A self-repairable polyurethane, modified bitumen, method of preparation, use

Abstract

The application discloses a self-repairable polyurethane, modified asphalt, a preparation method and application, and belongs to the technical field of high polymer materials. The preparation method of the self-repairable polyurethane comprises the following steps: (1) mixing and reacting polytetrahydrofuran and isophorone diisocyanate in the presence of a catalyst to obtain a prepolymer; (2) mixing the prepolymer and a chain extender, and extending the chain to obtain the self-repairable polyurethane, wherein the chain extender comprises adipic acid dihydrazide and bis(2-aminophenyl)disulfide; the molar ratio of the isophorone diisocyanate to the polytetrahydrofuran is (2-3):1; and the molar ratio of the bis(2-aminophenyl)disulfide to the adipic acid dihydrazide is (1-3):1. The polyurethane is added into asphalt to obtain modified asphalt. The self-repairable polyurethane modified asphalt has excellent low-temperature and high-temperature performance, toughness, active healing capacity and good regeneration performance.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a self-healing polyurethane, modified asphalt, preparation method, and application. Background Technology

[0002] Asphalt pavement refers to the road surface structure constructed by using asphalt as a binder and binder aggregate to build various base layers and subbase layers. Compared with cement concrete pavement, asphalt pavement has many advantages, such as smooth and comfortable driving, flat road surface, no joints, wear resistance, low driving noise, low vibration, short construction period, and the ability to be constructed in stages. Therefore, asphalt pavement has been increasingly widely used in daily life.

[0003] In recent years, with rapid economic development, people have gradually placed higher demands on road surfaces. Polymer-modified asphalt, as a promising material, possesses excellent physical and chemical properties. It can improve driving comfort and extend service life, and is currently widely used. However, long-term traffic loads and various severe weather conditions inevitably cause it to crack, which can accelerate damage and shorten its service life.

[0004] Because thermosetting polymers lack self-healing properties, the three-dimensional network structure they form within the base asphalt encapsulates the asphalt particles, limiting the healing properties of the base asphalt. Therefore, although thermosetting polymer-modified asphalt possesses high mechanical strength and temperature adaptability, it also suffers from drawbacks such as high brittleness, poor impact resistance, and insufficient crack resistance.

[0005] Therefore, how to provide a self-healing modified bitumen is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a self-healing polyurethane, modified asphalt, preparation method and application, so as to solve the problem that thermosetting polymer modified asphalt lacks self-healing properties in the above-mentioned background technology.

[0007] During the research and development process, the inventors discovered that polyurethane (PU) possesses excellent mechanical properties and low-temperature toughness. By introducing dynamic / non-dynamic covalent bonds into the chemical structure of polyurethane, it can be endowed with superior mechanical properties and self-healing capabilities, enabling crack repair. The disulfide bond in polyurethane is a reversible chemical bond; under heating or ultraviolet irradiation, a dynamic exchange reaction occurs through disulfide bond metathesis. When the material is damaged, hydrogen bonds and disulfide bonds can work together to provide the material with self-repair capabilities and improve thermal stability, allowing the material to be reprocessed and healed in a solid state.

[0008] To achieve the above objectives, the present invention provides the following technical solution.

[0009] This invention provides a method for preparing self-healing polyurethane, which includes the following steps:

[0010] (1) In the presence of a catalyst, polytetrahydrofuran and isophorone diisocyanate were mixed and reacted to obtain a prepolymer;

[0011] (2) The prepolymer and chain extender are mixed and chain extended to obtain the self-healing polyurethane, wherein the chain extender includes adipate dihydrazide and bis(2-aminophenyl) disulfide;

[0012] The molar ratio of isophorone diisocyanate to polytetrahydrofuran is (2-3):1;

[0013] The molar ratio of the bis(2-aminophenyl)disulfide and the adipate dihydrazide is (1-3):1.

[0014] In some embodiments of the present invention, the catalyst is dibutyltin dilaurate.

[0015] In some embodiments of the present invention, the mass of the catalyst is 0.1-1.0% of the reactants, for example 0.4%, where the percentage refers to the mass percentage.

[0016] In some embodiments of the present invention, prior to the reaction, the polytetrahydrofuran is dehydrated by vacuum distillation at 110°C for 0.5-2 hours.

