High-modulus polyurethane elastomer based on stereocomplex polylactic acid and preparation method of high-modulus polyurethane elastomer

Abstract

The invention belongs to the technical field of polymer materials, and relates to a high-modulus partial bio-based polyurethane elastomer based on stereocomplex polylactic acid and a preparation method thereof, and the preparation method comprises the following steps: in a protective atmosphere, carrying out block copolymerization on polycaprolactone diol and an L-lactide monomer or a D-lactide monomer according to different molar ratios to obtain a copolymer; the L < x >-Cy-Lx or D < x >-Cy-Dx triblock copolymer is obtained; mixing the two triblock copolymers, heating with diisocyanate under the catalytic action of a catalyst, and carrying out prepolymerization reaction to obtain an isocyanato-terminated polyurethane prepolymer; and adding a chain extender into the reaction system, mixing with the polyurethane prepolymer, and carrying out chain extension reaction to obtain the polyurethane elastomer. The preparation method is simple and controllable, and the selected raw materials are low in cost, contain high bio-based components and have wide application prospects; the polyurethane elastomer obtained by adopting the preparation method is stable in performance, and has high modulus, high strength, high toughness and high rebound resilience.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and relates to a thermoplastic polyurethane elastomer (TPU), and more particularly to a high-modulus polyurethane elastomer based on stereocomposite polylactic acid and its preparation method. Background Technology

[0002] With the rapid development of polymers, the market demand for high-performance polyurethane elastomers is becoming increasingly urgent. As a typical block copolymer, polyurethane elastomers consist of alternating soft and hard segments, and their mechanical behavior is closely related to their molecular structure, intermolecular interactions, polymer chain regularity, and microphase separation morphology. Due to their high performance, ease of processing, and excellent mechanical and wear resistance properties, polyurethane elastomers are widely used in many fields such as biomedical engineering, defense industry, wearable devices, flexible sensors, and flexible electronics.

[0003] Traditional polyurethane elastomers generally suffer from insufficient mechanical properties, especially low Young's modulus. To overcome this limitation, the industrial sector often adopts a strategy of increasing the proportion of hard segments and crystallinity, that is, using highly symmetric and easily crystallizable diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BDO) as isocyanates and chain extenders to synthesize polyurethane materials with a hard segment content exceeding 50%. However, while polyurethane materials prepared by this method achieve an increase in modulus, they are usually accompanied by a decrease in toughness and elastic recovery rate; in addition, the MDI required to prepare such polyurethanes is an energy-intensive, petroleum-based raw material, and the product is difficult to degrade and highly polluting. Therefore, in the molecular structure design, this invention introduces a stereopolymer polylactic acid with strong crystallinity, bio-based, and biodegradable properties through covalent bonding, aiming to replace the hard segments composed of energy-intensive and highly polluting petroleum-based raw materials. By optimizing the synthesis conditions and process parameters, a partially bio-based TPU material with beneficial effects such as high modulus, high strength, high toughness, and high resilience is prepared. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned problems existing in the prior art, and to propose a high-modulus polyurethane elastomer based on stereocomposite polylactic acid and its preparation method. The preparation method is simple and controllable, the raw materials used are low in cost and have a high proportion of bio-based raw materials, and has broad application prospects. The polyurethane elastomer obtained by this preparation method has stable performance and has high modulus, high strength, high toughness and high resilience.

[0005] The technical solution of this invention is: This invention provides a method for preparing a high-modulus, partially bio-based polyurethane elastomer based on stereopolymer polylactic acid, comprising the following steps: (1) Under a protective atmosphere, polycaprolactone diol is block copolymerized with L-lactide monomer or D-lactide monomer in different molar ratios to obtain L-polylactic acid-polycaprolactone-L-polylactic acid (PLLA). x - b -PCL y - b -PLLA x hereinafter referred to as L x -C y -L x ) or D-polylactic acid-polycaprolactone-D-polylactic acid (PDLA) x - b -PCL y - b -PDLA x hereinafter referred to as D x -C y -D x Triblock copolymer; where x and y are independent positive integers; specifically, x is any integer in the range of 5 to 17, and y is any integer in the range of 10 to 35. Optimize the length of PLA (PLLA or PDLA) chain segments and the length of PCL chain segments in the triblock copolymer to effectively improve the modulus of the elastomer in the subsequent polyurethane synthesis [steps (2) and (3)], and obtain a polyurethane elastomer with high modulus, high strength, high toughness and high resilience.

