Bifunctional self-repairing polyester resin as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of polyester resin powder coatings, and discloses bifunctional self-repairing polyester resin as well as a preparation method and application thereof. According to the polyester resin, a reversible dynamic recombination disulfide bond is introduced into a resin main chain; the outdoor self-repairing low-temperature curing powder coating can be cured to form a film at 140-160 DEG C by combining the polyester resin and the sealing curing agent B1530, cracks and defects are generated due to external temperature fluctuation, mechanical wear or environmental erosion in the service process, and chain segment migration and cross-linking strengthening can be triggered only by performing secondary heating at 180-200 DEG C; the self-healing of the damaged area without additional repairing agent is realized, and the coating structure is re-closed and densified.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polyester resin powder coatings, and particularly relates to a bifunctional self-repairing polyester resin and a preparation method and application thereof. BACKGROUND

[0002] Powder coatings are materials with the characteristics of no solvent and high utilization rate, which are formed by electrostatic spraying and heating curing with solid resin as the film-forming matrix. With the increasing proportion of outdoor applications, the requirements for powder coatings in terms of scratch resistance, wear resistance and environmental stress resistance are increasing, and higher requirements are put forward for the core resin system. Especially when micro-cracks or small notches appear in the coating, the self-repairing property of restoring continuity under subsequent thermal excitation is an important trend to improve the service life of outdoor powder coatings.

[0003] At present, the commonly used self-repairing powder coatings mainly rely on the microcapsule system to realize the repair function. The microcapsule structure is generally coated with a wall material to encapsulate liquid or solid repair agents. After the coating is damaged, the repair material is released to fill the damage. This kind of technology can improve the local scratches to a certain extent, but the repair behavior depends on physical rupture and content flow, and the microcapsules are prone to damage during high-temperature extrusion and baking, resulting in insufficient storage stability.

[0004] In summary, the technical problem to be solved by the present application is to provide a powder coating system that can reliably activate and effectively repair coating cracks or notches, so that the coating has stable and repeatable self-repairing ability, thereby improving the overall service life and performance stability. SUMMARY

[0005] The purpose of the present application is to provide a bifunctional self-repairing polyester resin and a preparation method thereof. By reasonably designing the resin structure, the coating can restore continuity under thermal excitation after damage, thereby improving the durability and service life of the powder coating.

[0006] The purpose of the present application is also to provide a bifunctional self-repairing polyester resin in application. The resin exhibits good film-forming property and self-repairing behavior in the powder coating system, and is suitable for outdoor or wear-resistant scenes that require high reliability.

[0007] The present application provides a bifunctional self-repairing polyester resin, which is prepared from the following raw materials in mass percentage:

[0008] Polyol 20-44%;

[0009] Aromatic polybasic acid 45-60%;

[0010] Branching agent 0-2%;

[0011] acidolysis agent 8-15%;

[0012] esterification catalyst 0.03-0.15%;

[0013] curing accelerator 0.1-0.8%;

[0014] disulfide compound 1.5-5%;

[0015] alcoholysis agent 1-4%;

[0016] antioxidant 0.2-0.4%.

[0017] In the above-mentioned bifunctional self-repairing polyester resin, the polyol is one or more of neopentyl glycol (NPG), ethylene glycol (EG), methylpropanediol (MPO), ethylbutylpropanediol (BEPD), or cyclohexanedimethanol (CHDM).

[0018] In the above-mentioned bifunctional self-repairing polyester resin, the aromatic polyacid is one or more of terephthalic acid (PTA) or isophthalic acid (IPA).

[0019] In the above-mentioned bifunctional self-repairing polyester resin, the branching agent is one or more of trimethylolpropane (TMP) or trimethyloloethane (TME).

[0020] In the above-mentioned bifunctional self-repairing polyester resin, the acidolysis agent is one or more of isophthalic acid (IPA), adipic acid (ADA), 1,4-cyclohexanedicarboxylic acid (CHDA), fumaric acid (FCC), or trimellitic anhydride.

