A high-toughness elastomer with super-strong tolerance and preparation method thereof

Abstract

The invention discloses a high-toughness elastomer with super-strong tolerance and a preparation method thereof. The elastomer is a polyurethane elastomer prepared by using polycaprolactone as a soft segment, 4,4'-dicyclohexylmethane diisocyanate as a hard segment, and long-chain hydrazide monomers and isophthalic acid dihydrazide as chain extenders; wherein the structural formula of the long-chain hydrazide monomer is. The elastomer of the invention is a bio-based polyurethane elastomer with excellent mechanical properties, super-strong tolerance and reprocessability, solving the problems of existing polyurethane elastomers such as environmental pollution, poor mechanical properties and single function.

Description

Technical Field

[0001] The present invention relates to the technical field of elastomers, and in particular to a high-toughness elastomer with super-strong tolerance and a preparation method thereof. Background Art

[0002] Polyurethane (PU) is an important class of polymer materials, produced by the reaction of isocyanates and polyols. Its molecular structure contains repeating urethane groups (-NHCOO-). Its discovery dates back to the early 1930s, when it was first synthesized by German scientist Otto Bayer and his team. After World War II, with the development of technology and the expansion of its application areas, PU gradually became a major commercial product. Due to its excellent physical and chemical properties, it is widely used in various industries.

[0003] Polyurethane is mainly produced through the addition reaction of isocyanates (such as MDI, TDI, etc.) and polyols (such as polyether polyols, polyester polyols, etc.) under the action of a catalyst. During the reaction, auxiliary components such as chain extenders, cross-linking agents, and foaming agents can also be added to regulate the performance of the final product. With the increasing global awareness of environmental protection and the proposal of the "dual carbon" strategy, traditional petroleum-based polyurethanes can no longer meet the needs of green chemistry. Therefore, bio-based polyurethanes have received increasing attention as a sustainable development alternative. The raw materials used in bio-based polyurethanes are mainly bio-based polyols and other bio-based compounds derived from renewable resources. These raw materials can come from a variety of different biomass sources, including but not limited to vegetable oils, sugars, cellulose derivatives, etc. In previous studies, the mechanical properties and solvent resistance of bio-based polyurethanes were relatively weak.

[0004] In the Chinese patent application document with publication number CN113736050A, castor seed oil polyol is introduced into a polyurethane system to prepare a recyclable plant-based polyurethane, but the tensile strength of the elastomer is only 20.8 MPa. Summary of the Invention

[0005] The technical problem to be solved by the present invention is how to improve the strength, toughness and tolerance of polyurethane elastomer.

[0006] The present invention solves the above technical problems through the following technical means:

[0007] A high-strength and tough elastomer with superb tolerance is prepared using polycaprolactone (PCL) as a soft segment, 4,4'-dicyclohexylmethane diisocyanate (HMDI) as a hard segment, and long-chain hydrazide monomer (FDH) and isophthalic acid dihydrazide as chain extenders. The structural formula of the long-chain hydrazide monomer is as follows:

[0008]

[0009] The elastomer of the present invention is a bio-based polyurethane elastomer with excellent mechanical properties, superb tolerance and reprocessability, which solves the problems of existing polyurethane elastomers such as environmental pollution, poor mechanical properties and single function.

[0010] Preferably, the polycaprolactone is a polycaprolactone with a number average molecular weight of 2000.

[0011] Preferably, the molar ratio of the polycaprolactone, 4,4'-dicyclohexylmethane diisocyanate, long-chain hydrazide monomer, and isophthalic acid dihydrazide is 10:20:2.5-7.5:2.5-7.5.

[0012] Preferably, the molar ratio of the polycaprolactone, 4,4'-dicyclohexylmethane diisocyanate, long-chain hydrazide monomer, and isophthalic acid dihydrazide is 10:20:2.5:7.5.

[0013] Preferably, the preparation process further includes adding a catalyst to catalyze the reaction.

[0014] The present invention also provides a method for preparing the high-toughness elastomer with super-strong tolerance, comprising the following steps: removing water from polycaprolactone, heating it with nitrogen, adding 4,4'-dicyclohexylmethane diisocyanate, then adding a catalyst to carry out a prepolymerization reaction, adding a mixture of a long-chain hydrazide monomer and isophthalic acid dihydrazide dissolved in a solvent after the reaction is completed, then adding a catalyst to carry out a chain extension reaction, and after the reaction is completed, obtaining the high-toughness elastomer with super-strong tolerance through post-processing.

