JP2007230851A - Lightweight amorphous silica and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an amorphous silica which comprises cleavable laminate particles in which SiO<SB>2</SB>thin layers are layered, is obtained by using vermiculite as a starting material and subjecting it to an acid treatment, shows advanced cleavage, has a low bulk density and lightweight and can be highly dispersed in a resin etc. in a small amount. <P>SOLUTION: The lightweight amorphous silica comprises the cleavable laminate particles in which the SiO<SB>2</SB>thin layers are layered. In the amorphous silica, pores with a diameter of 0.024-8.70 μm determined by a mercury intrusion technique account for a void volume of ≥2.2 ml/g, the bulk density is ≤0.19 g/ml, and the BET specific surface area is ≤200 m<SP>2</SP>/g. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to amorphous silica and a method for producing the same, and more particularly to amorphous silica obtained using vermiculite as a starting material and a method for producing the same.

  Amorphous silica is widely used in various fields such as paints, resin molded articles, paper, and cosmetics.

  The present applicant previously proposed amorphous silica obtained by acid treatment of vermiculite (see Patent Document 1).

That is, the amorphous silica obtained by acid treatment of vermiculite has a shape called a leaf shape, a scale shape, or a plate shape composed of cleaved laminate particles in which thin layers of SiO ₂ are laminated, A large number of thin silica layers are capable of exhibiting independent behavior as a layer, that is, cleaving properties, and are not found in conventionally known silica. Specifically, it can be dispersed in a thin form in a medium such as a resin, and has a characteristic that covering power, adhesion, protective effect, gas barrier property, and the like are improved.
Japanese Patent No. 3689174

However, even though amorphous silica obtained from vermiculite has a cleavage property, it has a structure in which many thin layers of SiO ₂ are laminated. Only the exfoliation occurs, and not all of the thin layer exfoliates and exhibits independent behavior. That is, the bulk density is high, and in order to achieve effects such as mechanical strength and gas barrier properties when blended with a resin or the like, it must be blended in a considerably large amount, and there is still room for improvement.

Accordingly, an object of the present invention is to obtain vermiculite as a starting material and to obtain it by acid treatment, and despite the fact that it consists of cleaved laminate particles in which thin layers of SiO ₂ are laminated, cleavage proceeds. In addition, since the bulk density is low, the weight is high, and the dispersibility is improved, an amorphous silica capable of exerting a desired effect on a resin or the like with a small amount of use and a method for producing the same are provided. There is to do.

  As a result of intensive studies on the above problems, the inventors of the present invention have a layered silicic acid structure derived from vermiculite when the acid-treated product of vermiculite is hydrothermally treated in a specific pH range, and the layered structure is cleaved. In addition, the present inventors have found that amorphous silica having excellent bulkiness and low bulk density and excellent lightness can be obtained, and the present invention has been completed.

That is, according to the present invention, it is composed of cleaved laminate particles in which a thin layer of SiO ₂ is laminated, and the space volume at a diameter of 0.024 to 8.70 μm measured by mercury porosimetry is 2.20 ml / g. There is provided a lightweight amorphous silica characterized in that the bulk density is in the range of 0.19 g / ml or less and the BET specific surface area is in the range of 200 m ² / g or less.

In the lightweight amorphous silica of the present invention,
(1) The average number of Si bonds calculated by ²⁹ Si-NMR measurement is in the range of 3.65 to 3.90;
(2) The equilibrium moisture content at 75% RH is 14.0% or less, and the oil absorption (JIS K 5101-13-2: 2004) is in the range of 120 ml / 100 g or more.
Is preferred.

According to the invention,
A process of preparing an aqueous dispersion of an acid-treated product by dispersing vermiculite in an acid aqueous solution, dispersing the filtered cake of the acid-treated product obtained by filtration and washing with water in water,
Adjusting the aqueous dispersion of the acid-treated product to a pH in the range of 5.0 to 10.0;
Hydrothermally treating the pH-adjusted acid-treated dispersion liquid at a temperature of 80 ° C. or higher,
A step of drying and crushing the obtained treatment liquid,
There is provided a method for producing a lightweight amorphous silica comprising:

In the production method of the present invention,
(1) The acid-treated product concentration of the aqueous dispersion of the acid-treated product is in the range of 15 to 25% by weight,
(2) As the pH adjustment, NH ₄ OH aqueous solution, sodium silicate aqueous solution or Mg (OH) ₂ slurry is used.
(3) performing the hydrothermal treatment under pressure;
Is preferred.

