Dyeing process for polylactic acid / nanocellulose composite fibers

Abstract

Provided is a dyeing process for polylactic acid and nanocellulose composite fibers, which includes a spinning solution preparation process, a spinning process, and a dyeing process. The spinning solution preparation process is to evenly mix a nanocellulose suspension, a polylactic acid solution and an additive together, stand at 30-80 °C for 1-2 h and conduct high-energy electron beam radiation to form a gel, and the gel is washed to obtain a hydrogel spinning solution; the spinning process is to send the hydrogel spinning solution to wet spinning equipment for spinning to form fibers. The fibers are strengthened by high-energy electron beam radiation drying to obtain fiber filaments. The preparation method is simple, easy to implement, and environmentally friendly. The dye uptake rate of the composite fiber obtained reaches 80%, the strength of the composite fiber is enhanced by 1-2 times, and the antigen fibrillation ability is increased by 1-2 times.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of International Application No. PCT / CN 2024 / 139805, filed on Dec. 17, 2024, which claims priority to Chinese Patent Application No. 202411002338.0, filed on Jul. 25, 2024 and Chinese Patent Application No. 202510757641.X, filed on Jun. 9, 2025, all of which are hereby incorporated by reference in their entireties.TECHNICAL FIELD

[0002] The present disclosure relates to the field of textile processing technologies, and in particular, to a dyeing process for polylactic acid / nanocellulose composite fibers.BACKGROUND

[0003] Polylactic acid fiber is a polyester fiber made by spinning polylactic acid esters obtained from natural sugars in agricultural products such as corn and grains. Polylactic acid fiber is characterized by biodegradability, environmental friendliness, and excellent performance. Polylactic acid fibers are suitable for dyeing with dispersed dyes, but they have shortcomings such as low dye uptake, low dye fastness, and low dye utilization. For example, CN202010905523.6 discloses a dyeing process for polylactic acid fiber cylinder yarn, which includes the following steps: step one: loosening a cylinder; by using a loose winding machine, different specifications of raw yarn are flipped onto a plastic tube according to planned requirements, removing certain defects and impurities on the yarn and improving its quality, knots of the yarn on the tube should be small and firm, and a larger yarn winding angle should be used; step two: cage installation; install the loose tube yarn onto the yarn rod of the yarn cage as required and secure it for dyeing; step three: staining; place the cylinder yarn on the cylinder yarn fixing frame in a cylinder yarn dyeing device; according to a bath ratio of 1:1-50, use dyeing pre-treatment solution to pretreat the cylinder yarn, add diffusion agent NN to the dyeing agent, and adjust the alkalinity; step four: dehydration; after the yarn dyeing process is completed, dehydration is carried out using a centrifugal dehydrator running at high speed; step five: drying; dry the dehydrated yarn in step four using a high-frequency dryer, and dry the yarn through two heating plates on top and bottom; and a fixed exhaust fan is installed behind the high-frequency dryer to extract steam; step six: reverse the cylinder; flip the dyed tube yarn over to form a well-formed tube yarn that meets the unwinding requirements.

[0004] For another example, CN200610012779.4 discloses that, the dyeing process of polylactic acid fiber / cotton blended shuttle fabric, which includes a. desizing process, b. boiling and bleaching process, c. silk polishing process, d. dyeing process.

[0005] Moreover, traditional cellulose fiber processing techniques result in low fiber strength and poor antigen fibrillation performance, rendering fabrics made from this fiber prone to shedding and pilling.SUMMARY

[0006] The present disclosure provides a dyeing process for polylactic acid / nanocellulose composite fibers, which addresses the shortcomings of existing technology. The process is simple, achieves good dyeing effects, and improves the strength and antigen fibrillation performance of polylactic acid / nanocellulose composite fibers.

[0007] To achieve the above objectives, the present disclosure provides the following technical solution: a dyeing process for polylactic acid / nanocellulose composite fibers, including: a spinning solution preparation process, a spinning process, and a dyeing process,

[0008] where the spinning solution preparation process is to uniformly mix a nanocellulose suspension, a polylactic acid solution and an additive together, stand at 30-80 °C for 1-2 h, and conduct high-energy electron beam radiation to form gel, where the gel is washed to obtain a hydrogel spinning solution, where an irradiation amount of high-energy electron beam radiation is 10-50 kGy, and an irradiation time is 20-40 minutes, where a mass ratio of the polylactic acid solution to a nanocellulose solution is 10:1-1:1, a mass ratio of the polylactic acid solution to an additive solution is 10:1-1:1, where the polylactic acid solution is to disperse polylactic acid in an organic solvent, a mass concentration of the polylactic acid is 5-10%, and the nanocellulose suspension is a dispersion of cellulose fibers with a length of 10-100 nm in water, with a mass concentration of the cellulose fibers being 5-20%;

