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 of the high-toughness elastomer. The elastomer is a polyurethane elastomer prepared by taking polycaprolactone as a soft segment, 4, 4 '-dicyclohexylmethane diisocyanate as a hard segment and a long-chain hydrazide monomer and isophthalic dihydrazide as chain extenders; wherein the structural formula of the long-chain hydrazide monomer is # imgabs0. The elastomer disclosed by the invention is a bio-based polyurethane elastomer which has excellent mechanical property and super-strong tolerance and can be reprocessed, and the problems that the existing polyurethane elastomer pollutes the environment, is poor in mechanical property and is single in function are solved.

Description

Technical Field

[0001] The 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, which is produced by the reaction of isocyanate and polyol. Its molecular structure contains repeated carbamate groups (-NHCOO-). Its discovery can be traced 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 application fields, polyurethane has gradually become an important commercial product and has been widely used in many industries due to its excellent physical and chemical properties.

[0003] Polyurethane is mainly produced by the addition reaction of isocyanates (such as MDI, TDI, etc.) and polyols (such as polyether polyols, polyester polyols, etc.) under the action of catalysts. During the reaction, auxiliary components such as chain extenders, crosslinkers, 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-toughness elastomer with super tolerance, which is a polyurethane elastomer prepared with 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; wherein the structural formula of the long-chain hydrazide monomer is as follows:

[0008]

[0009] The elastomer of the invention is a bio-based polyurethane elastomer with superior mechanical properties, superb tolerance and reprocessability, which solves the problems of existing polyurethane elastomers polluting the environment, having poor mechanical properties and single functions.

[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 also includes adding a catalyst to catalyze the reaction.

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

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

[0016] Preferably, the prepolymerization reaction is carried out at a temperature of 70° C. for 3 hours; and the chain extension reaction is carried out at a temperature of 70° C. for 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 ten thousandths of the mass of the polycaprolactone; and the amount of the catalyst added for the second time is the same as that for the first time.

[0019] The advantages of the present invention are:

[0020] The present invention uses polycaprolactone as a soft segment, 4,4'-dicyclohexylmethane diisocyanate as a 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-toughness elastomer with super tolerance. The rich hierarchical hydrogen bonds formed by urea bonds and carbamates in the system and the synergistic interaction of rigid benzene rings are utilized to greatly improve the mechanical properties of the elastomer, and its ultimate stress reaches 84.5Mpa, far exceeding the mechanical properties of other elastomers in the 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, and still maintains 80% of the initial mechanical strength after soaking in water and various solvents for 24 hours. Mechanical properties, can play a role in a variety of scenarios, and have a wide range of application scenarios. At the same time, the elastomer also has a recyclable performance, and can be completely recovered by physical methods after use, reducing pollution to the environment. The main raw material of this elastomer comes from biomass resources, which is environmentally friendly and easy to obtain. It conforms to the current synthesis concept of green chemistry and provides 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 nuclear magnetic hydrogen spectrum of the long-chain hydrazide monomer FDH prepared in Example 1 of the present invention;

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

[0024] Figure 4 This is the infrared spectrum of the high-toughness elastomer with super strong tolerance prepared in Example 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 in FIG. 2 ; wherein Example 2-4 in the figure represents Example 2-4, and Comparative Example 1-3 represents Comparative Example 1-3;

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

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

[0028] Figure 8The stress-strain curves of the high-toughness elastomer with super tolerance prepared in Example 4 of the present invention when immersed in water for different time periods;

[0029] Fig. 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] Fig.10 This is a picture 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] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are 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 creative work are 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 art or according to the product instructions.

[0034] Example 1

[0035] Preparation of long-chain hydrazide monomer: By molar proportion, 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 dripped into the flask at a 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 with water three times, 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 NMR hydrogen spectrum of the long-chain hydrazide monomer: Figure 2Characteristic peaks of 9.09ppm, 8.90ppm and 4.25ppm can be found in the sample, indicating the formation of hydrazide functional groups. The positions and ratios of the peaks are relatively accurate, and no extra peaks appear. All of these prove that the long-chain hydrazide monomer was successfully prepared.