  According to the present invention, there are further provided a compounding agent for resin, an enzyme carrier, and a compounding agent for paint comprising the above-mentioned lightweight amorphous silica.

Since the amorphous silica obtained by the present invention is obtained through an acid treatment step of vermiculite, it has a layered silicic acid structure in which thin layers of SiO ₂ are laminated. Or it has the shape called plate shape. For this reason, it can be dispersed in a thin form in a medium such as a resin, and exhibits extremely excellent characteristics such as covering power, adhesion, protective effect, and barrier property against gas.

In addition, the amorphous silica obtained by the present invention has an extremely high space volume of 2.2 ml / g or more at a diameter of 0.024 to 8.70 μm measured by mercury porosimetry. That is, the high space volume at such a diameter means a large interparticle distance, which means that the thin layer of SiO ₂ forming the layered silicate structure is highly independent, and most particles are It means that it has peeled to the state of few laminations. Therefore, such amorphous silica has a low bulk density of 0.19 g / ml or less, is excellent in light weight, and can be highly dispersed in a medium such as a resin with a small amount of blending. It has a great advantage that the above-mentioned various characteristics can be sufficiently exhibited in an amount.

Furthermore, the amorphous silica obtained by the present invention has a BET specific surface area of 200 m ² / g or less in a relatively small range and relatively low hygroscopicity. When blended in a resin or the like, foaming due to moisture absorption is effective. There is also an advantage that it can be avoided.

[Vermiculite]
Vermiculite used as a raw material for the lightweight amorphous silica of the present invention is a mineral mainly composed of hydromica classified as vermiculite group clay mineral or mica group clay mineral, and is also called meteorite. Yes. When this mineral is rapidly heated to a certain temperature or more, the name is derived from the fact that it significantly extends in the direction perpendicular to the plane index (001) (C-axis direction) and has a shape resembling cocoons. The vermiculite basically includes a trioctahedral type having a chemical structure represented by the following formula (1) and a bioctahedral type having a chemical structure represented by the following formula (2). Either can be used.

{E _0.6-0.8 · 4-5H ₂ O} (Mg, Fe ³⁺ , Fe ²⁺ , Al) ₃
[Si, Al] ₄ O ₁₀ (OH) ₂ (1)
{E _{0.6 to 0.8} · nH ₂ O} (Al, Fe, Mg) _2. [Si, Al] ₄
・ O ₁₀ (OH) ₂ (2)
In the above formula, E is an interlayer ion and is mainly composed of K or Mg.

The chemical composition of vermiculite varies depending on the production area, but typical compositions are as follows.
SiO _2: 35~45 weight%
Al ₂ O ₃ : 10 to 20% by weight
MgO: 7 to 30% by weight
Fe ₂ O _3: 5~22 wt%
CaO: 0 to 3% by weight
Na ₂ O: 0 to 1% by weight
K ₂ O: 0~10 weight%
Heavy metal content other than Fe (Pb, Cr, Cd, etc.): 0.2 wt% or less Loss on ignition (1050 ° C.): 3-25 wt%

(Production of lightweight amorphous silica)
In producing the lightweight amorphous silica of the present invention, first, the above vermiculite is acid-treated. By performing such an acid treatment, the crystal structure is destroyed, the colored component is removed, the whiteness is improved, and coloring when blended with a polymer or the like can be suppressed.

