Extinction transparent powder coating composition and preparation method thereof

Abstract

The invention relates to the technical field of transparent powder coatings, in particular to a matt transparent powder coating composition and a preparation method thereof, and the matt transparent powder coating composition comprises the following components by mass: 5-10 wt% of an acrylate copolymer I; 40 wt%-67 wt% of an acrylate copolymer II; a curing agent component: 20 wt%-50 wt%; a degassing agent component: 0.1 wt% to 1.0 wt%; and 0.1 wt%-2 wt% of a leveling agent component. GMA acrylic resin is modified through a divinyl monomer to obtain a first acrylate polymer with a large molecular weight, and then the modified first acrylate polymer and unmodified second GMA acrylic resin are subjected to melt blending according to the proportion of 1-9 to 2-8; the obtained acrylic resin composition can reduce the glossiness of a transparent coating and is good in transparency, the synthesis process of the method is simple, and the compatibility problem can be avoided by mixing the same type of GMA type acrylic resin.

Description

Technical Field

[0001] The present invention relates to the technical field of powder coatings, and more particularly to a matte transparent powder coating composition and a preparation method thereof. Background Art

[0002] Powder coating compositions have a very low volatile organic compound content and do not release a large amount of volatile substances into the environment during curing, so they are more conducive to widespread use. Among them, acrylic resin powder coatings are often used in various transparent coating fields due to their excellent weather resistance, chemical stability, and transparency. One of the widely used acrylic resins is glycidyl methacrylate (GMA) type acrylic resin, which is synthesized by copolymerizing GMA with other monomers.

[0003] Transparent powder coatings are commonly used in high-gloss transparent applications, and there are great challenges in their matte applications. One of the main problems is how to achieve a balance between matte and transparency. Currently, high molecular polymers are often grafted onto GMA acrylic resins to achieve this purpose, but the process involves complex procedures and may require chain breaking and re-grafting, which is expensive and time-consuming. In addition, there may be problems with the compatibility of the grafted high molecular polymers with GMA acrylic resins and other components in the powder coating formulation. Incompatibility can lead to phase separation or poor dispersion of the grafted polymer, thus having a negative impact on the properties of the coating such as transparency and leveling. Summary of the Invention

[0004] The purpose of the present invention is to provide a matte transparent powder coating composition and a preparation method thereof. The GMA acrylic resin is modified by a divinyl monomer to obtain a larger molecular weight acrylate polymer I, and then the modified acrylate polymer I and the unmodified GMA acrylic resin II are melt-blended in a ratio of 1-9 to 2-8. The obtained acrylic resin composition can reduce the gloss of the transparent coating and has good transparency. Moreover, the synthesis process of this method is simple, and the use of the same type of GMA type acrylic resin for mixing can avoid compatibility problems. In addition, acrylic resin compositions with significantly different epoxy equivalents and molecular weights are applied to powder coatings, and different curing rates generated during the curing process of the coating composition can further reduce the gloss of the transparent coating to solve the problems raised in the above background art.

[0005] To achieve the above object, the present invention provides the following technical solution: A matte transparent powder coating composition, comprising the following mass components:

[0006] Acrylate copolymer I: 5wt%-10wt%;

[0007] Acrylate copolymer II: 40wt%-67wt%;

[0008] Curing agent component: 20 wt% - 50 wt%;

[0009] Degassing agent component: 0.1 wt% - 1.0 wt%;

[0010] Leveling agent component: 0.1 wt% - 2 wt%.

[0011] Preferably, the epoxy equivalent of the acrylate copolymer I is 950 - 1500, having a number average molecular weight of 6000 - 8000 and a polydispersity coefficient of 1.6 - 2.0, and is composed of the following components:

[0012] 2 wt% - 5 wt% of polyethylene glycol diacrylate monomer;

[0013] 10 wt% - 15 wt% of glycidyl methacrylate;

[0014] 55 wt% - 78 wt% of alkyl methacrylate monomer;

[0015] 10 wt% - 25% of styrenic monomer;

[0016] And an initiator accounting for 1 wt% - 3 wt% of the total weight of the above monomer composition.

