JP2007204288A - Method for production of fibrous porous silica particle, and the fibrous porous silica particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of producing a fibrous porous silica particle having a pore size of ≥8 nm without using an additive such as a fluoride. <P>SOLUTION: The production method comprises: mixing an aqueous alkali silicate solution with a liquid mixture of an acidic aqueous solution and a nonionic surfactant while agitating under the temperature condition of 30 to <50°C; continuing agitation at the temperature as it is to confirm white turbidity in a reaction solution after the lapse of a definite time; then heating a reaction vessel as it is or a reactor which is kept at a definite temperature and has the reaction vessel transferred thereto at a certain temperature of 50-200°C; and aging by leaving at rest or agitating for a given period of time to remove the nonionic surfactant in the obtained fibrous particle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing micron-sized fibrous porous silica particles and the fibrous porous silica particles obtained by this method. More specifically, the present invention is based on the ability of the nonionic surfactant to form rod-like molecular aggregates, and is a fibrous high-order rule between a silica-dissolved species generated from an alkali silicate and a nonionic surfactant. After the structure is formed, the growth of the higher order ordered structure is aged at a higher temperature, and a method for producing fibrous porous silica particles characterized by having a mesopore arranged at the same time as the fibers. The present invention relates to porous silica particles having a shape. Furthermore, this invention relates to the fibrous porous silica particle excellent in heat resistance, and a nonporous fibrous silica particle.

  Since the synthesis method of porous MCM-41 was published in Nature in 1992, interest in mesoporous materials has increased, and many studies using ionic surfactants such as quaternary ammonium salts have been reported. Later, it was reported that non-toxic, biodegradable, easy removal, and mesoporous materials could be synthesized using inexpensive oligomer or polymer nonionic surfactants as templates. (Non-Patent Document 1).

  On the other hand, since the discovery of a mesoporous material, development of a porous material having not only a regular structure of mesopores but also a high-order ordered structure controlled from micron to millimeter size macro form has been attracting attention (Non-Patent Document 2). ).

  For substances with uniform pores, expanding the pore diameter enables large molecules that were previously impossible in chemical reactions using pores as a reaction field. And it is a very important research subject for practical use. The background of the development of zeolite, the invention of the porous mesopores and the subsequent high interest, and the expectation for basic research and application development that have not faded up to the present (Non-Patent Document 3). In the synthesis method of mesoporous materials, the pore size can be controlled depending on the reaction conditions such as the type of surfactant to be used, and in particular, the longer the hydrophobic group, the greater the tendency to obtain a product with a larger pore size. Yes. Furthermore, it is known that the pore diameter is expanded by using an organic compound such as 1,3,5-trimethylbenzene or triisopropylbenzene, which is an additive aid that enlarges micelles. Further, as a fluoride addition effect during the synthesis of a silica mesoporous material, not only the formation of a silica skeleton is promoted (Non-Patent Document 4), but also a limited pore size expansion effect of fluoride has been reported (Non-Patent Document). 5).

  However, in many studies so far, organic silica such as alkoxysilane is used as a silica source, and expensive ionic surfactant is used as a template agent, so it is not suitable for mass production for application. There's a problem. Then, research which started cheap silica sources, such as alkali silicate, as a starting material is reported for mass production which can expand an application field more (nonpatent literature 6). However, although it is considered to use a nonionic surfactant together with an alkali silicate as an inexpensive silica source, the investigation has not progressed so much. The reason is that it is very difficult to control the macro morphology together with the control of the pore diameter. Actually, for example, there are very few reports of using an alkali silicate and a polymer-based nonionic surfactant at the same time to control the macro form as well as the pore diameter (Non-Patent Document 7 and Non-Patent Document 8).

  In such a background, the present inventors proceeded with investigations based on the idea that control of macro form by an energy-saving synthesis method using low-cost raw materials is an important point in developing mesoporous materials. New technical proposals have been made based on the knowledge obtained in the process. For example, a method of synthesizing a spherical silica porous body (Patent Document 1) or rod-like and fibrous porous silica particles (Patent Document 2) using an alkali silicate and a triblock copolymer as a nonionic surfactant. Has proposed. In the latter method for synthesizing rod-like and fibrous porous silica particles, in a known technique for production, sodium silicate and a triblock copolymer (trade name Pluronic P123) are reacted in an acidic hydrochloric acid solution, and the presence or absence of stirring is determined. A monodispersed rod-like and fibrous silica mesoporous material is selectively synthesized. Furthermore, the property of the triblock copolymer, that is, the reaction temperature is increased to increase the hydrophobicity by increasing the hydrophobicity, and by controlling the reaction temperature to 40 ° C., the maximum peak of the pore diameter is 6. Synthesis of fibrous silica mesoporous material having 4 nm is realized.

  However, even in this new synthesis method by the present inventors, it is difficult to form a micelle structure having regularity at a long distance at 50 ° C. due to the properties of the triblock copolymer as a surfactant, and the fibrous form is not obtained. In fact, it is not possible to expect expansion of the pore diameter of 7 nm or more while maintaining this.

As described above, the expansion of the pore diameter brings about new developments in the application range of porous materials. In recent reports, it has been reported that the pore diameter can be expanded by using supercritical CO ₂ as a solvent. (Non-Patent Document 9) is complicated as a method for expanding the pores. In the example of the additive aid described above, the organic compound is expensive, and the regularity of the pores is likely to be lowered. There is a problem.

Fluoride, on the other hand, has been reported to expand pore size in the synthesis of mesoporous materials, but it has a strong effect of promoting the condensation of the silica skeleton and imparts a large pore size while maintaining a micron-sized fibrous form. It was difficult to do. Recently, the inventors have also closely controlled the method of adding fluoride to provide a fibrous pore having a micron-sized fibrous shape and an average pore size of 8 nm or more and a uniform pore size distribution. Has succeeded in the synthesis of porous silica particles and has filed a patent application (Patent Document 3). However, a large amount of fluoride is required to expand the pore diameter, and it is difficult to produce fibrous porous silica particles having a pore diameter of 10 nm or more with a reaction temperature of about 45 ° C. There existed problems, such as a residue of F element being recognized in a silica.
Bagshaw, SA; Prouzet, E .; Pinnavaia, TJScience 1995, 269, 1242. 1) Ciesla, U .; Schuth, F. Microporous Mesoporous Mater. 1999, 27, 131. 2) Stein, A. Adv. Mater. 2003, 15, 763. Davis, ME Nature 2002, 417, 813. Boissiere, C .; van der Lee, A .; El Mansouri, A .; Larbot, A .; Prouzet, E. C hem. Commun. 1999, 2047. Bagshaw, SAJ Mater. Chem. 2001, 11, 831. 1) Sierra, L .; Guth, JL. Microporous Mesoporous Mater. 1999, 28, 243. 2) Kim, SS; Pauly, TR; Pinnavaia T.J. Chem. Commun. 2000, 835. 3) Kim, SS; Pauly , TR; Pinnavaia T.J.Chem. Commun. 2000, 1661. Boissiere, C .; Larbot, A .; van der Lee, A .: Kooyman, PJ; Prouzet, E. Chem. Mater. 2000, 12, 2902. Sun, Q .; Kooyman, PJ; Grossmann, JG; Bomans, PHH; Frederik, PM; Magusin, PCMM; Beelen, TPM; van Santen, RA; Sommerdijk, NAJMAdv. Mater. 2003, 15, 1097. Hanrahan, JP; Copley, MP; Ryan, KM; Spalding, TR; Morris, MA; Holmes, JD Chem. Mater. 2004, 16, 424. JP2004-143026 JP2003-342019 Japanese Patent Application No. 2004-311836

  As described above, it is possible to synthesize porous materials having mesopores and micropores using inexpensive alkali silicate as a silica source, which is very excellent in the idea in order to expand the field of use of porous materials. However, the number of reported examples is very small compared to those using organic silicon such as expensive alkoxysilane as a raw material, and reports on macro form control in combination with nonionic surfactants are extremely limited. . Moreover, pure fibrous porous silica particles having a large pore diameter of 7 nm or more due to the dehydration behavior at a high temperature of a nonionic surfactant used in a normal reaction system and a method for producing the same have been heretofore known. Not reported at all.