As the acid used for the acid treatment, mineral acids such as sulfuric acid, hydrochloric acid, and nitric acid are used, and the amount used is excessive with respect to the basic component containing Fe ₂ O ₃ in vermiculite. The acid concentration is generally 15 to 40% by weight, particularly 20 to 35% by weight, and the acid treatment temperature is preferably 10 to 110 ° C. In particular, when the treatment temperature is high, the treatment can be performed in a short time even if the acid concentration is lowered. The acid treatment time varies depending on the acid concentration, the amount of acid used, the temperature, etc., and cannot be generally specified. However, the acid treatment results in a silica (SiO ₂ equivalent) content of 82% by weight or more, particularly 85% by weight. As described above, the acid treatment is preferably carried out for a time period in which the whiteness is increased to 85% or more, particularly 88% or more, and is usually about 6 to 48 hours.

  In addition, prior to the acid treatment, if necessary, heat treatment can be performed at a temperature of 200 to 500 ° C. This heat treatment is called expansion treatment, and is performed to separate the layered structure of vermiculite, and is particularly effective for obtaining amorphous silica having a high aspect ratio.

  Prior to the acid treatment as described above, it is preferable to separate contaminated gangue as necessary. For this separation, a wet classification method using a water tank, a liquid cyclone or the like and a dry classification method using a wind tank, a cyclone, a micron separator or the like can be generally applied.

In the present invention, the acid-treated product of vermiculite obtained above is adjusted to pH 5.0 to 10.0 and then subjected to a hydrothermal reaction, thereby obtaining the intended lightweight amorphous silica. That is, in each particle of amorphous silica obtained by acid treatment by such hydrothermal reaction at pH, small particles of SiO ₂ component are dissolved and rearranged on the surface of large particles through condensation or the like. As a result of the aging of the Ostwald that precipitates, the physical properties such as the spatial volume, bulk density, and BET specific surface area described later are expressed while maintaining the unique layered silicic acid structure and cleavage properties derived from vermiculite. Seem.

  In order to perform a hydrothermal reaction at such a pH, an aqueous dispersion of amorphous silica obtained by acid treatment of vermiculite is prepared (aqueous dispersion preparation step), and then the pH of the aqueous dispersion is adjusted. (PH adjustment step).

  The aqueous dispersion of the acid-treated product is obtained by filtering the acid-treated product obtained by the acid treatment of vermiculite, washing it with water, and removing the excess acid. And again by dispersing in water.

  The concentration of the acid-treated product in the aqueous dispersion of the acid-treated product thus prepared is usually preferably in the range of 15 to 25% by weight. When this concentration is low, productivity is lowered, and when the concentration is higher than necessary, stirring of the dispersion may be difficult in the subsequent steps.

The pH of the dispersion may be adjusted to be in the range of 5.0 to 10.0. Although what is used for pH adjustment is not particularly limited, NH ₄ OH aqueous solution, sodium silicate aqueous solution or Mg (OH) ₂ slurry is preferably used from the viewpoint of easy pH adjustment. Of course, in the step of preparing the aqueous dispersion of the acid-treated product, adjustment is not particularly required if it is within the above pH range.

In addition, it is extremely important to set the pH within the above range. If the pH is higher than the above range, most of the acid-treated product is dissolved, and the layered silicic acid structure and cleavage property derived from vermiculite disappear. End up. Further, if the pH is lower than the above range, dissolution of SiO ₂ present on the silica surface that is the acid-treated product does not occur effectively, and as a result, physical properties such as space volume and bulk density described later cannot be obtained. End up.

  The pH adjustment step as described above may be carried out to such an extent that the pH is stable within the above range and the acid-treated product is uniformly dispersed. Usually, the mixing with the pH adjusting agent is performed for about 30 to 60 minutes. Just do it.

In the present invention, the intended lightweight amorphous silica can be obtained by hydrothermally treating the pH-adjusted dispersion thus obtained at a temperature of 80 ° C. or higher, preferably 80 to 180 ° C. That is, such hydrothermal reaction causes dissolution and rearrangement of SiO ₂ , and various physical properties are modified. When the hydrothermal treatment temperature is lower than the above range, the dissolution and rearrangement of SiO ₂ is insufficient, and the modification of various physical properties is not performed to a satisfactory degree. For example, the spatial volume described later is reduced, and the bulk density is also low. It gets bigger. On the other hand, if the hydrothermal treatment temperature is higher than the above range, the layered silicic acid structure derived from vermiculite and the cleavage property are impaired.

