Polyurethane elastomer as well as preparation method and application thereof

Abstract

The invention relates to the field of high polymer materials, in particular to a polyurethane elastomer as well as a preparation method and application thereof, and the polyurethane elastomer is prepared from polyester-polyether-polyester triblock diol, aromatic isocyanate and micromolecule diol through a prepolymer method; the molecular chain of the micromolecular dihydric alcohol comprises ether bonds. According to the polyurethane elastomer disclosed by the invention, a chain extender is replaced by ether micromolecular dihydric alcohol, and a rigid structure of aromatic isocyanate is matched, so that the polyurethane elastomer can maintain relatively good mechanical properties under the condition that a soft segment is not designed; a soft segment structure is further designed, and a polyester-polyether-polyester triblock soft segment structure is introduced, so that soft and hard segments are distributed more uniformly in isocyanate; compared with the prior art, the preparation method has the advantages that the mechanical property of the prepared polyurethane elastomer is remarkably improved, the ionic conductivity is further improved due to the fact that the ester group has good ionic conductivity, and the ionic conductivity and the mechanical property are jointly improved.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, and in particular to a polyurethane elastomer, its preparation method, and its applications. Background Technology

[0002] Alkali metal rechargeable batteries, represented by lithium and sodium batteries, are widely used, and their commercially available electrolytes are mainly liquid electrolytes using carbonate-based organic small molecules as solvents. However, these electrolytes suffer from problems such as easy leakage, flammability, narrow electrochemical stability window, susceptibility to side reactions, and the formation of lithium dendrites, posing serious safety hazards to the batteries and limiting the development of high-energy-density batteries. To address the problems of traditional liquid electrolytes, researchers have developed novel electrolytes. Among them, polymer electrolytes exhibit great application potential due to their advantages such as light weight, flexibility, good processability, ease of large-area fabrication, low cost, and good interfacial compatibility. Polyurethane (PU) polymer electrolytes, with their unique hard-soft segment structure, designability, performance synergy, and good interfacial compatibility, have become an important research direction in the field of solid-state lithium batteries.

[0003] Improving the room-temperature ionic conductivity of polymer electrolytes is currently quite difficult. Traditional solid-state polymer electrolytes (SPEs) have low room-temperature ionic conductivity, which severely restricts the charge-discharge performance of batteries at room temperature. When attempting to improve polymer ionic conductivity, the challenge of balancing mechanical properties and ionic conduction is frequently encountered. Developing material systems that simultaneously possess high mechanical strength and good ionic conductivity remains a challenge, requiring in-depth research into the relationship between structure and performance. From the performance design perspective of polyurethane elastomers, it is easy to see that their excellent soft-hard segment synergy mechanism can overcome the inherent contradiction between conductivity, strength, and safety. However, based on past polymer electrolyte systems, hard segments typically play a role in improving mechanical properties while exhibiting relatively low ionic conductivity. Introducing ether chains into the polyurethane hard segment structure, on the other hand, reduces its mechanical properties. Therefore, rationally synergistically combining the soft and hard segments in polyurethane to achieve both overall ionic conductivity and good mechanical properties remains a challenge for polyurethane electrolytes. Summary of the Invention

[0004] Based on this, the purpose of this invention is to provide a polyurethane elastomer and its preparation method. By replacing the chain extender with a small molecule ether diol and combining it with the rigid structure of aromatic isocyanate, it can maintain good mechanical properties even without designing the soft segment. Furthermore, the soft segment structure is designed by introducing a polyester-polyether-polyester triblock soft segment structure, which makes the distribution of soft and hard segments in the isocyanate more uniform. This not only significantly improves the mechanical properties of the prepared polyurethane elastomer, but also further enhances the ionic conductivity due to the good ionic conductivity of the ester group itself, achieving a combined improvement in ionic conductivity and mechanical properties.

[0005] The technical solution of the present invention is achieved in the following ways:

[0006] A polyurethane elastomer is prepared by a prepolymer method from polyester-polyether-polyester triblock diol, aromatic isocyanate and small molecule diol; wherein the molecular chain of the small molecule diol includes ether bonds.

