Self-repairing polyurethane, modified asphalt, preparation method and application

Abstract

The invention discloses self-repairing polyurethane, modified asphalt, a preparation method and application, and belongs to the technical field of high polymer materials. The preparation method of the self-repairing polyurethane comprises the following steps: (1) in the presence of a catalyst, mixing and reacting polytetrahydrofuran and isophorone diisocyanate to obtain a prepolymer; (2) the prepolymer and a chain extender are mixed and subjected to chain extension, polyurethane capable of being self-repaired is obtained, and the chain extender comprises adipic acid dihydrazide and bis (2-aminophenyl) disulfide; the molar ratio of the isophorone diisocyanate to the polytetrahydrofuran is (2 to 3): 1; the molar ratio of the bis (2-aminophenyl) disulfide to the adipic dihydrazide is (1-3): 1. The polyurethane is added into asphalt to obtain modified asphalt. The self-repairing polyurethane modified asphalt disclosed by the invention has excellent low-temperature and high-temperature performance, toughness, active healing capability and good regeneration performance.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to self-repairable polyurethane, modified asphalt, a preparation method and application. Background Art

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

[0003] In recent years, with the rapid development of economy, people have gradually put forward higher requirements for traffic road pavement. Polymer modified asphalt is a promising material with excellent physical and chemical properties. It can not only improve driving comfort but also extend service life. It has been widely used. However, long-term traffic load and various bad weather make it inevitable to crack, which will accelerate damage and shorten service life.

[0004] Since thermosetting polymers do not have self-healing properties, the three-dimensional network structure they form inside the matrix asphalt wraps the asphalt particles, limiting the healing properties of the matrix asphalt. Therefore, although thermosetting polymer modified asphalt has high mechanical strength and temperature adaptability, it has the disadvantages of high brittleness, poor impact resistance and insufficient crack resistance.

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

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a self-repairing polyurethane, modified asphalt, preparation method and application to solve the problem that the thermosetting polymer modified asphalt in the above-mentioned background technology lacks self-repairing performance.

[0007] The inventors discovered during the research and development process that polyurethane (PU) has advantages such as good mechanical properties and low-temperature toughness. By introducing dynamic covalent bonds / non-dynamic covalent bonds into the chemical structure of polyurethane, it can be endowed with excellent mechanical properties and self-healing properties to achieve 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-healing ability and improve thermal stability, allowing the material to be reprocessed and healed in the solid state.

[0008] To achieve the above object, the present invention provides the following technical solutions.

[0009] The present invention provides a method for preparing a self-repairable polyurethane, which comprises the following steps:

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

[0011] (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;

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

[0013] The molar ratio of the bis(2-aminophenyl) disulfide to the adipic acid 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, such as 0.4%, where the percentage refers to the mass percentage.

[0016] In some embodiments of the present invention, before the reaction, the polytetrahydrofuran is dehydrated by reduced pressure distillation at 110° C. for 0.5-2 h.

[0017] In some embodiments of the present invention, the Mw (weight average molecular weight) of the polytetrahydrofuran is 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 to the adipic acid 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 to the adipic acid dihydrazide is 1:1, 2:1 or 3:1.

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

[0026] In some embodiments of the present invention, the reaction time of the chain extension 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-repairable polyurethane comprises the following steps:

[0030] Step S1, dehydrating polytetrahydrofuran by vacuum distillation at 110° C. for 0.5-2 h;

[0031] Step S2, adding polytetrahydrofuran and isophorone diisocyanate in a certain proportion into a three-necked flask;

[0032] Step S3, adding 0.4% of dibutyltin dilaurate by weight of the reactants into a three-necked flask, mechanically stirring at 70-90° C. for 2-3 hours to obtain a prepolymer;

[0033] Step S4, adding a certain amount of chain extenders adipic acid dihydrazide and bis(2-aminophenyl) disulfide into a three-necked flask, and continuing the reaction for 7-9 hours to extend the chain to obtain a toughened self-repairable polyurethane;

[0034] Step S5, pouring the toughened self-repairable polyurethane into the mold, drying it on a constant temperature heating platform, and then placing it in a vacuum drying oven to remove the solvent.

