A method for preparing a fully bio-based waterborne polyurethane leather finishing material

Abstract

This invention provides a method for preparing a fully bio-based waterborne polyurethane leather finishing material. The method is characterized by first reacting a chiral bio-based polymer diol with a bio-based diisocyanate to obtain a polyurethane prepolymer; then adding a chiral bio-based chain extender; and reacting under the action of a catalyst to prepare a bio-based polyurethane; finally, using bio-based nanoparticles as a stabilizer to disperse the polyurethane in water, resulting in a fully bio-based waterborne polyurethane finishing material. This method eliminates the need for polyurethane raw materials derived from petrochemical resources, including polyols, isocyanates, chain extenders, and hydrophilic chain extenders; all raw materials are derived from plant-based compounds, thus achieving a fully bio-based preparation of waterborne PU. Furthermore, by introducing chiral compounds into the polyurethane, this method imparts excellent antibacterial and adhesive properties to the polyurethane.

Description

Technical Field

[0001] This invention relates to the field of leather finishing materials, specifically to a method for preparing a fully bio-based waterborne polyurethane leather finishing material. Background Technology

[0002] Polyurethane, a high-performance block polymer, has been widely used in various fields such as daily life, agricultural production, industrial manufacturing, biomedicine, and aerospace. In the leather industry, due to environmental protection and product safety requirements, waterborne polyurethane (WPU), with water as the dispersion medium, has largely replaced solvent-based PU as the dominant coating material. However, existing WPUs have certain shortcomings compared to solvent-based ones in terms of abrasion resistance, water resistance, and adhesion. In particular, waterborne polyurethane requires waterborne emulsification during its preparation, and both existing external and internal emulsification methods require the introduction of hydrophilic components into the structure, resulting in disadvantages such as poor wet rubbing resistance and poor hand feel in the final leather product.

[0003] On the other hand, the three main raw materials for polyurethane production—polyols, isocyanates, and chain extenders—are currently primarily derived from petroleum resources. With the depletion of petroleum resources and the intensification of environmental problems, the synthesis of polyurethane using renewable biomass resources has become one of the important directions for the development of my country's strategic emerging materials industry and biomass industry. Compared with petroleum-based polyurethane raw materials, biomass materials are more abundant in sources, have lower toxicity, and exhibit greater structural diversity. Introducing biomass materials into polyurethane can improve the overall performance of polyurethane materials and help reduce production costs. Currently, research and development on bio-based polyurethane mainly focuses on three aspects: the separate preparation of bio-based polyols, bio-based isocyanates, and bio-based chain extenders. Existing reports on bio-based polyurethane raw materials are relatively limited to polyols, resulting in a relatively low actual bio-based content in bio-based polyurethane, approximately 30-40%. Furthermore, the development of bio-based waterborne polyurethane is still in its early stages. This is because, compared to traditional polyurethane, the preparation of waterborne polyurethane involves an essential process of waterborne dispersion and emulsification. Currently, the waterborne emulsification of waterborne polyurethane still relies entirely on hydrophilic chain extender monomers such as dimethylolpropionic acid, which are essential for petrochemical resources, resulting in a lower overall bio-based content.

[0004] To further increase the bio-based content of polyurethane, this invention proposes a method for preparing a fully bio-based waterborne polyurethane leather coating material. This invention starts from molecular design, selecting plant-derived rosin with a chiral structure as a raw material to prepare a chiral bio-based polymer diol and a bio-based chain extender, respectively. These are then synthesized into a bio-based polyurethane through an addition polymerization reaction with a bio-based diisocyanate. For the waterborne dispersion of the polyurethane, this invention uses bio-based nanoparticles that can be adsorbed at the water-oil interface as stabilizers, ultimately achieving waterborne emulsification of the PU. This method eliminates the need for polyols, isocyanates, chain extenders, and hydrophilic chain extenders derived from petrochemical resources, thus achieving a fully bio-based preparation of waterborne PU. Currently, no research reports on fully bio-based waterborne polyurethane leather finishing materials have been found.

