Preparation method of special water slurry titanium dioxide for decorative paper

Abstract

The invention belongs to the technical field of chemical engineering, particularly relates to a preparation method of special titanium dioxide for decorative paper, and discloses a preparation method of special water slurry titanium dioxide for decorative paper, which comprises the following steps: by taking a rutile type titanium dioxide primary product as a raw material, firstly, carrying out primary dispersion treatment on slurry containing the raw material; then sequentially adding water-soluble cerium salt and an aluminum-containing compound into the uniformly dispersed slurry step by step to carry out inorganic coating, so that a composite coating layer consisting of cerium oxide and aluminum oxide is formed on the surface of titanium dioxide, and finally, carrying out secondary dispersion treatment on the coated slurry to prepare the water slurry titanium dioxide. According to the method, in the water slurry titanium dioxide preparation process, titanium dioxide keeps high dispersity, the prepared product is good in dispersity, the whiteness, covering power and light resistance of the product all meet the industrial requirements, the pulping procedure of titanium dioxide dry powder adopted in the traditional process is omitted, the preparation process is low in cost, and energy is saved.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and in particular relates to a method for preparing titanium dioxide special for decorative paper. Background Art

[0002] Decorative paper has been a rapidly growing specialty paper product in recent years, offering the environmentally friendly advantage of replacing wood with paper. Made from titanium dioxide and high-quality wood pulp, it undergoes a specialized process, followed by impregnation and hot pressing, before being applied to the surfaces of man-made boards such as fiberboard and particleboard. Titanium dioxide acts as a filler in decorative paper, enhancing its whiteness, hiding power, and lightfastness. During the production process, titanium dioxide is first beaten to ensure thorough dispersion before being mixed evenly with the wood pulp for further processing. However, titanium dioxide's main component, TiO2, is a nanoparticle with high surface activity and prone to agglomeration, making it difficult to disperse evenly in the pulp. This uneven dispersion results in suboptimal performance characteristics, such as hiding power and lightfastness. Furthermore, traditional titanium dioxide production can create dust and pollute the environment. On the other hand, the post-processing production process of titanium dioxide includes inorganic surface treatment, filtration and washing, flash drying, air flow crushing and other processes, and then packaging into finished titanium dioxide, which will greatly increase the energy consumption of the factory.

[0003] Prior art patent CN118813073A discloses a surface treatment process for titanium dioxide specifically for decorative paper. The prior art sequentially coats the surface of titanium dioxide particles with zirconium oxide, aluminum phosphate, and hydrated aluminum oxide to form a multilayer inorganic coating. Each layer has a single function and lacks a synergistic effect. For example, zirconium oxide only improves light resistance but does not solve the dispersion problem. Although the aluminum phosphate and aluminum oxide layers improve dispersibility, their long-term stability has not been verified. Furthermore, the dry powder needs to be redissolved, which can easily lead to secondary agglomeration.

[0004] Based on this, it is urgent to develop a method for preparing a water-based titanium dioxide slurry specifically for decorative paper that comprehensively improves the light resistance, dispersibility and environmental friendliness of titanium dioxide. Summary of the Invention

[0005] In view of this, in order to solve the above problems, the purpose of the embodiments of the present invention is to provide a method for preparing titanium dioxide specifically for decorative paper, so as to solve the problems such as uneven dispersion of titanium dioxide during the pulping process, resulting in poor product application performance and high energy consumption in the preparation process. The process of the present invention combines a step-by-step coating process, a composite coating layer design and direct preparation in water slurry. The method has proper cost control, good dispersion of titanium dioxide in water slurry, and significantly improves the light resistance, hiding power and environmental protection of titanium dioxide.

[0006] The technical solutions adopted in the present invention include: On one hand, the present invention provides a method for preparing a water-slurry titanium dioxide specially used for decorative paper. The method uses primary rutile titanium dioxide as a raw material, firstly performs a preliminary dispersion treatment on a slurry containing the raw material, then sequentially and stepwisely adds a water-soluble cerium salt and an aluminum-containing compound to the uniformly dispersed slurry for inorganic coating, thereby forming a composite coating layer composed of cerium oxide and aluminum oxide on the surface of the titanium dioxide, and finally performs a secondary dispersion treatment on the coated slurry to obtain a water-slurry titanium dioxide.

