A modified organic pigment and a method for preparing the same

Abstract

This invention relates to the field of organic pigment preparation technology, specifically to a modified organic pigment and its preparation method. This invention overcomes the problems of easy quenching, poor migration resistance, and poor dispersibility of fluorescent pigments. In an isopropanol system, long-chain alkylsilanes and epoxysilanes are co-hydrolyzed to pre-crosslink the pigment surface, forming a flexible transition layer with a spatial buffering effect. Then, isocyanate-modified fluorescent monomers are modified with polyetheramine to prepare fluorescent intermediates with long-chain structures. The deformation ability of the flexible chain segments penetrates the gaps in the hybrid layer. The modified pigment is introduced into an isoalkyl oil phase containing a polymeric dispersant to form reverse microemulsion droplets, resulting in in-situ crosslinking to construct a highly crosslinked hydrophobic polymer barrier on the outermost layer. This enhances the thermo-photodynamic stability and chemical migration resistance of the pigment, achieving excellent nighttime fluorescence gain while improving its compatibility in engineering plastics.

Description

Technical Field

[0001] This invention relates to the field of organic pigment preparation technology, specifically to a modified organic pigment and its preparation method. Background Technology

[0002] Organic pigments, due to their wide color gamut, strong tinting strength, and vibrant colors, have been widely used in high-end industrial fields such as plastics, coatings, and specialty inks. However, organic pigments still face many technical limitations in practical applications. Because of their low surface energy and strong hydrophobicity, particles are prone to secondary agglomeration during processing, leading to decreased color uniformity. Simultaneously, during high-temperature extrusion or injection molding, conventional organic pigments often experience crystal drift due to insufficient thermal stability, resulting in color deviation and limited migration resistance, making it difficult to meet the stringent requirements of modern industry for high-performance colorants.

[0003] With the increasing demand for high-visibility performance in safety labeling and specialty coatings, the development of composite pigments with fluorescent effects has become a focus of the industry. Existing technologies mostly modify the surface of pigments by introducing fluorescent molecules or inorganic nanomaterials. However, existing physical coating or adsorption processes have significant drawbacks: on the one hand, the lack of strong chemical bonds between the modified layer and the pigment core makes it easy for functional components to detach at high temperatures or in polar solvents, resulting in bleeding and migration. On the other hand, when rigid nanomaterials with excellent thermal stability, such as cage-like polysilsesquioxanes, are introduced for modification, the significant steric hindrance of these molecules makes it difficult for them to achieve high-density arrangement at the pigment micro-interface, resulting in gaps in surface protection and preventing the formation of an effective physical shield.

[0004] Furthermore, current surface treatment methods largely rely on disordered polymerization within a macroscopic system, lacking precise control over the reaction space. This often leads to large-scale self-aggregation and adhesion of pigment particles during modification, resulting in massive aggregates. This not only causes a dramatic increase in the oil absorption of modified pigments, increasing resin consumption in downstream applications, but also generates extremely high filtration pressure during filtration and extrusion, easily clogging filter screens and severely impacting production efficiency.

[0005] In summary, overcoming the steric hindrance interference of rigid nanomodifiers at the interface, solving the migration problem of functional molecules under complex working conditions, and effectively controlling particle aggregation during the modification process to reduce oil absorption are objective and urgent technical challenges in the commercialization of high-performance organic pigments.

[0006] To address this, a modified organic pigment and its preparation method are proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a modified organic pigment and its preparation method. This overcomes the problems of easy quenching, poor migration resistance, and poor dispersibility of fluorescent pigments. In an isopropanol system, long-chain alkylsilanes and epoxysilanes are co-hydrolyzed to pre-crosslink the pigment surface, forming a flexible transition layer with a steric buffer effect. Then, isocyanate-modified fluorescent monomers are modified with polyetheramine to prepare a fluorescent intermediate with a long-chain structure. The deformation ability of the flexible chain segments penetrates the gaps in the hybrid layer. The modified pigment is introduced into an isoalkyl oil phase containing a polymeric dispersant to form reverse microemulsion droplets, resulting in in-situ crosslinking to construct a highly crosslinked hydrophobic polymer barrier on the outermost layer. This enhances the thermo-photodynamic stability and chemical migration resistance of the pigment, achieving excellent nighttime fluorescence gain, while also improving its compatibility in engineering plastics.

[0008] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing modified organic pigments, the preparation method being as follows: Diisocyanate was reacted with polyetheramine to generate a single-terminated flexible isocyanate prepolymer, which was then reacted with fluorescent molecules to obtain a fluorescent intermediate. The pigment core was mixed with a flexible long-chain silsesquioxane hybrid sol, a catalyst was added, and the mixture was injected into an oil phase containing a dispersant for high-speed shear activation. A fluorescent intermediate is added dropwise to the system, and the mixture is heated to a constant temperature of 82-95℃ and stirred for 8-15 hours to obtain a precursor. Polymer monomers are added to the precursor, and a confined polymerization reaction is carried out at 78-85℃ for 6-10 hours under the action of an initiator to obtain a modified organic pigment.

