A solvent-free phenolated lignin-based polyurethane elastomer, and a preparation method and application thereof

Abstract

The application discloses a solvent-free phenolated lignin-based polyurethane elastomer and a preparation method and application thereof. A phenolated lignin with high phenolic hydroxyl content is prepared first, and then the phenolated lignin is dispersed in a polyol, and a lignin-based polyurethane elastomer rich in dynamic phenol-type urethane bonds is synthesized by using a one-step solvent-free method, and the synthesis process is green and simple. The phenolated lignin has a lower molecular weight, a higher hydroxyl content and a higher reactivity, and the polyurethane elastomer synthesized by using the phenolated lignin has a double dynamic crosslinking network composed of a phenol-type urethane network and a hydrogen bond crosslinking network. The obtained solvent-free phenolated lignin-based polyurethane elastomer has excellent mechanical properties, reprocessing properties, light-heat self-healing properties and thermal-oxidative aging resistance. The contradiction between the mechanical properties and dynamic mechanical properties of traditional polyurethane elastomers is solved, and a new idea is provided for developing green and multifunctional polyurethane elastomers in future industrial fields.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane elastomer technology, specifically relating to a solvent-free phenolic lignin-based polyurethane elastomer, its preparation method, and its application. Background Technology

[0002] Polyurethane elastomers are widely used in smart wearables, flexible drives, automotive manufacturing, and biomedicine due to their excellent mechanical properties. However, in practical applications, these materials are inevitably subject to damage and have a limited lifespan; direct disposal would lead to resource waste and environmental pollution. Therefore, the preparation of polyurethane elastomers with both excellent mechanical and dynamic mechanical properties has attracted widespread attention. The good mechanical properties of polyurethane elastomers usually rely on strong covalent crosslinking, but strong covalent crosslinking limits the dynamic mechanical properties of the material. Currently, most research aims to balance the mechanical and dynamic mechanical properties of polyurethane by designing non-covalent crosslinks (such as hydrogen bonds, ionic bonds, and coordination bonds) and dynamic covalent crosslinks (such as disulfide bonds, DA bonds, and boron ester bonds). However, these methods rely on petroleum resources, are costly, and involve complex processes.

[0003] Lignin is an abundant natural green aromatic polymer, rich in active functional groups such as phenolic hydroxyl groups in its molecular structure. Replacing some petroleum-based polyols with lignin rich in phenolic hydroxyl groups in the synthesis of polyurethane elastomers would not only reduce petroleum resource consumption but also yield lignin-based polyurethane elastomers rich in dynamic phenolic carbamate bonds, potentially resolving the contradiction between the mechanical properties and dynamic mechanical properties of polyurethane elastomers.

[0004] Patent application CN109485824A discloses a method for preparing lignin-based polyurethane elastomers by using alkali-catalyzed depolymerization enzymes to hydrolyze lignin to obtain low molecular weight partially depolymerized lignin. Although this elastomer has good reprocessing properties, its mechanical properties are poor, and the toxic organic solvent dimethylacetamide is used.

[0005] Patent application CN117843904A discloses a method for synthesizing lignin-based polyurethane elastomers using low molecular weight lignin extracted with ethanol via a one-step solvent-free process. Although this synthesis process is simple and does not use volatile or high-boiling-point toxic organic solvents, the retention rate of its mechanical properties after a single reprocessing is less than 50%, indicating poor reprocessing performance.

[0006] Patent application CN114933689A discloses a one-step method for synthesizing lignin-based polyurethane elastomers under solvent-free and catalyst-free conditions. Although this elastomer has good reprocessing properties, its tensile strength is only 12.5 MPa, its mechanical properties are poor, and the lignin substitution amount is low.

[0007] Currently, there remains a significant challenge in preparing polyurethane elastomers with both excellent mechanical properties and good dynamic mechanical properties under solvent-free conditions. Summary of the Invention

[0008] To address the shortcomings and deficiencies of existing technologies, the primary objective of this invention is to provide a method for preparing a solvent-free phenolic lignin-based polyurethane elastomer.

[0009] Another object of the present invention is to provide a solvent-free phenolic lignin-based polyurethane elastomer prepared by the above preparation method.

[0010] The lignin-based polyurethane elastomer prepared by this invention is synthesized via a solvent-free one-step method. The synthesized elastomer exhibits high strength and toughness, as well as excellent reprocessing, photothermal self-healing, solvent resistance, and aging resistance. This invention overcomes the problems of traditional lignin-based polyurethane elastomers, such as the inability to simultaneously achieve mechanical and dynamic mechanical properties, poor compatibility between lignin and polyols during synthesis, low reactivity, low lignin substitution, and the need for toxic solvents.

[0011] Another object of the present invention is to provide the application of the above-mentioned solvent-free phenolic lignin-based polyurethane elastomer.

[0012] The objective of this invention is achieved through the following technical solution:

[0013] A method for preparing a solvent-free phenolic lignin-based polyurethane elastomer includes the following steps:

[0014] (1) Mix lignin with phenolic reagent at 110-140℃, add concentrated sulfuric acid, react at 90-140℃ for 2-4 hours, purify the product after the reaction to obtain phenolic lignin;

[0015] (2) Mix the long-chain polyol with the phenolic lignin from step (1) to obtain a mixed alcohol dispersion;

[0016] (3) After dehydrating the mixed alcohol dispersion from step (2), add catalyst and isocyanate, react, cure, and hot press to obtain solvent-free phenolic lignin-based polyurethane elastomer.

[0017] Preferably, the lignin in step (1) is at least one of industrial lignin and ethanol-extracted industrial lignin; the industrial lignin is at least one of enzymatic hydrolysis lignin extracted from ethanol by fermentation of wood fibers, alkali lignin by-product of alkali pulping, and organic solvent lignin extracted from wood fibers; more preferably, it is at least one of alkali lignin and ethanol-extracted alkali lignin.

[0018] Preferably, the phenolic reagent in step (1) is at least one of phenol, catechol, resorcinol, hydroquinone, and pyrogallol; more preferably, it is at least one of catechol and phenol.

[0019] Preferably, the concentrated sulfuric acid in step (1) has a mass concentration of 96-98%, and the amount of concentrated sulfuric acid used is 8-12% of the lignin content; more preferably, it is 10%.

[0020] Preferably, the mass ratio of the phenolic reagent to lignin in step (1) is (1-3):1; more preferably, it is 3:1.

[0021] Preferably, the reaction temperature in step (1) is 110°C and the reaction time is 2 hours.

[0022] Preferably, the method for purifying the product in step (1) is as follows: the reaction product mixture is added to an acetone-water mixture to dissolve the product, then the product is precipitated with dilute sulfuric acid, filtered to obtain a filter cake, and the filter cake is dried to obtain phenolic lignin.

