High-fluidity conductive titanium dioxide for papermaking and preparation method thereof

Abstract

The invention discloses high-fluidity conductive titanium dioxide for papermaking and a preparation method. The titanium dioxide comprises a titanium dioxide base material, an inorganic coating layer coating the surface of the titanium dioxide base material and an organic coating layer coating the surface of the inorganic coating layer, the inorganic coating layer comprises a film layer containing a BiO group; the organic coating layer is a film layer formed by introducing a carbon nano tube. Through comprehensive treatment of inorganic coating and organic coating, bismuth oxygen groups and CNT are introduced, so that the titanium dioxide has good fluidity and excellent conductivity and can be well applied to the field of papermaking.

Description

Technical Field

[0001] This invention belongs to the field of titanium dioxide preparation technology, specifically relating to a high-flowability conductive titanium dioxide for papermaking and its preparation method. Background Technology

[0002] In the paper industry, titanium dioxide (TiO2) has long held a core pigment position due to its high whiteness, high hiding power, and excellent optical properties, making it a key material for improving paper quality. However, with the upgrading of paper functionality requirements in high-end fields such as electronics and packaging, the shortcomings of traditional titanium dioxide are becoming increasingly apparent: its insulating properties make it unable to meet the requirements of antistatic and conductive applications; its powdery form is prone to agglomeration, resulting in poor dispersibility and problems such as uneven color and low gloss in paper; and in humid or high-temperature environments, titanium dioxide is prone to discoloration and fading, and its insufficient abrasion resistance limits its application in high-grade paper.

[0003] To overcome these bottlenecks, conductive titanium dioxide technology has emerged. Through nanoscale doping processes (such as introducing elements like tin, antimony, and zinc) and surface treatment technologies (such as phosphorus-silicon-aluminum coating), conductive titanium dioxide forms a conductive oxide layer on the surface of traditional titanium dioxide, achieving a leap from insulator to functional semiconductor. This meets the antistatic standards for applications such as electronic packaging paper, while retaining high whiteness and weather resistance, laying the foundation for the functional upgrading of the paper industry.

[0004] To address the stringent requirements of papermaking processes regarding filler flowability, dispersibility, and environmental stability, high-flowability conductive titanium dioxide has achieved breakthroughs through three core technologies: morphology control, composite doping, and surface modification. In terms of morphology design, existing technologies have abandoned the traditional granular structure, developing fibrous conductive titanium dioxide with a uniform aspect ratio and smooth surface, significantly reducing flow resistance and improving dispersion efficiency in pulp. A filler content of only 12-15% is sufficient to meet conductivity requirements. The composite doping system optimizes conductivity through the synergistic effect of elements such as tin, antimony, and zinc: tin-antimony doping increases carrier concentration, while zinc doping expands the cell volume to form a conductive network. Simultaneously, gradient doping technology preserves the high whiteness of the core region. Regarding surface modification, phosphorus-silicon-aluminum coating or phosphorus-zirconium-aluminum coating enhances the weather resistance and chemical stability of titanium dioxide, preventing damage to the conductive layer. The addition of polycarboxylate dispersants further solves the foaming problem during pulping, ensuring efficient dispersion of titanium dioxide with other components. These innovations enable high-flowability conductive titanium dioxide to achieve a comprehensive balance in whiteness, conductivity, dispersibility, and environmental adaptability.

[0005] However, existing high-flowability conductive titanium dioxide still has several shortcomings: In terms of morphology control, preparing fibrous conductive titanium dioxide with uniform aspect ratio and a smooth surface requires stringent processes and equipment, resulting in high costs and low efficiency. Furthermore, the morphology is easily damaged during papermaking and use, affecting performance. In composite doping systems, the synergistic mechanism of elements such as tin, antimony, and zinc is complex; even slight changes in process parameters can lead to unstable conductivity, and maintaining high whiteness is difficult when improving conductivity. Regarding surface modification, the uniformity of phosphorus-silicon-aluminum or phosphorus-zirconium-aluminum coating thickness is difficult to guarantee, and the conductive layer in some areas is easily exposed and damaged, affecting overall performance and lifespan. While polycarboxylate dispersants can solve pulping foaming and dispersion problems, different papermaking processes and pulp systems have different requirements for dispersants, limiting their adaptability. In certain complex environments, poor dispersion or adverse reactions may occur.

[0006] The development of high-flowability conductive titanium dioxide is the result of both market demand and industry trends. This invention designs a new process route for synthesizing high-flowability conductive titanium dioxide by introducing BiO groups and -CNTs. Its technological value is not only reflected in the improvement of product performance, but also in providing key material support for the functionalization and green transformation of the paper industry. Summary of the Invention

[0007] The purpose of this invention is to provide a high-flowability conductive titanium dioxide for papermaking and its preparation method to overcome the shortcomings of the prior art.

[0008] The objective of this invention is achieved through the following technical solution: A high-flowability conductive titanium dioxide for papermaking includes a titanium dioxide substrate, an inorganic coating layer covering the surface of the titanium dioxide substrate, and an organic coating layer covering the surface of the inorganic coating layer; the inorganic coating layer includes a film layer containing BiO groups; the organic coating layer is a film layer formed by introducing carbon nanotubes.

[0009] Preferably, the inorganic coating layer is at least one selected from basic bismuth carbonate, bismuth oxynitrate film, or bismuth oxychloride.

[0010] Preferably, the carbon nanotubes are single-walled carbon nanotubes and / or multi-walled carbon nanotubes.

[0011] Preferably, the carbon nanotubes are introduced via N3 groups.

[0012] Preferably, the coating amount of the inorganic coating layer, based on BiO, is 0.25~0.8% of the mass of the titanium dioxide substrate; Preferably, the coating amount of the organic coating layer, in terms of carbon nanotubes, is 1 to 6% of the mass of the titanium dioxide substrate.

[0013] This application also provides a method for preparing the high-flowability conductive titanium dioxide for papermaking as described above, comprising the following steps: S1. Preparation of titanium dioxide-based material slurry; S2. Perform an inorganic coating containing BiO groups; S3. Perform organic coating of carbon nanotubes.

[0014] Preferably, the inorganic coating in step S2 is at least one selected from basic bismuth carbonate coating, bismuth oxynitrate coating, or bismuth oxychloride coating; The basic bismuth carbonate coating includes the following steps: BiO-based source, as well as carbonate and / or bicarbonate source, are added to the slurry in a co-current manner, and (BiO)2CO3 is deposited under certain pH conditions. The bismuth oxynitrate coating process includes the following steps: Bi(NO3)3, H2O2 and HNO3 are added to the slurry in a co-current manner, and BiO(NO3) is deposited under certain pH conditions; The bismuth oxychloride coating includes the following steps: Bismuth trichloride and alkali are added to the slurry in a co-current manner, and BiOCl is deposited under certain pH conditions.

