A fluorocarbon primer with high adhesion and its preparation method

Abstract

This invention relates to the field of coating technology, specifically to a fluorocarbon primer with high adhesion and its preparation method. The primer is a two-component system comprising component A (fluorinated vinyl ether copolyfluoropolymer, directionally modified hydroxyl acrylic resin solution, pigments, fillers, additives, and solvents) and component B (aliphatic polyisocyanate curing agent). The core of this invention lies in synthesizing the resin solution through a specific stepwise polymerization process. By sequentially introducing phosphate esters, long-chain alkyl groups, rigid segments, and fluorinated segments, a gradient structure is formed from the substrate interface to the coating surface during film formation. This significantly improves the initial adhesion to metal substrates and greatly enhances adhesion retention and corrosion resistance under harsh environments such as humid heat and immersion, while simultaneously ensuring the mechanical properties of the coating and the inherent excellent weather resistance of the fluorocarbon resin.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a fluorocarbon primer with high adhesion and its preparation method. Background Technology

[0002] Solvent-based two-component fluorocarbon coatings are widely used in high-performance metal protection applications such as high-rise buildings and large stadiums due to their excellent weather resistance, superior chemical resistance, and good decorative effect. However, fluorocarbon resins (such as FEVE resin) often suffer from insufficient adhesion to metal substrates due to their extremely low surface energy and chemical inertness, which becomes a bottleneck restricting their direct application as primers.

[0003] To improve adhesion to metals, existing technologies typically employ the introduction of phosphate ester functional monomers (such as phosphate ester (meth)acrylate). These monomers are copolymerized with other (meth)acrylate monomers to prepare hydroxyl acrylic resins containing phosphate ester groups, which are then crosslinked with isocyanate curing agents. This method improves the initial dry adhesion between the coating and the metal substrate to some extent. However, the strong hydrophilicity of the phosphate ester groups makes it prone to absorbing water and swelling in harsh humid environments such as damp heat and immersion, disrupting the stability of the interfacial bonding. This results in a significant decrease in adhesion retention after damp heat exposure and poor water and salt spray resistance.

[0004] Some studies have attempted to improve the hydrophobicity of coatings by introducing long-chain alkyl monomers (such as octadecyl acrylate) to delay water penetration. However, in solvent-based two-component systems, the random copolymerization of phosphate functional monomers and long-chain alkyl monomers may lead to a disordered distribution of functional groups on the resin molecular chain, failing to form an oriented, ordered gradient structure at the coating-substrate interface. The strong polarity of phosphate groups and the strong hydrophobicity of long-chain alkyl groups may create internal repulsion, hindering both from achieving their optimal performance. Furthermore, the crystallinity of long-chain alkyl segments may affect the flexibility of the coating.

[0005] Furthermore, fluorocarbon primer systems typically require the addition of significant amounts of pigments and fillers to provide functions such as hiding power and rust prevention. The conventional process involves dispersing all resin components along with the pigments and fillers using high-speed shearing and milling. During this process, highly polar phosphate groups are readily competitively adsorbed onto the surfaces of inorganic particles such as pigments and fillers, drastically reducing the number of effective functional groups ultimately used for interfacial anchoring and weakening their contribution to adhesion to the metal substrate. This ineffective consumption of functional groups creates a bottleneck in adhesion improvement.

[0006] Therefore, how to overcome the limitations of introducing a single functional component in solvent-based two-component fluorocarbon primer systems, and solve the problems of low interface enrichment efficiency of functional groups, poor stability in wet environments, and difficulty in achieving both the weather resistance of fluorocarbon resins, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0007] In view of this, the purpose of this invention is to provide a fluorocarbon primer with high adhesion and its preparation method, so as to solve the problem that solvent-based two-component fluorocarbon primers are difficult to achieve while maintaining excellent weather resistance, high initial dry adhesion, high adhesion retention rate after humid heat / immersion, and good construction stability.

[0008] To achieve the above objectives, the present invention provides a fluorocarbon primer with high adhesion, comprising component A and component B;

[0009] By weight, component A comprises 197-205 parts of fluoroethylene-vinyl ether copolymer fluorinated resin, 122-129 parts of directionally modified hydroxyl acrylic resin solution, 20-26 parts of zinc phosphate, 18-22 parts of rutile titanium dioxide, 58-64 parts of barium sulfate, and 18-22 parts of talc; component B comprises 81-85 parts of aliphatic polyisocyanate curing agent.

[0010] The directionally modified hydroxy acrylic resin solution is a resin solution prepared by the following method: first, methyl methacrylate, n-butyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl methacrylate, and isoborneol methacrylate are polymerized to obtain a main hydroxy acrylic resin solution; then, a first post-stage monomer solution containing hydroxyethyl methacrylate and acrylic end-group polyphosphate, a second post-stage monomer solution containing acrylic end-group polyphosphate and octadecyl acrylate, a third post-stage monomer solution containing isoborneol methacrylate, and a fourth post-stage monomer solution containing octafluoropentyl methacrylate are sequentially polymerized with the main hydroxy acrylic resin solution to obtain the resin solution.

[0011] Preferably, component A is prepared by first dispersing and milling a portion of the fluoroethylene-vinyl ether copolyfluororesin with zinc phosphate, rutile titanium dioxide, barium sulfate and talc to form a pigment and filler slurry, and then adding the directionally modified hydroxyl acrylic resin solution and the remainder of the fluoroethylene-vinyl ether copolyfluororesin to form a mixture.

[0012] Preferably, based on the mass parts of the raw materials used to prepare the directionally modified hydroxy acrylic resin solution, the main hydroxy acrylic resin solution is obtained by polymerizing 70-80 parts of methyl methacrylate, 75-84 parts of n-butyl methacrylate, 45-55 parts of hydroxypropyl methacrylate, 12-17 parts of hydroxyethyl methacrylate and 18-24 parts of isobornyl methacrylate.

[0013] Preferably, the first downstream monomer solution comprises 8-12 parts hydroxyethyl methacrylate, 2.5-4 parts acrylic end-group polyphosphate, and 3-5 parts methyl methacrylate;

[0014] Preferably, the second downstream monomer solution comprises 5.5-7 parts of acrylate-terminated polyphosphate, 6-10 parts of octadecyl acrylate and 8-11 parts of n-butyl methacrylate;

[0015] Preferably, the third downstream monomer solution comprises 5-7 parts isobornyl methacrylate and 3-5 parts n-butyl methacrylate;

[0016] Preferably, the fourth downstream monomer solution comprises 4-6.5 parts of octafluoroamyl methacrylate and 3-5 parts of isobornyl methacrylate.

[0017] Preferably, when preparing the directionally modified hydroxyl acrylic resin solution, azobisisobutyronitrile (AIBN) is used as the initiator, dodecyl mercaptan (DOT) is used as the chain transfer agent, and the process is carried out at 95°C under nitrogen protection. Based on the mass fractions of the raw materials used to prepare the directionally modified hydroxyl acrylic resin solution, the amount of DOT used to prepare the main hydroxyl acrylic resin solution is 0.8-1.1 parts, the amount of AIBN is 2.3-2.7 parts, the amount of AIBN used for subsequent polymerization is 1.4-1.6 parts, and the amount of AIBN added is 0.7-0.8 parts.

[0018] Preferably, component A further comprises 3.8-4.2 parts of dispersant, 0.9-1.1 parts of leveling agent, 0.5-0.6 parts of bismuth neodecanoate, and additionally added 32-38 parts of xylene and 16-19 parts of butyl acetate.

