JP2005089240A - Mesoporous silica particulate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide mesoporous silica particulates useful as an ink absorbent for inkjet recording paper, low-dielectric film, catalyst support, separating agent, adsorbent and medical carrier for medicines, and to provide a dispersion and a granulated body consisting of the mesoporous silica particulates. <P>SOLUTION: The mesoporous silica particulates have an average particle diameter of 1 μm or less, wherein the volume of mesopores having a diameter of 2 to 50 nm is 0.7 mL/g or more and the geometric standard deviation of a mesopore distribution is 2.0 or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a novel fine particle mesoporous silica. Specifically, fine particle mesoporous silica having a particle size of the order of submicron and useful as a catalyst carrier, a separating agent, an adsorbent, a pharmaceutical carrier such as a pharmaceutical, a low dielectric constant film, an ink absorbent for ink jet recording paper, etc. It is to provide.

  Mesoporous silica is a new material having pores with pore diameters in the range of 2 to 50 nm (hereinafter referred to as mesopores) and is expected to be applied in various fields such as catalyst carriers and separation agents. At this time, like other inorganic materials, it is often preferable to be fine particles.

  For example, in the field used as a thin film such as an ink absorbent for ink jet recording paper and a low dielectric constant film, it is indispensable to make mesoporous silica fine particles in order to obtain a smooth and homogeneous film. Of fine particles is required.

  Further, in the fields of catalyst carriers, separating agents, adsorbents, drug carriers such as pharmaceuticals, etc., they are used after being granulated or molded, or are used by being uniformly dispersed in a matrix. In order to improve the mechanical strength of the molded body and the dispersibility in the matrix, it is necessary to make mesoporous silica fine particles.

  From the above requirements, it is necessary to make mesoporous silica into fine particles. However, when mesoporous silica is pulverized into fine particles, the mesopores, which are the biggest feature of mesoporous silica, collapse, and the value as a material is significantly reduced. There was a problem.

  In particular, when mesoporous silica is micronized to the submicron order, the mesopores are significantly collapsed and the mesoporous volume of mesoporous silica is greatly reduced.

  In view of the above problems, the present inventors have already proposed a method of obtaining fine-particle mesoporous silica by treating a mixed solution obtained by mixing mesoporous silica and a cationic resin in an aqueous solvent with a high-pressure homogenizer (Patent Document). 1).

  However, the mesoporous silica produced by such a method has a wide distribution of mesopores and has a problem in the uniformity of mesopores. It was difficult to apply. In addition, since a cationic resin is essential, its use is limited.

  Further, as a method for pulverizing while preventing the mesoporous structure from collapsing, a wet pulverizing method using an organic solvent as a dispersion medium has been proposed (see Patent Document 2).

  Although the above method has a certain effect, it can only be finely divided to about 10 μm, and there is a problem that the volume of mesoporous silica in mesoporous silica is greatly reduced when the fine particle is made to submicron order.

JP 2002-356621 A JP 2000-44227 A

  Accordingly, an object of the present invention is to provide fine particle mesoporous silica having a particle size on the order of submicron and having sufficient mesopore volume and mesopore uniformity.

  Another object of the present invention is to provide a mesoporous silica dispersion comprising the above-mentioned fine particle mesoporous silica, which is useful for a coating liquid for forming a thin film such as an ink receiving layer of an ink jet recording paper or a low dielectric constant film, and a catalyst carrier, Another object of the present invention is to provide a mesoporous silica granule composed of the fine particle mesoporous silica, which is useful as a separating agent, an adsorbent, a pharmaceutical carrier for pharmaceuticals, and the like.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, the present inventors have succeeded in producing fine particle mesoporous silica having a particle size on the order of submicron as disclosed below and having sufficient mesopore volume and mesopore uniformity, thereby completing the present invention. It came.

  That is, according to the present invention, fine mesoporous silica having an average particle size of 1 μm or less, the pore volume in the range of 2 to 50 nm is 0.7 mL / g or more, and the mesopore fineness is small. There is provided fine mesoporous silica characterized by a geometric standard deviation of pore distribution being 2.0 or less.

