JPS593008A - Molding of stabilized anhydrous dithionite and its manufacture - Google Patents

Abstract

PURPOSE:To obtain moldings suitable for pulp bleaching, etc., having superior stability and solubility, and scattering no dust by subjecting anhydrous dithionite contg. a stabilizer to dry compression molding in the presence of air having low relative humidity or an inert gas. CONSTITUTION:To finely powdered anhydrous dithionite is added at least 1 kind of stabilizer selected from the carbonates, phosphates, silicates and carboxylates of alkali metals, urea, hexamethylenetetramine and surfactants. The anhydrous dithionite blended with the stabilizer is charged into the hopper of a compression molding machine, air having <=50% relative humidity or an inert gas is substituted for the air in the molding machine, and dry compression molding is carried out under 30-200kg/cm<2> pressure while keeping the powder at <=50 deg.C. Thus, the desired moldings of stabilized anhydrous dithionite are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stable molded product of aluminum salt, zinc salt, etc. and a method for producing the same.

More specifically, the present invention relates to a molded product formed by dry compression molding anhydrous dithionite #jm containing a stabilizer such as a carbonate or a silicate (a method for molding the same).

Anhydrous dithionine #I salt has excellent reducing properties in an aqueous solution, and is therefore used in fields such as pulp bleaching, vat dye dyeing, azo dye dyed material decolorization, and food bleaching. However, the currently produced anhydrous dithionite salt usually has an average diameter of θ. Since it is a fine powder of less than /wa, it easily scatters during use, which often causes a deterioration of the working environment. Furthermore, it absorbs moisture and decomposes easily during storage.
H2S significantly deteriorates its reducing power.

It is well known that 0H3SH1 (OH3S)2 etc. increase and emit a bad odor, and that they can spontaneously ignite due to the heat generated during decomposition, causing a fire. Particularly when bleaching pulp, if such finely powdered anhydrous dithionite is added to a highly viscous valve slurry, it will float on the surface of the pulp slurry, and a considerable amount of the dithionite solution will be absorbed by the time the dithionite solution is finished. Nithionite decomposes.The higher the dissolution temperature, the lower the pH of the aqueous solution or slurry.
The viscosity tends to increase as the viscosity increases, and 20-j'0% of the added amount decomposes by the time the solution preparation is completed. Therefore, in general, the theoretical quantity /,,! ;-, 2,0 times more anhydrous dithionate is used.

In addition, in recent years, sulfur dithionite bath solution (USP3
1r01t91/-11 (Apr #, /9711)
UP; pH10009100O9/ha/97za)), blood sodium dithionate t7m7, rally (USpH2133
Patents have been issued for sodium dithionite (03cAng//, /91/)), but in order to suppress the decomposition of sodium dithionite, it must be stored at low temperatures and low concentrations, resulting in high equipment costs. Because it is a concentrated solution, it may be more expensive to transport than powder, making it unsuitable for small-scale pulp bleaching.

For this reason, suppressing the decomposition of anhydrous dithionates and using them effectively is a major challenge in the industry, and up to now various stabilization measures have been taken (for example, Japanese Patent Publication No. 11, 1983).
No. 2-20372, No. '72-211637, No. 1I
3-2≠No.771, Dohiro'/--/20/3, Dogut
-za 093, same gu, t-, 24 Otsu No. 10, same l Otsu-/
Otsu No. 659, same 1t-34t4t 3, same ll Otsu-
3atiq ke issue, Otsu-311'19! ; No. 11
．． Name-3t≠9otsu, same! ;/-/7/! ; No. 3, etc.), but the anhydrous pre-nithione obtained by the method proposed so far! ! Salt still has an average diameter of 0. This is aimed at fine powders of /rm or less. Therefore, it fundamentally solves the above-mentioned disadvantages of anhydrous dithionates, such as scattering during use, decomposition due to moisture absorption during storage, and increased malodor components due to floating in the upper layer of pulp slurry during pulp bleaching. Even today, solving this problem is one of the most pressing challenges in the industry.

As a result of extensive research, the present inventors have found that it is possible to compress and mold finely powdered anhydrous dithionate containing a stabilizer, and the resulting molded product has lower odor and purity than powdered products. It is more stable, there is no dust scattering, the working environment is improved, and when it is added to the pulp slurry during pulp bleaching, the sedimentation of the anhydrous pre-nithionate is also good.
The fluidity of the powder is improved and the bulk specific gravity is large, so the product filling container can be made smaller and economical.In addition, by molding, it is possible to transport a combination product of fine powdered anhydrous dithionate and a stabilizer. It was found that the final classification was almost reduced.

