Waterborne polyurethane emulsion, biodegradable polyurethane sterilization surgical gloves and preparation method and application of waterborne polyurethane emulsion and biodegradable polyurethane sterilization surgical gloves

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to a waterborne polyurethane emulsion, a biodegradable polyurethane sterilization surgical glove and a preparation method and application of the biodegradable polyurethane sterilization surgical glove. The waterborne polyurethane emulsion is prepared from the following components in parts by weight: 70 to 95 parts of degradable soft segments, 30 to 50 parts of hard segments, 5 to 9 parts of 2, 2-dimethylolpropionic acid, 1.5 to 3.2 parts of a neutralizing alkali agent, 2 to 6 parts of a chain extender, 0.02 to 0.08 part of a catalyst and 1 to 3 parts of lignin nanoparticles. The skin-friendly inner layer / hydrophobic outer layer functionally gradient glove is spontaneously formed through one-time impregnation by adopting the semi-neutralized emulsion and the lignin filler; irradiation sterilization synchronously enhances the mechanical property; the abandoned industrial compost is rapidly degraded, the core function is triggered by using the existing process in the whole process, additional steps or expensive additives are not needed, and the raw materials are easy to obtain, low in cost and environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and in particular relates to an aqueous polyurethane emulsion, biodegradable polyurethane sterilized surgical gloves, and a preparation method and application thereof. Background Art

[0002] Disposable surgical gloves, one of the most commonly used protective equipment in medical procedures, must provide excellent barrier protection, flexibility, and comfort, while also possessing excellent sterility and biocompatibility. Currently, mainstream surgical gloves on the market are primarily made from non-biodegradable materials such as natural latex, nitrile rubber, or polyvinyl chloride. While these materials offer excellent elasticity and strength, they face significant limitations in terms of environmental friendliness and sustainability. Traditional synthetic materials are difficult to degrade, leading to the accumulation of medical waste and severe white pollution. With tightening environmental regulations and increasing public awareness, the development of biodegradable medical glove materials has become a research priority. On the other hand, while some existing bio-based glove materials (such as starch / PLA) are biodegradable, their mechanical properties and film-forming flexibility are insufficient for high-intensity surgical procedures. Furthermore, they lack effective sterilization stability, limiting their widespread application. In recent years, waterborne polyurethane (WPU) has become a hot topic in medical glove research due to its environmental friendliness, adjustable structure, and excellent film-forming properties. However, conventional waterborne polyurethanes mostly adopt a fully neutralized formula and a homogeneous structure design. Although this is beneficial to the stability of the emulsion, it results in a lack of structural induction and functional stratification mechanism in the final film-forming process. The carboxyl groups are randomly distributed during the film-forming process, which can easily lead to problems such as homogenization of film performance, insufficient antibacterial barrier, or insensitive degradation response. In addition, the hydrophobicity of the polyurethane backbone also limits its biodegradation efficiency in high humidity, composting and other environments. In terms of preparation technology, the current molding of surgical gloves requires multiple dipping and high-temperature curing processes. The process is cumbersome and energy-intensive, which is not conducive to industrial automation and large-scale low-cost preparation. Although the use of some high-performance degradable materials has improved the overall performance of the film, it requires complex surface modification or multi-step collaborative assembly, which increases the complexity of the process and the difficulty of preparation. Therefore, it is extremely necessary to develop a waterborne polyurethane emulsion system with good film-forming properties and compost degradation capabilities. Summary of the Invention

[0003] In view of the defects of the prior art, the object of the present invention is to provide an aqueous polyurethane emulsion, a biodegradable polyurethane sterilized surgical gloves and a preparation method and application thereof.

[0004] In order to achieve the above-mentioned objectives, the technical effects described in the present invention are achieved through the following technical scheme: In the first aspect of the present invention, a water-based polyurethane emulsion is provided, which comprises the following components in parts by weight: 75 to 95 parts of a degradable soft segment, 30 to 50 parts of a hard segment, 5 to 9 parts of 2,2-dihydroxymethylpropionic acid, 1.5 to 3.2 parts of a neutralizing alkali agent, 2 to 6 parts of a chain extender, 0.02 to 0.08 parts of a catalyst and 1 to 3 parts of lignin nanoparticles.

