High-strength polyurethane based on carbon dioxide polycondensation and method for preparing the same

Abstract

The application belongs to the technical field of polyurethane materials, and particularly relates to a kind of high-strength polyurethane based on carbon dioxide polycondensation and a preparation method thereof. In terms of mole fraction, the composition raw materials of the high-strength polyurethane include 100 parts of diisocyanate; 0.05-0.5 parts of catalyst; and 100 parts of the sum of polycarbonate diol and chain extender, wherein the chain extender is 25-50 parts. The polyurethane soft segment provided by the application is based on direct carbon dioxide polycondensation instead of carbonate monomer, which greatly improves the utilization rate of carbon dioxide and is helpful to the sustainable development of the polyurethane material industry. Meanwhile, the chain extender used in the polyurethane contains adjustable high-density hydrogen bonds, so that the elastomer material has excellent mechanical properties, high strength and high toughness, and the tensile strength can reach more than 80 MPa; the chain extender is derived from sustainable resources, and the structure can be flexibly controlled. The polyurethane preparation method provided by the application is simple to operate, suitable for large-scale continuous line production, and has good implementation value and market prospect.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane materials technology, specifically relating to a class of high-strength polyurethanes based on carbon dioxide condensation and their preparation methods. Background Technology

[0002] Polyurethanes are a large class of polymers (-NHCOO-) whose main chain contains urethane bonds, formed from isocyanates and polyols. These polymers exhibit diverse structures and compositions. Polyurethanes were discovered in 1937 through the addition reaction of polyester diols and diisocyanates. Due to their simple preparation process, highly reactive raw materials, and widely tunable mechanical properties, polyurethane materials are widely favored in the market. However, currently, the polyurethane industry relies heavily on petroleum resources for raw materials, limiting its supply to non-renewable resources and necessitating the search for alternative sources.

[0003] One of the most important performance indicators for evaluating polyurethane materials is their mechanical properties, which often depend on the combined effect of soft and hard segments. Soft segments refer to the long-chain alcohol groups in the polyurethane molecular chain; their presence gives the polyurethane material flexibility and extensibility, improving its tear resistance and abrasion resistance. Hard segments refer to the diisocyanate or diol groups in the isocyanate molecular chain, determining the polyurethane's hardness, strength, and abrasion resistance, and increasing its chemical stability and mechanical properties. In recent years, there has been widespread attention to improving the environmental friendliness of polyurethane materials by introducing bio-based monomers, but the final mechanical properties of polyurethane materials have often been overlooked, affecting their practicality. Therefore, focusing not only on the greenness of monomer sources but also on improving the mechanical strength of polyurethane materials is an effective way to achieve sustainable development.

[0004] Carbon dioxide, a non-toxic, inexpensive, and widely available renewable resource, has gradually become a highly sought-after chemical raw material. Polycarbonate diols can be prepared by direct polymerization of carbon dioxide and diols. Their flexible chain segments are easily scalable, making them ideal for the soft segments in polyurethane synthesis. Therefore, actively exploring and developing the direct condensation polymerization of carbon dioxide and diols to produce polycarbonate diol soft segments and then preparing high-performance polyurethane materials is an ideal approach that aligns with the trend of green and low-carbon development.

[0005] Patent application CN202110958430.4 discloses a polycarbonate-type polyurethane elastomer sealing material, its preparation method, and its application. PCDL is reacted with toluene diisocyanate and the chain extender trimethylolpropane to synthesize a polycarbonate-type polyurethane elastomer sealing material that exhibits superior mechanical properties, hydrolysis resistance, heat resistance, oxidation resistance, abrasion resistance, and chemical resistance compared to traditional polyurethane materials. Patent application CN202310780358.X discloses a polyurethane rubber and its preparation method, using polycarbonate-type polyurethane instead of traditional polyester, polyether, or polycaprolactone-type polyurethane, resulting in better rubber performance. Although the polycarbonate diol soft segments used in the above-mentioned existing solutions are obtained by polymerizing DMC or DPC with diols, they still suffer from low carbon dioxide utilization and low bio-based content. Therefore, developing a high-strength polyurethane based on carbon dioxide condensation polymerization to improve the utilization rate of biomass resources is an urgent technical problem to be solved. Summary of the Invention

[0006] To address the technical problems of low carbon dioxide utilization and low bio-based content in existing polycarbonate-type polyurethane materials, this invention provides a high-strength polyurethane based on carbon dioxide condensation and its preparation method. This method is simple and can significantly improve the utilization rate of carbon dioxide and biomass resources.

