A method for preparing an environmentally friendly negative ion waterproof latex paint

Abstract

This invention relates to the field of coating preparation technology, and in particular to a method for preparing an environmentally friendly negative ion waterproof latex paint. The method includes preparing tourmaline@ZIF-8 core-shell structure powder, dynamically adjusting the molar ratio based on the particle size-time growth curve to achieve precise control of the shell thickness from 20 to 100 nm; synthesizing a polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer using RAFT polymerization to form a hydrophobic sea + hydrophilic island microphase separation structure; preparing a latent curing crosslinking agent dispersion by compounding a blocked isocyanate and a modified phosphate ester at a ratio of 2-5:1; and mixing the paint using a layered feeding sequence. This invention effectively solves three major technical problems: negative ion release attenuation under high humidity, the contradiction between waterproofing and release, and bubbling during high humidity construction.

Description

Technical Field

[0001] This invention relates to the field of coating preparation technology, and in particular to a method for preparing an environmentally friendly negative ion waterproof latex paint. Background Technology

[0002] Negative oxygen ions are known as "air vitamins," possessing various health benefits such as air purification, formaldehyde degradation, antibacterial and bacteriostatic properties, and improved sleep. In recent years, integrating negative oxygen ion release into architectural coatings has become an important research direction in the field of functional coatings. This is particularly relevant in semi-enclosed or fully enclosed spaces such as basements, underground garages, and civil defense projects, where poor air circulation, easy accumulation of pollutants, and problems like dampness and mold are prominent. Developing environmentally friendly latex paints that combine waterproofing and negative oxygen ion release functions is of significant practical importance.

[0003] Currently, the technology for releasing negative oxygen ions using tourmaline is relatively mature. Tourmaline is a boron-containing cyclic silicate mineral with an asymmetric crystal structure. When temperature and pressure change, it exhibits piezoelectric and thermoelectric effects, generating an electrostatic field on the crystal surface that ionizes water molecules in the air into H+. + and OH - , of which OH - Tourmaline combines with water molecules in the air to form negative oxygen ions. Based on this principle, a large number of studies have been conducted on adding tourmaline powder to coatings to prepare coating products with negative oxygen ion release function.

[0004] Chinese Patent Publication No. CN118165554A discloses a method for preparing negative ion liquid coating based on tourmaline plant extract. The method involves extracting tourmaline to obtain tourmaline extract, which is then mixed with plant extract and added to the coating to achieve the release of negative oxygen ions. This invention solves the problem of uneven dispersion of tourmaline in the coating to a certain extent and improves the release efficiency of negative ions.

[0005] However, most existing negative ion coatings still suffer from the following insurmountable technical defects in practical applications: 1. The negative ion release performance decreases sharply under high humidity. The premise for tourmaline to release negative oxygen ions is that it can continuously ionize water molecules in the air. However, in actual application scenarios such as basements and underground garages, the relative humidity of the environment is always above 85%. The surface of tourmaline powder is very easy to adsorb and condense a continuous water film. Although this water film provides abundant water molecules, it also shields the electrostatic field generated on the surface of tourmaline, causing water molecules to be unable to be effectively ionized. 2. There is an inherent contradiction between waterproofing and negative ion release. To achieve waterproofing, latex paint needs to form a dense film to prevent water penetration. However, the release of negative ions requires water molecules to reach the surface of the tourmaline and be ionized. At the same time, the negative ions generated by ionization also need to be able to penetrate the paint film and enter the air. In existing technologies, either the negative ion release capacity is sacrificed to ensure waterproofing, or the density of the paint film is reduced to ensure the release effect, resulting in substandard waterproofing performance. This contradiction between waterproofing and breathability is particularly prominent in high humidity environments.

[0006] 3. Construction defects in high-humidity environments have long been overlooked. Basements and other similar environments are not only humid, but the walls are also often in a high-humidity state during construction. When traditional latex paint is applied to high-humidity walls, the water evaporates slowly, and defects such as pinholes and bubbles are easily generated during the paint film drying process, which damages the integrity of the waterproof layer. Existing technologies mostly alleviate this problem by adding defoamers, but defoamers cannot fundamentally solve the problem of foaming caused by water retention.

[0007] In conclusion, developing an environmentally friendly waterproof latex paint that can maintain a stable and efficient release of negative oxygen ions in high-humidity environments such as basements and underground garages, while also possessing excellent waterproof performance and being easily applied to high-humidity walls, is a technical challenge that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] Therefore, this invention provides a method for preparing an environmentally friendly negative ion waterproof latex paint to overcome the problems in the prior art, such as the sharp decline in the release performance of negative ions under high humidity, the incompatibility between waterproof function and negative ion release function, and the easy formation of pinhole blistering defects in the paint film when applied to high humidity walls.

[0009] To achieve the above objectives, this invention provides a method for preparing an environmentally friendly negative ion waterproof latex paint, comprising: Tourmaline powder was dispersed in a 2-methylimidazole solution, and zinc nitrate solution was added. The growth state of the ZIF-8 core-shell was determined based on the particle size-time growth curve of the tourmaline@ZIF-8 core-shell particles during the reaction process, so as to dynamically adjust the molar ratio of zinc nitrate solution to 2-methylimidazole solution. Based on the particle size growth rate of tourmaline@ZIF-8 core-shell particles per unit time, the degree of reaction completion was determined. After terminating the reaction, tourmaline@ZIF-8 core-shell structure powder was obtained by centrifugation, washing, and drying. Based on the reversible addition-fragmentation chain transfer polymerization method, polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer was synthesized to prepare organosilicon-acrylic acid block copolymer emulsion; Blocked isocyanate and modified phosphate ester are mixed at a mass ratio of 2-5:1, and then deionized water is added for high-speed dispersion to obtain a latent curing crosslinking agent dispersion with a solid content of 25%-35%. By weight, 15-25 parts of deionized water, 0.5-1.5 parts of dispersant, and 0.2-0.5 parts of defoamer are mixed, and 5-15 parts of the tourmaline@ZIF-8 core-shell structure powder, 15-25 parts of titanium dioxide, and 5-10 parts of diatomaceous earth are added. The mixture is dispersed at high speed for 30-40 minutes. Subsequently, 30-50 parts of the organosilicon-acrylic block copolymer emulsion, 3-8 parts of the latent curing crosslinking agent dispersion, 1-3 parts of film-forming aid, and 0.3-0.8 parts of thickener are added. The mixture is stirred at medium speed for 20-30 minutes and filtered to obtain an environmentally friendly negative ion waterproof latex paint.

[0010] Furthermore, the process of determining the growth state of the ZIF-8 core-shell includes: The slope of the curve is determined based on the particle size-time growth curve of the tourmaline@ZIF-8 core-shell particles, and the growth state of the ZIF-8 core-shell is determined based on the change of the slope of the curve. The slope of the curve represents the rate of change of particle size over time, and the growth states of the ZIF-8 core-shell include the induction phase, the rapid growth phase, and the plateau phase.

[0011] Furthermore, the process of dynamically adjusting the molar ratio of zinc nitrate solution to 2-methylimidazole solution includes: The initial molar ratio of the zinc nitrate solution to the 2-methylimidazole solution is 1:2; Based on the induction period, the molar ratio of the zinc nitrate solution to the 2-methylimidazole solution is adjusted to 1:8-12; Based on the aforementioned rapid growth period regulation, the molar ratio of the zinc nitrate solution to the 2-methylimidazole solution is adjusted to 1:4-6; Based on the plateau period, the molar ratio of the zinc nitrate solution to the 2-methylimidazole solution is adjusted to 1:2-3.

