Surfactant-containing surface-treated silica sol and method for producing same

Abstract

[Problem] To provide a composition having excellent dispersion stability of silica particles under high temperature and / or high salt concentration conditions and having excellent salt resistance. [Solution] This composition comprises surface-modified silica particles, a surfactant, and a solvent, wherein, when the composition is diluted to a silica concentration of 2 mass% with a 5 mM sodium tetraborate aqueous solution to prepare a test solution, and affinity capillary electrophoresis is conducted under conditions of a capillary temperature of 25°C, a capillary applied voltage of 30 kV, a capillary inner diameter of 75 μm, a total capillary length of 112.5 cm, and an effective capillary length of 104 cm, using the surface-modified silica particles as a ligand and a surfactant containing an anionic surfactant, a nonionic surfactant, or a mixture of two or more thereof as an analyte, the composition has an electrophoretic mobility of -0.017 to -0.0010 cm2 / V·min.

Description

Surfactant-containing surface-treated silica sol and method for producing the same

[0001] The present invention relates to a composition comprising surface-treated (surface-modified) silica particles, a surfactant, and a solvent, and the composition exhibits behavior that exhibits a specific range of electrical mobility by affinity capillary electrophoresis (Affinity CE).

[0002] Because silica particles have high hardness and heat resistance, they are widely used as a modifier blended into resins, etc., to impart hardness and heat resistance to the resin. In recent years, silica particles have been used in enhanced oil recovery (EOR) flooding, in which silica particles are injected into an oil reservoir in an inland or offshore oil field to recover crude oil. For example, in anticipation of improving the effectiveness of stripping crude oil from the rock surface, proposals have been made to improve the crude oil recovery rate by blending fine particles such as aqueous silica sol (colloidal silica) into a crude oil recovery solution (Patent Document 1).

[0003] Meanwhile, electrophoretic analytical methods are known as a method for analyzing trace amounts of proteins, nucleic acids, and the like, and a representative example is capillary electrophoresis (also known as CE). Capillary electrophoresis is a method in which differences in charge of substances present in a solution sample are separated as differences in their mobility by applying a voltage within a capillary (see, for example, Patent Document 2). A technique called affinity capillary electrophoresis (also known as affinity CE) has also been proposed for capillary electrophoresis, which uses intermolecular affinities, such as specific affinities in biological systems (e.g., the affinity between DNA and its complementary DNA, DNA and RNA transcribed from DNA, enzymes and substrates, antigens and antibodies, etc.), to impart specificity to separation. Specifically, this analytical technique focuses on the fact that when one of two interacting components (ligand) is added to the electrophoresis solution in the capillary and the other component (analyte) is electrophoresed, only the interacting molecular species in the sample mixture undergoes a change in migration speed (see, for example, Patent Document 3).

[0004] International Publication No. 2019 / 054414 Special Publication No. Hei 9-504375 Publication Japanese Patent Application Publication No. Hei 7-311198

[0005] The present invention provides a composition comprising surface-treated (surface-modified) silica particles, a surfactant, and a solvent, and exhibiting a behavior that exhibits electrical mobility within a specific range by affinity capillary electrophoresis (Affinity CE). The composition provides excellent dispersion stability of the silica particles and excellent salt tolerance at high temperatures and / or high salt concentrations, and also provides a composition that has a high surfactant transport effect when injected into a geological formation.

[0006] That is, in a first aspect, the present invention provides a composition comprising surface-modified silica particles, a surfactant, and a solvent, wherein the composition is diluted with a 5 mM aqueous solution of sodium tetraborate to a silica concentration of 2 mass % to prepare a test solution, and when affinity capillary electrophoresis is performed with the composition under the conditions of a capillary temperature of 25°C, a capillary applied voltage of 30 kV, a capillary inner diameter of 75 μm, a capillary total length of 112.5 cm, and a capillary effective length of 104 cm, the composition exhibits a resolution of -0.017 to -0.0010 cm. ２ / V·min. As a second aspect, the present invention relates to the composition according to the first aspect, further comprising a polyorganosiloxane. As a third aspect, the present invention relates to the composition according to the first aspect, wherein the surface-modified silica particles, as unmodified silica particles prior to surface modification, have an average primary particle size of 5 to 100 nm. As a fourth aspect, the present invention relates to the composition according to the first aspect, wherein the surface-modified silica particles have an average particle size of 5 to 200 nm as measured by a dynamic light scattering method. As a fifth aspect, the present invention relates to the composition according to the first aspect, wherein the surface-modified silica particles are particles obtained by coating at least a portion of the surface of unmodified silica particles with a silane compound having an organic group, and the organic group is a hydrocarbon group-containing organic group, an epoxy group-containing organic group, an amino group-containing organic group, a (meth)acryloyl group-containing organic group, a hydroxy group-containing organic group, or a carboxy group-containing organic group. As a sixth aspect, the present invention relates to the composition according to the first aspect, in which the surfactant is an α-olefin sulfonate, a polyoxyethylene alkyl phenyl ether, a combination of an α-olefin sulfonate and a polyoxyethylene alkyl phenyl ether, or a combination of an α-olefin sulfonate, a sulfate salt of a higher alcohol having 6 to 24 carbon atoms, and a polyoxyethylene alkyl phenyl ether. As a seventh aspect, the present invention relates to the composition according to the first aspect, in which the solvent includes water or salt water. As an eighth aspect, the present invention relates to the composition according to the first aspect, in which the solvent includes methanol or ethanol. As a ninth aspect, the present invention relates to the composition according to the first aspect, in which, in a high-temperature salt resistance test in which the composition is stored at 100°C for 10 hours in an environment with a salt concentration of 4% by mass at a silica concentration of 0.1% by mass, 0.5% by mass, or 1.0% by mass, the ratio expressed as DLS average particle size after the high-temperature salt resistance test / DLS average particle size before the test is 1.5 or less (the rate of change in average particle size is 50% or less).As a tenth aspect, the present invention relates to a method for producing the composition according to the second aspect, comprising the steps of: heating a mixture containing silica particles, a silane compound having an organic group, and a solvent to 10 to 150°C while stirring to obtain a mixed solution containing silica particles, at least a portion of which is coated with a silane compound having an organic group, a polyorganosiloxane, and a solvent; and mixing the obtained mixed solution with a surfactant. As an eleventh aspect, the present invention relates to a method for producing the composition according to the tenth aspect, comprising, after the step of obtaining a mixed solution containing silica particles coated with the silane compound and a polyorganosiloxane, a step of maintaining the mixed solution at 10 to 80°C for 1 hour to 1 month before or after the step of mixing the obtained mixed solution with a surfactant.

[0007] The composition of the present invention exhibits a specific range of electrical mobility behavior by affinity capillary electrophoresis (Affinity CE). The composition exhibits excellent dispersion stability under conditions that may impair the dispersion stability of silica particles contained in the composition, such as high temperatures and / or high salt concentrations, resulting in a composition with excellent salt tolerance under such conditions. Furthermore, because the composition of the present invention exhibits a specific range of electrical mobility and has excellent salt tolerance under high temperatures and / or high salt concentrations, it is expected to be used as a component that contributes to stability in, for example, high-electrolyte media (aqueous emulsions). Furthermore, the fact that the composition of the present invention exhibits the specific range of electrical mobility means that the silica particles and surfactant contained in the composition interact sufficiently. When the composition is injected into a geological formation as a crude oil recovery solution, the sufficient interaction between the two is expected to enhance the transport efficiency of the surfactant within the formation, thereby enhancing crude oil recovery efficiency.

[0008] FIG. 1 shows CE charts (after data correction using a standard substance (terephthalic acid)) of affinity capillary electrophoresis measurements performed on samples containing aqueous silica sol, a surfactant, and an electrophoresis running solution in Examples 1-1 to 1-10 and Comparative Example 1-2.

[0009] The present invention relates to a composition comprising surface-modified silica particles, a surfactant, and a solvent.

[0010] The present inventors focused on intermolecular interactions in systems containing silica particles, surfactants, etc., and adopted affinity capillary electrophoresis as an analytical method. When affinity capillary electrophoresis was performed on a system containing silane particles surface-modified with a silane compound, a surfactant, and optionally a polyorganosiloxane derived from the silane compound, it was confirmed that the peak of electrical mobility shifted depending on the amount of surface modification with the silane compound, i.e., a change occurred in the intermolecular interactions within the system.

