Silica secondary particles and film-forming composition containing the same

Abstract

To identify silica secondary particles suitable for improvement of gas permeability coefficient of a gas separation membrane by employing, as an indicator for evaluating pore properties of porous silica particles, especially silica secondary particles prepared by an aggregation method, an average mesopore diameter determined from a melting peak temperature of pore ice of the silica secondary particles measured with differential scanning calorimetry (DSC).SOLUTION: Silica secondary particles obtained through a hydrolysate of at least one compound selected from the group consisting of tetraalkoxysilanes and trialkoxysilanes, the silica secondary particles being formed from silica particles having an average primary particle diameter (A1) of 5 to 50 nm as measured by the Sears method or a nitrogen gas adsorption method, and the silica secondary particles having pores composed of the silica secondary particles that contain moisture therein, the silica secondary particles exhibiting at least one endothermic peak associated with a phase transition from ice to water at -6°C or lower when measured by differential scanning calorimetry (DSC) by sweeping from low temperature to high temperature.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to secondary silica particles and a film-forming composition containing the secondary silica particles. [Background technology]

[0002] In recent years, as part of nanotechnology research, there has been active research into nanometer-order particles (nanoparticles) with average particle diameters ranging from about 1 nm to several hundred nm. Nanoparticles, which are made by nanosizing materials, are known to be able to express and impart a variety of mechanisms and properties, unlike conventional bulk materials, and are expected to be applied in a wide range of industrial fields.

[0003] Meanwhile, organic-inorganic composite materials, which can synergistically enhance the benefits of both inorganic and organic components by combining them at the nano- or molecular level, have been attracting attention. This concept has also been applied to polymer gas separation membranes, which are attracting attention for their usefulness in solving energy and environmental problems. By fabricating organic-inorganic composite materials by adding inorganic nanoparticles to a polymer matrix, it is hoped that they will achieve high mechanical strength, thermal stability, and gas permeability properties that could not be achieved by existing methods.

[0004] Gas separation methods that utilize the gas permeability properties of polymer membranes allow for the separation and recovery of gases without phase change, and are characterized by simpler operation and smaller equipment than other gas separation methods. Furthermore, gas separation can be performed continuously, resulting in a low environmental impact. Energy-saving polymer gas separation membrane methods have attracted attention in recent years, particularly as a technology for the separation and recovery of greenhouse gases, the production of oxygen-enriched air, and the purification of natural gas, and are expected to be put to practical use. However, further improvements in gas separation performance and gas permeability are required.

[0005] As mentioned above, attempts have been made to improve gas permeability by incorporating inorganic nanoparticles into polymer membranes. However, as the amount of inorganic nanoparticles added increases, the membrane strength decreases, and a high particle content cannot be achieved. This has led to the problem that gas permeability can only be improved by a few times.

[0006] For example, Patent Document 1 proposes a method for improving the properties of gas separation membranes by incorporating inorganic nanoparticles into polymer membranes. This method involves bonding bulky hyperbranched or dendrimer polymers to the surface of silica nanoparticles, resulting in a gas separation membrane that does not aggregate in organic solvents or polymer matrices, has excellent uniformity, and has a significantly improved gas permeability coefficient. However, the decrease in the gas permeability coefficient due to aging over time is a problem.

[0007] On the other hand, porous silica particles, especially those with mesopores with pore diameters of 2 to 50 nm or less, are generally produced by a template method using surfactant micelles as a template, a spray-drying method in which a colloidal solution of silica is spray-dried, or an aggregation method in which primary silica particles are aggregated with an inorganic binder to obtain secondary particles. Such porous silica particles can be used in fields such as adsorbents, catalyst supports, separation membranes, and sensors. Because the mesopores of porous silica particles are robust and thermally, mechanically, and chemically stable, adding porous silica particles to gas separation membranes can simultaneously improve the gas permeability coefficient and aging durability.

[0008] Non-Patent Document 1 describes a pore size of 2 to 10 nm, a pore volume of 0.18 to 1.34 cc / g, and a specific surface area of ​​270 to 630 m2 by nitrogen adsorption method. 2 The paper discloses porous silica particles having a particle diameter of 100 to 140 nm as determined by TEM observation and produced by a template method.

[0009] Patent Document 2 describes a pore radius peak of 5 to 10 nm, a mesopore volume of 0.5 to 2.0 cc / g, and a specific surface area of ​​90 to 350 m2 by nitrogen adsorption method. 2 / g, and an average particle diameter of 0.1 to 1.0 μm as measured by laser diffraction, and porous silica particles produced by an aggregation method are disclosed. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-222228 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-91589 [Non-patent literature]

[0011] [Non-Patent Document 1] John Ndayishimiye, Yuxue Cao, Tushar Kumeria, Mark AT Blaskovich, James Robert Falconera, Amirali Popat, J. Mater. Chem. B, 2021, 9, 7145-7166. Summary of the Invention [Problem to be solved by the invention]

[0012] As described above, when producing a gas separation membrane with excellent properties, it is desirable to use porous silica particles with controlled pore characteristics in order to improve the gas permeability coefficient and durability.

[0013] Regarding the pore characteristics of porous silica particles, the average pore diameter and total pore volume are particularly important indicators. These can be estimated by nitrogen adsorption and mercury intrusion methods. In particular, the Barrett-Joyner-Halenda (BJH) method, which measures the nitrogen adsorption / desorption isotherm at 77 K and analyzes it based on Kelvin's capillary condensation theory, is a commonly used method for analyzing pore distribution.

[0014] However, the BJH method is a theory that is valid when all of the following assumptions (a), (b), and (c) are met, and it is said that the analysis results of the pore characteristics of porous silica particles that do not meet any of the assumptions are likely to deviate from reality. (a) All mesopores are cylindrical. (b) There are no pores smaller than 2 nm (micropores); (c) At the maximum relative pressure, all pores are filled with adsorbed nitrogen gas.

[0015] For example, porous silica particles produced by the aggregation method disclosed in Patent Document 2 are expected to deviate from assumption (a) because the pore shape is irregular rather than cylindrical. Therefore, the BJH method cannot represent the actual pore characteristics, and there is a risk that the expected effect of adding the particles will not be obtained.

[0016] In view of the above circumstances, the present invention has discovered that secondary silica particles suitable for improving the gas permeability coefficient of a gas separation membrane can be identified by measuring the peak melting temperature of ice within the pores of the secondary silica particles using a differential scanning calorimeter (DSC) as an index for evaluating the pore characteristics of porous silica particles, particularly secondary silica particles produced by an aggregation method, and using the average mesopore diameter calculated from the measured value. [Means for solving the problem]

[0017] As a result of intensive research into the above-mentioned problems, the present inventors have discovered that secondary silica particles produced by a predetermined aggregation method using primary silica particles having a predetermined primary particle size, and that the secondary silica particles have predetermined mesopore characteristics evaluated by an average mesopore diameter using a differential scanning calorimeter (DSC), have a particle size and mesopore diameter suitable for gas separation membranes, and have completed the present invention.

[0018] That is, the present invention is summarized as follows: 1. to 12.

[0019] 1. Silica secondary particles, which are formed via a hydrolysis product of at least one compound selected from the group consisting of tetraalkoxysilanes and trialkoxysilanes of silica particles having an average primary particle diameter (A1) of 5 to 50 nm as measured by the Sears method or nitrogen gas adsorption method, and which have at least one endothermic peak at or below -6°C associated with a phase transition from ice to water, measured by sweeping the temperature of the silica secondary particles from low to high using a differential scanning calorimeter.

[0020] 2. Silica secondary particles according to 1., characterized in that they have at least one exothermic peak associated with the phase transition from water to ice between -40 and -20°C when measured by sweeping from high to low temperatures using a differential scanning calorimeter.

[0021] 3. Silica secondary particles according to 1., having mesopores with an average mesopore diameter of 3 to 15 nm as measured by a differential scanning calorimeter.

[0022] 4. Silica secondary particles according to 1., having a surface modifying group derived from a hydrolyzable silane according to formula (1) or formula (2). [ka] In formula (1), R 1 each contains an acryloxy group, a methacryloxy group, an aryl group, an alkyl group, a glycidoxy group, an amino group, or an alkylene group having 1 to 10 carbon atoms and containing such a functional group, and is bonded to a Si atom via a Si-C bond; R 2 are hydrolyzable groups each consisting of an alkoxy group, an acyloxy group, or a halogen group, and at least one R 2 The hydrolyzable group forms a Si—O—Si bond on the surface of the silica particle, and a represents an integer of 1 to 3. In formula (2), R 3 are alkyl groups bonded to silicon atoms by Si-C bonds, and R 4represents an alkoxy group, an acyloxy group, or a halogen group; Y represents an alkylene group, an arylene group, an NH group, or an oxygen atom; b represents an integer of 0 to 3; and c represents an integer of 0 or 1.

[0023] 5. A silica sol obtained by dispersing the silica secondary particles according to any one of 1. to 4. in an acidic or alkaline aqueous medium or organic solvent, in which the ratio (A2 / A1) of the average primary particle size (A1) to the average secondary particle size (A2) measured by dynamic light scattering is greater than 1 and not greater than 40.

