Degradable waterborne polyurethane and preparation method and application thereof

Abstract

This invention provides a biodegradable waterborne polyurethane, its preparation method, and its applications. The raw materials for preparing this biodegradable waterborne polyurethane include bio-based polyols and isocyanate monomers, wherein the bio-based polyols include polycarbonate-based polyols and polycaprolactone-based polyols. The waterborne polyurethane of this invention combines environmental friendliness and biodegradability with excellent abrasion resistance, high mechanical strength, and high flexibility, and is applied to the surface layer of microfiber synthetic leather.

Description

Technical Field

[0001] This invention relates to the field of polymer material synthesis technology, specifically to a biodegradable waterborne polyurethane, its preparation method, and its application. Background Technology

[0002] With increasingly stringent environmental regulations and rising consumer demand for green materials, the polyurethane materials used in traditional synthetic leather are mostly derived from petroleum-based raw materials. Their production and use not only rely on non-renewable resources but also typically require large amounts of organic solvents, easily generating volatile organic compounds (VOCs) that pose potential risks to the environment and human health. Furthermore, traditional solvent-based polyurethane synthetic leather production is energy-intensive, and waste gas and wastewater treatment costs are high, failing to meet current requirements for green manufacturing and sustainable development. In recent years, waterborne polyurethane has gradually become an important development direction in the synthetic leather industry due to its low VOC emissions and environmental friendliness. However, existing waterborne polyurethanes still primarily use petroleum-based polyols as raw materials, making it difficult to fundamentally solve the problem of dependence on fossil resources. Meanwhile, some bio-based polyurethane materials still suffer from insufficient mechanical properties, abrasion resistance, and durability in practical applications, limiting their widespread use in the synthetic leather field.

[0003] Therefore, developing a composite soft segment waterborne polyurethane system that combines environmental friendliness, biodegradability, excellent abrasion resistance, high mechanical strength, and high flexibility is urgently needed in the upgrading of the synthetic leather industry and has important practical significance for promoting the comprehensive waterborne and environmentally friendly transformation of the leather industry. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a biodegradable waterborne polyurethane, its preparation method, and its applications. The biodegradable waterborne polyurethane of this invention combines environmental friendliness and biodegradability with excellent wear resistance, high mechanical strength, and high flexibility.

[0005] In a first aspect, the present invention provides a biodegradable waterborne polyurethane, the raw materials for which include bio-based polyols and isocyanate monomers, wherein the bio-based polyols include polycarbonate-based polyols and polycaprolactone-based polyols.

[0006] By introducing polycarbonate-based polyols and polycaprolactone-based polyols, the waterborne polyurethane molecular chain possesses both ester and carbonate bond structures, forming a dual-soft-segment modified waterborne polyurethane. This significantly improves the mechanical properties, abrasion resistance, and flexibility of the waterborne polyurethane. Furthermore, compared to traditional petroleum-based polyols, bio-based polyols offer advantages such as low VOCs and low pollution.

[0007] Furthermore, polycaprolactone-based polyols possess excellent flexibility, while polycarbonate-based polyols exhibit superior hydrolysis resistance and high strength. Therefore, the introduction of polycarbonate-based polyols and polycaprolactone-based polyols enables the waterborne polyurethane of this invention to balance a soft feel with abrasion and folding resistance when applied to synthetic leather.

[0008] In some embodiments, the isocyanate monomer is selected from hexamethylene diisocyanate.

[0009] In some embodiments, the bio-based polyol is derived from straw.

[0010] In some embodiments, the polycarbonate-based polyol is selected from polycarbonate-based diols. In some embodiments, the polycarbonate-based polyol is selected from polycarbonate-based diols derived from straw from Anhui Fengyuan Group, preferably TBE2000. In some embodiments, the number-average molecular weight of the polycarbonate-based polyol is 1000-3000 g / mol, for example, 1000 g / mol, 1500 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, or any value between therewith. In some embodiments, the hydroxyl value of the polycarbonate-based polyol is 50-60 mg KOH / g, for example, 50 mg KOH / g, 55 mg KOH / g, 60 mg KOH / g, or any value between therewith.

[0011] In some embodiments, the polycaprolactone-based polyol is selected from polycaprolactone diol. In some embodiments, the polycaprolactone-based polyol is selected from polycaprolactone diol produced by Beijing Innocare Technology Co., Ltd., preferably A81646-500G. In some embodiments, the number-average molecular weight of the polycaprolactone-based polyol is 1000-3000 g / mol, for example, 1000 g / mol, 1500 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, or any value between these values. In some embodiments, the hydroxyl value of the polycaprolactone-based polyol is 50-60 mg KOH / g, for example, 50 mg KOH / g, 55 mg KOH / g, 60 mg KOH / g, or any value between these values.