[0021] In the above-mentioned bifunctional self-repairing polyester resin, the esterification catalyst is one or more of dibutyl tin oxide, tributyl tin oxide, dihydroxybutyl tin chloride, stannous oxalate, or monobutyl tin oxide.

[0022] In the above-mentioned bifunctional self-repairing polyester resin, the curing accelerator is one or more of tetraethylammonium bromide, tetramethylammonium bromide, benzyltriethylammonium chloride, triphenyl ethyl phosphonium bromide, or dibutyl tin dilaurate, preferably, the curing accelerator is two or three of triphenyl ethyl phosphonium bromide, benzyltriethylammonium chloride, or dibutyl tin dilaurate.

[0023] In the above-mentioned bifunctional self-repairing polyester resin, the disulfide compound is one or more of 2,2'-dithiodiacetic acid, 3,3'-dithiodipropionic acid, or 4,4'-dithiodibutyric acid.

[0024] In the above-mentioned bifunctional self-healing polyester resin, the alcoholysis agent is a mixture of neopentyl glycol and hydroxymethyl alkyl groups, wherein the mass proportion of neopentyl glycol in the alcoholysis agent is ≥50%, and the hydroxymethyl alkyl group is one or more of trimethylolpropane or trimethylolethane.

[0025] In the above-mentioned bifunctional self-healing polyester resin, the antioxidant comprises a phosphite antioxidant and a hindered phenolic antioxidant, wherein the mass ratio of the phosphite antioxidant to the hindered phenolic antioxidant is 1:3-3:1; the phosphite antioxidant is one or more of antioxidant 626 or antioxidant 168; and the hindered phenolic antioxidant is one or more of antioxidant 1010 or antioxidant 1076.

[0026] In the above-mentioned bifunctional self-healing polyester resin, the acid value of the bifunctional self-healing polyester resin is 25-55 mgKOH / g, the hydroxyl value is 5-20 mgKOH / g resin, and the glass transition temperature (Tg) is ≥60℃.

[0027] The present invention also provides a method for preparing the aforementioned bifunctional self-healing polyester resin, the method comprising the following steps:

[0028] 1) Under an inert gas atmosphere, polyols, branching agents, aromatic polyacids and esterification catalysts are added to a reaction vessel to carry out an esterification reaction;

[0029] 2) Under an inert gas atmosphere, after the esterification reaction in step 1) is completed, an acid hydrolysate and a disulfide compound are added for acid desealing.

[0030] 3) After the acid desealing reaction in step 2) is completed, lower the system temperature to carry out a vacuum polycondensation reaction;

[0031] 4) Under an inert gas atmosphere, after the polycondensation reaction described in step 3) is completed, the system temperature is lowered and an alcoholysis agent is added to carry out an ester exchange reaction. Subsequently, antioxidants and curing accelerators are added to obtain a bifunctional self-healing polyester resin.

[0032] In the above preparation method, the inert gas is either nitrogen or argon. In step 1) of the above preparation method, the esterification reaction is carried out at a temperature of 235-255°C, and the reaction continues until the acid value in the system is 5-20 mg KOH / g.

[0033] In step 2) of the above preparation method, the reaction temperature of the acid unsealing end is 235-250℃, and the reaction continues until the acid value in the system is 35-68 mgKOH / g.

[0034] In step 3) of the above preparation method, the reaction temperature of the polycondensation reaction is 230-240℃, the reaction pressure is -0.1MPa, and the reaction continues until the acid value in the system is 25-55mgKOH / g.

[0035] In step 4) of the above preparation method, the transesterification reaction is carried out at a temperature of 210-230°C for 20 min.

[0036] In step 4) of the above preparation method, the feeding temperature is 180-225℃, and the temperature is maintained for 5-30 minutes after feeding.