[0015] Preferably, the basic bismuth carbonate coating maintains a co-current pH of 8.5 to 9.5; The amount of BiO-based source added, calculated as BiO, is 0.25~0.8% of the mass of the titanium dioxide substrate; The amount of carbonate and / or bicarbonate source added is based on controlling the pH of the slurry to be 8.5~9.5.

[0016] Preferably, the coating temperature of the bismuth oxynitrate is 50~70℃, and the pH is controlled to be <3; The amount of Bi(NO3)3 added, calculated as BiO, is 0.25~0.8% of the mass of the titanium dioxide substrate. The amount of H2O2 added is 10~20% in excess of the theoretical amount. The amount of HNO3 added is based on maintaining the pH of the slurry.

[0017] Preferably, the bismuth oxychloride coating is maintained at a co-current pH of 6-8; The amount of bismuth trichloride added, calculated as BiO, is 0.25~0.8% of the mass of the titanium dioxide substrate; The amount of alkali added is based on controlling the pH of the slurry to be 6-8.

[0018] Preferably, step S3 further includes: Titanium dioxide coated with an inorganic coating layer is first reacted with a nitrating agent in a liquid medium to generate TiO2-O-NO2. Then, an azide salt is added to generate TiO2-N3. Finally, carbon nanotubes are added to generate TiO2-N=NN-CNT.

[0019] Preferably, the nitrating agent is nitric acid or NO2BF4; When the nitrating agent is nitric acid, step S3 further includes: The inorganic coated slurry was first adjusted to pH 4.5-5.5 with nitric acid to induce a nitration reaction and generate TiO2-O-NO2. After solid-liquid separation and drying, it was pulped with a nonprotonated solvent and azide salt was added to generate TiO2-N3. Then carbon nanotubes were added to generate TiO2-N=NN-CNT. When the nitrating agent is NO2BF4, step S3 further includes: After inorganic coating, the slurry is first separated into solid and liquid phases and dried. Then, it is pulped with a non-protonated solvent, and NO2BF4 is added to adjust the pH to 4.5~5.5. Nitration reaction occurs to generate TiO2-O-NO2. Then, azide salt is added to generate TiO2-N3. Finally, carbon nanotubes are added to generate TiO2-N=NN-CNT.

[0020] Preferably, the reaction temperature for adding the azide salt and the carbon nanotubes is 45~55℃; Preferably, the amount of carbon nanotubes used, based on the mass of the titanium dioxide substrate, is 1-6%. The amount of the azide salt added, calculated as azide groups, is 4 to 6% of the mass of the titanium dioxide substrate.

[0021] This application introduces bismuth oxygen and CNTs through a combination of inorganic and organic coating processes, giving titanium dioxide good flowability and excellent conductivity, making it suitable for use in the papermaking industry. Detailed Implementation

[0022] This application provides a high-flowability conductive titanium dioxide for papermaking, comprising a titanium dioxide substrate, an inorganic coating layer covering the surface of the titanium dioxide substrate, and an organic coating layer covering the surface of the inorganic coating layer; the inorganic coating layer includes a film layer containing BiO groups; the organic coating layer is a film layer formed by introducing carbon nanotubes.

[0023] This application employs a combination of inorganic and organic coating processes. The inorganic coating introduces bismuth oxygen groups, giving the titanium dioxide good flowability; the organic coating introduces CNTs onto the surface of the titanium dioxide, resulting in paper made from this titanium dioxide exhibiting excellent conductivity. Specifically: 1. By introducing BiO groups through an inorganic coating layer, on the one hand, the BiO-based titanium dioxide treated with the coating can make the particles more rounded, with a small contact area and low frictional resistance, which can significantly reduce the cohesive force of titanium dioxide; on the other hand, the introduction of BiO groups can regulate the particle size distribution, reduce the content of fine powder, and avoid agglomeration caused by excessive specific surface area; finally, BiO-based compounds can act as surface modifiers, filling the uneven structure on the surface of titanium dioxide through coating and reducing the adhesion between particles.

[0024] 2. Introducing CNTs into titanium dioxide imparts excellent conductivity. The mechanism is as follows: First, CNTs are formed by rolling up graphene. The delocalized π electron cloud generated by the sp2 hybridization of carbon atoms allows electrons to move freely within the tube, forming a conductive path. The smaller the tube diameter, the more significant the quantum confinement effect and the stronger the conductivity. Second, its conductivity is modulated by the band structure. It exhibits metallic properties when 2n + m = 3q (q is an integer), otherwise it exhibits semiconductor properties. This characteristic makes its conductivity intermediate between that of a conductor and a semiconductor. Third, defects or chemical doping in CNTs can alter the electron transport channels, further enhancing conductivity by inducing electron delocation or increasing carrier concentration. Finally, on the surface of titanium dioxide, CNTs, with their high aspect ratio and flexibility, easily interconnect to form a line-contact conductive network. Compared to the point-contact network of traditional conductive agents, this significantly reduces contact resistance and improves conductivity efficiency.

[0025] Moreover, carbon nanotubes offer significant advantages over graphene, which has similar properties, when combined with titanium dioxide. In terms of conductivity, the one-dimensional structure of carbon nanotubes easily forms a highly efficient conductive network, exhibiting excellent high-frequency current transmission. Appropriate addition can significantly reduce the resistivity of titanium dioxide composite fillers, while graphene is prone to agglomeration, leading to decreased conductivity. Regarding dispersibility, carbon nanotubes, after treatment with surfactants and a high-pressure homogenizer, can be uniformly dispersed in titanium dioxide to form a stable network. Graphene, due to its large specific surface area, is prone to agglomeration, making dispersion processes complex. Furthermore, the preparation process of carbon nanotubes is simple, such as electrostatic adsorption self-assembly, resulting in a lighter-colored product. The cost is also lower than that of high-quality graphene, which incurs high waste acid treatment costs during production. Overall, the combination of carbon nanotubes and titanium dioxide offers greater cost-effectiveness and application potential.

[0026] 3. The one-dimensional tubular structure of carbon nanotubes enables them to construct three-dimensional, interconnected conductive networks. In composite materials, carbon nanotubes act as conductive "bridges," connecting dispersed BiO group particles to form continuous conductive pathways. This conductive network not only reduces the resistance of electron transport but also further improves the overall conductivity of the composite material.

[0027] Both inorganic and organic coatings in this application preferably use wet coating methods, which have better uniformity and are easier to control compared to dry coating.

