JP2000012314A - Large bore magnetic silica particle and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic silica particle of large bore, together with a method for easily manufacturing it, which is useful as an adsorbent, adsorbing carrier, extractor-agent, extracting carrier, and catalyser carrier, etc., with small specific surface area, sufficient small bore volume, and large small bore. SOLUTION: Si alkoxide and magnetic silica particle of large bore wherein, the content of magnetic material is 5-50 wt.% of the entire amount, average particle size of the silica particle is 1-200 μm, BET specific surface area is less than 100 m2/g, small bore is 10 nm or less, and small bore volume is 0.3-2.5 ml/g, are allowed to generate Si alkoxide polymer, which is allowed to carry magnetic material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to magnetic silica particles having a large pore diameter and having magnetic properties and strength which can be used as an adsorbent, a carrier for adsorption, an extractant, a carrier for extraction, a catalyst carrier and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, silica gel and the like are well known as an adsorbent and a solid phase carrier for adsorption. In the case of using these, a centrifugal separation method or filtration with a filter is used for their recovery. It had to be done and was not a convenient method. In addition, in the adsorption and extraction operations, it is necessary to separate the target adsorbate or extract from other substances, but conventional centrifugation, column separation,
In a technique such as an electrophoresis method, there is a problem that it takes a long time only for separation, and it is not a simple method.

[0003] Therefore, as a means for separating a target substance, a method of collecting a target particle by adding a ferromagnetic substance to the particle and applying a magnetic field as described in JP-A-61-181967 is known. there were. However, in this method, even when it is desired to carry out the operation in a state where the particles are uniformly dispersed in the adsorption, extraction, reaction operation, etc., the ferromagnetic material itself self-associates, and the state of the particles can be freely determined. It had the disadvantage that it could not be controlled.

In recent years, as a method for eliminating self-association of a ferromagnetic material itself, a method using a superparamagnetic material as a magnetic material has been disclosed as described in the above-mentioned Japanese Patent Application Laid-Open No. 61-181967. Further, as described in Japanese Patent Application Laid-Open No. 4-501957, it is disclosed that magnetic particles containing a superparamagnetic substance can be used as a solid phase for immobilizing a sample, and can be used for separation, analysis, and the like of proteins, cells, and DNA. . Further, Patent No. 25
No. 54250 discloses a reagent carrier having high mobility in which a superparamagnetic magnetically reactive substance is captured in a gel matrix. The superparamagnetic magnetic particles described in these are ferromagnetic substances such as iron oxide, which are included in the particles as fine particles smaller than the size of a magnetic domain necessary for maintaining permanent magnetism,
It has the property of showing ferromagnetism by an external magnetic field. Utilizing this property, it is a method in which an external magnetic field is not applied when dispersing, and an external magnetic field is applied when aggregating, so that particles in a solution are aggregated. However, even in these methods, it cannot be said that the magnetic particles are obtained by a method in which the physical properties of the magnetic particles are sufficiently controlled, and the physical properties of the magnetic particles are sufficiently controlled in accordance with various uses to produce optimal magnetic particles. A way to do that was desired.

Further, as described in JP-A-9-19292, it has been shown that silica particles containing a superparamagnetic metal oxide having a specific surface area of 100 to 800 m ² / g can be used for nucleic acid binding. However, silica particles with a large specific surface area are expected to have the effect of the specific surface area on the adsorption and binding of low molecular weight molecules, but in the case of high molecular weight molecules such as nucleic acids, silica particles and nucleic acids The effect of specific surface area and pore structure is not as pronounced as low molecular weight materials, since most of the bonds occur on the particle surface. In addition, an increase in specific surface area, pore diameter, and pore volume causes problems such as adsorption of low-molecular-weight impurities and residual cleaning substances, and also causes problems such as a reduction in cleaning efficiency.

[0006] In particular, in the case of targeting a polymer such as a nucleic acid, the surface of silica gel is selectively used by reducing the specific surface area and the number of pores.
It is thought that the result will increase the accuracy of adsorption and extraction,
When only the surface of silica gel is used, the number of reaction sites decreases, and the efficiency of the reaction is not high. Therefore, it is desired to eliminate the small pores and leave the large pores so that the reaction occurs not only on the surface of the silica gel but also in the pores, thereby increasing the reaction sites and increasing the reaction efficiency. . In addition, it is expected that elimination of small pores can suppress the adsorption of low molecular weight impurities and a decrease in cleaning efficiency.

