Modified polyester resin for powder coating and preparation method thereof

Abstract

The invention belongs to the technical field of resin modification, and particularly relates to modified polyester resin for a powder coating and a preparation method of the modified polyester resin. Comprising the following materials in parts by mass: 100 parts of terephthalic acid, 12-15 parts of adipic acid, 45-60 parts of neopentyl glycol, 18-22 parts of propylene glycol, 6-10 parts of trimethylolpropane, 4-5 parts of glycerol, 2.5-3 parts of a silane coupling agent, 10-12 parts of an epoxy-organosilicon copolymer, 8-10 parts of a composite modifier, 0.2-0.3 part of zinc acetate, 1.5-2 parts of diphenyl ether and 3-4 parts of PVP (Polyvinyl Pyrrolidone). Epoxy and organic silicon are condensed to form a copolymer containing a Si-O-C bond, so that the weather resistance and other properties are improved, and the grafted resin enhances the flexibility and crosslinking property; and the MOF prepared from the waste plastic is compounded with the fluororesin, the MOF adsorbs and connects the MOF and the fluororesin to reduce phase separation, and the MOF structure supports a network to realize self-cleaning and corrosion-resistant functions.

Description

Technical Field

[0001] The present invention belongs to the technical field of resin modification, and in particular relates to a modified polyester resin for powder coatings and a preparation method thereof. Background Art

[0002] In the field of powder coatings, although traditional polyester resins are widely used, they often have deficiencies in terms of weather resistance, high temperature resistance, chemical resistance, adhesion, flexibility, mechanical properties, etc., and some products also face problems such as phase separation, poor compatibility, and difficulty in balancing self-cleaning and corrosion resistance, and cannot meet the use requirements of some high-end or special environments; at the same time, the recycling of waste plastics is also an environmental issue that needs to be urgently addressed. How to effectively apply it to material modification to improve performance and impart new functions is of great practical significance.

[0003] In summary, it is urgent to overcome the above defects through multiple modification methods, improve the comprehensive performance of the product and achieve the combination of environmental protection and functional enhancement. Summary of the Invention

[0004] In response to the defects of the prior art, the modified polyester resin for powder coating disclosed in the present invention, on the one hand, dehydrates and condenses epoxy resin and silicone resin to form an epoxy-silicone copolymer rich in Si-OC bonds, so that the modified polyester resin has high weather resistance, high temperature resistance, chemical resistance and adhesion. The silicone is enriched on the surface of the coating to provide weather resistance and hydrophobicity, and the epoxy resin is combined with the polyester and the substrate at the interface to enhance adhesion and cohesion. At the same time, acrylic resin and polyamide resin containing long-chain alkyl acrylate are grafted on the surface of the polyester resin to significantly improve its flexibility and cross-linking density; on the other hand, MOF material prepared by degrading waste plastics and fluororesin form a composite modifier. The porous MOF material can not only adsorb well, but also serve as a "bridge" to connect the fluororesin and polyester, reducing phase separation and improving compatibility. The fluororesin forms an outer weather-resistant barrier, and the MOF constructs a porous support network inside to enhance mechanical properties. The combination of the two realizes the dual functions of self-cleaning and corrosion resistance.

[0005] To achieve the above object, the technical solution adopted by the present invention is a modified polyester resin for powder coating, comprising the following raw materials in parts by weight: 100 parts of terephthalic acid, 12-15 parts of adipic acid, 45-60 parts of neopentyl glycol, 18-22 parts of propylene glycol, 6-10 parts of trimethylolpropane, 4-5 parts of glycerol, 2.5-3 parts of silane coupling agent, 10-12 parts of epoxy-organic silicon copolymer, 8-10 parts of composite modifier, 0.2-0.3 parts of zinc acetate, 1.5-2 parts of diphenyl ether and 3-4 parts of PVP;

[0006] Furthermore, the preparation method of the epoxy-organic silicon copolymer comprises the following steps:

[0007] a. Weigh 7-13 parts of xylene and 15 parts of n-butanol, mix, heat at 40 ° C for 30 min, and stir at 300 r / min, introduce nitrogen at a flow rate of 300 ml / min as a protective gas, weigh 25-40 parts of epoxy resin, add thereto, heat to 60 ° C and keep warm for 30 min to obtain a homogeneous resin;