[0007] In some embodiments, the preliminary dispersion treatment includes adding a dispersant to the slurry containing the raw materials, followed by a grinding process; the dispersant includes sodium hexametaphosphate; the grinding process includes grinding the slurry after adding the dispersant until the content of particles with a slurry particle size D50 greater than 1 μm is less than 1%.

[0008] In some embodiments, the inorganic coating comprises a multi-stage aging process, wherein the multi-stage aging process comprises the following steps: (a) adding a water-soluble cerium salt solution to the uniformly dispersed slurry, adjusting the pH value to 9-10, and aging at 60° C.-80° C. for 60 min-90 min; (b) adding a sodium hexametaphosphate solution to the slurry of step (a) and aging at 60° C. to 80° C. for 45 to 75 minutes; (c) adding the aluminum compound solution to the slurry of step (b) in two steps, adjusting the pH of the slurry to 7-9 for the first step and aging at 60°C-80°C for 60-90 min, and adjusting the pH of the slurry to 5-7 for the second step and aging at 60°C-80°C for 45-75 min.

[0009] In some embodiments, the secondary dispersion treatment includes performing solid-liquid separation on the coated slurry to obtain a filter cake, adding deionized water and a polymer dispersant to the filter cake and performing a secondary dispersion treatment, wherein the polymer dispersant includes a polycarboxylate dispersant.

[0010] In some embodiments, the secondary dispersion treatment further includes secondary grinding, the stirring speed of the secondary grinding is 600-800 r / min, and the stirring time of the secondary grinding is 45-60 min.

[0011] In some embodiments, the method comprises: (1) Mixing the primary rutile titanium dioxide with deionized water to prepare a slurry with a concentration of 250 g / L to 400 g / L, adding sodium hexametaphosphate with a concentration of 50 g / L to 90 g / L in terms of P2O5 in an amount of 0.5% to 1.5% of the mass of the titanium dioxide, stirring at a high speed of 1500 r / min to 2500 r / min for 30 min to 60 min, and then grinding once until the content of particles with a particle size D50 greater than 1 μm in the slurry is less than 1%; (2) heating the slurry obtained in step (1) to 60°C to 80°C, adding a water-soluble cerium salt solution, adjusting the pH value to 9 to 10, and stirring and aging for 60 min to 90 min; (3) adding a sodium hexametaphosphate solution having a concentration of 80 g / L to 120 g / L in terms of P2O5 to the slurry of step (2) in an amount of 1.0% to 2.0% of the mass of TiO2, stirring at 60°C to 80°C for 30 min to 60 min, and then aging for 45 min to 75 min; (4) Adding the aluminum compound solution to the slurry in step (3) in two steps: First, add an aluminum-containing compound with a concentration of 100g / L to 150g / L calculated as alumina, and the amount added is 1.0% to 3.0% of the mass of titanium dioxide. Simultaneously add sulfuric acid or hydrochloric acid to adjust the pH to 7 to 9, and mature at 60°C to 80°C for 60min to 90min. A second addition of an aluminum-containing compound at a concentration of 100 g / L to 150 g / L calculated as alumina, with the amount added being 1.0% to 2.0% of the mass of titanium dioxide, and sulfuric acid or hydrochloric acid added concurrently to adjust the pH to 5 to 7, followed by aging at 60°C to 80°C for 45 to 75 minutes; (5) The slurry treated in step (4) is filtered and washed, and the resulting filter cake is mixed with deionized water and a polycarboxylate dispersant in an amount of 0.2% to 0.5% of the mass of the filter cake. The mixture is stirred at 500 rpm to 800 rpm for 30 to 60 minutes, and then subjected to secondary grinding to obtain a water slurry of titanium dioxide with a solid content of 40% to 50%.

