JP2000143228A - High oil absorption silica gel and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the deterioration of characteristics caused by re-drying after dipping in water by emulsifying an alkali silicate aq. solution containing the specific quantity of >=1 kinds of anions in an organic solvent and gelating by carbon dioxide to give high specific surface area. SOLUTION: Equal to or above one kind of alkali metal salts or an alkaline earth metal salts are added into the alkali silicate aq. solution of sodium silicate or the like containing 3-20 wt.% silicic acid expressed in terms of SiO2 to incorporate >=1 kinds of chloride ion, sulfuric ion, nitric ion, fluoride ion, the content of which is controlled to 0.1-0.5 equivalent per 1 mol SiO2. The produced high oil absorption silica gel has 1-100 nm fine pore diameter 1.2-3.5 ml fine pore volume, 50-1000 m2/g specific surface area and >=300 ml/100 g oil absorption and when 1 wt.% high oil absorption silica gel is further dispersed in water having <=1 μS/cm electric conductivity, separated and dried at 120 deg.C for 5 hr, the fine pore volume and the oil absorption are kept at 90% of that obtained before the dispersion in water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a silica gel and a method for producing the same. In particular, it relates to a high oil absorption silica gel and a method for producing the same.

[0002]

2. Description of the Related Art The property that powder absorbs and retains an oily liquid is represented by the amount of oil absorbed. For example, silica with a high oil absorption is used for carriers such as medical and agricultural chemicals, cosmetics and toiletry materials, anti-through materials for newspapers, coating materials or fillers for recording media for inkjet printers, battery separators,
It is used for paint additives, catalyst carriers, etc.

Conventionally, so-called precipitated silica has been known as a typical high oil absorption silica. The precipitated silica is
For example, an aqueous solution of alkali silicate is neutralized by adding sulfuric acid.
It is manufactured by separating and washing the generated particles. Precipitated silica is characterized by having a specific surface area of 300 m ² / g or less. Because of the alkaline and relatively high temperature conditions, it is not possible to obtain precipitated silica having a specific surface area of 500 m ² / g or more. The primary particle size of the precipitated silica is usually 15 nm or more.

[0004] Japanese Patent Application Laid-Open No. 6-40714 discloses a method of obtaining silica having a high oil absorption of 350 ml / 100 g or more by supercritically drying the precipitated silica to prevent the silica from shrinking during drying. Is disclosed. But,
This is also essentially precipitated silica and has a specific surface area of approximately 40
0 m ² / g.

[0005] International Patent Publication No. WO 97/45366 discloses the use of precipitated silica for battery separators. The specific surface area of the precipitated silica is 60 to
200 m ² / g, oil absorption 180-300 ml / 100
g. On the other hand, ordinary silica gel used as a desiccant or the like has a specific surface area of 350 to 700 m ² / g, which is higher than that of precipitated silica, but has an oil absorption of about 100 to 170 ml / g.

[0006]

In the field where high oil-absorbing precipitated silicas have been used in the past, to improve the function,
Alternatively, in order to obtain a new function, silica having a higher oil absorption and a higher specific surface area is desired. The purpose of the present invention is
An object of the present invention is to provide a silica gel having a high oil absorption and a high specific surface area.

[0007]

According to the present invention, a pore volume in a range of pore radius of 1 to 100 nm by a nitrogen adsorption method is 1.5 or less.
Ｍｌ3.5 ml / g, specific surface area of 500-1000 m ² / g
g, silica gel having an oil absorption of 300 ml / 100 g or more, and 1% by weight of the silica gel dispersed in water having an electric conductivity of 1 μS / cm or less, separated, and further dried at 120 ° C. using a stationary dryer. The silica gel obtained by drying for 5 hours has a high oil absorption silica gel in which the pore volume and the oil absorption in the range of the pore radius of 1 to 100 nm by the nitrogen adsorption method are respectively 90% or more of the values before being dispersed in water. provide.

