A wide temperature range polyurethane elastomer and preparation method thereof

Abstract

The present invention discloses a wide-temperature range polyurethane elastomer and a preparation method thereof, wherein the wide-temperature range polyurethane elastomer is obtained by reacting a flexible segment with a low glass transition temperature, a diisocyanate and a large steric hindrance primitive, wherein the flexible segment with a low glass transition temperature is a flexible segment with a dihydroxyl end-capping terminal; and the large steric hindrance primitive is a metal ion-ligand coordination structure. The present invention utilizes diisocyanate to organically combine the flexible segment with a low glass transition temperature with a metal coordination structure with a large steric effect, weakening the hydrogen bond interaction between the polyurethane segments, thereby broadening the service temperature range of the polyurethane elastomer, significantly improving the cold resistance and heat resistance of the polyurethane elastomer, enabling the polyurethane elastomer to be normally used within a relatively wide temperature range (-60°C to 80°C), which is of great significance for promoting the application of polyurethane materials in extreme environments.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane preparation, and in particular to a wide-temperature-range polyurethane elastomer and a preparation method thereof. Background Art

[0002] Polyurethane elastomers, due to their unique physical and chemical properties, play an indispensable role in numerous applications. These materials have gained market traction due to their high tensile strength, adjustable mechanical properties, and toughening properties without the need for additional fillers. Within the polymer network structure of polyurethane elastomers, hydrogen bonds between chain segments drive the formation of a microphase separation structure, endowing them with excellent mechanical properties and enabling their widespread application in various industries, including construction, transportation, clothing, and healthcare.

[0003] In recent years, researchers have focused their attention on enhancing the mechanical properties of polyurethane elastomers by strengthening hydrogen bonding interactions. Patent document CN114773569B discloses a method for preparing and applying a self-healing elastomer with a three-dimensional network structure. This invention enhances the self-healing properties of polyurethane by modifying the molecules to introduce multiple hydrogen bonding interactions, forming a large number of hydrogen bond physical crosslinking points.

[0004] Patent document CN115010896B discloses a thermoplastic elastomer with excellent rebound properties and high strength, and its preparation method. The preparation method comprises the following steps: placing at least two soft segment monomers in a solvent and then adding a hard segment monomer, reacting them in the presence of a catalyst to obtain an initial reactant; and reacting a chain extender with the initial reactant to obtain a thermoplastic elastomer. This invention significantly enhances the tensile strength and toughness of the polyurethane by introducing urea bonds with stronger hydrogen bonding interactions into the system.

[0005] However, it is well known that hydrogen bonds are very sensitive to temperature. They easily induce strong interactions between chain segments under low temperature conditions and are easily broken under high temperature conditions. Therefore, polyurethane elastomers that rely on hydrogen bonds usually show strong temperature sensitivity, tend to harden under low temperature conditions, and tend to soften under high temperature conditions, which makes their use temperature range very limited, usually only 0℃-60℃. With the continuous development of high-tech industries and my country's continuous exploration of extreme environments, people's requirements for the heat resistance and cold resistance of polyurethane elastomers are increasing. In addition, border defense, polar scientific research and even high-tech fields such as aerospace have always been important directions for the development and application promotion of low-temperature / high-temperature resistant elastomer materials.

[0006] Therefore, in view of the above-mentioned shortcomings of the existing technology, finding a new method to prepare polyurethane elastomer materials with a wide temperature range and improve the cold resistance and heat resistance of polyurethane elastomers is of great significance for promoting the application of polyurethane materials in extreme environments. At the same time, it can also help the development of high-end equipment from the direction of materials and promote the advancement of polar scientific research or space exploration. Summary of the Invention

[0007] The present invention aims to provide a wide-temperature-range polyurethane elastomer and a method for preparing the same. The polyurethane elastomer of the present invention has a wide operating temperature range and excellent cold and heat resistance, resolving the problem of the limited operating temperature range of existing polyurethane materials due to hydrogen bonding interactions.

