Preparation method of milk protein modified regenerated cellulose fiber

Abstract

The invention belongs to the technical field of cellulose fibers, and particularly relates to a preparation method of milk protein modified regenerated cellulose fibers. Whey protein peptide extracted from milk is used as a raw material, N end and C end in a peptide chain are condensed by using a condensing agent to form amido bonds for connection, and the cyclic milk protein with an amide ring structure is obtained. The cyclic milk protein contains a large number of hydroxyl groups, part of the hydroxyl groups and acryloyl chloride are subjected to esterification reaction to obtain cyclic milk protein-acrylate, namely the modified milk protein, the amide ring structure in the cyclic milk protein-acrylate is more stable, the cyclic milk protein-acrylate is not easy to degrade or precipitate in an alkaline spinning solution and an acidic coagulating bath, and the protein content in the fiber is increased. Through detection, the prepared milk protein modified regenerated cellulose fiber is high in protein content, and the protein content accounts for 5.54-7.16% of the mass of the fiber; the size stability is good, and the shrinkage rate is lower than 3%.

Description

Technical Field

[0001] The invention belongs to the technical field of cellulose fibers, and particularly relates to a method for preparing milk protein-modified regenerated cellulose fibers. Background Art

[0002] Cellulose fiber is made from cellulose and boasts advantages such as good hygroscopicity, easy dyeing, and low static charge. It is widely used in the clothing and textile industries, including underwear, outerwear, and various decorative items. Milk protein, primarily casein and whey protein, contains a variety of polar and non-polar amino acids in its molecular structure, making it biocompatible and biodegradable. When added to fibers, they become softer, more skin-friendly, and promote metabolism. However, milk protein has poor biological stability, and the acidic and alkaline environment encountered during the preparation of cellulose fibers can easily affect the structure and bioactivity of the milk protein, resulting in a relatively low protein content in the fibers produced. This lack of stability limits its application in the fiber industry.

[0003] Patent number "CN201010184697.4" is named "Milk protein blended regenerated cellulose fiber and its preparation process and application". Milk protein is added to the viscose spinning solution, but the alkaline environment causes protein degradation, resulting in serious waste of resources. The protein content in the viscose fiber is low and the functionality is poor.

[0004] The patent number "CN21310528000.4" is named "A milk protein bamboo charcoal viscose fiber and its preparation method". It uses the adsorption properties of bamboo charcoal to adsorb milk protein, but it cannot solve the impact of acidic and alkaline environments on milk protein. In addition, this method is difficult to operate, has high process costs, and has a greater 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 drops significantly, and the functionality is not long-lasting. Summary of the Invention

[0006] In order to solve the problems existing in the prior art, the present invention provides a method for preparing milk protein-modified regenerated cellulose fiber, which achieves the invention objectives of improving the stability of milk protein and improving the binding property of milk protein to fiber.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions: A method for preparing milk protein-modified regenerated cellulose fiber comprises the following steps: S1. Preparation of cyclic intermediates The whey protein peptide is dissolved in dimethyl sulfoxide to obtain a whey protein peptide solution; the whey protein peptide solution is placed in an ice bath, a condensing agent is added to the whey protein peptide solution and stirred for 5 to 10 minutes, and then a promoter N,N-diisopropylethylamine is added to the whey protein peptide solution and stirred for 5 to 10 minutes. The ice bath is removed and the reaction is carried out at room temperature for 24 to 36 hours. After the reaction is completed, a hydrochloric acid solution is added to terminate the reaction. After extraction, the product is washed with a saturated sodium bicarbonate solution and a saturated saline solution in sequence, dried with anhydrous sodium sulfate, filtered and concentrated, and then purified by silica gel column chromatography to obtain a 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 the whey protein peptide, HATU and HOAt is 1:1-3:1-3.

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

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

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

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

[0016] Whey protein peptides are hydrolyzed products of whey protein. They are linear peptides with an N-terminus and a C-terminus in the peptide chain. Using whey protein peptides as raw materials, the N-terminus and C-terminus in the peptide chain are condensed with a condensing agent to form an amide bond, which connects them and produces a cyclic milk protein with an amide ring structure. Cyclic milk protein contains a large number of hydroxyl groups, some of which are esterified with acryloyl chloride to produce 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°C for 40-60 minutes. The alkali solution dissolves the low-polymerization hemicellulose and obtains the insoluble part, which is α-cellulose. Alpha-cellulose is squeezed to obtain alkali cellulose with a diameter of 15 to 20 μm, which is then crushed and aged at a temperature of 20 to 25° C. for 1.5 to 2 hours. After aging, CS2 (30 to 40% by mass of the α-cellulose) is added and mixed for a yellowing reaction at a temperature of 15 to 20° C. for 30 to 60 minutes to generate cellulose xanthate. The cellulose xanthate is dissolved in a sodium hydroxide solution with a mass fraction of 4 to 8%, and the solution is dissolved, filtered, degassed, and aged in sequence at a temperature of 15 to 20° C. for 12 to 24 hours to obtain a spinning solution.

