Preparation method of protein clothing synthetic leather PU wet resin

Abstract

The invention discloses a preparation method of protein clothing synthetic leather PU wet resin, and relates to the technical field of PU resin.The preparation method comprises the following steps that 1, raw material preparation is conducted, specifically, protein is subjected to hydrophobic modification to obtain modified protein, and the modified protein and a solvent are compounded to obtain a reaction solvent; step 2, preparation of resin slurry: low-temperature prepolymerization, low-temperature chain extension and modified protein blending are performed, and protein-PU resin slurry is obtained through crosslinking; wherein the hydrophobic modification of the protein comprises the step of grafting the protein with low-molecular-weight polycaprolactone and octadecyl isocyanate to obtain the modified protein. Through double hydrophobic modification of protein grafted low-molecular-weight polycaprolactone and octadecyl isocyanate, in cooperation with low-temperature prepolymerization, chain extension and blending crosslinking processes, the interfacial compatibility and dispersity of protein and PU resin are effectively improved; therefore, environmental protection is realized, and the mechanical properties and skin-friendly antibacterial properties of the protein clothing synthetic leather are improved.

Description

Technical Field

[0001] This application relates to the field of PU resin technology, and in particular to a method for preparing PU wet-process resin for protein-based synthetic leather. Background Technology

[0002] With increasing environmental awareness and the popularization of animal protection concepts, the application of natural leather is facing increasingly strict restrictions due to its long breeding cycle, high resource consumption, and serious environmental pollution. With the technological development of synthetic leather, it has become a core alternative material to natural leather and is gradually being widely used in clothing, footwear, bags, and other fields. The core requirements for synthetic leather used in clothing focus on softness and skin-friendliness, breathability, a full hand feel, and environmental friendliness and odorlessness. It also needs to possess certain mechanical strength, abrasion resistance, and washability to meet the comfort and durability requirements of clothing.

[0003] Polyurethane (PU) wet-process resin, due to its porous structure formed during preparation, possesses excellent moisture permeability, breathability, and a soft feel, making it the mainstream base material for synthetic leather in clothing. To further enhance the skin-friendliness, biocompatibility, and environmental performance of PU wet-process resin, the industry is gradually introducing protein components to modify it. The preparation of protein-PU composite wet-process resin combines the natural hydrophilicity and biocompatibility of proteins with the mechanical properties of PU, thereby improving comfort and performance while also achieving the resource utilization of bio-based raw materials.

[0004] In existing technologies, the main components of PU wet-process resin for protein-based clothing synthetic leather include four categories: main raw materials, modifiers, additives, and solvents. Among them, the main raw materials are mainly polyurethane prepolymers, combined with 1-5% plant or animal proteins by mass of the total polyurethane prepolymer.

[0005] However, due to the insufficient stability of proteins, the molecular chains are easily deformed during the prepolymerization and chain extension reactions of PU, which will prevent them from binding with the PU molecular chains. Furthermore, the poor interfacial compatibility between proteins and PU molecules makes them prone to phase separation and aggregation during the reaction, thus affecting the comfort and durability of synthetic leather in clothing, which needs to be improved. Summary of the Invention

[0006] In view of this, the first objective of this application is to provide a method for preparing PU wet-process resin for protein-based synthetic leather used in clothing, so as to significantly improve the comfort and durability of the garment. The specific solution is as follows: A method for preparing PU wet-process resin for synthetic protein clothing leather includes the following steps: Step 1, Raw material preparation: Hydrophobic modification of proteins to obtain modified proteins, and compounding with solvents to obtain reaction solvents; Step 2, Resin Slurry Preparation: Low-temperature prepolymerization, low-temperature chain extension, and modified protein blending are followed by crosslinking to obtain protein-PU resin slurry; The hydrophobic modification of the protein includes grafting low molecular weight polycaprolactone and octadecyl isocyanate onto the protein to obtain a modified protein.

[0007] Preferably, the steps of the protein hydrophobic modification include: step ① dissolving the protein in an ethanol / deionized aqueous solution to obtain a protein solution to be grafted; step ② adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide to the protein solution to be grafted and stirring to activate it to obtain an activated protein solution; step ③ adding low molecular weight polycaprolactone to the activated protein solution, and after a preliminary reaction, adding octadecyl isocyanate and completing the reaction, and finally obtaining the modified protein after dialysis and freeze-drying.

[0008] Preferably: in step ①, the volume ratio of ethanol to deionized water in the ethanol / deionized aqueous solution is 1:0.95-1.1; in step ②, the mass ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide to N-hydroxysuccinimide is 2-2.1:1, and the total amount added is 4-6% of the protein mass; the stirring activation time is 30-35 min; in step ③, the initial reaction is carried out at a controlled temperature of 45-50℃ for 2-3 h, and the reaction is completed by raising the temperature to 55-60℃ and reacting for 1-1.5 h; the number average molecular weight of the low molecular weight polycaprolactone is 500-1000, and the amount added is 20-40% of the protein mass; the amount of octadecyl isocyanate added is 10-15% of the protein mass.

