Titanium dioxide and its processing method and application in plastic color master batch

Abstract

This invention proposes a titanium dioxide and its processing method, as well as its application in plastic masterbatches. The method involves high-speed dispersion to expose the hydroxyl groups on the surface of the titanium dioxide, followed by deprotonation of cyclodextrin under alkaline conditions, leading to an in-situ reaction with the titanium dioxide to obtain a stable core-shell structure with titanium dioxide as the core and cyclodextrin as the shell. The modified titanium dioxide is firmly anchored through chemical bonding. Its shell acts as a physical barrier to prevent agglomeration and provides interfacial lubrication, while the cyclodextrin cavity allows for the targeted loading of functional molecules, achieving integrated coloring, antibacterial, and antioxidant functions. When this titanium dioxide is used to prepare highly filled masterbatches, it can significantly reduce processing viscosity and temperature, completely eliminate the risk of small molecule migration, and possess excellent dispersibility, processing flowability, and long-lasting functionality, making it widely applicable in high-end fields such as food packaging, medical devices, and engineering plastics.

Description

[Technical Field] This invention belongs to the field of titanium dioxide processing technology, and particularly relates to a titanium dioxide and its processing method, and its application in plastic masterbatch. [Background Technology] Titanium dioxide (TiO2) is a white powder with titanium dioxide as its main component. It has excellent optical properties and chemical stability, and is an essential white pigment and light-shielding agent in the plastics industry. However, the inherent high surface energy of nano- or submicron-sized titanium dioxide particles makes them prone to agglomeration in non-polar or weakly polar polymer matrices, which seriously affects the color uniformity, mechanical properties, and surface gloss of the products.

[0001] Currently, the main technology for improving the dispersibility of titanium dioxide is inorganic-organic composite coating technology, but it has some drawbacks. As shown in Chinese invention patent application CN107640785A, although this method can improve dispersibility, its effect drops sharply in masterbatches with high pigment content (>60%), resulting in high melt viscosity and difficult processing. Moreover, traditional organic treatment agents are mostly physical adsorption or weak bonding, which are prone to desorption and migration during high-temperature and high-shear processing, posing safety hazards, and cannot endow titanium dioxide with additional functional properties.

[0002] Cyclodextrin is a cone-shaped cyclic compound with a hydrophilic outer shell composed of hydroxyl groups and an internal hydrophobic cavity formed by CH bonds. Due to its unique structure, it plays a significant role in the synthesis of many drugs; however, its use in plastic modification is rarely reported, or it is only used as an additive in direct blending. As shown in Chinese invention patent application CN117866313A, although cyclodextrin has potential functional inclusion capabilities, its interaction with titanium dioxide as an antistatic agent is merely a physical mixture, failing to form a strong interfacial bond. Under the high-temperature, high-shear environment of plastic processing, free cyclodextrin is prone to migration or thermal decomposition, offering negligible improvement in dispersibility and failing to achieve site-specific, long-lasting loading of functional molecules at coloring sites. [Summary of the Invention] The purpose of this invention is to provide a titanium dioxide that solves the technical problems existing in the prior art, such as a sharp decline in dispersion effect at high pigment content, easy desorption and migration of traditional organic treatment agents, and difficult processing.

[0003] This invention is achieved by the following technical solution: A titanium dioxide, comprising titanium dioxide particles and an organic coating layer covering the surface of the titanium dioxide particles; The organic coating layer is formed from cyclodextrin or its derivatives; The organic coating layer is anchored to the surface of the titanium dioxide particles by chemical bonding or strong intermolecular forces. The content of the organic coating layer is 0.5-5% of the mass of the titanium dioxide particles.

[0004] This invention employs a core-shell structure design, with titanium dioxide particles as the "core" and an organic coating layer formed by cyclodextrin or its derivatives as the "shell." This organic coating layer is firmly anchored to the surface of the titanium dioxide particles through chemical bonding or strong intermolecular forces. This dense organic coating layer allows for better polymer compatibility, while the steric hindrance between cyclodextrin molecules effectively blocks contact between titanium dioxide particles, effectively inhibiting agglomeration. During melt processing, it significantly reduces interfacial friction, providing excellent lubrication. Furthermore, by utilizing the unique hydrophobic cavity structure of cyclodextrin, this shell layer can serve as a site-specific loading platform for functional molecules. Whether through pre-encapsulation before the reaction or secondary adsorption after the reaction, functional molecules (such as antibacterial agents, antioxidants, etc.) can be firmly fixed at the coloring sites, achieving an integrated "coloring as function," ensuring the long-lasting effectiveness and migration resistance of the functional properties.