[0012] Agricultural straw, as a widely available, renewable, and inexpensive biomass resource, contains abundant cellulose and hemicellulose. Through appropriate chemical conversion, it can be used to prepare bio-based polyols, providing a new raw material source for the development of environmentally friendly waterborne polyurethane materials. Introducing the aforementioned straw-derived polycarbonate-based and polycaprolactone-based polyols into waterborne polyurethane systems can not only significantly increase the bio-based content of the materials and reduce dependence on petroleum resources, but also improve the mechanical properties of the materials through composite soft segment structures, thus providing a new technical pathway for the preparation of high-performance and environmentally friendly synthetic leather.

[0013] In some embodiments, the mass ratio of the polycarbonate-based polyol to the polycaprolactone-based polyol in the bio-based polyol is (3-7):(7-3), for example, 3:7, 4:6, 1:1, 6:4, 7:3 or any value between them.

[0014] In some embodiments, the raw materials for preparation further include a first chain extender, a second chain extender, a solvent, a neutralizing agent, and a dispersion medium.

[0015] In some embodiments, based on the biodegradable waterborne polyurethane, the raw materials for preparation include, by mass percentage: Bio-based polyols 15-25% (e.g., 15%, 17%, 19%, 21%, 23%, 25%, etc.), isocyanate monomers 2-10% (e.g., 2%, 4%, 6%, 8%, 10%, etc.), first chain extender 1-2% (e.g., 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, etc.), second chain extender 1-5% (e.g., 1%, 2%, 3%, 4%, 5%, etc.), solvent 10-20% (e.g., 10%, 12%, 14%, 16%, 18%, 20%, etc.), neutralizer 0.5-3% (e.g., 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.), dispersion medium 50-60% (e.g., 50%, 52%, 54%, 56%, 58%, 60%, etc.).

[0016] The present invention calculates the amount of raw materials to be prepared based on biodegradable waterborne polyurethane. During the preparation process, solvent needs to be added multiple times. The amount of solvent mentioned above is the solvent content in the system after the second chain extension reaction.

[0017] In some embodiments, the first chain extender is selected from 2,2-dihydroxymethylbutyric acid. Compared to other chain extenders with carboxyl groups, 2,2-dihydroxymethylbutyric acid has better solubility in organic solvents, reducing the amount of solvent used while resulting in a more stable reaction.

[0018] In some embodiments, the second chain extender is selected from 1,4-butanediol. Compared to other alcohol chain extenders, 1,4-butanediol has a moderate carbon chain length, which can simultaneously improve hardness and tensile strength, and the reaction rate is stable, making the prepolymerization process easy to control.

[0019] In some embodiments, the solvent is selected from dimethylacetamide.

[0020] In some embodiments, the neutralizing agent is selected from triethylamine.

[0021] In some embodiments, the dispersion medium is selected from deionized water.

[0022] In some embodiments, the solid content of the biodegradable waterborne polyurethane is 20-30 wt%, for example, 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, 30 wt%, or any value between them.

[0023] In some embodiments, the degradable waterborne polyurethane has a particle size of 70-100 nm, for example, 70 nm, 72 nm, 74 nm, 76 nm, 78 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, or any value between them. Due to its extremely small particle size, the degradable waterborne polyurethane has the advantages of good film density and few defects when applied to the preparation of synthetic leather.

[0024] In some embodiments, the zeta potential of the biodegradable waterborne polyurethane is -40 mV to -30 mV, for example, -40 mV, -38 mV, -36 mV, -34 mV, -32 mV, -30 mV, or any value between them. Because of the high zeta potential of the biodegradable waterborne polyurethane, uniform distribution during film formation is ensured, resulting in excellent abrasion resistance when applied to the preparation of synthetic leather.

[0025] In a second aspect, the present invention provides a method for preparing the biodegradable waterborne polyurethane described in the first aspect, comprising the following steps: (1) Under the protection of an inert gas, bio-based polyols are reacted to obtain wear-resistant polyols, wherein the bio-based polyols include polycarbonate-based polyols and polycaprolactone-based polyols; (2) In the presence of a catalyst, the wear-resistant polyol, isocyanate monomer and solvent are mixed to carry out a prepolymerization reaction to obtain a prepolymer; (3) The prepolymer, solvent, and first chain extender are mixed to carry out a first chain extension reaction, and then mixed with a second chain extender and solvent to carry out a second chain extension reaction to obtain a polymer; (4) The polymer is mixed with a neutralizing agent to carry out a neutralization reaction, and then mixed with a dispersion medium to carry out an emulsification reaction to obtain the biodegradable waterborne polyurethane.