[0019] Preferably, component A is prepared by the following method: 137-143 parts of fluoroethylene-vinyl ether copolymer fluorinated resin, 3.8-4.2 parts of dispersant, 19-22 parts of xylene and 9-10 parts of butyl acetate are premixed, and then 20-26 parts of zinc phosphate, 18-22 parts of rutile titanium dioxide, 58-64 parts of barium sulfate and 18-22 parts of talc are added, dispersed, and milled to a fineness of no more than 25 μm to obtain a pigment and filler slurry; then 122-129 parts of the directionally modified hydroxyl acrylic resin solution, 60-62 parts of fluoroethylene-vinyl ether copolymer fluorinated resin, 0.9-1.1 parts of leveling agent, 0.5-0.6 parts of bismuth neodecanoate, 13-16 parts of xylene and 7-9 parts of butyl acetate are added to the pigment and filler slurry, mixed, and filtered through a 300-mesh filter to obtain component A.

[0020] Preferably, the fluoroethylene-vinyl ether copolyfluorinated resin is of the type LUMIFLON LF910LM.

[0021] Preferably, the acrylic end-group polyphosphate is of the type Sipomer PAM-200.

[0022] Preferably, the aliphatic polyisocyanate curing agent is Desmodur ultra N 3390 BA / SN; the dispersant is DISPERBYK-110; and the leveling agent is BYK-306.

[0023] Furthermore, the present invention also provides a method for preparing a fluorocarbon primer with high adhesion, comprising the following steps:

[0024] (1) Preparation of directionally modified hydroxyl acrylic resin solution;

[0025] (2) Disperse and mill a portion of vinyl fluoride-vinyl ether copolymer fluorine resin, dispersant, zinc phosphate, rutile titanium dioxide, barium sulfate, talc and organic solvent to obtain pigment and filler slurry;

[0026] (3) Add the directionally modified hydroxyl acrylic resin solution, the balance fluorinated vinyl ether copolyfluorinated resin, leveling agent, bismuth neodecanoate and organic solvent to the pigment and filler slurry, mix and filter to obtain component A;

[0027] (4) Before use, add the aliphatic polyisocyanate curing agent to component A and mix to obtain the fluorocarbon primer.

[0028] Preferably, in step (4), under the condition that the relative humidity of the environment is not higher than 75%, the aliphatic polyisocyanate curing agent is added to the component A, stirred at 400 r / min for 8 min and then allowed to stand for 10 min to mature, so as to obtain the fluorocarbon primer.

[0029] The beneficial effect of this invention is that, through a step-by-step, orderly resin synthesis process and a specific formulation design, the overall performance of the fluorocarbon primer is synergistically improved.

[0030] First, acrylic-terminated polyphosphate is introduced using a post-drop addition method, and the timing and order of its introduction are controlled so that the functional groups of the phosphate ester can be more effectively enriched at the coating-metal interface to form a stable and dense coordination adsorption layer, thereby significantly enhancing the initial adhesion and anchoring strength of the coating to metal substrates such as aluminum and galvanized steel.

[0031] Secondly, by introducing octadecyl acrylate long-chain alkyl monomers after the introduction of phosphate ester functional groups, an effective hydrophobic barrier layer can be constructed in the region near the interface. This structure can effectively slow down the penetration and diffusion rate of liquid water and water vapor along the coating-substrate interface, reduce the damage of moisture to the interface bonding layer under humid environments such as damp heat and immersion, and thus significantly improve the adhesion retention rate and long-term protective stability of the coating under harsh environments.

[0032] Furthermore, by introducing isobornyl methacrylate and octafluoroamyl methacrylate in the order of first providing rigid buffer and then fluorinated outer layer, a reasonable chain segment gradient distribution can be formed within the coating. The rigid segments provided by isobornyl methacrylate alleviate the internal stress and brittleness that may be caused by long-chain alkyl groups, while the fluorinated segments of octafluoroamyl methacrylate tend to migrate towards the coating-air interface, giving the coating surface excellent low surface energy characteristics, enhancing water resistance, stain resistance, and weather resistance, without affecting the overall mechanical properties.

[0033] In addition, adding the phosphate-containing directional modified hydroxyl acrylic resin after the pigment and filler dispersion is completed avoids the phosphate functional sites being largely adsorbed and rendered ineffective by the pigment and filler surfaces during high-speed dispersion and sand milling. This ensures that most of the functional groups can ultimately act on the metal interface, maximizing their adhesion contribution.

[0034] Finally, by precisely controlling the ratio of directional modified hydroxyl acrylic resin to fluoroethylene-vinyl ether copolyfluoropolymer, the optimal balance between strong interfacial adhesion and the weather resistance and media resistance of the fluorocarbon resin matrix was achieved, so that the coating can obtain excellent adhesion performance while still maintaining the long-term weather resistance and protective life of fluorocarbon coatings. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0036] Example 1:

[0037] Raw material specifications: The fluoroethylene-vinyl ether copolyfluorinated resin used is LUMIFLONLF910LM from AGC Chemicals; the acrylic-terminated polyphosphate used is Sipomer PAM-200 from Synesqo; the aliphatic polyisocyanate curing agent used is Desmodur ultra N 3390 BA / SN from Covestro; the dispersant used is DISPERBYK-110 from BYK; the leveling agent used is BYK-306 from BYK; the zinc phosphate used is ZincPhosphate ZP 10 from Heubach; the rutile titanium dioxide used is BILLIONS R-996 from LB Group; the barium sulfate used is Blanc Fixe JM3B from Solvay; and the talc used is Luzenac from Imerys. H70; Bismuth neodecanoate is a commercially available paint-grade product; the remaining methyl methacrylate, n-butyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl methacrylate, isobornyl methacrylate, octadecyl acrylate, octafluoropentyl methacrylate, azobisisobutyronitrile, dodecyl mercaptan, xylene, butyl acetate, and propylene glycol methyl ether acetate can all be commercially available paint-grade industrial products; zinc phosphate, rutile titanium dioxide, barium sulfate, and talc are dried at 105°C for 2 hours and then sealed for later use.

[0038] Step 1: Add 40g xylene, 25g butyl acetate, and 10g propylene glycol methyl ether acetate to a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen protection device. Heat to 95℃ with stirring at 300r / min. Separately, prepare a front-stage monomer mixture by mixing 75g methyl methacrylate, 80g n-butyl methacrylate, 50g hydroxypropyl methacrylate, 15g hydroxyethyl methacrylate, 20g isobornyl methacrylate, 1g dodecyl mercaptan, 15g xylene, and 10g butyl acetate. Prepare a front-stage initiator solution by dissolving 2.5g azobisisobutyronitrile in 12g butyl acetate. Under nitrogen protection, add the front-stage monomer mixture dropwise at a uniform rate over 180min, and simultaneously add the front-stage initiator solution dropwise over 200min. After the addition is complete, continue to maintain the temperature for 45min to obtain the main hydroxyl acrylic resin solution.

[0039] Step 2: Preheat 8g of octadecyl acrylate to 55℃ and hold until completely melted; first, prepare the first downstream monomer solution by mixing 10g of hydroxyethyl methacrylate, 3g of acrylate-terminated polyphosphate, 4g of methyl methacrylate, and 5g of butyl acetate; then prepare the second downstream monomer solution by mixing 6g of acrylate-terminated polyphosphate, 8g of molten octadecyl acrylate, 10g of n-butyl methacrylate, and 5g of butyl acetate; then prepare the third downstream monomer solution by mixing 6g of isobornyl methacrylate, 4g of n-butyl methacrylate, and 3g of butyl acetate; then prepare the third downstream monomer solution by mixing 5g of... Octafluoroamyl methacrylate, 4g isobornyl methacrylate, and 2g butyl acetate were used to prepare the fourth downstream monomer solution. The reactor temperature was maintained at 95℃. The first downstream monomer solution was added dropwise over 15 minutes, followed by the second downstream monomer solution over 20 minutes, then the third downstream monomer solution over 10 minutes, and finally the fourth downstream monomer solution over 10 minutes. During the addition of the downstream monomer solutions, 1.5g of azobisisobutyronitrile (AIBN) was dissolved in 8g of butyl acetate to prepare the downstream initiator solution, which was continuously added dropwise over 60 minutes. After all the solutions were added, 0.8g of AIBN was dissolved in 5g of butyl acetate to prepare the supplementary initiator solution, which was added and the temperature was maintained for another 60 minutes. After the reaction was completed, the temperature was lowered to 70℃, and 40g of xylene and 15g of butyl acetate were added to adjust the viscosity. The solution was then filtered through a 200-mesh filter to obtain a directionally modified hydroxyl acrylic resin solution.

