Comparative study on the dyeing properties of regenerated hemp fiber and natural hemp fiber

Regenerated hemp fiber is a new type of viscose fiber produced by using natural jute, kenaf and other hemp plants as raw materials, using patented invention technology to make pulp and solvent spinning. Regenerated hemp fiber has a dry strength similar to that of ordinary viscose fiber, and is higher than the wet strength of ordinary viscose fiber and Tianzhu fiber; it has good moisture absorption and air permeability; according to testing by relevant national departments (according to the Japan Association for Evaluation of New Functions of Fiber Products (JAFET) Antibacterial Standard) This fiber has antibacterial and antibacterial effects; the important thing is that the regenerated hemp fiber has good spinnability, weavability, dyeability, and soft hand feel, which is completely different from natural hemp fiber. Since regenerated hemp fiber is a regenerated cellulose fiber, its physical and chemical properties are different from those of natural hemp fiber. Its degree of crystallization, polymerization and orientation are much lower than those of natural hemp fiber. Therefore, its dyeing properties are different from those of natural hemp fiber. Hemp fibers vary widely. This article conducts a large number of comparative studies on the dyeing properties of regenerated hemp fiber and natural hemp fiber using various reactive dyes for reference by peers.

　1 Experimental Part

　1.1 Experimental Materials

Fiber: Natural ramie fiber (dried hemp strips), regenerated hemp fiber 1.67dtex×38mm

Dyeing materials: Cibaclone LS type reactive dyes (Shanghai Ciba Company), Cibaclone FN reactive dyes (Shanghai Ciba Company), Zhejiang Wenling M type reactive dyes (Wenling City, Zhejiang Province Dyes) Chemical Plant), Zhejiang Wenling B-type reactive dyes (Zhejiang Wenling Dyestuff Chemical Plant), anhydrous sodium sulfate (Tianjin Tanggu Dengzhong Chemical Plant), anhydrous sodium carbonate (Beijing Chemical Plant), sodium bicarbonate (Shanghai Hong Photochemical Plant), sodium phosphate (Tianjin Taixing Reagent Factory) (all chemically pure).

1.2 Experimental instruments: 721 spectrophotometer, HH-4 electronic constant temperature water bath, FA2004 electronic balance.

1.3 Experimental dyeing process

Process 1 (for M-type and B-type reactive dyes):

Process curve:

60℃15min15min45min

Fiber 1/2 yuan fenfen alkali cleaning

1/2 yuan fenfen/dye

Dyeing prescription 1: Fiber: 0.5g

Dye (owf ): 1%

Salt (Yuanming powder): 60g/l

Soda ash: 15g/l

Liquor ratio: 1:50

Process 2 (for Cibaclones LS type reactive dye):

Dyeing prescription 2: dye (owf) 0.5%

Fiber 0.5g

Yuanming powder 10g/l

Alkali agent 10g/l

Liquor ratio 1:50

Process 3 (used for Cibaclone FN reactive dyes):

Dye prescription 3: Dye (owf): 0.5%

Yuanming powder: 40g/l

Soda ash: 10g/l

Liquor ratio: 1:50

> 1.4 Experimental Method

1.4.1 Dyeing Rate Test Method

Take the dyed dye solution into a 10mL volumetric flask, add distilled water to the mark, and measure at λmax with a spectrophotometer its absorbance.

Dye uptake rate = (1-Ai/A0) × 100%

Where: Ai – the absorbance of the residual dyeing solution; A0 – the absorbance of the blank dyeing solution.

Specific steps:

[1] Weigh the medicine and 0.5g fiber according to the experimental formula.

[2] Add the required amount of salt to the dissolved dye. Divide into 25ml portions and place them in an Erlenmeyer flask.

[3] Place the Erlenmeyer flask into a water bath. After the temperature in the Erlenmeyer flask rises to the corresponding temperature, add fiber and use a glass rod. Stir evenly, cap the bottle and let it dye for a certain period of time.

[4] Add an appropriate amount of alkali to fix the color, use a glass rod to stir quickly and evenly, cap the bottle tightly and continue dyeing. During the dyeing process, use a glass rod to stir continuously to prevent staining.