Hitherto, anhydrous dithionates have not been manufactured into molded bodies because they are extremely flammable and dangerous in the presence of moisture and oxygen.

However, according to the present invention, it has been found that compression molding of anhydrous dithionate in air or an inert gaff (for example, nitrogen, helium, etc.) atmosphere is industrially possible with almost no danger during production. . Furthermore, since it is dry compression molded, there is no need for a drying process, making it economically valuable.

Next, a method for producing the anhydrous nithion rII salt molded article according to the present invention will be explained.

Finely powdered anhydrous dithionate containing a stabilizer was put into the hopper of the compression molding machine, and the air in the granulator was adjusted to a relative humidity of 30%.
Purge with air or inert gas below and reduce the powder temperature to 50
Dry compression molding while keeping the temperature below ℃. Compression molding generates compression heat, which increases the temperature of the molded product and makes it more likely to decompose.

Therefore, a powder containing a known stabilizer such as a subacid or a silicate is used in the raw material powder, and the temperature is kept at 30°C or lower, more preferably at 30°C or lower, by removing heat during molding. There is a need. Relative humidity is also 3 to prevent decomposition during molding.
It is preferable to keep it below 0%. The roll strength during molding is determined within a range in which the molded product is not crushed, chemical reactions due to compression heat during molding can be ignored, and the yield of the molded product is good, but it is usually 30 kq/d to 900 k(j/d). 14 preferably!; Okg/cd~/30 kg/14 is used.

Examples of the compression molding machine used in the present invention include a roller compactor, a briquette machine, etc., which compress and mold powder by sandwiching the powder between two rollers. A molded product obtained without adding a stabilizer will be decomposed by heat of compression and will generate a large amount of odor components, so it is necessary to add a stabilizer, and the amount added is 7 parts by weight per q100 parts by weight of dithionite anhydride. The amount is at least 2 parts by weight, preferably at least 2 parts by weight. The anhydrous dithionite thus compression-molded is in the form of a plate or rod, and if necessary, it can be further pulverized to any particle size using a pulverizer such as an oscillator or a power mill.

Furthermore, depending on the purpose, it is also possible to add various additives that do not impair the stability of the anhydrous dithionite to the raw material powder containing the stabilizer and perform compression molding.

Typical stabilizers include alkali metal subacids, phosphates, nitrates, carboxylates such as benzoic acid, sorbic acid, and acetic acid, urea, hexamethylenetetramine,
Examples include surfactants, but are not necessarily limited to these.

Further, the shape of the anhydrous dithionite molded product according to the present invention may be arbitrary, but granules are preferable from the viewpoint of handling, and granules of various particle sizes can be manufactured. However, considering production yield, stability of anhydrous dithionite, and ease of handling, larger particle size is preferable, and when expressed as an average diameter, it is 0.3 m or more, preferably 0.3 m or more. ! ; m or more shows excellent stability.

The anhydrous dithionite molded product according to the present invention is more stable in terms of odor and purity than powder, and is more stable than pulp.

When added to viscous liquids such as slurry and waste sludge, it does not float in the upper layer, making it possible to extremely reduce the amount of anhydrous dithionite #I salt decomposed.

In addition, since it is a molded product and has great strength, there is no need to worry about dust, making it extremely environmentally friendly.

If the anhydrous dithionite molded body according to the present invention is used,
It is extremely economical because the same effect can be achieved with a smaller amount than when using conventional finely powdered anhydrous dithionite. That is, the anhydrous dithionite molded product according to the present invention substantially solves the problems of the existing fine powder products mentioned above, and is useful in the field of bulb bleaching and the like with extremely high industrial value. The present invention will be specifically explained below with reference to Examples and Usage Examples, but the present invention is not limited by these.

Kasuri=Ratio Example-l Molding conditions for inoculation 4 in which a stabilizer was added and mixed with finely powdered anhydrous dithionite l-IJium (purity 9%, particle size 0./!; wm or less) It was compressed with a compactor to obtain an irregularly shaped molded body (plate-like or rod-like). After that, it is processed into granules (particle size 0.3!; ~0.I'1m) using an oscillator.
) as anhydrous sodium dithionite, decomposition rate during molding,
The molding rate (relative to raw material powder) and the granulation rate (relative to raw material powder) were measured.