The hydrothermal treatment is preferably performed under pressure by an autoclave. For example, the hydrothermal treatment is performed at a pressure of 1 atm or higher, preferably 2 atm or higher, to promote dissolution and rearrangement of SiO ₂ and hydrothermal treatment. It is suitable for performing in a short time.

  In the present invention, the above-described hydrothermal treatment is generally performed for about 1 to 10 hours, although it varies depending on the pressure.

  After the hydrothermal treatment, the obtained treatment liquid is filtered, washed with water as necessary, dried, and pulverized to an appropriate particle size according to the intended use, whereby the intended lightweight amorphous silica is obtained.

(Lightweight amorphous silica)
The lightweight amorphous silica of the present invention obtained as described above is derived from raw material vermiculite and has a cleaved laminate particle structure of a thin amorphous silica layer. FIG. 1 is an electron micrograph (magnification: 10,000 times) showing the particle structure of this lightweight amorphous silica.

That is, as understood from FIG. 1, such particles have a plate-like particle shape and have a cleaved laminate particle structure in which thin amorphous silica layers are laminated. Such lightweight amorphous silica has a median diameter (D ₅₀ ) of 1 to 20 μm, particularly 1 to 15 μm as measured by a laser diffraction method, and the aspect ratio represented by the maximum diameter / thickness in the plane direction is , 15 to 40, and the thickness is extremely thin, about 0.15 to 0.50 μm. That is, amorphous silica obtained by simply acid-treating vermiculite has a similar plate-like particle shape, but its thickness is thick (see FIG. 2). Therefore, the lightweight amorphous silica of the present invention has a high degree of independence (cleavage) of the thin layer of amorphous silica forming the laminate particles, and is peeled apart and separated into a small range. I understand.

  Such a lightweight amorphous silica of the present invention has a space volume of 0.024 to 8.70 μm measured by mercury porosimetry, and is not less than 2.20 ml / g, particularly 2.20 to 3.00 ml / g. It is in the range. That is, such a spatial volume indicates not the pore volume in the particles but the size of the interparticle voids, and is simply obtained by using amorphous silica obtained by acid treatment of vermiculite (see Comparative Example 1 described later). In comparison, this spatial volume is increased. Therefore, since the lightweight amorphous silica of the present invention has large interparticle voids, its bulk density is 0.19 g / ml or less, particularly in a very small range of 0.10 to 0.18 g / ml. . That is, it is extremely lightweight and can be highly dispersed even when used in a small amount when blended in a medium such as a resin, so that various characteristics can be sufficiently exhibited. In the space volume, the value of the diameter is the value of the pore diameter.

Furthermore, since the light amorphous silica of the present invention has undergone the thermal history by the hydrothermal treatment described above, its BET specific surface area is 200 m ² / g or less, preferably 150 m ² / g or less, more preferably 30 to 130 m ^2. As small as / g. Accordingly, hygroscopicity is suppressed, which is advantageous in that foaming can be suppressed when kneaded into the resin.

In the lightweight amorphous silica of the present invention, the average number of Si bonds calculated by ²⁹ Si-NMR measurement is in the range of 3.65 to 3.90. For example, amorphous silica obtained by acid treatment of vermiculite and not hydrothermally treated under a specific pH range according to the present invention (see Comparative Example 1) has an average Si bond number measured above. 3.58, which is smaller than the present invention. That is, the light-weight amorphous silica of the present invention has an average Si bond number shifted to a range close to 4 as compared to the acid-treated product of vermiculite. It is shown that condensation of silanol groups (SiOH groups) occurs simultaneously with the rearrangement of SiO ₂ by the hydrothermal treatment. As a result, in the lightweight amorphous silica of the present invention, the bonding force between the amorphous silica thin layers forming the layered silicate structure is weakened, the cleaving property is increased, and each thin layer behaves independently. As described above, it is considered to exhibit a high space volume and a low bulk density derived from voids formed from large particles as described above.