[0008] b weighed 0.5 parts of dibutyltin dilaurate was added to the homogeneous resin obtained in step a, the temperature was maintained at 60 ℃ for 10min, and stirred at a speed of 300r / min to obtain a polymerization reaction solution;

[0009] c. Weigh 15-25 parts of silicone resin and add it to the polymerization reaction solution obtained in step b. Heat the temperature to 90-120 ° C for 4-6 hours and stir at a speed of 300 r / min. Reflux treatment, introduce nitrogen at a flow rate of 300 ml / min as a protective gas, then reduce the temperature to 40 ° C, and add 2 parts of 0.5 mol / L phosphoric acid and stir for 10 minutes. Wash 5 times with a 0.2 mol / L citric acid solution as a cleaning liquid to obtain an epoxy-silicone copolymer.

[0010] Furthermore, the preparation method of the composite modifier comprises the following steps:

[0011] α. Weigh 30-50 parts of waste plastic (PET) and crush them into 5mm particles. Add them to 100 parts of sodium hydroxide solution with a concentration of 4 mol / L, heat to 80°C for 30 minutes, stir at 300 rpm, dehydrate at 180°C, then add 80 parts of concentrated nitric acid, heat to 50°C for 30 minutes, and cool naturally to room temperature to obtain an acidified degradation product.

[0012] β. Weigh 2-4 parts of nitrate and 6 parts of TPA and add them to 80 parts of DMF, wherein the nitrate is composed of the following mass ratio of materials: zinc nitrate and cobalt nitrate = 3:1, and stir at a speed of 300 r / min for 10 minutes. After that, the acidified degradation product obtained in step α is added thereto, and the temperature is heated to 120-150 ° C for 12-24 hours to obtain a metal-MOF complex;

[0013] γ weighed 12-18 parts of fluororesin was heated at a temperature of 260-300 ℃ under heating conditions for 10min, weighed 0.5 parts of dispersant and 0.05-0.15 parts of titanate coupling agent were added thereto, stirred at a speed of 300r / min for 10min to obtain a fluorinated reaction product;

[0014] δ. The metal-MOF complex obtained in step β was added to the fluorination reaction obtained in step γ, stirred at a speed of 500 r / min for 30 min, 10 parts of perfluoropolyether were weighed and added thereto, the temperature was heated to 130 ° C for 20 min, and then rapidly cooled to room temperature to prepare particles with a particle size of 2 mm to obtain a composite modifier;

[0015] The specific reactions are as follows:

[0016] MOF-OH+Ti(OR)X3-OP(=O)(O-)OP(=O)(O-)OR' → MOF-O-Ti-[-OP(=O)(O-)OP(=O)(O-)OR']X3.

[0017] The present invention also provides a method for preparing a modified polyester resin for powder coatings, comprising the following steps:

[0018] Step 1. Weigh 100 parts of terephthalic acid, 12 to 15 parts of adipic acid and 0.2 to 0.3 parts of zinc acetate and mix them, heat the temperature to 160-200 ° C for 30 min, and introduce argon at a flow rate of 300 ml / min as a protective gas, weigh 45 to 60 parts of neopentyl glycol and 18 to 22 parts of propylene glycol, add them, stir at a speed of 300 r / min for 30 min, weigh 6 to 10 parts of trimethylolpropane, 4 to 5 parts of glycerol and 1.5 to 2 parts of diphenyl ether, increase the temperature to 220-240 ° C, under a pressure of -0.09 MPa, stir at a speed of 300 r / min for 30 min, add 2-4 parts of phosphoric acid, wherein the phosphoric acid concentration is 0.1 mol / L, keep warm for 10 min, reflux to obtain an ester;

[0019] Step 2. Weigh 10 to 12 parts of epoxy - silicone copolymer and 8 to 10 parts of the composite modifier were added to the ester obtained in step 1, stirred at a speed of 300r / min, and kept at a temperature of 170-190 ℃ for 20min to obtain a modified polyester;

[0020] Step 3. Weigh 2.5-3 parts of silane coupling agent and 3-4 parts of PVP and add them to the modified polyester. Lower the temperature to 100-120°C and maintain for 30 minutes. Degas under a vacuum pressure of -0.08 MPa. Then lower the temperature to 40°C for curing to produce 2 mm resin particles to obtain modified polyester resin for powder coating.

