KR19980034990A - Method and apparatus for producing porous silica gel powder - Google Patents

Abstract

In the present invention, by adjusting the equivalence ratio of alkali silicate and inorganic acid with a metering pump, the raw material is introduced by using a rotary spraying means, and a homogeneous reaction is induced to generate a homogeneous reaction in an alkaline atmosphere, so that the specific surface area and pore volume of the gel are respectively It is possible to synthesize porous silica gel of at least 200m ₂ / g and 1.4cc / g (nitrogen adsorption), and also to increase the pore volume by 1.4 to 3.5cc / g by short-ageing in an alkaline atmosphere. And it is characterized by synthesizing a porous silica gel powder suitable for additives (anti blocking agent) of various films, to provide a manufacturing apparatus for this.

Description

Method and apparatus for producing porous silica gel powder

The present invention relates to a method and apparatus for producing porous silica gel powder. More specifically, in order to prepare high purity porous silica gel powder, alkali silicate aqueous solution and acid solution as raw materials are added and reacted in the form of a rotary spray to ensure homogeneity of the reaction, thereby significantly reducing aging and filtration time, and easy to control gel properties for each application. It relates to a method for producing a porous silica gel powder and a manufacturing apparatus therefor.

Porous silica powder controls porosity, e.g. pore volume, pore size and specific surface area and particle size, to prevent various types of films such as anti-sticking agents such as audio, video and packaging films, paint matting agents, sorbents for beer, toothpaste It is widely used in industrial applications such as thickeners and abrasives, reinforcements of plastics and rubber, and also has excellent thermal, electrical properties, and physicochemical stability.

Methods for producing porous silica powder include 1) vapor phase decomposition using silicon tetrachloride as a raw material (Japanese Patent Laid-Open Nos. 58-410,313, 62-2,011), and 2) sol-gel method using silicon alkoxide (Japanese Patent Laid-Open No. 63-166,777). No. 3), and 3) neutralization reaction of alkali silicate with acid (US Pat. No. 4,675,122, JP-A 3-23,487).

However, the method of 1) has the disadvantages of toxic and corrosive at the reaction, and the formation of pores only on the surface of the particles, the method of 2) has the advantage of obtaining a high-purity powder, but there is an economic problem. The production method of 3) is most widely used because of low raw material prices and easy handling. According to this method, an aqueous alkali silicate solution is neutralized with a strong acid to generate a silica sol in an acidic atmosphere, followed by gelation, washing with water and drying, and then pulverizing according to the use to prepare a porous powder. However, the silica powder produced by this method has a small pore volume (25 to 0.4 cc / g) and can be used only for some applications such as a desiccant, and since the mixing reaction between the raw materials is performed by dropping, The concentration of the alkali silicate solution should be 20% or less, and since the contact between the raw materials is made locally, there is a disadvantage in that the reaction is uneven.

In order to solve this problem, the gel synthesized in the acidic zone was hydrothermally synthesized with an alkaline solution for a long time (about 60 hours or more), and then washed for about 10 hours or more with an acid solution to overcome the nonuniformity and increase the pore size. The method of making the volume more than 1.2cc / g (Japanese Patent Application Laid-Open No. 2-289,670) was developed, but due to the long ripening and washing time, the one-time process is more than 2 to 3 days, and the size of the production equipment increases in mass production. And the required area is large, the manufacturing cost is high, there is a disadvantage that can not use a high concentration of raw materials. In addition, there is a disadvantage in that excessive time is required to control the gel properties for each use.

On the other hand, there is a patent for installing a raw material reaction tank outside the reaction tank and spraying the raw material through the spray nozzle therein, but a separate tank has to be manufactured, and there may be a blockage phenomenon between the tank and the heat pipe between the reactor and the raw material. There is a problem that care must be taken in the adjustment of the concentration and pressure during the input.

In the present invention, by introducing and applying an improved raw material input device, a high concentration of raw materials are added and mixed in a rotary spray method in the same reactor without a separate reaction tank to maximize the uniformity effect of mixing the raw materials, and greatly improve the aging and washing processes. It provides a manufacturing method and apparatus for manufacturing porous silica gel powder which can reduce manufacturing cost by improving the uniformity of each lot during production of the product by increasing the homogeneity of the porous powder for each use and reducing the production time of the product by use, and reducing the production cost. There is a purpose.