The silica gel of the present invention has a pore volume of 1.5 to 100 nm in a pore radius of 1 to 100 nm by a nitrogen adsorption method.
3.5 ml / g. Hereinafter, the term “pore volume” simply means a pore volume having a pore radius of 1 to 100 nm as determined by the nitrogen adsorption method. Pore volume is 1.8 ~
The case of 3.5 ml / g is more preferred. The pore volume is determined by analyzing the result of measurement at a nitrogen relative pressure of 0 to 0.99 by the nitrogen adsorption method using the BJH method. For the measurement, for example, Kantachrome Autosorb manufactured by Kantachrome Co., Ltd. can be used.

The silica gel of the present invention has a specific surface area of 500
１０００1000 m ² / g. A larger specific surface area is preferable because the number of adsorption sites on the surface increases. Specific surface area is 600
It is more preferred that it is 1000 m ² / g. Conventional precipitated silica has a specific surface area of about 4 as described above.
Although it is not more than 00 m ² / g, the silica gel of the present invention has a higher specific surface area. The primary particle diameter of this silica gel is 4 to 7 nm, assuming that the true specific gravity of the silica is spherical non-porous particles of 2.2 g / cm ³ , and is distinguishable from precipitated silica having a primary particle diameter of 15 nm or more. it can.
Similarly to the case of the pore volume, the specific surface area is determined by analyzing the result measured by the nitrogen adsorption method at a nitrogen relative pressure of 0 to 0.99 by the BET method.

The silica gel of the present invention has an oil absorption of 300 m
1/100 g or more. Oil absorption 350ml / 100
It is more preferable that the value is g or more. Oil absorption is JIS
It is measured according to K5101. That is, boiled linseed oil is added to the sample while kneading until the whole sample becomes one lump. The oil absorption is represented by the volume of boiled linseed oil per 100 g of the sample. Hereinafter, the oil absorption amount by this measurement method,
It is simply called oil absorption.

The silica gel of the present invention has an electric conductivity of 1 μm.
The silica gel obtained by dispersing 10% by weight of this silica gel in water of S / cm or less was separated, and dried at 120 ° C. for 5 hours using a stationary drier. The pore volume and the oil absorption in the range of 100 nm are respectively 90% or more of the values before being dispersed in water.

Conventionally, silica having a high oil absorption has been obtained by supercritical drying. However, when this silica is placed in a solvent such as water and dried again, its pore volume and oil absorption become extremely small. The silica gel of the present invention has a high oil absorption. Even if the silica gel is dried again in a solvent such as water, its pore volume and oil absorption hardly change. Therefore, when used as a filler or a coating material such as paper, there is no decrease in pore volume or apparent volume shrinkage during drying, and the oil absorption can be maintained large, which is suitable for these uses.

The average particle size of the silica gel of the present invention can be arbitrarily selected depending on the method of use, but is preferably from 1 to 100 μm. It is more preferable that the average particle diameter is 1 to 70 μm. Furthermore, when the particle shape of the silica gel is spherical, it improves the dispersibility when blended into resins and paints, improves the feel when blended into cosmetics, and improves the fluidity when used as a carrier for pharmaceuticals and agricultural chemicals. It is preferable in such points. Here, the spherical shape includes not only a true spherical shape but also a slightly distorted shape. In this case, the ratio of the minor axis to the major axis is preferably 0.8 to 1.0.

[0014] High oil absorption silica gel This spherical, when converted to silicic acid component in the aqueous alkali silicate solution into SiO _2, relative to the SiO ₂ 1 mole, chloride ion, sulfate ion, nitrate ion and fluoride Manufactured by emulsifying an alkali silicate aqueous solution containing a total of 0.1 to 0.5 equivalents of one or more anions selected from the group consisting of ions in an organic solvent and gelling with carbon dioxide gas. Is preferred.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The silica gel of the present invention can be obtained by emulsifying an alkali silicate aqueous solution containing an alkali metal salt or an alkaline earth metal salt in an organic solvent and gelling with carbon dioxide gas. As the alkali silicate, sodium silicate, potassium silicate and the like can be used. Sodium silicate is preferred in that it is economical. Hereinafter, a description will be given of sodium silicate as an example, but the same applies to the case of using potassium silicate.

