Calixarene-derived hydrazide chain extender as well as preparation method and application thereof

Abstract

The invention relates to the technical field of polyurethane elastomers, in particular to a calixarene-derived hydrazide chain extender as well as a preparation method and application thereof, and the calixarene-derived hydrazide chain extender has a structural formula as shown in a formula (I). The calixarene-derived hydrazide chain extender introduced into the polyurethane elastomer has multiple hydrogen bonds, and compared with a traditional hydrazide compound, the calixarene-derived hydrazide chain extender contains a phenolic hydroxyl group which is a hydrogen bond donor, so that the defect that the traditional hydrazide compound is poor in solubility in a low-boiling-point organic solvent is overcome; the calixarene-derived hydrazide compound is moderate in solubility and can be partially dissolved in low-boiling-point methyl tert-butyl ether, and the problems that a traditional amine catalyst is too high in catalytic activity and uncontrollable in reaction are solved; a product prepared by using the rigid calixarene as a polyurethane elastomer hard segment has excellent tensile strength and toughness, and the introduction of the rigid calixarene makes the polyurethane elastomer have excellent strength and high thermal weight loss temperature. # imgabs0 # (I)

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane elastomers, and in particular to a calixarene-derived hydrazide chain extender, a preparation method thereof, and an application thereof. Background Art

[0002] Polyurethane elastomers, with their excellent properties of high hardness and high elasticity, have been widely used in many fields. With the development of technology and the increase in market demand, the requirements for the performance of polyurethane elastomers are becoming increasingly diverse and stringent, especially in terms of thermal stability, mechanical properties, solubility, and reaction controllability.

[0003] Currently, several patents have been published that research and report on polyurethane elastomers and their chain extenders. For example, Chinese invention patent CN119955061A discloses a method for preparing a bio-based high-strength, high-toughness polyurethane and its application. This method uses a bio-based hydrazide derived from dimethyl 2,5-furandicarboxylate as a chain extender to produce the bio-based high-strength, high-toughness polyurethane. However, this polyurethane suffers from insufficient thermal stability, with a heat loss temperature of less than 450°C, which limits its application in areas requiring high thermal stability.

[0004] Chinese invention patent CN119118866A relates to a method for preparing aliphatic hydrazide chain extenders. This method synthesizes a series of secondary amine hydrazide chain extenders through Michael addition reactions of various aliphatic hydrazides with various α,β-unsaturated carbonyl compounds. Elastomers prepared using this chain extender exhibit good mechanical recovery, but other properties such as thermal stability and solubility have not been further optimized.

[0005] Chinese invention patent CN117362253A discloses a bio-based polyurethane chain extender and its preparation method. However, this chain extender suffers from poor solubility in low-boiling-point organic solvents, requiring large amounts of high-boiling-point organic solvents such as DMF and DMAc for dissolution and dispersion. The use of large amounts of high-boiling-point organic solvents not only increases production costs and creates environmental pressures, but also restricts the large-scale development of downstream synthetic applications.

[0006] In addition to hydrazide chain extenders, common small-molecule alcohol chain extenders also have significant drawbacks. Polyurethane products produced using these chain extenders lack sufficient strength and are unable to meet the requirements of certain applications requiring high strength.

[0007] Primary amine chain extenders also present numerous challenges. Existing primary amine chain extenders are difficult to control in terms of reaction rate and are prone to gelation during the reaction process. This significantly complicates production process control, reducing production efficiency and product quality stability. Furthermore, some amine catalysts are highly toxic and have poor solubility, posing a health risk to operators and impacting reaction uniformity and effectiveness.

[0008] Furthermore, amine chain extenders such as MOCA (4,4'-methylenebis(2-chloroaniline)) can oxidize and discolor under high or prolonged heating conditions. When used as chain extenders in the preparation of light-colored products, this can negatively impact the product's color, limiting their application in these applications.

[0009] In summary, existing polyurethane elastomers and their chain extenders have varying degrees of problems in thermal stability, mechanical properties, solubility, reaction controllability, and color stability, hindering their wider application and development. Therefore, developing polyurethane elastomers and their chain extenders with improved performance and wider applicability is of great practical significance. Summary of the Invention

[0010] In order to solve the above technical problems existing in the prior art, the present invention provides a calixarene-derived hydrazide chain extender and a preparation method and application thereof.