[0017] In some embodiments of the present invention, the polytetrahydrofuran has a weight-average molecular weight (Mw) of 2000.

[0018] In some embodiments of the present invention, the reaction is carried out under stirring conditions, for example at 100-150 rpm.

[0019] In some embodiments of the present invention, the reaction temperature is 70-90°C, for example 85°C.

[0020] In some embodiments of the present invention, the reaction time is 2-3 hours, for example, 3 hours.

[0021] In some embodiments of the present invention, the molar ratio of the isophorone diisocyanate to the polytetrahydrofuran is (2.0-2.5):1.

[0022] In some embodiments of the present invention, the molar ratio of the bis(2-aminophenyl)disulfide and the adipic dihydrazide is (1.5-2.5):1.

[0023] In some embodiments of the present invention, the molar ratio of the isophorone diisocyanate to the polytetrahydrofuran is 2.0:1 or 2.5:1.

[0024] In some embodiments of the present invention, the molar ratio of the bis(2-aminophenyl)disulfide and the adipic dihydrazide is 1:1, 2:1 or 3:1.

[0025] In some embodiments of the present invention, the chain extension reaction temperature is 40-70°C, for example 60°C.

[0026] In some embodiments of the present invention, the chain extension reaction time is 7-9 hours, for example, 7 hours.

[0027] As a further embodiment of the present invention, the molar ratio of the chain extender to the isophorone diisocyanate is 1:2.

[0028] In some embodiments of the present invention, the chain extension is carried out under stirring conditions, for example at 100-150 rpm.

[0029] In one embodiment of the present invention, the method for preparing the self-healing polyurethane includes the following steps:

[0030] Step S1: Dehydrate polytetrahydrofuran by vacuum distillation at 110℃ for 0.5-2 hours;

[0031] Step S2: Add polytetrahydrofuran and isophorone diisocyanate to a three-necked flask in a certain proportion;

[0032] Step S3: Add 0.4% by mass of dibutyltin dilaurate to a three-necked flask and mechanically stir at 70-90℃ for 2-3 hours to obtain the prepolymer.

[0033] Step S4: Add a certain amount of chain extender adipic acid dihydrazide and bis(2-aminophenyl) disulfide to a three-necked flask and continue the reaction for 7-9 hours to extend the chain and obtain toughened self-healing polyurethane.

[0034] Step S5: Pour the toughened self-healing polyurethane into the mold, dry it on a constant temperature heating platform, and then place it in a vacuum drying oven to remove the solvent.

[0035] The present invention also provides a self-healing polyurethane, which is prepared by the above method.

[0036] The present invention also provides a method for preparing modified asphalt, which includes the following steps:

[0037] The self-healing polyurethane particles are mixed with the base bitumen to obtain the final product.

[0038] In some embodiments of the present invention, the particle size of the self-healing polyurethane particles is 0.1-1.3 mm.

[0039] In some embodiments of the present invention, the amount of the self-healing polyurethane added is 1-10% of the base asphalt, for example 2%, 4%, 6%, 8%, where the percentage refers to the mass percentage.

[0040] As a further embodiment of the present invention, the base asphalt is heated to 140-160°C and then mixed with the self-healing polyurethane.

[0041] As a further embodiment of the present invention, the matrix asphalt is first mixed with maleic anhydride and then mixed with the self-healing polyurethane.

[0042] The amount of maleic anhydride added is 1-10% of the base asphalt, for example, 2%, 4%, 6%, 8%, where the percentage refers to the mass percentage.

[0043] As a further aspect of the present invention, the mixing process includes shearing and dispersion.

[0044] The shearing speed can be 1500-2000 rpm.

[0045] The shearing time can be 0.5-2 hours.

[0046] The dispersion speed can be 500-700 rpm.

[0047] The dispersion time can be 0.5-1 hour.

[0048] As a further embodiment of the present invention, the mixing process includes heating and melting the base asphalt at 140-160°C, adding maleic anhydride, shearing at 1500-2000 rpm for 30 min, then adding polyurethane, continuing shearing for 45 min, and then dispersing at 500 rpm for 30 min.

[0049] In one embodiment of the present invention, the method for preparing the modified asphalt includes the following steps:

[0050] Step S6: Heat the base asphalt to 140°C, add a certain mass of pulverized self-healing polyurethane to the asphalt, and mix the asphalt and toughening self-healing polyurethane evenly by mechanical stirring.