1 is a schematic diagram of a reaction apparatus for preparing porous silica gel powder according to the present invention.

FIG. 2 is a schematic diagram of a circular raw material injection nozzle and an input plate in the apparatus of FIG. 1. FIG.

3 is a schematic view of a circular rotating jet plate according to the present invention.

4 is a schematic view of another circular rotating jet plate according to the present invention.

5 is a schematic view of another circular rotating jet plate according to the present invention.

* Description of the symbols for the main parts of the drawings *

10 ---- Reactor 11 ---- Rotary spray raw material input means

12 ---- sight glass 13 ---- reactor heating jacket

14 ---- Temperature sensor 15 ---- pH sensor

16 ---- Stirrer 17 ---- Impeller

18 ----- Binder 19 ---- Reactant draw valve

20 ---- alkali silicate solution inlet tube

21 ---- Acid solution input tube 23 ---- Rotary spray raw material input means

24 ---- turntable speed control motor

The present invention is a method of producing a porous silica gel powder by mixing and reacting an aqueous alkali silicate solution and a raw material of an inorganic acid solution with each other to form a silica sol, followed by gelation, washing, drying and pulverization, the improvement of which is an aqueous alkali silicate solution of high concentration and After spraying the raw material of inorganic acid solution, the mixture was uniformly mixed by the rotary spray mixing method, and the synthesized silica gel was aged under a short time of 30 minutes to 3 hours in an alkaline atmosphere, and then washed, dried and pulverized to have a specific surface area of 200 to 900 m 2, pores. Characterized by a method for producing a porous silica gel powder having a volume of 1.4 to 3.5 cc / g, a pore size of 10 to 500 kPa.

In addition, the present invention is a means for inputting and spraying the raw material of the alkali aqueous silicate solution and inorganic acid solution, the means for making a sol by mixing and stirring the sprayed raw material, and the disintegration of the resulting gel, the mixing and disintegration of the raw material In the apparatus for producing a porous silica gel powder comprising a means for assisting, a means for adjusting and measuring the temperature and pH when mixing the raw material, and a means for discharging the disintegrated gel, the raw material is injected and sprayed Means for supplying a raw material injection tube for injecting each raw material into the reactor, a circular pipe having a nozzle that is connected to the input pipes and can spray the raw material on the lower surface, raw material sprayed from the nozzle of the circular tube It characterized in that consisting of a rotary jet plate configured to rotate at high speed in order to react.

In the present invention, by adjusting the equivalence ratio of alkali silicate and inorganic acid with a metering pump, a raw material is introduced by using a rotary spraying device, and a homogeneous reaction is induced to produce a homogeneous gel in an alkaline atmosphere, whereby the specific surface area and pore volume of the gel are respectively increased. It is possible to synthesize porous silica gel that is at least 200㎡ / g, 1.4cc / g (nitrogen adsorption), and also to increase the pore volume by 1.4 ~ 3.5cc / g by short aging in alkaline atmosphere, so that the paint matting agent And a porous silica gel powder suitable for additives (anti blocking agents) of various films.

Alkali silicate used as a raw material in the present invention may be of various kinds, such as sodium silicate solution or potassium silicate solution, but it is preferable to use a sodium silicate solution which can be easily supplied in large quantities at low cost. The concentration of soda silicate solution (based on silica) can be used from 10 to 28%, and the dilution ratio of less than 10% has a disadvantage of increasing the reaction tank, and if it exceeds 28%, it is more concentrated because it is the original concentration of the soda silicate feed solution. To do is meaningless.

In addition, various inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid or acetic acid may be used as the inorganic acid. However, sulfuric acid is particularly effective in consideration of reactivity with raw materials. At this time, the appropriate acid concentration is preferably 4 to 15% sulfuric acid. When the acid concentration is less than 4%, there is an advantage in that the reaction can be generated uniformly, but the size of the reaction tank is increased, and when the concentration is more than 15%, sufficient mixing with the raw materials is difficult to make a uniform reaction. .

