CN1830777A - The manufacture method of silica sol and prepared silica sol - Google Patents

Abstract

The invention discloses a method for producing silica sol, which is characterized in that, under heating and stirring, an alkaline catalyst and metal silicon powder are added to the silicon dioxide aqueous dispersion liquid as a seed liquid, so that the pH is in the range of 7-14 Under the conditions of the reaction, the active silicic acid particles hydrolyzed by the silica powder are attached to the silica seed particles to make the seed particles grow rapidly, and directly obtain a large-diameter silica sol. Compared with the general method for preparing large-particle silica sol, the production method of the present invention has the advantages of fast particle growth rate, uniform particle distribution, and can be prepared according to the size of the particle design; the preparation process does not need to be pressurized or ion exchanged; equipment investment Less, low cost, short reaction cycle and other advantages.

Description

The manufacture method of silica sol and prepared silica sol

technical field

The invention relates to a method for producing silica sol and the silica sol prepared therefrom.

Background technique

At present, there are generally the following methods for producing large-size silica sol in industry. One is the method of adopting high temperature and high pressure method in the ion exchange process and adding active silicic acid raw materials dropwise while heating and evaporating on the basis of seed liquid. Such as U.S. patents: US3012972 (1962), US4356107 (1982), are to use high temperature and high pressure to process alkaline small particle size silica sol in order to obtain large particle size silica sol; patent US3947376 (1976), US4304575 (1981) and China The patent CN1155514A (1997) basically adopts silicon dioxide with a certain particle size as the seed liquid, and then adopts the method of adding active silicic acid microparticles dropwise while heating and evaporating to obtain a silica sol with a large particle size. However, there are deficiencies in these processes: the particle size of the silica sol prepared by the high temperature and high pressure method is very limited, and the particle size is not uniform. For example, the preparation of a silica sol with an average particle diameter of about 20 nm requires a pressure of 10 to 15 atmospheres. And the water temperature of nearly 160-180 ℃; and high performance requirements for production equipment, high energy consumption, and a large number of concentration steps in the later stage; the method of adding active silicic acid particles to the seed liquid avoids high temperature and high pressure, and requires high equipment performance. low, and silica sol with relatively large particles can be prepared. However, there are still shortcomings such as long reaction time and large particle uniformity cannot be guaranteed, and because the concentration of active silicic acid particles added dropwise is very low, generally less than 5%, a large amount of silica sol needs to be evaporated to obtain a higher concentration of silica sol water, high energy consumption. Patent CN1506306A (2003) discloses a new method of preparing large particle size silica sol by using seed liquid. This patented method shortens the time of the dropping reaction by increasing the average particle size of active silicic acid particles, so that larger particles of silica sol can be obtained in a relatively short time. However, the silicon dioxide prepared by the method provided by this patent is porous, and the spherical feature is not obvious. Moreover, the optimum preparation temperature provided by the patented method is 70-120°C. At this temperature, a large amount of water cannot be evaporated, and the silica concentration of the seed liquid and the added active silicic acid raw material are both less than 5%. In some cases, the final concentration of silica sol is low, generally not more than 10%. To prepare high-concentration silica sol of 30% or even 50% widely demanded in the market, a large number of concentration steps must be carried out, whether it is evaporation concentration or concentration. Ultrafiltration membrane concentration will increase the production cycle and investment costs.

Another method of producing large particle size is the hydrolysis of silicon powder. In the patent US2614994 published in 1952, silica sol was prepared by hydrolyzing silicon powder under the action of organic alkali, but the particles of the obtained silica sol were low, generally 8-15nm; another patent US2614995 published in the same year passed Increase the concentration of ammonia water to hydrolyze silica powder to prepare silica sol with large particle size. Silica particles with a particle size of about 30nm were obtained under the condition that the mass percentage concentration of ammonia water was as high as 28%. In the invention patent with the application number CN86100503, a method for preparing silica sol by reacting a dilute alkali solution with a mass concentration of 1% and silicon powder is disclosed. The silica sol particles obtained by this method are in the range of 15 to 20 nm; in another In patent CN86104144A, the inventor adopts the method of directly reacting silicon powder with dilute sodium silicate or dilute potassium silicate to directly obtain silica sol with a particle size in the range of 20-30nm. However, in these methods of preparing silica sol using silica powder as the main raw material, the particles of the prepared silica sol are all low, and it is difficult to meet the requirements for preparing higher-grade silica sols, such as silica sols for semiconductor chip polishing.