[0037] This invention provides an application of the aforementioned bifunctional self-healing polyester resin in cured powder coatings.

[0038] This invention provides an outdoor self-healing low-temperature curing powder coating, which is prepared using the bifunctional self-healing polyester resin as a raw material. The outdoor self-healing low-temperature curing powder coating is prepared from the following raw materials in the indicated mass percentages:

[0039] Bifunctional self-healing polyester resin 40-63%;

[0040] Hardener 5-15%;

[0041] Leveling agent 0.8-1.2%;

[0042] Inorganic pigments: 0.7-30%;

[0043] Inorganic fillers 3-15%;

[0044] Additives 0-2%.

[0045] In the above-mentioned outdoor self-healing low-temperature curing powder coating, the curing agent includes triglycidyl isocyanurate (TGIC) and blocked isocyanate curing agent B1530, and the mass ratio of TGIC to blocked isocyanate curing agent B1530 in the curing agent is 1:0.5-1:2.

[0046] In the above-mentioned outdoor self-healing low-temperature curing powder coating, the leveling agent is GLP588 leveling agent.

[0047] In the aforementioned outdoor self-healing low-temperature curing powder coating, preferably, the inorganic pigment is one of iron oxide yellow, carbon black, or titanium dioxide.

[0048] In the above-mentioned outdoor self-healing low-temperature curing powder coating, the inorganic filler is one or more of nano-silica, barium sulfate, calcium carbonate or talc, and the particle size of the nano-silica is 20-200nm.

[0049] In the above-mentioned outdoor self-healing low-temperature curing powder coating, the additive is a mixture of benzoin and 701B wetting accelerator, wherein the mass ratio of benzoin to 701B wetting accelerator is 1:2-2:1.

[0050] In the above-mentioned outdoor self-healing low-temperature curing powder coating, the curing temperature of the outdoor self-healing powder coating is ≤160℃.

[0051] A method for preparing the aforementioned outdoor self-healing low-temperature curing powder coating, the method comprising the following steps:

[0052] The outdoor self-healing low-temperature curing powder coating is obtained by mixing, extruding, pressing, crushing and sieving the raw materials of each component according to the stated mass percentage.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] 1. The coating can be cured at 140-160℃, which is more energy-efficient than traditional powder systems that require higher curing temperatures. It can reduce the heat load during processing, reduce the risk of thermal impact on the substrate, and is suitable for temperature-sensitive outdoor components.

[0055] 2. If cracks and small gaps are caused by external temperature fluctuations, mechanical friction or environmental erosion during the service period, the self-healing behavior of the material can be triggered by reheating at 180-200℃, so that the damaged area can be closed again and the continuity can be restored. This process does not require external repair agents or mechanical intervention, which helps to reduce maintenance costs.

[0056] 3. The self-healing system constructed in this invention is driven by the dynamic recombination of disulfide bonds on the resin backbone and the reaction of the blocking curing agent B1530 after deblocking at high temperature. The reversible breaking and recombination of disulfide bonds provides the coating with the ability to migrate chain segments and repair damage. After the curing agent is deblocked, it forms urethane bonds with hydroxyl groups, which can further enhance the crosslinking density during the repair stage. The two work synergistically to make the repaired coating form a denser and more stable network structure.

[0057] 4. Compared with existing microencapsulated self-healing powder coatings, this invention achieves intrinsic self-healing by introducing dynamic disulfide bonds into the polyester resin backbone. This mechanism does not require the addition of easily damaged microcapsule structures, thus avoiding the problems of premature release of the repair agent and insufficient storage stability caused by capsule rupture during high-temperature extrusion and baking. Attached Figure Description

[0058] Figure 1 The image shows a comparison of the repair effects of Example 1, Example 3, and Comparative Example 1. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0060] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0061] Example 1

[0062] A method for preparing a bifunctional self-healing polyester resin, the method comprising the following steps:

[0063] 1) Add 1250g NPG, 150g EG, 300g BEPD, 15g TMP, 15g TME, 2000g PTA, 320g IPA, 2g monobutyltin oxide and 2g stannous oxalate to the reactor at the same time, raise the temperature to 250℃ and maintain it.

