Waterborne polyurethane color fixing agent, preparation method and pure cotton fabric dyeing method

Abstract

The invention relates to the technical field of polyurethane preparation, and discloses a waterborne polyurethane color fixing agent, a preparation method and a pure cotton fabric dyeing method. The preparation method of the waterborne polyurethane color fixing agent comprises the following steps: reacting trimethylolpropane, isophorone diisocyanate, dimethylolpropionic acid, polyethylene glycol, cationic hydroxyl silicone oil and tert-butylaminoethyl methacrylate, neutralizing and emulsifying to obtain waterborne polyurethane, and continuously reacting the obtained waterborne polyurethane with an ultraviolet absorbent to obtain the waterborne polyurethane color fixing agent. The waterborne polyurethane color fixing agent is a cationic color fixing agent, after pure cotton fabric dyed by reactive dye is subjected to color fixing finishing by the waterborne polyurethane color fixing agent, the fabric is good in softness, color fixing effect and washing fastness, dry and wet friction strength is improved, and the waterborne polyurethane color fixing agent also has a certain anti-ultraviolet effect.

Description

Technical Field

[0001] This invention relates to the field of polyurethane preparation technology, specifically to waterborne polyurethane fixing agents, preparation methods, and dyeing methods for pure cotton fabrics. Background Technology

[0002] After pure cotton fabric is dyed with reactive dyes, although stable covalent bonds can be formed between the reactive dyes and fibers, a large number of unfixed free dyes remain on the surface of the pure cotton fabric due to the formation of hydrolyzed groups. This makes it easy for the fabric to fade or lose color during washing or external friction, resulting in defects such as low wet rubbing fastness and easy color loss after washing. The formaldehyde-free fixing agents in the existing technology still cannot effectively improve the rubbing fastness. Therefore, new fixing agents remain a hot research topic.

[0003] Waterborne polyurethanes possess advantages such as being environmentally friendly, safe, and having good film-forming properties, making them widely used in textile finishing. Cationic waterborne polyurethanes have a color-fixing effect on reactive and direct dyes, improving various aspects of fabric color fastness. Therefore, the development of cationic waterborne polyurethane color-fixing agents has broad application prospects. Existing technologies, such as Chinese patent application CN112341594A, disclose a method for preparing a waterborne polyurethane color-fixing agent. This method involves reacting polycaprolactone diol with diisocyanate to obtain a polyurethane prepolymer, then extending the chain with a hydrophilic chain extender and a small molecule polyol. After neutralization and emulsification, a waterborne polyurethane color-fixing agent is obtained, which has the characteristics of improving the wet rubbing fastness and phase change temperature regulation of deeply dyed cellulose fiber fabrics. However, due to the limited number of active groups, this type of waterborne polyurethane color-fixing agent has a limited effect on improving the rubbing fastness of the fabric after color-fixing treatment, thus limiting its application. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a water-based polyurethane fixing agent, a preparation method, and a dyeing method for pure cotton fabric. The water-based polyurethane fixing agent is a cationic fixing agent. After fixing the pure cotton fabric dyed with reactive dyes with it, the fabric has good softness, good color fixing effect, good wash fastness, improved dry and wet rubbing strength, and also has a certain anti-ultraviolet effect.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing an aqueous polyurethane fixing agent includes the following steps:

[0007] Step (1): Mix trimethylolpropane, the first catalyst, and acetone, add isophorone diisocyanate, and react. After the reaction is complete, cool down, add the second catalyst, dimethylolpropionic acid, and polyethylene glycol, and continue the reaction. After the reaction is complete, add cationic hydroxyl silicone oil and react again. After the reaction is complete, add the end-capping agent tert-butylaminoethyl methacrylate (t-BAEMA) and perform the end-capping reaction. After the reaction is complete, cool down, add triethylamine for neutralization, cool after neutralization, add water for emulsification, and obtain waterborne polyurethane.

[0008] Cationic hydroxyl silicone oil is prepared by the following steps:

[0009] S11. Mix γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane, add triethylamine as a catalyst, and react. After the reaction is complete, continue the reaction. After the reaction is complete, evacuate and cool to room temperature to obtain piperazine-based silicone oil.

[0010] S12. Mix isopropanol, piperazine silicone oil, (2-chloroethyl)trimethylammonium chloride and sodium hydroxide, react, filter after the reaction is complete, take the filtrate, and remove the solvent isopropanol by rotary evaporation to obtain cationic hydroxy silicone oil.

[0011] Step (2): Mix waterborne polyurethane and UV absorber, add 2,2-azobis(2-methylpropylimidazolium) hydrochloride aqueous solution dropwise, react after the addition is complete, remove acetone by rotary evaporation after the reaction is complete, and obtain waterborne polyurethane fixing agent.

[0012] The ultraviolet absorber is prepared by the following steps:

[0013] 4-Bromomethylbenzophenone and chloroform were mixed and dissolved, and a chloroform solution of dimethylallylamine was added dropwise. After the addition was complete, the reaction was allowed to proceed. After the reaction was completed, the solvent chloroform was removed by rotary evaporation, cooled, filtered, and the filter cake was collected, washed, and dried to obtain the ultraviolet absorber.

[0014] Preferably, in step (1): the molar ratio of trimethylolpropane, isophorone diisocyanate, dimethylolpropionic acid, polyethylene glycol, tert-butylaminoethyl methacrylate, and triethylamine is 1:5:0.5:1-1.5:0.5-1:0.5; both the first catalyst and the second catalyst are dibutyltin dilaurate, the mass ratio of the first catalyst to the second catalyst is 1:1, and the total amount of dibutyltin dilaurate added is 0.1% of the mass of polyethylene glycol; the mass of cationic hydroxyl silicone oil added is equal to the mass of polyethylene glycol added; and the solid content of the waterborne polyurethane is 30%.

[0015] Preferably, in step (1): the reaction conditions are: reacting at 80°C for 1-1.5 hours in a nitrogen atmosphere; the continued reaction conditions are: continuing the reaction at 50-60°C for 3 hours; the second reaction conditions are: reacting again at 60°C for 1-1.5 hours; the end-capping reaction conditions are: end-capping reaction at 50-60°C for 2-3 hours; and the neutralization reaction conditions are: neutralization reaction at 40°C for 30 minutes.