[0007]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide an adsorbent, a carrier for adsorption,
Useful as an extractant or an extraction carrier, a catalyst carrier, etc., the specific surface area is small, having a sufficient pore volume, and the silica particles having a large pore diameter magnetism and a large pore diameter, such a large pore diameter An object of the present invention is to provide a method for easily producing magnetic silica particles.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a raw material for forming silica particles contains a certain amount of a magnetic substance to form a gel. When manufacturing magnetic silica particles provided with magnetism, by focusing on physical properties such as gel average particle size, BET specific surface area, pore diameter, pore volume, shape such as pore volume, pore characteristics, etc. The magnetic silica particles useful as various adsorption carriers, extraction carriers, and catalyst carriers are obtained, that is,
Magnetic silica particles having physical properties suitable for various carriers can be easily produced by contacting the Si alkoxide polymer with a magnetic material to form a sphere, then gelling, washing, hydrothermal treatment, drying and baking treatment. In particular, it has been found that large diameter pores in magnetic silica particles can be left or further increased by hydrothermal treatment, and small diameter pores can be reduced or eliminated, and the present invention has been completed.

That is, the present invention relates to a silica particle containing a magnetic substance, wherein the content of the magnetic substance is 5 to 50% by weight of the total amount, and the silica particle has an average particle diameter of 1 to 200 μm.
m, the BET specific surface area is less than 100 m ² / g, the pore diameter is 10 nm or more, and the pore volume is 0.1 μm.
The present invention relates to a magnetic silica particle having a large pore diameter, which is 3 to 2.5 ml / g, and a method for producing the same.

Hereinafter, the present invention will be described in detail.

First, the magnetic silica particles of the present invention will be described.

The magnetic substance used in the magnetic silica particles of the present invention is not particularly limited as long as it is a substance exhibiting magnetic properties. However, when a magnetic force is applied, strong magnetism is generated and the magnetic force disappears. And what shows what is called superparamagnetism and its magnetism also disappears is preferable. Examples of those exhibiting such properties include spinel-type and plumbite-type ferrites and alloys containing iron, nickel, cobalt, or the like as a main component. Among these, a magnetic fluid obtained by suspending ultrafine particles of magnetite or ferrite in water or an organic solvent is preferably used, and the magnetic fluid is a magnetic fluid having a diameter of about 10 nm or less such as magnetite or ferrite. And a colloidal fluid suspended in an organic solvent.

The content of the magnetic substance in the magnetic silica particles is preferably 5 to 50% by weight of the total amount of the magnetic silica particles, and more preferably 5 to 50% by weight.
Preferably, it is in the range of 25% by weight. Within this range, the magnetic properties of the obtained magnetic silica particles will be sufficient, and there will be no problem with the reaction efficiency and separation operation in application, and the surface of the obtained magnetic silica particles will be chemically modified. Easy. Further, also on the manufacturing side, the shape of the magnetic silica particles can be made spherical, and it is possible to avoid that the magnetic substances are not uniformly dispersed inside the silica particles due to strong aggregation of the magnetic substances.

The average particle size of the magnetic silica particles of the present invention is preferably from 1 to 200 μm. If the average particle size is less than 1 μm, the particles are too small, it takes too much time for separation, or it may not be possible to obtain a desired flow rate when used in a fixed bed as a catalyst carrier, If it exceeds 200 μm, the gel may be destroyed on the actual use surface, and the shape may not be maintained.

The range of the BET specific surface area of the magnetic silica particles of the present invention is such that the ratio of the area in the pores of the particles to the area of the particle surface is low, and a solvent or low molecular weight impurities are contained in the particles in the application. It is preferably less than 100 m ² / g in order to improve the accuracy of the operations such as adsorption and extraction and the processing time.

As shown in Examples, the pore structure of the magnetic silica particles of the present invention can be measured as a pore size distribution by a mercury intrusion method using a pore sizer or the like. Here, as the pore structure, a pore diameter and a pore volume are required, but as the pore diameter of the magnetic silica particles of the present invention, the measurement limit of the measuring device used and the size of the particles to be measured are taken into consideration. Is determined.

In the present specification, the pore diameter means a pore diameter within a certain range of pore diameter distribution to be measured. In terms of application, high molecular weight substances such as nucleic acids are not only present on the surface of magnetic silica particles but also on the surface of magnetic silica particles. Since the inside of the pores is also used as a site for adsorption or reaction, the thickness is preferably 10 nm or more in order to prevent low molecular weight impurities and the like from being trapped in the pores and remaining in the particles. In addition, the upper limit of the pore size is required to be such that the strength of the particles is not reduced and the object of the present invention cannot be achieved.However, when measuring the pore size, the gap between the particles, for example, , 5μm
When the spherical particles are closest packed, the gap is about 750 nm. Since it is difficult to distinguish between the gap and the pore diameter of the particles, it is difficult to clearly define the gap.
Any particles having a pore diameter of about 0 nm or less may be used.