  Moreover, in the manufacturing method of the fibrous porous silica particle of patent document 2 by the present inventors as mentioned above, there exists a limit in aiming at the expansion of the further pore diameter, maintaining a fibrous form. And in the manufacturing method of the fibrous porous silica particle of the said patent document 3, although it discovered that the fibrous porous silica particle which has a large pore diameter of 8 nm or more was produced for the first time, a large amount of fluoride was used. There are problems such as wastewater treatment and substantial quality deterioration, such as residual fluoride and shortening of fiber length, and mass production cannot be expected.

  Therefore, the present invention eliminates these conventional problems from the background as described above, uses inexpensive alkali silicate as a silica source, and uses a non-toxic or low-toxic nonionic surfactant as a template. Based on the technical knowledge developed so far by the inventor, the present invention provides industrial production technology for new fibrous porous silica particles, and has a pore diameter of 8 nm or more, which is not reported at all other than the conventional fluorine addition method. It is an object of the present invention to provide fibrous porous silica particles and the like having the above.

The present inventor recommended diligent studies to solve the above problems, and in the process, silica that maintains a fibrous form even when a triblock copolymer is used at a high reaction temperature without adding an additive. A method for producing a porous body has been found. Furthermore, the present inventors have succeeded in uniformly controlling the pore diameter in a wide range of, for example, 3 to 13 nm and controlling the fiber length. In particular, production of fibrous porous silica particles with extremely large mesochannels having a pore size of 10 nm or more, which has not been reported at all, and a specific surface area and pore volume of 600 m ² / g and 1 ml / g or more, respectively. Also succeeded.

  The present invention has been completed on the basis of such results, and the production method of the present invention includes a surfactant that is a precursor of fibrous porous particles generated at about normal temperature and under normal pressure. However, the growth of organic-inorganic nanocomposites is characterized by aging at higher temperatures. By this method, among the fibrous porous silica particles disclosed by the present inventor so far, all the fibrous porous silica particles having a diameter of less than 10 nm can be produced if defined by the pore diameter. And the novel fibrous porous silica particle whose pore diameter is 10 nm or more can be manufactured. In the synthesis of mesoporous materials, it is generally well known that the pore size can be expanded by using a triblock copolymer at a high temperature, but it is known that it can be maintained while maintaining a micron-sized fibrous form. It is not done. Further, the obtained large pore fibrous silica particles are also a novel substance that has not been reported in the past.

  That is, according to the present invention, a non-toxic or low-toxic, biodegradable nonionic surfactant is used to control the pore structure and fibrous morphology based on the conventional low-cost, low environmental load material design. In a reaction system using an agent, and an inexpensive alkali silicate as a silica source, and a simple reaction system that does not require the addition of other substances such as fluoride useful for pore size expansion, it is a fibrous porous material. Silica particles are provided. The production method of the present invention is a universal method for producing fibrous porous silica particles having a uniform pore diameter in a wide range of, for example, 3 to 13 nm, and in particular, fibrous porous silica particles that have never been reported in the past. Thus, it can be said that this is an epoch-making industrial production method capable of providing for the first time fibrous porous silica particles having a very large mesopore of 10 nm or more while having a micron-sized fibrous form.

  The present invention has been completed on the basis of the above-described completely new and unexpected knowledge. The manufacturing method of the present invention is characterized by the following.

  1. An aqueous alkali silicate solution was mixed with a mixed solution of an acidic aqueous solution and a nonionic surfactant while stirring under a temperature condition of 30 ° C. to less than 50 ° C. After the reaction solution was found to be cloudy, 50 ° C. to 200 ° C. After aging by raising the temperature to a temperature in the range of ° C., the produced solid is filtered and dried, and then the nonionic surfactant is removed.

2. Use nonionic surfactants in amounts of 0.002 to 0.25 per mole of SiO ₂ in the alkali silicate.

3. Use acid in an amount of 0.6 to 15 moles per mole of SiO ₂ in the alkali silicate.

4). Use water in an amount of 100 to 400 moles per mole of SiO ₂ in the alkali silicate.

The fibrous porous silica particles of the present invention are characterized by the following. ,
1. Fibrous porous silica particles containing no fluoride, the peak value of the pore size distribution curve is less than 10 nm, the BET specific surface area is 800 m ² / g or more, and the total pore volume is 0.6 ml / g or more. .

2. Fibrous porous silica particles having a pore size distribution curve peak value of 10 nm or more, a BET specific surface area of 600 m ² / g or more, and a total pore volume of 1 ml / g or more.

3. Fibrous porous silica particles having a BET specific surface area of 100 m ² / g or more at 1000 ° C. or more, a pore size distribution peak in the range of 3 to 10 nm, and a total pore volume of 0.1 ml / g or more. thing.

  4). The fibrous particles are composed of a chain of rod-like units or an assembly of the chain-like ones, and one-dimensional channel-like pores regularly arranged in a honeycomb shape penetrate between adjacent rod-like units.

  5. It has a plurality of X-ray diffraction peaks showing a regular arrangement structure of pores at a diffraction angle of 0.5 to 5 degrees (CuKα).

6). Fibrous silica particles composed of a chain of rod-like units or aggregates of the chain, and non-porous with a BET specific surface area of 5 m ² / g or less.

  7). The length of the major axis by scanning microscope observation is in the range of 10 to 2000 μm, the aspect ratio is 3 to 150, and the shape is fibrous.

  According to the present invention, an inexpensive alkali silicate is used as a silica source, a highly safe nonionic surfactant is used as a template, and a uniform pore size of 3 to 13 nm is obtained in a relatively short time. A method for producing fibrous porous silica particles is provided.

  According to the present invention, a nonionic surfactant is used as a pore structure control agent, and in a very simple reaction system in which an alkali silicate aqueous solution and an acidic aqueous solution are mixed, the mixing time of the reactants, the reaction temperature Furthermore, by changing the aging temperature and the aging time, an organic-inorganic nanocomposite containing a surfactant that becomes a precursor of the fibrous porous material is selectively produced in a relatively short time, and finally the organic matter A method for producing micron-order fibrous porous silica particles is provided.

  Moreover, according to the production method of the present invention, not only a fibrous macro form, but also a large pore volume fibrous porous silica having no regular report in which pores of 8 nm or more, further 10 nm or more are regularly arranged. Particles are provided.