[0007] The polyurethane elastomer of this invention, by replacing the chain extender with a small molecule ether diol and combining it with the rigid structure of aromatic isocyanate, can maintain good mechanical properties even without designing the soft segment. Furthermore, the soft segment structure is designed by introducing a polyester-polyether-polyester triblock soft segment structure, which makes the distribution of soft and hard segments in the isocyanate more uniform. This not only significantly improves the mechanical properties of the prepared polyurethane elastomer, but also further enhances the ionic conductivity due to the good ionic conductivity of the ester group itself, achieving a combined improvement in ionic conductivity and mechanical properties.

[0008] Further, by weight, it is prepared by a prepolymer method from aromatic isocyanate, 100 parts polyester-polyether-polyester triblock diol, 0.01~1 parts titanate catalyst and 5~20 parts small molecule diol; the molar ratio of NCO in the aromatic isocyanate to OH in the polyester-polyether-polyester triblock diol is (1~1.2):1.

[0009] Furthermore, the aromatic isocyanate is diphenylmethane diisocyanate.

[0010] Furthermore, the functionality of the small molecule diol is 2.

[0011] Furthermore, the small molecule diol includes one of diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol.

[0012] Furthermore, the hydroxyl value of the polyester-polyether-polyester triblock diol is 28~112 mgKOH / g.

[0013] Furthermore, the polyester-polyether-polyester triblock diol is obtained by ring-opening polymerization of polyethylene glycol or polytetrahydrofuran with ε-caprolactone as a macromolecular initiator.

[0014] The present invention also provides a method for preparing any of the above-described polyurethane elastomers, comprising the following steps: reacting the polyester-polyether-polyester triblock diol with an excess of the aromatic isocyanate at 40-100°C for 0.5-10 h to generate a prepolymer with isocyanate groups at the ends; adding the small molecule diol to the prepolymer and performing chain extension and curing at 60-120°C for 2-16 h to obtain the polyurethane elastomer.

[0015] The present invention also provides an application of any of the above-described polyurethane elastomers as a polymer electrolyte for solid-state lithium batteries.

[0016] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the preparation process of the polyurethane elastomer described in Example 1 of the present invention; Figure 2 The polyester-polyether-polyester triblock diol described in Example 1 of this invention 1 H-NMR spectrum; Figure 3 This is a schematic diagram showing the infrared characterization results of polyurethane elastomers in the embodiments and comparative examples of the present invention. Figure 4 The polyurethane elastomer of Embodiment 1 of the present invention 1 H-NMR spectrum; Figure 5 The polyurethane elastomer of Comparative Example 1 of the present invention 1 H-NMR spectrum; Figure 6 The polyurethane elastomer of Comparative Example 2 of the present invention 1 H-NMR spectrum; Figure 7 The polyurethane elastomer of Comparative Example 3 of the present invention 1 H-NMR spectrum; Figure 8 This is a schematic diagram of the GPC test results of polyurethane elastomers in the embodiments and comparative examples of the present invention. Figure 9 The strain-stress curves of polyurethane elastomers in the embodiments and comparative examples of the present invention are shown. Detailed Implementation

[0018] It should be understood that the described embodiments are merely some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of the embodiments of this application.

[0019] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0020] In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims. In the description of this application, it should be understood that the terms "first," "second," "third," etc., are used only to distinguish similar objects and are not necessarily used to describe a specific order or sequence, nor should they be construed as indicating or implying relative importance. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0021] Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0022] It should be understood that the embodiments of this application are not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from their scope. The scope of the embodiments of this application is limited only by the appended claims.

[0023] The physical properties and testing methods of the embodiments or comparative examples of the present invention are as follows: Infrared characterization: Analysis was performed using a Fourier transform infrared spectrometer (ThermoNicolet 6500). The sample was placed directly on the surface of a ZnSe crystal in the ATR~IR accessory, and the scanning range was 400~4000 cm⁻¹. -1 4cm resolution -1The number of scans was 32. Before the test, the blank background was measured to ensure the baseline was smooth. After the sample was placed on the detection stage and the infrared spectrum was acquired, the position and intensity of the functional group absorption peaks were analyzed by software and compared with the standard spectrum to confirm the material structure characteristics.