  Moreover, according to this invention, the mesoporous silica dispersion liquid and mesoporous silica granule which consist of the said fine particle mesoporous silica are also provided.

  According to the present invention, there is provided a novel fine particle mesoporous silica having both a sufficient mesopore volume and mesopore uniformity at an average particle size of 1 μm or less, which has not been achieved conventionally. For example, such fine particulate mesoporous silica exhibits a characteristic that glossiness and print density are greatly improved as compared with the conventional one when used for an ink absorbent for ink jet recording paper. The particulate mesoporous silica of the present invention is useful not only for the above-mentioned applications but also as a low dielectric constant film, a catalyst carrier, a separating agent, an adsorbent, a pharmaceutical carrier for pharmaceuticals, and the like.

  The fine particle mesoporous silica of the present invention is characterized by having an average particle diameter of 1 μm or less. The mesoporous silica having such an average particle diameter can obtain a smooth and homogeneous film in applications where the mesoporous silica is coated. Moreover, since the mechanical strength at the time of granulation or shaping | molding is high, it is useful for uses, such as a catalyst support | carrier, a separating agent, and an adsorption agent.

  In addition, among the particulate mesoporous silica having the above average particle size, those having an average particle size of 0.5 μm or less are preferable, and those having a particle size of 0.3 μm or less are particularly preferable. The lower limit of the average particle diameter is not particularly limited, but is generally 0.01 μm or more.

  The fine-particle mesoporous silica of the present invention is characterized in that the mesopore volume is as large as 0.7 mL / g or more while having fine particles as described above. When mesoporous silica having such mesopore volume is coated, the porosity of the resulting film increases, so that the ink absorption capacity can be increased in ink jet recording paper, and the dielectric constant in the low dielectric constant film can be increased. Can be reduced. Further, mesoporous silica having such a mesopore volume has excellent catalytic activity in the catalyst carrier, separation efficiency in the separating agent, adsorption capacity in the adsorbent, and loading on the drug carrier.

  In addition, among the particulate mesoporous silica having the mesopore volume, those having a mesopore volume of 1.0 mL / g or more are particularly preferable. The upper limit value of the mesopore volume is not particularly limited, but is generally 3 mL / g or less.

In addition to the above-described features, the fine-particle mesoporous silica of the present invention has a feature that the geometric standard deviation (hereinafter referred to as σ _p ) of the pore distribution of the mesopores is 2.0 or less.

Such sigma _p is an index representing the uniformity of the pore size of the mesopores, the pore size of the mesopores as the sigma _p is small becomes uniform.

The fine-grained mesoporous silica having the above σ _p has a very uniform pore size, so that it is possible to selectively treat a substance having a specific size in applications such as a catalyst carrier, a separating agent, and an adsorbent. .

Among the fine particulate mesoporous silica having the above σ _p , those having a geometric standard deviation of 1.7 or less are particularly preferable. The lower limit of σ _p of mesoporous silica is not particularly limited, but is generally 1 or more.

  The particulate mesoporous silica of the present invention is an amorphous silica and is extremely advantageous in terms of safety because there is no possibility of producing crystalline free silicic acid. On the other hand, crystalline silica often produces crystalline free silicic acid in the process of manufacture and use, and this crystalline free silicic acid causes silicosis, a disease that is difficult to treat. Cost.

In addition, the fine particle mesoporous silica of the present invention preferably has a geometric standard deviation (hereinafter referred to as σ _d ) of the particle size distribution of 1 to 3, particularly preferably 1.5 to 2.5.

The σ _d is an index representing the uniformity of the particle diameter. The smaller the σ _d is, the more uniform the particle diameter is.

