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CN-121975364-A - Special rutile type titanium dioxide for powder coating and preparation method thereof

CN121975364ACN 121975364 ACN121975364 ACN 121975364ACN-121975364-A

Abstract

The invention relates to the technical field of coatings, in particular to rutile titanium dioxide special for a powder coating and a preparation method thereof. According to the method, hydrated alumina anchoring, gradient coating of various phosphates and silica shell deposition are sequentially carried out on the surface of titanium dioxide, and a stable composite coating layer is formed by adopting stepwise pH regulation and specific prehydrolysis technology. The obtained product can effectively inhibit the photocatalytic activity, remarkably improve the weather resistance, chalking resistance and yellowing resistance of the coating film, and is suitable for the field of outdoor long-acting protection.

Inventors

  • ZENG CHUHONG
  • Ou Dingzhi

Assignees

  • 广西西陇化工有限公司

Dates

Publication Date
20260505
Application Date
20260316

Claims (9)

  1. 1. The preparation method of the special rutile titanium dioxide for the powder coating is characterized by comprising the following steps of: (1) Respectively preparing an aluminum sulfate solution, a sodium hexametaphosphate solution, a sodium tripolyphosphate solution, a sodium hexametaphosphate prehydrolysis solution, an ammonium dihydrogen phosphate solution and a diluted sodium silicate solution, wherein the sodium hexametaphosphate prehydrolysis solution is obtained by carrying out acidic heat preservation prehydrolysis treatment on the sodium hexametaphosphate solution and then adjusting the pH value; (2) Adding rutile type titanium dioxide into deionized water to disperse to form slurry, adding sulfuric acid aqueous solution to adjust the pH value of the slurry to 2.5 and preserving heat for 20min at 35 ℃, then adding the aluminum sulfate solution obtained in the step (1), raising the pH value of the slurry to 4.7-4.9 at 70 ℃ within 45-75min by dropwise adding ammonia aqueous solution, and preserving heat for 45-70min at 70 ℃; (3) Cooling the slurry obtained in the step (2) to 55 ℃, and adding sulfuric acid aqueous solution to adjust the pH value of the slurry to 4.3-4.5; (4) Sequentially adding the sodium hexametaphosphate solution, the sodium tripolyphosphate solution, the sodium hexametaphosphate prehydrolysis solution and the ammonium dihydrogen phosphate solution obtained in the step (1) into the slurry obtained in the step (3) under the stirring condition, and stabilizing the pH value of the slurry to be 4.30-4.50 by adding an ammonia water solution in the process of adding the ammonium dihydrogen phosphate solution; (5) Heating the slurry obtained in the step (4) to 80 ℃, then adding ammonia water solution within 3min to ensure that the pH value of the slurry is risen to 5.8-6.2, and preserving heat for 70-120min at 80 ℃; (6) Adding ammonia water solution to raise the pH value of the slurry obtained in the step (5) to 8.6-9.2, adding the diluted sodium silicate solution obtained in the step (1), adding sulfuric acid water solution to adjust the pH value of the slurry to 7.6-8.1 after the addition is finished, and preserving heat for 50-80min at 55 ℃; (7) And (3) filtering, washing, drying, crushing and calcining the slurry obtained in the step (6) to obtain the special rutile type titanium white for the powder coating.
  2. 2. The preparation method of the special rutile type titanium dioxide for the powder coating according to claim 1, which is characterized in that the preparation of the pre-hydrolysis solution of the sodium hexametaphosphate comprises the steps of dissolving the sodium hexametaphosphate in deionized water, adding sulfuric acid aqueous solution to adjust the pH value of the solution to 2.0-2.5, preserving heat for 25-40min at 75-85 ℃, cooling to 55 ℃, and adding ammonia aqueous solution to adjust the pH value of the solution back to 4.0-4.5.
  3. 3. The method for preparing the special rutile titanium dioxide for the powder coating according to claim 1, wherein the mass fraction of the sulfuric acid aqueous solution is 10%, and the mass fraction of the ammonia aqueous solution is 25%.
  4. 4. The preparation method of the special rutile type titanium dioxide for the powder coating, which is disclosed in claim 1, is characterized in that in the step (1), the aluminum sulfate solution is obtained by mixing and dissolving 430-450 parts by mass of deionized water and 130-180 parts by mass of aluminum sulfate octadecanoate, the sodium hexametaphosphate solution is obtained by mixing and dissolving 46-50 parts by mass of deionized water and 1.5-2.5 parts by mass of sodium hexametaphosphate, the sodium tripolyphosphate solution is obtained by mixing and dissolving 46-50 parts by mass of deionized water and 2-4 parts by mass of sodium tripolyphosphate, the ammonium dihydrogen phosphate solution is obtained by mixing and dissolving 130-160 parts by mass of deionized water and 45-65 parts by mass of ammonium dihydrogen phosphate, and the diluted sodium silicate solution is obtained by mixing 55-80 parts by mass of deionized water and 30-55 parts by mass of sodium silicate solution.
  5. 5. The method for preparing rutile titanium dioxide for powder coating according to claim 1, wherein the aluminum sulfate is 130-180 parts, sodium hexametaphosphate is 3-5 parts, sodium tripolyphosphate is 2-4 parts, ammonium dihydrogen phosphate is 45-65 parts, sodium silicate solution is 30-55 parts, and Na 2 O content is 10-12 wt% and SiO 2 content is 26-28 wt% based on 2000 parts by weight of rutile titanium dioxide.
  6. 6. The method for preparing rutile titanium dioxide for powder coating according to claim 1, wherein in the step (4), stirring is continued for 30min after adding sodium hexametaphosphate solution, stirring is continued for 30min after adding sodium tripolyphosphate solution, stirring is continued for 20min after adding sodium hexametaphosphate prehydrolysis solution, and in the step (5), stirring is continued for 10min at 80 ℃ before adding ammonia solution within 3min to raise the pH value of the slurry.
  7. 7. The method for preparing rutile titanium dioxide for powder coating according to claim 1, wherein the time for raising the pH of the slurry to 4.7-4.9 in the step (2) is 60min and the temperature is kept at 70 ℃ for 60min, the pH of the slurry is stabilized at 4.4 during the addition of the monoammonium phosphate solution in the step (4), the pH of the slurry is raised to 6.0 and the temperature is kept at 80 ℃ for 90min in the step (5), the pH of the slurry is raised to 8.9 in the step (6) and the pH of the slurry is adjusted back to 7.9 and the temperature is kept at 55 ℃ for 60min after the addition of the diluted sodium silicate solution.
  8. 8. The process for preparing rutile titanium dioxide for powder coating according to claim 1, wherein the calcination in step (7) is carried out by heating to 350-420 ℃ in air atmosphere at 2-3 ℃ per min for 60-90min, then heating to 630-700 ℃ for 30-50min and cooling.
  9. 9. The special rutile titanium dioxide for powder coating, which is characterized by being prepared by the preparation method of the special rutile titanium dioxide for powder coating according to any one of claims 1-8.