[0040] Step 3: Add 140g of fluoroethylene-vinyl ether copolymer fluorine resin, 4g of dispersant, 20g of xylene and 10g of butyl acetate to the dispersion tank. After premixing at 500r / min for 10min, add 25g of zinc phosphate, 20g of rutile titanium dioxide, 60g of barium sulfate and 20g of talc powder in sequence. Then disperse at 2000r / min for 20min and grind to a fineness of no more than 25μm to obtain pigment and filler slurry.

[0041] Step 4: At 600 r / min, add 125 g of directional modified hydroxyl acrylic resin solution, 60 g of fluoroethylene-vinyl ether copolymer fluorine resin, 1 g of leveling agent, 0.5 g of bismuth neodecanoate, 15 g of xylene and 8 g of butyl acetate to the pigment and filler slurry obtained in Step 3 in sequence. After stirring for 20 min, filter through a 300 mesh filter to obtain fluorocarbon primer component A.

[0042] Step 5: Before use, under conditions where the relative humidity of the environment is not higher than 75%, add 83g of aliphatic polyisocyanate curing agent to component A of the fluorocarbon primer obtained in Step 4, stir at 400r / min for 8min, and let stand for 10min to mature, to obtain a fluorocarbon primer with high adhesion; then spray it onto building aluminum panels or galvanized steel sheets that have been neutrally degreased, cleaned with deionized water, dried at 60℃ and dust-removed, so that the dry film thickness is 20μm, level at room temperature for 15min, cure at 80℃ for 30min, and then place at 23℃ for 24h before testing; or directly cure at 23℃ for 7d before use.

[0043] Example 2:

[0044] Raw material description: Same as the above-mentioned raw material source and model.

[0045] Step 1: Add 42g xylene, 24g butyl acetate, and 10g propylene glycol methyl ether acetate to a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen protection device. Heat to 95℃ with stirring at 300r / min. Separately, prepare a front-stage monomer mixture by mixing 72g methyl methacrylate, 82g n-butyl methacrylate, 52g hydroxypropyl methacrylate, 16g hydroxyethyl methacrylate, 18g isobornyl methacrylate, 0.9g dodecyl mercaptan, 15g xylene, and 10g butyl acetate. Prepare a front-stage initiator solution by dissolving 2.4g azobisisobutyronitrile in 12g butyl acetate. Under nitrogen protection, add the front-stage monomer mixture dropwise at a uniform rate over 175min, and simultaneously add the front-stage initiator solution dropwise over 195min. After the addition is complete, continue to maintain the temperature for 45min to obtain the main hydroxyl acrylic resin solution.

[0046] Step 2: Preheat 7g of octadecyl acrylate to 55℃ and maintain the temperature until completely melted; first, prepare the first downstream monomer solution by mixing 9g of hydroxyethyl methacrylate, 4g of acrylate-terminated polyphosphate, 4g of methyl methacrylate, and 5g of butyl acetate; then prepare the second downstream monomer solution by mixing 6g of acrylate-terminated polyphosphate, 7g of molten octadecyl acrylate, 10g of n-butyl methacrylate, and 5g of butyl acetate; then prepare the third downstream monomer solution by mixing 5g of isobornyl methacrylate, 4g of n-butyl methacrylate, and 3g of butyl acetate; finally, prepare the fourth downstream monomer solution by mixing 4.5g of octafluoroamyl methacrylate, 4g of isobornyl methacrylate, and 2g of butyl acetate; maintain the reactor temperature at 95℃, and first prepare the first downstream monomer solution... The monomer solution was added dropwise over 15 minutes, followed by the second stage monomer solution over 20 minutes, then the third stage monomer solution over 10 minutes, and finally the fourth stage monomer solution over 10 minutes. During the addition of the aforementioned stage monomer solutions, 1.4 g of azobisisobutyronitrile was dissolved in 8 g of butyl acetate to prepare a stage initiator solution, which was continuously added dropwise over 58 minutes. After all the solutions were added, 0.7 g of azobisisobutyronitrile was dissolved in 5 g of butyl acetate to prepare a supplementary initiator solution, which was added and the temperature was maintained for another 60 minutes. After the reaction was completed, the temperature was lowered to 70°C, and 40 g of xylene and 15 g of butyl acetate were added to adjust the viscosity. The solution was then filtered through a 200-mesh filter to obtain a directionally modified hydroxyl acrylic resin solution.

[0047] Step 3: Add 138g of fluoroethylene-vinyl ether copolymer fluorine resin, 4g of dispersant, 20g of xylene and 10g of butyl acetate to the dispersion tank. After premixing at 500r / min for 10min, add 24g of zinc phosphate, 20g of rutile titanium dioxide, 60g of barium sulfate and 20g of talc powder in sequence. Then disperse at 2000r / min for 20min and grind to a fineness of no more than 25μm to obtain pigment and filler slurry.

[0048] Step 4: At 600 r / min, add 128 g of directional modified hydroxyl acrylic resin solution, 60 g of fluoroethylene-vinyl ether copolymer fluorine resin, 1.0 g of leveling agent, 0.5 g of bismuth neodecanoate, 15 g of xylene and 8 g of butyl acetate to the pigment and filler slurry obtained in Step 3 in sequence. After stirring for 20 min, filter through a 300 mesh filter to obtain fluorocarbon primer component A.

[0049] Step 5: Before use, under conditions where the relative humidity of the environment is not higher than 75%, add 84g of aliphatic polyisocyanate curing agent to component A of the fluorocarbon primer obtained in Step 4, stir at 400r / min for 8min, and let stand for 10min to mature, to obtain a fluorocarbon primer with high adhesion; then spray it onto building aluminum panels or galvanized steel sheets that have been neutrally degreased, cleaned with deionized water, dried at 60℃ and dust-removed, so that the dry film thickness is 20μm, level at room temperature for 15min, cure at 80℃ for 30min, and then place at 23℃ for 24h before testing; or directly cure at 23℃ for 7d before use.

[0050] Example 3:

[0051] Raw material description: Same as the above-mentioned raw material source and model.

[0052] Step 1: Add 38g xylene, 28g butyl acetate, and 10g propylene glycol methyl ether acetate to a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen protection device. Heat to 95℃ with stirring at 300r / min. Separately, prepare a front-stage monomer mixture by mixing 78g methyl methacrylate, 76g n-butyl methacrylate, 48g hydroxypropyl methacrylate, 14g hydroxyethyl methacrylate, 22g isobornyl methacrylate, 1.0g dodecyl mercaptan, 16g xylene, and 10g butyl acetate. Prepare a front-stage initiator solution by dissolving 2.6g azobisisobutyronitrile in 13g butyl acetate. Under nitrogen protection, add the front-stage monomer mixture dropwise at a uniform rate over 185min, and simultaneously add the front-stage initiator solution dropwise over 205min. After the addition is complete, continue to maintain the temperature for 45min to obtain the main hydroxyl acrylic resin solution.

