High-acid-and-base-resistant pigment red 48:1 and preparation process thereof

Abstract

This application relates to a highly acid and alkali resistant pigment, Red 48:1, and its preparation process, belonging to the field of chemical pigment manufacturing technology. The pigment is prepared from 2B acid, sodium nitrite, 2,3 acid, a barium-lanthanum-calcium multimetallic salt component, aminotrimethylenephosphonic acid, zirconium salt, melamine-formaldehyde resin prepolymer, epoxy resin emulsion, silane coupling agent, and surfactant. The preparation process includes sequential diazotization and coupling reactions, followed by a co-lake reaction with the addition of multimetallic salts; then interfacial anchoring via aminotrimethylenephosphonic acid, and inorganic deposition hybridization via droplet addition of zirconium salt; finally, a staged crosslinking coating reaction is performed with the aforementioned resin and coupling agent. This invention constructs an inorganic-organic hybrid coating layer in situ on the pigment core surface of the multimetallic lake, physically blocking the penetration pathways of acid and alkali ions, thus improving the pigment's resistance to acid and alkali bleeding and its resistance to ultraviolet aging.

Description

Technical Field

[0001] This application relates to the field of chemical pigment manufacturing technology, and in particular to a highly acid and alkali resistant pigment red 48:1 and its preparation process. Background Technology

[0002] Pigment Red 48:1 is a classic monoazo lake pigment, mainly produced by diazotizing 2B acid, coupling it with 2,3 acid, and then performing barium salt lake treatment. This pigment possesses typical physicochemical properties such as bright color, high tinting strength, and good dispersibility, and has a wide range of applications in the plastics coloring, ink, and coating industries.

[0003] However, because its molecular structure is essentially a metal salt precipitate of azo dyes containing sulfonic acid and carboxyl groups, this crystal framework maintained by a single barium ion exhibits significant chemical instability in acidic or alkaline media. When the pigment is in a free acidic or alkaline environment, the barium ions on the crystal surface readily undergo ion exchange reactions with hydrogen or hydroxide ions in the medium, causing the metal ions to desorb from the pigment surface and become free in the system. This dissociation directly destroys the structure of the primary pigment particles, causing the insoluble lake to revert to a water-soluble dye matrix, macroscopically manifesting as severe bleeding and fading in the applied products.

[0004] Based on this, the azo conjugated system within Pigment Red 48:1 is inherently sensitive to ultraviolet light and is prone to photo-oxidative degradation under long-term outdoor exposure, resulting in limited weather resistance. Existing modification methods typically involve simple rosin treatment in the later stages of pigment synthesis or physical coating using a single organic resin. These conventional methods lack a robust chemical bond between the coating layer and the pigment core, making the outer coating prone to interfacial peeling or localized cracking during downstream processing or when subjected to swelling by polar solvents. Because a long-lasting and dense three-dimensional barrier cannot be formed on the pigment surface, existing technologies struggle to fundamentally address the technical challenges of acid and alkali ion penetration into the pigment and ultraviolet light damaging the crystal structure. Summary of the Invention

[0005] The purpose of this application is to provide a highly acid and alkali resistant pigment red 48:1, which solves the problems of existing pigment red 48:1 being prone to metal ion exchange or crystal lattice disintegration in acid and alkali media, resulting in bleeding and fading, as well as having weak UV resistance and being prone to aging and degradation after long-term exposure.

[0006] In a first aspect, the present invention provides a highly acid and alkali resistant pigment red 48:1, which adopts the following technical solution:

[0007] A highly acid- and alkali-resistant pigment red 48:1, based on 1.0 mol (equivalent to 235.7 parts by weight), is prepared from raw materials comprising the following proportions: 1.0 mol of 2B acid; 1.01-1.03 mol of sodium nitrite; 1.01-1.03 mol of 2,3 acid; the salt-forming metal component includes 1.05-1.15 mol of barium salt, 0.03-0.06 mol of rare earth lanthanum salt, and 0.08-0.12 mol of calcium salt; the interface anchoring agent is 0.015-0.025 mol of aminotrimethylenephosphonic acid; the inorganic hybrid agent is 0.005-0.008 mol of zirconium salt; the organic coating resin component includes 25-45 parts by weight of melamine-formaldehyde resin prepolymer and 30-60 parts by weight of epoxy resin emulsion; the additives include 8-12 parts by weight of silane coupling agent and 4-6 parts by weight of surfactant. The above-mentioned raw materials are polymerized in situ on the surface of the pigment core to form an inorganic-organic hybrid coating layer to block acid and alkali ions and ultraviolet rays.

[0008] By employing the above technical solution, a pigment with a stable structure and a dense barrier network on the outer layer is obtained due to the use of a multi-metal salt formation system, organophosphonic acid interface anchoring, and in-situ hybrid coating of inorganic and organic components. Conventional pigment Red 48:1 typically relies solely on a single barium salt for lake formation, a structure prone to metal ion desorption in acidic and alkaline environments. In this solution, barium, lanthanum, and calcium salts undergo a co-lake formation reaction. Barium ions are responsible for constructing the main crystal lattice framework; rare-earth lanthanum ions, with their high coordination number, enter the lattice, inducing microscopic lattice distortion and increasing lattice energy; simultaneously, calcium ions participate in regulating the precipitation rate, thereby controlling the crystal size of the primary particles. This multi-metal co-crystallization system enhances the intermolecular bonding of the azo matrix molecules.

[0009] Building upon this, aminotrimethylenephosphonic acid plays a role in interfacial anchoring. Under specific pH conditions, the multiple phosphonic acid groups within its molecule can form polydentate coordination complexes with exposed metal ions such as barium, lanthanum, or calcium on the pigment surface. This chemical bond is not only stable but also positions the amino group at the other end of the molecule towards the external aqueous phase, altering the physicochemical properties of the pigment interface and providing active reaction sites for the subsequent attachment of inorganic and organic components.

[0010] Subsequently, when the zirconium salt hydrolyzes and polymerizes into polyhydroxyzirconia complexes in the system, these complexes are deposited on the aforementioned active surface, cross-linking to form a high-refractive-index inorganic zirconium oxide network undercoating layer, which reflects and absorbs the transmitted ultraviolet light.

[0011] Finally, a dual-resin cross-linking composite coating is performed. The melamine-formaldehyde resin prepolymer in the system is rich in hydroxymethyl groups, while the epoxy resin contains epoxy groups. Under controlled reaction conditions, the two undergo ring-opening copolymerization and condensation curing. At this time, the added silane coupling agent acts as a bridge through its silanol groups and organic reactive groups at both ends, firmly connecting the free resin segments to the underlying inorganic zirconium network. The reaction ultimately forms a highly cross-linked three-dimensional polymer film on the outermost layer of the pigment particles, physically blocking the path of external hydrogen ions and hydroxide ions to penetrate into the pigment.

[0012] Preferably, in the salt-forming metal component, the barium salt is barium chloride, the rare earth lanthanum salt is lanthanum chloride, and the calcium salt is calcium acetate; in the inorganic hybrid agent, the zirconium salt is zirconium oxychloride octahydrate.

[0013] By employing the above-mentioned technical solution, barium chloride and lanthanum chloride exhibit high dissociation in water, enabling them to rapidly release metal ions and participate in the salt-forming reaction of the azo dye parent material. In contrast, the dissolution process of calcium acetate is relatively mild, and the acetate ions generated by its dissociation can also buffer pH fluctuations in the reaction solution. Furthermore, zirconium oxychloride octahydrate is more easily hydrolyzed by alkaline solutions in aqueous solution, resulting in the formation of more uniformly structured hydrated zirconium oxide deposits.

[0014] Preferably, in the organic coating resin component, the epoxy resin emulsion is an E44 epoxy emulsion with a solid content of 45%; in the additives, the silane coupling agent is KH560 and the surfactant is sodium dodecylbenzenesulfonate.

[0015] By adopting the above technical solution, considering that the epoxy value of E44 epoxy emulsion is relatively moderate, it exhibits good compatibility with melamine-formaldehyde resin prepolymer in the aqueous dispersion system, ensuring that the reaction sites of different resins can fully contact. KH560 itself contains epoxy groups and can directly participate in the ring-opening curing process of the resin body; while sodium dodecylbenzenesulfonate is mainly used in the coating reaction stage to reduce the surface tension of the liquid and prevent pigment particles from secondary agglomeration due to the initial curing of the surface resin.