[0026] This invention first utilizes the reaction of polycarbonate-based polyols and polycaprolactone-based polyols to form composite soft segments. Then, the composite soft segments are reacted with isocyanate monomers to form isocyanate-terminated (-NCO) prepolymers. Next, a first chain extension reaction introduces hydrophilic groups to provide emulsification function, and a second chain extension reaction introduces suitable hard segments to adjust mechanical properties. Then, a neutralizing agent is used for a neutralization reaction. The neutralized ionic polyurethane prepolymer spontaneously forms nanoscale latex particles in water due to the electrostatic interaction of the hydrophilic ammonium carboxylate groups, completing the phase transition process from an oil-phase system to an aqueous dispersion system, and finally forming a nanoscale, stable, water-dispersible polyurethane emulsion.

[0027] If only one chain extension reaction is carried out, a stable waterborne polyurethane emulsion cannot be synthesized.

[0028] In some embodiments, when the isocyanate monomer is hexamethylene diisocyanate, the polycarbonate-based polyol is polycarbonate-based diol, the polycaprolactone-based polyol is polycaprolactone diol, the first chain extender is 2,2-dimethylolbutyric acid, and the second chain extender is 1,4-butanediol, the specific reaction is as follows: (1) Prepolymerization reaction

[0029] (2) First chain extension reaction

[0030] (3) Second chain extension reaction

[0031] (4) Neutralization reaction

[0032] This invention does not impose any particular limitation on the inert gas used; any inert gas commonly used in the art can be applied to this invention. In some embodiments, in step (1), the inert gas is selected from nitrogen.

[0033] In some embodiments, in step (1), the temperature of the reaction is 100-200°C; for example, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C or any value between them.

[0034] In some implementations, the reaction time in step (1) is 3-10 h; for example, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h or any value between them.

[0035] In some embodiments, in step (1), the pressure of the reaction is 0.1-0.5 MPa, for example 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa or any value between them.

[0036] In some embodiments, in step (2), the catalyst is selected from dibutyltin dilaurate.

[0037] In some embodiments, in step (2), the amount of catalyst used is 0.1-0.5% of the total mass of the reaction system, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5% or any value between them.

[0038] In some embodiments, in step (2), the temperature of the prepolymerization reaction is 85-90°C; for example, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C or any value between them.

[0039] In some implementations, the prepolymerization reaction in step (2) takes 1-5 hours; for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours or any value between them.

[0040] In some embodiments, in step (3), the temperature of the first chain extension reaction is 65-75°C; for example, 65°C, 70°C, 75°C or any value between them.

[0041] In some implementations, in step (3), the time for the first chain extension reaction is 1-5 h; for example, 1 h, 2 h, 3 h, 4 h, 5 h or any value between them.

[0042] In some embodiments, in step (3), the temperature of the second chain extension reaction is 55-70°C, for example, 55°C, 60°C, 65°C, 70°C or any value between them.

[0043] In some implementations, in step (3), the second chain extension reaction takes 1-3 hours; for example, 1 hour, 2 hours, 3 hours or any value between them.

[0044] In some implementations, after the second chain extension reaction, the viscosity of the system can be adjusted by adding a solvent to avoid shaft wrapping (rod climbing) during the experiment.

[0045] In some implementations, the neutralization reaction in step (4) takes 0.1-1 h, for example, 0.1 h, 0.3 h, 0.5 h, 0.7 h, 1 h or any value between them.

[0046] In some embodiments, in step (4), the temperature of the emulsification reaction is 20-40°C; for example, 20°C, 25°C, 30°C, 35°C, 40°C or any value between them.

[0047] In some implementations, the emulsification reaction in step (4) takes 0.1-1 h, for example, 0.1 h, 0.3 h, 0.5 h, 0.7 h, 1 h or any value between them.

[0048] Thirdly, the present invention provides the application of the biodegradable waterborne polyurethane described in the first aspect or the biodegradable waterborne polyurethane prepared by the preparation method described in the second aspect in artificial leather or synthetic leather, coatings or coatings, and elastic fibers.

[0049] Fourthly, the present invention provides a bio-based synthetic leather, comprising the biodegradable waterborne polyurethane described in the first aspect or the biodegradable waterborne polyurethane prepared by the preparation method described in the second aspect.

[0050] Bio-based synthetic leather containing the biodegradable waterborne polyurethane of this invention is environmentally friendly and biodegradable, and has good abrasion resistance, folding resistance and flexibility.