[0009] The preferred method for preparing the flexible long-chain silsesquioxane hybrid sol is as follows: A solvent is added to the system and the temperature is raised. A silane monomer and a long-chain flexible coupling agent are added to the solvent and mixed. Hydrochloric acid aqueous solution is added dropwise under constant temperature stirring. After the addition is complete, a hydrolysis-condensation reaction is carried out at 60-65℃ for 8-16 hours to obtain the flexible long-chain silsesquioxane hybrid sol. Through the co-hydrolysis-condensation of the silane monomer and the long-chain coupling agent, a hybrid sol containing a cage-like silsesquioxane structure is generated in situ. The introduction of the long-chain coupling agent connects the POSS cages with flexible alkyl chains, forming an elastic underlayer with a steric buffering effect when subsequently anchored to the pigment surface.

[0010] Preferably, the silane monomer is selected from silanes with epoxy functional groups, such as 3-glycidoxypropyltrimethoxysilane or 2-(3,4-ethoxycyclohexyl)ethyltrimethoxysilane, where the epoxy group can provide chemical binding sites with the fluorescent intermediate and polymer shell in the later stage; the long-chain flexible coupling agent is selected from 1,10-bis(trimethoxysilyl)decane or 1,12-bis(trimethoxysilyl)dodecane, where the long alkyl chain provides steric buffer; the solvent is isopropanol, and in addition to isopropanol, alcohol solvents such as ethanol, n-butanol, and ethylene glycol monobutyl ether, or mixtures thereof with water can also be selected.

[0011] Preferably, the preparation method of the fluorescent intermediate is as follows: diisocyanate is added, nitrogen gas is introduced and polyetheramine is added to carry out a prepolymerization reaction at 45-50℃ to obtain a flexible isocyanate prepolymer; fluorescent molecules are added to the flexible isocyanate prepolymer, and the reaction is continued after heating to obtain the fluorescent intermediate; A single-terminated prepolymer formed by the reaction of isocyanate and polyetheramine allows fluorescent molecules to be attached to the ends of flexible polyether chains. Due to the extremely high degree of rotational freedom of polyetheramine, these tentacles can penetrate the gaps in the hybrid layer formed by POSS and react directly with the residual hydroxyl groups on the pigment surface. At the same time, the active groups on its chain segments undergo addition with the epoxy groups in the hybrid layer, thus avoiding the shielding effect of the rigid cage structure of POSS on the macromolecular fluorophores.

[0012] The diisocyanate is isophorone diisocyanate; the polyetheramine is selected from ED-600, ED-900, and D-400; ED-600 is an aliphatic polyether diamine with polyethylene oxide (EO) as the main backbone, an average molecular weight of 600, and an EO / PO ratio of 9.0 / 3.6, exhibiting good hydrophilicity and moderate span; ED-900 is an aliphatic polyether diamine containing high polyethylene oxide (EO), with longer flexible segments, an average molecular weight of 900, and an EO / PO ratio of 12.5 / 6.0, providing ultra-long flexible span; D-400 is polypropylene oxide diamine with a hydrophobic all-polypropylene oxide (PO) backbone and a pure PO backbone, providing high structural density and hydrophobicity, with an average molecular weight of 430.

[0013] The fluorescent molecule is FluoroYellow 8G.

[0014] The pigment core used in this invention is preferably a high-performance organic pigment, such as quinacridone red R-122, selected from products of Jiangsu Liwang New Material Technology Co., Ltd. This pigment has excellent weather resistance and brightness, but its surface polarity is low, making it difficult to form a strong interface using traditional coating methods. Besides R-122, the method of this invention can also be extended to other organic pigments with surface hydroxyl groups or active sites, such as DPP red, phthalocyanine blue, quinacridone yellow, and inorganic pigments such as titanium dioxide and iron oxide red.

[0015] Preferably, the activation process is as follows: Oil-phase isoalkanes are added to a reactor, and after dissolving the dispersant Hypermer 2296, a shearing process is initiated at 10000-15000 rpm for 30-60 minutes to obtain an oil-phase system. The pigment quinacridone red R-122 is mixed with a flexible long-chain silsesquioxane hybrid sol, and the catalyst triethylenediamine is added and injected into the oil-phase system for activation by shearing. In the isoalkane oil phase, high shear force confines the pigment particles within microemulsion droplets, allowing free radical polymerization to occur within the confined space inside the droplets. This ensures that the polymer shell is densely and uniformly wrapped around the flexible anchoring layer-POSS hybrid layer-fluorescent chain, forming a stable multilayer core-shell structure.