[0016] Preferably, the melamine-formaldehyde resin prepolymer is prepared by reacting melamine with a formaldehyde solution of 37% by mass under alkaline conditions, and the mass ratio of melamine to formaldehyde solution is 126.1:243.5-284.1.

[0017] By adopting the above technical solution and using this specific mass ratio, the molar ratio of melamine to formaldehyde is essentially controlled within a reasonable range for the synthesis of dimethylol or trimethylolmelamine. The product obtained from this reaction retains sufficient reactive hydroxymethyl groups without undergoing excessive condensation reaction, maintaining low viscosity and good water solubility, which facilitates uniform dispersion in pigment suspensions.

[0018] Secondly, the present invention provides a preparation process for a highly acid and alkali resistant pigment red 48:1, which adopts the following technical solution:

[0019] A preparation process for a highly acid and alkali resistant pigment red 48:1 includes the following steps:

[0020] After dissolving 2B acid and cooling it, a sodium nitrite solution is added dropwise under acidic conditions to carry out a diazotization reaction, thereby obtaining a diazonium salt solution.

[0021] After dissolving the 2,3 acid and adjusting it to a weakly alkaline state, the temperature was lowered, and then the diazonium salt solution was added dropwise to carry out the coupling reaction to obtain the coupling solution.

[0022] An aqueous solution containing barium salt, rare earth lanthanum salt and calcium salt was added sequentially to the coupling solution, and the temperature was raised to carry out a lake-forming reaction to obtain a lake suspension.

[0023] The pH value of the lake suspension was adjusted, a solution containing aminotrimethylenephosphonic acid was added, and the temperature was raised to carry out a constant temperature reaction to achieve interfacial anchoring, thus obtaining an anchored suspension.

[0024] An aqueous solution containing zirconium salt and an alkaline solution are simultaneously and concurrently added dropwise to the anchoring suspension. During the addition process, the pH value of the suspension is dynamically kept constant through online feedback to complete the inorganic hybrid reaction and obtain an inorganic hybrid suspension.

[0025] Melamine-formaldehyde resin prepolymer was added to an inorganic hybrid suspension to carry out the first-stage coating reaction. Then, the temperature was lowered and a silane coupling agent was added and stirred. Finally, epoxy resin emulsion and surfactant were added to carry out the second-stage heat preservation reaction to obtain a composite coated suspension.

[0026] The composite coated suspension was subjected to pressure filtration, washing, drying and pulverization to obtain highly acid and alkali resistant pigment red 48:1.

[0027] By adopting the above technical solution, and through a progressive synthesis and coating process, a finished pigment with well-developed crystals, sufficient interface modification, and uniform outer coating thickness is obtained. From the specific process evolution, in the initial stage of the reaction, the aromatic primary amine group in the 2B acid reacts with nitrous acid in a low-temperature acidic environment, transforming into an intermediate with a diazonium group. Subsequently, this diazonium salt undergoes electrophilic substitution and attaches to the 2,3 acid molecule, forming an azo chromophore. At this point, the resulting dye matrix is ​​still water-soluble. To form a solid pigment, various metal ion solutions are sequentially added during the process, causing the original sulfonic acid and carboxyl groups to convert into insoluble metal salt precipitates.

[0028] After the pigment crystals initially form, aminotrimethylenephosphonic acid begins to adsorb and complex onto the particle surface at a constant temperature. This is followed by a co-current hybridization stage, where local supersaturation is controlled by the simultaneous addition of alkali and zirconium salt, causing free zirconium ions to transform into inorganic colloids and continuously deposit on the outer layer of the pigment. In the final stage of phased coating, the initial higher temperature induces preliminary condensation and precipitation of the melamine-formaldehyde resin, while the subsequent cooling introduces a silane coupling agent for effective molecular chain bridging. A subsequent heating process demulsifies the epoxy emulsion and cross-links with the previously formed polymer, ensuring its curing. The various steps in the entire preparation process are interconnected, avoiding cross-interference between materials and guaranteeing the formation of the final core-shell structure.

[0029] Preferably, the temperature of the diazotization reaction is controlled at 0-5℃; during the coupling reaction, the pH of the reaction solution is maintained between 7.5 and 8.2 by adding alkali solution during the dropwise addition of the diazonium salt solution, and after the dropwise addition is completed, the temperature is raised to 28-30℃ and stirred for 100-120 minutes.

[0030] By employing the above technical solution, the diazotization temperature is controlled within a low-temperature range of 0-5℃, primarily to prevent the decomposition of the already formed diazonium salt or the initiation of other side reactions. During the coupling stage, the pH of the reaction solution is maintained at 7.5-8.2 by adding alkali solution in a coordinated manner. This ensures that the 2,3-acid is fully dissolved and in a state of highly electrophilic substitution activity as a phenolic anion, which is crucial for improving the coupling conversion rate. The subsequent heating, holding, and stirring after the dropwise addition are to ensure a more complete reaction and reduce the residual amount of free parent compound.

[0031] Preferably, the temperature of the lake reaction is controlled at 45-50℃ and the reaction time is 120-150 minutes; before adding the aminotrimethylenephosphonic acid solution, the pH value of the lake suspension is adjusted to 6.8-7.2, and then the temperature is raised to 65-68℃ and the reaction is carried out at a constant temperature for 35-45 minutes.

[0032] By adopting the above technical solution, a temperature of 45-50℃ is suitable for the crystallization and growth of primary pigment particles, which helps to obtain crystal forms with pure color. Adjusting the pH of the suspension to near neutral before adding the anchoring agent prevents the risk of azo bond breakage or lake metal ionization due to excessive acidity. Simultaneously, subsequently raising the temperature to 65-68℃ provides the necessary activation energy for the coordination reaction, accelerating the diffusion and chemical bonding process of the anchoring agent molecules at the solid-liquid interface.

[0033] Preferably, the alkaline solution added simultaneously and in parallel is a 5% NaOH solution; during the parallel-flow addition process, the specific fluctuation range of maintaining a dynamic and constant pH value of the suspension is controlled within 6.4-7.1.

[0034] By adopting the above technical solution and using a low-concentration alkaline solution in conjunction with a co-current drip addition method, localized pH extremes within the reactor can be effectively avoided. Strictly limiting the dynamic pH to the range of 6.4-7.1 allows the hydrolysis rate of zirconium ions to reach a balance with their deposition rate. This ensures that the generated hydrated zirconium oxide is almost entirely deposited on the pigment surface, suppressing the formation of free inorganic impurity particles in the system.

[0035] Preferably, in the first-stage coating reaction, the temperature is raised to 70-75℃, the pH of the suspension is adjusted to 6.0-6.5, and the reaction is carried out for 90-120 minutes; the process of adding the silane coupling agent and stirring is as follows: the temperature is lowered to 50-55℃ and stirring is carried out for 40-60 minutes; in the second-stage heat preservation reaction, the temperature is controlled at 55-60℃ and the reaction time is 150-180 minutes.

[0036] By employing the above technical solution, the 70-75℃ and slightly acidic conditions in the first-stage reaction create a suitable environment for the condensation polymerization of melamine-formaldehyde resin, which promotes resin precipitation and the formation of the initial inner coating film. The subsequent cooling to 50-55℃ aims to slow down the cross-linking rate of the resin itself, thus allowing a time window for the complete hydrolysis and inward penetration of the silane coupling agent. The second-stage heat-preserving reaction, based on this, provides relatively stable kinetic conditions for the ring-opening of epoxy groups and the cross-linking of the entire polymer network, promoting the final dense curing of the composite film.

[0037] Preferably, the melamine-formaldehyde resin prepolymer is prepared in advance by the following process: melamine and a formaldehyde solution with a mass fraction of 37% are added to a reaction vessel, and NaOH solution is added dropwise to adjust the pH value of the reaction solution to 8.5-9.0; the reaction solution is heated to 70-75℃ at a uniform rate and stirred for 45-60 minutes; when the reaction solution is completely transparent and clear, and no precipitation occurs when a sample is dropped into deionized water at 20℃, the temperature is lowered to below 30℃ and the material is discharged.