[0005] Preferably, the composition of the degradable soft segment comprises the following components in parts by weight: 65 to 85 parts of polycaprolactone diol, 10 to 30 parts of polylactic acid-polycaprolactone; Preferably, the hard segment is any one of isophorone diisocyanate and 4,4'-dicyclohexylmethane diisocyanate; Preferably, the neutralizing alkaline agent is any one of triethylamine and dimethylethanolamine; Preferably, the chain extender is ethylenediamine; Preferably, the catalyst is any one of zinc octoate, bismuth isooctanoate and bismuth octoate; Preferably, the particle size of the lignin nanoparticles is between 80 and 200 nm; Preferably, the second aspect of the present invention provides a biodegradable polyurethane sterilized surgical glove, which is prepared from the above-mentioned aqueous polyurethane emulsion by a single immersion method; Preferably, the third aspect of the present invention provides a method for preparing the biodegradable polyurethane sterilized surgical gloves, comprising the following steps: S1: Add the soft segment to acetone, stir and dissolve evenly at 60-65°C, then add 2,2-dimethylolpropionic acid, continue stirring until completely dissolved, raise the temperature to 75-80°C, add the hard segment and catalyst, keep the temperature to react for 1.5-2.5 hours, cool to 45-55°C, add 15-20wt% neutralizing alkali aqueous solution dropwise, and maintain the target pH between 6.8 and 7.2 for 3 minutes, then stop the reaction to obtain a prepolymer; S2: Stir deionized water at 800-1200 rpm at 10-15°C for 10 minutes to obtain an aqueous phase; slowly add the prepolymer from step S1 to the aqueous phase, emulsify at high shear speed, then reduce the speed to 400-600 rpm, and after 5 minutes, begin to dropwise add a 5-10 wt% aqueous solution of a chain extender, controlling the addition to be completed within 15-30 minutes, and keep warm for 30-60 minutes for standby use; S3: After completing the treatment of S2, remove acetone under reduced pressure, adjust the solid content to 38-42%, adjust the pH to 7.5-8.5, and allow to stand for degassing for 10-15 minutes to obtain an emulsion; S4: slowly adding the lignin nanoparticles to the emulsion of step S3, stirring at 200-500 rpm for 45-60 min, standing for degassing for 15 min, filtering through a 5 μm filter, and adjusting the viscosity to 100-300 mPa·s / 25°C to obtain an aqueous solution; S5: Clean and degrease the hand mold, preheat it at 60-70°C, and set aside; mix 6-10wt% calcium gluconate solution and 2-4wt% CaCl2 solution, and adjust the pH to 8-8.5 with 0.15wt% NH4OH solution to obtain a coagulation solution; immerse the preheated hand mold in the coagulation solution for 10-30 seconds, then remove it and treat it with hot air at 80-100°C for 20-40 seconds, and set aside; S6: Immerse the hand mold after the treatment in step S5 in the aqueous solution of step S4, with the bath temperature at 20-25°C, hold for 10-20 seconds, remove at a uniform speed of 0.5-1 m / min, drip for 30-60 seconds, spray the outside with softened water at 50-60°C and pH 6-6.5 for 3-6 minutes, treat at 80-95°C for 8-12 minutes, cool and demould, and sterilize with an electron beam at 25-35 kGy to obtain a surgical glove; Preferably, in step S2, the high-speed shear emulsification parameters are: 6000-8000 rpm shearing for 1-2 min, 3000-4000 rpm shearing for 2 min; Preferably, in step S3, the decompression parameters are: 40-50°C, -0.08 MPa, stop when acetone ppm is less than 500; Preferably, in step S4, the raw materials used to adjust the viscosity are: deionized water and polyurethane rheology modifier; Preferably, in step S6, the pH of the softened water is adjusted by 0.3 wt% citric acid; Preferably, the fourth aspect of the present invention provides a use of the above-mentioned biodegradable polyurethane sterilized surgical gloves in surgical operations.