[0037] Example 2

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

[0039] By mole, 10 parts of polycaprolactone with a number average molecular weight of 2000 are poured into a three-necked flask and placed in an oven for 12 hours to remove water. Take out the three-necked flask and place it in an oil bath pot and heat it at 70°C with nitrogen for 30 minutes. Weigh 20 parts of 4,4'-dicyclohexylmethane diisocyanate and slowly drop it into the reaction at a constant pressure, then add 5 parts of dibutyltin dilaurate by mass of polycaprolactone as a catalyst, and react for 3 hours. After the polyol reaction is completed and the prepolymerization is completed, by mole, 7.5 parts of the long-chain hydrazide monomer FDH in Example 1 and 2.5 parts of isophthalic acid dihydrazide are dissolved in DMF with a mass ratio of 1:1 to polycaprolactone, and then slowly drop it into the reaction at a constant pressure as a chain extender, and then add 5 parts of dibutyltin dilaurate by mass of polycaprolactone as a catalyst, and 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 and placed in a 100°C oven under negative pressure to remove the solvent, and a high-strength and tough elastomer with super tolerance can be obtained.

[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 be completely reacted. Therefore, Fourier transform infrared spectroscopy is required to ensure that the hydroxyl groups in the diol can be completely reacted during the reaction, and at the end of the reaction, it is necessary to ensure that the isocyanate group and the hydroxyl group can be completely reacted, 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 scale 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 elastomer with super tolerance is different from Example 2 only in that: 5 parts of long-chain hydrazide monomer FDH and 5 parts of isophthalic acid dihydrazide are dissolved in DMF with a mass ratio of 1:1 to polycaprolactone, and then slowly added to the reaction at a constant pressure as a chain extender, and the remaining steps are the same as Example 2.

[0043] The infrared spectrum of this embodiment is shown in 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 scale of 0.2mm×2.05mm, and a tensile test is performed on a mechanical testing machine. The length is kept at 10mm and the tensile rate is 50mm / min. The ultimate stress is measured to be 71.8MPa. Figure 5 shown.

[0044] Example 4

[0045] A method for preparing a high-toughness elastomer with super 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 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 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 scale of 0.2mm×2.05mm, and a tensile test is performed 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 84.5MPa. Figure 5 shown.

[0047] Comparative Example 1

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

[0049] Pour 10 parts of polycaprolactone with a number average molecular weight of 2000 into a three-necked flask by mole ratio and place it in an oven for 12 hours to remove water. Take out the three-necked flask and place it in an oil bath pot and heat it at 70℃ with nitrogen for 30 minutes. Weigh 10 parts of 4,4'-dicyclohexylmethane diisocyanate and slowly add it to the reaction at a constant pressure, then add 5 parts of dibutyltin dilaurate by mass of polycaprolactone as a catalyst and react for 3 hours. After the polyol reaction is completed and the prepolymerization is completed, the transparent and viscous polymer is transferred to a polytetrafluoroethylene mold to obtain an 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, which is different from Example 2 only in that: 10 parts of a long-chain hydrazide monomer FDH is 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, and 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, the tensile rate was 50 mm / min, and the ultimate stress was measured to be 56.6 MPa. Figure 5 shown.

[0054] Comparative Example 3

[0055] A method for synthesizing an elastomer, which is different from Example 2 only in that 10 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, and 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 , Fig. 9 )( Figure 7 The picture shows a comparison of photos taken before and after a dumbbell-shaped specimen with a specification of 0.2 mm × 2.05 mm was placed in five solvents, namely water, ethanol, tetrahydrofuran, DMF, and dichloromethane, and then taken out after 12 hours; Figure 8Comparison of mechanical properties of dumbbell-shaped specimens prepared from the elastomer in Example 4 after being placed in water for 6h, 12h, 24h, and 48h; Fig. 9 The dumbbell-shaped splines prepared from the elastomer in Example 4 were placed in five different solvents for 12 hours and then taken out for comparison of mechanical properties). 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 decrease 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). Fig.10 ,Depend on Fig.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 processed repeatedly (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 make it have a rich hierarchical hydrogen bond structure. The hydrazide monomer with a long chain of oil base makes the polyurethane have excellent tolerance and can remain stable in a variety of environments. At the same time, due to the reversible reconstruction of the rich hydrogen bonds, the elastomer can be repeatedly processed and reused.

[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 the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. 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 embodiments of the present invention.

Claims

1. A high-toughness elastomer with super strong tolerance, characterized in that: It is a polyurethane elastomer prepared with 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 as follows:

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

3. The high-toughness elastomer with super-strong 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 super-strong 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 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 super-strong tolerance as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: The polycaprolactone is dehydrated, heated and nitrogen is passed through, 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 super-strong tolerance according to claim 6, characterized in that: Heat to 70°C and then pass nitrogen.

8. The method for preparing a high-toughness elastomer with super-strong 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 super-strong 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 ten thousandths of the mass of the polycaprolactone; the amount of the catalyst added for the second time is the same as that for the first time.

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