[0017] Preferably, the epoxy equivalent of the acrylate copolymer II is 400 - 500, having a number average molecular weight of 4000 - 8000 and a polydispersity coefficient of 1.6 - 2.0, and is composed of the following components:

[0018] 30 wt% - 35 wt% of glycidyl methacrylate monomer;

[0019] 10 wt% - 25% of styrenic monomer;

[0020] 40 wt% - 60 wt% of alkyl methacrylate monomer;

[0021] And an initiator accounting for 1 wt% - 3 wt% of the total weight of the above monomer composition.

[0022] Preferably, the alkyl methacrylate monomer is one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, cyclohexyl acrylate, isobornyl acrylate, benzyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, tert-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate in any proportion mixture.

[0023] Preferably, the polyethylene glycol diacrylate monomer has a molecular weight range of 400-1000, preferably 400-800. When the molecular weight is too large, it is a solid, which is not conducive to use and is more likely to crosslink with the acrylate monomer, resulting in a gelled product.

[0024] A method for preparing a matte transparent powder coating composition, wherein the acrylate copolymer I and the acrylate copolymer II are prepared by radical polymerization reaction through the following steps:

[0025] S1. Add a solvent to a reaction vessel, stir and heat to the reflux state, mix each reaction monomer and an initiator evenly, and dropwise add them to refluxing xylene within 3 h - 3.5 h. After the dropping is completed, react for 2 h under the reflux state;

[0026] S2. Continue to slowly dropwise add a mixed solution of the remaining initiator and the solvent under the condition of xylene reflux, complete the dropping within 10 min, and then react under reflux for 2 h;

[0027] S3. After the reflux reaction ends, start to distill off the solvent. When the temperature of the reaction system reaches 160 °C, apply a vacuum of -0.1 MPa for 0.5 h, then release the vacuum, discharge the material and cool it to obtain the acrylate copolymer;

[0028] S4. Physically premix the acrylate copolymer I, the acrylate copolymer II, a curing agent, a leveling agent, and a degassing agent, then use a twin-screw extruder for melt extrusion, tablet pressing, cooling, and crushing into fine powder, and finally pass through a 200-mesh sieve to obtain the matte transparent powder coating composition of the present invention.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] The GMA acrylate resin is modified with a divinyl monomer to obtain a relatively high-molecular-weight acrylate polymer I, and then the modified acrylate polymer I and the unmodified GMA acrylate resin II are melt-blended in a ratio of 1-9 to 2-8. In this way, the obtained acrylate resin composition can reduce the gloss of the transparent coating and has good transparency. Moreover, the synthesis process of this method is simple, and the use of the same type of GMA acrylate resin for mixing can avoid compatibility problems. In addition, the acrylate resin composition with obvious differences in epoxy equivalent and molecular weight is applied to the powder coating, and different curing rates generated during the curing process of the coating composition can further reduce the gloss of the transparent coating. Description of the Drawings

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0032] Figure 1 It is the ingredient list of the matting transparent powder coating composition of the present invention;

[0033] Figure 2 It is the preparation flow chart of the matting transparent powder coating composition of the present invention. Specific Embodiments

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0035] Please refer to Figures 1 to 2 , the present invention provides a technical solution:

[0036] A matting transparent powder coating composition, comprising the following mass components:

[0037] Acrylate copolymer one: 5wt%-10wt%;

[0038] Acrylate copolymer two: 40wt%-67wt%;

[0039] Curing agent component: 20wt%-50wt%;

[0040] Degassing agent component: 0.1wt%-1.0wt%;

[0041] Flow leveling agent component: 0.1wt%-2wt%.

[0042] Specifically, the epoxy equivalent of the acrylate copolymer one is 950-1500, having a number average molecular weight of 6000-8000 and a polydispersity coefficient of 1.6-2.0, and is composed of the following components:

[0043] 2wt%-5wt% of polyethylene glycol diacrylate monomer;

[0044] 10wt%-15wt% of glycidyl methacrylate;

[0045] 55wt%-78wt% of alkyl methacrylate monomer;

[0046] 10 wt%-25% of a styrenic monomer;

[0047] and an initiator accounting for 1 wt%-3 wt% of the total weight of the above monomer composition.