[0005] Preferably, the cyclodextrin is selected from one of β-cyclodextrin and γ-cyclodextrin; the derivative is selected from one of hydroxypropyl-β-cyclodextrin, carboxymethyl-β-cyclodextrin, and succinyl-β-cyclodextrin.

[0006] This invention can use β-cyclodextrin or γ-cyclodextrin with specific cavity sizes to achieve precise matching between their molecular structure and the surface structure of titanium dioxide particles, ensuring high density and high loading capacity of the shell. Alternatively, water-soluble derivatives such as hydroxypropyl, carboxymethyl, or succinyl can be used to overcome the uneven reaction caused by the low solubility of natural cyclodextrin. The active groups introduced by the derivatives (such as carboxyl and hydroxyl groups) can undergo more efficient dehydration condensation reaction with the hydroxyl groups on the surface of titanium dioxide or form a strong hydrogen bond network under alkaline conditions, significantly improving the anchoring strength and heat resistance stability of the shell.

[0007] Preferably, the titanium dioxide particles are rutile titanium dioxide.

[0008] Preferably, the surface of the titanium dioxide particles is coated with an inorganic oxide layer.

[0009] The present invention does not restrict the source of the titanium dioxide; commercially available finished titanium dioxide with inorganic oxide surface treatment can be used directly, or self-prepared inorganic coated titanium dioxide can be used.

[0010] Preferably, the inorganic oxide layer is selected from one or more of alumina and silicon oxide.

[0011] This invention utilizes the high-density active hydroxyl groups abundant on the surface of inorganic oxide layers (such as alumina and silicon dioxide) to provide sufficient reaction sites for the in-situ construction of cyclodextrin molecules. This ensures efficient dehydration condensation or the formation of a dense, strong hydrogen bond network in an alkaline aqueous environment, thereby achieving a firm chemical anchoring and uniform coverage of the organic shell on the surface of titanium dioxide. Simultaneously, this inorganic oxide layer acts as a physical barrier to effectively shield the photocatalytic activity of the titanium dioxide core, preventing photogenerated free radicals from degrading and damaging the surface cyclodextrin organic layer and polymer matrix, significantly improving the weather resistance and long-term safety of the treated titanium dioxide. Furthermore, the inorganic oxide layer also synergistically optimizes the charge characteristics and wetting behavior of the particle surface, assisting in the rapid adsorption and directional arrangement of cyclodextrin molecules in the slurry, thus constructing an inorganic-organic dual protection system.

[0012] A method for treating titanium dioxide includes the following steps: S1. Slurry preparation: Add titanium dioxide granules to deionized water and disperse at 5000-8000 rpm for 2-6 hours to obtain titanium dioxide slurry. S2. Activation and reaction: Heat the titanium dioxide slurry from step S1 to 60-85℃, add an alkaline solution dropwise while stirring and adjust the pH to 9.5-11.0, then slowly add an aqueous solution of cyclodextrin or its derivatives and stir at a constant temperature for 6-12 hours to obtain a mixed slurry. S3. Post-processing: After the reaction in step S2 is completed, the mixed slurry is filtered and washed with deionized water to remove free unreacted substances and the alkaline solution until the conductivity of the filtrate is <50μS / cm. The filter cake is dried at 90-110℃ for 24h and then pulverized with airflow to a particle size of 0.2-0.3μm to obtain the final product.