[0005] Moreover, another important advantage of this invention is that the introduction of chiral bio-based polymer diols and bio-based chain extenders can endow polyurethane with antibacterial adhesive properties, thereby achieving antibacterial and antifungal effects. The chiral antibacterial structure is based on the recently developed stereochemical antibacterial strategy. Essentially, microbial adhesion at material interfaces is based on the interaction between the two. Previous studies have found that when microbial cells come into contact with external surfaces, they can sense and distinguish different chiral structures on the material surface, thus exhibiting significant differences in adhesion. Compared to traditional sterilization strategies, constructing novel antibacterial interfaces based on antibacterial adhesion mechanisms achieves antibacterial effects through a harmonious tactical approach of "subduing the bacteria without fighting (sterilization) through antibacterial adhesion," preventing the development of drug resistance in microorganisms from the source. Therefore, the fully bio-based waterborne polyurethane leather coating material prepared by this invention not only uses plant-based raw materials, making it green and low-carbon, but also possesses antibacterial, antifungal, and adhesive properties, imparting antifungal properties to leather when coated. Summary of the Invention

[0006] This invention provides a method for preparing a fully bio-based waterborne polyurethane leather finishing material. The method is characterized by first reacting a chiral bio-based polymer diol with a bio-based diisocyanate to obtain a bio-based polyurethane prepolymer; then adding a chiral bio-based chain extender; and reacting under the action of a catalyst to prepare the bio-based polyurethane; finally, using bio-based nanoparticles as a stabilizer to disperse and emulsify the polyurethane in water, resulting in the fully bio-based waterborne polyurethane leather finishing material. The specific steps are as follows: (1) Bio-based diisocyanate and bio-based polymer diol with chiral structure are added to the reactor at a molar ratio of (2-6):1 and dissolved in a certain amount of solvent. The solid content of the solution system is controlled by the solvent to be 20-30 wt%, the temperature is 60-90℃, the stirring speed is 800-1000 r pm, and the stirring reaction is carried out for 30-40 min to obtain bio-based polyurethane prepolymer. (3) Add a chiral bio-based chain extender to the reactor, with a molar ratio of diisocyanate to bio-based chain extender of (1-5):1, at a temperature of 80-100℃ and a stirring speed of 1000-1500 rpm, and react for 3-5 h under catalytic conditions to obtain a bio-based polyurethane solution; concentrate the above bio-polyurethane solution using a rotary evaporator to a solid content of 70-90 wt%. (4) Add a certain amount of bio-based nanoparticles and deionized water to another reactor, wherein the concentration of bio-based nanoparticles is 1~8 wt%, and stir and disperse at room temperature for 1-2 h at a stirring speed of 800~1500 rpm to obtain a bio-based nanoparticle dispersion. (5) Add the bio-based nanoparticle dispersion from step (4) to the concentrated bio-polyurethane solution, wherein the mass ratio of the bio-based nanoparticle dispersion to the polyurethane solution is (2~4):1. Immediately emulsify at high speed using a high-speed emulsifier for 5~15 min, with a stirring speed of 6000~10000 rpm. Then stir at low speed for 10~30 min with a stirring speed of 1000-3000 rpm. Remove the residual solvent by vacuum distillation and concentrate the product to a solid content of 20%~35% to obtain a fully bio-based waterborne polyurethane leather coating material.

[0007] The preparation steps of the bio-based polymer diol with chiral structure are as follows: a certain amount of fumaric rosin and diol compounds are added to a reactor, wherein the molar ratio of fumaric rosin to diol compounds is 1:(0.75~0.9), and the reaction is carried out at atmospheric pressure at a temperature of 160-200℃ for 3-5 hours, and then the reaction is carried out under reduced pressure for 2-4 hours. Bio-based polymer diols with different molecular chain lengths can be prepared by adjusting the monomer ratio and reaction time.