[0053] Step 2: Preheat 9g of octadecyl acrylate to 55℃ and maintain the temperature until completely melted; first, prepare the first downstream monomer solution by mixing 10g of hydroxyethyl methacrylate, 3.5g of acrylate-terminated polyphosphate, 4g of methyl methacrylate, and 5g of butyl acetate; then prepare the second downstream monomer solution by mixing 6g of acrylate-terminated polyphosphate, 9g of molten octadecyl acrylate, 9g of n-butyl methacrylate, and 5g of butyl acetate; then prepare the third downstream monomer solution by mixing 7g of isobornyl methacrylate, 4g of n-butyl methacrylate, and 3g of butyl acetate; finally, prepare the fourth downstream monomer solution by mixing 6g of octafluoroamyl methacrylate, 5g of isobornyl methacrylate, and 2g of butyl acetate; maintain the reactor temperature at 95℃, and first prepare the first downstream monomer solution... The monomer solution was added dropwise over 15 minutes, followed by the second stage monomer solution over 20 minutes, then the third stage monomer solution over 10 minutes, and finally the fourth stage monomer solution over 10 minutes. During the addition of the aforementioned stage monomer solutions, 1.6 g of azobisisobutyronitrile was dissolved in 8 g of butyl acetate to prepare a stage initiator solution, which was continuously added dropwise over 62 minutes. After all the solutions were added, 0.7 g of azobisisobutyronitrile was dissolved in 5 g of butyl acetate to prepare a supplementary initiator solution, which was added and the temperature was maintained for another 60 minutes. After the reaction was completed, the temperature was lowered to 70°C, and 38 g of xylene and 16 g of butyl acetate were added to adjust the viscosity. The solution was then filtered through a 200-mesh filter to obtain a directionally modified hydroxyl acrylic resin solution.

[0054] Step 3: Add 142g of fluoroethylene-vinyl ether copolymer fluorine resin, 4.2g of dispersant, 20g of xylene and 10g of butyl acetate to the dispersion tank. After premixing at 500r / min for 10min, add 22g of zinc phosphate, 18g of rutile titanium dioxide, 62g of barium sulfate and 20g of talc powder in sequence. Then disperse at 2000r / min for 20min and grind to a fineness of no more than 25μm to obtain pigment and filler slurry.

[0055] Step 4: At 600 r / min, add 122 g of directionally modified hydroxyl acrylic resin solution, 60 g of fluoroethylene-vinyl ether copolymer fluorine resin, 1.0 g of leveling agent, 0.5 g of bismuth neodecanoate, 14 g of xylene and 8 g of butyl acetate to the pigment and filler slurry obtained in Step 3 in sequence. After stirring for 20 min, filter through a 300 mesh filter to obtain fluorocarbon primer component A.

[0056] Step 5: Before use, under conditions where the relative humidity of the environment is not higher than 75%, add 81g of aliphatic polyisocyanate curing agent to component A of the fluorocarbon primer obtained in Step 4, stir at 400r / min for 8min, and let stand for 10min to mature, to obtain a fluorocarbon primer with high adhesion; then spray it onto building aluminum panels or galvanized steel sheets that have been neutrally degreased, cleaned with deionized water, dried at 60℃ and dust-removed, so that the dry film thickness is 20μm, level at room temperature for 15min, cure at 80℃ for 30min, and then place at 23℃ for 24h before testing; or directly cure at 23℃ for 7d before use.

[0057] Example 4:

[0058] Raw material description: Same as the above-mentioned raw material source and model.

[0059] Step 1: Add 44g xylene, 22g butyl acetate, and 9g propylene glycol methyl ether acetate to a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen protection device. Heat to 95℃ with stirring at 300r / min. Separately, prepare a front-stage monomer mixture by mixing 70g methyl methacrylate, 84g n-butyl methacrylate, 55g hydroxypropyl methacrylate, 17g hydroxyethyl methacrylate, 19g isobornyl methacrylate, 1.1g dodecyl mercaptan, 14g xylene, and 9g butyl acetate. Prepare a front-stage initiator solution by dissolving 2.3g azobisisobutyronitrile in 11g butyl acetate. Under nitrogen protection, add the front-stage monomer mixture dropwise at a uniform rate over 170min, and simultaneously add the front-stage initiator solution dropwise over 190min. After the addition is complete, continue to maintain the temperature for 45min to obtain the main hydroxyl acrylic resin solution.

[0060] Step 2: Preheat 6g of octadecyl acrylate to 55℃ and maintain the temperature until completely melted; first, prepare the first downstream monomer solution by mixing 8g of hydroxyethyl methacrylate, 2.5g of acrylate-terminated polyphosphate, 5g of methyl methacrylate, and 4g of butyl acetate; then prepare the second downstream monomer solution by mixing 5.5g of acrylate-terminated polyphosphate, 6g of molten octadecyl acrylate, 11g of n-butyl methacrylate, and 5g of butyl acetate; then prepare the third downstream monomer solution by mixing 6g of isobornyl methacrylate, 5g of n-butyl methacrylate, and 3g of butyl acetate; finally, prepare the fourth downstream monomer solution by mixing 4g of octafluoroamyl methacrylate, 3g of isobornyl methacrylate, and 2g of butyl acetate; maintain the reactor temperature at 95℃, and first prepare the first downstream monomer solution... The first monomer solution was added dropwise over 15 minutes, followed by the second monomer solution over 20 minutes, then the third monomer solution over 10 minutes, and finally the fourth monomer solution over 10 minutes. During the addition of the monomer solutions, 1.5 g of azobisisobutyronitrile was dissolved in 7 g of butyl acetate to prepare the initiator solution, which was continuously added dropwise over 56 minutes. After all the monomer solutions were added, 0.8 g of azobisisobutyronitrile was dissolved in 5 g of butyl acetate to prepare the supplementary initiator solution, which was added and the temperature was maintained for another 60 minutes. After the reaction was completed, the temperature was lowered to 70°C, and 42 g of xylene and 14 g of butyl acetate were added to adjust the viscosity. The solution was then filtered through a 200-mesh filter to obtain a directionally modified hydroxyl acrylic resin solution.

[0061] Step 3: Add 137g of fluoroethylene-vinyl ether copolymer fluorine resin, 4.0g of dispersant, 22g of xylene and 10g of butyl acetate to the dispersion tank. After premixing at 500r / min for 10min, add 26g of zinc phosphate, 20g of rutile titanium dioxide, 58g of barium sulfate and 22g of talc powder in sequence. Then disperse at 2000r / min for 20min and grind to a fineness of no more than 25μm to obtain pigment and filler slurry.

[0062] Step 4: At 600 r / min, add 129 g of directionally modified hydroxyl acrylic resin solution, 60 g of fluoroethylene-vinyl ether copolymer fluorine resin, 0.9 g of leveling agent, 0.6 g of bismuth neodecanoate, 16 g of xylene and 8 g of butyl acetate to the pigment and filler slurry obtained in Step 3 in sequence. After stirring for 20 min, filter through a 300 mesh filter to obtain fluorocarbon primer component A.

[0063] Step 5: Before use, under conditions where the relative humidity of the environment is not higher than 75%, add 85g of aliphatic polyisocyanate curing agent to component A of the fluorocarbon primer obtained in Step 4, stir at 400r / min for 8min, and let stand for 10min to mature, to obtain a fluorocarbon primer with high adhesion; then spray it onto building aluminum panels or galvanized steel sheets that have been neutrally degreased, cleaned with deionized water, dried at 60℃ and dust-removed, so that the dry film thickness is 20μm, level at room temperature for 15min, cure at 80℃ for 30min, and then place at 23℃ for 24h before testing; or directly cure at 23℃ for 7d before use.

