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CN-122013169-A - Composite coating of anti-mildew colored aluminum alloy profile and preparation method thereof

CN122013169ACN 122013169 ACN122013169 ACN 122013169ACN-122013169-A

Abstract

The invention relates to the technical field of aluminum alloy surface treatment, in particular to a composite coating of an antimycotic color aluminum alloy section and a preparation method thereof, wherein the composite coating sequentially comprises a rare earth-silane-phytic acid-dopamine composite passivation transition layer, an antimycotic mesoporous functional intermediate layer containing dynamic crosslinking groups and a hydrophobic color sealing surface layer which are constructed on the micro-nano textured surface of an aluminum alloy matrix from inside to outside, and all the layers form an interpenetrating crosslinked network structure through covalent bonds. The invention synchronously discloses a corresponding preparation method which comprises the steps of matrix pretreatment, composite passivation layer preparation, mesoporous intermediate layer preparation, surface layer coating and gradient heat curing. The invention has the advantages of no chromium, environmental protection, long-acting mildew resistance, high corrosion resistance, strong adhesive force, long-acting color retention and micro-damage self-repairing performance, solves the problems of poor mildew resistance and durability of the existing coating, easy interlayer stripping and other pain points in the industry, is suitable for the existing production line, and can realize industrialized mass production.

Inventors

  • WENG YUELONG
  • ZHENG JIANXUN
  • Lu Chengkun

Assignees

  • 衢州市岳泰铝业有限公司

Dates

Publication Date
20260512
Application Date
20260409

Claims (10)

