Bio-based polyurethane coating with self-cleaning and synergistic repairing functions and preparation method of bio-based polyurethane coating

Abstract

The invention discloses a bio-based polyurethane coating with a self-cleaning synergistic repairing function and a preparation method of the bio-based polyurethane coating. The preparation method comprises the following steps: (1) taking castor oil, polypropylene glycol, polydimethylsiloxane glycol, isophorone diisocyanate and dibutyltin dilaurate to react at 70-90 DEG C until the theoretical NCO value in a system is reached, and ending the reaction; (2) after the reaction in the step (1) is finished, adding 2, 2 '-diaminodiphenyl disulfide and 1, 4-butanediol, so that a polyurethane molecular chain is expanded, extended, branched and cross-linked; (3) adding an end-capping reagent ethanolamine, and fully reacting to obtain a prepolymer A; and (4) uniformly mixing the prepolymer A and the hexamethylene diisocyanate tripolymer, and adding acetone to adjust the viscosity of the system until the system can be uniformly stirred to obtain the coating. Castor oil is introduced to partially replace traditional petroleum-based polyol to react with diisocyanate to obtain the bio-based polyurethane coating, and the bio-based polyurethane coating has self-cleaning and repairing functions.

Description

Technical Field

[0001] The invention relates to the technical field of polymer coatings, and in particular to a bio-based polyurethane coating with self-cleaning and synergistic repairing functions and a preparation method thereof. Background Art

[0002] With the acceleration of industrialization and the rapid increase in the number of vehicles, there are more and more pollutants such as oily smoke, exhaust gas and dust, which are easy to adhere to and erode municipal infrastructure. Over time, their appearance and functionality have declined, their service life has been shortened, and the cleaning and maintenance costs have been greatly increased. In order to meet this challenge, reduce the adhesion and erosion of pollutants, reduce the maintenance cost of municipal infrastructure, and extend its service life, it is particularly important to perform "self-cleaning" treatment on its surface. However, in actual outdoor applications, environmental factors often interfere with the self-cleaning performance of the coating, causing its effect to weaken. Therefore, in order to extend the service life of the coating and reduce maintenance costs, it is of great significance to construct a bio-based self-cleaning and synergistic repair function of polyurethane coating. At present, there are still few coatings with excellent self-cleaning and repair functions, which cannot meet market demand. Summary of the invention

[0003] The purpose of the present invention is to provide a bio-based self-cleaning synergistic repairing polyurethane coating and a preparation method thereof in view of the above problems.

[0004] In order to achieve its purpose, the present invention adopts the following technical solution:

[0005] The first aspect of the present invention provides a method for preparing a bio-based self-cleaning synergistic repairing polyurethane coating, comprising the following steps:

[0006] (1) Castor oil (CO), polypropylene glycol (PPG), polydimethylsiloxane diol (PDMS), isophorone diisocyanate (IPDI) and dibutyltin dilaurate (DBTDL) are reacted at 70-90° C. until the theoretical NCO value in the system is reached and the reaction is terminated;

[0007] (2) After the reaction in step (1) is completed, 2,2'-diaminodiphenyl disulfide (DTDA) and 1,4-butanediol (BDO) are added to fully react so that the polyurethane molecular chain is extended, branched and cross-linked;

[0008] (3) After the reaction in step (2) is completed, adding a capping agent, ethanolamine (MEA), and reacting sufficiently to obtain a prepolymer A;

[0009] (4) mixing the obtained prepolymer A and hexamethylene diisocyanate trimer (HT-100) uniformly, adding acetone to adjust the viscosity of the system until it can be uniformly stirred, to obtain the coating;

[0010] Among them, the molar ratio of raw materials castor oil (CO), polypropylene glycol (PPG), polydimethylsiloxane diol (PDMS), isophorone diisocyanate (IPDI), dibutyltin dilaurate (DBTDL), 2,2'-diaminodiphenyl disulfide (DTDA), 1,4-butanediol (BDO), ethanolamine (MEA), and hexamethylene diisocyanate trimer (HT-100) is 1:9-13.5:0-9:61-73:55-65:180-195:20-25:57-66:57-66.

[0011] Preferably, the molar ratio of the raw materials castor oil (CO), polypropylene glycol (PPG), polydimethylsiloxane diol (PDMS), isophorone diisocyanate (IPDI), dibutyltin dilaurate (DBTDL), 2,2'-diaminodiphenyl disulfide (DTDA), 1,4-butanediol (BDO), ethanolamine (MEA), and hexamethylene diisocyanate trimer (HT-100) is 1:9-12:3-9:63-70:57-63:183-190:20-25:60-66:60-66.