[0064] 2) After the system has been clarified, take a sample and test the acid value. When it is 5.7 mgKOH / g, add 500g IPA, 40g CHDA, 40g ADA, 50g 2,2'-dithiodiacetic acid and 50g 4,4'-dithiodibutyric acid, and maintain the acid desealing end at 245℃.

[0065] 3) When the acid value reaches 48.9 mgKOH / g, the temperature is lowered to 230℃, and polycondensation is carried out under vacuum of -0.1 MPa until the acid value reaches 38.2 mgKOH;

[0066] 4) Then, the temperature was lowered to 210°C, 40g of NPG and 40g of TMP were added and maintained for 20 min; then the temperature was lowered to 190°C, 4g of triphenylethylphosphine bromide, 4g of dibutyltin dilaurate, 8g of antioxidant 626 and 8g of antioxidant 1010 were added and maintained for 30 min before discharging, thus obtaining the bifunctional self-healing polyester resin. The above steps 1), 2), and 4) were protected with industrial high-purity nitrogen gas with a purity greater than 99.99%. The resin obtained in Example 1 had an acid value of 33.7 mgKOH / g, a hydroxyl value of 12.5 mgKOH / g, a viscosity of 3240 mPa·s at 200°C, and a Tg of 64.2°C.

[0067] Example 2

[0068] A method for preparing a bifunctional self-healing polyester resin, the method comprising the following steps:

[0069] 1) Add 1250g NPG, 150g EG, 300g BEPD, 15g TMP, 15g TME, 2000g PTA, 320g IPA, 2g monobutyltin oxide and 2g stannous oxalate to the reactor at the same time, raise the temperature to 250℃ and maintain it.

[0070] 2) After the system has clarified, take a sample and test the acid value. When it reaches 5.7 mgKOH / g, add 480g IPA, 40g CHDA, 40g ADA, 60g 2,2'-dithiodiacetic acid and 60g 4,4'-dithiodibutyric acid, and maintain the acid desealing end at 245℃.

[0071] 3) When the acid value reaches 49.2 mgKOH / g, the temperature is lowered to 230℃, and polycondensation is carried out under vacuum of -0.1 MPa until the acid value reaches 37.9 mgKOH / g;

[0072] 4) Then, the temperature was lowered to 210°C, 40g of NPG and 35g of TMP were added and maintained for 20 min; then the temperature was lowered to 190°C, 4g of triphenylethylphosphine bromide, 4g of dibutyltin dilaurate, 8g of antioxidant 626 and 8g of antioxidant 1010 were added and maintained for 30 min before discharging, thus obtaining the bifunctional self-healing polyester resin. The above steps 1), 2), and 4) were protected with industrial high-purity nitrogen gas with a purity greater than 99.99%. The resin obtained in Example 2 had an acid value of 32.5 mgKOH / g, a hydroxyl value of 13.6 mgKOH / g, a viscosity of 3120 mPa·s at 200°C, and a Tg of 63.1°C.

[0073] Example 3

[0074] A method for preparing a bifunctional self-healing polyester resin, the method comprising the following steps:

[0075] 1) Add 1250g NPG, 150g EG, 300g BEPD, 15g TMP, 15g TME, 2000g PTA, 320g IPA, 2g monobutyltin oxide and 2g stannous oxalate to the reactor at the same time, raise the temperature to 250℃ and maintain it.

[0076] 2) After the system has clarified, take a sample and test the acid value. When it reaches 8.7 mgKOH / g, add 560g IPA, 40g CHDA, 70g 2,2'-dithiodiacetic acid and 70g 4,4'-dithiodibutyric acid, and maintain the acid desealing end at 245℃.