[0016] Preferred method for preparing modified organic pigments is as follows: After cooling the precursor, polymer monomers are added, nitrogen gas is introduced, and at the same time, the initiator is dissolved in toluene to obtain an initiator solution. The initiator solution is pumped into the initiator solution at a constant speed using a peristaltic pump, and the reaction is carried out after heating.

[0017] The polymer monomers are selected from at least two combinations of lauryl methacrylate, tripropylene glycol diacrylate, and isooctyl acrylate; lauryl methacrylate provides a hydrophobic shell; tripropylene glycol diacrylate acts as a crosslinking agent to improve shell strength; and isooctyl acrylate is used to adjust the shell's flexibility.

[0018] The initiator is selected from diisopropyl peroxide and benzoyl peroxide; when using diisopropyl peroxide, the temperature is controlled at 45-60℃ and the reaction time is controlled at 16-20h.

[0019] Preferably, the refining process involves pressure filtration and washing with toluene at elevated temperature; washing with n-hexane to remove residual oil-phase surfactants; washing with anhydrous ethanol 1-2 times; and finally washing with deionized water until neutral; followed by flash drying and air jet milling of the washed material.

[0020] The present invention also provides a modified organic pigment, the raw materials for which the modified organic pigment is prepared include a flexible long-chain silsesquioxane hybrid sol, a fluorescent intermediate, a polymer monomer and a dispersant; the modified organic pigment is used for coloring engineering plastics or for safety warning materials.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. A flexible transition layer composed of long-chain alkylsilane 1,12-bis(trimethoxysilyl)decane was pre-deposited on the surface of quinacridone red R-122. The free rotation of the long chain segments eliminated the steric hindrance caused by the rigid nanocage structure of polysilsesquioxane, and the inorganic hybrid layer was continuously coated on the pigment surface. This physical shielding layer effectively blocked environmental erosion, reducing the heat resistance color difference ΔE of Example 3 to 0.4 and improving the light fastness to level 8.

[0022] 2. Flexible polyetheramine molecular chains with an average molecular weight of 600-900 are attached to the ends of fluorescent molecules to construct an active intermediate with a high collision cross-sectional area. This allows the intermediate to overcome the physical barrier of the surface POSS layer and form strong urethane covalent bonds with the active functional groups on the pigment surface. The structure inhibits chromophore aggregation and quenching, resulting in a fluorescence gain of up to 156%, while ensuring a stable migration resistance of level 5 and preventing bleeding.

[0023] 3. In the continuous phase of nonpolar isoparaffin, reverse microemulsion droplets with diameters in the micrometer range are constructed using polymeric dispersants. This confines the monomer polymerization reaction within independent droplet spaces and induces in-situ crosslinking of the polymer on the pigment surface, forming a uniform hydrophobic shielding shell. This prevents particle aggregation and reduces the oil absorption of the single group from 52 ml / 100 g to 31 ml / 100 g, significantly improving the fluidity and surface gloss of the pigment in downstream applications.

[0024] 4. Utilizing the in-situ ring-opening addition reaction between the highly reactive epoxy groups remaining in the long-chain silsesquioxane hybrid sol and the outer acrylate monomer at 80-95℃, a cross-linked shell with a three-dimensional network structure is constructed. Furthermore, by introducing long-chain lauryl methacrylate monomers, the polar pigment surface is transformed into a non-polar oleophilic surface. By utilizing the highly reactive epoxy groups of the flexible long-chain silsesquioxane hybrid sol to undergo ring-opening addition with the outer monomer, a three-dimensional cross-linked network is constructed, and oleophilic long chains are introduced. This surface modification reduces polar repulsion, decreases dispersibility, and effectively solves the problem of filter clogging under high-load processing. Attached Figure Description

[0025] Figure 1 The results show the changes in elution rate of modified organic pigments with elution time, color difference with heating time, and average particle size with standing time in Examples 1 and Comparative Example 2 of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Please see Figure 1 This invention provides a modified organic pigment and its preparation method, the technical solution of which is as follows: Example 1

[0028] In a four-necked flask equipped with a stirrer, thermometer and condenser, 400 ml of isopropanol was added as a solvent. Stirring was started and the system was heated to 60 °C. Then, 120 g of 3-glycidoxypropyltrimethoxysilane and 30 g of 1,10-bis(trimethoxysilyl)decane were added to the solvent and mixed thoroughly. Under constant temperature and stirring conditions, 3g of 0.1mol / L hydrochloric acid aqueous solution was added dropwise at a rate of 3 drops / second using a constant pressure dropping funnel. After the addition was completed, the hydrolysis and condensation reaction was carried out at a constant temperature of 60℃ for 12h to obtain a semi-transparent flexible long-chain silsesquioxane hybrid sol.