[0006] (2) Under a protective atmosphere, the obtained triblock copolymer L x -C y -L x and D x -C y -D x The polyurethane prepolymer was prepolymerized with diisocyanate under the catalysis of a catalyst at a temperature of 70-90°C for 2-4 hours to obtain isocyanate-terminated polyurethane prepolymer. (3) Add the chain extender to the reaction system and mix it with the polyurethane prepolymer to carry out the chain extension reaction. The temperature of the chain extension reaction is 40~60℃ and the time is 12~24 h to obtain the polyurethane elastomer. In the polyurethane synthesis, the molar ratio of the triblock copolymer to the diisocyanate and chain extender in steps (2) and (3) is 1:(1+z):z, where z is any value in the range of 0.5 to 3. Preferably, the above molar ratio is 1:2:1. In this case, based on the sum of the masses of the triblock copolymer, diisocyanate, and chain extender, the content of the triblock copolymer is 80-90%, and the content of the diisocyanate + chain extender is 10-20%.

[0007] Furthermore, in step (1), under a nitrogen atmosphere, polycaprolactone diol, L-lactide monomer, stannous octoate (Sn(Oct)2), and anhydrous toluene solvent are mixed and reacted in an oil bath at 120-150°C for 100-150 min to obtain L... x -C y -L x The triblock copolymer is wherein the molar ratio of polycaprolactone diol to L-lactide is 1:(10~34), the amount of stannous octoate catalyst is 0.05~0.1% of the mass of L-lactide, and the amount of anhydrous toluene is 30% of the mass of L-lactide.

[0008] Furthermore, in step (1), under a nitrogen atmosphere, polycaprolactone diol, D-lactide monomer, stannous octanoate (Sn(Oct)2) and anhydrous toluene solvent are mixed and reacted in an oil bath at 120-150°C for 100-150 min to obtain D... x -C y -D x The triblock copolymer is wherein the molar ratio of polycaprolactone diol to D-lactide is 1:(10~34), the amount of stannous octoate catalyst is 0.05~0.1% of the mass of D-lactide, and the amount of anhydrous toluene is 30% of the mass of D-lactide.

[0009] Furthermore, the triblock copolymer prepared in step (1) has a molecular weight of 2500~9000.

[0010] Furthermore, in step (2), the obtained L x -C y -L x D x -C y -D x The triblock copolymer is heated under the action of a catalyst to carry out a prepolymerization reaction with diisocyanate. Before the reaction, the triblock copolymer is dehydrated under vacuum at 100~120℃ for 30~40 minutes.

[0011] Furthermore, in step (2), the diisocyanate is selected from any one or more of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), and toluene diisocyanate (TDI). The catalyst is dibutyltin dilaurate (DBTDL), and its dosage is 0.1% to 2% of the mass of the triblock copolymer.

[0012] Furthermore, in step (3), the chain extender is an acylhydrazine chain extender, including any one or more of adipate dihydrazine (ADH), sebacylhydrazine (SDH), malonyl hydrazine (MDH), and glutaric acid dihydrazine (GDH).

[0013] Furthermore, the solvents for the prepolymerization reaction in step (2) and the chain extension reaction in step (3) are any one or more of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), dichloromethane (CH2Cl2), and chloroform (CHCl3).

[0014] The present invention also provides a high-modulus polyurethane elastomer based on stereocomposite polylactic acid prepared by any of the preparation methods described in any one of the claims.

[0015] Furthermore, its polymer segments include soft segments and hard segments, the soft segments being triblock copolymers, and the hard segments comprising diisocyanate and chain extender, wherein the triblock copolymer comprises any one or more of the following structural formulas: L x -C y -L x / D x -C y -D x Where x and y are independent positive integers, with x ranging from 5 to 17 and y ranging from 10 to 35. Preferably, x is 9 and y is 17.