[0028] Precipitates containing BiO groups are numerous, such as basic bismuth carbonate, bismuth oxynitrate, and bismuth oxychloride, all of which can theoretically serve as the inorganic coating layer in this application. Therefore, preferably, the inorganic coating layer is selected from at least one of basic bismuth carbonate, bismuth oxynitrate, and bismuth oxychloride. Basic bismuth carbonate, bismuth oxynitrate, and bismuth oxychloride can be deposited on the surface of titanium dioxide using a wet coating method. More preferably, the basic bismuth carbonate film is obtained by adding a BiO-based source and carbonate and / or bicarbonate sources to a titanium dioxide slurry and depositing (BiO)₂CO₃ under specific pH conditions. The BiO-based source can be BiOCl, and the carbonate and / or bicarbonate sources can be (NH₄)HCO₃, etc. Taking BiOCl and (NH₄)HCO₃ as an example, the reaction formula is as follows:

[0029] BiOCl is generally insoluble in water but soluble in acids. To promote the reaction, BiOCl is preferably added to the slurry in the form of an acid solution. The specific steps are as follows: Dissolve solid BiOCl in an acid solution such as HNO3 or hydrochloric acid, which can dissolve BiOCl. The solution concentration, calculated as BiOCl, is 90-110 g / L. (NH4)HCO3 is also preferably added in solution form, with a solution concentration of 90-110 g / L. Other BiO sources and carbonate and / or bicarbonate sources are also preferably added in solution form.

[0030] The optimal pH for the reaction of the basic bismuth carbonate film is 8.5 to 9.5. Under these pH conditions, the reaction can fully produce basic bismuth carbonate precipitate.

[0031] As those skilled in the art will understand, in order to ensure sufficient reaction of the BiO-based source and the carbonate and / or bicarbonate sources and to uniformly deposit the reactants on the titanium dioxide surface, the BiO-based source and the carbonate and / or bicarbonate sources should be slowly added to the slurry, and the slurry should be allowed to mature for a certain period of time after addition. Preferably, the BiO-based source and the carbonate and / or bicarbonate sources are added over a period of 40-80 minutes, followed by a maturation period of 40-80 minutes.

[0032] Furthermore, to avoid the slurry pH affecting the BiO source and the carbonate and / or bicarbonate sources, the slurry pH can be adjusted to 8.5-9.5 before adding the BiO source and the carbonate and / or bicarbonate sources. Ammonia, sodium hydroxide, or other inorganic alkalis can be used as pH adjusters.

[0033] More preferably, the bismuth oxynitrate film is obtained by adding Bi(NO3)3, H2O2, and HNO3 to a titanium dioxide slurry, and then depositing BiO(NO3) under specific pH conditions. The reaction formulas for Bi(NO3)3, H2O2, and HNO3 are as follows: Bi(NO3)3+H2O2+2HNO3→BiO(NO3)↓+3H2O+2NO2↑ The specific reaction mechanism is as follows: 1. H2O2, as an oxidizing agent, can oxidize Bi... 3+ Oxidation to Bi 4+ (In BiO(NO3), the oxidation state of bismuth can be considered as +4, but it is actually BiO2.) + With NO3 - (combined with), while itself is reduced to H2O; 2. Precipitation formation: Bi 4+ With NO3 - The reaction produces BiO(NO3) precipitate. This precipitate is relatively stable in acidic environments, but may undergo hydrolysis or transformation in neutral or alkaline environments. Therefore, the reaction pH should be controlled to be <3.

[0034] Meanwhile, to promote the reaction, the preferred reaction temperature is 50~70℃ and the reaction time is 90~150min.

[0035] Bi(NO3)3 is soluble in water, and it is preferred to add it to the slurry in the form of an aqueous solution.

[0036] H2O2 is added in an aqueous solution with a mass percentage concentration of 20-40%, with an excess of 10-20% relative to the theoretical amount, to ensure that Bi(NO3)3 reacts fully.

[0037] HNO3 is concentrated nitric acid with a mass percentage of 65-68%, and the amount added is 20-30% in excess of the theoretical amount to maintain the acidic environment of the reaction system.

[0038] Preferably, the bismuth oxychloride film is formed by the following steps: Bismuth trichloride and alkali are added to the slurry in a co-current manner, and BiOCl is precipitated under certain pH conditions. The reaction formula is as follows: BiCl3 + H2O = BiOCl↓ + 2HCl Since the hydrolysis of bismuth trichloride is generally quite strong, in order to ensure the uniformity of the coating, bismuth trichloride and alkali are added slowly, preferably at a time of 60-120 minutes, followed by aging for 40-80 minutes.

[0039] Since the reaction produces hydrochloric acid, in order to avoid excessive hydrochloric acid content, which would cause large fluctuations in the pH of the slurry and affect the uniformity of the coating, and because excessive hydrochloric acid content would cause the reaction to proceed in reverse, alkali is added in parallel to keep the slurry at a neutral level.

[0040] The amount of BiCl3 added, based on BiO, is 0.25~0.8% of the mass of the titanium dioxide substrate, and the amount of alkali added is to maintain the pH of the slurry at 6~8.

[0041] To prevent premature hydrolysis of bismuth trichloride and to ensure uniform feeding, a hydrochloric acid solution of bismuth trichloride (hydrochloric acid can inhibit premature hydrolysis of bismuth trichloride) can be added to the slurry.

[0042] As those skilled in the art will understand, each film layer needs a certain amount of coating to achieve complete coating of the titanium dioxide surface and play its due role. At the same time, the coating amount cannot be too large.

[0043] Preferably, the coating amount of the inorganic coating layer, based on BiO, is 0.25~0.8% of the mass of the titanium dioxide substrate.

[0044] Preferably, the amount of the organic coating layer, calculated as carbon nanotubes, is 1 to 6% of the mass of the titanium dioxide substrate.

[0045] Preferably, the inorganic coating layer further includes an alumina film layer located between the titanium dioxide substrate and the film layer containing BiO groups.

[0046] Preferably, the pH of the alumina coating is 6.5-7.5, and the coating amount, based on alumina, is 3-5% of the mass of the titanium dioxide substrate. Under this pH condition, a boehmite alumina film can be obtained, further improving the dispersibility and flowability of titanium dioxide.

[0047] Conventional boehmite-type alumina films are generally located on the outermost side of the inorganic coating layer. However, the main function of the BiO-based film layer in this application is to improve the flowability of titanium dioxide. Flowability is a surface property, so the BiO-based film layer is placed on the outer side of the alumina to significantly improve the flowability of titanium dioxide.

[0048] More preferably, the alumina coating is achieved by co-currently adding an alkaline aluminum source and an acidic pH adjuster to the slurry, controlling the co-current pH to be 6.5–7.5, with the preferred co-current addition time being 90–150 min, followed by a curing period of 40–80 min. The alkaline aluminum source can be sodium aluminate, potassium aluminate, etc. The acidic pH adjuster can be hydrochloric acid, sulfuric acid, nitric acid, etc.

[0049] To maintain a stable pH in parallel flow, preferably, the pH of the slurry is first adjusted to 6.5-7.5 before adding the alkaline aluminum source and acidic pH adjuster to the slurry.

[0050] Preferably, carbon nanotubes can be introduced and attached to the surface of titanium dioxide via azide (-N3) groups. Azide groups possess high chemical reactivity, and their molecular structure contains both nucleophilic and electronophilic nitrogen atoms. Based on this unique structural characteristic, azide groups can chemically react with both titanium dioxide and carbon nanotubes, thereby stably anchoring the carbon nanotubes to the titanium dioxide surface and effectively preventing their detachment.

