Modified polyester resin for powder coating and method for preparing the same

Abstract

The application belongs to the technical field of resin modification, and particularly relates to a modified polyester resin for powder coating and a preparation method thereof, wherein the modified polyester resin for powder coating comprises 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 silane coupling agent, 10-12 parts of epoxy-silicone 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 application forms a copolymer containing Si-O-C bonds by condensation of epoxy and silicone, improves weather resistance and other properties, and grafts resin to enhance flexibility and crosslinking property; and the MOF prepared from waste plastics is compounded with fluororesin, the MOF adsorbs and connects the two to reduce phase separation, and the MOF structure supports a network to realize self-cleaning and corrosion resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of resin modification, and particularly relates to a modified polyester resin for powder coating and a preparation method thereof. BACKGROUND

[0002] In the field of powder coating, although traditional polyester resins are widely used, they often have deficiencies in weather resistance, high-temperature resistance, chemical resistance, adhesion, flexibility, mechanical properties and the like, and some products also face problems such as phase separation, poor compatibility and difficulty in balancing self-cleaning and corrosion resistance, and thus cannot meet the use requirements in some high-end or special environments; meanwhile, the recycling of waste plastics is also an environmental problem to be solved at present, and it is of important practical significance to effectively apply waste plastics to material modification to improve performance and endow new functions.

[0003] In view of the above, it is urgent to overcome the above-mentioned defects by means of multi-modification, improve the comprehensive performance of the product, and realize the combination of environmental protection and function enhancement. SUMMARY

[0004] In view of the defects of the prior art, the modified polyester resin for powder coating disclosed by the application has the following advantages: on the one hand, the epoxy-silicone copolymer rich in Si-O-C bonds is formed by dehydration condensation of epoxy resin and silicone resin, 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, the epoxy resin is combined with the polyester and the substrate at the interface to enhance the adhesion and cohesion, and the acrylic resin and the polyamide resin containing long-chain alkyl acrylate are grafted on the surface of the polyester resin to significantly improve the flexibility and cross-linking density of the polyester resin; on the other hand, the MOF material prepared from waste plastics and the fluororesin form a composite modifier, the porous MOF material not only can be well adsorbed, but also can be used as a “bridge” to connect the fluororesin and the polyester, thereby reducing phase separation and improving compatibility, the fluororesin forms an outer weather barrier, and the MOF constructs a porous support network in the interior to enhance the mechanical properties, and the combination of the two realizes the dual functions of self-cleaning and corrosion resistance.

[0005] To achieve the above-mentioned purposes, the technical scheme adopted by the application is a modified polyester resin for powder coating, which comprises the following raw 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 silane coupling agent, 10-12 parts of epoxy-silicone 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] Further, the preparation method of the epoxy-silicone copolymer comprises the following steps:

[0007] a. Take 7-13 parts of xylene and 15 parts of n-butanol, heat at 40℃ for 30 min, and stir at 300 r / min. Protect with nitrogen gas at a flow rate of 300 ml / min. Take 25-40 parts of epoxy resin and add it to the mixture. Heat to 60℃ for 30 min to obtain a homogeneous resin;

[0008] b. Take 0.5 parts of dibutyltin dilaurate and add it to the homogeneous resin obtained in step a. Control the temperature to 60℃ for 10 min and stir at 300 r / min to obtain a polymerization reaction solution;

[0009] c. Take 15-25 parts of silicone resin and add it to the polymerization reaction solution obtained in step b. Heat the temperature to 90-120℃ for 4-6 h and stir at 300 r / min. Perform reflux treatment and protect with nitrogen gas at a flow rate of 300 ml / min. Then reduce the temperature to 40℃ and add 2 parts of 0.5 mol / L phosphoric acid and stir for 10 min. Wash 5 times with 0.2 mol / L citric acid solution as cleaning solution to obtain an epoxy-silicone copolymer.