[0024] 6. A film-forming composition comprising the silica secondary particles according to any one of 1. to 4. and a matrix resin.

[0025] 7. The film-forming composition according to 6., which is for forming a gas separation film.

[0026] 8. The matrix resin is a cellulose acetate represented by the following formula (I), [ka] (n is an integer between 50 and 500, R 5 represents -H or -COCH3, and at least one is -COCH3. Tetracarboxylic dianhydride represented by the following formula (10) and aromatic diamine R 8 a polyimide having a repeating unit represented by the following formula (II) obtained by condensation polymerization of (NH2)2 with [ka] (R 6 represents a tetravalent organic group. [ka] (R 7 represents a tetravalent organic group. 8 is a residue obtained by removing amine from an aromatic diamine, and represents an aromatic group having 6 to 14 carbon atoms. n represents an integer of 50 to 500. 8. The film-forming composition according to 7., wherein the polymer is at least one selected from the group consisting of polymers having intrinsic microporosity.

[0027] 9. The film-forming composition according to 8., wherein the intrinsically microporous polymer is PIM-1 represented by the following formula (III): [ka] (n represents an integer between 50 and 1000.)

[0028] 10. A step of converting silica particles having an average primary particle diameter (A1) of 5 to 50 nm measured by the Sears method or nitrogen gas adsorption method into secondary particles using a hydrolyzate of at least one compound selected from the group consisting of tetraalkoxysilanes and trialkoxysilanes to obtain silica secondary particles; The method for producing secondary silica particles is characterized in that the secondary silica particles, which contain water in the pores formed by the secondary silica particles, are scanned from low to high temperatures using a differential scanning calorimeter to measure endothermic peaks associated with the phase transition from ice to water, and those having at least one endothermic peak at or below -6°C are used as secondary silica particles for gas separation membranes.

[0029] 11. The method for producing secondary silica particles according to paragraph 10, further characterized in that the secondary silica particles for gas separation membranes have at least one exothermic peak associated with the phase transition from water to ice between -40 and -20°C as measured by sweeping from high to low temperatures with a differential scanning calorimeter.

[0030] 12. A method for producing secondary silica particles according to 10. or 11., characterized in that the secondary silica particles for gas separation membranes have mesopores with an average mesopore diameter of 3 to 15 nm as measured by a differential scanning calorimeter. [Effects of the Invention]

[0031] In the present invention, the secondary silica particles, which contain water in their pores, have an endothermic peak at or below −6°C associated with the phase transition from ice to water as measured by sweeping from low to high temperatures in a differential scanning calorimeter (DSC) measurement, and have an average mesopore diameter of 3 to 15 nm as calculated by the DSC measurement, and the secondary silica particles are added to a polymer membrane material. This allows for significantly improved gas permeability in a gas separation membrane produced by adding the secondary silica particles to a polymer membrane material. DETAILED DESCRIPTION OF THE INVENTION

[0032] The present invention will be described in detail below. The secondary silica particles of the present invention are silica particles formed via a hydrolysate of at least one compound selected from the group consisting of tetraalkoxysilanes and trialkoxysilanes of silica particles having an average primary particle diameter (A1) of 5 to 50 nm as measured by the Sears method or nitrogen gas adsorption method, and are characterized in that the secondary silica particles, which contain water in pores formed by the secondary silica particles, have an endothermic peak of -6°C or lower associated with a phase transition from ice to water as measured by sweeping from low to high temperatures in differential scanning calorimetry (DSC) measurement, and have an average mesopore diameter calculated by DSC measurement of 3 to 15 nm.

[0033] The silica particles contained in the secondary silica particles of the present invention preferably have an average primary particle diameter of 5 to 50 nm, more preferably 5 to 30 nm, and even more preferably 5 to 15 nm, as measured by the Sears method or nitrogen gas adsorption method.

[0034] The average primary particle size of silica particles is usually measured by nitrogen gas adsorption method, but since measurement errors become large when the average primary particle size is less than 8 nm, the Sears method is preferably used.

[0035] The secondary silica particles may be in the form of a powder, or may be in the form of a silica sol dispersed in an aqueous medium or an organic solvent.The silica sol preferably has a silica concentration in the range of 0.1 to 50% by mass.

[0036] Here, by making the average secondary particle diameter of the silica secondary particles sufficiently small relative to the thickness of a practical gas separation membrane, it is possible to prevent performance degradation due to membrane defects. Generally, the thickness of the separation functional layer used in a gas separation membrane is about 100 to 1000 nm, so the average secondary particle diameter of the silica secondary particles measured by dynamic light scattering is preferably 10 to 1000 nm, more preferably 10 to 500 nm, and particularly preferably 50 to 200 nm.

[0037] The average mesopore diameter of silica secondary particles can be determined by measuring the degree of melting point depression due to capillary coagulation of water within the pores using DSC. This method utilizes the phenomenon that the melting point of ice trapped in mesopores is lower than the melting point (approximately 0°C) of ice outside the pores, known as bulk ice, and that the degree of melting point depression varies depending on the mesopore diameter. Using this phenomenon, the average mesopore diameter can be determined from the peak melting temperature of ice within the pores of silica secondary particles, measured by sweeping from low to high temperatures in DSC measurements.

[0038] For measuring the average mesopore diameter of silica secondary particles, reference can be made to the description in Kazuhiro Ishikiriyama et al.; JOURNAL OF COLLOID AND INTERFACE SCIENCE, 171, 103-111, (1995).

[0039] The silica secondary particles of the present invention have mesopores with an average mesopore diameter of 3 to 15 nm as calculated by DSC measurement, and particularly preferably have mesopores with an average mesopore diameter of 3 to 7 nm. Pores with a diameter of less than 3 nm make it difficult for substances to enter or exit, and gas permeability may decrease when the silica secondary particles are mixed with a matrix resin and used as a gas separation membrane. Furthermore, when silica secondary particles are mixed with a matrix resin, mesopores with a diameter of more than 15 nm are filled with the matrix resin, causing clogging of the pores and potentially preventing the improvement of gas permeability.

[0040] Examples of methods for incorporating moisture into the pores of the secondary silica particles include a method of immersing the secondary silica particles in water for a long period of time, a method of exposing the secondary silica particles to water vapor under high-temperature and high-humidity conditions, and a method of immersing the secondary silica particles in water and then reducing the pressure to remove the air trapped in the pores and simultaneously cause water to penetrate into the pores.

[0041] Furthermore, the secondary silica particles of the present invention preferably have at least one exothermic peak associated with the phase transition from water to ice between -40 and -20°C when measured by sweeping from high to low temperatures with a differential scanning calorimeter.

[0042] The measurement temperature range for DSC measurement preferably includes both the endothermic peak and the exothermic peak, and therefore the measurement temperature range for DSC measurement is preferably -80°C to 30°C, more preferably -60°C to 20°C.

[0043] The scanning speed of the DSC measurement is preferably 0.1°C / min to 10°C / min, more preferably 3°C / min to 10°C / min, so that the melting peak of ice inside the pores of the silica secondary particles and the melting peak of ice outside the pores can be observed independently.

[0044] In the present invention, the secondary silica particles, which contain water in their pores, have an endothermic peak at or below −6°C associated with the phase transition from ice to water as measured by sweeping from low to high temperatures in a differential scanning calorimeter (DSC) measurement, and have an average mesopore diameter of 3 to 15 nm as calculated by the DSC measurement, and the secondary silica particles are added to a polymer membrane material. This allows for significantly improved gas permeability in a gas separation membrane produced by adding the secondary silica particles to a polymer membrane material.

[0045] As explained above, the secondary silica particles of the present invention are silica particles formed via a hydrolysate of at least one compound selected from the group consisting of tetraalkoxysilanes and trialkoxysilanes of silica particles having an average primary particle diameter (A1) of 5 to 50 nm as measured by the Sears method or nitrogen gas adsorption method; the secondary silica particles have moisture contained in the pores of the silica secondary particles; the secondary silica particles have an endothermic peak associated with an ice-to-water phase transition of −6°C or less as measured by sweeping from low to high temperatures in differential scanning calorimetry (DSC) measurement; and the average mesopore diameter calculated by DSC measurement is 3 to 15 nm; and a gas separation membrane produced by adding the secondary silica particles to a polymer membrane material can have significantly improved gas permeability.

[0046] Therefore, the secondary silica particles are obtained by hydrolyzing at least one compound selected from the group consisting of tetraalkoxysilanes and trialkoxysilanes of silica particles having an average primary particle diameter (A1) of 5 to 50 nm as measured by the Sears method or nitrogen gas adsorption method, and the secondary silica particles contain water in the pores of the secondary silica particles. When the secondary silica particles are measured by a differential scanning calorimeter (DSC), the secondary silica particles have an endothermic peak of -6°C or less associated with the phase transition from ice to water as measured by sweeping from low to high temperatures, and the average mesopore diameter calculated by the DSC measurement is 3 to 15 nm. This makes it possible to obtain secondary silica particles that can significantly improve the gas permeability of gas separation membranes produced by adding them to polymer membrane materials.

[0047] The secondary silica particles of the present invention are obtained by converting silica particles having the above-described primary particle diameter into secondary particles via a hydrolyzate of at least one compound selected from the group consisting of tetraalkoxysilanes and trialkoxysilanes.