[0029] In a four-necked flask equipped with a stirrer, thermometer, constant pressure dropping funnel and nitrogen delivery tube, first add 50g of isophorone diisocyanate, and then slowly add 40g of polyetheramine ED-600 through the dropping funnel under nitrogen protection and stirring. The system temperature was controlled at 45℃ for 4 hours to allow one isocyanate group of isophorone diisocyanate to fully react with the amino group of polyetheramine, generating a single-terminated flexible isocyanate prepolymer. During the reaction, infrared spectroscopy was used to monitor the reaction at 2270 cm⁻¹. -1 The intensity change of the -NCO characteristic peak was observed. After it decreased to 50% of the initial intensity of the theoretical value, 20g of 8g of fluorescent yellow was added to the flask. Subsequently, the system was heated to 75°C and stirred continuously for 6 hours. At this time, the residual isocyanate groups at the end of the prepolymer formed covalent bonds with the active groups on the fluorescent molecules, and finally a fluorescent intermediate with flexible polyether segments and a tentacle-like structure was obtained.

[0030] S1: Flexible surface activation of pigment nuclei In a 5L clean jacketed reactor, 1800ml of isoparaffin was added as the oil phase, and 60g of the polymeric dispersant Hypermer 2296 was dissolved. The reactor was then subjected to high-speed shearing at 12000rpm for 5min. 500g of Liwang Quinacridone Red R-122 was mixed with 200g of flexible long-chain silsesquioxane hybrid sol, and 5g of triethylenediamine catalyst was added. This mixture was then injected into the oil phase; the reactor was sheared at 12000rpm for 45min. Within the microemulsion droplets, the long-chain coupling agent preferentially forms a flexible structure on the pigment surface, with the POSS cage positioned above the flexible structure, eliminating the influence of steric hindrance on anchoring.

[0031] S2: Directed chemical bonding of flexible tentacles 120g of fluorescent intermediate was slowly added dropwise to the S1 system. The addition was completed in 30min. The temperature was then increased from room temperature (20℃) to 88℃ at a rate of 4℃ / min, and the mixture was stirred at a constant temperature for 10h.

[0032] The isocyanate groups at the ends of the fluorescent intermediate react with the residual hydroxyl groups on the pigment surface through the gaps between the POSS cages; simultaneously, the segments of the fluorescent intermediate undergo ring-opening addition with the epoxy groups of the flexible long-chain silsesquioxane hybrid sol. The introduction of the flexible chain increases the effective collision rate of the reaction by more than 200%.

[0033] S3: Reverse micelle confinement polymerization The system was cooled to 75°C, and 120g of lauryl methacrylate and 60g of tripropylene glycol diacrylate were added. High-purity nitrogen was purged for 20 minutes, and 4g of initiator benzoyl peroxide was dissolved in 50g of toluene and added at a constant rate over 2 hours using a peristaltic pump. The temperature was raised to 80°C and the reaction was carried out for 8 hours. By utilizing the physically confined space of the reverse emulsion droplets, a dense hydrophobic cross-linked shell was in situ coated around the flexible POSS-fluorescent layer.

[0034] S4: Dynamic centrifugal washing and purification After the reaction is complete, the temperature is lowered. A dynamic washing and filtration system is used for treatment: three pressure filtrations with 60°C toluene are performed to ensure the elution of ungrafted free fluorescent molecules; two washes with n-hexane are performed to remove oil-phase surfactants; one to two replacement washes with anhydrous ethanol are performed; and finally, a final wash with deionized water is performed to adjust the pH to neutral.

[0035] S5: Airflow drying and pigment molding The wet powder is fed into a flash dryer with an inlet air temperature of 120°C and an outlet air temperature of 70°C. The resulting dry powder is then fed into a supersonic airflow pulverizer to obtain a composite fluorescent pigment with a multi-layer structure consisting of a flexible anchoring layer, a flexible long-chain silsesquioxane hybrid sol layer, a flexible fluorescent chain, and a polyacrylate shell.

[0036] Example 2

[0037] Add 400 ml of isopropanol as a solvent, start stirring and heat the system to 60 °C; then, add 105 g of 3-glycidoxypropyltrimethoxysilane and 45 g of 1,12-bis(trimethoxysilyl)dodecane to the solvent and mix thoroughly; under constant temperature stirring, add 3 g of 0.1 mol / L hydrochloric acid aqueous solution dropwise at a rate of 3 drops / second using a constant pressure dropping funnel; after the addition is complete, maintain a constant temperature of 60 °C for hydrolysis and polycondensation reaction for 16 h to obtain a semi-transparent flexible ultra-long chain silsesquioxane hybrid sol.

[0038] First, add 45g of isophorone diisocyanate and 70g of polyetheramine ED-900; under nitrogen protection and stirring, heat the system to 45℃ and react for 4h to generate a single-end-capped flexible isocyanate prepolymer; then, add 15g of fluorescent yellow 8G to the flask and further heat to 70℃ and react for 6h to obtain a fluorescent intermediate with ultra-long flexible chain segments.

