[China Aluminum Network] 1 Introduction At present, the domestic aluminum veneer coating fluorocarbon coating commonly used in 230 °C baking can be melted to form a PVDF fluorocarbon coating, not only a waste of more electrical energy, and PVDF fluorocarbon coating Unable to obtain a variety of colors to meet customer requirements, its low gloss, can not be re-painted to repair, limited the scope of application. The thermosetting solution fluorocarbon resin (FEVE) coating is cured by chemical reaction under the heating condition by introducing a melamine resin or a blocked isocyanate resin as a cross-linking agent, and thus can be made into a single-temperature curing (180° C.) cured single sheet. The component coating saves a lot of electric energy for the user; due to the strictly alternate arrangement of the FEVE fluorocarbon resin, its weather resistance is as good as that of the conventional PVDF fluorine resin; since the FEVE fluorocarbon resin is transparent, it can be made Coatings from no light to high light range; brighter and brighter colors of the coating film; fluorocarbon resin can be used as a 100% solution in the fluorocarbon base material, which can eliminate the performance loss due to the introduction of foreign resin; the coating film has a recoating property. , The cost can be reduced; the choice of solvent is convenient and flexible, so the construction performance is also improved, so the market prospect of this product is broad. 2 Experimental section 2.1 Main raw materials and formulations Fluorocarbon resin: JF-2X, Changshu San Aifu Zhonghao Chemical New Material Co., Ltd.; Melamine resin: Cymel303, Cytec, USA; Blocked isocyanate: BL3175, Bayer, Germany; Titanium dioxide: R960 , United States DuPont; Dispersant: BYK-110; Leveling agent: BYK-388, German BYK; Mixed solvent: From xylene, oxygenated solvents, high boiling point aromatic solvents. . 2.2 Coating preparation (1) Add a dispersant BYK-110 to a part of the fluorocarbon resin, stir well, add R-960 titanium dioxide, adjust the viscosity with solvent, and disperse it at high speed of 2800r/min for 30 minutes; (2) Grind to fineness with a sand mill Below 20μm; (3) Add the remaining fluorocarbon resin, melamine resin, blocked isocyanate, leveling agent, adjust the viscosity with solvent, stir for 15min; (4) Pack after filtering with 120 mesh nylon mesh. 2.3 Performance Test Coatings prepared by the above method were sprayed on aluminum plates of a predetermined size and pre-primed and baked at 180° C. for 20 minutes. After the sample is taken out, it shall be placed at 18-27°C for more than 1 hour, and then the corresponding film performance test shall be carried out to check the result. It can be seen that the performance indexes of the developed FEVE fluorocarbon baking paint all meet the requirements of HG/T3793-2005. 3 Results and Discussion 3.1 Selection of Curing System For baking paints, the choice of curing system is very important. It is directly related to the storage stability and coating film properties of the developed coating. Under certain temperature conditions, -CH2OCH3 and -CH2OC4H9 in -CH2OCH3 and partially methyl etherified amino resins in the fully methyl etherified amino resin can react with FEVE fluorocarbon resin containing -OH, -COOH and crosslink to form a film. . Therefore, the above amino resin can be made into a one-component curing coating with FEVE fluorocarbon resin. The reaction process is as follows: Compared with partially methyl etherified amino resins, the former has good compatibility with fluorocarbon resins, but has lower reactivity and needs a strong acidic catalyst; the latter has higher reactivity. No need to add a small amount of acid catalyst, but the compatibility with fluorocarbon resin is poor. From the consideration of the compatibility with FEVE fluorocarbon resin and the storage stability of the finished coating, the amino resin cross-linking agent used in this test was hexamethoxymethyl melamine (HMMM). Blocked isocyanates, as a derivative of isocyanates, differ from the HDI (hexamethylene diisocyanate) biuret and HDI trimers used in ambient-curing two-component fluorocarbon coatings in that their polyisocyanates have been found to contain active hydrogen. The chemical substance is blocked and does not react with the hydroxyl group-containing resin component at room temperature. When heated to a certain temperature, the blocking agent is deblocked to generate isocyanate, and the resulting isocyanate can be combined with a hydroxyl group-containing resin component (such as FEVE fluorine Carbon resin) reacts and cross-links to form a film. Therefore, the blocked isocyanate can be made into a storage-stable one-component curing coating with FEVE fluorocarbon resin. The reaction process is as follows: The blocking agent (BH) released during the reaction, depending on the species, is either volatilized as volatiles or filled in the coating as an inert substance. The more commonly used blocking agents in blocked isocyanates are caprolactam (ECAP), methyl ethyl ketone (MEKO), 3,5-dimethylpyrazole (DMP), diethyl malonate (DEM), etc., and their unblocking temperatures. It's different. The blocked isocyanate selected for this test was methyl ethyl ketone oxime (MEKO) blocked isocyanate from the standpoint of the sealant deblocking temperature and the storage stability of the finished coating. The thermosetting FEVE fluorocarbon coating cross-linking agent may be an all-methyl etherified amino resin and a blocked isocyanate, but the actual situation is usually dominated by the former. Because it is difficult to completely deblock the blocked isocyanate in a very short baking time, the butanone wipe resistance and durability are poor, so it is only introduced as an auxiliary crosslinking agent to improve the flexibility of the coating [1] .
