JPH04170315A - Water-insoluble sodium bicarbonate and its production - Google Patents

Abstract

PURPOSE:To obtain sodium bicarbonate which hardly solidifies by incorporating hydrophobia silica by a specified proportion to suppress water solubility and moisture absorptivity of sodium bicarbonate. CONSTITUTION:The water-insoluble sodium bicarbonate contains 0.1-10wt.% hydrophobia silica. This water-insoluble sodium bicarbonate is produced by mixing hydrophobia silica and sodium bicarbonate, or by dispersing hydrophobia silica in an org. solvent, mixing sodium bicarbonate with the dispersion, and vaporizing the org. solnvent. By using the org. solvent, the hydrophobic silica can easily and uniformly be dispersed in sodium bicarbonate, and moreover, a little amt. of hydrophobic silica gives the effect of making the sodium bicarbonate water-insoluble. As for the org. solvent, ethanol is practically preferable since it has no toxicity.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to poorly water-soluble sodium bicarbonate and a method for producing the same, and in particular, it is used as a fire extinguisher, a stripping agent, an abrasive, a filler for resins and rubber, etc. The present invention provides baking soda and a method for producing the same.

[Prior Art] Generally, baking soda is produced by reacting caustic soda and/or soda carbonate with carbon dioxide gas to precipitate crystals, separating and drying the crystals, and is handled as a powder. Baking soda is used for many purposes such as a fire extinguisher, a soil conditioner, and a desulfurizing agent for waste gas.

[Problem to be solved by the invention] However, when baking soda is used in powder form,
The problem is that baking soda absorbs moisture from the air, causing it to solidify during storage. This problem is caused by the fact that baking soda is water-soluble and hygroscopic. For example, if baking soda is used as a fire extinguisher, it will not accomplish its purpose if it solidifies inside the fire extinguisher. It is also being considered to use baking soda as a rust and paint remover, and for that purpose baking soda must have good fluidity, but conventional baking soda absorbs moisture depending on the environment and gradually becomes less fluid. Therefore, it cannot be used in reality.

Conventional solutions to this problem of baking soda caking include making the particle size of baking soda uniform, making the surface of baking soda smooth, making baking soda particles larger, and storing baking soda in a way that prevents it from absorbing moisture. Although countermeasures have been taken, they are not always sufficient to prevent caking.

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide baking soda that has suppressed water solubility and hygroscopicity and is difficult to caking.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present inventors made earnest efforts to develop baking soda with suppressed water solubility and hygroscopicity. The present invention was completed by discovering that baking soda can solve this problem. That is, the present invention uses hydrophobic silica in an amount of 0.1 to
It is a poorly water-soluble sodium bicarbonate characterized by containing 10'wt%.

The present invention will be explained in more detail below.

The baking soda used in the present invention is not particularly limited, and examples thereof include baking soda obtained by bicarbonating a caustic soda aqueous solution or a sodium carbonate aqueous solution in which synthetic soda ash or natural soda ash is dissolved, sodium carbonate crystals, and sesquicarbonate. Examples include baking soda, which is obtained by reacting soda crystals with carbon dioxide gas in the presence of water.

Furthermore, the hydrophobic silica used in the present invention has an M value of 1.
There is no particular limitation as long as it is 0% or more, for example, hydrated silicic acid (also known as white carbon, component: S1
0□) treated with organosilicon compounds (for example, silanes, silazane, polysiloxanes, etc.), and the surface of the silica is covered with hydrophobic groups such as methyl groups and alkyl groups. . Here, the M value is an index expressing hydrophobicity. Prepare several solutions of water and methanol with different mixing ratios, add a small amount of silica to the solution, shake it, and increase the ratio of methanol. It refers to the methanol ratio (volume %) of the solution in which silica begins to be suspended. In the present invention, it is preferable to use hydrophobic silica with an M value of 30 to 90% in order to exhibit the effect of making it difficult to dissolve in water.

The present invention relates to baking soda containing hydrophobic silica, and the content of hydrophobic silica in baking soda is 0.1
It needs to be ~10 wt%.

