Low-viscosity high-dispersity aluminum oxide slurry and preparation method thereof

Abstract

The invention belongs to the field of functional composite materials, and particularly relates to low-viscosity and high-dispersity aluminum oxide slurry and a preparation method thereof.The low-viscosity and high-dispersity aluminum oxide slurry is prepared from a newly-designed phosphono-carboxyl block copolymer and biquaternary ammonium salt polyether silane as composite modifiers; and efficient anchoring and stable dispersion of the surfaces of alumina particles are realized through the synergistic effect of molecular structures. The phosphono-carboxyl block copolymer is prepared through controllable polymerization and deprotection reaction, and strong chemical bonding is formed between a phosphono group and the surface of aluminum oxide; the biquaternary ammonium salt polyether silane is subjected to click chemical synthesis, and electrostatic adsorption of quaternary ammonium salt and the steric hindrance effect of a polyether chain are combined. When the slurry is prepared, the two modifiers are sequentially added into water, the aluminum oxide powder is added after the pH value is adjusted, finally, the isobutylene maleic anhydride copolymer and the defoaming agent are introduced, and the slurry is obtained through vacuum defoaming and filtering. The slurry prepared by the method has the characteristics of high solid content, low viscosity and good dispersion stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of functional composite materials, and particularly relates to a low-viscosity high-dispersibility alumina slurry and a preparation method thereof. BACKGROUND

[0002] As a key basic material, the alumina slurry has a wide application in the fields of advanced ceramic manufacturing, electronic device packaging and energy device, etc. With the continuous improvement of the performance requirements of modern industry on products, the traditional alumina slurry has been difficult to meet the stringent requirements of high-end application scenarios on material performance. The core contradiction faced by the current industry lies in the mutual restriction between the solid content and the fluidity of the slurry: increasing the solid content will cause the viscosity of the slurry to rise sharply, affecting the forming process performance; reducing the viscosity often needs to increase the solvent content, which not only reduces the forming efficiency, but also causes uneven shrinkage, increased defects and other quality problems in the drying and sintering process. Especially in the application field requiring high solid content, the slurry needs to have high solid content, low viscosity and long-term dispersion stability at the same time, while the slurry prepared by the traditional process often cannot meet these characteristics. In the prior art, the methods of simple physical mixing or conventional surfactant modification cannot fundamentally solve the problems of the agglomeration tendency of alumina particles under high solid content and the out-of-control viscosity, which seriously restricts the quality improvement and industrial development of high-performance ceramic products.

[0003] In terms of dispersant technology, the widely used ammonium polyacrylate dispersant can provide a certain electrostatic repulsion, but its single molecular structure has limited adsorption strength on the surface of alumina particles, and it is easy to desorb under complex working conditions, resulting in insufficient dispersion stability. Although the small molecule dispersant can temporarily reduce the viscosity, it lacks a long-term stability mechanism, and the slurry is prone to particle sedimentation and hard agglomeration during storage and processing. More troublesome is that the molecular structure of the traditional dispersant lacks intelligent response characteristics, and it cannot adjust the spatial conformation according to the changes in the slurry environment, resulting in large fluctuations in dispersion effect under different pH and ionic strength conditions. In recent years, although some researches have tried to modify by compounding multiple additives or introducing special monomers, these methods often complicate the interaction between components, and even produce competitive adsorption, which reduces the dispersion efficiency. Especially in the system that needs to realize dispersion and gelation at the same time, the traditional dispersant often interferes with the formation of the gel network, causing difficulties in solidification process control and affecting the uniformity of the green body.

[0004] For the application of alumina slurry in gel casting process, the prior art still has the problem of poor compatibility of the gelling agent and the dispersing system. Isobutylene and maleic anhydride copolymer as an effective gelling agent, the carboxyl group produced by the hydrolysis of the anhydride group on the molecular chain helps to interact with the particle surface, but how to make it synergistic with the dispersant rather than interfere with each other is always a technical difficulty. In the traditional process, the dispersant and the gelling agent often need to be added separately and the time sequence needs to be accurately controlled. Any slight deviation of the process parameters may lead to loss of control of the slurry rheology or uneven gelation. In addition, while pursuing high solid content and low viscosity, the slurry also needs to have good rheological properties and molding performance, which requires fine design of the entire formula system at the molecular level. The prior art lacks systematic study of the interaction between the components in the slurry, especially the lack of multifunctional composite modifier that can provide strong anchoring effect, electrostatic stabilization and steric hindrance effect, which makes it still a technical problem to be solved to prepare alumina slurry with excellent processing performance and use performance. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a low-viscosity high-dispersibility alumina slurry and a preparation method thereof

[0006] In the first aspect of the present application, a preparation method of a low-viscosity high-dispersibility alumina slurry is provided, and the steps include:

[0007] S1, deionized water is added to a reaction container, and the temperature is controlled at 23-27℃; under stirring conditions, phosphinyl-carboxyl block copolymer and double quaternary ammonium salt-polyether silane are added in sequence, and stirring is continued;

[0008] S2, then, ammonia water is added to adjust the pH to 8.5-9.5 to form a dispersant solution; α-alumina powder is added to the dispersant solution, and stirring is continued; isobutylene-maleic anhydride copolymer solution previously dissolved in deionized water is added, and stirring is continued; silicone defoaming agent is added to obtain a mixed slurry; the mixed slurry is transferred to a vacuum defoaming device for treatment;

[0009] S3, filter the slurry through a standard screen.