[0012] In some embodiments, the water-soluble cerium salt in step (2) is ammonium cerium nitrate, the solution concentration of which is 60 g / L to 80 g / L in terms of cerium oxide, the amount added is 0.5% to 1.0% of the mass of titanium dioxide in the slurry, and the addition time is 30 min to 60 min.

[0013] In some embodiments, the aluminum-containing compound in steps (4) and (5) is sodium metaaluminate.

[0014] In some embodiments, the polycarboxylate dispersant is sodium polycarboxylate.

[0015] In some embodiments, the primary grinding and secondary grinding are performed by a sand mill, the primary grinding speed is 13 m / s to 14 m / s, and the secondary grinding speed is controlled at 8 m / s to 10 m / s.

[0016] The beneficial effects of the present invention are as follows: the method of the present invention disperses titanium dioxide before coating, adds water-soluble cerium salt and aluminum-containing compound in steps, forms a composite coating layer composed of cerium oxide and aluminum oxide on the surface of titanium dioxide, and finally disperses it twice to obtain water-slurry titanium dioxide, which can increase the dispersibility of titanium dioxide. In the process of preparing water-slurry titanium dioxide by the method of the present invention, titanium dioxide maintains a high dispersibility, and the prepared product has good dispersibility. The stability, whiteness, hiding power and light resistance of the product meet industry requirements, and the pulping process using titanium dioxide dry powder is eliminated. The preparation process is low-cost and energy-saving, and solves the problems of uneven dispersion, insufficient light resistance and high energy consumption of titanium dioxide prepared by traditional processes.

[0017] The present invention summarizes various aspects of the embodiments and should not be used to limit the claims. Other embodiments are conceivable based on the technology described herein, which will be apparent to those skilled in the art after studying the following drawings and detailed description, and these embodiments are intended to be included within the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 The present invention provides a flow chart of an embodiment of a method for preparing a titanium dioxide water slurry specially used for decorative paper. DETAILED DESCRIPTION

[0020] In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. However, it should be understood that the disclosed embodiments are merely examples, and other embodiments may take various alternative forms. In addition, in the present invention, relational terms such as first and second, etc. are only used to distinguish one entity or action from another entity or action, and do not necessarily require or imply any actual such relationship or order between these entities or actions. The terms "include", "comprising" or any other variations thereof are intended to cover non-exclusive inclusions, so that a process, method, article or apparatus comprising a series of elements includes not only those elements, but may also include elements that are not explicitly listed or inherent to these processes, methods, articles or apparatuses.

[0021] In the present invention, the term "solid content" refers to the percentage of the total mass of solid matter (such as titanium dioxide) in the slurry to the mass of the entire slurry (solid + liquid), and is calculated as follows: (solid content = solid mass after drying / total mass of slurry) × 100%. This definition also covers solid components dissolved in the solvent (such as binder).

[0022] One or more embodiments of the present invention will be described below with reference to the accompanying drawings. The flowcharts illustrate processes performed by the system according to the present invention. It is understood that the flowcharts do not need to be executed in order, and one or more steps may be omitted, one or more steps may be added, and the steps may be executed in order or in reverse order, and in some embodiments, one or more steps may even be executed simultaneously.

[0023] On one hand, the present invention provides a method for preparing a water-slurry titanium dioxide specially used for decorative paper. The method uses primary rutile titanium dioxide as a raw material, firstly performs a preliminary dispersion treatment on a slurry containing the raw material, then sequentially and stepwisely adds a water-soluble cerium salt and an aluminum-containing compound to the uniformly dispersed slurry for inorganic coating, thereby forming a composite coating layer composed of cerium oxide and aluminum oxide on the surface of the titanium dioxide, and finally performs a secondary dispersion treatment on the coated slurry to obtain a water-slurry titanium dioxide.