[0009] Preferably, in step ③, the dialysis uses a dialysis bag with a molecular weight cutoff of 8000-10000 Da, the dialysis time is controlled at 24-36 h, and the deionized water is replaced every 8 h; the freeze-drying temperature is -40℃ to -30℃, the vacuum degree is 10-20 Pa, and the drying time is 12-16 h.

[0010] Preferably, the solvent compounding involves mixing N-methylpyrrolidone, propylene glycol methyl ether, and deionized water in a volume ratio of 6:3-3.2:0.9-1 to obtain a mixture, then adding 0.1-0.2% of polyethylene glycol 400 by mass of the mixture, and dissolving it by stirring to obtain a reaction solvent.

[0011] Preferably, the low-temperature prepolymerization involves mixing bio-based polyether polyol and polytetrahydrofuran ether diol at a mass ratio of 8:1.9-2.2, heating to 35-40°C, adding an antioxidant and stirring until homogeneous, continuing to add diisocyanate, raising the temperature to 45-50°C and holding the reaction for 2.5-3 hours, intermittently stirring, and preparing a low-viscosity polyurethane prepolymer.

[0012] Preferably, the low-temperature chain extension involves adding a chain extender to the polyurethane prepolymer, controlling the amount of chain extender added to be 5-15% of the mass of the bio-based polyether polyol, and reacting with stirring at 45-50℃ for 1-1.5 hours. Then, 0.3-0.5% of the mass of the bio-based polyether polyol is added to the silane coupling agent KH-550 and stirred for 30-40 minutes to obtain the modified linear PU slurry.

[0013] Preferably, the modified protein blending includes dissolving the modified protein in a reaction solvent and ultrasonically dispersing it for 15-20 minutes to obtain a modified protein solution, then adding the modified protein solution dropwise to a modified linear PU slurry, stirring and reacting at a controlled temperature of 40-45℃ for 1-1.5 hours, adding an epoxy propylene crosslinking agent and reacting for 30-45 minutes to obtain a protein-PU wet resin slurry.

[0014] Preferably, the ultrasonic dispersion treatment has a power of 200-300W and a frequency of 40kHz; the propylene oxide crosslinking agent is a glycidyl ether crosslinking agent, and the addition amount is 0.5-1.0% of the mass of the polyurethane prepolymer; the intermittent stirring treatment is stirring for 10 minutes every 30 minutes; the viscosity of the protein-PU wet resin slurry at 25℃ is 2000-3000mPa·s.

[0015] Preferably, the method further includes adding 0.8-1.2% of natural beeswax emulsion, 0.3-0.5% of nano-silica, and 0.2-0.4% of antibacterial agent by weight of the protein-PU wet-process resin slurry, and then sequentially stirring and ultrasonically degassing for 10-12 minutes to obtain antibacterial protein-PU resin slurry.

[0016] As can be seen from the above scheme, this application provides a method for preparing protein synthetic leather PU wet-process resin, which has the following beneficial effects: 1. By grafting protein with low molecular weight polycaprolactone and octadecyl isocyanate, dual hydrophobic modification is achieved. This allows the two hydrophobic groups to work together to break the hydrogen bond aggregation between protein molecules, thereby significantly improving the interfacial compatibility between the modified protein and the polyurethane prepolymer. This effectively solves the problems of phase separation and surface granulation, and achieves the goal of significantly improving molding uniformity. 2. By optimizing the temperature-controlled reaction in the hydrophobic modification of proteins, the reaction is carried out first at 45-50℃ with the grafting of polycaprolactone, and then at 55-60℃ with the grafting of octadecyl isocyanate. This avoids the thermal denaturation of proteins, thereby retaining the active groups and improving the stability of the modification. 3. Through low-temperature prepolymerization, low-temperature chain extension, and the reaction of modified protein blending with the addition of silane coupling agent, the molecular chain binding force between protein and polyurethane prepolymer is significantly enhanced by the bridging effect of silane coupling agent while protecting protein activity, thereby improving structural mechanical properties and skin-friendly effect. 4. Non-toxic, harmless, environmentally friendly and safe, suitable for leather raw materials in clothing products. Detailed Implementation