[0023] More preferably, the volume concentration of acetone in the acetone-water mixed solvent is 60-90%.

[0024] More preferably, the pH value of the dilute sulfuric acid is 1 to 2.

[0025] Preferably, the long-chain polyol in step (2) is at least one of polyethylene glycol (molecular weight 1000-6000), polytetrahydrofuran ether diol (molecular weight 1000-2000), polycarbonate diol (molecular weight 1000-4000), and polycaprolactone diol (molecular weight 1000-6000); more preferably, it is at least one of polyethylene glycol (molecular weight 1000-6000) and polytetrahydrofuran ether diol (molecular weight 1000-2000).

[0026] Preferably, the phenolic lignin in step (2) accounts for 5-50% of the mass fraction of the mixed alcohol dispersion; more preferably, it is 30%.

[0027] Preferably, the mixing in step (2) refers to blending at 90-120°C for 1-3 hours; more preferably, it refers to blending at 120°C for 1 hour.

[0028] Preferably, the dehydration in step (3) refers to vacuum dehydration at 105-120°C for 1-3 hours; more preferably, it is vacuum dehydration at 105°C for 1.5 hours.

[0029] Preferably, the reaction temperature in step (3) is 60-90°C and the reaction time is 0.5-4h; more preferably, the reaction temperature is 70°C and the reaction time is 0.5-2h.

[0030] Preferably, the isocyanate in step (3) is at least one of diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), 4,4'-dicyclohexylmethane diisocyanate (HMDI), polymethylene polyphenylene isocyanate (PMDI), and hexamethylene diisocyanate trimer; more preferably, it is polymethylene polyphenylene isocyanate.

[0031] Preferably, the molar ratio of the isocyanate group of the isocyanate in step (3) to the total hydroxyl group in the mixed alcohol dispersion is 0.8:1 to 1.4:1; more preferably, it is 1.2:1 to 1.3:1 or 0.9:1; most preferably, it is 1.2:1 and 0.9:1.

[0032] Preferably, the catalyst in step (3) is at least one of dibutyltin dilaurate, dibutyltin oxide, di(dodecyl sulfide)dibutyltin, bismuth isooctanoate, and bismuth neodecanoate; the mass of the catalyst accounts for 0.2 to 0.8% of the total mass of the mixed alcohol dispersion and the isocyanate; more preferably, it is 0.5%.

[0033] Preferably, the curing temperature in step (3) is 45-65°C and the curing time is 8-24h; more preferably, the curing temperature is 55°C and the curing time is 12h.

[0034] Preferably, the hot pressing temperature in step (3) is 160-170°C, the pressure is 10-12 MPa, and the time is 15-20 min; more preferably, the hot pressing temperature is 165-170°C, the pressure is 10 MPa, and the time is 20 min.

[0035] The present invention provides a solvent-free phenolic lignin-based polyurethane elastomer prepared by the above method.

[0036] The phenolic lignin prepared in this invention has a lower molecular weight and a significantly increased hydroxyl content, especially phenolic hydroxyl content, compared to untreated industrial lignin raw materials, resulting in higher reactivity. The lignin-based polyurethane elastomers prepared using phenolic lignin exhibit a higher chemical crosslinking network density and demonstrate excellent mechanical properties. Furthermore, thanks to the near 100% phenolic hydroxyl content of the phenolic lignin, the polyurethane elastomers construct a dual dynamic network composed of a phenolic carbamate bond network and a hydrogen-bonded crosslinking network. This dual dynamic network, especially the phenolic carbamate bond network, endows the lignin-based polyurethane elastomers with excellent reprocessing properties and photothermal self-healing properties.

[0037] Applications of the above-mentioned solvent-free phenolic lignin-based polyurethane elastomer.

[0038] More preferably, the solvent-free phenolic lignin-based polyurethane elastomer is used in smart wearables, automobile manufacturing, biomedical material preparation, and flexible drive applications.

[0039] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0040] 1. The phenolic hydroxyl content of the phenolic lignin prepared by this invention is as high as 99.8%, which is unprecedented in existing lignins. Moreover, the preparation process is simple and convenient and can be applied to various basic research.

[0041] 2. This invention utilizes a one-step method to synthesize high-performance solvent-free phenolic lignin-based polyurethane elastomers, avoiding the use of high-boiling-point or volatile toxic organic solvents. The synthesis process is green and simple, making it easier for industrial production.

[0042] 3. The solvent-free phenolic lignin-based polyurethane elastomer prepared by this invention is rich in dynamic phenolic hydroxyl-type urethane bonds. These phenolic urethane bonds are dissociative dynamic bonds, meaning they dissociate at high temperatures, significantly improving the mobility of polymer chain segments and enabling rapid polymer network reconstruction. This results in excellent reprocessing properties and photothermal self-healing properties, resolving the contradiction between the mechanical properties and dynamic mechanical properties of polyurethane elastomers. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0044] Unless otherwise specified in the embodiments of this invention, the conditions shall be performed according to conventional conditions or conditions recommended by the manufacturer. All raw materials and reagents used, unless otherwise specified, are commercially available conventional products.

[0045] Tensile test conditions: The thermoformed elastomer was cut into standard dumbbell-shaped strips with a length of 50 mm, a width of 4 mm, and a thickness of 0.5 mm. The tensile gauge length was selected as 20 mm. A CMT electronic universal testing machine was used, the test temperature was room temperature, and the tensile rate was 200 mm / min.

[0046] The preparation methods of phenolic lignin CAL and PAL are as follows: 60g of alkali lignin raw material (AKL) is mixed with 180g of catechol or phenol at 110℃ for 1h, 6g of concentrated sulfuric acid (mass concentration of 98%) is added, and the reaction is carried out for 2h. The product is then dissolved in an acetone aqueous solution (acetone volume concentration of 90%), and excess dilute sulfuric acid solution (pH 1.5) is added. The filter cake is obtained by filtration, dried in a vacuum oven at 55℃ for 24h, and then ground to obtain phenolic lignin powder CAL or PAL.

[0047] The preparation method of ethanol-extracted lignin is as follows: 1000g of alkali lignin raw material (AKL) is dissolved in 5L of anhydrous ethanol, mechanically stirred at 25℃ for 4h, filtered and separated, the filtrate is taken, the filtrate is concentrated by rotary evaporation, the concentrated liquid is evaporated and then placed in a vacuum oven to dry to obtain ethanol-extracted lignin powder AOH.

[0048] The preparation method of phenol-treated ethanol-extracted lignin (PAOH) is as follows: 60g of ethanol-extracted lignin (AOH) is mixed with 180g of phenol at 110℃ for 1h, then 6g of concentrated sulfuric acid (98% by mass) is added, and the reaction is carried out for 2h. The product is then dissolved in an acetone aqueous solution (90% by volume), and then excess dilute sulfuric acid solution (pH 1.5) is added. The filter cake is obtained by filtration and dried in a vacuum oven at 55℃ for 24h. After grinding, phenol-treated ethanol-extracted lignin powder (PAOH) is obtained.