[0012] Furthermore, the process of determining the degree of reaction completion includes: The particle size growth rate per unit time is compared with the preset rate. The reaction is determined to be complete if the particle size growth rate is less than or equal to a preset rate.

[0013] Furthermore, the process for synthesizing the polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer includes: Triblock copolymers were synthesized using a stepwise chain extension method; The polymerization of the first block involves dissolving methyl methacrylate monomer, bifunctional trithiocarbonate chain transfer agent, and azobisisobutyronitrile initiator in a dioxane solvent, purging with nitrogen to remove oxygen, and then heating to 70-80℃ for polymerization for 6-8 hours. After the reaction is complete, a polymethyl methacrylate macromolecular chain transfer agent with active chain transfer agent groups at the ends is obtained.

[0014] Furthermore, the process for synthesizing the polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer further includes: Chain extension of the second block involves adding double-bond-terminated polydimethylsiloxane macromonomers to the first block reaction system, heating to 80-100℃ and polymerizing for 10-14 hours. After polymerization, polymethyl methacrylate-b-polydimethylsiloxane diblock copolymer is obtained.

[0015] Furthermore, the process for synthesizing the polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer further includes: The chain extension of the third block involves cooling the reaction system after the second block polymerization to 50-60℃, adding acrylic monomers and polymerizing for 4-6 hours. After polymerization, polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer is obtained. The polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer has a number average molecular weight of 15,000-50,000 and a molecular weight distribution of less than or equal to 1.3.

[0016] Furthermore, the process of obtaining a latent curing crosslinking agent dispersion with a solid content of 25%-35% further includes: The blocked isocyanate is a blocked polyisocyanate, including HDI trimer blocking compounds, IPDI blocking compounds, TDI prepolymer blocking compounds, or water-dispersible blocked isocyanates.

[0017] Furthermore, the process of obtaining a latent curing crosslinking agent dispersion with a solid content of 25%-35% further includes: The modified phosphate ester molecule is a phosphate ester surfactant with an HLB value of 10-18, including polyoxyethylene ether phosphate ester, alkyl phosphate ester, phosphorylated polyester, phosphate ester containing polymerizable groups, or phosphate ester containing nitrogen mustard or lipophilic groups.

[0018] Furthermore, the process of obtaining the environmentally friendly negative ion waterproof latex paint includes: The dispersant is a high molecular weight copolymer containing pigment affinity groups; The defoamer is a polysiloxane-based defoamer; The film-forming aid is alcohol ester-12; The thickener is a polyurethane associative thickener.

[0019] Compared with the prior art, the beneficial effects of the present invention are that ZIF-8 is a metal-organic framework material formed by the self-assembly of zinc ions and 2-methylimidazole. Its pore surface is hydrophobic due to methyl modification, with a contact angle >120°. When the ZIF-8 shell coats the surface of tourmaline, the hydrophobic shell prevents liquid water from condensing into a continuous water film on the tourmaline surface under high humidity conditions. Simultaneously, its regular 3.4 Å pores allow water molecules (2.8 Å) and hydrated hydrogen ions to pass through. (Approximately 2.8 Å) through which the water supply and ion conduction required to maintain the piezoelectric effect of tourmaline are maintained, and the OH- produced by ionization is allowed. - or O2 - Negative oxygen ions (approximately 2.7-3.0 Å) are released into the air through the pores, thereby achieving continuous release of negative oxygen ions. Through the dual mechanism of hydrophobic protection and selective ion conduction, this invention effectively solves the problem of negative ion release attenuation caused by the formation of a water film on the surface of tourmaline in high humidity environments.

[0020] Furthermore, this invention uses an online particle size analyzer to monitor the particle size-time growth curve of tourmaline@ZIF-8 core-shell particles in real time. During the induction period, the molar ratio is adjusted to 1:8-12 by adding 2-methylimidazole to promote uniform nucleation on the tourmaline surface and ensure the formation of a continuous and dense seed layer. During the rapid growth period, the molar ratio is adjusted to 1:4-6 to maintain stable shell growth and prevent homogeneous nucleation in the solution. During the plateau period, the molar ratio is adjusted to 1:2-3 by adding zinc nitrate to slow down the growth rate and precisely control the final shell thickness. Through the above... Through dynamic adjustment, this invention achieves precise and controllable preparation of the shell thickness within the range of 20-100nm, with batch-to-batch shell thickness deviation controlled within ±5nm. Furthermore, comparative testing shows that the tourmaline@ZIF-8 core-shell structure powder prepared using this invention retains an 86.2% negative ion release rate after being placed in an environment with 90% relative humidity for 30 days, while the retention rate of ordinary tourmaline without ZIF-8 coating is only 33.0%. This demonstrates that the ZIF-8 shell has a significant protective effect on the negative ion release of tourmaline under high humidity conditions.

[0021] Furthermore, this invention synthesizes a polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer using reversible addition-fragmentation chain transfer living polymerization technology, and prepares an organosilicon-acrylic acid block copolymer emulsion therefrom. The PMMA block is a hard hydrophobic polymer with a glass transition temperature of approximately 105°C, providing mechanical strength and a rigid framework in the coating film. The PDMS block has extremely low surface energy and excellent hydrophobicity, with a glass transition temperature of approximately -123°C, and accumulates on the coating film surface during film formation. It forms a dense hydrophobic layer, effectively preventing water penetration; the PAA block is a hydrophilic polymer with a large number of carboxyl groups in its side chains. During film formation, it undergoes microphase separation from the hydrophobic matrix due to its hydrophilicity, and self-assembles to form hydrophilic microdomains with a diameter of about 50-100 nanometers; the three segments have significantly different chemical properties, and automatically form a bicontinuous network structure of hydrophobic sea + hydrophilic island during film formation. The hydrophobic continuous phase prevents water penetration, while the hydrophilic discrete microdomains allow hydrated ions and negative oxygen ions to pass through, effectively achieving the synergistic unity of waterproof function and negative ion release function.

[0022] Furthermore, this invention reacts the isocyanate groups of the blocked isocyanate with a blocking agent to generate an adduct. This adduct is chemically stable at room temperature and does not react with water or compounds containing active hydrogen. When the coating is heated and cured after application, the blocking agent desorbs and releases highly reactive -NCO groups, which crosslink with the hydroxyl groups in the organosilicon-acrylic block copolymer emulsion to form a dense three-dimensional network structure, effectively improving the density and water resistance of the paint film.

[0023] Furthermore, in this invention, the modified phosphate ester molecule has an amphiphilic structure, with the phosphate ester group being hydrophilic and the alkyl or polyoxyethylene chain being lipophilic. It can be adsorbed onto the surface of closed isocyanate droplets, reducing the oil-water interfacial tension. During high-speed dispersion, it breaks the oil phase into tiny droplets and prevents droplet aggregation, forming a stable oil-in-water dispersion. At the same time, the phosphate ester group has strong hydrophilicity, which can quickly combine with free water molecules in high-humidity environments, accelerating the migration and dissipation of moisture in the wet film, thereby shortening the surface drying time and eliminating the conditions for bubble nucleation from the source. This effectively solves the construction defects of pinholes and blistering that are prone to occur during the drying process of paint film in high-humidity environments.

[0024] Furthermore, this invention combines blocked isocyanate and modified phosphate at a mass ratio of 2-5:1, and prepares a latent curing crosslinking agent dispersion through high-speed dispersion. When the mass ratio is lower than 2:1, the proportion of modified phosphate is too high, the content of blocked isocyanate in the dispersion is too low, the crosslinking density is insufficient, the waterproof performance decreases, and the dispersion separates after 7 days of storage. When the mass ratio is higher than 5:1, the proportion of modified phosphate is too low, the emulsification effect deteriorates, the droplet size is greater than 5μm, and it separates within 24 hours, making stable storage impossible. This invention controls the mass ratio within the range of 2-5:1, balancing the crosslinking performance and dispersion stability.