[0008] The first aspect of the present invention provides a wide temperature range polyurethane elastomer, which is obtained by reacting a flexible chain segment with a low glass transition temperature, a diisocyanate and a large steric hindrance unit, wherein the flexible chain segment with a low glass transition temperature is a flexible chain segment with a dihydroxyl end cap; and the large steric hindrance unit is a metal ion-ligand coordination structure with multiple coordination bonds.

[0009] The present invention uses diisocyanate to organically combine flexible segments with low glass transition temperatures with metal coordination structures with significant steric hindrance, effectively weakening hydrogen bonding interactions between polyurethane segments and thus broadening the operating temperature range of the polyurethane elastomer. This design not only lowers the glass transition temperature of the polyurethane elastomer, improving its flexibility in extreme low-temperature environments, but also reduces its temperature sensitivity by weakening hydrogen bonding, maintaining good mechanical properties even at high temperatures, enabling the polyurethane elastomer to function normally over a wider temperature range (-60°C to 80°C).

[0010] Preferably, the flexible chain segment with a dihydroxyl-terminated end includes, but is not limited to, one or more of dihydroxyl-terminated polydimethylsiloxane, dihydroxyl-terminated polybutadiene, or dihydroxyl-terminated perfluoropolyether.

[0011] Preferably, the number average molecular weight of the dihydroxy-terminated flexible segment is 1000 to 6000 g / mol.

[0012] Preferably, in the metal ion-ligand coordination structure of the multiple coordination bond, the metal ion is a metal cation with a valence of +1 to +6, including but not limited to Eu 3+ 、Zn 2+ 、Tb 3+ 、Cu 2+ 、Al 3+ 、Ni 2+ 、Fe 3+ 、Co 2+ 、Mn2+ 、Ag + 、Pd 2+ The ligand motifs include, but are not limited to, one or more of the following: 2,6-bis(triazinyl)pyridine group, 2,6-bis(2-pyridyl)pyridine group, 2,2'-bipyridine-4,4'-dicarboxylic acid group, 2,2'-bipyridine group, 2,6-bis(2-benzimidazolyl)pyridine group, pyridine-2,6-dicarboxylic acid group, etc. The complex structure formed by these ligands and metal ions has a large steric hindrance effect, which is conducive to weakening the hydrogen bonds between chains.

[0013] Preferably, the diisocyanate includes but is not limited to one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, naphthalene diisocyanate, tetramethyl-m-xylylene diisocyanate, p-phenylene diisocyanate, norbornane diisocyanate, cyclohexane dimethylene diisocyanate, etc.

[0014] Preferably, the molar ratio of the flexible segment with a dihydroxyl end capping, the diisocyanate and the ligand unit in the metal ion-ligand coordination structure with multiple coordination bonds is 1:1.5-2.2:0.5-1.2.

[0015] A second aspect of the present invention provides a method for preparing the above-mentioned wide temperature range polyurethane elastomer, comprising the following steps:

[0016] (1) performing dihydroxy modification on a small molecule containing the above-mentioned ligand motif to obtain a dihydroxy-terminated ligand molecule;

[0017] (2) mixing the above-mentioned flexible chain segment with a dihydroxyl end capping with diisocyanate, an organic solvent and a catalyst, and performing a prepolymerization reaction to obtain a polyurethane prepolymer;

[0018] (3) adding a dihydroxyl-terminated ligand molecule to the polyurethane prepolymer, stirring and reacting to obtain an uncrosslinked linear polyurethane product;

[0019] (4) adding a metal salt solution to the uncrosslinked linear polyurethane product, stirring to react, and after the reaction is completed, removing the solvent to obtain the wide temperature range polyurethane elastomer.

[0020] Preferably, in step (1), the small molecules containing the above-mentioned ligand motif include but are not limited to the following structures:

[0021]

[0022] Preferably, in step (2), the molar ratio of the flexible chain segment terminated with dihydroxy groups to diisocyanate is 1:1.5 to 2.2.