[0016] The beneficial effects of this invention are: This invention proposes a design strategy for TPUs containing bio-based stereocomposite polylactic acid (PLLA), in which short chains of two polylactic acid stereoisomers (PLLA and PDLA) are covalently introduced into the chain structure, enabling the elastomer to simultaneously possess high modulus, high strength, high toughness, and high resilience. By fine-tuning the block lengths and ratios, an optimal combination (x=9, y=17) was determined, and the prepared TPU (see Example 3) exhibits extremely high Young's modulus (~100 MPa) and relatively high tensile strength (25 MPa), elongation at break (400%), and elastic recovery (0.7, at 100% strain), thus resolving to some extent the "modulus-toughness" contradiction of this type of material. Furthermore, the introduction of stereocomposite polylactic acid also endows the elastomer with excellent thermal stability (upper operating temperature limit 150°C), while simultaneously improving the material's environmental friendliness. Attached Figure Description

[0017] Figure 1 The results of gel permeation chromatography (GPC) of the triblock copolymer prepared in Example 1 of this invention are shown. Figure 2 The stress-strain curves for uniaxial tensile testing of polyurethane elastomers; Figure 3 The stress-strain curves of the polyurethane elastomer in Example 3 are obtained from the step cyclic tensile test. Figure 4The stress-strain curves of the polyurethane elastomer in Example 3 are obtained from the graded cyclic tensile test. Figure 5 The curve shows the elastic recovery rate (ER) of polyurethane elastomer as a function of strain. Figure 6 The curve showing the change of Young's modulus (E') of energy storage as a function of temperature for dynamic mechanical analysis of polyurethane elastomer. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] To further understand the present invention, it will be further described in conjunction with the accompanying drawings and embodiments.

[0020] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0021] Example 1 This embodiment provides a triblock copolymer L x -C y -L x Its preparation method is as follows: In a glove box under a nitrogen atmosphere, 15 g of polycaprolactone diol (7.5 mmol), 19.44 g (0.135 mol) of L-lactide, 0.015 g of Sn(Oct)₂ (0.0370 mmol), and 6 mL of anhydrous toluene were weighed and added to a pressure-resistant bottle. The bottle was then removed and reacted in an oil bath at 130 °C for 120 min. After the reaction was completed, the reaction was terminated with a chloroform solution of 10 mg / mL benzoic acid. The product was precipitated with methanol, and the triblock copolymer L-lactide was collected by filtration. x -C y -L x After the above operations were completed, the obtained product was placed in a vacuum oven at 35°C and vacuum dried to constant weight. The L obtained was determined using gel permeation chromatography (GPC). x -C y -L x The molecular weight and molecular weight distribution.

[0022] The triblock copolymer prepared according to the above method has x=9 and y=17, therefore it is named L9-C.17 -L9.

[0023] By changing the amount of L-lactide added in the above method to 10.80 g (75 mmol), while keeping other conditions unchanged, a triblock copolymer was prepared with x=5 and y=17, hence it was named L5-C. 17 -L5.

[0024] By changing the amount of L-lactide added in the above method to 6.48 g (45 mmol), while keeping other conditions unchanged, a triblock copolymer was prepared with x=3 and y=17, hence it was named L3-C. 17 -L3.

[0025] Example 2 This embodiment provides a triblock copolymer D x -C y -D x Its preparation method is as follows: In a glove box under a nitrogen atmosphere, 15 g of polycaprolactone diol (7.5 mmol), 19.44 g (0.135 mol) of D-lactide, 0.015 g of Sn(Oct)₂ (0.0370 mmol), and 6 mL of anhydrous toluene were weighed and added to a pressure-resistant bottle. The bottle was then removed and reacted in an oil bath at 130 °C for 120 min. After the reaction was completed, the reaction was terminated with a chloroform solution of 10 mg / mL benzoic acid. The product was precipitated with methanol, and the triblock copolymer D-lactide was collected by filtration. x -C y -D x After the above operations are completed, the obtained product is placed in a vacuum oven at 35°C and vacuum dried to constant weight. The D content is determined using gel permeation chromatography (GPC). x -C y -D x The molecular weight and molecular weight distribution.