[0051] In existing technologies, carbon nanotube-modified titanium dioxide is mainly achieved by constructing composite materials. Carbon nanotubes are introduced onto the surface of titanium dioxide using methods such as sol-gel and hydrothermal methods to form a stable heterostructure. Alternatively, surface modification of carbon nanotubes, such as acidification and plasma treatment, can enhance their interaction with titanium dioxide. Or, conditions such as calcination temperature can be controlled to optimize the crystal form and morphology of titanium dioxide before mixing it with carbon nanotubes to further improve performance. Furthermore, carbon nanotube / titanium dioxide composite materials can be prepared by combining transition metal doping with synergistic modification.

[0052] Compared with existing methods for modifying titanium dioxide with carbon nanotubes, this application offers significant advantages through the introduction of -N3 groups and substitution of carbon nanotubes: First, the interfacial charge transfer efficiency is greatly improved, and the formation of directional channels through chemical bonds overcomes the problems of high interfacial resistance and limited charge transfer in traditional methods. Second, by introducing -N3 groups to substitute carbon nanotubes, charge pathways can be precisely controlled at the molecular level. Third, the structural stability is enhanced; the chemical bonding enables the composite material to withstand extreme reaction conditions, and its performance does not degrade over long periods of light exposure.

[0053] Preferably, the carbon nanotubes can be single-walled carbon nanotubes and / or multi-walled carbon nanotubes.

[0054] Single-walled carbon nanotubes are formed by rolling up a single layer of graphene, while multi-walled carbon nanotubes are formed by coaxially nesting multiple layers of graphene. In terms of electrical properties, about one-third of single-walled carbon nanotubes are metallic, and two-thirds are semiconductor. Multi-walled carbon nanotubes have good overall conductivity, but the electron mobility is reduced due to interlayer electron scattering, so their overall conductivity is weaker than that of single-walled carbon nanotubes.

[0055] More preferably, the organic coating layer is prepared by the following steps: Titanium dioxide coated with an inorganic coating layer is first reacted with a nitrating agent in a liquid medium to generate TiO2-O-NO2. Then, an azide salt is added to generate TiO2-N3. Finally, carbon nanotubes are added to generate TiO2-N=NN-CNT.

[0056] Nitrating agents can include nitric acid or NO2BF4, etc.

[0057] Titanium dioxide has a large number of -OH groups on its surface. Adding HNO3 or NO2BF4 to titanium dioxide can trigger a nitration reaction, where the -OH groups on the titanium dioxide surface react with HNO3 or NO2BF4 to generate TiO2-O-NO2. Then, an azide salt is added, and at a certain temperature (preferably 45~55℃), TiO2-O-NO2 undergoes a substitution reaction with NaN3 to generate TiO2-N3. Finally, carbon nanotubes are added to obtain the final product TiO2-N=NN-CNT. Taking nitric acid and sodium azide as examples, the reaction formulas involved are as follows:

[0058] When nitric acid is used as the nitrating agent, the nitration reaction with titanium dioxide needs to be carried out in water. However, the azide substitution reaction needs to be avoided in water to prevent the hydrolysis of the azide salt. Therefore, when nitric acid is used as the nitrating agent, nitric acid is first added to the slurry coated with an inorganic coating layer to allow the nitration reaction to occur. After dehydration to remove the inorganic salts from the inorganic coating, the slurry is dried and then slurried with a non-protonated solvent. Azide salt is then added to carry out the reaction. Preferably, to ensure sufficient reaction between nitric acid and titanium dioxide, nitric acid is added to adjust the pH of the slurry to 4.5-5.5, and after pH adjustment, the slurry is allowed to mature for 20-40 minutes.

[0059] When NO2BF4 is used as the nitrating agent, the nitration reaction between NO2BF4 and titanium dioxide needs to be carried out in an anhydrous environment. Therefore, the slurry coated with the inorganic coating layer needs to be dehydrated first to remove the inorganic salts from the inorganic coating. After drying, the slurry is pulped using a non-protonated solvent, and then NO2BF4 and azide salt are added for the reaction. The amount of NO2BF4 used is adjusted to adjust the pH of the slurry to 4.5-5.5.

[0060] The slurry concentration after pulping with a non-protonated solvent is preferably 150-250 g / L. To ensure sufficient reaction between the azide salt and carbon nanotubes, the azide salt is added at a time of 90-150 min, and the reaction time after adding the azide salt is preferably 40-80 min. Similarly, the carbon nanotubes are added at a time of 90-150 min, and the reaction time after adding the carbon nanotubes is preferably 40-80 min.

[0061] Preferably, the amount of carbon nanotubes used is 1 to 6% of the mass of the titanium dioxide substrate, based on the amount of carbon nanotubes.

[0062] Experiments have shown that the increase in carbon nanotube content significantly improves the conductivity of titanium dioxide. However, introducing too many carbon nanotubes can have several adverse effects on the performance of titanium dioxide. In terms of dispersibility, carbon nanotubes, due to their high surface energy, are prone to agglomeration. Excessive addition will form large-particle agglomerates, disrupting the arrangement of titanium dioxide fillers and exceeding the stabilizing capacity of the dispersant, causing slurry stratification and weakening the bonding force with titanium dioxide. Regarding conductivity, exceeding a certain content will reduce the grayscale of the composite material, limiting its application in light-colored fields and potentially disrupting the original electrical balance of titanium dioxide. In terms of mechanical properties, excessive carbon nanotubes induce segregation in titanium-based composite materials, forming special structures that deepen cracks, increase material brittleness, and reduce practical application performance.

[0063] Preferably, after introducing carbon nanotubes in step S3, the process further includes alcohol washing, flash evaporation of the filter cake, steam evaporation, and preparation of the target titanium dioxide.

[0064] Another aspect of this application provides a method for preparing the high-flowability conductive titanium dioxide for papermaking as described above, comprising the following steps: S1. Preparation of titanium dioxide-based material slurry; S2. Perform coating containing BiO groups; S3. Perform organic coating of carbon nanotubes.

[0065] The preferred concentration of the titanium dioxide-based material slurry is 250~350 g / L, which is suitable for inorganic coating. Applying a certain high temperature can promote coating; the preferred coating temperature is 75~85℃.

[0066] Preferably, the inorganic coating is at least one selected from basic bismuth carbonate, bismuth oxynitrate, or bismuth oxychloride.

[0067] Basic bismuth carbonate coating includes the following steps: BiO-based source, as well as carbonate and / or bicarbonate source, are added to the slurry in a co-current manner, and (BiO)2CO3 is deposited under certain pH conditions. Preferably, the pH is maintained at 8.5-9.5, under which conditions the reaction can fully produce basic bismuth carbonate precipitate.

[0068] BiO source can be BiOCl, and carbonate and / or bicarbonate source can be (NH4)HCO3, etc.