[0006] The beneficial effects of the present invention are as follows: The polyurethane aqueous emulsion involved in the present invention has a formula in which the carboxyl groups are not completely neutralized as in traditional methods. Instead, an alkaline neutralizer is added with about half the amount of carboxyl groups, and about half of the carboxyl groups are intentionally retained in an unionized state. This "semi-neutralization" design not only ensures the stable dispersion of the particles during the emulsion preparation stage, but also provides feasibility for subsequent film formation. When a hand mold with a weak alkalinity is immersed in the emulsion from the coagulation liquid, the unionized carboxyl groups on the side close to the hand mold will be quickly neutralized for a second time. This local neutralization effect triggers the latex particles to self-organize in the radial direction: the layer adjacent to the inner surface (the side in contact with the hand mold) is rich in hydrophilic groups due to the sudden increase in charge, while the outer surface remains relatively hydrophobic. With the help of this inherent triggering mechanism, the functional gradient structure that originally required secondary dipping or additional coating to achieve is naturally formed during a single dipping process. The entire process is fully compatible with the production rhythm of existing nitrile or natural latex gloves, and the production line requires almost no modification. Furthermore, the introduction of a small amount of lignin nanoparticles into the emulsion system produces a two-stage synergistic effect. During the irradiation sterilization stage, the phenolic hydroxyl groups of lignin exhibit strong free radical scavenging ability, forming temporary micro-crosslinks with the polyurethane backbone, effectively inhibiting chain breakage caused by high-energy radiation, thereby instantly strengthening the mechanical and barrier properties of the gloves during sterilization. During the disposal or composting stage, the same lignin particles serve as preferential organic anchors for microbial attachment, accelerating the formation of hydrolytic cracks and erosion rates, significantly increasing the overall biodegradation rate of the gloves. This single, inexpensive natural filler effectively resolves the dilemma faced by traditional biodegradable polyurethanes in simultaneously balancing radiation resistance and rapid degradation. Notably, the delamination triggering of the semi-neutralized emulsion relies on a weak alkaline environment locally introduced into the hand model, which is precisely provided by a conventional calcium salt coagulant, eliminating the need for additional chemicals. The free radical scavenging properties of the lignin nanoparticles are effectively activated by exposure to gamma-ray or electron beam irradiation, making the irradiation sterilization step, a necessary step for medical gloves, a natural trigger for their effectiveness. Therefore, the key functions of the material are fully awakened by the existing process steps (immersion in coagulation liquid, irradiation sterilization), without the need for additional links or expensive additives. The final effect is reflected in the following: only one impregnation is required to simultaneously obtain a skin-friendly inner layer and a hydrophobic outer layer, and to meet the pinhole and mechanical requirements, and the production cycle and energy consumption do not increase due to functional improvements; the sterilization process not only completes the disinfection, but also synergistically enhances the performance of the gloves without the need for additional post-curing; the waste stage can be quickly decomposed in an industrial composting environment, alleviating the environmental burden of medical disposables. More importantly, all key raw materials are common industrial materials, and do not involve high-cost rare earth catalysts or complex plasma equipment, achieving the unity of excellent functional integration and environmental friendliness and economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0008] Figure 1 1 is a graph showing the mechanical properties test results of surgical gloves prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 3; Figure 2 1 is a graph showing the acid value test results of surgical gloves prepared in Example 1 of the present invention and Comparative Examples 1 to 3; Figure 3 1 is a graph showing the contact angle test results of surgical gloves prepared in Example 1 of the present invention and Comparative Examples 1 to 3; Figure 4 1 is a graph showing the biodegradation test results of the surgical gloves prepared in Example 1 of the present invention and Comparative Examples 1 to 3. DETAILED DESCRIPTION

[0009] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. It should be noted that unless otherwise specified, the raw materials involved in the present invention were purchased through conventional commercial channels.

[0010] Example 1: A waterborne polyurethane emulsion, comprising the following components in parts by weight: 90 parts of a degradable soft segment, 38 parts of a hard segment, 7.5 parts of 2,2-dihydroxymethylpropionic acid, 2.2 parts of a neutralizing alkali agent, 4.2 parts of a chain extender, 0.05 parts of a catalyst, and 2 parts of lignin nanoparticles.

