Method for preparing a milk protein modified regenerated cellulose fiber

Abstract

The present application belongs to the technical field of cellulose fibers, and particularly relates to a preparation method of milk protein modified regenerated cellulose fibers. Whey protein peptides extracted from milk are used as raw materials, and N terminals and C terminals in the peptide chains are condensed to form amide bonds for connection by using a condensing agent, so that cyclic milk proteins with amide ring structures are obtained. The cyclic milk proteins contain a large number of hydroxyl groups, and part of the hydroxyl groups are esterified with acryloyl chloride to obtain cyclic milk protein-acrylate, i.e. modified milk proteins. The amide ring structure in the modified milk proteins is more stable, and is not easy to degrade or precipitate in an alkaline spinning dope and an acidic coagulation bath, so that the protein content in the fibers is increased. It is detected that the milk protein modified regenerated cellulose fibers prepared by the present application have a high protein content, which accounts for 5.54-7.16% of the mass of the fibers, and have good dimensional stability, with a shrinkage rate of less than 3%.

Description

Technical Field

[0001] This invention belongs to the field of cellulose fiber technology, specifically relating to a method for preparing milk protein-modified regenerated cellulose fiber. Background Technology

[0002] Cellulose fibers, made from cellulose, possess advantages such as good moisture absorption, ease of dyeing, and low static electricity, making them widely used in clothing and textiles for underwear, outerwear, and various decorative items. Milk proteins, primarily casein and whey proteins, contain various polar and nonpolar amino acids, giving them good biocompatibility and biodegradability. When added to fibers, they become softer and more skin-friendly, and promote metabolism. However, milk proteins have poor biological stability, and the acidic or alkaline environment present during cellulose fiber preparation can easily affect their structure and bioactivity, resulting in fibers with lower protein content. This insufficient stability of milk proteins limits their application in the fiber industry.

[0003] The patent, numbered "CN201010184697.4" and titled "Milk Protein Blended Regenerated Cellulose Fiber and Its Preparation Process and Application," involves adding milk protein to viscose spinning solution. However, the alkaline environment causes protein degradation, resulting in significant resource waste. Consequently, the viscose fiber has a low protein content and poor functionality.

[0004] The patent, titled "A Milk Protein Bamboo Charcoal Viscose Fiber and Its Preparation Method," uses the adsorption properties of bamboo charcoal to adsorb milk protein. However, it cannot solve the problem of the influence of acidic and alkaline environments on milk protein. Furthermore, the method is difficult to operate, has high processing costs, and has a significant impact on the finished fiber product.

[0005] In addition, the binding force between milk protein and fiber is insufficient, and the binding is poor. After repeated washing, the protein content in the fiber decreases significantly, resulting in a lack of lasting functionality. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for preparing milk protein-modified regenerated cellulose fiber, thereby achieving the invention's objective of improving the stability of milk protein and enhancing the binding affinity between milk protein and fiber.

[0007] To solve the above technical problems, the present invention adopts the following technical solution: A method for preparing milk protein-modified regenerated cellulose fiber includes the following steps: S1. Preparation of cyclic intermediates Whey protein peptides were dissolved in dimethyl sulfoxide to obtain a whey protein peptide solution. The whey protein peptide solution was placed in an ice bath, and a condensing agent was added to the whey protein peptide solution and stirred for 5-10 min. Then, the accelerator N,N-diisopropylethylamine was added to the whey protein peptide solution and stirred for 5-10 min. The ice bath was removed, and the reaction was carried out at room temperature for 24-36 h. After the reaction was completed, hydrochloric acid solution was added to terminate the reaction. After extraction, the product was washed successively with saturated sodium bicarbonate solution and saturated brine, dried with anhydrous sodium sulfate, filtered and concentrated, and then purified by silica gel column chromatography to obtain cyclic milk protein.

[0008] Preferably, the mass ratio of the whey protein peptide to dimethyl sulfoxide is 1:12-15.