[0009] where the spinning process is to send the hydrogel spinning solution to wet spinning equipment for spinning to form fibers; the fibers are strengthened by high-energy electron beam radiation drying to obtain fiber filaments, where an irradiation amount is 10-50 kGy and an irradiation time is 3-5 minutes;

[0010] where in the dyeing process, a weight ratio of dye to fibers is 1-10%, a bath ratio is 1:45-55, an amount of a dispersant NN is 0.8-1.2 g / L, a pH value of a dyeing solution is 4.8-5.2, temperature is raised to 58 °C-62 °C at a rate of 1.5 °C-2.5 °C / min, the fibers is added, the temperature is raised to 108 °C-112 °C at a rate of 0.8 °C-1.2 °C / min, and an insulation dyeing time is 18-22 minutes, afterwards, cooling down to 58 °C-62 °C, adding an insurance powder, such as sodium hydrosulfite, 2.5-3.5 g / L, anhydrous sodium carbonate 2.5-3.5 g / L, and detergent 2.5-3.5 g / L to wash away floating color on the fibers, thoroughly washing with water, air drying or performing post-treatment processes.

[0011] In some embodiments of the present disclosure, where the hydrogel spinning solution is sprayed through spinneret holes of the spinning equipment, and silk thread enters a water coagulation solid bath to be washed, drawn, and dried by high-energy electron beam radiation to obtain the polylactic acid / nanocellulose fiber. A traction speed of the silk thread is controlled between 0 and 100 centimeters per minute.

[0012] In some embodiments of the present disclosure, the organic solvent is a mixture of one or more of N, N-dimethylformamide, tetrahydrofuran, 1,4-dioxane, chloroform, and acetone.

[0013] In some embodiments of the present disclosure, the additive is polyethylene glycol, glycerol, carboxymethyl chitosan, carboxymethyl cellulose, polyvinyl alcohol or polyethylene oxide.

[0014] In some embodiments of the present disclosure, the cellulose fibers are sugarcane fibers.

[0015] In some embodiments of the present disclosure, a molecular weight of the polylactic acid ranges from 10000-270000.

[0016] In some embodiments of the present disclosure, the dye is a mixture of dispersed dye and reactive dye.

[0017] In some embodiments of the present disclosure, the dispersed dye is azo type dispersed red 74, dispersed blue 79, or dispersed yellow 54; the reactive dye is reactive red CN-3B, reactive blue CN-2G, or reactive yellow CN-EX, where a chemical formula of the azo type dispersed red 74 C22H25N5O7, a chemical formula of the dispersed blue 79 is C24H27BrN6O10, a CAS No. of the dispersed yellow 54 is 12223-85-7, a chemical formula of the reactive blue CN-2G is C28H29N5Na4O21S6, and a CAS No. of the reactive yellow CN-EX is 115099-55-3.

[0018] Compared with existing technologies, the preparation method of the present disclosure is simple, easy to implement, environmentally friendly, and conducive to the industrial transformation of technology. The dyeing process of the polylactic acid / nanocellulose composite fiber of the present disclosure achieves a fiber dyeing rate of 80%, enhances the strength of the composite fiber by 1-2 times, and increases the antigen fibrillation ability by 1-2 times. By adopting the technical solution of the present disclosure, the polylactic acid / nanocellulose composite fiber is subjected to two irradiation treatments. The first irradiation enhances the pre crosslinking and condensation of hydroxyl or carboxyl groups between nanocellulose and polylactic acid, thereby forming moderate ether and ester bonds to form a suitable spinning solution. The second irradiation enhances the deep crosslinking and condensation degree of hydroxyl or carboxyl groups in the spinning components, improves fiber strength and antigen fibrillation ability, and increases the affinity between dispersed dyes and fibers, thereby improving fiber dyeing performance. The present disclosure uses polylactic acid / nanocellulose composite fiber hydrogel for spinning, without using the N-methylmorpholine N-oxide (NMM) solvent used in the traditional cellulose fiber spinning process, thus eliminating the solvent recovery process and saving equipment investment.DESCRIPTION OF EMBODIMENTS

[0019] In order to better understand the technical solution of the present disclosure, a more detailed explanation will be provided below in combination with the examples.Example 1