[5] After dyeing, take out the Erlenmeyer flask and quickly take out the fibers and wring them dry. After the temperature in the Erlenmeyer flask drops to room temperature, take out 2ml of the dye solution and put it into a small beaker. At the same time, add water to dilute it and measure the absorbance to get the dye uptake rate.

　1.4.2 Test method for fixation rate

This experiment uses the washing method to determine the fixation rate, that is, after the fiber is dyed, a spectrophotometer is used to measure the residual liquid and the soaping liquid. Compare the dye content with the dye content in the original dye solution to calculate the fixation rate.

Specific steps: Calculate the amount of dyestuff required for a 0.5g sample according to the prescribed prescription, and weigh two identical dyes (the dye must be weighed accurately, and the difference between the two parts should not be greater than 0.0004 g), configure two identical dye baths A and B respectively and put them into the same water bath.

No sample is added to dye bath A, but its operation is in accordance with the regulations of dye bath B. When the sample in dye bath B begins to soap, add the same amount of soap powder to dye bath A. After 15 minutes, take out dye bath A and cool it to room temperature, then dilute it to a certain volume. At its maximum absorption wavelength, Measure its absorbance AA.

Add the sample to dye bath B and dye it according to the specified conditions. After dyeing, take out the sample and wash it with water, soap and boil (soap powder 2g/l, 93-95℃, 15min, liquor ratio 25:1), wash ( Wash several times with a small amount of water until the color does not fade). Then combine the washing liquid, soaping liquid and dyeing residual liquid, dilute it to a certain volume, and measure the absorbance (AB) at its maximum absorption wavelength. Then

　X=(ABVB/AAVA)×100% Fixation rate = 1-X

Where: > VA——The volume after dilution in dye bath A; AA——The absorbance after dilution in dye bath A;

VB——The volume after dilution in dye bath B; AB——The absorbance after dilution in dye bath B.

　2. Experimental results

This topic uses four representative dyes from home and abroad to regenerate hemp?? M-3BE red, M- 2GE Blue, M-3RE Yellow, Reactive Red B-2BF, Reactive Dark Blue B-BF, Reactive Yellow B-4RFN, CibaClone LS-6G Red, CibaClone LS-RHC Yellow, CibaClone LS-6G Blue, Dyeing rate curves of CibaClone FN-R blue, CibaClone FN-R red, and CibaClone FN-4G yellow on regenerated hemp fiber and natural ramie fiber.

3. Analysis and discussion

3.1 Dyeing properties of regenerated hemp fiber

The three primary colors of the four dyes selected in the experiment are in the regenerated hemp fiber The dye uptake rate on the fiber is very high. This is mainly because the regenerated hemp fiber has good hygroscopicity and can swell in water. As a result, these reactive dyes with excellent water solubility and small molecules can be quickly adsorbed on the fiber and can be quickly absorbed on the fiber. Diffusion in the fiber, the initial dyeing rate is high, and the half-dying time is short; because the regenerated hemp fiber has low crystallinity, low orientation, and few fiber crystal areas, the accessible area of the dye increases, and hydrogen bonds and van der Waals forces exist between the dye and the fiber. The absolute number of multi-layer physical adsorption increases, so the equilibrium dyeing percentage is higher. Under the premise of high dyeing percentage, the number of reactive dyes participating in the bonding reaction with the fiber increases, resulting in a higher fixation rate. . At the same time, the above experiments show that using the above reactive dyes, regenerated hemp fiber has better dyeing performance, and the dyeing of regenerated hemp fiber can be achieved without changing the existing equipment and materials.