In the conventional general manufacturing method, a mixture of a raw material and a strong acid is rapidly reacted and gelled in an acidic atmosphere to prepare a cake-like gel body, followed by pulverization, washing, drying, and grinding to prepare a porous gel powder. However, the gel body produced at this time has a small pore size due to its compact structure (20 to 40 mm 3), a small pore volume (0.25 to 0.4 cc / g), and a specific surface area of 500 to 800 m 2 / g. However, its use is extremely limited. In order to solve this problem, there is a method of increasing the pore volume by washing the silica gel synthesized in an acidic atmosphere with an alkaline solution for a long time or by hydrothermal aging, but the production time is not good because it is more than 2 to 3 days. .

In addition, if the concentration of silicon soda as a raw material is high (SiO ₂ , 20% or more), the concentration of the acid causing the neutralization reaction is also high. The degree falls, the viscosity of the raw material itself is high, it is difficult to smoothly input the raw material. In addition, there is no reproducibility of each product at the time of production, which reduces the value of the product.

Therefore, when the soda silicate solution and the acid solution are introduced by using the improved raw material input device as in the present invention, sufficient mixing is possible before stirring, thereby increasing the concentration of soda silicate to 28% based on the silica concentration. And, it is possible to manufacture the porous silica gel powder in the same reactor without the installation of a separate mixing tank.

The porous silica gel powder production apparatus used in the present invention is as illustrated in FIG. 1, and is composed of a reaction tank 10 and a rotary spray raw material input means 11. It is preferable that the reactor 10 and the rotary spray raw material input means 11 are made of stainless steel, which is basically acid resistant, alkaline and heat resistant.

The upper end of the reaction tank 10 is equipped with a see-through window 12 that can visually confirm the reactants, the reactor heating jacket 13 is filled with fruit oil surrounds the outside of the reaction tank (10). By this reactor heating jacket 13, temperature control of the reaction tank 10 becomes possible to 200 degreeC. The fruit oil is circulated to the upper outlet after being injected from the bottom of the reactor heating jacket 13, as shown in the drawing, the temperature is controlled in a separate fruit oil reservoir.

The temperature sensor 14 and the pH sensor 15 are installed in the vicinity of the lower portion of the reactor 10 to automatically measure the temperature and pH in the reactor 10.

The stirrer 16 installed below the reactor 10 can rotate up to 150 rpm, allowing centrifugal spray mixing followed by secondary mixing and gel disintegration. In addition, the stirrer 16 is attached to the impeller 17, can be produced in two forms, paddles or propellers in order to enhance the effect of the mixing, the mixture or the hydration gel filled in the reactor 10 is sufficiently stirred It is mixed.

Both sides of the inner surface of the reaction vessel 10 are provided with a baffle plate 18, and the baffle plate 18 is able to enhance its effect upon mixing and disintegrating the gel. Reactor 10 used in the present invention is manufactured in a structure capable of lifting the top plate for the internal cleaning and replacement and repair of the centrifugal spray plate.

In addition, a reaction product withdrawal valve 19 capable of withdrawing the disintegrated hydrogel is provided at the bottom of the reaction tank 10, and transport to the cleaning equipment is possible.

On the other hand, the rotary spray raw material input means 11 of the reaction tank 10 is enlarged in Figs. 2 to 5, two raw material input pipes, that is, the alkali silicate solution input pipe 2 and the acid solution input pipe 21 ), Circular pipes 201 and 211 connected thereto, nozzles 202 and 212 below the circular pipe, and a rotating plate 23.

The alkali silicate solution and the acid solution as the raw materials are introduced into the reaction tank 10 through the alkali silicate solution inlet tube 20 and the acid solution inlet tube 21 which are the raw material inlet tubes, and are connected thereto as illustrated in FIG. 2A. Each alkali silicate solution injection round tube 201 and an acid solution injection round tube 211 are introduced.

The raw materials introduced into the circular tubes 201 and 211 are alkali silicate solution injection nozzles 202 and acid solution injection nozzles 212 formed at the bottom of the circular tubes 201 and 211 as illustrated in FIG. 2B. It is injected into the reactor 10 through. In FIG. 2B, eight nozzles 202 and 212 are arranged at equal intervals, but if necessary, the number of nozzles can be adjusted, and an alkali silicate solution injection nozzle 202 and an acid may be used to increase the mixing effect between the raw materials. It is preferable to arrange the solution injection nozzles 212 alternate with each other.