[0039] S1: Flexible surface activation of pigment nuclei Add 1800 ml of isoparaffin as the oil phase to a 5 L clean jacketed reactor, dissolve 70 g of Hypermer 2296 polymeric dispersant, start high-speed shearing at 10000 rpm for 5 min, mix 500 g of Liwang quinacridone red R-122 with 250 g of flexible long-chain silsesquioxane hybrid sol, add 5 g of triethylenediamine catalyst, and inject into the oil phase; maintain shearing at 10000 rpm for 60 min.

[0040] S2: Directed chemical bonding of flexible tentacles 150g of the fluorescent intermediate prepared in Example 2 was slowly added dropwise to the S1 system over 30 minutes. The temperature was then increased from room temperature (20°C) to 82°C at a rate of 4°C / min, and stirred at this constant temperature for 15 hours. The ultra-long polyether segments (ED-900) endow the fluorophore with higher spatial freedom, further reducing collisional steric hindrance.

[0041] S3: Reverse micelle confinement polymerization The system was cooled to 70°C, and 100g of lauryl methacrylate and 40g of isooctyl acrylate were added; high-purity nitrogen was purged for 20 minutes. 4g of benzoyl peroxide initiator was dissolved in 50g of toluene and added at a uniform rate over 2 hours using a peristaltic pump; the temperature was then raised to 78°C, and the reaction was allowed to proceed for 10 hours. A tough protective shell was constructed using monomers with low glass transition temperatures.

[0042] S4: Dynamic centrifugal washing and purification Same as in Example 1.

[0043] S5: Airflow drying and pigment molding Same operation as in Example 1. The product has a longer flexibility span and exhibits extremely high low-light sensitivity at night.

[0044] Example 3

[0045] Add 400 ml of isopropanol as a solvent, start stirring and heat the system to 65 °C; then, add 140 g of 2-(3,4-ethoxycyclohexyl)ethyltrimethoxysilane and 10 g of long-chain flexible coupling agent to the solvent and mix thoroughly; under constant temperature stirring, add 3 g of 0.1 mol / L hydrochloric acid aqueous solution at a rate of 3 drops / second using a constant pressure dropping funnel; after the addition is complete, maintain a constant temperature of 65 °C for hydrolysis and polycondensation reaction for 8 h to obtain a semi-transparent, highly active silsesquioxane hybrid sol.

[0046] First, add 60g of isophorone diisocyanate and 30g of polyetheramine D-400; under nitrogen protection and stirring, heat the system to 50℃ and react for 3h to generate a single-end-capped flexible isocyanate prepolymer; then, add 30g of fluorescent yellow 8G to the flask and further heat to 75℃ and react for 5h to obtain a flexible bridging fluorescent intermediate with high color intensity.

[0047] S1: Flexible surface activation of pigment nuclei Add 1800 ml of isoparaffin as the oil phase to a 5 L clean jacketed reactor, dissolve 60 g of polymeric dispersant, start high-speed shearing at 15000 rpm for 5 min, mix 500 g of Liwang Quinacridone Red R-122 with 200 g of the prepared flexible long-chain silsesquioxane hybrid sol, add 5 g of triethylenediamine catalyst, and inject into the oil phase; maintain shearing at 15000 rpm for 30 min.

[0048] S2: Directed chemical bonding of flexible tentacles 120 g of the prepared fluorescent intermediate was slowly added dropwise to the S1 system over 30 min. The temperature was then increased from room temperature (20 °C) to 95 °C at a rate of 4 °C / min, and stirred at this constant temperature for 8 h. High-density bonding was achieved using the highly reactive cyclohexyl epoxy group under high-temperature kinetics.

[0049] S3: Reverse micelle confinement polymerization The system was cooled to 75°C, and 80g of lauryl methacrylate and 100g of tripropylene glycol diacrylate were added. High-purity nitrogen was purged for 20 min, and 5g of initiator BPO was dissolved in 50g of toluene and added at a constant rate over 2 h using a peristaltic pump. The temperature was then raised to 85°C, and the reaction was allowed to proceed for 6 h. A dense shell with high cross-linking density was constructed.

[0050] S4: Dynamic centrifugal washing and purification Same as in Example 1.

[0051] S5: Airflow drying and pigment molding The procedure is the same as in Example 1. The product exhibits excellent resistance to processing temperatures above 295°C and weather resistance.

[0052] Comparative Example 1: Rigid shielding group lacking flexible chain segments In a four-necked flask equipped with a stirrer, thermometer, and condenser, 400 ml of isopropanol was first added as a solvent. Stirring was started and the system was heated to 60 °C. Then, 150 g of 3-glycidoxypropyltrimethoxysilane was added to the solvent. Under constant temperature and stirring, 3 g of 0.1 mol / L hydrochloric acid aqueous solution was added dropwise at a rate of 3 drops / second using a constant pressure dropping funnel. After the addition was completed, the hydrolysis and polycondensation reaction was carried out at a constant temperature of 60 °C for 12 h to obtain a rigid silsesquioxane sol without a flexible substrate.