[0011] The composition of the degradable soft segment comprises the following components in parts by weight: 68 parts of polycaprolactone diol and 22 parts of polylactic acid-polycaprolactone; The preparation of the biodegradable polyurethane sterilized surgical gloves comprises the following steps: S1: Add polycaprolactone diol and polylactic acid-polycaprolactone to 30 parts by weight of acetone, stir and dissolve evenly at 62°C, then add 2,2-dimethylolpropionic acid, continue stirring until completely dissolved, raise the temperature to 78°C, add isophorone diisocyanate and bismuth isooctanoate, keep the temperature and react for 2 hours, cool to 50°C, add 15wt% triethylamine aqueous solution dropwise, and maintain the target pH between 6.8 and 7.2 for 3 minutes, stop the reaction, and obtain a prepolymer; S2: Stir deionized water at 1000 rpm for 10 min at 10°C to obtain an aqueous phase; slowly add the prepolymer from step S1 to the aqueous phase, shear at 6000 rpm for 1.5 min, shear at 4000 rpm for 2 min to emulsify, then reduce the speed to 500 rpm, and after 5 min, begin dropwise addition of a 5 wt% aqueous solution of ethylenediamine, controlling the addition to be completed within 25 min, keep warm for 45 min, and set aside; S3: After completing the treatment in S2, remove acetone at 45°C and -0.08 MPa, adjust the solid content to 40%, adjust the pH to 8, and allow to stand for degassing for 10 minutes to obtain an emulsion; S4: slowly adding the lignin nanoparticles to the emulsion of step S3, stirring at 300 rpm for 50 min, standing for degassing for 15 min, filtering with a 5 μm filter, and adjusting the viscosity to 150-200 mPa·s / 25°C with deionized water and a polyurethane rheology modifier to obtain an aqueous solution; S5: Clean and degrease the hand model, preheat at 65°C, and set aside; mix 8wt% calcium gluconate solution and 3wt% CaCl2 solution, and adjust the pH to 8.3 with 0.15wt% NH4OH solution to obtain a coagulation solution; immerse the preheated hand model in the coagulation solution for 20 seconds, then remove and treat with hot air at 90°C for 30 seconds, and set aside; S6: Immerse the hand mold that has completed the treatment in step S5 in the aqueous solution of step S4, with a bath temperature of 22°C, stay for 15 seconds, take it out at a uniform speed of 0.8 m / min, drip for 40 seconds, spray it on the outside with softened water at 55°C and adjusted to pH 6.5 with 0.3wt% citric acid for 4 minutes, treat it at 85°C for 10 minutes, cool and demold, and sterilize it with an electron beam at 30 kGy to obtain surgical gloves.

[0012] Example 2: A waterborne polyurethane emulsion comprising the following components in parts by weight: 75 parts of a degradable soft segment, 30 parts of a hard segment, 5 parts of 2,2-dihydroxymethylpropionic acid, 1.5 parts of a neutralizing alkali agent, 2 parts of a chain extender, 0.02 parts of a catalyst, and 1 part of lignin nanoparticles.

[0013] The composition of the degradable soft segment comprises the following components in parts by weight: 65 parts of polycaprolactone diol and 10 parts of polylactic acid-polycaprolactone; The preparation of the biodegradable polyurethane sterilized surgical gloves comprises the following steps: S1: Add polycaprolactone diol and polylactic acid-polycaprolactone to 30 parts by weight of acetone, stir and dissolve evenly at 60°C, then add 2,2-dihydroxymethylpropionic acid, continue stirring until completely dissolved, raise the temperature to 75°C, add 4,4'-dicyclohexylmethane diisocyanate and bismuth isooctanoate, keep the temperature for reaction for 2.5 hours, cool to 45°C, add 20wt% dimethylethanolamine aqueous solution dropwise, and maintain the target pH between 6.8 and 7.2 for 3 minutes, stop the reaction, and obtain a prepolymer; S2: Stir deionized water at 800 rpm at 15°C for 10 min to obtain an aqueous phase; slowly add the prepolymer from step S1 to the aqueous phase, shear at 8000 rpm for 1 min, shear at 3000 rpm for 2 min to emulsify, then reduce the speed to 400 rpm, and after 5 min, start dropwise adding a 10 wt% aqueous solution of ethylenediamine, controlling the addition to be complete within 15 min, keep warm for 60 min, and set aside; S3: After completing the treatment of S2, remove acetone at 40°C, -0.08 MPa, adjust the solid content to 38%, adjust the pH to 7.5, and let it stand for 15 minutes to degas. Then, obtain an emulsion. S4: slowly adding the lignin nanoparticles to the emulsion of step S3, stirring at 200 rpm for 60 min, standing for degassing for 15 min, filtering through a 5 μm filter, and adjusting the viscosity to 100-300 mPa·s / 25°C with deionized water and a polyurethane rheology modifier to obtain an aqueous solution; S5: Clean and degrease the hand model, preheat at 60°C, and set aside; mix 5wt% calcium gluconate solution and 2wt% CaCl2 solution, and adjust the pH to 8.5 with 0.15wt% NH4OH solution to obtain a coagulation solution; immerse the preheated hand model in the coagulation solution for 30 seconds, then remove and treat with hot air at 80°C for 40 seconds, and set aside; S6: Immerse the hand mold that has completed the treatment in step S5 in the aqueous solution of step S4, with a bath temperature of 20°C, stay for 20 seconds, take it out at a uniform speed of 1m / min, drip for 30 seconds, spray it on the outside with softened water at 50°C, adjust the pH to 6 with 0.3wt% citric acid for 6 minutes, treat it at 80°C for 12 minutes, cool and demold, and sterilize it with an electron beam of 25kGy to obtain surgical gloves.