  1. 1. The composite coating of the anti-mold colored aluminum alloy section is characterized by comprising a rare earth-silane-phytic acid-dopamine composite passivation transition layer, an anti-mold mesoporous functional intermediate layer and a hydrophobic colored sealing surface layer, wherein the rare earth-silane-phytic acid-dopamine composite passivation transition layer is sequentially constructed on the micro-nano textured surface of an aluminum alloy section substrate from inside to outside, the intermediate layer is chemically bonded on the surface of the passivation transition layer and contains dynamic crosslinking groups, and the hydrophobic colored sealing surface layer is crosslinked and solidified on the surface of the mesoporous functional intermediate layer; the composite passivation transition layer is a chromium-free reticular passivation film formed by in-situ chelating condensation of rare earth salt, an aminosilane coupling agent, phytic acid and dopamine, the thickness is 80-250nm, and the surface of the passivation film is rich in active hydroxyl and phenolic hydroxyl; The mesoporous functional intermediate layer takes mesoporous silicon dioxide as a carrier, a quaternary phosphonium salt type antimycotic agent is loaded in a mesoporous pore canal, a silane coupling agent containing disulfide bonds is grafted on the surface of the mesoporous silicon dioxide, and the dry film thickness of the intermediate layer is 2-6 mu m; The hydrophobic color sealing surface layer takes fluorine-containing siloxane modified acrylate resin as a film forming matrix, color inorganic pigment with a core-shell structure and rare earth weather-resistant complex are uniformly dispersed in the matrix, the surface layer and the middle layer form an interpenetrating cross-linked network structure through disulfide bonds and siloxane bonds, the dry film thickness of the surface layer is 15-35 mu m, and the water contact angle is more than or equal to 115 degrees.
  2. 2. The composite coating of the anti-mildew colored aluminum alloy profile according to claim 1, wherein the rare earth salt of the composite passivation transition layer is one or more of cerium nitrate, cerium chloride or lanthanum nitrate, the aminosilane coupling agent is gamma-aminopropyl triethoxysilane, the mass ratio of phytic acid to dopamine is 1:1-2:1, and the mass ratio of rare earth elements in the passivation film is 3% -10%.
  3. 3. The composite coating of the anti-mildew colored aluminum alloy profile according to claim 1, wherein the disulfide bond-containing silane coupling agent is bis- (3-triethoxysilylpropyl) disulfide, and the grafting amount of the disulfide bond-containing silane coupling agent is 20% -45% of the mass of mesoporous silica; the quaternary phosphonium salt type antimycotic agent is one or two of tributyl dodecyl phosphonium chloride and triphenyl hexadecyl phosphonium chloride, and the mass of the antimycotic agent accounts for 12-35% of the total mass of the mesoporous functional intermediate layer.
  4. 4. The composite coating of the anti-mildew colored aluminum alloy profile according to claim 1, wherein the fluorine content of the fluorine-containing siloxane modified acrylate resin is 10% -20%, and the hydroxyl value is 35-55mgKOH/g; the core of the core-shell structure color inorganic pigment is iron-based, cobalt-based or rare earth-based color inorganic pigment, the shell is a silicon dioxide coating layer, and the particle size of the pigment is 200-800nm.
  5. 5. The composite coating of the mildew-resistant colored aluminum alloy profile according to claim 1, wherein the rare earth weather-resistant complex is an organic carboxylic acid complex of cerium or praseodymium, and the total mass of the core-shell structure colored inorganic pigment and the rare earth weather-resistant complex accounts for 6% -18% of the total mass of the surface layer.
  6. 6. A method for preparing a composite coating of an antimycotic colored aluminum alloy profile according to any one of claims 1 to 5, characterized by comprising the following steps: S1, carrying out micro-nano texturing pretreatment on an aluminum alloy section, namely sequentially carrying out alkaline degreasing, chemical micro-etching texturing, nitric acid light emitting, multi-stage cleaning and cold air drying treatment on the aluminum alloy section to obtain a pretreated base material with a uniform micro-nano rough texture on the surface; S2, preparing a rare earth-silane-phytic acid-dopamine composite passivation treatment solution, immersing a pretreated substrate in the treatment solution for in-situ chelating condensation reaction, taking out, flushing with absolute ethyl alcohol, and performing low-temperature pre-curing to form a composite passivation transition layer on the surface of the substrate; S3, preparing mesoporous silica dispersion liquid of a quaternary phosphonium salt-carried antimycotic agent grafted with a disulfide bond-containing silane coupling agent, diluting the dispersion liquid to a set solid content by using absolute ethyl alcohol to obtain an intermediate layer coating liquid, coating the intermediate layer coating liquid on the surface of a passivation transition layer, and pre-curing to form the mesoporous functional intermediate layer; S4, preparing a surface layer coating liquid containing core-shell structure color inorganic pigment and rare earth weather-resistant complex, coating the surface of the mesoporous functional intermediate layer, leveling at room temperature, and performing gradient heat curing to obtain the composite coating.
  7. 7. The method of claim 6, wherein the microetching solution used in the chemical microetching texturing treatment in the step S1 comprises 10-20g/L of sodium hydroxide, 3-8g/L of sodium fluoride, 1-3g/L of sodium gluconate, and the balance deionized water, wherein the treatment temperature is 35-45 ℃ and the treatment time is 3-8min.
  8. 8. The preparation method of claim 6, wherein the composite passivation treatment liquid in the step S2 comprises 0.3-1.0g/L of rare earth salt, 10-25g/L of aminosilane coupling agent, 2-5g/L of phytic acid, 1-3g/L of dopamine, 200-350g/L of absolute ethyl alcohol and the balance deionized water according to 1L, wherein the pH value of the treatment liquid is regulated to 4.0-5.5 by glacial acetic acid, the in-situ chelating condensation reaction temperature is 25-40 ℃, the reaction time is 15-30min, the pre-curing temperature is 60-80 ℃ and the time is 5-15min.
  9. 9. The preparation method of the mesoporous silica dispersion liquid according to claim 6, wherein the preparation method of the mesoporous silica dispersion liquid in the step S3 is characterized in that tetraethoxysilane, absolute ethyl alcohol, deionized water and an acidic catalyst are mixed and hydrolyzed to obtain silica sol, a template agent cetyl trimethyl ammonium bromide is added for heating reaction to obtain a mesoporous silica precursor, a quaternary phosphonium salt type antimycotic agent is added for stirring and loading, and a silane coupling agent containing disulfide bonds is added for grafting modification reaction to obtain the dispersion liquid.
  10. 10. The method according to claim 6, wherein the gradient heat curing process in the step S4 is performed by heating to 90-110 ℃ at a rate of 3-5 ℃ per minute, maintaining the temperature for 15-25min, heating to 130-150 ℃ at a rate of 2-3 ℃ per minute, maintaining the temperature for 25-40min, and naturally cooling to room temperature after the heat preservation is finished.