[0018] Preferably, the viscosity of the spinning solution is controlled at 55-65s (falling ball method), the maturity is controlled at 10-14mL (10% NH4CL), the NaOH content is 3.5-5.0wt%, and the methylcellulose content is 8.2-9.4wt%.

[0019] S4. Blending The modified cyclic milk protein is added to the spinning solution and stirred for 20 to 30 minutes, and then ammonium cerium nitrate is added, and the temperature is raised to 30 to 40° C. and reacted for 60 to 80 minutes to graft the modified cyclic milk protein onto the cellulose macromolecule to obtain a blended spinning solution.

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

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

[0022] S5. Spinning In a spinning machine, the blended spinning solution is extruded from a nozzle and passed through a coagulation bath to obtain a nascent fiber bundle; the nascent fiber bundle is shaped after being subjected to 30-60% nozzle drawing, 40-60% spinning disk drawing, 10-30% bunching drawing and -2--1% retraction drawing, and then desulfurized, washed, oiled, dried and loosened to obtain milk protein modified regenerated cellulose fiber.

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

[0024] Preferably, the concentration of Na2S in the desulfurization 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 1-2% of the absolute dry mass of the fiber.

[0026] Due to the adoption of the above technical solution, the technical effects achieved by the present invention are: 1. The milk protein modified regenerated cellulose prepared by the present invention has a high protein content, accounting for 5.54-7.16% of the fiber mass.

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

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

[0029] 4. Using whey protein peptides extracted from milk as raw material, the N-terminus and C-terminus of the peptide chain are condensed with a condensing agent to form an amide bond, which connects them and produces a cyclic milk protein with an amide ring structure. The cyclic milk protein contains a large number of hydroxyl groups, some of which are esterified with acryloyl chloride to produce a cyclic milk protein-acrylate ester, or modified milk protein. The amide ring structure is more stable, making the modified milk protein less susceptible to degradation or precipitation in alkaline spinning solution and acidic coagulation bath, thereby increasing the protein content in the fiber.

[0030] 5. Acrylate is modified in the modified milk protein, which is further grafted with cellulose macromolecules under the action of ammonium cerium nitrate. This not only improves the mechanical strength and dimensional stability of the fiber, but also the chemical bond connection makes the combination of protein and fiber stronger. After multiple washings, the protein content of the fiber still remains at a high level.

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

[0032] The present invention will be further described 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 The whey protein peptide is dissolved in dimethyl sulfoxide to obtain a whey protein peptide solution; the whey protein peptide solution is placed in an ice bath, a condensing agent is added to the whey protein peptide solution and stirred for 8 minutes, and then a promoter N,N-diisopropylethylamine is added to the whey protein peptide solution and stirred for 8 minutes. The ice bath is removed and the reaction is carried out at room temperature for 30 hours. After the reaction is completed, a hydrochloric acid solution is added to terminate the reaction. After extraction, the product is washed with a saturated sodium bicarbonate solution and a saturated brine in sequence, dried with anhydrous sodium sulfate, filtered and concentrated, and then purified by silica gel column chromatography to obtain a 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 was 0°C.

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

[0037] The molar ratio of the whey protein peptide to 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 Dissolve the cyclic milk protein in tetrahydrofuran, add the acid-binding agent triethylamine, stir for 15 minutes under nitrogen protection, slowly add acryloyl chloride under ice bath conditions, react for 14 hours, the hydroxyl groups of the cyclic milk protein react with acryloyl chloride for esterification, and part of the hydroxyl groups of the cyclic milk protein are grafted with unsaturated double bonds to obtain cyclic milk protein-acrylate. After the reaction, concentrate, extract with ethyl acetate, and then wash with saturated sodium chloride solution. Concentrate under reduced pressure and dry to obtain modified cyclic milk protein.