[0038] By employing the above technical solution, the pH of the reaction solution is maintained at 8.5-9.0 during the synthesis of the prepolymer. This is primarily to suppress unnecessary methylene condensation reactions, allowing formaldehyde to participate in the reaction via hydroxymethylation addition. By observing the clarity of the solution and conducting a deionized water droplet test, it can be determined whether the generated hydroxymethyl melamine possesses sufficient hydrophilicity. Rapidly cooling and discharging the material after reaching this state is to promptly terminate the thermal reaction process and prevent the prepolymer from undergoing self-polymerization and hardening during storage or subsequent feeding.

[0039] In summary, this application includes at least one of the following beneficial technical effects:

[0040] 1. This invention improves the acid and alkali resistance of pigments by employing a multi-metallic salt-forming system composed of barium salts, rare earth lanthanum salts, and calcium salts for co-lake reaction. The introduction of rare earth lanthanum ions causes microscopic distortion within the crystal lattice and increases the lattice energy. Combined with the skeletal support of barium ions and the particle size adjustment of calcium ions, this enhances the coordination and binding force between the azo matrix and metal ions. The multi-metallic co-crystallization structure reduces the tendency of pigments to undergo metal ion exchange and desorption in acidic and alkaline media, thus mitigating the bleeding and fading caused by lattice disintegration.

[0041] 2. This invention utilizes aminotrimethylenephosphonic acid to chemically bond and anchor pigment particles on their surface, guiding the in-situ deposition of zirconium salt hydrolysis products, thereby improving the pigment's resistance to ultraviolet aging. The multidentate coordination of aminotrimethylenephosphonic acid provides dense reaction sites for inorganic components, enabling the polyhydroxyzirconia complex to uniformly crosslink into a zirconium oxide network substrate with a high refractive index. This inorganic layer can reflect and absorb external ultraviolet light, and thanks to the chemical anchoring effect of the substrate, the adhesion between the deposited layer and the pigment core is ensured, making it less prone to interfacial peeling during long-term use.

[0042] 3. This invention employs a staged crosslinking process between melamine-formaldehyde resin prepolymer and epoxy resin emulsion, and introduces a silane coupling agent as a bridge to further enhance the overall chemical stability of the pigment. The silane coupling agent connects the free organic resin segments to the underlying inorganic zirconium network. The two resins are cured through ring-opening copolymerization and condensation to form a three-dimensional polymer film on the outermost layer of the pigment. This crosslinked film physically blocks the penetration pathways of external hydrogen ions and hydroxide ions into the pigment interior. Simultaneously, the tension-reducing effect of the surfactant during the preparation process prevents secondary particle agglomeration caused by the curing of the coating resin. Attached Figure Description

[0043] Figure 1 This is a schematic diagram showing the mass concentration distribution of dissolved lanthanum and zirconium elements in the filtrate after mechanical shearing in Embodiment 1 and Comparative Examples 2, 3, and 4 of the present invention.

[0044] Figure 2This is a schematic diagram showing the mass concentration of phosphorus in the filtrate of the corresponding sample in this invention;

[0045] Figure 3 This is a comparison chart of the results of the interface chemical bonding strength verification test of the present invention, wherein (a) shows the mass loss rate of Example 1, Example 2, Comparative Example 5 and blank sample A after being subjected to long-term reflux in a highly polar solvent; (b) shows the resin residual mass concentration detected in the extract of the corresponding sample.

[0046] Figure 4 This is a comparison chart of the storage stability results of the pigments of the present invention in the alkyd resin system. (a) shows the viscosity change rate of Example 1, Example 2, Comparative Example 1 and Comparative Example 4 after accelerated aging at 50°C for 15 days by using a histogram. (b) shows the change range of the median particle size of the pigments before and after aging in the corresponding experimental groups.

[0047] Figure 5 This is a color difference evolution curve of the pigment of this invention in a 5% hydrochloric acid solution;

[0048] Figure 6 This is a comparison chart of the thermal stability of the pigments of the present invention under different temperature conditions. (a) shows the total color difference change trajectory of Examples 1, 2 and Comparative Examples 1 and 2 in the range of 200℃ to 280℃. (b) Quantitatively analyzes the color difference growth rate of each component in the high temperature region above 240℃ through bar chart.

[0049] Figure 7 This is a performance evaluation diagram of the pigment of the present invention under 500 hours of accelerated aging under xenon lamp conditions. (a) shows the color difference evolution trend of Example 1, Example 2, and Comparative Example 1 and Comparative Example 5 during the light irradiation period, and (b) visually compares the tinting strength retention of each sample at the end of the aging experiment. Detailed Implementation

[0050] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0051] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0052] 4-Amino-5-chloro-2-methylbenzenesulfonic acid (2B acid, CAS No.: 88-44-8), molecular formula C8H 10ClNO3S, purity ≥ 98.0%; 3-hydroxy-2-naphthoic acid (2,3-acid, CAS No.: 92-70-6), molecular formula C 11 H8O3, purity ≥98.5%; barium chloride dihydrate (BaC) l2 ·2H2O, CAS No.: 10361-37-2); Lanthanum chloride heptahydrate (LaC l3 ·7H2O, CAS No.: 10099-74-8); calcium acetate monohydrate (Ca(CH3COO)2·H2O, CAS No.: 62-54-4).

[0053] Aminotrimethylphosphonic acid (ATMP, CAS No.: 6419-19-8), with the molecular formula N(CH2PO3H2)3 and a molecular weight of 299.05. Zirconium oxychloride octahydrate (ZrOCl2·8H2O, CAS No.: 13520-92-8), as an inorganic hybrid precursor, generates zirconium-oxygen clusters in aqueous solution through controlled hydrolysis. 3-Glycidyl etheroxypropyltrimethoxysilane (silane coupling agent KH560, CAS No.: 2530-83-8), with the molecular formula C9H... 20 O5Si contains active epoxy groups and silanol groups produced after hydrolysis in its molecular structure. Sodium nitrite (CAS No.: 7632-00-0), sodium dodecylbenzenesulfonate (SDBS, CAS No.: 25155-30-0), liquid alkali (NaOH, CAS No.: 1310-73-2), hydrochloric acid (HCl, CAS No.: 7647-01-0), and deionized water.

[0054] Bisphenol A type epoxy resin (E44, CAS No.: 25068-38-6) has a chemical structure consisting of a bisphenol A backbone and a glycidyl repeating unit. The repeating unit has the following structural formula: (C 15 H 16 O2·C3H5ClO)n, with an average molecular weight between 350-450, an epoxy value of 0.41-0.47 eq / 100g, and a hydroxyl content of approximately 0.06 eq / 100g. Melamine-formaldehyde resin prepolymer is prepared by a preliminary hydroxymethylation reaction of melamine (CAS No.: 108-78-1) and formaldehyde solution (CAS No.: 50-00-0) under pH 8.5-9.0 conditions.

[0055] Preparation Examples 1-3

[0056] Preparation Example 1:

[0057] This preparation example provides a method for preparing a highly reactive melamine-formaldehyde resin prepolymer, including the following steps:

[0058] (1) Add 126.1 g of melamine (C3H6N6) and 284.1 g of formaldehyde solution (CH2O) with a mass fraction of 37% to the reactor and start stirring;

[0059] (2) Slowly add a 10% NaOH solution to the above mixture to adjust the pH of the system to 9.0;

[0060] (3) Heat the system to 75°C at a constant rate and stir at this temperature for 60 minutes.

[0061] (4) When the reaction solution changes from turbid to completely transparent and clear, and no obvious white precipitate is formed when a sample is dropped into 20℃ deionized water, the reaction has reached its endpoint.

[0062] (5) Turn on the cooling water to quickly cool the reaction liquid to below 30°C, and discharge the material to obtain the highly active melamine-formaldehyde resin prepolymer.

[0063] Preparation Example 2:

[0064] This preparation example provides a method for preparing a standard reactive melamine-formaldehyde resin prepolymer, including the following steps:

[0065] (1) Add 126.1 g of melamine (C3H6N6) and 259.7 g of formaldehyde solution (CH2O) with a mass fraction of 37% to the reactor and start stirring;

[0066] (2) Slowly add a 10% NaOH solution to the above mixture to adjust the pH of the system to 8.8;

[0067] (3) Heat the system to 72°C at a constant rate and stir at this temperature for 50 minutes;

[0068] (4) Observe the reaction solution until it reaches the clear and transparent endpoint, and there is no precipitate when tested with cold water, to confirm that the reaction is complete;

[0069] (5) Turn on the cooling water to quickly cool the reaction liquid to 25°C, and discharge the material to obtain the standard active melamine-formaldehyde resin prepolymer.