[0011] In detail, as shown in the examples described later, silane particles whose surfaces have been modified with a silane compound (the amount of the silane compound added as a modifying agent is 2 to 46 particles / nm ２ In a system containing a surfactant and a surface-modified silica particle as the ligand, affinity capillary electrophoresis was performed using the surfactant as the analyte. As a result, when the same surfactants (two anionic surfactants and one nonionic surfactant) were used (Examples 1-3 and 1-4, Comparative Example 1-2), as shown in the CE chart (Figure 1) and the results of electrical mobility (Table 2) of the affinity capillary electrophoresis measurement, the silane compound treatment amount (addition amount) relative to the silica particle was 8.0 particles / nm. ２ In the aqueous silica sol of (Synthesis Example 3), the minimum peak of electrical mobility was −0.0121 cm ２ / V·min (Examples 1-3) (Note that the minimum peak and maximum peak here refer to the electrical mobility values ​​(peak positions), not the peak intensity (height)). This peak can be attributed to an anionic surfactant, which has a charge, among the surfactants that are analytes. As the treatment amount (addition amount) of the silane compound increases, this minimum peak moves to the uncharged side, and when the treatment amount (addition amount) is 31 particles / nm ２ (Synthesis Example 4), the shape of the minimum peak changes (Examples 1-4), and the treatment amount (addition amount) is 46 particles / nm ２ In (Synthesis Example 5), the minimum peak is −0.0080 cm ２The maximum peak of electrical mobility was observed at 0.0005 to 0.0007 cm / V·min (Comparative Example 1-2). The fluctuation of the maximum peak of electrical mobility due to the amount of silane compound added (amount of silane compound added) was small. ２ / V·min, and this peak can be attributed to an uncharged nonionic surfactant (and to the uncharged standard substance, N-methyl-2-pyrrolidone (NMP)). The peak of electrical mobility is often observed as a sharp peak, but it can also be observed as a gentle peak toward the maximum (see, for example, Figure 1 and Example 1-8).

[0012] In this example, in the region where the amount of surface treatment with the silane compound is small, the surface-modified silica particles have SiO －The silica particles are anionic due to the addition of the silane compound. However, as the amount of surface modification increases, the shielding ability of the silica particles by the silane compound increases, blocking the charge on the anionic surface. As a result, the charge of the surface-modified silica particles is thought to shift toward the uncharged side. Therefore, it is thought that the surface-modified silica particles gradually increase their interaction with the uncharged nonionic surfactant, which increases the steric hindrance effect near the silica particle surface and improves the stability of the silica particles. Furthermore, as revealed by the results of affinity CE, as the amount of surface modification of the silica particles increases, the electrical mobility of the anionic surfactant shifts toward the uncharged side, and the anionicity decreases. In the presence of a slightly anionic polyorganosiloxane, the anionic surfactant is thought to gradually increase its interaction with the polyorganosiloxane. The formed structure efficiently prevents the silica particles from approaching each other, improving the stability of the silica particles. On the other hand, if the amount of polyorganosiloxane present is excessive, not only the anionic surfactant but also more nonionic surfactants will interact with the polyorganosiloxane. As a result, the amount of nonionic surfactant that interacts with the surface of the surface-modified silica particles decreases, making it impossible to impart a sufficient stabilizing effect due to steric hindrance to the surface-modified silica particles, thereby reducing the stabilizing effect of the surface-modified silica particles. Note that, although the interaction was confirmed when an anionic surfactant and a nonionic surfactant were used as surfactants in this example, the addition of other surfactants is permitted as long as the above-mentioned interaction is not impaired.

[0013] [Electrical Mobility] The composition of the present invention is characterized in that it exhibits an electrical mobility in a specific range when affinity capillary electrophoresis (Affinity CE) is performed. Specifically, a composition of the present invention containing surface-modified silica particles, a surfactant, and a solvent is diluted with a 5 mM aqueous solution of sodium tetraborate to a silica concentration of 2 mass% to prepare a test solution. When this test solution is subjected to affinity capillary electrophoresis under the conditions of a capillary temperature of 25°C, a capillary applied voltage of 30 kV, a capillary inner diameter of 75 μm, a capillary total length of 112.5 cm, and a capillary effective length of 104 cm, using the surface-modified silica particles as the ligand and the surfactant as the analyte, the electrical mobility is −0.017 to −0.0010 cm. ２ The peak of the electrical mobility is in the range of -0.017 to -0.0085 cm / V·min. The preferred range of the peak of the electrical mobility varies somewhat within the above range depending on the selection of the components of the composition, etc. ２ / V·min, or, for example, −0.014 to −0.0085 cm ２ The peak of the electrical mobility is at 1 / V·min.

[0014] For measuring the electrical mobility, for example, a capillary electrophoresis system (trade name: Agilent 7100 Capillary Electrophoresis System, manufactured by Agilent Technologies, Inc.) can be used as the measuring device, an Agilent model G1600-64311 capillary (inner diameter 75 μm, total length 112.5 cm, effective length 104 cm, fused silica capillary), and a PDA detector (195 nm±5 nm) can be used as the capillary. Furthermore, N-methyl-2-pyrrolidone (NMP), methacrylic acid, and terephthalic acid can be used as standard substances. After performing electrophoresis, the electrical mobility (cm) can be calculated from the migration time (min) based on the following formula: ２ / V·min) can be calculated. ２ / V・min)=(L ｅｆｆ ×L ｔｏｔ ) / V × (1 / t ｅｐ -1 / t ｅｏ ) Formula (1) L ｅｆｆ : Effective length of capillary (104 cm) L ｔｏｔt: Total length of capillary (112.5 cm) ｅｐ t: Migration time of various surfactants (min) ｅｏ : Migration time (min) of uncharged standard substance (NMP) *t ｅｐ and t ｅｏ is the detection time under UV = 195 nm conditions, V is the voltage (30 kV), and the data obtained is based on the electrical mobility (-0.00283 cm) of terephthalic acid, a standard substance (stable specimen), to eliminate the influence of different instruments. ２ / V·min) are corrected to the same value. Alternatively, the surface-modified silica particles, surfactant, etc. may be separated from a composition containing surface-modified silica particles, a surfactant, and a solvent, and a sample containing the separated surface-modified silica particles and a separately prepared analyte (surfactant) and solvent may be prepared, and affinity capillary electrophoresis may be performed on the sample to determine the electrical mobility. The method for separating the surface-modified silica particles, etc. is not particularly limited, and examples include a separation method using ultrafiltration. The filtrate obtained by ultrafiltration may also be used as a sample containing the analyte (surfactant) and solvent.

[0015] In the composition of the present invention, by having an electrical mobility within the above-mentioned specific range, intermolecular interactions within the system are optimized, and the composition has excellent dispersion stability, for example, under high temperatures and / or high salt concentrations, and therefore has excellent salt resistance under such environments. Each component will be described in detail below.

[0016] [Surface-modified silica particles] The composition of the present invention contains surface-modified silica particles. In the present invention, surface-modified silica particles include particles having at least a portion of their surface bonded to at least a portion of a silane compound (surface modifier) ​​described below, and particles having at least a portion of their surface coated with a silane compound (surface modifier) ​​described below. In this specification, the "surface modification" of silica particles with a silane compound may also be referred to as "surface treatment," and "surface-modified silica particles" may also be referred to as "surface-treated silica particles." In other words, in this specification, "surface modification" includes both a case in which the silica particle surface is coated with a surface modifier and a case in which the surface modifier is bonded to the silica particle surface, and these cases are collectively referred to as "surface-modified silica particles." In the present invention, the embodiment in which "at least a portion of the surface modifier is bonded to at least a portion of the surface of the silica particles" refers to an embodiment in which the surface modifier is bonded to at least a portion of the surface of the silica particles, i.e., an embodiment in which the surface modifier is bonded to a portion of the surface of the silica particles, an embodiment in which the surface modifier is bonded to a portion of the surface of the silica particles and covers at least a portion of the surface, and even an embodiment in which the surface modifier is bonded to the entire surface of the silica particles and covers the entire surface. Furthermore, in the present invention, the embodiment in which "at least a portion of the surface of the silica particles is coated with the surface modifier" refers to an embodiment in which the surface modifier covers at least a portion of the surface of the silica particles, i.e., an embodiment in which the surface modifier is coated to a portion of the surface of the silica particles, and an embodiment in which the surface modifier is coated to the entire surface of the silica particles. In this embodiment, it is not important whether or not an organosilicon compound, which is an example of a surface modifier, is bonded to the surface of the silica particles.

[0017] <Unmodified silica particles> As the unmodified silica particles constituting the surface-modified silica particles, for example, silica particles derived from aqueous silica sol can be used.Aqueous silica sol refers to a colloidal dispersion system in which aqueous solvent is used as a dispersion medium and colloidal silica particles are dispersoids, and can be produced by a known method using water glass (aqueous sodium silicate solution) as raw material.The average particle size of aqueous silica sol refers to the average particle size of colloidal silica particles as dispersoids.