[0010] In the present application, the preparation of low viscosity and high dispersibility alumina slurry is based on the multiple action mechanism of surface modification, steric stabilization and rheological regulation. In the initial dispersion stage, two functional polymers undergo molecular conformation adjustment and pre-dispersion in a specific pH water medium. The carboxyl groups in the phosphono-carboxyl block copolymer ionize under alkaline conditions to form negatively charged polymer chains, while the double quaternary ammonium salt-polyether silane maintains its cationic characteristics and stretched polyether chain conformation. The two polymers form a preliminary composite dispersion system in solution through electrostatic interaction. When the alumina powder is added into the key surface modification stage, the phosphono-carboxyl block copolymer forms a strong coordination bond with the aluminum atoms on the surface of alumina through its terminal phosphonic acid groups. This bonding strength is much higher than that of traditional physical adsorption, ensuring the firm anchoring of the dispersant molecules on the particle surface. At the same time, the double quaternary ammonium salt-polyether silane produces strong electrostatic attraction with the negatively charged areas on the surface of alumina through its quaternary ammonium salt cations, and achieves multiple anchoring effects through the condensation reaction of the silane end groups with the surface hydroxyl groups. In the steric stabilization mechanism establishment stage, the two polymers form a composite adsorption layer on the particle surface. The carboxyl segment of the phosphono-carboxyl block copolymer provides a primary stable barrier through electrostatic repulsion, while the polyether segment of the double quaternary ammonium salt-polyether silane provides a secondary stable barrier through steric hindrance effect. The synergistic effect of the two stabilization mechanisms effectively prevents the tendency of particle aggregation. The subsequently introduced isobutylene-maleic anhydride copolymer plays a dual function in the slurry. Part of its chain segments participate in the adsorption process on the particle surface, and the remaining chain segments form a three-dimensional network structure precursor in the slurry, laying the foundation for the subsequent gelation process. In the vacuum defoaming stage, the pressure change promotes the inflation and escape of air bubbles entrained in the slurry, and the shearing action promotes the homogenization of the dispersion system. In the final obtained slurry system, the two functional polymers form a dense and orderly composite adsorption layer on the surface of alumina particles, achieving effective repulsion between particles through the electrostatic-steric synergistic stabilization mechanism, thereby maintaining low viscosity characteristics at high solid content, and having excellent storage stability and rheological properties.

[0011] In the present application, the mass fraction of ammonia water is 25%. The ammonia water in this concentration range has moderate volatility and alkalinity, which can efficiently adjust the pH of the slurry system to the optimal range of 8.5-9.5, thereby ensuring the full ionization of the carboxyl groups in the phosphono-carboxyl block copolymer and producing strong electrostatic repulsion. At the same time, this concentration avoids the problem of volatile organic compounds control caused by excessive use of ammonia water, and prevents local pH fluctuations caused by high concentration, which is beneficial to the long-term stability of the slurry system.

[0012] As a preferred technical solution of the present application, in step S1, the time of continuous stirring is 30-40 min.

[0013] As a preferred technical solution of the present application, in step S2, the processing time in the vacuum defoaming device is 10-15 min.

[0014] As a preferred technical scheme of the present application, the preparation method of the phosphono-carboxyl block copolymer comprises: A1, reacting 2-phosphonobutane-1, 2, 4-tricarboxylic acid with 2-bromoisobutyryl bromide in anhydrous tetrahydrofuran at 0-2℃ to generate a phosphonated ATRP initiator; adding the phosphonated ATRP initiator, t-butyl acrylate and pentamethyldiethylenetriamine into a reaction kettle, protecting by introducing nitrogen, then adding cuprous chloride, and performing atom transfer radical polymerization at 58-62℃ to obtain a phosphono-terminated poly(t-butyl acrylate) prepolymer; A2, dissolving the phosphono-terminated poly(t-butyl acrylate) prepolymer in dichloromethane, adding trifluoroacetic acid to perform a t-butyl protection removal reaction at room temperature; precipitating, filtering and washing the reaction mixture in ethyl ether, and then vacuum drying.

