Method for pretreating pure linen yarns by alkali-urea

An alkali treatment and pretreatment technology, applied in the field of textile sizing, can solve the problems of small elongation at break, no curling, difficulty in dry splitting, etc. The effect of neatly arranged fibers

Active Publication Date: 2019-09-10
JIANGYIN XIANGFEI APPAREL
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AI-Extracted Technical Summary

Problems solved by technology

However, there are many problems in the linen yarn itself as a wet-spun fiber bundle: due to the high crystallinity and high degree of orientation of the fiber itself, small elongation at break, and no crimp, it is difficult to sizing and dyeing the linen yarn, and it is difficult to dry and tw...
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Method used

[0039] Fig. 2 is a comparison diagram of the influence of urea concentration on yarn breaking strength and elongation at break. It can be seen from Figure 2 that with the increase of urea concentration, the breaking strength of the yarn first decreases and then increases, and when it reaches more than 6%, it shows a decreasing trend, and the elongation at break decreases to a certain extent when the ...
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Abstract

A method for pretreating pure linen yarns by alkali-urea includes the steps of sampling, alkali treatment, neutralization, dehydration, impregnation with a urea solution, and drying. In the alkali treatment step, the pure linen yarns are impregnated with a sodium hydroxide solution for 10-25 minutes according to the bath ratio of 1:12.5 to 1:20, wherein the concentration of the sodium hydroxide solution ranges from 10% to 20%; in the step of impregnation with the urea solution, the neutralized and dehydrated pure linen yarns are soaked in the urea solution for 10-15 minutes according to the bath ratio of 1:12.5 to 1:20, wherein the concentration of the urea solution ranges from 4% to 6%. The method has the advantages that after the pure linen yarns are pretreated by the alkali-urea, the orientation and crystallinity of linen fibers themselves are obviously reduced, the intermolecular forces of the fibers are increased, the fibers are arranged neatly and tightly, the breaking strength of the yarns is decreased, and the elongation at break is increased.

Application Domain

Vegetal fibres

Technology Topic

UreaIntermolecular force +6

Image

  • Method for pretreating pure linen yarns by alkali-urea
  • Method for pretreating pure linen yarns by alkali-urea
  • Method for pretreating pure linen yarns by alkali-urea

Examples

  • Experimental program(3)

Example Embodiment

[0029] Example 1
[0030] The method for alkali-urea pretreatment pure flax yarn provided in this embodiment comprises: sampling (by skein length measuring device, get 100m long 24 public support pure flax yarns, weigh)→alkali treatment (under normal temperature Configure a certain concentration of sodium hydroxide solution, immerse the yarn in the solution for a period of time according to a certain bath ratio) → neutralization (after alkali treatment, wash with water, and neutralize in glacial acetic acid) → dehydration → urea solution immersion (configuration A certain concentration of urea solution, the neutralized and dehydrated yarn is immersed in the solution for a period of time according to a certain bath ratio)→drying (washing, drying in an oven at 90°C, and balancing in a constant temperature and humidity box for 24 hours) to be used) → test.
[0031] The alkali treatment is to immerse the pure flax yarn in a sodium hydroxide solution for 10 to 25 minutes according to a bath ratio of 1:12.5 to 1:20, and the concentration of the sodium hydroxide solution is 10 to 20%; The pure flax yarn after neutralization and dehydration is immersed in urea solution for 10-15 minutes according to the bath ratio of 1:12.5-1:20, and the concentration of urea solution is 4-6%.