[0069] Preferably, the BiO-based source and the carbonate and / or bicarbonate source are slowly added to the slurry, and the slurry should be matured for a certain period of time after addition. Preferably, the BiO-based source and the carbonate and / or bicarbonate source are added over a period of 40-80 minutes, followed by a maturity period of 40-80 minutes.

[0070] Furthermore, the pH of the slurry can be adjusted to 8.5-9.5 before adding the BiO source and carbonate and / or bicarbonate sources. Inorganic bases such as ammonia can be used as pH adjusters.

[0071] Preferably, the amount of BiO source added, calculated as BiO, is 0.25~0.8% of the mass of the titanium dioxide substrate; the amount of carbonate and / or bicarbonate source added is based on controlling the pH of the slurry to be 8.5~9.5.

[0072] Preferably, BiOCl is added in the form of its acid solution. The specific steps are as follows: BiOCl solid is dissolved in an acid solution such as HNO3 or hydrochloric acid that can dissolve BiOCl, and the solution concentration, calculated as BiOCl, is 90~110 g / L. (NH4)HCO3 is also preferably added in the form of a solution (solvent is water), and the solution concentration, calculated as (NH4)HCO3, is 90~110 g / L.

[0073] Preferably, the bismuth oxynitrate film is obtained by adding Bi(NO3)3, H2O2 and HNO3 to a titanium dioxide slurry and depositing BiO(NO3) under certain pH conditions.

[0074] The reaction equations for Bi(NO3)3, H2O2, and HNO3 are as follows: Bi(NO3)3+H2O2+2HNO3→BiO(NO3)↓+3H2O+2NO2↑ Preferably, the coating temperature of bismuth oxynitrate is 50~70℃, the pH is controlled to be <3, and the coating time is 90~150min.

[0075] The amount of Bi(NO3)3 added, calculated as BiO, is 0.25~0.8% of the mass of the titanium dioxide substrate. The amount of H2O2 added is 10~20% in excess of the theoretical amount. The amount of HNO3 added is based on controlling the pH of the slurry.

[0076] Preferably, the bismuth oxychloride coating process includes the following steps: Bismuth trichloride and alkali are added to the slurry in a co-current manner, and BiOCl is precipitated under certain pH conditions. The reaction formula is as follows: BiCl3 + H2O = BiOCl↓ + 2HCl Since the hydrolysis of bismuth trichloride is generally quite strong, in order to ensure the uniformity of the coating, bismuth trichloride and alkali are added slowly, preferably at a time of 60-120 minutes, followed by aging for 40-80 minutes.

[0077] Since the reaction produces hydrochloric acid, in order to avoid excessive hydrochloric acid content, which would cause large fluctuations in the pH of the slurry and affect the uniformity of the coating, alkali is added in parallel to keep the slurry at a neutral level.

[0078] The amount of BiCl3 added, based on BiO, is 0.25~0.8% of the mass of the titanium dioxide substrate, and the amount of alkali added is to maintain the pH of the slurry at 6~8.

[0079] To prevent premature hydrolysis of bismuth trichloride and to ensure uniform feeding, a hydrochloric acid solution of bismuth trichloride (hydrochloric acid can inhibit the hydrolysis of bismuth trichloride) can be added to the slurry.

[0080] Preferably, an alumina coating is further included between step S1 and step S2; Preferably, the pH of the alumina coating is 6.5-7.5, and the coating amount, based on alumina, is 3-5% of the mass of the titanium dioxide substrate. Under this pH condition, a boehmite alumina film can be obtained, further improving the dispersibility and flowability of titanium dioxide.

[0081] More preferably, the alumina coating is achieved by co-currently adding an alkaline aluminum source and an acidic pH adjuster to the slurry, controlling the co-current pH to be 6.5–7.5, with the preferred co-current addition time being 90–150 min, followed by a curing period of 40–80 min. The alkaline aluminum source can be sodium aluminate, potassium aluminate, etc. The acidic pH adjuster can be hydrochloric acid, sulfuric acid, nitric acid, etc.

[0082] To maintain a stable pH in parallel flow, preferably, the pH of the slurry is first adjusted to 6.5-7.5 before adding the alkaline aluminum source and acidic pH adjuster to the slurry.

[0083] Preferably, step S3 further includes: Titanium dioxide coated with an inorganic coating layer is first reacted with a nitrating agent in a liquid medium to generate TiO2-O-NO2. Then, an azide salt is added to generate TiO2-N3. Finally, carbon nanotubes are added to generate TiO2-N=NN-CNT.

[0084] Nitrating agents can include nitric acid or NO2BF4, etc.

[0085] When the nitrating agent is nitric acid, step S3 further includes: The inorganically coated slurry is first adjusted to pH 4.5-5.5 with nitric acid to induce a nitration reaction, generating TiO2-O-NO2. After solid-liquid separation and drying, it is pulped with a non-protonated solvent, and azide salt is added to generate TiO2-N3. Then, carbon nanotubes are added to generate TiO2-N=NN-CNT.

[0086] To ensure that nitric acid reacts fully with titanium dioxide, nitric acid is added to adjust the pH of the slurry to 4.5-5.5, and then it is allowed to mature for 20-40 minutes.

[0087] When the nitrating agent is NO2BF4, step S3 further includes: After inorganic coating, the slurry is first separated into solid and liquid phases and dried. Then, it is pulped with a non-protonated solvent, and NO2BF4 is added to adjust the pH to 4.5~5.5. Nitration reaction occurs to generate TiO2-O-NO2. Then, azide salt is added to generate TiO2-N3. Finally, carbon nanotubes are added to generate TiO2-N=NN-CNT.

[0088] Preferably, the amount of carbon nanotubes used is 1 to 6% of the mass of the titanium dioxide substrate, based on the amount of carbon nanotubes.

[0089] Preferably, the reaction temperature for adding azide salts and carbon nanotubes is 45~55℃; Preferably, the amount of azide salt added, calculated as N3, is 4 to 6% of the mass of the titanium dioxide substrate.

[0090] The slurry concentration after pulping with a non-protonated solvent is preferably 150-250 g / L. To ensure sufficient reaction between the azide salt and carbon nanotubes, the azide salt is added at a time of 90-150 min, and the reaction time after adding the azide salt is preferably 40-80 min. Similarly, the carbon nanotubes are added at a time of 90-150 min, and the reaction time after adding the carbon nanotubes is preferably 40-80 min.

[0091] Nonprotic solvents can be selected from dimethyl sulfoxide, acetone, diethyl ether, toluene, etc.

[0092] Preferably, the azide salt is added in solution form, and the solvent is liquid ammonia, ethanol, etc., which can dissolve the azide salt. The solution concentration is preferably 140~160g / L.

[0093] Preferably, the carbon nanotubes are added in the form of a dispersion. The dispersion preparation steps are as follows: solid carbon nanotubes are decomposed into a specific solvent, such as esters or epoxy resins, to prepare a carbon nanotube dispersion. The concentration of the dispersion is controlled at 90~110g / L.