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

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

[0042] S3. Preparation of spinning solution The bamboo pulp was immersed in a 16% sodium hydroxide solution at a temperature of 55°C for 50 minutes. The alkali solution dissolved the low-polymerization hemicellulose and the insoluble part was α-cellulose. Alkali cellulose with a diameter of 15 μm is obtained by squeezing α-cellulose, which is then crushed and aged at a temperature of 23°C for 2 hours. After aging, CS2 (35% by mass of the α-cellulose) is added to the mixture for yellowing reaction at a temperature of 18°C ​​for 50 minutes to generate cellulose xanthate. The cellulose xanthate is dissolved in a sodium hydroxide solution with a mass fraction of 6%, and dissolved, filtered, degassed, and aged in sequence at a temperature of 18°C ​​for 20 hours to obtain a spinning solution.

[0043] The viscosity of the spinning solution was controlled at 60 s (falling ball method), the maturity was controlled at 13 mL (10% NH 4 CL), the NaOH content was 4 wt %, and the methylcellulose content was 8.8 wt %.

[0044] S4. Blending The modified cyclic milk protein was added to the spinning solution and stirred for 25 minutes, and then ammonium cerium nitrate was added, and the temperature was raised to 35°C and reacted for 70 minutes to graft the modified cyclic milk protein onto the cellulose macromolecule to obtain a blended spinning solution.

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

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

[0047] S5. Spinning In the spinning machine, the blended spinning solution is extruded from the nozzle and the nascent fiber bundle is obtained after passing through the coagulation bath; the nascent fiber bundle is shaped after 40% nozzle drawing, 50% spinning disk drawing, 15% bunching drawing and -2% retraction drawing, and the milk protein modified regenerated cellulose fiber is obtained after desulfurization, washing, oiling, drying and loosening.

[0048] The coagulation bath components include 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 is 3g / L, and the concentration of urea is 0.8g / L.

[0050] The oiling agent is SJ-718, and the amount used is 1.5% of the absolute dry mass 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 The whey protein peptide is dissolved in dimethyl sulfoxide to obtain a whey protein peptide solution; the whey protein peptide solution is placed in an ice bath, a condensing agent is added to the whey protein peptide solution and stirred for 5 minutes, and then a promoter N,N-diisopropylethylamine is added to the whey protein peptide solution and stirred for 10 minutes. The ice bath is removed and the reaction is carried out at room temperature for 24 hours. After the reaction is completed, a hydrochloric acid solution is added to terminate the reaction. After extraction, the product is washed with a saturated sodium bicarbonate solution and a saturated brine in sequence, dried with anhydrous sodium sulfate, filtered and concentrated, and then purified by silica gel column chromatography to obtain a 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 was 5°C.

[0054] The condensing agent is a mixture of HATU and HOAt, and the molar ratio of the 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 Dissolve the cyclic milk protein in tetrahydrofuran, add the acid-binding agent triethylamine, stir for 10 minutes under nitrogen protection, slowly add acryloyl chloride under ice bath conditions, react for 12 hours, the hydroxyl groups of the cyclic milk protein react with acryloyl chloride for esterification, and part of the hydroxyl groups of the cyclic milk protein are grafted with unsaturated double bonds to obtain cyclic milk protein-acrylate. After the reaction, concentrate, extract with ethyl acetate, and then wash with saturated sodium chloride solution. Concentrate under reduced pressure and dry to obtain modified cyclic milk protein.

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

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

[0060] S3. Preparation of spinning solution The bamboo pulp was immersed in a 14% sodium hydroxide solution at a temperature of 50°C for 60 minutes. The alkali solution dissolved the low-polymerization hemicellulose and obtained the insoluble part, which is α-cellulose. Alpha-cellulose is squeezed to obtain alkali cellulose with a diameter of 20 μm, which is then crushed and aged at a temperature of 20°C for 1.5 h. After aging, CS2 (30% by mass of the α-cellulose) is added to the mixture for a yellowing reaction at a temperature of 15°C for 30 min to generate cellulose xanthate. The cellulose xanthate is dissolved in a sodium hydroxide solution with a mass fraction of 4%, and dissolved, filtered, degassed, and aged in sequence at a temperature of 15°C for 12 h to obtain a spinning solution.

[0061] The viscosity of the spinning solution was controlled at 55 s (falling ball method), the maturity was controlled at 10 mL (10% NH 4 CL), the NaOH content was 3.5 wt %, and the methylcellulose content was 8.2 wt %.

[0062] S4. Blending The modified cyclic milk protein was added to the spinning solution and stirred for 20 minutes, and then ammonium cerium nitrate was added, and the temperature was raised to 30°C and reacted for 60 minutes to graft the modified cyclic milk protein onto the cellulose macromolecule to obtain a blended spinning solution.

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

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

[0065] S5. Spinning In the spinning machine, the blended spinning solution is extruded from the nozzle and the nascent fiber bundle is obtained after passing through the coagulation bath; the nascent fiber bundle is shaped after 30% nozzle drawing, 60% spinning disk drawing, 10% bunching drawing and -1% retraction drawing, and the milk protein modified regenerated cellulose fiber is obtained after desulfurization, washing, oiling, drying and loosening.