[0008] The preparation steps of the bio-based chain extender with chiral structure are as follows: a certain amount of diethanolamine and dichloromethane solvent are added to a three-necked flask, dihydropyran and bis(trimethylsilane) sulfate catalyst are added, and the reaction is carried out at 0~10℃ for 15~30 min; then a certain amount of methyl rosinate and sodium ethoxide catalyst are added, and the reaction is carried out at 70~110℃ for 3~8 h; finally, organotin-phosphate catalyst is added, and the reaction is carried out under reflux for 1.5~3 h; dichloromethane is removed by rotary evaporation to obtain the bio-based chain extender; wherein the molar ratio of diethanolamine to methyl rosinate is (1~2):1.

[0009] The bio-based diisocyanate is one of pentamethylene diisocyanate, ethyl L-lysine diisocyanate, and isosorbide diisocyanate. The number-average molecular weight of the chiral bio-based polymer diol is 1000-4000. The diol compound is one of ethylene glycol, diethylene glycol, and triethylene glycol.

[0010] The method for preparing a fully bio-based waterborne polyurethane leather finishing material is characterized in that the bio-based nanoparticles are one of starch-based nanoparticles, lignin nanoparticles, and polyphenol-based nanoparticles. The method further specifies that the bio-based nanoparticles have a particle size of 30-100 nm and a contact angle of 40-85 degrees. o .

[0011] The method for preparing a fully bio-based waterborne polyurethane leather finishing material is characterized in that the solvent is one of tetrahydrofuran, acetone and ethyl acetate. Detailed Implementation

[0012] The following three embodiments of the present invention are given to illustrate the preparation method of the all-biomass-based waterborne polyurethane leather finishing material.

[0013] Example 1

[0014] Preparation of bio-based polymer diol with chiral structure: 40g fumarosin and 4.8g ethylene glycol were added to a reactor and reacted at atmospheric pressure for 3h at 180℃ and then at reduced pressure for 2h to obtain bio-based polymer diol.

[0015] Preparation of a chiral bio-based chain extender: 50 g of diethanolamine and 100 ml of dichloromethane were added to a 1000 ml three-necked flask, along with 84.13 g of dihydropyran and the catalyst bis(trimethylsilane) sulfate. The mixture was reacted at 0 °C for 15 min. Then, 75 g of methyl rosinate and the catalyst sodium ethoxide were added, and the mixture was reacted at 80 °C for 4 h. Finally, the catalyst organotin-phosphate was added, and the mixture was refluxed for 1.5 h. The dichloromethane was removed by rotary evaporation to obtain the bio-based chain extender.

[0016] Weigh 20.00 g of the bio-based polymer diol and add it to a 250 ml three-necked flask. Dry the mixture under vacuum at 110 °C for 2 h. Lower the temperature to 70 °C, add 6.2 g of pentamethylene diisocyanate (dissolved in THF) and 100 ml of tetrahydrofuran solvent, and stir mechanically for 40 min under nitrogen protection. Add 12.3 g of the bio-based chain extender, and stir at 80 °C for 4 h to carry out the chain extension reaction. Cool the temperature to 40 °C and concentrate the polyurethane solution at 40 °C to a solid content of 80 wt%.

[0017] Then, 180 g of starch-based nanoparticles with a concentration of 5% were poured into the above-concentrated polyurethane solution, and immediately emulsified for 5 min using a high-speed emulsifier at a speed of 10,000 rpm, followed by low-speed emulsification for 29 min with a stirring speed of 3,000 rpm, and then concentrated by rotary evaporation to a solid content of 30%.

[0018] Example 2

[0019] Preparation of bio-based polymer diol with chiral structure: 40g fumarosin and 11.6g triethylene glycol were added to a reactor and reacted at atmospheric pressure for 4h at 200℃ and then at reduced pressure for 3h to obtain bio-based polymer diol.