[0051] Fifthly, the present invention provides a method for preparing the bio-based synthetic leather described in the fourth aspect, comprising the following steps: S1, the biodegradable waterborne polyurethane described in the first aspect or the biodegradable waterborne polyurethane prepared by the preparation method described in the second aspect is mixed with color paste, defoamer and thickener, and then subjected to defoaming treatment to obtain slurry; S2, the slurry is coated onto the surface of release paper and dried to obtain a film; S3, the film is bonded to the base fabric, and after curing and peeling off the release paper, the bio-based synthetic leather is obtained.

[0052] In the process of preparing bio-based synthetic leather, the slurry is dried into a film, and then physically cross-linked and mechanically anchored with the base fabric through an adhesive, so that it is firmly bonded to the base fabric with a tight interfacial bond.

[0053] Due to its extremely small particle size, biodegradable waterborne polyurethane exhibits advantages such as high film density and few defects. Furthermore, the presence of numerous urethane and carbonate bonds in the molecular chain, coupled with a high zeta potential, ensures uniform film distribution during formation. Consequently, the resulting bio-based synthetic leather possesses excellent abrasion resistance.

[0054] In some embodiments, the above preparation process is as follows: Figure 1 As shown.

[0055] To avoid stress concentration and microbubble formation, in some embodiments, the drying in step S2 is gradient drying. In some embodiments, the drying temperature in step S2 is 60-90°C. In some embodiments, the drying process includes drying at a gradient temperature of 60°C for 15-25 minutes, 75°C for 25-35 minutes, and 90°C for 25-35 minutes. In some embodiments, the drying process includes drying at a gradient temperature of 60°C for 20 minutes, 75°C for 30 minutes, and 90°C for 30 minutes.

[0056] According to an embodiment of the present invention, during the dry transfer molding process, the slurry is gradient-dried to form a film, which is then physically cross-linked and mechanically anchored to the microfiber base fabric through an adhesive, resulting in a tight interfacial bond that firmly adheres to the base fabric. Because the waterborne polyurethane molecular chain contains a large number of urethane bonds and carbonate structures, and the high zeta potential ensures uniform distribution during film formation, the resulting bio-based synthetic leather exhibits excellent abrasion resistance. Simultaneously, the gradient drying process effectively avoids internal stress concentration and microbubble generation. Therefore, the bio-based synthetic leather prepared by this invention, under environmentally friendly and biodegradable conditions, not only demonstrates good abrasion resistance but also good folding strength and flexibility.

[0057] In some embodiments, the coloring component of the pigment is selected from iron oxide, titanium oxide, carbon black, and mixtures thereof. In some embodiments, the pigment is Suzhou Shiming Technology Co., Ltd.'s TSE LR01 Black.

[0058] In some embodiments, the defoamer is selected from nonionic defoamers, preferably from one or more of emulsified silicone oil, higher carbon alcohol fatty acid ester complex, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene, polyoxypropylene glycerol ether, or polyoxypropylene, and more preferably from defoamer NXZ from Shandong Yousuo Chemical Technology Co., Ltd.

[0059] In some embodiments, the thickener is selected from one or more of polyacrylic acid thickeners or polyurethane associative thickeners, preferably YC-101B waterborne polyurethane thickener from Anhui Yuanchen New Material Technology Co., Ltd.

[0060] In some embodiments, the amount of defoamer added, by mass percentage, is 0.1-2% of the biodegradable waterborne polyurethane, for example, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2% or any value between them.

[0061] In some embodiments, the amount of thickener added is 0.1-1% of the biodegradable waterborne polyurethane, for example, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1% or any value between them.

[0062] The present invention has the following beneficial effects: The biodegradable waterborne polyurethane of this invention has both ester and carbonate bond structures in its molecular chain, making it a system with synergistic modification of two soft segments. Because polycaprolactone-based polyols possess excellent flexibility, while polycarbonate-based polyols exhibit superior hydrolysis resistance and high strength, the biodegradable waterborne polyurethane of this invention can balance the soft feel and abrasion and folding resistance required for synthetic leather.

[0063] The bio-based synthetic leather prepared by this invention, under environmentally friendly and biodegradable conditions, not only exhibits good abrasion resistance but also good folding strength and flexibility.

[0064] Furthermore, during the preparation process, by using different temperatures in the prepolymerization reaction, the first chain extension reaction, and the second chain extension reaction to carry out stepwise temperature control and chain extension technology, the biodegradable waterborne polyurethane is formed into nano-sized particles. As a result, the bio-based synthetic leather prepared from it has the advantages of good film density and few defects. Attached Figure Description

[0065] Figure 1 A flowchart illustrating the preparation of synthetic leather according to embodiments of this application; Figure 2 The image shows the morphology of the film synthesized in Example 2 in the soil environment as a function of burial time. Figure 3 The image shows the appearance of the bio-based synthetic leather prepared in Application Example 1. Detailed Implementation

[0066] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way.