[0016] Preferably, in step (1) when preparing cationic hydroxyl silicone oil, in S11: the molar ratio of γ-piperazinylpropylmethyldimethoxysilane to dihydroxypolydimethylsiloxane is 0.8-0.9:1.2; the amount of triethylamine catalyst is 1.2-1.5% of the total mass of γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane.

[0017] Preferably, in step (1), when preparing cationic hydroxyl silicone oil, in S11: the reaction conditions are: reacting at 100-110℃ for 5-6 hours in a nitrogen atmosphere; the continued reaction conditions are: continuing the reaction at 130-135℃ for 0.5-1 hours; the vacuum conditions are: vacuuming at 0.05MPa for 0.5 hours.

[0018] Preferably, in step (1), when preparing cationic hydroxy silicone oil, the mass ratio of isopropanol, piperazine silicone oil, (2-chloroethyl)trimethylammonium chloride, and sodium hydroxide in S12 is 85-90:80:3.35-3.4:0.75-0.8; the reaction conditions are: reacting at 60-65℃ for 7-8 hours.

[0019] Preferably, in step (2): the mass ratio of aqueous polyurethane, ultraviolet absorber, and aqueous solution of 2,2-azobis(2-methylpropylimidazolium) hydrochloride is 100:5-8:8-10; the aqueous solution of 2,2-azobis(2-methylpropylimidazolium) hydrochloride is 10wt%; the reaction conditions are: reaction at 60-70℃ for 30-40 min.

[0020] Preferably, in step (1), when preparing the ultraviolet absorber, the ratio of 4-bromomethylbenzophenone, dimethylallylamine, and chloroform is 1 mol: 1.1 mol: 70-80 mL; the reaction conditions are: reacting at 60-65℃ for 3-4 h.

[0021] Preferably, an aqueous polyurethane fixing agent is prepared using the method described above.

[0022] This invention discloses a dyeing method for pure cotton fabric, comprising the following steps:

[0023] Step (1): Immerse the pure cotton fabric in the reactive dye solution, dye it, add sodium chloride, continue dyeing, raise the temperature, add sodium carbonate, dye it again, cool down, wash with water, soap, wash with water again, and dry to obtain dyed pure cotton fabric.

[0024] Step (2): Immerse the dyed pure cotton fabric in a color-fixing finishing solution and bake it to obtain the dyed pure cotton fabric after color fixation.

[0025] Preferably, in step (1): the ratio of pure cotton fabric to reactive dye solution is 1:30; the dyeing conditions are: dyeing at 40℃ for 15-20 min; the conditions for continued dyeing are: continuing dyeing at 40℃ for 15-20 min; and the conditions for re-dyeing are: re-dyeing at 60℃ for 30 min.

[0026] Preferably, in step (1): the reactive dye in the reactive dye solution is an M-type reactive dye with a concentration of 4-5% owf; during the dyeing process, the amount of sodium chloride is 25-30 g / L and the amount of sodium carbonate is 10-15 g / L; during soaping, the bath ratio is 1:30 and the amount of soap powder is 2-3 g / L.

[0027] Preferably, in step (2), the color-fixing solution is prepared from the above-mentioned water-based polyurethane color-fixing agent, and the amount of water-based polyurethane color-fixing agent is 170-180 g / L.

[0028] Preferably, in step (2): the ratio of dyed pure cotton fabric to color-fixing solution is 1:30; the impregnation operation includes: impregnation at room temperature for 20-30 minutes, after impregnation, two impregnations and two nippings, with a nipping rate of 72-75%; the baking conditions are: pre-baking at 60°C for 150 seconds, and baking at 160°C for 180 seconds.

[0029] Preferably, a dyed pure cotton fabric after color fixing is prepared using the dyeing method for pure cotton fabric as described above.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. The waterborne polyurethane fixing agent prepared in this invention is a cationic waterborne polyurethane fixing agent. Due to the presence of cations, it has a good fixing effect on pure cotton fabric dyed with reactive dyes. This is because the cationic groups in the fixing agent can react with the anionic groups in the reactive dyes on the surface of pure cotton fibers to form an insoluble electrolyte lake. Furthermore, since the main component of the fixing agent is polyurethane material, the polymer chains containing urethane structures can form hydrogen bonds with the reactive groups on pure cotton fibers and dyes, thereby improving the bonding force between reactive dyes, pure cotton fabrics, and waterborne polyurethane fixing agents, and thus enhancing the adhesion strength of reactive dyes on pure cotton fibers.

[0032] In addition, waterborne polyurethane fixing agents have good film-forming properties. When fixing pure cotton fabrics, they can not only form a continuous polymer film on the fabric surface to encapsulate the active dye molecules and inhibit their shedding, thus improving the fabric's rubbing fastness, but also, during the fixing process, the urea bonds in the waterborne polyurethane fixing agent can reversibly form isocyanates and amines under heating conditions, thereby increasing the isocyanate active sites and further improving the fixing performance.

[0033] 2. In this invention, γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane are polymerized in bulk to form piperazine-based silicone oil, which is then further reacted with (2-chloroethyl)trimethylammonium chloride to obtain cationic hydroxy silicone oil with a cationic quaternary ammonium salt structure in the side chain. Introducing this into waterborne polyurethane fixing agent can effectively improve the washing resistance and fixing performance of the fixing agent, and the siloxane segments can also improve the softness of the fabric.

[0034] 3. The present invention prepares an ultraviolet absorber by reacting 4-bromomethylbenzophenone with dimethylallylamine through a quaternization reaction. It can not only react and polymerize with waterborne polyurethane, but also has ultraviolet absorption properties and color-fixing effect. As a functional additive, it improves the comprehensive performance of waterborne polyurethane color-fixing agents.