In the lightweight amorphous silica of the present invention, the average number of Si bonds is increased to a value close to 4 as described above, the amount of SiOH groups is reduced, and the specific surface area is 200 m ² / g by hydrothermal treatment. For this reason, the hygroscopicity is low. For example, the equilibrium water content at 75% RH is in the range of 14.0% or less.
Furthermore, since the lightweight amorphous silica of the present invention has the above-described space volume, the oil absorption (JIS K 5101-13-1: 2004) is 120 ml / 100 g or more, particularly in the range of 120 to 150 ml / 100 g. is there.

  Thus, since the lightweight amorphous silica of the present invention is obtained through acid treatment, the content of colored components such as iron is remarkably low, and therefore, the Hunter whiteness is 85% or more, particularly 88% or more. And has the advantage that coloring when blended in a resin or the like can be suppressed.

  The above-described lightweight amorphous silica of the present invention alone is used for coatings, inks, various resins and elastomers, fillers, reinforcing agents, insulation improvers, rust inhibitors, rheology modifiers, flame retardants. It can be blended as an auxiliary agent, etc., and can be oriented and highly dispersed, especially when used in a small amount. For example, the blending amount varies depending on the application, but generally 100 parts by weight per 100 parts by weight of resin solids. A small amount of about 30 parts by weight is sufficient.

  Such lightweight amorphous silica may be used alone in a resin or the like, but is treated with another inorganic or organic surface modifier to further increase dispersibility in the resin or the like. You can also. Such a surface modifier is preferably used in an amount of 0.5 to 30% by weight, particularly 1 to 25% by weight, based on the silica.

  Examples of inorganic surface modifiers include fine-particle silica such as aerosil and hydrophobically treated aerosil, silicates such as calcium silicate and magnesium silicate, metal oxides such as calcia, magnesia, zinc white, iron oxide and titania, water Metal hydroxides such as magnesium oxide and aluminum hydroxide, metal carbonates such as calcium carbonate, synthetic zeolites such as A-type, P-type and ZSM-5, acid-treated products thereof, or metal ion-exchanged products thereof, hydrotalcite, etc. These can be blended as appropriate, or can be used by coating or coating depending on the application.

  Organic surface modifiers include fatty acids such as stearic acid, palmitic acid and lauric acid, metal soaps such as calcium salts, zinc salts, magnesium salts and barium salts of fatty acids, silane coupling agents, and aluminum couplings. Agents, titanium coupling agents, zirconium coupling agents, silicone oils, various waxes, various unmodified or modified resins (for example, rosin, petroleum resin, etc.), etc., depending on the application, such surface The modifier can be coated for use.

In addition, since the lightweight amorphous silica obtained by using Mg (OH) ₂ slurry as the alkali described above is coated with Mg, it can be treated with the surface modifier as described above alone. There is an advantage that the same high dispersibility is exhibited. Besides Mg (OH) ₂ slurry, Ca (OH) ₂ slurry and ZnO slurry can also be used.

  In addition, the lightweight amorphous silica of the present invention has improved cleaving property and increased independence of the silica thin layer. Therefore, when blended into a paint or resin, and dispersed or kneaded, the particles are dispersed. By such shearing force, it is possible to easily disperse and align in layers by flow orientation at the time of coating or molding, to give a layered distribution structure suitable in terms of each physical property, and to remarkably enhance characteristics such as gas barrier properties.

  Such paints include thermosetting resin paints such as phenol-formaldehyde resins, xylene-formaldehyde resins, ketone-formaldehyde resins, urea-formaldehyde resins, melamine-formaldehyde resins, alkyd resins, unsaturated polyester resins, epoxy resins. , Bismaleimide resin, triallyl cyanurate resin, thermosetting acrylic resin, silicone resin, oil-based resin, or thermoplastic paint such as vinyl chloride-vinyl acetate copolymer, vinyl chloride-maleic acid copolymer, vinyl chloride -Maleic acid-vinyl acetate copolymer, acrylic polymer, saturated polyester resin, etc. can be mentioned.