Further, as a result of detailed examination of changes in the pore structure at high temperature, heat-resistant fibrous porous silica particles having a BET specific surface area of 100 m ² / g or more at 1000 ° C. or more, and further, non-porous while maintaining the fiber form Of fibrous silica particles are provided.

  The production method of the present invention uses an inexpensive raw material, and most of the reaction time is an aging step under standing or stirring conditions, so that it can be easily applied to an industrial scale. Silica particles have characteristics such as high specific surface area, uniformity of pore diameter, and monodispersibility, so that they use molecular sieves, adsorbents, and highly dispersible fibrous particles that utilize shape selectivity. Suitable for use as additives, gas separation membranes, plus catalyst carriers, catalysts, and chromatographic carriers. In addition, fibrous porous silica particles are large, amorphous silica having a uniform aspect ratio, so asbestos substitutes that are toxic to the human body and reinforcing agents that increase the strength of the resin, Furthermore, it can be used as a thickener.

  That is, the fibrous porous silica particles according to the present invention are used for applications such as resin additives, ink adsorbing fillers, humidity control agents, asbestos substitute materials, and thickeners. Furthermore, it can be processed and molded in a felt-like manner by mixing it alone or with other inorganic substances and organic compounds using a fibrous form, and can be widely used as various filter materials. In particular, those having a large pore size can be used as an adsorbing / separating / occluding / fixing agent for large molecules having an enzyme or an organic functional group. In addition, using micropores that are connected to mesopores, they can be applied to purification processes for environmental pollutant exhaust gas substances with excellent intra-particle diffusivity, or new uses as micropore porous materials to replace zeolite and silica gel. Is expected to lead. It can also be developed in the development of various catalysts by chemically modifying the surface of the pores with metals and metal oxides. Furthermore, various uses are expected as a porous material and a composite material in a high heat-resistant environment.

  In the present invention, in the production of micron-order fibrous porous silica particles, alkali silicate is used as a silica source, it is not necessary to use expensive organic silica such as metal alkoxide, and expensive quaternary ammonium salt is used as a template. Non-toxic, biodegradable and inexpensive nonionic surfactants can be used without using other materials, and high yields of fibrous particles can be obtained in a short time. Acid concentration, reaction concentration, especially reaction time The basic feature is that the aspect ratio can be adjusted. What is remarkable is that fibrous porous silica particles having mesopores of 8 nm or more, particularly 10 nm or more can be provided while maintaining the fibrous form without adding a fluoride as a pore expanding agent. Since nonionic surfactants have extremely low hydrophilicity at high temperatures, it has been difficult to form micelle aggregates having a stable higher-order structure. In the present invention, a rod-like micelle structure is first formed and a continuous body of rod-like micelle structures is being formed in a stirred state, or at a time when it is almost formed, while still standing or slowly stirring at a higher temperature. It is characterized by aging. These new technologies have a remarkable inventive step compared to the prior art.

  That is, in the method for producing fibrous porous silica particles according to the present invention, an aqueous alkali silicate solution is mixed with a mixture of an acidic aqueous solution and a nonionic surfactant while stirring at a temperature of 30 ° C. to less than 50 ° C. Then, after stirring for a certain period of time and white turbidity was observed in the reaction solution, the temperature of the reaction vessel was increased as it was, or the reaction vessel was transferred to a reactor maintained at a constant temperature, The temperature is raised to a constant temperature of 200 ° C., and after aging for a certain time while standing or stirring, the produced solid is filtered and dried, and then the nonionic surfactant is removed. The production mechanism of the fibrous porous particles in which mesopores are regularly arranged at the same time as exhibiting a micron-order fibrous shape by the production method of the present invention is estimated as follows.

Alkali silicates have positively charged silica dissolved species in a strongly acidic aqueous solution [I ⁺ ], while nonionic surfactants [N ⁰ ] dissolved in strong acids also have hydrophilic groups on the surface of the surfactant. The mesostructure is electrically stable because it is positively charged by being covered with proton [H ⁺ ], and an anion [X ⁻ ] is interposed between both surfaces of the positively charged silica and the surfactant. It is estimated to form [N ⁰ H ⁺ ] [X ⁻ I ⁺ ].

Furthermore, the solution contains alkali ions (P ⁺ ) generated by the reaction between the alkali silicate and the acid, and the charges between the silica whose surfaces are charged by these ions cancel each other. It proceeds to produce an organic-inorganic mesostructure containing a nonionic surfactant in the silica skeleton. It is presumed that the organic-inorganic mesostructure grows into particles having a fibrous form on the order of microns by selecting a nonionic surfactant [N ⁰ ] that is easily generated as a rod-like structure. In other words, fibrous porous particle precursors are formed by growing rod-like structures in a chain, and the final product obtained by removing organic components by baking or solvent extraction is a micron order. The one-dimensional channel also has mesopores regularly arranged in a hexagonal system and has an ordered structure at two different scales.

However, as the reaction temperature increases, the hydrophilic group in the nonionic surfactant changes to be hydrophobic, which prevents the growth of the rod-like structure and makes it difficult to form a fibrous form. This is shown in Comparative Example 1. When an alkali silicate aqueous solution is mixed with an acidic solution of a nonionic surfactant and the reaction is carried out under stirring conditions throughout, fibrous porous particles can be synthesized up to 45 ° C., but at 50 ° C., no fibrous particles. Is not recognized (for example, Comparative Example 1 shown in FIG. 13). The macro form is significantly affected by the reaction temperature, and it is considered that the limit of the pore diameter of the fibrous porous particles obtained by a normal production method is 7 nm. On the other hand, F ⁻ is excellent in the effect of promoting the condensation polymerization of the silica skeleton, and strongly promotes the mediation of the [X ⁻ ] ion. Therefore, the pore diameter can be expanded by strictly controlling the method of adding fluoride at a reaction temperature of 45 ° C., and fibrous porous particles having a pore diameter close to 10 nm can be produced as shown in Comparative Example 2 (Comparison) Example 2, FIG. 14). However, even in the case of using fluoride, in the synthesis reaction based on stirring, the pore diameter is limited to 10 nm, and a pure silica porous body cannot be produced with the fluorine element remaining in the product.

According to a recent report (Non-Patent Document 10), Pluronic 123 begins to coalesce in flocs due to the aggregation of spherical micelles formed in a hydrochloric acid solution and interaction with dissolved silica species. (A) It is reported that a large (micron order) two-dimensional hexagonal-like ordered structure is formed (C) via a wormhole-like mesostructure which is an intermediate.
Flodstrom, K .; Wennerstrom, H .; Alfredsson, V. Langmuir, 2004, 20, 680. If the organic-inorganic mesostructure with a two-dimensional hexagonal structure is maintained in a monodispersed state, rod-like silica mesoporous particles will eventually be obtained Will be obtained as The fibrous particles of the present invention are formed by connecting and growing rod-like particles. If the reaction conditions are such that the wormhole-like mesostructure changes to a hexagonal-like ordered structure, the mesostructures are connected. Occurrence (D), the regularity of the mesostructure of each rod-like particle becomes high in the process (E) in which the connected body is entangled while the connected body is extended, and finally the fibrous mesosilica precursor (F) Will be generated.