[0007] In a first aspect, the present invention provides a class of high-strength polyurethanes based on carbon dioxide polycondensation, comprising the following raw material components in molar amounts:

[0008] The sum of polycarbonate diol and chain extender is 100 parts;

[0009] 100 parts of diisocyanate;

[0010] Catalyst 0.05-0.5 parts;

[0011] The chain extender is 25-50 parts;

[0012] The chain extender has the following structure:

[0013] or

[0014] Where n = 0, 1.

[0015] Furthermore, the diisocyanate is selected from at least one of hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), 4,4'-dicyclohexylmethane diisocyanate (HMDI), isophorone diisocyanate (IPDI), lysine diisocyanate, 1,4-cyclohexane diisocyanate, and toluene diisocyanate (TDI), preferably IPDI.

[0016] Furthermore, the catalyst is selected from at least one of dibutyltin dilaurate, stannous octoate, stannous isooctanoate, phosphoric acid, oleic acid, adipic acid, and triethylamine, preferably dibutyltin dilaurate.

[0017] Furthermore, the polycarbonate diol has a number-average molecular weight of 800-2000 g / mol, preferably 2000 g / mol.

[0018] Furthermore, the molar ratio of the polycarbonate diol to the chain extender is (1-3):1, preferably 1:1.

[0019] Secondly, the present invention provides a method for preparing a type of high-strength polyurethane based on carbon dioxide polycondensation, comprising the following steps:

[0020] S1. Add polycarbonate diol to the reactor and dehydrate it under vacuum heating;

[0021] Under S2 and inert gas protection, diisocyanate, catalyst, and solvent are added to react and a prepolymer is obtained.

[0022] S3. Under inert gas protection, the chain extender is mixed with the solvent and then added to the reactor to carry out the chain extension reaction; after casting, curing and drying, the high-strength polyurethane based on carbon dioxide polycondensation is obtained.

[0023] Furthermore, the solvent is selected from at least one of toluene, xylene, acetone, dichloromethane, chloroform, tetrahydrofuran, acetonitrile, ethyl acetate, butyl acetate, 1,4-dioxane, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide, preferably N,N-dimethylformamide or N,N-dimethylacetamide.

[0024] Furthermore, the amount of solvent added in step S2 is 3-10 times the amount of diisocyanate; the amount of solvent added in step S3 is 30-100 times the amount of diisocyanate.

[0025] Furthermore, in step S1, the vacuum degree is less than 200 Pa, the heating temperature is 90-120℃, and the dehydration time is 1-6 h, preferably 2-3 h.

[0026] Furthermore, in step S2, the heating temperature is 80-100℃ and the prepolymerization time is 1-3h.

[0027] Furthermore, in step S3, the heating temperature of the chain extension reaction is 50-100℃, and the reaction time is 4-12h; the casting and curing temperature is 80-120℃, and the casting and curing time is 24-48h.

[0028] Furthermore, the polycarbonate diol has a number-average molecular weight of 800-2000 g / mol.

[0029] Furthermore, the polycarbonate diol is prepared by the following method:

[0030] R1. Dehydration polycondensation of carbon dioxide and aliphatic diols: Aliphatic diols, organic base catalysts, and carbodiimide compounds are put into a pressure vessel and heated to 130°C in a carbon dioxide atmosphere at 1 MPa for dehydration polycondensation. The reaction is carried out for 6-24 hours and then post-processed to obtain oligocarbonates.

[0031] R2. Melt polycondensation of oligocarbonate: The oligocarbonate obtained in step R1 and the polycondensation catalyst are placed in a reactor and heated to 160-230°C under an inert gas atmosphere and mechanical stirring. Then, the pressure is reduced to 50-200Pa for melt polycondensation. The reaction is carried out for 0.5-1h to obtain the polycarbonate diol.

[0032] Furthermore, the structural formula of the aliphatic diol is as follows:

[0033]

[0034] Where n = 2, 3, 4, 5.

[0035] Further, the organic base catalyst is selected from at least one of N,N,N',N'-tetramethylethylenediamine (TMEDA), 4-dimethylaminopyridine (DMAP), 4-pyrrolylpyridine (PPY), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5,7-triazabicyclo[4.4.0]decen-5-ene (TBD), 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), 1,1,3,3-tetramethylguanidine (TMG), and 2-tert-butyl-1,1,3,3-tetramethylguanidine (t-Bu-TMG).

[0036] Furthermore, the condensing agent is selected from at least one of dicyclohexylcarbodiimide and diisopropylcarbodiimide.

[0037] Furthermore, the polycondensation catalyst is at least one selected from sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, lithium acetylacetonate, zirconium acetylacetonate, and cesium carbonate.

[0038] Furthermore, the mass ratio of the low molecular weight prepolymer to the polycondensation catalyst is 1:(0.001-0.005).