[0015] In the present application, the preparation of the phosphono-carboxyl block copolymer is based on the scientific principles of active controlled polymerization and selective deprotection. The preparation process starts from the synthesis stage of the phosphonated initiator, which utilizes the selective esterification reaction of the specific phosphonic acid group in the di-phosphonic acid butane-tricarboxylic acid molecule and the bromoacyl bromide compound under low temperature conditions to generate an atom transfer radical polymerization initiator with a phosphonic acid end group. The key of this step lies in strictly controlling the reaction temperature and material ratio to ensure the effective introduction of the phosphonic acid group in the initiator without affecting its initiation activity. Then, it enters the block polymerization stage, in which the newly generated phosphonated initiator and t-butyl acrylate monomer are subjected to atom transfer radical polymerization in a catalytic system composed of a copper-based catalyst and a polyamine ligand under the protection of an inert atmosphere. In this process, the catalyst system controls the active species concentration through a reversible oxidation-reduction process to realize uniform growth of the polymer chain and form a phosphono-terminated poly(t-butyl acrylate) prepolymer with narrow molecular weight distribution. The accurate control of the polymerization reaction temperature and time is crucial to ensure the regularity of the polymer chain structure. Finally, the deprotection conversion stage is performed, in which the obtained prepolymer is dissolved in a suitable solvent, and a strong protonic acid is added to remove the t-butyl ester protecting group. This deprotection process causes selective hydrolysis of the t-butyl ester group through an acid catalysis mechanism, converting the t-butyl ester structure of the polymer side chain into a carboxyl group while maintaining the integrity of the main chain structure and the phosphonic acid end group. After the reaction is completed, the residual reagents and by-products are removed by precipitation purification method, and finally the block copolymer with both phosphonic acid anchoring groups and carboxyl dispersing segments is obtained. The mechanism design of the entire preparation process ensures the accurate controllability of the product molecular structure and the effective retention of functional groups.

[0016] As a preferred technical scheme of the present application, in step A1, the reaction time at 0-2℃ is 12-14h; the atom transfer radical polymerization reaction is performed at 58-62℃ for 24-30h.

[0017] As a preferred technical scheme of the present application, the de-tert-butyl protection reaction time in step A2 is 10-14 h.

[0018] As a preferred technical scheme of the present application, the preparation method of the double-quaternary ammonium salt-polyether silane comprises: B1, refluxing 3-chloropropyltrimethoxysilane and N-methyl imidazole in acetonitrile to generate a double-imidazole salt intermediate; adding polyethylene glycol monomethyl ether, 3-bromopropargyl and sodium hydride into toluene to react at 68-72℃ to obtain a polyether intermediate; reacting the polyether intermediate with 3-azidopropyltrimethoxysilane to generate a polyether silane precursor; quaternary ammoniation of the double-imidazole salt intermediate with methyl iodide in tetrahydrofuran at 38-42℃ to obtain a double-quaternary ammonium salt silane; B2, mixing the double-quaternary ammonium salt silane with the polyether silane precursor, adding sodium ascorbate and copper sulfate pentahydrate, and performing copper-catalyzed azide-yne cycloaddition in a 38-42℃ aqueous solution, and then extracting, drying and concentrating after the reaction is completed.

[0019] In the present application, the construction of the double-quaternary ammonium salt-polyether silane is based on the combination of multi-step organic synthesis and efficient click chemistry. The preparation process starts from the parallel synthesis of double-active intermediates. On the one hand, a double-imidazole salt silane intermediate is generated by nucleophilic substitution reaction of chloropropyl silane and methyl imidazole, which is carried out under reflux conditions. The nitrogen atom on the imidazole ring attacks the chloromethyl group in the silane to form a quaternary ammonium salt structure. On the other hand, a terminal alkyne polyether intermediate is prepared by Williamson ether synthesis reaction of polyethylene glycol monomethyl ether and bromopropargyl under the action of strong base. In this reaction, the hydroxyl group at the end of the polyether forms an oxygen anion under the action of base, and then nucleophilic substitution with bromopropargyl occurs to form an ether bond. Subsequently, in the azide-silane precursor preparation stage, the terminal alkyne polyether intermediate is connected with azidopropylsilane through copper-catalyzed click chemistry reaction. This process follows the classical azide-yne cycloaddition mechanism and forms a stable triazole ring connection structure under the action of a catalyst. In the deep modification stage of the quaternary ammonium salt silane, the double-imidazole salt intermediate undergoes secondary quaternary ammoniation with methyl iodide. Methyl iodide undergoes nucleophilic substitution with the remaining nitrogen sites in the imidazole salt to form a double-quaternary ammonium salt structure. In the final molecular assembly stage, the obtained azide-terminated polyether silane precursor is connected with the terminal alkyne double-quaternary ammonium salt silane in the presence of a copper catalyst through click chemistry. This cycloaddition reaction has the characteristics of high selectivity and high efficiency, ensuring the connection of the two functional molecules through a stable covalent bond. The entire preparation process involves multiple nucleophilic substitution and click chemistry reactions, and each step has mild reaction conditions and high yield. The final product has both the strong adsorption properties of quaternary ammonium salt and the spatial stability function of polyether chain.

[0020] As a preferred technical scheme of the present application, in step B1, the reaction time at 68-72℃ is 7-9 h; and the quaternary ammoniation reaction time at 38-42℃ is 12-14 h.

[0021] As a preferred technical scheme of the present application, in step B2, the azide-yne cycloaddition reaction time is 22-26 h.