[0020] Preparation of a chiral bio-based chain extender: 50 g of diethanolamine and 100 ml of dichloromethane were added to a 1000 ml three-necked flask, along with 84.13 g of dihydropyran and the catalyst bis(trimethylsilane) sulfate. The mixture was reacted at 0 °C for 15 min. Then, 75 g of methyl rosinate and the catalyst sodium ethoxide were added, and the mixture was reacted at 80 °C for 4 h. Finally, the catalyst organotin-phosphate was added, and the mixture was refluxed for 1.5 h. The dichloromethane was removed by rotary evaporation to obtain the bio-based chain extender.

[0021] Weigh 20.00 g of the bio-based polymer diol and add it to a 250 ml three-necked flask. Dry the mixture under vacuum at 110 °C for 2 h. Lower the temperature to 70 °C, add 6.2 g of pentamethylene diisocyanate (dissolved in THF) and 100 ml of tetrahydrofuran solvent, and stir mechanically for 40 min under nitrogen protection. Add 12.3 g of the bio-based chain extender, and stir at 80 °C for 4 h to carry out the chain extension reaction. Cool the mixture to 40 °C and concentrate the polyurethane solution at 40 °C to a solid content of 80 wt%.

[0022] Then, 200 g of lignin-based nanoparticles with a concentration of 5% were poured into the above-concentrated polyurethane solution, and emulsified immediately with a high-speed emulsifier for 5 minutes at a speed of 10,000 rpm, followed by low-speed emulsification for 29 minutes with a stirring speed of 3,000 rpm, and concentrated by rotary evaporation until the solid content was 30%.

[0023] Example 3

[0024] Preparation of bio-based polymer diol with chiral structure: 40g fumarosin and 8,19-diethylene glycol were added to a reactor and reacted at atmospheric pressure for 4h at 200℃ and then at reduced pressure for 3h to obtain the bio-based polymer diol.

[0025] Preparation of a chiral bio-based chain extender: 50 g of diethanolamine and 100 ml of dichloromethane were added to a 1000 ml three-necked flask, along with 84.13 g of dihydropyran and the catalyst bis(trimethylsilane) sulfate. The mixture was reacted at 0 °C for 15 min. Then, 75 g of methyl rosinate and the catalyst sodium ethoxide were added, and the mixture was reacted at 80 °C for 4 h. Finally, the catalyst organotin-phosphate was added, and the mixture was refluxed for 1.5 h. The dichloromethane was removed by rotary evaporation to obtain the bio-based chain extender.

[0026] Weigh 20.00 g of bio-based polymer diol and add it to a 250 ml three-necked flask. Dry under vacuum at 110 °C for 2 h. Lower the temperature to 70 °C, add 6.5 g of L-lysine diisocyanate (dissolved in THF) and 100 ml of tetrahydrofuran solvent, and stir mechanically for 40 min under nitrogen protection. Add 12.3 g of bio-based chain extender, stir at 80 °C for 4 h to extend the chain. Cool to 40 °C and concentrate the polyurethane solution at 40 °C to a solid content of 80 wt%.

[0027] Then, 250g of 4% polyphenol nanoparticles were poured into the above-concentrated polyurethane solution and immediately emulsified for 5 minutes at 10,000 rpm using a high-speed emulsifier, followed by low-speed emulsification for 25 minutes at a stirring speed of 3,000 rpm, and then concentrated by rotary evaporation until the solid content was 30%.

Claims

1. A method for preparing a fully bio-based waterborne polyurethane leather finishing material, characterized in that, First, a bio-based polyurethane prepolymer is obtained by reacting a chiral bio-based polymer diol with a bio-based diisocyanate. Then, a chiral bio-based chain extender is added, and the reaction is carried out under the action of a catalyst to prepare bio-based polyurethane. Finally, bio-based nanoparticles are used as stabilizers to disperse and emulsify the polyurethane in water, resulting in a fully bio-based waterborne polyurethane leather finishing material. The specific steps are as follows: (1) Bio-based diisocyanate and bio-based polymer diol with chiral structure are added to the reactor at a molar ratio of (2-6):1 and dissolved in a certain amount of solvent. The solid content of the solution system is controlled to be 20-30 wt% by the solvent. The reaction is carried out at a temperature of 60-90℃ and a stirring speed of 800-1000 r pm for 30-40 min to obtain bio-based polyurethane prepolymer. (2) Add a chiral bio-based chain extender to the reactor, with a molar ratio of diisocyanate to bio-based chain extender of (1-5):

