JPH08143309A - Production of amorphous sodium silicate-sodium carbonate compound body - Google Patents

Abstract

PURPOSE: To produce an amorphous sodium silicate-sodium carbonate compound body having high softening property with water and small moisture absorption which is suitable as a builder of a detergent by pulverizing specified sodium silicate cullet and bringing them into contact with gaseous carbon dioxide. CONSTITUTION: After sodium silicate cullet having the molar ratio n=SiO2 /Na2 O between 1.0 to 3.3 are pulverized, the pulverized material is brought into contact with gaseous carbon dioxide, or at same time of pulverizing, the material is brought into contact with gaseous carbon dioxide to obtain the amorphous sodium silicate-sodium carbonate composite body of the purpose. If n in the sodium silicate as the source material is smaller than 1.0, the silica component in the composite body dissolves fast and Ca ion and Mg ion once bonded with the silica component elude again into water. This decreases the softening property with water, which is not preverable. On the other hand, if n is larger than 3.3, the dissolving amt. of Na ion decreases and the site to bond Ca ion and Mg ion decreases, which is not preferable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an amorphous sodium silicate / sodium carbonate composite having a water softening property and a small hygroscopicity and useful as a detergent builder.

[0002]

Amorphous sodium silicate has been known for a long time. A typical example thereof is amorphous sodium silicate cullet (small piece of sodium silicate glass) obtained by heating and melting silica sand and sodium carbonate or sodium hydroxide.
The molar ratio n of iO ₂ / Na ₂ O is generally n = 2 to 3.3. A water glass solution prepared by dissolving amorphous sodium silicate cullet in water under high pressure is the most versatile material in the manufacturing industry in all fields, but amorphous sodium silicate cullet itself is an intermediate product. There is no report of amorphous sodium silicate cullet which has strong color and is useful as a detergent builder.

The present inventors have found that the pulverized product of amorphous sodium silicate cullet exhibits water softening property and can be suitably used as a detergent builder, and has already proposed it (Japanese Patent Application No. 6-242242).
-161867). However, such an amorphous sodium silicate cullet pulverized product has a high hygroscopic property, and it absorbs moisture during storage for a long time to change into a water candy-like product, and in that case, water softening property is lost. there were.

[0004]

Therefore, an object of the present invention is to provide a method for producing a powder mainly composed of amorphous sodium silicate which has a large water softening property and a small hygroscopicity and can be suitably used as a detergent builder. To provide.

[0005]

The present inventors have been involved in the production of sodium silicate cullet for a long time, and have conducted extensive research on the production and physical properties of sodium silicate cullet. As a result, they have found that the hygroscopicity can be reduced by absorbing carbon dioxide gas in the crushed product of amorphous sodium silicate cullet, and have proposed the present invention.

That is, according to the present invention, sodium silicate cullet having a SiO ₂ / Na ₂ O molar ratio n of 1.0 ≦ n ≦ 3.3 is crushed and then contacted with carbon dioxide gas, or simultaneously with crushing. A method for producing an amorphous sodium silicate / sodium carbonate complex, which comprises contacting carbon dioxide gas.

The raw material sodium silicate cullet is SiO
The molar ratio n of ₂ / Na ₂ O must be in the range of 1.0 ≦ n ≦ 3.3. When n becomes smaller than 1.0,
The amorphous sodium silicate / sodium carbonate complex obtained by the present invention dissolves the silica component faster, and Ca ions and Mg ions once bound to the silica component are eluted into water again, resulting in water softening property. It becomes scarce and is not preferable. On the other hand, when n is larger than 3.3, the elution amount of Na ions is reduced and the number of sites binding to Ca ions and Mg ions is reduced, resulting in poor water softening property, which is not preferable. In order to exhibit more favorable water softening property, it is preferable to satisfy 1.3 ≦ n ≦ 2.0.

The molar ratio n of SiO ₂ / Na ₂ O is 1.0 ≦ n
The sodium silicate cullet with ≦ 3.3 can be manufactured by the following method. For example, SiO ₂ and sodium carbonate or sodium hydroxide may be combined with SiO ₂ / N
This is a method of heating and melting so that the molar ratio n of a ₂ O is 1.0 ≦ n ≦ 3.3, and then cooling.

As SiO ₂ as a raw material, known substances containing SiO ₂ as a main component such as silica stone, silica sand, cristobalite, fused silica, amorphous silica and silica sol can be used without any limitation. Industrially, silica sand is preferably used because it is inexpensive and easy to handle. One of the raw materials, sodium carbonate or sodium hydroxide, may be used alone, or may be mixed and used at an arbitrary ratio.