[0024] The method of the present invention can solve the problems of poor product application performance caused by uneven dispersion of titanium dioxide during the pulping process and high energy consumption in the preparation process. The present invention forms a composite coating layer of cerium oxide (CeO2) and aluminum oxide (Al2O3) by step-by-step addition of cerium salt and aluminum compound. The cerium oxide layer generated by the hydrolysis of cerium salt in the composite coating layer has high light stability and UV resistance, inhibits the photocatalytic activity of titanium dioxide, and reduces degradation caused by ultraviolet rays. The aluminum oxide layer (such as boehmite structure) formed by the hydrolysis of aluminum compound enhances the wettability of the particle surface and electrostatic repulsion, thereby improving the dispersion stability of titanium dioxide. The cerium layer and the aluminum layer in the composite coating layer are functionally complementary. The former inhibits photodegradation, and the latter optimizes dispersibility. The two work synergistically to significantly improve the light resistance, hiding power and dispersibility of titanium dioxide. The composite coating layer further ensures uniform dispersion during the preparation of water-slurry titanium dioxide through the synergistic effect of cerium and aluminum (electrostatic repulsion + improved wettability). The prepared water-slurry titanium dioxide has good performance and does not settle after standing for 48 hours. In addition, the present invention directly prepares water-slurry titanium dioxide by first dispersing the raw material water-slurry titanium dioxide, inorganically coating it, and then dispersing it twice. This not only maintains good dispersibility during the preparation process and improves the quality of the water-slurry titanium dioxide, but also eliminates the pulping process using titanium dioxide dry powder, saves energy and reduces costs.

[0025] In some embodiments, the initial dispersion process includes adding a dispersant to a slurry containing the raw materials, followed by a primary grinding process; the dispersant includes sodium hexametaphosphate. The primary grinding process includes grinding the dispersant-added slurry until the content of particles with a particle size D50 greater than 1 μm is less than 1%. Sodium hexametaphosphate adsorbs onto the surface of titanium dioxide particles through phosphate groups, generating electrostatic repulsion. Combined with the refined particles from the primary grinding process, the content of coarse particles with a D50 greater than 1 μm is reduced to less than 1%, providing a uniformly dispersed slurry foundation for subsequent coating. Compared to traditional processes, sodium hexametaphosphate has higher dispersion efficiency and better thermal stability.

[0026] In order to better inorganically coat titanium dioxide, in some embodiments, the inorganic coating includes multi-stage aging, and the multi-stage aging includes the following steps: (a) adding a water-soluble cerium salt solution to the uniformly dispersed slurry, adjusting the pH value to 9-10, and aging at 60° C.-80° C. for 60 min-90 min; (b) adding a sodium hexametaphosphate solution to the slurry of step (a) and aging at 60° C. to 80° C. for 45 to 75 minutes; (c) adding the aluminum compound solution to the slurry of step (b) in two steps, adjusting the pH of the slurry to 7-9 for the first step and aging at 60°C-80°C for 60-90 min, and adjusting the pH of the slurry to 5-7 for the second step and aging at 60°C-80°C for 45-75 min.

[0027] The present invention achieves a functionalized gradient coating through staged aging by precisely controlling pH and temperature. In step (a), cerium salt is hydrolyzed under alkaline conditions (pH 9-10) to generate CeO2, forming a dense inner layer that blocks the migration of photogenerated electrons. Then, in step (b), sodium hexametaphosphate is added to enhance dispersion and prevent particle agglomeration during the coating process. In step (c), the first aluminum coating (pH 7-9) generates Al(OH)3, and the second aluminum coating (pH 5-7) induces the conversion of Al(OH)3 to boehmite (AlOOH), enhancing the density and acid resistance of the coating layer. Compared to existing inorganic coating methods, the dispersion stability is improved by over 30%. In some embodiments, the secondary dispersion process includes subjecting the coated slurry to solid-liquid separation to obtain a filter cake, and then adding deionized water and a polymer dispersant to the filter cake for secondary dispersion. The polymer dispersant includes a polycarboxylate dispersant. This method removes unreacted salt impurities through solid-liquid separation and, combined with the long-chain steric hindrance of the polycarboxylate dispersant (such as sodium polycarboxylate), prevents secondary particle agglomeration. Compared to the existing drying-crushing process, direct pulping eliminates the drying step, reduces energy consumption by over 25%, and avoids dust pollution.