[0025] Furthermore, this invention employs a layered feeding sequence of first dispersing the powder, then adding the emulsion, and finally adding the crosslinking agent. This systematically integrates tourmaline@ZIF-8 core-shell structure powder, organosilicon-acrylic block copolymer emulsion, and latent curing crosslinking agent dispersion to prepare an environmentally friendly negative ion waterproof latex paint, achieving synergistic and stable dispersion of each functional component. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the preparation method of the environmentally friendly negative ion waterproof latex paint according to an embodiment of the present invention; Figure 2 This is a flowchart illustrating the process of determining the growth state of ZIF-8 core-shell as described in an embodiment of the present invention; Figure 3 This is a logic diagram for determining the degree of reaction completion as described in an embodiment of the present invention; Figure 4 This is a flowchart illustrating the synthesis of polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer according to an embodiment of the present invention. Detailed Implementation

[0027] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0028] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0029] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0030] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0031] Please see Figure 1 As shown, it is a flowchart of the preparation method of the environmentally friendly negative oxygen ion waterproof latex paint according to the embodiment of the present invention.

[0032] The preparation method of the environmentally friendly negative ion waterproof latex paint described in this embodiment of the invention includes: S1. Disperse tourmaline powder in 2-methylimidazole solution, add zinc nitrate solution, and determine the growth state of ZIF-8 core-shell based on the particle size-time growth curve of tourmaline@ZIF-8 core-shell particles during the reaction process, so as to dynamically adjust the molar ratio of zinc nitrate solution to 2-methylimidazole solution. S2. Based on the particle size growth rate of tourmaline@ZIF-8 core-shell particles per unit time, the degree of reaction completion was determined. After terminating the reaction, tourmaline@ZIF-8 core-shell structure powder was obtained by centrifugation, washing, and drying. S3. Based on the reversible addition-fragmentation chain transfer polymerization method, a polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer was synthesized to prepare an organosilicon-acrylic acid block copolymer emulsion. S4. Mix the blocked isocyanate and the modified phosphate ester at a mass ratio of 2-5:1, add deionized water and disperse at high speed to obtain a latent curing crosslinking agent dispersion with a solid content of 25%-35%. S5. By weight, mix 15-25 parts of deionized water, 0.5-1.5 parts of dispersant, and 0.2-0.5 parts of defoamer, add 5-15 parts of the tourmaline@ZIF-8 core-shell structure powder, 15-25 parts of titanium dioxide, and 5-10 parts of diatomaceous earth, and disperse at high speed for 30-40 minutes; then add 30-50 parts of the organosilicon-acrylic block copolymer emulsion, 3-8 parts of the latent curing crosslinking agent dispersion, 1-3 parts of film-forming aid, and 0.3-0.8 parts of thickener, stir at medium speed for 20-30 minutes, and filter to obtain environmentally friendly negative oxygen ion waterproof latex paint.

[0033] In this embodiment of the invention, ZIF-8 is a metal-organic framework material formed by the self-assembly of zinc ions and 2-methylimidazole through coordination bonds. When tourmaline powder is dispersed in a 2-methylimidazole solution, the nitrogen atoms in the 2-methylimidazole molecule can form hydrogen bonds or coordination interactions with polar sites such as hydroxyl groups on the tourmaline surface, thereby preferentially adsorbing and accumulating on the tourmaline surface. When zinc nitrate solution is added, zinc ions will preferentially react with the 2-methylimidazole accumulated on the tourmaline surface, nucleating and growing in situ on the tourmaline surface to form a core-shell structure. If 2-methylimidazole and zinc nitrate are mixed first and then contacted with tourmaline, ZIF-8 will nucleate homogeneously in the solution and will not be able to form a continuous core-shell structure. Therefore, the feeding sequence of this invention has key technical significance.

[0034] In this embodiment of the invention, during the reaction process, the particle size change of tourmaline@ZIF-8 core-shell particles in the reaction system is monitored in real time by an online particle size analyzer. As the ZIF-8 shell layer gradually grows on the surface of tourmaline, the total volume average particle size shows a regular increase over time. Particle size data is collected at fixed time intervals of 1-5 minutes to plot the particle size-time growth curve.

[0035] Please see Figure 2 As shown, it is a flowchart of determining the growth state of ZIF-8 core-shell according to an embodiment of the present invention.

[0036] Specifically, the process of determining the growth state of the ZIF-8 core-shell includes: S11. Determine the slope of the curve based on the particle size-time growth curve; S12. Determine the growth state of ZIF-8 core-shell based on the change in the slope of the curve; The slope of the curve represents the rate of change of particle size over time, and the growth states of the ZIF-8 core-shell include the induction phase, the rapid growth phase, and the plateau phase. During the induction period, between 0 and 30 minutes, which is the initial stage of the reaction, ZIF-8 nucleates on the tourmaline surface. The particle size grows slowly, with a growth rate of less than 0.01 μm / min. During this stage, a high concentration of 2-methylimidazole needs to be maintained to promote nucleation. During the rapid growth phase, which lasts between 30 and 90 minutes, the ZIF-8 crystal nuclei grow into a continuous shell, with the particle size increasing rapidly at a rate of 0.01-0.05 μm / min. During this phase, it is necessary to balance the ratio of ligands to metal ions to maintain stable growth. During the plateau phase, between 90 and 150 minutes, which is the later stage of the reaction, the shell growth is close to saturation, the particle size growth tends to slow down, and the growth rate gradually decreases to below 0.005 μm / min. At this stage, it is necessary to reduce the reaction rate in order to precisely control the final shell thickness.

[0037] In this embodiment of the invention, the theoretical chemical formula of ZIF-8 is: ,Right now The theoretical molar ratio of 2-methylimidazole to 2-methylimidazole is 1:2; however, in actual synthesis, The molar ratio of ligand to 2-methylimidazole directly affects the nucleation density, crystal size, and growth rate of ZIF-8; a high ligand ratio, i.e., an excess of 2-methylimidazole, is beneficial for forming more nucleation sites and obtaining smaller crystallites; a low ligand ratio, i.e., Excessive amounts of water can promote crystal growth and result in larger crystal grains.

[0038] Specifically, the process of dynamically adjusting the molar ratio of zinc nitrate solution to 2-methylimidazole solution includes: The initial molar ratio of the zinc nitrate solution to the 2-methylimidazole solution is 1:2; Based on the induction period, the molar ratio of the zinc nitrate solution to the 2-methylimidazole solution is adjusted to 1:8-12; Based on the aforementioned rapid growth period regulation, the molar ratio of the zinc nitrate solution to the 2-methylimidazole solution is adjusted to 1:4-6; Based on the plateau period, the molar ratio of the zinc nitrate solution to the 2-methylimidazole solution is adjusted to 1:2-3.

[0039] Among them, the induction period adjustment is as follows: when the particle size growth rate is less than 0.01 μm / min, it is determined that the nucleation is insufficient. By adding 2-methylimidazole solution, the molar ratio is adjusted to between 1:8 and 12. The high ligand ratio can increase the nucleation site density on the tourmaline surface and ensure the formation of a continuous and uniform seed layer. The rapid growth period is regulated as follows: when the particle size growth rate is between 0.01 and 0.05 μm / min, it is considered normal growth. By adjusting the molar ratio to between 1:4 and 6, the appropriate ligand ratio can maintain the stable growth of the shell and prevent homogeneous nucleation in the solution. The plateau phase adjustment is achieved when the particle size growth rate drops below 0.005 μm / min but has not yet reached the target particle size. By adding zinc nitrate solution, the molar ratio is adjusted to between 1:2 and 3. Reducing the ligand ratio can slow down the growth rate and achieve precise control over the final shell thickness.