[0049] GPC test conditions for lignin:

[0050] (1) Before testing, the lignin sample was dried in a vacuum oven at 55°C for 24 hours.

[0051] (2) Dissolve the dried lignin in chromatographically pure tetrahydrofuran (THF) to prepare a solution with a concentration of approximately 2 mg / mL. Then filter the prepared solution through a 0.45 μm organic phase filter membrane. Inject the filtrate into a gel permeation chromatograph with chromatographically pure THF as the mobile phase and a flow rate of 1.0 mL / min.

[0052] Table 1 GPC data before and after alkali lignin phenolization

[0053]

[0054] The molecular weights of AKL, CAL, PAL, AOH and PAOH were determined. Table 1 shows that the relative molecular weights and dispersibility coefficients of lignin CAL and PAL were significantly reduced after phenolation. The phenolation process involved depolymerization, catechol grafting and demethylation reactions.

[0055] NMR phosphorus spectroscopy test conditions for lignin:

[0056] (1) AKL, CAL, PAL, AOH, PAOH and consumables (small glass bottles, magnetic tubes, NMR tubes, tweezers, pipette tips, etc.) were dried in a vacuum oven at 55°C for 10 hours;

[0057] (2) Preparation of solvent A: Deuterated pyridine and deuterated chloroform are mixed in a volume ratio of 1.6:1 to prepare mixed solvent A;

[0058] (3) Preparation of internal standard solution (IS): Peel a 4mL glass bottle and weigh about 0.018g of norborneol (internal standard), and record the actual mass m1; after peeling, add about 0.005g of chromium acetylacetone (relaxant), and record the actual mass m2; after peeling the bottle with the cap on, add 1mL of solvent A, shake well and weigh to obtain the mass m3;

[0059] (4) Preparation of lignin NMR solution: Peel the vial, weigh approximately 0.03 g of the lignin to be tested, and record the actual mass m. L After adding the small magnetic slab, remove the tare while keeping the cap on, then add 0.1 mL of internal standard solution and record its actual mass m. IS Add 0.5 mL of solvent A and shake well. Stir magnetically for 12 hours to ensure complete dissolution. Finally, add 0.15 mL of phosphating reagent and the test can be performed.

[0060] Table 2. Alkali lignin before and after phenolation. 31 P NMR data

[0061]

[0062] The hydroxyl content of lignin before and after phenolation was determined. Table 2 shows that the hydroxyl content of lignin after catechol phenolation (CAL) was significantly reduced, while the phenolic hydroxyl content (99.8%) was significantly increased, and the total hydroxyl content was significantly higher than that of AKL. Whether using alkali lignin raw materials or lignin extracted with ethanol, the hydroxyl content of lignin was significantly reduced and the phenolic hydroxyl content significantly increased after phenol phenolation. This will be beneficial for preparing lignin-based polyurethane elastomers rich in dynamic phenolic carbamate bonds.

[0063] Example 1

[0064] (1) 60g of alkali lignin raw material (AKL) and 180g of catechol were mixed at 110℃ for 1h, 6g of concentrated sulfuric acid (98% by mass) was added, and the reaction was carried out for 2h. The product was then dissolved in an acetone aqueous solution (90% by volume), and then excess dilute sulfuric acid solution (pH 1.5) was added. The filter cake was obtained by filtration and dried in a vacuum oven at 55℃ for 24h. After grinding, catechol-phenolized lignin powder (CAL) was obtained.

[0065] (2) Mix 14 parts by mass of polyethylene glycol 1000 and 6 parts by mass of the above-mentioned phenolic lignin at 120°C and stir for 1 hour to obtain a dispersion of lignin and long-chain polyol polyethylene glycol 1000 with a CAL mass ratio of 30%.

[0066] (3) Eight parts by mass of the above dispersion were vacuum dehydrated at 105℃ for 1.5 h, then cooled to 70℃. 0.059 parts by mass of dibutyltin dilaurate and 3.82 parts by mass of polymethylene polyphenylene isocyanate (the molar ratio of isocyanate groups in the isocyanate to the total hydroxyl groups in the polyol and lignin was 1.4) were added. The mixture was stirred for 30 min, and the resulting product was placed in a vacuum oven and cured at 55℃ for 12 h. Using a flat vulcanizing apparatus, the sample was hot-pressed at 170℃ and 10 MPa for 20 min to obtain a solvent-free lignin-based polyurethane elastomer with excellent mechanical and dynamic mechanical properties. Tensile testing revealed that the sample had an elongation at break of 513.3%, a tensile strength of 34.4 MPa, a Young's modulus of 66.1 MPa, and a toughness of 83.2 MJ / m. 3 The elastic recovery rate is 99.0%.

[0067] Example 2

[0068] Step (1) is the same as in Example 1.

[0069] Step (2) is the same as in Example 1.

[0070] Step (3) is as follows: 8 parts by mass of a dispersion of lignin and polyol with a CAL mass ratio of 30% were vacuum dehydrated at 105℃ for 1.5h, then cooled to 70℃. 0.058 parts by mass of dibutyltin dilaurate and 3.55 parts by mass of polymethylene polyphenylene isocyanate (the molar ratio of isocyanate groups in the isocyanate to the total hydroxyl groups in the polyol and lignin was 1.3) were added. The mixture was stirred for 30min, and the resulting product was placed in a vacuum oven and cured at 55℃ for 12h. Using a flat vulcanizing apparatus, the sample was hot-pressed at 170℃ and 10MPa for 20min to obtain a solvent-free lignin-based polyurethane elastomer with excellent mechanical and dynamic mechanical properties. Tensile testing revealed that the sample had an elongation at break of 614.9%, a tensile strength of 38.0MPa, a Young's modulus of 17.4MPa, and a toughness of 96.3MJ / m. 3 The elastic recovery rate is 99.6%.

[0071] Example 3

[0072] Step (1) is the same as in Example 1.

[0073] Step (2) is the same as in Example 1.

[0074] Step (3) is as follows: 8 parts by mass of a dispersion of lignin and polyol with a CAL mass ratio of 30% were vacuum dehydrated at 105℃ for 1.5h, then cooled to 70℃. 0.056 parts by mass of dibutyltin dilaurate and 3.28 parts by mass of polymethylene polyphenylene isocyanate (the molar ratio of isocyanate groups in the isocyanate to the total hydroxyl groups in the polyol and lignin was 1.2) were added. The mixture was stirred for 30min, and the resulting product was placed in a vacuum oven and cured at 55℃ for 12h. Using a flat vulcanizing apparatus, the sample was hot-pressed at 170℃ and 10MPa for 20min to obtain a solvent-free lignin-based polyurethane elastomer with excellent mechanical and dynamic mechanical properties. Tensile testing revealed that the sample had an elongation at break of 812.0%, a tensile strength of 41.0MPa, a Young's modulus of 16.2MPa, and a toughness of 140.9MJ / m. 3 The elastic recovery rate is 99.4%.