[0035] 4. In the waterborne polyurethane fixing agent prepared in this invention, trimethylolpropane increases the degree of crosslinking, thereby increasing the number of active sites during fixing. The cationic hydroxy silicone oil introduces siloxane segments and cationic quaternary ammonium salt structures, which improves the water resistance and fixing performance of the fixing agent. Both cationic hydroxy silicone oil and polyethylene glycol have flexible segments, so the pure cotton fabric has good softness after fixing treatment. Tert-butylaminoethyl methacrylate, as a capping agent, not only has thermally reversible urea bonds but also carbon-carbon double bonds. On the one hand, it can react with isocyanate groups for capping and then decapsulate under heating conditions to regenerate isocyanate groups, which can continue to react with the active groups on the dyed pure cotton fabric to improve the fixing performance. On the other hand, it can polymerize with ultraviolet absorbers to improve the fabric's UV resistance and durability. Attached Figure Description

[0036] Figure 1 This is a process flow diagram for preparing the waterborne polyurethane fixing agent in this invention;

[0037] Figure 2 This is a bar chart of UPF for samples 1-8 in the comprehensive performance test of this invention. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0039] Example 1

[0040] This embodiment discloses a method for preparing an aqueous polyurethane fixing agent, comprising the following steps:

[0041] Step (1): Trimethylolpropane, the first catalyst, and acetone are mixed. Isophorone diisocyanate is added in a nitrogen atmosphere at 80°C and reacted for 1 hour. After the reaction is completed, the temperature is lowered and the second catalyst, dimethylolpropionic acid, and polyethylene glycol are added. The reaction is continued at 50°C for 3 hours. After the reaction is completed, cationic hydroxyl silicone oil is added and reacted again at 60°C for 1.5 hours. After the reaction is completed, the end-capping agent tert-butylaminoethyl methacrylate is added and the end-capping reaction is carried out at 50°C for 3 hours. After the reaction is completed, the temperature is lowered to 40°C and triethylamine is added for neutralization reaction for 30 minutes. After neutralization, the temperature is cooled to 30°C and water is added and stirred, dispersed, and emulsified for 30 minutes to obtain waterborne polyurethane with a solid content of 30%.

[0042] The molar ratio of trimethylolpropane, isophorone diisocyanate, dimethylolpropionic acid, polyethylene glycol, tert-butylaminoethyl methacrylate, and triethylamine is 1:5:0.5:1:1:0.5; both the first and second catalysts are dibutyltin dilaurate, with a mass ratio of 1:1, and the total amount of dibutyltin dilaurate added is 0.1% of the mass of polyethylene glycol; the mass of cationic hydroxyl silicone oil added is equal to the mass of polyethylene glycol added.

[0043] Cationic hydroxyl silicone oil is prepared by the following steps:

[0044] S11. γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane are mixed in a molar ratio of 0.8:1.2. Triethylamine is added as a catalyst under a nitrogen atmosphere at 100°C and the reaction is carried out for 6 hours. After the reaction is completed, the temperature is raised to 130°C and the reaction is continued for 1 hour. After the reaction is completed, the mixture is evacuated under a vacuum of 0.05 MPa for 0.5 hours and cooled to room temperature to obtain piperazine-based silicone oil.

[0045] The amount of triethylamine catalyst used is 1.2% of the total mass of γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane;

[0046] S12. Isopropanol, piperazine silicone oil, (2-chloroethyl)trimethylammonium chloride and sodium hydroxide are mixed in a mass ratio of 85:80:3.35:0.75 and reacted at 60°C for 8 hours. After the reaction is completed, the mixture is filtered, and the filtrate is evaporated to remove the solvent isopropanol to obtain cationic hydroxy silicone oil.

[0047] Step (2): Mix waterborne polyurethane and UV absorber, and add 10wt% of 2,2-azobis(2-methylpropylimidazolium)dihydrochloride aqueous solution dropwise over 20 min. After the addition is complete, react at 60℃ for 40 min. After the reaction is complete, remove acetone by rotary evaporation to obtain waterborne polyurethane fixing agent.

[0048] The mass ratio of aqueous polyurethane, ultraviolet absorber, and 10wt% aqueous solution of 2,2-azobis(2-methylpropylimidazolium) hydrochloride is 100:5:8.

[0049] The ultraviolet absorber is prepared by the following steps:

[0050] 4-Bromomethylbenzophenone and chloroform were mixed and dissolved, and a chloroform solution of dimethylallylamine was added dropwise over 20 minutes. After the addition was complete, the mixture was reacted at 60°C for 4 hours. After the reaction was completed, the solvent chloroform was removed by rotary evaporation, the mixture was cooled to room temperature, filtered, and the filter cake was washed with ethanol and dried at 50°C for 24 hours to obtain the ultraviolet absorber.

[0051] The ratio of 4-bromomethylbenzophenone, dimethylallylamine, and chloroform is 1 mol: 1.1 mol: 70 mL.

[0052] Example 2

[0053] This embodiment discloses a method for preparing an aqueous polyurethane fixing agent, comprising the following steps:

[0054] Step (1): Trimethylolpropane, the first catalyst, and acetone are mixed. Isophorone diisocyanate is added in a nitrogen atmosphere at 80°C and reacted for 1 hour. After the reaction is completed, the temperature is lowered, and the second catalyst, dimethylolpropionic acid, and polyethylene glycol are added. The reaction is continued at 55°C for 3 hours. After the reaction is completed, cationic hydroxyl silicone oil is added and reacted again at 60°C for 1.3 hours. After the reaction is completed, the end-capping agent tert-butylaminoethyl methacrylate is added and the end-capping reaction is carried out at 55°C for 2.5 hours. After the reaction is completed, the temperature is lowered to 40°C, and triethylamine is added to neutralize the reaction for 30 minutes. After neutralization, the temperature is cooled to 30°C, and water is added and stirred to disperse and emulsify for 30 minutes to obtain a waterborne polyurethane with a solid content of 30%.

[0055] The molar ratio of trimethylolpropane, isophorone diisocyanate, dimethylolpropionic acid, polyethylene glycol, tert-butylaminoethyl methacrylate, and triethylamine is 1:5:0.5:1.2:0.8:0.5; both the first and second catalysts are dibutyltin dilaurate, with a mass ratio of 1:1, and the total amount of dibutyltin dilaurate added is 0.1% of the mass of polyethylene glycol; the mass of cationic hydroxyl silicone oil added is equal to the mass of polyethylene glycol added.

[0056] Cationic hydroxyl silicone oil is prepared by the following steps:

[0057] S11. γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane are mixed at a molar ratio of 0.83:1.2. Triethylamine is added as a catalyst under a nitrogen atmosphere at 100°C and the reaction is carried out for 6 hours. After the reaction is completed, the temperature is raised to 130°C and the reaction is continued for 1 hour. After the reaction is completed, the mixture is evacuated under a vacuum of 0.05 MPa for 0.5 hours and cooled to room temperature to obtain piperazine-based silicone oil.