[0009] Preferably, the temperature of the ice bath is 0-5°C.

[0010] Preferably, the condensing agent is a mixture of HATU and HOAt, and the molar ratio of whey protein peptide, HATU, and HOAt is 1:1 to 3:1 to 3.

[0011] Preferably, the molar ratio of the whey protein peptide to N,N-diisopropylethylamine is 1:3 to 4.

[0012] Preferably, the concentration of the hydrochloric acid solution is 0.1 mol / L, and the amount added is 50-60% of the mass of the whey protein peptide solution.

[0013] S2. Preparation of modified cyclic milk protein Cyclic milk protein was dissolved in tetrahydrofuran, and then triethylamine, an acid-binding agent, was added. The mixture was stirred for 10–20 min under nitrogen protection, and acryloyl chloride was slowly added under ice bath conditions. The reaction was carried out for 12–16 h. The hydroxyl groups of the cyclic milk protein were esterified with acryloyl chloride, and some of the hydroxyl groups of the cyclic milk protein were grafted with unsaturated double bonds to obtain cyclic milk protein-acrylate. After the reaction was completed, the mixture was concentrated, extracted with ethyl acetate, washed with saturated sodium chloride solution, concentrated under reduced pressure, and dried to obtain modified cyclic milk protein.

[0014] Preferably, the amount of triethylamine added is 10-13% of the cyclic milk protein mass, and the amount of acryloyl chloride added is 30-36% of the cyclic milk protein mass.

[0015] Preferably, the temperature of the ice bath is 0-5°C.

[0016] Whey protein peptides are hydrolyzed products of whey protein, possessing a linear peptide structure with N-terminus and C-terminus. Using whey protein peptides as raw materials, amide bonds are formed by condensing the N-terminus and C-terminus of the peptide chain using a condensing agent, resulting in cyclic milk protein with an amide ring structure. Cyclic milk protein contains a large number of hydroxyl groups; some of these hydroxyl groups react with acryloyl chloride to esterify cyclic milk protein-acrylate, i.e., modified cyclic milk protein.

[0017] S3. Preparation of spinning solution The pulp raw material is immersed in a sodium hydroxide solution with a mass fraction of 14-18% at a temperature of 50-60℃ for 40-60 minutes. The alkali solution dissolves the low degree of polymerization hemicellulose, and the insoluble part is obtained, which is α-cellulose. α-cellulose is pressed to obtain alkali cellulose with a diameter of 15-20 μm. After pulverization, it is aged at 20-25℃ for 1.5-2 hours. After aging, 30-40% CS2 by mass of α-cellulose is added to carry out xanthation reaction at 15-20℃ for 30-60 minutes to generate cellulose xanthate. The cellulose xanthate is dissolved in a 4-8% sodium hydroxide solution and subjected to dissolution, filtration, degassing, and aging in sequence for 12-24 hours at 15-20℃ to obtain the spinning solution.

[0018] Preferably, the viscosity of the spinning solution is controlled at 55-65s (falling ball method), the degree of maturity is controlled at 10-14mL (10% NH4Cl), the NaOH content is 3.5-5.0wt%, and the cellulose content is 8.2-9.4wt%.

[0019] S4, blending Modified cyclic milk protein was added to the spinning solution and stirred for 20-30 minutes. Then, cerium ammonium nitrate was added, and the temperature was raised to 30-40℃ and reacted for 60-80 minutes. The modified cyclic milk protein was grafted onto the cellulose macromolecules to obtain the blended spinning solution.

[0020] Preferably, the amount of modified cyclic milk protein added is 8-10% of the methyl cellulose content in the spinning solution.

[0021] Preferably, the amount of cerium ammonium nitrate added is 2-3% of the modified cyclic milk protein.