These raw materials are heated and melted. Any conditions such as temperature and time can be adopted as long as the raw materials are melted and a sodium silicate melt is produced. A suitable temperature condition is 1000 to 1400 ° C. from the viewpoint of alkali resistance and economical efficiency of the furnace wall, and a shorter heating and melting time is economically preferable, and a sufficiently uniform sodium silicate melt is formed in 10 hours or less. To do.

The cooling method of the sodium silicate melt may be such that the sodium silicate cullet produced is amorphous. Generally, cooling to such an extent that the molten state is taken out to the room temperature environment is sufficient. As a cooling method, water cooling or the like can be adopted in addition to a method of simply cooling by air.

The amorphous sodium silicate cullet obtained by cooling is then ground. For the pulverization, a known pulverization method can be adopted. For example, ball mill, stirring mill, high-speed rotary fine crusher, jet crusher, shear mill,
A fine crusher such as a colloid mill can be used. Among these, a ball mill can be mentioned as the most common crusher. Specific examples thereof include rolling mills such as pot mills, tube mills and conical mills; vibrating ball mills such as circular vibration mills, rotary vibration mills and centrifugal mills; and planetary mills.

In order to improve the efficiency of crushing by the above-mentioned fine crusher, before the fine crushing operation, a medium crusher such as a jaw crusher, a gyratory crusher, a cone crusher, a hammer crusher, or a coarse crusher is used to adjust the crushing to about several mm. It is preferable to crush it into grains.

In the present invention, carbon dioxide gas is brought into contact with pulverization at the same time, or carbon dioxide gas is brought into contact after pulverization. As a result, a part of the amorphous sodium silicate reacts with carbon dioxide gas to generate sodium carbonate. Therefore,
The amorphous sodium silicate / sodium carbonate composite obtained by the present invention has amorphous sodium silicate inside the particles and a sodium carbonate layer on the surface of the particles.

In the present invention, the amorphous sodium silicate cullet crushed product easily reacts with carbon dioxide gas, so that even if no special method is adopted, the amorphous sodium silicate cullet crushed product and carbon dioxide gas are simply mixed. These can be reacted simply by contacting. The reaction temperature is not particularly limited as long as it is a temperature at which the amorphous sodium silicate cullet does not cause crystallization due to heat, and is generally -10 to 50.
It can be adopted from a wide range of 0 ° C. Further, the reaction pressure may be any of reduced pressure, normal pressure and increased pressure. Further, the contact time is not particularly limited, and generally, it may be selected from a wide range of 10 minutes to 100 hours.

The carbon dioxide gas source is also not particularly limited, and it is a combustion exhaust gas, a hydrogen carbonate salt such as sodium hydrogen carbonate or calcium carbonate, or a pyrolysis product gas of the carbonate salt, or a gas product of a reaction between the hydrogen carbonate salt or the carbonate salt and an acid. , A gas produced in an ammonia synthesis reaction, a gas produced in alcohol fermentation, a sublimation gas of dry ice, and the like.

Amorphous sodium silicate thus obtained
The sodium carbonate complex has the following formula 1.0 ≦ n ≦ 3.3 0.10 ≦ S ≦, where n is the molar ratio of SiO ₂ / Na ₂ O and S (m ² / g) is the specific surface area. It is preferable that 0.90 is satisfied in order to exhibit good water softening property. In order to exhibit more favorable water softening property, it is preferable that 1.3 ≦ n ≦ 2.0 0.20 ≦ S ≦ 0.80.

In the amorphous sodium silicate-sodium carbonate composite obtained by the present invention, the sodium silicate part is amorphous and the sodium carbonate part is crystalline.
The amorphous part of the sodium silicate does not mean that it is completely amorphous, but also includes the case where it has a very small amount of fine crystals. This will be described with reference to FIG. FIG. 1 is an X-ray diffraction pattern of an amorphous sodium silicate / sodium carbonate complex obtained in Example 1 described later. In FIG. 1, 2θ =
A broad peak is observed around 33 °. This broad peak is due to fine crystals slightly contained in the amorphous material. Also, during this broad peak, 2θ
The sharp peaks observed around 30 °, 34 °, and 35 ° are derived from crystalline sodium carbonate.

The amount of fine crystals slightly contained in the amorphous material is calculated from the broad peak area occupied in the halo pattern.
The particle size of the fine crystals can be obtained from the half width of the broad peak. In the case of this figure, the amount of fine crystals obtained from the area of the broad peaks occupied in the halo pattern is 12% by volume, and the particle size of the fine crystals calculated from the half-value width of the broad peaks by Scherrer's formula is 2.5 nm. is there.