[0058] The amount of triethylamine catalyst used is 1.2% of the total mass of γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane;

[0059] S12. Isopropanol, piperazine silicone oil, (2-chloroethyl)trimethylammonium chloride and sodium hydroxide are mixed in a mass ratio of 85:80:3.36:0.76 and reacted at 60°C for 8 hours. After the reaction is completed, the mixture is filtered, and the filtrate is evaporated to remove the solvent isopropanol to obtain cationic hydroxy silicone oil.

[0060] Step (2): Mix waterborne polyurethane and UV absorber, and add 10wt% of 2,2-azobis(2-methylpropylimidazolium)dihydrochloride aqueous solution dropwise over 25 min. After the addition is complete, react at 65℃ for 35 min. After the reaction is complete, remove acetone by rotary evaporation to obtain waterborne polyurethane fixing agent.

[0061] The mass ratio of waterborne polyurethane, UV absorber, and 10 wt% aqueous solution of 2,2-azobis(2-methylpropylimidazolium) hydrochloride was 100:6:9; the preparation of the UV absorber was the same as in Example 1.

[0062] Example 3

[0063] This embodiment discloses a method for preparing an aqueous polyurethane fixing agent, comprising the following steps:

[0064] Step (1): Trimethylolpropane, the first catalyst, and acetone are mixed. Isophorone diisocyanate is added under a nitrogen atmosphere at 80°C and reacted for 1.3 hours. After the reaction is completed, the temperature is lowered, and the second catalyst, dimethylolpropionic acid, and polyethylene glycol are added. The reaction is continued at 55°C for 3 hours. After the reaction is completed, cationic hydroxyl silicone oil is added and reacted again at 60°C for 1.3 hours. After the reaction is completed, the end-capping agent tert-butylaminoethyl methacrylate is added and the end-capping reaction is carried out at 55°C for 2.5 hours. After the reaction is completed, the temperature is lowered to 40°C, and triethylamine is added to neutralize the reaction for 30 minutes. After neutralization, the temperature is cooled to 30°C, and water is added and stirred to disperse and emulsify for 30 minutes to obtain a waterborne polyurethane with a solid content of 30%.

[0065] The molar ratio of trimethylolpropane, isophorone diisocyanate, dimethylolpropionic acid, polyethylene glycol, tert-butylaminoethyl methacrylate, and triethylamine is 1:5:0.5:1.3:0.7:0.5; both the first and second catalysts are dibutyltin dilaurate, with a mass ratio of 1:1, and the total amount of dibutyltin dilaurate added is 0.1% of the mass of polyethylene glycol; the mass of cationic hydroxyl silicone oil added is equal to the mass of polyethylene glycol added.

[0066] Cationic hydroxyl silicone oil is prepared by the following steps:

[0067] S11. γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane are mixed in a molar ratio of 0.85:1.2. Triethylamine is added as a catalyst under a nitrogen atmosphere at 105°C and the reaction is carried out for 5.5 h. After the reaction is completed, the temperature is raised to 130°C and the reaction is continued for 1 h. After the reaction is completed, the mixture is evacuated under a vacuum of 0.05 MPa for 0.5 h and cooled to room temperature to obtain piperazine-based silicone oil.

[0068] The amount of triethylamine catalyst used is 1.3% of the total mass of γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane;

[0069] S12. Isopropanol, piperazine silicone oil, (2-chloroethyl)trimethylammonium chloride and sodium hydroxide are mixed in a mass ratio of 85:80:3.38:0.78 and reacted at 60°C for 8 hours. After the reaction is completed, the mixture is filtered, and the filtrate is evaporated to remove the solvent isopropanol to obtain cationic hydroxy silicone oil.

[0070] Step (2): Mix waterborne polyurethane and UV absorber, and add 10wt% of 2,2-azobis(2-methylpropylimidazolium)dihydrochloride aqueous solution dropwise over 25 min. After the addition is complete, react at 65℃ for 35 min. After the reaction is complete, remove acetone by rotary evaporation to obtain waterborne polyurethane fixing agent.

[0071] The mass ratio of aqueous polyurethane, UV absorber, and 10 wt% aqueous solution of 2,2-azobis(2-methylpropylimidazolium) hydrochloride was 100:6.5:9; the preparation of the UV absorber was the same as in Example 1.

[0072] Example 4

[0073] This embodiment discloses a method for preparing an aqueous polyurethane fixing agent, comprising the following steps:

[0074] Step (1): Trimethylolpropane, the first catalyst, and acetone are mixed. Isophorone diisocyanate is added in a nitrogen atmosphere at 80°C and reacted for 1.5 hours. After the reaction is completed, the temperature is lowered, and the second catalyst, dimethylolpropionic acid, and polyethylene glycol are added. The reaction is continued at 60°C for 3 hours. After the reaction is completed, cationic hydroxyl silicone oil is added and reacted again at 60°C for 1.5 hours. After the reaction is completed, the end-capping agent tert-butylaminoethyl methacrylate is added and the end-capping reaction is carried out at 55°C for 2.5 hours. After the reaction is completed, the temperature is lowered to 40°C, and triethylamine is added to neutralize the reaction for 30 minutes. After neutralization, the temperature is cooled to 30°C, and water is added and stirred to disperse and emulsify for 30 minutes to obtain a waterborne polyurethane with a solid content of 30%.

[0075] The molar ratio of trimethylolpropane, isophorone diisocyanate, dimethylolpropionic acid, polyethylene glycol, tert-butylaminoethyl methacrylate, and triethylamine is 1:5:0.5:1.4:0.6:0.5; both the first and second catalysts are dibutyltin dilaurate, with a mass ratio of 1:1, and the total amount of dibutyltin dilaurate added is 0.1% of the mass of polyethylene glycol; the mass of cationic hydroxyl silicone oil added is equal to the mass of polyethylene glycol added.