[0048] Specifically, the epoxy equivalent of the acrylate copolymer II is 400-500, with a number average molecular weight of 4000-8000 and a polydispersity coefficient of 1.6-2.0, and it is composed of the following components:

[0049] 30 wt%-35 wt% of glycidyl methacrylate monomer;

[0050] 10 wt%-25% of a styrenic monomer;

[0051] 40 wt%-60 wt% of an alkyl methacrylate monomer;

[0052] and an initiator accounting for 1 wt%-3 wt% of the total weight of the above monomer composition.

[0053] Specifically, the alkyl methacrylate monomer is one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, cyclohexyl acrylate, isobornyl acrylate, benzyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, tert-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate in any proportion mixture.

[0054] Specifically, the polyethylene glycol diacrylate monomer has a molecular weight range of 400-1000, preferably a polyethylene glycol diacrylate with a molecular weight of 400-800. When the molecular weight is too large, it is a solid, which is not conducive to use, and it is more likely to crosslink with the acrylate monomer, making the product gel.

[0055] A method for preparing a matte transparent powder coating composition, wherein the acrylate copolymer I and the acrylate copolymer II are prepared by free radical polymerization reaction through the following steps:

[0056] S1. Add a solvent to a reaction vessel, stir and heat to the reflux state, mix each reaction monomer and the initiator evenly, and drop them into the refluxing xylene within 3 h-3.5 h. After the dropping is completed, react for 2 h under the reflux state;

[0057] S2. Continue to slowly dropwise add the mixed solution of the remaining initiator and solvent under the condition of xylene reflux, and finish the dropwise addition within 10 min, then carry out reflux reaction for 2 h;

[0058] S3. After the reflux reaction ends, start to distill off the solvent. When the temperature of the reaction system reaches 160 °C, apply a vacuum of -0.1 MPa for 0.5 h, then release the vacuum, discharge the material and cool it to obtain the acrylate copolymer;

[0059] S4. Physically premix acrylate copolymer one, acrylate copolymer two, curing agent, leveling agent, and degassing agent, then use a twin-screw extruder for melt extrusion, tablet pressing, cooling, and crushing into fine powder, and finally pass through a 200-mesh sieve to obtain the matte transparent powder coating composition of the present invention.

[0060] Synthesis Example 1:

[0061] Synthesis of acrylate copolymer one:

[0062] Add 90 wt% xylene to a 500 ML three-necked flask, heat and stir until reflux. Add the mixed solution of 30 wt% glycidyl methacrylate, 2 wt% polyethylene glycol diacrylate, 25 wt% styrene, 20 wt% methyl methacrylate, 20 wt% butyl acrylate and 4 wt% benzoyl peroxide. After the dropwise addition is completed in 3 h, maintain the reflux reaction for 2 h and supplement the mixed solution of 0.5 wt% benzoyl peroxide and 10 wt% xylene, and react for another 2 h. After the reaction is completed, carry out temperature-raising distillation and decompression operation to remove the solvent in the polymer resin to obtain acrylate copolymer one of the present invention. The number-average molecular weight of this acrylate copolymer one is measured to be 6600, and the polydispersity coefficient is 1.94.

[0063] Synthesis Examples 2 - 4:

[0064] Examples 2 - 4 of the present invention are carried out in the same manner as Example 1, except that the formulation components in Table 1 are used instead of those in Example 1.

[0065] Table 1

[0066]

[0067]

[0068] In this application, PEG600DA is from Shanghai Yinchang New Materials Co., Ltd., polyethylene glycol (600) diacrylate.

[0069] Application Examples 1 - 4

[0070] The crosslinking agents obtained in Examples 1-4 were physically blended according to the respective powder coating components given in Table 2, and then melt-mixed, tableted, cooled, and crushed into fine powders using a twin-screw extruder. Finally, it was passed through a 200-mesh sieve and sprayed onto the surface of the substrate by the high-voltage electrostatic spraying method. The substrate was baked at 200 °C for 10 min to be completely cured.

[0071] Table 2

[0072]

[0073]

[0074] In this application, K7572 uses the leveling agent of Liuan Jietongda New Materials Co., Ltd.

[0075] The test methods are as follows:

[0076] Glossiness: Spray a transparent powder coating on a standard aluminum plate and bake it for curing. Measure it at 60° with a Keshijia WGG60-E4 glossiness meter.

[0077] Film thickness: Measure it with a film thickness gauge A-3430 from BYK Company, Germany.