  The change from (A) to (B) and (C) is induced regardless of the presence or absence of stirring. In order to obtain fibrous porous silica particles, (A) to (B), (C) In addition, it is an essential condition to induce all the changes from (D) to (F) by stirring. According to the conventional knowledge, stirring must be continued during the reaction in order to produce a fibrous mesosilica precursor. (Patent Document 2). In addition, when fluoride is used, in order to finally maintain the fibrous form, it is necessary to add fluoride after the stage of changing from (B) to (C) under stirring conditions. (Patent Document 3).

  On the other hand, as described above, in order to expand the pore diameter, it is conceivable to utilize the fact that the hydrophilic part of the nonionic surfactant becomes hydrophobic in a high temperature state. However, as apparent from Comparative Example 1, even if the reaction temperature is simply increased under stirring, it cannot be grown in a fibrous form. The inventor found that the change from (A) to (B) and (C) needs to be agitated based on the examination results in various reaction conditions, but once the rod-like particles reaching (C) are chained together. In this case, it was confirmed that it was promoted more at a high temperature rather than stirring, and it was found that the fibrous particles grow by aging at a high temperature even if the (C) and after are not allowed to stir but simply allowed to stand. In particular, when the aging temperature is high, the hydrophobic portion of the nonionic surfactant becomes large, and the dehydration condensation of the silica phase forming the organic inorganic mesostructure, which is a precursor of the fibrous silica mesoporous material, is rapid. When the silica phase shrinks and the silica phase contracts, the internal micelle phase induces a wider space, and fibrous silica having large mesopores is obtained. The hydrophilic group of the surfactant that constitutes the organic / inorganic mesostructure has penetrated into the silica skeleton, and as a result of its removal, micropores are formed, and the mesopores of the resulting porous body are connected by micropores. Yes. When the ripening temperature is increased, the hydrophilic portion of the nonionic surfactant has an extremely strong hydrophobic behavior, and micropores are not formed, but only one-dimensional channels of mesopores are provided.

  In addition, as shown in the examples, this production method is also characterized in that pore characteristics and fiber length can be effectively controlled by controlling not only the aging temperature but also the stirring and mixing time or aging time before aging. It is.

  The fibrous porous silica particles obtained by the production method of the present invention have a micron-sized fibrous form as shown in the scanning electron micrograph of FIG. FIG. 2 is an electron emission scanning electron microscope (FE-SEM) photograph of the fibrous porous silica particles of the present invention, where one fibrous particle is an aggregate of finer fibrous silica particles. It can be seen that the aggregate is a chain of rod-like particles or an intertwined chain. From these scanning electron micrographs, it can be seen that the fibrous porous silica particles of the present invention have a fibrous macro morphology with a uniform aspect ratio.

  FIG. 3 is a high-resolution electron microscope (TEM) photograph showing the structure in the stretching direction of one example of the fibrous porous silica particles of the present invention. The fibrous porous silica particles of the present invention are a continuum of rod-shaped particles which are basic structural units as shown in FIG. 2, and are one-dimensional mesochannels extending through the longitudinal direction of the rod-shaped particles from the TEM image of FIG. Is clearly recognized, and it is clear that the regularity of the mesostructure is remarkably excellent.

  Furthermore, as shown in the XRD diffraction pattern of FIG. 4, the fibrous porous silica particles of the present invention have a plurality of peaks showing a regular arrangement of mesopores at a diffraction angle 2θ = 0.5 to 5.0 degrees. 3 shows that the channels recognized in the TEM image of FIG. 3 are stacked in a honeycomb shape.

  FIG. 5 is a pore size distribution curve of the fibrous porous silica particles of the present invention obtained by changing the aging temperature. Each of the pore size distribution curves has a sharp pore size distribution. It is clear that becomes larger.

  Further, as is apparent from Table 1 shown for the examples described later, the present production method can control not only the aging temperature but also the stirring and mixing time before aging or the aging time, thereby controlling the pore characteristics and fiber length. It is also a great feature that it can be controlled effectively. FIG. 6 shows an example of this, and shows an SEM image of short porous fibrous porous silica particles.

  As already pointed out, the production method of the present invention is a universal method for producing fibrous porous silica particles having a uniform pore diameter in a wide range of 3 to 13 nm and exhibiting a fibrous shape on the order of microns. It is clear that this is a typical method. Furthermore, in a simple reaction system without using a pore expanding agent, fibrous porous silica particles having 8 to 10 nm pores obtained by using fluoride, and more than 10 nm which has never been reported so far It is a remarkable feature that fibrous porous silica particles having pores can be synthesized and fibrous porous silica particles having a uniform pore diameter in a wide range can be provided. That is, in the present invention, the length of the major axis by scanning microscope observation is in the range of 5 to 2000 μm, the aspect ratio is 3 to 150, and the micropore has a uniform pore diameter in a wide range of 3 to 13 nm. Sized porous silica particles are provided.

  In the production method of the present invention based on the aging reaction in a stationary or stirred state, the aging time and the stirring and mixing time before aging depend on the macro form of the product, the regularity of the mesostructure, and the size of the mesopores. Affects equiporous properties. Furthermore, these physicochemical properties will be affected not only by the reaction time in each of the two stages, but also by the respective reaction temperatures. The stirring and mixing time of the reaction solution before aging needs to be strictly determined according to the reaction temperature at each stage, but is desirably 10 minutes or more, and if too short, the fiber as shown in FIG. 15 (Comparative Example 3). It is difficult to grow into a shape. On the other hand, in the case of a long period, the fibrous porous silica particles can be synthesized even if the stirring and mixing operation exceeds 3 hours. In the production method of the present invention, as an effect of controlling the stirring and mixing time, in particular, it is possible to synthesize fibrous porous silica particles having substantially the same pore characteristics and different aspect ratios. For example, from FIG. 1 (Example 2-3) and FIG. 6 left (Example 3-1), particles having a short fiber length can be effectively synthesized by relatively shortening the stirring and mixing time. Further, by slightly increasing the stirring and mixing time, long and supple fibrous porous silica particles are obtained as shown in the right of FIG. 6 (Example 3-2), and the appearance is controlled by controlling the stirring and mixing time. Can be synthesized.

  Furthermore, it is a major feature of the production method of the present invention that the pore diameter can be controlled by controlling the aging time. It is clear from Table 1 (for example, Example 2-3 and Example 3) that the fibrous porous silica particles having a large pore diameter can be synthesized by increasing the aging time after stirring and mixing. In order to produce high-quality fibrous porous silica particles having a large aspect ratio, the aging time tends to be shorter as the aging temperature is higher. For example, at 60 ° C., as shown in FIG. 16 (Comparative Example 4), it is difficult to obtain the desired fibrous particles in 30 minutes. In the case of 100 ° C., fibrous porous silica particles can be synthesized although the fiber length is short in 1 hour. However, even if the aging time is lengthened, there is a limit to the expansion of the pore diameter, and the aging time is considered to be sufficient within 10 hours.