[0022] S5, spinning In a spinning machine, the co-blended spinning solution is extruded from the nozzle and passed through a coagulation bath to obtain nascent fiber bundles. The nascent fiber bundles are then shaped by 30-60% nozzle stretching, 40-60% spinning disc stretching, 10-30% bundle stretching, and -2--1% retraction stretching. After desulfurization, washing, oiling, drying, and opening, milk protein modified regenerated cellulose fibers are obtained.

[0023] Preferably, in the coagulation bath components, sulfuric acid is 120-170 g / L, zinc sulfate is 35-50 g / L, sodium sulfate is 230-260 g / L, the reaction temperature is 40-50℃, and the spinning rate is 30-80 m / min.

[0024] Preferably, the concentration of Na2S in the desulfurization process is 2.5–3.5 g / L, and the concentration of urea is 0.5–1 g / L.

[0025] Preferably, the oiling agent is SJ-718, and the amount used is 1 to 2% of the oven-dry weight of the fiber.

[0026] By adopting the above technical solution, the technical effect achieved by the present invention is as follows: 1. The milk protein modified regenerated cellulose prepared by this invention has a high protein content, accounting for 5.54 to 7.16% of the fiber mass.

[0027] 2. The milk protein modified regenerated cellulose fiber prepared by this invention has excellent mechanical properties, with a dry breaking strength of 2.84-3.15 cN / dtex and a wet breaking strength of 1.96-2.18 cN / dtex.

[0028] 3. The milk protein modified regenerated cellulose fiber prepared by this invention has good hygroscopicity, with a moisture regain of 14.3-15.1%.

[0029] 4. Using whey protein peptides extracted from milk as raw materials, condensing agents are used to condense the N-terminus and C-terminus of the peptide chains to form amide bonds, resulting in cyclic milk protein with an amide ring structure. Cyclic milk protein contains a large number of hydroxyl groups. Some of these hydroxyl groups react with acryloyl chloride to produce cyclic milk protein-acrylate, i.e., modified milk protein. The amide ring structure in this modified milk protein is more stable, making it less prone to degradation or precipitation in alkaline spinning solutions and acidic coagulation baths, thus increasing the protein content in the fiber.

[0030] 5. The modified milk protein is modified with acrylate, which is further grafted onto cellulose macromolecules under the action of cerium ammonium nitrate. This not only improves the mechanical strength and dimensional stability of the fiber, but also makes the chemical bond connection between the protein and the fiber stronger. Even after multiple washes, the protein content of the fiber remains at a high level.

[0031] 6. The milk protein modified regenerated cellulose fiber prepared by this invention has good dimensional stability and a shrinkage rate of less than 3%. Detailed Implementation

[0032] The present invention will be further illustrated below with reference to specific embodiments.

[0033] Example 1: A method for preparing milk protein-modified regenerated cellulose fiber, comprising the following steps: S1. Preparation of cyclic intermediates Whey protein peptides were dissolved in dimethyl sulfoxide to obtain a whey protein peptide solution. The whey protein peptide solution was placed in an ice bath, and a condensing agent was added to the whey protein peptide solution and stirred for 8 min. Then, the accelerator N,N-diisopropylethylamine was added to the whey protein peptide solution and stirred for 8 min. The ice bath was removed, and the reaction was carried out at room temperature for 30 h. After the reaction was completed, hydrochloric acid solution was added to terminate the reaction. After extraction, the product was washed successively with saturated sodium bicarbonate solution and saturated brine, dried with anhydrous sodium sulfate, filtered and concentrated, and then purified by silica gel column chromatography to obtain cyclic milk protein.

[0034] The mass ratio of the whey protein peptide to dimethyl sulfoxide is 1:13.

[0035] The temperature of the ice bath is 0°C.

[0036] The condensing agent is a mixture of HATU and HOAt, and the molar ratio of whey protein peptide, HATU, and HOAt is 1:2:2.

[0037] The molar ratio of the whey protein peptide and N,N-diisopropylethylamine is 1:3.5.