[0017] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0018] It should be noted that the protein in this embodiment is soy protein isolate with a molecular weight of 20,000-30,000 Da. Other proteins, such as recombinant collagen, can also be used, but will not be elaborated upon here. The bio-based polyether polyol is polylactic acid polyether polyol with a number average molecular weight of 2,000-3,000 Da; the number average molecular weight of polytetrahydrofuran ether diol is 1,000-2,000 Da; the diisocyanate is diphenylmethane diisocyanate, and the molar ratio of its addition to the bio-based polyether polyol is 1.2-1.5:1; the antioxidant consists of antioxidant 1010 and antioxidant 168 in a 1:1 mass ratio, and the addition amount is 0.1-0.3% of the mass of the bio-based polyether polyol. Furthermore, the viscosity of the polyurethane prepolymer obtained by low-temperature prepolymerization in this embodiment is 500-800 mPa·s at 25°C. The chain extender was obtained by mixing ethylene glycol and 1,4-butanediol in a 1:1 mass ratio. The solid content of the natural beeswax emulsion was 30-40%, the particle size of the nano-silica was 50-100 nm, and the antibacterial agent was a commercially available chitosan quaternary ammonium salt with a molecular weight of 5000-10000 Da. The ultrasonic degassing power was 150-200 W, and the frequency was 40 kHz. The intermittent stirring treatment was performed by stirring for 10 minutes every 30 minutes.

[0019] The following will describe in detail a method for preparing a protein synthetic leather (PU) wet-process resin according to this application.

[0020] A method for preparing PU wet-process resin for synthetic protein clothing leather includes the following steps: Step 1, Raw material preparation: Hydrophobic modification of proteins to obtain modified proteins, and compounding with solvents to obtain reaction solvents; Step 2, Resin Slurry Preparation: Low-temperature prepolymerization, low-temperature chain extension, and modified protein blending are followed by crosslinking to obtain protein-PU resin slurry; In raw material preparation, hydrophobic modification of proteins involves grafting low molecular weight polycaprolactone and octadecyl isocyanate onto proteins to obtain modified proteins. Specifically, the steps of hydrophobic modification of proteins include: Step ① dissolving the protein in an ethanol / deionized aqueous solution to obtain a protein solution to be grafted; Step ② adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide to the protein solution to be grafted and stirring for 30-35 minutes to activate it, obtaining an activated protein solution; Step ③ adding low molecular weight polycaprolactone to the activated protein solution for a preliminary reaction, then adding octadecyl isocyanate and completing the reaction, and finally dialysis and freeze-drying to obtain the modified protein.

[0021] It should be noted that in step ①, the volume ratio of ethanol to deionized water in the ethanol / deionized aqueous solution is 1:0.95-1.1; in step ②, the mass ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide to N-hydroxysuccinimide is 2-2.1:1, and the total amount added is 4-6% of the protein mass. In step ③, the initial reaction is carried out at a controlled temperature of 45-50℃ for 2-3 hours, and the reaction is completed by raising the temperature to 55-60℃ and reacting for 1-1.5 hours; the number average molecular weight of low molecular weight polycaprolactone is 500-1000, and the amount added is 20-40% of the protein mass; the amount of octadecyl isocyanate added is 10-15% of the protein mass. In step ③, dialysis is performed using dialysis bags with a molecular weight cutoff of 8000-10000 Da, and the dialysis time is controlled at 24-36 hours, with deionized water being replaced every 8 hours; the freeze-drying temperature is -40℃ to -30℃, the vacuum degree is 10-20 Pa, and the drying time is 12-16 hours.

[0022] Meanwhile, the solvent compounding process involves mixing N-methylpyrrolidone, propylene glycol methyl ether, and deionized water in a volume ratio of 6:3-3.2:0.9-1 to obtain a mixture, then adding 0.1-0.2% of polyethylene glycol 400 by mass of the mixture, and stirring to dissolve the mixture to obtain the reaction solvent.

[0023] In the preparation of the resin slurry, low-temperature prepolymerization involves mixing bio-based polyether polyol and polytetrahydrofuran ether diol at a mass ratio of 8:1.9-2.2, heating to 35-40℃, adding an antioxidant and stirring until homogeneous, then adding diisocyanate, and raising the temperature to 45-50℃ and holding the reaction for 2.5-3 hours with intermittent stirring to obtain a low-viscosity polyurethane prepolymer. Low-temperature chain extension involves adding a chain extender to the polyurethane prepolymer, controlling the amount of chain extender to 5-15% of the mass of the bio-based polyether polyol, stirring at 45-50℃ for 1-1.5 hours, then adding 0.3-0.5% of the mass of the bio-based polyether polyol as a silane coupling agent KH-550 and stirring for 30-40 minutes to obtain a modified linear PU slurry.