[0023] Preferably, in step (2), the organic solvent is a mixture of one or more of dimethyl sulfoxide, tetrahydrofuran, N,N-dimethylformamide, dichloromethane, toluene, n-hexane, petroleum ether, and acetone.

[0024] Preferably, in step (2), the catalyst is dibutyltin dilaurate, stannous octoate or N,N-dimethylcyclohexylamine.

[0025] Preferably, in step (2), the amount of the catalyst used is 0.1 to 2% of the molar amount of the flexible segment terminated with dihydroxy groups.

[0026] Preferably, in step (2), the temperature of the prepolymerization reaction is 40-80° C., and the reaction time is 2-6 hours.

[0027] Preferably, in step (3), the molar ratio of the dihydroxy-terminated ligand molecule to the dihydroxy-terminated flexible segment is 0.5 to 1.2:1.

[0028] Preferably, in step (3), the reaction temperature is 40-80° C., and the reaction time is 6-12 h.

[0029] In step (4), the metal salt solution mainly includes metal salt and solvent. Preferably, the cation in the metal salt is a metal cation with a valence of +1 to +6, such as Eu 3+ 、Zn 2+ 、Tb 3+ 、Cu 2+ 、Al 3+ 、Ni 2+ 、Fe 3+ 、Co 2+ 、Mn 2+ 、Ag + 、Pd 2+ anion is a counter anion with a valence of -1 to -3, including one or more of chloride, bromide, fluoride, iodide, acetate, sulfate, trifluoroacetate, trifluoromethanesulfonate, bis(trifluoromethanesulfonyl)imide, hexafluorophosphate, tetrafluoroborate, etc.

[0030] Preferably, the amount of the metal salt is determined according to the coordination number between the ligand and the metal ion.

[0031] Preferably, the solvent of the metal salt solution is a mixture of one or more of dimethyl sulfoxide, tetrahydrofuran, N,N-dimethylformamide, dichloromethane, toluene, n-hexane, petroleum ether, acetone, ethanol, and methanol.

[0032] Preferably, in step (4), the reaction temperature is 40-80° C., and the reaction time is 1-4 h.

[0033] Preferably, in step (4), after the reaction is completed, the reaction product is coated on a substrate by a coating process, and the solvent is evaporated to obtain the wide temperature range polyurethane elastomer.

[0034] Preferably, the volatilization temperature is 20-80° C., and the volatilization time is 6-24 hours.

[0035] Compared with the prior art, the present invention has at least the following beneficial effects:

[0036] This invention proposes an innovative molecular structure design strategy, using diisocyanates to organically combine flexible segments with low glass transition temperatures with metal coordination structures with significant steric hindrance, weakening the hydrogen bonding interactions between the polyurethane segments and thus broadening the operating temperature range of the polyurethane elastomer. The introduction of flexible segments can lower the material's glass transition temperature, thereby improving its flexibility at low temperatures; while the addition of high steric hindrance units can spatially weaken hydrogen bonding, thereby maintaining good mechanical properties at high temperatures. This significantly improves the cold and heat resistance of the polyurethane elastomer, enabling normal use within a wide temperature range (-60°C to 80°C). BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the dynamic mechanical analysis temperature scanning curve of the sample in Comparative Example 1.

[0038] Figure 2 This is the dynamic mechanical analysis temperature scanning curve of the sample in Example 1.

[0039] Figure 3 This is the dynamic mechanical analysis temperature scanning curve of the sample in Example 2.

[0040] Figure 4 This is the dynamic mechanical analysis temperature scanning curve of the sample in Example 3.

[0041] Figure 5 The mechanical tensile curves of the sample in Comparative Example 1 at different temperatures.

[0042] Figure 6 1 is the mechanical tensile curve of the sample in Example 1 at different temperatures.