[0094] Preferably, after introducing carbon nanotubes in step S3, the process further includes alcohol washing, flash evaporation of the filter cake, steam evaporation, and preparation of the target titanium dioxide.

[0095] One preferred embodiment of this application provides a method for preparing high-flowability conductive titanium dioxide for papermaking, comprising the following steps: S1. Prepare a titanium dioxide-based material slurry with a slurry concentration of 250~350 g / L; then heat to 75~85℃; adjust the pH of the slurry to 6.5~7.5, and then mature for 20~40 min; S2. Add alkaline aluminum source and acidic pH adjuster to the slurry in parallel within 90~150min, maintain the pH of the parallel flow at 6.5~7.5, and then mature for 40~80min; S3. Adjust the pH of the slurry to 8.5~9.5 and mature for 20~40 minutes; S4. Add BiOCl and (NH4)HCO3 to the slurry in a co-current manner, control the pH of the co-current flow to be 8.5~9.5, add the slurry in a co-current manner for 40~80 min, and then let it mature for 40~80 min. S5. Adjust the pH to 4.5-5.5 with nitric acid, and then let it mature for 20-40 minutes; S6. The slurry is pressure filtered, washed with water, and dried; S7. Use a non-protonated solvent to pulp the material, with a pulp concentration of 150~250g / L, and then adjust the temperature to 45~55℃; S8. Then add azide salt within 90~150min and mature for 20~40min; S9. Then add the carbon nanotube dispersion within 90~150min and let it mature for 20~40min; S10. Filter by pressure, wash with alcohol, and then flash evaporate the filter cake to obtain the finished titanium dioxide product.

[0096] In the preparation process of this application, no polycarboxylate dispersant is required, nor are elements such as tin, antimony, or zinc used for doping. Furthermore, the titanium dioxide does not require special morphology control. Therefore, it does not present the technical problems found in the prior art. Moreover, the inorganic coating amount in this application is relatively small, and the thickness uniformity is easily controlled, avoiding the technical problem in the prior art where it is difficult to guarantee the thickness uniformity of phosphorus-silicon-aluminum or phosphorus-zirconium-aluminum coatings.

[0097] Example 1 The slurry with qualified particle size from the sand mill is introduced into the coating tank, the concentration is controlled at 300 g / L, and the temperature is raised to 80℃; within 20 min, NaOH solution is added to adjust the pH to 7.0, and then it is matured for 30 min; within 120 min, NaAlO2 solution and H2SO4 solution with a mass fraction of 3.7% of titanium dioxide are added in parallel, the pH of the parallel flow is controlled at 7.0, and the amount of H2SO4 solution added is to control the pH of the parallel flow at 7.0, and then it is matured for 60 min.

[0098] Within 20 min, add NH3·H2O solution to adjust pH to 9.0 and let it mature for 30 min; within 60 min, add BiOCl solution and (NH4)HCO3 solution with a mass fraction of 0.5% of titanium dioxide in a co-current flow, control pH to 9.0, and add (NH4)HCO3 solution in such a way that the pH is controlled at 9.0 in a co-current flow, and then let it mature for 60 min.

[0099] Within 20 minutes, add HNO3 solution to adjust pH to 5.0 and mature for 30 minutes; wash the titanium dioxide slurry obtained in the above steps with water and dry it; use toluene to slurry the filter cake obtained in the above steps, control the concentration at 200 g / L, and heat to 50℃; within 120 minutes, add NaN3 solution with a mass fraction of 5% of titanium dioxide and mature for 60 minutes; within 120 minutes, add single-walled carbon nanotube dispersion with a mass fraction of 1% of titanium dioxide and mature for 60 minutes; wash with alcohol, flash evaporate the filter cake, and steam to obtain the target titanium dioxide.

[0100] Example 2 The slurry with qualified particle size from the sand mill is introduced into the coating tank, the concentration is controlled at 300 g / L, and the temperature is raised to 80℃; within 20 min, NaOH solution is added to adjust the pH to 7.0, and then it is matured for 30 min; within 120 min, NaAlO2 solution and H2SO4 solution with a mass fraction of 3.7% of titanium dioxide are added in parallel, the pH of the parallel flow is controlled at 7.0, and the amount of H2SO4 solution added is to control the pH of the parallel flow at 7.0, and then it is matured for 60 min.

[0101] Within 20 min, add NH3·H2O solution to adjust pH to 9.0 and let it mature for 30 min; within 60 min, add BiOCl solution and (NH4)HCO3 solution with a mass fraction of 0.5% of titanium dioxide in a co-current flow, control the co-current pH to 9.0, and add the amount of (NH4)HCO3 solution to control the co-current pH to 9.0, and then let it mature for 60 min.

[0102] Within 20 minutes, add HNO3 solution to adjust pH to 5.0 and mature for 30 minutes; wash the titanium dioxide slurry obtained in the above steps with water and dry it; use toluene to slurry the filter cake obtained in the above steps, control the concentration at 200 g / L, and heat to 50℃; within 120 minutes, add NaN3 solution with a mass fraction of 5% of titanium dioxide and mature for 60 minutes; within 120 minutes, add single-walled carbon nanotube dispersion with a mass fraction of 3% of titanium dioxide and mature for 60 minutes; wash with alcohol, flash evaporate the filter cake, and steam to obtain the target titanium dioxide.

[0103] Example 3 S1. Pour the slurry with qualified particle size from the sand mill into the coating tank, control the concentration at 300 g / L, and heat it to 80℃; within 20 min, add NaOH solution to adjust the pH to 7.0, and mature for 30 min; within 120 min, add NaAlO2 solution and H2SO4 solution with a mass fraction of 3.7% of titanium dioxide in a co-current flow, control the co-current pH to 7.0, and add H2SO4 solution to control the co-current pH to 7.0, and then mature for 60 min.

[0104] Within S2.20 min, add NH3·H2O solution to adjust pH=9.0 and mature for 30 min; within 60 min, add BiOCl solution and (NH4)HCO3 solution with a mass fraction of 0.5% of titanium dioxide in a co-current flow, control the co-current pH=9.0, and the amount of (NH4)HCO3 solution added is such that the co-current pH is controlled at 9.0, and then mature for 60 min.

[0105] Within 20 minutes, add HNO3 solution to adjust pH to 5.0 and mature for 30 minutes; wash the titanium dioxide slurry obtained in the above steps with water and dry it; use toluene to slurry the filter cake obtained in the above steps, control the concentration at 200 g / L, and heat to 50℃; within 120 minutes, add NaN3 solution with a mass fraction of 5% of titanium dioxide and mature for 60 minutes; within 120 minutes, add single-walled carbon nanotube dispersion with a mass fraction of 5% of titanium dioxide and mature for 60 minutes; wash with alcohol, flash evaporate the filter cake, and steam to obtain the target titanium dioxide.

[0106] Example 4 Example 4 is similar to Example 3, except that the amount of BiO group introduced is changed from 0.5% to 0.3%.