[0075] Step (4) is as follows: After the tensile test is completed, the sample is cut into pieces, and hot pressing is continued. The above steps are repeated twice to obtain a reprocessed sample, and its mechanical properties are tested.

[0076] Step (5) is as follows: Place the sample in a 100°C thermo-oxidative aging chamber and perform mechanical property testing after aging for 3 days.

[0077] Table 3 Mechanical property parameters of polyurethane elastomer after multiple hot pressing in Example 3

[0078]

[0079] As shown in Table 3, after two hot-pressing cycles, the tensile strength, elongation at break, and toughness of the samples remained as high as 38.4 MPa, 901.4%, and 131.4 MJ / m, respectively. 3 The tensile strength, elongation at break, and toughness retention rates were 93.7%, 111.0%, and 93.3%, respectively. The sample exhibited excellent reprocessing properties, which is related to its abundant phenolic carbamate bonds. However, after three hot-pressing cycles, the mechanical properties of the sample decreased significantly, which was due to the aging of the PEG segments after repeated hot processing.

[0080] Table 4 Mechanical property parameters of polyurethane elastomer after three days of aging in Example 3

[0081]

[0082] As shown in Table 4, the mechanical properties of the samples remained essentially unchanged after three days of thermo-oxidative aging. After three days of aging, the tensile strength and elongation at break of the samples were 40.9 MPa and 704.1%, respectively, with retention rates as high as 99.8% and 86.7%, demonstrating excellent resistance to thermo-oxidative aging. This is attributed to the abundant phenolic hydroxyl groups in the lignin.

[0083] Example 4

[0084] Step (1) is the same as in Example 1.

[0085] Step (2) is the same as in Example 1.

[0086] Step (3) is as follows: 8 parts by mass of a dispersion of lignin and polyol with a CAL mass ratio of 30% were vacuum dehydrated at 105℃ for 1.5h, then cooled to 70℃. 0.055 parts by mass of dibutyltin dilaurate and 3.00 parts by mass of polymethylene polyphenylene isocyanate (the molar ratio of isocyanate groups in the isocyanate to the total hydroxyl groups in the polyol and lignin was 1.1) were added. The mixture was stirred for 30min, and the resulting product was placed in a vacuum oven and cured at 55℃ for 12h. Using a flat vulcanizing apparatus, the sample was hot-pressed at 170℃ and 10MPa for 20min to obtain a solvent-free lignin-based polyurethane elastomer with excellent mechanical and dynamic mechanical properties. Tensile testing revealed that the sample had an elongation at break of 850.5%, a tensile strength of 34.6MPa, a Young's modulus of 8.5MPa, and a toughness of 111.3MJ / m. 3 The elastic recovery rate is 99.4%.

[0087] Example 5

[0088] Step (1) is the same as in Example 1.

[0089] Step (2) is as follows: 14 parts by mass of polytetrahydrofuran ether diol 1000 and 6 parts by mass of phenolic lignin CAL from step (1) are mixed and stirred at 120°C for 1 hour to obtain a dispersion of lignin and long-chain polyol polytetrahydrofuran ether diol 1000 with a CAL mass ratio of 30%.

[0090] Step (3) is as follows: 8 parts by mass of a dispersion of lignin and polyol with a CAL mass ratio of 30% were vacuum dehydrated at 105℃ for 1.5h, then cooled to 70℃, and 0.056 parts by mass of dibutyltin dilaurate and 3.28 parts by mass of polymethylene polyphenylene isocyanate (the molar ratio of isocyanate groups in the isocyanate to the total hydroxyl groups in the polyol and lignin was 1.2) were added. The mixture was stirred and reacted for 2h. The resulting product was placed in a vacuum oven and cured at 55℃ for 12h. Using a flat vulcanizing apparatus, the sample was hot-pressed at 165℃ and 10MPa for 20min to obtain a solvent-free lignin-based polyurethane elastomer with excellent mechanical and dynamic mechanical properties. Tensile testing showed that the sample had an elongation at break of 167.0%, a tensile strength of 27.5MPa, a Young's modulus of 117.4MPa, and a toughness of 30.2MJ / m. 3 The elastic recovery rate was 91.0%.

[0091] Example 6

[0092] Step (1) is the same as in Example 1.

[0093] Step (2) is the same as in Example 5.

[0094] Step (3) is as follows: 8 parts by mass of a dispersion of lignin and polyol with a CAL mass ratio of 30% were vacuum dehydrated at 105℃ for 1.5h, then cooled to 70℃, and 0.055 parts by mass of dibutyltin dilaurate and 3.00 parts by mass of polymethylene polyphenylene isocyanate (the molar ratio of isocyanate groups in the isocyanate to the total hydroxyl groups in the polyol and lignin was 1.1) were added. The mixture was stirred and reacted for 2h. The resulting product was placed in a vacuum oven and cured at 55℃ for 12h. Using a flat vulcanizing apparatus, the sample was hot-pressed at 165℃ and 10MPa for 20min to obtain a solvent-free lignin-based polyurethane elastomer with excellent mechanical and dynamic mechanical properties. Tensile testing showed that the sample had an elongation at break of 293.0%, a tensile strength of 27.8MPa, a Young's modulus of 81.6MPa, and a toughness of 47.2MJ / m. 3 The elastic recovery rate was 89.8%.

[0095] Example 7

[0096] Step (1) is the same as in Example 1.

[0097] Step (2) is the same as in Example 5.

[0098] Step (3) is as follows: 8 parts by mass of a dispersion of lignin and polyol (CAL content 30%) were vacuum dehydrated at 105℃ for 1.5h, then cooled to 70℃. 0.054 parts by mass of dibutyltin dilaurate and 2.73 parts by mass of polymethylene polyphenylene isocyanate (the molar ratio of isocyanate groups in the isocyanate to the total hydroxyl groups in the polyol and lignin was 1.0) were added. The mixture was stirred for 2h, and the resulting product was placed in a vacuum oven and cured at 55℃ for 12h. Using a flat vulcanizing apparatus, the sample was hot-pressed at 165℃ and 10MPa for 20min to obtain a solvent-free lignin-based polyurethane elastomer with excellent mechanical and dynamic mechanical properties. Tensile testing revealed that the sample had an elongation at break of 390.3%, a tensile strength of 30.9MPa, a Young's modulus of 53.2MPa, and a toughness of 66.0 MJ / m. 3 The elastic recovery rate was 89.8%.