[0015] Preferably, nitrogen is passed through after heating to 70°C.

[0016] Preferably, the temperature of the prepolymerization reaction is 70° C. and the time is 3 hours; the temperature of the chain extension reaction is 70° C. and the time is 4 hours.

[0017] Preferably, the catalyst is dibutyltin dilaurate; and the solvent is N,N-dimethylformamide.

[0018] Preferably, the amount of the catalyst added for the first time is 0.5% by weight of the polycaprolactone; the amount of the catalyst added for the second time is the same as that of the first time.

[0019] The advantages of the present invention are:

[0020] The present invention uses polycaprolactone as the soft segment, 4,4'-dicyclohexylmethane diisocyanate as the hard segment, isophthalic acid dihydrazide and long-chain hydrazide monomers as chain extenders to synthesize an elastomeric material with high-density hierarchical hydrogen bonds. The present invention uses oil-based hydrazide monomers as raw materials to synthesize a high-strength and tough elastomer with superb tolerance. By utilizing the rich hierarchical hydrogen bonds formed by urea bonds and carbamates in this system and the synergistic interaction of rigid benzene rings, the mechanical properties of the elastomer are greatly improved, and its ultimate stress reaches 84.5 MPa, far exceeding the mechanical properties of other elastomers in this field. At the same time, due to the addition of long-chain hydrazide monomer FDH prepared from castor oil as raw material, the elastomer has good water resistance and solvent resistance. After soaking in water and various solvents for 24 hours, it still maintains 80% of the initial mechanical strength. It can function in a variety of scenarios and has a wide range of applications. At the same time, the elastomer is also recyclable and can be completely recovered by physical methods after use, reducing pollution to the environment. The main raw materials of this elastomer are derived from biomass resources, which are environmentally friendly and easy to obtain. They are in line with the current synthesis concept of green chemistry and provide a certain theoretical basis and data support for the synthesis and preparation work in the field of bio-based polyurethane elastomers. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a synthesis diagram of the long-chain hydrazide monomer FDH in Example 1 of the present invention;

[0022] Figure 2 This is the FDH H NMR spectrum of the long-chain hydrazide monomer prepared in Example 1 of the present invention;

[0023] Figure 3 This is a synthetic diagram of a high-toughness elastomer with superb tolerance in Example 4 of the present invention;

[0024] Figure 4 This is the infrared spectrum of the high-toughness elastomer with super tolerance prepared in Examples 2-4 of the present invention;

[0025] Figure 5 The stress-strain curves of the elastomers prepared in Examples 2-4 and Comparative Examples 1-3 of the present invention are shown; wherein, Examples 2-4 in the figure represent Examples 2-4, and Comparative Examples 1-3 represent Comparative Examples 1-3;

[0026] Figure 6 This is a diagram of the repeatable processing of the high-toughness elastomer with super tolerance prepared in Example 4 of the present invention;

[0027] Figure 7 This is a diagram of the high-toughness elastomer with super-strong tolerance prepared in Example 4 of the present invention after being soaked in different solvents;

[0028] Figure 8Graphs showing stress-strain curves of the high-toughness elastomer with superb tolerance prepared in Example 4 of the present invention when immersed in water for different times;

[0029] Figure 9 The stress-strain curves of the high-toughness elastomer with super tolerance prepared in Example 4 of the present invention after being immersed in different solvents for 12 hours;

[0030] Figure 10 This is a diagram of the high-toughness elastomer with super tolerance prepared in Example 4 of the present invention and the elastomer in Comparative Example 1 after being immersed in water for 24 hours. DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments 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 shall fall within the scope of protection of the present invention.

[0032] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0033] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0034] Example 1

[0035] Preparation of long-chain hydrazide monomer: By molar ratio, 100 parts of 10-undecenoic acid methyl ester and 250 parts of methyl thioglycolate are put into a round-bottom flask, stirred at 35°C for 48 hours, and then the excess methyl thioglycolate is distilled off under reduced pressure to obtain a white solid product. The white solid product is placed in a three-necked flask, and ethanol solvent is added to the three-necked flask to dissolve it. Hydrazine hydrate is then added dropwise at constant pressure, and the mixture is condensed and refluxed at 70°C for 12 hours, wherein the molar ratio of the white solid product to hydrazine hydrate is 1:5, and the ratio of the white solid product to ethanol is 100mmol:100g. After the reaction is completed, the solid product is filtered out from the ethanol solution, washed three times with water, and then filtered out from the water to obtain a white powdery solid, i.e., the long-chain hydrazide monomer FDH, whose structural formula is Synthetic picture Figure 1 shown.