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

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

[0037] The self-repairable polyurethane particles are mixed with base asphalt to obtain the 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%, and the percentage refers to the mass percentage.

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

[0041] As a further solution of the present invention, the base 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, such as 2%, 4%, 6%, 8%, and the percentage refers to the mass percentage.

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

[0044] Wherein, the shearing speed may be 1500-2000 rpm.

[0045] Wherein, the shearing time may be 0.5-2h.

[0046] Wherein, the dispersing speed may be 500-700 rpm.

[0047] The dispersion time may be 0.5-1h.

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

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

[0050] Step S6, heating the base asphalt to 140° C., adding a certain mass of crushed self-repairable polyurethane into the asphalt, and mixing the asphalt and the toughened self-repairable polyurethane uniformly by mechanical stirring;

[0051] Step S7: pour the mixed modified asphalt into a mold to cool it, and then put it into an oven for curing to obtain self-repairing 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-repairable polyurethane as an asphalt repair agent.

[0054] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0055] The reagents and raw materials used in the present invention are commercially available.

[0056] The positive and progressive effects of the present invention are:

[0057] Compared with the existing thermosetting polymer modified asphalt, the self-repairing polyurethane modified asphalt prepared by the present invention not only has a high-strength three-dimensional network structure, but also introduces self-repairing groups such as hydrogen bonds and disulfide bonds, so that the polyurethane modified asphalt has good toughness and self-repairing properties. This allows the self-repairing polyurethane modified asphalt to have self-repairing properties while ensuring excellent mechanical properties. When small cracks appear on the road surface, under the action of flow properties and dynamic bonds, the pendant chains containing dynamic bonds diffuse with each other at the two interfaces of the cracks to form a cross-linked network, thereby restoring mechanical strength. By adjusting the ratio of the soft and hard segments of the polyurethane and the ratio of the chain extender, polyurethane modified asphalt with different road performance and self-repairing properties can be designed, with good toughness, long road service life, excellent self-repairing properties and other effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 The diagram is a stretching effect diagram of the polyurethane prepared under different conditions in Examples 1, 2, 3, and 5.

[0059] Figure 2 These are the self-repairing microscope and stretching effect diagrams of the polyurethane strips in Example 2 after being cut at 60°C.

[0060] Figure 3 This is a stress-strain curve diagram of the polyurethane strip in Example 2 at different healing times at 60°C after being cut.

[0061] Figure 4 This is a flow chart for preparing the toughened self-repairable polyurethane modified asphalt in Examples 1-6.

[0062] Figure 5 This is the fluorescence microscopy result of the toughened self-repairable polyurethane modified asphalt in Example 2.

[0063] Figure 6 Schematic diagram of fatigue-healing-fatigue test of toughened self-repairable polyurethane modified asphalt in Example 2; Graph showing the change of complex shear modulus over time.

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

[0065] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific 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 work are within the scope of protection of the present invention.

[0066] In the following examples, the terms for each raw material are described as follows:

[0067] Polytetrahydrofuran: referred to as PTMEG, Mw = 2000;

[0068] Isophorone diisocyanate: IPDI for short;

[0069] N,N-dimethylacetamide: DMAC for short;

[0070] Dibutyltin dilaurate: referred to as DBTDL;

[0071] Adipic acid dihydrazide: referred to as ADH;

[0072] Bis(2-aminophenyl) disulfide: APD for short;

[0073] Polyurethane: referred to as PU;

[0074] Maleic anhydride: MA for short;

[0075] Base asphalt: referred to as BA.

[0076] Examples 1-6

[0077] The preparation process of toughened self-repairable polyurethane modified asphalt is as follows: Figure 4 shown. Specifically:

[0078] 1) Polytetrahydrofuran (4 g) was dehydrated by vacuum distillation at 110° C. for 1 h, and then cooled to room temperature. Isophorone diisocyanate (0.889 g or 1.112 g) was added to a three-necked flask at a molar ratio of 2 or 2.5 (i.e., PU2.5 and PU2) with polytetrahydrofuran and 5 ml of N,N-dimethylacetamide. Dibutyltin dilaurate with a mass of 0.4% (the percentage refers to the mass percentage) of the reactants was added to the three-necked flask, and mechanically stirred (100 rpm) at 85° C. for 3 h to obtain a prepolymer, and the heating was stopped and cooled to 60° C.