[0024] Meanwhile, the modified protein blending process includes dissolving the modified protein in a reaction solvent and ultrasonically dispersing it for 15-20 minutes to obtain a modified protein solution. The modified protein solution is then added dropwise to a modified linear PU slurry, and the mixture is stirred at 40-45°C for 1-1.5 hours. An epoxy propylene crosslinking agent is added and the mixture is reacted for 30-45 minutes to obtain a protein-PU wet resin slurry.

[0025] The ultrasonic dispersion process uses a power of 200-300W and a frequency of 40kHz. The propylene oxide crosslinking agent is a glycidyl ether crosslinking agent, and its addition amount is 0.5-1.0% of the mass of the polyurethane prepolymer. The viscosity of the protein-PU wet resin slurry in the embodiments of this application is 2000-3000mPa·s at 25℃, as tested.

[0026] To improve the functionality of the protein-based synthetic leather PU wet-process resin prepared by this method, the method further includes adding 0.8-1.2% of natural beeswax emulsion, 0.3-0.5% of nano-silica, and 0.2-0.4% of antibacterial agent (by mass of the protein-PU wet-process resin slurry) to the slurry, followed by stirring and ultrasonic degassing for 10-12 minutes to obtain an antibacterial protein-PU resin slurry.

[0027] Example 1 A method for preparing PU wet-process resin for synthetic protein clothing leather includes the following steps: Step 1, Raw material preparation: Hydrophobic modification of proteins to obtain modified proteins, and compounding with solvents to obtain reaction solvents; Step 2, Resin Slurry Preparation: Low-temperature prepolymerization, low-temperature chain extension, and modified protein blending are followed by crosslinking to obtain protein-PU resin slurry; In raw material preparation, hydrophobic modification of proteins involves grafting low molecular weight polycaprolactone and octadecyl isocyanate onto proteins to obtain modified proteins. Specifically, the steps of hydrophobic modification of proteins include: Step ① dissolving the protein in an ethanol / deionized aqueous solution to obtain a protein solution to be grafted; Step ② adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide to the protein solution to be grafted and stirring for 30 min to activate it, obtaining an activated protein solution; Step ③ adding low molecular weight polycaprolactone to the activated protein solution for a preliminary reaction, then adding octadecyl isocyanate and completing the reaction, and finally dialysis and freeze-drying to obtain the modified protein.

[0028] It should be noted that in step ①, the volume ratio of ethanol to deionized water in the ethanol / deionized aqueous solution is 1:0.95; in step ②, the mass ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide to N-hydroxysuccinimide is 2:1, and the total amount added is 4% of the protein mass. In step ③, the initial reaction is carried out at 45℃ for 3 hours, and the reaction is completed by raising the temperature to 55℃ and reacting for 1.5 hours; the number average molecular weight of low molecular weight polycaprolactone is 500, and the amount added is 20% of the protein mass; the amount added is 10% of the protein mass. In step ③, dialysis is performed using a dialysis bag with a molecular weight cutoff of 8000 Da, the dialysis time is controlled at 24 hours, and the deionized water is replaced every 8 hours; the freeze-drying temperature is -40℃, the vacuum degree is 10 Pa, and the drying time is 12 hours.

[0029] Meanwhile, the solvent preparation involves mixing N-methylpyrrolidone, propylene glycol methyl ether, and deionized water in a volume ratio of 6:3:0.9 to obtain a mixture, then adding 0.1% polyethylene glycol 400 by mass of the mixture, and stirring to dissolve to obtain the reaction solvent.

[0030] In the preparation of the resin slurry, the low-temperature prepolymerization involves mixing bio-based polyether polyol and polytetrahydrofuran ether diol at a mass ratio of 8:1.9, heating to 35°C, adding an antioxidant and stirring until homogeneous, then adding diisocyanate, and raising the temperature to 45°C and holding the reaction for 3 hours with intermittent stirring to obtain a low-viscosity polyurethane prepolymer. The low-temperature chain extension involves adding a chain extender to the polyurethane prepolymer, controlling the amount of chain extender to 5% of the mass of the bio-based polyether polyol, stirring at 45°C for 1.5 hours, then adding 0.3% (by mass) of silane coupling agent KH-550 of the bio-based polyether polyol and stirring for 30 minutes to obtain a modified linear PU slurry.

[0031] Meanwhile, the modified protein blending process includes dissolving the modified protein in a reaction solvent and ultrasonically dispersing it for 15 minutes to obtain a modified protein solution. The modified protein solution is then added dropwise to a modified linear PU slurry, and the mixture is stirred at 40°C for 1.5 hours. An epoxy propylene crosslinking agent is added and the mixture is reacted for 30 minutes to obtain a protein-PU wet resin slurry.

[0032] The ultrasonic dispersion process uses a power of 200W and a frequency of 40kHz; the propylene oxide crosslinking agent is a glycidyl ether crosslinking agent, and its addition amount is 0.5% of the mass of the polyurethane prepolymer.