[0067] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0068] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the reagents used in the following embodiments are conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or by existing methods; unless otherwise specified, the reagent dosages are those used in routine experimental operations; unless otherwise specified, the experimental methods are conventional methods.

[0069] The test methods for particle size and zeta potential of waterborne polyurethane in the embodiments and comparative examples of this invention are as follows: The sample was diluted to 0.01 wt%, sonicated for 30 min, and then placed in a cuvette. The particle size and zeta potential of the waterborne polyurethane were measured at room temperature using a BeNano 90 nanoparticle size analyzer from Baxter Instruments. Each sample was measured three times and the average value was taken.

[0070] In this invention, the terms "polyurethane emulsion", "waterborne polyurethane", and "biodegradable waterborne polyurethane" all have the same meaning.

[0071] Example 1

[0072] Based on mass percentage, the raw materials used in this embodiment to prepare waterborne polyurethane include 19.1% bio-based polyol (including polycarbonate-based diol and polycaprolactone diol in a mass ratio of 1:1), 1.5% first chain extender (2,2-dimethylolbutyric acid), 2.1% second chain extender (1,4-butanediol), 4.7% hexamethylene diisocyanate, 14.2% solvent (dimethylacetamide), 1.3% neutralizing agent (triethylamine), and 57.1% dispersion medium (deionized water).

[0073] Polycaprolactone diol was selected from Beijing Inokai Technology Co., Ltd.'s polycaprolactone diol (brand name A81646-500G), with a number-average molecular weight of 2000 g / mol and a hydroxyl value of 56.1 ± 3 mg KOH / g; polycarbonate-based diol was selected from Anhui Fengyuan Group's straw-derived polycarbonate-based diol (brand name TBE2000), with a number-average molecular weight of 2000 g / mol and a hydroxyl value of 56.1 ± 3 mg KOH / g.

[0074] The method for preparing waterborne polyurethane for abrasion-resistant synthetic leather surface layer in this embodiment includes the following steps: (1) Add the polycaprolactone diol and polycarbonate diol in the above ratio into the reactor, purge with nitrogen for protection, gradually raise the temperature to 150°C, then evacuate to a vacuum of 0.1 MPa, react for 4 hours, and then stop the reaction to obtain wear-resistant polyol. Cool down to 90°C for later use. (2) Using dibutyltin dilaurate as a catalyst (the amount of catalyst is 0.1% of the total reaction mass), the above wear-resistant polyol, dimethylacetamide and hexamethylene diisocyanate were subjected to a prepolymerization reaction at 85~90℃ for 2 hours, wherein the solvent dimethylacetamide accounted for 3% of the total reaction mass; a prepolymer was obtained; (3) Add the first chain extender 2,2-dimethylolbutyric acid and the solvent dimethylacetamide to the above prepolymer and carry out the first chain extension reaction at 70~75℃ for 2 hours. At this time, the solvent accounts for 8.5% of the total mass of the reaction. Then add the second chain extender 1,4-butanediol and the solvent dimethylacetamide and carry out the second chain extension reaction at 60~65℃ for 1 hour. At this time, the solvent accounts for 11.5% of the total mass of the reaction. The viscosity gradually increases during the reaction. Continue to add solvent to adjust the viscosity of the system. At this time, the solvent accounts for 14.2% of the total mass of the reaction. The reaction is then stopped to obtain the polymer. (4) Add triethylamine as a neutralizing agent to the above polymer, stir for 0.5 hours for neutralization reaction, and finally add deionized water as a dispersion medium and emulsify at 35°C for 0.5 hours to obtain a waterborne polyurethane that can be used for wear-resistant synthetic leather surface layer. The solid content of this waterborne polyurethane is 24.80 wt%, the particle size is 85.56 nm, and the potential is -32.88 mV.

[0075] Example 2 The only difference from Example 1 is that the mass ratio of polycarbonate-based diol to polycaprolactone diol in the bio-based polyol is 4:6. Specifically, the raw materials are as follows: Based on mass percentage, the raw materials used in this embodiment to prepare waterborne polyurethane include 19.1% bio-based polyol (including polycarbonate-based diol and polycaprolactone diol in a mass ratio of 4:6), 1.5% first chain extender (2,2-dimethylolbutyric acid), 2.1% second chain extender (1,4-butanediol), 4.7% hexamethylene diisocyanate, 14.2% solvent (dimethylacetamide), 1.3% neutralizing agent (triethylamine), and 57.1% dispersion medium (deionized water).