[0038] The concentration of the hydrochloric acid solution is 0.1 mol / L, and the amount added is 55% of the mass of the whey protein peptide solution.

[0039] S2. Preparation of modified cyclic milk protein Cyclic milk protein was dissolved in tetrahydrofuran, and then triethylamine, an acid-binding agent, was added. The mixture was stirred for 15 min under nitrogen protection, and acryloyl chloride was slowly added under ice bath conditions. The reaction was carried out for 14 h. The hydroxyl groups of the cyclic milk protein were esterified with acryloyl chloride, and some of the hydroxyl groups of the cyclic milk protein were grafted with unsaturated double bonds to obtain cyclic milk protein-acrylate. After the reaction was completed, the mixture was concentrated, extracted with ethyl acetate, washed with saturated sodium chloride solution, concentrated under reduced pressure, and dried to obtain modified cyclic milk protein.

[0040] The amount of triethylamine added is 12% of the cyclic milk protein mass, and the amount of acryloyl chloride added is 34% of the cyclic milk protein mass.

[0041] The temperature of the ice bath is 0°C.

[0042] S3. Preparation of spinning solution Bamboo pulp is soaked in a 16% sodium hydroxide solution at 55°C for 50 minutes. The alkali solution dissolves the low-polymerization degree hemicellulose, leaving the insoluble part, which is α-cellulose. α-cellulose was pressed to obtain alkali cellulose with a diameter of 15 μm. After pulverization, it was aged at 23℃ for 2 hours. After aging, 35% CS2 (by mass of α-cellulose) was added to carry out xanthation reaction at 18℃ for 50 minutes to generate cellulose xanthate. The cellulose xanthate was dissolved in a 6% sodium hydroxide solution and subjected to dissolution, filtration, degassing, and aging in sequence for 20 hours at 18℃ to obtain the spinning solution.

[0043] The viscosity of the spinning solution is controlled at 60s (falling ball method), the maturity is controlled at 13mL (10% NH4Cl), the NaOH content is 4wt%, and the methyl cellulose content is 8.8wt%.

[0044] S4, blending Modified cyclic milk protein was added to the spinning solution and stirred for 25 minutes. Then, cerium ammonium nitrate was added, and the temperature was raised to 35°C and reacted for 70 minutes. The modified cyclic milk protein was grafted onto the cellulose macromolecules to obtain the blended spinning solution.

[0045] The amount of modified cyclic milk protein added is 9% of the methyl cellulose content in the spinning solution.

[0046] The amount of cerium ammonium nitrate added is 2.5% of the modified cyclic milk protein.

[0047] S5, spinning In a spinning machine, the co-blended spinning solution is extruded from the nozzle and passed through a coagulation bath to obtain nascent fiber bundles. The nascent fiber bundles are then shaped by 40% nozzle stretching, 50% spinning disc stretching, 15% bundle stretching and -2% retraction stretching. After desulfurization, washing, oiling, drying and opening, milk protein modified regenerated cellulose fibers are obtained.

[0048] The coagulation bath composition includes 150 g / L sulfuric acid, 40 g / L zinc sulfate, and 240 g / L sodium sulfate. The reaction temperature is 45°C, and the spinning rate is 60 m / min.

[0049] The concentration of Na2S in the desulfurization process is 3 g / L, and the concentration of urea is 0.8 g / L.

[0050] The oiling agent is SJ-718, and the amount used is 1.5% of the oven-dry weight of the fiber.

[0051] Example 2: A method for preparing milk protein-modified regenerated cellulose fiber, comprising the following steps: S1. Preparation of cyclic intermediates Whey protein peptides were dissolved in dimethyl sulfoxide to obtain a whey protein peptide solution. The whey protein peptide solution was placed in an ice bath, and a condensing agent was added to the whey protein peptide solution and stirred for 5 min. Then, the accelerator N,N-diisopropylethylamine was added to the whey protein peptide solution and stirred for 10 min. The ice bath was removed, and the reaction was carried out at room temperature for 24 h. After the reaction was completed, hydrochloric acid solution was added to terminate the reaction. After extraction, the product was washed successively with saturated sodium bicarbonate solution and saturated brine, dried with anhydrous sodium sulfate, filtered and concentrated, and then purified by silica gel column chromatography to obtain cyclic milk protein.