[0011] The technical solution of the present invention to solve the above technical problems is as follows: The first aspect of the present invention is to provide a calixarene-derived hydrazide chain extender having the structural formula (I):

[0012] (I) Wherein, n=0, 1, 2; R is selected from a hydrogen atom or a tertiary hydrocarbon group; R2 is selected from a hydrogen atom or CH2CONHNH2.

[0013] On the basis of the above technical solution, the present invention can also make the following improvements: Further, selected from the following structural formula:

[0014] (I-1)

[0015] (I-2)

[0016] (I-3).

[0017] When R is a hydrogen atom, the hydrazide chain extender derived from calix[4]arene represented by formula (I-1) comprises the following two structures: , .

[0018] When R is a hydrogen atom, the hydrazide chain extender derived from calix[5]arene shown in formula (I-2) includes the following two structures: , .

[0019] When R is a hydrogen atom, the hydrazide chain extender derived from calix[6]arene shown in formula (I-3) includes the following three structures: , , .

[0020] Furthermore, the above-mentioned calixarene-derived hydrazide chain extender is prepared by the following method: under the protection of an inert atmosphere, calixarene is reacted with ethyl chloroacetate under the action of a base to obtain compound 1, and then compound 1 is subjected to a hydrazinolysis reaction with hydrazine hydrate to obtain the calixarene-derived hydrazide chain extender.

[0021] Furthermore, the compound 1 has the structural formula shown in formula (II):

[0022] (II) Wherein, R1 is selected from a hydrogen atom or CH2COOEt.

[0023] The second aspect of the present invention is to provide a method for preparing the above-mentioned calixarene-derived hydrazide chain extender, comprising the following steps: S1. Under nitrogen protection, calixarene and ethyl chloroacetate undergo nucleophilic substitution reaction in the presence of a base. After the reaction, the compound is washed with water and extracted to obtain compound 1. S2. Under nitrogen protection, compound 1 is reacted with hydrazine hydrate to undergo hydrazinolysis reaction. After the reaction is completed, the compound is washed with water, filtered, and dried to obtain the calixarene-derived hydrazide chain extender.

[0024] When R is a hydrogen atom, the reaction formula for preparing a calixarene-derived hydrazide chain extender is as follows: .

[0025] After the first step of the reaction, the base and high-boiling-point DMF (N,N-dimethylformamide, used as a solvent to dissolve calixarene) are removed by water washing and extraction.

[0026] Furthermore, in step S1, the molar ratio of the calixarene to ethyl chloroacetate is 1:(2-2.2).

[0027] Another aspect of the present invention is to provide a polyurethane elastomer prepared by using the hydrazide chain extender derived from the calixarene.

[0028] Furthermore, the polyurethane elastomer is prepared by the following method: using polycaprolactone polyol, naphthalene diisocyanate (NDI) and a hydrazide chain extender derived from calixarene as raw materials, and synthesizing the polyurethane elastomer through a prepolymerization-chain extension method.

[0029] Furthermore, the molecular weight of the polycaprolactone polyol is 1000-3000.

[0030] Furthermore, the molecular weight of the polycaprolactone polyol is 2000.

[0031] Compared with the prior art, the present invention has the following technical effects: The present invention designs and synthesizes a series of calixarene-derived hydrazide chain extenders of different sizes through hydrogen bond engineering. Then, using polycaprolactone polyol, naphthalene diisocyanate and different chain extenders as raw materials, a series of polyurethane elastomers with different chain extender structures are synthesized through a prepolymerization-chain extension method. The calixarene-derived hydrazide chain extender introduced in the present invention has multiple hydrogen bonds. Compared with traditional hydrazide compounds, it contains a phenolic hydroxyl group as a hydrogen bond donor, which overcomes the poor solubility of traditional hydrazide compounds in low-boiling point organic solvents. The calixarene-derived hydrazide compound has moderate solubility and is partially soluble in low-boiling point MTBE (methyl tert-butyl ether). Low-boiling point solvents are easily volatile, eliminating the cumbersome step of later processing high-boiling point solvents. Existing amine compounds have good solubility and high nucleophilicity of nitrogen atoms, so their reaction speed is fast when used as chain extenders, but there is a problem that the reaction speed is difficult to control. The calixarene-derived hydrazide chain extender provided by the present invention has an electron-withdrawing acyl group that reduces the nucleophilicity of the hydrazide nitrogen atom. However, the introduction of a phenolic hydroxyl group makes its solubility better than that of traditional hydrazide chain extenders, resulting in moderate solubility and stable reaction. This overcomes the problems of high activity and difficult reaction control of traditional amine catalysts. The moderate solubility eliminates the need for high-boiling point organic solvents for dissolution, while also taking into account the advantages of moderate and controllable reaction activity. The product prepared using the hydrazide chain extender derived from the calixarene provided by the present invention as the hard segment of the polyurethane elastomer has excellent tensile strength and toughness. At the same time, the introduction of rigid calixarene enables the polyurethane elastomer to have excellent strength and a high thermal weight loss temperature. DETAILED DESCRIPTION