[0099] Step (4) is as follows: After the tensile test is completed, the sample is cut into pieces, and hot pressing is continued. The above process is repeated four times to obtain a reprocessed sample, and its mechanical properties are tested.

[0100] Table 5 Mechanical property parameters of polyurethane elastomer after multiple hot pressing in Example 7

[0101]

[0102]

[0103] As shown in Table 5, after two hot-pressing cycles, the tensile strength, elongation at break, and toughness of the samples remained as high as 35.3 MPa, 504.7%, and 91.3 MJ / m, respectively. 3 The tensile strength, elongation at break, and toughness retention rates were 114.2%, 129.3%, and 138.3%, respectively. Even after five hot pressing cycles, the toughness retention rate of the sample was still as high as 112.2%, demonstrating excellent reprocessing performance, which is related to its abundant phenolic carbamate bonds.

[0104] Example 8

[0105] Step (1) is the same as in Example 1.

[0106] Step (2) is the same as in Example 5.

[0107] Step (3) is as follows: 8 parts by mass of a dispersion of lignin and polyol with a CAL mass ratio of 30% were vacuum dehydrated at 105℃ for 1.5h, then cooled to 70℃. 0.052 parts by mass of dibutyltin dilaurate and 2.46 parts by mass of polymethylene polyphenylene isocyanate (the molar ratio of isocyanate groups in the isocyanate to the total hydroxyl groups in the polyol and lignin was 0.9) were added. The mixture was stirred and reacted for 2h. The resulting product was placed in a vacuum oven and cured at 55℃ for 12h. Using a flat vulcanizing apparatus, the sample was hot-pressed at 165℃ and 10MPa for 20min to obtain a solvent-free lignin-based polyurethane elastomer with excellent mechanical and dynamic mechanical properties. Tensile testing revealed that the sample had an elongation at break of 714.6%, a tensile strength of 44.6MPa, a Young's modulus of 26.0MPa, and a toughness of 148.0MJ / m. 3 The elastic recovery rate was 93.7%.

[0108] Step (4) is as follows: After the tensile test is completed, the sample is cut into pieces, and hot pressing is continued. The above process is repeated four times to obtain a reprocessed sample, and its mechanical properties are tested.

[0109] Step (5) is as follows: Place the sample in a 100°C thermo-oxidative aging chamber and perform mechanical property testing after aging for 3 days.

[0110] Step (6) is as follows: Cut the dumbbell-shaped spline in half, and then use a power of 0.58W / cm 2 The cross-section was irradiated with near-infrared laser for 30 minutes to allow it to heal, and the mechanical properties of the samples before and after photothermal self-healing were compared.

[0111] Table 6 Mechanical property parameters of polyurethane elastomer after multiple hot pressing in Example 8 (Table 6)

[0112]

[0113] As shown in Table 6, after two hot-pressing cycles, the tensile strength, elongation at break, and toughness of the samples remained as high as 43.7 MPa, 700.5%, and 139.7 MJ / m, respectively. 3 The tensile strength, elongation at break, and toughness retention rates were 98.0%, 98.0%, and 94.4%, respectively. Even after five hot pressing cycles, the toughness retention rate of the sample was still as high as 93.2%, demonstrating excellent reprocessing performance, which is related to its abundant phenolic carbamate bonds.

[0114] Table 7 Mechanical property parameters of polyurethane elastomer after three days of aging in Example 8

[0115]

[0116] As shown in Table 7, the mechanical properties of the samples remained essentially unchanged after three days of thermo-oxidative aging. After three days of aging, the tensile strength and elongation at break of the samples were 40.7 MPa and 730.5%, respectively, with retention rates as high as 91.3% and 102.2%, demonstrating excellent resistance to thermo-oxidative aging. This is attributed to the abundant phenolic hydroxyl groups in the lignin.

[0117] Table 8 Mechanical property parameters of polyurethane elastomer after photothermal self-healing in Example 8 for 30 min

[0118]

[0119] As shown in Table 8, the power of the cut sample was 0.58 W / cm. 2 After irradiating the cross-section with near-infrared laser for 30 minutes, the tensile strength and elongation at break were 36.3 MPa and 631.6%, respectively, and the photothermal self-healing efficiency was as high as 81.4% and 88.4%, respectively, demonstrating excellent photothermal self-healing performance. Therefore, the polyurethane elastomer prepared in Example 8 achieves a balance between mechanical properties and dynamic mechanical properties, while also exhibiting excellent resistance to thermo-oxidative aging.

[0120] Example 9

[0121] Step (1) is the same as in Example 1.

[0122] Step (2) is the same as in Example 5.

[0123] Step (3) is as follows: 8 parts by mass of a dispersion of lignin and polyol with a CAL mass ratio of 30% were vacuum dehydrated at 105℃ for 1.5h, then cooled to 70℃, and 0.051 parts by mass of dibutyltin dilaurate and 2.18 parts by mass of polymethylene polyphenylene isocyanate (the molar ratio of isocyanate groups in the isocyanate to the total hydroxyl groups in the polyol and lignin was 0.8) were added. The mixture was stirred and reacted for 2h. The resulting product was placed in a vacuum oven and cured at 55℃ for 12h. Using a flat vulcanizing apparatus, the sample was hot-pressed at 165℃ and 10MPa for 20min to obtain a solvent-free lignin-based polyurethane elastomer with excellent mechanical and dynamic mechanical properties. Tensile testing showed that the sample had an elongation at break of 713.8%, a tensile strength of 32.4MPa, a Young's modulus of 11.2MPa, and a toughness of 91.7MJ / m. 3 The elastic recovery rate was 94.4%.

[0124] Example 10

[0125] Step (1) is as follows: 60g of alkali lignin raw material (AKL) and 180g of phenol are mixed at 110℃ for 1h, 6g of concentrated sulfuric acid (mass concentration of 98%) is added, and after reacting for 2h, the product is dissolved in an acetone aqueous solution (acetone volume concentration of 90%), and then excess dilute sulfuric acid solution (pH of 1.5) is added. The filter cake is obtained by filtration, and the filter cake is dried in a vacuum oven at 55℃ for 24h. After grinding, phenol-phenolized lignin powder (PAL) is obtained.

[0126] Step (2) is as follows: 14 parts by mass of polytetrahydrofuran ether diol 1000 and 6 parts by mass of phenolic lignin PAL from step (1) are mixed and stirred at 120°C for 1 hour to obtain a dispersion of lignin and long-chain polyol polytetrahydrofuran ether diol 1000 with a phenolic lignin PAL mass ratio of 30%.