[0033] To improve the functionality of the protein-based synthetic leather PU wet-process resin prepared by this method, the method further includes adding 0.8% natural beeswax emulsion, 0.3% nano-silica, and 0.2% antibacterial agent (by mass of the protein-PU wet-process resin slurry) to the slurry, followed by stirring and ultrasonic degassing for 10 minutes to obtain an antibacterial protein-PU resin slurry.

[0034] Example 2 A method for preparing PU wet-process resin for synthetic protein clothing leather includes the following steps: Step 1, Raw material preparation: Hydrophobic modification of proteins to obtain modified proteins, and compounding with solvents to obtain reaction solvents; Step 2, Resin Slurry Preparation: Low-temperature prepolymerization, low-temperature chain extension, and modified protein blending are followed by crosslinking to obtain protein-PU resin slurry; In raw material preparation, hydrophobic modification of proteins involves grafting low molecular weight polycaprolactone and octadecyl isocyanate onto proteins to obtain modified proteins. Specifically, the steps of hydrophobic modification of proteins include: Step ① dissolving the protein in an ethanol / deionized aqueous solution to obtain a protein solution to be grafted; Step ② adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide to the protein solution to be grafted and stirring for 32 min to activate it, obtaining an activated protein solution; Step ③ adding low molecular weight polycaprolactone to the activated protein solution for a preliminary reaction, then adding octadecyl isocyanate and completing the reaction, and finally dialysis and freeze-drying to obtain the modified protein.

[0035] It should be noted that in step ①, the volume ratio of ethanol to deionized water in the ethanol / deionized aqueous solution is 1:1; in step ②, the mass ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide to N-hydroxysuccinimide is 2.05:1, and the total amount added is 5% of the protein mass. In step ③, the initial reaction is carried out at 48℃ for 2.5 hours, and the reaction is completed by raising the temperature to 58℃ and reacting for 1.2 hours; the number average molecular weight of low molecular weight polycaprolactone is 700, and the amount added is 30% of the protein mass; the amount added is 12% of the protein mass. In step ③, dialysis is performed using a dialysis bag with a molecular weight cutoff of 9000 Da, the dialysis time is controlled at 30 hours, and the deionized water is replaced every 8 hours; the freeze-drying temperature is -35℃, the vacuum degree is 15 Pa, and the drying time is 14 hours.

[0036] Meanwhile, the solvent preparation involves mixing N-methylpyrrolidone, propylene glycol methyl ether, and deionized water in a volume ratio of 6:3.1:0.95 to obtain a mixture, then adding 0.15% polyethylene glycol 400 by mass of the mixture, and stirring to dissolve to obtain the reaction solvent.

[0037] In the preparation of the resin slurry, the low-temperature prepolymerization involves mixing bio-based polyether polyol and polytetrahydrofuran ether diol at a mass ratio of 8:2.1, heating to 38°C, adding an antioxidant and stirring until homogeneous, then adding diisocyanate, and raising the temperature to 47°C and holding the reaction for 2.8 hours with intermittent stirring to obtain a low-viscosity polyurethane prepolymer. The low-temperature chain extension involves adding a chain extender to the polyurethane prepolymer, controlling the amount of chain extender to be 10% of the mass of the bio-based polyether polyol, stirring at 46°C for 1.2 hours, then adding 0.4% (by mass) of the bio-based polyether polyol silane coupling agent KH-550 and stirring for 35 minutes to obtain a modified linear PU slurry.

[0038] Meanwhile, the modified protein blending process involves dissolving the modified protein in a reaction solvent and ultrasonically dispersing it for 18 minutes to obtain a modified protein solution. The modified protein solution is then added dropwise to a modified linear PU slurry, and the mixture is stirred at 42°C for 1.2 hours. An epoxy propylene crosslinking agent is added and the mixture is reacted for 40 minutes to obtain a protein-PU wet resin slurry.

[0039] The ultrasonic dispersion process uses a power of 250W and a frequency of 40kHz; the propylene oxide crosslinking agent is a glycidyl ether crosslinking agent, and its addition amount is 0.8% of the mass of the polyurethane prepolymer.

[0040] To improve the functionality of the protein-based synthetic leather PU wet-process resin prepared by this method, the method further includes adding 1% natural beeswax emulsion, 0.4% nano-silica, and 0.3% antibacterial agent (by mass of the protein-PU wet-process resin slurry) to the slurry, followed by stirring and ultrasonic degassing for 11 minutes to obtain an antibacterial protein-PU resin slurry.