If the amount of hydrophobic silica is less than 0.1 wt%, there is no substantial effect, and if it exceeds 10 wt%, the fluidity of the baking soda will deteriorate, which is not preferable.

The method for producing baking soda containing 0.1 to 10 wt% of hydrophobic silica is not particularly limited, and includes, for example, a method of mixing baking soda and hydrophobic silica, an organic solvent (e.g.
Examples include a method in which hydrophobic silica is dispersed in a mixed solvent of ethanol, methanol, acetone, alcohol and water, etc., mixed well with baking soda, and then dried to vaporize the organic solvent. By using an organic solvent, hydrophobic silica can be easily and uniformly dispersed in baking soda, and even a small amount of hydrophobic silica can be effective in making it poorly water soluble. It is preferable to use ethanol due to its practicality. The amount of organic solvent to be used can be selected depending on the ratio of baking soda and hydrophobic silica, the mixer used, etc., but hydrophobic silica 1. It is preferable to use an organic solvent of 2 to 100 c'c with respect to the amount of organic solvent. - The extent to which baking soda's water solubility and hygroscopicity are suppressed can be easily observed visually by floating on the surface of water when baking soda is placed in water, but more quantitatively, it is
of sodium bicarbonate is added, and the weight of the sodium bicarbonate dissolved within 5 minutes is taken as the dissolution rate, and this dissolution rate can be used as a guideline.

The mechanism by which baking soda containing hydrophobic silica becomes poorly soluble in water is thought to be that primary particles or aggregated particles of silica are dispersed on the surface of baking soda crystals, thereby preventing contact with water.

[Example] Baking soda used > Hydrophobic silica manufactured by Tosoh Corporation (average particle size: 240 microns) Hydrophobic silica manufactured by Nippon Silikani Corporation (Nipsfl5)
S-50, M value: 60%) Measurement of dissolution rate> In a 200 cc beaker, 100 cc of water at a temperature of 20°C was added, and 10% of baking soda was added. Add little by little.

Stir gently and sample only the aqueous solution after 5 minutes.
Analyze dissolved baking soda.

Example 1 1 kg of sodium bicarbonate was mixed with 10 g of hydrophobic silica and mixed well to prepare poorly water-soluble sodium bicarbonate. We measured the dissolution rate of this baking soda and also confirmed whether it floated on water. The results are shown in Table 1.

Example 2 1 g of hydrophobic silica was dispersed in 60 cc of ethanol, and this was added to 1 kg of baking soda and mixed well.

Then, the mixture was treated in a dryer at 70° C. for 10 minutes to remove ethanol, thereby preparing slightly water-soluble sodium bicarbonate. The dissolution rate of this baking soda was measured, and it was also confirmed whether it would float on water. The results are also shown in Table 1.

Examples 3 to 6 Same as Example 2 except that the amount of hydrophobic silica was changed to 2 g (Example 3), 5 g (Example 4), 10 g (Example 5), and 80 g (Example 6) Slightly water-soluble sodium bicarbonate was prepared under these conditions, and the dissolution rate of each was measured. Furthermore, it was confirmed whether or not it floated on water. The results are also shown in Table 1.

Comparative Example The dissolution rate of hydrophobic silica-free baking soda was measured, and it was also confirmed whether it floated on water.

The results are also shown in Table 1.

[Effects of the Invention] As is clear from the above description, the present invention has the effect of suppressing the water solubility and hygroscopicity of sodium bicarbonate, thereby producing poorly water-soluble sodium bicarbonate that does not easily solidify. By obtaining poorly water-soluble sodium bicarbonate, it can be used as a stripping agent, etc., which could not be used until now, and has the effect of expanding new uses.

Claims (3)

[Claims] (1) A sparingly water-soluble sodium bicarbonate characterized by containing 0.1 to 10 wt% of hydrophobic silica. (2) The method for producing poorly water-soluble sodium bicarbonate according to claim (1), which comprises mixing hydrophobic silica and sodium bicarbonate. (3) The method for producing poorly water-soluble sodium bicarbonate according to claim (1), which comprises dispersing hydrophobic silica in an organic solvent, mixing it with sodium bicarbonate, and then vaporizing the organic solvent.