[0053] 50g of isophorone diisocyanate and 20g of fluorescein 8G were added directly; under nitrogen protection and stirring, the system was heated to 70℃ and forced to react at a constant temperature for 10h to obtain a rigid fluorescent product without a flexible buffer chain.

[0054] S1: Rigid surface activation of pigment nuclei Add 1800 ml of isoalkanes as the oil phase to the jacketed reactor, dissolve 60 g of dispersant, and start high-speed shearing at 12000 rpm for 5 min. Mix 500 g of Liwang R-122 with 200 g of the rigid-flexible long-chain silsesquioxane hybrid sol prepared in Comparative Example 1, and inject into the oil phase; maintain shearing at 12000 rpm for 45 min, and the POSS cage adheres tightly to the pigment surface, forming a physical shield.

[0055] S2: Hindered directional chemical bonding 120 g of the rigid fluorescent intermediate prepared in Comparative Example 1 was slowly added dropwise to the S1 system over 30 min. The temperature was then increased from 20 °C to 88 °C and maintained at this temperature with stirring for 10 h. Due to the high rigidity of the molecular chain and the lack of a flexible pedestal support, the fluorophore had difficulty penetrating the steric hindrance layer.

[0056] S3: Reverse micelle confinement polymerization Following the same steps as in Example 1, a polyacrylate shell is wrapped around the surface.

[0057] S4: Dynamic centrifugal washing and purification Same as in Example 1.

[0058] S5: Airflow drying and pigment molding Same procedure as in Example 1. The product exhibits poor migration resistance, significant loss of fluorescent molecules during washing, and extremely low fluorescence brightness at night. Comparative Example 2 This group does not involve the pre-preparation of intermediates. All raw materials, including 3-glycidyl etheroxypropyltrimethoxysilane, long-chain coupling agent, isopropanol, hydrochloric acid, isophorone diisocyanate, polyetheramine, and fluorescent yellow, will be added directly to the reaction system according to the process nodes during the subsequent implementation phase of the complete technical solution.

[0059] S1: Macroscopic Dispersion Activation Instead of using the oil phase, 2000ml of ethanol was used as the medium. The mixture was stirred at 800rpm. 500g of Liwang R-122, 120g of 3-glycidyl etheroxypropyltrimethoxysilane monomer, 30g of long-chain coupling agent, 40g of polyetheramine, 50g of isophorone diisocyanate and 20g of fluorescent yellow 8G were added at once without stepwise pre-processing or reverse emulsification.

[0060] S2: Disordered thermal reaction The temperature was increased from 20℃ to 65℃ and stirred at a constant temperature for 24 hours. Due to the lack of confined control, the components underwent random self-aggregation and physical stacking.

[0061] S3: Macroscopic solution polymerization Add 120g lauryl methacrylate and 60g tripropylene glycol diacrylate, and purge with nitrogen for 20 minutes. Add 4g of ammonium persulfate aqueous solution dropwise, and react for 8 hours.

[0062] S4: Centrifugal purification Conventional centrifugal washing processes are inefficient due to the disordered adhesion of particles.

[0063] S5: Airflow drying and molding The procedure is the same as in Example 1. The product has extremely high oil absorption, contains a large number of coarse color spots, easily clogs the screen during processing, and has no obvious fluorescence.

[0064] Test Example 1 The control group consisted of pure organic pigment powder, specifically high-performance quinacridone red R-122 raw. To verify the practical performance of the pigments in the examples and comparative examples in plastic systems, the following performance tests were conducted: Dispersibility was determined according to GB / T 21867.2-2008, using a twin-screw extruder, passing through a 630-mesh filter under specific pressure, and measuring the increase in filtration pressure as the amount of pigment passed through.

[0065] The heat resistance stability is in accordance with GB / T 1713-2008. After the pigment is made into a masterbatch, it is held at 280℃ for 5 minutes in an injection molding machine and compared with a standard sample processed at 200℃. The color difference ΔE is measured using a colorimeter.

[0066] For migration resistance, refer to GB / T 5211.10-2020. Overlap the injection-molded color film with a white PVC sheet and place it under 70℃ and 5kg load for 24 hours. Observe the staining of the white sheet and evaluate the level according to the gray scale, from level 1 to 5, with level 5 being the best.

[0067] The nighttime fluorescence sensitivity was determined according to the laboratory's own standards, referring to the ISO 3864-4 safety color standard. In a completely dark room, 365nm ultraviolet light was used for excitation, and the luminous intensity per unit area was measured with a luminance meter. The ratio was calculated with the control group. The relative intensity (%) = (sample luminance / standard sample luminance) × 100%.

[0068] The characteristics were primarily described through visual observation, assessing the pigment's transparency, color bias (red / yellow hue), and surface gloss within the resin. The final test results are summarized in Table 1.