[0021] The beneficial effects achieved by the present invention are:

[0022] The modified polyester resin for powder coatings prepared in this application is formed by dehydrating and condensing an epoxy resin and a silicone resin to form an epoxy-silicone copolymer. This copolymer is rich in Si-OC bonds, resulting in the modified polyester resin exhibiting high weather resistance, high temperature resistance, chemical resistance, and adhesion. Furthermore, the silicone is concentrated on the coating surface, providing weather resistance and hydrophobicity. The epoxy resin bonds with the polyester and substrate at the interface, enhancing adhesion and cohesion. Furthermore, acrylic resin and polyamide resin, rich in long-chain alkyl acrylates, are grafted onto the surface of the polyester resin, significantly improving its flexibility and crosslinking density.

[0023] The modified polyester resin for powder coating prepared in this application is a composite modifier obtained by degrading waste plastics to obtain MOF materials and fluororesin. The porous MOF material can be adsorbed well. In addition, MOF acts as a "bridge" to connect fluororesin and polyester, reducing phase separation and improving compatibility. The fluororesin forms an outer weather-resistant barrier, and the MOF constructs a porous support network inside to enhance mechanical properties. The low surface energy of the fluororesin is combined with the adsorption of MOF to achieve the dual functions of self-cleaning and corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a diagram of the preparation method of the modified polyester resin for powder coatings proposed by the present invention;

[0025] Figure 2 This is a physical picture of the modified polyester resin for powder coating prepared in Example 2;

[0026] Figure 3 The figure is a test chart of the acid value of the modified polyester resin for powder coating prepared in Examples and Comparative Examples;

[0027] Figure 4 The figure is a test chart of the hardness of the powder coatings prepared by applying the modified polyester resin for the powder coatings prepared in Examples and Comparative Examples;

[0028] Figure 5 This is a test chart of the glossiness of the powder coatings prepared by applying the modified polyester resin for the powder coatings prepared in Examples and Comparative Examples;

[0029] Figure 6 The test graphs of the stability and adhesion of the powder coatings prepared by applying the modified polyester resin for the powder coatings prepared in Examples and Comparative Examples are as follows;

[0030] Figure 7 These are test charts showing the color difference and thermochromic properties of the powder coatings prepared using the modified polyester resins used in the powder coatings prepared in Examples and Comparative Examples.

[0031] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all 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.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods and materials similar or equivalent to those described herein can be applied to the present invention. The preferred embodiments and materials described herein are for illustrative purposes only and are not intended to limit the scope of this application.

[0034] The preparation methods and related tests in the following examples are referenced to Figure 1-Figure 7 Unless otherwise specified, the conventional method is used; the materials used in the following embodiments, unless otherwise specified, are in parts by mass, and the nitrate is composed of the following materials in the following mass ratio: zinc nitrate and cobalt nitrate = 3:1.

[0035] Example 1: A modified polyester resin for powder coating, comprising the following raw materials in parts by weight: 100 parts of terephthalic acid, 12 parts of adipic acid, 45 parts of neopentyl glycol, 18 parts of propylene glycol, 6 parts of trimethylolpropane, 4 parts of glycerol, 2.5 parts of a silane coupling agent, 10 parts of an epoxy-organic silicon copolymer, 8 parts of a composite modifier, 0.2 parts of zinc acetate, 1.5 parts of diphenyl ether, and 3 parts of PVP;

[0036] The preparation method of epoxy-organic silicon copolymer comprises the following steps:

[0037] a. Weigh 7 parts of xylene and 15 parts of n-butanol, mix them, heat them at 40 ° C for 30 min, stir them at 300 r / min, introduce nitrogen at a flow rate of 300 ml / min as a protective gas, weigh 25 parts of epoxy resin and add them, heat to 60 ° C and keep warm for 30 min to obtain a homogeneous resin;