In addition, it is preferable that the pore mode diameter, which is the most frequent in the pore diameter distribution, is large. In terms of application, high molecular weight substances such as nucleic acids are adsorbed or reacted not only on the surface of the magnetic silica particles but also inside the pores. In order to prevent impurities such as low molecular weight from being trapped in the pores and remaining in the particles, a substance having a molecular weight of 10 nm or more and a high molecular weight substance is more likely to enter the pores. It is preferable that the thickness be 25 nm or more in order to make it usable.

Further, the range of the pore volume of the magnetic silica particles of the present invention is preferably from 0.3 to 2.5 ml / g. When the pore volume is less than 0.3 ml / g, the number of reaction sites decreases, and the reaction efficiency may decrease,
If the pore volume is larger than 2.5 ml / g, the gel strength may be reduced and the gel may be broken during use. further,
When this range is 0.5 to 2.0 ml / g, it is even more preferable in terms of reaction efficiency and gel strength.

Next, the method for producing the magnetic silica particles of the present invention will be described.

The starting material of the magnetic substance in the magnetic silica particles of the present invention is desirably a magnetic fluid, and its production method can be carried out by a known method. Can be manufactured.

A) hydrolyzing the Si alkoxide with an acid,
Forming a Si alkoxide polymer, at least Si
B) a step of obtaining a solution containing an alkoxide polymer; b) a step of adding a magnetic substance to the solution containing at least the Si alkoxide polymer obtained in step a) to obtain a mixture containing the Si alkoxide polymer and the magnetic substance; Contacting the mixture obtained in the step with water to form a spheroid, and then adding a basic substance to form a gel; d) washing the gel obtained in the step c), followed by hydrothermal treatment under pressure while heating; E) replacing the gel obtained in step d) with a solvent, and then drying the gel to obtain magnetic silica particles.

Step a) The Si alkoxide used in the production method of the present invention can be used without particular limitation as long as it produces a polymer by hydrolysis in the production method described below. OCH ₃ ) ₄ , Si (OC _{2
H 5) 4, Si (O} -n-C 3 H 7) 4, Si (O-i-C 3
H ₇ ) ₄ , Si (On-C ₄ H ₉ ) ₄ , Si (O-i-C ₄₎
H ₉ ) _{4 and the} like. In the production method of the present invention, in addition to the Si alkoxide, Ti, Zr,
Other metal alkoxides such as Al may be added.

First, the alkoxide of Si is partially hydrolyzed in an acidic solution so as not to gel. As the acidic solution, a mixed solution of an acid, water and an organic solvent is preferable. Examples of the acid used at this time include inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid, and organic acids such as acetic acid and formic acid. As the organic solvent, those which are uniformly mixed with an acid, water and a Si alkoxide are preferable, and alcohols such as methanol and ethanol are particularly preferable. The amount of water to be added is preferably an amount that partially hydrolyzes the Si alkoxide, that is, within 4 moles per mole of the Si alkoxide. The conditions of the hydrolysis reaction may be such that the mixed solution is stirred at a temperature of 10 to 80 ° C. for 30 minutes to 5 hours in order to uniformly hydrolyze the Si alkoxide.

After hydrolyzing the Si alkoxide, the Si alkoxide solution is polymerized. The polymerization may be carried out at a temperature in the range of 10 to 200 ° C. for 1 to 48 hours. After the reaction, a solvent or an alcohol generated by the reaction is removed to obtain a Si alkoxide polymer.
The degree of polymerization, ie, the molecular weight, of the Si alkoxide polymer can be controlled by the amount of water, the polymerization temperature, the polymerization time, and the like.

There is a correlation between the degree of polymerization of the Si alkoxide polymer and the viscosity. The higher the degree of polymerization of the Si alkoxide polymer, the higher the viscosity. The degree of polymerization of the Si alkoxide polymer is such that gelation does not occur, and the viscosity at room temperature is preferably in the range of 10 to 1000 mPa · s, more preferably 20 to 500 mPa · s. The reason is that if the viscosity exceeds 1000 mPa · s, it may be difficult to uniformly disperse the magnetic substance in the Si alkoxide polymer in the subsequent step b), and if the viscosity is less than 10 mPa · s, c)
This is because gelation may be difficult to occur when gelling is performed. The viscosity referred to herein is, for example, 25 ° C. in accordance with JIS-K-7117-1987.
Can be confirmed by measuring the viscosity at.

