CN103496724B - The preparation method of a kind of nano alumina sol and gel - Google Patents

Abstract

The present invention proposes a method for preparing nano-alumina sol and gel, by using nano-alumina particles as raw materials, lactic acid as a dispersant, and combining high-speed stirring with high-energy ball mill dispersion to prepare nano-alumina sol with high solid content; The prepared nano-alumina sol is added with a certain amount of hexamethylenetetramine aqueous solution under stirring, and heated for a certain period of time for gelation to obtain a nano-alumina gel. The invention is simple and easy, and the nano-alumina sol obtained by dispersion has a solid content greater than or equal to 30 percent, a small particle size, uniform distribution, and can exist stably in water for a long time.

Description

A kind of preparation method of nano alumina sol and gel

technical field

The invention relates to a preparation method of nano-alumina sol and gel, which belongs to the technical field of chemical industry.

Background technique

Nano-alumina sol has excellent physical and chemical properties, and is widely used in production and life. It is used to make catalysts and carriers, fine ceramics, fiber-reinforced alumina ceramic composite materials, and new coatings. However, due to the small particle size of nano-alumina, the specific surface area and surface energy are large, it is easy to agglomerate, and it is difficult to increase the solid content. There are very few research reports on nano-alumina sol and gel with high solid content at home and abroad. According to relevant research, the main reason is that the solubility of alumina in water is very limited.

At present, some domestic and foreign patents on nano-alumina sol are mostly related to the preparation technology of nano-alumina sol. In the preparation method of alumina sol, organic alkoxide or inorganic salt is usually used as the main raw material. For example, the organic salt raw material method using aluminum isopropoxide as a raw material, the nano-alumina sol prepared by this method is expensive, which limits the application of the sol-gel method; another method is based on the inorganic salt raw material method, Dissolve metallic aluminum in hydrochloric acid or aluminum chloride to obtain a colorless and transparent aluminum sol. Or dissolve aluminum nitrate and ammonium citrate in water according to a certain ratio, and adjust the pH value of the solution with concentrated nitric acid or concentrated ammonia water to obtain aluminum sol. The preparation process of these two preparation methods is harmful to the environment, and the cost is high, and the solid content of the finally prepared nano-alumina sol is low, generally lower than 20 wt%. Chinese patent CN201210120945.8 discloses a stable and dispersed nano-alumina slurry prepared by a sol-gel method, and the solid content of the alumina sol is up to 13wt%. Chinese patent CN201010274945.4 discloses a nano-alumina sol prepared by using boehmite as a raw material, dispersing and adjusting the pH value of the solution to 2-5, but the maximum concentration of nano-alumina does not exceed 25wt%. At present, in the methods reported in literature and patents, the solid content of the prepared nano-alumina sol is not ideal.

Contents of the invention

The object of the present invention is to overcome the deficiencies in the prior art, and provides an environment-friendly, nano-alumina particle size, uniform particle size distribution, solid content ≥ 30% [solid content=nano-alumina quality/(nano-alumina and detoxified aluminum oxide) The total mass of ionized water)] the preparation method of sol and gel.

Technical solution of the present invention: a preparation method of nano-alumina sol, realized by the following steps:

The first step is to prepare nano-alumina suspension,

A1.1. Weigh nano-alumina particles and deionized water according to a certain ratio;

The mass ratio of nano-alumina particles to deionized water is 3:7-1:1; the particle size distribution of alumina inorganic nanoparticles is mainly 5-500nm, and the average particle size is 20-100nm. Stone nanoparticles are used as raw materials, and other types of alumina inorganic nanoparticles can also be used.

A1.2, adding nano-alumina particles into deionized water by stirring to obtain a mixed solution of nano-alumina;

A1.3. Add a certain amount of lactic acid and an appropriate amount of additives to the nano-alumina mixture, and stir to obtain a nano-alumina suspension;

Lactic acid is a dispersant, the addition amount is 0.2-5% of the mass of the nano-alumina particles, preferably 2-3%, the addition amount starts to increase from 0.2%, the viscosity of the nano-alumina suspension gradually decreases, and the prepared The solid content of nano-alumina sol gradually increases from 30%, and when the addition amount is 2-3%, the viscosity of nano-alumina suspension reaches the trough, and the solid content of the prepared nano-alumina sol can reach 50%. increase, the viscosity of the nano-alumina suspension increases gradually, and the solid content of the prepared nano-alumina sol gradually decreases from 50%; when the addition amount is less than 0.2% or greater than 5%, the viscosity of the nano-alumina suspension is large, and the The solid content of nano-alumina sol cannot reach 30%.