[0069] Table 1 Comprehensive performance test results

[0070] The example group exhibits good overall performance. Fluorescent molecules are firmly attached to the pigment surface through covalent bonds, preventing migration problems caused by physical adsorption. At the same time, flexible bridging counteracts the steric hindrance of POSS, resulting in a modified layer coverage of nearly 100% and a low ΔE value. Furthermore, reverse emulsification ensures that pigment particles are individually coated in micron-sized droplets, preventing particle fusion and accumulation.

[0071] The control group exhibited typical characteristics of high-performance organic pigments. Although it had a certain degree of temperature resistance, its molecular structure began to undergo microscopic crystal form shift at 280℃, resulting in a large ΔE. Due to the complete lack of fluorescent loading and a closed shell, its migration resistance was poor among polar materials, which could not meet the requirements of high-end labeling.

[0072] The results of the comparative examples were lower than those of the control group. Comparative Example 1 showed a migration resistance of only level 2 and weak fluorescence gain. Due to the lack of a flexible long-chain coupling agent as a flexible link, the rigid POSS cage structure was tightly distributed on the pigment surface. Due to the steric hindrance effect, the fluorescent intermediate could not effectively approach and react with the hydroxyl groups on the pigment core surface, resulting in most fluorescent molecules being physically adsorbed on the surface. During processing tests, free molecules easily migrated to the PVC sheet under high temperature and load. Comparative Example 2 showed even higher dispersibility than the control group, but the worst heat resistance. Without the confinement effect of the microreactor for reverse emulsification, the reaction probability of each component became disordered in the macroscopic ethanol medium. Due to the difference in solubility of monomers and coupling agents in water / alcohol, self-aggregation often occurred. This not only led to large-scale bridging of pigment particles to form hard aggregates, but also caused fluorescent molecules to be randomly encapsulated, resulting in concentration quenching. Consequently, the fluorescence brightness was even lower than the background noise caused by heat-induced color change.

[0073] Test Example 2 Further physicochemical constants and chemical stability tests were conducted. For oil absorption, referring to GB / T 5211.15-2014, linseed oil was added dropwise to the pigment sample, and the mixture was ground with a palette knife until a continuous clump was formed.

[0074] The solvent resistance stability is determined according to GB / T 5211.9-2008. The pigment powder is placed in a strong polar solvent such as toluene and soaked at room temperature for 24 hours. The clear liquid is then filtered out. The solvent staining grade is evaluated by measuring the transmittance of the clear liquid or by using a gray scale, ranging from 1 to 5, with grade 5 indicating no staining.

[0075] Lightfastness was tested according to GB / T 1710-2008, using a xenon lamp aging test chamber with an irradiance of 550 W / m². The color difference was tested after the cumulative energy reached a specific threshold, and the blue wool standard was used for rating, from 1 to 8, with 8 being the highest. The final test results are summarized in Table 2.

[0076] The study included: immersing the modified pigment in toluene and continuously monitoring the absorbance changes of free fluorescent molecules in the solvent; placing the modified pigment in a 200°C air oven and measuring the color difference every few hours to examine the duration of antioxidant protection of the polyacrylate hydrophobic shell on the pigment core; and dispersing the pigment in an oil phase and allowing it to stand, using dynamic light scattering to monitor the average particle size to examine the ability of the modified layer to prevent secondary aggregation of pigment particles. The final test results over time are as follows: Figure 1 As shown.

[0077] Table 2. Physicochemical constants and chemical stability results

[0078] Figure 1 The comparative test over time showed that, due to the construction of the three-in-one structure of covalent anchoring-flexible buffering-sealing packaging, the fluorescence elution rate of Example 1 remained below 0.1% for 168 hours, which was much lower than that of Comparative Example 1. This indicates that the flexible chain bridging not only improves the collision probability in the early stage of the reaction, but also solves the problem of easy bleeding and color change of high-performance organic pigments during long-term use on a macroscopic scale.

[0079] As shown in Table 2, the example group formed a dense inorganic POSS-organic crosslinked resin hybrid shell on the pigment surface through reverse emulsification confined polymerization. This shell greatly reduced the free energy and microporosity of the pigment surface, thereby reducing the amount of oil absorbed. At the same time, the dense physical shielding layer blocked the dissolution of pigment molecules by external solvents and the chemical degradation of organic chromophores by ultraviolet light.

[0080] The control group R-122 pigment has the typical high specific surface area characteristics of organic pigments, resulting in a relatively high oil absorption of 52ml / 100g. Although R-122 itself has a lightfastness rating of 7, it exhibits partial dissolution in the highly polar solvent toluene due to the lack of a chemically inert shell, and shows limitations under the more stringent lightfastness requirement of 8.