The obtained Si alkoxide polymer is used as it is, or is diluted with an organic solvent to prepare a mixed solution to prepare a solution containing at least the Si alkoxide polymer. When diluting the Si alkoxide polymer with an organic solvent, hexane,
Those which are hardly soluble in water, such as hydrocarbons such as cyclohexane and benzene, and alcohols such as 1-butanol, 2-butanol, 1-pentanol, 2-pentanol, 1-hexanol and 2-hexanol are preferred. The reason for this is that when producing magnetic silica particles, the phase containing the Si alkoxide polymer is dispersed in water to perform spheroidization.
Further, the concentration of the Si alkoxide polymer when diluted with an organic solvent is preferably 20% by weight or more based on the total amount of the solution diluted to obtain a spherical gel.

Step b) Next, a magnetic substance is added to the solution containing at least the Si alkoxide polymer obtained in step a) to obtain a mixture containing the Si alkoxide polymer and the magnetic substance. As the magnetic substance to be used, from the aspect of dispersibility in the Si alkoxide polymer, those obtained by dispersing in water or an organic solvent to form a suspension or solution are preferable, and those further containing an organic solvent as a dispersant are preferable. In particular, a magnetic fluid having a small particle diameter of about 10 nm and having good dispersibility of the magnetic particles in a Si alkoxide polymer and good stability thereof is preferably used. As the magnetic fluid, a commercially available product or the like can be used as it is or after performing solvent substitution or the like.

Here, in dispersing the magnetic substance into the polymer, it is preferable to uniformly disperse the magnetic substance in a mixed solution of the Si alkoxide polymer and its diluent solvent.

When the magnetic substance is added to the Si alkoxide polymer, a predetermined amount of the magnetic substance can be directly added, or a solution in which the magnetic substance is dispersed in a solvent in advance is added to the S alkoxide polymer.
It can also be added to i-alkoxide polymers.

In preparing a solution in which the magnetic substance is dispersed in a solvent, it is preferable to use a low-polarity organic solvent as the solvent in order to ensure the dispersibility of the magnetic substance in the Si alkoxide polymer. . Specific examples of such organic solvents include hydrocarbons such as hexane, cyclohexane, and benzene, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol, 1-hexanol,
-Alcohols such as hexanol. Further, among these, alcohols having 4 to 6 carbon atoms are preferably used. The reason for this is that the mixture containing the Si alkoxide polymer and the magnetic substance is brought into contact with water in the following step c) to form a suspension, and spheroidization is performed. This is because it is suitable to maintain the following and to promptly perform the subsequent gelation reaction.

Further, in order to disperse the magnetic material mixed with the solvent or the magnetic material in the magnetic fluid and to stabilize the dispersion state by eliminating the aggregation of the magnetic materials, the surface of the magnetic material or the vicinity of the surface is surface-active. It is preferable to treat with an agent or the like or to add a surfactant. In addition, when the magnetic material is mixed with the Si alkoxide polymer, the degree of polymerization of the Si alkoxide polymer may be within the above-described viscosity range in order to uniformly disperse the magnetic material. Within this range, S
This is because the molecular weight of the i-alkoxide polymer contributes to the dispersibility and stability of the magnetic material, and the operation becomes easy because the i-alkoxide polymer does not become viscous.

As described above, by combining the type of the magnetic substance, the degree of polymerization of the Si alkoxide polymer, and the solvent for diluting the Si alkoxide polymer, the magnetic substance is uniformly dispersed in the Si alkoxide polymer to contain the Si alkoxide polymer and the magnetic substance. A mixture can be obtained.

Step c) Next, the mixture containing the Si alkoxide polymer and the magnetic substance obtained in step b) is dispersed in water with stirring, suspended, and spheroidized. Here, in order to further improve the dispersibility of the magnetic substance, a dispersant such as a surfactant and polyvinyl alcohol may be added to water used.

After the spheroidization, a basic substance is added to the above-mentioned mixture or mixture to gel. Although the detailed mechanism of the gelation is not clear, the alkoxide group in the Si alkoxide polymer is hydrolyzed by the action of a basic substance to form a silanol group, and the silanol group is bonded three-dimensionally by a condensation reaction to form silica. It is considered that the formation of a polymer causes gelation. Examples of the basic substance to be used include inorganic basic compounds such as ammonia, sodium hydroxide and potassium hydroxide, and organic basic compounds such as amine and urea. In order to almost completely hydrolyze the alkoxy group in the Si alkoxide polymer during gelation, stirring may be performed for 1 to 10 hours in a pH range of pH 8 to 11 and a temperature range of 30 to 100 ° C.