[0066] The coagulation bath components include 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 is 2.5g / L, and the concentration of urea is 0.5g / L.

[0068] The oiling agent is SJ-718, and the amount used is 1% of the absolute dry mass 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 The whey protein peptide is dissolved in dimethyl sulfoxide to obtain a whey protein peptide solution; the whey protein peptide solution is placed in an ice bath, a condensing agent is added to the whey protein peptide solution and stirred for 10 minutes, and then a promoter N,N-diisopropylethylamine is added to the whey protein peptide solution and stirred for 5 minutes. The ice bath is removed and the reaction is carried out at room temperature for 36 hours. After the reaction is completed, a hydrochloric acid solution is added to terminate the reaction. After extraction, the product is washed with a saturated sodium bicarbonate solution and a saturated brine in sequence, dried with anhydrous sodium sulfate, filtered and concentrated, and then purified by silica gel column chromatography to obtain a 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 was 2°C.

[0072] The condensing agent is a mixture of HATU and HOAt, and the molar ratio of the 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 Dissolve the cyclic milk protein in tetrahydrofuran, add the acid-binding agent triethylamine, stir for 20 minutes under nitrogen protection, slowly add acryloyl chloride under ice bath conditions, react for 16 hours, the hydroxyl groups of the cyclic milk protein react with acryloyl chloride for esterification, and part of the hydroxyl groups of the cyclic milk protein are grafted with unsaturated double bonds to obtain cyclic milk protein-acrylate. After the reaction, concentrate, extract with ethyl acetate, and then wash with saturated sodium chloride solution. Concentrate under reduced pressure and dry to obtain modified cyclic milk protein.

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

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

[0078] S3. Preparation of spinning solution The bamboo pulp was immersed in a sodium hydroxide solution with a mass fraction of 18% at a temperature of 60°C for 40 minutes. The alkali solution dissolved the low-polymerization hemicellulose and obtained the insoluble part, which is α-cellulose. Alpha-cellulose is squeezed to obtain alkali cellulose with a diameter of 18 μm, which is then crushed and aged at a temperature of 25°C for 2 hours. After aging, CS2 (40% by mass of the α-cellulose) is added to the mixture for a yellowing reaction at a temperature of 20°C for 60 minutes to generate cellulose xanthate. The cellulose xanthate is dissolved in a sodium hydroxide solution with a mass fraction of 8%, and dissolved, filtered, degassed, and aged in sequence at a temperature of 20°C for 24 hours to obtain a spinning solution.

[0079] The viscosity of the spinning solution was controlled at 65 s (falling ball method), the maturity was controlled at 14 mL (10% NH 4 CL), the NaOH content was 5.0 wt %, and the methylcellulose content was 9.4 wt %.

[0080] S4. Blending The modified cyclic milk protein was added to the spinning solution and stirred for 30 minutes, and then ammonium cerium nitrate was added, and the temperature was raised to 40°C and reacted for 80 minutes to graft the modified cyclic milk protein onto the cellulose macromolecule to obtain a blended spinning solution.

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

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

[0083] S5. Spinning In the spinning machine, the blended spinning solution is extruded from the nozzle and the nascent fiber bundle is obtained after passing through the coagulation bath; the nascent fiber bundle is shaped after 60% nozzle drawing, 40% spinning disk drawing, 10% bunching drawing and -1% retraction drawing, and the milk protein modified regenerated cellulose fiber is obtained after desulfurization, washing, oiling, drying and loosening.

[0084] The coagulation bath components include 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 is 3.5g / L, and the concentration of urea is 1g / L.

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

[0087] Comparative Example 1 Representative Example 1 was selected, step S2 was removed, and an equal proportion of cyclic milk protein was directly added to the spinning solution. The rest was consistent with Example 1, as Comparative Example 1.

[0088] Comparative Example 2 Comparative Example 2 is obtained by replacing the cyclic milk protein in Comparative Example 1 with an equal amount of whey protein and adding the resulting solution into the spinning solution. The remaining steps are the same as those in Comparative Example 1.

[0089] The cellulose fibers prepared in the examples and comparative examples were subjected to performance tests, as shown 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 and stable protein properties. After washing fifty times, the protein content in the fibers decreases by less than 5%. They also have good mechanical properties, good dimensional stability, and strong hygroscopicity.