[0041] Example 3 A method for preparing PU wet-process resin for synthetic protein clothing leather includes the following steps: Step 1, Raw material preparation: Hydrophobic modification of proteins to obtain modified proteins, and compounding with solvents to obtain reaction solvents; Step 2, Resin Slurry Preparation: Low-temperature prepolymerization, low-temperature chain extension, and blending with modified protein are followed by crosslinking to obtain protein-PU resin slurry.

[0042] In raw material preparation, hydrophobic modification of proteins involves grafting low molecular weight polycaprolactone and octadecyl isocyanate onto proteins to obtain modified proteins. Specifically, the steps of hydrophobic modification of proteins include: Step ① dissolving the protein in an ethanol / deionized aqueous solution to obtain a protein solution to be grafted; Step ② adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide to the protein solution to be grafted and stirring for 30 min to activate it, obtaining an activated protein solution; Step ③ adding low molecular weight polycaprolactone to the activated protein solution for a preliminary reaction, then adding octadecyl isocyanate and completing the reaction, and finally dialysis and freeze-drying to obtain the modified protein.

[0043] It should be noted that in step ①, the volume ratio of ethanol to deionized water in the ethanol / deionized aqueous solution is 1:1.1; in step ②, the mass ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide to N-hydroxysuccinimide is 2.1:1, and the total amount added is 6% of the protein mass. In step ③, the initial reaction is carried out at 50℃ for 2 hours, and the reaction is completed by raising the temperature to 60℃ and reacting for 1 hour; the number average molecular weight of low molecular weight polycaprolactone is 1000, and the amount added is 40% of the protein mass; the amount added is 15% of the protein mass. In step ③, dialysis is performed using a dialysis bag with a molecular weight cutoff of 10000 Da, the dialysis time is controlled at 36 hours, and the deionized water is replaced every 8 hours; the freeze-drying temperature is -30℃, the vacuum degree is 20 Pa, and the drying time is 16 hours.

[0044] Meanwhile, the solvent preparation involves mixing N-methylpyrrolidone, propylene glycol methyl ether, and deionized water in a volume ratio of 6:3.2:1 to obtain a mixture, then adding 0.2% polyethylene glycol 400 by mass of the mixture, and stirring to dissolve to obtain the reaction solvent.

[0045] In the preparation of the resin slurry, the low-temperature prepolymerization involves mixing bio-based polyether polyol and polytetrahydrofuran ether diol at a mass ratio of 8:2.2, heating to 40°C, adding an antioxidant and stirring until homogeneous, then adding diisocyanate, and raising the temperature to 50°C and holding the reaction for 2.5 hours with intermittent stirring to obtain a low-viscosity polyurethane prepolymer. The low-temperature chain extension involves adding a chain extender to the polyurethane prepolymer, controlling the amount of chain extender to be 15% of the mass of the bio-based polyether polyol, stirring at 50°C for 1.5 hours, then adding 0.5% (by mass) of silane coupling agent KH-550 of the bio-based polyether polyol and stirring for 40 minutes to obtain a modified linear PU slurry.

[0046] Meanwhile, the modified protein blending process involves dissolving the modified protein in a reaction solvent and ultrasonically dispersing it for 20 minutes to obtain a modified protein solution. The modified protein solution is then added dropwise to a modified linear PU slurry, and the mixture is stirred at 45°C for 1 hour. An epoxy propylene crosslinking agent is added and the mixture is reacted for 45 minutes to obtain a protein-PU wet resin slurry.

[0047] The ultrasonic dispersion process uses a power of 300W and a frequency of 40kHz; the propylene oxide crosslinking agent is a glycidyl ether crosslinking agent, and its addition amount is 1.0% of the mass of the polyurethane prepolymer.

[0048] To improve the functionality of the protein-based synthetic leather PU wet-process resin prepared by this method, the method further includes adding 1.2% natural beeswax emulsion, 0.5% nano-silica, and 0.4% antibacterial agent (by mass of the protein-PU wet-process resin slurry) to the slurry, followed by stirring and ultrasonic degassing for 12 minutes to obtain an antibacterial protein-PU resin slurry.

[0049] Example 4 The difference between Example 4 and Example 2 is that no natural beeswax emulsion, nano silica, or antibacterial agent were added in Example 4.

[0050] Comparative Example 1 The difference between Comparative Example 1 and Example 2 is that the protein in Comparative Example 1 was not hydrophobically modified.

[0051] Comparative Example 2 The difference between Comparative Example 2 and Example 2 is that the protein in Comparative Example 2 did not have octadecyl isocyanate added during hydrophobic modification.

[0052] Comparative Example 3 The difference between Comparative Example 3 and Example 2 is that no silane coupling agent KH-550 was added in the preparation of the modified linear PU slurry in Comparative Example 3.