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

[0011] α. Take 30-50 parts of waste plastic (PET) and crush it to 5 mm particles. Add it to 100 parts of sodium hydroxide solution with a concentration of 4 mol / L. Heat the temperature to 80℃ for 30 min and stir at 300 r / min. Dehydrate at a temperature of 180℃. Then add 80 parts of concentrated nitric acid. Heat the temperature to 50℃ for 30 min and naturally cool to room temperature to obtain an acidified degradation product;

[0012] β. Take 2-4 parts of nitrate and 6 parts of TPA and add them to 80 parts of DMF. The nitrate is composed of zinc nitrate and cobalt nitrate in a mass ratio of 3:1. Stir at 300 r / min for 10 min. Then add the acidified degradation product obtained in step α. Heat the temperature to 120-150℃ for 12-24 h to obtain a metal-MOF composite;

[0013] γ. Take 12-18 parts of fluororesin and heat it at a temperature of 260-300℃ for 10 min. Take 0.5 parts of a dispersant aid and 0.05-0.15 parts of a titanate coupling agent and add them to the mixture. Stir at 300 r / min for 10 min to obtain a fluorination reaction product;

[0014] δ. The metal-MOF composite obtained in step β is added to the fluorination reactant obtained in step γ, stirring is carried out at a rotation speed of 500 r / min for 30 min, 10 parts of perfluoropolyether is weighed and added, the temperature is heated to 130 DEG C and kept for 20 min, rapid cooling is carried out to room temperature, particles with a particle size of 2 mm are prepared, and a composite modifier is obtained;

[0015] The specific reaction is 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 application further provides a preparation method of the modified polyester resin for powder coating, comprising the following steps:

[0018] Step one. 100 parts of terephthalic acid, 12-15 parts of adipic acid and 0.2-0.3 parts of zinc acetate are mixed, the temperature is heated to 160-200 DEG C and kept for 30 min, argon gas with a flow rate of 300 ml / min is introduced as a protective gas, 45-60 parts of neopentyl glycol and 18-22 parts of propylene glycol are weighed and added, stirring is carried out at a rotation speed of 300 r / min for 30 min, 6-10 parts of trimethylolpropane, 4-5 parts of glycerol and 1.5-2 parts of diphenyl ether are weighed and added, the temperature is increased to 220-240 DEG C, stirring is carried out at a rotation speed of 300 r / min for 30 min under a pressure of -0.09 MPa, 2-4 parts of phosphoric acid with a concentration of 0.1 mol / L is added, heat preservation is carried out for 10 min, and reflux treatment is carried out, so that an esterification product is obtained.

[0019] Step two. 10-12 parts of epoxy-silicone copolymer and 8-10 parts of the composite modifier are weighed and added to the esterification product obtained in step one, stirring is carried out at a rotation speed of 300 r / min, heat preservation is carried out at a temperature of 170-190 DEG C for 20 min, and a modified polyester product is obtained.

[0020] Step three. 2.5-3 parts of a silane coupling agent and 3-4 parts of PVP are weighed and added to the modified polyester product, the temperature is reduced to 100-120 DEG C and kept for 30 min, defoaming is carried out under a vacuum pressure of -0.08 MPa, then the temperature is reduced to 40 DEG C for solidification, resin particles with a particle size of 2 mm are prepared, and the modified polyester resin for powder coating is obtained.

[0021] The application has the following beneficial effects:

[0022] The modified polyester resin for powder coating prepared in the application is prepared by dehydrating and condensing an epoxy resin and an organic silicon resin to form an epoxy-silicone copolymer, which is rich in Si-O-C bonds, so that the modified polyester resin has high weather resistance, high temperature resistance, chemical resistance and adhesion, and the organic silicon is rich on the surface of the coating, providing weather resistance and hydrophobicity; the epoxy resin is combined with the polyester and the substrate at the interface, enhancing the adhesion and cohesion. And the surface of the polyester resin is grafted with an acrylic resin and a polyamide resin, which is rich in long-chain alkyl acrylate, which can significantly improve the flexibility of the polyester resin and improve the cross-linking density of the polyester resin.