The content of the silicic acid component in the aqueous sodium silicate solution is preferably 3 to 20% by weight in terms of SiO ₂ . Hereinafter, the amount of the silicic acid component is shown in terms of SiO ₂ . A more preferable range of the concentration of SiO ₂ in the aqueous solution of sodium silicate is 5 to 15% by weight. The SiO ₂ / Na ₂ O ratio of the aqueous sodium silicate solution is preferably 1 to 4. A more preferred range of the SiO ₂ / Na ₂ O ratio is 2.5 to 3.5.

In the aqueous sodium silicate solution, at least one anion selected from the group consisting of chloride ion, sulfate ion, nitrate ion and fluoride ion is added to one mole of SiO ₂ in the aqueous sodium silicate solution. 0.1 ~
It is preferable to include it at a ratio of 0.5 equivalent. A more preferred range is from 0.2 to 0.4 equivalents.

In order to include the above anion in the aqueous sodium silicate solution, a water-soluble metal chloride, metal sulfate,
It is preferred to carry out by adding a metal nitrate or a metal fluoride. Specifically, alkali metal chlorides, alkali metal sulfates, alkali metal nitrates, alkali metal fluorides, alkaline earth metal chlorides, and alkaline earth metal nitrates are preferred. In particular, sodium chloride, potassium chloride,
Alkali metal chlorides such as sodium sulfate and alkali metal sulfates are preferred.

As the organic solvent for emulsifying the aqueous solution of sodium silicate, a substance capable of dissolving carbon dioxide gas is preferable.
Such organic solvents include, for example, aliphatic hydrocarbons such as hexane and octane, aromatic hydrocarbons such as xylene and toluene, chlorinated hydrocarbons such as chloroform, trichloroethylene and tetrachloroethylene, trichlorotrifluoroethane, and dichlorotrifluoroethane. And chlorinated fluorinated hydrocarbons such as dichlorofluoroethane and dichloropentafluoropropane.

It is preferable that a surfactant is dissolved and used in the organic solvent. As the surfactant, polyethylene glycol fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, sorbitan fatty acid ester, and polyoxyethylene sorbitan fatty acid ester are preferable. Its usage is
0.05 to 10% by weight based on the organic solvent is preferred.

When an aqueous solution of sodium silicate is added to an organic solvent and emulsified, the aqueous solution of sodium silicate is added to the organic solvent in a volume ratio of 0.1 to 1 so as to form a W / O type emulsion. It is preferable to add them. The emulsification is preferably performed by means such as a turbine type stirrer or a high-speed shearing type emulsifier. In the emulsion, the droplets of the aqueous solution of sodium silicate preferably have an average particle diameter of 1 to 100 μm.

Next, an aqueous alkali silicate solution is gelled by introducing carbon dioxide gas into the emulsion. Since the gel is formed in an emulsified state, spherical silica gel is obtained. The partial pressure and flow rate of the carbon dioxide gas can be appropriately selected. After completion of the gelation, the organic solvent is removed, heat treatment or chemical treatment is performed as appropriate, washing and drying. At the end of gelation, silica gel with high oil absorption and high specific surface area has already been generated, so heat treatment and hydrothermal treatment under alkaline conditions conventionally performed to obtain silica with high oil absorption are not performed here. .

As the drying method, known methods can be used, but in order to prevent shrinkage of pores during drying, flash drying, spray drying, freeze drying, supercritical drying and the like can be preferably used. In addition, before drying, the water can be replaced with an organic solvent having a low surface tension, which is compatible with water, and then dried. By doing so, the contraction of the pores during drying can be prevented. The high oil absorption silica gel thus obtained may be further calcined. The firing temperature and firing time can be appropriately selected so that the specific surface area does not become 500 m ² / g or less.

The high oil absorption silica gel of the present invention can be surface-treated with an inorganic salt or a hydrolyzate thereof. For example, put in aluminum chloride aqueous solution, filtration,
The aluminum chloride treatment can be performed by drying. When this is hydrolyzed, a high oil absorption silica gel treated with aluminum hydroxide can be obtained. In addition, calcium salts, magnesium salts, and the like can be similarly treated. The surface can be treated with a silane coupling agent, silicone oil, a fluorine-based surface treatment agent, a titanate-based coupling agent, an alcohol, a surfactant, another surface treatment agent, or a surface modifier.