[0028] To achieve a more uniform powder, in some embodiments, the secondary dispersion treatment is followed by secondary grinding, with a stirring speed of 600-800 r / min and a stirring time of 45-60 minutes. This secondary grinding further refines the particles to submicron size. Combined with a stirring speed of 600-800 r / min, this ensures a uniform particle size distribution (D90 < 2 μm) and a stable solids content of 40%-50% for the titanium dioxide slurry, allowing direct use in decorative paper production without the uneven dispersion issues associated with traditional dry powder reconstitution.

[0029] To ensure process controllability, such as Figure 1 As shown, the present invention optimizes the process parameters throughout the entire process, which in some embodiments includes: (1) Mixing the primary rutile titanium dioxide with deionized water to prepare a slurry with a concentration of 250 g / L to 400 g / L, adding sodium hexametaphosphate with a concentration of 50 g / L to 90 g / L in terms of P2O5 in an amount of 0.5% to 1.5% of the mass of the titanium dioxide, stirring at a high speed of 1500 r / min to 2500 r / min for 30 min to 60 min, and then grinding once until the content of particles with a particle size D50 greater than 1 μm in the slurry is less than 1%; (2) heating the slurry obtained in step (1) to 60°C to 80°C, adding a water-soluble cerium salt solution, adjusting the pH value to 9 to 10, and stirring and aging for 60 min to 90 min; (3) adding a sodium hexametaphosphate solution having a concentration of 80 g / L to 120 g / L in terms of P2O5 to the slurry of step (2) in an amount of 1.0% to 2.0% of the mass of TiO2, stirring at 60°C to 80°C for 30 min to 60 min, and then aging for 45 min to 75 min; (4) Adding the aluminum compound solution to the slurry in step (3) in two steps: First, add an aluminum-containing compound with a concentration of 100g / L to 150g / L calculated as alumina, and the amount added is 1.0% to 3.0% of the mass of titanium dioxide. Simultaneously add sulfuric acid or hydrochloric acid to adjust the pH to 7 to 9, and mature at 60°C to 80°C for 60min to 90min. A second addition of an aluminum-containing compound at a concentration of 100 g / L to 150 g / L calculated as alumina, with the amount added being 1.0% to 2.0% of the mass of titanium dioxide, and sulfuric acid or hydrochloric acid added concurrently to adjust the pH to 5 to 7, followed by aging at 60°C to 80°C for 45 to 75 minutes; (5) The slurry treated in step (4) is filtered and washed, and the resulting filter cake is mixed with deionized water and a polycarboxylate dispersant in an amount of 0.2% to 0.5% of the mass of the filter cake. The mixture is stirred at 500 rpm to 800 rpm for 30 to 60 minutes, and then subjected to secondary grinding to obtain a water slurry of titanium dioxide with a solid content of 40% to 50%.

[0030] Among them, in step (1), a slurry with a concentration of (250-400 g / L) is combined with sodium hexametaphosphate for dispersion to improve production efficiency; in steps (2) to (4), the step-by-step coating and aging parameters are matched with the material reaction kinetics, so that the coverage rate of the CeO2-Al2O3 composite layer is greater than 95%; in step (5), the polycarboxylate dispersant and the secondary grinding work synergistically, so that the water slurry titanium dioxide does not settle after being left to stand for 48 hours, and the dispersion stability is better than the dry powder re-dissolution system in the prior art.

[0031] In some embodiments, the water-soluble cerium salt in step (2) is ammonium cerium nitrate, the solution concentration of which is 60 g / L to 80 g / L in terms of cerium oxide, the amount added is 0.5% to 1.0% of the mass of titanium dioxide in the slurry, and the addition time is 30 min to 60 min (the addition time of 30 min to 60 min is within 30 min to 60 min when the slurry obtained in step (1) is heated to 60° C. to 80° C. in step (2).