Step d) The gel obtained in step c) is separated by filtration, centrifugation, etc., and washed. A known method can be used as a method for filtration and separation, and water that is generally used such as water or warm water can be used for washing.

Next, the washed magnetic silica gel is subjected to hydrothermal treatment while applying pressure under heating.

The apparatus used for this hydrothermal treatment includes:
Any device such as an autoclave that can apply conditions of pressure and heating while charging a solution may be used. Then, the magnetic silica gel is charged into an autoclave, an aqueous alkali solution such as water or aqueous ammonia is added, and the conditions of predetermined temperature and pressure are set to perform the hydrothermal treatment.

The conditions of the hydrothermal treatment are 110 to 380
The reaction is preferably performed at a temperature of 150C and a pressure of 1.4 to 220 atmospheres, and more preferably at a temperature of 150 to 250C and a pressure of 4 to 40 atmospheres. Within this range, as a result of the hydrothermal treatment, although the specific surface area of the obtained magnetic silica gel is reduced, the average pore diameter is increased, which is extremely useful in terms of reaction efficiency. On the other hand, when the temperature is lower than 110 ° C., the hydrothermal conditions may be insufficient, and the pore diameter may not be increased.
If the temperature is higher than ° C., the apparatus may be so large that temperature control may not be performed well or it may not be economical. The time for the hydrothermal treatment is not constant depending on the temperature and pressure conditions, but usually 1 to 24 hours is sufficient.

Step e) Further, the gel obtained in step d) is solvent-substituted and dried.

As for the drying conditions, if the water inside the gel and the surface of the gel is directly evaporated, the gel shrinks and agglomerates.

That is, after the water in the washed gel is replaced with an organic solvent, the gel is dried by removing the organic solvent by heating or the like. This substitution treatment with an organic solvent
In order to prevent the gels from aggregating strongly due to the capillary force generated when water present inside the gel evaporates, the gel is replaced with an organic solvent with a low surface tension in advance to weaken the capillary force and facilitate drying of the gel. This is because As the organic solvent used in the substitution treatment, a solvent having a lower surface tension than water is preferable, and a solvent that dissolves in water at an arbitrary ratio is more preferable. Here, a solvent having a lower surface tension than water can be selected as a solvent having a surface tension smaller than that of water having a surface tension of 72 dyn / cm (= 10 Nm) at 25 ° C. by the Wilhelm method with respect to air. For example, methanol, ethanol, 1-
Examples include alcohols such as propanol, 2-propanol and 1-butanol, formamide, N, N-dimethylformamide, ethylene glycol, propylene glycol and the like.

The water and solvent remaining in the gel after the replacement with the organic solvent are usually removed by heating at normal pressure.
It can also be carried out under reduced pressure only under reduced pressure or under heating.
If the gel is strongly aggregated, the gel may be dispersed again in water or an organic solvent, replaced with an organic solvent, and then heated and removed to prevent the gel from aggregating.

The magnetic silica particles can also be dried by adding an organic solvent and heating to remove water in the gel together with the solvent used. As the organic solvent used here, a solvent having a higher boiling point and a lower surface tension than water is preferable, and alcohols such as 1-butanol, isobutyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, and isoamyl alcohol; Esters such as methyl butyrate and ethyl butyrate; ketones such as cyclopentanone, 3-heptanone and 4-heptanone; The removal of water and the solvent is usually performed at normal pressure, but may be performed under reduced pressure.

Further, the dried silica gel obtained in step e) may be calcined to improve the strength. As the firing conditions, magnetic silica particles can be obtained by firing in an air atmosphere, an inert atmosphere such as nitrogen gas, or a reducing atmosphere such as hydrogen gas. The temperature condition at the time of firing is preferably 1000 ° C. or lower in order to maintain the pore structure of the obtained magnetic silica particles.
If the sintering temperature exceeds 1000 ° C., the magnetic silica particles shrink and the pore diameter becomes small, so that particles having a large pore diameter may not be obtained.

When the surface of the obtained magnetic silica particles is chemically modified, the specific surface area of the magnetic silica particles is small,
When the amount of silanol groups present on the surface is small, silica particles can be brought into contact with hydrofluoric acid or the like in advance to adjust the amount of silanol groups on the surface before use.