[0038] b weighed 0.5 parts of dibutyltin dilaurate was added to the homogeneous resin obtained in step a, the temperature was maintained at 60 ℃ for 10min, and stirred at a speed of 300r / min to obtain a polymerization reaction solution;

[0039] c. Weigh 15 parts of silicone resin and add it to the polymerization reaction solution obtained in step b. Heat the temperature to 90 ° C and maintain it for 4-6 hours. Stir it at a speed of 300 r / min and reflux it. Nitrogen is introduced at a flow rate of 300 ml / min as a protective gas. Then, the temperature is lowered to 40 ° C. 2 parts of 0.5 mol / L phosphoric acid are added and stirred for 10 minutes. Wash it 5 times with a 0.2 mol / L citric acid solution as a cleaning liquid to obtain an epoxy-silicone copolymer.

[0040] The preparation method of the composite modifier comprises the following steps:

[0041] α. Weigh 30 parts of waste plastic (PET) and crush it into 5 mm particles. Add it to 100 parts of sodium hydroxide solution with a concentration of 2 mol / L. Heat the mixture to 80°C for 30 minutes while stirring at 300 rpm. Dehydrate the mixture at 110°C. Then, add it to 80 parts of concentrated nitric acid, heat it to 50°C for 30 minutes, and cool it naturally to room temperature to obtain an acidified degradation product.

[0042] β. Weigh 2 parts of nitrate and 6 parts of TPA and add 80 parts of DMF, stir at 300r / min for 10min, then add the acidified degradation product obtained in step α, and heat to 120°C for 12h to obtain a metal-MOF complex;

[0043] γ weighed 12 parts of fluororesin was heated at a temperature of 260 ℃ under heating conditions for 10min, weighed 0.5 parts of SiO2 and 0.05 parts of a titanate coupling agent were added thereto, stirred at a speed of 300r / min for 10min to obtain a fluorinated reaction product;

[0044] δ. The metal-MOF complex obtained in step β was added to the fluorination reaction obtained in step γ, stirred at a speed of 500 r / min for 30 min, 10 parts of perfluoropolyether were weighed and added thereto, the temperature was heated to 130 ° C for 20 min, and then rapidly cooled to room temperature to prepare particles with a particle size of 2 mm to obtain a composite modifier;

[0045] The specific reactions are as follows:

[0046] MOF-OH+Ti(OR)X3-OP(=O)(O-)OP(=O)(O-)OR' → MOF-O-Ti-[-OP(=O)(O-)OP(=O)(O-)OR']X3.

[0047] This embodiment also provides a method for preparing a modified polyester resin for powder coatings, comprising the following steps:

[0048] Step 1. Weigh 100 parts of terephthalic acid, 12 parts of adipic acid and 0.2 parts of zinc acetate and mix them, heat the temperature to 160 ° C for 30min, and introduce argon at a flow rate of 300ml / min as a protective gas, weigh 45 parts of neopentyl glycol and 18 parts of propylene glycol, add them, stir at a speed of 300r / min for 30min, weigh 6 parts of trimethylolpropane, 4 parts of glycerol and 1.5 parts of diphenyl ether, increase the temperature to 220 ° C, at a pressure of -0.09MPa, stir at a speed of 300r / min for 30min, add 2 parts of phosphoric acid, wherein the phosphoric acid concentration is 0.1mol / L, keep warm for 10min, reflux to obtain an ester;

[0049] Step 2. Weigh 10 parts of epoxy - silicone copolymer and 8 parts of the composite modifier were added to the ester obtained in step 1, stirred at a speed of 300r / min, and kept at a temperature of 170 ℃ for 20min to obtain a modified polyester;

[0050] Step 3. Weigh 2.5 parts of silane coupling agent and 3 parts of PVP and add them to the modified polyester. Lower the temperature to 100°C and maintain for 30 minutes. Degas under a vacuum pressure of -0.08 MPa. Then lower the temperature to 40°C for curing to produce 2 mm resin particles to obtain modified polyester resin for powder coating.