[0051] Step S7: Pour the mixed modified asphalt into a mold to cool, and then place it in an oven for curing to obtain self-healing polyurethane modified asphalt.

[0052] The present invention also provides a modified asphalt, which is prepared by the above method.

[0053] The present invention also provides an application of the self-healing polyurethane as an asphalt repair agent.

[0054] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0055] The reagents and raw materials used in this invention are all commercially available.

[0056] The positive and progressive effects of this invention are as follows:

[0057] Compared with existing thermosetting polymer-modified asphalt, the self-healing polyurethane modified asphalt prepared in this invention not only possesses a high-strength three-dimensional network structure but also introduces self-healing groups such as hydrogen bonds and disulfide bonds, giving the polyurethane modified asphalt excellent toughness and self-healing properties. This allows the self-healing polyurethane modified asphalt to maintain excellent mechanical properties while also possessing self-healing capabilities. When small cracks appear in the pavement, under the influence of flow properties and dynamic bonds, the overhanging chains containing dynamic bonds diffuse across the two interfaces of the crack to form a cross-linked network, thereby restoring mechanical strength. Different pavement performance and self-healing properties of polyurethane modified asphalt can be designed by adjusting the ratio of soft and hard segments of polyurethane to the chain extender, achieving effects such as good toughness, long pavement service life, and excellent self-healing performance. Attached Figure Description

[0058] Figure 1 The images show the tensile effects of polyurethanes prepared under different conditions in Examples 1, 2, 3, and 5.

[0059] Figure 2 The images show the self-healing effect of the polyurethane strip after it was cut in Example 2, as well as the microscopic and tensile images at 60°C.

[0060] Figure 3 The image shows the stress-strain curves of the polyurethane sample cut in Example 2 after different healing times at 60°C.

[0061] Figure 4 The flowchart shows the preparation process of toughened, self-healing polyurethane modified asphalt in Examples 1-6.

[0062] Figure 5 The image shows the fluorescence microscopy results of the toughened, self-healing polyurethane-modified asphalt in Example 2.

[0063] Figure 6 This is a schematic diagram of the fatigue-healing-fatigue test of the toughened self-healing polyurethane modified asphalt in Example 2; and a graph showing the change of complex shear modulus over time.

[0064] Figure 7The figure shows the fatigue-healing-fatigue test results of the toughened self-healing polyurethane modified asphalt in Example 2; the healing efficiency of BA and BP after 0.5h and 1h healing. Detailed Implementation

[0065] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0066] In the following examples, the terminology for each raw material is explained as follows:

[0067] Polytetrahydrofuran (PTMEG), Mw=2000;

[0068] Isophorone diisocyanate: abbreviated as IPDI;

[0069] N,N-Dimethylacetamide: Abbreviated as DMAC;

[0070] Dibutyltin dilaurate: Abbreviated as DBTDL;

[0071] Adipic acid dihydrazide: abbreviated as ADH;

[0072] bis(2-aminophenyl)disulfide: abbreviated as APD;

[0073] Polyurethane (PU)

[0074] Maleic anhydride: abbreviated as MA;

[0075] Base bitumen: Abbreviated as BA.

[0076] Examples 1-6

[0077] The preparation flow chart of toughened, self-healing polyurethane modified asphalt is as follows: Figure 4 shown. Specifically:

[0078] 1) Dehydrate polytetrahydrofuran (4g) by vacuum distillation at 110℃ for 1h, then cool to room temperature. Add isophorone diisocyanate (0.889g or 1.112g) to a three-necked flask at a molar ratio of 2 or 2.5 with polytetrahydrofuran (i.e., PU2.5 and PU2) and 5ml of N,N-dimethylacetamide. Add dibutyltin dilaurate at 0.4% (by mass) of the reactants to the three-necked flask. Stir mechanically at 85℃ (100rpm) for 3h to obtain the prepolymer. Stop heating and cool to 60℃.

[0079] 2) Chain extenders adipic acid dihydrazide (0.174 g) and bis(2-aminophenyl) disulfide (0.248 g, 0.497 g, 0.744 g) in molar ratios of 1:1, 1:2, and 1:3 were dissolved in 15 ml of N,N-dimethylacetamide and added to a three-necked flask. The mixture was mechanically stirred at 60 °C (100 rpm) for 7 h to continue chain extension, yielding polyurethane. The products were named PU(2.5-P), PU(2.5-2P), PU(2.5-3P), PU(2-P), PU(2-2P), and PU(2-3P).