[0022] In a second aspect of the present application, the low-viscosity high-dispersibility alumina slurry prepared by the preparation method of the low-viscosity high-dispersibility alumina slurry comprises the following raw materials by weight: 80-120 parts of alpha-alumina powder; 0.5-1.5 parts of phosphinyl-carboxyl block copolymer; 0.3-1 part of bis-quaternary ammonium salt-polyether silane; 0.1-0.5 parts of isobutene-maleic anhydride copolymer; 30-45 parts of deionized water; 0.5-2.0 parts of ammonia; and 0.05-0.2 parts of silicone defoaming agent.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] (1) The low-viscosity high-dispersibility alumina slurry and the preparation method thereof provided by the present application exhibit significant technical progress and practical effects in many aspects through innovative molecular structure design and process optimization. First, in terms of basic performance of the slurry, the high dispersion of alumina particles in the aqueous medium is achieved through the synergistic effect of phosphinyl-carboxyl block copolymer and bis-quaternary ammonium salt-polyether silane. The phosphinyl-carboxyl block copolymer is firmly combined with the particle surface through strong coordination bonds, providing long-lasting electrostatic stabilization; and the bis-quaternary ammonium salt-polyether silane forms a double stabilization mechanism through steric hindrance effect and secondary anchoring. This composite dispersion system enables the slurry to maintain low viscosity characteristics while achieving high solid content, and also has excellent storage stability, no sedimentation and caking during long-term standing, and good shear thinning characteristics of slurry rheological performance, facilitating subsequent various forming processing operations.

[0025] (2) In terms of dispersion stability and rheological properties, the slurry system exhibits unique advantages. Due to the fundamental improvement in dispersion uniformity, the slurry can maintain a stable dispersion state during storage and use, effectively avoiding the common problems of stratification and hard precipitation of traditional slurries. The synergistic effect of the two novel modified compounds builds a triple stabilization system enhanced by electrostatic steric hindrance anchoring, enabling the slurry to maintain excellent dispersion effect in a wide range of pH. In particular, the polyether segment of bis-quaternary ammonium salt-polyether silane has temperature response characteristics, which fully plays a role in steric stabilization under slurry preparation and storage conditions, and can adapt to process requirements during subsequent processing. This intelligent response characteristic is not possessed by traditional dispersants. In addition, the system has good compatibility with isobutene-maleic anhydride copolymer gelling agent, which can ensure the stability of the slurry during storage and will not affect the gelling effect during subsequent forming process.

[0026] (3) In terms of practical application performance, the product prepared by using the slurry system exhibits excellent comprehensive performance. The high solid content characteristics of the slurry significantly improve the molding efficiency, reduce the energy consumption and shrinkage deformation risk in the drying process. The uniform dispersion state ensures the compactness and uniformity of the microstructure of the product, thereby improving the mechanical strength and reliability of the final product. Compared with the slurry prepared by the traditional method, the slurry obtained by the present application has wider process adaptability, can meet the requirements of various molding processes, and the process parameter control in the production process is more simple, and the product qualified rate is significantly improved. These excellent performance characteristics make the slurry have obvious advantages in the application of high-end ceramic products, electronic components and other fields, and provide reliable raw material guarantee for the quality improvement and performance optimization of related products. DETAILED DESCRIPTION

[0027] For the purpose of facilitating the understanding of the present application, the present application is illustrated by the following examples. It should be understood by those skilled in the art that the examples are only for the purpose of understanding the present application, and should not be regarded as specific limitations of the present application.

[0028] Some components in the examples and comparative examples are as follows:

[0029] The α-alumina powder is purchased from Shandong Aluminum Co., Ltd.

[0030] The isobutylene-maleic anhydride copolymer is purchased from Jihaichem Co., Ltd.

[0031] The silicone defoaming agent is purchased from Bluestar Silicones Co., Ltd.

[0032] The vacuum defoaming device is purchased from Shenzhen Jinzong Technology Co., Ltd.

[0033] The 2-phosphonic acid butane-1, 2, 4-tricarboxylic acid is purchased from Shandong Taihe Science and Technology Co., Ltd.

[0034] The 2-bromoisobutyryl bromide is purchased from Anjier Chemical Co., Ltd.

[0035] The tert-butyl acrylate is purchased from Wanhua Chemical Group Co., Ltd.

[0036] The pentamethyl diethylene triamine is purchased from Shanghai Aladdin Biochem Technology Co., Ltd.

[0037] The cuprous chloride is purchased from Sinopharm Chemical Reagent Co., Ltd.

[0038] The trifluoroacetic acid is purchased from Beijing Inokai Technology Co., Ltd.

[0039] The 3-chloropropyl trimethoxysilane is purchased from Jingzhou Jianghan Fine Chemical Co., Ltd.

[0040] The N-methylimidazole is purchased from Changzhou Huamao Petrochemical Co., Ltd.

[0041] The polyethylene glycol monomethyl ether is purchased from Jiangsu Hai'an Petrochemical Factory.

[0042] The 3-bromopropynyl is purchased from Jinan Henghua Technology Co., Ltd.

[0043] The sodium hydride is purchased from Tianjin Bonasun Technology Co., Ltd.

[0044] The 3-azidopropyl trimethoxysilane is purchased from Wuhan Huaxiang Kejie Biotechnology Co., Ltd.

[0045] The iodomethane is purchased from Chengdu Xiyax Chemical Co., Ltd.

[0046] The sodium ascorbate is purchased from Shenzhen Vipoint Pharmaceutical Co., Ltd.