[0076] Cationic hydroxyl silicone oil is prepared by the following steps:

[0077] S11. γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane are mixed at a molar ratio of 0.88:1.2. Triethylamine is added as a catalyst under a nitrogen atmosphere at 110°C and the reaction is carried out for 6 hours. After the reaction is completed, the temperature is raised to 135°C and the reaction is continued for 0.5 hours. After the reaction is completed, the mixture is evacuated under a vacuum of 0.05 MPa for 0.5 hours and cooled to room temperature to obtain piperazine-based silicone oil.

[0078] The amount of triethylamine catalyst used is 1.4% of the total mass of γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane;

[0079] S12. Isopropanol, piperazine silicone oil, (2-chloroethyl)trimethylammonium chloride and sodium hydroxide are mixed in a mass ratio of 90:80:3.39:0.79 and reacted at 65°C for 7 hours. After the reaction is completed, the mixture is filtered, and the filtrate is evaporated to remove the solvent isopropanol to obtain cationic hydroxy silicone oil.

[0080] Step (2): Mix waterborne polyurethane and UV absorber, and add 10wt% of 2,2-azobis(2-methylpropylimidazolium)dihydrochloride aqueous solution dropwise over 25 min. After the addition is complete, react at 65℃ for 35 min. After the reaction is complete, remove acetone by rotary evaporation to obtain waterborne polyurethane fixing agent.

[0081] The mass ratio of waterborne polyurethane, UV absorber, and 10 wt% aqueous solution of 2,2-azobis(2-methylpropylimidazolium) hydrochloride was 100:7:9; the preparation of the UV absorber was the same as in Example 1.

[0082] Example 5

[0083] This embodiment discloses a method for preparing an aqueous polyurethane fixing agent, comprising the following steps:

[0084] Step (1): Trimethylolpropane, the first catalyst, and acetone are mixed. Isophorone diisocyanate is added under a nitrogen atmosphere at 80°C and reacted for 1.5 hours. After the reaction is completed, the temperature is lowered and the second catalyst, dimethylolpropionic acid, and polyethylene glycol are added. The reaction is continued at 60°C for 3 hours. After the reaction is completed, cationic hydroxyl silicone oil is added and reacted again at 60°C for 1 hour. After the reaction is completed, the end-capping agent tert-butylaminoethyl methacrylate is added and the end-capping reaction is carried out at 60°C for 2 hours. After the reaction is completed, the temperature is lowered to 40°C and triethylamine is added for neutralization reaction for 30 minutes. After neutralization, the temperature is cooled to 30°C and water is added and stirred, dispersed, and emulsified for 30 minutes to obtain waterborne polyurethane with a solid content of 30%.

[0085] The molar ratio of trimethylolpropane, isophorone diisocyanate, dimethylolpropionic acid, polyethylene glycol, tert-butylaminoethyl methacrylate, and triethylamine is 1:5:0.5:1.5:0.5:0.5; both the first and second catalysts are dibutyltin dilaurate, with a mass ratio of 1:1, and the total amount of dibutyltin dilaurate added is 0.1% of the mass of polyethylene glycol; the mass of cationic hydroxyl silicone oil added is equal to the mass of polyethylene glycol added.

[0086] Cationic hydroxyl silicone oil is prepared by the following steps:

[0087] S11. γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane are mixed in a molar ratio of 0.9:1.2. Triethylamine is added as a catalyst under a nitrogen atmosphere at 110°C and the reaction is carried out for 5 hours. After the reaction is completed, the temperature is raised to 135°C and the reaction is continued for 0.5 hours. After the reaction is completed, the mixture is evacuated under a vacuum of 0.05 MPa for 0.5 hours and cooled to room temperature to obtain piperazine-based silicone oil.

[0088] The amount of triethylamine catalyst used is 1.5% of the total mass of γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane;

[0089] S12. Isopropanol, piperazine silicone oil, (2-chloroethyl)trimethylammonium chloride and sodium hydroxide are mixed in a mass ratio of 90:80:3.4:0.8 and reacted at 65°C for 7 hours. After the reaction is completed, the mixture is filtered, and the filtrate is evaporated to remove the solvent isopropanol to obtain cationic hydroxy silicone oil.

[0090] Step (2): Mix waterborne polyurethane and UV absorber, and add 10wt% of 2,2-azobis(2-methylpropylimidazolium)dihydrochloride aqueous solution for 30 min. After the addition is complete, react at 70℃ for 30 min. After the reaction is complete, remove acetone by rotary evaporation to obtain waterborne polyurethane fixing agent.

[0091] The mass ratio of waterborne polyurethane, UV absorber, and 10 wt% aqueous solution of 2,2-azobis(2-methylpropylimidazolium) hydrochloride was 100:8:10; the preparation of the UV absorber was the same as in Example 1.

[0092] Example 6

[0093] This embodiment discloses a dyeing method for pure cotton fabric, including the following steps:

[0094] Step (1): Immerse the pure cotton fabric in the reactive dye solution with a liquor ratio of 1:30, dye at 40℃ for 15 minutes, add sodium chloride, continue dyeing for 15 minutes, raise the temperature to 60℃, add sodium carbonate, dye again for 30 minutes, cool to room temperature, wash with water, soap, wash with water again, and air dry to obtain dyed pure cotton fabric.

[0095] In the reactive dyeing solution, the reactive dye is an M-type reactive dye with a concentration of 5% owf; during the dyeing process, the amount of sodium chloride used is 25 g / L and the amount of sodium carbonate used is 10 g / L; during soaping, the liquor ratio is 1:30 and the amount of soap powder used is 2 g / L.

[0096] Step (2): Immerse the dyed pure cotton fabric in the color-fixing finishing solution with a liquor ratio of 1:30 and immerse for 20 minutes at room temperature. After immersion, perform two dips and two nips with a nips ratio of 75%. Pre-bake at 60°C for 150 seconds and bake at 160°C for 180 seconds to obtain the dyed pure cotton fabric after color fixation.

[0097] The color-fixing solution was prepared using the water-based polyurethane color-fixing agent prepared in Examples 1-5 as raw material, and the amount of water-based polyurethane color-fixing agent was 170 g / L; the dyed pure cotton fabrics after color fixing were respectively recorded as Samples 1-5.