[0077] 3) When the acid value reaches 59.7 mgKOH / g, the temperature is lowered to 230℃, and polycondensation is carried out under vacuum of -0.1 MPa until the acid value reaches 46.3 mgKOH / g;

[0078] 4) Then, the temperature was lowered to 210°C, 40g of NPG and 50g of TMP were added and maintained for 20 min; then the temperature was lowered to 190°C, 4g of triphenylethylphosphine bromide, 4g of dibutyltin dilaurate, 8g of antioxidant 626 and 8g of antioxidant 1010 were added and maintained for 30 min before discharging, thus obtaining the bifunctional self-healing polyester resin. The above steps 1), 2), and 4) were protected with industrial high-purity nitrogen gas with a purity greater than 99.99%. The resin obtained in Example 3 had an acid value of 40.7 mgKOH / g, a hydroxyl value of 40.7 mgKOH / g, a viscosity of 15.4 mPa·s at 200°C, and a Tg of 65.2°C.

[0079] Comparative Example 1

[0080] A method for preparing a polyester resin, the method comprising the following steps:

[0081] 1) Add 1250g NPG, 150g EG, 300g BEPD, 15g TMP, 15g TME, 2000g PTA, 320g IPA, 2g monobutyltin oxide and 2g stannous oxalate to the reactor at the same time, raise the temperature to 250℃ and maintain it.

[0082] 2) After the system has clarified, take a sample and test the acid value. When it reaches 5.7 mgKOH / g, add 500g of IPA, 40g of CHDA and 40g of ADA, and maintain the acid desealing end at 250℃.

[0083] 3) When the acid value reaches 48.9 mgKOH / g, the temperature is lowered to 240℃, and polycondensation is carried out under vacuum of -0.1 MPa until the acid value reaches 38.2 mgKOH / g;

[0084] 4) Cool down to 190℃, add 4g of triphenylethylphosphine bromide, 4g of dibutyltin dilaurate, 6268g of antioxidant, and 8g of antioxidant 1010, and maintain for 30 min before discharging to obtain polyester resin. In steps 1), 2), and 4), industrial high-purity nitrogen with a purity greater than 99.99% is used for protection. The resin obtained in Comparative Example 1 has an acid value of 32.5 mgKOH / g, a hydroxyl value of 2.4 mgKOH / g, a viscosity of 3240 mPa·s at 200℃, and a Tg of 65.7℃.

[0085] Comparative Example 2

[0086] A method for preparing a polyester resin, the method comprising the following steps:

[0087] 1) Add 1250g NPG, 150g EG, 300g BEPD, 15g TMP, 15g TME, 2000g PTA, 320g IPA, 2g monobutyltin oxide and 2g stannous oxalate to the reactor at the same time, raise the temperature to 250℃ and maintain it.

[0088] 2) After the system has clarified, take a sample and test the acid value. When it reaches 8.7 mgKOH / g, add 580g of IPA, 40g of CHDA, and 40g of ADA, and maintain the acid desealing end at 245℃.

[0089] 3) When the acid value reaches 49.6 mgKOH / g, the temperature is lowered to 230℃, and polycondensation is carried out under vacuum of -0.1 MPa until the acid value reaches 39.7 mgKOH / g;

[0090] 4) Then, the temperature was lowered to 210℃, 40g of NPG and 40g of TMP were added and maintained for 20 min; then the temperature was lowered to 190℃, 4g of triphenylethylphosphine bromide, 4g of dibutyltin dilaurate, 8g of antioxidant 626 and 8g of antioxidant 1010 were added and maintained for 30 min before discharging to obtain polyester resin. In the above steps 1), 2), and 4), industrial high-purity nitrogen with a purity greater than 99.99% was used for protection. The resin obtained in Comparative Example 2 had an acid value of 33.5 mgKOH / g, a hydroxyl value of 13.6 mgKOH / g, a viscosity of 3920 mPa·s at 200℃, and a Tg of 65.3℃.