[0040] In this embodiment of the invention, the hydrophobic properties of ZIF-8 originate from the methyl groups on the ligands. To achieve effective hydrophobic protection, the shell layer must be sufficiently continuous and dense. Studies have shown that 20 nm is the minimum critical thickness to ensure a continuous coverage of the ZIF-8 shell layer on the tourmaline surface. Below this value, even with shell coverage, excessively large grain gaps may lead to localized water leakage. During the in-situ growth of ZIF-8 on the tourmaline surface, internal stress is generated between the grains as the shell layer thickens. Studies have shown that the crystal growth of ZIF-8 follows a classic nucleation-growth mechanism. When the shell layer is greater than 100 nm, problems such as internal stress accumulation, shell layer cracking risk, and decreased batch consistency may occur. Therefore, this embodiment of the invention, through the above dynamic adjustment, can achieve precise and controllable preparation of the shell layer thickness within the range of 20-100 nm.

[0041] In this embodiment of the invention, the degree of reaction completion is determined based on the degree of decay of the particle size growth rate per unit time. During the growth of the ZIF-8 shell, as the shell thickness gradually approaches saturation, the concentrations of available zinc ions and 2-methylimidazole in the reaction system decrease, while the effective nucleation sites on the tourmaline surface are gradually occupied, resulting in a rapid, gradual, and then stagnant decay trend in the particle size growth rate.

[0042] Please see Figure 3 As shown, it is a logic diagram for determining the degree of reaction completion according to an embodiment of the present invention.

[0043] Specifically, the process of determining the degree of reaction completion includes: The particle size growth rate per unit time is compared with the preset rate. Based on the fact that the particle size growth rate is less than or equal to the preset rate, it indicates that the shell growth has been basically completed, and further extending the reaction time has a limited contribution to the shell thickness, thus confirming that the reaction is complete. Since the particle size growth rate is greater than the preset rate, it indicates that the shell growth has not yet been completed, and the reaction continues until the next unit of time for comparison.

[0044] In this embodiment of the invention, the unit time is preferably 30 minutes. Since it takes about 5.1-6.8 minutes for ZIF-8 to reach 50% equilibrium mass, the 30-minute window can fully capture the dynamic characteristics of the transition from rapid growth to the plateau phase, ensuring accurate identification of the growth state. Furthermore, using a continuous 30-minute interval instead of instantaneous judgment can effectively smooth the measurement noise in online particle size monitoring and avoid misjudgment due to single measurement deviation.

[0045] In this embodiment of the invention, the preset rate is preferably set to 5%. Since the target shell thickness is 20-100 nm, the batch-to-batch shell thickness deviation is required to be controlled within ±5 nm. Based on the relationship between particle size growth rate and shell thickness (shell thickness growth rate = particle size growth rate / 2), when the particle size growth rate is 5% / 30 min, if the current shell thickness is 50 nm, the shell will grow by approximately 2.5 nm within 30 minutes, resulting in a relative deviation of 5%. This deviation is within an acceptable range. Continuing the reaction to 60 minutes may accumulate the deviation to 8-10%, exceeding the control target. Therefore, 5% is the optimal threshold for balancing reaction completion and thickness accuracy. In practice, the preset rate can be adjusted within the range of 3%-8% depending on the accuracy requirements of the shell thickness for different application scenarios.

[0046] In this embodiment of the invention, when the particle size increase is less than 5% within 30 consecutive minutes, the reaction is determined to be complete and the reaction is immediately terminated. This endpoint determination mechanism ensures the consistency of shell thickness between different batches of products.

[0047] In this embodiment of the invention, after the reaction is completed, the reaction solution contains tourmaline@ZIF-8 core-shell particles, unreacted 2-methylimidazole and zinc nitrate, as well as reaction byproducts. The core-shell particles can be separated from the reaction solution by centrifugation. The centrifugation speed is controlled at 3000-4000 rpm and the centrifugation time is 10-15 minutes. Under these conditions, the core-shell particles precipitate at the bottom of the centrifuge tube, while the supernatant contains unreacted small molecules.

[0048] The precipitate obtained by centrifugation contains residual 2-methylimidazole and zinc nitrate. If these impurities remain in the final product, they may affect the stability of the subsequent paint mixing process. Therefore, the precipitate needs to be washed multiple times with deionized water, usually 4-6 times. After each washing, centrifugation is performed again. During the washing process, ultrasonic treatment can be used to promote the desorption of impurities from the surface of the core-shell particles.

[0049] The washed product contains a large amount of moisture and needs to be dried. The drying is carried out in a vacuum drying oven, with the drying temperature controlled at 60-80℃ and the vacuum degree controlled at -0.08 to -0.1MPa. The drying time is 8-12 hours. Vacuum drying can prevent the thermal degradation of the ZIF-8 structure that may occur at high temperatures, and at the same time, it can prevent the re-adsorption of moisture in the air. The dried tourmaline@ZIF-8 core-shell structure powder is white to light gray powder and can be sealed and stored for a long time.

[0050] This invention utilizes reversible addition-fracture chain transfer (RAFT) active polymerization technology to synthesize triblock copolymers with specific block sequences and formulate them into emulsions to achieve a synergistic unity of waterproofing and negative ion release functions.

[0051] Please see Figure 4 The diagram shown is a flowchart of the synthesis of polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer according to an embodiment of the present invention.

[0052] Specifically, the process for synthesizing the polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer includes: The triblock copolymer was synthesized using a stepwise chain extension method, specifically including the following three stages. S31. Polymerization of the first block (PMMA): Methyl methacrylate monomer, bifunctional trithiocarbonate chain transfer agent, and azobisisobutyronitrile initiator are dissolved in dioxane solvent. After nitrogen deoxygenation, the temperature is raised to 70-80℃ for polymerization for 6-8 hours. At this temperature, the initiator decomposition rate is moderate, and the polymerization reaction is stable and controllable. After the reaction is completed, a PMMA macromolecular chain transfer agent with active chain transfer agent groups at the end is obtained. S32. Chain extension of the second block (PDMS): Add double-bond-terminated PDMS macromonomer (polydimethylsiloxane with vinyl end groups, molecular weight 1000-5000) to the above reaction system, heat to 80-100℃ and polymerize for 10-14 hours. The polymerization of PDMS blocks needs to be above 80℃ to proceed effectively, but the PDMS segments may degrade when the temperature exceeds 100℃. After polymerization, PMMA-b-PDMS diblock copolymer is obtained. S33, chain extension of the third block (PAA): the reaction system is cooled to 50-60℃, acrylic monomers are added and polymerized for 4-6 hours. The polymerization of PAA blocks must be carried out at less than 60℃ to prevent cross-linking reaction between acrylic chains. After polymerization, PMMA-b-PDMS-b-PAA triblock copolymer is obtained.

[0053] After each polymerization stage is completed, samples can be taken for gel permeation chromatography and proton nuclear magnetic resonance spectroscopy to confirm that the molecular weight and block structure meet expectations.