Contents of the invention

The purpose of the present invention is to overcome above-mentioned defect, provide a kind of silica sol, especially the new manufacture method of large particle size silica sol.

The technical scheme of the present invention to achieve the above-mentioned purpose is: a method for producing silica sol, which uses an aqueous dispersion of silicon dioxide with a specified particle size as the seed liquid, and adds a basic catalyst and a metal to the seed liquid under heating and stirring. Silica powder reacts under the condition of pH 7-14, and the active silicic acid microparticles hydrolyzed by the silicon powder are attached to the silica seed particles to increase the seed particles, thereby producing a large-diameter silica sol.

Here, the particle size of the silica particles serving as the seed particles in the seed liquid can be appropriately selected according to the particle size of the silica particles of the finally desired silica sol and the like. The present invention generally selects silica particles whose particle diameter measured by scanning electron microscope (SEM) is not more than 1 μm, preferably in the range of 5-500 nm. Wherein, when its particle diameter is more than 1 μ m, because the particle of seed particle is too big, the activity of the hydroxyl group on the surface of seed particle is low, active silicic acid microparticle is not easy to adhere to the surface of seed particle, easily produces new seed particle, makes the obtained The uniformity of the final silica is affected; and when the particle size is less than 5nm, because the seed particles are too small, a long reaction time is required to prepare larger particles of silica (such as above 20nm), which is not conducive to shortening the preparation cycle .

The mass percent concentration of the silicon dioxide seed particles in the seed liquid is in the range of 0.5-30%, preferably 2-10%, more preferably 3.5-10%. Wherein, the concentration of silica seed particles is too low, especially when it is lower than 0.1%, because the number of seed particles per unit volume is relatively rare, the chances of the active silicic acid microparticles colliding with the seed particles and then the condensation reaction will be greatly reduced. Therefore, the growth rate of the seed particles and the uniformity of the final silica particles will be affected; if the concentration of the seed particles is too high, the silica concentration of the system will soon reach a higher value during the reaction, and the viscosity of the system will It will become larger earlier, which will affect the growth rate of the seed particles and the stability of the silica sol. At the same time, the quality of the silica powder that can be added will decrease, thereby limiting the further growth of the seed particles.

In the production method of the present invention, heating is preferably carried out in the range of 60 to 100°C. Among them, if the temperature is too low, such as less than 60°C, the reaction will be slow; if the temperature is too high, when it exceeds 100°C, it must be pressurized to obtain a temperature above 100°C, so the performance of the equipment will be increased, and the preparation process will not be safe. Because the temperature is too high, the reaction is too violent, the process is difficult to control, and the uniformity of the final silicon dioxide is also difficult to be guaranteed.

The basic catalyst used in the present invention is sodium hydroxide, potassium hydroxide, lithium hydroxide and ammonium hydroxide and other inorganic bases, or/and in organic bases such as ethanolamine, diethanolamine, triethanolamine, ethylamine and ethylenediamine. one or a mixture of several.

The addition of the basic catalyst can be done by one-time addition before adding the silicon powder, or by adding the catalyst while adding the silicon powder. The catalyst is preferably diluted with water to an aqueous solution with a mass content of 2-20% before adding.

The silicon powder used is in the range of 30-800 mesh, among which the silicon powder in the range of 100-400 mesh, especially in the range of 200-400 mesh is the best. If the silicon powder particles are too coarse, the reaction will be slow, which will lead to a long reaction time; if the particles are too fine, the reaction speed will be too fast, which is difficult to control.

The amount of silicon powder added can be estimated based on the yield of silicon powder under certain conditions and the average particle size of the seed particles and the silica particles in the desired final silica sol product. Under certain conditions, the yield of silicon powder can be calculated according to the following formula:

$\mathrm{<span\; class="notranslate">\; \&eta;</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 28.08</span>}}{\mathrm{<span\; class="notranslate">\; 60.08</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; the\; si</span>}}}<span\; class="notranslate">\; )</span>$

Wherein, w _x is after the reaction finishes, and in the gained silica sol product SiO ₂ mass content; w ₀ is the SiO ₂ mass content in the original seed liquid; w _si is the quality of the silicon powder that adds; 28.08 and 60.08 are respectively Si and 60.08 Relative atomic mass of _SiO2 .