[0051] Example 2: A modified polyester resin for powder coating, comprising the following raw materials in parts by weight: 100 parts of terephthalic acid, 14 parts of adipic acid, 53 parts of neopentyl glycol, 20 parts of propylene glycol, 8 parts of trimethylolpropane, 4.5 parts of glycerol, 2.8 parts of a silane coupling agent, 11 parts of an epoxy-organic silicon copolymer, 9 parts of a composite modifier, 0.25 parts of zinc acetate, 1.8 parts of diphenyl ether, and 3.5 parts of PVP;

[0052] The preparation method of epoxy-organic silicon copolymer comprises the following steps:

[0053] a. Weigh 10 parts of xylene and 15 parts of n-butanol, mix them, heat them at 40 ° C for 30 min, stir them at 300 r / min, introduce nitrogen at a flow rate of 300 ml / min as a protective gas, weigh 33 parts of epoxy resin and add them, heat to 60 ° C and keep warm for 30 min to obtain a homogeneous resin;

[0054] b weighed 0.5 parts of dibutyltin dilaurate was added to the homogeneous resin obtained in step a, the temperature was maintained at 60 ℃ for 10min, and stirred at a speed of 300r / min to obtain a polymerization reaction solution;

[0055] c. Weigh 20 parts of silicone resin and add them to the polymerization reaction solution obtained in step b. Heat the temperature to 110 ° C and maintain for 5 hours. Stir at a speed of 300 r / min and reflux. Nitrogen is introduced at a flow rate of 300 ml / min as a protective gas. Then, the temperature is lowered to 40 ° C and 2 parts of 0.5 mol / L phosphoric acid are added and stirred for 10 minutes. Wash 5 times with a 0.2 mol / L citric acid solution as a cleaning liquid to obtain an epoxy-silicone copolymer.

[0056] The preparation method of the composite modifier comprises the following steps:

[0057] α. Weigh 40 parts of waste plastics and crush them into 5mm particles, add them to 100 parts of sodium hydroxide solution, wherein the concentration of the sodium hydroxide solution is 2mol / L, heat the temperature to 80 ° C for 30min, and stir at a speed of 300r / min, dehydrate at a temperature of 180 ° C, then add 80 parts of concentrated nitric acid, heat the temperature to 50 ° C for 30min, and cool naturally to room temperature to obtain an acidified degradation product;

[0058] β. Weigh 3 parts of nitrate and 6 parts of TPA and add 80 parts of DMF, stir at 300r / min for 10min, then add the acidified degradation product obtained in step α, and heat to 135°C for 18h to obtain a metal-MOF complex;

[0059] γ weighed 15 parts of fluororesin was heated at a temperature of 280 ℃ under heating conditions for 10min, weighed 0.5 parts of SiO2 and 0.1 parts of a titanate coupling agent were added thereto, stirred at a speed of 300r / min for 10min to obtain a fluorinated reaction product;

[0060] δ. The metal-MOF complex obtained in step β is added to the fluorination reactant obtained in step γ, and the mixture is stirred at a speed of 500 r / min for 30 min. 10 parts of perfluoropolyether are weighed and added thereto. The mixture is heated to 130°C and maintained for 20 min. The mixture is rapidly cooled to room temperature to prepare particles with a particle size of 2 mm to obtain a composite modifier.

[0061] This embodiment also provides a method for preparing a modified polyester resin for powder coatings, comprising the following steps:

[0062] Step 1. Weigh 100 parts of terephthalic acid, 14 parts of adipic acid and 0.25 parts of zinc acetate and mix them, heat the temperature to 180 ° C for 30min, and introduce argon at a flow rate of 300ml / min as a protective gas, weigh 53 parts of neopentyl glycol and 20 parts of propylene glycol, add them, stir at a speed of 300r / min for 30min, weigh 8 parts of trimethylolpropane, 4.5 parts of glycerol and 1.8 parts of diphenyl ether, increase the temperature to 230 ° C, at a pressure of -0.09MPa, stir at a speed of 300r / min for 30min, add 3 parts of phosphoric acid, wherein the phosphoric acid concentration is 0.1mol / L, keep warm for 10min, reflux to obtain an ester;