[0020] A 10% nanocellulose suspension solution is obtained by dispersing sugarcane fibers into nanocellulose suspension in water using a high-speed shearing machine. Polylactic acid (produced by Aladdin Reagent (Shanghai) Co., Ltd., model of Mw-60000, the same below) is dissolved in a mixed solution of dichloromethane / N, N-dimethylformamide (volume ratio of 4:1) to obtain a 5% mass fraction of polylactic acid solution. The nanocellulose suspension solution, polylactic acid solution, and polyethylene glycol solution are mixed uniformly in a mass ratio of 6:3:1, and then left to stand at 50 °C for 12 hours before being irradiated with a high-energy electron beam at a radiation dose of 30 kGy to obtain a polylactic acid / nanocellulose gel sample, soak the gel sample in deionized water, change water every 3 hours, repeat 5-8 times, wash the gel to replace the organic solvent, and the water content of the hydrogel is 60% (mass percentage, the same below), forming the hydrogel spinning solution. The spinning solution is spun by wet spinning equipment, and the spun material is irradiated with a high-energy electron beam at a radiation dose of 30 kGy for 5 minutes for secondary drying and strengthening treatment. Where the hydrogel spinning solution is sprayed through spinneret holes of the spinning equipment, and the silk thread enters the aqueous coagulation bath for washing, drafting, and radiation drying to prepare the PLA / nanocellulose fiber. The traction and stretching thread speed is controlled at 15 centimeters per minute. Prepare dye at room temperature: disperse yellow 54.1% (on weight of fabric, o.w.f), reactive yellow CN-EX 1% (on weight of fabric, o.w.f), dispersant NN 1 g / L, bath ratio 1:50, adjust pH to 5 with acetic acid and sodium acetate. After the dye solution is prepared, it is heated from room temperature at a rate of 2 °C / minute to 60 °C, and then polylactic acid / nanocellulose composite fibers are added to start dyeing. Then heat up to 110 °C at a rate of 1 °C / minute and hold for 20 minutes. Then start cooling down, from 110 °C to 60 °C, and control a cooling time within 30 minutes. Prepare a cleaning solution by adding 3 g / L of insurance powder, such as sodium hydrosulfite, 3 g / L of anhydrous sodium carbonate, and 3 g / L of detergent 6501 (detergent 6501 is non-ionic surface-active substance, marketed as Ninl 6501 in foreign countries, and can be used in a 1:1 ratio, the same applies below). Of course, the present disclosure is not limited to using this type of detergent, and other detergents in the field of fiber dyeing can also be used to wash away the floating color on the fibers, improve the wet fastness of the dyeing, and thoroughly wash, air dry, or perform post-treatment processes after cleaning.

[0021] Using the wet spinning method in example 1, the dyeing rate of fibers is 70%, and the strength obtained by wet spinning is improved by 1 time to 80CN·tex-1. The mechanical properties of the fibers are tested using a single filament tensile strength tester according to GB / T14337-2008 “Test Method for Tensile Properties of Chemical Fiber Short Fibers”. The clamping distance is 20 mm, and the stretching speed is 20 mm / minute. Use scissors to cut a fiber sample with a length of about 40 mm, place it flat on an operating board, select a suitable clip to clamp one section of a single fiber, clamp the other end of the fiber with tweezers, place the fiber at the instrument clamp, clamp the fiber and stretch it until it is pulled apart. Fiber samples are subjected to multiple tests, and the results are averaged and recorded. The fiber antigen fibrillation performance is improved by 1 time, and the wet friction value reaches 180 seconds. The antigen fibrillation performance test (the same below) uses the wet friction method, which applies frictional stress to the fiber under wet conditions until it fractures. The time taken from the beginning of friction to fiber fracture is defined as the wet friction value. The larger the wet friction value measured, the less likely the original fibers are to peel off from the fibers, indicating that the fibers have better antigen fibrillation ability.Example 2

[0022] The sugarcane fiber is dispersed into nanocellulose suspension in water through a high-speed shear machine to obtain 15% nanocellulose suspension solution. The polylactic acid is dissolved in a mixed solution of chloroform / N,N-dimethylformamide (the volume ratio of the two is 3:1) to obtain a polylactic acid solution with a mass fraction of 8%. After the nanocellulose suspension solution, polylactic acid solution and glycerol solution are mixed evenly according to the mass ratio of 7:2:1, they are left standing at 30 °C for 24 hours, and then irradiated by high-energy electron beam with a radiation dose of 50 kGy to obtain a strengthened cross-linked gel sample. The gel sample is immersed in deionized water, and the water is changed every 3 hours, repeating 5 to 8 times. The gel is washed to replace the organic solvent. The water content of the hydrogel is 70%, forming a nanocellulose / polylactic acid hydrogel spinning solution. The spinning solution is spun by wet spinning equipment, and the spun material is subjected to high-energy electron beam irradiation with a radiation dose of 50 kGy, for 3 minutes, followed by secondary drying and strengthening treatment.