  In addition, improvement of the heat resistance of the porous material and the fibrous material is generally very important for expanding applications and developing new applications. 7 and 11 are SEM photographs obtained by heat treatment at 1000 ° C. and 1200 ° C., respectively. It can be seen that high heat-resistant fibrous silica particles can be produced without destruction of the form even by high-temperature baking. The pore characteristics of several examples are shown in Table 2. Although the pore diameter decreases at 1000 ° C., the pore diameter distribution is sharp, and from FIG. 8 and FIG. 9, the regularity of the pore structure is not lost at all. As in the case of firing at 600 ° C. (FIG. 3), it can be seen that the one-dimensional mesochannels penetrate through the adjacent rod-like particles. Even at 1100 ° C., exactly the same characteristics as 1000 ° C. are recognized, but at 1200 ° C., the pore structure is destroyed and nonporous fibrous silica particles can be produced. As shown in FIG. 12, rod-like particles can be confirmed at 1200 ° C., but the appearance is such that adjacent particles are melted together.

  The reaction temperature in the production method of the present invention is preferably in the range of 30 ° C. to less than 50 ° C. in the stirring and mixing operation. If it is higher than this, dehydration of the hydrophilic group portion in the nonionic surfactant is likely to occur, so that stirring prevents the formation of rod-shaped particles, which are the basic structure of the fibrous particles, and the aging causes fibrous porous It is difficult to synthesize silica particles. The aging temperature is preferably 50 ° C. or higher, and the efficient reaction condition is desirably 180 ° C. or lower.

  In the production method of the present invention, after satisfying the condition that the fibrous porous silica particle precursor is generated by the stirring reaction in the initial stage, the mixing ratio of the reactants such as surfactant, acid, silica and the like, and further stirring By controlling the temperature and time, and the aging temperature and time, it is possible to control the form of the fibrous particles such as length, aspect ratio, flexibility, and pore characteristics. In particular, utilizing the fact that the hydrophilic part of the nonionic surfactant becomes hydrophobic at high temperature, it has a pore size of 8 nm or more without adding other substances such as fluoride when it is aged at 80 ° C. or higher. In addition, fibrous porous silica particles having a highly regular mesostructure can be produced, and in particular when the temperature exceeds 120 ° C., fibrous porous silica particles having a pore diameter of 10 nm or more can be synthesized.

  In the production method of the present invention, as described above, the alkali silicate aqueous solution was mixed with the mixed solution of the acidic aqueous solution and the nonionic surfactant for a predetermined time while stirring, and the reaction solution was found to be cloudy, It is produced by removing the nonionic surfactant in the fibrous particles obtained by aging at the above constant temperature.

In the present invention, the order of addition of the raw materials is extremely important, and in order to form a fibrous form, an aqueous alkali silicate solution diluted with water is added to a nonionic surfactant solution dissolved in an acid. There must be.
[material]
The silica raw material, nonionic surfactant, and acid used in the present invention will be further described.

As the silica raw material used in the present invention, alkali silicate can be used, and sodium silicate which is relatively inexpensive is preferable. As the sodium silicate, a sodium silicate aqueous solution having a composition in which m is a number of 1 to 5, particularly 1.5 to 4.5 in the Na ₂ O · mSiO ₂ formula is preferably used.

  As the nonionic surfactant, a polymer surfactant containing polyethylene oxide (PEO) can be used, and in particular, a triblock copolymer containing PEO is preferable, and further, polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-). The use of PPO-PEO) is optimal.

  The polymerization ratio, average molecular weight, and weight ratio of the hydrophobic group used in the present invention are important. The average molecular weight is about 4800 or more, and the weight ratio of the hydrophobic group is 65% or more. It is desirable to be.

  The acid is preferably hydrochloric acid, which is most effective in producing fibrous particles.

In the synthesis of the fibrous porous silica particles of the present invention, the mixing molar ratio of the starting materials is as follows: SiO ₂ : nonionic surfactant: Na ₂ O: acid: water = 1: 0.002-0.25: 0 .25 to 1: 0.6 to 15: 100 to 400 is preferable.

Further, the mixing method of the starting materials will be described in detail. In the synthesis of fibrous fibrous particles, an alkali silicate aqueous solution diluted in water in a nonionic surfactant solution (1) dissolved in a predetermined concentration of acid. (2) was added under stirring, and stirring of the mixed solution (1 and 2) was stopped after 10 minutes to 2 hours, and white turbidity was observed in the reaction solution, and the temperature was higher than 50 ° C or higher. Aging is performed for 30 minutes or longer, preferably 50 minutes to 12 hours. After the reaction, the solid product is separated from the suspension and sufficiently dried at room temperature to 100 ° C. Finally, in order to remove the organic component and produce fibrous porous silica particles, heat treatment is performed at 200 ° C. or higher for 2 hours or longer, preferably 400 ° C. or higher for 1 hour.
[Usage]
The production method of the present invention uses inexpensive raw materials, and since most of the reaction time is an aging process, it can be easily applied to an industrial scale. Furthermore, the produced fibrous porous silica particles have a high ratio. Since it has features such as surface area, uniformity of pore diameter, and monodispersity, it uses molecular sieves and adsorbents that utilize shape selectivity, and resin additives and gas separation membranes that use highly dispersible fibrous particles. In addition, it is suitable for use as a catalyst carrier, a catalyst, and a chromatographic carrier. In addition, fibrous porous silica particles are large, amorphous silica having a uniform aspect ratio, so asbestos substitutes that are toxic to the human body and reinforcing agents that increase the strength of the resin, Furthermore, it can be used as a thickener.

  That is, the fibrous porous silica particles according to the present invention are used for applications such as resin additives, ink adsorbing fillers, humidity control agents, asbestos substitute materials, and thickeners. Furthermore, it can be processed and molded in a felt-like manner by mixing it alone or with other inorganic substances and organic compounds using a fibrous form, and can be widely used as various filter materials. In particular, those having a large pore size can be used as an adsorbing / separating / occluding / fixing agent for large molecules having an enzyme or an organic functional group. In addition, using micropores that are connected to mesopores, they can be applied to purification processes for environmental pollutant exhaust gas substances with excellent intra-particle diffusivity, or new uses as micropore porous materials to replace zeolite and silica gel. Is expected to lead. It can also be developed in the development of various catalysts by chemically modifying the surface of the pores with metals and metal oxides. Furthermore, various uses are expected as a porous material and a composite material in a high heat-resistant environment.

  EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited by this Example.