[0070] Preparation Example 3:

[0071] This preparation example provides a method for preparing a medium-to-low activity melamine-formaldehyde resin prepolymer, including the following steps:

[0072] (1) Add 126.1 g of melamine (C3H6N6) and 243.5 g of formaldehyde solution (CH2O) with a mass fraction of 37% to the reactor and start stirring;

[0073] (2) Slowly add a 10% NaOH solution to the above mixture to adjust the pH of the system to 8.5;

[0074] (3) Heat the system to 70°C at a constant rate and stir at this temperature for 45 minutes;

[0075] (4) Stop heating when the system changes from turbid to transparent and meets the water dilution requirements;

[0076] (5) Turn on the cooling water to quickly cool the reaction liquid to below 30°C, and discharge the material to obtain the medium-low activity melamine-formaldehyde resin prepolymer.

[0077] Examples 1-5

[0078] Example 1:

[0079] To address the differences in the metering systems used in the pigment core synthesis stage and the outer coating modification stage, a unified definition of the raw material proportioning basis in the technical solution and specific embodiments of this invention is made here. This solution selects the reactant 2B acid as the global conversion basis. Based on the relative molecular mass of 2B acid of 235.7 grams, 235.7 parts by weight of 2B acid is defined as equivalent to 1.0 mole.

[0080] This embodiment provides a method for preparing a highly acid and alkali resistant pigment red 48:1, comprising the following steps:

[0081] (1) Diazotization: 235.7 g (1.0 mol) of 2B acid (C8H) was added to the reactor. 10 Add 1200 g of deionized water, and add 15% NaOH solution to adjust the pH to 10.5 to completely dissolve the solution. Add crushed ice to cool to 3°C, and add 31% hydrochloric acid to adjust the pH to 1.5. Add 30% sodium nitrite solution containing 1.02 mol NaNO2 dropwise over 40 minutes, controlling the temperature at 0-5°C, and react for 60 minutes to obtain a diazonium salt solution.

[0082] (2) Coupling: 191.9 g (1.02 mol) of 2,3 acid (C 11 Dissolve H8O3 in 2500g of deionized water, adjust the pH to 8.8 with liquid alkali, and cool to 8℃; steadily add the above diazonium salt solution dropwise into the coupling vessel over 80 minutes, maintaining the pH of the system at 7.8-8.0 during the dropwise addition using a 5% NaOH solution; after the dropwise addition is complete, heat to 28℃ and stir for 100 minutes.

[0083] (3) Multimetal bridging: Add 1.1 mol of 20% aqueous solution containing BaCl2·2H2O, 0.05 mol of 10% aqueous solution containing LaCl3·7H2O, and 0.1 mol of 10% aqueous solution containing Ca(CH3COO)2·H2O to the coupling solution in sequence; heat the system to 48℃ and react for 130 minutes to perform lake formation;

[0084] (4) Interface anchoring: Adjust the pH of the system to 7.0, add 5.98 g (0.02 mol) of ATMP solution, and heat to 66 °C for 40 minutes.

[0085] (5) Parallel flow hybridization: Turn on the dual metering pumps. Flow A adds a 15% aqueous solution containing 0.007 moles of ZrOCl2·8H2O, while Flow B adds a 5% NaOH solution. The flow rate of Flow B is adjusted in real time by an online pH meter to ensure that the pH fluctuation of the reaction system is controlled within 6.8±0.1. The dropping process lasts for 70 minutes.

[0086] (6) Composite coating: Add 35 g of the standard active MF prepolymer obtained in Preparation Example 2 to the system, heat to 72°C, adjust the pH to 6.2, and react for 100 minutes; cool to 52°C, add 10 g of KH560 solution, and stir for 50 minutes; then add 40 g of E44 epoxy emulsion with a solid content of 45% and 5 g of SDBS, and keep the reaction at 58°C for 160 minutes;

[0087] (7) Post-processing: The product was filtered by pressure, washed with warm water at 45°C until the conductivity of the filtrate was 450 μS / cm; dried at 90°C, and then air-jet pulverized to a particle size D. 50 It is 2.8μm.

[0088] Example 2:

[0089] This embodiment provides a method for preparing a high-load hybrid modified pigment red 48:1, including the following steps:

[0090] (1) Diazotization: Dissolve 1.0 mol of 2B acid and cool it to 2℃, adjust the pH value to 1.2; add 1.03 mol of sodium nitrite solution, react at 0-3℃ for 50 minutes to obtain a diazonium salt solution;

[0091] (2) Coupling: Dissolve 1.03 mol of 2,3 acid and adjust the pH to 9.2, then cool to 6°C; steadily add the diazonium salt solution, maintaining the pH at 8.0-8.2; after adding, raise the temperature to 30°C and keep warm for 120 minutes;

[0092] (3) Polymetallic bridging: Add solutions containing 1.15 moles of BaCl2, 0.06 moles of LaCl3 and 0.12 moles of calcium acetate in sequence; heat to 50°C and react for 150 minutes;

[0093] (4) Interface anchoring: Adjust the pH of the system to 7.2, add 7.48 g (0.025 mol) of ATMP solution, and heat to 68 °C for 45 minutes.

[0094] (5) Parallel flow hybridization: Turn on the dual-channel pump, add a solution containing 0.008 moles of ZrOCl2·8H2O dropwise from channel A, and add 5% NaOH solution dropwise from channel B simultaneously, maintaining the pH value at 7.0±0.1, and continue the dropwise addition for 80 minutes;

[0095] (6) Composite coating: Add 45 g of the highly active MF prepolymer obtained in Preparation Example 1, heat to 75°C, maintain pH at 6.5, and react for 120 minutes; cool to 55°C, add 12 g of KH560 solution, and stir for 60 minutes; add 50 g of E44 epoxy emulsion and 6 g of SDBS, and react at 60°C for 180 minutes;

[0096] (7) Post-processing: The finished product is obtained by pressure filtration, washing, drying and pulverizing.

[0097] Example 3:

[0098] This embodiment provides a method for preparing low-load hybrid modified pigment red 48:1, including the following steps:

[0099] (1) Diazotization: Dissolve 1.0 mol of 2B acid and cool to 5℃, adjust the pH to 1.8; add 1.01 mol of sodium nitrite solution and react at 5℃ for 45 minutes;

[0100] (2) Coupling: Dissolve 1.01 mol of 2,3 acid and adjust the pH to 8.5, then cool to 10°C; maintain the pH at 7.5-7.7 to complete the coupling;

[0101] (3) Polymetallic bridging: Add solutions containing 1.05 mol BaCl2, 0.03 mol LaCl3 and 0.08 mol calcium acetate sequentially; heat to 45℃ and react for 120 minutes;

[0102] (4) Interface anchoring: Adjust the pH of the system to 6.8, add 4.49 g (0.015 mol) of ATMP solution, and heat to 65 °C for 35 minutes.

[0103] (5) Parallel flow hybridization: Turn on the dual-channel pump, add a solution containing 0.005 moles of ZrOCl2·8H2O dropwise from channel A, and add 5% NaOH solution dropwise from channel B simultaneously, maintaining the pH value at 6.6±0.2, and continue the dropwise addition for 60 minutes;

[0104] (6) Composite coating: Add 25g of the low-activity MF prepolymer obtained in Preparation Example 3, heat to 70°C, keep the pH at 6.0, and react for 90 minutes; cool to 50°C, add 8g of KH560 solution, stir for 40 minutes; add 30g of E44 epoxy emulsion and 4g of SDBS, and react at 55°C for 150 minutes;

[0105] (7) Post-processing: The finished product is obtained by pressure filtration, washing, drying and pulverizing.

[0106] Example 4:

[0107] This embodiment provides a method for preparing rare earth reinforced pigment red 48:1. The process steps are basically the same as those in Example 1, except that: in step (3), the amount of LaCl3·7H2O added is adjusted to 22.3 grams (i.e., containing 0.06 moles of solute), and the amount of Ca(CH3COO)2·H2O added is adjusted to 21.1 grams (i.e., containing 0.12 moles of solute).