[0024] Molecular weight and polydispersity index (PDI) distribution: determined using Waters 150CV gel permeation chromatography (GPC), specifically a GPC instrument equipped with a differential refractive index detector; the mobile phase was degassed dimethylformamide (DMF), and the standard was polystyrene particles of known molecular weight; experimental conditions included: flow rate 0.5 mL / min, column temperature 40 °C; during sample preparation, approximately 5–10 mg of dried polyol / polyol composition / polyurethane was weighed and dissolved in an appropriate amount of solvent, with the concentration controlled at 0.1–1% w / w; after ensuring system stability, the test was performed, and finally, the number-average molecular weight (Mn) and PDI were calculated using calibration curves and data analysis software.

[0025] 1 H-NMR spectra: obtained using a Bruker 400MHz Fourier transform nuclear magnetic resonance spectrometer. The sample was dissolved in deuterated chloroform at a concentration of 10 wt%; chemical shifts were measured at room temperature using tetramethylsilane (TMS) as an internal standard.

[0026] Tensile strength and elongation at break: Polyurethane elastomer samples were cut using a dumbbell-shaped cutter to a size of 1mm × 2mm × 12mm, with a quantity of n=5. Tensile tests were performed using an Instron 5966 electronic universal testing machine equipped with a 1kN load sensor, stretched at a rate of 10mm / min until fracture. The elastic modulus, tensile strength, and elongation at break were calculated from the resulting engineering stress-strain curves. The elastic modulus was calculated using the secant modulus at 2% strain.

[0027] Ionic conductivity: The ionic conductivity of polyurethane was measured using a blocked electrode (copper) and calculated according to the formula σ = Calculate, where σ-ion conductivity, R b 1 represents resistance, l represents diaphragm thickness, and S represents effective contact area.

[0028] Lithium-ion transference number: A symmetrical lithium-ion battery was assembled and tested using the following steps: The polyurethane elastomer was pressed into a film of uniform thickness, which served as the electrolyte separator and was placed between two lithium metal electrodes. The battery was then assembled into a CR2032 coin cell in an argon-protected glove box. The prepared battery was first allowed to stand for 12 hours to stabilize its internal resistance, and then tested using an electrochemical workstation. Electrochemical impedance spectroscopy (EIS) was first performed at a frequency range of 0.1 Hz to 1 MHz and an amplitude of 10 mV to obtain the initial resistance (R0). Subsequently, a constant DC voltage polarization (ΔV) of 30 mV was applied to the battery, and the current change over time was recorded until the current reached a steady state (I0). s After removing the polarization voltage, the EIS test was performed again immediately to obtain the steady-state resistance (R). s According to the formula: The lithium-ion transport number T is calculated, where ΔV is the applied voltage polarization value, and I... s and R s These represent steady-state current and resistance, respectively, while I0 and R0 represent initial current and resistance, respectively; the applied voltage polarization value used in this experiment is 30mV.

[0029] It should be noted that the percentages mentioned in the embodiments or comparative examples of this invention are all weight percentages.

[0030] It should be noted that the same polyester-polyether-polyester triblock diol is used in the embodiments or comparative examples of the present invention. The preparation method includes the following steps: weigh 10-50 wt% of macromolecular initiator and 10-50 wt% of ε-caprolactone, and additionally weigh 10-50 ppm of titanate catalyst. Add polyethylene glycol, ε-caprolactone and titanate catalyst to a four-necked flask at room temperature. After creating a nitrogen atmosphere and connecting a vacuum pump, place the four-necked flask in an oil bath. First, stir and react at 100-150°C for 2-16 h, and then stir and react at 150 mbar and 100-150°C for 2-12 h to obtain polyester-polyether-polyester triblock diol (HO~PCL~PEG~PCL~OH). After cooling to 80°C, take a sample for hydroxyl value titration and GPC test. The hydroxyl value should be between 28-112 mgKOH / g.

[0031] It should be noted that, as an optional implementation, the small molecule diol may be selected from one of diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol.