Mesoporous silica having σ _d of 1 or more further improves the packing density of particles when granulated or molded. This is because, as described in Chemical Engineering Papers, Vol. 11, No. 4, No. 4, 1985, p. 438, the space ratio of the packed bed decreases as the particle size distribution increases. Therefore, such mesoporous silica is easily densified when granulated or molded, and can form a granulated body or molded body with higher mechanical strength with a small amount of binder. Further, when the container is filled with mesoporous silica, the container can be made compact. On the other hand, mesoporous silica with σ _d exceeding 3 contains coarse particles and extreme fine particles, and thus may cause a problem in handling.

  Moreover, it is preferable that the fine particle mesoporous silica of this invention has an average pore diameter of mesopores of 5 nm or more. In other words, mesoporous silica having an average pore diameter of 5 nm or more is useful for the above-mentioned various uses, and can adsorb, separate, or carry high-molecular substances such as proteins. Is possible.

  Moreover, it is preferable that the particulate mesoporous silica of the present invention has a diffraction peak corresponding to a d value of 2 to 50 nm in X-ray diffraction. Fine-grained mesoporous silica having such a diffraction peak not only has a uniform mesopore diameter, but also can be applied to functional materials such as optical materials and electronic materials because the mesopores are regularly arranged. . Moreover, more stable performance can be exhibited in other applications.

  The method for producing the particulate mesoporous silica of the present invention is not particularly limited, but can be suitably produced by the method exemplified below.

  That is, first, alkali metal silicate, a surfactant, and an acid are mixed to precipitate silica to obtain mesoporous silica using the surfactant as a template. Then, the mesoporous silica is wet-pulverized, and then the mesoporous silica is used. This is a method of extracting and removing a surfactant.

In addition, it is preferable that the addition amount of the said surfactant shall be 100 weight part or more with respect to 100 weight part of silica. By making the addition amount of the surfactant 100 parts by weight or more, the mesopore volume can be increased. Moreover, σ _p can be reduced, and mesoporous silica having a uniform pore diameter can be obtained.

Further, it is preferable to use a block copolymer of ethylene glycol and propylene glycol as the surfactant. By using the block copolymer, mesoporous silica having a small σ _p and an average pore diameter of 5 nm or more can be obtained. When a surfactant other than the block copolymer is used, σ _p tends to increase when the mesoporous silica is wet pulverized, and it is difficult to obtain mesoporous silica having an average pore diameter of 5 nm or more. It is.

  Moreover, when precipitating a silica, after hold | maintaining at 20-40 degreeC for 0.5 to 10 hours, it is preferable to hold | maintain at 80-100 degreeC for 5 to 20 hours. According to such a method, not only the mesopore diameter becomes uniform, but also the mesopores are regularly arranged, so that mesoporous silica having a diffraction peak in X-ray diffraction can be obtained.

  In the wet pulverization, a method of pulverizing without removing the surfactant used as a template of mesoporous silica is preferable. According to such a pulverization method, it becomes easy to make fine particles without impairing the mesopore volume and mesopore uniformity of mesoporous silica. The most preferable aspect in the wet pulverization is a method of wet pulverization using part or all of the reaction liquid in the reaction as a dispersion medium.

  Further, a wet media type pulverizer is preferable as the pulverizer used for the wet pulverization. The wet media type pulverizer has a high pulverization efficiency and can efficiently make fine particles of mesoporous silica to 1 μm or less.

In the case of using a wet media type pulverizer, the mesoporous silica obtained by appropriately selecting the particle size of the beads as the medium and the processing time (in the continuous pulverizer, the residence time in the pulverization unit) is selected. The average particle diameter and σ _d can be adjusted.

That is, when the particle size of the beads is small, the average particle size tends to be small, and when the processing time is long, σ _d tends to be small. In this case, mesoporous silica having a small average particle diameter and σ _d is obtained, and when a large bead is used for a short time, mesoporous silica having a large average particle diameter and σ _d is obtained.

  In addition, as a method for extracting and removing the surfactant from the mesoporous silica, there is a method in which fine particle mesoporous silica containing a surfactant is dispersed in an extraction solvent, stirred for a specific time under heating, and then solid-liquid separated. Is preferred. The extraction solvent is preferably an alcohol such as methanol, ethanol or propanol, and the solid-liquid separation method is preferably a method such as centrifugation, ultrafiltration or microfiltration.