According to the above method, the magnetic silica particles of the present invention can be obtained.

Further, the magnetic silica particles of the present invention have silanol groups on the surface, and can be used as they are for adsorption, extraction and reaction mainly by utilizing hydrophilic interaction. The surface of the magnetic silica particles can be chemically modified, for example, by introducing a hydrophobic group, and can be used for applications utilizing hydrophobic interaction.

Further, it is combined with proteins such as antibodies and enzymes, peptides and nucleic acids, which are biological materials, and used for various measuring methods such as immunoassay and nucleic acid measurement, and separation means such as affinity chromatography. It can also be used as an immobilization carrier. Further, it can be used as a magnetic material or a spacer.

Although the magnetic silica particles of the present invention have a small specific surface area despite having a large pore diameter, the silica in the gel is dissolved and reprecipitated by subjecting the obtained magnetic silica particles to a hydrothermal treatment. Thus, the pores with small diameters in the pores hardly disappear, however, those with large diameters in the pores are considered to maintain or rather increase in diameter, and as a result, the silica matrix becomes strong, It is expected that the compressive strength, abrasion resistance, and impact resistance are improved, and the ratio of the large-diameter pores increases.

However, such presumption does not restrict the present invention at all.

[0052]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. In addition, each evaluation was implemented by the method shown below.

The magnetic fluid used in the examples was measured for magnetic hysteresis using a vibrating sample magnetometer (VSM) (manufactured by RIKEN ELECTRONICS, model: BHV-50). It was shown.

(1) Content of magnetic substance Regarding Si, magnetic silica particles were decomposed by aqua regia,
It was treated with perchloric acid and measured by a gravimetric method. Fe (iron) was decomposed with nitric acid / hydrofluoric acid, treated with perchloric acid, and measured by ICP emission method.

(2) Average Particle Size A part of the magnetic silica particles was subjected to scanning electron microscope ISI-1.
30 (manufactured by COULTER) and determined by an intercept method.

(3) Pore Structure The pore structure was measured in a pressure range of 0 to 207 MPa by a mercury intrusion method using a pore sizer 9320 (manufactured by MICROMERITICS). In addition, as a result obtained, 6 nm which is a measurement limit was set as the lower limit of measurement, and 500 nm was set as the upper limit of measurement in order to prevent the gap between particles from being reflected in the measurement.
Then, the pore diameter range, the pore mode diameter indicating the most frequent pore diameter in the pore diameter distribution, and the pore volume were measured.

(4) BET specific surface area The BET specific surface area was measured by MONOSORB (manufactured by QUANTACHROME, USA) according to the BET one-point method.

(5) Viscosity In accordance with JIS-K-7118-1987, the viscosity at 25 ° C. was measured with a B-type viscometer (manufactured by Tokyo Keiki, Model: BH).

(6) Internal Analysis of Gel The distribution of the magnetic substance inside the magnetic silica particles was measured by the following method. That is, the magnetic silica particles were embedded in an epoxy resin and cut with a microtome. After this, C (carbon) is deposited on the surface, and this is JCMA-
Using 733 (manufactured by JEOL Ltd.), a scanning electron microscope (SEM) was first used to confirm the shape of the magnetic silica particles.
EPMA (Electron Probe Mi)
(Croanalysis), the distribution of Si and Fe in the magnetic silica particles was analyzed.

Example 1 75.0 g of Si (OC ₂ H ₅ ) ₄ and ethanol.
0 g of the mixed solution was stirred at 40 ° C. for 30 minutes. While stirring this mixed solution at 40 ° C., a 1/100 N aqueous hydrochloric acid solution is used.
7.5 g were added dropwise. After stirring this solution for 1 hour, 9
The mixture was stirred at 0 ° C. for 4 hours and further at 165 ° C. for 12 hours to remove distillate to obtain a Si alkoxide polymer. This operation was performed in a nitrogen atmosphere. When the viscosity of the obtained Si alkoxide polymer was measured by the method described above, the viscosity was 75 centipoise at room temperature. 35.0 g of the obtained Si alkoxide polymer was dissolved in 35.0 g of 1-pentanol. To this solution, 10 ml of a commercially available magnetic fluid (manufactured by Ferrotec Co., Ltd .: 35% by weight of magnetic substance, 10% by weight of surfactant, containing 1-butanol solution, based on the total amount) was added, and the homogeneous solution was added. Obtained. This solution was added to 280.0 g of a 5% aqueous solution of polyvinyl alcohol at 80 ° C. while stirring. After stirring for 30 minutes, 12.5 ml of a 5% by weight aqueous ammonia solution was added, and the mixture was stirred at 80 ° C. for 3 hours. 70 ° C.
Was poured into 500 ml of warm water, and the solid was collected by filtration and washed with warm water. After washing, the magnetic silica particles were subjected to hydrothermal treatment in an autoclave at a temperature of 180 ° C. under a pressure of 10 atm for 4 hours. Next, substitution with 2-propanol three times,
Drying under vacuum yielded magnetic silica particles. The Fe content, the Si / Fe composition (molar ratio), the average particle size, and the BET specific surface area of the obtained magnetic silica particles were measured by the methods described above, and the results are shown in Table 1. When the obtained magnetic silica particles were observed by the above-mentioned SEM, they were spherical. Furthermore, when the distribution of Si and Fe in the magnetic silica particles was analyzed by EPMA, it was confirmed that Fe, that is, the magnetic substance was uniformly dispersed in the magnetic silica particles.