The dyeing of regenerated hemp fiber with reactive dyes is also divided into two stages: dyeing and color fixation. During the dyeing stage, in the neutral dye liquor in the presence of electrolytes, the Coulomb repulsive force of the negative charge generated by the ionization of the water-soluble groups of the dye on the surface of the regenerated hemp fiber is overcome, and the negative charge is transferred from the dye liquor to the fiber and is absorbed by the fiber. adsorbed on the surface. Due to the concentration gradient between the fiber surface and the interior, it diffuses into the interior of the fiber until the dye solution concentration reaches an equilibrium between the dye solution and the fiber, and the dye concentration on the fiber surface and inside is close to equal. This process is shown in the dyeing curve from 0-30min in the figure. In the fixation stage, due to the addition of alkali agent, the pH value of the dye bath rises, and the balance formed in the adsorption stage is destroyed. The cellulose fiber becomes negatively ionized, and can undergo nucleophilic reaction with the active group; β-sulfate vinyl sulfone undergoes β-elimination After the reaction, it becomes vinyl sulfone, which is easy to produce nucleophilic addition reaction with cellulose fiber negative ions; water molecules gradually dissociate into hydroxide negative ions, and undergo hydrolysis reaction with active groups.

3.2 Comparison of the dyeing performance of natural hemp fiber and that of regenerated hemp fiber

The dyeing rate of natural hemp fiber is lower than that of regenerated hemp fiber, and the dyeability of natural hemp fiber is poor. Although natural ramie fiber and regenerated hemp fiber are both cellulose fibers, the microstructure and chemical composition of natural hemp fiber are very different from those of regenerated hemp fiber. Our research on the basic properties of regenerated hemp fiber shows that the surface of regenerated hemp fiber has many vertical stripes and grooves, and the transverse cross-section is plum blossom-shaped. The fiber has good hygroscopicity. Its hygroscopicity is similar to that of bamboo fiber, better than cotton fiber, and much higher than natural hemp fiber. At the same time, regenerated hemp fiber is soft, fluffy and has good drape. The fiber length is 38.1mm and the single fiber is 1.48 denier. , low crystallinity and degree of polymerization. These properties are enough to make the dyeability of regenerated hemp fiber better than that of natural hemp fiber.

The cross-sectional shape of natural hemp fiber is mostly polygonal, with a rough longitudinal surface and vertical lines; natural hemp fiber has high crystallinity and orientation, macromolecules are arranged neatly and densely, and there are fewer gaps and voids. The binding force of each group between the molecules is saturated and tight with each other, making it difficult for the fiber to swell, the dye to penetrate during dyeing, and the dye uptake rate is low. Secondly, a high degree of orientation means that the arrangement direction of macromolecules is highly consistent with the axial direction of the fiber. The deformation of natural hemp fiber is small, the fiber tensile strength is high, the elongation ability is small, and the elasticity is poor. During dyeing, there is less contact between the fiber and the dye liquor, and the dye is large. The space that molecules can occupy is small, the penetration capacity is low, and the dyeing property is poor, which also leads to difficulty in dye penetration, low dye uptake rate, and poor dyeing fastness. Secondly, the content of non-cellulose components in natural ramie fiber accounts for about 30%. In particular, natural ramie fiber contains a relatively high amount of lignin, lipid waxes and pectin. The existence of these non-cellulose substances causes problems during dyeing. Penetration is difficult, and dyes are difficult to react with cellulose, so that although natural ramie fiber has been pre-treated, its dyeing performance is adversely affected. To sum up, natural hemp fibers are difficult to dye, with dull color and poor dye fastness.

　4. Conclusion

　4.1 Reactive dyes are suitable for dyeing regenerated hemp fiber and have good dyeing performance. Since regenerated hemp fiber is mostly used in summer textiles, reactive dyes should be the first choice for dyeing regenerated hemp fiber. The three primary colors of the four dyes selected in the experiment all have higher fixation rates on regenerated hemp fiber. In practice, according to the product Grade selection.

4.2 Comparative experiments on dyeing regenerated hemp fiber and natural hemp fiber with reactive dyes show that the dyeability of regenerated hemp fiber is far better than that of natural hemp fiber.

4.3 When the dyeing of regenerated hemp fiber and natural hemp fiber is blended, the same color products with uniform color and luster cannot be obtained, but the same color and flash products with different shades of color can be obtained. Such products can be used as hemp fiber textiles. A new development direction.
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AAAA new development direction for dimensional textiles.
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