In addition, each test method performed in the Example was performed by the following method.
(Measurement method)
(1) Scanning electron microscope: JSM5300 manufactured by JEOL Ltd. was used and observed at an acceleration voltage of 10 kV and a WD of 10 mm.
(2) Specific surface area and pore size distribution: BELSORP28 manufactured by Nippon Bell was used to determine the BET specific surface area from the nitrogen adsorption isotherm measured at the liquid nitrogen temperature, and the pore size distribution was analyzed by the BJH method.
(3) Shape: Observed from scanning electron micrograph.
(4) Particle size: measured by scanning electron micrograph.
(5) X-ray diffraction: Rigaku Rotorflex RU-300 was used and measured with a CuKα radiation source, an acceleration voltage of 40 kV, and 80 mA.
(6) High-resolution electron microscope: HI-2000 made by HITACHI was used and observed at an acceleration voltage of 200 kV.
(7) Electrolytic emission scanning electron microscope (FE-SEM): JSM-6700F manufactured by JEOL Ltd. was used, and measurement was performed with a pretreatment Pt coating and an acceleration voltage of 3 kV.
Example 1
Commercially available JIS No. 3 sodium silicate (SiO ₂ : 23.6%, Na ₂ O: 7.59%) diluted with water was dissolved in 2N hydrochloric acid, a triblock copolymer Pluronic P123 (PEO ₂₀ PPO ₇₀ Added to the PEO ₂₀ ) solution with stirring. Both raw material solutions were adjusted in advance to a predetermined temperature of 36 ° C. and mixed, and stirring was stopped one hour after mixing both raw material solutions. The open mouth of the glass reaction vessel containing the mixed solution was closed with a glass plate, quickly transferred to a constant temperature water bath adjusted to 60 ° C., and allowed to stand for 300, 120 and 240 minutes for aging. The molar ratio of the mixed solution is SiO ₂ : Pluronic P123: Na ₂ O: HCl: H ₂ O = 1: 0.017: 0.312: 5.88: 202. H ₂ O contains water derived from all raw materials. After the reaction, the solid product is filtered off, washed and sufficiently dried at 65 ° C. Finally, the organic component is removed by baking in an electric furnace at 600 ° C. for 1 hour to obtain fibrous porous silica particles.

Table 1 shows the BET specific surface area, total pore volume, and micropore volume of the fibrous porous silica particles of this example. This result shows that in this production method, when the aging temperature is constant, fibrous porous silica particles having a large pore diameter can be synthesized by extending the aging time.
(Example 2)
Commercially available JIS No. 3 sodium silicate (SiO ₂ : 23.6%, Na ₂ O: 7.59%) diluted with water was dissolved in 2N hydrochloric acid, a triblock copolymer Pluronic P123 (PEO ₂₀ PPO ₇₀ Added to the PEO ₂₀ ) solution with stirring. Both raw material solutions were adjusted in advance to a predetermined temperature of 36 ° C. and mixed, and stirring was stopped one hour after mixing both raw material solutions. The mixed solution was transferred to a Teflon (registered trademark) reaction vessel, sealed in a simple stainless steel vessel, and adjusted to 60 ° C., 80 ° C., 100 ° C., 120 ° C., 150 ° C., and 160 ° C. in advance. Aging was carried out by standing for 300 minutes in a thermostatic bath. The molar ratio of the mixed solution is SiO ₂ : Pluronic P123: Na ₂ O: HCl: H ₂ O = 1: 0.017: 0.312: 5.88: 202. H ₂ O contains water derived from all raw materials. After the reaction, the solid product is filtered off, washed and sufficiently dried at 65 ° C. Finally, the organic component is removed by baking in an electric furnace at 600 ° C. for 1 hour to obtain fibrous porous silica particles.

  Table 1 shows the BET specific surface area, total pore volume, and micropore volume of the fibrous porous silica particles of this example obtained by changing the aging temperature. From Table 1, it can be seen that the pore diameter increases as the aging temperature increases. In addition, from comparison between Example 2-1 and Example 1-1 having the same aging temperature, in Example 2-1, the mixed solution was transferred to a reaction container made of Tecolon. It can be seen that there is a delay in the arrival time up to a certain 60 ° C., and as a result, the pore diameter and the like are also different.

  From the above, it can be seen that according to the present invention, fibrous porous silica particles having not only large pore diameters but also small pore diameters can be produced by simple temperature control.

  And from the SEM photographs of several examples (2-1, 2-3, and 2-5) of this example shown in FIG. 1, in each case, the aspect ratio is large, and the high quality with relatively uniform thickness and length. It can be seen that these are fine fibrous particles. FIG. 2 is an electrolytic emission scanning electron microscope (FE-SEM) photograph of the fibrous porous silica particles of Example 2-5. One fibrous particle is an aggregate of finer fibrous silica particles. In other words, it is confirmed that the aggregate is a chain-like chain of rod-like particles or an entanglement of the chain-like bodies. FIG. 3 is a TEM image, and it is clear that mesochannels exist in the extending direction of the rod-shaped particles that are the basic structural units and continuously penetrate through the adjacent rod-shaped particles. FIG. 4 is an XRD diffraction pattern of several examples (2-3, 2-4, and 2-5) of this example. Three clear peaks and broad peaks are observed in the low angle region (1 to 5 degrees). Peaks are observed, indicating that the mesochannel pores are regularly arranged in a two-dimensional hexagonal crystal.

  FIG. 5 is a pore size distribution curve of the fibrous porous silica particles of this example (2-1 to 2-6), both having a sharp pore size distribution, and the pore size peak is increased when the aging temperature is increased. It is clear that it will grow.

In this example, those having a peak value of the pore size distribution at 8 nm or more are large porous fibrous silica particles of a pure silica component that cannot be produced by the conventional synthesis method. It is a novel fibrous porous silica that cannot be produced using fluoride.
(Example 3)
Commercially available JIS No. 3 sodium silicate (SiO ₂ : 23.6%, Na ₂ O: 7.59%) diluted with water was dissolved in 2N hydrochloric acid, a triblock copolymer Pluronic P123 (PEO ₂₀ PPO ₇₀ Added to the PEO ₂₀ ) solution with stirring. Both raw material solutions were adjusted in advance to a predetermined temperature of 36 ° C. and mixed, and stirring was stopped at 20 minutes and 30 minutes after mixing of both raw material solutions. This mixed solution was transferred to a Teflon (registered trademark) reaction vessel, sealed in a simple stainless steel vessel, and allowed to stand for 340 minutes and 330 minutes in a constant temperature and temperature controlled bath adjusted in advance to 100 ° C. for aging. went. The molar ratio of the mixed solution is SiO ₂ : Pluronic P123: Na ₂ O: HCl: H ₂ O = 1: 0.017: 0.312: 5.88: 202. H ₂ O contains water derived from all raw materials. After the reaction, the solid product is filtered off, washed and sufficiently dried at 65 ° C. Finally, the organic component is removed by baking in an electric furnace at 600 ° C. for 1 hour to obtain fibrous porous silica particles.

Table 1 shows the BET specific surface area, total pore volume, and micropore volume of the fibrous porous silica particles of this example. By comparing the SEM image of Example 3-1 shown in the left of FIG. 6 and FIG. 1 (Example 2-3), the mixing and stirring time before aging is shortened, so that the fibrous porous silica of short fibers It can be seen that particles are obtained. On the other hand, the length in the case of Example 3-2 shown on the right side of FIG. 6 is almost the same as that in FIG. 1 (Example 2-3), but the appearance is slightly bent and is recognized as being somewhat supple. . Therefore, in the present invention, it is possible to control the fiber length and the flexibility by changing the mixing and stirring time before aging, and it has various pore characteristic parameter diameters with different aspect ratios. This shows that it is possible to produce simple fibrous porous silica particles.
Example 4
Commercially available JIS No. 3 sodium silicate (SiO ₂ : 23.6%, Na ₂ O: 7.59%) diluted with water was dissolved in 2N hydrochloric acid, a triblock copolymer Pluronic P123 (PEO ₂₀ PPO ₇₀ Added to the PEO ₂₀ ) solution with stirring. Both raw material solutions were adjusted in advance to a predetermined temperature of 36 ° C. and mixed, and stirring was stopped one hour after mixing both raw material solutions. This mixed solution was transferred to a Teflon (registered trademark) reaction vessel, sealed in a simple stainless steel vessel, and allowed to stand for 60, 90, 150, and 780 minutes in a constant temperature and temperature controlled bath adjusted to 100 ° C. in advance. Then ripened. The molar ratio of the mixed solution is SiO ₂ : Pluronic P123: Na ₂ O: HCl: H ₂ O = 1: 0.017: 0.312: 5.88: 202. H ₂ O contains water derived from all raw materials. After the reaction, the solid product is filtered off, washed and sufficiently dried at 65 ° C. Finally, the organic component is removed by baking in an electric furnace at 600 ° C. for 1 hour to obtain fibrous porous silica particles.