[0108] Example 5:

[0109] This embodiment provides a method for preparing pigment red 48:1 with optimized resin coating ratio. The process steps are basically the same as those in Example 1, except that the amount of MF prepolymer added in step (6) is adjusted to 25 grams and the amount of E44 epoxy emulsion added is adjusted to 60 grams.

[0110] Comparative Examples 1-5

[0111] Comparative Example 1:

[0112] Compared with Example 1, the difference is that in step (3), only 268.6 grams of 20% BaCl2·2H2O solution is added, and LaCl3·7H2O and Ca(CH3COO)2·H2O solutions are not added, and steps (4) and (5) are omitted, while the rest are the same.

[0113] Comparative Example 2:

[0114] Compared with Example 1, the difference is that ATMP solution is not added in step (4), but the rest are the same.

[0115] Comparative Example 3:

[0116] Compared with Example 1, the difference is that ZrOCl2·8H2O solution and the corresponding pH compensation process are not added in step (5), but the rest are the same.

[0117] Comparative Example 4:

[0118] Compared with Example 1, the difference is that in step (5), the parallel flow control process is not used. Instead, 0.007 moles of ZrOCl2·8H2O solution is directly added to the system at once, and the synchronous dynamic pH compensation of NaOH solution is not performed. All other steps are the same.

[0119] Comparative Example 5:

[0120] Compared with Example 1, the difference is that KH560 solution is not added in step (6), but the rest are the same.

[0121] Test Cases 1-5

[0122] Test Example 1:

[0123] This test case is used to quantitatively evaluate the chemical bonding strength of the modified layer on the pigment particle surface. By simulating extreme mechanical shear environments, the stability of the zirconium-phosphonic acid hybrid layer and rare earth bridging components under strong physical impact is examined, thereby verifying the effectiveness of the interface anchoring logic.

[0124] (1) Take 50.0g of the pigment products prepared in Example 1, Comparative Example 2 and Comparative Example 3 respectively, put them in beakers, add 450.0g of deionized water to each, and stir with a glass rod until the pigment is completely wetted to prepare a pigment suspension with a mass fraction of 10%.

[0125] (2) The above suspension was placed in a high-speed shear emulsifier, the rotation speed was set to 10,000 rpm, and shearing was performed continuously at room temperature for 30 minutes. During this period, the system temperature was maintained at no more than 35°C by using a circulating water jacket to eliminate the interference of thermal motion on the interface stability.

[0126] (3) After shearing, the slurry is transferred to a high-speed centrifuge and centrifuged at 12,000 rpm for 20 minutes. The supernatant is collected.

[0127] (4) The obtained clear liquid is filtered a second time using a microporous filter membrane with a pore size of 0.22 μm to ensure that the filtrate does not contain any solid pigment particles.

[0128] (5) The mass concentrations of lanthanum (La), zirconium (Zr) and phosphorus (P) in the filtrate were accurately quantitatively detected using an inductively coupled plasma optical emission spectrometer (ICP-OES). Each sample was tested in parallel three times and the average value was taken.

[0129] Test data:

[0130] Table 1. Detection results of key element content in the filtrate after high-speed shearing treatment

[0131] Detection object Lanthanum (La) concentration (mg / L) Zirconium (Zr) concentration (mg / L) Phosphorus (P) concentration (mg / L) Example 1 0.043 0.012 0.087 Example 2 0.056 0.018 0.114 Comparative Example 2 2.845 4.321 — Comparative Example 3 1.124 — 3.562 Comparative Example 4 0.782 1.456 0.893

[0132] Note: “—” in the table indicates that the component was not added during the preparation process, and therefore no specific testing was performed.

[0133] in conclusion:

[0134] The test data in Table 1 and Figure 1 and Figure 2 The distribution trend can be determined, and the interface modification system of the present invention shows obvious application advantages in terms of stability. In Example 1, the loss of the three core elements, La, Zr and P, was controlled at a trace level of less than 0.1 mg / L. This phenomenon indicates that the interface layer not only covers the pigment surface, but also forms a strong bond between the components that is difficult to be destroyed by physical shearing.

[0135] Observing the data of Comparative Example 2, after the absence of ATMP as an interfacial anchoring component, the concentrations of La and Zr in the filtrate reached 2.762 mg / L and 4.108 mg / L, respectively, which is two orders of magnitude higher than that of Example 1. Experimental observation revealed that the filtrate of the sample lacking ATMP was slightly turbid after shearing, indicating that zirconium salts and rare earth salts, without phosphonic acid groups as mediators, adhere to the pigment particle surface only through weak charge adsorption or unstable hydroxyl groups, and cannot remain stable under high-speed shear forces. Similarly, in Comparative Example 3, due to the absence of zirconium salts in constructing the hybrid framework, the loss of phosphorus reached 3.427 mg / L, reflecting that the interfacial binding energy of organophosphonic acid molecules alone is insufficient to support the high-intensity machining environment.

[0136] The test results for Comparative Example 4, although the distribution ratio was consistent with Example 1, showed a higher loss of Zr and P due to the lack of a co-current dynamic pH compensation process. This is related to the instantaneous increase in local acidity during zirconium salt addition. This uncontrolled reaction environment inhibited the coordination efficiency of zirconium ions and ATMP phosphonic acid groups, resulting in microscopic defects in the formed hybrid layer structure. Combined with experimental data, it is demonstrated that through the co-current hybrid process of this invention, zirconium ions and ATMP can achieve in-situ cross-linking on the surface of Pigment Red 48:1. The resulting network structure firmly anchors the modified components through chemical bonds. This ensures that the protective components of the pigment remain intact during subsequent extrusion, grinding, and complex media applications, thus providing a fundamental guarantee for improving the product's acid and alkali resistance.

[0137] Test Example 2:

[0138] This experiment evaluated the bonding strength between the organic coating layer and the inorganic hybrid layer on the pigment surface using a highly polar solvent reflux extraction method. Unbonded free resin components were exfoliated using a methyl ethyl ketone (MEK) / xylene mixed solvent. The effectiveness of the silane coupling agent in constructing covalent bonds at the inorganic-organic interface was verified by measuring the mass loss rate and the content of residual organic matter in the extract.

[0139] (1) Examples 1, 2 and Comparative Example 5 without KH560 coupling agent were selected as experimental subjects. The modified core without resin coating was taken as blank sample A. Each group of samples was placed in an oven at 105℃ and dried to constant weight.

[0140] (2) Accurately weigh 20.00g of each of the above groups of pigment samples (record as follows). The solvents were added separately to 250 mL stoppered ground-glass round-bottom flasks, and then 150 mL of a mixed solvent prepared by mixing butanone and xylene in a 1:1 volume ratio was added to the flasks.

[0141] (3) Connect the flask to the reflux condenser and place it in a constant temperature oil bath for heating. Maintain the solvent system at about 80°C in a micro-reflux state and continue extraction for 6 hours to ensure that the physically adsorbed epoxy resin and MF resin fully enter the solvent phase.

[0142] (4) After the extraction system has cooled to room temperature, transfer the slurry to a high-speed centrifuge tube and centrifuge at 12,000 rpm for 30 minutes.

[0143] (5) Carefully aspirate and collect the supernatant for subsequent organic content determination; add 100 mL of fresh mixed solvent to the remaining solid precipitate, treat with an ultrasonic disperser for 15 minutes to wash away the residual solvent, and then centrifuge again to collect the solid.

[0144] (6) Place the collected solid sample in a vacuum drying oven at 85℃ for 12 hours, cool it, weigh it, and record the mass of the solid obtained (recorded as follows). ).

[0145] (7) According to the formula, the mass loss rate Calculate the extraction loss of each component; at the same time, calculate the resin solids content (g / L) in the first extract using the non-volatile matter content determination method.

[0146] Test data:

[0147] Table 2. Results of pigment mass loss and organic matter content in the extract before and after solvent extraction.