[0091] Application Example 1

[0092] An outdoor self-healing low-temperature curing powder coating, wherein the outdoor self-healing low-temperature curing powder coating is prepared from the following raw materials in the following mass percentages:

[0093] 558g of the bifunctional self-healing polyester resin prepared in Example 1;

[0094] TGIC 42g;

[0095] B1530 60g;

[0096] GLP588 10g;

[0097] 3g of benzoin;

[0098] 701B 3g;

[0099] 250g of titanium dioxide;

[0100] 134g of barium sulfate.

[0101] A method for preparing an outdoor self-healing low-temperature curing powder coating, the method comprising the following steps:

[0102] The outdoor self-healing low-temperature curing powder coating is obtained by mixing the raw materials of each component according to the mass percentage, extruding, pressing into tablets, grinding in a coffee mill, and sieving through a 200-mesh sieve.

[0103] Application Example 2

[0104] An outdoor self-healing low-temperature curing powder coating, wherein the outdoor self-healing low-temperature curing powder coating is prepared from the following raw materials in the following mass percentages:

[0105] 558g of the bifunctional self-healing polyester resin prepared in Example 2;

[0106] TGIC 42g;

[0107] B1530 60g;

[0108] GLP588 10g;

[0109] 3g of benzoin;

[0110] 701B 3g;

[0111] 250g of titanium dioxide;

[0112] 134g of barium sulfate.

[0113] A method for preparing an outdoor self-healing low-temperature curing powder coating, the method comprising the following steps:

[0114] The preparation method described in this application example is the same as that in application example 1.

[0115] Application Example 3

[0116] An outdoor self-healing low-temperature curing powder coating, wherein the outdoor self-healing low-temperature curing powder coating is prepared from the following raw materials in the following mass percentages:

[0117] 552g of the bifunctional self-healing polyester resin prepared in Example 3;

[0118] TGIC 48g;

[0119] B1530 60g;

[0120] GLP588 10g;

[0121] 3g of benzoin;

[0122] 701B 3g;

[0123] 250g of titanium dioxide;

[0124] 134g of barium sulfate.

[0125] A method for preparing an outdoor self-healing low-temperature curing powder coating, the method comprising the following steps:

[0126] The preparation method described in this application example is the same as that in application example 1.

[0127] Application Comparative Example 1

[0128] A powder coating, said powder coating being prepared from the following raw materials in the following mass percentages:

[0129] 558g of polyester resin prepared in Comparative Example 1;

[0130] TGIC 42g;

[0131] B1530 60g;

[0132] GLP588 10g;

[0133] 3g of benzoin;

[0134] 701B 3g;

[0135] 250g of titanium dioxide;

[0136] 134g of barium sulfate.

[0137] A method for preparing a powder coating, the method comprising the following steps:

[0138] The preparation method described in this comparative example is the same as that in Application Example 1.

[0139] Application Comparative Example 2

[0140] A powder coating, said powder coating being prepared from the following raw materials in the following mass percentages:

[0141] 558g of polyester resin was prepared in Comparative Example 2;

[0142] TGIC 42g;

[0143] B1530 60g;

[0144] GLP588 10g;

[0145] 3g of benzoin;

[0146] 701B 3g;

[0147] 250g of titanium dioxide;

[0148] 134g of barium sulfate.

[0149] A method for preparing a powder coating, the method comprising the following steps:

[0150] The preparation method described in this comparative example is the same as that in Application Example 1.