[0048] The tetraalkoxysilane (tetraalkyl orthosilicate) is the compound (a) shown below or an oligomer thereof, and the trialkoxysilane (trialkyl orthosilicate) is the compound (b) shown below or an oligomer thereof. Compounds (a) and (b) may be used alone or in combination.

[0049] [ka] Here, Q 1 , Q 2 is selected from alkyl groups having 1 to 8 carbon atoms, and a plurality of Q 1 and Q 2 may be the same or different. 3 is selected from alkyl groups having 1 to 18 carbon atoms, cyclic alkyl groups, aryl groups, glycidoxyalkyl groups, arylalkyl groups, and aminoalkyl groups.

[0050] The secondary silica particles are produced by mixing silica particles with a compound and heating the mixture, as will be described in detail later. As a result, the silica particles bond together via the hydrolyzate of at least one compound selected from the group consisting of tetraalkoxysilanes and trialkoxysilanes to form the secondary silica particles.

[0051] Furthermore, multiple silica particles are bonded together to form secondary silica particles, and the average size of the pores, which are spaces surrounded by multiple silica particles within the secondary silica particles, is measured as the average mesopore diameter.

[0052] Such secondary silica particles of the present invention can be produced as follows. Silica secondary particles can be produced by adding at least one compound selected from the group consisting of compound (a) and compound (b) to colloidal silica having an average primary particle diameter of 5 to 50 nm as measured by the Sears method or nitrogen gas adsorption method in a hydrophilic organic solvent in the presence of a basic catalyst, and heating at 40 to 100°C.

[0053] The size and volume of the pores in the secondary silica particles can be controlled by changing the average primary particle diameter of the raw colloidal silica, as measured by the Sears method or nitrogen gas adsorption method. Using raw materials with a small average primary particle diameter reduces the average mesopore diameter and increases the volume of mesopores between 3 and 15 nm. Therefore, adding this material to gas separation membranes can significantly improve gas permeability.

[0054] In the present invention, as the primary particle size of the raw material silica nanoparticles decreases, the specific surface area of ​​the secondary silica particles increases, and gelation due to excessive aggregation of the silica nanoparticles becomes more likely, making it difficult to control the secondary silica particle size and mesopore size. Therefore, it is necessary to appropriately adjust the silica concentration during the reaction, the amount of basic catalyst added, and the amount of at least one compound selected from the group consisting of tetraalkyl silicates and trialkoxysilanes added.

[0055] For example, when colloidal silica having an average primary particle size of 5 nm is used, the silica concentration is preferably 1 to 10 mass %; when colloidal silica having an average primary particle size of 12 nm is used, the silica concentration is preferably 5 to 15 mass %; when colloidal silica having an average primary particle size of 22 nm is used, the silica concentration is preferably 20 to 40 mass %; and when colloidal silica having an average primary particle size of 45 nm is used, the silica concentration is preferably 30 to 50 mass %.

[0056] The amount of at least one compound selected from the group consisting of tetraalkoxysilanes and trialkoxysilanes used in the production of secondary silica particles of the present invention is determined based on the surface area of ​​the raw silica primary particles per m 2 The number of Si atoms in at least one compound selected from the group consisting of tetraalkoxysilanes and trialkoxysilanes is 1.0 × 10 -7 ~1.0×10 -5 The preferred range is 1.0 x 10 -6 ~1.0×10 -5The amount of at least one compound selected from the group consisting of tetraalkoxysilanes and trialkoxysilanes is more preferably in the range of 1.0 × 10 mol. -7 mol / m 2 If the amount is less than 1.0 × 10, the particles will not bond together, and secondary silica particles with mesopores of 3 to 15 nm will not be formed. -5 mol / m 2 If the amount is larger than this, the silica nanoparticles will over-aggregate and gel too quickly, making it difficult to control the secondary particle size, which is undesirable.

[0057] In the method for producing secondary silica particles of the present invention, silica sol is heated to 40 to 100°C in an aqueous medium in the presence of a basic catalyst and at least one compound selected from the group consisting of tetraalkoxysilanes and trialkoxysilanes. If the heating temperature is below 40°C, the hydrolysis reaction rate of the at least one compound selected from the group consisting of tetraalkyl silicates and trialkoxysilanes is slow, making it impossible to obtain the desired secondary silica particles. Furthermore, if the heating temperature exceeds 100°C, the silica nanoparticles will over-aggregate and gel too quickly, making it difficult to control the secondary particle size, which is undesirable. Therefore, a heating temperature of 40 to 100°C is particularly preferred.

[0058] Usable base catalysts include ammonia, primary amines, secondary amines, and tertiary amines. Examples of primary amines include aliphatic amines such as methylamine, ethylamine, propylamine, isopropylamine, butylamine, isobutylamine, sec-butylamine, tert-butylamine, pentylamine, hexylamine, aminocyclohexane, methoxyethylamine, ethoxyethylamine, 3-methoxypropylamine, 3-ethoxypropylamine, ethylenediamine, hexamethylenediamine, N,N-dimethylethylenediamine, 3-(diethylamino)propylamine, and 3-(dibutylamino)propylamine; unsaturated alkylamines such as allylamine; and aromatic amines such as benzylamine, phenethylamine, and xylylenediamine.

[0059] Examples of secondary amines include aliphatic monoamines such as dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, dipentylamine, dihexylamine, and dicyclohexylamine; aromatic monoamines such as diphenylamine and dibenzylamine; benzylamines such as N-methylbenzylamine, N-ethylbenzylamine, N-butylbenzylamine, N-pentylbenzylamine, and N-hexylbenzylamine; and cyclic amines such as pyrrolidine, methylpyrrolidine, piperidine, methylpiperidine, piperazine, and morpholine.

[0060] Examples of tertiary amines include trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, and pyridine.

[0061] Of the above bases, ammonia and water-soluble amines are preferred, and amines with low boiling points of 120° C. or less are more preferred, with ammonia, methylamine, dimethylamine, ethylamine, diethylamine, propylamine, dipropylamine, isopropylamine, diisopropylamine, trimethylamine, and triethylamine being particularly preferred. These bases have relatively low boiling points (for example, approximately 120° C. or less) and are therefore easily removed by distillation or the like, and are unlikely to remain in the dispersion of the secondary silica particles and adversely affect the formation of over-aggregates of the secondary silica particles over time.

[0062] The amount of base catalyst used in the production of secondary silica particles of the present invention is determined based on the surface area of ​​the raw material primary silica particles per m 2 1.0 × 10 moles of base catalyst -8 ~1.0×10 -4 The preferred range is 1.0 x 10 -8 ~1.0×10 -6 The range of 1.0 × 10 mol is more preferable. -8 mol / m 2If the amount is less than 1.0 × 10, the particles will not bond together, and secondary silica particles with mesopores of 3 to 15 nm will not be formed. -4 mol / m 2 If the amount is larger than this, the silica nanoparticles will over-aggregate and gel too quickly, making it difficult to control the secondary particle size, which is undesirable.

[0063] In the present invention, the solvent used in producing the secondary silica particles may be a hydrophilic organic solvent, preferably an alcohol, more preferably methanol, ethanol, or isopropanol.

[0064] The alcohol dispersion (alcohol sol) of the secondary silica particles of the present invention obtained in the above step can be subjected to a step of replacing the organic solvent with a different organic solvent to obtain an organosilica sol. The method of replacing the alcohol with an organic solvent can be carried out by a known method such as evaporation at normal or reduced pressure, ultrafiltration, or sedimentation separation and redispersion. The organic solvent is preferably replaced when the silica concentration of the alcohol sol in which the secondary silica particles of the present invention are dispersed is in the range of 1 to 50% by mass, more preferably 5 to 40% by mass.

[0065] Examples of organic solvents that can be used include alcohols such as methanol, ethanol, isopropanol, and butanol; polyhydric alcohols such as ethylene glycol and propylene glycol; ethers such as ethylene glycol monomethyl ether, dimethyl ether, tetrahydrofuran, and 4-methyltetrahydropyran; and amides such as N-methylpyrrolidone, dimethylacetamide, and dimethylformamide.

[0066] Furthermore, by treating the surfaces of the secondary silica particles of the present invention with a silane coupling agent, a silylating agent, or the like, it is possible to obtain an aqueous sol with improved dispersibility in hydrophilic solvents, or an organosol dispersed in hydrophobic solvents such as toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, acrylic monomers, etc. In other words, by adding a surface modifying group to the surfaces of the secondary silica particles, it is possible to improve dispersibility in hydrophilic solvents or dispersibility in hydrophobic solvents.

[0067] The hydrolyzable silane used in producing the secondary silica particles of the present invention having such surface modifying groups can include a hydrolyzable silane of formula (1) and / or a hydrolyzable silane of formula (2). The hydrolyzable silane of formula (1) and the hydrolyzable silane of formula (2) can be used in combination with other hydrolyzable silanes, and the weight ratio of the hydrolyzable silane of formula (1) and / or the hydrolyzable silane of formula (2) to other hydrolyzable silanes can be in the range of 1:0.1 to 1.0, or 1:0.5 to 1.0.