Auxiliaries include leveling agent, defoamer and wetting agent. One or more fluorocarbon modified polyacrylates are used. The dosage is selected according to the actual situation. The general engineering experience is 0% of the mass of nano-alumina particles. ~10%.

Add lactic acid and additives to adjust the pH value of the mixture to 2-5, and stir at a high speed for 2-5 hours to obtain a nano-alumina suspension.

In the second step, the nano-alumina suspension obtained in the first step is pulverized and dispersed by a ball mill to obtain a nano-alumina sol.

A high-energy ball mill is used to further pulverize and disperse the nano-alumina suspension to reduce the particle size of the nano-alumina to obtain a uniformly dispersed nano-alumina sol with high solid content. Among them, the ball-to-material ratio of the ball mill is generally selected from 1:1 to 3:1, and a suitable ball-to-material ratio can also be selected according to the actual situation; under the same preparation conditions, the smaller the particle size of the ball, the smaller the particle size of the nano-alumina after ball milling. The smaller the size, the particle size of the grinding balls in the actual project is 0.5-5mm, and you can also choose the grinding balls with a suitable particle size according to your needs; the speed of the ball milling is generally 100-450rmp, and it can also be decelerated or accelerated according to the actual situation; ball milling The longer the time, the smaller the particle size of nano-alumina after ball milling, and the higher the solid content, the longer the corresponding ball milling time. In engineering practice, the ball milling time is generally selected from 5 to 80 hours, and it can be extended or shortened according to the actual situation.

A preparation method of nano-alumina gel, realized through the following steps:

The first step is to prepare nano-alumina suspension,

A1.1. Weigh nano-alumina particles and deionized water according to a certain ratio;

A1.2, adding nano-alumina particles into deionized water by stirring to obtain a mixed solution of nano-alumina;

A1.3. Add a certain amount of lactic acid and an appropriate amount of additives to the nano-alumina mixture, and stir to obtain a nano-alumina suspension;

In the second step, the nano-alumina suspension obtained in the first step is pulverized and dispersed by a ball mill to obtain a nano-alumina sol;

The third step, the gel,

The nano-alumina sol obtained in the second step is added with a certain amount of hexamethylenetetramine aqueous solution under stirring, and gelled at a certain temperature for a certain period of time to obtain a nano-alumina gel.

(1) Under high-speed stirring (500-1000rpm), adding a concentration of 20-50wt% hexamethylenetetramine aqueous solution, the amount of hexamethylenetetramine is to add 0.4-1.4g of hexamethylenetetramine per 100ml of nano-alumina sol Hexamethylenetetramine.

Hexamethylenetetramine is formulated into a 20-50wt% aqueous solution for the sake of manufacturability, and its concentration change does not have much impact on the gel, and the concentration should not be too high, otherwise it will cause instant solidification and affect the quality of the gel; The speed and strength are related to the quality of hexamethylenetetramine. Add 0.4-1.4g of hexamethylenetetramine per 100m1 nano-alumina sol. The more hexamethylenetetramine is used, the better the gel speed and strength . The amount of hexamethylenetetramine added is related to the solid content of the nano-alumina sol. To obtain the same gel strength (under the same conditions of gel time and temperature), the smaller the solid content of the nano-alumina sol, the corresponding hexa-alumina sol The more methyltetramine is added; the addition of nano-alumina sol exceeds the range of 0.4-1.4g per 100ml. If the amount of hexamethylenetetramine is too small, less than 0.4g, the gel speed will be slow. If hexamethylene If the amount of tetramine added is too much, higher than 1.4g, the nano-alumina sol solidifies instantly, and the gel strength is not high.

(2) Sealing the nano-alumina sol and putting it into an oven, heating at 80-90° C. for 48-96 hours for gelation, and obtaining a nano-alumina gel.

The higher the gel temperature, the higher the gel degree under the same conditions; the longer the gel time, the higher the gel degree under the same conditions; the gel temperature and time can be adjusted according to the actual situation in the project. Situation selection.