[0013] This invention utilizes vigorous physical stirring to break up agglomerates of titanium dioxide particles, maximizing the exposure of their specific surface area and surface-active hydroxyl groups, laying the physical foundation for subsequent uniform contact with cyclodextrin molecules; furthermore, under alkaline conditions, it induces the deprotonation of the hydroxyl groups (-OH) on the outer edge of the cyclodextrin to form highly nucleophilic oxygen anions (-O). - This process promotes a highly efficient reaction between the cyclodextrin and the titanium dioxide surface, forming a strong chemical bond or strong hydrogen bond network in situ. At the same time, slow feeding effectively avoids the self-agglomeration of cyclodextrin caused by local supersaturation. Subsequently, by strictly controlling the washing endpoint to a low conductivity, unreacted free cyclodextrin and residual alkali are thoroughly removed, thereby eliminating the safety hazard of small molecule migration and precipitation. Finally, with the help of specific drying and air jet milling processes, the soft agglomeration during the drying process is further broken up, giving the product excellent flowability and long-term dispersion stability.

[0014] Preferably, the solid content of the titanium dioxide slurry in step S1 is 20-40%.

[0015] This invention achieves excellent rheological properties in the reaction system by controlling the solid content of the titanium dioxide slurry. On the one hand, it ensures that the titanium dioxide particles are fully depolymerized and the surface active hydroxyl groups are maximized during high-speed dispersion, while also ensuring that subsequent cyclodextrin molecules diffuse rapidly and uniformly to the particle surface, thereby achieving a dense and uniform coating. On the other hand, it imparts a suitable heat capacity to the system, facilitating rapid temperature response and uniform distribution during heating, effectively avoiding side reactions or coating layer structural defects caused by local temperature differences, and ensuring the integrity of the core-shell structure.

[0016] Preferably, the mass ratio of the cyclodextrin or its derivative to the titanium dioxide in step S2 is (0.5-5):100.

[0017] Preferably, the alkaline solution in step S2 is selected from one of NaOH, KOH, or NH3•H2O.

[0018] An application of titanium dioxide in plastic masterbatch, wherein the plastic masterbatch comprises the following components by weight: 45-75 parts titanium dioxide; 20-55 parts of carrier resin; Dispersing lubricant 1-8 parts; Antioxidant 0-3 parts.

[0019] The carrier resin is selected from polypropylene (PP), polyethylene (PE), acrylonitrile-butadiene-styrene copolymer (ABS), polystyrene (PS), polyethylene terephthalate (PET), and other high molecular weight compounds in granular or powder form; the dispersing lubricant is selected from waxes, stearic acid and its salts, or amide dispersants.

[0020] This invention applies high-concentration cyclodextrin-coated titanium dioxide to plastic masterbatches, utilizing the unique effect of its surface organic coating in the molten state to significantly reduce interparticle frictional resistance and the interfacial frictional resistance between particles and between particles and the resin matrix, thereby greatly reducing shear heat generation. Compared to using ordinary titanium dioxide, the extrusion temperature of the finished product is significantly lower, effectively avoiding the risk of thermal degradation and yellowing of the carrier resin and functional additives caused by high temperatures.

[0021] This invention proposes a titanium dioxide with a stable core-shell structure, consisting of titanium dioxide particles as the "core" and cyclodextrin and its derivatives as the "shell." This structure is firmly anchored through chemical bonding, acting as a physical barrier to prevent aggregation and providing interfacial lubrication. Furthermore, the cyclodextrin cavity serves as a site-specific loading platform for functional molecules, achieving a long-lasting integrated effect of coloring properties and functional characteristics (such as antibacterial and antioxidant properties).

[0022] This invention proposes a method for treating titanium dioxide. High-speed dispersion breaks up titanium dioxide agglomerates, exposing surface-active hydroxyl groups. Under alkaline conditions, cyclodextrin hydroxyl groups are deprotonated, enabling them to react efficiently with the titanium dioxide surface, constructing a robust chemical bond or strong hydrogen bond network in situ. Slow feeding prevents self-agglomeration. Low-conductivity washing removes free impurities to eliminate migration risks. Finally, drying and air-jet milling break up soft agglomerates. The resulting product exhibits excellent flowability, dispersion stability, and low migration characteristics, making it suitable for preparing high-performance plastic masterbatches.

[0023] This invention proposes an application of titanium dioxide in plastic masterbatch. The masterbatch contains high-concentration cyclodextrin-coated titanium dioxide, which has low processing viscosity, high coloring efficiency and optional multifunctional properties. It can effectively solve the problems of high-filler processing and functional migration risks, and can be widely used in high-end products such as food packaging, medical devices, children's products and engineering plastics.