[0026] The triblock copolymer prepared according to the above method has x=9 and y=17, therefore it is named D9-C. 17 -D9.

[0027] By changing the amount of D-lactide added in the above method to 10.80 g (75 mmol), while keeping other conditions unchanged, a triblock copolymer was prepared with x=5 and y=17, hence it was named D5-C. 17 -D5.

[0028] By changing the amount of D-lactide added in the above method to 6.48 g (45 mmol), while keeping other conditions unchanged, a triblock copolymer was prepared with x=3 and y=17, hence it was named D3-C. 17 -D3.

[0029] Example 3 This embodiment provides a polyurethane elastomer LD9-C. 17 -LD9-TPU, its preparation method is as follows: In a 100 mL Schlenk flask filled with nitrogen, 2.3 g of L9-C was added. 17 -L9 (0.5 mmol) and 2.3 g D9-C 17 -D9 (0.5 mmol) triblock copolymer was heated under vacuum at 110 °C for 40 minutes to remove residual moisture, and then cooled to 80 °C. 0.45 g IPDI (2.0 mmol) and 15 µL DBTDL were dissolved in 8 mL DMAc, and the mixture was mechanically stirred for 3 hours under a nitrogen atmosphere to obtain a prepolymer solution. Subsequently, 0.176 g ADH (1.0 mmol) and 16 mL DMAc were added, and the reaction was continued overnight at 40 °C. At the end of the reaction, all ADH dissolved, and the reaction mixture became a viscous, transparent solution. This solution was poured into a glass petri dish and heated on a hot plate at 80 °C for 12 hours to evaporate the solvent. Finally, it was heated in a vacuum oven at 80 °C for 20 hours to obtain a polyurethane elastomer film. In this example, x=9, y=17, and the polyurethane product simultaneously contains equimolar amounts of L9-C. 17 -L9 and D9-C 17 -D9 are two triblock copolymers. This elastomer is named LD9-C. 17 -LD9-TPU.

[0030] Example 4 This embodiment provides a polyurethane elastomer LD5-C. 17 -LD5-TPU, its preparation method is as follows: In a 100 mL Schlenk flask filled with nitrogen, 1.72 g of L5-C was added. 17 -L5 (0.5 mmol) and 1.72 gD5-C 17 -D5 (0.5 mmol) triblock copolymer was heated under vacuum at 110°C for 40 minutes to remove residual moisture, and then cooled to 80°C. The remaining steps were the same as in Example 3. In this example, x=5, y=17, and the polyurethane product simultaneously contained equimolar amounts of L5-C. 17 -L5 and D5-C 17 -D5 are two triblock copolymers. This elastomer is named LD5-C. 17 -LD5-TPU.

[0031] Comparative Example 1 This embodiment provides a polyurethane elastomer LD3-C. 17-LD3-TPU, its preparation method is as follows: The triblock copolymer was prepared using 1.43 g L3-C. 17 -L3 (0.5 mmol) and 1.43 g D3-C 17 -D3 (0.5 mmol). The remaining steps are the same as in Example 3. In this example, x=3, y=17, and the polyurethane product contains equimolar amounts of L3-C. 17 -L3 and D3-C 17 -D3 are two triblock copolymers. This elastomer is named LD3-C. 17 -LD3-TPU.

[0032] Comparative Example 2 This comparative example provides a polyurethane elastomer L9-C. 17 -L9-TPU, its preparation method is as follows: The triblock copolymer uses 4.6 g L9-C 17 -L9 (1.0 mmol), the remaining steps are the same as in Example 3. In this example, x=9, y=17, and the polyurethane product contains only L9-C. 17 -L9 is a triblock copolymer. This elastomer is named L9-C. 17 -L9-TPU.

[0033] Comparative Example 3 This comparative example provides a polyurethane elastomer L5-C. 17 -L5-TPU, its preparation method is as follows: The triblock copolymer uses 3.44 g L5-C 17 -L5 (1.0 mmol), the remaining steps are the same as in Example 3. In this example, x=5, y=17, and the polyurethane product contains only L5-C. 17 -L5 is a triblock copolymer. This elastomer is named L5-C. 17 -L5-TPU.