[0098] Comparative Example 1

[0099] This comparative example discloses a method for preparing an aqueous polyurethane fixing agent, comprising the following steps:

[0100] Step (1): Trimethylolpropane, the first catalyst, and acetone are mixed. Isophorone diisocyanate is added under a nitrogen atmosphere at 80°C and reacted for 1 hour. After the reaction is completed, the temperature is lowered and the second catalyst, dimethylolpropionic acid, and polyethylene glycol are added. The reaction is continued at 50°C for 3 hours. After the reaction is completed, the end-capping agent tert-butylaminoethyl methacrylate is added and the end-capping reaction is carried out at 50°C for 3 hours. After the reaction is completed, the temperature is lowered to 40°C and triethylamine is added for neutralization reaction for 30 minutes. After neutralization, the temperature is cooled to 30°C and water is added and stirred to disperse and emulsify for 30 minutes to obtain waterborne polyurethane with a solid content of 30%.

[0101] The molar ratio of trimethylolpropane, isophorone diisocyanate, dimethylolpropionic acid, polyethylene glycol, tert-butylaminoethyl methacrylate, and triethylamine is 1:5:0.5:2:1:0.5; both the first and second catalysts are dibutyltin dilaurate, with a mass ratio of 1:1, and the total amount of dibutyltin dilaurate added is 0.1% of the mass of polyethylene glycol;

[0102] Step (2): Mix waterborne polyurethane and UV absorber, and add 10wt% of 2,2-azobis(2-methylpropylimidazolium)dihydrochloride aqueous solution dropwise over 20 min. After the addition is complete, react at 60℃ for 40 min. After the reaction is complete, remove acetone by rotary evaporation to obtain waterborne polyurethane fixing agent.

[0103] The mass ratio of aqueous polyurethane, UV absorber, and 10 wt% aqueous solution of 2,2-azobis(2-methylpropylimidazolium) hydrochloride was 100:5:8; the preparation of the UV absorber was the same as in Example 1.

[0104] Comparative Example 2

[0105] This comparative example discloses a method for preparing an aqueous polyurethane fixing agent, comprising the following steps:

[0106] Step (1): Trimethylolpropane, the first catalyst, and acetone are mixed. Isophorone diisocyanate is added in a nitrogen atmosphere at 80°C and reacted for 1 hour. After the reaction is completed, the temperature is lowered, and the second catalyst, dimethylolpropionic acid, and polyethylene glycol are added. The reaction is continued at 50°C for 3 hours. After the reaction is completed, cationic hydroxyl silicone oil is added and reacted again at 60°C for 1.5 hours. After the reaction is completed, the end-capping agent tert-butylaminoethyl methacrylate is added and the end-capping reaction is carried out at 50°C for 3 hours. After the reaction is completed, the temperature is lowered to 40°C, and triethylamine is added to neutralize the reaction for 30 minutes. After neutralization, the temperature is cooled to 30°C, and water is added and stirred to disperse and emulsify for 30 minutes. Acetone is removed by rotary evaporation to obtain a waterborne polyurethane colorant with a solid content of 30%.

[0107] The molar ratio of trimethylolpropane, isophorone diisocyanate, dimethylolpropionic acid, polyethylene glycol, tert-butylaminoethyl methacrylate, and triethylamine is 1:5:0.5:1:1:0.5; both the first and second catalysts are dibutyltin dilaurate, with a mass ratio of 1:1, and the total amount of dibutyltin dilaurate added is 0.1% of the mass of polyethylene glycol; the mass of cationic hydroxyl silicone oil added is equal to the mass of polyethylene glycol added.

[0108] Cationic hydroxyl silicone oil is prepared by the following steps:

[0109] S11. γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane are mixed in a molar ratio of 0.8:1.2. Triethylamine is added as a catalyst under a nitrogen atmosphere at 100°C and the reaction is carried out for 6 hours. After the reaction is completed, the temperature is raised to 130°C and the reaction is continued for 1 hour. After the reaction is completed, the mixture is evacuated under a vacuum of 0.05 MPa for 0.5 hours and cooled to room temperature to obtain piperazine-based silicone oil.

[0110] The amount of triethylamine catalyst used is 1.2% of the total mass of γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane;

[0111] S12. Isopropanol, piperazine silicone oil, (2-chloroethyl)trimethylammonium chloride, and sodium hydroxide are mixed in a mass ratio of 85:80:3.35:0.75 and reacted at 60°C for 8 hours. After the reaction is complete, the mixture is filtered, and the filtrate is evaporated to remove the solvent isopropanol, thus obtaining cationic hydroxy silicone oil.

[0112] Comparative Example 3

[0113] This comparative example discloses a method for preparing an aqueous polyurethane fixing agent, comprising the following steps:

[0114] Step (1): Trimethylolpropane, the first catalyst, and acetone are mixed. Isophorone diisocyanate is added in a nitrogen atmosphere at 80°C and reacted for 1 hour. After the reaction is completed, the temperature is lowered and the second catalyst, dimethylolpropionic acid, and polyethylene glycol are added. The reaction is continued at 50°C for 3 hours. After the reaction is completed, cationic hydroxyl silicone oil is added and reacted again at 60°C for 1.5 hours. After the reaction is completed, hydroxyethyl methacrylate, the end-capping agent, is added and the end-capping reaction is carried out at 50°C for 3 hours. After the reaction is completed, the temperature is lowered to 40°C and triethylamine is added for neutralization reaction for 30 minutes. After neutralization, the temperature is cooled to 30°C and water is added and stirred, dispersed, and emulsified for 30 minutes to obtain waterborne polyurethane with a solid content of 30%.

[0115] The molar ratio of trimethylolpropane, isophorone diisocyanate, dimethylolpropionic acid, polyethylene glycol, hydroxyethyl methacrylate, and triethylamine is 1:5:0.5:1:1:0.5; both the first and second catalysts are dibutyltin dilaurate, with a mass ratio of 1:1, and the total amount of dibutyltin dilaurate added is 0.1% of the mass of polyethylene glycol; the mass of cationic hydroxyl silicone oil added is equal to the mass of polyethylene glycol added.

[0116] Cationic hydroxyl silicone oil is prepared by the following steps:

[0117] S11. γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane are mixed in a molar ratio of 0.8:1.2. Triethylamine is added as a catalyst under a nitrogen atmosphere at 100°C and the reaction is carried out for 6 hours. After the reaction is completed, the temperature is raised to 130°C and the reaction is continued for 1 hour. After the reaction is completed, the mixture is evacuated under a vacuum of 0.05 MPa for 0.5 hours and cooled to room temperature to obtain piperazine-based silicone oil.