[0148] Detection object initial mass (g) Post-extraction quality (g) Quality loss rate (%) Extraction solution resin concentration (g / L) Example 1 20.00 19.31 3.45 4.28 Example 2 20.00 19.23 3.85 5.06 Comparative Example 5 20.00 17.14 14.30 18.27 Blank Sample A 20.00 19.79 1.05 1.32

[0149] in conclusion:

[0150] Based on the detection data in Table 2 and Figure 3The numerical evolution trends of each sample reveal the decisive role of the coupling agent in the stability of the coating layer structure during the modification process. After high-temperature extraction with a mixed solvent, the mass loss rates of Examples 1 and 2 remained at low levels of 3.45% and 3.85%, respectively, which is roughly equivalent to the natural loss caused by the extremely fine pigment particles in blank sample A. The filtrate remained transparent after extraction, indicating that most of the MF prepolymer and epoxy resin had been stably chemically bonded to the pigment surface without large-scale dissolution or loss.

[0151] In contrast, Comparative Example 5, lacking the KH560 component, saw its mass loss rate rapidly increase to 14.30%, while the resin concentration in the extract reached 18.27 g / L. Through comparison... Figure 3 The abrupt change in slope in (a) shows that, in the absence of a silane coupling agent as a bridging medium, the subsequently added organic resin can only coat the inorganic hybrid layer through intermolecular van der Waals forces or weak physical entanglement. Due to the poor compatibility between the organic polymer and the inorganic oxide interface, the penetration of the mixed solvent easily disrupts this unstable physical adsorption, leading to severe detachment of the coating layer during reflux.

[0152] This difference stems from the unique interface design logic of this scheme. During the preparation process of this embodiment, the siloxane end of KH560 forms Si-O-Zr / P covalent bonds with the zirconium and phosphorus hydroxyl groups on the pigment surface through a hydrolysis reaction, while the epoxy functional groups at its other end enter the organic layer and undergo cross-linking reactions with E44 epoxy resin and MF prepolymer. This chemical bonding across the inorganic-organic phases integrates the originally discrete modified components into a unified whole. The experimentally measured low leaching rate directly proves that this chemical anchoring layer possesses extremely strong resistance to solvent erosion, providing solid experimental evidence for the long-term color stability and chemical inertness of Pigment Red 48:1 in various ink and coating systems.

[0153] Test Example 3:

[0154] This experiment assesses the effect of the modified layer on the surface polarity of pigments and its steric hindrance effect in the application medium by monitoring the viscosity evolution and particle size distribution fluctuations of pigments in organic resin systems, thereby verifying the actual contribution of interface modification to inhibiting pigment particle flocculation.

[0155] (1) Example 1, Example 2, Comparative Example 1 (unmodified raw powder) and Comparative Example 4 were selected as experimental subjects. Each group of samples was placed at 80°C and vacuum dried for 4 hours to remove physically adsorbed water.

[0156] (2) Weigh 60.0g of long-oil alkyd resin, 30.0g of xylene and 10.0g of the above pigment sample and put them into a stainless steel grinding jar. Add an equal mass of glass beads and disperse them using a vibrating mill. The grinding time is uniformly set to 60 minutes to prepare a paint with a pigment mass fraction of 10%.

[0157] (3) After grinding, use a 200-mesh filter to remove the glass beads and transfer the resulting paint to a sealed glass bottle.

[0158] (4) The initial dynamic viscosity of the paint was measured using a rotational viscometer, and the initial median particle size of the pigment in the system was determined using a laser particle size analyzer.

[0159] (5) The sealed paint sample was placed in a 50℃ constant temperature drying oven for accelerated aging test for 15 days to simulate long-term storage process.

[0160] (6) After the set time is reached, take out the sample and wait for it to return to room temperature. Measure its viscosity and median particle size again without additional stirring.

[0161] (7) The dispersion stability of pigments in organic media is quantitatively evaluated by calculating the viscosity growth rate and particle size change rate.

[0162] Test data:

[0163] Table 3 Comparison of viscosity and median particle size of paint before and after storage

[0164] Detection object Initial viscosity (mPa·s) Viscosity after aging (mPa·s) Initial particle size (μm) Particle size after aging (μm) Example 1 246.3 278.5 0.284 0.312 Example 2 258.7 294.6 0.296 0.337 Comparative Example 1 312.4 845.2 0.342 1.156 Comparative Example 4 284.1 532.8 0.315 0.684

[0165] in conclusion:

[0166] Based on the test data shown in Table 3 and Figure 4 The numerical trends reflect that the modified structure of the pigment surface has a decisive influence on improving its rheological stability in the application medium. In Example 1, the viscosity increase after aging was minimal, increasing only from the initial 246.3 mPa·s to 278.5 mPa·s. This physical stability mainly stems from the successfully constructed zirconium-phosphonic acid hybrid layer on the pigment surface and the subsequent cross-linked organic shell. As a typical metallic lake pigment, Pigment Red 48:1 has a large number of highly active metal sites on its surface, which readily chemically associate with the acid groups of resins in polar systems such as alkyd resins, leading to a severe tendency for flocculation and thickening.

[0167] Comparative experiments clearly revealed the consequences of the lack of a protective layer. After the aging period, the viscosity of untreated Comparative Example 1 surged to 845.2 mPa·s, and the median particle size increased from 0.342 μm to 1.156 μm, indicating irreversible and strong agglomeration between particles. In actual observation, this group of samples exhibited typical gelation phenomena in the later stages of storage. Even Comparative Example 4, which underwent chemical modification but lacked dynamic pH compensation control, still showed a particle size increase exceeding 100%, reflecting that the loose hybrid network could not block the resin chain's induction of activity on the particle surface during prolonged thermal motion.

[0168] This performance difference further confirms the technical value of the multi-layer gradient modification mechanism in this scheme. The dense hybrid network formed by zirconium, phosphorus, and rare earth elements not only physically shields the high-energy active sites on the pigment surface but also provides sufficient steric hindrance by introducing long-chain organic components. Figure 4 The data in (b) show that the particle size fluctuation in Example 1 was successfully limited to within 10%, meaning that the pigment particles maintained a stable dispersion of primary particles even during the accelerated thermal motion lasting up to 15 days. This result provides a closed-loop proof that the precise interface modification process not only improves the adhesion of the coating layer but also fundamentally solves the coarsening defect commonly found in lake pigments in industrial coating applications.

[0169] Test Example 4:

[0170] This test simulates an extreme acidic application environment and monitors the changes in colorimetric parameters of pigments in a strongly acidic medium in real time. The aim is to quantitatively evaluate the chemical shielding effectiveness of the interface modification layer against hydrogen ions and its protective strength against the core structure of lake pigments.

[0171] (1) The finished pigments prepared in Examples 1 and 2 were selected as experimental groups, and Comparative Example 1 (untreated raw powder) and Comparative Example 3 (lacking zirconium salt hybrid components) were selected as control samples. The samples in each group were dried at 60°C and mechanically crushed and sieved.

[0172] (2) Accurately weigh 15.0g of each group of pigment samples and put them into ground glass bottles containing 200mL of 5% hydrochloric acid solution. Place the ground glass bottles on a magnetic stirrer, keep the system temperature at 25℃ and set the speed at 300rpm, so that the pigment particles are in a uniform suspension state in the acidic medium.

[0173] (3) At five characteristic time points after the start of the immersion experiment, 2h, 6h, 12h, 24h and 48h, 10mL of suspension was taken with a pipette and quickly filtered under reduced pressure through a 0.45μm filter membrane.

[0174] (4) Wash the filter cake multiple times with deionized water until the pH of the filtrate returns to between 6.8 and 7.2 to ensure that residual acid is washed away. Then place the sample in an 80°C vacuum drying oven to dry to constant weight.

[0175] (5) Using a precision colorimeter, under D65 standard light source and 10° observation angle conditions, the colorimetric properties of pigment particles at various time points after drying were measured, and the initial sample and samples at each stage were recorded. , , value.

[0176] (6) According to the color difference calculation formula Calculate the total color difference of the pigment at each time point relative to its initial untreated state.

[0177] Test data:

[0178] Table 4. Record of the evolution of total color difference value of pigments during strong acid impregnation.

[0179] Detection object 2h 6h 12h 24h 48h Example 1 0.42 0.67 1.03 1.22 1.48 Example 2 0.49 0.82 1.18 1.56 1.94 Comparative Example 1 3.56 8.12 14.73 23.41 36.85 Comparative Example 3 1.94 4.38 8.95 13.72 21.06

[0180] in conclusion:

[0181] Based on the experimental data in Table 4 and Figure 5 The slope change of the color difference evolution curve shows that the protective layer constructed by the in-situ interface hybridization technology of this invention exhibits excellent chemical inertness under extremely acidic conditions. In Example 1, after 48 hours of continuous strong acid etching, the total color difference only slightly increased from the initial state to 1.48, and the color difference curve as a whole showed obvious passivation characteristics, without the exponential increase seen in the comparative example. This phenomenon directly reflects the extremely high cross-linking density of the hybrid network formed by zirconium ions, ATMP, and rare earth elements, whose physical barrier effectively restricts the diffusion of hydrogen ions into the pigment crystal.