[0032] The following specific embodiments illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Although the description of the present invention will be introduced in conjunction with the preferred embodiment, this does not mean that the features of this invention are limited to this embodiment. On the contrary, the purpose of introducing the invention in conjunction with the embodiment is to cover other options or modifications that may be extended based on the claims of the present invention. In order to provide a deep understanding of the present invention, the following description will contain many specific details. The present invention can also be implemented without using these details. In addition, in order to avoid confusion or blurring the focus of the present invention, some specific details will be omitted in the description. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other unless there is a conflict.

[0033] Example 1 Preparation of hydrazide chain extenders derived from calix[4]arene (n=0, R=tert-butyl): S1. Under nitrogen protection, 0.30 mol of calix[4]arene and 0.63 mol of ethyl chloroacetate undergo nucleophilic substitution reaction in the presence of a base to obtain compound 1. After the reaction, the compound is washed with water and the base and high-boiling-point DMF are removed by extraction. S2. Under nitrogen protection, compound 1 was reacted with 0.60 mol hydrazine hydrate to undergo hydrazinolysis reaction. After the reaction, the filter cake was washed with water and filtered several times. o C oven drying for 24 h to obtain a calix[4]arene-derived hydrazide chain extender.

[0034] Example 2 Preparation of hydrazide chain extenders derived from calix[4]arene (n=0, R=H): S1. Under nitrogen protection, 0.30 mol of calix[4]arene and 0.63 mol of ethyl chloroacetate undergo nucleophilic substitution reaction in the presence of a base to obtain compound 1. After the reaction, the compound is washed with water and the base and high-boiling-point DMF are removed by extraction. S2. Under nitrogen protection, compound 1 was reacted with 0.60 mol hydrazine hydrate to undergo hydrazinolysis reaction. After the reaction, the filter cake was washed with water and filtered several times. o C oven drying for 24 h to obtain a calix[4]arene-derived hydrazide chain extender.

[0035] Example 3 Preparation of hydrazide chain extenders derived from calix[5]arene (n=1, R=tert-butyl): Calix[5]arene was used to replace the calix[4]arene in Example 1. The rest was the same as in Example 1 and will not be described again here.

[0036] Example 4 Preparation of hydrazide chain extenders derived from calix[5]arene (n=1, R=H): Calix[5]arene was used to replace the calix[4]arene in Example 1. The rest was the same as in Example 1 and will not be described again here.

[0037] Example 5 Preparation of hydrazide chain extenders derived from calix[6]arene (n=2, R=tert-butyl): Calix[6]arene was used to replace the calix[4]arene in Example 1. The rest was the same as in Example 1 and will not be described again here.

[0038] Example 6 Preparation of hydrazide chain extenders derived from calix[6]arene (n=2, R=H): Calix[6]arene was used to replace the calix[4]arene in Example 1. The rest was the same as in Example 1 and will not be described again here.

[0039] Example 7 Synthesis of polyurethane elastomer PCL-1: Under nitrogen protection, first, 100.00 g (50 mmol) of vacuum-dehydrated PCL 220CPT produced by Dasai, 21.02 g (100 mmol) of NDI, 0.50 g of dibutyltin dilaurate (0.5% mass fraction of PCL 220CPT) and 10 mL of DMF were mixed and heated to 80 ° C, and stirred for 2 h to obtain a prepolymer; then the temperature was cooled to 50 ° C, 39.65 g (50 mmol) of the calix[4]arene-derived hydrazide chain extender prepared in Example 1 was dissolved in 20 mL of MTBE and slowly added to the above-prepared prepolymer (NCO%=3.5%), and stirred for 30 min; The polymer solution prepared above was poured into a polytetrafluoroethylene mold, degassed in a vacuum oven, and then the solvent was evaporated on a horizontal hot plate at 80 °C for 24 h to obtain a pre-cured product; after demoulding, the product was heated at 60 °C and a vacuum degree of 10 -4 After drying at 400 Pa for 72 h, a polyurethane elastomer PCL-1 sheet with a thickness of 2 mm was finally obtained.