[0018] In this specification, the average particle diameter of aqueous silica sol (colloidal silica particles) refers to the specific surface area diameter or the Sears particle diameter measured by the nitrogen adsorption method (BET method) unless otherwise specified. The average particle diameter here represents the average value of the primary particle diameters, and is therefore also referred to as the average primary particle diameter. The specific surface area diameter (average particle diameter (specific surface area diameter) D (nm)) measured by the nitrogen adsorption method (BET method) is the specific surface area S (m ２ From the particle size (D / g), the particle size is given by the formula D(nm) = 2720 / S. The Sears particle size refers to the average particle size measured based on the literature: G. W. Sears, Anal. Chem. 28(12) 1981, 1956, Rapid Method for Measuring Colloidal Silica Particle Size. Specifically, when 1.5 g of SiO ２ The equivalent diameter (specific surface area diameter) is calculated by determining the specific surface area of ​​the colloidal silica from the amount of 0.1 N NaOH required to titrate colloidal silica equivalent to 1000 ppm from pH 4 to pH 9. The average particle diameter of the aqueous silica sol (colloidal silica particles) measured by the nitrogen adsorption method (BET method) or the Sears method can be, for example, 3 to 500 nm, 3 to 300 nm, 3 to 200 nm, 5 to 150 nm, 5 to 100 nm, 5 to 50 nm, or 5 to 30 nm. If the average particle diameter is less than 3 nm, the particles will tend to aggregate, while if the average particle diameter is greater than 500 nm, the particles may clog pores or act as foreign matter depending on the application, causing adverse effects in compositions using the particles.

[0019] Furthermore, the average particle size of silica particles in aqueous silica sol (DLS average particle size: Z-average particle size, harmonic mean particle size) can be measured by dynamic light scattering to determine whether the silica particles in the aqueous silica sol are in a dispersed or aggregated state. The DLS average particle size represents the average value of secondary particle sizes (dispersed particle sizes), and the DLS average particle size in a completely dispersed state is said to be about twice the average particle size (specific surface area diameter obtained by measurement using the nitrogen adsorption method (BET method) or the Sears method, and represents the average value of primary particle sizes). The larger the DLS average particle size, the more aggregated the silica particles in the aqueous silica sol can be determined to be. For example, as an example of an aqueous silica sol, the aqueous silica sol Snowtex (trade name) ST-O manufactured by Nissan Chemical Industries, Ltd. has an average particle size (BET method) of 10 to 11 nm and a DLS average particle size of 15 to 20 nm, and this result indicates that the silica particles are almost dispersed in the aqueous silica sol. The average particle size of the aqueous silica sol (colloidal silica particles) measured by dynamic light scattering (DLS average particle size) can be, for example, 3 to 500 nm, 5 to 200 nm, 5 to 100 nm, or 5 to 50 nm.

[0020] The aqueous silica sol may be a commercially available product. Aqueous silica sols with a silica concentration of 5 to 50% by mass are generally commercially available and are easily available, making them preferable. ２ The concentration of the aqueous silica sol is preferably 5 to 55% by mass. Both alkaline and acidic aqueous silica sols can be used, but acidic aqueous silica sols are more preferred. Examples of commercially available acidic aqueous silica sols include Snowtex (trade name) ST-OXS, ST-OS, ST-O, ST-O-40, ST-OL, ST-OYL, and ST-OZL-35 (all manufactured by Nissan Chemical Industries, Ltd.).

[0021] <Particle Diameter of Surface-Modified Silica Particles> The particle diameter of the surface-modified silica particles according to the present invention can be easily measured using a commercially available device as the dynamic light scattering particle diameter described above, i.e., as the DLS particle diameter of the surface-modified silica particles in a dispersion medium (solvent) (surface-modified silica particles in silica sol). As described above, the dispersion state of the surface-modified silica particles in the dispersion medium can be estimated. In the present invention, the average particle diameter of the surface-modified silica particles measured using dynamic light scattering (DLS average particle diameter: Z-average particle diameter, harmonic mean particle diameter) can be, for example, 3 to 500 nm, 5 to 200 nm, 5 to 100 nm, or 5 to 50 nm. As described above, the unmodified silica particles: Snowtex (trade name) ST-O used in producing the surface-modified silica particles in Synthesis Examples 1 to 5 described below had an average particle size (BET method) of 10 to 11 nm, while the DLS average particle size of the compositions containing the surface-modified silica particles and the salt-resistant samples (before testing) prepared from the compositions was 20 to 30 nm. From these results, it can be inferred that the surface-modified silica particles were in a substantially dispersed state in the compositions and samples in the examples.

[0022] The DLS average particle size is an index for evaluating the stability of silica particles in the composition of the present invention, for example, salt tolerance. That is, if the composition has good salt tolerance at high temperatures and / or high salt concentrations, the DLS average particle size after the salt tolerance test will be almost the same as the DLS average particle size before the test. For example, if the ratio of the DLS average particle size after the salt tolerance test to the DLS average particle size before the test is 1.5 or less, it can be said that the composition maintains the same dispersion state as before the test even after the salt tolerance test. However, if the composition has poor salt tolerance at high temperatures and / or high salt concentrations, the DLS particle size after the salt tolerance test will be very large, indicating that the silica particles are in an aggregated state after the test. The composition of the present invention can be determined to have good salt resistance if the ratio of the DLS average particle size after a high-temperature salt resistance test (for example, held for 100 hours at 100°C under conditions of a silica concentration of 0.1 mass%, 0.5 mass%, or 1.0 mass%, and a salt concentration of 4 mass%) to the average particle size before the test is 1.5 or less (the rate of change in the average particle size is 50% or less).

[0023] <Silane Compound (Surface Modifier)> Examples of the silane compound used for surface modification of silica particles include silane compounds having an organic group, specifically silane compounds containing, as the organic group, a hydrocarbon group-containing organic group, an epoxy group-containing organic group, an amino group-containing organic group, a (meth)acryloyl group-containing organic group, a hydroxy group-containing organic group, or a carboxy group-containing organic group.

[0024] Preferred examples of the silane compound include silane coupling agents having at least one group selected from the group consisting of a vinyl group, an epoxy group, a styryl group, a methacryl group, an acrylic group, an amino group, and an isocyanurate group, as well as alkoxysilanes other than those mentioned above, silazanes, siloxanes, etc. Examples of the silane coupling agents having a vinyl group or a styryl group include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, vinylmethyldimethoxysilane, vinyltriacetoxysilane, allyltrichlorosilane, allyltrimethoxysilane, allyltriethoxysilane, p-styryltrimethoxysilane, etc. Examples of the silane coupling agent having an epoxy group include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)propyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)propyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 2-(3,4-epoxycyclohexyl)methyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)methyltriethoxysilane, [(3-ethyl-3-oxetanyl)methoxy]propyltrimethoxysilane, [(3-ethyl-3-oxetanyl)methoxy]propyltriethoxysilane, and the like. Examples of the silane coupling agent having a methacryl group (methacryloyl group) or an acrylic group (acryloyl group) include 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, 3-acryloyloxypropyltrimethoxysilane, and 3-acryloyloxypropyltriethoxysilane.Examples of the silane coupling agent having an amino group include 3-(2-(2-aminoethylamino)ethylamino)propyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrichlorosilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltriethoxysilane. Examples of the silane coupling agent having an isocyanurate group include tris-(3-trimethoxysilylpropyl)isocyanurate and tris-(3-triethoxysilylpropyl)isocyanurate, and examples of the silane coupling agent having an isocyanate group include 3-isocyanatepropyltriethoxysilane and 3-isocyanatepropyltrimethoxysilane.

[0025] Additionally, alkoxysilanes such as methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, ethyltrimethoxysilane, tetraethoxysilane, n-propyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, n-propyltrimethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, cyclohexylmethyldimethoxysilane, n-octyltriethoxysilane, and n-decyltrimethoxysilane; silazanes such as hexamethyldisilazane; and siloxanes such as methylmethoxysiloxane and dimethylphenylmethoxysiloxane can also be used.

[0026] Among these silane compounds, amphiphilic silane coupling agents having an epoxy group, a methacryl group, or an acrylic group are more preferred, such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, and 3-acryloyloxypropyltrimethoxysilane.