[0054] Specifically, the process for preparing the organosilicon-acrylic block copolymer emulsion includes: The product obtained by RAFT polymerization is a triblock copolymer solid or viscous liquid, insoluble in water. To use it in water-based latex paints, it needs to be prepared into an emulsion via solvent displacement. Specific procedures include... The triblock copolymer was dissolved in a volatile organic solvent such as tetrahydrofuran or acetone. Deionized water was slowly added under high-speed stirring. During the water addition process, the system underwent an inversion: from an oil-in-water type to an oil-in-water type. The copolymer self-assembled to form a micelle structure with hydrophobic segments as the core and hydrophilic PAA segments as the shell. After the water addition was completed, the organic solvent was removed by rotary evaporation under reduced pressure. Deionized water was added to adjust the solid content to 40-50%, and an organosilicon-acrylic acid block copolymer emulsion was obtained. The latex particles of this emulsion had a particle size of 100-300 nm and exhibited excellent storage stability.

[0055] The block copolymer of this invention is a polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid (PMMA-b-PDMS-b-PAA) triblock copolymer, in which each of the three blocks performs a different function. PMMA block (first block), polymethyl methacrylate is a rigid hydrophobic polymer with a glass transition temperature of about 105°C. This block provides mechanical strength and a rigid skeleton in the coating film, ensuring the hardness and abrasion resistance of the coating film. PDMS block (second block), polydimethylsiloxane is an organosilicon polymer with extremely low surface energy and excellent hydrophobicity. Its glass transition temperature is about -123℃. During the film formation process, this block tends to accumulate on the surface of the paint film, forming a dense hydrophobic layer that effectively prevents water penetration. PAA block (third block): Polyacrylic acid is a hydrophilic polymer with a large number of carboxyl groups (-COOH) in its side chains, which have ion conduction capabilities. During film formation, this block undergoes microphase separation from the hydrophobic matrix due to its hydrophilicity, forming nanoscale hydrophilic microdomains with a diameter of about 50-100 nanometers. These microdomains allow hydrated ions and negative oxygen ions to pass through while preventing liquid water from penetrating, thus solving the technical contradiction of waterproof coatings hindering the release of negative ions.

[0056] The three blocks are precisely connected through RAFT polymerization to form a hydrophobic-hydrophobic-hydrophilic sequence structure. During the film formation process, due to the significant differences in the chemical properties of the three segments, the system will automatically undergo microphase separation: PMMA and PDMS form a continuous hydrophobic matrix, while PAA self-assembles to form nanoscale hydrophilic channels dispersed in the matrix. This dual continuous network structure of hydrophobic sea + hydrophilic island is the core mechanism for achieving the waterproof and non-clogging ion function in the embodiments of the present invention.

[0057] In this embodiment of the invention, RAFT polymerization is a living / controlled free radical polymerization technology. Unlike traditional free radical polymerization, RAFT polymerization adds a chain transfer agent to the system, usually a trithiocarbonate compound. The chain transfer agent can undergo a reversible addition-fragmentation reaction with the growing chain free radical, enabling the free radical to transfer rapidly between the active chain and the dormant chain, thereby inhibiting chain termination and chain transfer side reactions.

[0058] The active characteristics of RAFT polymerization are reflected in the fact that the polymer chain ends always remain active, and a second monomer can be added after the first block polymerization is completed to extend the chain and synthesize a diblock copolymer; similarly, a third monomer can be added after the second block polymerization to extend the chain and synthesize a triblock copolymer. The triblock copolymer in the embodiments of the present invention is synthesized by a stepwise chain extension method.

[0059] The controllable characteristics of RAFT polymerization are reflected in the fact that the molecular weight of the polymer can be preset by the initial molar ratio of monomer to chain transfer agent, and the molecular weight distribution is narrow, with PDI usually less than 1.3. This allows the embodiments of the present invention to accurately control the chain length of each block and the total molecular weight of the copolymer, thereby regulating the size and distribution of the microphase separation structure.

[0060] Specifically, the process of obtaining a latent curing crosslinking agent dispersion with a solid content of 25%-35% includes: After mixing the blocked isocyanate and modified phosphate ester in a selected ratio, emulsification dispersion is carried out in a high-speed disperser. The dispersion linear velocity is controlled at 15-20 m / s, and the dispersion time is 15-20 minutes. The high shear force breaks the oil phase into tiny droplets, and the modified phosphate ester is adsorbed on the surface of the droplets to form a protective layer, preventing the droplets from merging. During the dispersion process, the system temperature should be controlled to ≤40℃. Cooling can be achieved by using jacket cooling water to prevent local overheating that could cause premature desealing of the blocked isocyanate. After dispersion, a milky white latent curing crosslinking agent dispersion with a solid content of 25%-35% is obtained. This dispersion shows no stratification or precipitation after standing at room temperature for 6 months.

[0061] In this embodiment of the invention, blocked isocyanate is a mature technology in polyurethane chemistry. Its core principle is that the isocyanate group (-NCO) reacts with a blocking agent containing active hydrogen to form an adduct. The blocking agent containing active hydrogen includes methyl ethyl ketone oxime, ε-caprolactam, phenol, etc. The adduct is chemically stable at room temperature and does not react with water or compounds containing active hydrogen, such as alcohols, amines, carboxylic acids, etc. When heated to 80-150°C, the blocking agent dissociates and desorbs from the adduct, releasing the highly reactive -NCO group.

[0062] Specifically, the blocked isocyanate is a blocked polyisocyanate, including HDI trimer blocking compounds, IPDI blocking compounds, TDI prepolymer blocking compounds, or water-dispersible blocked isocyanates. Specifically, it includes hexamethylene diisocyanate trimer-methyl ethyl ketone oxime adduct, isophorone diisocyanate-ε-caprolactam adduct, toluene diisocyanate prepolymer-phenol adduct, or hydrophilically modified blocked HDI trimer.

[0063] In this embodiment of the invention, the latent curing properties of the blocked isocyanate allow it to be premixed with the silicone-acrylic block copolymer emulsion to form a single-component stable coating system. During storage and transportation, the blocked isocyanate remains in a blocked state and does not react with hydroxyl, carboxyl, or other groups in the emulsion. When the coating is heated and cured after application (usually 80-150°C), the blocker desorbs, and the released -NCO groups react with the hydroxyl (-OH) groups in the emulsion to form a dense three-dimensional network structure.

[0064] In this embodiment of the invention, the modified phosphate ester molecule has an amphiphilic structure, with the phosphate ester group being hydrophilic and the alkyl or polyoxyethylene chain being lipophilic. This structure allows it to adsorb onto the surface of closed isocyanate droplets, reducing the oil-water interfacial tension. During high-speed dispersion, it breaks the oil phase into tiny droplets (submicron level) and prevents the droplets from re-merging, forming a stable oil-in-water dispersion. Simultaneously, the phosphate ester group has strong hydrophilicity, enabling it to quickly bind with free water molecules in high-humidity environments, accelerating the migration and dissipation of moisture in the wet film, thereby shortening the surface drying time and eliminating the conditions for bubble nucleation at the source. Some modified phosphate esters contain active groups that can participate in cross-linking reactions, such as hydroxyl groups or double bonds, which can react with isocyanates during the curing process, further increasing the cross-linking density.

[0065] Specifically, the modified phosphate ester molecule is a phosphate ester surfactant with an HLB value of 10-18, including polyoxyethylene ether phosphate ester, alkyl phosphate ester, phosphorylated polyester, phosphate ester containing polymerizable groups, or phosphate ester containing nitrogen mustard or lipophilic groups, specifically including nonylphenol polyoxyethylene ether phosphate ester, hexadecyl phosphate ester, and mixtures of mono- and diester phosphate esters, etc.