[0063] Step 2. Weigh 11 parts of epoxy - silicone copolymer and 9 parts of the composite modifier were added to the ester obtained in step 1, stirred at a speed of 300r / min, and kept at a temperature of 180 ℃ for 20min to obtain a modified polyester;

[0064] Step 3. Weigh 2.8 parts of silane coupling agent and 3.5 parts of PVP and add them to the modified polyester. Lower the temperature to 110°C and maintain for 30 minutes. Degas under a vacuum pressure of -0.08 MPa. Then lower the temperature to 40°C for curing to produce 2 mm resin particles to obtain modified polyester resin for powder coating.

[0065] Example 3: A modified polyester resin for powder coating, comprising the following raw materials in parts by weight: 100 parts of terephthalic acid, 15 parts of adipic acid, 60 parts of neopentyl glycol, 22 parts of propylene glycol, 10 parts of trimethylolpropane, 5 parts of glycerol, 3 parts of a silane coupling agent, 12 parts of an epoxy-organic silicon copolymer, 10 parts of a composite modifier, 0.3 parts of zinc acetate, 2 parts of diphenyl ether, and 4 parts of PVP;

[0066] The preparation method of epoxy-organic silicon copolymer comprises the following steps:

[0067] a. Weigh 13 parts of xylene and 15 parts of n-butanol, mix, heat at 40 ° C for 30 min, and stir at 300 r / min, introduce nitrogen at a flow rate of 300 ml / min as a protective gas, weigh 40 parts of epoxy resin, add thereto, heat to 60 ° C and keep warm for 30 min to obtain a homogeneous resin;

[0068] b weighed 0.5 parts of dibutyltin dilaurate was added to the homogeneous resin obtained in step a, the temperature was maintained at 60 ℃ for 10min, and stirred at a speed of 300r / min to obtain a polymerization reaction solution;

[0069] c. Weigh 25 parts of silicone resin and add them to the polymerization reaction solution obtained in step b. Heat the temperature to 120 ° C and maintain for 6 hours, and stir at a speed of 300 r / min. Reflux treatment, introduce nitrogen at a flow rate of 300 ml / min as a protective gas, then reduce the temperature to 40 ° C, and add 2 parts of 0.5 mol / L phosphoric acid and stir for 10 minutes. Use a 0.2 mol / L citric acid solution as a cleaning liquid and wash 5 times to obtain an epoxy-silicone copolymer.

[0070] The preparation method of the composite modifier comprises the following steps:

[0071] α. Weigh 50 parts of waste plastics and crush them into 5mm particles, add them to 100 parts of sodium hydroxide solution, wherein the concentration of the sodium hydroxide solution is 2mol / L, heat the temperature to 80 ° C for 30min, and stir at a speed of 300r / min, dehydrate at a temperature of 180 ° C, then add 80 parts of concentrated nitric acid, heat the temperature to 50 ° C for 30min, and cool naturally to room temperature to obtain an acidified degradation product;

[0072] β. Weigh 4 parts of nitrate and 6 parts of TPA and add 80 parts of DMF, stir at 300r / min for 10min, then add the acidified degradation product obtained in step α, and heat to 150°C for 24h to obtain a metal-MOF complex;

[0073] γ weighed 18 parts of fluororesin was heated at a temperature of 300 ℃ under heating conditions for 10min, weighed 0.5 parts of SiO2 and 0.15 parts of a titanate coupling agent were added thereto, stirred at a speed of 300r / min for 10min to obtain a fluorinated reaction product;

[0074] δ. The metal-MOF complex obtained in step β is added to the fluorination reactant obtained in step γ, and the mixture is stirred at a speed of 500 r / min for 30 min. 10 parts of perfluoropolyether are weighed and added thereto. The mixture is heated to 130°C and maintained for 20 min. The mixture is rapidly cooled to room temperature to prepare particles with a particle size of 2 mm to obtain a composite modifier.