[0076] The preparation method of the waterborne polyurethane used for the wear-resistant synthetic leather surface layer in this embodiment is the same as that in Example 1. The synthesized waterborne polyurethane has a solid content of 26.56 wt%, a particle size of 82.85 nm, and a potential of -32.62 mV.

[0077] The polyurethane emulsion prepared in Example 2 was dispersed in an ultrasonic disperser for 30 min, then naturally cast onto a polytetrafluoroethylene mold lined with a mesh cotton gauze pad. After standing for 12 h, it was dried in an oven at 50°C for 48 h to obtain a polyurethane film. Its morphology in the soil environment changed significantly with prolonged burial time, such as... Figure 2As shown in the figure, the initial (day 0) sample surface was smooth and intact with a regular structure. On day 14, localized discoloration and uneven dark spots gradually appeared on the film surface, indicating the onset of surface degradation and microbial attachment. By day 28, the film color had deepened, surface roughness had significantly increased, and localized pores and a loose structure were observed, indicating that moisture, microorganisms, and enzymatic activity in the soil had caused some damage to the polyurethane molecular chains. As time progressed to day 42 and day 56, the overall structure of the sample further deteriorated, with edges curling and breaking, and surface peeling. By day 70, the overall color of the film had darkened, the structure had become loose and fragile, and obvious cracks or even fragmentation appeared in some areas. In summary, the above-mentioned film exhibited a relatively obvious time-dependent degradation characteristic in the soil environment. Its degradation process progressed from surface erosion to internal structural destruction, demonstrating the degradable potential of straw-derived diol soft segments (i.e., bio-based polyols) in the natural environment, providing experimental evidence for its application as an environmentally friendly waterborne polyurethane synthetic leather.

[0078] Example 3 The only difference from Example 1 is that the mass ratio of polycarbonate-based diol to polycaprolactone diol in the bio-based polyol is 3:7. Specifically, the raw materials are as follows: Based on mass percentage, the raw materials used in this embodiment to prepare waterborne polyurethane include 19.1% bio-based polyol (including polycarbonate-based diol and polycaprolactone diol in a mass ratio of 3:7), 1.5% first chain extender (2,2-dimethylolbutyric acid), 2.1% second chain extender (1,4-butanediol), 4.7% hexamethylene diisocyanate, 14.2% solvent (dimethylacetamide), 1.3% neutralizing agent (triethylamine), and 57.1% dispersion medium (deionized water).

[0079] The preparation method of the waterborne polyurethane used for the wear-resistant synthetic leather surface layer in this embodiment is the same as that in Example 1.

[0080] The synthesized waterborne polyurethane is a translucent milky white substance with a solid content of 27.48 wt%, a particle size of 75.28 nm, and a potential of -36.16 mV. It exhibits characteristics such as fine particle size, excellent film-forming properties, and high electrostatic stability. The moderate solid content ensures drying efficiency and application flowability, while the fine particle size facilitates the formation of a dense and smooth film. The high absolute value of the zeta potential endows the emulsion with excellent storage stability and anti-agglomeration ability, resulting in overall excellent comprehensive performance.

[0081] Comparative Example 1 The difference from Example 1 is that the bio-based polyol is composed of 100% polycarbonate-based diol. Specifically, the raw materials are as follows: Based on mass percentage, the raw materials used in this embodiment to prepare waterborne polyurethane include 19.1% polycarbonate-based diol, 1.5% first chain extender (2,2-dimethylolbutyric acid), 2.1% second chain extender (1,4-butanediol), 4.7% hexamethylene diisocyanate, 14.2% solvent (dimethylacetamide), 1.3% neutralizing agent (triethylamine), and 57.1% dispersion medium (deionized water).

[0082] The polycarbonate-based diol was selected from straw-derived polycarbonate-based diol (brand name TBE2000) from Anhui Fengyuan Group. The number-average molecular weight of the polycarbonate-based diol was 2000 g / mol, and the hydroxyl value was 56.1 ± 3 mg KOH / g.

[0083] The preparation method of this comparative example of waterborne polyurethane is the same as that of Example 1.

[0084] The synthesized waterborne polyurethane has a solid content of 21.68 wt%, a particle size of 64.05 nm, and a potential of -38.78 mV.

[0085] Comparative Example 2 Comparative Example 2 is YC-F204 waterborne polyurethane resin purchased from Anhui Yuanchen New Material Technology Co., Ltd.