[0107] Example 5 Example 5 is similar to Example 3, except that the amount of BiO group introduced is changed from 0.5% to 0.7%.

[0108] Example 6 Example 6 is similar to Example 3, except that the method of introducing the BiO group is changed from introducing (BiO)₂CO₃ to BiO(NO₃). Specifically, step S2 is replaced with: Within 20 minutes, add nitric acid solution to adjust pH to 2.5 and mature for 30 minutes. Within 60 minutes, add Bi(NO3)3 solution (0.5% by mass of titanium dioxide), H2O2, and HNO3 in a co-current flow, controlling the pH to 2.5. Use 30% H2O2, which is 120% of the theoretical amount. Use 65% concentrated nitric acid for HNO3, adding the amount to maintain the pH of the slurry. Then mature for 120 minutes.

[0109] Example 7 Example 7 is similar to Example 3, except that single-walled carbon nanotubes are replaced with multi-walled carbon nanotubes.

[0110] Example 8 Example 8 is similar to Example 3, except that nitric acid is replaced with NO2BF4. Specifically, step S3 is replaced with: The inorganically coated slurry was first subjected to solid-liquid separation and drying, and then pulped with toluene to a concentration controlled at 200 g / L. NO2BF4 was then added to adjust the pH to 5.0, and the mixture was allowed to mature for 30 min. The temperature was then raised to 50℃, and a NaN3 solution (5% by mass of titanium dioxide) was added, followed by maturation for 60 min. Within 120 min, a single-walled carbon nanotube dispersion (5% by mass of titanium dioxide) was added, and the mixture was allowed to mature for another 60 min. After alcohol washing, the filter cake was flash-evaporated and vaporized to obtain the target titanium dioxide.

[0111] Example 9 Example 9 is similar to Example 3, except that the method of introducing the BiO group is changed from the deposition of (BiO)₂CO₃ to the deposition of BiOCl. Specifically, step S2 is replaced with: Within 120 min, a hydrochloric acid solution and a NaOH solution containing 0.5% (by mass) of BiCl3 were added in parallel flow to control the pH at 7.0. The amount of NaOH solution added was based on controlling the pH at 7.0 in parallel flow. Then, the mixture was allowed to mature for 60 min.

[0112] Comparative Example 1 (Conventional alumina coating) The slurry with qualified particle size from the sand mill is introduced into the coating tank, the concentration is controlled at 300 g / L, and the temperature is raised to 80℃; within 20 min, NaOH solution is added to adjust the pH to 7.0, and it is matured for 30 min; within 120 min, NaAlO2 solution and H2SO4 solution with a mass fraction of 3.7% of titanium dioxide are added in parallel, the pH of the parallel flow is controlled at 7.0, and the amount of H2SO4 solution added is such that the pH of the parallel flow is controlled at 7.0, and then it is matured for 60 min.

[0113] Within 20 minutes, add HNO3 solution to adjust pH to 5.0 ± 0.2 and mature for 30 minutes; wash the titanium dioxide slurry obtained in the above steps with water, and flash evaporate and steam the filter cake to prepare titanium dioxide.

[0114] Comparative Example 2 (alumina coating, basic bismuth carbonate coating) The slurry with qualified particle size from the sand mill is introduced into the coating tank, the concentration is controlled at 300 g / L, and the temperature is raised to 80℃; within 20 min, NaOH solution is added to adjust the pH to 7.0, and it is matured for 30 min; within 120 min, NaAlO2 solution and H2SO4 solution with a mass fraction of 3.7% of titanium dioxide are added in parallel, the pH of the parallel flow is controlled at 7.0, and the amount of H2SO4 solution added is to control the pH of the parallel flow at 7.0, and then it is matured for 60 min.

[0115] Within 20 min, add NH3·H2O solution to adjust pH to 9.0 and let it mature for 30 min; within 60 min, add BiOCl solution and (NH4)HCO3 solution with a mass fraction of 0.5% of titanium dioxide in a co-current flow, control the co-current pH to 9.0, and add the amount of (NH4)HCO3 solution to control the co-current pH to 9.0, and then let it mature for 60 min.

[0116] Within 20 minutes, add HNO3 solution to adjust pH to 5.0 and mature for 30 minutes; wash the titanium dioxide slurry obtained in the above steps with water, and flash evaporate the filter cake to obtain titanium dioxide.

[0117] Comparative Example 3 (alumina coating, carbon nanotube coating) The slurry with qualified particle size from the sand mill is introduced into the coating tank, the concentration is controlled at 300 g / L, and the temperature is raised to 80℃; within 20 min, NaOH solution is added to adjust the pH to 7.0, and it is matured for 30 min; within 120 min, NaAlO2 solution and H2SO4 solution with a mass fraction of 3.7% of titanium dioxide are added in parallel, the pH of the parallel flow is controlled at 7.0, and the amount of H2SO4 solution added is to control the pH of the parallel flow at 7.0, and then it is matured for 60 min.

[0118] Within 20 minutes, add HNO3 solution to adjust pH to 5.0 and mature for 30 minutes; wash the titanium dioxide slurry obtained in the above steps with water and dry it; use toluene to slurry the filter cake obtained in the above steps, control the concentration at 200 g / L, and heat to 50℃; within 120 minutes, add NaN3 solution with a mass fraction of 5% of titanium dioxide and mature for 60 minutes; within 120 minutes, add single-walled carbon nanotube dispersion with a mass fraction of 5% of titanium dioxide and mature for 60 minutes; wash with alcohol, flash evaporate the filter cake, and steam to obtain titanium dioxide.

[0119] Comparative Example 4 (the order of exchange alumina and BiO-based coating) The difference between Comparative Example 4 and Example 3 is that the order of exchanging alumina and BiO-based coating is different.

[0120] Experimental results The application performance of the titanium dioxide obtained in Examples 1-9 and Comparative Examples 1-4 was evaluated.

[0121] 1. Test the flowability of titanium dioxide The flowability was determined using a powder-property analyzer. Specifically, 30g of sample was weighed and poured from the funnel into the platform below it. The height h was measured, and eight radius data points were recorded. The average value was taken, and finally, the tan φ was calculated. i = h / r, the results are shown in Table 1 (the smaller the value, the better the liquidity).

[0122] Table 1

[0123] Data from Examples 1-9 and Comparative Examples 1-3 show that -CNTs have a relatively small effect on improving the flowability of titanium dioxide, while BiO groups are the key to improving the flowability of titanium dioxide, and the improvement in flowability is positively correlated with the amount of BiO groups introduced. Data from Example 3 and Comparative Example 4 show that BiO groups can only improve the flowability of titanium dioxide when they are coated on the outer layer.

[0124] Testing the resistivity of titanium dioxide Test method: Weigh 5g of titanium dioxide sample, compact the titanium dioxide in the groove of the resistivity meter, and record the instantaneous resistivity when the pressure is 30 MPa.