[0023] The modified polyester resin for powder coating prepared in the application is prepared by using waste plastics to prepare MOF materials and fluororesin to obtain a composite modifier, wherein the porous MOF material can be well adsorbed, in addition, the MOF serves as a "bridge" to connect the fluororesin and the polyester, reduces phase separation, and improves compatibility, the fluororesin forms an outer weather resistance barrier, the MOF constructs a porous support network inside, enhances the mechanical properties, and the low surface energy of the fluororesin is combined with the adsorbability of the MOF to realize the dual functions of self-cleaning and corrosion resistance. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The preparation method of the modified polyester resin for powder coating proposed in the application is shown in the figure;

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

[0026] Figure 3 The test figure of the acid value of the modified polyester resin for powder coating prepared in the examples and the comparative examples is shown in the figure;

[0027] Figure 4 The test figure of the hardness of the powder coating prepared after the application of the modified polyester resin for powder coating prepared in the examples and the comparative examples is shown in the figure;

[0028] Figure 5 The test figure of the gloss of the powder coating prepared after the application of the modified polyester resin for powder coating prepared in the examples and the comparative examples is shown in the figure;

[0029] Figure 6 The test figure of the stability and adhesion of the powder coating prepared after the application of the modified polyester resin for powder coating prepared in the examples and the comparative examples is shown in the figure;

[0030] Figure 7 The test figure of the color difference and thermal discoloration of the powder coating prepared after the application of the modified polyester resin for powder coating prepared in the examples and the comparative examples is shown in the figure.

[0031] The accompanying drawings are included to provide a further understanding of the application, and are incorporated in and constitute a part of the specification, illustrate embodiments of the application, and are used to explain the present application, but are not intended to limit the present application. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by one of ordinary skill in the art. In addition, any method and material similar or equivalent to those described herein can be used in the present application. The preferred methods and materials described herein are only used for demonstration, but cannot limit the content of the present application.

[0034] The preparation methods and related tests in the following embodiments refer to Figures 1-7 Unless otherwise specified, all are conventional methods; the materials used in the following embodiments, unless otherwise specified, the part ratio in the present application is mass part, and the nitrate is composed of the following mass ratio materials: zinc nitrate and cobalt nitrate = 3:1.

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

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

[0037] a. 7 parts of xylene and 15 parts of n-butanol were weighed and mixed, heated at a temperature of 40℃ for 30 min, and stirred at a speed of 300 r / min, and nitrogen gas with a flow rate of 300 ml / min was introduced as protective gas, 25 parts of epoxy resin was weighed and added, and the temperature was raised to 60℃ for 30 min, to obtain a homogeneous resin;

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

[0039] c. Take 15 parts of silicone resin into the polymerization reaction liquid obtained in step b, heat the temperature to 90℃ for 4-6h, and stir at a speed of 300r / min, reflux treatment, and then reduce the temperature to 40℃, and add 2 parts of 0.5mol / L phosphoric acid and stir for 10min, and then use 0.2mol / L citric acid solution as the cleaning liquid to wash 5 times, to obtain an epoxy-silicone copolymer.

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

[0041] α. Take 30 parts of waste plastic (PET) and crush it into 5mm particles, and then add it into 100 parts of sodium hydroxide solution, wherein the concentration of the sodium hydroxide solution is 2mol / L, heat the temperature to 80℃ for 30min, and stir at a speed of 300r / min, and then dehydrate at a temperature of 110℃, and then add 80 parts of concentrated nitric acid, heat the temperature to 50℃ for 30min, and then naturally cool to room temperature to obtain an acid degradation product;

[0042] β. Take 2 parts of nitrate and 6 parts of TPA and add them into 80 parts of DMF, and then stir at a speed of 300r / min for 10min, and then add the acid degradation product obtained in step α into it, and then heat the temperature to 120℃ for 12h to obtain a metal-MOF composite;

[0043] γ. Take 12 parts of fluororesin and heat it at a temperature of 260℃ for 10min, and then take 0.5 parts of SiO2 and 0.05 parts of titanate coupling agent and add them into it, and then stir at a speed of 300r / min for 10min to obtain a fluorination reaction product;