[0182] Performance gaps were observed in the comparative experiments. Comparative Example 1, the unmodified raw powder, showed a color difference exceeding 14.73 after 12 hours of immersion. During the experiment, the acid solution gradually changed from colorless to pale red, indicating that the strong acid had destroyed the barium salt bridging structure in the pigment molecules, leading to hydrolysis and decolorization of the azo pigment groups. Even Comparative Example 3, which included some modified components but lacked zirconium salt to construct the hybrid framework, achieved a final color difference value of 21.06. This demonstrates that a single organophosphonic acid adsorption layer, under the osmotic pressure of a strong electrolyte, struggles to maintain interfacial integrity and cannot fundamentally block the chemical erosion of the acidic medium.

[0183] The corrosion resistance of this embodiment stems from its unique gradient interface design. The zirconate-phosphonate network structure generated under the co-current dynamic pH compensation process not only microscopically blocks the active sites on the pigment surface but also firmly anchors the subsequent epoxy-MF resin layer through covalent bonding, thereby forming a dense shell layer with a "molecular sieve" effect on the pigment particle surface. This multi-coordination synergistic shielding mechanism ensures that Pigment Red 48:1 maintains long-term hue stability in acidic application environments, successfully overcoming the technical defects of traditional lake pigments that are susceptible to fading or discoloration due to acidic ion attack.

[0184] Test Example 5:

[0185] This experiment simulates the high-temperature environment of industrial processing and monitors the fluctuation of chromaticity parameters of pigments under different temperature gradients. The aim is to verify the thermal protection effectiveness of the surface hybrid coating layer for pigment chromophores and its application adaptability in high-temperature plastic processing or baking paint systems.

[0186] (1) Example 1, Example 2, Comparative Example 1 (untreated raw powder) and Comparative Example 2 (only organic resin coating without inorganic hybrid layer) were selected as experimental objects, and the pigments in each group were vacuum dried at 80°C to constant weight.

[0187] (2) Weigh 100.0g of low-density polyethylene (LDPE) granules, add 0.5g of the pigment sample to be tested, and premix in a high-speed mixer for 5 minutes to ensure that the pigment is evenly distributed in the resin matrix.

[0188] (3) Granulation was performed using a twin-screw extruder, and then the resulting masterbatch was fed into an injection molding machine. The injection pressure was set to 80 MPa, the residence time to 5 minutes, and the processing temperatures were set to 180℃, 200℃, 220℃, 240℃, 260℃ and 280℃ respectively.

[0189] (4) Five standard color patches (50mm×50mm×3mm) were continuously injection molded at each temperature node, and three of the color patches in the middle state were used for subsequent color measurement experiments.

[0190] (5) A precision colorimeter was used to measure the color difference of each group of color samples at different temperatures. , , Value. Using a color sample processed at 180℃ as a reference, calculate the total color difference value corresponding to each of the other temperature points. .

[0191] (6) By analyzing the evolution of color difference with increasing temperature, the effect of the modified layer on the thermo-oxidative degradation process of pigment core is evaluated.

[0192] Test data:

[0193] Table 5. Results of total color difference detection for pigment chips at different processing temperatures.

[0194] Detection object 200℃ 220℃ 240℃ 260℃ 280℃ Example 1 0.32 0.54 0.87 1.21 1.63 Example 2 0.38 0.61 0.94 1.35 1.88 Comparative Example 1 2.15 5.48 12.33 24.15 38.62 Comparative Example 2 1.24 3.12 7.56 13.84 22.47

[0195] in conclusion:

[0196] Based on the measured data recorded in Table 5 and Figure 6 The kinetic curve of color difference change with processing temperature reveals the protective mechanism of the interface-modified structure of this invention on the pigment color development system under extreme processing conditions. In Example 1, under a high-temperature injection molding environment of 280℃, the total color difference value was recorded as only 1.63, and this value remained consistent throughout the entire temperature range of 200℃ to 280℃. Figure 6 The slope of the curve in (a) remains stable throughout, without any significant numerical jumps. This improvement in thermal stability is mainly due to the dense coating network formed by the in-situ hybridization reaction of zirconium ions, ATMP, and rare earth elements. This network acts as the main protective layer, isolating the pigment particles from the physical impact and chemical degradation caused by external high heat energy.

[0197] The numerical differences in the comparative experiments further revealed the influence of different interface layers on the thermo-oxidative degradation process. In the unmodified Comparative Example 1, the color difference value showed an almost exponential increase after the processing temperature exceeded 220℃, reaching 38.62 at 280℃, accompanied by a decrease in the transmittance of the pigment slices and obvious carbonization color shift observed in the experiments. This phenomenon is usually related to the vibrational failure and oxidative breakage of azo bonds and metal salt bridges in the Pigment Red 48:1 molecular structure at high temperatures. Even in Comparative Example 2, which had an organic resin coating layer, the rate of color difference increase increased after 240℃ (final color difference 22.47), indicating that a single organic polymer layer, when approaching its decomposition temperature, loses its shielding effectiveness due to intensified chain segment movement or thermal softening, making it difficult to block the conduction of heat energy to the pigment core during plastic melting and processing.

[0198] This performance hierarchy validates the thermodynamic stability advantage of the zirconium-phosphonic acid hybrid layer constructed in this scheme. By introducing rare earth elements at the interface, the atomic packing density and lattice matching between the modified layer and the pigment core are enhanced, microscopically suppressing thermally induced structural stress relaxation. Figure 6 The color difference growth rate analysis in the high-temperature range reflected in (b) shows that the fading kinetic frequency of Example 1 is much lower than that of other control groups, which proves that the multilayer gradient structure has a very strong physical barrier effect in high-temperature melts. The experimental results demonstrate that the present invention, by accurately constructing an inorganic-organic hybrid interface, not only solves the problem of chemical stability of pigments in room temperature systems, but also significantly broadens the application temperature window of metallic lake pigments in the field of high-heat plastic processing.

[0199] Test Example 6:

[0200] This experiment simulates the ultraviolet radiation environment in natural sunlight, monitors the color difference evolution and tinting strength retention rate of pigments during continuous exposure, thereby evaluating the shielding and protection effectiveness of the surface hybrid coating layer on the color development structure of pigment molecules, and verifying the absorption and quenching effect of rare earth elements on ultraviolet light energy.

[0201] (1) Example 1, Example 2, Comparative Example 1 (untreated raw powder) and Comparative Example 5 (modified sample lacking rare earth element doping) were selected as experimental subjects.

[0202] (2) Each group of pigments was formulated into standard polyethylene masterbatch, and a standard sample with a thickness of 1.5 mm was prepared by compression molding machine at 180°C.

[0203] (3) Accelerated exposure experiments were conducted using a xenon lamp aging test chamber, with the blackboard temperature set at 65℃, relative humidity at 50%, and irradiance at 0.51 W / m². 2 It simulates the sunlight exposure environment under hot and humid climate.

[0204] (4) The total experimental duration was set to 500 hours. Samples were taken out at time points of 100h, 200h, 300h, 400h and 500h respectively, and the colorimetric parameters of each sample were measured using a colorimeter.

[0205] (5) Record the total color difference value of each sample relative to the initial state (0h). The relative tinting strength retention rate of the pigment was calculated using a multi-point measurement method.

[0206] (6) By comparing the color difference growth slope of different test nodes, the ability of the modified layer to block free radical oxidation reaction under long-term light irradiation is evaluated.

[0207] Test data:

[0208] Table 6. Results of total color difference and tinting strength retention of pigments during accelerated photoaging.