  In addition to surfactants, mesoporous silica may contain impurities such as acids, alkalis, and salts, but these impurities may be removed at the same time when the surfactant is removed, If it is difficult to remove, it may be removed separately.

  The mesoporous silica dispersion of the present invention can be obtained by dispersing the fine particle mesoporous silica in a dispersion medium. Such a mesoporous silica dispersion can form a smooth and homogeneous film, and is useful, for example, as a coating liquid for forming a thin film such as an ink receiving layer or a low dielectric constant film of ink jet recording paper.

  In the present invention, the dispersion medium can be used without particular limitation as long as it can disperse mesoporous silica. Water or alcohols such as methanol, ethanol and isopropanol, ethers and ketones can be used. An organic solvent such as, or a mixed solvent thereof can be used. Among them, it is most preferable to use water alone in consideration of the ease of handling.

  The concentration of mesoporous silica in the mesoporous silica dispersion is not particularly limited, but is preferably 5 to 50% by weight, particularly preferably 10 to 40% by weight.

  That is, when the amount of mesoporous silica in the mesoporous silica dispersion is higher than 50% by weight, the fluidity of the dispersion tends to decrease, and conversely when it is lower than 5% by weight, the desired thickness is obtained. It is difficult to obtain a thin film, and the energy cost required for drying after coating tends to increase.

  Further, in the mesoporous silica dispersion of the present invention, a dispersant may be added separately for the purpose of improving the dispersion stability of mesoporous silica.

  Suitable examples of such dispersants include, for example, cationic, anionic and nonionic resins and surfactants, among which cationic having a primary to tertiary amine or a quaternary ammonium salt. Resins are particularly preferred.

  In particular, in the application of inkjet recording paper, the fixing property to an anionic dye contained in the inkjet ink can be improved by the action of the cationic resin, and an inkjet recording paper having excellent water resistance and printing density is obtained. It becomes possible.

  The mesoporous silica granule of the present invention can be obtained by granulating the fine particle mesoporous silica.

  In conventional mesoporous silica with a large particle size, all the pores are composed of mesopores, and it is difficult for the substance to diffuse inside the mesopores and reach the inside of the particles. Could not be used.

  On the other hand, since the mesoporous silica granule of the present invention has macropores composed of gaps between fine particles, the substance diffuses in the macropores and can easily reach the inside of the particles. Therefore, the mesoporous silica granule can be effectively used up to the inside, and is useful for a catalyst carrier, a separating agent, an adsorbent, a pharmaceutical carrier such as a pharmaceutical, and the like.

  Furthermore, since the mesoporous silica granule can be granulated to an arbitrary size of several μm to several tens of mm depending on the application, it is easier to handle in separation or recovery than when used in the form of fine particles. Etc. are extremely advantageous.

  The method for obtaining the mesoporous silica granule is not particularly limited, and any known method can be employed without any limitation. For example, spray granulation by granulating a dispersion of fine particle mesoporous silica by spray drying, or rolling granulation, fluidized bed granulation, stirring granulation of powdery fine particle mesoporous silica. Examples of the method include granulation by granulation, compression granulation, extrusion granulation, and the like.

  In addition, you may add a binder in the case of the said granulation in order to raise the mechanical strength of a mesoporous silica granulation body more. As such a binder, gelatin, polyvinyl pyrrolidone, polyvinyl alcohol, cellulose and derivatives thereof are suitable.

  Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

  In addition, the physical property measurement of the particulate mesoporous silica was performed by the following method.

(1) Measurement of mesoporous volume, average pore diameter, and σ _p of mesoporous silica Using a sufficiently dried mesoporous silica as a sample, a high-speed specific surface area / pore distribution measuring device (manufactured by Micromeritics, ASAP2010) An adsorption isotherm of nitrogen at 75K was prepared using this, and a pore distribution curve was obtained from the adsorption isotherm by the BJH method. The pore diameter axis of the pore distribution curve was a logarithmic scale.