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

[0092] Compared with Comparative Example 1, the fiber properties of Comparative Example 2 are all reduced, especially the protein content, which shows that the cyclic milk protein is more stable and is not easily affected by the acid-base environment, which leads to a decrease in the protein content in the fiber and even affects the mechanical properties of the fiber.

[0093] Unless otherwise specified, the ratios and percentages described in the present invention are all by mass; all raw materials are commercially available.

[0094] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing milk protein modified regenerated cellulose fiber, characterized in that: The preparation method includes preparation of a cyclic intermediate, preparation of a modified cyclic milk protein, preparation of a spinning solution, blending and spinning; The modified cyclic milk protein is cyclic milk protein-acrylate having an amide ring structure and an acrylate group.

2. The method for preparing a milk protein modified regenerated cellulose fiber according to claim 1, wherein The cyclic intermediate is prepared by dissolving a whey protein peptide in dimethyl sulfoxide to obtain a whey protein peptide solution; placing the whey protein peptide solution in an ice bath, adding a condensing agent to the whey protein peptide solution and stirring for 5 to 10 minutes, then adding a promoter N,N-diisopropylethylamine to the whey protein peptide solution and stirring for 5 to 10 minutes, removing the ice bath, reacting at room temperature for 24 to 36 hours, adding a hydrochloric acid solution after the reaction is completed to terminate the reaction, extracting, washing the product with a saturated sodium bicarbonate solution and a saturated saline solution in sequence, drying with anhydrous sodium sulfate, filtering and concentrating, and then purifying with a silica gel column chromatography to obtain a cyclic milk protein.

3. The method for preparing a milk protein modified regenerated cellulose fiber according to claim 2, 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.

4. The method for preparing a milk protein modified regenerated cellulose fiber according to claim 2, characterized in that: The condensing agent is a mixture of HATU and HOAt, and the molar ratio of the whey protein peptide, HATU, and HOAt is 1:1-3:1-3; The molar ratio of the whey protein peptide to N, N-diisopropylethylamine is 1:3-4; 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.

5. The method for preparing a milk protein modified regenerated cellulose fiber according to claim 1, characterized in that: The modified cyclic milk protein is prepared by dissolving the cyclic milk protein in tetrahydrofuran, adding triethylamine as an acid-binding agent, stirring for 10 to 20 minutes under nitrogen protection, slowly adding acryloyl chloride under ice bath conditions, reacting for 12 to 16 hours, allowing the hydroxyl groups of the cyclic milk protein to esterify with the acryloyl chloride, and grafting unsaturated double bonds onto some hydroxyl groups of the cyclic milk protein to obtain cyclic milk protein-acrylate. After the reaction is completed, the mixture is concentrated, extracted with ethyl acetate, and then washed with a saturated sodium chloride solution. The mixture is concentrated under reduced pressure and then dried to obtain the modified cyclic milk protein.

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

7. The method for preparing milk protein modified regenerated cellulose fiber according to claim 1, characterized in that: The spinning solution is prepared by soaking, pressing, crushing, aging, yellowing, dissolving, filtering, degassing, and maturing the pulp raw material to obtain the spinning solution; The viscosity of the spinning solution is controlled at 55-65s (falling ball method), the maturity is controlled at 10-14mL (10% NH4CL), the NaOH content is 3.5-5.0wt%, and the methylcellulose content is 8.2-9.4wt%.

8. The method for preparing milk protein modified regenerated cellulose fiber according to claim 1, characterized in that: The blending comprises adding the modified cyclic milk protein to the spinning solution and stirring for 20 to 30 minutes, then adding ammonium cerium nitrate, heating to 30 to 40° C. and reacting for 60 to 80 minutes, thereby grafting the modified cyclic milk protein onto the cellulose macromolecule to obtain a blended spinning solution; The amount of the modified cyclic milk protein added is 8-10% of the methylcellulose content in the spinning solution; The added amount of the cerium ammonium nitrate is 2-3% of the modified cyclic milk protein.

9. The method for preparing milk protein modified regenerated cellulose fiber according to claim 1, characterized in that: The spinning method comprises the following steps: in a spinning machine, a blended spinning solution is extruded from a nozzle, and a nascent fiber bundle is obtained after passing through a coagulation bath; the nascent fiber bundle is shaped after being subjected to 30-60% nozzle drawing, 40-60% spinning disk drawing, 10-30% bunching drawing, and -2--1% retraction drawing; and after being desulfurized, washed, oiled, dried, and loosened, the milk protein modified regenerated cellulose fiber is obtained.

10. The method for preparing milk protein modified regenerated cellulose fiber according to claim 9, characterized in that: The coagulation bath components include 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 1-2% of the absolute dry mass of the fiber.

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