[0118] The amount of triethylamine catalyst used is 1.2% of the total mass of γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane;

[0119] S12. Isopropanol, piperazine silicone oil, (2-chloroethyl)trimethylammonium chloride and sodium hydroxide are mixed in a mass ratio of 85:80:3.35:0.75 and reacted at 60°C for 8 hours. After the reaction is completed, the mixture is filtered, and the filtrate is evaporated to remove the solvent isopropanol to obtain cationic hydroxy silicone oil.

[0120] Step (2): Mix waterborne polyurethane and UV absorber, and add 10wt% of 2,2-azobis(2-methylpropylimidazolium)dihydrochloride aqueous solution dropwise over 20 min. After the addition is complete, react at 60℃ for 40 min. After the reaction is complete, remove acetone by rotary evaporation to obtain waterborne polyurethane fixing agent.

[0121] The mass ratio of aqueous polyurethane, UV absorber, and 10 wt% aqueous solution of 2,2-azobis(2-methylpropylimidazolium) hydrochloride was 100:5:8; the preparation of the UV absorber was the same as in Example 1.

[0122] Comparative Example 4

[0123] This comparative example discloses a dyeing method for pure cotton fabric, including the following steps:

[0124] Step (1): Immerse the pure cotton fabric in the reactive dye solution with a liquor ratio of 1:30, dye at 40℃ for 15 minutes, add sodium chloride, continue dyeing for 15 minutes, raise the temperature to 60℃, add sodium carbonate, dye again for 30 minutes, cool to room temperature, wash with water, soap, wash with water again, and air dry to obtain dyed pure cotton fabric.

[0125] In the reactive dyeing solution, the reactive dye is an M-type reactive dye with a concentration of 5% owf; during the dyeing process, the amount of sodium chloride used is 25 g / L and the amount of sodium carbonate used is 10 g / L; during soaping, the liquor ratio is 1:30 and the amount of soap powder used is 2 g / L.

[0126] Step (2): Immerse the dyed pure cotton fabric in the color-fixing finishing solution with a liquor ratio of 1:30 and immerse for 20 minutes at room temperature. After immersion, perform two dips and two nips with a nips ratio of 75%. Pre-bake at 60°C for 150 seconds and bake at 160°C for 180 seconds to obtain the dyed pure cotton fabric after color fixation.

[0127] The color-fixing solution was prepared using the water-based polyurethane color-fixing agent prepared in Comparative Examples 1-3 as raw material, and the amount of water-based polyurethane color-fixing agent was 170 g / L; the dyed pure cotton fabrics obtained after color fixing were respectively recorded as samples 6-8.

[0128] In the above examples and comparative examples: polyethylene glycol Aladdin Biochemical Technology Co., Ltd., specification PEG1000; tert-butylaminoethyl methacrylate (t-BAEMA) from Maclean Biochemical Technology Co., Ltd., CAS No.: 3775-90-4; γ-piperazinylpropylmethyldimethoxysilane from Maclean Biochemical Technology Co., Ltd., CAS No.: 128996-12-3; dihydroxypolydimethylsiloxane from Wacker Chemicals, product name WS-62M; (2-chloroethyl)trimethylammonium chloride from Kaiwei Chemical Technology Co., Ltd., CAS No.: 999-81-5; 2,2-azobis(2-methylpropylimidazolium)dihydrochloride from Sinopharm Chemical Reagent Co., Ltd., CAS No.: 2997-92-4.

[0129] Test case

[0130] The comprehensive performance of samples 1-8 prepared in Example 6 and Comparative Example 4 was tested, and the specific test results are shown in Table 1:

[0131]

[0132]

[0133] The tests for each indicator in Table 1 were conducted according to the following standards: Color fastness to rubbing was determined according to GB / T 3920-2008 "Textiles - Tests for Color Fastness to Rubbing"; Color fastness to washing was determined according to GB / T 3921-2008 "Textiles - Tests for Color Fastness to Washing: Test 3"; Softness was expressed by hand feel, and the specific test method included: placing samples 1-8 indoors for 24 hours, touching and scoring the softness of the fabric, comparing the softness of different samples, with grade 5 being the best and grade 0 the worst; UV protection was expressed by UPF, and was determined according to GB / T18830-2009 "Evaluation of UV Protection Performance of Textiles".

[0134] In Comparative Example 1, no cationic hydroxyl silicone oil was added when preparing the waterborne polyurethane fixing agent. The siloxane segments and cationic groups lacked the effect of improving the fixing and softness properties. Therefore, the fixing and softness properties of Sample 6 prepared by Comparative Example 1 were not as good as those of the Example.

[0135] In Comparative Example 2, no UV absorber was added when preparing the waterborne polyurethane fixing agent. The benzophenone group in the UV absorber lacked the effect of improving UV absorption and fixing performance. Therefore, the fixing performance and UV resistance of Sample 7 prepared by Comparative Example 2 were not as good as those of the Example.

[0136] In Comparative Example 3, when preparing the waterborne polyurethane fixing agent, the end-capping agent was replaced with hydroxyethyl methacrylate. Since tert-butylaminoethyl methacrylate containing urea bonds can react with isocyanate groups and be de-encapsulated under heating conditions to regenerate isocyanate groups, which continue to react with the active groups on the dyed pure cotton fabric to improve the color-fixing performance, the number of active groups in the fixing agent decreased after the end-capping agent was replaced. Therefore, the color-fixing performance of sample 8 prepared by Comparative Example 3 was not as good as that of the example.

[0137] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an aqueous polyurethane fixing agent, characterized in that, Includes the following steps: Step (1): Mix trimethylolpropane, the first catalyst, and acetone, add isophorone diisocyanate, and react. After the reaction is complete, cool down, add the second catalyst, dimethylolpropionic acid, and polyethylene glycol, and continue the reaction. After the reaction is complete, add cationic hydroxy silicone oil and react again. After the reaction is complete, add the end-capping agent tert-butylaminoethyl methacrylate and perform the end-capping reaction. After the reaction is complete, cool down, add triethylamine for neutralization, cool after neutralization, add water for emulsification, and obtain waterborne polyurethane. Step (2): Mix waterborne polyurethane and UV absorber, add 2,2-azobis(2-methylpropylimidazolium) hydrochloride aqueous solution dropwise, and react after the addition is complete. After the reaction is complete, remove acetone by rotary evaporation to obtain waterborne polyurethane fixing agent.