The mesopore volume in the range of 2 to 50 nm, the average pore diameter (av _p ), and σ _p were calculated from the pore distribution curve. The following equations (1) and (2) were used for calculating av _p and σ _p , respectively.

logav _p = Σ {v _i logp _i } / Σv _i (1)
_{logσ p = [Σ {v i} (logp i -logav p) 2} / Σv i] 0.5 (2)
However, in the above formulas (1) and (2), the subscript i represents the i-th section when the hole diameter axis is divided into N sections, and is a natural number of 1 to N. Further, v _i represents the volume of a pore having a pore diameter in the i-th compartment, and p _i is a geometric average of the lower limit pore diameter and the upper limit pore diameter of the i-th compartment.

(2) Measurement of average particle diameter of mesoporous silica and σ _d Mesoporous silica was dispersed in ion-exchanged water so as to have a concentration of 3% by weight, and treated with an ultrasonic disperser to prepare a sample. The sample was measured using a light scattering diffraction type particle size distribution measuring device (Coulter, Coulter LS-230) with a dispersion medium (water) having a refractive index of 1.332 and a silica having a refractive index of 1.458. The volume-based particle size distribution curve was obtained. The particle diameter axis of the particle size distribution curve was a logarithmic scale.

The average particle diameter (av _d ) and σ _d were calculated from the particle size distribution curve. The following equations (3) and (4) were used for calculating av _d and σ _d , respectively.

logav _d = Σ {v _i logd _i } / Σv _i (3)
logσ _d = [Σ {v _i (logd _i −logav _d ) ² } / Σv _i ] ^0.5 (4)
However, in the above formulas (3) and (4), the subscript i represents the i-th section when the particle diameter axis is divided into N sections, and is a natural number of 1 to N. Further, v _i represents the volume fraction of particles having a particle diameter in the i-th section, and d _i is a geometric average of the lower limit particle diameter and the upper limit particle diameter of the i-th section.

(3) X-ray diffraction measurement of mesoporous silica Mesoporous silica powder was filled in a measurement holder, and measurement was performed with CuKα rays using an X-ray diffractometer (Rigaku Corporation, RINT-1400).

Example 1
A block copolymer of ethylene glycol and propylene glycol (manufactured by BASF, Pluronic-P123) was dissolved in ion-exchanged water to obtain a 20 wt% surfactant solution. 150 g of the surfactant solution, 44 g of 25% by weight sulfuric acid, and 73 g of ion-exchanged water were mixed to obtain a transparent liquid. While this solution was stirred, 133 g of sodium silicate (15 wt% SiO ₂ , 5.1 wt% Na ₂ O) was gradually added to obtain a cloudy reaction mixture.

  While stirring the reaction mixture at 30 ° C. for 1 hour, the temperature was raised to 95 ° C. and held for 12 hours to generate mesoporous silica having a surfactant in the mesopores.

  Next, 390 g of the reaction mixture and 1520 g of zirconia balls having a diameter of 2 mm were filled into a polyethylene pot, sealed with no dead volume in the pot, and wet-pulverized with a pot mill.

  After the wet pulverized reaction mixture was centrifuged to obtain a precipitate, the operation of dispersing the precipitate in ion-exchanged water and centrifuging again was repeated to remove sulfuric acid and sodium sulfate.

  Subsequently, it was dispersed in ethanol so that the concentration of mesoporous silica was 1% by weight, stirred while heating, and then centrifuged to collect a precipitate. The precipitate was recovered again by stirring and centrifuging in ethanol to remove the surfactant and dried to obtain fine-particle mesoporous silica.

  As a result of X-ray diffraction measurement of the fine particle mesoporous silica obtained, three diffraction peaks corresponding to d values of 9.2, 5.8, and 5.2 were observed, and the structure had a regular pore structure. It was confirmed that On the high angle side, only a broad halo was observed, and no peak derived from crystalline silica was observed. Thus, it was confirmed that the mesoporous silica was amorphous.

