JPH04198013A - Crystalline layer sodium borosilicate, production and use thereof - Google Patents

Abstract

PURPOSE:To obtain the title compound having excellent solubility, transparency and ion exchange properties by dehydrating a uniform aqueous composition containing amorphous sodium silicate, an alkali borate, etc., to dryness and heating the composition at >= a given temperature in a solid phase. CONSTITUTION:When amorphous sodium silicate (e.g. sodium silicate No.3) is deficient in sodium content, the amorphous sodium silicate is supplied with an alkali hydroxide (carbonate) and blended with an alkali borate. Then the amorphous sodium silicate is dissolved or dispersed into an aqueous medium to give a homogenized aqueous composition having 30-80wt.% water content. The composition is dehydrated to dryness at 60-200 deg.C under normal pressure to under reduced pressure of 150mmHg. Then the composition is heat-treated at 550-850 deg.C and converted to delta type crystal to give the title compound having a chemical composition shown by the formula (x is 0.02-0.2; n is >=1; m is <=1; n+m is 2) and X-ray diffraction diagram corresponding to delta type sodium disilicate, useful as an ion exchanger.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a crystalline layered sodium borosilicate useful as an ion exchanger, etc., and a method for producing the same.

(Conventional technology) Crystalline layered sodium silicate, especially formula Na.

Sodium disilicate Si, 05 is a compound that has been known for a long time, and its crystals are known in various forms such as α type, β type, γ type, and δ type.

Recently, Japanese Patent Publication No. 1-41116 describes the composition NaMS ix 02x++'3'H20- (1) where M means sodium or hydrogen, and X is 1.9 to
4, and y is a number from O to 20.

A water softening side is described that contains a crystalline layered sodium silicate having the following properties:

In addition, Japanese Patent Application Laid-open No. 60-239320 states that 1.7
: 0.01 to 30 parts by weight of crystalline sodium disilicate to be prepared in hydrous amorphous sodium silicate having a SiO2/Na2O molar ratio of 1 to 3.75:1 and a water content of 5 to 95% by weight. and dehydrating the reaction mixture by heating, and maintaining such dehydrated reaction mixture at a temperature of at least 450° C., but below the melting point, until the sodium silicate crystallizes. A method for producing sodium is described.

(Problems to be Solved by the Invention) Among the above-mentioned crystalline layered sodium disilicates, those with a δ (delta) type crystal structure have a large ion exchange capacity (for example, calcium exchange capacity), and when used, for example, as a detergent builder. Although these products are excellent in their ability to assist or enhance the cleaning action, the known products have not yet been fully satisfactory in their performance.

First, it is relatively difficult to synthesize δ-type crystalline layered sodium disilicate in pure form, and the
According to Publication No. 320, when hydrous amorphous sodium silicate is dehydrated and the reaction product is heated to a high temperature, α-type sodium disilicate (Na-3KS-5) and δ-type sodium disilicate (Na-3KS -6) is formed (see Examples 1 and 2 of all publications), but prior to this reaction, δ
It is recognized that by adding seed crystals of type sodium disilicate to the reaction system, δ type sodium disilicate can be selectively synthesized.

However, when the known δ-type sodium silicate is dissolved in water, it is not completely transparent and remains as cloudy colloidal particles (400 nm visible light as shown in the comparative example below). (see transmittance in )
. This is because in the known δ-type sodium disilicate, something other than water-soluble sodium disilicate is produced as a by-product.
This also indicates that even with sodium disilicate, a highly polymerized component is produced.

The present inventors discovered that when synthesizing crystalline layered sodium borosilicate from amorphous sodium silicate, when a predetermined amount of sodium borate is coexisting, the δ-type crystal structure becomes an impurity without the addition of seed crystals. This product also incorporates boric acid in addition to silicic acid, which has excellent solubility in water and is extremely transparent when dissolved in water. It has been found that this solution provides an excellent solution (see the transmittance in visible light at 400 nm shown in Examples below) and also has excellent ion exchange properties.