[0086] Application Example 1 according to Figure 1 The process shown involves using the polyurethane emulsion obtained in Example 1 as the film-forming resin. Appropriate amounts of color paste (TSE LR01 Black from Suzhou Shiming Technology Co., Ltd.), 1% defoamer (NXZ defoamer from Shandong Yousuo Chemical Technology Co., Ltd.), and 0.5% thickener (YC-101B waterborne polyurethane thickener from Anhui Yuanchen New Material Technology Co., Ltd.) are added by mass fraction and mixed uniformly through high-speed shearing for 10 minutes. Subsequently, the slurry undergoes vacuum degassing and is allowed to stand to eliminate internal micro-bubbles, ensuring the density of the coating, resulting in a slurry. The prepared slurry is then uniformly coated onto the surface of release paper with a specific texture using an automatic coating machine, and subjected to gradient drying at 60 °C for 20 minutes, 75 °C for 30 minutes, and 90 °C for 30 minutes to obtain a film. Finally, through a lamination process, the resulting film is bonded to a microfiber base fabric pre-coated with a high-performance adhesive (YC-110 waterborne polyurethane resin adhesive from Anhui Yuanchen New Material Technology Co., Ltd.). After curing and peeling off the release paper, bio-based synthetic leather is finally obtained, such as... Figure 3 As shown.

[0087] Application Example 2-3, Application Comparative Example 1-2 The only difference from Application Example 1 is that the polyurethanes obtained in Examples 2-3 and Comparative Examples 1-2 are used.

[0088] The synthetic leather produced using the above application examples and comparative examples conforms to the national standard GB / T 39507-2020 "Leather". Physical and mechanical tests The abrasion resistance of synthetic leather samples was determined using a Martindale abrasion tester. The test was conducted under standard environmental conditions (temperature 23℃±2℃, relative humidity 50%±5%RH). Leather samples were cut into circular pieces with a diameter of 38 mm. Six parallel samples were used in each test group. All samples were conditioned for 24 hours under standard conditions before testing. Standard wool felt was used as the abrasive, with a loading pressure of 595 g (9 kPa). The test trajectory followed a Lissajous curve, and the frequency was controlled at 50-60 times / min. The test results show that the waterborne polyurethane coated leather prepared according to this invention exhibits good abrasion resistance under standard loading conditions, with an average abrasion resistance of 10,000 cycles. No obvious substrate exposure or coating peeling was observed on the sample surface; only slight changes in gloss were observed, indicating a tight bond between the coating layer and the leather matrix, a dense resin film, and excellent abrasion resistance and durability, meeting practical application requirements.

[0089] The resulting synthetic leather conforms to the national standard GB / T 3903.1-2021 "Leather". Physical and mechanical tests The test was conducted to determine the flexural strength. The test was carried out under standard environmental conditions (temperature 23℃±2℃, relative humidity 50%±5%RH).

[0090] Leather samples were cut into rectangular pieces measuring 70 mm × 30 mm, with 3–5 parallel samples per group. All samples were conditioned in a standard environment for 24 hours. A vertical leather flexural endurance testing machine was used, with the samples clamped face out in the fixture. The bending angle was set to 22.5°, and the bending frequency to 100 times / min. The target number of bends was set for each test. The test results showed that after 10,000 consecutive bends, the waterborne polyurethane-coated leather prepared in this study did not exhibit whitening or peeling of the coating layer, only slight creases, demonstrating excellent flexibility and fatigue resistance. This indicates that the waterborne polyurethane resin forms a uniform and dense film, bonding firmly to the leather matrix, and can meet the requirements of high flexibility in various applications.

[0091] The test results are shown in Table 1.

[0092] Table 1

[0093] As can be seen from the test results in Table 1, compared with ordinary waterborne polyurethane synthetic leather (i.e., using Comparative Examples 1-2), the synthetic leather prepared using the bio-based waterborne polyurethane resin of Application Examples 1-3 has better overall performance and its performance is significantly improved. The bio-based synthetic leather of Application Examples 1-3 has good wear resistance and folding resistance, and is also biodegradable.

[0094] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A biodegradable waterborne polyurethane, the raw materials for which it is prepared include bio-based polyols and isocyanate monomers, wherein the bio-based polyols include polycarbonate-based polyols and polycaprolactone-based polyols.

2. The biodegradable waterborne polyurethane according to claim 1, characterized in that, The isocyanate monomer is selected from hexamethylene diisocyanate; and / or The bio-based polyols are derived from straw; and / or The polycarbonate-based polyol is selected from polycarbonate-based diols; and / or the number average molecular weight of the polycarbonate-based polyol is 1000-3000 g / mol; and / or the hydroxyl value of the polycarbonate-based polyol is 50-60 mg KOH / g; and / or The polycaprolactone-based polyol is selected from polycaprolactone diol; and / or the number average molecular weight of the polycaprolactone-based polyol is 1000-3000 g / mol; and / or the hydroxyl value of the polycaprolactone-based polyol is 50-60 mg KOH / g. Preferably, the mass ratio of the polycarbonate-based polyol to the polycaprolactone-based polyol is (3-7):(7-3).