  Table 1 shows the physical properties of the fine particle mesoporous silica.

Comparative Example 1
Mesoporous silica was obtained in the same manner as in Example 1 except that wet pulverization by a pot mill was not performed.

  As a result of X-ray diffraction measurement of the obtained mesoporous silica, three diffraction peaks corresponding to d values of 9.4, 5.9, and 5.3 were observed, and the structure had a regular pore structure. It was confirmed that

  Table 1 shows the physical properties of the mesoporous silica.

Comparative Example 2
A block copolymer of ethylene glycol and propylene glycol (manufactured by BASF, Pluronic-P123) was dissolved in ion-exchanged water to obtain a 20 wt% surfactant solution. 150 g of the surfactant solution, 44 g of 25% by weight sulfuric acid, and 73 g of ion-exchanged water were mixed to obtain a transparent liquid. While this solution was stirred, 133 g of sodium silicate (15 wt% SiO ₂ , 5.1 wt% Na ₂ O) was gradually added to obtain a cloudy reaction mixture.

  While stirring the reaction mixture at 30 ° C. for 1 hour, the temperature was raised to 95 ° C. and held for 12 hours to generate mesoporous silica having a surfactant in the mesopores.

  The reaction mixture was centrifuged to obtain a precipitate, and then the precipitate was dispersed in ion-exchanged water and centrifuged again to remove sulfuric acid and sodium sulfate.

  Subsequently, it was dispersed in ethanol so that the concentration of mesoporous silica was 1% by weight, stirred while heating, and then centrifuged to collect a precipitate. The surfactant was removed by repeating the stirring in ethanol and collecting the precipitate by centrifugation again.

  20 g of mesoporous silica from which the surfactant was removed, 371 g of ion-exchanged water, and 1520 g of zirconia balls having a diameter of 2 mm were filled in a polyethylene pot, sealed with no dead volume in the pot, and wet-ground by a pot mill.

  The liquid to be treated for wet pulverization was centrifuged to collect the precipitate, and the mesoporous silica of Comparative Example 2 was obtained.

  As a result of the X-ray diffraction measurement of the obtained mesoporous silica, it was found that a diffraction peak corresponding to a d value of 2 to 50 nm was not observed, and that there was no regular pore structure.

  Table 1 shows the physical properties of the mesoporous silica.

Comparative Example 3
Sodium silicate (4.0 wt% SiO ₂ , 1.4 wt% Na ₂ O) was treated with a strongly acidic cation exchange resin to obtain an active silica solution. The active silica solution is gradually added to an aqueous solution containing 150 parts by weight of hexadecyltrimethylammonium hydroxide and 200 parts by weight of 1,3,5-trimethylbenzene with respect to 100 parts by weight of silica while stirring with a propeller mixer. did. Subsequently, sodium hydroxide was added to adjust the pH of the reaction solution to 8.5. The reaction was continued at 80 ° C. for 3 hours while continuing the stirring, and the resulting precipitate was filtered and washed with water to obtain mesoporous silica having a surfactant in the mesopores.

  Next, the dispersion was dispersed in ethanol so that the concentration of the mesoporous silica was 1% by weight, stirred while heating, and then centrifuged to collect the precipitate. The surfactant was removed by repeating the stirring in ethanol and collecting the precipitate by centrifugation again.

  20 parts by weight of mesoporous silica after removal of the surfactant, 1 part by weight of diallyldimethylammonium chloride polymer, and 79 parts by weight of ion-exchanged water are mixed, and a homogenizer (manufactured by Squid, Ultra Tax T-50) is used. Preliminary dispersion was performed to obtain a mesoporous silica dispersion having a silica concentration of 20% by weight.

  Subsequently, the dispersion was repeatedly passed through an orifice with a high-pressure homogenizer (manufactured by Nanomizer, Nanomizer LA-31, treatment pressure 80 MPa), and wet pulverized to obtain fine particle mesoporous silica of Comparative Example 3.