[0027] <Surface Treatment (Surface Modification)> The surface-modified silica particles according to the present invention are surface-treated (surface modification amount) with the silane compound as a surface modifier, that is, the silane compound added to be bonded to the silica particle surface is added within 1 nm of the silica particle surface. ２Preferably, the number of particles per unit area is, for example, 0.1 or more but less than 46, or 2.0 or more but less than 40. The surface-modified silica particles can be obtained by adding the silane compound (surface modifier) ​​to the aqueous silica sol at a mass ratio of, for example, 0.1 to 4.0 relative to the silica particles (unmodified silica particles) in the aqueous silica sol, followed by treatment at, for example, 10 to 150°C, preferably 50 to 100°C, for 1 to 20 hours. By setting the treatment temperature to 50°C or higher, the rate of partial hydrolysis is increased, improving the efficiency of the surface treatment. Furthermore, by setting the treatment temperature to 100°C or lower, the formation of a dry silica gel can be further suppressed. Furthermore, if the heat treatment time is less than 1 hour, the partial hydrolysis reaction of the silane compound is insufficient. Even if the heat treatment time is longer than 20 hours, the partial hydrolysis reaction of the silane compound is almost saturated, so further heating time is not necessary. Although the composition of the present invention contains the surface-modified silica particles, unmodified silica particles may remain in the composition. Furthermore, the amount of silane compound bonded to the surface-modified silica particles (also referred to as the silane bond amount or the bound silane amount) can be calculated by removing the polyorganosiloxane described below if it is present in the system (in the aqueous sol), drying the aqueous sol to obtain a dried sample such as silica sol powder, and measuring the carbon content of the dried sample using an organic trace element metal analyzer or the like, using the following formula: The amount of bound silane calculated by this formula is, for example, ２ The number of particles per particle may be 0.1 to 5.5, 0.5 to 5.5, 0.7 to 5.5, 0.9 to 5.5, 0.9 to 5.0, or 0.9 to 4.7.

[0028] In this specification, the silica solids concentration is a value determined by a calcination method, and specifically, is the value obtained by dividing the mass of the calcination residue obtained by calcining an aqueous silica sol (or an aqueous silica sol that has been surface-treated) at 1000°C for 30 minutes or more by the mass of the aqueous silica sol (or the aqueous silica sol that has been surface-treated). The mass of the calcination residue is also referred to as the "silica solids content."

[0029] In the present invention, the surface-modified silica particles are contained in an amount of preferably 0.01% by mass to 30.0% by mass, more preferably 10.0% by mass to 30.0% by mass, for example, 15.0% by mass to 30.0% by mass, 15.0% by mass to 25.0% by mass, or 15% by mass to 20% by mass, based on the total mass of the composition of the present invention.

[0030] [Polyorganosiloxane] The composition of the present invention can be embodied as further comprising a polyorganosiloxane. By incorporating a polyorganosiloxane, it is expected that the high-temperature salt resistance of the aqueous silica sol containing the surface-modified silica particles at high temperatures and / or high salt concentrations will be significantly improved. Polyorganosiloxane (also referred to as organopolysiloxane) is a general term for polymers having -SiO- repeating units in the main chain and organic groups in the side chains, and can be produced by the hydrolysis and polycondensation of a silane compound having a hydrolyzable group such as an alkoxy group.

[0031] For example, the polyorganosiloxane can be a polycondensate (a polymer of dimer or higher) of the silane compound used for the surface modification of the silica particles. For example, when preparing surface-modified silica particles, a polycondensate can be produced from the silane compound (a silane compound having an organic group) that does not contribute to the surface modification and is free in the medium. This polycondensate can be used as the polyorganosiloxane without being removed from the system. That is, after preparing the surface-modified silica particles, the reaction solution can be used as is in the production of the composition of the present invention as a liquid containing surface-modified silica particles and polyorganosiloxane. In addition to the polyorganosiloxane, unreacted silane compounds (monomers) may also be present in the reaction solution. These do not contribute to the surface modification of the silica particles and exist independently in the system, and are therefore sometimes referred to as "free silanes" or "unbonded silanes."

[0032] Alternatively, the polyorganosiloxane may include a product obtained by heating the silane compound (a silane compound having an organic group) to 10 to 150°C in an aqueous solution having a pH of 1 to 7. The polyorganosiloxane may be a polycondensation product of one compound selected from the compounds listed as the silane compound having an organic group, or a polycondensation product of two or more compounds selected from the compounds. The silane compound having one or more organic groups constituting the polycondensation product (polyorganosiloxane) may include the silane compound used for the surface modification of the silica particles described above, or may be a silane compound other than the compound used for surface modification. Furthermore, the polyorganosiloxane may be a polycondensation product of a compound listed as the silane compound having an organic group and another polycondensable silane compound. Alternatively, the polyorganosiloxane may be a polyorganosiloxane other than the polyorganosiloxane derived from the compound listed as the silane compound having an organic group.

[0033] When the composition of the present invention contains a polyorganosiloxane, the amount thereof is preferably 0.01% by mass to 30.0% by mass, based on the total mass of the composition of the present invention, and more preferably 0.1% by mass to 25.0% by mass, for example, 1.0% by mass to 25.0% by mass, or 1.5% by mass to 23% by mass. Furthermore, for example, when the polyorganosiloxane contains a polycondensate of the silane compound used for the surface modification of the silica particles, the ratio of the silane compound that contributed to the surface modification (bonded silane compound) to the silane compound that did not contribute to the surface modification (non-bonded silane compound) (non-bonded silane compound / bonded silane compound) can be, for example, 1.0 to 6.0. The non-bonded silane compound may be present in an amount of, for example, 1.0 to 30 particles / nm relative to the unmodified silica particles. ２ The unbonded silane compound may be present in the system in a proportion of, for example, 1.0 mass % or more and less than 40 mass % after preparation of the surface-modified silica particles.

[0034] [Surfactant] The composition of the present invention contains a surfactant, and an anionic surfactant, a nonionic surfactant, or a mixture of two or more thereof can be used. However, the incorporation of other surfactants is permitted as long as the effects of the present invention are not impaired. For example, in one embodiment of the present invention, two or more anionic surfactants and one or more nonionic surfactants can be used. That is, the composition of the present invention having the specific electrical mobility can be a composition comprising surface-modified silica particles, two or more anionic surfactants, one or more nonionic surfactants, a solvent, and optionally a polyorganosiloxane. In another embodiment, the composition of the present invention can be a composition comprising surface-modified silica particles, one or more anionic surfactants, a solvent, and optionally a polyorganosiloxane; a composition comprising surface-modified silica particles, one or more nonionic surfactants, a solvent, and optionally a polyorganosiloxane; or a composition comprising surface-modified silica particles, one or more anionic surfactants, one or more nonionic surfactants, a solvent, and optionally a polyorganosiloxane.

[0035] <Anionic Surfactants> Examples of anionic surfactants include sodium and potassium salts of fatty acids, alkylbenzenesulfonates, sulfuric acid ester salts of higher alcohols having 6 to 24 carbon atoms, polyoxyethylene alkyl ether sulfates, α-sulfofatty acid esters, α-olefinsulfonates, monoalkyl phosphate ester salts, and alkanesulfonates.

[0036] For example, alkylbenzene sulfonates include sodium salts, potassium salts, and lithium salts, such as sodium C10-C16 alkylbenzene sulfonate, C10-C16 alkylbenzene sulfonic acid, and sodium alkylnaphthalene sulfonate. Higher alcohol sulfates having 6 to 24 carbon atoms include sodium dodecyl sulfate (sodium lauryl sulfate), triethanolamine lauryl sulfate, and triethanolammonium lauryl sulfate. Polyoxyethylene alkyl ether sulfates include sodium polyoxyethylene styrenated phenyl ether sulfate, ammonium polyoxyethylene styrenated phenyl ether sulfate, sodium polyoxyethylene decyl ether sulfate, ammonium polyoxyethylene decyl ether sulfate, sodium polyoxyethylene lauryl ether sulfate, ammonium polyoxyethylene lauryl ether sulfate, sodium polyoxyethylene tridecyl ether sulfate, and sodium polyoxyethylene oleyl cetyl ether sulfate. Alpha-olefin sulfonates include sodium alpha-olefin sulfonate. Alkanesulfonates include sodium 2-ethylhexyl sulfate.

[0037] Among these, examples of the anionic surfactant include an embodiment in which an α-olefin sulfonate is used alone, and an embodiment in which an α-olefin sulfonate is used in combination with a higher alcohol sulfate having 6 to 24 carbon atoms. In the latter combination embodiment, the blend ratio of the α-olefin sulfonate to the higher alcohol sulfate having 6 to 24 carbon atoms is not particularly limited, but can be, for example, a molar ratio of α-olefin sulfonate to higher alcohol sulfate having 6 to 24 carbon atoms of 5:1 to 1:5, such as 3:1 to 1:3, 2:1 to 1:3, or 1:1 to 1:2. The anionic surfactants can be blended in a total amount of 0.001% to 20% by mass, based on the total mass of the composition of the present invention. A content of less than 0.001% by mass is undesirable because it reduces the salt tolerance of the composition at high temperatures and / or high salt concentrations. If the amount exceeds 20 mass%, for example, when the composition of the present invention is used as a chemical liquid for crude oil recovery as described below, it is expected that the recovered oil and the surfactant may be emulsified severely, making it difficult to separate the oil from the surfactant and making it difficult for the chemical liquid to perform its intended role, which is not desirable.