[0014] Example 3: A waterborne polyurethane emulsion, comprising the following components in parts by weight: 95 parts of a degradable soft segment, 50 parts of a hard segment, 9 parts of 2,2-dihydroxymethylpropionic acid, 3.2 parts of a neutralizing alkali agent, 6 parts of a chain extender, 0.08 parts of a catalyst, and 3 parts of lignin nanoparticles.

[0015] The composition of the degradable soft segment comprises the following components in parts by weight: 65 parts of polycaprolactone diol and 30 parts of polylactic acid-polycaprolactone; The preparation of the biodegradable polyurethane sterilized surgical gloves comprises the following steps: S1: Add polycaprolactone diol and polylactic acid-polycaprolactone to 30 parts by weight of acetone, stir and dissolve evenly at 65°C, then add 2,2-dihydroxymethylpropionic acid, continue stirring until completely dissolved, raise the temperature to 80°C, add isophorone diisocyanate and zinc octoate, keep the temperature for reaction for 1.5 hours, cool to 55°C, add 16wt% triethylamine aqueous solution dropwise, and maintain the target pH between 6.8 and 7.2 for 3 minutes, stop the reaction, and obtain a prepolymer; S2: Stir deionized water at 1200 rpm for 10 min at 12°C to obtain an aqueous phase; slowly add the prepolymer from step S1 to the aqueous phase, shear at 7000 rpm for 2 min, shear at 3500 rpm for 2 min to emulsify, then reduce the speed to 600 rpm, and after 5 min, start dropwise addition of 5 wt% ethylenediamine aqueous solution, control the addition to be completed within 30 min, keep warm for 30 min, and set aside; S3: After completing the treatment of S2, remove acetone at 50°C, -0.08 MPa, adjust the solid content to 42%, adjust the pH to 8.5, and let it stand for 12 minutes to degas. Then, obtain an emulsion. S4: slowly adding the lignin nanoparticles to the emulsion of step S3, stirring at 500 rpm for 45 minutes, standing for degassing for 15 minutes, filtering through a 5 μm filter, and adjusting the viscosity to 200-300 mPa·s / 25°C with deionized water and a polyurethane rheology modifier to obtain an aqueous solution; S5: Clean and degrease the hand model, preheat at 70°C, and set aside; mix 10wt% calcium gluconate solution and 4wt% CaCl2 solution, and adjust the pH to 8.5 with 0.15wt% NH4OH solution to obtain a coagulation solution; immerse the preheated hand model in the coagulation solution for 10 seconds, then remove and treat with hot air at 100°C for 20 seconds, and set aside; S6: Immerse the hand mold that has completed the treatment in step S5 in the aqueous solution of step S4, with a bath temperature of 25°C, stay for 10 seconds, take it out at a uniform speed of 0.5 m / min, drip for 60 seconds, spray it on the outside with softened water at 60°C, adjust the pH to 6.3 with 0.3wt% citric acid for 3 minutes, treat it at 95°C for 8 minutes, cool and demold, and sterilize it with an electron beam of 35 kGy to obtain surgical gloves.

[0016] Comparative Example 1: The operating procedures of Comparative Example 1 and Example 1 are basically the same, the main difference being that no lignin nanoparticles are added in Comparative Example 1, and the other parameters remain the same as in Example 1.

[0017] Comparative Example 2: The operating procedures of Comparative Example 2 and Example 1 are basically the same, the main difference being that double the weight of the neutralizing alkali agent is used in Comparative Example 2, and the other parameters remain the same as in Example 1.