[0075] This embodiment also provides a method for preparing a modified polyester resin for powder coatings, comprising the following steps:

[0076] Step 1. Weigh 100 parts of terephthalic acid, 15 parts of adipic acid and 0.3 parts of zinc acetate and mix them. The temperature is heated to 200 ° C for 30min, and argon is introduced at a flow rate of 300ml / min as a protective gas. Weigh 60 parts of neopentyl glycol and 22 parts of propylene glycol, add them, and stir at a speed of 300r / min for 30min. Weigh 10 parts of trimethylolpropane, 5 parts of glycerol and 2 parts of diphenyl ether. Add the mixture, raise the temperature to 240 ° C, stir at a pressure of -0.09MPa at a speed of 300r / min for 30min, add 4 parts of phosphoric acid, wherein the phosphoric acid concentration is 0.1mol / L, keep warm for 10min, and reflux to obtain an ester.

[0077] Step 2. Weigh 12 parts of epoxy - silicone copolymer and 10 parts of the composite modifier were added to the ester obtained in step 1, stirred at a speed of 300r / min, and kept at a temperature of 190 ℃ for 20min to obtain a modified polyester;

[0078] Step 3. Weigh 3 parts of silane coupling agent and 4 parts of PVP and add them to the modified polyester. Lower the temperature to 120°C and maintain for 30 minutes. Degas under a vacuum pressure of -0.08 MPa. Then lower the temperature to 40°C for curing to produce 2 mm resin particles to obtain modified polyester resin for powder coating.

[0079] Comparative Example:

[0080] The difference between Comparative Example 1 and Example 2 is that no epoxy-organic silicon copolymer is added, and the rest of the process is the same as Example 2;

[0081] The difference between Comparative Example 2 and Example 2 is that no composite modifier is added, and the rest of the process is the same as Example 2;

[0082] The difference between Comparative Example 3 and Example 2 is that the epoxy-organic silicon copolymer is replaced with an organic silicon resin, and the rest of the process is the same as Example 2;

[0083] The difference between Comparative Example 4 and Example 2 is that the composite modifier is replaced with fluororesin, and the rest of the parts are the same as Example 2;

[0084] Comparative Example 5 is untreated coating powder.

[0085] In order to verify the specific performance of the prepared modified polyester resin for powder coating, the following research was done. The prepared modified polyester resin for powder coating ( Figure 2 ) is introduced into the powder coating, and the specific powder coating ratio is shown in Table 1 below:

[0086]

[0087] The above materials were weighed and mixed according to the number of parts, extruded by a twin-screw extruder at a temperature of 120°C and a rotation speed of 600r / min, and then rolled into 1-2mm thin sheets by a water-cooled roller. A 50μm powder coating was prepared by using an ACM grinder. Figure 3 The acid value test data of modified polyester resin for powder coatings is as follows: the overall acid value is less than 35mg KOH / g (reference standard: GB / T2895), which is in line with the curing range of TGIC. Figure 4 The hardness test data of the powder coating is based on the GB / T 6739 standard. The overall hardness of the embodiment is greater than 3H, which is much higher than the hardness of the powder coating of the comparative example. This shows that the modified polyester resin has a good effect on improving the hardness of the powder coating. Figure 5 The glossiness test data of the powder coating is shown in FIG. 1 , wherein the overall glossiness of the embodiment and the comparative example is greater than 90%, according to the reference standard GB / T 9754, and the glossiness of the embodiment is higher than that of the comparative example. The stability and adhesion of the prepared powder coating are further tested. Figure 6 As shown, the stability test conditions are as follows (GB / T 21782.8): constant temperature 40°C for 30 days, the caking rate of the powder coatings prepared in the examples is less than 0.1%, and the overall caking rate of the comparative examples is higher than that of the examples, indicating that the powder coatings have good stability. In addition, the adhesion test (GB / T 9286, substrate: phosphated steel plate) showed that the results were all level 0. The color difference (GB / T 11186.3) and thermochromicity (GB / T 1735) of the prepared powder coatings were further tested, and the results are shown as follows. Figure 7 As shown, the color difference values ​​of the examples are all lower than those of the comparative examples and close to those of comparative example 5, indicating that the modified polyester resin for powder coatings of the examples has little effect on the color difference of the powder coatings. Further testing of the thermochromic properties at high temperatures shows that the thermochromic properties of the comparative examples vary greatly under high temperature conditions, indicating that they are more seriously affected by temperature.