[0127] Step (3) is as follows: 8 parts by mass of a dispersion of lignin and polyol (30% by mass of PAL) were vacuum dehydrated at 105℃ for 1.5h, then cooled to 70℃. 0.051 parts by mass of dibutyltin dilaurate and 2.29 parts by mass of polymethylene polyphenylene isocyanate (the molar ratio of isocyanate groups in the isocyanate to the total hydroxyl groups in the polyol and lignin was 0.9) were added. The mixture was stirred for 2h, and the resulting product was placed in a vacuum oven and cured at 55℃ for 12h. Using a flat vulcanizing apparatus, the sample was hot-pressed at 165℃ and 10MPa for 20min to obtain a solvent-free lignin-based polyurethane elastomer with excellent mechanical and dynamic mechanical properties. Tensile testing revealed that the sample had an elongation at break of 640.8%, a tensile strength of 37.1MPa, a Young's modulus of 13.1MPa, and a toughness of 90.7MJ / m. 3 The elastic recovery rate was 92.4%.

[0128] Step (4) is as follows: After the tensile test is completed, the sample is cut into pieces, and then hot-pressed to obtain a reprocessed sample, and its mechanical properties are tested.

[0129] Table 9 Mechanical property parameters of polyurethane elastomer after multiple hot pressing in Example 10

[0130]

[0131] As shown in Table 9, the mechanical properties of the samples remained essentially unchanged after two hot-pressing processes, with tensile strength, elongation at break, and toughness still reaching 35.6 MPa, 719.4%, and 101.1 MJ / m, respectively. 3 The tensile strength, elongation at break, and toughness retention rates were 96.0%, 112.3%, and 114.5%, respectively, demonstrating excellent reprocessing properties, which is related to its abundant phenolic carbamate bonds.

[0132] Example 11

[0133] Step (1) is as follows: 60g of ethanol-extracted lignin (AOH) is mixed with 180g of phenol at 110℃ for 1h, 6g of concentrated sulfuric acid (98% by mass) is added, and the reaction is carried out for 2h. The product is then dissolved in an acetone aqueous solution (90% by volume) and excess dilute sulfuric acid solution (pH 1.5) is added. The filter cake is obtained by filtration and dried in a vacuum oven at 55℃ for 24h. After grinding, phenolic ethanol-extracted lignin powder PAOH is obtained.

[0134] Step (2) is as follows: Mix 14 parts by mass of polytetrahydrofuran ether diol 1000 and 6 parts by mass of phenolic ethanol-extracted lignin PAOH from step (1) at 120°C and stir for 1 hour to obtain a dispersion of lignin and long-chain polyol polytetrahydrofuran ether diol 1000 with a phenolic ethanol-extracted lignin PAOH mass ratio of 30%.

[0135] Step (3) is as follows: 8 parts by mass of a dispersion of lignin and polyol (PAOH content 30%) were vacuum dehydrated at 105℃ for 1.5h, then cooled to 70℃. 0.052 parts by mass of dibutyltin dilaurate and 2.43 parts by mass of polymethylene polyphenylene isocyanate (the molar ratio of isocyanate groups in the isocyanate to the total hydroxyl groups in the polyol and lignin was 0.9) were added. The mixture was stirred for 2h, and the resulting product was placed in a vacuum oven and cured at 55℃ for 12h. Using a flat vulcanizing apparatus, the sample was hot-pressed at 165℃ and 10MPa for 20min to obtain a solvent-free lignin-based polyurethane elastomer with excellent mechanical and dynamic mechanical properties. Tensile testing revealed that the sample had an elongation at break of 762.2%, a tensile strength of 39.4MPa, a Young's modulus of 7.6MPa, and a toughness of 89.3MJ / m. 3 The elastic recovery rate was 95.4%.

[0136] Step (4) is the same as in Example 10.

[0137] Table 10 Mechanical property parameters of polyurethane elastomer after multiple hot pressing in Example 11

[0138]

[0139] As shown in Table 10, the mechanical properties of the samples remained basically unchanged after two hot-pressing processes, with tensile strength, elongation at break, and toughness still reaching 36.3 MPa, 866.4%, and 111.2 MJ / m, respectively. 3 The tensile strength, elongation at break, and toughness retention rates were 92.1%, 113.7%, and 124.5%, respectively, demonstrating excellent reprocessing properties, which is related to its abundant phenolic carbamate bonds.

[0140] Comparative Example 1

[0141] Step (1) is as follows: Mix 14 parts by mass of polyethylene glycol 1000 and 6 parts by mass of alkali lignin raw material AKL at 120°C for 1 hour to obtain a dispersion of lignin and long-chain polyol polyethylene glycol 1000 with AKL mass ratio of 30%.

[0142] Step (2) is as follows: 8 parts by mass of a dispersion of lignin and polyol (AKL, 30% by mass) were vacuum dehydrated at 105℃ for 1.5h, then cooled to 70℃. 0.054 parts by mass of dibutyltin dilaurate and 2.71 parts by mass of polymethylene polyphenylene isocyanate (the molar ratio of isocyanate groups in the isocyanate to the total hydroxyl groups in the polyol and lignin was 1.2) were added. The mixture was stirred for 30min, and the resulting product was placed in a vacuum oven and cured at 55℃ for 12h. Using a flat vulcanizing apparatus, the sample was hot-pressed at 170℃ and 10MPa for 20min to obtain a solvent-free lignin-based polyurethane elastomer. Tensile testing revealed that the sample had an elongation at break of 512.7%, a tensile strength of 14.4MPa, a Young's modulus of 7.1MPa, and a toughness of 30.4MJ / m. 3 The elastic recovery rate is 99.0%.

[0143] Step (3) is as follows: After the tensile test is completed, the sample is cut into pieces, and then hot-pressed to obtain a reprocessed sample, and its mechanical properties are tested.

[0144] Step (4) is as follows: Place the sample in a 100°C thermo-oxidative aging chamber and perform mechanical property testing after aging for 3 days.

[0145] Table 11 Mechanical property parameters of polyurethane elastomers after multiple hot pressing in Comparative Example 1 and Example 3

[0146]

[0147] Table 11 shows the mechanical properties of the polyurethane elastomers prepared by AKL (Comparative Example 1) and CAL (Example 3) after multiple hot pressings. As can be seen from the table, the elastomer prepared by CAL has significantly better mechanical properties than the elastomer prepared by AKL. This is because CAL has a low molecular weight, high hydroxyl content, and a high crosslinking density. The elastomer prepared by Comparative Example 1, after two hot pressings, has a tensile strength, elongation at break, and toughness of 6.98 MPa, 376.1%, and 10.7 MJ / m, respectively. 3 The tensile strength, elongation at break, and toughness retention were 48.5%, 73.4%, and 35.2%, respectively, showing a significant decrease in mechanical properties. Its reprocessing performance was significantly worse than that of Example 3, which is because the elastomer prepared by AKL has fewer dynamic phenolic urethane bonds.

[0148] Table 12 Mechanical property parameters of polyurethane elastomers in Comparative Example 1 and Example 3 after three days of aging.