The spherical silica gel of the present invention may be used after being ground. As a pulverizing method, a known method such as a jet pulverizer can be adopted. Even when pulverized, it can be used as silica gel maintaining a high oil absorption and a high specific surface area.

[0026]

EXAMPLE 1 To 240 ml of an aqueous solution of sodium silicate having a SiO ₂ concentration of 10.0% by weight and a SiO ₂ / Na ₂ O molar ratio of 2.7, sodium chloride was added in an amount of 0.1 to 0.1 mol of SiO ₂ per mole of SiO ₂ . It dissolved so that it might become 36 equivalents. This aqueous solution was added to a solution in which 3.36 g of sorbitan monooleate was dissolved in 960 ml of trichlorotrifluoroethane, and emulsified with a homomixer.

A carbon dioxide gas (CO ₂ concentration: 30% by volume) diluted with air was blown into the emulsion to gel at 15 ° C. After blowing carbon dioxide gas for 15 minutes, trichlorotrifluoroethane was separated to obtain a slurry composed of spherical silica and water. The pH of this slurry was 9.0. Sulfuric acid is added to the slurry to adjust the pH to 2.5,
Heat treatment was performed at 60 ° C. for 1 hour.

This slurry was filtered, and the cake was washed with ion-exchanged water 100 times the solid content, and dried with a spray drier to obtain spherical silica gel. The pore volume is 2.
8 ml / g, specific surface area 758 m ² / g, oil absorption 55
0 ml / 100 g, and the average particle size was 4.8 μm.
The ratio of the minor axis to the major axis of the spherical silica gel is 0.9.
That was all.

1 g of this spherical silica gel was dispersed in 99 g of ion-exchanged water having an electric conductivity of 0.5 μS / cm, and dried at 120 ° C. for 5 hours using a stationary dryer to obtain silica gel. When the pore characteristics of the silica gel after this treatment were similarly evaluated, the pore volume was 2.8 ml /
g, specific surface area: 760 m ² / g, oil absorption: 553 ml / g
100 g.

Example 2 The sodium chloride of Example 1 was changed to sodium sulfate (the amount of sulfate ions was 0.30 equivalents per mole of SiO ₂ ) to obtain spherical silica gel. The pore volume is 2.3ml /
g, specific surface area is 810 m ² / g, oil absorption is 440 ml / g
100 g, and the average particle size was 5.2 μm. The ratio of the minor axis to the major axis of the spherical silica gel was 0.9 or more.

1 g of the spherical silica gel was dispersed in 99 g of ion-exchanged water having an electric conductivity of 0.5 μS / cm, and dried at 120 ° C. for 5 hours using a stationary drier to obtain silica gel. When the pore characteristics of the silica gel after this treatment were evaluated in the same manner, the pore volume, the specific surface area, and the oil absorption did not substantially change. That is, they were respectively 90% or more of the values before being dispersed in water.

Example 3 The amount of sodium chloride added in Example 1 was
The amount was changed to 0.32 equivalent to 1 mol of O ₂ ,
A spherical silica gel was obtained. The pore volume is 2.1 ml / g, the specific surface area is 797 m ² / g, and the oil absorption is 420 ml / 100.
g, the average particle size was 4.6 μm. The ratio of the minor axis to the major axis of the spherical silica gel was 0.9 or more.

1 g of this spherical silica gel was dispersed in 99 g of ion-exchanged water having an electric conductivity of 0.5 μS / cm, and dried at 120 ° C. for 5 hours using a stationary dryer to obtain silica gel. When the pore characteristics of the silica gel after this treatment were evaluated in the same manner, the pore volume, the specific surface area, and the oil absorption did not substantially change. That is, they were respectively 90% or more of the values before being dispersed in water.

Example 4 The spherical silica gel obtained in Example 1 was treated with a jet pulverizer to obtain a fine powder silica gel. This silica gel has a pore volume of 2.3 ml / g, a specific surface area of 743 m ² / g,
Oil absorption is 450ml / 100g, average particle size is 1.2μ
m.