[0088] Obviously, the above comparative examples and embodiments are only a part of the comparative examples and embodiments of the present invention, and they and the comparative examples and embodiments based on such references are all within the scope of protection of this invention.

[0089] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

[0090] The present invention and its embodiments are described above. Such description is not restrictive. The drawings show only one embodiment of the present invention, and actual applications are not limited thereto. In short, if a person skilled in the art is inspired by the above, and does not deviate from the purpose of the present invention, any method and embodiment similar to the technical solution without creative design shall fall within the scope of protection of the present invention.

Claims

1. A modified polyester resin for powder coating, characterized in that: The invention comprises the following raw materials in parts by weight: 100 parts of terephthalic acid, 12-15 parts of adipic acid, 45-60 parts of neopentyl glycol, 18-22 parts of propylene glycol, 6-10 parts of trimethylolpropane, 4-5 parts of glycerol, 2.5-3 parts of silane coupling agent, 10-12 parts of epoxy-organic silicon copolymer, 8-10 parts of composite modifier, 0.2-0.3 parts of zinc acetate, 1.5-2 parts of diphenyl ether and 3-4 parts of PVP; The epoxy-organic silicon copolymer comprises the following raw materials in a mass ratio: epoxy resin:organic silicon resin:dibutyltin dilaurate=25-40:15-25:0.5; The composite modifier comprises the following raw materials in a mass ratio: waste plastic: fluororesin = 30-50:12-18.

2. The modified polyester resin for powder coating according to claim 1, characterized in that: The preparation method of the epoxy-organic silicon copolymer comprises the following steps: a. Heat xylene and n-butanol, stir, add epoxy resin, raise the temperature, and reflux to obtain a homogeneous resin; b. Said dibutyltin dilaurate was added to the homogeneous resin, the temperature was controlled and stirred to obtain a polymerization reaction solution; c. Add the organosilicon resin to the polymerization reaction solution, heat and stir, reflux, cool and add acid, wash, and obtain epoxy-organosilicon copolymer.

3. The modified polyester resin for powder coating according to claim 2, characterized in that: The acid described in step c is phosphoric acid with a concentration of 0.5 mol / L, and the cleaning liquid used in the washing process is a 0.2 mol / L citric acid solution.

4. The modified polyester resin for powder coating according to claim 1, characterized in that: The preparation method of the composite modifier comprises the following steps: α. Crushed waste plastics, added to alkali solution, dehydrated, added to acid to obtain acidified degradation products; β. Weigh nitrate and TPA in DMF, stir, add the acidified degradation product, and heat to obtain a metal-MOF complex; γ said fluororesin heated, said dispersant and titanate coupling agent added, stirred to obtain a fluorinated reaction product; δ. Add the metal-MOF complex to the fluorination reactant, stir, add perfluoropolyether, heat, and granulate to obtain a composite modifier.

5. The modified polyester resin for powder coating according to claim 4, characterized in that: The alkali solution described in step α is a sodium hydroxide solution with a concentration of 2 mol / L, the acid is concentrated nitric acid, the nitrate described in step β is composed of the following materials in a mass ratio: zinc nitrate: cobalt nitrate = 3:1, and the dispersant described in step γ is SiO2.

6. A method for preparing a modified polyester resin for powder coating according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1. Said terephthalic acid, adipic acid and zinc acetate are mixed, heated, said neopentyl glycol and propylene glycol are added, stirred, said trimethylolpropane, glycerol and diphenyl ether are added, heated, stirred, acid is added to obtain an ester; Step 2. Said epoxy - silicone copolymer and composite modifier are added to the esterified product, stirred, and kept warm to obtain a modified polyester; Step 3. Weigh the silane coupling agent and PVP and add them to the modified polyester, cool, degas, solidify, and granulate to obtain a modified polyester resin for powder coating.

7. The method for preparing a modified polyester resin for powder coating according to claim 6, characterized in that: The acid in step 1 is phosphoric acid with a concentration of 0.1 mol / L.

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