[0064] Example 5:

[0065] Raw material description: Same as the above-mentioned raw material source and model.

[0066] Step 1: Add 40g xylene, 27g butyl acetate, and 11g propylene glycol methyl ether acetate to a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen protection device. Heat to 95℃ with stirring at 300r / min. Separately, prepare a front-stage monomer mixture by mixing 80g methyl methacrylate, 75g n-butyl methacrylate, 45g hydroxypropyl methacrylate, 12g hydroxyethyl methacrylate, 24g isobornyl methacrylate, 1.0g dodecyl mercaptan, 16g xylene, and 11g butyl acetate. Prepare a front-stage initiator solution by dissolving 2.7g azobisisobutyronitrile in 13g butyl acetate. Under nitrogen protection, add the front-stage monomer mixture dropwise at a uniform rate over 180min, and simultaneously add the front-stage initiator solution dropwise over 200min. After the addition is complete, continue to maintain the temperature for 45min to obtain the main hydroxyl acrylic resin solution.

[0067] Step 2: Preheat 10g of octadecyl acrylate to 58℃ and maintain the temperature until completely melted; first, prepare the first downstream monomer solution by mixing 12g of hydroxyethyl methacrylate, 4g of acrylate-terminated polyphosphate, 3g of methyl methacrylate, and 6g of butyl acetate; then prepare the second downstream monomer solution by mixing 7g of acrylate-terminated polyphosphate, 10g of molten octadecyl acrylate, 8g of n-butyl methacrylate, and 6g of butyl acetate; then prepare the third downstream monomer solution by mixing 7g of isobornyl methacrylate, 3g of n-butyl methacrylate, and 3g of butyl acetate; finally, prepare the fourth downstream monomer solution by mixing 6.5g of octafluoroamyl methacrylate, 5g of isobornyl methacrylate, and 2g of butyl acetate; maintain the reactor temperature at 95℃, and first prepare the first downstream monomer solution... The first monomer solution was added dropwise over 15 minutes, followed by the second monomer solution over 20 minutes, then the third monomer solution over 10 minutes, and finally the fourth monomer solution over 10 minutes. During the addition of the monomer solutions, 1.6 g of azobisisobutyronitrile was dissolved in 9 g of butyl acetate to prepare the initiator solution, which was continuously added dropwise over 63 minutes. After all the monomer solutions were added, 0.7 g of azobisisobutyronitrile was dissolved in 5 g of butyl acetate to prepare the supplementary initiator solution, which was added and the temperature was maintained for another 60 minutes. After the reaction was completed, the temperature was lowered to 70°C, and 37 g of xylene and 17 g of butyl acetate were added to adjust the viscosity. The solution was then filtered through a 200-mesh filter to obtain a directionally modified hydroxyl acrylic resin solution.

[0068] Step 3: Add 143g of fluoroethylene-vinyl ether copolymer fluorine resin, 4.0g of dispersant, 19g of xylene and 10g of butyl acetate to the dispersion tank. After premixing at 500r / min for 10min, add 20g of zinc phosphate, 22g of rutile titanium dioxide, 64g of barium sulfate and 18g of talc powder in sequence. Then disperse at 2000r / min for 20min and grind to a fineness of no more than 25μm to obtain pigment and filler slurry.

[0069] Step 4: At 600 r / min, add 123 g of directionally modified hydroxyl acrylic resin solution, 62 g of fluoroethylene-vinyl ether copolymer fluorine resin, 1.1 g of leveling agent, 0.5 g of bismuth neodecanoate, 13 g of xylene and 9 g of butyl acetate to the pigment and filler slurry obtained in Step 3 in sequence. After stirring for 20 min, filter through a 300 mesh filter to obtain fluorocarbon primer component A.

[0070] Step 5: Before use, under conditions where the relative humidity of the environment is not higher than 75%, add 81g of aliphatic polyisocyanate curing agent to component A of the fluorocarbon primer obtained in Step 4, stir at 400r / min for 8min, and let stand for 10min to mature, to obtain a fluorocarbon primer with high adhesion; then spray it onto building aluminum panels or galvanized steel sheets that have been neutrally degreased, cleaned with deionized water, dried at 60℃ and dust-removed, so that the dry film thickness is 20μm, level at room temperature for 15min, cure at 80℃ for 30min, and then place at 23℃ for 24h before testing; or directly cure at 23℃ for 7d before use.

[0071] Example 6:

[0072] Raw material description: Same as the above-mentioned raw material source and model.

[0073] Step 1: Add 41g xylene, 26g butyl acetate, and 9g propylene glycol methyl ether acetate to a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen protection device. Heat to 95℃ with stirring at 300r / min. Separately, prepare a front-stage monomer mixture by mixing 74g methyl methacrylate, 81g n-butyl methacrylate, 53g hydroxypropyl methacrylate, 15g hydroxyethyl methacrylate, 21g isobornyl methacrylate, 0.8g dodecyl mercaptan, 15g xylene, and 10g butyl acetate. Prepare a front-stage initiator solution by dissolving 2.5g azobisisobutyronitrile in 12g butyl acetate. Under nitrogen protection, add the front-stage monomer mixture dropwise at a uniform rate over 178min, and simultaneously add the front-stage initiator solution dropwise over 198min. After the addition is completed, continue to maintain the temperature for 45min to obtain the main hydroxyl acrylic resin solution.

[0074] Step 2: Preheat 8g of octadecyl acrylate to 55℃ and maintain the temperature until completely melted; first, prepare the first downstream monomer solution by mixing 11g of hydroxyethyl methacrylate, 3g of acrylate-terminated polyphosphate, 5g of methyl methacrylate, and 5g of butyl acetate; then prepare the second downstream monomer solution by mixing 6.5g of acrylate-terminated polyphosphate, 8g of molten octadecyl acrylate, 10g of n-butyl methacrylate, and 5g of butyl acetate; then prepare the third downstream monomer solution by mixing 6g of isobornyl methacrylate, 4g of n-butyl methacrylate, and 3g of butyl acetate; finally, prepare the fourth downstream monomer solution by mixing 5.5g of octafluoroamyl methacrylate, 4g of isobornyl methacrylate, and 2g of butyl acetate; maintain the reactor temperature at 95℃, and first prepare the first downstream monomer solution... The first monomer solution was added dropwise over 15 minutes, followed by the second monomer solution over 20 minutes, then the third monomer solution over 10 minutes, and finally the fourth monomer solution over 10 minutes. During the addition of the monomer solutions, 1.5 g of azobisisobutyronitrile was dissolved in 8 g of butyl acetate to prepare the initiator solution, which was continuously added dropwise over 60 minutes. After all the monomer solutions were added, 0.7 g of azobisisobutyronitrile was dissolved in 5 g of butyl acetate to prepare the supplementary initiator solution, which was added and the temperature was maintained for another 60 minutes. After the reaction was completed, the temperature was lowered to 70°C, and 41 g of xylene and 15 g of butyl acetate were added to adjust the viscosity. The solution was then filtered through a 200-mesh filter to obtain a directionally modified hydroxyl acrylic resin solution.

[0075] Step 3: Add 139g of fluoroethylene-vinyl ether copolymer fluorine resin, 3.8g of dispersant, 21g of xylene and 9g of butyl acetate to the dispersion tank. After premixing at 500r / min for 10min, add 23g of zinc phosphate, 19g of rutile titanium dioxide, 61g of barium sulfate and 21g of talc powder in sequence. Then disperse at 2000r / min for 20min and grind to a fineness of no more than 25μm to obtain pigment and filler slurry.