[0052] The mass ratio of the whey protein peptide to dimethyl sulfoxide is 1:12.

[0053] The temperature of the ice bath is 5°C.

[0054] The condensing agent is a mixture of HATU and HOAt, and the molar ratio of whey protein peptide, HATU, and HOAt is 1:1:3.

[0055] The molar ratio of the whey protein peptide to N,N-diisopropylethylamine is 1:3.

[0056] The concentration of the hydrochloric acid solution is 0.1 mol / L, and the amount added is 50% of the mass of the whey protein peptide solution.

[0057] S2. Preparation of modified cyclic milk protein Cyclic milk protein was dissolved in tetrahydrofuran, and then triethylamine, an acid-binding agent, was added. The mixture was stirred for 10 min under nitrogen protection, and acryloyl chloride was slowly added under ice bath conditions. The reaction was carried out for 12 h. The hydroxyl groups of the cyclic milk protein were esterified with acryloyl chloride, and some of the hydroxyl groups of the cyclic milk protein were grafted with unsaturated double bonds to obtain cyclic milk protein-acrylate. After the reaction was completed, the mixture was concentrated, extracted with ethyl acetate, washed with saturated sodium chloride solution, concentrated under reduced pressure, and dried to obtain modified cyclic milk protein.

[0058] The amount of triethylamine added is 10% of the cyclic milk protein mass, and the amount of acryloyl chloride added is 30% of the cyclic milk protein mass.

[0059] The temperature of the ice bath is 5°C.

[0060] S3. Preparation of spinning solution Bamboo pulp is soaked in a 14% sodium hydroxide solution at 50°C for 60 minutes. The alkali solution dissolves the low-polymerization degree hemicellulose, leaving the insoluble part, which is α-cellulose. α-cellulose was pressed to obtain alkali cellulose with a diameter of 20 μm. After pulverization, it was aged at 20℃ for 1.5 h. After aging, 30% CS2 by mass of α-cellulose was added to carry out xanthation reaction at 15℃ for 30 min to generate cellulose xanthate. The cellulose xanthate was dissolved in a 4% sodium hydroxide solution and subjected to dissolution, filtration, degassing, and aging in sequence for 12 h at 15℃ to obtain the spinning solution.

[0061] The viscosity of the spinning solution is controlled at 55s (falling ball method), the maturity is controlled at 10mL (10% NH4Cl), the NaOH content is 3.5wt%, and the methyl cellulose content is 8.2wt%.

[0062] S4, blending Modified cyclic milk protein was added to the spinning solution and stirred for 20 minutes. Then, cerium ammonium nitrate was added, and the temperature was raised to 30°C and reacted for 60 minutes. The modified cyclic milk protein was grafted onto the cellulose macromolecules to obtain the blended spinning solution.

[0063] The amount of modified cyclic milk protein added is 8% of the methyl cellulose content in the spinning solution.

[0064] The amount of cerium ammonium nitrate added is 2% of the modified cyclic milk protein.

[0065] S5, spinning In a spinning machine, the co-blended spinning solution is extruded from the nozzle and then passed through a coagulation bath to obtain nascent fiber bundles. The nascent fiber bundles are then shaped by 30% nozzle stretching, 60% spinning disc stretching, 10% bundle stretching and -1% retraction stretching. After desulfurization, washing, oiling, drying and opening, milk protein modified regenerated cellulose fibers are obtained.

[0066] The coagulation bath composition includes 120 g / L sulfuric acid, 50 g / L zinc sulfate, and 230 g / L sodium sulfate. The reaction temperature is 40°C, and the spinning rate is 30 m / min.