The rotary jet plate 23 according to the present invention is driven by a drive shaft 25 connected to a motor 24 located at the top of the reactor 10 and rotates about 600 times per minute. The rotary jet plate 23 may be conical as illustrated in FIG. 3, and may be assembled by screwing with the drive shaft 25.

In the present invention, the rotary jet plate 23 may have a shape as illustrated in FIGS. 4 and 5. That is, the rotary jet plate 23 of FIG. 4A has a disc shape, but protrusions 231 protrude at regular intervals along the edge. 4B is a plan view of the rotary jet plate 23, and a center portion thereof is a portion that is screwed to the driving shaft 25 and a protrusion 231 is formed to protrude along the edge. In addition, in the present invention, but the shape of the rotary jet plate 23 as shown in Figure 5a and 5b to have a hollow inverted cone shape, but also used that the protrusion 231 is formed to protrude on the inner surface is empty Can be.

Mixing between the raw materials according to the present invention is made by the raw material reaction apparatus illustrated in FIG. That is, an alkali silicate solution (based on 10 to 28% silica) and an acid solution (4 to 15%), which are raw materials, are respectively supplied to the raw material input pipes 20 and 21 and the circular tubes 201 and 202 by a metering pump in the raw material tank. Through the injection nozzles (202, 212) is introduced into the reaction tank 10 through. The injected raw materials are dispersed while colliding with the rotary jet plate 23 rotating at a high speed, and thus the primary mixing reaction between the raw materials is performed. As described above, since the inlet tubes 20 and 21 of the alkali silicate solution and the acid solution are disposed to be staggered with each other, the effect of mixing can be further increased. In this way, the primary mixed reaction raw material is secondary mixing is made by the impeller 17 which is rotated by the stirrer 16 located in the reaction tank (10).

After the injection and injection of the raw material by the rotary spray raw material feeding means, the addition of the aqueous alkali silicate solution is stopped to prepare the silica hydrogel, and the acid solution is continuously added so that the acid solution is added when the concentration of the mixture reaches the gelation point. Abort. Gelling points usually occur in the range of pH 10.8 to 11.4. The hydrosol thus prepared turns into a hydrogel in minutes.

The resulting hydrogel is disintegrated into a slurry by as much stirring as possible before the gel solidifies. At this time, the disintegration time is suitable 20 to 30 minutes. The gel slurry produced by partial neutralization and disintegration in this way is completely neutralized by adding acid solution (pH 2) again to remove residual unreacted alkali components to prepare pure silica gel slurry. The fully neutralized gel slurry can be aged in an alkaline atmosphere to increase the interstitial pores, so that the specific surface area and pore volume can be adjusted to suit the purpose. Alkali used in alkali aging may be NaOH, NH ₄ OH, HN ₃ gas, etc., but ammonia water is the best because of the mixing of impurities and the like.

Alkali aging conditions are in the range of temperature 60 to 100 ℃, pH 7.5 to 10.5 aging time is 30 minutes to 3 hours is good, by changing the conditions according to the desired properties can be prepared for a gel suitable for the application. The higher the aging temperature and pH, the longer the aging time, the lower the specific surface area and the higher the pore volume. In the case of paint matting agent and anti-sticking agent for film, silica gel having a pore volume of 1.2 to 2.2 cc / g and a specific surface area of 250 to 350 m 2 / g at a temperature of 80 to 95 ° C. and a pH of 8.5 to 9.0 for 30 to 80 minutes. Manufacturing is possible.

After aging, the synthetic slurry is solid-liquid separated by a centrifuge. The solid-liquid separated gel cake is washed in a centrifuge to remove impurities such as forget-me-not (Na ₂ SO ₄ ) remaining in the gel. Industrial water or pure water may be used as the washing water, and may be selectively used depending on the grade required for the purpose. In order to increase the cleaning effect, hot water (above 50 ° C), cleaning agents (ammonium carbonate, acidic water, etc.) may be used.