[0040] Example 8 Synthesis of polyurethane elastomer PCL-2: The polyurethane elastomer PCL-2 was synthesized using the hydrazide chain extender derived from calix[4]arene obtained in Example 2. The rest of the steps were the same as in Example 7 and will not be described again here.

[0041] Example 9 Synthesis of polyurethane elastomer PCL-3: The polyurethane elastomer PCL-3 was synthesized using the hydrazide chain extender derived from calix[5]arene obtained in Example 3. The rest of the steps were the same as in Example 7 and will not be described again here.

[0042] Example 10 Synthesis of polyurethane elastomer PCL-4: The polyurethane elastomer PCL-4 was synthesized using the hydrazide chain extender derived from calix[5]arene obtained in Example 4. The rest of the steps were the same as in Example 7 and will not be described again here.

[0043] Example 11 Synthesis of polyurethane elastomer PCL-5: The polyurethane elastomer PCL-5 was synthesized using the hydrazide chain extender derived from calix[6]arene obtained in Example 5. The rest of the steps were the same as in Example 7 and will not be described again here.

[0044] Example 12 Synthesis of polyurethane elastomer PCL-6: The polyurethane elastomer PCL-6 was synthesized using the hydrazide chain extender derived from calix[6]arene obtained in Example 6. The rest of the steps were the same as in Example 7 and will not be described again here.

[0045] Comparative Example 1 Synthesis of polyurethane elastomer PCL-7: First, 100.00 g (50 mmol) of PCL 220CPT (2000 molecular weight polycaprolactone polyol produced by Dasailu), 21.07 g (100 mmol) of NDI (naphthalene diisocyanate), 0.50 g of dibutyltin dilaurate (0.5% by mass of PCL 220CPT), and 10 mL of DMF were mixed and heated to 80°C. The mixture was stirred and reacted for 2 h to obtain a prepolymer. The mixture was then cooled to 50°C, and 5.81 g (50 mmol) of 1,4-cyclohexanediol (chain extender) was dissolved in 10 mL of DMF and slowly added to the prepolymer (NCO% = 3.5%) prepared above. The mixture was stirred and reacted for 30 min. The obtained polymer solution was poured into a polytetrafluoroethylene mold, degassed in a vacuum oven, and then the solvent was evaporated on a horizontal hot plate at 80°C for 24 hours to obtain a pre-cured product; after demoulding, the product was heated at 60°C and a vacuum degree of 10 -4 The mixture was dried at 400 Pa for 72 h to obtain a polyurethane elastomer PCL-7 sheet with a thickness of 2 mm.

[0046] Comparative Example 2 Synthesis of polyurethane elastomer PCL-8: 4,4'-methylenebis(2-chloroaniline), namely MOCA, was used as the chain extender. The rest of the process was the same as that of Comparative Example 1 and will not be described in detail here.

[0047] Comparative Example 3 Synthesis of polyurethane elastomer PCL-9: Hydroquinone dihydroxyethyl ether was used as the chain extender, and the rest was the same as in Comparative Example 1, which will not be described again.

[0048] Comparative Example 4 Synthesis of polyurethane elastomer PCL-10: 1,4-Butanediol was used as the chain extender, and the rest was the same as that of Comparative Example 1, which will not be described again.

[0049] Comparative Example 5 Synthesis of polyurethane elastomer PCL-11: 4,4'-methylenebis(2,6-diisopropylaniline), namely M-DIPA, was used as the chain extender. The rest of the process was the same as that of Comparative Example 1 and will not be described in detail here.

[0050] Comparative Example 6 Synthesis of polyurethane elastomer PCL-12: Adipic acid dihydrazide was used as the chain extender, and the rest was the same as in Comparative Example 1, which will not be described again.

[0051] Comparative Example 7 Synthesis of polyurethane elastomer PCL-13: Furan-2,5-dicarboxylic acid hydrazide was used as the chain extender, and the rest was the same as that of Comparative Example 1, which will not be described again.