[0078] Leveling performance: Conduct leveling rating according to the leveling effect rating standard plate of PCI in the United States. 1 is poor and 10 is excellent.

[0079] Transparency: Spray a transparent powder coating on a standard transparent thin glass plate and bake it for curing. Visually compare the transparency of the standard transparent thin glass plate and the transparent powder coating-coated layer under transmitted light and conduct rating. 1 is poor and 10 is excellent. The rating of the standard transparent thin glass plate is 10.

[0080] Adhesion: Conduct rating according to the cross-cut test of GB / T 9286-2021 Paints and varnishes—Cross-cut test, which is divided into grades 0-5. Grade 0 means that the cutting edge is completely smooth and there is no peeling; Grade 1 means that there is a little peeling at the cutting intersection, but the affected area is less than 5%; Grade 2 means that there is peeling at the cutting intersection and the affected area is between 5-15%; Grade 3 means that there are large fragments peeling at the cutting intersection and the affected area is between 15-35%; Grade 4 means that there are large fragments peeling at the cutting intersection and the affected area is between 35-65%; Grade 5 means that the degree of peeling is greater than that of Grade 4.

[0081] Table 3

[0082]

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A matte transparent powder coating composition, characterized in that Includes the following quality components: Acrylate copolymer 1: 5wt%-10wt%; Acrylate copolymer II: 40wt%-67wt%; Curing agent component: 20wt%-50wt%; Degassing agent component: 0.1wt%-1.0wt%; Leveling agent component: 0.1wt%-2wt%.

2. A matte transparent powder coating composition according to claim 1, characterized in that: The acrylate copolymer has an epoxy equivalent of 950-1500, a number average molecular weight of 6000-8000 and a polydispersity coefficient of 1.6-2.0, and is composed of the following components: 2wt%-5wt% of polyethylene glycol diacrylate monomer; 10wt%-15wt% of glycidyl methacrylate; 55 wt%-78 wt% of alkyl methacrylate monomer; 10wt%-25% styrene-based monomer; and an initiator accounting for 1wt%-3wt% of the total weight of the monomer composition.

3. A matte transparent powder coating composition according to claim 1, characterized in that: The acrylate copolymer II has an epoxy equivalent of 400-500, a number average molecular weight of 4000-8000 and a polydispersity coefficient of 1.6-2.0, and is composed of the following components: 30wt%-35wt% of glycidyl methacrylate monomer; 10wt%-25% styrene-based monomer; 40wt%-60wt% of alkyl methacrylate monomer; and an initiator accounting for 1wt%-3wt% of the total weight of the monomer composition.

4. A matte transparent powder coating composition according to claim 2, characterized in that: The alkyl methacrylate monomer is a mixture of one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, cyclohexyl acrylate, isobornyl acrylate, benzyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, tert-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, and isobornyl methacrylate in any proportion.

5. A matte transparent powder coating composition according to claim 2, characterized in that: The polyethylene glycol diacrylate monomer has a molecular weight range of 400-1000.

6. A method for preparing a matte transparent powder coating composition according to any one of claims 1 to 5, characterized in that: The acrylate copolymer 1 and the acrylate copolymer 2 are prepared by free radical polymerization reaction in the following steps: S1. Add the solvent to the reaction vessel, stir and heat to reflux state, mix the reaction monomers and initiator evenly, add dropwise to the refluxing xylene within 3h-3.5h, and react for 2h under reflux state after the addition is completed; S2, continue to slowly drop the remaining mixed solution of initiator and solvent under the condition of xylene reflux, complete the dropwise addition within 10 minutes, and then reflux for reaction for 2 hours; S3, after the reflux reaction is completed, the solvent is removed by distillation. When the temperature of the reaction system reaches 160°C, a vacuum of -0.1 MPa is applied for 0.5 h, and then the vacuum is released, the material is discharged and cooled, and an acrylate copolymer is obtained; S4, physically premixing the acrylate copolymer 1, the acrylate copolymer 2, the curing agent, the leveling agent and the degassing agent, and then using a twin-screw extruder to melt-extrude, tablet, cool and crush into fine powder, and finally pass through a 200-mesh sieve to obtain the matte transparent powder coating composition of the present invention.

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