[0023] Where the hydrogel spinning solution is sprayed through the spinneret holes of the spinning equipment, and the silk thread enters the aqueous coagulation bath for washing, drafting, and radiation drying to prepare the polylactic acid / nanocellulose fiber. The traction and stretching thread speed is controlled at 25 centimeters per minute. Prepare dyes at room temperature: disperse red 74.2% (on weight of fabric, o.w.f), reactive red CN-3B 2% (on weight of fabric, o.w.f), dispersant NN 1 g / L, bath ratio 1:50, pH adjusted to 5 with acetic acid and sodium acetate, the dye solution is prepared and heated from room temperature to 60 °C at a rate of 2 °C / minute. Then, polylactic acid / nanocellulose composite fibers are added to start dyeing. Then heat up to 110 °C at a rate of 1 °C / minute and hold for 20 minutes. Then start cooling down, from 110 °C to 60 °C, with a cooling time controlled at 25 minutes. Add 3 g / L of insurance powder, such as sodium hydrosulfite, 3 g / L of anhydrous sodium carbonate, and 3 g / L of detergent 6501 to wash away the floating color on the fibers, improve the wet fastness of dyeing, and thoroughly wash, air dry, or perform post-treatment processes after cleaning. Using the wet spinning method in example 2, the dyeing rate of the fibers is 80%. The strength of the fibers obtained by wet spinning is doubled to 120CN·tex-1, and the antigen fibrillation performance is doubled to 270 s.Example 3

[0024] The sugarcane fiber is dispersed into nanocellulose suspension in water through a high-speed shear machine to obtain 20% nanocellulose suspension solution. Polylactic acid is dissolved in the trichloromethane / N, N-dimethylformamide (volume ratio: 4:1) mixed solution to obtain 8% polylactic acid solution by mass fraction. After the nanocellulose suspension solution, polylactic acid solution, and carboxymethyl cellulose solution are mixed evenly by mass ratio of 6:2:2, they are left standing at 30 °C for 24 hours, and then irradiated by high-energy electron beam with a radiation dose of 45 kGy for 30 minutes to obtain an enhanced cross-linked nanocellulose / polylactic acid gel sample. The gel sample is soaked in deionized water, and the water is changed every 3 hours, repeating 5-8 times. The organic solvent is replaced by washing the gel, and the water content of the hydrogel is 50%, forming a nanocellulose / polylactic acid hydrogel spinning solution. The spinning solution is spun by wet spinning equipment, and the spun material is irradiated with a high-energy electron beam at a radiation dose of 30 kGy for 5 minutes for secondary drying and strengthening treatment. Where the hydrogel spinning solution is sprayed through the spinneret holes of the spinning equipment, and then enters the water coagulation solid bath for washing, drafting, and radiation drying to prepare the polylactic acid / nanocellulose fiber. The traction and stretching thread speed is controlled at 35 centimeters per minute. Prepare dyes at room temperature: disperse blue 79.3% (on weight of fabric, o.w.f), reactive blue CN-2G 3% (on weight of fabric, o.w.f), dispersant NN 1 g / L, bath ratio 1:50, adjust pH to 5 with acetic acid and sodium acetate. After the dye solution is prepared, it is heated from room temperature at a rate of 2 °C / minute to 60 °C, and then polylactic acid / nanocellulose composite fibers are added to start dyeing. Then heat up to 110 °C at a rate of 1 °C / minute and hold for 20 minutes. Then start cooling down, from 110 °C to 60 °C, and control the cooling time within 30 minutes. Add 3 g / L of insurance powder, such as sodium hydrosulfite, 3 g / L of anhydrous sodium carbonate, and 3 g / L of detergent 6501 to wash away the floating color on the fibers, improve the wet fastness of dyeing, and thoroughly wash, air dry, or perform post-treatment processes after cleaning. Using the wet spinning method in Example 3, the dyeing rate of the fibers is 78%. The strength of the fibers obtained by wet spinning is increased by 2.5 times, reaching 100 CN·tex-1, and the antigen fibrillation performance is doubled, reaching 180 seconds.Example 4