[0081] Due to the lack of bridging effect of flexible long chains, the rigid POSS cage structure in Comparative Example 1 could not form a complete flat coverage on the irregular surface of the pigment. Instead, it was deposited in a dotted or island-like manner. The discontinuous modification resulted in the pigment surface still retaining a large number of high-energy sites and microporous structures, making the oil absorption close to that of the control group. Furthermore, steric hindrance prevented the fluorescent molecules and polymer shell from being tightly grafted. Solvent molecules could penetrate into the pigment core through the gaps between the POSS cages, causing solvent discoloration. At the same time, ultraviolet light could directly irradiate the unprotected pigment area, thus impairing the lightfastness. In Comparative Example 2, the microemulsion confinement effect was lost, and the components underwent random polymerization in the macroscopic system. The pigment particles adhered randomly to the polymers and silanes, forming a large number of loose and porous giant aggregates. The capillary effect greatly enhanced the adsorption of oil, resulting in a surge in oil absorption to 68 ml / 100 g. Due to the non-directional coating, the pigment particles were not completely encapsulated but were fragmented and embedded in the matrix. The solvent easily dissolved the pigments through the pores inside the aggregates. The low average molecular weight oligomers formed by self-segmentation were easily decomposed under ultraviolet light, accelerating the aging and fading of the overall color.

Claims

1. A method for preparing a modified organic pigment, characterized by, The preparation method is as follows: Diisocyanate was reacted with polyetheramine to generate a single-terminated flexible isocyanate prepolymer, followed by the addition of fluorescent molecules to obtain a fluorescent intermediate; pigment cores were mixed with flexible long-chain silsesquioxane hybrid sol, a catalyst was added and injected into an oil phase containing a dispersant for shear activation. The fluorescent intermediate was added dropwise to the system, and the mixture was heated and stirred at a constant temperature to obtain a precursor. Polymer monomers were added to the precursor, and a confined polymerization reaction was carried out under the action of an initiator to obtain the modified organic pigment.

2. The method for producing a modified organic pigment according to claim 1, characterized by, The preparation method of the flexible long-chain silsesquioxane hybrid sol is as follows: a solvent is added to the system and the temperature is raised. The silane monomer and the long-chain flexible coupling agent are added to the solvent and mixed. Hydrochloric acid aqueous solution is added dropwise under constant temperature stirring. After the addition is completed, a hydrolysis and polycondensation reaction is carried out at 60-65℃ for 8-16 hours to obtain the flexible long-chain silsesquioxane hybrid sol.

3. The method for preparing the modified organic pigment according to claim 2, characterized in that, The silane monomer is selected from one of 3-glycidoxypropyltrimethoxysilane and 2-(3,4-ethoxycyclohexyl)ethyltrimethoxysilane; The long-chain flexible coupling agent is selected from 1,10-bis(trimethoxysilyl)decane and 1,12-bis(trimethoxysilyl)dodecane; the solvent is isopropanol.

4. The method for preparing the modified organic pigment according to claim 1, characterized in that, The fluorescent intermediate is prepared as follows: the diisocyanate is added, nitrogen gas is introduced, and the polyetheramine is added and prepolymerized at 45-50°C to obtain the flexible isocyanate prepolymer; the fluorescent molecule is added to the flexible isocyanate prepolymer, and the reaction is continued after heating to obtain the fluorescent intermediate. The diisocyanate is isophorone diisocyanate; the polyetheramine is selected from ED-600, ED-900 and D-400; the fluorescent molecule is fluorescent yellow 8G.

5. The method for preparing the modified organic pigment according to claim 1, characterized in that, The activation is as follows: the oil-phase isoparaffin is added to the reactor, the dispersant is dissolved and then sheared to obtain the oil-phase system; the pigment quinacridone red R-122 is mixed with the flexible long-chain silsesquioxane hybrid sol, triethylenediamine is added and injected into the oil-phase system, and the activation is performed by shearing.

6. The method for preparing the modified organic pigment according to claim 1, characterized in that, The modified organic pigment is prepared as follows: after cooling the precursor, the polymer monomer is added, nitrogen gas is introduced, and at the same time, the initiator is dissolved in toluene to obtain an initiator solution. The initiator solution is pumped into the initiator solution at a constant speed through a peristaltic pump, and the reaction is carried out after heating. The polymer monomer is selected from at least two combinations of lauryl methacrylate, tripropylene glycol diacrylate, and isooctyl acrylate; the initiator is selected from one of diisopropyl peroxide and benzoyl peroxide.

7. The method for preparing the modified organic pigment according to claim 1, characterized in that, The refining process involves pressure filtration and washing with toluene; washing with n-hexane to remove residual oil-phase surfactants; washing with deionized water until neutral; and then flash drying and air jet milling of the washed product.

8. A modified organic pigment obtained by the preparation method of claim 1, characterized in that, The raw materials for preparing the modified organic pigment include flexible long-chain silsesquioxane hybrid sol, fluorescent intermediates, polymer monomers, and dispersants; the modified organic pigment is used for coloring engineering plastics or safety warning materials.

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