The term "amorphous" in the present invention includes the case where such an amorphous material contains a very small amount of fine crystals. In order to be amorphous, it is generally preferable that the amount of fine crystals obtained from the area of the broad peak in the halo pattern is 20% by volume or less. Further, from the half width of the broad peak, The calculated crystallite particle size is 5
It is preferably nm or less.

The average particle size of the amorphous sodium silicate / sodium carbonate composite obtained by the present invention is preferably in the range of 1 to 100 μm as measured by a liquid phase spontaneous sedimentation method particle size distribution meter.

[0022]

INDUSTRIAL APPLICABILITY The amorphous sodium silicate / sodium carbonate composite obtained according to the present invention exhibits an excellent water softening ability, and since it has a low hygroscopicity, it is also excellent in storage stability.

[0023]

The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The measured values in Examples and Comparative Examples were measured by the following methods.

(1) Amount of fine crystals and particle size of fine crystals In the X-ray diffraction pattern of the amorphous sodium silicate / sodium carbonate complex, as shown in FIG. 1, a broad peak is recognized around 2θ = 33 °. In this case, the amount of fine crystals can be obtained from the area of the broad peak, and the fine crystal particle size can be obtained from the half width. This broad peak is bent from the halo pattern around 2θ = 28 ° and around 2θ = 36 °. In addition, a peak derived from crystalline sodium carbonate overlaps with this broad peak.

Therefore, first, the peak derived from sodium carbonate is removed from the broad peak, and further 2θ = 28.
A straight line was connected between both inflection points around 2 ° and around 2θ = 36 °, and the integrated intensity of the broad peak was calculated using this line as a background (this value is referred to as NI _B ). At the same time, the full width at half maximum D (unit: radian) and the peak position 2θ _P (unit: °) were measured. On the other hand, the integrated intensities of all patterns are 2θ = 10 ° and 2θ = 10 °.
0 ° point to a knot in a straight line when the were calculated the linear as a background (this value and NI _T). The amount of fine crystals was calculated using the above values, and the particle size of fine crystals was determined from Scherrer's equation.

Amount (% by volume) of microcrystals = (NI _B / NI _T ) × 100 Particle size of microcrystals = (K × λ) / (D × cos θ _P ), where K = 0.94 and λ is X 0.15405 at linear wavelength
It was 6 nm.

(2) Molar ratio n The amorphous sodium silicate / sodium carbonate complex is completely dissolved in water, the amount of sodium oxide and the amount of silica in the aqueous solution are individually measured, and the molar ratio n is calculated from the ratio. I calculated.

Amount of sodium oxide: Methyl orange solution was used as an indicator and neutralized and titrated with hydrochloric acid.

Amount of silica: Sodium fluoride was reacted with the sample as shown by the following formula, and the liberated sodium hydroxide was neutralized and titrated with hydrochloric acid. The amount of silica was obtained by subtracting the amount of sodium oxide obtained by the above method from the required amount of hydrochloric acid.

H ₂ SiO ₃ + 6NaF + H ₂ O → Na ₂ Si
F ₆ + 4NaOH (4 mol of sodium hydroxide is deposited per 1 mol of silica.) (3) Specific surface area It was measured using a permeation method (constant pressure air permeation method). Specifically, the specific surface area Sw was obtained by measuring the mass W and the time t from the following Kozeny-Carman equation.

Sw = (140 / ρ) × ((ΔP × A × t) / (η
XLxQ) x [epsilon] ³ / (1- [epsilon]) ² ) ^1/2 , where [epsilon] is the porosity of the sample packed layer, [epsilon] = 1-W / ([rho] xAx
L) ρ: Density of powder (g / cm ³ ) η: Viscosity coefficient of air (mPa sec) L: Thickness of sample layer (cm) Q: Amount of air permeated in sample layer (cm ³ ) ΔP: Sample layer Pressure difference between both ends (g / cm ² ) A: Cross-sectional area of sample layer (cm ² ) t: Time required for air of Qcm ³ to pass through the sample layer (sec) W: Weight of sample (g) . Here, L = 1.2 cm, Q = 20 cm ³ , ΔP =
10 g / cm ² , A = 2 cm ² , ρ is the true specific gravity of the cullet before crushing, and η is 1a from the Chemical Handbook (Revised 3rd Edition Basic Edition II).
0.0182 mPa sec which is the value of tm and 25 ° C was adopted.

(4) Carbon dioxide gas absorption amount Carbon dioxide gas absorption amount is the carbon amount C of the sample before and after the carbon dioxide gas is brought into contact with the organic analyzer.
₀ (% by weight) and C (% by weight) were measured and determined from the following formula.

