JPH0220563B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing silicate granules, particularly a method for producing fine silicate granules with uniform particle size. Fine silicate particles are relatively lightweight and inexpensive, and are chemically stable against various substances, so they are used as fillers in various synthetic resin materials, as matting agents in paints, and as viscosity control agents. It has been proposed to be used for various purposes, such as as a conditioning agent and a performance improver for specially processed paper, and some of them have been put into practical use. This type of granular material has a wider range of uses as the particle size is smaller (10 μm or less, preferably 5 μm or less) and in any case, the particle size is as uniform as possible. In addition, although several methods have been proposed in the past for making the particle sizes uniform, there is still no method that is industrially satisfactory, except for very special methods that are expensive. . In view of this point, the present inventor conducted various research and examinations with the aim of finding a means to industrially easily obtain silicate granules having a uniform particle size. It has been found that the above object can be achieved by forming the gel in advance under specific conditions in a liquid medium and gelling it. Thus, the present invention is characterized in that a silicate is stirred in a non-polar liquid medium containing a surfactant to form fine droplets of the silicate, and then the droplets are gelled with carbon dioxide gas. The present invention provides a method for producing silicate granules. Examples of the surfactant used in the present invention include nonionic surfactants such as polyethylene glycol fatty acid ester, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ether, sorbitan fatty acid ester, and polyoxyethylene sorbitan fatty acid monoester. can be used as appropriate. The amount of surfactant used is generally 100
It is appropriate to adopt approximately 50,000 ppm. If the amount used is less than the above range, the droplets will not be stably atomized, and if it exceeds the above range, there is a risk that the particles produced will agglomerate and become more likely to produce secondary particles. I don't like either of them because of that. Among these ranges, it is particularly preferable to use 200 to 10,000 ppm because the droplets are stably atomized and there is no risk of the generated particles agglomerating. Further, as the liquid medium used in the present invention, for example, non-polar organic liquid media such as benzene, toluene, xylene, kerosene, trichlorethylene, perchlorethylene, etc. can be appropriately used alone or in combination. The appropriate amount of these liquid media to be used is about 2 to 20 per silicate aqueous solution. If the amount used is less than the above range, a stable emulsion cannot be obtained, and conversely, if it exceeds the above range,
The amount of granules produced per unit volume becomes insufficient,
Both are unfavorable as they result in poor productivity. Among these liquid media, toluene, perchloroethylene, and kerosene are particularly preferred since they can be used in small amounts and high droplet dispersion stability can be obtained with a small amount of surfactant. As the silicate used in the present invention, for example, water glass, sodium silicate, silica sol, etc. can be used as appropriate. An aqueous silicate solution is then added to the non-polar liquid medium to which a surfactant has been added and stirred to form a sol. The stirring performed here has such a large effect that it determines the particle size of the granules finally obtained. It is not preferable to stir too slowly or for too long because the dispersibility of the droplets may deteriorate and the particle size may become uneven. The particle size of this kind of granular material varies depending on its use, but in general, granular material having an average particle size of about 1 to 10 μm is often used. As the stirring conditions, it is appropriate to adopt a stirring power of 0.2 to 5 KW per 1 m ³ of a silicate aqueous solution dispersed and emulsified in a nonpolar medium. In addition, when stirring, the liquid temperature of the non-polar liquid medium is not desirable because if it is too high or too low, the viscosity of the liquid will change and the dispersion stability of the droplets will be impaired, so a temperature of 10 to 80°C is generally adopted. It is appropriate to do so. In addition, in this case, if the silicate is acidic, the silicate will not form the desired fine particles, and some of the silicate will become lumpy and gel, which is undesirable. The droplet-like gel thus obtained is then gelled with carbon dioxide gas. In the present invention, if gelation is carried out using a liquid such as hydrochloric acid, the desired granular sol droplets will be broken, and conversely, lumps will be formed in some areas, which is unsuitable. When carbon dioxide gas is used for gelation, the droplet-like sol produced in a preferred form can be gelled as is, and the carbon dioxide gas dissolved in the nonpolar medium can surely cause gelation of the silicate through the emulsion film. It becomes possible to do so. It is appropriate that the amount of carbon dioxide gas used during gelation be at least 1.5 times the theoretical amount required to convert all of the sodium in the water vitreous into sodium carbonate. The thus gelled granules are separated from the liquid medium by sieving, and the adhering liquid medium is removed by steam distillation or alcohol, followed by drying. As specific means for such drying, for example, a direct heating method using a combustion flame, a spray dryer method, a fluidized drying method, etc. can be adopted. Next, the present invention will be explained by examples. Example 1 Liquid composition obtained by diluting 250g of No. 3 water glass with 500g of water
An aqueous solution containing 9.7 wt% SiO ₂ and 3.2 wt% Na ₂ O was prepared and used as a reaction solution. Next, toluene 3 containing 5000 ppm of nonionic surfactants Tween 80 and Span 60 (weight ratio 3:1) was added to a separable flask with a capacity of 5 and equipped with a stirrer and a gas injection nozzle, and the stirring intensity was 2000 rpm. While stirring, the above reaction solution was added dropwise to form an emulsion. The particle size of the sol obtained here is close to a true sphere of about 2μ, and then
Carbon dioxide gas was blown in from a gas blowing nozzle at a rate of 0.2/min for 10 minutes, and stirring was continued for an additional 60 minutes. During this time, the liquid temperature was maintained at 30°C. Next, the slurry in the flask was taken out and the solid content was separated, and the toluene adhering to the solid content was removed by steam treatment. Next, since the solid content contained sodium carbonate in the particles, it was removed by washing with 20 g of water, and the solid content after washing was dried to obtain a fine silica gel powder. The SiO ₂ purity of the powder was 99.5%, and as a result of scanning electron microscopy (SEM) observation, it was found that the average particle size was 2 μ, maintaining the particle size in the sol state. The specific surface area determined by the BET method was 140 m ² /g. Examples 2 to 4 Using the same reactor as in Example 1, a predetermined liquid medium was put therein, and the reaction solution was added dropwise while stirring, and then carbon dioxide gas was blown into the reactor to form a gel. below,
As a result of performing the same treatment as in Example 1, fine silica gel powder was obtained. Table 1 shows the synthesis conditions and the physical properties of the obtained product. 【table】

Claims (1)

[Claims] 1. A method characterized by stirring a silicate in a non-polar liquid medium containing a surfactant to form fine droplets, and then gelling the droplets with carbon dioxide gas. Method for producing silicate granules. 2. The method according to claim 1, wherein the surfactant is polyethylene glycol fatty acid ester, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ether, sorbitan fatty acid ester, or polyoxyethylene sorbitan fatty acid monoester. 3. The method according to claim 1, wherein the liquid medium is toluene, kerosene, benzene, xylene, trichlorethylene, perchlorethylene. 4. The method according to claim 1, wherein the silicate is water glass, sodium silicate, or silica sol.