Table 1 shows the BET specific surface area, total pore volume, and micropore volume of the fibrous porous silica particles of this example. From this example, it can be seen that the pore size increases as the aging time increases. Therefore, in the present invention, the pore characteristic parameters can be controlled by changing the aging time, and fibrous porous silica particles having different pore diameters can be produced.
(Comparative Example 1)
Triblock copolymer Pluronic P123 (PEO ₂₀ PPO ₇₀ ) in which commercially available JIS No. 3 sodium silicate (SiO ₂ : 23.6%, Na ₂ O: 7.59%) diluted with water was dissolved in 2N hydrochloric acid. PEO ₂₀ ) (average molecular weight 5800) (Aldrich) is added with stirring. Both raw material solutions were previously adjusted to a predetermined temperature of 45 ° C. and 50 ° C., mixed, and reacted for 6 hours. The molar ratio of the mixed solution was SiO ₂ : Pluronic P123: Na ₂ O: HCl: H ₂ O = 1: 0.0169: 0.312: 5.88: 202. H ₂ O contains water derived from all raw materials. After the reaction, the solid product is filtered off, washed and sufficiently dried at 50 ° C. Finally, the organic component is removed by baking in an electric furnace at 600 ° C. for 1 hour to obtain fibrous porous silica particles.

An SEM photograph of the porous silica particles of this comparative example is shown in FIG. Table 1 shows the specific surface area of this comparative example and the pore diameter and pore volume determined from the pore diameter distribution curve. From this comparative example, when the raw material solution is mixed under stirring and stirring is continued as it is to produce fibrous porous silica particles, the reaction temperature has a sensitive effect on the form, and as shown in FIG. It can be seen that no particles are observed. Therefore, the upper limit of the pore diameter of the fibrous porous silica particles obtained by simple stirring reaction is 7 nm.
(Comparative Example 2)
Commercial JIS3 No. sodium silicate diluted by adding water _{(SiO 2: 23.6%, Na} 2 O: 7.59%) and tri-block copolymer Pluronic was dissolved in hydrochloric acid 2N P123 (PEO ₂₀ PPO ₇₀ PEO ₂₀ ) (average molecular weight 5800) (Aldrich) is added with stirring. Both raw material solutions were previously adjusted to 45 ° C. and 50 ° C., mixed, and after mixing both raw material solutions, NaF was added 1 hour later, and further reacted for 5 hours for a total of 6 hours. The molar ratio of the mixed solution is SiO ₂ : Pluronic P123: Na ₂ O: HCl: NaF: H ₂ O = 1: 0.0169: 0.312: 5.88: 1.04: 202. H ₂ O contains water derived from all raw materials. After the reaction, the solid product is filtered off, washed and sufficiently dried at 50 ° C. Finally, the organic component is removed by baking in an electric furnace at 600 ° C. for 1 hour to obtain fibrous porous silica particles.

  Table 1 shows the specific surface area of the fibrous porous silica particles of this comparative example prepared at a mixing temperature of 45 ° C., and the pore diameter and pore volume determined from the pore diameter distribution curve. The product produced at a reaction temperature of 45 ° C. in this Comparative Example showed a fibrous form as shown in FIG. 14, but no fibrous particles were observed at 50 ° C. as in Comparative Example 1.

According to this comparative example, fibrous porous silica particles having a pore diameter close to 10 nm can be produced by an appropriate method for adding fluoride, but it is difficult to expand to 10 nm or more. Further, as apparent from this comparative example, there are problems that a large amount of fluoride is required, and that the product contains 0.7 wt% of F, so that it is not pure silica particles. Compared with the production method of the present invention, the method using a fluorinated compound cannot be said to be an efficient production method because of wastewater treatment costs associated with the synthesis, and further has problems in physicochemical properties such as the size of the pore diameter. is there.
(Comparative Example 3)
Commercially available JIS No. 3 sodium silicate (SiO ₂ : 23.6%, Na ₂ O: 7.59%) diluted with water was dissolved in 2N hydrochloric acid, a triblock copolymer Pluronic P123 (PEO ₂₀ PPO ₇₀ Added to the PEO ₂₀ ) solution with stirring. Both raw material solutions were adjusted in advance to a predetermined temperature of 36 ° C. and mixed, and stirring was stopped 9 minutes after mixing the raw material solutions. This mixed solution was transferred to a Teflon (registered trademark) reaction vessel, sealed in a simple stainless steel vessel, and allowed to stand for 351 minutes in a constant temperature and temperature controlled bath adjusted in advance to 100 ° C. for aging. The molar ratio of the mixed solution is SiO ₂ : Pluronic P123: Na ₂ O: HCl: H ₂ O = 1: 0.017: 0.312: 5.88: 201.5. H ₂ O contains water derived from all raw materials. After the reaction, the solid product is filtered off, washed and sufficiently dried at 65 ° C. Finally, the organic component is removed by baking in an electric furnace at 600 ° C. for 1 hour to obtain fibrous porous silica particles.

Table 1 shows the BET specific surface area, total pore volume, and micropore volume of the fibrous porous silica particles of this example. From the SEM image shown in FIG. 15, it can be seen that if the stirring time before aging is too short, fibrous particles are not easily generated. This comparative example shows that the stirring time before aging is an important factor for forming fibrous particles in the production method of the present invention.
(Comparative Example 4)
Commercially available JIS No. 3 sodium silicate (SiO ₂ : 23.6%, Na ₂ O: 7.59%) diluted with water was dissolved in 2N hydrochloric acid, a triblock copolymer Pluronic P123 (PEO ₂₀ PPO ₇₀ Added to the PEO ₂₀ ) solution with stirring. Both raw material solutions were adjusted in advance to a predetermined temperature of 36 ° C. and mixed, and stirring was stopped one hour after mixing both raw material solutions. The open mouth of the glass reaction vessel containing the mixed solution was closed with a glass plate, transferred to a constant temperature water bath adjusted to 60 ° C., and allowed to stand for 30 minutes for aging. The molar ratio of the mixed solution is SiO ₂ : Pluronic P123: Na ₂ O: HCl: H ₂ O = 1: 0.017: 0.312: 5.88: 201.5. H ₂ O contains water derived from all raw materials. After the reaction, the solid product is filtered off, washed and sufficiently dried at 65 ° C. Finally, the organic component is removed by baking in an electric furnace at 600 ° C. for 1 hour to obtain fibrous porous silica particles.