The beneficial effect of the present invention compared with prior art:

(1) The present invention adopts lactic acid as a dispersant, utilizes the unique structure of lactic acid (containing hydroxyl and carboxyl groups), effectively reduces the agglomeration of nano-alumina, and improves the solubility of nano-alumina in water;

(2) The nano-alumina sol prepared by the present invention has a high solid content, which can reach 30%, up to 50%, and has uniform dispersion, good stability, and can exist stably in water for a long time;

(3) The process of the present invention is simple, environmentally friendly, and environmentally friendly, and the obtained nano-alumina sol has small particle size, high purity, and uniform particle size distribution, and is suitable for large-scale industrial production;

(4) In the present invention, the nano-alumina sol with a high solid content is successfully gelled by adding an aqueous solution of hexamethylenetetramine to prepare a nano-alumina gel with a high solid content.

Instructions attached

Fig. 1 is a process flow diagram of the present invention;

Fig. 2 is the SEM photograph of nano-alumina suspension;

Fig. 3 is the SEM picture of nano-alumina sol;

Fig. 4 is before and after ball milling treatment, the particle size comparison chart of nano-alumina;

Fig. 5 is a graph showing the change trend of nano-alumina particle size in a sol with a solid content of 40 wt% after different ball milling times.

detailed description

The present invention will be described in detail below in conjunction with accompanying drawing 1 and specific examples.

Example 1

The preparation process is shown in Figure 1,

(1) Preparation of nano-alumina suspension

Introduce 3.5kg of alumina nanoparticles into 6.5kg of deionized water by high-speed stirring to obtain a mixed solution of nano-alumina, add 0.2% of the mass of alumina nanoparticles to the mixed solution of lactic acid and an appropriate amount of additives, stir A nano-alumina suspension with a particle content of 35% was prepared in 5 hours.

(2) Pulverize and disperse to obtain nano-alumina sol

Add 3.5 kg of agate balls to the nano-alumina suspension with a solid content of 35% according to the ball-to-material ratio of 1:1. The particle size of the balls is 5 mm, and the balls are further pulverized and dispersed by a planetary ball mill at a speed of 250 rpm. Under the condition of ball milling for 24 hours, the nano-alumina sol with a solid content of 35% was prepared.

Scanning electron microscope S-4800 (Hitachi Co., Japan) was used to characterize the morphology of alumina nanoparticles, as shown in Figure 2 and 3, and the particle size distribution of nano-alumina suspension was characterized by Malvern laser particle size analyzer (ZetasizerNanoZS), as shown in the table One and Figure 4.

Embodiment 2-8

0.5%, 0.7%, 1.0%, 2.0%, 3.0%, 4.0% and 5.0% of the mass of alumina nanoparticles were added to the mixed liquid of lactic acid and an appropriate amount of auxiliary agents, and the rest were the same as in Example 1.

The particle size of the nano-alumina dispersion was measured by a Malvern laser particle size analyzer ZetasizerNanoZS, and the test results are shown in Table 1 and Figure 4.

Table I

specific embodiment 1 2 3 4 5 6 7 8 Nano Al ₂ O ₃ solid content (wt%) 35 35 35 35 35 35 35 35 Grinding ball particle size (mm) 5 5 5 5 5 5 5 5 Milling time (h) twenty four twenty four twenty four twenty four twenty four twenty four twenty four twenty four Lactic acid dispersant content (%) 0.2 0.5 0.7 1.0 2.0 3.0 4.0 5.0 Nano-Al ₂ O ₃ particle size (nm) 886 869 796 515 321 309 380 411

It can be seen from Table 1 that under the same conditions, the particle size of nano-alumina decreases gradually when the amount of lactic acid dispersant is increased. At 2.0-3.0%, the particle size reaches the trough, and then the particle size begins to increase.

Examples 9-13

4.0kg of nano-alumina particles were introduced into 6.0kg of deionized water by high-speed stirring, 2.0% lactic acid dispersant was added, and stirred for 5 hours to obtain a nano-alumina suspension with a particle content of 40%; the above-mentioned particle content was 40% 4.0kg of agate balls were added to the nano-alumina suspension at a ball-to-material ratio of 1:1. The particle size of the balls was 5mm, and they were further pulverized and dispersed by planetary ball mills. Ball milling of 0, 10, 20, 40, 60 hours to prepare nano-alumina sol with a content of 40%. The particle size of the nano-alumina dispersion is shown in Table 2 and Figure 5.