Example Embodiment

[0032] Example 2
[0033] Using the breaking strength and elongation at break of pure flax yarn before and after treatment as indicators, single factor analysis was carried out on sodium hydroxide concentration, urea concentration, alkali treatment time, urea treatment time and liquor ratio, and the optimal factor level was determined.
[0034] (1) Sodium hydroxide concentration
[0035] According to the step of embodiment 1, control urea concentration at 2%, alkali treatment time 10min, urea treatment time 10min, bath ratio 1: 20, change sodium hydroxide concentration at 5%, 10%, 15%, 20%, 25% respectively %; test the breaking strength and elongation at break of the yarn after pretreatment, carry out single factor analysis, determine the range of alkali concentration level, the results can be found in figure 1.
[0036] figure 1 It is a comparison chart of the influence of sodium hydroxide concentration on yarn breaking strength and elongation at break. Depend on figure 1 It can be seen that with the increase of the alkali concentration, the change law of the breaking strength of the flax yarn shows a decreasing trend, and the changing law of the breaking elongation shows an increasing trend. The alkali solution swells the cellulose, resulting in a decrease in the breaking strength of the yarn; the swelling of the cellulose reduces the internal stress; the destruction of lignin and hemicellulose increases the crystallinity inside the fiber, which increases the elongation at break of the yarn. After pretreatment, in order to ensure the breaking strength and improve the breaking elongation of flax yarn, the alkali concentration should be controlled at 10%-20%.
[0037] (2) Urea concentration
[0038] Carry out single factor analysis of sodium hydroxide concentration to determine the optimum level range of alkali concentration, control sodium hydroxide concentration at 15%, alkali treatment time 10min, urea treatment time 10min, liquor ratio are 1: 20, change urea concentration at 2 %, 3%, 4%, 5%, 6%; after treatment, test the breaking strength and elongation at break of the yarn, and conduct single factor analysis to determine the range of urea concentration level. For the results, see figure 2.
[0039] figure 2 It is a comparison chart of the influence of urea concentration on yarn breaking strength and breaking elongation. Depend on figure 2 It can be seen that with the increase of urea concentration, the breaking strength of the yarn first decreases and then increases, and then decreases when it reaches above 6%, and the elongation at break decreases to a certain extent when the urea concentration is 3%. Low concentration of urea basically does not change the tensile properties of the yarn, and the concentration of urea above 4% can cause the flax fiber to swell. Adding urea can improve the pretreatment effect and better ensure the strong elongation of the flax yarn. In order to obtain a better treatment effect, the urea concentration should be controlled at 4%-6%.
[0040] (3) Alkali treatment time
[0041] Carry out the single factor analysis of urea concentration to determine the optimal level range of urea concentration, control urea concentration at 5%, sodium hydroxide concentration at 15%, urea treatment time 10min, bath ratio is 1: 20, change alkali treatment time at 5min, 10min, 15min, 20min, 25min; test the breaking strength and elongation at break of the yarn after treatment, and conduct single factor analysis to determine the optimal level range of alkali treatment time. For the results, see image 3.
[0042] image 3 It is a comparison chart of the influence of alkali treatment time on yarn breaking strength and elongation at break. Depend on image 3 It can be seen that with the extension of alkali treatment time, the breaking strength and elongation at break both increase first and then decrease. At 5 minutes, the alkali solution and the yarn are in a state of equilibrium. About 10 minutes, the lignin and pectin in the fiber react with the alkali solution to reduce the content of lignin and pectin, and the breaking strength and elongation at break are significantly improved. As time goes by, the alkali solution swells the cellulose, resulting in a decrease in the breaking strength of the yarn, a gradual increase in fiber damage, and a decrease in the elongation at break of the yarn. In order to ensure the strong elongation of the yarn, the alkali treatment time should be 10-25min.
[0043] (4) Urea treatment time
[0044] Carry out the single factor analysis of alkali treatment time to determine the optimal alkali treatment time level range, control the alkali treatment time at 15min, sodium hydroxide concentration 15%, urea concentration 5%, bath ratio to be 1: 20, change the urea treatment time at 5min respectively , 10min, 15min, 20min, 25min; after treatment, test the breaking strength and elongation at break of the yarn, and conduct single factor analysis to determine the optimal level range of urea treatment time. For the results, see Figure 4.
[0045] Figure 4 It is a comparison chart of the influence of urea treatment time on yarn breaking strength and elongation at break. Depend on Figure 4 It can be seen that with the prolongation of urea treatment time, the breaking strength first increases and then decreases, and then tends to be stable; the breaking elongation first increases, and then tends to be stable. Adding urea can improve the strength and elongation of the yarn. In order to obtain a good treatment effect, the urea treatment time should be controlled at 10-15min.
[0046] (5) liquor ratio
[0047] In order to facilitate the analysis, the alkali treatment solution and the urea solution were used to impregnate the yarn according to the same liquor ratio in this test.
[0048] Carry out the single factor analysis of urea treatment time to determine the best urea treatment time level, control urea treatment time is 10min, alkali concentration is 15%, urea concentration is 5%, alkali treatment time is 15min, change liquor ratio respectively to be 1: 10, 1:12.5, 1:15, 1:17.5, 1:20; test the breaking strength and elongation at break of the yarn after treatment, and conduct single factor analysis to determine the optimum level range of bath ratio. For the results, see figure 1.
[0049] Figure 5 It is a comparison chart of the effect of bath ratio on yarn breaking strength and breaking elongation. Depend on Figure 5 It can be seen that when the bath ratio is reduced, the breaking strength of the yarn generally shows an upward trend, and the breaking elongation first increases and then decreases. When the bath ratio of alkali treatment solution and urea solution is high, the yarn swelling effect is greater, and the yarn breaking strength loses the most, and the bath ratio decreases, and the breaking strength decreases less. The cellulose swells, the internal stress decreases, and the elongation at break of the yarn increases. When the bath ratio is small, the elongation at break of the yarn decreases significantly compared with that when the bath ratio is large. In order to ensure the strong elongation of the yarn, the bath ratio should be controlled between 1:12.5-1:20.