[0047] The copper sulfate pentahydrate is purchased from Tongling Chemical Industry Group Co., Ltd.

[0048] Example 1

[0049] Preparation of phosphono-carboxyl block copolymer: 12.00 g of 2-phosphonobutane-1,2,4-tricarboxylic acid and 14.52 g of 2-bromoisobutyryl bromide were first weighed and dissolved in 150 mL of anhydrous tetrahydrofuran, and the reaction was continuously stirred at 0 °C in an ice water bath for 13 h to obtain a phosphonylated ATRP initiator. Then the initiator was added to a 500 mL polymerization reactor with 60.00 g of tert-butyl acrylate and 0.60 g of pentamethyldiethylenetriamine, and 0.30 g of cuprous chloride catalyst was added after 30 min of high-purity nitrogen protection. The reaction was continuously stirred at 60 °C for 26 h to obtain a phosphono-terminated poly(tert-butyl acrylate) prepolymer. The obtained prepolymer was completely dissolved in 120 mL of dichloromethane, and 50 mL of trifluoroacetic acid was added to perform the de-tert-butyl protection reaction at 25 °C for 12 h. After the reaction was completed, the mixed solution was slowly poured into 800 mL of ice ethanol to precipitate, and the white solid was collected by vacuum filtration and washed with fresh ethanol for 3 times. Finally, it was dried in a vacuum drying oven at 40 °C for 48 h to obtain the final product. Preparation of bis-quaternary ammonium salt-polyether silane: 10.00 g of 3-chloropropyltrimethoxysilane and 12.36 g of N-methylimidazole were weighed and added to 100 mL of acetonitrile as a solvent, and the reaction was refluxed at 85 °C for 26 h to obtain a bis-imidazole salt intermediate. Another 20.00 g of polyethylene glycol monomethyl ether (molecular weight 1000), 3.00 g of 3-bromopropyne, and 1.20 g of sodium hydride were reacted in 80 mL of anhydrous toluene at 70 °C for 8 h to obtain a terminal alkyne polyether intermediate. The intermediate was reacted with 8.00 g of 3-azidopropyltrimethoxysilane at 70 °C for 6 h to generate an azide-terminated polyether silane precursor. At the same time, the bis-imidazole salt intermediate was subjected to quaternary ammonium reaction with 10.00 g of iodomethane at 40 °C for 13 h to obtain a bis-quaternary ammonium salt silane. Finally, 0.50 g of sodium ascorbate and 0.20 g of copper sulfate pentahydrate were added to 50 mL of deionized water, and the above two products were added, and the reaction was continuously stirred at 40 °C water bath for 24 h. After the reaction was completed, it was extracted with dichloromethane for 3 times, and the combined organic phase was dried with anhydrous magnesium sulfate, and concentrated by rotary evaporation to obtain the final product. Preparation of alumina slurry: 450 mL of deionized water was weighed into a 1 L glass reactor, and the temperature was controlled at 25 °C. 10.00 g of phosphono-carboxyl block copolymer and 6.00 g of bis-quaternary ammonium salt-polyether silane were added in sequence under the condition of 500 rpm stirring, and the stirring was continued for 35 min. Then 8.00 g of 25% ammonia water was added to adjust the pH to 9.0, and a uniform dispersant solution was formed. 1000 g of α-alumina powder (D50 = 0.5 μm) was added in three batches, and after each batch was added, it was stirred for 10 min. Finally, the stirring speed was increased to 1200 rpm and continuously stirred for 60 min. 3.00 g of isobutylene-maleic anhydride copolymer was pre-dissolved in 50 mL of deionized water, and slowly added to the slurry system, and stirred at 600 rpm for 20 min.Finally, 1.00 g of silicone defoaming agent was added, and the mixed slurry was transferred into a vacuum defoaming device, treated at a vacuum degree of -0.095 MPa for 12 min, and finally filtered through a 400-mesh standard sieve to obtain the finished slurry.