[0066] In this embodiment of the invention, the mass ratio of blocked isocyanate to modified phosphate is controlled within the range of 2-5:1. When the mass ratio is lower than 2:1, that is, when the proportion of modified phosphate is too high, the content of blocked isocyanate in the dispersion is too low, the crosslinking density is insufficient, and the waterproof performance decreases. When the mass ratio is higher than 5:1, that is, when the proportion of modified phosphate is too low, the emulsification effect deteriorates, the stability of the dispersion decreases, and it is easy to separate and precipitate during storage. The range of 2-5:1 is the preferred range for balancing crosslinking performance and dispersion stability.

[0067] In this embodiment of the invention, the tourmaline@ZIF-8 core-shell structure powder, organosilicon-acrylic block copolymer emulsion, latent curing crosslinking agent dispersion prepared in the aforementioned steps are systematically integrated with conventional pigments, fillers, and additives to prepare a finished latex paint.

[0068] Specifically, the process of obtaining the environmentally friendly negative ion waterproof latex paint includes: The feeding sequence employs a layered approach: first dispersing the powder, then adding the emulsion, and finally adding the crosslinking agent. In the first stage (dispersion medium preparation), deionized water, dispersant, and some defoamer are premixed. The dispersant needs to be dissolved in the aqueous phase first so that it can be immediately adsorbed onto the powder surface when the powder is added. The defoamer is added in advance to prevent a large number of bubbles from being generated during the subsequent high-speed dispersion process. The second stage (powder dispersion) involves adding tourmaline@ZIF-8 core-shell structure powder, titanium dioxide, and diatomaceous earth for high-speed dispersion. The high shear force of high-speed dispersion breaks down powder agglomerates, and the dispersant is adsorbed on the powder surface. Electrostatic repulsion and steric hindrance prevent the powder from re-agglomerating. The high-speed dispersion time is 30-40 minutes until the fineness detected by the scraper fineness meter is ≤50 microns. In this stage, the porous structure of diatomaceous earth can adsorb some tourmaline@ZIF-8 core-shell particles, physically isolating them to prevent agglomeration. At the same time, diatomaceous earth itself also has auxiliary purification functions such as adsorbing formaldehyde and regulating indoor humidity. In the third stage (addition of film-forming substances), after switching to medium-speed stirring, add the silicone-acrylic block copolymer emulsion, latent curing crosslinking agent dispersion, film-forming aid, and thickener in sequence. The emulsion and crosslinking agent need to be added under low shear conditions to avoid high shear force damaging the latex particle structure or causing premature desealing of the crosslinking agent. The film-forming aid temporarily plasticizes the polymer chain segments, lowers the minimum film-forming temperature of the emulsion, and enables the paint film to form continuously at room temperature. The thickener adjusts the viscosity of the system to a suitable range for application, 80-110 KU, to prevent sedimentation during storage and sagging during application.

[0069] In this embodiment of the invention, high-speed dispersion is a linear velocity of 15-20 m / s, which is suitable for the powder dispersion stage; high shear force is a necessary condition to overcome the internal forces of powder agglomerates and break them down to the submicron level, but the linear velocity should not exceed 20 m / s, otherwise the following negative effects may occur: (1) the system temperature rises sharply, which may cause thermal damage to the ZIF-8 shell; (2) high shear force may cause the ZIF-8 shell to fall off the tourmaline surface; (3) a large number of bubbles are generated and difficult to eliminate; medium-speed stirring is a linear velocity of 5-8 m / s, which is suitable for the mixing stage after the emulsion and crosslinking agent are added. Under this shear condition, the components can be mixed evenly, and at the same time, the latex particle structure will not be damaged, a large number of bubbles will not be introduced, and the crosslinking agent will not be prematurely desealed.

[0070] In this embodiment of the invention, the components in the finished latex paint work synergistically. The ZIF-8 shell protects the tourmaline from being encased in a water film in a high-humidity environment, the silicone emulsion provides a dense waterproof layer, and the PAA hydrophilic microdomains in the emulsion provide a release channel for negative ions. The combination of the three achieves the core function of waterproofing without blocking ions. The latent curing crosslinking agent reacts with the hydroxyl groups in the emulsion after construction to form a crosslinking network, which improves the density and water resistance of the paint film. At the same time, the crosslinking reaction accelerates the surface drying of the paint film and reduces blistering defects caused by water retention in a high-humidity environment. The porous structure of diatomaceous earth serves as a dispersion carrier for ZIF-8 particles, preventing their aggregation. Meanwhile, pollutants such as formaldehyde adsorbed by diatomaceous earth can be degraded under the action of negative ions.

[0071] In this embodiment of the invention, after the paint is mixed, the finished paint contains a small amount of undispersed particles or impurities, which need to be removed by filtration. The filtration is carried out using an 80-120 mesh vibrating screen. The filtered finished paint is then filled into packaging barrels by an automatic filling machine. Air bubbles should be avoided during the filling process, and the packaging barrels should be well sealed to prevent moisture evaporation and surface crusting during storage.

[0072] In this embodiment of the invention, to obtain a finished latex paint with stable performance and good workability, it is necessary to add conventional additives in the coatings field, specifically including: Dispersant is used to wet and disperse pigments and fillers to prevent powder agglomeration. In this embodiment of the invention, the dispersant is preferably a high molecular weight block copolymer solution containing pigment affinity groups, specifically, DISPERBYK-190 from BYK Chemicals (Germany). This dispersant does not contain organic solvents and can be effectively adsorbed on the surface of inorganic powders, achieving stable dispersion through steric hindrance and electrostatic repulsion.

[0073] Defoamer is used to eliminate bubbles generated during production and construction to prevent pinholes in the paint film. In this embodiment of the invention, the defoamer is preferably a polysiloxane defoamer, specifically BYK-024. This defoamer is highly efficient and has good compatibility with water-based systems. It is added twice, during the high-speed dispersion stage and the paint mixing stage, to effectively suppress bubble generation.

[0074] Film-forming aids are used to lower the minimum film-forming temperature of the emulsion, ensuring the formation of a continuous and dense paint film at ambient temperature. In this embodiment of the invention, the film-forming aid is preferably alcohol ester-12, the chemical name of which is 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate. This film-forming aid can effectively temporarily plasticize polymer segments, and slowly evaporates after film formation without affecting the final hardness of the paint film.

[0075] Thickeners are used to adjust the viscosity of finished paints and prevent storage settling and sagging during application. In this embodiment of the invention, the thickener is preferably a polyurethane associative rheology modifier, specifically, Dow Chemical's ACRYSOL. ™ RM-8W; This thickener provides excellent medium shear viscosity, resulting in a full-bodied paint film with a good brushing feel.

[0076] When mixing paint, all the above-mentioned additives are added and used in accordance with conventional paint preparation processes.

[0077] Example 1: The preparation method of the environmentally friendly negative ion waterproof latex paint of the present invention includes: (1) Preparation of tourmaline@ZIF-8 core-shell structure powder: 100 g of tourmaline powder with an 800 mesh size and a volume average particle size of 1.5 μm was dispersed in a solution of 65 g of 2-methylimidazole dissolved in 800 mL of deionized water. The stirring speed was set to 200 rpm, and the system was heated to 55°C. Subsequently, a zinc nitrate solution of 50 g of zinc nitrate hexahydrate dissolved in 200 mL of deionized water was added dropwise at a rate of 0.5 mL / min. During the reaction, the particle size change of the core-shell particles was monitored in real time using an online particle size analyzer, and a particle size-time growth curve was plotted accordingly. The molar ratio of 2-methylimidazole to zinc nitrate was dynamically adjusted according to the slope of the curve. During the induction period, the molar ratio was adjusted to 1:8 by adding 2-methylimidazole; during the rapid growth period, the molar ratio was adjusted to 1:4; during the plateau period, the molar ratio was adjusted to 1:2 by adding zinc nitrate. The reaction was terminated when the particle size increase was less than or equal to 5% for 30 consecutive minutes.