[0076] Step 4: At 600 r / min, add 126 g of directional modified hydroxyl acrylic resin solution, 60 g of fluoroethylene-vinyl ether copolymer fluorine resin, 1.0 g of leveling agent, 0.5 g of bismuth neodecanoate, 15 g of xylene and 7 g of butyl acetate to the pigment and filler slurry obtained in Step 3 in sequence. After stirring for 20 min, filter through a 300 mesh filter to obtain fluorocarbon primer component A.

[0077] Step 5: Before use, under conditions where the relative humidity of the environment is not higher than 75%, add 84g of aliphatic polyisocyanate curing agent to component A of the fluorocarbon primer obtained in Step 4, stir at 400r / min for 8min, and let stand for 10min to mature, to obtain a fluorocarbon primer with high adhesion; then spray it onto building aluminum panels or galvanized steel sheets that have been neutrally degreased, cleaned with deionized water, dried at 60℃ and dust-removed, so that the dry film thickness is 20μm, level at room temperature for 15min, cure at 80℃ for 30min, and then place at 23℃ for 24h before testing; or directly cure at 23℃ for 7d before use.

[0078] Comparative Example 1:

[0079] The difference from Example 1 is that 9g of acrylic acid-terminated polyphosphate was added to the front monomer mixture in step 1, and acrylic acid-terminated polyphosphate was not added to the first and second rear monomer solutions in step 2. The other conditions were the same as in Example 1.

[0080] Comparative Example 2:

[0081] The difference from Example 1 is that 3g of acrylate-terminated polyphosphate in the first post-stage monomer solution and 6g of acrylate-terminated polyphosphate in the second post-stage monomer solution in step 2 are replaced with methyl methacrylate of equal mass, while the other conditions are the same as in Example 1.

[0082] Comparative Example 3:

[0083] The difference from Example 1 is that in step 2, the second post-stage monomer solution is added dropwise over 20 minutes, and then the first post-stage monomer solution is added dropwise over 15 minutes. The other conditions are the same as in Example 1.

[0084] Comparative Example 4:

[0085] The difference from Example 1 is that 8g of octadecyl acrylate in the second post-stage monomer solution of step 2 is replaced with an equal mass of n-butyl methacrylate, and the other conditions are the same as in Example 1.

[0086] Comparative Example 5:

[0087] The difference from Example 1 is that in step 2, the fourth post-stage monomer solution is added dropwise within 10 minutes, and then the third post-stage monomer solution is added dropwise within 10 minutes. The other conditions are the same as in Example 1.

[0088] Comparative Example 6:

[0089] The difference from Example 1 is that: before adding zinc phosphate, rutile titanium dioxide, barium sulfate and talc in step 3, 125g of directionally modified hydroxyl acrylic resin solution and 140g of fluoroethylene-vinyl ether copolyfluoride resin are added together to the dispersion tank for dispersion and milling, and 125g of directionally modified hydroxyl acrylic resin solution is not added in step 4. The other conditions are the same as in Example 1.

[0090] Comparative Example 7:

[0091] The difference from Example 1 is that the directionally modified hydroxyl acrylic resin solution in step 4 is changed to 87g, and the total amount of fluorinated vinyl ether copolyfluorinated resin added in steps 3 and 4 is changed to 234g, of which 174g is added in step 3 and 60g is added in step 4, so that the resin solid mass ratio of the directionally modified hydroxyl acrylic resin to the fluorinated vinyl ether copolyfluorinated resin is about 25:75. The other conditions are the same as in Example 1.

[0092] Comparative Example 8:

[0093] The difference from Example 1 is that the directional modified hydroxy acrylic resin solution in step 4 is changed to 155g, and the total amount of fluorinated vinyl ether co-fluorinated resin added in steps 3 and 4 is changed to 172g, of which 112g is added in step 3 and 60g is added in step 4, so that the resin solid mass ratio of the directional modified hydroxy acrylic resin to the fluorinated vinyl ether co-fluorinated resin is about 45:55. The other conditions are the same as in Example 1.

[0094] Performance testing:

[0095] Sample Preparation: Primer samples were prepared according to Examples 1-6 and Comparative Examples 1-8, respectively. The substrate used for coating was 3003-H24 architectural aluminum single-layer panels, with uniform panel dimensions of 150mm × 70mm × 1.0mm. The panels were first degreased with a neutral degreaser at 40℃ for 5 minutes, then rinsed with deionized water until no residue remained, dried at 60℃ for 20 minutes, and then dusted with a lint-free cloth before use. HVLP spray guns were used for coating, with a nozzle diameter of 1.3mm, atomization pressure of 0.30MPa, and a distance of 180mm between the spray gun and the panel surface. One horizontal and one vertical pass was applied to control the dry film thickness at 20±2μm. The film thickness was measured at 5 locations on each panel according to GB / T 13452.2-2008, and the average value was taken. After spraying, the coating was leveled at room temperature for 15 minutes, then cured at 80±2℃ for 30 minutes, and placed at 23±2℃ and 50±5% relative humidity for 24 hours before routine testing. Samples used for room temperature curing evaluation were placed at 23±2℃ and 50±5% relative humidity for 7 days before testing.

[0096] Pull-off adhesion test: conducted according to GB / T 5210-2006; samples from Examples 1-6 and Comparative Examples 1-8 on aluminum single-layer boards were tested separately. A steel pull-out head with a diameter of 20 mm was used, and high-strength two-component epoxy adhesive was used to bond the coating surface. After curing at 23±2℃ for 24 h, pull-out was performed; the loading speed was controlled at 1 MPa / s, and 5 pull-out points were tested on each test board. After discarding obvious accidental failure points, the average value was taken and expressed in MPa.

[0097] Resistance to damp heat and adhesion retention rate after damp heat: According to GB / T 1740-2007, three test panels were taken from each aluminum single panel and vertically suspended in a constant temperature and humidity chamber for continuous exposure for 240 hours at 47±1℃ and 96±2% relative humidity. After exposure, the test panels were removed and restored at 23±2℃ for 2 hours. The pull-off adhesion after damp heat was then measured. The adhesion retention rate was calculated as pull-off adhesion after damp heat / initial pull-off adhesion × 100%.

[0098] Water resistance and adhesion retention rate after immersion: Tested according to Method A of GB / T 1733-1993; three test panels were taken from each aluminum single-layer panel. The edges and back of the panel, except for the test surface, were sealed with epoxy edge sealant. After the edge sealant dried, the test panels were vertically immersed in Class III water conforming to GB / T 6682, with an immersion depth of 2 / 3 of the panel height. The water temperature was controlled at 23±2℃, and the immersion was continued for 240 hours. After the test, the test panels were removed, and the surface water was gently blotted dry with filter paper. After being placed in an environment of 23±2℃ and 50±5% relative humidity for 3 hours, the pull-off adhesion after immersion was measured. The adhesion retention rate was calculated as (pull-off adhesion after immersion / initial pull-off adhesion) × 100%.

[0099] Neutral salt spray performance: The neutral salt spray test was conducted according to GB / T 10125-2021. Three test panels were taken from each aluminum single panel, and a 60mm long scratch was made along the length of the panel, penetrating to the metal substrate, with the test areas on both sides of the scratch remaining intact. The test solution used was a 5% sodium chloride solution. The test chamber temperature was controlled at 35±2℃, the pH of the collected solution was controlled at 6.5-7.2, and the angle between the test panel and the vertical direction was controlled at 20°. After 500 hours of continuous spraying, the test panels were removed, the surface salt was gently rinsed with flowing deionized water, and the panels were left at room temperature for 2 hours. The corrosion propagation distance on one side of the scratch was recorded.