[0068] [ka]

[0069] In formula (1), R 1 each contains an acryloxy group, a methacryloxy group, an aryl group, an alkyl group, a glycidoxy group, an amino group, or an alkylene group having 1 to 10 carbon atoms and containing such a functional group, and is bonded to a Si atom via a Si-C bond; R 2 are hydrolyzable groups each consisting of an alkoxy group, an acyloxy group, or a halogen group, and at least one R 2 The hydrolyzable group forms a Si—O—Si bond on the surface of the silica particle, and a represents an integer of 1 to 3.

[0070] In formula (2), R 3 are alkyl groups bonded to silicon atoms by Si-C bonds, and R 4 represents an alkoxy group, an acyloxy group, or a halogen group; Y represents an alkylene group, an arylene group, an NH group, or an oxygen atom; b represents an integer of 0 to 3; and c represents an integer of 0 or 1.

[0071] The alkyl group is an alkyl group having 1 to 10 carbon atoms, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, a cyclopropyl group, an n-butyl group, an i-butyl group, an s-butyl group, a t-butyl group, a cyclobutyl group, a 1-methyl-cyclopropyl group, a 2-methyl-cyclopropyl group, an n-pentyl group, a 1-methyl-n-butyl group, a 2-methyl-n-butyl group, a 3-methyl-n-butyl group, a 1,1-dimethyl-n-propyl group, a 1,2-dimethyl-n-propyl group, a 2,2-dimethyl-n-propyl group, a 1-ethyl- n-Propyl, cyclopentyl, 1-methylcyclobutyl, 2-methylcyclobutyl, 3-methylcyclobutyl, 1,2-dimethylcyclopropyl, 2,3-dimethylcyclopropyl, 1-ethylcyclopropyl, 2-ethylcyclopropyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl , 2,2-dimethyl-n-butyl, 2,3-dimethyl-n-butyl, 3,3-dimethyl-n-butyl, 1-ethyl-n-butyl, 2-ethyl-n-butyl, 1,1,2-trimethyl-n-propyl, 1,2,2-trimethyl-n-propyl, 1-ethyl-1-methyl-n-propyl, 1-ethyl-2-methyl-n-propyl, cyclohexyl, 1-methyl-cyclopentyl, 2-methyl-cyclopentyl, 3-methyl-cyclopentyl, 1-ethyl-cyclobutyl, 2-ethyl-cyclobutyl group, 3-ethyl-cyclobutyl group, 1,2-dimethyl-cyclobutyl group, 1,3-dimethyl-cyclobutyl group, 2,2-dimethyl-cyclobutyl group, 2,3-dimethyl-cyclobutyl group, 2,4-dimethyl-cyclobutyl group, 3,3-dimethyl-cyclobutyl group, 1-n-propyl-cyclopropyl group, 2-n-propyl-cyclopropyl group, 1-i-propyl-cyclopropyl group, 2-i-propyl-cyclopropyl group, 1,2,2-trimethyl-cyclopropyl group, 1,2,3-trimethyl-cyclopropyl group, 2,2,Examples include a 3-trimethyl-cyclopropyl group, a 1-ethyl-2-methyl-cyclopropyl group, a 2-ethyl-1-methyl-cyclopropyl group, a 2-ethyl-2-methyl-cyclopropyl group, and a 2-ethyl-3-methyl-cyclopropyl group. The alkylene group may be an alkylene group derived from the alkyl group described above. Examples of the aryl group include a phenyl group, a naphthyl group, and an anthryl group, and the arylene group is a group derived from the above aryl group, and examples thereof include a phenylene group, a naphthylene group, and an anthrylene group.

[0072] The alkoxy group may be an alkoxy group having 1 to 10 carbon atoms, such as a methoxy group, an ethoxy group, an n-propoxy group, an i-propoxy group, an n-butoxy group, an i-butoxy group, an s-butoxy group, a t-butoxy group, an n-pentyloxy group, a 1-methyl-n-butoxy group, a 2-methyl-n-butoxy group, a 3-methyl-n-butoxy group, a 1,1-dimethyl-n-propoxy group, a 1,2-dimethyl-n-propoxy group, a 2,2-dimethyl-n-propoxy group, a 1-ethyl-n-propoxy group, an n-hexyloxy group, a 1-methyl-n-pentyloxy group, a 2-methyl-n-butoxy group, a 1-ethyl-n-propoxy group, a 2-methyl-n-but ... -n-pentyloxy group, 3-methyl-n-pentyloxy group, 4-methyl-n-pentyloxy group, 1,1-dimethyl-n-butoxy group, 1,2-dimethyl-n-butoxy group, 1,3-dimethyl-n-butoxy group, 2,2-dimethyl-n-butoxy group, 2,3-dimethyl-n-butoxy group, 3,3-dimethyl-n-butoxy group, 1-ethyl-n-butoxy group, 2-ethyl-n-butoxy group, 1,1,2-trimethyl-n-propoxy group, 1,2,2-trimethyl-n-propoxy group, 1-ethyl-1-methyl-n-propoxy group and 1-ethyl-2-methyl- Examples of cyclic alkoxy groups include cyclopropoxy, cyclobutoxy, 1-methylcyclopropoxy, 2-methylcyclopropoxy, cyclopentyloxy, 1-methylcyclobutoxy, 2-methylcyclobutoxy, 3-methylcyclobutoxy, 1,2-dimethylcyclopropoxy, 2,3-dimethylcyclopropoxy, 1-ethylcyclopropoxy, 2-ethylcyclopropoxy, cyclohexyloxy, 1-methylcyclopentyloxy, 2-methylcyclopentyl ...1,2-dimethylcyclopropoxy, 2,3-dimethylcyclopropoxy, 1-ethylcyclopropoxy, 2-ethylcyclopropoxy, 1,2-dimethylcyclopropoxy, 2,3-dimethylcyclopropoxy, 1-ethylcyclopropoxy, 2-ethylcyclopropoxy, 1,2-dimethylcyclopropoxy, 2,3-dimethylcyclopropoxy, 1-ethylcyclopentyloxy, 2-methylcyclopentyloxy, 3-methylcyclobutoxy, 1,2-dimethylcyclopropoxy, 2,3-dimethylcyclopropoxy, 1-ethylcyclopropoxy, 2-ethylcyclopropoxy, 1,2-dimethylcyclopropoxy, 2,3-dimethylcyclopropoxy, 1-ethylcyclopropoxy, 2-ethylcyclopropoxy, 1,2-dimethylcyclopropoxy, 2,3-dimethylcyclopropoxy, 1-ethylcyclopentyloxy, 2-methylcyclopentyloxy, 1-methylcyclopentyloxy, 2-methylcyclopentyloxy, 1-methylcyclopentyloxy, 1-methylcyclopentyloxy, 1-methylcyclopentyloxy, -methyl-cyclopentyloxy group, 1-ethyl-cyclobutoxy group, 2-ethyl-cyclobutoxy group, 3-ethyl-cyclobutoxy group, 1,2-dimethyl-cyclobutoxy group, 1,3-dimethyl-cyclobutoxy group, 2,2-dimethyl-cyclobutoxy group, 2,3-dimethyl-cyclobutoxy group, 2,4-dimethyl-cyclobutoxy group, 3,3-dimethyl-cyclobutoxy group, 1-n-propyl-cyclopropoxy group, 2-n-propyl-cyclopropoxy group, 1-i-propyl-cyclopropoxy group, 2-i-propyl-cyclopropoxy group, 1,2,Examples include a 2-trimethyl-cyclopropoxy group, a 1,2,3-trimethyl-cyclopropoxy group, a 2,2,3-trimethyl-cyclopropoxy group, a 1-ethyl-2-methyl-cyclopropoxy group, a 2-ethyl-1-methyl-cyclopropoxy group, a 2-ethyl-2-methyl-cyclopropoxy group, and a 2-ethyl-3-methyl-cyclopropoxy group.

[0073] The acyloxy group is an acyloxy group having 2 to 10 carbon atoms, and examples thereof include a methylcarbonyloxy group, an ethylcarbonyloxy group, an n-propylcarbonyloxy group, an i-propylcarbonyloxy group, an n-butylcarbonyloxy group, an i-butylcarbonyloxy group, an s-butylcarbonyloxy group, a t-butylcarbonyloxy group, an n-pentylcarbonyloxy group, a 1-methyl-n-butylcarbonyloxy group, a 2-methyl-n-butylcarbonyloxy group, a 3-methyl-n-butylcarbonyloxy group, a 1,1-dimethyl-n-propylcarbonyloxy group, a 1,2-dimethyl-n-propylcarbonyloxy group, a 2,2-dimethyl-n-propylcarbonyloxy group, a 1-ethyl-n-propylcarbonyloxy group, an n-hexylcarbonyloxy group, a 1-methyl-n-pentylcarbonyloxy group, a 2-methyl-n-pentylcarbonyloxy group, a oxy group, a 3-methyl-n-pentylcarbonyloxy group, a 4-methyl-n-pentylcarbonyloxy group, a 1,1-dimethyl-n-butylcarbonyloxy group, a 1,2-dimethyl-n-butylcarbonyloxy group, a 1,3-dimethyl-n-butylcarbonyloxy group, a 2,2-dimethyl-n-butylcarbonyloxy group, a 2,3-dimethyl-n-butylcarbonyloxy group, a 3,3-dimethyl-n-butylcarbonyloxy group, a 1-ethyl-n-butylcarbonyloxy group, a 2-ethyl-n-butylcarbonyloxy group, a 1,1,2-trimethyl-n-propylcarbonyloxy group, a 1,2,2-trimethyl-n-propylcarbonyloxy group, a 1-ethyl-1-methyl-n-propylcarbonyloxy group, a 1-ethyl-2-methyl-n-propylcarbonyloxy group, a phenylcarbonyloxy group, and a tosylcarbonyloxy group. The halogen group includes fluorine, chlorine, bromine, iodine, and the like.