[0078] The reaction solution was centrifuged at 3500 r / min for 12 minutes, then washed 5 times with deionized water and subjected to ultrasonic treatment at 300 W for 8 minutes. Finally, it was dried at 70 degrees Celsius and -0.09 MPa vacuum for 10 hours to obtain tourmaline@ZIF-8 core-shell structure powder.

[0079] Transmission electron microscopy revealed that its shell thickness was approximately 52 nanometers; X-ray diffraction patterns showed distinct ZIF-8 characteristic diffraction peaks at 2θ angles of 7.3 degrees, 10.4 degrees, and 12.7 degrees.

[0080] (2) Preparation of organosilicon-acrylic acid block copolymer emulsion: A stepwise chain extension method using reversible addition-fragmentation chain transfer polymerization was employed to synthesize a polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer. First, the first block, polymethyl methacrylate, was polymerized: 50 g of methyl methacrylate, 2.5 g of S-dodecyl-S'-(α,α'-dimethyl-α''-acetic acid) trithiocarbonate, and 0.15 g of azobisisobutyronitrile were dissolved in 100 mL of dioxane. After purging with nitrogen to remove oxygen, polymerization was carried out at 75°C for 6 hours to obtain the polymethyl methacrylate macromolecular chain transfer agent. According to gel permeation chromatography, its number-average molecular weight is 8200 and its molecular weight distribution is 1.12.

[0081] The chain extension of the second block, namely polydimethylsiloxane, was then carried out: 20 g of double-bonded PDMS macromonomer (containing vinyl end groups, Mn≈2000) and 0.05 g of azobisisobutyronitrile were added to the above reaction system, and the mixture was heated to 90 degrees Celsius and polymerized for 12 hours to obtain polymethyl methacrylate-b-polydimethylsiloxane diblock copolymer; The number-average molecular weight was 18,500, the molecular weight distribution was 1.18, and the 1H NMR spectrum showed a characteristic peak of silicon-methyl at a chemical shift of 0.1 ppm.

[0082] Finally, the chain extension of the third block, namely polyacrylic acid, is carried out: the reaction system is cooled to 55 degrees Celsius, 5 grams of acrylic acid are added and polymerized for 5 hours, and finally polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer is obtained. The number-average molecular weight was 25,200, the molecular weight distribution was 1.22, and the proton NMR spectrum showed a broad peak of carboxyl groups at a chemical shift of 12.5 ppm.

[0083] 20 g of the above triblock copolymer was dissolved in 50 mL of tetrahydrofuran. Under high-speed stirring at 800 rpm, 150 mL of deionized water was slowly added dropwise at a rate of 2 mL per minute. The tetrahydrofuran was removed by rotary evaporation under reduced pressure, and deionized water was added to adjust the solid content to 45%. Finally, an organosilicon-acrylic block copolymer emulsion with a latex particle size of about 180 nm was obtained.

[0084] (3) Preparation of latent curing crosslinking agent dispersion: Take 22.5 g of hexamethylene diisocyanate trimer blocked by methyl ethyl ketone oxime and mix it with 7.5 g of polyoxyethylene ether phosphate. Stir the mixture in a high-speed disperser at a linear velocity of 18 m / s while slowly adding 70 g of deionized water. Control the system temperature to not exceed 40 degrees Celsius and disperse for 18 minutes to obtain a milky white latent curing crosslinking agent dispersion with a solid content of 30%. The dispersion showed no stratification or precipitation after standing at room temperature for 6 months.

[0085] (4) Preparation of environmentally friendly negative ion waterproof latex paint: By weight, 20 parts deionized water, 1.0 part dispersant, and 0.2 parts defoamer were mixed and stirred at 300 rpm for 5 minutes. Then, 10 parts of the above-prepared tourmaline@ZIF-8 core-shell structure powder, 20 parts titanium dioxide, and 8 parts diatomaceous earth were added, and the stirring speed was gradually increased to 1500 rpm, corresponding to a linear velocity of 16 meters per second. High-speed dispersion was carried out for 35 minutes. The slurry fineness was ≤50 micrometers, the temperature was 42 degrees Celsius, and the pH value was 8.2. Then, switch to medium-speed stirring at 500 revolutions per minute and a linear velocity of 5.5 meters per second. Add 40 parts of the prepared organosilicon-acrylic block copolymer emulsion, 5 parts of latent curing crosslinking agent dispersion, 2 parts of film-forming aid, and 0.5 parts of thickener in sequence, and continue stirring for 25 minutes. The viscosity of the finished paint is 95 KU. Finally, filter through a 100-mesh sieve and fill into a container to obtain an environmentally friendly negative ion waterproof latex paint.

[0086] (5) Product performance testing, as shown in Table 1:

[0087] Table 1 Comparative Example 1 The difference between this comparative example and Example 1 is that ordinary tourmaline powder without ZIF-8 coating of the same particle size was used and directly added as a functional filler to the paint mixing step.

[0088] The results showed that the ZIF-8 shell has a significant protective effect on the release of negative ions from tourmaline under high humidity conditions.

[0089] Comparative Example 2 The difference between this comparative example and Example 1 is that a conventional random copolymer silicone-modified acrylate emulsion with the same solid content is used instead of the PMMA-b-PDMS-b-PAA triblock copolymer emulsion.

[0090] The results show that the microphase separation structure of the triblock copolymer is the key to simultaneously achieving waterproofing and negative ion release.

[0091] Comparative Example 3 The difference between this comparative example and Example 1 is that no latent curing crosslinking agent dispersion is added.

[0092] The results showed that the latent curing crosslinking agent significantly improved the high-humidity application performance and enhanced the water resistance and adhesion of the coating film.

[0093] Comparative Example 4 The difference between this comparative example and Example 1 is that the method of Example 1 is used, except that the mass ratio of blocked isocyanate to modified phosphate is changed to blocked isocyanate: modified phosphate = 1:1.

[0094] The results showed that when the mass ratio was less than 2:1, the latent curing crosslinking agent dispersion separated after 7 days of storage, the paint film bubbled after 48 hours of water resistance, and the crosslinking density was insufficient. The mass ratio of blocked isocyanate to modified phosphate ester must be in the range of 2-5:1 in order to ensure both dispersion stability and crosslinking performance.

[0095] Comparative Example 5 The difference between this comparative example and Example 1 is that the method of Example 1 is used, except that the mass ratio of blocked isocyanate to modified phosphate is changed to blocked isocyanate: modified phosphate = 8:1.

[0096] The results showed that when the mass ratio was higher than 5:1, the latent curing crosslinking agent dispersion was not sufficiently emulsified, the droplet size was greater than 5μm, and it separated into layers within 24 hours, making it impossible to store stably. The mass ratio of blocked isocyanate to modified phosphate ester must be in the range of 2-5:1 in order to ensure both dispersion stability and crosslinking performance.

[0097] Comparative Example 6 The difference between this comparative example and Example 1 is that the preparation of tourmaline@ZIF-8 core-shell structure powder adopts the opposite feeding sequence, that is: first, 2-methylimidazole solution and zinc nitrate solution are mixed, and then tourmaline powder is dispersed in the mixed solution. The remaining steps are exactly the same as in Example 1.