[0034] Comparative Example 4 This comparative example provides a polyurethane elastomer L3-C. 17 -L3-TPU, its preparation method is as follows: The triblock copolymer uses 2.86 g L3-C 17 -L3 (1.0 mmol), the remaining steps are the same as in Example 3. In this example, x=3, y=17, and the polyurethane product contains only L3-C. 17 -L3 is a triblock copolymer. This elastomer is named L3-C. 17 -L3-TPU.

[0035] Experimental Example 1 The triblock copolymer (L3-C) prepared in Example 1 17 -L3, L5-C 17 -L5 and L9-C 17 -L9), and its raw material polycaprolactone diol (PCL) 17 Perform gel permeation chromatography (GPC) testing, as follows: Approximately 5 mg of the test sample was dissolved in 1 mL of tetrahydrofuran (THF), filtered, and then injected using a gel permeation chromatography system equipped with an autosampler (mobile phase: THF, flow rate: 1 mL / min). The elution curve of the sample was recorded. The molecular weight and molecular weight distribution of the sample were obtained from the elution curve and the calibration curve (based on a polystyrene standard). Figure 1 ).

[0036] The results are as follows Figure 1 As shown, compared to the raw material PCL 17 triblock copolymer L3-C 17 -L3, L5-C 17 -L5 and L9-C 17 The elution curves of -L9 shifted to the left sequentially, indicating that their molecular weight increased sequentially; all curves had narrow peak widths, indicating that all triblock copolymers had narrow molecular weight distributions.

[0037] Furthermore, based on the peak position of the effluent curve and the calibration curve (grey data points and straight line) based on the polystyrene standard, L3-C was calculated. 17 -L3, L5-C 17 -L5 and L9-C 17 The number-average molecular weights of -L9 are consistent with the reaction feed ratios in Example 1.

[0038] Experimental Example 2 The polyurethane elastomer films (approximately 0.4 mm thick) prepared in Examples 3-4 and Comparative Examples 1-4 were tested, as follows: (1) Uniaxial tensile test: The polyurethane elastomer film was cut into dumbbell-shaped strips with a working area length of 20 mm and a width of 4 mm. The strips were subjected to uniaxial, uniform tensile testing using a universal tensile testing machine at a tensile rate of 50 mm / min, and the stress-strain curves of the strips were recorded. Figure 2 ).

[0039] (2) Step-by-step cyclic tensile test: The polyurethane elastomer film was cut into dumbbell-shaped strips with a working area length of 20 mm and a width of 4 mm. The strips were subjected to a reciprocating "tension-unloading" cycle using a universal tensile testing machine at a rate of 50 mm / min. In each cycle, the maximum strain of the sample was successively 100%, 200%, 300%, 400%, 500%, and 600%. The stress-strain curves of the strips were recorded. Figure 3 The elastic recovery rate (ER) is defined as the ratio of recoverable strain to maximum strain. The elastic recovery rate-strain curve is calculated using the summation hysteresis loops at corresponding strains on the stress-strain curve. Figure 5 ).

[0040] (3) Fixed-order cyclic tensile test: The polyurethane elastomer film was cut into dumbbell-shaped strips with a working area length of 20 mm and a width of 4 mm. Ten "tension-unloading" cycles were performed on the strips using a universal tensile testing machine at a tension and unloading rate of 50 mm / min. In each cycle, the maximum strain of the sample was fixed at 100% ( Figure 4 ).

[0041] (4) Dynamic Mechanical Analysis (DMA) Test: The polyurethane elastomer film was cut into rectangular strips 10 mm long and 4 mm wide. A small strain (0.2%) at a frequency of 1 Hz was applied to the sample using a dynamic mechanical analyzer, and a temperature scan was performed in the range of -80 to 160℃ (heating rate of 3 ℃ / min). The changes in the storage modulus (E') and loss modulus (E'') of the sample with temperature were recorded. Figure 6 ).