Carbon dioxide absorption (% by weight) = (44/1
2) x (C- _C0 ) (5) Water softening property (Ca sequestering ability) The water softening property of the amorphous sodium silicate / sodium carbonate composite was represented by the Ca sequestering ability. 1 L of 5 mmol / L calcium chloride aqueous solution adjusted to pH = 10 with ethanolamine and hydrochloric acid is stirred at 350 rpm at 20 ° C.
It was a constant temperature. Next, about 0.2 g of the amorphous sodium silicate / sodium carbonate complex as a sample is precisely weighed (unit: g)
And added to the above solution. After stirring at 350 rpm for 15 minutes, 10 ml was sampled and filtered through a 0.2 μm filter. The Ca concentration in the obtained filtrate was measured by an inductively coupled plasma emission spectrophotometer (ICP-AES), and the Ca ion amount C (unit: mg) was calculated from this value. The Ca blocking ability was evaluated by the value calculated by the following formula.

Ca blocking ability = (20-C) /0.2
(Unit: mg / g of sample) (6) Hygroscopicity 20 g of a sample is put in a resin cup and the temperature is 20 ° C. and the humidity is 5
The weight increase after standing for 5 days in a 0% thermostatic chamber was measured, and the moisture absorption amount (% by weight) was determined from the ratio with the initial weight.

Example 1 177 g of silica sand (SiO ₂ 99.8%) and 223 g of sodium carbonate (Na ₂ CO ₃ 99%) were mixed, and 100 g of water was added.
And further mixed. Put the mixture in a platinum crucible,
The temperature was raised from room temperature to 1300 ° C in 1.5 hours in an electric furnace, and then the temperature was maintained at 1300 ° C for 5 hours. After heating and melting, the crucible containing the contents in a burning state was taken out of the electric furnace, and the crucible was immersed in a water bath and rapidly cooled to obtain colorless and transparent sodium silicate cullet. The obtained sodium silicate cullet was crushed with a jaw crusher (gap 5 mm). Then, ball mill (pot; inner diameter 135 mm, capacity 2 L, balls; diameter 30 mm x 33, made of Al ₂ O ₃ )
Then, it was pulverized at a rotation speed of 60 rpm for 1 hour. afterwards,
Diethylene glycol was added to 0.5% by weight of sodium silicate powder, and the mixture was further pulverized for 91 hours under the same conditions.

About 20 g of this powder was put in a resin cup,
It was left for 48 hours in a plastic bag (capacity: about 35 L) filled with carbon dioxide gas obtained by vaporizing dry ice, and brought into contact with carbon dioxide gas.

When the crystallinity of the obtained amorphous sodium silicate / sodium carbonate composite was evaluated by X-ray diffraction, it showed a halo pattern as shown in FIG. 2θ = 33
A broad peak was observed in the vicinity of °, the amount of fine crystals obtained from the area of the broad peak in the halo pattern was 12% by volume, and the particle size of the fine crystals calculated from the half-width of the broad peak was 2.5 nm. Met. The physical properties of the amorphous sodium silicate / sodium carbonate complex are summarized in Table 1.

Comparative Example 1 An amorphous sodium silicate powder was obtained in the same manner as in Example 1 except that carbon dioxide gas was not contacted. The physical properties of this powder are also shown in Table 1.

Example 2 About 2 sodium silicate powder obtained in the same manner as in Example 1
0 g was left at 300 ° C. for 4 hours in an electric furnace in which carbon dioxide gas was made to flow, and carbon dioxide gas was brought into contact therewith. The obtained amorphous sodium silicate / sodium carbonate complex had the same amount of microcrystals and the same crystal grain size as in Example 1, and other physical properties are also shown in Table 1.

Example 3 About 2 sodium silicate powder obtained in the same manner as in Example 1
0 g was left at 80 ° C. for 60 hours in an oven in which the atmosphere was completely replaced with carbon dioxide, and carbon dioxide was brought into contact therewith. The obtained amorphous sodium silicate / sodium carbonate complex had the same amount of microcrystals and the same crystal grain size as in Example 1, and other physical properties are also shown in Table 1.

[0041]

[Table 1]

[Brief description of drawings]

FIG. 1 shows an X-ray diffraction pattern of the amorphous sodium silicate / sodium carbonate composite obtained in Example 1 of the present invention.

Claims (1)

[Claims] 1. A SiO ₂ / Na ₂ O molar ratio n is 1.0 ≦ n.
A method for producing an amorphous sodium silicate / sodium carbonate composite, which comprises contacting carbon dioxide gas after crushing sodium silicate cullet with ≦ 3.3 or contacting carbon dioxide gas simultaneously with crushing.