[0151] Test Example 1

[0152] The powder coatings described in the above embodiments and comparative examples were sprayed onto the surface of an iron plate using electrostatic spraying. After baking at 160°C for 15 minutes, the different properties of the coatings were tested. The film thickness test method followed GB / T 13452.2-2008, the gelation time test method followed GB / T 16995-1997, the gloss (60°) test method followed GB / T 9754-2007, and the frontal and back impact strength test methods followed GB / T 1732-2020. The adhesion test method followed GB / T According to 9286-2021, the leveling rating PCI was tested using a standard PCI board. Ratings from 1 to 10 represent improvements in leveling performance, with rating 1 indicating severe orange peel (poor leveling) and rating 10 indicating no orange peel and a smooth surface. For each embodiment and comparative example, the iron plate surface coated with powder coating was scratched, and then baked at 200℃ for 10 minutes. Image analysis was used to quantify the self-healing ratio of the coating. MATLAB software was used to process scanning electron microscope images before and after scratch or crack repair to calculate the percentage reduction in scratch defect area. The repair ratio η = (initial scratch area - repaired scratch area) / initial scratch area × 100%. Weather resistance was tested using UVB, following the test method in GSB AL631-2012: 9.22.1. The time it took for the gloss to decrease to 50% of the original gloss was recorded; a longer time indicates better outdoor weather resistance. The test results are shown in Table 1.

[0153] Table 1 Performance Test Table

[0154]

[0155] As shown in Table 1, the dry film thickness of the coatings in Examples 1-3 of the present invention is controlled at 70-90 μm, which is comparable to that of Comparative Examples 1-2. The conventional properties such as gelation time, gloss (60°), leveling grade (PCI), front impact strength, back impact strength and adhesion are comparable to or consistent with those of the comparative examples. The impact strength reaches 50 kg·cm, the adhesion is grade 0, and the outdoor weather resistance can reach >350h, indicating that the introduction of self-healing components has no adverse effect on the basic physical properties of the coating.

[0156] Meanwhile, the coatings of Examples 1-3 exhibited significant self-healing capabilities. After scratch damage and room temperature repair, the self-healing rates reached 40%, 70%, and 80%, respectively, with Example 3 showing the best self-healing effect. In contrast, the self-healing rates of Comparative Examples 1-2 were all 0%, indicating no self-healing ability. The iron plates of Examples 1, 3, and Comparative Example 1, coated with powder coating, were scratched. After a second baking at 200°C for 10 minutes, the surface conditions of Examples 1, 3, and Comparative Example 1 were as follows: Figure 1 As shown, from Figure 1 As can be seen from the above, Examples 1 and 3 of the present invention are significantly superior to Comparative Example 1. The results show that the bifunctional self-healing polyester resin provided by the present invention significantly improves the self-healing ability of the coating while maintaining excellent conventional properties.

[0157] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0158] The above description of the embodiments is intended to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A bifunctional self-healing polyester resin, characterized in that, The bifunctional self-healing polyester resin is prepared from the following raw materials in the indicated mass percentages: Polyols 20-44%; Aromatic polyacids 45-60%; Branching agent 0-2%; Acid hydrolysate 8-15%; Esterification catalyst: 0.03-0.15%; Curing accelerator 0.1-0.8%; Disulfide compounds 1.5-5%; Alcohololysis agent 1-4%; Antioxidant 0.2-0.4%.

2. The bifunctional self-healing polyester resin according to claim 1, characterized in that, The polyol is one or more of neopentyl glycol, ethylene glycol, methyl propylene glycol, ethyl butyl propylene glycol, or cyclohexanediol; the aromatic polyacid is one or more of terephthalic acid or isophthalic acid; the branching agent is one or more of trimethylolpropane or trimethylolethane; the acid hydrolysate is one or more of isophthalic acid, adipic acid, 1,4-cyclohexanedicarboxylic acid, fumaric acid, or trimellitic anhydride; the esterification catalyst is one or more of dibutyltin oxide, tributyltin oxide, dihydroxybutyltin chloride, stannous oxalate, or monobutyltin oxide; and the curing accelerator is one or more of tetraethylammonium bromide, tetramethylammonium bromide, benzyltriethylammonium chloride, triphenylethylphosphine bromide, or dibutyltin dilaurate.