[0038] <Nonionic Surfactant> Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyalkylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyalkylene alkylamines, alkylglucosides, polyoxyethylene fatty acid esters, sucrose fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and fatty acid alkanolamides.

[0039] For example, examples of polyoxyethylene alkyl ethers include polyoxyethylene dodecyl ether (polyoxyethylene lauryl ether), polyoxyethylene tridecyl ether, polyoxyethylene myristyl ether, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene behenyl ether, polyoxyethylene-2-ethylhexyl ether, and polyoxyethylene isodecyl ether. Examples of polyoxyalkylene alkyl ethers include polyoxyalkylene lauryl ether and polyoxyalkylene tridecyl ether. Examples of polyoxyethylene alkyl phenyl ethers include polyoxyethylene styrenated phenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene distyrenated phenyl ether, and polyoxyethylene tribenzyl phenyl ether. Examples of polyoxyalkylene alkylamines include polyoxyethylene hexylamine, polyoxypropylene hexylamine, polyoxyethylene octylamine, polyoxypropylene octylamine, polyoxyethylene decylamine, polyoxypropylene decylamine, polyoxyethylene dodecylamine, polyoxypropylene dodecylamine, polyoxyethylene oleylamine, polyoxypropylene oleylamine, polyoxyethylene laurylamine, polyoxypropylene laurylamine, polyoxyethylene stearylamine, polyoxypropylene stearylamine, polyoxyethylene tallow amine, and polyoxypropylene tallow amine. Examples of alkyl glucosides include decyl glucoside and lauryl glucoside. Examples of polyoxyethylene fatty acid esters include polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate, polyethylene glycol distearate, polyethylene glycol dioleate, and polypropylene glycol dioleate.Sorbitan fatty acid esters include sorbitan monocaprylate, sorbitan monolaurate, sorbitan monomyristate, sorbitan monopalmitate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate, sorbitan monosesquioleate, and ethylene oxide adducts thereof. Polyoxyethylene sorbitan fatty acid esters include polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, and polyoxyethylene sorbitan triisostearate. Fatty acid alkanolamides include coconut oil fatty acid diethanolamide, beef tallow fatty acid diethanolamide, lauric acid diethanolamide, and oleic acid diethanolamide. Further usable are polyoxyalkyl ethers or polyoxyalkyl glycols such as polyoxyethylene polyoxypropylene glycol, polyoxyethylene fatty acid esters, polyoxyethylene hydrogenated castor oil ether, sorbitan fatty acid ester alkyl ethers, alkyl polyglucosides, sorbitan monooleate, sucrose fatty acid esters, etc. Among the nonionic surfactants, polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers are more preferred because they provide the composition with good salt tolerance at high temperatures and / or high salt concentrations.

[0040] The HLB value of a nonionic surfactant is a numerical value that represents the balance between hydrophobicity and hydrophilicity. A substance having no hydrophilic groups has an HLB of 0, and a substance having only hydrophilic groups but no hydrophobic groups has an HLB of 20. In the present invention, nonionic surfactants having an HLB value of 3.0 or more and 20.0 or less are preferably used. From the viewpoint of the stability of the composition of the present invention at high temperatures and / or high salt concentrations, it is more preferable to use nonionic surfactants having an HLB value of 10.0 or more and 20.0 or less. Furthermore, from the viewpoint of safety for the human body and the environment, it is more preferable to use nonionic surfactants having an HLB value of 14.0 or more and 20.0 or less, which are not harmful to the aquatic environment for long periods of time and are not a concern as so-called endocrine disrupters. Furthermore, when two or more nonionic surfactants with different HLB values ​​are used, it is preferable to adjust the HLB value of the mixture, calculated from the weight average of the HLB values ​​and the blending ratio, to 10.0 or more and 20.0 or less. If the HLB value is less than 3.0, the nonionic surfactant is highly hydrophobic, and therefore in the prepared composition, the aqueous silica sol containing the surface-modified silica particles or various water-soluble surfactants and the nonionic surfactant do not mix, and the composition is separated into two layers, which is not preferable.

[0041] The nonionic surfactant can be blended in an amount of 0.001% to 30% by mass, based on the total mass of the composition of the present invention. Amounts less than 0.001% by mass are undesirable because the heat resistance and salt tolerance of the composition are poor. Amounts greater than 30% by mass are undesirable because the viscosity of the composition may become very high. The nonionic surfactant can be blended in at a mass ratio of 0.001 to less than 0.4 relative to the silica solids content of the composition of the present invention. Blending in this ratio can improve the salt tolerance of the composition at high temperatures and / or high salt concentrations. Good salt tolerance at high temperatures and / or high salt concentrations can be achieved whether the composition contains only one type of nonionic surfactant or two to five types of nonionic surfactants.

[0042] In the composition of the present invention, preferably two or more of the above-mentioned anionic surfactants can be used in combination with one or more nonionic surfactants. Alternatively, one or more of the above-mentioned anionic surfactants can be used in combination with one or more nonionic surfactants. For example, a combination of 1 to 5 anionic surfactants, 1 to 4 anionic surfactants, 1 to 3 anionic surfactants, 1 to 2 anionic surfactants, or 1 surfactant, or 2 to 5 anionic surfactants, 2 to 4 anionic surfactants, 2 to 3 anionic surfactants, or 2 anionic surfactants can be used in combination with 1 to 5 nonionic surfactants, 1 to 4 nonionic surfactants, 1 to 3 nonionic surfactants, 1 to 2 nonionic surfactants, or 1 nonionic surfactant. More specifically, examples of surfactants used in the composition of the present invention include α-olefin sulfonate (anionic surfactant), polyoxyethylene alkyl phenyl ether (nonionic surfactant), a combination of α-olefin sulfonate (anionic surfactant) and polyoxyethylene alkyl phenyl ether (nonionic surfactant), or a combination of α-olefin sulfonate (anionic surfactant), a higher alcohol sulfate having 6 to 24 carbon atoms (anionic surfactant), and polyoxyethylene alkyl phenyl ether (nonionic surfactant). In the present invention, a composition containing two or more anionic surfactants, rather than a composition containing only one anionic surfactant, is expected to achieve a more desirable effect of improving the dispersibility of silica particles themselves by the surfactants, as the surfactants penetrate each other and form denser micelles (packing effect). Furthermore, in the present invention, a composition containing both an anionic surfactant and a nonionic surfactant is expected to achieve a more desirable effect of improving the dispersibility of silica particles themselves by the surfactants, as the anionic surfactant and nonionic surfactant penetrate each other and form denser micelles than those containing only anionic surfactants.In particular, in the present invention, as shown by the results of the affinity capillary electrophoresis measurement described above, as the amount of silane compound added increases, the anionic surfactant shifts to the uncharged side, and when the anionic surfactant arranges to form micelles, the charge repulsion between adjacent agents weakens, and further, the uncharged nonionic surfactant can more easily penetrate, forming denser micelles and enhancing the packing effect, which is expected to further improve the dispersibility of silica particles by the surfactant.In this way, the composition of the present invention can stabilize the composition in high-temperature salt water by utilizing the packing effect achieved by blending multiple surfactants.

[0043] [Solvent] The composition of the present invention contains a solvent, and examples of the solvent include water or brine, as well as methanol or ethanol. When the primary solvent is water or brine, it can also be used as a solvent containing methanol or ethanol, and the methanol or ethanol content can be 0.01% by mass to 20% by mass, 0.1% by mass to 15% by mass, 1.0% by mass to 15% by mass, or 0.5% by mass to 10% by mass. By adjusting the methanol or ethanol content to 0.01% by mass to 20% by mass, it is expected that the stability of the polyorganosiloxane at high temperatures and / or high salt concentrations can be improved. Methanol or ethanol is produced by hydrolysis of the alkoxy groups of the silane compound when silica particles and a silane compound are mixed and reacted. By refluxing the reaction at a temperature of 5°C to 30°C, the amount of methanol or ethanol evaporated can be controlled to a content of 0.01% by mass to 20% by mass, which is expected to improve the stability of the polyorganosiloxane.

[0044] [Other Components] In order to increase the viscosity of the composition of the present invention, water-soluble polymers such as hydroxyethyl cellulose and salts thereof, hydroxypropyl methyl cellulose and salts thereof, carboxymethyl cellulose and salts thereof, pectin, guar gum, xandancum, damarind gum, and carrageenan may be further added.

[0045] The composition of the present invention is considered to be a composition that improves the compatibility between the silica particles and surfactant by using surface-modified silica particles and polyorganosiloxane in combination.At this time, for example, by using surfactants in combination, such as two or more kinds of anionic surfactants and one or more kinds of nonionic surfactants, a plurality of surfactants can be interpenetrated with each other, form denser micelles, and the dispersibility of silica particles themselves by surfactants can be stabilized, and as a result, it can be expected to be a composition that realizes excellent salt tolerance under high temperature and / or high salt concentration.