[0036] Figure 2 The nuclear magnetic hydrogen spectrum of the long-chain hydrazide monomer: Figure 2Characteristic peaks at 9.09 ppm, 8.90 ppm, and 4.25 ppm can be observed, indicating the formation of hydrazide functional groups. The peak positions and ratios are accurate, and no extraneous peaks are present. This demonstrates the successful preparation of long-chain hydrazide monomers.

[0037] Example 2

[0038] A method for preparing a high-toughness elastomer with super-strong tolerance comprises the following steps:

[0039] Pour 10 parts by mole of polycaprolactone with a number average molecular weight of 2000 into a three-necked flask and place it in an oven for 12 hours to remove water. Remove the three-necked flask and place it in an oil bath heated at 70°C with nitrogen for 30 minutes. Weigh 20 parts of 4,4'-dicyclohexylmethane diisocyanate and slowly add it dropwise to the reaction at a constant pressure. Then, add dibutyltin dilaurate at a concentration of 0.5 parts by mass of the polycaprolactone as a catalyst and let it react for 3 hours. After the polyol reaction is complete and the prepolymerization is complete, dissolve 7.5 parts of the long-chain hydrazide monomer FDH from Example 1 and 2.5 parts of isophthalic acid dihydrazide in DMF at a mass ratio of 1:1 to polycaprolactone. Then, add them dropwise to the reaction at a constant pressure as a chain extender. Then, add dibutyltin dilaurate at a concentration of 0.5 parts by mass of the polycaprolactone as a catalyst and let it react at 70°C for 4 hours. After the reaction is completed and the chain extension is completed, the light yellow viscous polymer is transferred to a polytetrafluoroethylene mold, placed in a 100°C oven under negative pressure, and the solvent is removed to obtain a high-strength elastomer with super tolerance.

[0040] During the entire reaction process, each time the next step of feeding is carried out, it is necessary to ensure that the previous step can react completely. Therefore, Fourier transform infrared spectroscopy is required to ensure that the hydroxyl groups in the diol can react completely during the reaction. At the same time, at the end of the reaction, it is necessary to ensure that the isocyanate group and the hydroxyl group can react completely, and multiple characteristic peaks in the carbamate are obvious. The infrared spectrum of this embodiment is shown in FIG. Figure 4 As shown by Figure 4 It can be seen that the preparation of a high-strength and tough elastomer with super tolerance is completed. The obtained elastomer is made into a dumbbell-shaped specimen with an intermediate size of 0.2mm×2.05mm. The tensile test is carried out by a mechanical testing machine. The length is kept at 10mm and the tensile rate is 50mm / min. The ultimate stress is measured to be 69.5MPa. Figure 5 shown.

[0041] Example 3

[0042] A method for preparing a high-strength and tough elastomer with super-strong tolerance, which differs from Example 2 only in that: 5 parts of a long-chain hydrazide monomer FDH and 5 parts of isophthalic acid dihydrazide are dissolved in DMF at a mass ratio of 1:1 to polycaprolactone, and then slowly added dropwise to the reaction at a constant pressure as a chain extender. The remaining steps are the same as Example 2.

[0043] The infrared spectrum of this embodiment is shown in FIG. Figure 4 As shown by Figure 4 It can be seen that the preparation of a high-strength and tough elastomer with super-strong tolerance is completed. The obtained elastomer is made into a dumbbell-shaped specimen with an intermediate size of 0.2mm×2.05mm. The tensile test is carried out on a mechanical testing machine with the length kept at 10mm and the tensile rate at 50mm / min. The ultimate stress is measured to be 71.8MPa. Figure 5 shown.

[0044] Example 4

[0045] A method for preparing a high-strength and tough elastomer with superb tolerance is different from Example 2 only in that 2.5 parts of long-chain hydrazide monomer FDH and 7.5 parts of isophthalic acid dihydrazide are dissolved in DMF with a mass ratio of 1:1 to polycaprolactone and then slowly added dropwise to the reaction at a constant pressure as a chain extender. The remaining steps are the same as Example 2. The synthesis diagram is shown in FIG. Figure 3 shown.