The washed wet silica cake is dried using a flash grinding dryer. Drying methods and means vary, but if the drying time is prolonged, since the pore structure is collapsed by the drying stress generated during drying, rapid drying is essential for producing porous silica. Vacuum dryers, spray dryers, flash grinding dryers, etc. may be used as the rapid drying machine, and a flash grinding dryer suitable for drying in a few seconds and suitable for mass production and continuous processes is suitable.

The dried dry gel body is pulverized according to the particle size suitable for the application. Ball mills, hammer mills, grind mills, jet mills, and the like may be used as the pulverizer, but jet mills may be used to prepare fine porous silica powder having an average particle diameter of 4 µm or less.

According to the present invention, a porous silica gel powder having a pore volume of 1.4 to 3.5 cc / g and a specific surface area of 200 to 900 m 2 / g can be produced in a short time by using a rotary spray raw material input means, and also a high concentration (28%) silicic acid It is possible to increase the homogeneous mixing of the alkali silicate solution and the acid solution as raw materials while increasing the homogeneity of the alkali solution, while improving productivity and lowering the manufacturing cost, and it is possible to manufacture porous silica gel that can easily control gel properties for each application.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

Silicon starting soda 3 (silica concentration 28%) and sulfuric acid (98%) was used as a starting material, in the case of sulfuric acid was diluted with water to prepare an aqueous sulfuric acid solution (6%).

It is made of stainless steel (SUS 361), and has a diameter of 400mm and a conical rotary jetting plate of 400mm in diameter and a propeller type impeller installed in a reactor with a diameter of 640mm, a height of 760mm and a capacity of 250ℓ. Was operated at 600 rpm and 150 rpm, respectively, with a diameter of 25 mm, 275 mm and 300 mm diameter round tubes, and a diameter of 5 mm and a raw material injection nozzle with 8 nozzles. 37.2 L of aqueous sodium silicate solution and 20.9 L of sulfuric acid aqueous solution were added over 4 minutes.

After the addition, 8.3 L of an aqueous sulfuric acid solution (6%) was added thereto to generate silica hydrogel. PH of the reaction mixture at this time was 11. As soon as the gel was produced, the gel was disintegrated for 30 minutes by vigorous stirring to prepare a gel slurry containing fine gel particles. In order to neutralize the unreacted alkali component, 25.1 L of sulfuric acid (6%) was further added to lower the pH of the gel slurry to 1.

In order to adjust the specific surface area and pore amount, the pure neutralized silica gel slurry (pH 1) was heated to 100 ° C., and 9.5 L of ammonia water (28%) was added to increase the pH to 10 and maintained for 1 hour. The synthetic slurry was then solid-liquid separated using a centrifuge. The solid-liquid separated gel cake was washed with hot water at about 70 ° C., and dried using a flash grinding dryer to dry within a few seconds to prepare a porous silica gel powder. The silica gel powder prepared here was used as an adsorbent for beer, and the specific surface area, pore volume and pore size of the porous silica gel powder were shown in Table 1 below.

Example 2

In Example 1, in order to control the specific surface area and pore amount, the fully neutralized gel slurry (pH 1) was heated to 80 ° C., and then 10.82 L of ammonia water (28%) was added to pH 9 and maintained for 1 hour. A porous silica gel was prepared in the same manner as in Example 1 except for the above. The silica gel powder prepared herein was used as an additive for film and a matting agent for pate. The specific surface area, pore volume and pore size of the porous silica gel powder are shown in Table 1 below.

Example 3

In Example 1, in order to control the specific surface area and the pore amount, the fully neutralized gel slurry (pH 1) was added to 8.5 l of ammonia water (28%) at room temperature (20 ° C), and then maintained at pH 8 for 1 hour. A porous silica gel was prepared in the same manner as in Example 1 except for the above. The silica gel powder prepared here was used as a catalyst carrier, and the specific surface area, pore volume and pore size of the porous silica gel powder are shown in Table 1 below.