[0032] Example 1 This embodiment provides a polyurethane elastomer; for its preparation method, please refer to [link / reference]. Figure 1 This includes the following steps: Polyethylene glycol (PEG~1000, molecular weight 1000 Dal) and ε-caprolactone were weighed in a 1:1 mass ratio. At room temperature, polyethylene glycol, ε-caprolactone, and 10 ppm titanate catalyst were added to a four-necked flask. A nitrogen atmosphere was created and a vacuum pump was connected. The flask was then placed in an oil bath and stirred at 100°C for 4 hours, followed by stirring at 150 mbar and 120°C for another 4 hours to obtain a polyester-polyether-polyester triblock diol (HO~PCL~PEG~PCL~OH). After cooling to 80°C, a sample was taken for hydroxyl titration, yielding a hydroxyl value of 52-58 mgKOH / g. GPC analysis showed that the molecular weight of the prepared polyester-polyether-polyester triblock diol was 2100 Dal, and the polydispersity index (PDI) was 1.8. 6.03 g of diphenylmethane diisocyanate (MDI) was added to a 500 mL three-necked round-bottom flask and heated in an oil bath at 60 °C under a nitrogen atmosphere until melted. Then, 10 g of polyester-polyether-polyester triblock diol (HO~PCL~PEG~PCL~OH) was added, and the oil bath was heated to 80 °C and reacted for 2.5 h to obtain the prepolymer. After thoroughly mixing 16.03g of the prepolymer prepared in this example and 2.18g of diethylene glycol (DEG), the mixture was poured into a mold preheated to 80°C and cured at 100°C for 12 hours to obtain polyurethane elastomer (PU). PCL~PEG~PCL / MDI / DEG ).

[0033] Comparative Example 1 This embodiment provides a polyurethane elastomer, the preparation method of which includes the following steps: 6.03 g of diphenylmethane diisocyanate (MDI) was added to a 500 mL three-necked round-bottom flask and heated in a 60 °C oil bath under a nitrogen atmosphere until melted. Then, 10 g of polyethylene glycol (PEG~2000, molecular weight 2000Dal) was added, the oil bath temperature was raised to 80 °C, and the reaction was carried out for 2 h to obtain the prepolymer. After thoroughly mixing 16.03g of the prepolymer prepared in this example and 2.18g of diethylene glycol (DEG), the mixture was poured into a mold preheated to 70°C and cured at 70°C for 13 hours to obtain polyurethane elastomer (PU). PEG / MDI / DEG ).

[0034] Comparative Example 2 This comparative example provides a polyurethane elastomer, the preparation method of which includes the following steps: The preparation method of the polyester-polyether-polyester triblock diol in this comparative example is the same as that in Example 1, so it will not be described again. 7.25 g of diphenylmethane diisocyanate (MDI) was added to a 500 mL three-necked round-bottom flask and heated in a 60 °C oil bath under a nitrogen atmosphere until melted. Then, 10 g of polyester-polyether-polyester triblock diol (HO~PCL~PEG~PCL~OH) was added, and the oil bath was heated to 80 °C and reacted for 2 h to obtain the prepolymer. 17.25g of the prepolymer prepared in this comparative example and 1.82g of 1,4-butanediol (BDO) were thoroughly mixed and poured into a mold preheated to 110°C. The mixture was then cured at 110°C for 3 hours to obtain polyurethane elastomer (PU). PCL~PEG~PCL / MDI / BDO ).

[0035] Comparative Example 3 This comparative example provides a polyurethane elastomer, the preparation method of which includes the following steps: 7.25g of diphenylmethane diisocyanate (MDI) was added to a 500mL three-necked round-bottom flask and heated in a 60℃ oil bath under a nitrogen atmosphere until melted. Then, 10g of polyethylene glycol (PEG~2000, molecular weight 2000Dal) was added, and the oil bath was heated to 80℃ and reacted for 2h to obtain the prepolymer. After thoroughly mixing 17.25g of the prepolymer prepared in this example and 1.82g of 1,4-butanediol (BDO), the mixture was poured into a mold preheated to 70°C and cured at 80°C for 5 hours to obtain polyurethane elastomer (PU). PEG / MDI / BDO ).

[0036] The polyester-polyether-polyester triblock diol prepared in Example 1 was subjected to NMR analysis, and the results are shown in [reference needed]. Figure 2 It can be seen that the NMR characteristic peaks correspond one-to-one with the target structure of polyester-polyether-polyester triblock diol, proving that the target polyester-polyether-polyester triblock diol has been successfully synthesized.

[0037] The polyurethane elastomers prepared in Example 1 and Comparative Examples 1-3 were characterized by infrared spectroscopy. The characterization results are available in the [reference needed]. Figure 3 .

[0038] The polyurethane elastomers prepared in Example 1 and Comparative Examples 1-3 were subjected to NMR spectroscopy tests, and the test results are shown in [reference needed]. Figures 4-7 .