[0044] δ. Add the metal-MOF composite obtained in step β into the fluorination reaction product obtained in step γ, and then stir at a speed of 500r / min for 30min, and then take 10 parts of perfluoropolyether and add it into it, and then heat the temperature to 130℃ for 20min, and then quickly cool to room temperature to form particles with a particle size of 2mm, and then obtain a composite modifier;

[0045] The specific reaction is 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] The embodiment also provides a preparation method of a modified polyester resin for powder coating, comprising the following steps:

[0048] Step one. Take 100 parts of terephthalic acid, 12 parts of adipic acid and 0.2 parts of zinc acetate, mix them, heat the temperature to 160℃ for 30 min, and introduce argon gas as protective gas with a flow rate of 300 ml / min, take 45 parts of neopentyl glycol and 18 parts of propylene glycol and add them, stir at a speed of 300 r / min for 30 min, take 6 parts of trimethylolpropane, 4 parts of glycerol and 1.5 parts of diphenyl ether and add them, raise the temperature to 220℃, stir at a speed of 300 r / min under a pressure of-0.09 MPa for 30 min, add 2 parts of phosphoric acid with a concentration of 0.1 mol / L, keep warm for 10 min, and treat by reflux to obtain an esterification product;

[0049] Step two. Take 10 parts of epoxy-silicone copolymer and 8 parts of composite modifier and add them to the esterification product obtained in step one, stir at a speed of 300 r / min, keep warm at a temperature of 170℃ for 20 min to obtain a modified polyester product;

[0050] Step three. Take 2.5 parts of silane coupling agent and 3 parts of PVP and add them to the modified polyester product, reduce the temperature to 100℃ and keep it for 30 min, and then deaerate under a vacuum pressure of-0.08 MPa, and then reduce the temperature to 40℃ for curing to prepare resin particles with a thickness of 2 mm, thereby obtaining a modified polyester resin for powder coating.

[0051] Example 2: A modified polyester resin for powder coating, which comprises the following mass parts of raw materials: terephthalic acid 100 parts, adipic acid 14 parts, neopentyl glycol 53 parts, propylene glycol 20 parts, trimethylolpropane 8 parts, glycerol 4.5 parts, silane coupling agent 2.8 parts, epoxy-silicone copolymer 11 parts, composite modifier 9 parts, zinc acetate 0.25 parts, diphenyl ether 1.8 parts, and PVP 3.5 parts.

[0052] A method for preparing an epoxy-silicone copolymer, which comprises the following steps:

[0053] a. Take 10 parts of xylene and 15 parts of n-butanol and mix them, heat them at a temperature of 40℃ for 30 min, and stir at a speed of 300 r / min, introduce nitrogen gas as protective gas with a flow rate of 300 ml / min, take 33 parts of epoxy resin and add it, raise the temperature to 60℃ and keep it for 30 min to obtain a homogeneous resin;

[0054] b. Take 0.5 parts of dibutyltin dilaurate and add it to the homogeneous resin obtained in step a, control the temperature to 60℃ and keep it for 10 min, and stir at a speed of 300 r / min to obtain a polymerization solution;

[0055] c. 20 parts of silicone resin are weighed into the polymerization reaction solution obtained in step b, the temperature is heated to 110℃ and maintained for 5h, and stirring is carried out at a rotation speed of 300r / min, reflux treatment is carried out, nitrogen gas with a flow rate of 300ml / min is introduced as a protective gas, then the temperature is lowered to 40℃, 2 parts of phosphoric acid with a concentration of 0.5mol / L is added and stirred for 10min, and a citric acid solution with a concentration of 0.2mol / L is used as a cleaning solution to carry out washing for 5 times, to obtain an epoxy-silicone copolymer.