[0100] Pencil hardness: conducted according to GB / T 6739-2022; the coating of each sample on the aluminum single plate was cured at 23±2℃ for 7 days before testing. 6B to 6H pencils were used, with the lead ground flat and the pencils angled at 45° to the test plate surface. The pencils were pushed at a uniform speed of 6.5 mm under standard load, and the test was conducted at 3 different locations. The highest pencil hardness grade that did not scratch the paint film was taken as the result.

[0101] Impact resistance: Tested according to GB / T 1732-2020; the coating of each sample on the aluminum panel was cured at 23±2℃ for 7 days before testing. A paint film impactor with a drop weight of 1000g, a punch ball diameter of 8mm, and a penetration depth of 2mm was used. The test was conducted in a forward impact manner, starting from 20cm and increasing by 5cm each time, until the paint film cracked, peeled, or significantly lost its adhesion. The result was expressed as the maximum impact height when the paint film showed no abnormalities. Three test panels were tested for each sample.

[0102] Bending test: Conducted according to GB / T 6742-2007; the coating test pieces of each sample on the aluminum plate were cut into 100mm×25mm pieces, cured at 23±2℃ for 7 days, and then bent sequentially around cylindrical axes of 2mm, 3mm, 4mm, 5mm, and 6mm. Immediately after bending, the film was observed under natural light and checked with a 10x magnifying glass for cracks, peeling, or chalking. The result was represented by the smallest cylindrical axis diameter at which no abnormalities were observed. Three pieces were tested for each sample. The test results are shown in Table 1.

[0103] Table 1 Performance test results of the examples and comparative examples

[0104] Sample Pull-off adhesion / MPa Adhesion strength by pull-off test after 240 hours of humid heat / MPa Adhesion retention rate after wet heat / % Adhesion strength by pull-off test after immersion in water for 240 hours / MPa Adhesion retention rate after immersion in water / % Salt spray 500h unilateral corrosion spread / mm Pencil hardness Maximum impact height / cm Minimum diameter of cylindrical shaft without abnormalities / mm Example 1 7.86 7.19 91.5 7.42 94.4 1.3 2H 50 2 Example 2 7.98 7.23 90.6 7.39 92.6 1.5 2H 50 2 Example 3 7.82 7.20 92.1 7.50 95.9 1.1 3H 45 3 Example 4 7.64 6.88 90.1 7.08 92.7 1.8 2H 50 2 Example 5 7.88 7.21 91.5 7.55 95.8 1.2 3H 45 3 Example 6 7.92 7.24 91.4 7.49 94.6 1.3 2H 50 2 Comparative Example 1 6.96 5.79 83.2 6.08 87.4 2.3 2H 45 3 Comparative Example 2 5.78 4.26 73.7 4.61 79.8 3.4 2H 45 3 Comparative Example 3 6.58 5.14 78.1 5.48 83.3 2.7 2H 45 3 Comparative Example 4 7.08 5.93 83.8 6.26 88.4 2.5 2H 50 2 Comparative Example 5 7.34 6.36 86.6 6.70 91.3 1.9 2H 45 3 Comparative Example 6 6.82 5.42 79.5 5.82 85.3 2.6 2H 40 4 Comparative Example 7 6.32 5.29 83.7 5.63 89.1 2.2 3H 40 4 Comparative Example 8 7.26 6.03 83.1 6.25 86.1 2.4 2H 45 3

[0105] Data Analysis:

[0106] As can be seen from the data in the table of examples, the fluorocarbon primer with high adhesion prepared by this invention exhibits a relatively balanced improvement trend in adhesion under pull-out test, adhesion retention rate after wet heat, adhesion retention rate after immersion in water, and salt spray scratch protection, while still maintaining good pencil hardness, impact resistance, and flexural adaptability. This indicates that after the formation of the main hydroxyl acrylic resin, the sequential introduction of acrylic end-group polyphosphate, octadecyl acrylate, isobornyl methacrylate, and octafluoropentyl methacrylate can form a segment distribution within the coating film that gradually transitions from the metal interface to the air side. The phosphate ester functional side group near the substrate side is conducive to the formation of a stable coordination adsorption layer, octadecyl acrylate reduces the penetration rate of water along the interface, isobornyl methacrylate provides a rigid buffering effect, and octafluoropentyl methacrylate promotes the distribution of fluorinated segments towards the air side. Therefore, it can simultaneously achieve interfacial adhesion, water resistance, and surface protection, demonstrating a significant synergistic effect.

[0107] As can be seen from the data in Example 1 and Comparative Example 1, after adding the acrylic end-group polyphosphate to the front-end random copolymerization, the initial adhesion and retention ability after wet heat and immersion in water both decreased significantly. The main reason is that the phosphate ester functional side groups are dispersed into the overall chain segments during the main resin formation stage, making it difficult to form sufficiently concentrated action sites near the metal interface. Furthermore, it is difficult to form a clear polar transition—hydrophobic and water-blocking structure—with the octadecyl acrylate subsequently. Therefore, although this comparative example still exhibits some adhesion, interface anchoring and subsequent water blocking cannot be simultaneously strengthened, making it difficult to achieve the comprehensive improvement effect embodied in this invention.

[0108] As can be seen from the data in Example 1 and Comparative Example 2, when the acrylic end-group polyphosphate in the latter segment was replaced by methyl methacrylate, the most significant decreases were observed in pull-off adhesion, adhesion retention after wet heat, adhesion retention after immersion in water, and salt spray scratch protection. This is because methyl methacrylate can only provide a general chain segment structure and cannot form a stabilizing effect at the metal interface like acrylic end-group polyphosphate, nor can it work with subsequent hydrophobic segments to construct an effective interfacial gradient structure.

[0109] As can be seen from the data in Example 1 and Comparative Example 3, simply changing the order of adding the first and second post-stage monomer solutions simultaneously reduces dry adhesion, resistance to damp heat, and water resistance. This result indicates that the effectiveness of the present invention does not depend on the simple presence of monomer types, but rather on the construction of a structure that prioritizes polarity followed by hydrophobicity. If segments containing octadecyl acrylate are formed first, and then segments containing hydroxyl monomers and acrylic end-group polyphosphates are introduced, the polar layer near the substrate is weakened, making it easier for moisture to penetrate along the interface. This makes it difficult to form a continuous gradient structure that balances adhesion and water resistance, exhibiting significant unpredictability.

[0110] As can be seen from the data in Example 1 and Comparative Example 4, replacing octadecyl acrylate with n-butyl methacrylate did not result in the most significant decrease in initial adhesion, but the retention ability after humid heat and immersion in water, as well as the decrease in salt spray scratch protection, were more pronounced. This indicates that the role of octadecyl acrylate is not merely to increase hydrophobicity, but more importantly, to form water-blocking segments in the near-interface region that slow down water penetration, allowing the interfacial anchoring formed by the acrylic end-group polyphosphate to continue to function under humid heat and immersion conditions. In other words, when there is only interfacial effect without a near-interface water-blocking layer, the enhanced adhesion is difficult to maintain in the long term; only when both are present does the synergistic effect exceed the sum of its parts.

[0111] As can be seen from the data in Example 1 and Comparative Example 5, prioritizing the addition of octafluoroamyl methacrylate before isobornyl methacrylate did not significantly decrease the initial adhesion, but weakened the water retention rate, salt spray scratch protection, and mechanical adaptability. This is because the present invention first constructs a rigid buffer chain segment formed by isobornyl methacrylate, and then introduces octafluoroamyl methacrylate to form a fluorinated outer layer, which is beneficial for balancing density and surface protection. If the order is reversed, the outer layer distribution and internal buffer connection are affected, resulting in insufficient improvement in overall performance. This result indicates that prioritizing rigidity followed by fluorination also has a significant synergistic effect.