Detailed Implementation Methods

[0024] Example 2 A method for treating titanium dioxide includes the following steps: S1. Pulping: Add titanium dioxide particles with an alumina layer on the surface and a particle size of 0.2-0.3μm to deionized water and disperse at 6000rpm for 6h to obtain titanium dioxide slurry with a solid content of 30%. S2. Activation and reaction: The titanium dioxide slurry from step S1 is heated to 70°C, and 10% NaOH solution is added dropwise while stirring and the pH is adjusted to 11. Then, 5% γ-cyclodextrin aqueous solution is slowly added at a rate of 3 drops / s and the mixture is stirred at a constant temperature for 12 hours to obtain a mixed slurry. The mass ratio of γ-cyclodextrin to titanium dioxide is 3:100. S3. Post-processing: After the reaction in step S2 is completed, the mixed slurry is filtered and washed with deionized water to remove free unreacted substances and the alkaline solution until the conductivity of the filtrate is <50μS / cm. The filter cake is dried at 110℃ for 24h and then air-jet pulverized to a particle size of 0.2-0.3μm to obtain the final product.

[0025] Example 3 A method for treating titanium dioxide includes the following steps: S1. Pulping: Add titanium dioxide particles with an alumina layer on the surface and a particle size of 0.2-0.3μm to deionized water and disperse at 8000rpm for 6h to obtain titanium dioxide slurry with a solid content of 40%. S2. Activation and Reaction: The titanium dioxide slurry from step S1 is heated to 80°C. While stirring, 10% NaOH solution is added dropwise and the pH is adjusted to 11. Then, 5% hydroxypropyl-β-cyclodextrin aqueous solution is slowly added at a rate of 3 drops / s and the mixture is stirred at a constant temperature for 6 hours to obtain a mixed slurry. The mass ratio of hydroxypropyl-β-cyclodextrin to titanium dioxide is 3:100. S3. Post-processing: After the reaction in step S2 is completed, the mixed slurry is filtered and washed with deionized water to remove free unreacted substances and the alkaline solution until the conductivity of the filtrate is <50μS / cm. The filter cake is dried at 105℃ for 24h and then air-jet pulverized to a particle size of 0.2-0.3μm to obtain the final product.

[0026] Example 4 A method for treating titanium dioxide includes the following steps: S1. Pulping: Add titanium dioxide particles with an alumina layer on the surface and a particle size of 0.2-0.3μm to deionized water and disperse at 8000rpm for 6h to obtain titanium dioxide slurry with a solid content of 40%. S2. Activation and Reaction: The titanium dioxide slurry from step S1 is heated to 80°C. While stirring, 10% NaOH solution is added dropwise and the pH is adjusted to 11. Then, 5% hydroxypropyl-β-cyclodextrin aqueous solution is slowly added at a rate of 3 drops / s and the mixture is stirred at a constant temperature for 6 hours to obtain a mixed slurry. The mass ratio of hydroxypropyl-β-cyclodextrin to titanium dioxide is 5:100. S3. Post-processing: After the reaction in step S2 is completed, the mixed slurry is filtered and washed with deionized water to remove free unreacted substances and the alkaline solution until the conductivity of the filtrate is <50μS / cm. The filter cake is dried at 105℃ for 24h and then air-jet pulverized to a particle size of 0.2-0.3μm to obtain the final product.

[0027] Example 5 Take the titanium dioxide obtained from Example 1 and set it aside.

[0028] A method for preparing plastic masterbatch includes the following steps: Weigh 60 parts of titanium dioxide treated in Example 1, 38 parts of Mobil Exxon LLDPE6201 powder, 5 parts of Clariant PE520 wax, and 0.5 parts of BASF antioxidant (1010:168=1:1). Mix them in a high-speed mixer at 1000 rpm for 8 minutes, and then melt-extrude and granulate them through a twin-screw extruder at 140-160°C.

[0029] Example 6 Take the titanium dioxide obtained from the treatment in Example 2 and set it aside.

[0030] A method for preparing plastic masterbatch includes the following steps: Weigh 45 parts of titanium dioxide treated in Example 2, 55 parts of powder ground from Chimei ABS757K, 3 parts of commercially available EBS wax, and 1.5 parts of BASF antioxidant (245:168=1:2). Mix them in a high-speed mixer at 800 rpm for 10 min, and then melt-extrude and granulate them through a twin-screw extruder at 160-220°C.