[0053] Performance testing: 1. Resin viscosity test: The viscosity was measured by rotational viscometer method according to GB / T 2794-2013 Determination of viscosity of adhesives. 2. Synthetic leather tensile strength test: The tensile strength was obtained by testing according to GB / T 1040.1-2018 "Tension Properties of Plastics"; 3. Elongation at break test of synthetic leather: The elongation at break was obtained by testing in accordance with GB / T 1040.1-2018 Tensile properties of plastics. 4. Hydrolysis resistance test of synthetic leather: According to "QB / T 1873-2010 Artificial leather and synthetic leather for shoe uppers", the strength retention rate was measured at 70℃, relative humidity of 95% for 168h. 5. Synthetic leather air permeability test: Refer to GB / T 5453-1997 "Textiles - Determination of air permeability" to measure and obtain the air permeability rate; 6. Antibacterial performance test of synthetic leather: The antibacterial rate of Escherichia coli was obtained by referring to the "Evaluation of Antibacterial Performance of Textiles - Oscillation Method" in GB / T 20944.3-2008.

[0054] The performance test results are shown in Table 1 below.

[0055] Table 1 Performance Test Results

[0056] As shown in Table 1 above, the viscosity of Comparative Example 1 in this application is significantly higher than that of other examples and comparative examples, indicating that the aggregation of modified proteins leads to increased viscosity. Furthermore, because the modified proteins in Examples 1 to 4 are modified with low molecular weight polycaprolactone and octadecyl isocyanate for dual hydrophobic modification, the polarity is significantly reduced while compatibility is improved. This allows the antibacterial agent to be uniformly dispersed and stably loaded within the formed synthetic leather, achieving a highly efficient and long-lasting antibacterial effect. In Comparative Example 1, due to its high polarity and protein aggregation, and in Comparative Example 2, insufficient hydrophobic modification results in uneven dispersion and encapsulation of the antibacterial agent, making it difficult to exert an effective antibacterial and bacteriostatic effect, significantly reducing the antibacterial efficacy.

[0057] In summary, this application provides a method for preparing protein-based synthetic leather (PU) wet-process resin. In the raw material preparation stage, this method employs protein grafting with low molecular weight polycaprolactone and octadecyl isocyanate to achieve dual hydrophobic modification. This allows the two hydrophobic groups to synergistically break down the hydrogen bond aggregation between protein molecules, significantly improving the interfacial compatibility between the modified protein and the polyurethane prepolymer. This effectively solves the problems of phase separation and surface granulation, achieving a significant improvement in molding uniformity. Simultaneously, this method optimizes the temperature-controlled reaction in the protein hydrophobic modification process, first grafting polycaprolactone at 45-50℃ and then grafting octadecyl isocyanate at 55-60℃ to avoid protein thermal denaturation, thereby retaining active groups and improving modification stability. In the resin slurry preparation stage, low-temperature prepolymerization, low-temperature chain extension, and the addition of modified protein blending and silane coupling agents are employed. This process protects the protein's activity while significantly enhancing the molecular chain bonding between the protein and the polyurethane prepolymer through the bridging effect of the silane coupling agent, thereby improving structural mechanical properties and skin-friendly performance. Therefore, the protein-based synthetic leather PU wet-process resin prepared using this method is effective in producing non-toxic, harmless, environmentally friendly, and safe protein-based synthetic leather, suitable for use as a raw material in leather products for clothing.

[0058] The terms “first,” “second,” “third,” “fourth,” etc., used in this application (if applicable) are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, or apparatus that includes a series of steps or units is not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, or apparatus.

[0059] It should be noted that the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of those features. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0060] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for preparing PU wet-process resin for synthetic protein leather clothing, characterized in that, Includes the following steps: Step 1, Raw material preparation: Hydrophobic modification of proteins to obtain modified proteins, and compounding with solvents to obtain reaction solvents; Step 2, Resin Slurry Preparation: Low-temperature prepolymerization, low-temperature chain extension, and modified protein blending are followed by crosslinking to obtain protein-PU resin slurry; The steps of the protein hydrophobic modification include: Step ① dissolving the protein in an ethanol / deionized water solution to obtain a protein solution to be grafted; Step ② adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide to the protein solution to be grafted and stirring to activate it, obtaining an activated protein solution; Step ③ adding low molecular weight polycaprolactone to the activated protein solution, followed by a preliminary reaction, then adding octadecyl isocyanate and completing the reaction, and finally dialysis and freeze-drying to obtain the modified protein; the solvent includes mixing N-methylpyrrolidone, propylene glycol methyl ether, and deionized water and adding polycaprolactone. Ethylene glycol 400 is used to prepare the reaction solvent; the low-temperature prepolymerization includes mixing bio-based polyether polyol with polytetrahydrofuran ether glycol, adding diisocyanate, and preparing a polyurethane prepolymer; the low-temperature chain extension includes adding a chain extender to the polyurethane prepolymer, stirring and reacting, then adding a silane coupling agent KH-550 and stirring to obtain a modified linear PU slurry; the modified protein blending includes dissolving the modified protein in the reaction solvent to obtain a modified protein solution, then adding the modified protein solution dropwise to the modified linear PU slurry, stirring and reacting, and adding a propylene oxide crosslinking agent to obtain a protein-PU wet-process resin slurry.