[0067] The concentration of Na2S in the desulfurization process is 2.5 g / L, and the concentration of urea is 0.5 g / L.

[0068] The oiling agent is SJ-718, and the amount used is 1% of the oven-dry weight of the fiber.

[0069] Example 3: A method for preparing milk protein-modified regenerated cellulose fiber, comprising the following steps: S1. Preparation of cyclic intermediates Whey protein peptides were dissolved in dimethyl sulfoxide to obtain a whey protein peptide solution. The whey protein peptide solution was placed in an ice bath, and a condensing agent was added to the whey protein peptide solution and stirred for 10 min. Then, the accelerator N,N-diisopropylethylamine was added to the whey protein peptide solution and stirred for 5 min. The ice bath was removed, and the reaction was carried out at room temperature for 36 h. After the reaction was completed, hydrochloric acid solution was added to terminate the reaction. After extraction, the product was washed successively with saturated sodium bicarbonate solution and saturated brine, dried with anhydrous sodium sulfate, filtered and concentrated, and then purified by silica gel column chromatography to obtain cyclic milk protein.

[0070] The mass ratio of the whey protein peptide to dimethyl sulfoxide is 1:15.

[0071] The temperature of the ice bath is 2°C.

[0072] The condensing agent is a mixture of HATU and HOAt, and the molar ratio of whey protein peptide, HATU, and HOAt is 1:3:1.

[0073] The molar ratio of the whey protein peptide to N,N-diisopropylethylamine is 1:4.

[0074] The concentration of the hydrochloric acid solution is 0.1 mol / L, and the amount added is 60% of the mass of the whey protein peptide solution.

[0075] S2. Preparation of modified cyclic milk protein Cyclic milk protein was dissolved in tetrahydrofuran, and then triethylamine, an acid-binding agent, was added. The mixture was stirred for 20 min under nitrogen protection, and acryloyl chloride was slowly added under ice bath conditions. The reaction was carried out for 16 h. The hydroxyl groups of the cyclic milk protein were esterified with acryloyl chloride, and some of the hydroxyl groups of the cyclic milk protein were grafted with unsaturated double bonds to obtain cyclic milk protein-acrylate. After the reaction was completed, the mixture was concentrated, extracted with ethyl acetate, washed with saturated sodium chloride solution, concentrated under reduced pressure, and dried to obtain modified cyclic milk protein.

[0076] The amount of triethylamine added is 13% of the cyclic milk protein mass, and the amount of acryloyl chloride added is 36% of the cyclic milk protein mass.

[0077] The temperature of the ice bath is 2°C.

[0078] S3. Preparation of spinning solution Bamboo pulp is soaked in a sodium hydroxide solution with a mass fraction of 18% at a temperature of 60℃ for 40 minutes. The alkali solution dissolves the low degree of polymerization hemicellulose, and the insoluble part is obtained, which is α-cellulose. α-cellulose was pressed to obtain alkali cellulose with a diameter of 18 μm. After pulverization, it was aged at 25℃ for 2 hours. After aging, 40% of CS2 by mass of α-cellulose was added to carry out xanthation reaction at 20℃ for 60 minutes to generate cellulose xanthate. The cellulose xanthate was dissolved in an 8% sodium hydroxide solution and subjected to dissolution, filtration, degassing, and aging in sequence for 24 hours at 20℃ to obtain the spinning solution.

[0079] The viscosity of the spinning solution is controlled at 65s (falling ball method), the maturity is controlled at 14mL (10% NH4Cl), the NaOH content is 5.0wt%, and the cellulose content is 9.4wt%.

[0080] S4, blending Modified cyclic milk protein was added to the spinning solution and stirred for 30 minutes. Then, cerium ammonium nitrate was added, and the temperature was raised to 40°C and reacted for 80 minutes. The modified cyclic milk protein was grafted onto the cellulose macromolecules to obtain the blended spinning solution.