[0031] Example 7 Take the titanium dioxide obtained from the treatment in Example 3 and set it aside.

[0032] A method for preparing plastic masterbatch includes the following steps: Weigh 60 parts of titanium dioxide treated in Example 3, 38 parts of Maoming Petrochemical PP150 powder, 6 parts of Clariant PP wax 6102, and 0.5 parts of BASF antioxidant (1010:168=1:2). Mix them in a high-speed mixer at 1200 rpm for 12 min, and then melt-extrude and granulate them through a twin-screw extruder at 160-190℃.

[0033] Example 8 Take the titanium dioxide obtained from the treatment in Example 4 and set it aside.

[0034] A method for preparing plastic masterbatch includes the following steps: Weigh 75 parts of titanium dioxide treated in Example 4, 25 parts of CR PETCR8863 powder, 8 parts of PETS dispersing lubricant, and 2 parts of BASF antioxidant B900. Mix them in a high-speed mixer at 1200 rpm for 12 min, and then melt-extrude and granulate them through a twin-screw extruder at 210-270°C.

[0035] Comparative Example 1 A method for preparing plastic masterbatch includes the following steps: Weigh 60 parts of titanium dioxide (0.2-0.3 μm in particle size) with an alumina coating that was not treated in Example 1, 38 parts of Mobil Exxon LLDPE6201 powder, 5 parts of Clariant PE520 wax, and 0.5 parts of BASF antioxidant (1010:168=1:1). Mix them in a high-speed mixer at 1000 rpm for 8 minutes, and then melt-extrude and granulate them through a twin-screw extruder at 140-160°C.

[0036] Comparative Example 2 A method for preparing plastic masterbatch includes the following steps: Weigh 45 parts of titanium dioxide (0.2-0.3 μm in particle size) with an alumina layer on the surface that was not treated in Example 2, 55 parts of powder ground from Chimei ABS757K, 3 parts of commercially available EBS wax, and 1.5 parts of BASF antioxidant (245:168=1:2). Mix them in a high-speed mixer at 800 rpm for 10 min, and then melt-extrude and granulate them through a twin-screw extruder at 160-220°C.

[0037] Comparative Example 3 A method for preparing plastic masterbatch includes the following steps: Weigh 60 parts of titanium dioxide (0.2-0.3 μm in particle size) with an alumina layer on the surface that was not treated in Example 3, 38 parts of Maoming Petrochemical PP150 powder, 6 parts of Clariant PP wax 6102, and 0.5 parts of BASF antioxidant (1010:168=1:2). Mix them in a high-speed mixer at 1200 rpm for 12 min, and then melt-extrude and granulate them through a twin-screw extruder at 160-190℃.

[0038] Comparative Example 4 A method for preparing plastic masterbatch includes the following steps: Weigh 75 parts of titanium dioxide (0.2-0.3 μm in particle size) with an alumina layer on the surface that was not treated in Example 4, 25 parts of CR PET CR8863 powder, 8 parts of PETS dispersing lubricant, and 2 parts of BASF antioxidant B900. Mix them in a high-speed mixer at 1200 rpm for 12 min, and then melt-extrude and granulate them through a twin-screw extruder at 200-260°C.

[0039] Table 1. Composition of titanium dioxide in Examples 1-4

[0040] Table 2 Composition of plastic masterbatches in Examples 5-8 and Comparative Examples 1-4

[0041] The performance of the plastic masterbatches from Examples 5-8 and Comparative Examples 1-4 was tested under the following standards and conditions: Test sample preparation: The masterbatch to be tested was added to the corresponding matrix resin at a dosage of 4%. After thorough mixing, it was then used to prepare standard color charts with a size of 5 cm × 5 cm using an injection molding machine. Specifically: Table 3 Injection molding process parameters for Examples 5-8 and Comparative Examples 1-4

[0042] Filtration pressure test: A CMSI-35 / 05 filtration pressure tester was used, with a 500-mesh filter screen and the material prepared with 4% color masterbatch added. The pressure change of the melt as it passed through the filter screen was measured at a test temperature that matches the above injection molding temperature.