[0074] Examples of the hydrolyzable silane include the following compounds:

[0075] [ka]

[0076] In the above formula, R 2 represents a hydrolyzable group consisting of an alkoxy group, an acyloxy group, or a halogen group. These are available as silane coupling agents manufactured by Shin-Etsu Chemical Co., Ltd.

[0077] The compound of formula (2) contains a trimethylsilylating agent, and examples thereof include hexamethyldisilane, hexamethyldisiloxane, hexamethyldisilazane, etc. These silylating agents are available from Tokyo Chemical Industry Co., Ltd.

[0078] The surface treatment of silica particles with a silane compound can be carried out, for example, by adding hydrolyzable silane of formula (1) and / or formula (2) to a methanol sol of silica particles to carry out hydrolysis and surface modification.

[0079] For the hydrolysis of an alkoxysilyl group, an acyloxysilyl group, or a halogenated silyl group, 0.5 to 100 moles, preferably 1 to 10 moles, of water is used per mole of the hydrolyzable group.

[0080] Furthermore, 0.001 to 10 mol, preferably 0.001 to 1 mol of the hydrolysis catalyst can be used per 1 mol of the hydrolyzable group.

[0081] The reaction temperature during hydrolysis and condensation is usually 20 to 80°C. The hydrolysis may be complete or partial, that is, the hydrolyzed product may contain residual hydrolyzates or monomers. A catalyst can be used in the hydrolysis and condensation. As the hydrolysis catalyst, a chelate compound, an organic acid, an inorganic acid, an organic base, or an inorganic base can be used in combination.

[0082] The secondary silica particles of the present invention can be dried and used as silica powder, but can also be used as silica sol.

[0083] When the secondary silica particles of the present invention are used as silica powder, an alcohol sol or organosol of the secondary silica particles can be dried under normal pressure, reduced pressure, or freezing, then pulverized in a dry pulverizer such as a mortar mill, mill, or mixer, and then fired at 100 to 600°C to obtain silica powder. In this case, if the dry pulverization is too intense, some of the silica particles will be destroyed, but moderate pulverization can prevent this. These silica powders can be used as catalyst supports, adsorbents, substitutes for mesoporous silica, and the like.

[0084] The film-forming composition of the present invention contains the secondary silica particles of the present invention and a matrix resin, and is useful for gas separation membranes. This is because the secondary silica particles of the present invention are solvent-dispersed porous silica that is easy to composite with polymers and whose particle size is not too large compared to the thickness of the gas separation membrane, and are secondary aggregated silica with a particle size and mesopores suitable for gas separation membranes.

[0085] The secondary silica particles of the present invention can be mixed with a matrix resin solution as a silica secondary particle dispersion sol to produce a membrane-forming composition that is a composite material in which the secondary silica particles are dispersed at the nano-level in the matrix resin, and this can be used to form a gas separation membrane.

[0086] When producing this film-forming composition, as described above, it is possible to simply mix the silica secondary particle dispersion sol with a matrix resin solution, but it is preferable to use a masterbatch method, as described below, in which a masterbatch is produced in advance and the film-forming composition is produced from this masterbatch. In this way, gas separation membranes produced by the masterbatch method can suppress membrane defects and improve permeation rates by reducing the thickness.

[0087] The matrix resin used in the film-forming composition of the present invention may be, for example, any known resin conventionally used to form gas separation membranes. Specific examples include, but are not limited to, polyimide, cellulose acetate, polysulfone, polyethersulfone, polyethylene glycol crosslinked bodies, dimethyl silicone, polyvinyl alcohol, modified polyvinyl alcohol, polysubstituted acetylene, poly-4-methylpentene, natural rubber, and microporous polymers. In the present invention, microporous polymers, dimethyl silicone, polyvinyl alcohol, polyimide, and cellulose acetate are preferred, with polyimide, cellulose acetate, and microporous polymers being particularly preferred.

[0088] Cellulose acetate has a structure represented by the following formula (I).

[0089] [ka] (n is an integer between 50 and 500, R 5 represents -H or -COCH3, and at least one is -COCH3.

[0090] The matrix resin is a mixture of tetracarboxylic dianhydride represented by the following formula (10) and aromatic diamine R 8 A polyimide having a repeating unit represented by the following formula (II) obtained by condensation polymerization with (NH2)2 is preferred.

[0091] [ka] (R 6 represents a tetravalent organic group.

[0092] [ka] (R 7 represents a tetravalent organic group. 8 is a residue obtained by removing amine from an aromatic diamine, and represents an aromatic group having 6 to 14 carbon atoms. n represents an integer of 50 to 500.

[0093] where R 7 is a tetravalent residue obtained by removing a carboxy group from the tetracarboxylic acid of formula (10), and is preferably at least one organic group selected from the following general formulae (3) to (5) (wherein in general formula (5), X represents at least one group selected from -C(CF3)2-, -C(CF3)(CH6H5)-, -C(CH3)(C6H5)-, -CH2-, -C(CH3)2-, -CO-, -SO2-, -O-, -S-, -NH-, -COO-, -CONH-, -Si(CH3)2-, -O-C6H4-C(CH3)2-C6H4-O-, -O-C6H4-O-, -O-CH2-CH2-O-, -CF2CF2CF2-, -CO-C6H4-CO-, -O-C6H4-S-C6H4-O-).

[0094] [ka]

[0095] Furthermore, the matrix resin is preferably a microporous polymer. Here, the microporous polymer is an intrinsically microporous polymer, which is one of the microporous organic materials, and is one class of microporous organic materials, and reference can be made to the following documents. (Reference 1) Budd, P. M. et al., Solution-Processed, Organophilic Membrane Derived from a Polymer of Intrinsic Microporosity. Adv. Mater. 16, 456-459 (2004). (Reference 2) McKeown, N. B. et al., Polymers of intrinsic microporosity (PIMs): Bridging the void between microporous and polymeric materials. Chemistry - A European Journal 11, 2610-2620 (2005). (Reference 3) Budd, P. M. et al., Gas separation membranes from polymers of intrinsic microporosity. J. Membr. Sci. 251, 263-269 (2005). (Reference 4) McKeown, N. B. & Budd, P. M., Polymers of intrinsic microporosity (PIMs): Organic materials for membrane separations, heterogeneous catalysis and hydrogen storage. Chem. Soc. Rev.35, 675-683 (2006). (Reference 5) Du, N. et al., Polymer nanosieve membranes for CO2-capture applications. Nat. Mater. 10, 372-375 (2011). (Reference 6) Carta, M. et al., An Efficient Polymer Molecular Sieve for Membrane Gas Separations. Science 339, 303-307 (2013). (Reference 7) Japanese Patent Publication No. 2017-509744

[0096] The concept of intrinsic microporous polymers was first proposed by Budd and McKeown in 2002. International Publication WO 2003 / 000774 A1 describes organic microporous network materials comprising rigid 3-dimensional networks of planar porphyrin macrocycles, in which the pyrrole residues of adjacent macrocycles are connected by rigid linkers that immobilize these adjacent macrocycles, resulting in non-coplanar orientation of the porphyrin planes. A preferred material of this invention is a phthalocyanine network. These organic microporous materials are known as network PIMs.

[0097] Another invention by Budd and McKeown, International Publication No. WO 2005 / 012397 A2 and US Patent No. 7,690,514 B2, describes a microporous organic macromolecule that includes first generally planar species connected by a rigid linker at points of distortion, where two adjacent first planar species connected by the linker are in a non-coplanar orientation, with the proviso that the first planar species is other than a porphyrin macrocycle.

[0098] Among these microporous polymers, PIM-1 represented by the structure shown in the following formula (III) is particularly preferred.

[0099] [ka] (n represents an integer between 50 and 1000.)

[0100] The solvent used in producing the film-forming composition can be of any type as long as it dissolves the polymer and is compatible with the solvent used to disperse the silica secondary particles. Examples of such solvents include tetrahydrofuran (THF), 4-methyltetrahydropyran (MTHP), chloroform, dimethylacetamide (DMAc), toluene, linear alcohols having 1 to 6 carbon atoms, branched alcohols having 1 to 6 carbon atoms, hexane, heptane, octane, decane, N-methyl-2-pyrrolidone (NMP), and N,N-dimethylformamide (DMF), either alone or in combination.

[0101] The mass ratio of the matrix resin to the silica secondary particles in the film-forming composition is 0.1 to 50 parts by mass, preferably 1 to 30 parts by mass, and more preferably 1 to 15 parts by mass, per 100 parts by mass of the matrix resin.