[0025] The sugarcane fiber is dispersed into nanocellulose suspension in water through a high-speed shear machine to obtain a nanocellulose suspension solution with a mass fraction of 5%. Polylactic acid is dissolved in the mixed solution of dichloromethane / N, N-dimethylformamide (volume ratio of 3:1) to obtain a polylactic acid solution with a mass fraction of 8%. After the nanocellulose suspension solution, polylactic acid solution and polyvinyl alcohol solution are mixed evenly according to the mass ratio of 8:1:1, they are left standing at 30 °C for 24 hours, and then irradiated by high-energy electron beam with a radiation dose of 50 kGy for 30 minutes to obtain an enhanced cross-linked nanocellulose / polylactic acid gel sample. The gel sample is soaked in deionized water, and the water is changed every 3 hours, repeating 5-8 times, the gel is washed to replace the organic solvent, and the water content of the hydrogel is 30%, forming a nanocellulose / polylactic acid hydrogel spinning solution. The spinning solution is spun using wet spinning equipment, and the spun material is subjected to high-energy electron beam irradiation with a radiation dose of 40 kGy, followed by a secondary drying and strengthening treatment after 3 minutes of irradiation. Where the hydrogel spinning solution is sprayed through the spinneret holes of the spinning equipment, and the silk thread enters the aqueous coagulation bath for washing, drafting, and radiation drying to prepare the polylactic acid / nanocellulose fiber. The traction and stretching thread speed is controlled at 40 centimeters per minute. Prepare dye at room temperature: disperse yellow 54 1.5% (on weight of fabric, o.w.f), reactive yellow CN-EX 1.5% (on weight of fabric, o.w.f), diffusion agent NN 1 g / L, bath ratio 1:50, adjust pH value to 5 with acetic acid and sodium acetate. After the dye solution is prepared, it is heated from room temperature at a rate of 2 °C / minute to 60 °C, and then polylactic acid / nanocellulose composite fibers are added to start dyeing. Then heat up to 110 °C at a rate of 1 °C / minute and hold for 20 minutes. Then start cooling down, from 110 °C to 60 °C, and control the cooling time within 30 minutes. Add 3 g / L insurance powder, such as sodium hydrosulfite, 3 g / L anhydrous sodium carbonate, and 3 g / L detergent 6501 to wash away the floating color on the fibers, improve the wet fastness of dyeing, and thoroughly wash with water after cleaning, air dry, or perform post-treatment processes. Using the wet spinning method in Example 4, the dyeing rate of the fibers is 76%. The strength of the fibers obtained by wet spinning is increased by 1.5 times, reaching 100CN·tex-1, and the antigen fibrillation performance is improved by 1.2 times, reaching 200 s.Example 5

[0026] The sugarcane fiber is dispersed into nanocellulose suspension in water through a high-speed shear machine to obtain a 15% mass fraction of nanocellulose suspension solution. Polylactic acid is dissolved in the dichloromethane / N, N-dimethylformamide (volume ratio: 4:1) mixed solution to obtain an 8% mass fraction of polylactic acid solution. After the nanocellulose suspension solution, polylactic acid solution and polyethylene glycol solution are mixed evenly according to the mass ratio of 5:3:2, they are left standing at 30 °C for 24 hours, and then irradiated by high-energy electron beam with a radiation dose of 50 kGy to obtain a strengthened cross-linked nanocellulose / polylactic acid gel sample. The gel sample is immersed in deionized water, and the water is changed every 3 hours, repeating 5-8 times. The organic solvent is replaced from the gel after washing, and the water content of the hydrogel is 50%, forming a nanocellulose / polylactic acid hydrogel spinning solution. The spinning solution is spun using wet spinning equipment, and the spun material is subjected to high-energy electron beam irradiation with a radiation dose of 50 kGy, followed by a 5-minute secondary drying and strengthening treatment. Where the hydrogel spinning solution is sprayed through the spinneret holes of the spinning equipment, and then enters the water coagulation solid bath for washing, drafting, and radiation drying to prepare the polylactic acid / nanocellulose fiber. The traction and stretching thread speed is controlled at 30 centimeters per minute. Prepare dyes at room temperature: disperse blue 79 1.5% (on weight of fabric, o.w.f), reactive blue CN-2G 1.5% (on weight of fabric, o.w.f), anionic surfactant Sodium fatty alcohol ether sulfate, (AES) 0.2 g / L, leveling agent SL 0.4 g / L, bath ratio 1:30, pH adjusted to 5 with acetic acid and sodium acetate. After the dye solution is prepared, it is heated from room temperature at a rate of 2 °C / minute to 60 °C, and then polylactic acid / nanocellulose composite fibers are added to start dyeing. Then heat up to 110 °C at a rate of 1 °C / minute and hold for 20 minutes. Then start cooling down, from 110 °C to 60 °C, and control the cooling time within 30 minutes. Add 3 g / L of insurance powder, such as sodium hydrosulfite, 3 g / L of anhydrous sodium carbonate, and 3 g / L of detergent 6501 to wash away the floating color on the fibers, improve the wet fastness of dyeing, and thoroughly wash, air dry, or perform post-treatment processes after cleaning. Using the wet spinning method in Example 5, the dyeing rate of fibers is 79%. The strength of the fibers obtained by wet spinning is increased by 2.8 times, reaching 112CN·tex-1, and the antigen fibrillation performance is doubled, reaching 180 s.Comparative Example 1

[0027] According to preparation method of example 1, the spinning solution obtained without irradiation crosslinking is spun, and the secondary radiation process is not carried out to prepare composite fibers for dyeing.