[0079] 2) Dissolve the 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 in 15 ml of N,N-dimethylacetamide and add the mixture into a three-necked flask. Continue the reaction at 60°C with mechanical stirring (100 rpm) for 7 h to extend the chain and obtain polyurethane. The products are 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 on a 60°C constant temperature heating platform in a fume hood, and then place it in a vacuum dryer at 70°C for one day to remove the solvent. The sample is crushed in a grinder to small particles (0.1-1.3 mm);

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

[0082] 5) Heat No. 1 asphalt on a constant temperature heating jacket at 140-150℃ to melt, add 2% maleic anhydride, shear at 1500-2000rpm for 30min, then add 2% (BP-2), 4% (BP-4), 6% (BP-6) or 8% (BP-8) polyurethane, continue shearing for 45min, and then disperse at 500rpm for 30min. To obtain modified asphalt, add No. 2, No. 3, No. 4, No. 5 asphalt in other proportions, and operate the same as No. 1 asphalt.

[0083] Table 1

[0084]

[0085] Effect Example 1 Polyurethane tensile properties test

[0086] The prepared polyurethane (the test object is the un-crushed sample in step 3 of Example 1-6, which is cut and then subjected to a tensile test, and the sample size is 3mm (width) × 25mm (length) × 0.6mm (thickness)) was subjected to a tensile test. Only PU (2.5-P), PU (2.5-2P), PU (2.5-3P), and PU (2-2P) can be formed in the mold, and the others are viscous. The sample was subjected to a tensile test for screening, such as Figure 1 As shown, it can be seen that 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] Effect Example 2 Polyurethane Self-Healing Performance Test

[0088] Microscope observation: The polyurethane film in Example 2 (a specimen obtained by cutting the un-crushed sample in step 3, with a specimen size of 3 mm (width) × 25 mm (length) × 0.6 mm (thickness)) was cut with a knife, and repaired in a vacuum drying oven at 60°C, and photos were taken continuously to observe the repair of the crack. Figure 2 It can be seen that after 24 hours of self-repair, the cracks were largely repaired. And the specimens of 3mm (width) × 25mm (length) × 0.6mm (thickness) were cut and the mechanical properties were tested after healing at 60℃ for 24 hours. The 3kg Teflon reactor can be stretched. This shows that good self-repair can be achieved after healing at 60℃ for 24 hours.

[0089] Self-repair efficiency test: The 3mm (width) × 25mm (length) × 0.6mm (thickness) sample strips in step 3 of Example 2 were cut in the middle, then spliced ​​together and placed in a 60°C vacuum drying oven for repair for 4h, 8h, 12h, and 24h. Then a tensile test was performed. The self-repair efficiency is the degree of recovery of mechanical properties. Figure 3 From the tensile data in Table 1, we can see that the self-healing efficiency is as high as over 95% after 8 hours of healing. And from the stress and strain, we can see that the material has strong mechanical properties and very high elongation at break, indicating that it has good toughness and self-healing properties.

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

[0091] Table 2 Self-repair efficiency at different times at 60°C

[0092] Sample name Tensile stress (MPa) Tensile strain (%) Self-healing efficiency (%) PU heating 0h 15.75 1741.42 / PU heating 4h 11.98 1461.28 76.06 PU heating 8h 15.01 1824.47 95.30 PU heating 12h 15.69 1985.95 99.60 PU heating 24h 15.85 1982.51 100.60

[0093] Effect Example 3 Asphalt Performance Test

[0094] (1) Take the modified asphalt in 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 it is added to asphalt. Because polyurethane will glow under ultraviolet light, while asphalt will not, this allows us to clearly observe the dispersion of polyurethane and whether problems such as agglomeration occur.

[0096] pass Figure 5The fluorescence image shown illustrates that polyurethane can be evenly dispersed in asphalt. As the proportion increases, the particles of polyurethane gradually become larger. The reason is that when the modified asphalt sample is heated, the hydrogen bonds between the hard segments cause the polyurethane molecules to attract each other, resulting in agglomeration. In addition to hydrogen bonds, the dynamic covalent bonds between the polyurethane molecules containing disulfide bonds make the molecules more tightly connected, so PU (2.5-2P) shows obvious agglomeration.