[0032] The optimization of the concentration of ammonium cerium nitrate (60-80 g / L in terms of CeO2) and the addition time (30-60 min) ensures the uniform hydrolysis of the cerium salt to form a nano-scale CeO2 coating layer, which can better control the coating thickness, significantly reduce the photocatalytic activity of titanium dioxide, and improve the light resistance by more than 20%.

[0033] In some embodiments, the aluminum-containing compound in steps (4) and (5) is sodium aluminate. Sodium aluminate (NaAlO2) is hydrolyzed stepwise at pH 7-9 and 5-7 to generate Al(OH)3 and boehmite (AlOOH), respectively. The former improves surface wettability, while the latter enhances the mechanical strength of the coating layer, making titanium dioxide less likely to fall off during the hot pressing process of dipping and the covering power of the decorative paper increased by 15%. In some embodiments, the polycarboxylate dispersant is sodium polycarboxylate. Sodium polycarboxylate is adsorbed on the surface of titanium dioxide particles via carboxylic acid groups. Its long chain structure creates steric hindrance. Combined with mechanical dispersion from secondary grinding, this results in an absolute zeta potential of titanium dioxide slurry greater than 30 mV, achieving industry-leading suspension stability.

[0034] In some embodiments, the primary and secondary grinding processes are performed in a sand mill, with the primary grinding speed at 13-14 m / s and the secondary grinding speed controlled at 8-10 m / s. The high shear force of the sand mill (12-15 m / s for primary grinding and 8-10 m / s for secondary grinding) ensures efficient particle refinement, avoids the risk of metal contamination associated with traditional ball mills, and reduces energy consumption. The resulting slurry has a narrow particle size distribution (D50 < 0.5 μm), meeting the high gloss requirements for decorative paper.

[0035] The present invention is further illustrated below by means of specific examples.

[0036] Example 1 The primary rutile titanium dioxide was mixed with deionized water to form a slurry with a concentration of 300 g / L. 0.5% sodium hexametaphosphate was added and stirred at 1500 r / min for 60 minutes using a high-speed mixer. The mixture was then initially ground in a sand mill at a speed of 13 m / s until the slurry contained 0.8% particles with a D50 greater than 1 μm. The sand-milled slurry was added to a four-necked round-bottom flask and stirred. The temperature was raised to 60°C by heating. Over 30 minutes, 70 g / L ammonium cerium nitrate solution (0.5% of the mass of the TiO2, calculated as CeO2) was added. The pH was adjusted to 9.5 with sodium hydroxide solution and the mixture was stirred and aged for 75 minutes. Over 45 minutes, 100 g / L sodium hexametaphosphate (1% of the mass of the titanium dioxide, calculated as P2O5) was added to the aged slurry and aged for 60 minutes. Over 90 minutes, add 100 g / L of sodium metaaluminate solution (2% of the mass of the titanium dioxide, calculated as Al2O3) to the slurry. Simultaneously, add dilute sulfuric acid to control the slurry pH to 8-9. Mature for 60 minutes. Over 90 minutes, add 100 g / L of sodium metaaluminate solution (2% of the mass of the titanium dioxide, calculated as Al2O3) to the slurry again. Simultaneously, add dilute sulfuric acid to control the slurry pH to 6-7. Mature for 60 minutes to obtain a surface-treated titanium dioxide slurry. Wash with deionized water and filter to obtain a filter cake. Add deionized water and 0.2% sodium polycarboxylate as a dispersant to the filter cake, stir at 600 r / min for 45 minutes, and sand-mill again to obtain a titanium dioxide water-based slurry for decorative paper.