  As the thermoplastic resin, those which are molded into a film, sheet, container, lid or the like, particularly those which can be used as a packaging material from the viewpoint that the gas barrier property can be improved, for example, polyethylene, polypropylene, etc. Olefin resins such as polyisoprene and polyolefin having an alicyclic structure; ester resins such as polyethylene terephthalate and polyethylene naphthalate; amide resins such as nylon 6, nylon 66, nylon 11 and nylon 12; polyhydroxybutyrate and polylactic acid Biodegradable resins such as polycaprolactone, polybutylene succinate, polyglycolic acid, polyalkylene carbonate; acrylic resins such as polymethyl methacrylate; ethylene-vinyl acetate copolymer; polyvinyl alcohol; Alcohol copolymers; polystyrene; polysulfones, cellophane, polyvinyl chloride, polyvinylidene chloride, polycarbonates, polyacrylonitrile, chlorinated polyethylene, chlorinated polypropylene, soft polyvinyl chloride, and the like can be exemplified.

  As the elastomer, natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, nitrile-butadiene rubber, butyl rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, acrylic rubber, polysulfide rubber, Examples include so-called rubbers such as silicone rubber, fluororubber, and urethane rubber, and thermoplastic elastomers such as styrene, olefin, vinyl chloride, urethane, ester, and amide.

The amorphous silica of the present invention can be used as a catalyst carrier or an enzyme carrier, particularly an ester synthesis catalyst carrying a lipase.
As an example, such amorphous silica particles have a cleaved laminate particle structure in which a thin layer of SiO ₂ is laminated, and in connection with such a particle structure, fats and oils are synthesized during ester synthesis. Since glycerin generated by hydrolysis is not released to the outside and is stably held inside the silica particles, even when repeated ester synthesis is performed, reaction inhibition by glycerin is avoided and stable ester synthesis is performed. Seems to be able to. As a result, the catalyst activity is long and ester synthesis can be performed repeatedly over a long period of time. As the silica carrier, for example, amorphous silica of Example 1 described later can be suitably used.

  The amorphous silica of the present invention can be used as a compounding agent for paints. In particular, when blended in an aqueous paint, it is blended as an aqueous slurry suspended and dispersed in water in combination with an anionic or nonionic polymer flocculant. The anionic or nonionic polymer flocculant is preferably used in an amount of 0.5 to 4.0 parts by weight per 100 parts by weight of amorphous silica. The storage stability of this aqueous slurry is extremely high.

  The silica-based aqueous slurry described above is blended in an aqueous coating material, the fluidity is improved, and the fluidity at the time of application is improved to improve the applicability. For example, a thin film can be easily formed. Moreover, the dripping of the coating film after application | coating can be prevented effectively. Furthermore, when a coating film is formed, it is oriented and dispersed in layers in the coating film, and as a result, the coating film strength can be effectively increased.

  In addition to the aqueous solution type paint, a self-emulsification type or surfactant emulsification type paint can be used as the aqueous paint in which the aqueous slurry is blended. As the polymer of the water-based paint, an alkyd polymer, a polyester polymer, an acrylic polymer, an epoxy polymer or a combination of two or more of these which are water-solubilized or self-emulsified in an aqueous medium can be used.

  The aqueous slurry varies depending on the use of the aqueous paint, but in order to develop an excellent coating strength improvement effect and fluidity modification effect, the amorphous silica in the aqueous slurry is based on the solid content of the aqueous paint. What is necessary is just to mix | blend in a water-based coating material so that it may become the quantity of about 1 to 60 weight%.

  Further, when the aqueous slurry is used for an aqueous coating, it is preferable to disperse colloidal silica in the aqueous slurry. That is, colloidal silica is a remarkably fine particle having a particle size of 150 nm or less. Therefore, when a coating film is formed using this aqueous slurry, a denser coating film can be formed by a synergistic effect, and storage stability is improved. Properties such as hardness, adhesion, and water resistance of the coating film can be enhanced without impairing the properties. Such colloidal silica is usually preferably blended in an amount of 5 to 240 parts by weight, particularly 10 to 150 parts by weight, per 100 parts by weight of amorphous silica. When colloidal silica is dispersed more than necessary, the hardness of the coating film increases, but flexibility is impaired and cracks and the like are likely to occur.