[0028] The sugarcane fiber is dispersed into nanocellulose suspension in water through a high-speed shear machine to obtain 10% nanocellulose suspension solution. Polylactic acid is dissolved in the mixed solution of dichloromethane / N, N-dimethylformamide (the volume ratio of the two is 4:1) to obtain a 5% polylactic acid solution. After the nanocellulose suspension solution, polylactic acid solution and polyethylene glycol solution are mixed evenly according to the mass ratio of 6:3:1, the sample of polylactic acid / nanocellulose gel is obtained by standing at 50 °C for 12 hours. The gel sample is immersed in deionized water, and the water is changed every 3 hours, repeating for 5-8 times. The gel is washed to replace the organic solvent, and the water content of the hydrogel is 60%. The solvent of the gel is replaced by water washing to form a hydrogel spinning solution. The spinning solution is spun by wet spinning equipment, and the spinning solution is sprayed into the spinning holes of the spinning equipment. The silk thread enters the water coagulation bath and is washed, stretched, and dried with hot air to prepare polylactic acid / nanocellulose fibers. The traction and stretching thread speed is controlled at 15 centimeters per minute, and the winding and stretching speed ratio is 1.5. Dry in hot air at a temperature of 110 °C for 30 minutes. Prepare dye at room temperature: disperse yellow 54.1% (on weight of fabric, o.w.f), reactive yellow CN-EX 1% (on weight of fabric, o.w.f), dispersant NN 1 g / L, bath ratio 1:50, adjust pH to 5 with acetic acid and sodium acetate. After the dye solution is prepared, it is heated from room temperature at a rate of 2 °C / minute to 60 °C, and then polylactic acid / nanocellulose composite fibers are added to start dyeing. Then heat up to 110 °C at a rate of 1 °C / minute and hold for 20 minutes. Then start cooling down, from 110 °C to 60 °C, and control the cooling time within 30 minutes. Add 3 g / L of insurance powder, such as sodium hydrosulfite, 3 g / L of anhydrous sodium carbonate, and 3 g / L of detergent 6501 to wash away the floating color on the fibers, improve the wet fastness of dyeing, and thoroughly wash, air dry, or perform post-treatment processes after cleaning. The dye uptake rate of the obtained spun fibers is 50%, the fracture strength decreased by 30% to 56CN·tex-1, and the fiber antigen fibrillation performance decreased by 40% to 108 s.Comparative Example 2

[0029] The sugarcane fiber is dispersed into nanocellulose suspension in water through a high-speed shear machine to obtain 15% nanocellulose suspension solution. The polylactic acid is dissolved in the mixed solution of chloroform / N,N-dimethylformamide (the volume ratio of the two is 3:1) to obtain a polylactic acid solution with a mass fraction of 8%. After the nanocellulose suspension solution, polylactic acid solution and glycerin solution are mixed evenly according to the mass ratio of 7:2:1, they are left standing at 30 °C for 24 hours to obtain a strengthened cross-linked gel sample. The gel sample is immersed in deionized water, and the water is changed every 3 hours, repeating for 5-8 times. The gel is washed to replace the organic solvent, and the water content of the hydrogel is 70%, forming nanocellulose / polylactic acid hydrogel spinning solution. The spinning solution is spun by wet spinning equipment, and the spinning solution is sprayed into the spinning holes of the spinning equipment. The silk thread enters the water coagulation bath and is washed, stretched, and dried with hot air to prepare polylactic acid / nanocellulose fibers. The traction and stretching thread speed is controlled at 15 centimeters per minute, and the winding and stretching speed ratio is 1.5. Dry in hot air at a temperature of 110 °C for 5 minutes. Prepare dyes at room temperature: disperse red 74.2% (on weight of fabric, o.w.f), reactive red CN-3B 2% (on weight of fabric, o.w.f), dispersant NN 1 g / L, bath ratio 1:50, pH is adjusted to 5 with acetic acid and sodium acetate, the dye solution is prepared and heated from room temperature to 60 °C at a rate of 2 °C / minute. Then, polylactic acid / nanocellulose composite fibers are added to start dyeing. Then heat up to 110 °C at a rate of 1 °C / minute and hold for 20 minutes. Then start cooling down, from 110 °C to 60 °C, and control the cooling time within 30 minutes. Add 3 g / L of insurance powder, such as sodium hydrosulfite, 3 g / L of anhydrous sodium carbonate, and 3 g / L of detergent 6501 to wash away the floating color on the fibers, improve the wet fastness of dyeing, and thoroughly wash, air dry, or perform post-treatment processes after cleaning. Compared with Example 2, the dye uptake rate of the obtained spun fibers is 55%, the fracture strength of the spun fibers is reduced by 50%, reaching 60CN·tex-1, and the fiber antigen fibrillation performance is reduced by 30%, reaching 189 s.Comparative Example 3