[0039] Furthermore, the post-treatment method for the low molecular weight prepolymer in step R1 is as follows: add an appropriate amount of solvent to fully dissolve the low molecular weight prepolymer at -20 to 0°C, filter, and acid-wash, dry, rotary evaporate, and vacuum dry the filtrate.

[0040] Thirdly, the present invention provides a method for preparing a class of high-strength polyurethane bio-based chain extenders, comprising the following steps:

[0041] T1. Add β-alanine methyl ester hydrochloride, acid-binding agent and first solvent to the reactor, slowly add diacyl chloride solution between -10 and 10℃, and reflux the reaction between 25 and 60℃ to generate the corresponding dicarboxylic acid dimethyl ester.

[0042] T2. Add the dimethyl dicarboxylic acid hydrate, hydrazine hydrate, and second solvent prepared in step T1 to the reactor and reflux at 70-100℃ to generate the corresponding diacylhydrazine. After separation and purification, the bio-based chain extender is obtained.

[0043] Furthermore, the diacyl chloride is selected from at least one of oxaloyl chloride, succinyl chloride, and 2,5-furandicarboxyl chloride.

[0044] Further, the molar ratio of β-alanine methyl ester hydrochloride, diacyl chloride, and acid-binding agent in step T1 is 2:(0.8-1.2):(3.6-4.4).

[0045] Furthermore, the molar ratio of dimethyl dicarboxylic acid and hydrazine hydrate in step T2 is 1:(2.5-4).

[0046] Furthermore, the acid-binding agent mentioned in step T1 is selected from at least one of triethylamine and pyridine.

[0047] Further, the first solvent in step T1 is selected from at least one of dichloromethane, chloroform, tetrahydrofuran, acetonitrile, acetone, methyl tert-butyl ether, and 1,4-dioxane, preferably dichloromethane or tetrahydrofuran.

[0048] Further, the second solvent mentioned in step T2 is selected from at least one of methanol, ethanol, isopropanol, n-butanol, and tert-butanol, preferably methanol or ethanol.

[0049] Beneficial effects:

[0050] (1) The polyurethane soft segment provided by the present invention is obtained by direct polymerization of carbon dioxide, without the need to use downstream chemical product DMC of carbon dioxide, which is conducive to the sustainable development of the polyurethane material industry.

[0051] (2) The polyurethane chain extender provided by the present invention is green and inexpensive, and belongs to bio-based chain extender, which reduces the dependence of polyurethane materials on petroleum resources;

[0052] (3) In the polyurethane material provided by the present invention, the polycarbonate diol soft segment, isocyanate unit and bio-based chain extender unit containing adjustable high-density hydrogen bonds work together to make the elastomer material have excellent mechanical properties, with a tensile strength of more than 80MPa, which far exceeds the tensile performance index of the average polyurethane elastomer on the market, and greatly expands the application range of polyurethane elastomer materials.

[0053] (4) The method for preparing high-strength polyurethane based on carbon dioxide polycondensation and biomass resources provided by the present invention is simple, suitable for large-scale continuous production, and has good implementation value and market prospects. Attached Figure Description

[0054] Figure 1 The stress-strain curves for tensile tests in Example 3 and Comparative Examples 1-3 are shown. Detailed Implementation

[0055] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0056] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0057] The preferred embodiments of the present invention will now be described in detail with reference to specific examples. It should be understood that the following examples are given for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications and substitutions to the present invention without departing from its spirit and essence.

[0058] Test instrument model: The universal tensile testing machine used is an Instron 5567A.

[0059] Example 1 (soft segment is PBCDL, number average molecular weight is 2000 g / mol)

[0060] (1) Preparation of chain extender containing oxalamide structure: 13.96 g, 0.1 mol of β-alanine methyl ester hydrochloride, 20.24 g, 0.2 mol of triethylamine and 150 mL of anhydrous dichloromethane were placed in a reaction flask. Oxaloyl chloride (6.35 g, 0.05 mol) was dissolved in 50 mL of anhydrous dichloromethane and added dropwise to the reaction system at 0 °C. After the addition was completed, the temperature was raised to 35 °C and the reaction was carried out for 8 h. After the reaction was completed, the mixture was washed three times with water, the solvent was removed by rotary evaporation, and the mixture was recrystallized with ethanol to obtain the dimethyl ester compound containing oxalamide structure. A dimethyl ester compound containing an oxamide structure (7.81 g, 0.03 mol), 80 wt% hydrazine hydrate (4.5 g, 0.072 mol), and 40 mL of ethanol were placed in a reaction flask and refluxed at 80 °C for 12 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was washed three times with ethanol. After drying, 7.62 g of white powder was obtained, which is the dihydrazide chain extender containing an oxamide structure, with a yield of 97.5%.