[0046] The infrared spectrum of this embodiment is shown in FIG. Figure 4 As shown by Figure 4 It can be seen that the preparation of a high-strength and tough elastomer with super-strong tolerance is completed. The obtained elastomer is made into a dumbbell-shaped specimen with an intermediate size of 0.2mm×2.05mm. The tensile test is carried out on a mechanical testing machine with the length kept at 10mm and the tensile rate at 50mm / min. The ultimate stress is measured to be 84.5MPa. Figure 5 shown.

[0047] Comparative Example 1

[0048] A method for synthesizing an elastomer comprises the following steps:

[0049] Pour 10 parts by molar ratio of polycaprolactone (2000 number-average molecular weight) into a three-necked flask and place in an oven for 12 hours to remove water. Remove the flask and place it in an oil bath at 70°C with nitrogen for 30 minutes. Weigh 10 parts of 4,4'-dicyclohexylmethane diisocyanate and slowly add it dropwise to the reaction mixture at a constant pressure. Add dibutyltin dilaurate (0.5 parts by weight of polycaprolactone) as a catalyst and allow the reaction to proceed for 3 hours. After the polyol reaction is complete and prepolymerization is complete, transfer the transparent, viscous polymer into a polytetrafluoroethylene mold to yield the elastomer.

[0050] The obtained elastomer was made into dumbbell-shaped specimens with an intermediate size of 0.2 mm × 2.05 mm, and subjected to tensile testing by a mechanical testing machine. The length was kept at 10 mm and the tensile rate was 50 mm / min. The ultimate stress was measured to be 41.9 MPa. Figure 5 shown.

[0051] Comparative Example 2

[0052] A method for synthesizing an elastomer differs from Example 2 only in that 10 parts of a long-chain hydrazide monomer FDH is dissolved in DMF at a mass ratio of 1:1 to polycaprolactone and then slowly added dropwise to the reaction at a constant pressure as a chain extender. The remaining steps are the same as Example 2.

[0053] The obtained elastomer was made into dumbbell-shaped specimens with an intermediate size of 0.2 mm × 2.05 mm, and subjected to tensile testing by a mechanical testing machine. The length was kept at 10 mm and the tensile rate was 50 mm / min. The ultimate stress was measured to be 56.6 MPa. Figure 5 shown.

[0054] Comparative Example 3

[0055] A method for synthesizing an elastomer differs from Example 2 only in that 10 parts of isophthalic acid dihydrazide are dissolved in DMF at a mass ratio of 1:1 to polycaprolactone and then slowly added dropwise to the reaction at a constant pressure as a chain extender. The remaining steps are the same as Example 2.

[0056] The obtained elastomer was made into dumbbell-shaped specimens with an intermediate size of 0.2 mm × 2.05 mm, and subjected to tensile testing by a mechanical testing machine. The length was kept at 10 mm and the tensile rate was 50 mm / min. The ultimate stress was measured to be 64.6 MPa. Figure 5 shown.

[0057] Data Analysis:

[0058] Table 1. Mechanical properties of elastomers

[0059] sample Stress (MPa) strain(%) Toughness (KJ / mol) Young's modulus (MPa) Example 2 69.5 1103 304.04 8.73 Example 3 71.8 1013 292.55 10.56 Example 4 84.5 855 266.36 13.96 Comparative Example 1 41.9 1305 152.11 3.55 Comparative Example 2 56.6 800 187.86 10.8 Comparative Example 3 64.6 826 212.52 11.09

[0060] It can be seen from Table 1 that a series of polyurethane elastomers with different mechanical properties can be obtained by regulating the difference in the content of long-chain hydrazide FDH and isophthalic acid dihydrazide. Among them, the mechanical properties in Example 4 are the best. Isophthalic acid dihydrazide has a rigid benzene ring structure, which gives the elastomer a higher Young's modulus and stress. As the content of isophthalic acid dihydrazide increases, the stress of the elastomer gradually increases and the strain decreases. FDH, as a long-chain oil-based chain extender, gives the elastomer important water and solvent resistance, allowing the elastomer to be used in a variety of environments (see Figure 7 、 Figure 8 、 Figure 9 )( Figure 7 The figure shows a comparison of photos taken before and after a dumbbell-shaped specimen with a size of 0.2 mm × 2.05 mm was placed in five solvents: water, ethanol, tetrahydrofuran, DMF, and dichloromethane. Figure 8Comparison of mechanical properties of dumbbell-shaped specimens prepared from the elastomer in Example 4 after being placed in water for 6 hours, 12 hours, 24 hours, and 48 hours; Figure 9 Comparison of mechanical properties of dumbbell-shaped splines prepared from the elastomer in Example 4 after being placed in five different solvents for 12 hours). The combination of long-chain hydrazide FDH and isophthalic acid dihydrazide forms a rich hierarchical hydrogen bond structure. During the stretching process of the elastomer, hydrogen bonds break in batches under different strains, making it have higher mechanical properties than the elastomers of Comparative Example 2 and Comparative Example 3 formed by a single chain extender. In Comparative Example 1, no hydrazide chain extender was added, resulting in a reduction in the types of hydrogen bonds in the elastomer, low mechanical properties, and poor tolerance (see the result of soaking the sample in water for 24 hours). Figure 10 ,Depend on Figure 10 It can be seen that the sample of Comparative Example 1 expanded and turned white after treatment, while the sample of Example 4 did not expand), which is far inferior to the excellent performance of the elastomer of the example with the addition of chain extender.