[0030] The sugarcane fiber is dispersed into nanocellulose suspension in water through a high-speed shear machine to obtain 15% nanocellulose suspension solution. The polylactic acid is dissolved in the mixed solution of chloroform / N, N-dimethylformamide (the volume ratio of the two is 3:1) to obtain a polylactic acid solution with a mass fraction of 8%. After the nanocellulose suspension solution, polylactic acid solution and glycerin solution are mixed evenly according to the mass ratio of 7:2:1, they are left standing at 30 °C for 24 hours to obtain a strengthened cross-linked gel sample. The gel sample is soaked in deionized water, and the water is changed every 3 hours, repeated for 5-8 times. The gel is washed to replace the organic solvent, and the water content of the hydrogel is 70%, forming nanocellulose / polylactic acid hydrogel spinning solution. The spinning solution is spun by wet spinning equipment, and the spinning solution is sprayed into the spinning holes of the spinning equipment. The silk thread enters the water coagulation bath and is washed, stretched, and dried irradiated to prepare polylactic acid / nanocellulose fibers. The traction and stretching thread speed is controlled at 25 centimeters per minute. Where a radiation dose of the irradiation drying is 50 kGy, and the irradiation drying treatment lasts for 3 minutes. Prepare dyes at room temperature: disperse red 74.2% (on weight of fabric, o.w.f), reactive red CN-3B 2% (on weight of fabric, o.w.f), dispersant NN 1 g / L, bath ratio 1:50, adjust the pH value to 5 with acetic acid and sodium acetate. After preparing the dye solution, heat it up from room temperature at a rate of 2 degrees per minute to 60 degrees, and then add polylactic acid / nanocellulose composite fibers to start dyeing. Then heat up to 110 °C at a rate of 1 °C / minute and hold for 20 minutes. Then start cooling down, from 110 °C to 60 °C, and control the cooling time within 30 minutes. Add 3 g / L of insurance powder, such as sodium hydrosulfite, 3 g / L of anhydrous sodium carbonate, and 3 g / L of detergent 6501 to wash away the floating color on the fibers, improve the wet fastness of dyeing, and thoroughly wash, air dry, or perform post-treatment processes after cleaning.

[0031] In this embodiment, a single irradiation is used. Compared with example 2, the dye uptake rate of the obtained spun fibers is 65%, the fracture strength of the spun fibers is reduced by 40%, reaching 72CN·tex-1, and the fiber antigen fibrillation performance is reduced by 50%, reaching 135 s.Comparative Example 4

[0032] The sugarcane fiber is dispersed into nanocellulose suspension in water through a high-speed shear machine to obtain 15% nanocellulose suspension solution. The polylactic acid is dissolved in the mixed solution of chloroform / N,N-dimethylformamide (the volume ratio of the two is 3:1) to obtain a polylactic acid solution with a mass fraction of 8%. After the nanocellulose suspension solution, polylactic acid solution and glycerol solution are mixed evenly according to the mass ratio of 7:2:1, they are left standing at 30 °C for 24 hours, and then irradiated by high-energy electron beam with a radiation dose of 50 kGy to obtain an enhanced cross-linking gel, the gel sample is soaked in deionized water, change the water every 3 hours, repeating 5-8 times, and the gel is washed to replace the organic solvent, and the water content of the gel is 70%, forming a nanocellulose / polylactic acid hydrogel spinning solution. The spinning solution is spun by wet spinning equipment, and the spinning solution is sprayed into the spinning holes of the spinning equipment. The silk thread enters the water coagulation bath and is washed, stretched, and dried with hot air to prepare polylactic acid / nanocellulose fibers. The traction and stretching thread speed is controlled at 25 cm / min. Dry in hot air at a temperature of 110 °C for 30 minutes. Prepare dyes at room temperature: disperse red 74.2% (on weight of fabric, o.w.f), reactive red CN-3B 2% (on weight of fabric, o.w.f), dispersant NN 1 g / L, bath ratio 1:50, pH is adjusted to 5 with acetic acid and sodium acetate, the dye solution is prepared and heated from room temperature to 60 °C at a rate of 2 °C / minute. Then, polylactic acid / nanocellulose composite fibers are added to start dyeing. Then heat up to 110 °C at a rate of 1 °C / minute and hold for 20 minutes. Then start cooling down, from 110 °C to 60 °C, and control the cooling time within 30 minutes. Add 3 g / L of insurance powder, such as sodium hydrosulfite, 3 g / L of anhydrous sodium carbonate, and 3 g / L of detergent 6501 to wash away the floating color on the fibers, improve the wet fastness of dyeing, and thoroughly wash, air dry, or perform post-treatment processes after cleaning.