[0061]

[Table 1]

When the obtained magnetic silica particles were measured for pore size distribution, pore volume and the like by the mercury intrusion method using the above-mentioned pore sizer 9320, the pore size range was 10 as shown in Table 1. ５００500 nm (measurement upper limit), and the pore mode diameter showing the peak is 25 nm.
The pore volume was 1.56 ml / g.

Example 2 In the same manner as in Example 1, the gel, which had been subjected to the water washing treatment, was placed in a 1.5% by weight aqueous ammonia solution and placed in an autoclave at a temperature of 220 ° C. and a pressure of 23 atm. Hydrothermal treatment was performed for 4 hours. The viscosity of the Si alkoxide polymer was 68 centipoise at room temperature. continue,
Next, the mixture was replaced with 2-propanol three times and dried under vacuum to obtain magnetic silica particles. The obtained magnetic silica particles were measured in the same manner as in Example 1, and the results are shown in Table 1. When the obtained magnetic silica particles were observed by the above-mentioned SEM, they were spherical. Furthermore, when the distribution of Si and Fe in the magnetic silica particles was analyzed by EPMA, it was confirmed that Fe, that is, the magnetic substance was uniformly dispersed in the magnetic silica particles.

Further, the obtained magnetic silica particles were prepared in Example 1.
The pore size distribution, pore volume, and the like were measured in the same manner as in Example 1. As shown in Table 1, the pore size was 10 to 500 nm (measurement upper limit), and the pore mode size showing the peak was 40 n.
m and the pore volume was 1.58 ml / g.

Comparative Example 1 In the same manner as in Example 1, the gel which had been subjected to the water washing treatment was used as it was without hydrothermal treatment, replaced with 2-propanol three times, and dried under vacuum to obtain spherical magnetic silica particles. Obtained. The viscosity of the Si alkoxide polymer is 8 at room temperature.
It was 2 centipoise. The obtained magnetic silica particles were measured in the same manner as in Example 1, and the results are shown in Table 1.

Further, the obtained magnetic silica particles were prepared in Example 1.
When the pore diameter distribution, the pore volume, and the like were measured in the same manner as described above, the pore diameter was 300 nm or less, as shown in Table 1,
The pore mode diameter showing the peak was 30 nm,
The peak height is also low, and the lower limit of this measurement is 6
There are pores near nm, and the BE
From the fact that the T specific surface area is as large as 356 m ² / g, it can be estimated that pores are present at 6 nm or less, which is below the measurement limit. Further, the pore volume was as small as 0.87 ml / g.

Comparative Example 2 In the same manner as in Example 1, the gel which had been subjected to the water-washing treatment was placed in a 1.5% by weight aqueous ammonia solution and placed in an autoclave at a temperature of 105 ° C. and a pressure of 1.2 atm. And a hydrothermal treatment for 4 hours. The viscosity of the Si alkoxide polymer was 70 centipoise at room temperature. Subsequently, the resultant was replaced with 2-propanol three times and dried under vacuum to obtain magnetic silica particles. The obtained magnetic silica particles were measured in the same manner as in Example 1, and the results are shown in Table 1.

Further, the obtained magnetic silica particles were prepared in Example 1.
The pore size distribution was measured in the same manner as in Example 1. As shown in Table 1, the pore size was 300 nm or less, and the pore mode size showing the peak was 10 nm, but the lower limit value of this measurement was 6 nm. Since the particles have a large BET specific surface area of 132 m ² / g, it can be estimated that pores exist at 6 nm or less, which is below the measurement limit. Further, the pore volume is 1.44 ml /
g.