[0112] As can be seen from the data in Example 1 and Comparative Example 6, when the directionally modified hydroxyl acrylic resin is added to the dispersion and milling of pigments and fillers in advance, the adhesion and wet-state retention performance decrease significantly, and the bending and impact performance also deteriorates. The main reason is that the functional sites of the acrylic end-group polyphosphate are more easily occupied by the pigment and filler surface during the pigment and filler dispersion stage, reducing the number of effective sites that can subsequently act on the metal interface. Furthermore, the milling process disrupts the desired interfacial gradient distribution. Therefore, the addition of this resin after the pigment and filler slurry is completed is not a conventional process choice, but rather an important condition to ensure the full realization of the interface control effect.

[0113] As can be seen from the data in Example 1 and Comparative Examples 7 and 8 in the table, simply changing the resin solids mass ratio of the directionally modified hydroxyl acrylic resin and the fluoroethylene-vinyl ether copolyfluoropolymer can lead to a significant imbalance in overall performance. In Comparative Example 7, the proportion of functional resin is too low. Although the hardness remains high, the lack of interfacial interaction sites results in a decrease in adhesion and wet-state performance. In Comparative Example 8, the proportion of functional resin is too high. Although the initial adhesion is still good, the contribution of the fluoroethylene-vinyl ether copolyfluoropolymer to surface protection and long-term resistance to media is insufficient, and the performance after salt spray and immersion actually declines. Therefore, it can be seen that the two types of resins can only achieve a balance between enhanced interfacial adhesion and fluorocarbon weather resistance within a specific window.

[0114] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A fluorocarbon primer with high adhesion, characterized in that, Includes component A and component B; By weight, component A comprises 197-205 parts of fluoroethylene-vinyl ether copolymer fluorinated resin, 122-129 parts of directionally modified hydroxyl acrylic resin solution, 20-26 parts of zinc phosphate, 18-22 parts of rutile titanium dioxide, 58-64 parts of barium sulfate, and 18-22 parts of talc; component B comprises 81-85 parts of aliphatic polyisocyanate curing agent. The directionally modified hydroxy acrylic resin solution is a resin solution prepared by the following method: first, methyl methacrylate, n-butyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl methacrylate, and isoborneol methacrylate are polymerized to obtain a main hydroxy acrylic resin solution; then, a first post-stage monomer solution containing hydroxyethyl methacrylate and acrylic end-group polyphosphate, a second post-stage monomer solution containing acrylic end-group polyphosphate and octadecyl acrylate, a third post-stage monomer solution containing isoborneol methacrylate, and a fourth post-stage monomer solution containing octafluoropentyl methacrylate are sequentially polymerized with the main hydroxy acrylic resin solution to obtain the resin solution. The first component is prepared by first dispersing and milling a portion of the fluoroethylene-vinyl ether copolyfluororesin with zinc phosphate, rutile titanium dioxide, barium sulfate and talc to form a pigment and filler slurry, and then adding the directionally modified hydroxyl acrylic resin solution and the remainder of the fluoroethylene-vinyl ether copolyfluororesin.

2. The fluorocarbon primer with high adhesion according to claim 1, characterized in that, Based on the mass fractions of the raw materials used to prepare the directionally modified hydroxy acrylic resin solution, the main hydroxy acrylic resin solution is obtained by polymerizing 70-80 parts of methyl methacrylate, 75-84 parts of n-butyl methacrylate, 45-55 parts of hydroxypropyl methacrylate, 12-17 parts of hydroxyethyl methacrylate and 18-24 parts of isobornyl methacrylate. The first downstream monomer solution comprises 8-12 parts of hydroxyethyl methacrylate, 2.5-4 parts of acrylic-terminated polyphosphate, and 3-5 parts of methyl methacrylate; The second downstream monomer solution comprises 5.5-7 parts of acrylic-terminated polyphosphate, 6-10 parts of octadecyl acrylate and 8-11 parts of n-butyl methacrylate; The third downstream monomer solution comprises 5-7 parts isobornyl methacrylate and 3-5 parts n-butyl methacrylate; The fourth downstream monomer solution comprises 4-6.5 parts of octafluoroamyl methacrylate and 3-5 parts of isobornyl methacrylate.

3. The fluorocarbon primer with high adhesion according to claim 1, characterized in that, In preparing the directionally modified hydroxyl acrylic resin solution, azobisisobutyronitrile (AIBN) is used as the initiator, dodecyl mercaptan (DIM) is used as the chain transfer agent, and the process is carried out at 95°C under nitrogen protection. Based on the mass fractions of the raw materials used to prepare the directionally modified hydroxyl acrylic resin solution, the DIM is 0.8-1.1 parts, the AIBN is 2.3-2.7 parts, the AIBN is 1.4-1.6 parts, and the added AIBN is 0.7-0.8 parts.

4. The fluorocarbon primer with high adhesion according to claim 1, characterized in that, The A component also includes 3.8-4.2 parts of dispersant, 0.9-1.1 parts of leveling agent, 0.5-0.6 parts of bismuth neodecanoate, and additionally added 32-38 parts of xylene and 16-19 parts of butyl acetate.

5. The fluorocarbon primer with high adhesion according to claim 4, characterized in that, The first component is prepared by the following method: 137-143 parts of fluoroethylene-vinyl ether copolymer fluorinated resin, 3.8-4.2 parts of dispersant, 19-22 parts of xylene and 9-10 parts of butyl acetate are premixed, and then 20-26 parts of zinc phosphate, 18-22 parts of rutile titanium dioxide, 58-64 parts of barium sulfate and 18-22 parts of talc are added, dispersed and milled to a fineness of no more than 25 μm to obtain a pigment and filler slurry; then 122-129 parts of the directionally modified hydroxyl acrylic resin solution, 60-62 parts of fluoroethylene-vinyl ether copolymer fluorinated resin, 0.9-1.1 parts of leveling agent, 0.5-0.6 parts of bismuth neodecanoate, 13-16 parts of xylene and 7-9 parts of butyl acetate are added to the pigment and filler slurry, mixed and filtered through a 300-mesh filter to obtain the first component.

6. The fluorocarbon primer with high adhesion according to claim 1, characterized in that, The model of the fluoroethylene-vinyl ether copolyfluorinated resin is LUMIFLON LF910LM.

7. The fluorocarbon primer with high adhesion according to claim 1, characterized in that, The acrylic-terminated polyphosphate is designated as Sipomer PAM-200.

8. The fluorocarbon primer with high adhesion according to claim 1, characterized in that, The aliphatic polyisocyanate curing agent is Desmodur ultra N 3390 BA / SN; the dispersant is DISPERBYK-110; and the leveling agent is BYK-306.

9. A method for preparing a fluorocarbon primer with high adhesion according to any one of claims 1-8, characterized in that, Includes the following steps: (1) Preparation of directionally modified hydroxyl acrylic resin solution; (2) Disperse and mill a portion of vinyl fluoride-vinyl ether copolymer fluorine resin, dispersant, zinc phosphate, rutile titanium dioxide, barium sulfate, talc and organic solvent to obtain pigment and filler slurry; (3) Add the directionally modified hydroxyl acrylic resin solution, the balance fluorinated vinyl ether copolyfluorinated resin, leveling agent, bismuth neodecanoate and organic solvent to the pigment and filler slurry, mix and filter to obtain component A; (4) Before use, add the aliphatic polyisocyanate curing agent to component A and mix to obtain the fluorocarbon primer.

10. The method for preparing a fluorocarbon primer with high adhesion according to claim 9, characterized in that, In step (4), under the condition that the relative humidity of the environment is not higher than 75%, the aliphatic polyisocyanate curing agent is added to the component A, stirred at 400 r / min for 8 min and then allowed to stand for 10 min to mature, so as to obtain the fluorocarbon primer.