[0061] (2) Preparation of soft segments: 4.506 g of 1,4-butanediol (50 mmol), 0.0761 g of DBU (0.5 mmol), and 5.679 g of diisopropylcarbodiimide (45 mmol) were added to a pressure vessel. High-purity carbon dioxide was introduced into the vessel to 1 MPa, and then the pressure was released to atmospheric pressure. This process was repeated three times. Subsequently, carbon dioxide was introduced to 1 MPa, and the mixture was heated to 130 °C for 24 h. After cooling to room temperature, the pressure was released, and 15 mL of dichloromethane was added to the system. The mixture was filtered, and the filtrate was washed with 10 mL of 1.0 M hydrochloric acid and 10 mL of deionized water, respectively. The filtrate was then dried with anhydrous magnesium sulfate, filtered, rotary evaporated, and vacuum dried at 50 °C for 12 h to obtain a low molecular weight prepolymer. The obtained low molecular weight prepolymer and 0.004 g of lithium acetylacetonate were placed in a three-necked flask, and the inert gas was purged three times. The mixture was then heated to 200 °C and reacted with mechanical stirring for 1 h. The system pressure was slowly reduced to approximately 50 Pa to obtain PBCDL with controllable molecular weight. The number-average molecular weight was determined to be 2000 by 1H NMR spectroscopy.

[0062] (3) Preparation of polyurethane: The reaction was carried out in a three-necked reaction flask equipped with a mechanical stirrer and nitrogen inlet and outlet. PBCDL (8g, 0.004mol) was added to the reactor, the oil bath temperature was raised to 120℃, and vacuum was applied for 3h (<100Pa) to remove water. Then isophorone diisocyanate (IPDI, 1.78g, 0.008mol), dibutyltin dilaurate (0.0074g), and 3mL DMF were added, the temperature was lowered to 85℃, and the reaction was carried out for 1h to obtain the prepolymer. Then, a bio-based chain extender containing oxalamide structure (1.04g, 0.004mol) was dispersed in 50mL DMF, mixed evenly with the prepolymer, and the reaction was continued at 85℃ for 6h. The polymer solution was cast into uniform sheets with a thickness of 1-2mm. Then the synthesized polymer was placed in a hot air circulating oven at 80℃ for 24h and dried in a vacuum oven at 120℃ for another 24h to further remove the solvent.

[0063] Example 2 (soft segment is PBCDL, number average molecular weight is 2000 g / mol)

[0064] (1) Preparation of chain extender containing succinamide structure: 13.96 g, 0.1 mol of β-alanine methyl ester hydrochloride, 20.24 g, 0.2 mol of triethylamine and 150 ml of anhydrous dichloromethane were placed in a reaction flask. Succinyl chloride (7.75 g, 0.05 mol) was dissolved in 50 ml of anhydrous dichloromethane and added dropwise to the reaction system at 0 °C. After the addition was completed, the temperature was raised to 35 °C and the reaction was carried out for 8 h. After the reaction was completed, the mixture was washed three times with water, the solvent was removed by rotary evaporation, and the mixture was recrystallized with ethanol to obtain a dimethyl ester compound containing succinamide structure. A dimethyl ester compound containing a succinamide structure (8.65 g, 0.03 mol), 80 wt% hydrazine hydrate (4.5 g, 0.072 mol), and 40 mL of ethanol were placed in a reaction flask and refluxed at 80 °C for 12 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was washed three times with ethanol. After drying, 8.24 g of white powder was obtained, which is the dihydrazide chain extender containing a succinamide structure, with a yield of 95.2%.

[0065] (2) Preparation of soft segments: Same as (2) in Example 1.

[0066] (3) Preparation of polyurethane: The reaction was carried out in a three-necked reaction flask equipped with a mechanical stirrer and nitrogen inlet and outlet. PBCDL (8g, 0.004mol) was added to the reactor, the oil bath temperature was raised to 120℃, and vacuum was applied for 3h (<100Pa) to remove water. Then isophorone diisocyanate (IPDI, 1.78g, 0.008mol), dibutyltin dilaurate (0.0074g), and 3mL DMF were added, the temperature was lowered to 85℃, and the reaction was carried out for 1h to obtain the prepolymer. Then, a bio-based chain extender containing a succinamide structure (1.15g, 0.004mol) was dispersed in 50mL DMF, mixed evenly with the prepolymer, and the reaction was continued at 85℃ for 6h. The polymer solution was cast into uniform sheets with a thickness of 1-2mm. Then the synthesized polymer was placed in a hot air circulating oven at 80℃ for 24h and dried in a vacuum oven at 120℃ for another 24h to further remove the solvent.