2. The method for preparing PU wet-process resin for synthetic protein clothing leather according to claim 1, characterized in that: In step ①, the volume ratio of ethanol to deionized water in the ethanol / deionized aqueous solution is 1:0.95-1.1; in step ②, the mass ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide to N-hydroxysuccinimide is 2-2.1:1, and the total amount added is 4-6% of the protein mass; the stirring activation time is 30-35 min; in step ③, the initial reaction is carried out at a controlled temperature of 45-50℃ for 2-3 h, and the reaction is completed by raising the temperature to 55-60℃ and reacting for 1-1.5 h; the number average molecular weight of the low molecular weight polycaprolactone is 500-1000, and the amount added is 20-40% of the protein mass; the amount of octadecyl isocyanate added is 10-15% of the protein mass.

3. The method for preparing PU wet-process resin for synthetic protein clothing leather according to claim 1, characterized in that: In step ③, the dialysis uses a dialysis bag with a molecular weight cutoff of 8000-10000 Da, and the dialysis time is controlled at 24-36 h, with deionized water replaced every 8 h; the freeze-drying temperature is -40℃ to -30℃, the vacuum degree is 10-20 Pa, and the drying time is 12-16 h.

4. The method for preparing PU wet-process resin for synthetic protein clothing leather according to claim 1, characterized in that: The solvent comprises N-methylpyrrolidone, propylene glycol methyl ether and deionized water in a volume ratio of 6:3-3.2:0.9-1 to obtain a mixture, and then adding 0.1-0.2% of polyethylene glycol 400 by mass of the mixture, and stirring to dissolve to obtain a reaction solvent.

5. The method for preparing PU wet-process resin for synthetic protein clothing leather according to claim 1, characterized in that: The low-temperature prepolymerization process involves mixing bio-based polyether polyol and polytetrahydrofuran ether diol at a mass ratio of 8:1.9-2.2, heating to 35-40°C, adding an antioxidant and stirring until homogeneous, adding diisocyanate, raising the temperature to 45-50°C and holding the reaction for 2.5-3 hours, intermittently stirring, and preparing a low-viscosity polyurethane prepolymer.

6. The method for preparing PU wet-process resin for synthetic protein clothing leather according to claim 5, characterized in that: The low-temperature chain extension involves adding a chain extender to the polyurethane prepolymer, controlling the amount of chain extender added to be 5-15% of the mass of the bio-based polyether polyol, stirring and reacting at 45-50℃ for 1-1.5 hours, and then adding 0.3-0.5% of the mass of the bio-based polyether polyol silane coupling agent KH-550 and stirring for 30-40 minutes to obtain the modified linear PU slurry.

7. The method for preparing PU wet-process resin for synthetic protein clothing leather according to claim 6, characterized in that: The modified protein blending process includes dissolving the modified protein in a reaction solvent and ultrasonically dispersing it for 15-20 minutes to obtain a modified protein solution. The modified protein solution is then added dropwise to a modified linear PU slurry, and the mixture is stirred at 40-45°C for 1-1.5 hours. An epoxy propylene crosslinking agent is added and the mixture is reacted for 30-45 minutes to obtain a protein-PU wet resin slurry.

8. The method for preparing PU wet-process resin for synthetic protein clothing leather according to claim 7, characterized in that: The ultrasonic dispersion treatment has a power of 200-300W and a frequency of 40kHz; the propylene oxide crosslinking agent is a glycidyl ether crosslinking agent, and the addition amount is 0.5-1.0% of the mass of the polyurethane prepolymer; the intermittent stirring treatment is stirring for 10 minutes every 30 minutes; the viscosity of the protein-PU wet resin slurry at 25℃ is 2000-3000mPa·s.

9. The method for preparing PU wet-process resin for synthetic protein clothing leather according to claim 1, characterized in that: The method also includes adding 0.8-1.2% of natural beeswax emulsion, 0.3-0.5% of nano-silica, and 0.2-0.4% of antibacterial agent by weight of the protein-PU wet-process resin slurry to the slurry, and then stirring and ultrasonically degassing for 10-12 minutes to obtain antibacterial protein-PU resin slurry.

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