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

[0057] α. 40 parts of waste plastics are weighed and crushed into particles with a particle size of 5mm, which are added into 100 parts of sodium hydroxide solution with a concentration of 2mol / L, the temperature is heated to 80℃ and maintained for 30min, and stirring is carried out at a rotation speed of 300r / min, dehydration is carried out at a temperature of 180℃, then 80 parts of concentrated nitric acid is added, the temperature is heated to 50℃ and maintained for 30min, and natural cooling is carried out to room temperature to obtain acidified degradation products;

[0058] β. 3 parts of nitrate and 6 parts of TPA are weighed and added into 80 parts of DMF, stirring is carried out at a rotation speed of 300r / min for 10min, then the acidified degradation products obtained in step α are added, the temperature is heated to 135℃ and maintained for 18h to obtain metal-MOF composite;

[0059] γ. 15 parts of fluororesin are weighed and heated at a temperature of 280℃ for 10min, 0.5 parts of SiO2 and 0.1 parts of titanate coupling agent are added, stirring is carried out at a rotation speed of 300r / min for 10min to obtain fluorination reaction products;

[0060] δ. The metal-MOF composite obtained in step β is added into the fluorination reaction products obtained in step γ, stirring is carried out at a rotation speed of 500r / min for 30min, 10 parts of perfluoropolyether is added, the temperature is heated to 130℃ and maintained for 20min, rapid cooling is carried out to room temperature to form particles with a particle size of 2mm, and a composite modifier is obtained.

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

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

[0063] Step two. Take 11 parts of epoxy-silicone copolymer and 9 parts of composite modifier, add to the esterification product obtained in step one, stir at a speed of 300 r / min, keep warm at a temperature of 180℃ for 20 min to obtain a modified polyester product;

[0064] Step three. Take 2.8 parts of silane coupling agent and 3.5 parts of PVP, add to the modified polyester product, reduce the temperature to 110℃ and keep for 30 min, and then degas under a vacuum pressure of-0.08 MPa, and then reduce the temperature to 40℃ for solidification to prepare resin particles with a thickness of 2 mm, thereby obtaining a modified polyester resin for powder coating.

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

[0066] A preparation method of an epoxy-silicone copolymer, comprising the following steps:

[0067] a. Take 13 parts of xylene and 15 parts of n-butanol, mix, heat at a temperature of 40℃ for 30 min, and stir at a speed of 300 r / min, introduce nitrogen gas as protective gas at a flow rate of 300 ml / min, take 40 parts of epoxy resin, add, increase the temperature to 60℃ and keep warm for 30 min to obtain a homogeneous resin;

[0068] b. Take 0.5 parts of dibutyltin dilaurate, add to the homogeneous resin obtained in step a, control the temperature to 60℃ and keep for 10 min, and stir at a speed of 300 r / min to obtain a polymerization reaction solution;

[0069] c. 25 parts of silicone resin are weighed into the polymerization reaction solution obtained in step b, the temperature is heated to 120℃ and maintained for 6h, and stirring is carried out at a rotation speed of 300r / min, reflux treatment is carried out, nitrogen gas with a flow rate of 300ml / min is introduced as a protective gas, then the temperature is lowered to 40℃, 2 parts of phosphoric acid with a concentration of 0.5mol / L are added and stirred for 10min, and a citric acid solution with a concentration of 0.2mol / L is used as a cleaning solution to carry out washing for 5 times, to obtain an epoxy-silicone copolymer.

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

[0071] α. 50 parts of waste plastics are weighed and crushed into particles with a particle size of 5mm, which are added into 100 parts of a sodium hydroxide solution with a concentration of 2mol / L, the temperature is heated to 80℃ and maintained for 30min, and stirring is carried out at a rotation speed of 300r / min, dehydration is carried out at a temperature of 180℃, then 80 parts of concentrated nitric acid are added, the temperature is heated to 50℃ and maintained for 30min, and natural cooling is carried out to room temperature to obtain acidified degradation products;

[0072] β. 4 parts of nitrate and 6 parts of TPA are weighed and added into 80 parts of DMF, stirring is carried out at a rotation speed of 300r / min for 10min, then the acidified degradation products obtained in step α are added, the temperature is heated to 150℃ and maintained for 24h to obtain a metal-MOF composite;