[0081] The amount of modified cyclic milk protein added is 10% of the methyl cellulose content in the spinning solution.

[0082] The amount of cerium ammonium nitrate added is 3% of the modified cyclic milk protein.

[0083] S5, spinning In a spinning machine, the co-blended spinning solution is extruded from the nozzle and passed through a coagulation bath to obtain nascent fiber bundles. The nascent fiber bundles are then shaped by 60% nozzle stretching, 40% spinning disc stretching, 10% bundle stretching and -1% retraction stretching. After desulfurization, washing, oiling, drying and opening, milk protein modified regenerated cellulose fibers are obtained.

[0084] The coagulation bath composition includes 170 g / L sulfuric acid, 35 g / L zinc sulfate, and 260 g / L sodium sulfate. The reaction temperature is 50°C, and the spinning rate is 80 m / min.

[0085] The concentration of Na2S in the desulfurization process is 3.5 g / L, and the concentration of urea is 1 g / L.

[0086] The oiling agent is SJ-718, and the amount used is 2% of the oven-dry weight of the fiber.

[0087] Comparative Example 1 Example 1, a representative example, was selected. Step S2 was omitted, and cyclic milk protein was directly added to the spinning solution in an equal proportion. All other aspects were the same as in Example 1. This example served as Comparative Example 1.

[0088] Comparative Example 2 In Comparative Example 1, the cyclic milk protein was replaced with an equal amount of whey protein and added to the spinning solution. All other aspects were the same as in Comparative Example 1, which was then used as Comparative Example 2.

[0089] The cellulose fibers prepared in the examples and comparative examples were subjected to performance testing, as detailed in Table 1.

[0090] Table 1 As can be seen from Table 1, the milk protein modified regenerated cellulose fibers prepared in Examples 1-3 have high protein content, stable protein properties, and a protein content decrease rate of less than 5% after fifty water washings. They also have good mechanical properties, good dimensional stability, and strong hygroscopicity.

[0091] In Comparative Example 1, step S2 was omitted, and cyclic milk protein was directly added to the spinning solution. The fiber strength decreased, especially the wet breaking strength. After fifty washes, the protein content in the fiber decreased at a higher rate, and the shrinkage rate increased. This indicates that the modified cyclic milk protein contains acrylate, which has a better grafting effect with the fiber. Furthermore, the addition of acrylate increases the fiber strength and reduces the shrinkage rate. However, since acrylate has hydrophobic properties, the moisture regain of Comparative Example 1 increased slightly.

[0092] Compared with Comparative Example 1, Comparative Example 2 showed a decrease in all fiber properties, especially protein content. This indicates that cyclic milk protein is more stable and less susceptible to acidic or alkaline environments, which can lead to a decrease in protein content in the fiber and even affect the mechanical properties of the fiber.

[0093] Unless otherwise specified, all proportions and percentages mentioned in this invention are mass proportions and mass percentages; all raw materials are commercially available.