3. The biodegradable waterborne polyurethane according to claim 1 or 2, characterized in that, The raw materials for preparation further include a first chain extender, a second chain extender, a solvent, a neutralizing agent, and a dispersion medium; and / or Based on the biodegradable waterborne polyurethane, the raw materials for preparation, calculated by mass percentage, include: Bio-based polyol 15-25%, isocyanate monomer 2-10%, first chain extender 1-2%, second chain extender 1-5%, solvent 10-20%, neutralizer 0.5-3%, dispersion medium 50-60%.

4. The biodegradable waterborne polyurethane according to claim 3, characterized in that, The first chain extender is selected from 2,2-dihydroxymethylbutyric acid; and / or The second chain extender is selected from 1,4-butanediol; and / or The solvent is selected from dimethylacetamide; and / or The neutralizing agent is selected from triethylamine; and / or The dispersion medium is selected from deionized water; and / or The biodegradable waterborne polyurethane has a solid content of 20-30 wt%; and / or The biodegradable waterborne polyurethane has a particle size of 70-100 nm; and / or The zeta potential of the biodegradable waterborne polyurethane is -40mV to -30mV.

5. A method for preparing a biodegradable waterborne polyurethane according to any one of claims 1-4, comprising the following steps: (1) Under the protection of an inert gas, bio-based polyols are reacted to obtain wear-resistant polyols, wherein the bio-based polyols include polycarbonate-based polyols and polycaprolactone-based polyols; (2) In the presence of a catalyst, the wear-resistant polyol, isocyanate monomer and solvent are mixed to carry out a prepolymerization reaction to obtain a prepolymer; (3) The prepolymer, solvent, and first chain extender are mixed to carry out a first chain extension reaction, and then mixed with a second chain extender and solvent to carry out a second chain extension reaction to obtain a polymer; (4) The polymer is mixed with a neutralizing agent to carry out a neutralization reaction, and then mixed with a dispersion medium to carry out an emulsification reaction to obtain the biodegradable waterborne polyurethane.

6. The preparation method according to claim 5, characterized in that, In step (1), the inert gas is selected from nitrogen; and / or In step (1), the reaction temperature is 100-200℃; and / or In step (1), the reaction time is 3-10 hours; and / or In step (1), the reaction pressure is 0.1-0.5 MPa; and / or In step (2), the catalyst is selected from dibutyltin dilaurate; and / or In step (2), the temperature of the prepolymerization reaction is 85-90℃; and / or In step (2), the prepolymerization reaction takes 1-5 hours; and / or In step (3), the temperature of the first chain extension reaction is 65-75℃; and / or In step (3), the first chain extension reaction takes 1-5 hours; and / or In step (3), the temperature of the second chain extension reaction is 55-70℃; and / or In step (3), the second chain extension reaction takes 1-3 hours; and / or In step (4), the neutralization reaction takes 0.1-1 h; and / or In step (4), the temperature of the emulsification reaction is 20-40°C; and / or In step (4), the emulsification reaction takes 0.1-1 h.

7. The use of the biodegradable waterborne polyurethane according to any one of claims 1-4 or the biodegradable waterborne polyurethane prepared by the preparation method according to any one of claims 5-6 in artificial leather or synthetic leather, coatings or coatings, and elastic fibers.

8. A bio-based synthetic leather comprising the biodegradable waterborne polyurethane of any one of claims 1-4 or the biodegradable waterborne polyurethane prepared by the preparation method of any one of claims 5-6.

9. A method for preparing the bio-based synthetic leather according to claim 8, comprising the following steps: S1, the biodegradable waterborne polyurethane obtained by any one of claims 1-4 or any one of claims 5-6 is mixed with color paste, defoamer and thickener, and then subjected to defoaming treatment to obtain slurry; S2, the slurry is coated onto the surface of release paper and dried to obtain a film; S3, the film is bonded to the base fabric, and after curing and peeling off the release paper, the bio-based synthetic leather is obtained.

10. The preparation method according to claim 9, characterized in that, The defoamer is selected from nonionic defoamers, preferably from one or more of emulsified silicone oil, higher carbon alcohol fatty acid ester complex, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene alcohol amine ether, polyoxypropylene glycerol ether, or polyoxypropylene. The thickener is selected from one or more of polyacrylic acid thickeners or polyurethane associative thickeners; and / or The amount of the defoamer added is 0.1-2% of the biodegradable waterborne polyurethane by mass percentage, and / or the amount of the thickener added is 0.1-1% of the biodegradable waterborne polyurethane.

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