[0018] Comparative Example 3: The operating procedures of Comparative Example 3 and Example 1 are basically the same, the main difference is that the NH4OH solution is removed in step S5 of Comparative Example 3, and the other parameters are consistent with Example 1.

[0019] Performance testing: Mechanical properties test: The dry glove samples prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were tested for tensile strength and elongation at break using a universal material testing machine in accordance with GB / T 1040.1-2018. The test results are as follows: Figure 1 shown.

[0020] based on Figure 1 Results analysis shows that the embodiments of the present invention perform well in terms of tensile strength and elongation, reflecting excellent overall structural density and flexibility. Based on the results of Example 1 and Comparative Example 1, the tensile strength and elongation of Comparative Example 1 are lower than those of the embodiment. This may be due to the lack of lignin nanoparticles, the lack of nanoscale reinforcing skeleton and physical cross-linking structure between chains, which makes the molecular chain arrangement degree low during film formation, the film structure loose, and microcracks easily expand under tension. At the same time, the lack of LNP also weakens the stress dispersion ability, resulting in a decrease in elongation at break. Based on the results of Example 1 and Comparative Example 2, the tensile strength and elongation of Comparative Example 2 decrease more significantly, showing enhanced brittleness and weakened deformation ability. This may be due to the complete neutralization of all carboxyl groups in the formula, resulting in a lack of spatial regulation of the neutralization site on the chain segment. The neutralization reaction is completed prematurely, the charge stability of the particles decreases during the aqueous phase dispersion process, the regularity of the polyurethane network structure is insufficient, and there is a lack of hydrogen bond, electrostatic or acid-base support between the chain segments. Finally, a film layer with low crosslinking density and high stress concentration is formed. Based on the analysis of the results of Example 1 and Comparative Example 3, Comparative Example 3 is also weaker than the Example in mechanical performance, especially the elongation at break is significantly reduced. This may be because the non-introduction of NH4OH causes the carboxyl groups on both sides of the film layer to be evenly distributed, and the neutralization trigger mechanism of the film formation direction is lost, resulting in the lack of the inner and outer layer gradient structure during film formation; and the non-directional aggregation state is prone to produce defect areas at the interface, the outer layer is more prone to brittle cracking, and the entire film body lacks a soft gradient transition zone, which makes it impossible to effectively conduct and disperse stress during the stretching process, manifested as enhanced strain sensitivity and reduced elastic reserve.

[0021] Acid value test of inner and outer layers: Take dry glove samples prepared in Example 1 and Comparative Examples 1-3 (not subjected to electron beam sterilization) and cut a 4 cm x 4 cm area of ​​film from the palm plane with clean scissors. Use a non-metal scraper to scrape off 200 mg of each of the outer layer (air contact side) and the inner layer (hand mold contact side) from the film. Dry at 40°C for 12 hours and determine the acid value according to GB / T 1676-2008. Set up three independent samples for each test. The results are shown as follows: Figure 2 shown.

[0022] based on Figure 2 Results analysis, based on the acid value analysis of Example 1 and Comparative Example 1, the acid value of the outer layer of Comparative Example 1 is slightly higher than that of the inner layer, but the difference is smaller than that of the embodiment. This may be due to the fact that the absence of lignin nanoparticles makes it difficult for carboxyl groups to migrate in a directional manner during film formation, lacking synergistic enhancement and structural support; therefore, the carboxyl distribution still has some differences, but it is unstable and not concentrated, and the gradient structure is weaker than that of the embodiment, and an effective functional outer layer cannot be formed. Based on the acid value analysis of Example 1 and Comparative Example 2, the acid values ​​of the inner and outer layers in Comparative Example 2 are both as low as about 2 mg KOH / g, and the difference is almost zero, indicating that complete neutralization causes the carboxyl groups to be completely consumed in the prepolymer stage. Even if there is subsequent film formation and stratification, the functional acid group distribution cannot be reflected; therefore, the film structure tends to be chemically symmetrical, and it also lacks subsequent degradation initiation sites, resulting in reduced functionality. Based on the acid value analysis of Example 1 and Comparative Example 3, Comparative Example 3 did not undergo NH4OH outer layer induction treatment. Although the formula was semi-neutralized, the carboxyl groups were evenly distributed in the inner and outer layers, lacking a directional enrichment process, resulting in a medium overall acid value.