[0209] Detection object 100h 200h 300h 400h 500h Coloring power retention (%) Example 1 0.45 0.88 1.12 1.67 2.14 97.2 Example 2 0.52 0.94 1.35 1.92 2.48 96.1 Comparative Example 1 3.12 7.45 12.86 21.04 32.75 64.3 Comparative Example 5 1.28 2.67 4.82 7.15 11.34 85.6

[0210] in conclusion:

[0211] According to the data in Table 6, after 500 hours of continuous xenon lamp accelerated exposure, the total color difference increment in Example 1 was controlled at 2.14, and the final measured tinting strength retention rate reached 97.2%. From the appearance of the samples in the later stages of the experiment, the surface gloss of the modified pigment was basically consistent with the initial state, and no obvious whitening of the resin matrix or fading of the pigment was observed. This resistance to photodegradation is mainly attributed to the zirconium-phosphonic acid-rare earth ternary hybrid layer constructed on the pigment surface. In the test environment of alternating strong ultraviolet radiation and humid heat, this dense interface layer effectively blocked the diffusion rate of oxygen and moisture into the pigment lattice, thereby physically cutting off the reaction pathway for the generation of free radicals such as hydrogen peroxide.

[0212] Comparative analysis of the data from Comparative Example 1 (raw powder) reveals that untreated metallic lake pigments exhibit extremely high sensitivity to ultraviolet radiation. After 200 hours of exposure, the color difference curve of Comparative Example 1 shows a sharp increase, ultimately reaching 32.75, accompanied by significant fading and surface chalking during the experiment. This failure is mainly attributed to the breakage of the azo bonds in the Pigment Red 48:1 molecule under the influence of high-energy photons, leading to the disruption of the chromogenic conjugated system. In Comparative Example 5, although the inorganic-organic framework provides some physical shielding, the lack of rare earth element doping still results in a color difference of 11.34 after 500 hours. This observation confirms the importance of rare earth components in improving photostability.

[0213] From a microscopic perspective, the long-term stability exhibited by the embodiments stems from the synergistic effect of multiple protective mechanisms. The hybrid network not only provides physical shielding but also converts high-energy radiation into harmless heat energy through the absorption and quenching mechanism of rare-earth ions on ultraviolet light, preventing free radical-induced chain degradation. Combined with... Figure 7 The tinting strength data shown in (b) demonstrates that this interface modification process enables the pigment to maintain the optical properties of the primary particles even under long-term irradiation. The above experimental closed-loop results prove that this scheme solves the technical problem of easy fading of lake pigments in outdoor high ultraviolet environments by controlling the composition and structure of the interface layer, providing reliable data support for its long-term application in the field of high-performance coatings.

Claims

1. A highly acid and alkali resistant pigment red 48:1, characterized in that, Based on 1.0 mol, which is equivalent to 235.7 parts by weight, it is prepared from the following proportions of raw materials: 2B acid: 1.0 mol; Sodium nitrite: 1.01-1.03 mol; 2,3-acid: 1.01-1.03 mol; Barium salt: 1.05-1.15 mol; Rare earth lanthanum salts: 0.03-0.06 mol; Calcium salt: 0.08-0.12 mol; Aminotrimethylenephosphonic acid: 0.015-0.025 mol; Zirconium salt: 0.005-0.008 mol; Melamine-formaldehyde resin prepolymer: 25-45 parts by weight; Epoxy resin emulsion: 30-60 parts by weight; Silane coupling agent: 8-12 parts by weight; Surfactant: 4-6 parts by weight; The raw materials are polymerized in situ on the surface of the pigment core to form an inorganic-organic hybrid coating layer.

2. The highly acid and alkali resistant pigment red 48:1 according to claim 1, characterized in that, The barium salt is barium chloride, the rare earth lanthanum salt is lanthanum chloride, and the calcium salt is calcium acetate; The zirconium salt is zirconium oxychloride octahydrate.

3. The highly acid and alkali resistant pigment red 48:1 according to claim 1, characterized in that, The epoxy resin emulsion is an E44 epoxy resin emulsion with a solid content of 45%. The silane coupling agent is KH560, and the surfactant is sodium dodecylbenzenesulfonate.

4. The highly acid and alkali resistant pigment red 48:1 according to claim 1, characterized in that, The melamine-formaldehyde resin prepolymer is prepared by reacting melamine with a formaldehyde solution of 37% by mass under alkaline conditions, and the mass ratio of melamine to formaldehyde solution is 126.1:(243.5-284.1).

5. A preparation process for a highly acid and alkali resistant pigment red 48:1, characterized in that, The preparation of the highly acid and alkali resistant pigment red 48:1 according to any one of claims 1-4 comprises the following steps: The 2B acid is dissolved and cooled, and then a solution of sodium nitrite is added dropwise under acidic conditions to carry out a diazotization reaction to obtain a diazonium salt solution. The 2,3 acid was dissolved and adjusted to a weakly alkaline state, then cooled. The diazonium salt solution was then added dropwise to carry out a coupling reaction to obtain a coupling solution. An aqueous solution containing the barium salt, the rare earth lanthanum salt, and the calcium salt is added sequentially to the coupling solution, and the temperature is raised to carry out a lake-forming reaction to obtain a lake suspension. The pH value of the lake suspension is adjusted, a solution containing the aminotrimethylenephosphonic acid is added, and the temperature is raised to carry out a constant temperature reaction to achieve interface anchoring, thereby obtaining an anchored suspension. An aqueous solution containing the zirconium salt and an alkaline solution are simultaneously and concurrently added dropwise to the anchoring suspension. During the dropwise addition process, the pH value of the reaction system is dynamically kept constant through online feedback to complete the inorganic hybrid reaction and obtain an inorganic hybrid suspension. The pH value of the lake suspension is adjusted, a solution containing the aminotrimethylenephosphonic acid is added, and the temperature is raised to carry out a constant temperature reaction to achieve interface anchoring, thereby obtaining an anchored suspension. The melamine-formaldehyde resin prepolymer was added to the inorganic hybrid suspension to carry out the first-stage coating reaction, followed by cooling and adding the silane coupling agent while stirring. Finally, the epoxy resin emulsion and the surfactant were added to carry out the second-stage heat preservation reaction to obtain the composite coated suspension. The composite-coated suspension was subjected to pressure filtration, washing, drying and pulverization to obtain highly acid and alkali resistant pigment red 48:

1.

6. The preparation process of a highly acid and alkali resistant pigment red 48:1 according to claim 5, characterized in that, The temperature of the diazotization reaction is controlled at 0-5℃; In the coupling reaction, during the addition of the diazonium salt solution, the pH of the reaction system is maintained between 7.5 and 8.2 by adding alkali solution in conjunction with the addition. After the addition is completed, the temperature is raised to 28-30℃ and stirred for 100-120 minutes.

7. The preparation process of a highly acid and alkali resistant pigment red 48:1 according to claim 5, characterized in that, The temperature of the lake formation reaction is controlled at 45-50℃, and the reaction time is 120-150 minutes; Before adding the aminotrimethylenephosphonic acid solution, adjust the pH of the lake suspension to 6.8-7.2, and then heat it to 65-68℃ and react at a constant temperature for 35-45 minutes.

8. The preparation process of a highly acid and alkali resistant pigment red 48:1 according to claim 5, characterized in that, The alkaline solution added simultaneously and in parallel is a 5% (w / w) NaOH solution; During the parallel-flow dropwise addition process, the specific fluctuation range of the pH value of the reaction system is controlled within 6.4-7.1 to maintain a dynamic constant pH value.

9. The preparation process of a highly acid and alkali resistant pigment red 48:1 according to claim 5, characterized in that, In the first-stage coating reaction, the temperature is raised to 70-75℃, the pH of the reaction system is adjusted to 6.0-6.5, and the reaction is carried out for 90-120 minutes; The process of adding the silane coupling agent and stirring is as follows: cool down to 50-55℃ and stir for 40-60 minutes; In the second stage of the heat preservation reaction, the temperature is controlled at 55-60℃ and the reaction time is 150-180 minutes.

10. The preparation process of a highly acid and alkali resistant pigment red 48:1 according to claim 5, characterized in that, The melamine-formaldehyde resin prepolymer was prepared in advance through the following process: Melamine and a 37% formaldehyde solution were added to the reaction vessel, and NaOH solution was added dropwise to adjust the pH of the reaction system to 8.5-9.

0. Heat the reaction solution to 70-75℃ at a constant rate and stir for 45-60 minutes. When the reaction solution is completely transparent and clear, and no precipitation occurs when a sample is dropped into 20°C deionized water, cool it down to below 30°C and discharge the material.

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