3. The bifunctional self-healing polyester resin according to claim 1, characterized in that, The disulfide compound is one or more of 2,2'-dithiodiacetic acid, 3,3'-dithiodipropionic acid, or 4,4'-dithiodibutyric acid.

4. The bifunctional self-healing polyester resin according to claim 1, characterized in that, The alcoholysis agent is a mixture of neopentyl glycol and hydroxymethyl alkyl groups, wherein the mass proportion of neopentyl glycol in the alcoholysis agent is ≥50%, and the hydroxymethyl alkyl group is one or more of trimethylolpropane or trimethylolethane; the antioxidant comprises phosphite antioxidants and hindered phenolic antioxidants, wherein the mass ratio of phosphite antioxidants to hindered phenolic antioxidants in the antioxidant is 1:3-3:1; the phosphite antioxidant is one or more of antioxidant 626 or antioxidant 168; the hindered phenolic antioxidant is one or more of antioxidant 1010 or antioxidant 1076.

5. A method for preparing the bifunctional self-healing polyester resin as described in any one of claims 1-4, characterized in that, The preparation method includes the following steps: 1) Under an inert gas atmosphere, polyols, branching agents, aromatic polyacids and esterification catalysts are added to a reaction vessel to carry out an esterification reaction; 2) Under an inert gas atmosphere, after the esterification reaction in step 1) is completed, an acid hydrolysate and a disulfide compound are added for acid desealing. 3) After the acid desealing reaction in step 2) is completed, lower the system temperature to carry out the polycondensation reaction; 4) Under an inert gas atmosphere, after the polycondensation reaction described in step 3) is completed, the system temperature is lowered and an alcoholysis agent is added to carry out an ester exchange reaction. Subsequently, an antioxidant and a curing accelerator are added to obtain a bifunctional self-healing polyester resin.

6. The method for preparing the bifunctional self-healing polyester resin according to claim 5, characterized in that, The esterification reaction is carried out at a temperature of 235-255℃ and continues until the acid value in the system is 5-20 mg KOH / g; the acid desealing reaction is carried out at a temperature of 235-250℃ and continues until the acid value in the system is 35-68 mg KOH / g; the polycondensation reaction is carried out at a temperature of 230-240℃ and a pressure of -0.1 MPa, and continues until the acid value in the system is 25-55 mg KOH / g; the transesterification reaction is carried out at a temperature of 210-230℃ and a reaction time of 20 min.

7. The application of the bifunctional self-healing polyester resin as described in claim 1 in cured powder coatings.

8. An outdoor self-healing low-temperature curing powder coating, characterized in that, The outdoor self-healing low-temperature curing powder coating is prepared using the bifunctional self-healing polyester resin of claim 1 as a raw material, and the outdoor self-healing low-temperature curing powder coating is prepared from the following raw materials in the indicated mass percentages: Bifunctional self-healing polyester resin 40-63%; Hardener 5-15%; Leveling agent 0.8-1.2%; Inorganic pigments: 0.7-30%; Inorganic fillers 3-15%; Additives 0-2%.

9. The outdoor self-healing low-temperature curing powder coating according to claim 8, characterized in that, The curing agent comprises triglycidyl isocyanate and blocked isocyanate curing agent B1530, wherein the mass ratio of TGIC to blocked isocyanate curing agent B1530 in the curing agent is 1:0.5-1:22; the leveling agent is GLP588 leveling agent; the inorganic filler is one or more of nano silica, barium sulfate, calcium carbonate or talc; the auxiliary agent is a mixture of benzoin and 701B wetting accelerator, wherein the mass ratio of benzoin to 701B wetting accelerator in the auxiliary agent is 1:2-2:

1.

10. A method for preparing an outdoor self-healing low-temperature curing powder coating as described in claim 9, characterized in that, The preparation method includes the following steps: The outdoor self-healing low-temperature curing powder coating is obtained by mixing, extruding, pressing, crushing and sieving the raw materials of each component according to the stated mass percentage.

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