Therefore, an object of the present invention is to provide a δ-type crystalline sodium borosilicate which has excellent solubility in water, transparency when made into an aqueous solution, and ion exchange properties, and a method for producing the same.

Another object of the present invention is to provide a method for producing the δ-type crystalline sodium borosilicate using amorphous sodium silicate as a raw material without using seed crystals.

(Means for Solving the Problems) According to the present invention, substantially the following formula % formula % (2) where X is a number from 0.02 to 0.2, n is a number of 1 or more, It is assumed that m is a number less than or equal to 1, and n+m is 2.

A crystalline layered sodium borosilicate is provided which is characterized by having a chemical composition represented by the following and an X-ray diffraction pattern substantially corresponding to δ-type sodium disilicate.

According to the invention, a homogenized aqueous composition containing substantially stoichiometric amounts of amorphous sodium silicate and sodium borate or even an additional amount of sodium hydroxide is dehydrated to dryness; Provided is a method for producing crystalline layered sodium borosilicate, which is characterized by heating a product at a temperature of 550 t: or higher and in a solid phase.

The present invention further provides an ion exchanger comprising the above sodium borosilicate.

(Function) Sodium disilicate is said to have a chemical structure consisting of basic units represented by the following formula. On the other hand, the crystalline sodium borosilicate of the present invention has a chemical structure represented by the above formula (2), but the chemical structure is such that some of the four-coordinated St atoms in formula (3) are four-coordinated. It is thought that the B atom was substituted. That is, the crystalline sodium borosilicate of the present invention has the above formula (3
) is believed to consist of a disilicate basic unit of the formula and a borosilicate basic unit of the formula.

The number p of moles of disilicate units in formula (3) and formula (4)
The ratio of borosilicate units to the mole number q is in the range of 98:2 to 80:20, especially 97:3 to 90:10, and when the content of borosilicate units is less than the above range, this Improvements in solubility and the like as intended in the invention cannot be achieved, and on the other hand, if the amount exceeds the above range, it is difficult to obtain a δ-type crystal structure.

The cations present in the disilicate unit and the borosilicate unit are preferably Na ions, but as is clear from the general formula (2), less than half of the total cations,
In particular, Na ions may be substituted with hydrogen ions in a range of 30% or less.

FIG. 1 of the accompanying drawings shows an X-ray diffraction image of the crystalline layered sodium borosilicate of the present invention. Further, Table A below shows the relationship between the interplanar spacing and relative strength.

Table A = X-ray diffraction image 8.06 14 4.92 13 4.21 13 3.97 100 3.79 40 3.64 15 3.45 10 3.03 232.91
1 12.85 17 2.57 12 2.43 38 Above X! s diffraction image and X-ray diffraction image of δ-type sodium silicate (ASTM
It can be seen that the crystalline layered sodium borosilicate of the present invention has an X-ray diffraction pattern almost corresponding to δ-type sodium disilicate.

Although the δ-type sodium borosilicate of the present invention has a relatively low content of borosilicate units, it
The fact that it has superior solubility, transparency as a solution, and various properties as an ion exchanger compared to sodium disilicate was discovered as a phenomenon as a result of numerous experiments. The reason for this has not yet been confirmed, but it is believed to be as follows. That is, in the δ-type sodium borosilicate of the present invention, as is clear from the above formula (4), a four-coordinated boron atom exists in the unit, and this 5t
The -0-B bond distorts the crystal structure and also provides break points in the silicate polymer chain, which gives the sodium borosilicate of the present invention excellent solubility and when dissolved in water. It is recognized that the generation of colloidal particles is prevented. In addition, it is thought that these properties are related to the excellent ion exchange properties.

The crystalline sodium borosilicate of the present invention is obtained by dehydrating to dryness a homogenized composition containing substantially stoichiometric amounts of amorphous sodium silicate and sodium borate or even an additional amount of alkali hydroxide or alkali carbonate. and this dry matter was
It can be obtained by heating at a temperature of 50°C or higher in a solid phase, but the δ-type crystal structure is stable and the seeds are stable despite the presence of boric acid in the reaction system, which causes distortion in the crystal structure. It was a completely unexpected finding that it was produced efficiently even in the absence of crystals.