The mass ratio of the basic catalyst to silicon powder is generally 1:5-200, preferably 1:10-100, especially 1:27-100. Wherein, the amount of basic catalyst is too low, especially when it is less than 1:200, the reaction cycle is long, the silicon powder is difficult to react completely, and the utilization rate of silicon powder is low; the amount is too high, especially when the above-mentioned ratio is greater than 1:5, then Because the alkali content of the system is too high, the stability of the silica sol will be affected and become unstable. At the same time, the pH of the final silica sol product will be too high. According to the market demand, the pH reduction treatment will be carried out, which will increase the post-treatment. workload.

The reaction system of the method of the present invention is generally under alkaline conditions, preferably at a pH of 8-14. Because the pH is too low, such as less than 7, it is difficult or impossible to react.

The present invention is the same as other chemical reactions. After adding all the NaOH and silicon powder, keep warm for a period of time to allow the silicon powder to react completely, thereby improving the utilization rate of silicon powder. The length of time can be determined according to the actual silicon powder reaction conditions. Certainly.

Another object of the present invention is to provide the silica sol prepared by the above-mentioned manufacturing method of the present invention, especially the large particle size silica sol with good uniformity, wherein the ratio of the long axis and the short axis of the silica particles is approximately equal to 1 , the appearance is a solid particle in the shape of a sphere.

Utilizing the manufacturing method of the large particle size silica sol of the present invention can make the active silicic acid microparticles produced by the hydrolysis of the silicon powder under the action of the alkaline catalyst be attached to the seed particles quickly and uniformly, so that the seed particles can be obtained in a relatively short period of time. Rapid growth, so that the large particle size silica sol can be obtained quickly and conveniently under extremely economical conditions, and the large particle size silica sol with good uniformity can be obtained. Compared with the existing preparation method, the method for producing large-diameter silica sol of the present invention has the following advantages: the growth rate of the particles is fast, and the diameter of the silica particles can increase by about 2 to 6 nm per hour; it is not necessary to use high temperature and high pressure, The reaction conditions are mild and easy to control, and the requirements for equipment performance are low; the concentration of silica sol obtained after the reaction is high, generally in the range of 30 to 60%, and no long-term concentration is necessary. The production process is simple and the cost is low; the obtained Silica particle size is uniform, good dispersion and stability.

Detailed ways

The present invention is further illustrated by the following examples, but the present invention is not limited to these examples. The seed particle dispersion liquid that following embodiment adopts can be obtained by any method for manufacturing silica sol, as mentioned above application number is the method for preparing silica sol that CN1155514A provides; High-quality silica sol products, such as SNOWTEX of NISSAN in Japan, NAYCOL of Eka Chemicals and other brands of silica sol. The silicon powder used is commercially available; the basic catalyst is commercially available analytically pure or chemically pure.

The particle size of the silica involved in the following examples is measured by a scanning electron microscope (SEM), and the mass content of _SiO in the silica sol is measured by a gravimetric method, and the viscosity of the silica sol is measured by a rotary viscometer. The utilization rate is calculated using the formula mentioned above.

Example 1

In a 2000 ml four-necked flask equipped with a reflux device, dilute 200 g of silica sol with a solid content (silicon dioxide particles) of 30% (mass) and a particle size of 40 to 50 nm with 1000 ml of water to SiO ₂ The mass concentration is about 5%. Stirring and heating are started, and another 6g of NaOH solid is weighed and dissolved with a small amount of water to form a solution with a concentration of about 10%. When the temperature rises to 85°C, start to add the commercially available 200-300 mesh silicon powder while adding the NaOH solution. NaOH was added at a rate to keep the pH of the system in the range of 9.0 to 10.0; the silicon powder was added at a rate to keep the reaction temperature not exceeding 90° C., and a total of 220 g (catalyst: silicon powder=1:37) silicon powder was added. After adding all the NaOH and silicon powder, keep the temperature and react for 5 hours, then keep stirring, cool to below 60°C and filter. The obtained silica sol index is as follows:

SiO ₂ mass content: 35.0% SiO ₂ particle size: 90~100nm

Viscosity (20°C): 3.5mp _a s Silica fume utilization rate: 89%

Example 2

Using the same conditions as in Example 1, the difference is that: 300g of silica sol with a solid content of 20% and a particle diameter of 5 to 8nm is diluted with 10000 milliliters of water to SiO _The mass content is about 0.6%; Dissolve in water to make the concentration about 2% before adding. Finally obtained silica sol index is as follows:

SiO ₂ mass content: 3.0% SiO ₂ particle size: 5~20nm

Viscosity (20°C): 1.4mp _a s Silica fume utilization rate: 80%

Example 3

Using the same conditions as in Example 1, the difference is: using silica sol with a particle size of 10-15 nm as the seed liquid; dissolving NaOH in water to a concentration of about 20% before adding. Finally obtained silica sol index is as follows:

SiO ₂ mass content: 35.0% SiO ₂ particle size: 20~30nm

Viscosity (20°C): 10.5mp _a s Silica fume utilization rate: 89%

Example 4

The same conditions as in Example 1 were adopted, except that a silica sol with a particle diameter of 90-100 nm was used as the seed solution. The index of the silica sol obtained at last is as follows:

SiO ₂ mass content: 35.0% SiO ₂ particle size: 180~210nm

Viscosity (20°C): 2.6mp _a s Silica fume utilization rate: 89%

According to the method of the above-mentioned Example 4, Siyi circulated rice and used the large particle size silica sol prepared by the present invention as the seed solution to prepare a larger particle size silica sol.

Example 5

The same conditions as in Example 1 were adopted, except that the mass of silicon powder added was increased to 300 g (catalyst: silicon powder=1:50). The index of the silica sol obtained at last is as follows:

SiO ₂ mass content: 44.0% SiO ₂ particle size: 100~120nm

Viscosity (20°C): 4.0mp _a s Silica fume utilization rate: 88%

Example 6

Adopt the same condition as embodiment 1, difference is: the four-necked flask of 3000 milliliters of reactors is adopted; Seed liquid is diluted to the concentration of 3.5% with 1500 milliliters of water; The silicon powder quality that adds is 600g (catalyst: silicon powder= 1:100). The index of the silica sol obtained at last is as follows:

SiO ₂ mass content: 46.5% SiO ₂ particle size: 100~140nm

Viscosity (20°C): 15.5mp _a s Silica fume utilization rate: 70%

Example 7

Adopt the same condition as embodiment 6, difference is: the consumption of seed liquid is reduced to 100g, and is diluted to 2% solid content with 1400 milliliters of water; The silicon powder quality that adds is 1080g (catalyst: silicon powder=1: 180 ). The index of the silica sol obtained at last is as follows:

SiO ₂ mass content: 51.5% SiO ₂ particle size: 90~145nm

Viscosity (20°C): 25.5mp _a s Silica fume utilization rate: 45%

Example 8

Adopt the same condition as embodiment 1, difference is: the seed liquid is diluted to SiO with 400 milliliters of water Mass concentration is about 10%, because system concentration rises _faster , viscosity increases, the silicon powder quality that can add reduces, The silicon powder quality that finally adds is 160g (catalyst: silicon powder=1: 27), and the index of the silica sol that obtains is as follows:

SiO ₂ mass content: 52.0% SiO ₂ particle size: 80~90nm

Viscosity (20°C): 14.5mp _a s Silica fume utilization rate: 92%

Example 9

Adopt the same condition as embodiment 1, difference is: 30% _SiO The seed liquid of mass content is directly used without water dilution; Adopt 8.5g KOH to replace NaOH as catalyst. Under this condition, the silicon powder quality that can add reduces, and the silicon powder quality that finally adds is 30g (catalyst: silicon powder=1: 6), and the index of the silica sol that obtains is as follows:

SiO ₂ mass content: 55.0% SiO ₂ particle size: 50~60nm

Viscosity (20°C): 25.0mp _a s Silica fume utilization rate: 94%

Example 10

Using the same conditions as in Example 1, the difference is: use 400-600 mesh silicon powder as the raw material instead; use 15g ethanolamine instead of NaOH as the basic catalyst; the speed of adding the catalyst is to keep the pH of the system in the range of 7-8; The index of the silica sol obtained at last is as follows:

SiO ₂ mass content: 26.0% SiO ₂ particle size: 35~80nm

Viscosity (20°C): 6.5mp _a s Silica fume utilization rate: 60%

Example 11

Using the same conditions as in Example 1, the difference is: the temperature of the reaction is controlled in the range of 95 to 100 ° C, and the index of the finally obtained silica sol is as follows:

SiO ₂ mass content: 37.0% SiO ₂ particle size: 40~90nm

Viscosity (20°C): 6.4mp _a s Silica fume utilization rate: 92%

Example 12

Using the same conditions as in Example 1, the difference is: 20g of ethylenediamine is used as the basic catalyst; the speed of adding the catalyst is to keep the pH of the system in the range of 10 to 11; the temperature of the reaction is controlled in the range of 80 to 85°C. The index of the silica sol obtained at last is as follows:

SiO ₂ mass content: 36.0% SiO ₂ particle size: 70~100nm

Viscosity (20°C): 3.0mp _a s Powder utilization rate: 90%

Example 13

Using the same conditions as in Example 1, the difference is: using 400-600 mesh silicon powder as raw material; using 3g NaOH and 8g ethylenediamine as a composite basic catalyst; adding catalyst speed to keep the pH of the system in the range of 12-13 ; The reaction temperature is controlled in the range of 60-70°C. The index of the silica sol obtained at last is as follows:

SiO ₂ mass content: 36.5% SiO ₂ particle size: 45~110nm

Viscosity (20°C): 5.5mp _a s Silica fume utilization rate: 92%

Example 14

The same conditions as in Example 1 were adopted, except that 30-60 mesh silicon powder was used as the raw material; after all the raw materials were added, the reaction was kept for 20 hours. The index of the silica sol obtained at last is as follows:

SiO ₂ mass content: 23.0% SiO ₂ particle size: 70~85nm

Viscosity (20°C): 2.0mp _a s Silica fume utilization rate: 50%

Example 15

The same conditions as in Example 1 were adopted, except that 100-200 mesh silicon powder was used as the raw material, and after all the raw materials were added, the reaction was kept for 15 hours. The index of the silica sol obtained at last is as follows:

SiO ₂ mass content: 29.2% SiO ₂ particle size: 70~90nm

Viscosity (20°C): 3.0mp _a s Silica fume utilization rate: 70%

Example 16

In a 2000 ml four-necked flask equipped with a reflux device, dilute 200 g of silica sol with a solid content of 30% and a particle size of 40 to 50 nm with 1000 ml of water to _a SiO mass concentration of about 5%, and start Stir and heat, weigh 6g of NaOH solid and dissolve it with a small amount of water to form a solution with a concentration of about 10%, and then add it all into the reaction flask at one time, so that the pH of the system is about 13.5. When the temperature rises to 80°C, start to add common commercially available silicon powder of 200-300 mesh. The speed of adding silicon powder is to keep the reaction temperature not exceeding 85° C., and a total of 220 g (catalyst: silicon powder=1:37) silicon powder is added. After adding the silicon powder, keep it warm for 4 to 6 hours, then keep stirring and cool to below 60°C for filtration. The obtained silica sol index is as follows:

SiO ₂ mass content: 36.0% SiO ₂ particle size: 55-80nm

Viscosity (20°C): 5.5mp _a ·s Utilization rate of silicon powder: 90%.

Claims (10)

1, a kind of manufacture method of silicon sol, it is characterized in that under heated and stirred, in as the silica aqueous dispersion of seed liquor, add basic catalyst and metallic silicon power, making it is to react under the condition of 7～14 scopes at pH, the active silicic acid micropartical that goes out by the silica flour hydrolysis is attached to making seed particles increase on the silicon-dioxide seed particles, thereby makes the silicon sol of big particle diameter.

2, manufacture method as claimed in claim 1 is characterized in that the silicon-dioxide in the described seed liquor is the silica dioxide granule of particle diameter in 5～500nm scope of measuring by scanning electronic microscope.

3, manufacture method as claimed in claim 1, the mass percentage concentration that it is characterized in that the silicon-dioxide seed particles in the described seed liquor is in 0.5～30% scope.

4, manufacture method as claimed in claim 1 is characterized in that described Heating temperature is 60～100 ℃.

5, manufacture method as claimed in claim 1 is characterized in that described basic catalyst is that mineral alkali is or/and one or several mixing in the organic bases.

6, manufacture method as claimed in claim 5 is characterized in that described mineral alkali is a sodium hydroxide, potassium hydroxide, lithium hydroxide and ammonium hydroxide; Described organic bases is thanomin, diethanolamine, trolamine, ethamine and quadrol.

7, manufacture method as claimed in claim 1, the particle diameter that it is characterized in that described metallic silicon power is 30～800 orders.

8, manufacture method as claimed in claim 1, the mass ratio that it is characterized in that described basic catalyst and silica flour is 1: 5～200.

9, as the described manufacture method of the arbitrary claim of claim 1～8, the mass percentage concentration that it is characterized in that the silicon-dioxide in the described seed liquor is 2～10%; The particle diameter of described metallic silicon power is 100～400 orders; The mass ratio of this basic catalyst and silica flour is 1: 10～100; The pH of described reaction is 8～14.

10, the silicon sol that makes of the manufacture method of silicon sol as claimed in claim 1.