[0043] Color value testing: The color charts were tested using an X-Rite Ci7 spectrophotometer under D65 light source and 10° standard conditions. Five test points were randomly selected on each standard color chart, and the L, a, and b values ​​were recorded. The average ΔE value of the five test points was calculated.

[0044] Table 4 Performance Tests of Examples 5-8 and Comparative Examples 1-4

[0045] As shown in Table 4, under the same conditions, Examples 5-8 all have lower filtration pressure values ​​than Comparative Examples 1-4, indicating that the masterbatch and raw materials are more evenly dispersed and have better compatibility during the production process. This can be translated into lower processing temperatures or pressures. Simultaneously, the higher L values ​​of the products indicate better whiteness and brightness, further demonstrating that the modified titanium dioxide of this invention disperses better and has less agglomeration than the unmodified titanium dioxide. The average ΔE values ​​of Examples 5-8 are also smaller than those of the comparative examples, indicating more uniform coloring and less color difference.

[0046] The above description is one implementation method provided in conjunction with specific content. It is not intended that the specific implementation of the present invention is limited to these descriptions. Any technical deductions, substitutions, improvements, etc., that are similar to or based on the present invention should be considered within the scope of protection of this patent.

Claims

1. A titanium dioxide, characterized in that: It includes titanium dioxide particles and an organic coating layer covering the surface of the titanium dioxide particles; The organic coating layer is formed from cyclodextrin or its derivatives; The organic coating layer is anchored to the surface of the titanium dioxide particles by chemical bonding or strong intermolecular forces.

2. The titanium dioxide according to claim 1, characterized in that: The cyclodextrin is selected from one of β-cyclodextrin and γ-cyclodextrin; the derivative is selected from one of hydroxypropyl-β-cyclodextrin, carboxymethyl-β-cyclodextrin, and succinyl-β-cyclodextrin.

3. The titanium dioxide according to claim 1, characterized in that: The titanium dioxide particles are rutile titanium dioxide.

4. The titanium dioxide according to claim 1, characterized in that: The surface of the titanium dioxide particles is coated with an inorganic oxide layer; the inorganic oxide layer is selected from one or more of alumina and silicon oxide.

5. The titanium dioxide treatment method according to any one of claims 1-4, characterized in that: Includes the following steps: S1. Slurry preparation: Add titanium dioxide particles to deionized water and disperse at 5000-8000 rpm for 2-6 hours to obtain titanium dioxide slurry. S2. Activation and reaction: Heat the titanium dioxide slurry from step S1 to 60-85℃, add an alkaline solution dropwise while stirring and adjust the pH to 9.5-11.0, then slowly add an aqueous solution of cyclodextrin or its derivatives and stir at a constant temperature for 6-12 hours to obtain a mixed slurry. S3. Post-processing: After the reaction in step S2 is completed, the mixed slurry is filtered and washed with deionized water to remove free unreacted substances and the alkaline solution until the conductivity of the filtrate is <50μS / cm. The filter cake is dried at 90-110℃ for 24h and then pulverized with airflow to a particle size of 0.2-0.3μm to obtain the final product.

6. The titanium dioxide treatment method according to claim 5, characterized in that: The solid content of the titanium dioxide slurry in step S1 is 20-40%.

7. The titanium dioxide treatment method according to claim 5, characterized in that: In step S2, the mass ratio of the cyclodextrin or its derivative to the titanium dioxide is (0.5-5):100; the alkaline solution is selected from NaOH, KOH or NH3•H2O.

8. The application of titanium dioxide as described in any one of claims 1-4 in plastic masterbatches, characterized in that: The plastic masterbatch, by weight, comprises the following components: 45-75 parts titanium dioxide; 20-55 parts of carrier resin; Dispersing lubricant 1-8 parts; Antioxidant 0-3 parts.

9. The application of titanium dioxide in plastic masterbatch according to claim 8, characterized in that: The carrier resin is a granular or powdered material, selected from one of polypropylene (PP), polyethylene (PE), acrylonitrile-butadiene-styrene copolymer (ABS), polystyrene (PS), or polyethylene terephthalate (PET); the dispersing lubricant is selected from one of waxes, stearic acid, stearates, or amide dispersants.

Images