1 g of this silica gel has an electric conductivity of 0.5
The particles were dispersed in 99 g of μS / cm ion-exchanged water and dried at 120 ° C. for 5 hours using a stationary dryer to obtain silica gel. When the pore characteristics of the silica gel after this treatment were similarly evaluated, the pore volume was 2.3 ml / g, the specific surface area was 755 m ² / g, and the oil absorption was 443 ml / 100.
g.

Example 5 (Comparative Example) After hydrolyzing tetraethyl silicate in ethanol under acidic conditions, the water was replaced with ethanol.
After the pressure and temperature were increased to the supercritical point of ethanol or higher, the pore characteristics of the silica gel that was supercritically dried while maintaining the temperature were similarly evaluated. The pore volume is 6.9 ml
/ G, specific surface area is 453m ² / g, oil absorption is 640ml
/ 100 g, and the average particle size was 1.2 μm.

1 g of this silica gel has an electric conductivity of 0.5
The particles were dispersed in 99 g of μS / cm ion-exchanged water and dried at 120 ° C. for 5 hours using a stationary dryer to obtain silica gel. When the pore characteristics of the silica gel after this treatment were similarly evaluated, the pore volume was 1.8 ml / g, the specific surface area was 475 m ² / g, and the oil absorption was 265 ml / 100.
g.

[0038]

Industrial Applicability The high oil absorption silica gel of the present invention has a large specific surface area as compared with the conventional precipitated silica, a carrier for medical and agricultural chemicals, a raw material for cosmetics and toiletries, a material for preventing strike-through of newsprint, an ink jet printer. It is suitably used for applications such as coating materials or fillers for recording media, battery separators, paint additives, catalyst carriers, lightweight materials, heat insulating materials, and fillers for resins and rubbers.

The recording medium for an ink jet printer using the spherical silica gel of the present invention has a high ink absorption rate and a high color density. The battery separator using the spherical silica gel of the present invention has low electric resistance.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ryo Kusaka 10 Goi Kaigan, Ichihara-shi, Chiba Prefecture Asahi Glass Co., Ltd. Incorporated F term (reference) 4G072 AA28 BB07 CC10 DD03 DD04 GG01 GG03 HH21 HH22 JJ12 JJ28 JJ30 LL06 LL15 MM01 PP03 PP05 TT01 TT05 TT08 TT09 TT11 UU07 UU17 UU30

Claims (4)

[Claims] 1. A pore radius of 1 to 100 nm by a nitrogen adsorption method.
Is 1.5 to 3.5 ml / g, specific surface area is 500 to 1000 m ² / g, and oil absorption is 300 ml / 1.
More than 00g of silica gel with electric conductivity of 1μS
Of silica gel obtained by dispersing 1% by weight of this silica gel in water at a concentration of not more than / 100 cm / cm and then drying at 120 ° C. for 5 hours using a stationary dryer. A high oil absorption silica gel having a pore volume and an oil absorption of 90% or more of the values before dispersion in water, respectively. 2. The high oil absorption silica gel according to claim 1, wherein the average particle diameter is 1 to 100 μm and the particle shape is spherical. 3. The method of claim 1, wherein the silicate component in the aqueous alkali silicate solution is S
When converted to iO ₂ , one or more anions selected from the group consisting of chloride ions, sulfate ions, nitrate ions and fluoride ions are added in a total amount of 0.1 to 0.5 per mole of the SiO _2. The method for producing silica gel according to claim 1 or 2, wherein an aqueous solution of an alkali silicate contained in an equivalent ratio is emulsified in an organic solvent and gelled with carbon dioxide gas. 4. An alkali metal silicate aqueous solution containing at least one selected from the group consisting of alkali metal chlorides, sulfates, nitrates and fluorides, and alkaline earth metal chlorides, sulfates, nitrates and fluorides. The method for producing a high oil absorption silica gel according to claim 3, wherein the above is added to contain one or more anions selected from the group consisting of chloride ions, sulfate ions, nitrate ions and fluoride ions.