[0102] The mass ratio of the matrix resin to the solvent in the film-forming composition is 500 to 10,000, preferably 1,000 to 3,000, and more preferably 1,000 to 2,000, relative to 100 parts by mass of the matrix resin.

[0103] In order to uniformly disperse the silica secondary particles in the matrix resin, it is preferable to produce the film-forming composition via a step of producing a masterbatch.

[0104] Any type of solvent can be used when producing the masterbatch as long as it dissolves the polymer and is compatible with the dispersion medium for the silica secondary particles. Examples of the first solvent include tetrahydrofuran (THF), 4-methyltetrahydropyran (MTHP), chloroform, dimethylacetamide (DMAc), toluene, linear alcohols having 1 to 6 carbon atoms, branched alcohols having 1 to 6 carbon atoms, hexane, heptane, octane, nonane, decane, N-methyl-2-pyrrolidone (NMP), and N,N-dimethylformamide (DMF), either alone or in combination.

[0105] In this step, a good dispersion state can be easily obtained using a stirring means such as a mixer, but if necessary, ultrasonic treatment, wet jet mill treatment, wet bead mill treatment, high-pressure homogenizer treatment, etc. may also be carried out, which will further improve the dispersion state.

[0106] The first solvent is then dried to obtain a masterbatch. Drying can be performed by a known method such as reduced pressure drying using an evaporator, vacuum drying, or hot air drying. Some solvent may remain in the masterbatch after drying, as long as the dispersibility of the silica secondary particles is not impaired.

[0107] The amount of the silica secondary particles may be set to be in the range of 0.1 to 50 parts by mass, preferably 1 to 30 parts by mass, and more preferably 1 to 15 parts by mass, relative to 100 parts by mass of the matrix resin.

[0108] By uniformly dispersing the masterbatch in an appropriate second solvent, such as THF, MTHP, chloroform, toluene, linear alcohols having 1 to 6 carbon atoms, branched alcohols having 1 to 6 carbon atoms, hexane, heptane, octane, nonane, decane, DMAc, NMP, or DMF, or a mixture of two or more of these solvents, a film-forming composition in which the silica secondary particles are uniformly dispersed can be obtained.

[0109] The film is produced by applying the composition to a support (substrate) and then evaporating the second solvent. The support to be applied can be of any material as long as it is not deteriorated by the solvent, and examples thereof include silicon wafers, polyethersulfone (PES), polysulfone (PSF), polypropylene (PP), polyethylene (PE), polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), polyacrylonitrile (PAN), polyimide, polyamide, cellulose acetate, triacetate, polyacrylonitrile, and epoxy resins.

[0110] Furthermore, the pore size of the porous support is not particularly limited. For example, in the case of a porous support used for a gas separation membrane, taking into consideration gas permeability and coatability, the pore size is preferably 0.01 μm or more and 1 μm or less, more preferably 0.02 μm or more and 0.50 μm or less, and most preferably 0.025 μm or more and 0.20 μm or less.

[0111] The coating method is preferably one that can apply the coating uniformly and without unevenness onto the substrate, and known coating methods and techniques such as dip coating (immersion method), spin coating, blade coating, spray coating, bar coater method, microgravure method, gravure method, and slot die method can be used, but are not particularly limited. Blade coating method is preferred, and it is particularly preferred to use a doctor blade. [Example]

[0112] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

[0113] <Measuring device / method> [Primary particle size of colloidal silica] The average primary particle size of silica particles with an average primary particle size of less than 8 nm was measured using the Sears method, and the average primary particle size of silica particles with an average primary particle size of 8 nm or more was measured using the nitrogen gas adsorption method.

[0114] [Water content of silica secondary particle dispersion sol] The moisture content was measured three times by amperometric titration using a Karl Fischer moisture meter MKC-520 (manufactured by Kyoto Electronics Manufacturing Co., Ltd.), and the average value was calculated.

[0115] [Solid content of secondary silica particle dispersion sol] Approximately 1 g of the silica secondary particle dispersion sol was placed in an aluminum dish and dried at 130°C, after which the residue was weighed and calculated.

[0116] [Average secondary particle size of silica particles measured by dynamic light scattering] The dispersion of secondary silica particles was diluted 100 times by weight with the dispersion medium, and the particle size was measured using a dynamic light scattering particle size measuring device "Zetasizer Nano" (manufactured by the Malvern Division of Spectrix Co., Ltd.).

[0117] [Peak melting temperature of ice inside the pores of secondary silica particles] Approximately 0.05 g of silica secondary particle powder dried at 130°C was weighed into a 5 mL glass vial, immersed in 1 mL of ion-exchanged water, and then placed in a glass desiccator. The vial was then depressurized at room temperature for 2 hours to remove air trapped within the pores and allow water to penetrate the pores. The peak melting temperature of the ice within the pores of the silica secondary particles was measured by differential scanning calorimetry (DSC) using a DSC7020 (Hitachi High-Tech Corporation). Approximately 3–8 mg of water-entrained silica secondary particle samples were cooled from room temperature to −60°C at a scanning rate of 5°C / min to induce a phase transition from water to ice, then held at −60°C for 1 minute. The sample was then heated from −60°C to +20°C at a scanning rate of 5°C / min. The endothermic peak temperature was measured during this process. The endothermic peak observed in the range of -3 to +1°C was excluded from the measurement because it is due to the phase transition of the ice outside the pores. [Average mesopore diameter of silica secondary particles] The average mesopore diameter of the silica secondary particles was calculated using the following formula. Average mesopore diameter [nm] = 2 × (33.39 - 0.1903 × melting point depression [°C]) / peak melting temperature of ice in the pores [°C] The melting point depression was calculated using the following formula. Melting point depression [℃] = Peak melting temperature of ice outside the pores [℃] - Peak melting temperature of ice inside the pores [℃]

[0118] [Gas permeability measurement] The gas permeability of the membrane was measured using a gas permeability measuring device GTR-2ADF (manufactured by GTR Tech Co., Ltd.) at 35°C and a measurement pressure of 100 kPa by the differential pressure manometer method. The measurement was performed using nitrogen and carbon dioxide as the supply gases.

[0119] [Calculation of the composition ratio of masterbatch powder using a differential thermobalance] Approximately 5 mg of the masterbatch powder was placed on a platinum pan, and a differential thermal balance TG-8120 (Rigaku) ​​was used to measure the mass loss of the organic matter contained in the sample at a heating rate of 3°C / min and measurement temperatures of 40 to 1000°C. At 1000°C, all organic matter was burned off. However, mass loss up to 210°C was excluded as it was attributed to adsorbed moisture.

[0120] [Example 1-1] <Synthesis of Silica Secondary Particles-1> 103.6 g of a water-dispersed sol of silica nanoparticles (ST-OXS, manufactured by Nissan Chemical Industries, Ltd., SiO concentration 10.5% by mass, average primary particle size measured by Sears method 5.4 nm) and 103.6 g of isopropanol (IPA) were weighed into a 500 mL eggplant-shaped flask, and the water was distilled off using an evaporator while adding 1 L of IPA at 60 Torr, yielding 160.0 g of an IPA-dispersed sol (IPA-ST-XS) in which the water had been replaced with IPA. The solids concentration of the resulting IPA-dispersed sol was 7.0% by mass, and the water content was 0.6% by mass.

[0121] Next, 70.0 g of IPA-ST-XS, 26.3 g of IPA, and 0.69 g of triethoxysilane (TEOS) (Alfa Aesar) were added to a 250 mL three-necked round-bottom flask equipped with a condenser. After stirring for 30 minutes at room temperature using a magnetic stirrer, 1.34 g of a 1% by weight solution of triethylamine (TEA) (Tokyo Chemical Industry Co., Ltd.) in IPA was added, and the mixture was heated and refluxed for 5 hours using an oil bath. 1.56 g of trimethylsilane (TMS) (Tokyo Chemical Industry Co., Ltd.) was added to the reaction solution, and the mixture was refluxed for 1 hour to obtain an IPA dispersion sol of silica secondary particles-1. The resulting IPA dispersion sol of silica secondary particles-1 had a solids concentration of 5.1% by mass, an average particle size of 131.7 nm measured by dynamic light scattering, a peak melting temperature of ice inside the pores of -15.5°C, a peak melting temperature of ice outside the pores of -2.2°C measured by DSC, and an average mesopore size of 4.0 nm. The analytical results are summarized in Table 1.

[0122] [Example 1-2] <Synthesis of Silica Secondary Particles-2> A 250 mL three-necked round-bottom flask equipped with a condenser was charged with 30.1 g of an IPA dispersion sol of silica nanoparticles (IPA-ST, manufactured by Nissan Chemical Co., Ltd., SiO2 concentration 30.2 mass%, average primary particle diameter 11.3 nm as determined by nitrogen gas adsorption), 58.9 g of IPA, 0.35 g of pure water, and 1.21 g of TEOS. Stirred magnetically at room temperature for 30 minutes, then added 0.30 g of a 10 mass% TEA / IPA solution and heated to reflux in an oil bath for 5 hours. 2.75 g of TMS was added to the reaction solution, and the mixture was refluxed for 1 hour to obtain an IPA dispersion sol of silica secondary particles-2. The resulting IPA-dispersed sol of secondary silica particles-2 had a solids concentration of 10.6% by mass, an average particle size of 102.4 nm as measured by dynamic light scattering, a peak melting temperature of ice inside the pores of -12.6°C, a peak melting temperature of ice outside the pores of +0.1°C as measured by DSC, and an average mesopore size of 4.9 nm. The analytical results are summarized in Table 1.