(Preferred embodiment of the invention) As the amorphous sodium silicate as the silicic acid raw material and the sodium raw material, water-soluble sodium silicate, especially the formula % formula % (5) where r is 1,8 to 4.0, especially between 2.0 and 3.3.

No. 3 sodium silicate (JIS) is preferred from the viewpoint of ease of reaction and handling. Although it is not particularly necessary in the case of No. 1 sodium silicate (JIS), when the sodium content is insufficient as in No. 3 sodium silicate, an additional amount of alkali hydroxide or alkali carbonate is used. As the boric acid component, sodium borate is used, and both anhydrous and hydrated salts can be used for the purpose of the present invention.

These raw materials are uniformly dissolved or dispersed in an aqueous medium to form a homogenized aqueous composition.

The water content in this aqueous composition is generally desirably in the range of 30 to 80% by weight, particularly 50 to 70% by weight.

The homogenized aqueous composition is then dehydrated to dryness. Dehydration to dryness is generally carried out at a temperature of 60 to 200°C and from normal pressure to 15°C.
It can be carried out under reduced pressure of 0 mmHg. This dehydration to dryness may be carried out in one step, or may be carried out in two steps of concentration and drying. The drying method is not limited to this, but can be carried out by any known means such as spray drying, fluidized drying, flaking drying, etc.

In order to convert the dried sodium borosilicate into δ-type crystals, the dried product is heated to a crystallization temperature of 550° C.
Heat treatment may be performed at a temperature higher than that.

At this time, it is important to crystallize the treated product while maintaining it in a solid phase; if the treated product melts, the ion exchange ability of the product tends to decrease. From this point of view, heat treatment at a temperature of 850° C. or lower is preferable.

The sodium borosilicate obtained by the heat treatment is, if desired, ground and classified to produce a product.

Stacked stone top” 20 euros! 2nd attached drawing of Hajime Kohi Hekiri
The figure is an electron micrograph (5000x magnification) showing the particle structure of the crystalline layered sodium borosilicate of the present invention.

It can be seen from FIG. 2 that this material has a layered primary particle structure.

The crystalline layered sodium borosilicate of the present invention generally has a content of 155 to 185 rng/g, as measured by the method described below.
In particular, it has a CaO binding capacity of 165 to 180 mg/g. As shown in the example below, the CaO crystallinity of the crystalline layered sodium silicate produced in the same manner as in the present invention except without using boric acid is on the order of 150 mg/g. Therefore, the sodium borosilicate according to the present invention has an ion It can be seen that the exchangeability is excellent.

In addition, the crystalline layered sodium borosilicate of the present invention has excellent solubility and almost no residual colloidal particles are observed, so it has a light transmittance of 80% when measured by the turbidity method described below. % or more, which is significantly superior to the conventional method which is about 40%.

(Example) Examples 1 to 9 Commercially available liquid No. 3 sodium silicate (molar ratio 5i02/N
a20 = 3.17, moisture = 70%), add a predetermined amount of sodium hydroxide and anhydrous sodium borate (Naz B40?) dissolved in water so as to have the composition ratio shown in Table 1, After homogenization, water is evaporated to dryness at 200°C. The resulting foamed solidified product is crushed in a mortar to form a powder. This was placed in a magnetic crucible and heated at 700°C for 90 minutes. All of the obtained sodium borosilicate products have X-ray diffraction patterns corresponding to δ-type sodium disilicate, and both Ca binding ability and solubility in water are those that do not contain boron (comparative example) It was better.

Examples 10 to 13 Commercially available powder No. 3 sodium silicate was used as the sodium silicate raw material (molar ratio S i 02 / N C20 = 3.2, moisture = 2
Sodium borosilicate was obtained in the same manner as in the previous example except that 2%) was used. Both are δ type, and both Ca binding ability and solubility are those that do not contain boron (comparative example)
It was better.