[0046] [Production Method] The composition of the present invention can be produced by appropriately mixing the above-mentioned components: surface-modified silica particles, surfactant, solvent, and optionally, polyorganosiloxane and other components. For example, the composition of the present invention can be obtained by preparing a mixed solution (aqueous sol) containing surface-modified silica particles and polyorganosiloxane simultaneously, and then adding a surfactant to the resulting solution. That is, the production method includes the following steps (1) and (2): (1) a step of heating a mixture containing (unmodified) silica particles, a silane compound having an organic group (surface modifier), and a solvent to 10 to 150°C while stirring to obtain a mixed solution containing silica particles at least partially coated with a silane compound having an organic group and polyorganosiloxane; and (2) a step of mixing the resulting mixed solution with a surfactant. Furthermore, between steps (1) and (2), a step of maintaining the mixture at 10 to 80°C for 1 hour to 1 month may be included. Furthermore, after the step (1), for example, before the step (2), or if the step (2) is included, before the step (2), a step of removing polyorganosiloxane from the mixed liquid may be included.

[0047] [Chemical Solution for Crude Oil Recovery] The composition of the present invention has excellent salt tolerance under high temperatures and / or high salt concentrations. Therefore, one example of its use is as a chemical solution for crude oil recovery, which is injected into a subterranean formation from an injection well and then recovered from a production well in order to recover crude oil from a hydrocarbon-containing formation underground. In this case, the injection well and the production well may be the same. A crude oil recovery method using the composition of the present invention as a chemical solution for crude oil recovery may include, for example, (a) a step of injecting the composition of the present invention (chemical solution for crude oil recovery) into a subterranean formation, and (b) a step of recovering crude oil from a production well together with the composition (chemical solution for crude oil recovery) injected into the subterranean formation. Through these steps, a method for recovering crude oil from a hydrocarbon-containing formation underground can be carried out. The electrical mobility of the composition (chemical solution for crude oil recovery) can be set to -0.017 to -0.0010 cm under the above-mentioned conditions. ２By adjusting the composition's electrical conductivity to fall within the above range, and further adjusting the content of the various surfactants contained in the composition, it is expected that the composition will have good salt tolerance at higher temperatures and / or higher salinity. The composition of the present invention is expected to be a useful, stable chemical solution that does not experience problems such as gelation, even when used as a crude oil recovery chemical solution, for example, by diluting it with brine having a low to high salinity, or by injecting the diluted composition into a high-temperature environment such as an oil reservoir in an inland or offshore oil field. Furthermore, when the composition of the present invention is used as a crude oil recovery chemical solution, the surfactant contained in the composition can provide a crude oil stripping effect, and the wedge effect of the surface-modified silica particles is expected to improve the effectiveness of stripping crude oil from the rock surface, resulting in a chemical solution that can recover crude oil with a high recovery rate. As mentioned above, the fact that the composition of the present invention exhibits an electrical mobility within the above-mentioned specific range means that the silica particles and surfactant contained in the composition interact sufficiently. Therefore, when the composition of the present invention is injected into a geological formation as a chemical solution for crude oil recovery, the sufficient interaction between the silica particles and the surfactant enhances the transport effect of the surfactant within the geological formation, and both are transported deeper into the geological formation than when either the silica particles or the surfactant are used alone, further promoting the above-mentioned peeling effect and expected to enhance the crude oil recovery effect.

[0048] In addition, the composition of the present invention has excellent salt resistance at high temperatures and / or high salt concentrations, and is therefore expected to be used as a dispersion stabilizer in high electrolyte media (aqueous emulsions), for example.

[0049] The present invention will be described in further detail below based on synthesis examples, examples, and comparative examples, but it should be understood that the present invention is not limited to these examples in any way.

[0050] (Measurement Equipment) The compositions or aqueous silica sols prepared and used in the Examples and Comparative Examples (pH value, electrical conductivity, viscosity, DLS average particle size, silane bond amount), samples prepared using the compositions or aqueous silica sols, and samples after high-temperature salt resistance tests were analyzed using the following equipment. Electrical mobility: A capillary electrophoresis system (trade name: Agilent 7100 Capillary Electrophoresis System, manufactured by Agilent Technologies, Inc., using a PDA detector (195 nm ± 5 nm)) was used. DLS average particle size (dynamic light scattering particle size): A dynamic light scattering particle size measurement device (trade name: Zetasizer Nano, manufactured by Spectris, Malvern Panalytical Division) was used. The Z-average particle size was used as the DLS average particle size. pH: Measured at 20°C using a pH meter (manufactured by DKK-TOA Corporation). Electrical conductivity: Measured at 20°C using an electrical conductivity meter (manufactured by DKK-TOA Corporation). Viscosity: Measured at 25°C using a BII type viscometer (manufactured by Toki Sangyo Co., Ltd.). Silane bond amount: Measured using an organic trace element analyzer, trade name CHNS / O Analyzer (PerkinElmer Japan Co., Ltd.).

[0051] (Evaluation of Silane Bonding Amount) <Removal of Free Silane (Silane Not Bonded to the Silica Particle Surface)> 2 g of the aqueous silica sol (aqueous sol containing aqueous silica sol surface-treated with a silane compound) of Synthesis Examples 1 to 5 described below and 4 g of pure water were placed in a 15 ml centrifugal filter unit (trade name: Amicon Ultra 15, Merck Ltd.) and centrifuged at a centrifugal force of 2770 G for 20 minutes. After centrifugation, the liquid discharged to the bottom of the unit was discarded, and the same mass of pure water as the discarded liquid was added to the aqueous silica sol concentrated on the filter to redisperse it, followed by another centrifugation at a centrifugal force of 2770 G for 20 minutes. The above procedure was repeated a total of four times to obtain an aqueous silica sol from which free silane had been removed. <Measurement of Carbon Amount> The aqueous silica sol from which free silane had been removed was heated and dried at 100°C and pulverized in a mortar to obtain a silica sol powder. The carbon content of the obtained silica sol powder was measured using an organic trace element metal analyzer, and the silane bond amount was calculated from the obtained carbon content using the following formula.

[0052] (Affinity CE Measurement) Affinity capillary electrophoresis (Affinity CE) was performed using an Agilent 7100 (detector: PDA detector (195 nm±5 nm)). Agilent capillaries with model number G1600-64311 (inner diameter 75 μm, total length 112.5 cm, effective length 104 cm) were used. The electrophoresis buffer used was a solution prepared by diluting the aqueous silica sols of Synthesis Examples 1 to 5 described below and an unmodified aqueous sol (Snowtex (trade name) ST-O, manufactured by Nissan Chemical Industries, Ltd.) with a 5 mM sodium tetraborate solution (pH 9.3) to a silica concentration of 2% by mass. The measurement target (analyte) used was a surfactant solution (Surfactant Solution-0, Surfactant Solution-1, Surfactant Solution-2, Surfactant Solution-3, Surfactant Solution-4, Surfactant Solution-5, or Surfactant Solution-6) described below.

[0053] For the electrophoresis standard substances, 10 mg each of N-methyl-2-pyrrolidone (NMP), methacrylic acid, and terephthalic acid were weighed out, 20 mL of 5 mM sodium tetraborate solution was added, and the mixture was stirred for 30 seconds with a vortex mixer to dissolve. The mixture was then adjusted to a final volume of 50 mL with 5 mM sodium tetraborate solution to obtain the standard substances (the concentrations of NMP, methacrylic acid, and terephthalic acid in the standard substances were all 200 ppm).

[0054] <Electrophoresis Measurement> The surfactant solution, the electrophoresis buffer, and the standard substance were mixed in a CE (capillary electrophoresis) measurement vial in a ratio of 50 μL, 450 μL, and 20 μL, and the mixture was stirred for 10 seconds using a vortex mixer to prepare a measurement sample. Prior to measurement, the electrophoresis buffer was passed through the capillary at a pressure of 915 mbar for 20 minutes to perform preconditioning. The capillary was then washed before and after each sample measurement by passing ethanol (Junsei Chemical Co., Ltd., special-grade reagent) for 180 seconds, 0.1 M aqueous sodium hydroxide solution (Fujifilm Wako Pure Chemical Co., Ltd., for volumetric analysis) for 360 seconds, ultrapure water (trade name Milli-Q) for 300 seconds, and the electrophoresis buffer for 300 seconds, all at a pressure of 915 mbar. Thereafter, the obtained measurement sample was injected into the capillary under conditions of 50 mbar and 6 s (pressure injection method), a voltage of 30 kV was applied to both ends of the capillary, and the components contained in the measurement sample were separated by electrophoresis at a capillary temperature of 25°C, and the migration time was measured.