[0050] Example 2

[0051] Preparation of phosphono-carboxyl block copolymer: 10.00 g of 2-phosphonobutane-1,2,4-tricarboxylic acid and 12.10 g of 2-bromoisobutyryl bromide were first weighed and dissolved in 130 mL of anhydrous tetrahydrofuran, and the reaction was continuously stirred at 0°C in an ice water bath for 12 h to obtain a phosphonylated ATRP initiator; then the initiator was added to a 500 mL polymerization reactor together with 50.00 g of tert-butyl acrylate and 0.55 g of pentamethyldiethylenetriamine, and after 28 min of high-purity nitrogen protection, 0.28 g of cuprous chloride catalyst was added, and the reaction was continuously stirred at 58°C in an oil bath for 24 h to obtain a phosphonyl-terminated poly(t-butyl acrylate) prepolymer; the obtained prepolymer was completely dissolved in 110 mL of dichloromethane, and 45 mL of trifluoroacetic acid was added, and the de-tert-butyl protection reaction was carried out at 25°C for 11 h; after the reaction was completed, the mixed solution was slowly poured into 750 mL of ice ethanol to precipitate, and white solids were collected by vacuum filtration and washed with fresh ethanol 3 times, and finally dried in a 40°C vacuum drying oven for 48 h to obtain the final product. Preparation of bis-quaternary ammonium salt-polyether silane: 9.00 g of 3-chloropropyltrimethoxysilane and 11.12 g of N-methylimidazole were weighed and added to 90 mL of acetonitrile as a solvent, and the reaction was carried out at 85°C in an oil bath for 25 h to obtain a bis-imidazole salt intermediate; another 15.00 g of polyethylene glycol monomethyl ether (molecular weight 1000), 2.50 g of 3-bromopropargyl, and 1.00 g of sodium hydride were reacted in 70 mL of anhydrous toluene at 70°C for 8 h to obtain a terminal alkyne-terminated polyether intermediate; the intermediate was reacted with 7.00 g of 3-azidopropyltrimethoxysilane at 70°C for 6 h to form an azide-terminated polyether silane precursor; at the same time, the bis-imidazole salt intermediate was subjected to quaternary ammonium reaction with 9.00 g of iodomethane at 40°C for 12 h to obtain a bis-quaternary ammonium salt silane; finally, 0.45 g of sodium ascorbate and 0.18 g of copper sulfate pentahydrate were added to 45 mL of deionized water, and the above two products were added, and the reaction was continuously stirred at 40°C for 22 h, and then extracted with dichloromethane 3 times, and the organic phase was combined and dried with anhydrous magnesium sulfate, and concentrated by rotary evaporation to obtain the final product.Preparation of alumina slurry: 400 mL of deionized water was measured into a 1 L glass reactor, the temperature was controlled at 25 °C, and 7.00 g of phosphono-carboxyl block copolymer and 4.00 g of bis-quaternary ammonium salt-polyether silane were added successively under the condition of 500 rpm stirring, and the stirring was continued for 35 min; then 7.00 g of 25% mass fraction ammonia water was added to adjust the pH to 9.0, forming a uniform dispersant solution; 800 g of a-alumina powder (D50 = 0.5 μm) was added in three batches, and after each batch was added, the stirring was continued for 10 min, and finally the stirring speed was increased to 1200 rpm and the stirring was continued for 60 min; 2.00 g of isobutylene-maleic anhydride copolymer was previously dissolved in 40 mL of deionized water, and was slowly added to the slurry system, and the stirring was continued for 20 min at 600 rpm; finally, 0.80 g of silicone defoaming agent was added, and the mixed slurry was transferred into a vacuum defoaming device, and was treated under a vacuum degree of -0.095 MPa for 12 min, and finally the finished product slurry was filtered through a 400 mesh standard screen.

[0052] Example 3

[0053] Preparation of phosphono-carboxyl block copolymer: 13.00 g of 2-phosphonobutane-1,2,4-tricarboxylic acid and 15.75 g of 2-bromoisobutyryl bromide were first weighed and dissolved in 160 mL of anhydrous tetrahydrofuran, and the reaction was continuously stirred at 0°C in an ice water bath for 14 h to obtain a phosphonylated ATRP initiator; then the initiator was added to a 500 mL polymerization reactor together with 65.00 g of tert-butyl acrylate and 0.65 g of pentamethyldiethylenetriamine, and after 32 min of high-purity nitrogen protection, 0.32 g of cuprous chloride catalyst was added, and the reaction was continuously stirred at 62°C in an oil bath for 30 h to obtain a phosphonyl-terminated poly(t-butyl acrylate) prepolymer; the obtained prepolymer was completely dissolved in 130 mL of dichloromethane, and 55 mL of trifluoroacetic acid was added, and the de-tert-butyl protection reaction was carried out at 25°C for 13 h; after the reaction was completed, the mixed solution was slowly poured into 850 mL of ice ethanol to precipitate, and white solids were collected by vacuum filtration and washed with fresh ethanol 3 times, and finally dried in a 40°C vacuum drying oven for 48 h to obtain the final product. Preparation of bis-quaternary ammonium salt-polyether silane: 11.00 g of 3-chloropropyltrimethoxysilane and 13.60 g of N-methylimidazole were weighed and added to 110 mL of acetonitrile as a solvent, and the reaction was carried out at 85°C in an oil bath for 27 h to obtain a bis-imidazole salt intermediate; 25.00 g of polyethylene glycol monomethyl ether (molecular weight 1000), 3.50 g of 3-bromopropargyl, and 1.40 g of sodium hydride were reacted in 90 mL of anhydrous toluene at 70°C for 8 h to obtain a terminal alkyne-terminated polyether intermediate; the intermediate was reacted with 9.00 g of 3-azidopropyltrimethoxysilane at 70°C for 6 h to form an azide-terminated polyether silane precursor; at the same time, the bis-imidazole salt intermediate was subjected to quaternary ammonium reaction with 11.00 g of iodomethane at 40°C for 14 h to obtain a bis-quaternary ammonium salt silane; finally, 0.55 g of sodium ascorbate and 0.22 g of copper sulfate pentahydrate were added to 55 mL of deionized water, and the above two products were added, and the reaction was continuously stirred at 40°C in a water bath for 26 h, and then extracted with dichloromethane 3 times, and the organic phase was combined and dried with anhydrous magnesium sulfate, and concentrated by rotary evaporation to obtain the final product.Preparation of alumina slurry: 500 mL of deionized water was measured into a 1 L glass reactor, the temperature was controlled at 25°C, and 13.00 g of phosphono-carboxyl block copolymer and 8.00 g of bis-quaternary ammonium salt-polyether silane were added in turn under the condition of 500 rpm stirring, and the stirring was continued for 35 min; then 9.00 g of 25% mass fraction of ammonia water was added to adjust the pH to 9.0, and a uniform dispersant solution was formed; 1200 g of α-alumina powder (D50 = 0.5 μm) was added in three batches, and after each batch was added, the stirring was continued for 10 min, and finally the stirring speed was increased to 1200 rpm and the stirring was continued for 60 min; 4.00 g of isobutylene-maleic anhydride copolymer was previously dissolved in 60 mL of deionized water, and was slowly added to the slurry system, and the stirring was continued for 20 min at 600 rpm; finally, 1.20 g of silicone defoaming agent was added, and the mixed slurry was transferred into a vacuum defoaming device, and was treated at a vacuum degree of -0.095 MPa for 15 min, and finally the finished product slurry was filtered through a 400 mesh standard sieve.