Description

Special rutile type titanium dioxide for powder coating and preparation method thereof Technical Field The invention relates to the technical field of coatings, in particular to rutile titanium dioxide special for powder coatings and a preparation method thereof. Background The rutile type titanium dioxide is widely applied to powder coating due to the high refractive index and hiding power, but under severe environments such as outdoor strong ultraviolet rays, wet heat circulation and the like, the surface photocatalytic active sites (such as lattice defects and non-coordinated titanium sites) of the rutile type titanium dioxide can induce free radical chain reaction of a resin matrix, so that polymer degradation is accelerated. This process is manifested by chalking of the coating film, loss of gloss and yellowing of color, and severely limits the application of the coating film in the fields of long-term protection of building profiles and engineering machinery. In order to inhibit the photocatalytic activity of titanium dioxide, conventional techniques mainly use inorganic coating modification, for example, by hydration of alumina, silica, and the like, to form a physical barrier layer on the particle surface. However, single aluminum coating layer is easy to generate phase change or dissolve in an acidic or alkaline environment, the coating uniformity is obviously influenced by hydrolysis pH and temperature dynamics factors, and local coating discontinuity is easy to be caused, while the silicon aluminum composite coating can improve weather resistance, but has poor interfacial compatibility between layers, and is easy to generate microcracks under thermal stress, so that water vapor permeation is accelerated. In recent years, phosphate modification is focused on the strong coordination ability of the phosphate modified titanium and aluminum ions, but the existing technology mostly adopts single phosphate (such as sodium hexametaphosphate) for direct adsorption, the anchoring density of the phosphate modified titanium on the surface of titanium dioxide is low, and the steric hindrance effect of long-chain phosphate can prevent the formation of a compact passivation layer. In addition, the combination of phosphate and aluminum coating layer is mostly dependent on simple coprecipitation, and the problem of directional immobilization of phosphate on the particle surface is not solved, so that partial phosphate is free in a solution phase or amorphous precipitate is formed, passivation efficiency is reduced, and water-soluble ions can be introduced to influence salt fog resistance of the coating film. Still further modification attempts include the introduction of multilayer coating structures such as sequential coating of aluminum followed by phosphorus and then silicon, but lack of timing control of the interfacial reaction between the layers, especially too fast or too slow a pH adjustment rate during the phosphate deposition phase, can result in an increase in passivation layer porosity. Meanwhile, the prior art fails to coordinate adsorption kinetics differences of phosphates with different chain lengths, short-chain phosphates rapidly occupy active sites, long-chain phosphates are difficult to fully spread, and the capability of a passivation layer for shielding photo-generated holes and electrons is limited. Therefore, the surface modification technology of titanium dioxide for powder coating still needs to solve the synergistic problem among passivation layer continuity, interface stability and long-acting weather resistance, and especially needs to break through the technical bottlenecks of directional immobilization of phosphate, densification of multilayer structure and chemical stability of interface. Disclosure of Invention Therefore, the invention aims to provide the special rutile type titanium dioxide for the powder coating and the preparation method thereof, so as to solve the problems that the existing rutile type titanium dioxide for the powder coating is easy to cause resin photooxidation at surface active sites under outdoor weather-proof conditions, so that a coating film is atomized, shined and yellow, and a surface modification layer has insufficient uniformity and poor long-term stability. Based on the above purpose, the invention provides a preparation method of special rutile titanium dioxide for powder coating, which comprises the following steps: (1) Respectively preparing an aluminum sulfate solution, a sodium hexametaphosphate solution, a sodium tripolyphosphate solution, a sodium hexametaphosphate prehydrolysis solution, an ammonium dihydrogen phosphate solution and a diluted sodium silicate solution, wherein the sodium hexametaphosphate prehydrolysis solution is obtained by carrying out acidic heat preservation prehydrolysis treatment on the sodium hexametaphosphate solution and then adjusting the pH value; (2) Adding rutile type titanium dioxide into deionized water to dis