  The colloidal silica may be anything as long as it is of an alkaline and stable type. The grades such as DuPont Ludox can be listed.

  Before adding colloidal silica to the silica slurry, it is preferable to add ammonia water, aqueous caustic soda solution or aqueous sodium silicate solution to maintain the pH (/ 20 ° C.) at 8.5 to 10.0.

  The amorphous silica of the present invention is useful as a filler for adhesives, makeup cosmetics and the like, and as a filler for papermaking.

  Hereinafter, the present invention will be described in detail with reference to examples. In addition, the measuring method in an Example is as follows.

(1) Space volume
Using Auto Pore IV manufactured by Micromeritics, the pore volume was measured by mercury porosimetry, and the spatial volume was determined from the pore volume at a diameter of 0.024 to 8.70 μm.

(2) Bulk density Measured according to JIS K 6220-1 7.7: 2001.

(3) BET specific surface area
Nitrogen adsorption isotherm was measured using TriStar 3000 manufactured by Micromeritics. It was determined by the BET method from the adsorption side nitrogen adsorption isotherm with a specific pressure of 0.2 or less.

(4) NMR measurement (average number of Si bonds)
The measurement of ²⁹ Si-MASNMR of each sample was performed under the following conditions using a JEOL EX270 type NMR apparatus manufactured by JEOL Ltd.
Observation frequency 53.54MHz
Pulse delay 100.000sec
Pulse width 2.9μsec (90 °)
Standard sample Polydimethylsilane -33.8ppm
Integration count 200
From the obtained results, the average number of Si bonds was determined.

(5) Equilibrium moisture amount About 1 g of a sample is put in a 50 mmφ weighing bottle whose weight has been measured in advance, dried in an electric constant temperature dryer at 110 ° C. for 3 hours, and then allowed to cool in a desiccator. Next, the weight of the sample was precisely weighed, placed in a desiccator adjusted to 75% relative humidity (RH) with saturated saline, and measured until the weight reached equilibrium to determine the equilibrium moisture content.

(6) Oil absorption amount It measured based on JISK5101-13-1: 2004.

(7) Median diameter (D ₅₀ )
Measurement was performed by laser diffraction scattering using a Mastersizer 2000 manufactured by Malvern.

(Comparative Example 1)
5.2 kg of water and 2.3 kg of 98% sulfuric acid were added to 1.0 kg of South African vermiculite ore and heated at 95 ° C. for 20 hours. Subsequently, filtration, washing with water, drying at 150 ° C., pulverization and classification were performed to obtain amorphous silica. Table 1 shows the physical properties of the obtained amorphous silica. Moreover, the electron micrograph (magnification: 10000 times) of this amorphous silica is shown in FIG.

Example 1
In Comparative Example 1, 500 g of cake having a solid content of 50% after filtration and washing with water was dispersed and stirred in 600 g of water after the acid treatment of vermiculite to prepare an aqueous dispersion of a vermiculite acid-treated product. Next, NH ₄ OH aqueous solution adjusted to 6 mol / L was dropped into the aqueous dispersion and stirred well, and the pH of the dispersion was adjusted to 6.88 / 22.5 ° C. The obtained dispersion was transferred to an autoclave and hydrothermally treated at 160 ° C. for 6 hours with stirring at 300 rpm. The treated liquid was filtered, dried, pulverized, and classified to obtain the lightweight amorphous silica of the present invention. The obtained lightweight amorphous silica was measured for physical properties, and the results are shown in Table 1. Moreover, the electron micrograph (magnification: 10000 times) of this lightweight amorphous silica is shown in FIG.

(Example 2)
A light amorphous silica was obtained in the same manner as in Example 1 except that the pH of the dispersion was adjusted to 8.57 / 23.7 ° C. The obtained lightweight amorphous silica was measured for physical properties, and the results are shown in Table 1.

(Example 3)
A light amorphous silica was obtained in the same manner as in Example 1 except that a sodium silicate aqueous solution was used instead of the NH ₄ OH aqueous solution and the pH of the dispersion was adjusted to 8.57 / 22.6 ° C. It was. The obtained lightweight amorphous silica was measured for physical properties, and the results are shown in Table 1.