  Table 1 shows the BET specific surface area, total pore volume, and micropore volume of the fibrous porous silica particles of this example. From the SEM image shown in FIG. 16, it can be seen that it is difficult to obtain fibrous particles if the aging time is too short. This comparative example shows that the aging time is an important factor for the formation of fibrous particles in the production method of the present invention.

(Example 5)
A part of the reaction products described in Example 2 was heated to 1000 ° C. in 2 hours, and further maintained at 1000 ° C. for 1 hour to prepare a heated product. Table 2 shows structural characteristic parameters of the obtained fibrous porous silica particles. The BET specific surface area, total pore volume, and pore diameter of the 1000 ° C. heat-treated product are all reduced as compared with the case of firing at 600 ° C. (Table 1), and the presence of micropores is not recognized. However, as shown in FIG. 7 (Example 5-4), the fibrous form does not change with the heat treatment temperature, and it is confirmed that the 1000 ° C. treated product has the same macro form as in FIG. . FIG. 8 is a TEM photograph of the present Example 5-4 (corresponding to Example 2-5 in Table 1). Although the pore diameter decreases, one-dimensional mesochannels are regularly arranged and adjacent to each other as in FIG. It is clear that they exist through the rod-shaped particles. This regular arrangement structure is recognized as a plurality of peaks existing at a low angle of the XRD diffraction pattern shown in FIG. FIG. 10 is a pore size distribution curve of this example, which shows a sharp distribution even at 1000 ° C., although the pore size becomes small.
(Example 6)
A part of the reaction product described in Example 2 was heated to 1200 ° C. in 2 hours, and further maintained at 1200 ° C. for 1 hour to prepare a heated product. The BET specific surface area of the 1200 ° C. heat-treated product is the measurement limit of the apparatus, and is estimated to be 5 m ² / g or less. At the low angle of the XRD diffraction pattern, the diffraction peaks observed in FIGS. 4 and 9 do not exist, indicating that the pore structure has been destroyed. However, as shown in FIG. 11, the fibrous form is maintained, and nonporous silica fibers can be synthesized. FIG. 12 is a photograph of an electrolytic emission scanning electron microscope (FE-SEM) of the fibrous silica particles of this example. Even if the pore structure is destroyed, the macro form at low temperature is taken over, and a single fibrous shape is obtained. The particles are aggregates of finer fibrous silica particles, and it can be seen that the aggregates are a chain of continuous rod-shaped particles or entanglements of the chain. However, when compared with FIG. 2, each rod-like particle is clearly recognized at a low temperature, but in the treatment at a high temperature at which the pore structure is destroyed, the boundary of the rod-like particle is vague and seemingly fused. It is a state.

It is a scanning electron micrograph of several examples (Examples 2-1, 2-3, and 2-5) of the fibrous porous silica particle synthesize | combined with the manufacturing method of this invention. It is an electrolysis type | mold scanning electron microscope (FE-SEM) photograph of an example (Example 2-5) of the fibrous porous silica particle of this invention. It is a high-resolution electron microscope (TEM) photograph which shows the structure of an extending | stretching direction about an example (Example 2-5) of the fibrous porous silica particle of this invention. It is an X-ray diffraction pattern of several examples of fibrous porous silica particles synthesized in Examples 2-3, 2-4 and 2-5 of the present invention. It is a pore diameter distribution curve of several examples of fibrous porous silica particles synthesized in Example 2 of the present invention. It is a scanning electron micrograph of several examples of fibrous porous silica particles synthesized in Examples 3-1 and 3-2 of the present invention. It is a scanning electron micrograph of an example of the fibrous porous silica particle synthesize | combined in Example 5-4 of this invention. It is a high-resolution electron microscope (TEM) photograph which shows the structure of an extending | stretching direction about an example (Example 5-4) of the heat resistant fibrous porous silica particle of this invention. It is an X-ray-diffraction pattern of an example (Example 5-4) of the heat-resistant fibrous porous silica particle of this invention. It is a pore diameter distribution curve of several examples (Example 5) of the heat-resistant fibrous porous silica particles of the present invention. It is a scanning electron micrograph of an example (Example 6) of the nonporous fibrous silica particle of this invention. It is an electrolysis emission scanning electron microscope (FE-SEM) photograph of an example of nonporous fibrous silica particles of the present invention (Example 6). It is a SEM image of two types of porous silica particles of Comparative Examples 1-1 and 1-2. It is a SEM image of the silica porous particle obtained by adding NaF of the comparative example 2. 10 is a SEM image of an example of porous silica particles of Comparative Example 3. 6 is an SEM image of an example of porous silica particles of Comparative Example 4.

Claims (16)

An aqueous alkali silicate solution was mixed with a mixed solution of an acidic aqueous solution and a nonionic surfactant while stirring under a temperature condition of 30 ° C. to less than 50 ° C. After the reaction solution was found to be cloudy, 50 ° C. to 200 ° C. A method for producing fibrous porous silica particles, wherein after heating to a temperature in the range of ° C. and aging, the produced solid is filtered and dried, and then the nonionic surfactant is removed. The method according to claim 1, wherein the nonionic surfactant is used in an amount of 0.002 to 0.25 per mole of SiO ₂ in the alkali silicate. _{3. The process according} to claim 1, wherein the acid is used in an amount of 0.6 to 15 mol per mol of SiO ₂ in the alkali silicate. The method according to any one of claims 1 to 3, wherein water is used in an amount of 100 to 400 mol per mol of SiO ₂ in the alkali silicate. Fibrous porous silica particles containing no fluoride, the peak value of the pore size distribution curve is less than 10 nm, the BET specific surface area is 800 m ² / g or more, and the total pore volume is 0.6 ml / g or more. Fibrous porous silica particles characterized by Fibrous porous silica particles having a pore size distribution curve having a peak value of 10 nm or more, a BET specific surface area of 600 m ² / g or more, and a total pore volume of 1 ml / g or more. Silica particles. Fibrous porous silica particles having a BET specific surface area of 100 m ² / g or more at 1000 ° C. or more, a pore size distribution peak in the range of 3 to 10 nm, and a total pore volume of 0.1 ml / g or more. Heat-resistant fibrous porous silica particles characterized by the above. The fibrous particle is composed of a chain of rod-shaped units or an assembly of the chain, and one-dimensional channel-shaped pores regularly arranged in a honeycomb form exist between adjacent rod-shaped units. The fibrous porous silica particles according to any one of claims 5 to 7. The fibrous porous silica particle according to any one of claims 5 to 8, which has a plurality of X-ray diffraction peaks showing a regular arrangement structure of pores at a diffraction angle of 0.5 to 5 degrees (CuKα). . A fibrous silica particle comprising a chain of rod-like units or an aggregate of the chain, and nonporous with a BET specific surface area of 5 m ² / g or less. The length of the long axis by scanning microscope observation is in the range of 10 to 2000 μm, the aspect ratio is 3 to 150, and the shape is fibrous. Fibrous silica particles. A resin additive comprising the fibrous porous silica particles according to any one of claims 5 to 11. An ink adsorbing filler comprising the fibrous porous silica particles according to any one of claims 5 to 11. An asbestos substitute material comprising the fibrous porous silica particles according to any one of claims 5 to 11. A thickener comprising the fibrous porous silica particles according to any one of claims 5 to 11. A catalyst or catalyst carrier comprising the fibrous porous silica particles according to any one of claims 5 to 11.