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

[0098] DSR (Dynamic Shear Rheometer) is used to evaluate the healing ability after fatigue cracking. It uses an 8mm plate with a gap of 2mm, a temperature of 25°C, a strain of 4% and 10Hz. Figure 6 As shown, when the complex shear modulus of the test sample decreases to 70% of the initial value, the loading is stopped, and after resting for 0.5h and 1h, the loading is resumed. The healing index equation is as follows:

[0099]

[0100] |G * | initial is the initial complex shear modulus, |G * | terminal is the complex shear modulus when loading stops,

[0101] |G * | healing is the complex shear modulus after rest.

[0102] like Figure 7 As shown in the figure, compared with BA, the healing efficiency (HI) of the modified asphalt with the addition of PU (2.5-2P) increased significantly after 0.5h and 1h. This shows that the disulfide bond polyurethane elastomer does promote the healing of the asphalt binder after fatigue damage. The HI of 0.5h decreases with the increase of the dosage, and the HI of 1h is the best when the dosage is 4%, and then decreases with the increase of the dosage. The reason may be that excessive disulfide bonds will cause severe reorganization of the fracture surface, thereby weakening the healing ability of the modified asphalt.

Claims

1. A method for preparing a self-repairable polyurethane, characterized in that: It includes the following steps: (1) in the presence of a catalyst, polytetrahydrofuran and isophorone diisocyanate are mixed and reacted 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; The molar ratio of the bis(2-aminophenyl) disulfide to the adipic acid dihydrazide is (1-3):

1.

2. The method for preparing the self-repairable polyurethane according to 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 the percentage refers to the mass percentage; and / or, before the reaction, the polytetrahydrofuran is dehydrated by distillation under reduced pressure at 110° C. for 0.5-2 h; And / or, the Mw of the polytetrahydrofuran is 2000.

3. The method for preparing the self-repairable polyurethane according to claim 1, characterized in that: The reaction is carried out at 100-150 rpm; And / or, the reaction temperature is 70-90°C; And / or, the reaction time is 2-3h.

4. The method for preparing the self-repairable polyurethane according to claim 1, characterized in that: The molar ratio of the isophorone diisocyanate to the polytetrahydrofuran is (2-2.5):1; and / or, the molar ratio of the bis(2-aminophenyl) disulfide to the adipic acid dihydrazide is (1.5-2.5):1; And / or, the reaction temperature of the chain extension is 40-70°C; And / or, the reaction time of the chain extension is 7-9h; and / or, the molar ratio of the chain extender to the isophorone diisocyanate is 1:2; And / or, the chain extension is carried out at 100-150 rpm.

5. A self-repairable polyurethane, characterized in that: The self-repairable polyurethane is prepared by the preparation method of any one of claims 1 to 4.

6. A method for preparing modified asphalt, characterized in that: It includes the following steps: The self-repairable polyurethane particles as described in claim 5 are mixed with matrix asphalt to obtain the product.

7. The method for preparing modified asphalt according to claim 6, characterized in that: The particle size of the self-repairable polyurethane particles is 0.1-1.3 mm; And / or, the amount of the self-repairable polyurethane added is 1-10% of the base asphalt, and the percentage refers to the mass percentage; and / or, heating the base asphalt to 140-160° C. and then mixing it with the self-repairable polyurethane; And / or, the matrix asphalt is first mixed with maleic anhydride and then mixed with the self-healing polyurethane; wherein the amount of maleic anhydride added is 1-10% of the matrix asphalt, and the percentage refers to the mass percentage.

8. The method for preparing modified asphalt according to claim 6 or 7, characterized in that: The mixing process includes shearing and dispersing; Wherein, the shearing speed is 1500-2000rpm; Wherein, the shearing time is 0.5-2h; Wherein, the dispersing speed is 500-700rpm; Wherein, the dispersion time is 0.5-1h.

9. A modified asphalt, characterized in that: The modified asphalt is prepared by the method for preparing the modified asphalt as described in any one of claims 6 to 8.

10. Use of the self-repairable polyurethane as claimed in claim 5 as an asphalt repair agent.

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