[0080] 3) Pour the polyurethane containing solvent into the mold, dry it overnight in a fume hood at a constant temperature of 60°C, and then place it in a vacuum dryer at 70°C for one day to remove the solvent. Then, pulverize the sample in a pulverizer to small particles (0.1-1.3 mm).

[0081] 4) The barrelled asphalt was heated in an oven at 160℃ for 4 hours, and then divided into five portions. The portions are numbered ① (503.96g), ② (486.55g), ③ (480.39g), ④ (531.50g), and ⑤ (505.09g).

[0082] 5) Melt No. ① asphalt in a constant temperature jacket at 140-150℃, add 2% maleic anhydride, shear at 1500-2000 rpm for 30 min, then add 2% (BP-2), 4% (BP-4), 6% (BP-6), or 8% (BP-8) polyurethane, continue shearing for 45 min, and then disperse at 500 rpm for 30 min. This yields modified asphalt. Add No. ②, ③, ④, and ⑤ asphalt in other proportions, following the same procedure as No. ① asphalt.

[0083] Table 1

[0084] ;

[0085] Example 1: Polyurethane Tensile Properties Test

[0086] The prepared polyurethane samples (the uncrushed samples from step 3 of Examples 1-6 were cut and then subjected to tensile testing; the sample dimensions were 3mm (width) × 25mm (length) × 0.6mm (thickness)) were subjected to tensile tests. Only PU(2.5-P), PU(2.5-2P), PU(2.5-3P), and PU(2-2P) could be molded; the others were viscous substances. Tensile tests were then conducted on the samples for screening. Figure 1 As shown, PU(2.5-2P) has better mechanical properties and elongation at break, so the PU(2.5-2P) material in Example 2 was selected as the preparation material.

[0087] Example 2: Polyurethane self-healing performance test

[0088] Microscopic observation: A crack was made in the polyurethane film from Example 2 (a strip obtained by cutting the undisturbed sample in step 3, with dimensions of 3mm (width) × 25mm (length) × 0.6mm (thickness)). The film was then repaired in a vacuum drying oven at 60°C, and the repair process was continuously observed by taking photographs. Figure 2 The results showed that the crack was largely repaired after 24 hours of self-healing. Furthermore, a 3mm (width) × 25mm (length) × 0.6mm (thickness) strip was cut and its mechanical properties were tested after healing at 60℃ for 24 hours. The strip was able to stretch a 3kg Teflon reactor. This indicates that good self-healing can be achieved after healing at 60℃ for 24 hours.

[0089] Self-healing efficiency test: The 3mm (width) × 25mm (length) × 0.6mm (thickness) strip from step 3 of Example 2 was cut in half, then spliced ​​together and placed in a 60℃ vacuum drying oven for 4h, 8h, 12h, and 24h for repair. A tensile test was then performed; the self-healing efficiency is the degree of recovery of mechanical properties. Figure 3 As shown in Table 2, the self-healing efficiency is over 95% after 8 hours of healing. Furthermore, the stress and strain data indicate that the material has strong mechanical properties and a very high elongation at break, demonstrating its good toughness and self-healing performance.

[0090] Table 2 shows the stress-strain and self-healing efficiency of the cut specimens at different healing times at 60°C in Example 2.

[0091] Table 2 Self-repair efficiency at different times under 60℃

[0092] ;

[0093] Example 3: Asphalt Performance Test

[0094] (1) Take the modified asphalt from step 5) of Example 2 and observe it under a fluorescence microscope.

[0095] Fluorescence microscopy is mainly used to observe the dispersion of polyurethane after the addition of asphalt. This is because polyurethane emits light under ultraviolet light, while asphalt does not. This allows for a clear observation of the dispersion of polyurethane and whether problems such as agglomeration occur.

[0096] pass Figure 5The fluorescence spectrum shown illustrates that polyurethane can be uniformly dispersed in asphalt. As the proportion increases, the polyurethane particles gradually become larger. This is because when the modified asphalt sample is heated, the hydrogen bonds between the hard segments cause the polyurethane molecules to attract each other, leading to aggregation. In addition to hydrogen bonds, the dynamic covalent bonds between polyurethane molecules containing disulfide bonds make the molecular connections more compact. Therefore, PU(2.5-2P) exhibits obvious aggregation.