[0061] The hierarchical hydrogen bond structure not only gives the elastomer excellent mechanical properties, but also gives it the ability to be repeatedly processed (see Figure 6 : After the shredded samples are hot-pressed at 180°C by a tablet press, they can be restored to sheets and then made into dumbbell-shaped samples again. After use, the dumbbell-shaped samples can be shredded and hot-pressed again to achieve the purpose of recycling).

[0062] The present invention introduces two hydrazide monomers to create a rich hierarchical hydrogen-bonded structure. The long, oil-based hydrazide monomers impart excellent durability and stability to the polyurethane under various environmental conditions. Furthermore, the reversible reconfigurability of these hydrogen bonds allows for reusable processing.

[0063] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A high-toughness elastomer with superb tolerance, characterized by: It is a polyurethane elastomer prepared with polycaprolactone as the soft segment, 4,4'-dicyclohexylmethane diisocyanate as the hard segment, and long-chain hydrazide monomer and isophthalic acid dihydrazide as chain extenders; wherein the structural formula of the long-chain hydrazide monomer is as follows:

2. The high-toughness elastomer with superb tolerance according to claim 1, characterized in that: The polycaprolactone has a number average molecular weight of 2000.

3. The high-toughness elastomer with superb tolerance according to claim 1 or 2, characterized in that: The molar ratio of the polycaprolactone, 4,4'-dicyclohexylmethane diisocyanate, long-chain hydrazide monomer and isophthalic acid dihydrazide is 10:20:2.5-7.5:2.5-7.

5.

4. The high-toughness elastomer with superb tolerance according to claim 3, characterized in that: The molar ratio of the polycaprolactone, 4,4'-dicyclohexylmethane diisocyanate, long-chain hydrazide monomer and isophthalic acid dihydrazide is 10:20:2.5:7.

5.

5. The high-toughness elastomer with super-strong tolerance according to any one of claims 1 to 4, characterized in that: The preparation process also includes adding a catalyst to catalyze the reaction.

6. A method for preparing a high-toughness elastomer with superb tolerance according to any one of claims 1 to 5, characterized in that: The following steps are involved: The polycaprolactone is dehydrated, heated and purged with nitrogen, and then 4,4'-dicyclohexylmethane diisocyanate is added, and then a catalyst is added to carry out a prepolymerization reaction. After the reaction is completed, a mixture of a long-chain hydrazide monomer and isophthalic acid dihydrazide dissolved in a solvent is added, and then a catalyst is added to carry out a chain extension reaction. After the reaction is completed, the high-strength and tough elastomer with super tolerance is obtained through post-treatment.

7. The method for preparing a high-toughness elastomer with superb tolerance according to claim 6, characterized in that: Heat to 70°C and then purge with nitrogen.

8. The method for preparing a high-toughness elastomer with superb tolerance according to claim 6, characterized in that: The temperature of the prepolymerization reaction is 70° C. and the time is 3 hours; the temperature of the chain extension reaction is 70° C. and the time is 4 hours.

9. The method for preparing a high-toughness elastomer with superb tolerance according to claim 6, characterized in that: The catalyst is dibutyltin dilaurate; and the solvent is N,N-dimethylformamide.

10. The method for preparing a high-toughness elastomer with super-strong tolerance according to any one of claims 6 to 9, characterized in that: The amount of the catalyst added for the first time is 0.5% of the mass of the polycaprolactone; the amount of the catalyst added for the second time is the same as that of the first time.

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