chemical structure of lignin is still unclear, and the chemical structure of flax lignin is not clear, creating obstacles for the study and formulation of the pretreatment process. It also caused people to try to remove the flax lignin in the fabric scouring process, so that the linen fabric pretreatment strength is reduced more.
It is worth noting that the harvest period of flax plants has a greater impact on the content of flax lignin and cellulose. During the yellow ripening period of flax plants, the cellulose content is higher and the lignin content is lower. Before harvesting, the raw stem of the flax plant harvested had a lower cellulose content and a lower lignin content, while the hemicellulose content was relatively increased; if the raw stems of the flax were harvested, the cellulose content was reduced and the lignin content was greatly increased. improve. To define lignin and hemicellulose in this sense, "lignin is an aged cellulose" and "hemicellulose is an immature cellulose" can be considered.
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