[0037] Example 2 The primary rutile titanium dioxide was mixed with deionized water to form a slurry with a concentration of 300 g / L. 1.0% sodium hexametaphosphate was added and stirred at 2500 r / min for 50 minutes using a high-speed mixer. The mixture was then initially ground in a sand mill at 14 m / s until the slurry contained 0.6% particles with a D50 greater than 1 μm. The sand-milled slurry was added to a four-necked round-bottom flask and stirred. The temperature was raised to 80°C and 70 g / L of ammonium cerium nitrate solution (0.5% of the mass of the TiO2, calculated as CeO2) was added over 30 minutes. The pH was adjusted to 9.5 with sodium hydroxide solution and the mixture was stirred and aged for 75 minutes. Over 90 minutes, 100 g / L of sodium hexametaphosphate (2% of the mass of the titanium dioxide, calculated as P2O5) was added to the aged slurry and aged for 90 minutes. Over 120 minutes, add 100 g / L of sodium metaaluminate solution (3% of the mass of the titanium dioxide, calculated as Al2O3) to the slurry. Simultaneously, add dilute sulfuric acid to control the slurry pH to 8-9. Mature for 90 minutes. Again, add 100 g / L of sodium metaaluminate solution (2% of the mass of the titanium dioxide, calculated as Al2O3) to the slurry. Simultaneously, add dilute sulfuric acid to control the slurry pH to 6-7. Mature for 90 minutes to obtain a surface-treated titanium dioxide slurry. Wash with deionized water and filter to obtain a filter cake. Add deionized water and 0.24% sodium polycarboxylate as a dispersant to the filter cake, stir at 800 r / min for 60 minutes, and sand-mill again to obtain a titanium dioxide water-based slurry for decorative paper.

[0038] The samples of the embodiment were tested for water dispersion stability and application performance. Application test method: Add the above-prepared water slurry titanium dioxide to deionized water and paper pulp, and use a papermaking machine to make paper samples. After the paper samples are dipped in glue and hot-pressed, the whiteness, hiding power and light resistance are compared with the control samples (visual comparison).

[0039] Water dispersion stability test method: Pour the prepared titanium dioxide water slurry into a 200 mL graduated cylinder and let it stand, and observe the sedimentation height of the slurry at different times.

[0040] The test results are as follows: Table 1 Application results of different samples

[0041] Note: Comparison standard 1 is titanium dioxide specially used for domestic chloride papermaking; comparison standard 2 is titanium dioxide specially used for foreign chloride papermaking.

[0042] Table 2 Water dispersion stability test results

[0043] It can be seen from the above examples that the titanium dioxide water slurry for decorative paper prepared by the present invention has good dispersibility and application performance, and the preparation method is simple and low-cost, suitable for industrial production, and has broad application prospects.

[0044] This invention document is intended to illustrate how to use the disclosed technology and various embodiments, and is not intended to limit the scope and spirit to which it is actually directed and to which it is equivalent. Furthermore, the above description is not intended to be exhaustive of all possibilities or to limit the scope of protection to the precise form disclosed. In accordance with the above teachings, changes and variations are possible. The selected and illustrated embodiments provide the best illustration of the principles of the technology and its practical application, and enable those skilled in the art to use the disclosed technology for various changes in various conceivable specific applications. Therefore, without substantially departing from the spirit and principles of the technology described in this invention, various changes and modifications made to the above embodiments are intended to be included within the scope of this invention.

Claims

1. A method for preparing a titanium dioxide slurry specially used for decorative paper, characterized in that: Using primary rutile titanium dioxide as raw material, the slurry containing the raw material is first subjected to a preliminary dispersion treatment, and then water-soluble cerium salts and aluminum-containing compounds are added step by step to the evenly dispersed slurry for inorganic coating, so that a composite coating layer composed of cerium oxide and aluminum oxide is formed on the surface of the titanium dioxide. Finally, the coated slurry is subjected to a secondary dispersion treatment to obtain water-slurry titanium dioxide.

2. The method according to claim 1, characterized in that The preliminary dispersion treatment includes adding a dispersant to the slurry containing the raw materials, and then performing a grinding process; the dispersant includes sodium hexametaphosphate; the grinding process includes grinding the slurry after adding the dispersant until the content of particles with a slurry particle size D50 greater than 1 μm is less than 1%.