Table II

specific embodiment 9 10 11 12 13 Nano Al ₂ O ₃ solid content (%) 40 40 40 40 40 Grinding ball particle size (mm) 5 5 5 5 5 Milling time (h) 0 10 20 40 60 Lactic acid dispersant content (%) 2 2 2 2 2 Nano-Al ₂ O ₃ particle size (nm) 1044 647 485 326 288

It can be seen from Table 2 and Figure 4 that under the same conditions, the longer the ball milling time, the smaller the particle size of nano-alumina in the sol.

Example 14

The particle diameter of the grinding balls is 2 mm, and the rest are the same as in Example 11. The particle diameter results of the dispersion liquid are shown in Table 3.

Table three

specific embodiment 11 14 Nano Al ₂ O ₃ solid content (%) 40 40 Grinding ball particle size (mm) 5 2 Milling time (h) 20 20 Lactic acid dispersant content (%) 2 2 Nano-Al ₂ O ₃ particle size (nm) 485 319

It can be seen from Table 3 that under the same conditions, the smaller the particle size of the ball, the smaller the particle size of the nano-alumina in the sol.

Example 15, 16

Introduce 4.5kg and 5kg of nano-alumina particles into 5.5kg and 5kg of deionized water respectively by high-speed stirring, add 3.0% lactic acid dispersant, and stir for 10 hours to prepare nano-alumina suspensions with particle content of 45%, 50%. The above-mentioned content is 45%, 50% nano-alumina suspension, add 4.5kg, 5.0kg of agate balls according to the ball-to-material ratio of 1:1, the particle diameter of the balls is 2mm, further pulverized and dispersed by planetary ball mills, Ball milling for 20 hours at a rotational speed of 250 r/min prepared a nano-alumina sol with a solid content of 45% and 50%. The particle size results of the measured dispersion are shown in Table 4.

Example 17

Introduce 3.0kg of nano-alumina particles into 7.0kg of deionized water by high-speed stirring respectively, add 0.2% lactic acid dispersant, and stir for 10 hours to obtain a nano-alumina suspension with a particle content of 30%; Add 3.0kg of agate balls to the nano-alumina suspension at a ball-to-material ratio of 1:1, the particle size of the balls is 2mm, further pulverize and disperse through a planetary ball mill, and ball mill for 20 hours at a speed of 250 rpm. A nano-alumina sol with a solid content of 30% was obtained. The particle size results of the measured dispersion are shown in Table 4.

Table four

specific embodiment 15 16 17 Nano Al ₂ O ₃ solid content (%) 45 50 30 Grinding ball particle size (mm) 2 2 2 Milling time (h) 20 20 20 Lactic acid dispersant content (%) 3 3 0.2 Nano-Al ₂ O ₃ particle size (nm) 1329 3015 880

Examples 18-20

The nano-alumina sol prepared in Example 12 was stirred at a high speed of 500 rpm, and 0.89 g of hexamethylenetetramine (formed into a 20-50 wt % hexamethylenetetramine aqueous solution) was added. Then seal the nano-alumina sol and put it into an oven, heat at 80°C for 24, 48, and 96 hours for gelation to obtain a nano-alumina gel. The results are shown in Table 5.

Table five

specific embodiment 18 19 20 Nano Al ₂ O ₃ solid content (%) 40 40 40 Nano Al ₂ O ₃ sol volume (ml) 100 100 100 Gel temperature (°C) 80 80 80 Gel time (h) twenty four 48 96 Hexamethylenetetramine (g) 0.89 0.89 0.89 Gel strength (finger pressure) Ungelled weaker medium

Examples 21-23

The nano-alumina sol prepared in Example 12 was stirred at a high speed of 500 rpm, and 0.89 g of hexamethylenetetramine (formed into a 20-50 wt % hexamethylenetetramine aqueous solution) was added. Then seal the nano-alumina sol and put it into an oven, heat at 90°C for 24, 48, and 96 hours for gelation to obtain a nano-alumina gel. The results are shown in Table 6.