[0055] <Electric Mobility Analysis> After performing the electrophoresis measurement, the electrical mobility (cm) was calculated from the migration time (min) based on the following formula (1): ２ The electrical mobility (V / min) was calculated. Furthermore, the data was corrected so that the electrical mobility of terephthalic acid in each measurement sample was the same value, and a CE chart (Fig. 1) was created. ２ The minimum (start point) and maximum (end point) values ​​of the peak detected at or above 1 / V·min were used as analytical values. ２ / V・min)=(L ｅｆｆ ×L ｔｏｔ ) / V × (1 / t ｅｐ -1 / t ｅｏ ) Formula (1) L ｅｆｆ : Effective length of capillary (104 cm) L ｔｏｔ t: Total length of capillary (112.5 cm) ｅｐ t: Migration time of various surfactants (min) ｅｏ : Migration time (min) of uncharged standard substance (NMP) *t ｅｐ and t ｅｏ is the detection time under UV = 195 nm conditions, V: voltage (30 kV)

[0056] [Preparation of Aqueous Silica Sol] (Synthesis Example 1) 1,000 g of aqueous silica sol (Snowtex (trade name) ST-O, manufactured by Nissan Chemical Industries, Ltd., silica concentration = 20.5 mass %, BET average particle size 11.7 nm, DLS average particle size 18.6 nm) and a magnetic stirrer were placed in a 2,000 ml glass recovery flask, and the silane compound was added to the aqueous silica sol at a concentration of 2.0 particles / nm with respect to the surface area of ​​the silica particles (also referred to as silica) in the aqueous silica sol while stirring with the magnetic stirrer. ２ 37.4 g of 3-glycidoxypropyltrimethoxysilane (manufactured by Evonik, trade name Dynasylan GLYMO) was added so that the silica particles (unmodified silica particles) in the aqueous silica sol were mixed. The mass ratio of the silane compound used as a surface modifier to the silica particles in the aqueous silica sol (unmodified silica particles) was 0.18. A cooling tube through which tap water at 25°C was passed was then placed on top of the recovery flask, and the aqueous sol was heated to 60°C while refluxing. The temperature was maintained at 60°C for 4 hours, including the time required for heating, and then cooled. After cooling to room temperature, the mixture was filtered through a nylon 460 mesh with a 28 μm mesh size, yielding 1,037 g of an aqueous sol containing an aqueous silica sol surface-treated with the silane compound according to Synthesis Example 1. The resulting aqueous sol was then maintained at 20°C for 7 days. The silica solids content of the resulting aqueous sol was 20.6 mass%. The silane bond amount of the aqueous sol of Synthesis Example 1 was evaluated according to (Evaluation of Silane Bond Amount). The results are shown in Table 1.

[0057] Synthesis Example 2 The silane compound was dispersed at a concentration of 4.0 particles / nm relative to the surface area of ​​silica in an aqueous silica sol (Snowtex (trade name) ST-O, manufactured by Nissan Chemical Industries, Ltd., silica concentration = 20.5 mass %, average particle size by BET method = 11.7 nm, average particle size by DLS = 18.6 nm). ２The same procedure as in Synthesis Example 1 was performed, except that 74.8 g of 3-glycidoxypropyltrimethoxysilane (manufactured by Evonik, trade name Dynasylan GLYMO) was added so that the aqueous silica sol surface-treated with the silane compound of Synthesis Example 2 was obtained in an amount of 1,074 g. The aqueous sol obtained was then kept at 20°C for 7 days. The silica solids content of the aqueous sol obtained was 20.7 mass%. The mass ratio of the silane compound used as a surface modifier to the silica particles (unmodified silica particles) in the aqueous silica sol was 0.36. The silane bond amount of the aqueous sol of Synthesis Example 2 was evaluated according to (Evaluation of Silane Bond Amount). The results are shown in Table 1.

[0058] Synthesis Example 3 The silane compound was dispersed at a concentration of 8.0 particles / nm relative to the surface area of ​​silica in an aqueous silica sol (Snowtex (trade name) ST-O, manufactured by Nissan Chemical Industries, Ltd., silica concentration = 20.5 mass %, average particle size by BET method = 11.7 nm, average particle size by DLS = 18.6 nm). ２ The same procedure as in Synthesis Example 1 was performed, except that 150 g of 3-glycidoxypropyltrimethoxysilane (manufactured by Evonik, trade name Dynasylan GLYMO) was added so that the total mass of the aqueous silica sol was 1,150 g, to obtain 1,150 g of an aqueous sol containing the aqueous silica sol surface-treated with the silane compound of Synthesis Example 3. The mass ratio of the silane compound, which served as a surface modifier, to the silica particles (unmodified silica particles) in the aqueous silica sol was 0.73. The aqueous sol was then kept at 20°C for 7 days. The silica solids content of the aqueous sol was 21.1 mass%. The silane bond amount of the aqueous sol of Synthesis Example 3 was evaluated according to (Evaluation of silane bond amount). The results are shown in Table 1.

[0059] Synthesis Example 4 The silane compound was dispersed at a concentration of 31 particles / nm2 relative to the surface area of ​​silica in an aqueous silica sol (pH = 2.7, silica concentration = 25.5 mass %, average particle size by BET method = 11.7 nm, average particle size by DLS = 18.6 nm). ２The same procedure as in Synthesis Example 1 was performed, except that 580 g of 3-glycidoxypropyltrimethoxysilane (manufactured by Evonik, trade name Dynasylan GLYMO) was added so that the total mass of the aqueous silica sol was 1,580 g, thereby obtaining 1,580 g of an aqueous sol containing an aqueous silica sol surface-treated with the silane compound of Synthesis Example 4. The mass ratio of the silane compound, which served as a surface modifier, to the silica particles (unmodified silica particles) in the aqueous silica sol was 2.8. The aqueous sol was then kept at 20°C for 7 days. The silica solids content of the aqueous sol was 25.5 mass%. The silane bond amount of the aqueous sol of Synthesis Example 4 was evaluated according to (Evaluation of silane bond amount). The results are shown in Table 1.

[0060] Synthesis Example 5: The silane compound was dispersed at a concentration of 46 particles / nm2 relative to the surface area of ​​silica in an aqueous silica sol (pH = 2.7, silica concentration = 25.5 mass%, average particle size by BET method = 11.7 nm, average particle size by DLS = 18.6 nm). ２ The same procedure as in Synthesis Example 1 was performed, except that 861 g of 3-glycidoxypropyltrimethoxysilane (manufactured by Evonik, trade name Dynasylan GLYMO) was added so that the total mass of the aqueous silica sol surface-treated with the silane compound of Synthesis Example 5 was 1,861 g. The mass ratio of the silane compound used as a surface modifier to the silica particles (unmodified silica particles) in the aqueous silica sol was 4.2. The aqueous sol was then kept at 20°C for 7 days. The silica solids content of the aqueous sol was 25.6 mass%. The silane bond content of the aqueous sol of Synthesis Example 5 was evaluated according to (Evaluation of silane bond content). The results are shown in Table 1.

[0061] (Synthesis Example 6) 800 g of pure water was added to 200 g of the aqueous sol obtained in (Synthesis Example 3), and the mixture was filtered by ultrafiltration (using an ultrafilter made of polysulfone with a molecular weight cutoff of 200,000) until 800 g was discharged. 800 g of pure water was added again, and the same procedure was repeated four times to obtain 200 g of an aqueous sol from which free silanes had been removed (an aqueous sol from which silane compounds not bonded to the surfaces of silica particles had been removed) according to Synthesis Example 6. The resulting aqueous sol was then kept at 20° C. for 7 days. The silica solids content of the resulting aqueous sol was 21.1% by mass.

[0062] The evaluation results of the silane bond amount of the aqueous sol containing the aqueous silica sol surface-treated with a silane compound prepared in Synthesis Examples 1 to 6 are shown in Table 1. In Table 1, the amount of silane added, the amount of bound silane, and the amount of free silane (unbound silane compound) are calculated based on the amount of silane added within 1 nm of the surface of the silica particles. ２ The number of silane compounds per unit area is shown.