[0043] Figure 7 2 are the mechanical tensile curves of the sample in Example 2 at different temperatures.

[0044] Figure 8 3 are the mechanical tensile curves of the sample at different temperatures in Example 3. DETAILED DESCRIPTION

[0045] The following will combine the comparative examples and embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] Comparative Example 1: Synthesis of a polyurethane elastomer for use in a conventional temperature range

[0047] (1) Weigh 2.0 g of 2,6-diethynylpyridine and 2.9 g of 2-azidoethanol, add a mixed solvent of 40 mL of deionized water and 40 mL of anhydrous ethanol, then add 0.2 g of copper sulfate pentahydrate and 0.3 g of sodium L-ascorbate, and stir at 30°C for 24 hours. Then purify by column chromatography (methanol:dichloromethane = 3:1) and finally dry in a vacuum oven at 50°C for 10 hours to obtain a dihydroxy-terminated ligand molecule (BTP) with the following structural formula.

[0048]

[0049] (2) Weigh 20 g of dihydroxy-terminated polybutadiene with a molecular weight of 4000 g / mol and dissolve it in 20 mL of anhydrous tetrahydrofuran. Then, add 2.2 g of isophorone diisocyanate and 2 drops of catalyst dibutyltin dilaurate. Stir and react at 50° C. for 6 hours to obtain a polyurethane prepolymer solution.

[0050] (3) Weigh 1.5 g of dihydroxy-terminated ligand molecule BTP, dissolve it in 2 mL of N,N-dimethylformamide, and add it dropwise to the above prepolymer solution. Stir and react at 50°C for 12 hours.

[0051] (4) The solution after the reaction was poured into a polytetrafluoroethylene mold, evaporated in a ventilated environment at room temperature for 12 hours, and then dried in a vacuum oven at 60° C. for 12 hours to obtain a polyurethane elastomer film without metal coordination.

[0052] Example 1

[0053] (1) Weigh 2.0 g of 2,6-diethynylpyridine and 2.9 g of 2-azidoethanol, add a mixed solvent of 40 mL of deionized water and 40 mL of anhydrous ethanol, then add 0.2 g of copper sulfate pentahydrate and 0.3 g of sodium L-ascorbate, and stir at 30°C for 24 hours. Then purify by column chromatography (methanol:dichloromethane = 3:1) and finally dry in a vacuum oven at 50°C for 10 hours to obtain a dihydroxy-terminated ligand molecule (BTP) with the following structural formula.

[0054]

[0055] (2) Weigh 20 g of dihydroxy-terminated polybutadiene with a molecular weight of 4000 g / mol and dissolve it in 20 mL of anhydrous tetrahydrofuran. Then, add 2.2 g of isophorone diisocyanate and 2 drops of catalyst dibutyltin dilaurate. Stir and react at 50° C. for 6 hours to obtain a polyurethane prepolymer solution.

[0056] (3) Weigh 1.5 g of dihydroxy-terminated ligand molecule BTP, dissolve it in 2 mL of N,N-dimethylformamide, and add it dropwise to the above prepolymer solution. Stir and react at 50°C for 12 hours.

[0057] (4) Weigh 0.9 g of zinc trifluoromethanesulfonate Zn(OTf)2, dissolve it in 1 mL of organic solvent N,N-dimethylformamide, and add it dropwise to the above solution. Stir and react at 50°C for 2 hours.

[0058] (5) The reaction solution was poured into a polytetrafluoroethylene mold, volatilized in a ventilated environment at room temperature for 12 hours, and then dried in a vacuum oven at 60°C for 12 hours to obtain a Zn-BTP coordinated cross-linked wide temperature range polyurethane elastomer material.