[0073] γ. 18 parts of fluororesin are weighed and heated at a temperature of 300℃ for 10min, 0.5 parts of SiO2 and 0.15 parts of a titanate coupling agent are added, stirring is carried out at a rotation speed of 300r / min for 10min to obtain a fluorination reaction product;

[0074] δ. The metal-MOF composite obtained in step β is added into the fluorination reaction product obtained in step γ, stirring is carried out at a rotation speed of 500r / min for 30min, 10 parts of perfluoropolyether are added, the temperature is heated to 130℃ and maintained for 20min, rapid cooling is carried out to room temperature to form particles with a particle size of 2mm, and a composite modifier is obtained.

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

[0076] Step one. Take 100 parts of terephthalic acid, 15 parts of adipic acid and 0.3 parts of zinc acetate, mix them, heat the temperature to 200℃ for 30 min, and introduce argon gas as protective gas with a flow rate of 300 ml / min, take 60 parts of neopentyl glycol and 22 parts of propylene glycol and add them, stir at a speed of 300 r / min for 30 min, take 10 parts of trimethylolpropane, 5 parts of glycerol and 2 parts of diphenyl ether and add them, increase the temperature to 240℃, stir at a speed of 300 r / min under a pressure of-0.09 MPa for 30 min, add 4 parts of phosphoric acid with a concentration of 0.1 mol / L, keep warm for 10 min, and treat by reflux to obtain an esterification product;

[0077] Step two. Take 12 parts of epoxy-silicone copolymer and 10 parts of composite modifier and add them to the esterification product obtained in step one, stir at a speed of 300 r / min, keep warm at a temperature of 190℃ for 20 min to obtain a modified polyester product.

[0078] Step three. Take 3 parts of silane coupling agent and 4 parts of PVP and add them to the modified polyester product, reduce the temperature to 120℃ and keep it for 30 min, and then deaerate under a vacuum pressure of-0.08 MPa, and then reduce the temperature to 40℃ for curing to prepare resin particles with a size of 2 mm, i.e. a modified polyester resin for powder coating.

[0079] Comparative example:

[0080] The difference between Comparative Example 1 and Example 2 is that no epoxy-silicone copolymer is added, and the rest 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 is the same as Example 2.

[0082] The difference between Comparative Example 3 and Example 2 is that the epoxy-silicone copolymer is replaced by silicone resin, and the rest is the same as Example 2.

[0083] The difference between Comparative Example 4 and Example 2 is that the composite modifier is replaced by fluororesin, and the rest is the same as Example 2.

[0084] Comparative Example 5 is a coating powder without treatment.

[0085] In order to verify the specific performance of the prepared modified polyester resin for powder coating, the following studies are carried out. The prepared modified polyester resin for powder coating is introduced into powder coating, and the specific powder coating ratio is shown in Table 1 below: Figure 2

[0086]

[0087] ​The above materials were mixed according to the parts, and then extruded by a double screw extruder at a temperature of 120°C and a rotation speed of 600 r / min, and then pressed into 1-2 mm thin sheets by a water-cooled roller, and then 50 μm powder coating was prepared by an ACM powder mill, Figure 3 The acid value test data of the modified polyester resin for powder coating, wherein the overall acid value < 35 mg KOH / g (reference standard: GB / T 2895), meets the curing range of TGIC, Figure 4 The hardness test data of the powder coating, reference standard: GB / T 6739, wherein the overall hardness of the examples > 3H, which is much higher than the hardness of the powder coating of the comparative examples, indicating that the modified polyester resin has a good effect on the hardness improvement of the powder coating, Figure 5 The glossiness test data of the powder coating, wherein the overall glossiness of the examples and the comparative examples > 90%, reference standard: GB / T 9754, and the glossiness of the examples is close to that of the high-grade comparative examples, and the stability and adhesion of the prepared powder coating were further tested, as shown in Table 3, Figure 6 The test conditions of the stability are as follows (GB / T 21782.8): constant temperature 40°C for 30 days, the caking rate of the powder coating prepared by introducing 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 coating has good stability, and the adhesion test (GB / T 9286, selected substrate: phosphatized steel plate) results are all 0 grade, and the color difference (GB / T 11186.3) and heat discoloration (GB / T 1735) of the prepared powder coating were further tested, as shown in Table 4, Figure 7 The color difference values of the examples are all lower than those of the comparative examples and close to those of the comparative example 5, indicating that the modified polyester resin for powder coating of the examples has less effect on the color difference of the powder coating, and the heat discoloration at high temperature was further tested, and it can be seen that the heat discoloration of the comparative examples is quite different under high temperature conditions, indicating that it is seriously affected by temperature.