Comparative Example 3

40 kg of a solution of Soda Silicate No. 3 (silica concentration 28%) was diluted with 16 kg of water to prepare an aqueous solution containing about 20% silica concentration. In addition, dilute sulfuric acid aqueous solution (6%) was prepared by diluting 1.5 L of sulfuric acid (98%) and 35 L of water, and 56 kg of sodium silicate solution and 30.5 L of sulfuric acid solution were added through a raw material injection spray nozzle for 6 minutes. After the addition, 5 L of the remaining sulfuric acid aqueous solution was added through a spray nozzle attached to the reactor to generate silica hydrosol. At this time, the pH of the reaction mixture was 11.06. The resulting hydrosol was changed into a gel in water, at which time the gel was disintegrated with vigorous stirring to prepare a slurry containing microgels. Disintegration time was carried out for 30 minutes. Next, 25.1 L of sulfuric acid (6%) was added to lower the pH of the slurry to 1. The fully neutralized gel slurry was heated to 80 ° C., and then 10.82 L of ammonia water (28%) was added to pH 9 and maintained for 1 hour. After filtration separation and washing and drying to prepare a porous silica gel. The specific surface area, pore volume and pore size of the prepared porous silica gel powder are shown in Table 1 below.

Comparative Example 2

40 kg of a solution of Soda Silicate No. 3 (silica concentration 28%) was diluted with 16 kg of water to prepare an aqueous solution containing about 20% silica concentration. In addition, 6 liters of sulfuric acid (98%) and 60 liters of water were prepared to dilute sulfuric acid aqueous solution, and added to the aqueous sodium silicate solution while stirring. The concentration of the mixture after addition was pH 1.5. The hydrogel thus prepared was gelled in minutes. In order to increase the pore volume, the prepared gel was washed with an aqueous ammonia solution of pH 8 for 10 hours, filtered off, washed and dried to prepare a porous silica gel. The specific surface area, pore volume and pore size of the prepared porous silica gel powder are shown in Table 1 below.

TABLE 1

Claims (7)

In the method of producing a porous silica gel powder by mixing and reacting the alkali silicate aqueous solution and the raw material of the inorganic acid solution with each other to produce a silica sol and then gelled, crushed, washed, dried and pulverized, Silica gel synthesized by spraying high concentration alkali aqueous silicate solution and inorganic acid solution raw material and uniformly reacting by rotary spray mixing method is aged in 30 minutes to 3 hours under alkaline atmosphere, and then washed, dried and pulverized. A method for producing a porous silica gel powder having a specific surface area of 200 to 900 m 2, pore volume of 1.4 to 3.5 cc / g, and pore size of 10 to 500 mm 3. The method of claim 1, wherein the concentration of the alkali silicate aqueous solution is 10 to 28% based on silica, and the concentration of the inorganic acid solution is 4 to 15%. The method of claim 1, wherein the rotary spray mixing method is characterized in that the first injection of the raw material injected through the nozzle into the reaction tank by rotating the rotating jet rotating at high speed to mix firstly and further by agitating the stirrer. The manufacturing method of the porous silica gel powder made into. The method of claim 1, wherein the alkali aging temperature is a method of producing a porous silica gel powder, characterized in that carried out in the range of pH 7.5 to 10.5 at a temperature of 60 to 100 ℃. Means for injecting and spraying a raw material of an aqueous alkali silicate solution and an inorganic acid solution, a means for making a sol by mixing and stirring the sprayed raw material and crushing the resulting gel, a means for helping mixing and crushing the raw material, In the apparatus for producing a porous silica gel powder consisting of a reaction tank comprising a means for adjusting and measuring the temperature and pH at the time of mixing the raw material and the means for discharging the disintegrated gel, the means for adding and spraying the raw material, respectively A raw material inlet tube for injecting the raw material into the reactor, a circular tube having a nozzle capable of injecting the raw material on the lower surface while being connected to the input tubes, and mixing and reacting the raw material injected from the nozzles of the circular tube Porous silica gel, characterized in that consisting of a rotating jet plate configured to rotate at a high speed for Apparatus for producing powder. 6. The apparatus of claim 5, wherein the nozzles of the raw material input pipe and the circular pipe are alternately arranged to increase the mixing effect between the raw materials. According to claim 5, wherein the rotary jet plate is conical, a disk shape having a protrusion at regular intervals on the edge, the inverted conical shape having a protrusion in the hollow interior, the central portion is screwed with the drive shaft rotated by a motor Apparatus for producing porous silica gel powder, characterized in that.