[0054] Comparative Example 1

[0055] The difference between this comparative example and Example 1 is that no modified compound is added, and 1000 g of α-alumina powder is directly added to 450 mL of deionized water, 8.00 g of 25% mass fraction of ammonia water is added to adjust the pH to 9.0, and 3.00 g of isobutylene-maleic anhydride copolymer and 1.00 g of silicone defoaming agent are added after stirring for 60 min, and the same vacuum defoaming and filtering process is used for treatment.

[0056] Comparative Example 2

[0057] The difference between this comparative example and Example 1 is that only 10.00 g of phosphono-carboxyl block copolymer is added, and no bis-quaternary ammonium salt-polyether silane is added, and the rest of the raw material ratio and preparation process is exactly the same as Example 1.

[0058] Comparative Example 3

[0059] The difference between this comparative example and Example 1 is that 10.00 g of traditional polyacrylammonium dispersant is used to completely replace the two modified compounds, and the rest of the raw material ratio and preparation process is consistent with Example 1.

[0060] The properties of the low viscosity and high dispersibility alumina slurries obtained in Examples 1-3 and Comparative Examples 1-3 were tested according to the test specifications of national and industrial standards. The viscosity of the slurry was measured using a rotational viscometer in a 25°C constant temperature water bath, using an SC4-28 rotor system, and recording stable readings at four shear rates of 10 rpm, 20 rpm, 50 rpm and 100 rpm, respectively. Each sample was tested in triplicate and the average value was taken. The solid content of the slurry was determined using a rapid moisture meter. 5.00 g of the slurry sample was dried to constant weight at 105°C, and the mass percentage of solid matter was calculated. The stability of the slurry was evaluated by the static sedimentation method. 100 mL of the slurry was placed in a graduated transparent glass cylinder and left to stand for 30 days in a 25°C constant temperature environment. The height of the supernatant and the volume of the sediment at the bottom were recorded. The rheological properties of the slurry were determined by dynamic frequency scanning using a rheometer. The frequency range was 0.1-100 rad / s, and the strain was controlled within the linear viscoelastic region at 1%. The curves of storage modulus G' and loss modulus G" versus frequency were recorded. The particle size distribution of the slurry was measured using a laser particle size analyzer. The sample was diluted to a concentration of 0.1% with deionized water, and measured after ultrasonic dispersion for 5 min. The D50 average value was taken from three repeated measurements. The Zeta potential of the slurry was measured using a nano particle size and Zeta potential analyzer. The average value was taken from three parallel measurements at pH 9.0. The thixotropy of the slurry was determined by a cycle test using a viscometer. The shear rate was increased from 0 rpm to 100 rpm and then decreased to 0 rpm within 3 min. The hysteresis loop area was calculated.

[0061] The performance test data are shown in Table 1.

[0062] Table 1 Performance test results

[0063]

[0064]

[0065] The test results of Table 1 clearly show that the slurry systems of Examples 1-3 using the synergistic effect of two new modified compounds are significantly better than the comparative examples in various performance indicators. Example 3 exhibits the best overall performance, with a viscosity of only 580 mPa·s and a solid content as high as 62.2%, proving that the dual-modifier system can achieve higher solid content while maintaining low viscosity; the 30-day sedimentation rate is less than 2%, and the absolute value of Zeta potential is close to 50 mV, showing excellent long-term stability and static stability effect; the thixotropy and leveling performance of the slurry are both significantly better than those of the comparative examples. Comparative Example 1 does not add any modifier, the slurry viscosity is as high as 2850 mPa·s and the sedimentation is serious, the absolute value of Zeta potential is only 25.3 mV, and the dispersion stability is poor; Comparative Example 2 uses only a single modifier, and the performance is between the examples and Comparative Example 1; Comparative Example 3 uses a traditional dispersant, and the stability and rheological properties of the slurry are significantly lower than those of the examples, proving the unique advantages of the new dual-modified compound design. These results fully prove that the present application effectively solves the technical problems of high solid content alumina slurry viscosity control difficulty and poor dispersion stability through the synergistic effect of two newly designed modified compounds.