[0052] Comparative Example 8 Synthesis of polyurethane elastomer PCL-14: Phthalic acid dihydrazide was used as the chain extender, and the rest was the same as in Comparative Example 1, which will not be described again.

[0053] Comparative Example 9 Synthesis of polyurethane elastomer PCL-15: Pyridine-2,6-dicarboxylic acid dihydrazide was used as the chain extender, and the rest was the same as that of Comparative Example 1, which will not be described again.

[0054] Performance Testing Hardness: Refer to standard GB / T 531-1999.

[0055] Tensile strength: refer to standard GB / T 528-1998, sample width 6mm, thickness 2mm, tensile rate 200mm / min, and take the average value of multiple tests.

[0056] Resilience: Refer to standard GB / T 1681-2009.

[0057] Compression set: tested in accordance with GB / T7759-1996.

[0058] Thermogravimetric analysis (TGA): The test temperature range was room temperature to 600 °C using a TGA-50 thermogravimetric analyzer from Shimadzu Corporation of Japan, with a heating rate of 10 °C / min and an atmosphere protection flow rate of 30 mL / min.

[0059] The polyurethane elastomers of Examples 7-12 and Comparative Examples 1-9 were subjected to performance tests according to the above performance test standards. The performance test results are shown in Table 1.

[0060] Table 1 Performance test data of polyurethane elastomers of Examples 7-12 and Comparative Examples 1-9

[0061] The present invention introduces a calixarene-derived hydrazide chain extender with multiple hydrogen bonds during the polyurethane synthesis process. The hydrazide and phenolic hydroxyl groups with multiple hydrogen bond structures serve as the hard segment of the polyurethane elastomer. The soft and hard segments are less mixed, and the microphase separation is high. The resulting elastomer products have the advantages of both high strength and high toughness. The introduction of the rigid calixarene structure gives the elastomer a higher thermal decomposition temperature. In summary, the calixarene-derived hydrazide chain extender is expected to be used in high-value-added elastomer products.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A calixarene-derived hydrazide chain extender, characterized in that: It has the structural formula shown in formula (I): （I） Wherein, n=0, 1, 2; R is selected from a hydrogen atom or a tertiary hydrocarbon group; R2 is selected from a hydrogen atom or CH2CONHNH2.

2. The calixarene-derived hydrazide chain extender according to claim 1, characterized in that Select any one of the following structural formulas: （I-1） （I-2） （I-3）。 3. The calixarene-derived hydrazide chain extender according to claim 1, characterized in that The compound is prepared by the following method: under the protection of an inert atmosphere, calixarene and ethyl chloroacetate are reacted under the action of a base to obtain compound 1, and then compound 1 is reacted with hydrazine hydrate to obtain the hydrazide chain extender derived from calixarene.

4. The calixarene-derived hydrazide chain extender according to claim 3, characterized in that The compound 1 has the structural formula shown in formula (II): (II) Wherein, R1 is selected from a hydrogen atom or CH2COOEt.

5. A method for preparing a calixarene-derived hydrazide chain extender according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Under nitrogen protection, calixarene and ethyl chloroacetate undergo nucleophilic substitution reaction in the presence of a base. After the reaction, the compound is washed with water and extracted to obtain compound 1. S2. Under nitrogen protection, compound 1 is reacted with hydrazine hydrate to undergo hydrazinolysis reaction. After the reaction is completed, the compound is washed with water, filtered, and dried to obtain the calixarene-derived hydrazide chain extender.

6. The method for preparing a calixarene-derived hydrazide chain extender according to claim 5, wherein: In step S1, the molar ratio of the calixarene to ethyl chloroacetate is 1:(2-2.2).

7. A polyurethane elastomer, characterized in that The invention is prepared by using the hydrazide chain extender derived from calixarene according to any one of claims 1 to 4.

8. The polyurethane elastomer according to claim 7, characterized in that The polyurethane elastomer is prepared by the following method: polycaprolactone polyol, naphthalene diisocyanate and hydrazide chain extender derived from calixarene are used as raw materials, and the polyurethane elastomer is synthesized by a prepolymerization-chain extension method.

9. The polyurethane elastomer according to claim 8, characterized in that The molecular weight of the polycaprolactone polyol is 1000-3000.

10. The polyurethane elastomer according to claim 9, characterized in that The molecular weight of the polycaprolactone polyol is 2000.

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