[0094] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing milk protein-modified regenerated cellulose fiber, characterized in that, The preparation method includes the preparation of cyclic intermediates, the preparation of modified cyclic milk protein, the preparation of spinning solution, blending and spinning; The cyclic intermediate is prepared by dissolving whey protein peptides in dimethyl sulfoxide to obtain a whey protein peptide solution. The whey protein peptide solution was placed in an ice bath. The condensing agent was added to the whey protein peptide solution and stirred for 5-10 min. Then, the promoter N,N-diisopropylethylamine was added to the whey protein peptide solution and stirred for 5-10 min. The ice bath was removed, and the reaction was carried out at room temperature for 24-36 h. After the reaction was completed, hydrochloric acid solution was added to terminate the reaction. After extraction, the product was washed successively with saturated sodium bicarbonate solution and saturated brine, dried with anhydrous sodium sulfate, filtered and concentrated, and then purified by silica gel column chromatography to obtain cyclic milk protein. The modified cyclic milk protein was prepared by dissolving cyclic milk protein in tetrahydrofuran, adding triethylamine as an acid-binding agent, stirring under nitrogen protection for 10-20 min, slowly adding acryloyl chloride under ice bath conditions, and reacting for 12-16 h. The hydroxyl groups of the cyclic milk protein reacted with acryloyl chloride to esterify, and some hydroxyl groups of the cyclic milk protein were grafted with unsaturated double bonds to obtain cyclic milk protein-acrylate. After the reaction was completed, the mixture was concentrated, extracted with ethyl acetate, washed with saturated sodium chloride solution, concentrated under reduced pressure, and dried to obtain the modified cyclic milk protein. The blending process involves adding modified cyclic milk protein to the spinning solution and stirring for 20-30 minutes, then adding cerium ammonium nitrate and heating to 30-40°C for 60-80 minutes to graft the modified cyclic milk protein onto the cellulose macromolecules, thus obtaining the blended spinning solution.

2. The method for preparing milk protein-modified regenerated cellulose fiber according to claim 1, characterized in that, The mass ratio of the whey protein peptide to dimethyl sulfoxide is 1:12-15; The temperature of the ice bath is 0–5°C.

3. The method for preparing milk protein-modified regenerated cellulose fiber according to claim 1, characterized in that, The condensing agent is a mixture of HATU and HOAt, and the molar ratio of whey protein peptide, HATU and HOAt is 1:1 to 3:1 to 3. The molar ratio of whey protein peptides to N,N-diisopropylethylamine is 1:3 to 4; The concentration of the hydrochloric acid solution is 0.1 mol / L, and the amount added is 50-60% of the mass of the whey protein peptide solution.

4. The method for preparing milk protein-modified regenerated cellulose fiber according to claim 1, characterized in that, The amount of triethylamine added is 10-13% of the cyclic milk protein, and the amount of acryloyl chloride added is 30-36% of the cyclic milk protein. The temperature of the ice bath is 0–5°C.

5. The method for preparing milk protein-modified regenerated cellulose fiber according to claim 1, characterized in that, The spinning solution is prepared by impregnating, pressing, crushing, aging, xanthating, dissolving, filtering, defoaming, and maturing pulp raw materials to obtain the spinning solution. The viscosity of the spinning solution by the falling ball method is controlled at 55-65s, the degree of maturity under 10% NH4Cl is controlled at 10-14mL, the NaOH content is 3.5-5.0wt%, and the methyl cellulose content is 8.2-9.4wt%.

6. The method for preparing milk protein-modified regenerated cellulose fiber according to claim 1, characterized in that, The amount of modified cyclic milk protein added is 8-10% of the methyl cellulose content in the spinning solution; The amount of cerium ammonium nitrate added is 2-3% of the modified cyclic milk protein.

7. The method for preparing milk protein-modified regenerated cellulose fiber according to claim 1, characterized in that, The spinning process involves extruding the co-blended spinning solution through a nozzle in a spinning machine, obtaining nascent fiber bundles after passing through a coagulation bath, and then shaping the nascent fiber bundles by 30-60% nozzle stretching, 40-60% spinning disc stretching, 10-30% bundle stretching, and -2--1% retraction stretching. After desulfurization, washing, oiling, drying, and opening, milk protein modified regenerated cellulose fibers are obtained.

8. The method for preparing milk protein-modified regenerated cellulose fiber according to claim 7, characterized in that, The coagulation bath composition contains 120–170 g / L sulfuric acid, 35–50 g / L zinc sulfate, and 230–260 g / L sodium sulfate. The reaction temperature is 40–50 °C, and the spinning rate is 30–80 m / min. The concentration of Na2S in the desulfurization process is 2.5–3.5 g / L, and the concentration of urea is 0.5–1 g / L. The oiling agent is SJ-718, and the amount used is 1 to 2% of the oven-dry weight of the fiber.

Images