The results are shown in Table 1.

As shown in Table 1, when the roll pressure is low, the powder temperature is low, and the relative humidity is low, the decomposition rate during molding is low and stable, but the higher the roll pressure, the better the molding rate and granulation rate. .

Example-2 Finely powdered anhydrous sodium dithionite (purity?/, 4%)
, particle size 0. /j■ or less), add stabilizers in respective proportions and mix, then roll pressure /j Okg/cd.

This blended product was compressed using a roller compactor under the molding conditions of ambient gas dry nitrogen and powder temperature 30°C to obtain an irregularly shaped molded body (plate-like or rod-like). After that, an oscillator is used to make granular (particle size 0.3J to 0.J'4'ma) anhydrous sodium dithionate, and 100 y of this anhydrous sodium dithionate is placed in an aluminum vapor-deposited film and dried air after reducing the pressure. After injecting SO- and sealing, it was left to stand in a constant temperature oven at 30°C for 3 days, and the purity of sodium dithionate on the anhydrous surface was measured. The results are shown in Table 2.

As shown in Table 2, the molded product prepared by adding a stabilizer to anhydrous sodium dithionate has a slightly lower decomposition rate and is more stable than a fine powder product having the same composition. In addition, the molded product containing IJium carbonate has a lower decomposition rate and is more stable than the molded product without the addition and the fine powder product.

Incidentally, the dust scattering properties of the molded bodies were not uniform.

Example-3 Granules produced in Example-7 (particle size 0.3j to 0, II
The anhydrous sodium dithionite aged body of Iws) was backed on an aluminum vapor-deposited film in the same manner as in Example-2, and
The gas odor in the aluminum vapor-deposited film was measured after several days. The gas odor referred to here refers to sulfur compounds that are gaseous at room temperature, mainly H2S, 0H38H, and (OH3
S) means 2. The total amount of gas components measured by gas chromatography was 10OV of anhydrous sodium dithionate.
The total amount of sulfur in the gas components is shown in Da units. For comparison, granular anhydrous sodium dithionate obtained after compression molding (purity 19.1%, particle size 0.
(purity fj, lI
%, particle size o, and the gas odor was measured in the same manner.

The results are shown in Table 3.

As shown in Table 3, the molded product according to the present invention is more stable in terms of odor than a fine powder product of the same composition. In addition, it is more stable than a molded product without the addition of sodium legate.

Usage example j% refined ground pulp woly 5ooy 7
Put it in a 000- beaker, length 11wm 5 width 201m
1+ λ blade paddle type wing, 20r, pom.

The mixture was stirred at a speed of 20°C and heated to 0°C. This was added to the anhydrous sodium dithionite molded product of Example-/&t (purity 1
3. lI%) 27.954 was input.

As a result, the entire amount settled as soon as it was added, and there was no floating.

In addition, anhydrous sodium dithionite powder (purity rs3%
, particle size 0. /! ; m or less) 27. ．． 2p was added. As a result, about 20% of the water was suspended, and it took about 20% of the time to completely settle.
I loaded it for a minute.

Changes over time were measured at the same time as the addition, and the results are shown in Table V.

As shown in Table 1, it was confirmed that the molded article according to the present invention quickly settled in the pulp slurry, and the anhydrous sodium dithionite introduced therein was effectively utilized.

No person) 2

Claims (1)

[Claims] l) An anhydrous dithionite molded product containing at least a stabilizer and dry compression molded. , 2) the stabilizer is an alkali metal carbonate, a phosphorus flI salt,
The molded article according to claim 1, which is at least one compound selected from the group consisting of silicates, carboxylates, urea, hexamethylenetetramine, and surfactants. 3) The molded product according to claim 1, wherein the average diameter of the molded product is 0.3 wa or more. l) Anhydrous dithionite containing at least a stabilizer is dry compression molded in the presence of air or inert gas with a relative humidity of not more than 50% while keeping the temperature at 30° C. or less. A method for producing an acid salt molded body. S) A method for producing a molded body according to claim 1, wherein the molding pressure is 30 to 200 -. 6) A method for producing a molded body according to claim 1, in which the anhydrous dithionite after compression molding is pulverized to a desired particle size.