[0023] Contact angle test: Take the dry glove samples prepared in Example 1 and Comparative Examples 1 to 3, cut a 4 cm × 4 cm area of ​​film from the palm plane area with clean scissors, dry it at 40°C for 12 hours, and measure it with 5 μL deionized water using a contact angle meter. Set up three independent samples for each test. The results are as follows: Figure 3 shown.

[0024] based on Figure 3 The results show that the contact angles of the inner and outer layers of the embodiment show a significant functional layered structure, with the outer layer being hydrophobic and the inner layer being hydrophilic, and the contact angle gradient being significant. Based on the results of Example 1 and Comparative Example 1, there is a certain contact angle gradient in Comparative Example 1, but the stratification is unstable and the transition zone is fuzzy. This may be due to the fact that the formula is still semi-neutralized, but there is no LNP, resulting in a lack of a structural template during the film formation process. The migration direction of the carboxyl group is unstable, and part of it is distributed in the inner layer of the film. The surface energy gradient is limited by the self-assembly driving force, resulting in weak stratification and enhanced interface diffusion. Based on the results of Example 1 and Comparative Example 2, there is no obvious stratification in the contact angle of Comparative Example 2, and the overall performance is a slightly hydrophilic film. This may be due to the fact that the carboxyl groups are completely neutralized in the prepolymer stage, and there is no longer a polarity distribution difference after film formation. There is no interface to induce migration, and the film surface structure is homogeneous. The film composition tends to be neutral and lacks functional interface characteristics. Based on the analysis of the results of Example 1 and Comparative Example 3, the contact angle of Comparative Example 3 has no significant interfacial stratification structure and is close in hydrophilicity. This may be because the formula is semi-neutralized but there is no NH4OH induction step; the carboxyl groups are randomly distributed during the water chain extension process and cannot form directional migration; the acid group content of the inner and outer layers tends to be consistent, and a contact angle gradient cannot be established.

[0025] Accelerated degradation test: According to the standard ISO 14855 (biodegradable plastics), dry glove samples prepared in Example 1 and Comparative Examples 1 to 3 were cut into 2 cm × 2 cm pieces and placed in a breathable nylon bag. The samples were tested in a simulated compost soil environment at 58°C, 90% humidity, and pH 7.2. Sampling tests were performed on the 0th, 15th, 30th, 60th, and 90th day. Mass loss (%) = (weight before test - weight after test) / mass before test × 100%. Three independent samples were set for each test. The results are shown in the figure below. Figure 4 shown.

[0026] based on Figure 4 The results show that the surgical gloves prepared in the embodiment of the present invention have an excellent degradation rate, with a mass loss rate of more than 90% in 90 days, which is significantly better than the comparative examples. Based on the analysis of the results of Example 1 and Comparative Example 1, the degradation curve of Comparative Example 1 has a slow start and a delayed peak. This may be because although the formula has not yet been semi-neutralized, the lack of LNP leads to a lack of nanoscale structural templates during the film formation process, and no stable polarity-enriched interface is formed; the directionality of carboxyl migration is weak, the distribution of polar functional groups tends to be random, the propagation of hydrolysis inside the film is limited, the degradation path presents a discontinuous diffusion characteristic, and the overall degradation is limited to the dominant surface corrosion, which is difficult to penetrate deeply. Based on the analysis of the results of Example 1 and Comparative Example 2, the mass loss of Comparative Example 2 at 90 days was significantly weaker than that of Example 1, and the degradation efficiency was extremely low, indicating that its polyurethane main chain structure was almost not recognizable or hydrolyzed by microorganisms in a composting environment. This may be because the carboxyl groups in the prepolymer stage have been completely neutralized, resulting in no longer any polarity difference between the inside and outside of the film layer, and lacking any inductive structure and an enriched interface of hydrophilic functional groups, forming a highly hydrophobic, dense, non-reactive film body, which significantly inhibited the entire degradation process. Based on the analysis of the results of Example 1 and Comparative Example 3, the degradation of Comparative Example 3 started slowly within the first 15 days, but gradually accelerated in the middle and late stages. Although it showed a certain degradation ability, it was still significantly weaker than the embodiment. This may be because although a semi-neutralized formula was used, the NH4OH induction step was lacking, resulting in a random distribution of carboxyl groups inside and outside the film layer, failing to form a directional polar interface; the degradation starting surface was unclear, resulting in a slow expansion of the hydrolysis path, and the film structure lacked a stress dispersion design, resulting in local peeling or uneven cracking during the degradation process, making it difficult to achieve an efficient and complete degradation pathway.