[0067] Example 3 (soft segment is PBCDL, number average molecular weight is 2000 g / mol)

[0068] (1) Preparation of chain extender containing furan dicarboxamide structure: 13.96 g, 0.1 mol of β-alanine methyl ester hydrochloride, 20.24 g, 0.2 mol of triethylamine and 150 ml of anhydrous dichloromethane were placed in a reaction flask. 9.65 g, 0.05 mol of 2,5-furan dicarboxyl chloride was dissolved in 50 ml of anhydrous dichloromethane and added dropwise to the reaction system at 0 °C. After the addition was completed, the temperature was raised to 35 °C and the reaction was carried out for 8 h. After the reaction was completed, the mixture was washed three times with water, the solvent was removed by rotary evaporation, and the mixture was recrystallized with ethanol to obtain a dimethyl ester compound containing furan dicarboxamide structure. A dimethyl ester compound containing a furanyl diamide structure (9.79 g, 0.03 mol), 80 wt% hydrazine hydrate (4.5 g, 0.072 mol), and 40 mL of ethanol were placed in a reaction flask and refluxed at 80 °C for 12 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was washed three times with ethanol. After drying, 9.42 g of white powder was obtained, which is the dihydrazide chain extender containing a 2,5-furanyl dimethylamide structure, with a yield of 96.2%.

[0069] (2) Preparation of soft segments: Same as (2) in Example 1.

[0070] (3) Preparation of polyurethane: The reaction was carried out in a three-necked reaction flask equipped with a mechanical stirrer and nitrogen inlet and outlet. PBCDL (8g, 0.004mol) was added to the reactor, the oil bath temperature was raised to 120℃, and vacuum was applied for 3h (<100Pa) to remove water. Then isophorone diisocyanate (IPDI, 1.78g, 0.008mol), dibutyltin dilaurate (0.0074g), and 3mL DMF were added, the temperature was lowered to 85℃, and the reaction was carried out for 1h to obtain the prepolymer. Then, a bio-based chain extender containing furan dicarboxamide structure (1.31g, 0.004mol) was dispersed in 50mL DMF, mixed evenly with the prepolymer, and the reaction was continued at 85℃ for 6h. The polymer solution was cast into uniform sheets with a thickness of 1-2mm. Then the synthesized polymer was placed in a hot air circulating oven at 80℃ for 24h and dried in a vacuum oven at 120℃ for another 24h to further remove the solvent.

[0071] Example 4 (The chain extender is the same as that in Example 3)

[0072] (1) Preparation of chain extender: Same as in Example 3 (1).

[0073] (2) Preparation of soft segments: 5.906 g of 1,6-hexanediol (50 mmol), 0.0761 g of DBU (0.5 mmol), and 5.679 g of diisopropylcarbodiimide (45 mmol) were added to a pressure vessel. High-purity carbon dioxide was introduced into the vessel to 1 MPa, and then the pressure was released to atmospheric pressure. This process was repeated three times. Subsequently, carbon dioxide was introduced to 1 MPa, and the mixture was heated to 130 °C for 24 h. After cooling to room temperature, the pressure was released, and 15 mL of dichloromethane was added to the system. The mixture was filtered, and the filtrate was washed with 10 mL of 1.0 M hydrochloric acid and 10 mL of deionized water, respectively. The filtrate was then dried with anhydrous magnesium sulfate, filtered, rotary evaporated, and vacuum dried at 50 °C for 12 h to obtain a low molecular weight prepolymer. The obtained low molecular weight prepolymer and 0.005 g of lithium acetylacetonate were placed in a three-necked flask, and the inert gas was purged three times. The mixture was then heated to 200 °C and reacted with mechanical stirring for 1 h. The system pressure was slowly reduced to approximately 50 Pa to obtain PHCDL with a controllable molecular weight. The number-average molecular weight was determined to be 2000 by 1H NMR spectroscopy.

[0074] (3) Preparation of polyurethane: The reaction was carried out in a three-necked reaction flask equipped with a mechanical stirrer and nitrogen inlet and outlet. PHCDL (8g, 0.004mol) was added to the reactor, the oil bath temperature was raised to 120℃, and vacuum was applied for 3h (<100Pa) to remove water. Then, isophorone diisocyanate (IPDI, 1.78g, 0.008mol), dibutyltin dilaurate (0.0074g), and 3mL DMF were added, the temperature was lowered to 85℃, and the reaction was carried out for 1h to obtain the prepolymer. Then, a bio-based chain extender containing furan dicarboxamide structure (1.31g, 0.004mol) was dispersed in 50mL DMF, mixed evenly with the prepolymer, and the reaction was continued at 85℃ for 6h. The polymer solution was cast into uniform sheets with a thickness of 1-2mm. Then, the synthesized polymer was placed in a hot air circulating oven at 80℃ and dried for 24h, and then dried in a vacuum oven at 120℃ for another 24h to further remove the solvent.