[0012] Further preferably, the molar ratio of the raw materials castor oil (CO), polypropylene glycol (PPG), polydimethylsiloxane diol (PDMS), isophorone diisocyanate (IPDI), dibutyltin dilaurate (DBTDL), 2,2'-diaminodiphenyl disulfide (DTDA), 1,4-butanediol (BDO), ethanolamine (MEA), and hexamethylene diisocyanate trimer (HT-100) is 1:9-10.5:6-9:65-67:59-61:185-187:21-23:63-66:63-66.

[0013] Preferably, step (1) is stirred for reaction for 2-5 hours; step (2) is stirred for reaction for 1.5-4 hours; and step (3) is stirred for reaction for 1.5-4 hours.

[0014] Preferably, the Mn of the polypropylene glycol is 400-2000.

[0015] A second aspect of the present invention provides a bio-based self-cleaning synergistic repairing polyurethane coating, which is prepared by any of the preparation methods described above.

[0016] The third aspect of the present invention provides a bio-based self-cleaning synergistic repairing polyurethane coating, which is formed by curing the above-mentioned polyurethane coating.

[0017] The polyurethane coating is formed by applying the polyurethane coating on a substrate and drying and curing it.

[0018] Preferably, the polyurethane coating is formed by applying the polyurethane coating on a substrate, and then curing it by baking at 90-105° C. for 4-6 hours after the surface is dried.

[0019] The beneficial effects of the present invention are:

[0020] (1) Introducing castor oil to partially replace traditional petroleum-based polyols and reacting with diisocyanates to obtain bio-based polyurethane coatings;

[0021] (2) The bio-based self-cleaning and synergistic repair functional polyurethane mainly consists of two parts: prepolymer A and curing agent. Among them, the isocyanate group in prepolymer A is capped to improve the storage stability and construction convenience.

[0022] (3) The coating of the present invention can be used as a coating for municipal infrastructure, thereby reducing the cleaning and maintenance costs of municipal infrastructure and improving its durability and service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 are the stress-strain curves of different polyurethane coatings.

[0024] Figure 2 is the cross-linking density of different polyurethane coatings.

[0025] Figure 3 This is a microscope observation image of the scratch repair of the polyurethane coating at 100°C.

[0026] Figure 4 These are the water contact angle test results of different polyurethane coatings. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with embodiments, but the present invention is not limited thereto.

[0028] The experimental methods in the following examples are conventional methods unless otherwise specified.

[0029] Example 1 Bio-based self-cleaning synergistic repair functional polyurethane coating of the present invention

[0030] 1. Preparation of the bio-based self-cleaning synergistic repair functional polyurethane coating of the present invention

[0031] The raw materials were prepared as follows:

[0032] Castor oil (CO), polypropylene glycol (PPG-2000, molecular weight Mn = 2000), polydimethylsiloxane diol (PDMS), isophorone diisocyanate (IPDI), dibutyltin dilaurate (DBTDL, CAS No. 77-58-7, catalyst), 2,2'-diaminodiphenyl disulfide (DTDA, CAS No. 1141-88-4, self-healing monomer containing disulfide bonds), 1,4-butanediol (BDO), ethanolamine (MEA), hexamethylene diisocyanate trimer (HT-100, molecular weight Mn = 504.6), acetone (for adjusting reaction viscosity). CO, PPG-2000, PDMS are used as soft segments, and IPDI is used as hard segments.

[0033] The specific synthesis steps are as follows:

[0034] (1) At 80°C, castor oil (CO), polypropylene glycol (PPG-2000), polydimethylsiloxane diol (PDMS), isophorone diisocyanate (IPDI) and dibutyltin dilaurate (DBTDL, catalyst) were added into a 250 ml three-necked flask and stirred for 3 h.

[0035] (2) After the reaction in step (1) is completed, 2,2'-diaminodiphenyl disulfide (DTDA) and 1,4-butanediol (BDO) are added to the three-necked flask as chain extenders to promote the extension, branching and cross-linking of the polyurethane molecular chain, and the reaction is continued for 2 hours;

[0036] (3) After the reaction in step (2) is completed, adding a metered amount of ethanolamine (MEA) as a capping agent for the synthesis reaction and reacting for 2 hours to obtain prepolymer A;

[0037] (4) The obtained prepolymer A and curing agent HT-100 are uniformly mixed according to the metered amount, and 5 to 10 g of acetone is added to adjust the viscosity of the system to enable uniform stirring. The mixed solution is then poured into a polytetrafluoroethylene mold, and after the surface is dried for 24 hours, it is further cured in an oven at 100° C. for 5 hours to obtain a bio-based self-cleaning synergistic repairing polyurethane coating.