[0059] Example 2

[0060] (1) Weigh 2.0 g of 2,6-diethynylpyridine and 2.9 g of 2-azidoethanol, add a mixed solvent of 40 mL of deionized water and 40 mL of anhydrous ethanol, then add 0.2 g of copper sulfate pentahydrate and 0.3 g of sodium L-ascorbate, and stir at 30°C for 24 hours. Then purify by column chromatography (methanol:dichloromethane = 3:1) and finally dry in a vacuum oven at 50°C for 10 hours to obtain a dihydroxy-terminated ligand molecule (BTP) with the following structural formula.

[0061]

[0062] (2) Weigh 20 g of dihydroxy-terminated polybutadiene with a molecular weight of 4000 g / mol and dissolve it in 20 mL of anhydrous tetrahydrofuran. Then, add 2.2 g of isophorone diisocyanate and 2 drops of catalyst dibutyltin dilaurate. Stir and react at 50° C. for 6 hours to obtain a polyurethane prepolymer solution.

[0063] (3) Weigh 1.5 g of dihydroxy-terminated ligand molecule BTP, dissolve it in 2 mL of N,N-dimethylformamide, and add it dropwise to the above prepolymer solution. Stir and react at 50°C for 12 hours.

[0064] (4) Weigh 1.0 g of europium trifluoromethanesulfonate Eu(OTf)3, dissolve it in 1 mL of organic solvent N,N-dimethylformamide, and add it dropwise to the above solution. Stir and react at 50°C for 2 hours.

[0065] (5) The solution after the reaction was poured into a polytetrafluoroethylene mold, evaporated in a ventilated environment at room temperature for 12 hours, and then dried in a vacuum oven at 60°C for 12 hours to obtain a Eu-BTP coordinated cross-linked wide temperature range polyurethane elastomer material.

[0066] Example 3

[0067] (1) Weigh 2.3 g of [2,2′-bipyridine]-5,5′-diacetonitrile, 1.0 g of anhydrous ethanol, and 0.2 g of cuprous iodide catalyst, add them to 10 mL of deionized water, then add dilute hydrochloric acid solution to the water to adjust the pH to 3, stir and react at 30°C for 12 hours, then add sodium bicarbonate solution to adjust the pH to 7, then add 20 mL of poor solvent n-hexane for recrystallization to obtain an intermediate product. After the intermediate product is dried, 10 mL of ultra-dry tetrahydrofuran is added to dissolve it in an anhydrous and oxygen-free environment, then 1.0 g of reducing agent lithium aluminum hydride is added, and the reaction is stirred at 60°C for 5 hours. Then, it is purified by column chromatography and finally dried in a vacuum drying oven at 60°C for 5 hours to obtain a 2,2′-bipyridine group [2,2′-bipyridine]-5,5′-diethanol ligand small molecule (BPy), the structural formula of which is as follows.

[0068]

[0069] (2) Weigh 20 g of dihydroxy-terminated polybutadiene with a molecular weight of 4000 g / mol and dissolve it in 20 mL of anhydrous tetrahydrofuran. Then, add 2.2 g of isophorone diisocyanate and 2 drops of catalyst dibutyltin dilaurate. Stir and react at 50° C. for 6 hours to obtain a polyurethane prepolymer solution.

[0070] (3) Subsequently, 1.2 g of ligand molecule BPy was weighed, dissolved in 2 mL of N,N-dimethylformamide, and added dropwise to the above prepolymer solution. The mixture was stirred and reacted at 50 °C for 12 h.

[0071] (4) Next, 0.6 g of zinc trifluoromethanesulfonate Zn(OTf)2 was weighed, dissolved in 1 mL of organic solvent N,N-dimethylformamide, and added dropwise to the above solution. The mixture was stirred at 50°C for 2 h.

[0072] (5) The reaction solution was poured into a polytetrafluoroethylene mold, evaporated in a ventilated environment at room temperature for 12 hours, and then dried in a vacuum oven at 60°C for 12 hours to obtain a Zn-BPy coordinated cross-linked wide temperature range polyurethane elastomer material.