[0098] The results showed that if 2-methylimidazole was mixed with zinc nitrate before being brought into contact with tourmaline, ZIF-8 would homogeneously nucleate in the solution and would not be able to form a continuous core-shell structure on the tourmaline surface. This resulted in a significant decrease in the negative ion release performance under high humidity conditions, with the high humidity retention rate dropping from 86.2% to 41.5%. 2-methylimidazole must first be adsorbed and enriched on the tourmaline surface before it can guide the release of Zn. 2+ In situ reaction on the tourmaline surface forms a ZIF-8 shell. If the two reactants are mixed in solution first, the nucleation reaction of ZIF-8 will occur rapidly in solution, generating a large number of independent ZIF-8 crystals, and thus failing to form a coating layer on the tourmaline surface.

[0099] Comparative Example 7 The difference between this comparative example and Example 1 is that the silicone emulsion was first mixed with the latent curing agent, and then tourmaline@ZIF-8 core-shell structure powder was added.

[0100] The results showed that the key to achieving good dispersion and stability is to follow the stratified feeding sequence of first dispersing the powder, then adding the emulsion, and finally adding the crosslinking agent.

[0101] Comparative Example 8 The difference between this comparative example and Example 1 is that diatomaceous earth is not added.

[0102] The results showed that the porous structure of diatomaceous earth acts as a dispersing carrier for ZIF-8 particles, preventing agglomeration and improving the negative ion release efficiency and batch consistency.

[0103] The results of comparative tests conducted on Example 1 and Comparative Examples 1-8 are shown in Table 2.

[0104] Table 2 The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0105] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an environmentally friendly negative ion waterproof latex paint, characterized in that, include: Tourmaline powder was dispersed in a 2-methylimidazole solution, and zinc nitrate solution was added. The growth state of the ZIF-8 core-shell was determined based on the particle size-time growth curve of the tourmaline@ZIF-8 core-shell particles during the reaction process, so as to dynamically adjust the molar ratio of zinc nitrate solution to 2-methylimidazole solution. Based on the particle size growth rate of tourmaline@ZIF-8 core-shell particles per unit time, the degree of reaction completion was determined. After terminating the reaction, tourmaline@ZIF-8 core-shell structure powder was obtained by centrifugation, washing, and drying. Based on the reversible addition-fragmentation chain transfer polymerization method, polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer was synthesized to prepare organosilicon-acrylic acid block copolymer emulsion; Blocked isocyanate and modified phosphate ester are mixed at a mass ratio of 2-5:1, and then deionized water is added for high-speed dispersion to obtain a latent curing crosslinking agent dispersion with a solid content of 25%-35%. By weight, 15-25 parts of deionized water, 0.5-1.5 parts of dispersant, and 0.2-0.5 parts of defoamer are mixed, and 5-15 parts of the tourmaline@ZIF-8 core-shell structure powder, 15-25 parts of titanium dioxide, and 5-10 parts of diatomaceous earth are added. The mixture is dispersed at high speed for 30-40 minutes. Subsequently, 30-50 parts of the organosilicon-acrylic block copolymer emulsion, 3-8 parts of the latent curing crosslinking agent dispersion, 1-3 parts of film-forming aid, and 0.3-0.8 parts of thickener are added. The mixture is stirred at medium speed for 20-30 minutes and filtered to obtain an environmentally friendly negative ion waterproof latex paint.

2. The preparation method of the environmentally friendly negative ion waterproof latex paint according to claim 1, characterized in that, The process of determining the growth state of ZIF-8 core-shell includes: The slope of the curve is determined based on the particle size-time growth curve of the tourmaline@ZIF-8 core-shell particles, and the growth state of the ZIF-8 core-shell is determined based on the change of the slope of the curve. The slope of the curve represents the rate of change of particle size over time, and the growth states of the ZIF-8 core-shell include the induction phase, the rapid growth phase, and the plateau phase.

3. The preparation method of the environmentally friendly negative ion waterproof latex paint according to claim 2, characterized in that, The process of dynamically adjusting the molar ratio of zinc nitrate solution to 2-methylimidazole solution includes: The initial molar ratio of the zinc nitrate solution to the 2-methylimidazole solution is 1:2; Based on the induction period, the molar ratio of the zinc nitrate solution to the 2-methylimidazole solution is adjusted to 1:8-12; Based on the aforementioned rapid growth period regulation, the molar ratio of the zinc nitrate solution to the 2-methylimidazole solution is adjusted to 1:4-6; Based on the plateau period, the molar ratio of the zinc nitrate solution to the 2-methylimidazole solution is adjusted to 1:2-3.

4. The preparation method of the environmentally friendly negative ion waterproof latex paint according to claim 1, characterized in that, The process of determining the degree of reaction completion includes: The particle size growth rate per unit time is compared with the preset rate. The reaction is determined to be complete if the particle size growth rate is less than or equal to a preset rate.

5. The preparation method of the environmentally friendly negative ion waterproof latex paint according to claim 1, characterized in that, The process for synthesizing the polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer includes: Triblock copolymers were synthesized using a stepwise chain extension method; The polymerization of the first block involves dissolving methyl methacrylate monomer, bifunctional trithiocarbonate chain transfer agent, and azobisisobutyronitrile initiator in a dioxane solvent, purging with nitrogen to remove oxygen, and then heating to 70-80℃ for polymerization for 6-8 hours. After the reaction is complete, a polymethyl methacrylate macromolecular chain transfer agent with active chain transfer agent groups at the ends is obtained.

6. The preparation method of the environmentally friendly negative ion waterproof latex paint according to claim 5, characterized in that, The process for synthesizing the polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer further includes: Chain extension of the second block involves adding double-bond-terminated polydimethylsiloxane macromonomers to the first block reaction system, heating to 80-100℃ and polymerizing for 10-14 hours. After polymerization, polymethyl methacrylate-b-polydimethylsiloxane diblock copolymer is obtained.

7. The preparation method of the environmentally friendly negative ion waterproof latex paint according to claim 6, characterized in that, The process for synthesizing the polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer further includes: The chain extension of the third block involves cooling the reaction system after the second block polymerization to 50-60℃, adding acrylic monomers and polymerizing for 4-6 hours. After polymerization, polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer is obtained. The polymethyl methacrylate-b-polydimethylsiloxane-b-polyacrylic acid triblock copolymer has a number average molecular weight of 15,000-50,000 and a molecular weight distribution of less than or equal to 1.

3.

8. The preparation method of the environmentally friendly negative ion waterproof latex paint according to claim 1, characterized in that, The process of obtaining a latent curing crosslinking agent dispersion with a solid content of 25%-35% further includes: The blocked isocyanate is a blocked polyisocyanate, including HDI trimer blocking compounds, IPDI blocking compounds, TDI prepolymer blocking compounds, or water-dispersible blocked isocyanates.

9. The preparation method of the environmentally friendly negative ion waterproof latex paint according to claim 1, characterized in that, The process of obtaining a latent curing crosslinking agent dispersion with a solid content of 25%-35% further includes: The modified phosphate ester molecule is a phosphate ester surfactant with an HLB value of 10-18, including polyoxyethylene ether phosphate ester, alkyl phosphate ester, phosphorylated polyester, phosphate ester containing polymerizable groups, or phosphate ester containing nitrogen mustard or lipophilic groups.

10. The preparation method of the environmentally friendly negative ion waterproof latex paint according to claim 1, characterized in that, The process of obtaining the environmentally friendly negative ion waterproof latex paint includes: The dispersant is a high molecular weight copolymer containing pigment affinity groups; The defoamer is a polysiloxane-based defoamer; The film-forming aid is alcohol ester-12; The thickener is a polyurethane associative thickener.

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