Comparing the results of Examples 1 and 2 with the results of Comparative Examples 1 and 2, it was found that by subjecting the magnetic silica particles to an appropriate hydrothermal treatment, the shape and particle size of the particles were almost unchanged. It can be seen that the pore diameter increases and the specific surface area further decreases. This is because the magnetic silica obtained by increasing the conditions of hydrothermal temperature and hydrothermal pressure in Comparative Example 1 without hydrothermal treatment and Comparative Example 2, Example 1, and Example 2 was gradually increased. This is supported by the large pore mode diameter of the particles. Further, it can be seen that the pore volume is increased by performing the hydrothermal treatment.

[0070]

The magnetic silica particles of the present invention are spherical,
It contains a sufficient amount of magnetic material inside and has a sufficiently large pore volume. And, despite its large pore size, the specific surface area is relatively small. Furthermore, since the silica bond is reconstructed by the hydrothermal treatment, the silica matrix is strengthened, and it can be expected that the compressive strength, abrasion resistance and impact resistance are improved. Therefore, it can be suitably used as an adsorbent, an adsorption carrier, an extractant, an extraction carrier, and a catalyst carrier.

Further, according to the production method of the present invention, magnetic silica particles having a small specific surface area, a large pore diameter, and a sufficiently large pore volume can be easily produced.

Continued on front page F-term (reference) 4G069 AA01 AA08 BA02A BA02B BA08B BA21C BA38 BC66B BE06C BE32C EA04X EB18X EB18Y EC02X EC02Y EC03Y EC06X EC07X EC07Y EC08X EC08Y EC11X EC12X EC13X EC14 EC02 EB08 EB14 BB07 BB15 CC13 GG01 GG03 HH30 JJ09 JJ11 JJ13 KK01 KK03 LL06 LL11 LL15 MM01 PP17 RR05 RR12 RR20 TT01 TT06 TT08 TT09 UU11 UU17 5E040 AA11 AB02 AB04 CA12 CA20 HB03 HB07 NN17NN

Claims (9)

[Claims] 1. A silica particle containing a magnetic substance, wherein the content of the magnetic substance is 5 to 50% by weight of the total amount, the average particle diameter of the silica particle is 1 to 200 μm, and the BET specific surface area is 100 m ^2. / G, a pore diameter of 10 nm or more, and a pore volume of 0.3 to 2.5 ml / g. 2. The large-diameter magnetic silica particles according to claim 1, wherein the magnetic silica particles are spherical. 3. The magnetic silica particles having a large pore diameter according to claim 1, wherein the magnetic material has a superparamagnetic structure. 4. A process for producing magnetic silica particles having a large pore size, comprising the steps of: a) hydrolyzing a Si alkoxide with an acid to form a Si alkoxide polymer and obtaining a solution containing at least the Si alkoxide polymer; Adding a magnetic substance to the solution containing at least the Si alkoxide polymer obtained in the step to obtain a mixture containing the Si alkoxide polymer and the magnetic substance; c) bringing the mixture obtained in the step b) into contact with water to form a spheroid; Then, a step of gelling by adding a basic substance, d) a step of subjecting the gel obtained in the step c) to washing, and then performing a hydrothermal treatment while applying pressure under heating, and e) removing the gel obtained in the step d) Solvent-substituting, and then drying to obtain magnetic silica particles, wherein at least five steps are performed.
4. The method for producing magnetic silica particles having a large pore diameter according to any one of 3. 5. The method for producing magnetic silica particles according to claim 4, wherein the gel is dried and then calcined in step e) of the method for producing magnetic silica particles according to claim 4. 6. The process for producing magnetic silica particles having a large pore diameter according to claim 4 or 5, wherein the Si alkoxide polymer has a viscosity of 10 to 100 at 25 ° C.
A method for producing magnetic silica particles having a large pore diameter, which is 0 mPa · s. 7. A large-pore magnetic material according to claim 4, wherein a magnetic fluid is used as a raw material of the magnetic material in step b) of the method for producing large-pore magnetic silica particles according to claim 4. A method for producing silica particles. 8. In the step d) of the method for producing magnetic silica particles having a large pore diameter according to any one of claims 4 to 7, hydrothermal treatment is performed in an autoclave at 110 to 380 ° C. and 1.4 to 220 atm. A method for producing magnetic silica particles having a large pore diameter, characterized by comprising: 9. The method according to claim 4, wherein in the step e) of the process for producing magnetic silica particles having a large pore diameter, the treatment comprises replacing water in the gel with an organic solvent having a lower surface tension than water. And then removing the silica particles.