[0123] [Example 1-3] <Synthesis of Silica Secondary Particles-3> A 50 mL eggplant-shaped flask equipped with a condenser was charged with 15.0 g of a methanol dispersion sol of silica nanoparticles (MA-ST-M, manufactured by Nissan Chemical Co., Ltd.; SiO concentration: 40.2% by mass; average primary particle diameter: 21.0 nm as determined by nitrogen gas adsorption) and 0.54 g of TEOS. The mixture was stirred at room temperature for 30 minutes using a magnetic stirrer. After this, 0.53 g of a 10% by mass solution of TEA in IPA was added and the mixture was heated and refluxed in an oil bath for 5 hours. 1.24 g of TMS was added to the reaction solution, and the mixture was refluxed for 1 hour to obtain a methanol dispersion sol of silica secondary particles-3. The resulting methanol dispersion sol of silica secondary particles-3 had a solids concentration of 31.8% by mass, an average particle diameter of 111.8 nm as determined by dynamic light scattering, a peak melting temperature of intrapore ice of -8.2°C, a peak melting temperature of extrapore ice of -0.4°C, and an average mesopore diameter of 7.8 nm as measured by DSC. The analytical results are summarized in Table 1.

[0124] [Example 1-4] <Synthesis of Silica Secondary Particles-4> A 250 mL three-neck round-bottom flask equipped with a condenser was charged with 80.1 g of a methanol dispersion sol of silica nanoparticles (MA-ST-L, Nissan Chemical Co., Ltd., SiO concentration 40.5 wt%, average primary particle diameter 44.0 nm as determined by nitrogen gas adsorption) and 1.67 g of TEOS. The mixture was stirred at room temperature for 30 minutes using a magnetic stirrer, after which 0.81 g of TEA was added and the mixture was heated and refluxed in an oil bath for 5 hours. 3.80 g of TMS was added to the reaction solution, and the mixture was refluxed for 1 hour to obtain a methanol dispersion sol of silica secondary particles-4. The resulting methanol dispersion sol of silica secondary particles-4 had a solids concentration of 40.9 wt%, an average particle diameter of 115.0 nm as determined by dynamic light scattering, a peak melting temperature of intrapore ice of -6.3°C, a peak melting temperature of extrapore ice of -0.4°C, and an average mesopore diameter of 10.3 nm as measured by DSC. The analytical results are summarized in Table 1.

[0125] [Comparative Example 1-1] <Synthesis of Silica Secondary Particle Dispersion Sol IPA-Silica Secondary Particles-5> A 50 mL eggplant-shaped flask equipped with a condenser was charged with 15.0 g of an IPA dispersion sol of silica nanoparticles (IPA-ST-ZL, manufactured by Nissan Chemical Co., Ltd.; SiO concentration 30.5% by mass; average primary particle diameter as determined by nitrogen gas adsorption: 82.6 nm) and 0.16 g of TEOS. The mixture was stirred at room temperature for 30 minutes using a magnetic stirrer, after which 0.23 g of TEA was added and the mixture was heated and refluxed in an oil bath for 5 hours. 0.36 g of TMS was added to the reaction solution, and the mixture was refluxed for 1 hour to obtain an IPA dispersion sol of silica secondary particles-5. The resulting IPA dispersion sol of silica secondary particles-5 had a solids concentration of 31.1% by mass, an average particle diameter of 197.9 nm measured by dynamic light scattering, a peak melting temperature of intrapore ice of -4.0°C, a peak melting temperature of extrapore ice of -1.1°C measured by DSC, and an average mesopore diameter of 16.4 nm. The analytical results are summarized in Table 1.

[0126] [Table 1]

[0127] [Example 2-1] (Preparation of PIM-1 / silica secondary particle-1 composite film) In a 5 mL vial, 0.0087 g of the dried powder of silica secondary particles-1 synthesized in Example 1-1 and the intrinsic microporous polymer (PIM-1, weight-average molecular weight 2.9 × 10) shown in structural formula 1 were placed. 5 0.28 g of silica secondary particle-1-containing PIM-1 (weight average molecular weight / number average molecular weight = 4.2) and 3.71 g of tetrahydrofuran (THF, manufactured by Kanto Chemical) were weighed out and dissolved using a magnetic stirrer at room temperature. The mixture was then dispersed in an ultrasonic cleaner for 5 minutes. The resulting PIM-1 solution containing silica secondary particle-1 was poured into a glass dish (diameter 6.0 cm) and allowed to stand at room temperature to produce a composite membrane. The gas permeability of the resulting composite membrane was measured, and the results are shown in Table 2.

[0128] [ka] (Structural formula 1)

[0129] [Example 2-2] (Preparation of PIM-1 / silica secondary particle-2 composite film) A composite membrane was prepared in the same manner as in Example 2-1, except that the dry powder of silica secondary particles-2 synthesized in Example 1-2 was used instead of the dry powder of silica secondary particles-1, and gas permeation measurements were performed. The results are shown in Table 2.

[0130] [Example 2-3] (Preparation of PIM-1 / silica secondary particle-3 composite film) A composite membrane was prepared in the same manner as in Example 2-1, except that the dry powder of silica secondary particles-3 synthesized in Example 1-3 was used instead of the dry powder of silica secondary particles-1, and gas permeation measurements were performed. The results are shown in Table 2.

[0131] [Example 2-4] (Preparation of PIM-1 / silica secondary particle-4 composite film) A composite membrane was prepared in the same manner as in Example 2-1, except that the dry powder of silica secondary particles-4 synthesized in Example 1-4 was used instead of the dry powder of silica secondary particles-1, and gas permeation measurements were performed. The results are shown in Table 2.

[0132] [Comparative Example 2-1] (Preparation of PIM-1 Single Membrane) 0.28 g of PIM-1 and 3.72 g of THF were weighed into a 5 mL vial and dissolved by stirring at room temperature using a magnetic stirrer. The PIM-1 solution was then poured into a glass petri dish (6.0 cm diameter) and allowed to stand at room temperature to produce a composite membrane, from which gas permeation measurements were performed. The results are shown in Table 2.

[0133] [Comparative Example 2-2] (Preparation of PIM-1 / silica secondary particle-5 composite film) A composite membrane was prepared in the same manner as in Example 2-1, except that the dry powder of silica secondary particles-5 synthesized in Comparative Example 1-1 was used instead of the dry powder of silica secondary particles-1, and gas permeation measurements were performed. The results are shown in Table 2.

[0134] [Example 2-5] (Preparation of 6FDA-3MPA / silica secondary particle-1 composite film) Instead of PIM-1, polyimide (6FDA-3MPA, weight-average molecular weight 1.7 × 10) shown in structural formula 2 was used. 5 A composite membrane was prepared in the same manner as in Example 2-1, except that a cellulose ester copolymer (weight average molecular weight / number average molecular weight=2.1) was used, and gas permeation measurements were carried out. The results are shown in Table 2.

[0135] [ka] (Structural formula 2)

[0136] [Example 2-6] (Preparation of 6FDA-3MPA / silica secondary particle-2 composite film) A composite membrane was prepared in the same manner as in Example 2-2, except that 6FDA-3MPA was used instead of PIM-1, and gas permeation measurements were carried out. The results are shown in Table 2.

[0137] [Example 2-7] (Preparation of 6FDA-3MPA / silica secondary particle-3 composite film) A composite membrane was prepared in the same manner as in Example 2-3, except that 6FDA-3MPA was used instead of PIM-1, and gas permeation measurements were carried out. The results are shown in Table 2.

[0138] [Example 2-8] (Preparation of 6FDA-3MPA / silica secondary particle-4 composite film) A composite membrane was prepared in the same manner as in Example 2-4, except that 6FDA-3MPA was used instead of PIM-1, and gas permeation measurements were carried out. The results are shown in Table 2.

[0139] [Comparative Example 2-3] (Preparation of 6FDA-3MPA Single Membrane) A composite membrane was prepared in the same manner as in Comparative Example 2-1, except that 6FDA-3MPA was used instead of PIM-1, and gas permeation measurements were carried out. The results are shown in Table 2.

[0140] Comparative Example 2-4 (Preparation of 6FDA-3MPA / silica secondary particle-5 composite film) A composite membrane was prepared in the same manner as in Comparative Example 2-2, except that 6FDA-3MPA was used instead of PIM-1, and gas permeation measurements were carried out. The results are shown in Table 2.

[0141] [Example 2-9] (Preparation of CA / silica secondary particle-1 composite film) A composite membrane was prepared in the same manner as in Example 2-1, except that cellulose acetate (CA, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., substitution degree: 2.4, average degree of polymerization: approximately 150, average molecular weight: approximately 40,000) shown in structural formula 3 was used instead of PIM-1, and gas permeation measurements were carried out. The results are shown in Table 2.