1. React at 80-100℃, stirring speed of 1000-1500 rpm, and under catalyst conditions for 3-5 h to obtain a bio-based polyurethane solution. Concentrate the above bio-based polyurethane solution using a rotary evaporator to a solid content of 70-90 wt%. (3) Add a certain amount of bio-based nanoparticles and deionized water to another reactor, stir and disperse at room temperature for 1-2 hours at a stirring speed of 800-1500 rpm to obtain a bio-based nanoparticle dispersion, wherein the concentration of bio-based nanoparticles is 1-8 wt%; (4) Add the bio-based nanoparticle dispersion from step (3) to the concentrated bio-based polyurethane solution, wherein the mass ratio of the bio-based nanoparticle dispersion to the polyurethane solution is (2~4):

1. Emulsify at high speed for 5~15 min using a high-speed emulsifier at a speed of 6000~10000 rpm, then emulsify at low speed for 10~30 min at a speed of 1000-3000 rpm. Remove the residual solvent by vacuum distillation and concentrate the product to a solid content of 20%~35% to obtain a fully bio-based waterborne polyurethane leather coating material. The preparation steps of bio-based polymer diols with chiral structures are as follows: a certain amount of fumaric rosin and diol compounds are added to a reactor, wherein the molar ratio of fumaric rosin to diol compounds is 1:(0.75~0.9), and the reaction is carried out at atmospheric pressure at a temperature of 160-200℃ for 3-5 hours, and then the reaction is carried out under reduced pressure for 2-4 hours. Bio-based polymer diols with different molecular chain lengths are prepared by adjusting the monomer ratio and reaction time. The preparation steps of the bio-based chain extender with chiral structure are as follows: a certain amount of diethanolamine and dichloromethane solvent are added to a three-necked flask, dihydropyran and bis(trimethylsilane) sulfate catalyst are added, and the reaction is carried out at 0~10℃ for 15~30 min; then a certain amount of methyl rosinate and sodium ethoxide catalyst are added, and the reaction is carried out at 70~110℃ for 3~8 h; finally, organotin-phosphate catalyst is added, and the reaction is carried out under reflux for 1.5~3 h; dichloromethane is removed by rotary evaporation to obtain the bio-based chain extender; wherein the molar ratio of diethanolamine to methyl rosinate is (1~2):

1.

2. The preparation method of a fully bio-based waterborne polyurethane leather finishing material according to claim 1, characterized in that, The bio-based diisocyanate is one of pentamethylene diisocyanate, L-lysine diisocyanate, and isosorbide diisocyanate.

3. The method for preparing a fully bio-based waterborne polyurethane leather finishing material according to claim 1, characterized in that, The number-average molecular weight of the bio-based polymer diol with a chiral structure is 1000-4000.

4. The method for preparing a fully bio-based waterborne polyurethane leather finishing material according to claim 1, characterized in that, The diol compound mentioned is one of ethylene glycol, diethylene glycol, and triethylene glycol.

5. The method for preparing a fully bio-based waterborne polyurethane leather finishing material according to claim 1, characterized in that, The bio-based nanoparticles are one of starch-based nanoparticles, lignin nanoparticles, and polyphenol-based nanoparticles.

6. The method for preparing a fully bio-based waterborne polyurethane leather finishing material according to claim 1, characterized in that, The bio-based nanoparticles have a particle size of 30-100 nm and a contact angle of 40-85°. o .

7. The method for preparing a fully bio-based waterborne polyurethane leather finishing material according to claim 1, characterized in that, (1) The solvent is one of tetrahydrofuran, acetone and ethyl acetate.