[0042] The uniaxial tensile stress-strain curve of polyurethane elastomer is as follows: Figure 2 As shown, the initial slopes of each curve indicate that LD9-C 17 -LD9-TPU has the highest Young's modulus (~100 MPa) and high tensile strength (~25 MPa) and elongation at break (~400%), LD5-C 17 -LD5-TPU has the second highest Young's modulus (>10 MPa), but its tensile strength (~40 MPa) and elongation at break (~800%) are both higher than LD9-C. 17 -LD9-TPU. The Young's modulus of the polyurethane elastomer samples prepared in Comparative Examples 1-4 were all below 10 MPa.

[0043] The bio-based component (polylactic acid) content and mechanical property data of all polyurethane elastomers prepared in Examples 3-4 and Comparative Examples 1-4 are summarized in Table 1.

[0044] Figure 3The polyurethane elastomer LD9-C prepared in Example 3 17 -LD9-TPU's step-cycle tensile curve. As can be seen from the hysteresis loop in the figure, within the strain range of 100%~600%, the recoverable strain of this elastomer is always maintained at more than half of the maximum strain, indicating that it has good instantaneous rebound capability.

[0045] Figure 4 The polyurethane elastomer LD9-C prepared in Example 3 17 - LD9-TPU's order-determined cyclic tensile curve. As can be seen from the hysteresis loop in the figure, within 10 "stretch-unload" cycles with a fixed strain of 100%, except for the first cycle which shows a significant "strain softening" effect, the curves of cycles 2 to 10 are not significantly different, and the recoverable strain is always maintained at more than half of the maximum strain, indicating that it still has good instantaneous rebound capability under repeated deformation.

[0046] Figure 5 The elastic recovery rate (ER)-strain curves of the polyurethane elastomers prepared in Examples 3-4 and Comparative Examples 1-4, as well as a commercially available polyurethane elastomer (BASF's Elastollan 1164D polyurethane), are summarized. As shown in the figures, all samples exhibit good elastic recovery rates (ER>0.5) within the strain range of 100%-600%; among them, LD9-C... 17 -LD9-TPU has a slightly better elastic recovery rate than BASF's Elastollan 1164D, which has a similar modulus.

[0047] Figure 6 The dynamic mechanical analysis (DMA) test results of the polyurethane elastomers prepared in Examples 3-4 and Comparative Examples 1-4 are reflected as "storage Young's modulus (E') - temperature" curves. The arrows indicate the curves at E'=10. 6 The intersection of Pa can be used to indicate the upper limit of the service temperature (T) of the elastomer. uu As shown in the figure, the polyurethane elastomer LD9-C containing stereocomposite polylactic acid in Examples 3 and 4... 17 -LD9-TPU, LD5-C 17 -LD5-TPU, compared to L9-C, a polyurethane elastomer with the same chemical composition but without stereocomplex polylactic acid. 17 -L9-TPU, L5-C 17 For L5-TPU (comparative examples 2 and 3), the upper limit of its operating temperature has been significantly improved; especially for LD9-C. 17 -LD9-TPU offers a more significant improvement, with an upper operating temperature limit of 150℃.