[0075] Example 5 (The chain extender is the same as that in Example 3)

[0076] (1) Preparation of chain extender: Same as in Example 3 (1).

[0077] (2) Preparation of soft segments: 7.312 g of 1,8-octanediol (50 mmol), 0.0761 g of DBU (0.5 mmol), and 5.679 g of diisopropylcarbodiimide (45 mmol) were added to a pressure vessel. High-purity carbon dioxide was introduced into the vessel to 1 MPa, and then the pressure was released to atmospheric pressure. This process was repeated three times. Subsequently, carbon dioxide was introduced to 1 MPa, and the mixture was heated to 130 °C for 24 h. After cooling to room temperature, the pressure was released, and 15 mL of dichloromethane was added to the system. The mixture was filtered, and the filtrate was washed with 10 mL of 1.0 M hydrochloric acid and 10 mL of deionized water, respectively. The filtrate was then dried with anhydrous magnesium sulfate, filtered, rotary evaporated, and vacuum dried at 50 °C for 12 h to obtain a low molecular weight prepolymer. The obtained low molecular weight prepolymer and 0.007 g of lithium acetylacetonate were placed in a three-necked flask, and the inert gas was purged three times. The mixture was then heated to 200 °C and reacted with mechanical stirring for 1 h. The system pressure was slowly reduced to approximately 50 Pa to obtain POCDL with a controllable molecular weight. The number-average molecular weight was determined to be 2000 by 1H NMR spectroscopy.

[0078] (3) Preparation of polyurethane: The reaction was carried out in a three-necked reaction flask equipped with a mechanical stirrer and nitrogen inlet and outlet. POCDL (8g, 0.004mol) was added to the reactor, the oil bath temperature was raised to 120℃, and vacuum was applied for 3h (<100Pa) to remove water. Then isophorone diisocyanate (IPDI, 1.78g, 0.008mol), dibutyltin dilaurate (0.0074g), and 3mL DMF were added, the temperature was lowered to 85℃, and the reaction was carried out for 1h to obtain the prepolymer. Then, a bio-based chain extender containing furan dicarboxamide structure (1.31g, 0.004mol) was dispersed in 50mL DMF, mixed evenly with the prepolymer, and the reaction was continued at 85℃ for 6h. The polymer solution was cast into uniform sheets with a thickness of 1-2mm. Then the synthesized polymer was placed in a hot air circulating oven at 80℃ for 24h and dried in a vacuum oven at 120℃ for another 24h to further remove the solvent.

[0079] Example 6 (The chain extender is the same as that in Example 3)

[0080] (1) Preparation of chain extender: Same as in Example 3 (1).

[0081] (2) Preparation of soft segments: 8.714 g of 1,10-decanediol (50 mmol), 0.0761 g of DBU (0.5 mmol), and 5.679 g of diisopropylcarbodiimide (45 mmol) were added to a pressure vessel. High-purity carbon dioxide was introduced into the vessel to 1 MPa, and then the pressure was released to atmospheric pressure. This process was repeated three times. Subsequently, carbon dioxide was introduced to 1 MPa, and the mixture was heated to 130 °C for 24 h. After cooling to room temperature, the pressure was released, and 15 mL of dichloromethane was added to the system. The mixture was filtered, and the filtrate was washed with 10 mL of 1.0 M hydrochloric acid and 10 mL of deionized water, respectively. The filtrate was then dried with anhydrous magnesium sulfate, filtered, rotary evaporated, and vacuum dried at 50 °C for 12 h to obtain a low molecular weight prepolymer. The obtained low molecular weight prepolymer and 0.008 g of lithium acetylacetonate were placed in a three-necked flask, and the inert gas was purged three times. The mixture was then heated to 200 °C and reacted with mechanical stirring for 1 h. The system pressure was slowly reduced to about 50 Pa to obtain PDeCDL with controllable molecular weight. The number-average molecular weight was determined to be 2000 by 1H NMR spectroscopy.