[0027] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. An aqueous polyurethane emulsion, characterized in that The composition includes the following components in parts by weight: 75-95 parts of degradable soft segments, 30-50 parts of hard segments, 5-9 parts of 2,2-dihydroxymethylpropionic acid, 1.5-3.2 parts of neutralizing alkali agent, 2-6 parts of chain extender, 0.02-0.08 parts of catalyst and 1-3 parts of lignin nanoparticles; The chain extender is ethylenediamine; The particle size of the lignin nanoparticles is between 80 and 200 nm.

2. An aqueous polyurethane emulsion according to claim 1, characterized in that, The composition of the degradable soft segment comprises the following components in parts by weight: 65 to 85 parts of polycaprolactone diol and 10 to 30 parts of polylactic acid-polycaprolactone.

3. An aqueous polyurethane emulsion according to claim 2, characterized in that, The hard segment is any one of isophorone diisocyanate and 4,4'-dicyclohexylmethane diisocyanate.

4. An aqueous polyurethane emulsion according to claim 3, characterized in that, The neutralizing alkali agent is any one of triethylamine and dimethylethanolamine.

5. An aqueous polyurethane emulsion according to claim 4, characterized in that, The catalyst is any one of zinc octoate, bismuth isooctanoate and bismuth octoate.

6. A biodegradable polyurethane sterilized surgical glove prepared according to the aqueous polyurethane emulsion according to any one of claims 1 to 5, characterized in that: The specific preparation steps are as follows: S1: adding the soft segment to acetone, stirring and dissolving uniformly, then adding 2,2-dihydroxymethylpropionic acid, continuing to stir until completely dissolved, heating, adding the hard segment and catalyst, keeping the temperature to react, cooling, and dropwise adding a neutralizing alkaline aqueous solution. When the target pH is reached, stopping the reaction to obtain a prepolymer; S2: Stirring deionized water to obtain an aqueous phase; slowly adding the prepolymer from step S1 to the aqueous phase, emulsifying it at high shear speed, then reducing the speed and starting to dropwise add the chain extender aqueous solution, completing the addition within a controlled time, keeping the mixture warm, and setting aside; S3: After completing the treatment of S2, remove acetone under reduced pressure, adjust the solid content, adjust the pH, and let it stand for degassing to obtain an emulsion; S4: slowly adding the lignin nanoparticles to the emulsion of step S3, stirring, standing to degas, filtering, adjusting the viscosity, and obtaining an aqueous solution; S5: Clean and degrease the hand model, preheat it, and set it aside; mix the calcium gluconate solution and the CaCl2 solution, and adjust the pH with NH4OH solution to obtain a coagulation solution; immerse the preheated hand model in the coagulation solution, remove it, and heat-air treat it for later use; S6: Immerse the hand mold that has completed the treatment in step S5 into the aqueous solution of step S4, keep it at the bath temperature, take it out at a uniform speed, drip it, spray softened water on the outside, heat it, cool it and demould it, and sterilize it with an electron beam to obtain a surgical glove.

7. A biodegradable polyurethane sterilized surgical glove prepared from the aqueous polyurethane emulsion according to claim 6, characterized in that: In step S2, the high-speed shear emulsification parameters are: 6000-8000 rpm shearing for 1-2 min, and 3000-4000 rpm shearing for 2 min.

8. A biodegradable polyurethane sterilized surgical glove prepared from the aqueous polyurethane emulsion according to claim 7, characterized in that: In step S3, the decompression parameters are: 40-50°C, -0.08 MPa, and stop when acetone ppm is less than 500.

9. A biodegradable polyurethane sterilized surgical glove prepared from the aqueous polyurethane emulsion according to claim 8, characterized in that: In step S4, the raw materials used to adjust the viscosity are: deionized water and polyurethane rheology modifier; in step S6, the pH of the softened water is adjusted by 0.3 wt% citric acid.

10. Use of the biodegradable polyurethane sterilized surgical gloves according to claim 6 in surgical operations.

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