  As a result of X-ray diffraction measurement of the obtained mesoporous silica, a diffraction peak corresponding to a d value of 7.7 was observed, and it was confirmed that it had a regular pore structure. Compared with the case of Example 1, it was a broad peak. Therefore, it turned out that the fine particle mesoporous silica of the comparative example 3 is inferior to the structural regularity compared with the fine particle mesoporous silica of Example 1.

  Table 1 shows the physical properties of the mesoporous silica.

実施例２
実施例１で得られた微粒子状メソポーラスシリカを濃度が１５重量％となるようにイオン交換水に加え、強攪拌することによって本発明のメソポーラスシリカ分散液を得た。

Example 2
The mesoporous silica dispersion of the present invention was obtained by adding the particulate mesoporous silica obtained in Example 1 to ion-exchanged water so as to have a concentration of 15% by weight and stirring vigorously.

  A thin film-forming coating solution was prepared by mixing 60 g of the mesoporous silica dispersion and 45 g of a 10% by weight polyvinyl alcohol solution. The thin film-forming coating solution was applied to a hydrophilized PET film and then dried to obtain a thin film.

  The thin film had a glossy surface, and when the cross section was observed with an optical microscope, it was confirmed to be a smooth and homogeneous film.

Comparative Example 4
A thin film was obtained in the same manner as in Example 3 except that the mesoporous silica obtained in Comparative Example 1 was used.

  The thin film showed roughness on the surface, and when the cross section was observed with an optical microscope, the surface was markedly uneven, and coarse particles were scattered in the film.

Example 3
Ion exchange water was added to the particulate mesoporous silica obtained in Example 1 to prepare a dispersion having a mesoporous silica concentration of 10% by weight. The dispersion was introduced into a spray dryer and spray granulation was performed to obtain the mesoporous silica granule of the present invention.

  When the obtained mesoporous silica granule was observed with a scanning electron microscope, the granule had a structure in which fine particles were aggregated, and the size thereof was about 120 μm. The granulated body had many macropores having a pore diameter of about 100 to about 300 nm, which originated from the gaps between the fine particles.

Further, the mesoporous silica granule was measured for mesopore volume, average pore diameter, σ _p , and X-ray diffraction. As a result, the same results as in Example 1 were obtained, and the characteristics of the fine particle mesoporous silica were retained. As it is, it was confirmed to be a granulated body also having macropores for facilitating the diffusion of the substance in the particles.

Comparative Example 5
Spray granulation was performed in the same manner as in Example 2 except that the mesoporous silica obtained in Comparative Example 1 was used. The resulting granulate was fragile and immediately powdered.

  When the granulated body was observed with a scanning electron microscope, it was a particle having a size of about 10 to about 100 μm. These individual particles were just lumps and no macropores were observed.

The particulate mesoporous silica of the present invention can be used in the fields of catalyst carriers, separating agents, adsorbents, pharmaceutical carriers such as pharmaceuticals, low dielectric constant films, and ink absorbents for ink jet recording paper.

Claims (6)

  Fine mesoporous silica having an average particle size of 1 μm or less, the volume of pores having a pore size in the range of 2 to 50 nm is 0.7 mL / g or more, and the geometric standard deviation of pore distribution is 2.0 or less Fine particulate mesoporous silica, characterized in that   The particulate mesoporous silica according to claim 1, wherein the geometric standard deviation of the particle size distribution is 1 to 3.   The fine particle mesoporous silica according to claim 1 or 2, wherein the average pore diameter of the pores is 5 nm or more.   The fine particle mesoporous silica according to any one of claims 1 to 3, which has a diffraction peak corresponding to a d value of 2 to 50 nm in X-ray diffraction.   A mesoporous silica dispersion containing the particulate mesoporous silica according to any one of claims 1 to 4. A mesoporous silica granule obtained by granulating the particulate mesoporous silica according to any one of claims 1 to 4.