Description

Composite coating of anti-mildew colored aluminum alloy profile and preparation method thereof Technical Field The invention relates to the technical field of aluminum alloy surface treatment, in particular to a composite coating of an antimycotic color aluminum alloy section and a preparation method thereof. Background The aluminum alloy section bar has been widely used in a plurality of fields such as building door and window curtain walls, bathroom houses, food processing workshops, medical health care places, coastal municipal works and the like by virtue of the core advantages of light weight, high strength, easy processing and forming, excellent appearance texture and the like. However, in the application scene, the aluminum alloy section is in an environment with high humidity, high salt fog and easy adhesion of organic pollutants for a long time, and common pathogenic mold such as aspergillus niger, aspergillus flavus, aspergillus terreus, trichoderma viride and the like are extremely easy to grow on the surface of the aluminum alloy section. The growth of mould not only can seriously damage the color decorative appearance of the section bar, but also can continuously erode the aluminum alloy matrix by organic acid and enzyme substances generated by metabolism, thereby inducing the failure problems of pitting corrosion, crevice corrosion and the like, and greatly shortening the service life of the section bar, meanwhile, the diffusion of mould spores can also cause indoor environmental pollution, thereby directly threatening the health of human bodies, and especially in the scenes of severe requirements on the sanitary grade of foods, medical treatment and the like, the mould resistance of the aluminum alloy section bar has become a core index for determining the application boundary of the aluminum alloy section bar. Currently, the mainstream surface protection technology for aluminum alloy sections in the industry mainly comprises three major categories of anodic oxidation, electrophoretic coating, fluorocarbon coating and powder coating. The anodic oxidation and electrophoresis coating process is the most commonly used treatment mode of the aluminum alloy section bar for building, although the corrosion resistance and the color decoration effect of the section bar foundation can be endowed, the electrophoresis coating is strong in hydrophilicity and extremely easy to adsorb moisture and organic nutrient substances in the environment, excellent conditions are provided for the attachment and propagation of mold, no mold resistance is provided, and obvious mold growth phenomenon can occur within 3 months in a humid environment. The fluorocarbon coating prepared by the powder spraying process has excellent weather resistance and corrosion resistance, but does not have the mildew resistance, and the conventional modification mode in the industry is to directly add inorganic antibacterial agents such as silver ions, copper ions and the like into surface layer resin, so that the method has a plurality of inherent defects which cannot be overcome, firstly, the antibacterial agents can only act on the surface of the coating, and the internal antibacterial agents cannot effectively migrate to the surface along with abrasion and aging of the surface of the coating, the mildew resistance is attenuated after 1-2 years of use, the durability is extremely poor, secondly, silver and copper ions are extremely easy to separate out in a humid environment, the loss of the mildew resistance is accelerated, the environment-friendly risk of exceeding heavy metal is also caused, the compatibility of the inorganic antibacterial agents and an organic resin matrix is extremely poor, the agglomeration and sedimentation problems occur, the film forming property and impact resistance of the coating are damaged, the color coating color difference and the color development effect are also caused, and the decoration effect is seriously influenced. In addition, the aluminum alloy protective coating with a part of multilayer structure also appears in the prior art, but most of the aluminum alloy protective coating has a simple physical superposition structure, layers are combined by means of mechanical force, the problems of water seepage, foaming, interlayer peeling and the like are very easy to occur at interfaces in an environment of cold and hot alternation and long-term wet soaking, so that the whole protective system of the coating is fast invalid, meanwhile, the passivation transition layer of the existing coating mostly adopts a chromate passivation system with extremely strong carcinogenicity, the environmental protection risk is extremely high, the conventional chromium-free zirconium-titanium passivation system has insufficient bonding force with an aluminum alloy substrate, the corrosion inhibition protective performance is limited, a stable bonding substrate cannot be provided for the upper layer coating, and the prot