[0088] Obviously, the above comparative examples and examples are only a part of the comparative examples and examples of the present application, and the reference comparative examples and examples based on them are also within the scope of the present application.

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

[0090] The above describes the present application and its embodiments, which are not limited, and the drawings only show one of the embodiments of the present application, and the actual application is not limited thereto. In general, if a person skilled in the art is inspired by it, without departing from the purpose of the present application, without creative design, similar ways and embodiments of the technical solution should belong to the protection scope of the present application.

Claims

1. A modified polyester resin for powder coating, characterized by, The polyester resin comprises the following raw materials by mass: terephthalic acid 100 parts, adipic acid 12-15 parts, neopentyl glycol 45-60 parts, propylene glycol 18-22 parts, trimethylolpropane 6-10 parts, glycerol 4-5 parts, silane coupling agent 2.5-3 parts, epoxy-silicone copolymer 10-12 parts, composite modifier 8-10 parts, zinc acetate 0.2-0.3 parts, diphenyl ether 1.5-2 parts, and PVP 3-4 parts; The epoxy-silicone copolymer comprises the following raw materials by mass ratio: epoxy resin: silicone resin: dibutyltin dilaurate = 25-40: 15-25: 0.5; The composite modifier comprises the following raw materials by mass ratio: waste plastic: fluororesin = 30-50: 12-18; The preparation method of the epoxy-silicone copolymer comprises the following steps: a. Heat and stir the xylene and n-butanol, add the epoxy resin, heat, reflux, and obtain a homogeneous resin; b. Add dibutyltin dilaurate to the homogeneous resin, control the temperature and stir, and obtain a polymerization reaction solution; c. Add the silicone resin to the polymerization reaction solution, heat and stir, reflux, cool, add acid, wash, and obtain the epoxy-silicone copolymer; The preparation method of the composite modifier comprises the following steps: α. Crush the waste plastic, add it to lye, dehydrate, add it to acid, and obtain acidified degradation product; β. Add the nitrate and TPA to DMF, stir, add the acidified degradation product, heat, and obtain a metal-MOF composite; γ. Heat the fluororesin, add the dispersant aid and titanate coupling agent, stir, and obtain a fluorination reaction product; δ. Add the metal-MOF composite to the fluorination reaction product, stir, add the perfluoropolyether, heat, and granulate to obtain the composite modifier.

2. The modified polyester resin for powder coating according to claim 1, characterized in that, The acid in step c is phosphoric acid with a concentration of 0.5 mol / L, and the cleaning solution used in the washing process is a 0.2 mol / L citric acid solution.

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

4. A method for producing a modified polyester resin for powder coating according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: Step one. Mix terephthalic acid, adipic acid, and zinc acetate, heat, add neopentyl glycol and propylene glycol, stir, add trimethylolpropane, glycerol, and diphenyl ether, heat, stir, add acid, and obtain an esterification product; Step two. Add the epoxy-silicone copolymer and the composite modifier to the esterification product, stir, and heat to obtain a modified polyester product; Step three. Add the silane coupling agent and PVP to the modified polyester product, cool, deaerate, solidify, granulate, and obtain a modified polyester resin for powder coating.

5. The method for preparing a modified polyester resin for powder coatings according to claim 4, characterized in that, The acid in step one is phosphoric acid with a concentration of 0.1 mol / L.

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