[0048] Table 1 contains data on the bio-based component content and mechanical properties (tensile strength, elongation at break, Young's modulus, toughness, and elastic recovery at 100% and 400% strain) of all the polyurethane elastomers involved in this invention, as detailed below: Table 1. Bio-based component content, tensile strength, elongation at break, Young's modulus, toughness, and elastic recovery rate at 100% and 400% strain of the polyurethane elastomers involved in this invention. polyurethane elastomer Bio-based component content [wt%] Tensile strength [MPa] Elongation at break [%) Young's modulus [MPa] <![CDATA[Toughness [MJ / m 3 > Elastic recovery rate at 100% strain [-] Elastic recovery rate at 400% strain [-] <![CDATA[L3-C 17 -L3-TPU]]> 25 27±2 1256±33 5.1±0.6 132±6 0.86 0.85 <![CDATA[LD3-C 17 -LD3-TPU]]> 25 46±1 1118±44 6.4±1.0 184±15 0.87 0.88 <![CDATA[L5-C 17 -L5-TPU]]> 36 23±4 1018±44 4.6±0.4 97±18 0.85 0.84 <![CDATA[LD5-C 17 -LD5-TPU]]> 36 37±2 811±3 13±1 141±7 0.84 0.82 <![CDATA[L9-C 17 -L9-TPU]]> 50 41±3 671±66 9.1±0.5 109±16 0.61 0.71 <![CDATA[LD9-C 17 -LD9-TPU]]> 50 24±2 375±75 95±15 69±15 0.65 0.54 The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, alterations, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-modulus polyurethane elastomer based on stereochemical composite polylactic acid, characterized in that, Includes the following steps: (1) Under a protective atmosphere, polycaprolactone diol is block copolymerized with L-lactide monomer or D-lactide monomer in different molar ratios to obtain triblock copolymer L x -C y -L x Or D x -C y -D x Where x is any integer in the range of 5 to 17, and y is any integer in the range of 10 to 35; (2) Under a protective atmosphere, the obtained triblock copolymer L x -C y -L x D x -C y -D x The polyurethane prepolymer was prepolymerized with diisocyanate under the catalysis of a catalyst at a temperature of 70-90°C for 2-4 hours to obtain isocyanate-terminated polyurethane prepolymer. (3) Add the chain extender to the reaction system and mix it with the polyurethane prepolymer to carry out the chain extension reaction. The temperature of the chain extension reaction is 40~60℃ and the time is 12~24 h to obtain the polyurethane elastomer. The molar ratio of the triblock copolymer to the diisocyanate and the chain extender is 1:(1+z):z, where z is any value in the range of 0.5 to 3.

2. The preparation method according to claim 1, characterized in that, In step (1), under a nitrogen atmosphere, polycaprolactone diol, L-lactide monomer, stannous octoate, and anhydrous toluene solvent are mixed and reacted in an oil bath at 120-150°C for 100-150 min to obtain L... x -C y -L x The triblock copolymer is wherein the molar ratio of polycaprolactone diol to L-lactide is 1:(10~34), the amount of stannous octoate catalyst is 0.05~0.1% of the mass of L-lactide, and the amount of anhydrous toluene is 30% of the mass of L-lactide.

3. The preparation method according to claim 1, characterized in that, In step (1), under a nitrogen atmosphere, polycaprolactone diol, D-lactide monomer, stannous octoate, and anhydrous toluene solvent are mixed and reacted in an oil bath at 120-150°C for 100-150 min to obtain D... x -C y -D x The triblock copolymer is wherein the molar ratio of polycaprolactone diol to D-lactide is 1:(10~34), the amount of stannous octoate catalyst is 0.05~0.1% of the mass of D-lactide, and the amount of anhydrous toluene is 30% of the mass of D-lactide.

4. The preparation method according to claim 1, characterized in that, The triblock copolymer prepared in step (1) has a molecular weight of 2500~9000.

5. The preparation method according to claim 1, characterized in that, In step (2), the obtained L x -C y -L x D x -C y -D x The triblock copolymer is heated under the action of a catalyst to carry out a prepolymerization reaction with diisocyanate. Before the reaction, the triblock copolymer is dehydrated under vacuum at 100~120℃ for 30~40 minutes.

6. The preparation method according to claim 1, characterized in that, In step (2), the diisocyanate is selected from any one or more of isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, and toluene diisocyanate. The catalyst is dibutyltin dilaurate, and its dosage is 0.1% to 2% of the mass of the triblock copolymer.

7. The preparation method according to claim 1, characterized in that, In step (3), the chain extender is an acylhydrazine chain extender, including any one or more of adipic acid dihydrazine, sebacylhydrazine, malonyl hydrazine, and glutaric acid dihydrazine.

8. The preparation method according to claim 1, characterized in that, The solvents for the prepolymerization reaction in step (2) and the chain extension reaction in step (3) are any one or more of N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, dichloromethane, and trichloromethane.

9. A high-modulus polyurethane elastomer based on stereocomposite polylactic acid prepared by the preparation method according to any one of claims 1-8.

10. The polyurethane elastomer according to claim 9, characterized in that, Its polymer segments include soft segments and hard segments, the soft segments being triblock copolymers, and the hard segments comprising diisocyanate and chain extender; wherein, the triblock copolymer comprises L x -C y -L x and D x -C y -D x One or more of the following, where x and y are independent positive integers, with x ranging from 5 to 17 and y ranging from 10 to 35.

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