[0082] (3) Preparation of polyurethane: The reaction was carried out in a three-necked reaction flask equipped with a mechanical stirrer and nitrogen inlet and outlet. PDeCDL (8g, 0.004mol) was added to the reactor, the oil bath temperature was raised to 120℃, and vacuum was applied for 3h (<100Pa) to remove water. Then, isophorone diisocyanate (IPDI, 1.78g, 0.008mol), dibutyltin dilaurate (0.0074g), and 3mL DMF were added, the temperature was lowered to 85℃, and the reaction was carried out for 1h to obtain the prepolymer. Then, a bio-based chain extender containing furan dicarboxamide structure (1.31g, 0.004mol) was dispersed in 50mL DMF, mixed evenly with the prepolymer, and the reaction was continued at 85℃ for 6h. The polymer solution was cast into uniform sheets with a thickness of 1-2mm. Then, the synthesized polymer was placed in a hot air circulating oven at 80℃ for 24h and dried in a vacuum oven at 120℃ for another 24h to further remove the solvent.

[0083] Comparative Example 1 (Chain extender: adipic acid dihydrazide; soft segment: polytetrahydrofurandimethyl alcohol (PTMG-2000))

[0084] (1) Preparation of polyurethane: The reaction was carried out in a three-necked reaction flask equipped with a mechanical stirrer and nitrogen inlet and outlet. PTMG-2000 (8g, 0.004mol) was added to the reactor, the oil bath temperature was raised to 120℃, and vacuum was applied for 3h (<100Pa) to remove water. Then, isophorone diisocyanate (IPDI, 1.78g, 0.008mol), dibutyltin dilaurate (0.0074g), and 3mL DMF were added, the temperature was lowered to 85℃, and the reaction was carried out for 1h to obtain the prepolymer. Then, adipic acid dihydrazide (0.70g, 0.004mol) was dispersed in 50mL DMF and mixed evenly with the prepolymer. The reaction was continued at 85℃ for 6h. The polymer solution was cast into uniform sheets with a thickness of 1-2mm. The synthesized polymer was then placed in a hot air circulating oven at 80℃ for 24h and dried in a vacuum oven at 120℃ for another 24h to further remove the solvent.

[0085] Comparative Example 2 (Chain extender: the chain extender in Example 3; soft segment: PTMG-2000)

[0086] (1) Preparation of chain extender: Same as in Example 3 (1).

[0087] (2) Preparation of polyurethane: The reaction was carried out in a three-necked reaction flask equipped with a mechanical stirrer and nitrogen inlet and outlet. PTMG-2000 (8g, 0.004mol) was added to the reactor, the oil bath temperature was raised to 120℃, and vacuum was applied for 3h (<100Pa) to remove water. Then, isophorone diisocyanate (IPDI, 1.78g, 0.008mol), dibutyltin dilaurate (0.0074g), and 3mL DMF were added, the temperature was lowered to 85℃, and the reaction was carried out for 1h to obtain the prepolymer. Then, a bio-based chain extender containing furan dicarboxamide structure (1.31g, 0.004mol) was dispersed in 50mL DMF, mixed evenly with the prepolymer, and the reaction was continued at 85℃ for 6h. The polymer solution was cast into uniform sheets with a thickness of 1-2mm. The synthesized polymer was then placed in a hot air circulating oven at 80℃ for 24h and dried in a vacuum oven at 120℃ for another 24h to further remove the solvent.

[0088] Comparative Example 3 (Chain extender: adipic acid dihydrazide; soft segment: PBCDL)

[0089] (1) Preparation of soft segments: Same as (2) in Example 1.

[0090] (2) Preparation of polyurethane: The reaction was carried out in a three-necked reaction flask equipped with a mechanical stirrer and nitrogen inlet and outlet. PBCDL (8g, 0.004mol) was added to the reactor, the oil bath temperature was raised to 120℃, and vacuum was applied for 3h (<100Pa) to remove water. Then isophorone diisocyanate (IPDI, 1.78g, 0.008mol), dibutyltin dilaurate (0.0074g), and 3mL DMF were added, the temperature was lowered to 85℃, and the reaction was carried out for 1h to obtain the prepolymer. Then adipate dihydrazide (0.70g, 0.004mol) was dispersed in 50mL DMF and mixed evenly with the prepolymer. The reaction was continued at 85℃ for 6h. The polymer solution was cast into uniform sheets with a thickness of 1-2mm. The synthesized polymer was then placed in a hot air circulating oven at 80℃ for 24h and dried in a vacuum oven at 120℃ for another 24h to further remove the solvent.

[0091] Comparison table of mechanical properties of polyurethanes prepared in Examples 1-6 and Comparative Examples 1-3

[0092] Tensile strength (MPa) Elongation at break (%) Example 1 81.6 663.8 Example 2 75.4 738.6 Example 3 85.2 671.8 Example 4 78.7 864.8 Example 5 74.5 785.6 Example 6 72.0 774.7 Comparative Example 1 42.1 1365.3 Comparative Example 2 56.4 1370.1 Comparative Example 3 69.6 876.22

[0093] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the scope of protection of the present invention.