Comparative Examples 1-4 Comparative Examples 1-5 and 10-13 were carried out in the same manner as in Examples 1-5 and 10-13, except that the amount of sodium borate added was increased (X value of 0.2 or more). All of the obtained products were of the β type.

Comparative Example 5 Commercially available No. 1 sodium silicate (molar ratio 5in2/Na20=
2.17, water molecules 47%) was dehydrated to dryness at 200°C and then heated at 700°C for 90 minutes. The product was δ-type sodium disilicate, but its Ca binding ability and solubility were poor.

Comparative Example 6 An aqueous sodium hydroxide solution was added to the commercially available liquid No. 3 sodium silicate used in Examples 1 to 9 to give a predetermined composition.
After dehydration to dryness at 200°C, the mixture was heated at 700°C for 90 minutes. The product was β-type sodium disilicate, and its Ca binding ability and solubility were poor.

Comparative Example 7 The Ca binding strength and solubility of commercially available δ-type sodium disilicate (Na-5O5-6) were measured. It was no better than any of the borosilicate sodium salts of the invention examples.

"Solubility test" 0.5 g of sample and 50 g of water are placed in a 100 ml Erlenmeyer flask and heated. After it starts to boil, heat it for 30 seconds, then let it cool naturally until it reaches room temperature. After replenishing the amount of evaporated water, the liquid is placed in a glass cell with a length of 10 mm, and the transmittance at wavelength λ=400 nm is measured using a spectrophotometer.

"rCa binding ability measurement" A sample amount of 041 g was accurately weighed and poured into a 200 ml Erlenmeyer flask. Next, hard water (CaC12 aqueous solution, concentration 300m
Add 100ml of gCaO/1) and stir with a magnetic stirrer for 7 minutes. Immediately after stirring, filter with No. 6 filter paper, and collect exactly 10 ml of the liquid. After adding deionized water to make about 100ml, NHs was added with a pipette.
- Add 2-3 ml of NH4C1 buffer (pH = 10),
Titration was performed with an N/100 EDTA standard solution using Black T as an indicator, and the CaO binding capacity was determined from the following formula.

CaO binding capacity (CaOmg/g) = 56X (c 1
-C'2) (Effects of the Invention) According to the present invention, by allowing sodium borate to coexist in the reaction system, selectively, without using a seed crystal or the like,
Crystalline sodium borosilicate, which has a crystal structure corresponding to δ-type sodium disilicate, has been synthesized and has excellent solubility, transparency when made into an aqueous solution, and ion exchange properties, and is useful for detergent builders and other ions. Useful as an exchanger.

[Brief explanation of the drawing]

FIG. 1 shows an X-ray diffraction image of crystalline layered sodium borosilicate of the present invention. FIG. 2 is an electron micrograph showing the particle structure of the crystalline layered sodium borosilicate of the present invention. Patent applicant Mizusawa Chemical Industry Co., Ltd. 2θ Figure 1 Figure 2

Claims (3)

[Claims] (1) Substantially the following formula Na_nH_mSi_2_−_xB_xO_5・Na_
x In the formula, x is a number from 0.02 to 0.2, n is a number of 1 or more, m is a number of 1 or less, and n+m is 2. A crystalline layered sodium borosilicate characterized by having a chemical composition represented by the following and an X-ray diffraction pattern substantially corresponding to δ-type sodium disilicate. (2) dehydrating a homogenized aqueous composition containing substantially stoichiometric amounts of amorphous sodium silicate and an alkali borate or an additional amount of an alkali hydroxide or alkali carbonate; A method for producing crystalline layered sodium borosilicate, which comprises heating a solid substance at a temperature of 550°C or higher in a solid phase. (3) Substantially the following formula Na_nH_mSi_2_−_xB_xO_5・Na_
x In the formula, x is a number from 0.02 to 0.2, n is a number of 1 or more, m is a number of 1 or less, and n+m is 2. An ion exchanger comprising crystalline layered sodium borosilicate having a chemical composition represented by the formula and an X-ray diffraction pattern corresponding to δ-type sodium disilicate.