[0097] (2) Self-healing efficiency test: The modified asphalt in step 5) of Example 2 was subjected to fatigue-healing-fatigue test.

[0098] Dynamic shear rheometer (DSR) is used to evaluate the healing ability after fatigue cracking. An 8mm plate with a 2mm gap is used, and the test is performed at 25°C with a strain of 4% and a frequency of 10Hz. Figure 6 As shown, loading was stopped when the complex shear modulus of the test sample decreased to 70% of its initial value. After resting for 0.5 h and 1 h, loading was resumed. The healing index equation is as follows:

[0099] ;

[0100] It is the initial complex shear modulus. It is the complex shear modulus at the point where loading stops. It is the complex shear modulus after rest.

[0101] like Figure 7 As shown, compared with BA, the modified asphalt with added PU (2.5-2P) exhibited significantly increased healing efficiency (HI) after both 0.5 h and 1 h. This indicates that the disulfide-bonded polyurethane elastomer indeed promotes the healing of asphalt binders after fatigue damage. The HI at 0.5 h decreased with increasing dosage, while the HI at 1 h was optimal at a dosage of 4%, then decreased with further increases in dosage. This may be because excessive disulfide bonds lead to drastic remodeling of the fracture surface, thereby weakening the healing ability of the modified asphalt.

Claims

1. A method for preparing a self-healing polyurethane, characterized in that, It includes the following steps: (1) In the presence of a catalyst, polytetrahydrofuran and isophorone diisocyanate were mixed and reacted to obtain a prepolymer; (2) The prepolymer and chain extender are mixed and chain extended to obtain the self-healing polyurethane, wherein the chain extender includes adipate dihydrazide and bis(2-aminophenyl) disulfide; The molar ratio of isophorone diisocyanate to polytetrahydrofuran is (2-2.5):1; The molar ratio of the bis(2-aminophenyl)disulfide to the adipate dihydrazide is 2:1; The molar ratio of the chain extender to the isophorone diisocyanate is 1:

2.

2. The method for preparing the self-healing polyurethane as described in claim 1, characterized in that, The catalyst is dibutyltin dilaurate; And / or, the mass of the catalyst is 0.1-1.0% of the reactants, where percentage refers to mass percentage; And / or, prior to the reaction, the polytetrahydrofuran is dehydrated by vacuum distillation at 110°C for 0.5-2 hours; And / or, the Mw of the polytetrahydrofuran is 2000.

3. The method for preparing the self-healing polyurethane as described in claim 1, characterized in that, The reaction was carried out at 100-150 rpm. And / or, the temperature of the reaction is 70-90°C; And / or, the reaction time is 2-3 hours.

4. The method for preparing the self-healing polyurethane as described in claim 1, characterized in that, The chain extension reaction temperature is 40-70℃; And / or, the chain extension reaction time is 7-9 hours; And / or, the chain extension is performed at 100-150 rpm.

5. A self-healing polyurethane, characterized in that, It is prepared by the method for preparing self-healing polyurethane as described in any one of claims 1-4.

6. A method for preparing modified asphalt, characterized in that, It includes the following steps: The base bitumen is first mixed with maleic anhydride and then mixed with the self-healing polyurethane as described in claim 5 to obtain the product. The amount of maleic anhydride added is 1-10% of the base asphalt, where the percentage refers to the mass percentage. The amount of the self-healing polyurethane added is 1-10% of the base asphalt, where the percentage refers to the mass percentage.

7. The method for preparing modified asphalt as described in claim 6, characterized in that, The self-healing polyurethane particles have a particle size of 0.1-1.3 mm; And / or, the base bitumen is heated to 140-160°C and then mixed with the self-healing polyurethane.

8. The method for preparing modified asphalt as described in claim 6 or 7, characterized in that, The mixing process includes shearing and dispersion; The shearing speed is 1500-2000 rpm; The shearing time is 0.5-2 hours. The dispersion speed is 500-700 rpm; The dispersion time is 0.5-1 hour.

9. A modified asphalt, characterized in that, It is prepared by the method of any one of claims 6-8 for the preparation of modified asphalt.

10. The application of the self-healing polyurethane as described in claim 5 as an asphalt repair agent.

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