[0038] Based on the above preparation method, different polyurethane coatings were obtained with the PDMS dosage as a variable (the ratio of -OH molar amount to the total molar amount of the soft segment, 0%, 10%, 20% and 30%), which were named QXPU-0, QXPU-1, QXPU-2 and QXPU-3 respectively. The specific ratio of the raw materials of each sample is shown in Table 1:

[0039] Table 1 Formula (dosage / mol)

[0040] Sample name QXPU-0 QXPU-1 QXPU-2 QXPU-3 PPG-2000(mol) 0.0135 0.012 0.0105 0.009 CO(mol) 0.001 0.001 0.001 0.001 PDMS(mol) 0 0.003 0.006 0.009 IPDI(mol) 0.066 0.066 0.066 0.066 BDO(mol) 0.0225 0.0225 0.0225 0.0225 DTDA(mmol) 0.186 0.186 0.186 0.186 DBTDL(mmol) 0.06 0.06 0.06 0.06 MEA(mol) 0.057 0.06 0.063 0.066 HT-100(mol) 0.057 0.06 0.063 0.066

[0041] 2. Performance Testing

[0042] 1. Tensile test:

[0043] The mechanical properties of polyurethane coatings QXPU-0, QXPU-1, QXPU-2, and QXPU-3 were evaluated by tensile tests. The polyurethane coatings were cut into IV-type dumbbell specimens according to the ASTM D638-2014 standard. The tensile properties were measured at a speed of 50 mm / min using a universal testing machine (DR-508AL), and the stress-strain curves were recorded. The test was carried out in an environment with a temperature of 30 ± 2 °C and a humidity of 53 ± 8%.

[0044] from Figure 1 It can be seen that as the PDMS dosage increases, the tensile strength of the coating shows an increasing trend. The QXPU-0 sample exhibits poor mechanical properties at a lower cross-linking density, with a tensile strength of only 5.31 MPa and an elongation at break of only 140.18%. At this time, the internal molecular structure of the polyurethane coating is loose and soft, and does not have sufficient cohesion to resist deformation caused by external forces, and its overall tensile strength and toughness are poor. With the introduction of PDMS, the mechanical strength and elongation at break of QXPU are improved, among which the tensile strength of the QXPU-3 sample is the highest, reaching 11.09 MPa.

[0045] 2. Swelling test:

[0046] According to the method provided in the reference (Sekkar V, Narayanaswamy K, Scariah KJ, et al. Evaluation by various experimental approaches of the crosslink density of urethane networks based on hydroxyl-terminated polybutadiene [J]. Journal of applied polymer science, 2007, 103 (5): 3129-3133.), QXPU-0, QXPU-1, QXPU-2, and QXPU-3 samples with a size of 7 × 7 × 3 mm were immersed in toluene for 48 hours. The swollen samples were then removed from the solvent and weighed after gently wiping off the solvent. Subsequently, the absorbed solvent was removed by placing the sample in a vacuum oven at 100 ° C for 2 hours, and the weight of the sample was measured.

[0047] The crosslinking density was calculated based on the weight of the sample before and after swelling and the Flory-Rehner formula.

[0048] like Figure 2As shown in the figure, with the increase of PDMS dosage, the crosslinking density of QXPU gradually increases. This is because although the number of crosslinking sites in the polymer structure has not increased, the PDMS structure shortens the distance between the crosslinking sites and the urethane groups, increases the hydrogen bond interaction, enriches the network structure inside the polyurethane, and increases the crosslinking density.

[0049] 3. Self-repair test

[0050] According to the method provided in the reference (Liu Q, Liu Y, Zheng H, et al. Design and development of self-repairable and recyclable crosslinked poly (thiourethane-urethane) via enhanced aliphatic disulfide chemistry [J]. Journal of Polymer Science, 2020, 58 (8): 1092-1104.), the self-healing effect of the coating was analyzed based on the scratch repair observation test under an optical microscope. The sample was cut from the middle with a blade. Subsequently, the cut sample was kept in close contact with the broken incision surface and placed in a hot oven at 100 ° C for repair for 60 minutes, and the self-healing of the incision was monitored every 20 minutes.