Table six

specific embodiment twenty one twenty two twenty three Nano Al ₂ O ₃ solid content (%) 40 40 40 Nano Al ₂ O ₃ sol volume (ml) 100 100 100 Gel temperature (°C) 90 90 90 Gel time (h) twenty four 48 96 Hexamethylenetetramine (g) 0.89 0.89 0.89 Gel strength (finger pressure) weaker medium stronger

It can be seen from Table 5 and Table 6 that under the same conditions, the longer the gel time, the higher the gel degree, and under the same conditions, the higher the gel temperature, the higher the gel degree.

Examples 24-29

With the nano-alumina sol prepared in Examples 16 and 17, under high-speed stirring at 500 rpm, add 0.4 to 1.4 g of hexamethylenetetramine (to make 20 to 50 wt % hexamethylenetetramine aqueous solution) . Then the nano-alumina sol was sealed and placed in an oven, and heated at 90° C. for 48 hours for gelation to obtain a nano-alumina gel. The results are shown in Table VII.

Table seven

specific embodiment twenty four 25 26 27 28 29 Nano Al ₂ O ₃ solid content (%) 30 30 30 50 50 50 Nano Al ₂ O ₃ sol volume (nl) 100 100 100 100 100 100 Gel temperature (°C) 90 90 90 90 90 90 Gel time (h) 48 48 48 48 48 48 Hexamethylenetetramine (g) 0.4 0.89 1.4 0.4 0.88 1.4 Gel strength (finger pressure) weaker weaker medium medium stronger stronger

It can be seen from Table 7 that under the condition of low solid content, the gel degree is low; with the increase of the amount of hexamethylenetetramine, the gel strength increases.

Parts not described in detail in the present invention are well-known technologies for those skilled in the art.

Claims (5)

1. A preparation method of nano-alumina sol, characterized in that it is realized through the following steps: The first step is to prepare nano-alumina suspension, A1.1, weigh nano-alumina particles and deionized water according to a certain ratio, the mass ratio of nano-alumina particles and deionized water is 3:7～1:1; A1.2, adding nano-alumina particles into deionized water by stirring to obtain a mixed solution of nano-alumina; A1.3. Add a certain amount of lactic acid and an appropriate amount of additives to the nano-alumina mixture, and stir evenly to obtain a nano-alumina suspension. The additives are leveling agents, defoamers and wetting agents. The amount of lactic acid added is 0.2% to 5% of the mass of the nano-alumina particles, the additive amount is (0, 10%] of the mass of the nano-alumina particles, and the auxiliaries include one or more fluorocarbon-modified polyacrylates; In the second step, the nano-alumina suspension obtained in the first step is pulverized and dispersed by a ball mill to obtain a nano-alumina sol. 2. The preparation method of a nano-alumina sol according to claim 1, characterized in that: the amount of lactic acid added in the step A1.3 is 2-3% of the mass of the nano-alumina particles. 3. A preparation method of nano-alumina gel, characterized in that it is realized through the following steps: The first step is to prepare nano-alumina suspension, A1.1, weigh nano-alumina particles and deionized water according to a certain ratio, the mass ratio of nano-alumina particles and deionized water is 3:7～1:1; A1.2, adding nano-alumina particles into deionized water by stirring to obtain a mixed solution of nano-alumina; A1.3. Add a certain amount of lactic acid and an appropriate amount of additives to the nano-alumina mixture, and stir evenly to obtain a nano-alumina suspension. The additives are leveling agents, defoamers and wetting agents. The amount of lactic acid added is 0.2% to 5% of the mass of the nano-alumina particles, the additive amount is (0, 10%] of the mass of the nano-alumina particles, and the auxiliaries include one or more fluorocarbon-modified polyacrylates; In the second step, the nano-alumina suspension obtained in the first step is pulverized and dispersed by a ball mill to obtain a nano-alumina sol; The third step, the gel, The nano-alumina sol obtained in the second step is added with a certain amount of hexamethylenetetramine aqueous solution under stirring, and gelled at a certain temperature for a certain period of time to obtain a nano-alumina gel. 4. the preparation method of a kind of nano-alumina gel according to claim 3 is characterized in that: in the described third step hexamethylenetetramine aqueous solution, hexamethylenetetramine consumption is every 100mL nano-alumina Add 0.4-1.4 g of hexamethylenetetramine to the sol. 5. The preparation method of a nano-alumina gel according to claim 3, characterized in that: the amount of lactic acid added in the step A1.3 is 2-3% of the mass of the nano-alumina particles.