3. The method according to claim 1, characterized in that The inorganic coating includes multi-stage aging, and the multi-stage aging includes the following steps: (a) adding a water-soluble cerium salt solution to the uniformly dispersed slurry, adjusting the pH value to 9-10, and aging at 60° C.-80° C. for 60 min-90 min; (b) adding a sodium hexametaphosphate solution to the slurry of step (a) and aging at 60° C. to 80° C. for 45 to 75 minutes; (c) adding the aluminum compound solution to the slurry of step (b) in two steps, adjusting the pH of the slurry to 7-9 for the first step and aging at 60°C-80°C for 60-90 min, and adjusting the pH of the slurry to 5-7 for the second step and aging at 60°C-80°C for 45-75 min.

4. The method according to claim 1, wherein The secondary dispersion treatment includes performing solid-liquid separation on the coated slurry to obtain a filter cake, adding deionized water and a polymer dispersant to the filter cake and performing secondary dispersion treatment, wherein the polymer dispersant includes a polycarboxylate dispersant.

5. The method according to claim 4, characterized in that The secondary dispersion treatment further includes secondary grinding, the stirring speed of the secondary grinding is 600-800 r / min, and the stirring time of the secondary grinding is 45-60 min.

6. The method according to claim 1, characterized in that include: (1) Mixing the primary rutile titanium dioxide with deionized water to prepare a slurry with a concentration of 250 g / L to 400 g / L, adding sodium hexametaphosphate with a concentration of 50 g / L to 90 g / L in terms of P2O5 in an amount of 0.5% to 1.5% of the mass of the titanium dioxide, stirring at a high speed of 1500 r / min to 2500 r / min for 30 min to 60 min, and then grinding once until the content of particles with a particle size D50 greater than 1 μm in the slurry is less than 1%; (2) heating the slurry obtained in step (1) to 60°C to 80°C, adding a water-soluble cerium salt solution, adjusting the pH value to 9 to 10, and stirring and aging for 60 min to 90 min; (3) adding a sodium hexametaphosphate solution having a concentration of 80 g / L to 120 g / L in terms of P2O5 to the slurry of step (2) in an amount of 1.0% to 2.0% of the mass of TiO2, stirring at 60°C to 80°C for 30 min to 60 min, and then aging for 45 min to 75 min; (4) Adding the aluminum compound solution to the slurry in step (3) in two steps: First, add an aluminum-containing compound with a concentration of 100g / L to 150g / L calculated as alumina, and the amount added is 1.0% to 3.0% of the mass of titanium dioxide. Simultaneously add sulfuric acid or hydrochloric acid to adjust the pH to 7 to 9, and mature at 60°C to 80°C for 60min to 90min. A second addition of an aluminum-containing compound at a concentration of 100 g / L to 150 g / L calculated as alumina, with the amount added being 1.0% to 2.0% of the mass of titanium dioxide, and sulfuric acid or hydrochloric acid added concurrently to adjust the pH to 5 to 7, followed by aging at 60°C to 80°C for 45 to 75 minutes; (5) The slurry treated in step (4) is filtered and washed, and the resulting filter cake is mixed with deionized water and a polycarboxylate dispersant in an amount of 0.2% to 0.5% of the mass of the filter cake. The mixture is stirred at 500 rpm to 800 rpm for 30 to 60 minutes, and then subjected to secondary grinding to obtain a water slurry of titanium dioxide with a solid content of 40% to 50%.

7. The method according to claim 6, characterized in that The water-soluble cerium salt in step (2) is ammonium cerium nitrate, the solution concentration of which is 60 g / L to 80 g / L in terms of cerium oxide, the amount added is 0.5% to 1.0% of the mass of titanium dioxide in the slurry, and the addition time is 30 min to 60 min.

8. The method according to claim 6, characterized in that The aluminum-containing compound in steps (4) and (5) is sodium metaaluminate.

9. The method according to claim 6, characterized in that The polycarboxylate dispersant is sodium polycarboxylate.

10. The method according to claim 6, characterized in that The primary grinding and secondary grinding are performed by a sand mill, the primary grinding speed is 13m / s to 14m / s, and the secondary grinding speed is controlled at 8m / s to 10m / s.

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