[0033] In this example, a single irradiation is used. Compared with Example 2, the dye uptake rate of the obtained spun fibers is 66%, the fracture strength of the spun fibers is reduced by 30%, reaching 84CN·tex-1, and the fiber antigen fibrillation performance is reduced by 40%, reaching 162 s.

[0034] The protection scope of the present disclosure is not limited to the examples. Anyone who makes similar changes to it shall be deemed not to deviate from the protection scope of the present disclosure.

Claims

1. A dyeing process for polylactic acid and nanocellulose composite fibers, comprising: a spinning solution preparation process, a spinning process, and a dyeing process,wherein the spinning solution preparation process is to uniformly mix a nanocellulose suspension, a polylactic acid solution and an additive together, stand at 30-80 °C for 1-2 h, and conduct high-energy electron beam radiation to form a gel, wherein the gel is washed to obtain a hydrogel spinning solution, wherein an irradiation amount of high-energy electron beam radiation is 10-50 kGy, and an irradiation time is 20-40 minutes, wherein a mass ratio of the polylactic acid solution to a nanocellulose solution is 10:1-1:1, a mass ratio of the polylactic acid solution to an additive solution is 10:1-1:1, wherein the polylactic acid solution is to disperse polylactic acid in an organic solvent, a mass concentration of the polylactic acid is 5-10%, and the nanocellulose suspension is a dispersion of cellulose fibers with a length of 10-100 nm in water, with a mass concentration of the cellulose fibers being 5-20%;wherein the spinning process is to send the hydrogel spinning solution to wet spinning equipment for spinning to form fibers; the fibers are strengthened by high-energy electron beam radiation drying to obtain fiber filaments, wherein an irradiation amount is 10-50 kGy and an irradiation time is 3-5 minutes;wherein in the dyeing process, a weight ratio of dye to fibers is 1-10%, a bath ratio is 1:45-55, an amount of a dispersant NN is 0.8-1.2 g / L, a pH value of a dyeing solution is 4.8-5.2, temperature is raised to 58 °C-62 °C at a rate of 1.5 °-2.5 °C / min, the fibers is added, the temperature is raised to 108 °C-112 °C at a rate of 0.8 °C-1.2 °C / min, and an insulation dyeing time is 18-22 minutes, afterwards, cooling down to 58 °C-62 °C, adding an insurance powder 2.5-3.5 g / L, anhydrous sodium carbonate 2.5-3.5 g / L, and detergent 2.5-3.5 g / L to wash away floating color on the fibers, thoroughly washing with water, air drying or performing post-treatment processes;wherein the dye is a mixture of dispersed dye and reactive dye, and the dispersed dye is azo type dispersed red 74, dispersed blue 79, or dispersed yellow 54; the reactive dye is reactive red CN-3B, reactive blue CN-2G, or reactive yellow CN-EX.wherein a chemical formula of the azo type dispersed red 74 C22H25N5O7, a chemical formula of the dispersed blue 79 is C24H27BrN6O10, a CAS No. of the dispersed yellow 54 is 12223-85-7, a chemical formula of the reactive blue CN-2G is C28H29N5Na4O21S6, and a CAS No. of the reactive yellow CN-EX is 115099-55-3.

2. The dyeing process for polylactic acid and nanocellulose composite fibers according to claim 1, wherein the organic solvent is a mixture of one or more of N,N-dimethylformamide, tetrahydrofuran, 1,4-dioxane, chloroform, and acetone.

3. The dyeing process for polylactic acid and nanocellulose composite fibers according to claim 2, wherein the additive is polyethylene glycol, glycerol, carboxymethyl chitosan, carboxymethyl cellulose, polyvinyl alcohol or polyethylene oxide.

4. The dyeing process for polylactic acid and nanocellulose composite fibers according to claim 3, wherein the cellulose fibers are sugarcane fibers.