[0039] based on Figures 3-7 The results show that all characteristic peaks of polyurethane appeared and corresponded one-to-one, indicating that the target polyurethane elastomer was successfully synthesized.

[0040] The weight-average molecular weight, polydispersity index (PDI), tensile strength, elongation at break, ionic conductivity, and lithium-ion transference number of the polyurethane elastomers prepared in Example 1 and Comparative Examples 1-3 were tested. The test results are shown in Table 1 below. Please refer to the GPC test chart. Figure 8 Please refer to the strain-stress curve. Figure 9 .

[0041] Table 1

[0042] The weight-average molecular weights of the polyurethane elastomers prepared in Examples 1 and Comparative Examples 1-3 are all around 100,000 Da, and their PDI is similar, which eliminates the influence of molecular weight and PDI on the mechanical and electrical properties of the polyurethane elastomers.

[0043] Compared with Example 1, Comparative Example 1 did not use polyester-polyether-polyester triblock diol. Although the tensile strength was greater, the electrical conductivity and elongation at break were significantly reduced.

[0044] Compared with Example 1, Comparative Example 2 did not use ether-based small molecule diol chain extenders, and its overall mechanical properties decreased significantly. At the same time, its ionic conductivity was also lower than that of Example 1.

[0045] Compared to Comparative Example 3, Comparative Example 2, which used polyester-polyether-polyester triblock diol, showed a significant decrease in elongation at break and a significant increase in conductivity. In contrast, Example 1, compared to Comparative Example 1, showed a significant increase in elongation at break after using polyester-polyether-polyester triblock diol. This indicates that polyester-polyether-polyester triblock diol and ether-based small molecule diol chain extenders have a synergistic effect, which can synergistically improve elongation at break. This is the key to the polyurethane elastomer of the present invention achieving a combined improvement in ionic conductivity and mechanical properties.

[0046] The polyurethane elastomer of this invention can achieve a simultaneous improvement in ionic conductivity and mechanical properties, and can be used as a polymer electrolyte for solid-state lithium batteries, enabling solid-state lithium batteries to achieve excellent mechanical properties and high conductivity at the same time, breaking through the inherent contradiction of "conductivity-strength-safety" in existing solid-state lithium battery polymer electrolytes.

[0047] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and the present invention also intends to include these modifications and variations.

Claims

1. A polyurethane elastomer, characterized in that, It is prepared by a prepolymer method from polyester-polyether-polyester triblock diol, aromatic isocyanate and small molecule diol; the molecular chain of the small molecule diol includes ether bonds.

2. The polyurethane elastomer according to claim 1, characterized in that, The product is prepared by prepolymerization from aromatic isocyanate, 100 parts polyester-polyether-polyester triblock diol, 0.01-1 parts titanate catalyst and 5-20 parts small molecule diol, by weight. The molar ratio of NCO in the aromatic isocyanate to OH in the polyester-polyether-polyester triblock diol is (1-1.2):

1.

3. The polyurethane elastomer according to claim 1, characterized in that, The aromatic isocyanate is diphenylmethane diisocyanate.

4. The polyurethane elastomer according to claim 1, characterized in that, The functionality of the small molecule diol is 2.

5. The polyurethane elastomer according to claim 1, characterized in that, The small molecule diols include one of diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol.

6. The polyurethane elastomer according to claim 1, characterized in that, The hydroxyl value of the polyester-polyether-polyester triblock diol is 28~112 mgKOH / g.

7. The polyurethane elastomer according to claim 1, characterized in that, The polyester-polyether-polyester triblock diol is obtained by ring-opening polymerization of polyethylene glycol or polytetrahydrofuran as macromolecular initiators with ε-caprolactone.

8. A method for preparing a polyurethane elastomer as described in any one of claims 1 to 7, characterized in that, Includes the following steps: The polyester-polyether-polyester triblock diol is reacted with an excess of the aromatic isocyanate at 40-100°C for 0.5-10 hours to generate a prepolymer with isocyanate groups at the end; the small molecule diol is added to the prepolymer, and the mixture is subjected to chain extension and curing at 60-120°C for 2-16 hours to obtain the polyurethane elastomer.

9. An application of the polyurethane elastomer as described in any one of claims 1 to 7, characterized in that, Polymer electrolyte used in solid-state lithium batteries.

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