[0125] The volume resistivity of conductive titanium dioxide was determined using an FT-500 powder resistivity meter. The volume resistivity of conductive titanium dioxide was calculated using the following formula: ρ=R·A / L Where: ρ - resistivity, Ω·cm; R - Measured resistance value using a multimeter, in Ω; A - Cross-sectional area (inner diameter) of the groove in the resistivity measuring instrument, in cm 2 ; L - Powder height, cm.

[0126] The results are shown in Table 2.

[0127] Table 2

[0128] Data from Examples 1-3 and Comparative Example 1 show that the introduction of BiO groups and -CNTs significantly reduces the volume resistivity of titanium dioxide and improves its conductivity. Furthermore, as the -CNT content increases, the volume resistivity of titanium dioxide exhibits a negative correlation (while conductivity shows a positive correlation). Data from Examples 3-5 and Comparative Example 3 show that the simultaneous introduction of BiO groups and -CNTs significantly improves the conductivity of titanium dioxide. This is because the two form a continuous conductive pathway, resulting in a synergistic effect in improving conductivity. Data from Comparative Examples 1-3 show that the reduction in volume resistivity of titanium dioxide by introducing BiO groups is far less significant than the reduction by introducing -CNTs. This indicates that the presence of -CNTs is the key to reducing the volume resistivity of titanium dioxide (i.e., improving conductivity) in this invention.

[0129] As can be seen from the data in Examples 3 and 7, the introduction of single-walled carbon nanotubes significantly improves the conductivity of titanium dioxide compared to multi-walled carbon nanotubes. This is because the conductivity of single-walled carbon nanotubes is superior to that of multi-walled carbon nanotubes.

[0130] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A high-flowability conductive titanium dioxide for papermaking, characterized in that, The invention includes a titanium dioxide substrate, an inorganic coating layer covering the surface of the titanium dioxide substrate, and an organic coating layer covering the surface of the inorganic coating layer; the inorganic coating layer includes a film layer containing BiO groups; and the organic coating layer is a film layer formed by introducing carbon nanotubes.

2. The high-flowability conductive titanium dioxide for papermaking as described in claim 1, characterized in that, The inorganic coating layer is selected from at least one of basic bismuth carbonate, bismuth oxynitrate film, or bismuth oxychloride.

3. The high-flowability conductive titanium dioxide for papermaking as described in claim 1, characterized in that, The carbon nanotubes are single-walled carbon nanotubes and / or multi-walled carbon nanotubes.

4. The high-flowability conductive titanium dioxide for papermaking as described in claim 1, characterized in that, The carbon nanotubes are introduced via N3 groups.

5. The high-flowability conductive titanium dioxide for papermaking as described in claim 1, characterized in that, The coating amount of the inorganic coating layer, calculated based on BiO, is 0.25~0.8% of the mass of the titanium dioxide substrate; Preferably, the coating amount of the organic coating layer, in terms of carbon nanotubes, is 1 to 6% of the mass of the titanium dioxide substrate.

6. A method for preparing high-flowability conductive titanium dioxide for papermaking as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Preparation of titanium dioxide-based material slurry; S2. Perform an inorganic coating containing BiO groups; S3. Perform organic coating of carbon nanotubes.

7. The method for preparing high-flowability conductive titanium dioxide for papermaking as described in claim 6, characterized in that, The inorganic coating in step S2 is selected from at least one of basic bismuth carbonate coating, bismuth oxynitrate coating, or bismuth oxychloride coating; The basic bismuth carbonate coating includes the following steps: BiO-based source, as well as carbonate and / or bicarbonate source, are added to the slurry in a co-current manner, and (BiO)2CO3 is deposited under certain pH conditions. The bismuth oxynitrate coating process includes the following steps: Bi(NO3)3, H2O2 and HNO3 are added to the slurry in a co-current manner, and BiO(NO3) is deposited under certain pH conditions; The bismuth oxychloride coating includes the following steps: Bismuth trichloride and alkali are added to the slurry in a co-current manner, and BiOCl is deposited under certain pH conditions.

8. The method for preparing high-flowability conductive titanium dioxide for papermaking as described in claim 7, characterized in that, The basic bismuth carbonate coating maintains a co-current pH of 8.5~9.5; The amount of BiO-based source added, calculated as BiO, is 0.25~0.8% of the mass of the titanium dioxide substrate; The amount of carbonate and / or bicarbonate source added is based on controlling the pH of the slurry to be 8.5~9.

5.

9. The method for preparing high-flowability conductive titanium dioxide for papermaking as described in claim 7, characterized in that, The coating temperature of the bismuth oxynitrate is 50~70℃, and the pH is controlled to be <3; The amount of Bi(NO3)3 added, calculated as BiO, is 0.25~0.8% of the mass of the titanium dioxide substrate. The amount of H2O2 added is 10~20% in excess of the theoretical amount. The amount of HNO3 added is based on maintaining the pH of the slurry.

10. The method for preparing high-flowability conductive titanium dioxide for papermaking as described in claim 7, characterized in that, The bismuth oxychloride coating maintains a co-current pH of 6-8; The amount of bismuth trichloride added, calculated as BiO, is 0.25~0.8% of the mass of the titanium dioxide substrate; The amount of alkali added is based on controlling the pH of the slurry to be 6-8.

11. The method for preparing high-flowability conductive titanium dioxide for papermaking as described in claim 6, characterized in that, Step S3 further includes: Titanium dioxide coated with an inorganic coating layer is first reacted with a nitrating agent in a liquid medium to generate TiO2-O-NO2. Then, an azide salt is added to generate TiO2-N3. Finally, carbon nanotubes are added to generate TiO2-N=NN-CNT.

12. The method for preparing high-flowability conductive titanium dioxide for papermaking as described in claim 11, characterized in that, The nitrifying agent is nitric acid or NO2BF4; When the nitrating agent is nitric acid, step S3 further includes: The inorganic coated slurry was first adjusted to pH 4.5-5.5 with nitric acid to induce a nitration reaction and generate TiO2-O-NO2. After solid-liquid separation and drying, it was pulped with a nonprotonated solvent and azide salt was added to generate TiO2-N3. Then carbon nanotubes were added to generate TiO2-N=NN-CNT. When the nitrating agent is NO2BF4, step S3 further includes: After inorganic coating, the slurry is first separated into solid and liquid phases and dried. Then, it is pulped with a non-protonated solvent, and NO2BF4 is added to adjust the pH to 4.5~5.

5. Nitration reaction occurs to generate TiO2-O-NO2. Then, azide salt is added to generate TiO2-N3. Finally, carbon nanotubes are added to generate TiO2-N=NN-CNT.

13. The method for preparing high-flowability conductive titanium dioxide for papermaking as described in claim 12, characterized in that, The reaction temperature for adding the azide salt and the carbon nanotubes is 45~55℃; Preferably, the amount of carbon nanotubes used, based on the mass of the titanium dioxide substrate, is 1-6%. The amount of the azide salt added, calculated as azide groups, is 4 to 6% of the mass of the titanium dioxide substrate.

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