[0149]

[0150] As shown in Table 12, the elastomer prepared in Comparative Example 1 exhibited a tensile strength and elongation at break of 18.7 MPa and 392.2% respectively after three days of thermo-oxidative aging, with retention rates as high as 129.9% and 76.5%, demonstrating excellent resistance to thermo-oxidative aging. Meanwhile, the elastomer prepared in Example 3 also exhibited excellent resistance to thermo-oxidative aging. This is because, under the one-step solvent-free synthesis conditions, some phenolic hydroxyl groups in lignin, especially AKL, did not participate in the reaction. During the aging process, these unreacted phenolic hydroxyl groups, on the one hand, slowed down the erosion of the sample by heat and oxygen, and on the other hand, may have undergone transesterification with urethane bonds.

[0151] Comparative Example 2

[0152] Step (1) is as follows: Mix 14 parts by mass of polytetrahydrofuran ether diol 1000 and 6 parts by mass of alkali lignin lignin raw material AKL at 120°C and stir for 1 hour to obtain a dispersion of lignin and long-chain polyol polytetrahydrofuran ether diol 1000 with AKL mass ratio of 30%.

[0153] Step (2) is as follows: 8 parts by mass of a dispersion of lignin and polyol (AKL, 30% by mass) were vacuum dehydrated at 105℃ for 1.5h, then cooled to 70℃. 0.050 parts by mass of dibutyltin dilaurate and 2.04 parts by mass of polymethylene polyphenylene isocyanate (the molar ratio of isocyanate groups in the isocyanate to the total hydroxyl groups in the polyol and lignin was 0.9) were added. The mixture was stirred for 2h, and the resulting product was placed in a vacuum oven and cured at 55℃ for 12h. Using a flat vulcanizing apparatus, the sample was hot-pressed at 165℃ and 10MPa for 20min to obtain a solvent-free lignin-based polyurethane elastomer. Tensile testing revealed that the sample had an elongation at break of 1064.8%, a tensile strength of 12.2MPa, a Young's modulus of 6.3MPa, and a toughness of 63.5MJ / m. 3 The elastic recovery rate was 97.7%.

[0154] Step (3) is the same as Comparative Example 1.

[0155] Step (4) is the same as Comparative Example 1.

[0156] Step (5) is as follows: Cut the dumbbell-shaped spline in half, and then use a power of 0.58W / cm 2 The cross-section was irradiated with near-infrared laser for 30 minutes to allow it to heal, and the mechanical properties of the samples before and after photothermal self-healing were compared.

[0157] Table 13 Mechanical property parameters of polyurethane elastomers after multiple hot pressing in Comparative Example 2 and Example 8

[0158]

[0159]

[0160] Table 13 shows the mechanical properties of the polyurethane elastomers prepared by AKL (Comparative Example 2) and CAL (Example 8) after multiple hot pressings. As can be seen from the table, the elastomer prepared by CAL has significantly better mechanical properties than the elastomer prepared by AKL. This is because CAL has a low molecular weight, high hydroxyl content, and a high crosslinking density. The elastomer prepared by Comparative Example 2, after two hot pressings, has a tensile strength, elongation at break, and toughness of 7.98 MPa, 991.7%, and 41.8 MJ / m, respectively. 3 The tensile strength, elongation at break, and toughness retention were 65.4%, 93.1%, and 65.8%, respectively, showing a significant decrease in mechanical properties. Its reprocessing performance was significantly worse than that of Example 8, which is because the elastomer prepared by AKL has fewer dynamic phenolic urethane bonds.

[0161] Table 14 Mechanical property parameters of polyurethane elastomers in Comparative Example 2 and Example 8 after three days of aging.

[0162]

[0163] As shown in Table 14, the elastomer prepared in Comparative Example 2 exhibited a tensile strength and elongation at break of 21.6 MPa and 866.0% respectively after three days of thermo-oxidative aging, with retention rates as high as 177.0% and 81.3%, demonstrating excellent resistance to thermo-oxidative aging. Meanwhile, the elastomer prepared in Example 8 also exhibited excellent resistance to thermo-oxidative aging. This is because, under the one-step solvent-free synthesis conditions, some phenolic hydroxyl groups in lignin, especially AKL, did not participate in the reaction. During the aging process, these unreacted phenolic hydroxyl groups, on the one hand, slowed down the erosion of the sample by heat and oxygen, and on the other hand, may have undergone transesterification with urethane bonds.

[0164] Table 15 Mechanical property parameters of polyurethane elastomers in Comparative Example 2 and Example 8 after 30 min of photothermal self-healing.

[0165]

[0166] As can be seen from Table 15, the elastomer prepared in Comparative Example 2, after being cut, was subjected to a power of 0.58 W / cm². 2 After irradiating the cross-section with near-infrared laser for 30 minutes, its tensile strength and elongation at break were 7.4 MPa and 990.6%, respectively, and its photothermal self-healing efficiency was 60.7% and 93.0%, respectively. Its photothermal self-healing performance was significantly worse than that of Example 8. The reason is that the elastomer prepared by AKL has fewer dynamic phenolic urethane bonds.

[0167] Comparative Example 3

[0168] Step (1) is as follows: 14 parts by mass of polytetrahydrofuran ether diol 1000 and 6 parts by mass of ethanol are mixed and stirred at 120°C for 1 hour to obtain a dispersion of lignin and long-chain polyol polytetrahydrofuran ether diol 1000 with an AOH mass ratio of 30%.

[0169] Step (2) is as follows: 8 parts by mass of a dispersion of lignin and polyol (30% by mass of AOH) are vacuum dehydrated at 105℃ for 1.5h, then cooled to 70℃. 0.052 parts by mass of dibutyltin dilaurate and 2.46 parts by mass of polymethylene polyphenylene isocyanate (the molar ratio of isocyanate groups in the isocyanate to the total hydroxyl groups in the polyol and lignin is 0.9) are added. The mixture is stirred for 2h, and the resulting product is placed in a vacuum oven and cured at 55℃ for 12h. Using a flat vulcanizing apparatus, the sample is hot-pressed at 165℃ and 10MPa for 20min to obtain a solvent-free lignin-based polyurethane elastomer. Tensile testing revealed that the sample had an elongation at break of 777.7%, a tensile strength of 37.2MPa, a Young's modulus of 15.1MPa, and a toughness of 113.5MJ / m. 3 The elastic recovery rate was 96.1%.

[0170] Step (3) is the same as Comparative Example 1.

[0171] Step (4) is as follows: Cut the dumbbell-shaped spline in half, and then use a power of 0.58W / cm 2 The cross-section was irradiated with near-infrared laser for 30 minutes to allow it to heal, and the mechanical properties of the samples before and after photothermal self-healing were compared.