Claims

1. A high-strength polyurethane based on carbon dioxide polycondensation, characterized in that, The raw material components include polycarbonate diol, diisocyanate, catalyst, and chain extender; Wherein, by molar parts, the diisocyanate is 100 parts; the catalyst is 0.05-0.5 parts; the sum of the polycarbonate diol and the chain extender is 100 parts, and the chain extender is 25-50 parts; The chain extender has the following structure: or Where n = 0, 1; The catalyst is selected from at least one of dibutyltin dilaurate, stannous octoate, stannous isooctanoate, phosphoric acid, oleic acid, adipic acid, and triethylamine.

2. The high-strength polyurethane based on carbon dioxide polycondensation according to claim 1, characterized in that, The diisocyanate is selected from at least one of hexamethylene diisocyanate, diphenylmethane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, lysine diisocyanate, 1,4-cyclohexane diisocyanate, and toluene diisocyanate.

3. The high-strength polyurethane based on carbon dioxide polycondensation according to claim 1, characterized in that, The polycarbonate diol has a number-average molecular weight of 800-2000 g / mol.

4. The high-strength polyurethane based on carbon dioxide polycondensation according to claim 1, characterized in that, The polycarbonate diol is prepared by the following method: R1. Dehydration polycondensation of carbon dioxide and aliphatic diols: Aliphatic diols, organic base catalysts, and carbodiimide compounds are put into a pressure vessel and heated to 130°C in a carbon dioxide atmosphere at 1 MPa for dehydration polycondensation. The reaction is carried out for 6-24 hours and then post-processed to obtain oligocarbonates. R2. Melt polycondensation of oligocarbonate: The oligocarbonate obtained in step R1 and the polycondensation catalyst are placed in a reactor and heated to 160-230°C under an inert gas atmosphere and mechanical stirring. Then, the pressure is reduced to 50-200Pa for melt polycondensation. The reaction is carried out for 0.5-1h to obtain the polycarbonate diol. The structural formula of the aliphatic diol is: Where n = 2, 3, 4, 5; The organic base catalyst is selected from at least one of N,N,N',N'-tetramethylethylenediamine, 4-dimethylaminopyridine, 4-pyrrolylpyridine, 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5,7-triazabicyclo[4.4.0]decen-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,1,3,3-tetramethylguanidine, and 2-tert-butyl-1,1,3,3-tetramethylguanidine; The carbodiimide compound is selected from at least one of dicyclohexylcarbodiimide and diisopropylcarbodiimide.

5. The high-strength polyurethane based on carbon dioxide polycondensation according to claim 4, characterized in that, The condensation catalyst is at least one of sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, lithium acetylacetonate, zirconium acetylacetonate, and cesium carbonate.

6. The high-strength polyurethane based on carbon dioxide polycondensation according to claim 4, characterized in that, The mass ratio of the oligocarbonate to the polycondensation catalyst is 1:(0.001-0.005).

7. A method for preparing high-strength polyurethane based on carbon dioxide polycondensation according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Add polycarbonate diol to the reactor and dehydrate it under vacuum heating; Under S2 and inert gas protection, diisocyanate, catalyst and solvent are added to react and a prepolymer is obtained. S3. Under inert gas protection, the chain extender is mixed with the solvent and then added to the reactor to carry out the chain extension reaction; after casting, curing and drying, the high-strength polyurethane based on carbon dioxide polycondensation is obtained.

8. The method for preparing high-strength polyurethane based on carbon dioxide polycondensation according to claim 7, characterized in that, The solvent is selected from at least one of toluene, xylene, acetone, dichloromethane, chloroform, tetrahydrofuran, acetonitrile, ethyl acetate, butyl acetate, 1,4-dioxane, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

9. The method for preparing high-strength polyurethane based on carbon dioxide polycondensation according to claim 7, characterized in that, In step S2, the amount of solvent added is 3-10 times the amount of diisocyanate; in step S3, the amount of solvent added is 30-100 times the amount of diisocyanate.

10. The method for preparing high-strength polyurethane based on carbon dioxide polycondensation according to claim 7, characterized in that, In step S1, the vacuum degree is less than 200 Pa, the heating temperature is 90-120℃, and the dehydration time is 1-6 h; in step S2, the heating temperature is 80-100℃, and the prepolymerization time is 1-3 h; in step S3, the heating temperature of the chain extension reaction is 50-100℃, and the reaction time is 4-12 h; the casting and curing temperature is 80-120℃, and the casting and curing time is 24-48 h.

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