Claims

1. A process for the preparation of a low viscosity, high dispersibility alumina slurry, characterized by the steps of The application relates to a preparation method of a dispersant for alpha-alumina powder. S1, deionized water is added into a reaction container, and the temperature is controlled to be 23-27 DEG C; under stirring, phosphono-carboxyl block copolymer and double-quaternary ammonium salt-polyether silane are sequentially added, and stirring is continuously carried out; S2, then, ammonia water is added to adjust the pH value to 8.5-9.5, and a dispersant solution is formed; alpha-alumina powder is added into the dispersant solution, and stirring is continuously carried out; A solution of isobutylene-maleic anhydride copolymer dissolved in deionized water in advance is added, and stirring is carried out; a silicone defoaming agent is further added, and a mixed slurry is obtained; the mixed slurry is transferred into a vacuum defoaming device for treatment; S3, the slurry is filtered through a standard screen.

2. The method for preparing the low-viscosity, highly dispersible alumina slurry according to claim 1, characterized in that, In step S1, the time for continuously stirring is 30-40 min.

3. The method for preparing the low-viscosity, highly dispersible alumina slurry according to claim 1, characterized in that, In step S2, the time for treatment in the vacuum defoaming device is 10-15 min.

4. The method for preparing the low-viscosity, highly dispersible alumina slurry according to claim 1, characterized in that, The preparation method of the phosphono-carboxyl block copolymer comprises the following steps: A1, 2-phosphonobutane-1, 2, 4-tricarboxylic acid is reacted with 2-bromoisobutyryl bromide in anhydrous tetrahydrofuran under the condition of 0-2 DEG C to generate a phosphono-ATRP initiator; the phosphono-ATRP initiator, t-butyl acrylate and pentamethyl divinyl triamine are added into a reaction kettle, nitrogen is introduced for protection, cuprous chloride is added, and atom transfer radical polymerization is carried out under the condition of 58-62 DEG C to obtain a phosphono-terminated poly-t-butyl acrylate prepolymer; A2, the phosphono-terminated poly-t-butyl acrylate prepolymer is dissolved in dichloromethane, trifluoroacetic acid is added, and a t-butyl protection reaction is carried out at room temperature; the reaction mixture is precipitated in ice ether, filtered and washed, and then vacuum dried.

5. The method for preparing the low-viscosity, highly dispersible alumina slurry according to claim 4, characterized in that, In step A1, the reaction time under the condition of 0-2 DEG C is 12-14 h; the atom transfer radical polymerization is carried out under the condition of 58-62 DEG C for 24-30 h.

6. The method for preparing the low-viscosity, highly dispersible alumina slurry according to claim 4, characterized in that, In step A2, the t-butyl protection reaction time is 10-14 h.

7. The method for preparing the low-viscosity, highly dispersible alumina slurry according to claim 1, characterized in that, The preparation method of the double-quaternary ammonium salt-polyether silane comprises the following steps: B1, 3-chloropropyl trimethoxysilane is refluxed with N-methyl imidazole in acetonitrile to generate a double-imidazole salt intermediate; polyethylene glycol monomethyl ether, 3-bromopropargyl and sodium hydride are added into toluene, and a reaction is carried out under the condition of 68-72 DEG C to obtain a polyether intermediate; the polyether intermediate is reacted with 3-azidopropyl trimethoxysilane to generate a polyether silane precursor; the double-imidazole salt intermediate is subjected to quaternary ammonium reaction with iodomethane in tetrahydrofuran under the condition of 38-42 DEG C to obtain a double-quaternary ammonium salt silane; B2, the double-quaternary ammonium salt silane and the polyether silane precursor are mixed, sodium ascorbate and copper sulfate pentahydrate are added, and copper-catalyzed azide-alkyne cycloaddition is carried out in a 38-42 DEG C aqueous solution; after the reaction is completed, extraction, drying and concentration are carried out.

8. The method for preparing the low-viscosity, highly dispersible alumina slurry according to claim 7, characterized in that, In step B1, the reaction is carried out under the condition of 68-72 DEG C for 7-9 h; the quaternary ammonium reaction is carried out under the condition of 38-42 DEG C for 12-14 h.

9. The method for preparing the low-viscosity, highly dispersible alumina slurry according to claim 7, characterized in that, In step B2, the azide-alkyne cycloaddition reaction time is 22-26 h.

10. A low viscosity, high dispersibility alumina slurry prepared according to the method of any one of claims 1-9, characterized in that, The raw materials include the following components by weight: alpha-alumina powder 80-120 parts; phosphono-carboxyl block copolymer 0.5-1.5 parts; bis-quaternary ammonium salt-polyether silane 0.3-1 part; isobutylene-maleic anhydride copolymer 0.1-0.5 part; deionized water 30-45 parts; ammonia water 0.5-2.0 parts; silicone defoaming agent 0.05-0.2 parts.

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