2. The method for preparing an aqueous polyurethane fixing agent according to claim 1, characterized in that, In step (1): the molar ratio of trimethylolpropane, isophorone diisocyanate, dimethylolpropionic acid, polyethylene glycol, tert-butylaminoethyl methacrylate, and triethylamine is 1:5:0.5:1-1.5:0.5-1:0.5; both the first and second catalysts are dibutyltin dilaurate, with a mass ratio of 1:1, and the total amount of dibutyltin dilaurate added is 0.1% of the mass of polyethylene glycol; the cationic hydroxyl silicone oil is added... The mass of the added material is equal to the mass of polyethylene glycol; the solid content of the waterborne polyurethane is 30%; the reaction conditions are: reaction at 80℃ for 1-1.5h in a nitrogen atmosphere; the continued reaction conditions are: reaction at 50-60℃ for 3h; the second reaction conditions are: reaction at 60℃ for 1-1.5h; the end-capping reaction conditions are: end-capping reaction at 50-60℃ for 2-3h; the neutralization reaction conditions are: neutralization reaction at 40℃ for 30min.

3. The method for preparing an aqueous polyurethane fixing agent according to claim 1, characterized in that, In step (1), the cationic hydroxyl silicone oil is prepared by the following steps: S11. Mix γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane, add triethylamine as a catalyst, and react. After the reaction is complete, continue the reaction. After the reaction is complete, evacuate and cool to room temperature to obtain piperazine-based silicone oil. S12. Mix isopropanol, piperazine silicone oil, (2-chloroethyl)trimethylammonium chloride, and sodium hydroxide. After the reaction is complete, filter the mixture and remove the solvent isopropanol by rotary evaporation to obtain cationic hydroxy silicone oil.

4. The method for preparing an aqueous polyurethane fixing agent according to claim 3, characterized in that, When preparing the cationic hydroxyl silicone oil in step (1): In S11: the molar ratio of γ-piperazinylpropylmethyldimethoxysilane to dihydroxypolydimethylsiloxane is 0.8-0.9:1.2; the amount of triethylamine catalyst is 1.2-1.5% of the total mass of γ-piperazinylpropylmethyldimethoxysilane and dihydroxypolydimethylsiloxane; the reaction conditions are: reaction at 100-110℃ for 5-6 hours under a nitrogen atmosphere; the reaction continues at 130-135℃ for 0.5-1 hours; the vacuum condition is: vacuum at 0.05MPa for 0.5 hours. In S12, the mass ratio of isopropanol, piperazine silicone oil, (2-chloroethyl)trimethylammonium chloride, and sodium hydroxide is 85-90:80:3.35-3.4:0.75-0.8; the reaction conditions are: reacting at 60-65℃ for 7-8 hours.

5. The method for preparing an aqueous polyurethane fixing agent according to claim 1, characterized in that, In step (2), the mass ratio of aqueous polyurethane, UV absorber, and 2,2-azobis(2-methylpropylimidazolium) dihydrochloride aqueous solution is 100:5-8:8-10; the 2,2-azobis(2-methylpropylimidazolium) dihydrochloride aqueous solution is 10wt%; the reaction conditions are: reaction at 60-70℃ for 30-40 min.

6. The method for preparing an aqueous polyurethane fixing agent according to claim 1, characterized in that, In step (2), the ultraviolet absorber is prepared by the following steps: 4-Bromomethylbenzophenone and chloroform are mixed and dissolved, and a chloroform solution of dimethylallylamine is added dropwise. After the addition is complete, the reaction is allowed to proceed. After the reaction is complete, the solvent chloroform is removed by rotary evaporation, cooled, filtered, and the filter cake is taken, washed, and dried to obtain the ultraviolet absorber. The ratio of 4-bromomethylbenzophenone, dimethylallylamine, and chloroform is 1 mol: 1.1 mol: 70-80 mL; the reaction conditions are: reaction at 60-65℃ for 3-4 hours.

7. An aqueous polyurethane fixing agent prepared by the method described in any one of claims 1-6.

8. A dyeing method for pure cotton fabric using the water-based polyurethane fixing agent according to claim 7, characterized in that, Includes the following steps: Step (1): Immerse the pure cotton fabric in the reactive dye solution, dye it, add sodium chloride, continue dyeing, raise the temperature, add sodium carbonate, dye it again, cool down, wash with water, soap, wash with water again, and dry to obtain dyed pure cotton fabric. Step (2): Immerse the dyed pure cotton fabric in a color-fixing solution containing water-based polyurethane color-fixing agent, and bake to obtain the color-fixed dyed pure cotton fabric.

9. The dyeing method for pure cotton fabric according to claim 8, characterized in that, In step (1): the ratio of pure cotton fabric to reactive dye liquor is 1:30; the dyeing conditions are: dyeing at 40℃ for 15-20 minutes; the continued dyeing conditions are: continuing dyeing at 40℃ for 15-20 minutes; the second dyeing conditions are: dyeing again at 60℃ for 30 minutes; in the reactive dye liquor, the reactive dye is type M reactive dye with a concentration of 4-5% owf; during the dyeing process, the amount of sodium chloride is 25-30 g / L, and the amount of sodium carbonate is 10-15 g / L; during soaping, the liquor ratio is 1:30, and the amount of soap powder is 2-3 g / L. In step (2): the color-fixing solution is prepared from the above-mentioned water-based polyurethane color-fixing agent, and the amount of water-based polyurethane color-fixing agent is 170-180g / L; the bath ratio of dyed pure cotton fabric to color-fixing solution is 1:30; the impregnation operation includes: impregnation at room temperature for 20-30min, after impregnation, two dips and two nips, with a nip-off rate of 72-75%; the baking conditions are: pre-baking at 60℃ for 150s, and baking at 160℃ for 180s.

10. A dyed pure cotton fabric after color fixation, prepared by the dyeing method of pure cotton fabric as described in any one of claims 8-9.

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