[0172] Table 16 Mechanical property parameters of polyurethane elastomers after multiple hot pressing in Comparative Example 3 and Example 8

[0173]

[0174] As shown in Table 16, the tensile strength, elongation at break, and toughness of the elastomer prepared in Comparative Example 3 after two hot pressings are 11.7 MPa, 439.4%, and 27.5 MJ / m, respectively. 3 The tensile strength, elongation at break, and toughness retention rates were 31.5%, 56.5%, and 24.2%, respectively, indicating a significant decrease in mechanical properties. Although the total hydroxyl content of AOH was the same as that of CAL, the reprocessing performance of Comparative Example 3 prepared from AOH was significantly worse than that of Example 8 prepared from CAL. This is because the phenolic hydroxyl content of AOH was significantly lower than that of CAL.

[0175] Table 17 Mechanical property parameters of polyurethane elastomers in Comparative Example 3 and Example 8 after 30 min of photothermal self-healing.

[0176]

[0177] As shown in Table 17, the elastomer prepared in Comparative Example 3 has a cutting power of 0.58 W / cm. 2 After irradiating the cross-section with near-infrared laser for 30 minutes, its tensile strength and elongation at break were 16.2 MPa and 683.8%, respectively, and its photothermal self-healing efficiency was 43.5% and 87.9%, respectively. Its photothermal self-healing performance was significantly worse than that of Example 8. The reason is that the elastomer prepared by AOH has fewer dynamic phenolic urethane bonds.

[0178] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A process for the preparation of a solvent-free phenolated lignin based polyurethane elastomer characterized in that, The method comprises the following steps: The lignin is mixed with a phenolation reagent at 110-140 ℃, concentrated sulfuric acid is added, and the mixture is reacted at 90-140 ℃ for 2-4 h. After the reaction is completed, the product is purified to obtain phenolated lignin. The long-chain polyol is mixed with the phenolated lignin obtained in step (1) to obtain a mixed alcohol dispersion liquid. After the mixed alcohol dispersion liquid obtained in step (2) is dehydrated, a catalyst and isocyanate are added, and the mixture is reacted, solidified, and hot-pressed to obtain a solvent-free phenolated lignin-based polyurethane elastomer. In step (1), the mass ratio of the phenolation reagent to lignin is (1-3):

1. In step (1), the lignin is at least one of industrial lignin and industrial lignin extracted by ethanol; the industrial lignin is at least one of enzymatic hydrolysis lignin extracted by fermentation of lignocellulose to produce ethanol, by-product alkali lignin of alkali pulping, and organic solvent lignin extracted from lignocellulose. In step (1), the phenolation reagent is at least one of phenol, o-dihydroxybenzene, m-dihydroxybenzene, p-dihydroxybenzene, and o-trihydroxybenzene. In step (2), the mass fraction of the phenolated lignin in the mixed alcohol dispersion liquid is 5%-50%. In step (3), the molar ratio of isocyanate groups in the isocyanate to total hydroxyl groups in the mixed alcohol dispersion liquid is 0.8:1-1.4:

1.

2. The method for preparing a solvent-free phenolated lignin-based polyurethane elastomer according to claim 1, wherein In step (2), the long-chain polyol is at least one of polyethylene glycol with a molecular weight of 1000-6000, polytetrahydrofuran ether diol with a molecular weight of 1000-2000, polycarbonate diol with a molecular weight of 1000-4000, and polycaprolactone diol with a molecular weight of 1000-6000. In step (3), the isocyanate is at least one of diphenylmethane diisocyanate, hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, poly-methylene polyphenylene isocyanate, and hexamethylene diisocyanate trimer.

3. The process for the preparation of a solvent-free phenolated lignin based polyurethane elastomer as claimed in claim 2, wherein, In step (3), the reaction temperature is 60-90 ℃, and the reaction time is 0.5-4 h. In step (3), the solidification temperature is 45-65 ℃, and the solidification time is 8-24 h. In step (3), the hot-pressing temperature is 160-170 ℃, the hot-pressing pressure is 10-12 MPa, and the hot-pressing time is 15-20 min.

4. The process for the preparation of a solvent-free phenolated lignin based polyurethane elastomer as claimed in claim 2, wherein, In step (1), the mass concentration of the concentrated sulfuric acid is 96-98%, and the amount of the concentrated sulfuric acid is 8-12% of the mass of the lignin. In step (3), the catalyst is at least one of dibutyltin dilaurate, dibutyltin oxide, bis(dodecylthio)dibutyltin, bismuth isooctoate, and bismuth neodecanoate; the mass of the catalyst accounts for 0.2-0.8% of the total mass of the mixed alcohol dispersion liquid and the isocyanate.

5. The process for the preparation of a solvent-free phenolated lignin based polyurethane elastomer as claimed in claim 2, wherein, In step (1), the mass ratio of the phenolation reagent to lignin is 3:

1. In step (1), the lignin is at least one of alkali lignin and ethanol-extracted alkali lignin. In step (1), the phenolation reagent is at least one of o-dihydroxybenzene and phenol. In step (1), the reaction temperature is 110 ℃, and the reaction time is 2 h.

6. The process for the preparation of a solvent-free phenolated lignin based polyurethane elastomer as claimed in claim 2, wherein, The long-chain polyol in step (2) is at least one of polyethylene glycol with a molecular weight of 1000-6000 and polytetrahydrofuran ether diol with a molecular weight of 1000-2000; The mass fraction of the phenolated lignin in the mixed alcohol dispersion liquid in step (2) is 30%; The reaction temperature in step (3) is 70 ℃, and the time is 0.5-2 h; The molar ratio of isocyanate isocyanate groups to total hydroxyl groups in the mixed alcohol dispersion liquid in step (3) is 1.2:1-1.3:1 or 0.9:1; The isocyanate in step (3) is poly-methylene-poly-phenylene isocyanate.

7. The process for the preparation of a solvent-free phenolated lignin based polyurethane elastomer as claimed in claim 1, wherein, The method for purifying the product in step (1) is: adding the reaction product mixture into an acetone-water mixed solvent to dissolve the product, then precipitating the product with dilute sulfuric acid, filtering to obtain a filter cake, drying the filter cake, and obtaining phenolated lignin; The volume concentration of acetone in the acetone-water mixed solvent is 60-90%; The pH value of the dilute sulfuric acid is 1-2; The mixing in step (2) is mixing at 90-120 ℃ for 1-3 h; The dehydration in step (3) is vacuum dehydration at 105-120 ℃ for 1-3 h.

8. A solvent-free phenolated lignin-based polyurethane elastomer prepared by the preparation method in any one of claims 1-7.

9. The use of the solvent-free phenolated lignin-based polyurethane elastomer in claim 8 in the fields of smart wear, automobile manufacturing, biological medical material preparation, and flexible driving.

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