[0073] In order to evaluate the cold resistance and heat resistance of the wide temperature range polyurethane elastomer of the present invention, dynamic mechanical analysis (DMA) test and mechanical property test at high and low temperature were carried out on each polyurethane elastomer. Figure 1-8 As shown. From the DMA temperature scanning spectrum, it can be seen that ( Figure 1-Figure 4 ), the typical rubber platform range of the comparative sample is narrow, and the storage modulus is relatively stable only between 0 and 50°C; while the rubber platform range of the samples of Examples 1-3 is wide, and the storage modulus is basically stable between -60°C and 120°C, reflecting that the examples have a wide operating temperature range. It can be seen from the tensile strength at high and low temperatures ( Figure 5-Figure 8 ), the comparative example sample exhibited a very low tensile strength of only 0.5 MPa at 80°C; whereas the samples of Examples 1-3 exhibited good tensile strength at both high and low temperatures, maintaining a tensile strength exceeding 3 MPa even at 80°C. These two tests demonstrate that polyurethane elastomers based on flexible segments and metal coordination crosslinking have a wide operating temperature range and exhibit both good cold and heat resistance.

Claims

1. A wide temperature range polyurethane elastomer, characterized in that: The wide temperature range polyurethane elastomer is obtained by reacting a flexible segment with a low glass transition temperature, a diisocyanate and a large steric hindrance unit, wherein: The wide temperature range is -60 to 80°C; The flexible chain segment with a low glass transition temperature is a flexible chain segment with a dihydroxyl group at the end, and the flexible chain segment with a dihydroxyl group at the end is a dihydroxyl-terminated polybutadiene; The large steric hindrance unit is a metal ion-ligand coordination structure. In the metal ion-ligand coordination structure, the metal ion is one or more metal cations with a valence of +1 to +6, and the ligand unit includes one or more of a 2,6-bis(triazine)pyridine group, a 2,6-di(2-pyridyl)pyridine group, a 2,2'-bipyridine group, and a 2,6-bis(2-benzimidazolyl)pyridine group.

2. The wide temperature range polyurethane elastomer according to claim 1, characterized in that: The number average molecular weight of the flexible chain segment with dihydroxyl end capping is 1000-6000 g / mol.

3. The wide temperature range polyurethane elastomer according to claim 1, characterized in that: The molar ratio of the flexible chain segment with dihydroxyl end capping, diisocyanate and ligand unit in the metal ion-ligand coordination structure is 1:1.5-2.2:0.5-1.

2.

4. The method for preparing a wide temperature range polyurethane elastomer according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) performing dihydroxy modification on a small molecule containing a ligand moiety to obtain a dihydroxy-terminated ligand molecule; (2) mixing the flexible chain segment having a dihydroxyl end capping with diisocyanate, an organic solvent and a catalyst, and performing a prepolymerization reaction to obtain a polyurethane prepolymer; (3) adding a dihydroxyl-terminated ligand molecule to the polyurethane prepolymer, stirring and reacting to obtain an uncrosslinked linear polyurethane product; (4) adding a metal salt solution to the uncrosslinked linear polyurethane product, stirring and reacting, and obtaining the wide temperature range polyurethane elastomer.

5. The preparation method according to claim 4, characterized in that In step (2), the molar ratio of the flexible chain segment with dihydroxyl end capping to diisocyanate is 1:1.5-2.2; the temperature of the prepolymerization reaction is 40-80° C., and the reaction time is 2-6 hours.

6. The preparation method according to claim 4, characterized in that In step (3), the molar ratio of the dihydroxy-terminated ligand molecule to the dihydroxy-terminated flexible chain segment is 0.5-1.2:1; the reaction temperature is 40-80° C., and the reaction time is 6-12 hours.

7. The preparation method according to claim 4, characterized in that In step (4), the cation of the metal salt is one or more metal cations with a valence of +1 to +6, and the anion is one or more counter anions with a valence of -1 to -3; the reaction temperature is 40 to 80° C., and the reaction time is 1 to 4 hours.

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