[0142] [ka] (Structural formula 3) (R 5 is -H or -COCH3)

[0143] [Example 2-10] (Preparation of CA / silica secondary particle-2 composite film) A composite membrane was prepared in the same manner as in Example 2-2, except that CA was used instead of PIM-1, and gas permeation measurements were carried out. The results are shown in Table 2.

[0144] [Example 2-11] (Preparation of CA / silica secondary particle-4 composite film) A composite membrane was prepared in the same manner as in Example 2-4, except that CA was used instead of PIM-1, and gas permeation measurements were carried out. The results are shown in Table 2.

[0145] [Comparative Example 2-5] (Preparation of CA Single Membrane) A composite membrane was prepared in the same manner as in Comparative Example 2-1, except that CA was used instead of PIM-1, and gas permeation measurements were carried out. The results are shown in Table 2.

[0146] [Table 2]

[0147] The results in Table 2 confirm that the gas separation membrane, which has a peak melting temperature of ice in the pores measured by DSC of -20 to -6°C and contains silica secondary particles with an average mesopore diameter of 3 to 15 nm, has an improved gas permeability coefficient.

[0148] [Preparation of PIM-1 / silica secondary particle-1 masterbatch powder] 1.19 g of PIM-1 and 58.8 g of 4-methyltetrahydropyran (MTHP) (Tokyo Chemical Industry Co., Ltd.) were weighed into a 200 mL eggplant-shaped flask and dissolved by stirring at room temperature using a magnetic stirrer. Then, 10.0 g of the IPA dispersion sol of silica secondary particles-1 prepared in Example 1-1 (solid content concentration 5.1 mass%) was added to prepare a mixed solution in which 100 parts by mass of PIM-1 and 42.9 parts by mass of silica secondary particles-1 were used. Next, the solvent was distilled off using an evaporator at 10 Torr to obtain a precipitate. To remove the MTHP remaining in the precipitate, ethanol was added to the flask, and the mixture was refluxed in an oil bath for 2 hours for boiling and washing, and the supernatant was removed by decantation. This boiling and washing operation was performed twice, followed by 2 hours of vacuum heating and drying at 150 °C to obtain a PIM-1 / silica secondary particle-1 masterbatch powder (MB). The composition ratio of the masterbatch powder calculated by differential thermobalance was 100 parts by mass of PIM-1 and 46.8 parts by mass of secondary silica particles-1, which was the same as when the powder was charged.

[0149] [Example 3-1] (Preparation of PIM-1 / silica secondary particle-1 composite film) 0.0174 g of the MB powder prepared in Example 1-1, 0.163 g of PIM-1, and 2.33 g of THF were weighed into a 5 mL vial and stirred at room temperature using a magnetic stirrer to dissolve the mixture. This prepared a solution containing 100 parts by mass of PIM-1 and 3.1 parts by mass of silica secondary particles-1. The mixture was then subjected to a dispersion treatment in an ultrasonic cleaner for 5 minutes. The resulting PIM-1 solution containing silica secondary particles-1 was poured into a glass dish (diameter 6.0 cm) and allowed to stand at room temperature to produce a composite membrane. The gas permeation of the resulting composite membrane was measured, and the results are shown in Table 3.

[0150] [Example 3-2] (Preparation of PIM-1 / silica secondary particle-1 composite film) A composite membrane was prepared in the same manner as in Example 3-1, except that 0.0542 g of MB powder, 0.138 g of PIM-1, and 2.31 g of THF were weighed out to prepare a solution containing 100 parts by mass of PIM-1 and 9.9 parts by mass of silica secondary particles-1. The gas permeation measurement was performed. The results are shown in Table 3.

[0151] [Example 3-3] (Preparation of PIM-1 / silica secondary particle-1 composite film) A composite membrane was prepared in the same manner as in Example 3-1, except that 0.0968 g of MB powder, 0.110 g of PIM-1, and 2.30 g of THF were weighed out to prepare a solution containing 17.6 parts by mass of silica secondary particles-1 per 100 parts by mass of PIM-1, and gas permeation measurements were performed. The results are shown in Table 3.

[0152] [Example 3-4] (Preparation of PIM-1 / silica secondary particle-1 composite film) A composite membrane was prepared in the same manner as in Example 3-1, except that 0.146 g of MB powder, 0.0762 g of PIM-1, and 2.29 g of THF were weighed out to prepare a solution containing 26.6 parts by mass of silica secondary particles-1 per 100 parts by mass of PIM-1. Gas permeation measurements were performed on the composite membrane. The results are shown in Table 3.

[0153] [Table 3]

[0154] The results in Table 3 confirmed that the gas permeability coefficient improved when the silica content was in the range of 9 to 27 parts by mass per 100 parts by mass of the matrix resin PIM-1.Furthermore, it was shown that the gas permeability coefficient reached its maximum when the silica content was 17.6 parts by mass.

Claims

1. The average primary particle diameter (A) measured by the Sears method or the nitrogen gas adsorption method １ ) are secondary silica particles formed via a hydrolysis product of at least one compound selected from the group consisting of tetraalkoxysilanes and trialkoxysilanes of silica particles of 5 to 50 nm, and the secondary silica particles have moisture contained in pores formed by the secondary silica particles, and the secondary silica particles have at least one endothermic peak associated with a phase transition from ice to water at -6°C or lower when measured by sweeping from low to high temperatures with a differential scanning calorimeter.

2. The secondary silica particles according to claim 1, characterized in that they have at least one exothermic peak associated with a phase transition from water to ice between −40°C and −20°C, as measured by sweeping from high to low temperatures with a differential scanning calorimeter.

3. 2. The secondary silica particles according to claim 1, which have mesopores with an average mesopore diameter of 3 to 15 nm as measured by a differential scanning calorimeter.

4. 2. The secondary silica particles according to claim 1, having a surface modifying group derived from a hydrolyzable silane represented by formula (1) or (2). 【Chemical 1】 In formula (1), R １ each contains an acryloxy group, a methacryloxy group, an aryl group, an alkyl group, a glycidoxy group, an amino group, or an alkylene group having 1 to 10 carbon atoms and containing such a functional group, and is bonded to a Si atom via a Si-C bond; R ２ are hydrolyzable groups each consisting of an alkoxy group, an acyloxy group, or a halogen group, and at least one R ２ The hydrolyzable group forms a Si—O—Si bond on the surface of the silica particle, and a represents an integer of 1 to 3. In formula (2), R ３ are each an alkyl group bonded to a silicon atom by a Si—C bond, and R ４ represents an alkoxy group, an acyloxy group, or a halogen group; Y represents an alkylene group, an arylene group, an NH group, or an oxygen atom; b represents an integer of 0 to 3; and c is an integer of 0 or 1.

5. The silica secondary particles according to any one of claims 1 to 4 are dispersed in an acidic or alkaline aqueous medium or organic solvent, and the average primary particle diameter (A １ ) and the average secondary particle diameter (A ２ ) and the ratio (A ２ / A １ ) is more than 1 and 40 or less.

6. A film-forming composition comprising the silica secondary particles according to any one of claims 1 to 4 and a matrix resin.

7. The film-forming composition according to claim 6, which is for gas separation.

8. The matrix resin is a cellulose acetate represented by the following formula (I), 【Chemistry 2】 (n is an integer from 50 to 500, R ５ is -H or -COCH ３ At least one of the groups is -COCH ３ It is.) A tetracarboxylic dianhydride represented by the following formula (10) and an aromatic diamine R ８ (NH ２ ) ２ a polyimide having a repeating structure represented by the following formula (II) obtained by condensation polymerization of 【Chemistry 3】 (R ６ represents a tetravalent organic group. 【Chemistry 4】 (R ７ represents a tetravalent organic group. ８ is a residue obtained by removing the amine from an aromatic diamine, and represents an aromatic group having 6 to 14 carbon atoms. n represents an integer of 50 to 500.

8. The film-forming composition according to claim 7, wherein the polymer is at least one selected from the group consisting of polymers having intrinsic microporosity.

9. 9. The film-forming composition according to claim 8, wherein the intrinsic microporous polymer is PIM-1 represented by the following formula (III): 【Chemistry 5】 (n represents an integer of 50 to 1000.)

10. The average primary particle diameter (A) measured by the Sears method or the nitrogen gas adsorption method １ a step of converting silica particles having a particle size of 5 to 50 nm into secondary particles via a hydrolyzate of at least one compound selected from the group consisting of tetraalkoxysilanes and trialkoxysilanes to obtain secondary silica particles; The method for producing secondary silica particles is characterized in that the secondary silica particles, which contain water in their pores, are scanned from low to high temperatures with a differential scanning calorimeter to measure endothermic peaks associated with the phase transition from ice to water, and those having at least one endothermic peak at or below -6°C are used as secondary silica particles for gas separation membranes.

11. The method for producing secondary silica particles according to claim 10, characterized in that the secondary silica particles for gas separation membranes have at least one exothermic peak associated with a phase transition from water to ice between −40 and −20° C., as measured by sweeping from high to low temperatures with a differential scanning calorimeter.

12. The method for producing secondary silica particles according to claim 10 or 11, characterized in that the secondary silica particles for use in a gas separation membrane have mesopores with an average mesopore diameter of 3 to 15 nm as measured by a differential scanning calorimeter.

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