Example 4
In Example 1, instead of the NH ₄ OH aqueous solution, a slurry in which 12.5 g of Mg (OH) ₂ was added to 100 mL of water was used, and the pH of the dispersion was adjusted to 9.12 / 23.4 ° C. In the same manner, lightweight amorphous silica was obtained. The obtained lightweight amorphous silica was measured for physical properties, and the results are shown in Table 1.

(Example 5)
In Example 1, the same procedure was performed except that the pH of the dispersion was adjusted to 8.06 / 23.7 ° C. and the hydrothermal treatment was changed to 140 ° C. for 6 hours. The obtained lightweight amorphous silica was measured for physical properties, and the results are shown in Table 1.

(Example 6)
In Example 1, the same procedure was performed except that the pH of the dispersion was adjusted to 8.45 / 20.7 ° C. and the hydrothermal treatment was changed to 120 ° C. for 3 hours. The obtained lightweight amorphous silica was measured for physical properties, and the results are shown in Table 1.

(Example 7)
In Example 1, it carried out similarly except having adjusted the pH of the dispersion liquid to 8.67 / 17.5 degreeC, and having changed the hydrothermal treatment to 110 degreeC for 6 hours. The obtained lightweight amorphous silica was measured for physical properties, and the results are shown in Table 1.

(Example 8)
In Example 1, the same procedure was carried out except that the pH of the dispersion was adjusted to 7.93 / 20.9 ° C. and the hydrothermal treatment was changed to 90 ° C. for 6 hours. The obtained lightweight amorphous silica was measured for physical properties, and the results are shown in Table 1.

Example 9
In Example 1, it was performed in the same manner except that the pH of the aqueous dispersion of the acid-treated product was not adjusted (pH was 5.28 / 18.5 ° C.). The obtained lightweight amorphous silica was measured for physical properties, and the results are shown in Table 1.

The electron micrograph (magnification: 10000 times) of the lightweight amorphous silica particle (Example 1) of this invention. The electron micrograph of the amorphous silica particle of the comparative example 1 (magnification: 10000 times).

Claims (10)

It consists of cleaved laminate particles in which a thin layer of SiO ₂ is laminated, the spatial volume at a diameter of 0.024 to 8.70 μm measured by mercury porosimetry is 2.20 ml / g or more, and the bulk density is 0 A lightweight amorphous silica having a BET specific surface area of 200 m ² / g or less in a range of .19 g / ml or less. The lightweight amorphous silica according to claim 1, wherein the average number of Si bonds calculated by ²⁹ Si-NMR measurement is in the range of 3.65 to 3.90.   The lightweight amorphous silica according to claim 1, wherein the equilibrium water content at 75% RH is 14.0% or less and the oil absorption (JIS K 5101-13-2: 2004) is in the range of 120 ml / 100 g or more. . A process of preparing an aqueous dispersion of an acid-treated product by dispersing vermiculite in an acid aqueous solution, dispersing the filtered cake of the acid-treated product obtained by filtration and washing with water in water,
Adjusting the aqueous dispersion of the acid-treated product to a pH in the range of 5.0 to 10.0;
Hydrothermally treating the pH-adjusted acid-treated dispersion liquid at a temperature of 80 ° C. or higher,
A step of drying and crushing the obtained treatment liquid,
A process for producing lightweight amorphous silica, comprising:   The production method according to claim 4, wherein the concentration of the acid-treated product in the aqueous dispersion of the acid-treated product is in the range of 15 to 25% by weight. The production method according to claim 4 or 5, wherein an NH ₄ OH aqueous solution, a sodium silicate aqueous solution, or a Mg (OH) ₂ slurry is used as pH adjustment.   The manufacturing method according to claim 4, wherein the hydrothermal treatment is performed under pressure.   The compounding agent for resin which consists of the lightweight amorphous silica in any one of Claims 1 thru | or 3.   An enzyme carrier comprising the lightweight amorphous silica according to any one of claims 1 to 3.   A paint compounding agent comprising the lightweight amorphous silica according to any one of claims 1 to 3.

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