[0051] from Figure 3 It can be seen that for sample QXPU-3, at a repair temperature of 100°C, the scratches gradually closed as the repair time increased. This was attributed to the dynamic exchange of disulfide bonds under high temperature stimulation and the reorganization of the abundant hydrogen bonds in the polymer structure, which in turn repaired the scratches.

[0052] 4. Water contact angle detection

[0053] The water contact angle of QXPU-1, QXPU-2 and QXPU-3 coatings was tested to characterize the hydrophobicity of the coatings. Figure 4 As shown. Since PDMS has a low surface energy, it will migrate to the coating surface during the film formation process, making the coating have good hydrophobic properties. The coating prepared by adding PDMS shows water non-wetting characteristics, and the water contact angle of the QXPU-3 coating is the largest, which is 125°. This hydrophobic property helps water droplets roll away pollutants on the coating surface and has a good self-cleaning effect.

Claims

1. A method for preparing a bio-based self-cleaning synergistic repairing polyurethane coating, characterized in that: The steps include: (1) Castor oil (CO), polypropylene glycol (PPG), polydimethylsiloxane diol (PDMS), isophorone diisocyanate (IPDI) and dibutyltin dilaurate (DBTDL) are reacted at 70-90° C. until the theoretical NCO value in the system is reached and the reaction is terminated; (2) After the reaction in step (1) is completed, 2,2'-diaminodiphenyl disulfide (DTDA) and 1,4-butanediol (BDO) are added to fully react so that the polyurethane molecular chain is extended, branched and cross-linked; (3) After the reaction in step (2) is completed, adding a capping agent, ethanolamine (MEA), and reacting sufficiently to obtain a prepolymer A; (4) mixing the obtained prepolymer A and hexamethylene diisocyanate trimer (HT-100) uniformly, adding acetone to adjust the viscosity of the system until it can be uniformly stirred, to obtain the coating; Among them, the molar ratio of raw materials castor oil (CO), polypropylene glycol (PPG), polydimethylsiloxane diol (PDMS), isophorone diisocyanate (IPDI), dibutyltin dilaurate (DBTDL), 2,2'-diaminodiphenyl disulfide (DTDA), 1,4-butanediol (BDO), ethanolamine (MEA), and hexamethylene diisocyanate trimer (HT-100) is 1:9-13.5:0-9:61-73:55-65:180-195:20-25:57-66:57-66.

2. The preparation method according to claim 1, characterized in that: in, The molar ratio of the raw materials castor oil (CO), polypropylene glycol (PPG), polydimethylsiloxane diol (PDMS), isophorone diisocyanate (IPDI), dibutyltin dilaurate (DBTDL), 2,2'-diaminodiphenyl disulfide (DTDA), 1,4-butanediol (BDO), ethanolamine (MEA), and hexamethylene diisocyanate trimer (HT-100) is 1:9-12:3-9:63-70:57-63:183-190:20-25:60-66:60-66.

3. The preparation method according to claim 2, characterized in that: in, The molar ratio of the raw materials castor oil (CO), polypropylene glycol (PPG), polydimethylsiloxane diol (PDMS), isophorone diisocyanate (IPDI), dibutyltin dilaurate (DBTDL), 2,2'-diaminodiphenyl disulfide (DTDA), 1,4-butanediol (BDO), ethanolamine (MEA), and hexamethylene diisocyanate trimer (HT-100) is 1:9-10.5:6-9:65-67:59-61:185-187:21-23:63-66:63-66.

4. The preparation method according to claim 1, characterized in that: Step (1) is stirred for reaction for 2-5 hours; step (2) is reacted for 1.5-4 hours; step (3) is reacted for 1.5-4 hours.

5. The preparation method according to claim 1, characterized in that: The Mn of polypropylene glycol is 400-2000.

6. A bio-based self-cleaning synergistic repairing polyurethane coating, characterized in that: The preparation method is described in any one of claims 1 to 5.

7. A bio-based self-cleaning synergistic repairing polyurethane coating, characterized in that: It is formed by curing the polyurethane coating according to claim 6.

8. The polyurethane coating according to claim 7, characterized in that: The polyurethane coating is applied on a substrate and then dried and solidified.

9. The polyurethane coating according to claim 8, characterized in that: The polyurethane coating is applied on a substrate, and after the surface is dried, it is baked at 90-105° C. for 4-6 hours for curing.

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