Example Embodiment

[0050] Embodiment 3 Five Factors Four Levels Pretreatment Experimental Data Analysis
[0051] According to the test results of single factor analysis, the optimal sodium hydroxide concentration, urea concentration, alkali treatment time, urea treatment time, liquor ratio level were selected, and an orthogonal experiment design with 5 factors and 4 levels was carried out. The level of each factor is shown in Table 3, and the design table of the orthogonal experiment is shown in Table 4.
[0052] Table 3 Test conditions
[0053] factor NaOH concentration Urea concentration Alkali treatment time Urea treatment time bath ratio level 1 13% 4.5% 10min 10min 1∶12.5 level 2 15% 5.0% 15min 15min 1∶15 level 3 17% 5.5% 20min 20min 1∶17.5 level 4 19% 6.0% 25min 25min 1∶20
[0054] Table 4 Orthogonal experiment design table with 5 factors and 4 levels
[0055]
[0056] The alkali-urea pretreatment experiment was carried out according to the conditions of experiments 1-16 in Table 4, see the steps of Example 1. The yarn strength test was carried out on Shimadzu SHIMADZU electronic tensile testing machine, each experiment was measured 30 times, and the average values ​​of the breaking strength and elongation at break were obtained. Calculate the standard deviation and variation coefficient of elongation at break, strength at break and elongation at break. According to the following formulas (1) to (3) for weight analysis based on the yarn breaking strength and elongation at break, the weight coefficient of each index is determined by the variation coefficient method, and finally the best experimental plan is determined according to the experimental results.
[0057] f i = m i f i +n i g i (1)
[0058]
[0059]
[0060] Among them, F i is the result of the orthogonal experiment;
[0061] f i , g i is the breaking strength and breaking length of each experimental scheme, i represents experiment 1-16;
[0062] m i , n i represent the weights of the fracture strength and fracture length of each scheme, respectively;
[0063] alpha i , β i are the coefficients of variation of breaking strength and breaking length, respectively.
[0064] Utilize 16 groups of experimental results calculated by formula (1), fill in 5 factors 4 levels in the orthogonal test design table by corresponding position, calculate mean value I i 、II i 、III i , IV i , poor R i (i=A, B, C, D, E), the result is as shown in table 5, wherein,
[0065] I i is the average value of the four experimental results corresponding to the level "1" in the i-th column, then:
[0066] I A =388.812,I B =320.393,I C =321.155,I D =337.419,I E = 339.024;
[0067] II i is the average value of the four experimental results corresponding to the i-th column level "2", then:
[0068] II A =337.720,II B =331.277,II C =360.467, II D =350.193,II E = 310.125;
[0069] III i is the average value of the four experimental results corresponding to the level "3" in the i-th column, then:
[0070] III A =355.394, III B =349.625, III C =313.654, III D =316.202,III E = 368.285;
[0071] IV i is the average value of the four experimental results corresponding to the level "4" in the i-th column, then:
[0072] IV A = 362.520, IV B = 343.151, IV C = 349.170, IV D = 340.630, IV E = 327.012.
[0073] After the orthogonal test, the maximum value of the sum of the levels of each factor can be combined to obtain the best experimental conditions, and the optimal combination parameter of the pretreatment experiment is A 1 B 3 C 2 D. 2 E. 3. That is to say, the optimal parameters of alkali-urea two-step pretreatment experiment are: sodium hydroxide concentration 13%, urea concentration 5.5%, alkali treatment time 15 minutes, urea treatment time 15 minutes, liquor ratio 1:17.5. After alkali-urea pretreatment of pure flax yarn according to the optimal process parameters, the breaking strength of the yarn decreased from 1083.98cN to 698.612cN, and the breaking elongation increased from 1.9388% to 9.976%.
[0074] The size of the range R reflects the size of the effect of the corresponding factors. A factor with a large range indicates that its different levels have a small impact on the experimental results, and is a major factor; a factor with a small range indicates that its different levels have a small impact on the experimental results, and is a secondary factor. Arrange the ranges of the five factors according to their size, and the primary and secondary effects of the factors are EACDB. Therefore, in the pretreatment experiment, the strength of each influencing factor is as follows: sodium hydroxide concentration>bath ratio>alkali treatment time>urea treatment time> urea concentration.
[0075] Optimum process is in the present invention: sodium hydroxide concentration 13%, urea concentration 5.5%, alkali treatment time 15min, urea treatment time 15min, bath ratio are 1: 17.5; And the strength of each influence factor is, sodium hydroxide bath Ratio>bath ratio>alkali treatment time>urea treatment time>urea concentration.
[0076] Table 5 Orthogonal experiment result table
[0077]
[0078]

PUM

PropertyMeasurementUnit
Breaking strength699.0cN

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