[0063]

[0064] [Preparation of Surfactant Solution] (Surfactant Solution-0) A stirrer was placed in a 120 ml polystyrene bottle, and 93.9 g of pure water was added. 0.8 g of the anionic surfactant sodium α-olefin sulfonate (AOS: manufactured by Lion Specialty Chemicals Co., Ltd., Lipolan (trade name) LB-440, active ingredient 36.3% by mass) was then added and stirred until completely dissolved. 0.30 g of the anionic surfactant sodium dodecyl sulfate (SDS: manufactured by New Japan Chemical Co., Ltd., Shinorin (trade name) 90TK-T, active ingredient 100% by mass) was then added and stirred until completely dissolved. 1.7 g of a nonionic surfactant polyoxyethylene styrenated phenyl ether with an HLB of 14.3 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., Noigen (trade name) EA-157, active ingredient 100% by mass) diluted with pure water to 70% by mass of the active ingredient was then added and stirred until completely dissolved. The concentrations of AOS, SDS, and EA-157 were adjusted with pure water to 0.29% by mass, 0.29% by mass, and 1.21% by mass, respectively, and the mixture was stirred with a magnetic stirrer for 30 minutes to obtain surfactant solution-0.

[0065] (Surfactant solution-1) A stirrer was placed in a 120 ml polystyrene bottle, and 93.9 g of pure water was added thereto, followed by 0.8 g of the anionic surfactant sodium α-olefin sulfonate (AOS: Liporan (trade name) LB-440, manufactured by Lion Specialty Chemicals Co., Ltd., active ingredient 36.3% by mass), and the mixture was stirred until completely dissolved. The AOS concentration was adjusted to 0.29% by mass with pure water, and the mixture was stirred with a magnetic stirrer for 30 minutes to obtain surfactant solution-1.

[0066] (Surfactant solution-2) A stirrer was placed in a 120 ml polystyrene bottle, and 93.9 g of pure water was added thereto, followed by 3.3 g of the anionic surfactant sodium α-olefin sulfonate (AOS: Liporan (trade name) LB-440, manufactured by Lion Specialty Chemicals Co., Ltd., active ingredient 36.3% by mass), and the mixture was stirred until completely dissolved. The AOS concentration was adjusted to 1.2% by mass with pure water, and the mixture was stirred with a magnetic stirrer for 30 minutes to obtain surfactant solution-2.

[0067] (Surfactant solution-3) A stirrer was placed in a 120 ml polystyrene bottle, and 93.9 g of pure water was added thereto. Subsequently, 1.7 g of a nonionic surfactant, polyoxyethylene styrenated phenyl ether with an HLB of 14.3 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., Noigen (trade name) EA-157, active ingredient 100 mass%) diluted with pure water to 70 mass% active ingredient, was added and stirred until completely dissolved. Further pure water was added so that the concentration of EA-157 became 1.21 mass%, and the mixture was stirred with a magnetic stirrer for 30 minutes to obtain surfactant solution-3.

[0068] (Surfactant Solution-4) A stirrer was placed in a 120 ml polystyrene bottle, and 93.9 g of pure water was added thereto. Subsequently, 0.8 g of the anionic surfactant sodium α-olefin sulfonate (AOS: manufactured by Lion Specialty Chemicals Co., Ltd., Liporan (trade name) LB-440, active ingredient 36.3% by mass) was added and stirred until completely dissolved. Subsequently, 1.7 g of a nonionic surfactant polyoxyethylene styrenated phenyl ether having an HLB of 14.3 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., Noigen (trade name) EA-157, active ingredient 100% by mass) diluted with pure water to 70% by mass of active ingredient was added and stirred until completely dissolved. The concentration of AOS was adjusted to 0.29% by mass and the concentration of EA-157 to 1.21% by mass with pure water, and the mixture was stirred for 30 minutes with a magnetic stirrer to obtain surfactant solution-4.

[0069] (Surfactant Solution-5) A stirrer was placed in a 120 ml polystyrene bottle, and 93.9 g of pure water was added thereto. Subsequently, 1.7 g of the anionic surfactant sodium α-olefin sulfonate (AOS: manufactured by Lion Specialty Chemicals Co., Ltd., Liporan (trade name) LB-440, active ingredient 36.3% by mass) was added and stirred until completely dissolved. Subsequently, 1.7 g of a nonionic surfactant polyoxyethylene styrenated phenyl ether having an HLB of 14.3 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., Noigen (trade name) EA-157, active ingredient 100% by mass) diluted with pure water to 70% by mass of active ingredient was added and stirred until completely dissolved. The concentration of AOS was adjusted with pure water to 0.62% by mass, and the concentration of EA-157 was adjusted to 1.21% by mass, and the mixture was stirred with a magnetic stirrer for 30 minutes to obtain surfactant solution-5.

[0070] (Surfactant Solution-6) A stirrer was placed in a 120 ml polystyrene bottle, and 90.0 g of pure water was added. 2.3 g of the anionic surfactant sodium α-olefin sulfonate (AOS: manufactured by Lion Specialty Chemicals Co., Ltd., Lipolan (trade name) LB-440, active ingredient 36.3% by mass) was then added and stirred until completely dissolved. 0.9 g of the anionic surfactant sodium dodecyl sulfate (SDS: manufactured by New Japan Chemical Co., Ltd., Shinorin (trade name) 90TK-T, active ingredient 100% by mass) was then added and stirred until completely dissolved. 5.1 g of a nonionic surfactant polyoxyethylene styrenated phenyl ether with an HLB of 14.3 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., Noigen (trade name) EA-157, active ingredient 100% by mass) diluted with pure water to 70% by mass of the active ingredient was then added and stirred until completely dissolved. The concentrations of AOS, SDS, and EA-157 were adjusted with pure water to 0.85% by mass, 0.85% by mass, and 3.60% by mass, respectively, and the mixture was stirred with a magnetic stirrer for 30 minutes to obtain surfactant solution-6.

[0071] (Examples 1-1 to 1-10, Comparative Examples 1-1 and 1-2) According to the above-mentioned (Affinity CE measurement), affinity capillary electrophoresis was performed using the aqueous silica sols shown in Table 2 as the electrophoresis running solutions (solutions in which each silica sol was diluted to a silica concentration of 2% by mass), each surfactant solution as an analyte, and the standard substance, and the electrical mobility was calculated. The results are shown in Table 2 and Figure 1. Note that when affinity capillary electrophoresis was performed in a system that did not contain silica particles, the result was -0.013 cm ２ The peak of the electrical mobility around 0.0006 cm / V min is due to the anionic surfactant (sodium α-olefin sulfonate (AOS) + sodium dodecyl sulfate (SDS)). ２ The peaks in the electrical mobility around / V·min could be attributed to the nonionic surfactant (polyoxyethylene styrenated phenyl ether (EA-157)).

[0072]

[0073] As shown in FIG. 1 and Table 2, the amount of the silane compound added to the silica particles in the aqueous silica sol was 2.0 particles / nm ２ In (Synthesis Example 1 (Example 1-1)), the minimum peak of electrical mobility was −0.0137 cm ２ As the amount of treatment with the silane compound increases, this minimum peak tends to move to the uncharged side. ２ (Synthesis Example 3 (Example 1-3)) ２ / V·min. The processing amount was the same as in Synthesis Example 3 (8.0 particles / nm ２ Synthesis Example 6 (Example 1-5) (free silane amount: 0) is slightly anion side -0.0129 cm ２ The minimum peak was observed at 31 particles / nm. ２ In (Synthesis Example 4 (Example 1-4)), the shape of the minimum peak changed and the minimum peak shifted to the uncharged side (-0.0088 cm ２ / V·min), processing rate 46 pieces / nm ２ In (Synthesis Example 5 (Comparative Example 1-2)), the minimum peak is −0.0080 cm ２ / V·min. Furthermore, when the type of surfactant was the same, increasing the amount of anionic surfactant added tended to shift the minimum peak to the uncharged side (Examples 1-6 and 1-7, Examples 1-9 and 1-10). The maximum peak of electrical mobility showed little variation depending on the amount of silane compound treated, ranging from 0.0005 to 0.0007 cm ２ On the other hand, in the case of ST-O (unmodified silica particles), the (unmodified) silica particles and surfactant were mixed during preparation of the electrophoresis sample, resulting in aggregation and gelation, making it impossible to measure the electrical mobility (electrical mobility peak not detected).

[0074] (Salt Tolerance Evaluation) <Preparation of Brine Test Samples for Salt Tolerance Evaluation> A stirrer was placed in a 200 ml polystyrene bottle, and the compositions produced in Examples 2-1 to 2-10 or Comparative Example 2-2, or the aqueous silica sol used in Comparative Example 2-1, described below, were added. While stirring each composition or aqueous silica sol with a magnetic stirrer, pure water and a brine solution with a salt concentration of 6% by mass were added and stirred for 1 hour to obtain brine test samples for evaluating heat resistance and salt tolerance, each adjusted to a silica concentration of 0.5% by mass (Examples 2-1 to 2-3, 2-6 to 2-10), 0.1% by mass (Example 2-4, Comparative Example 2-2), or 1.0% by mass (Example 2-5, Comparative Example 2-1) at a salt concentration of 4% by mass. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the resulting brine test samples were evaluated.

[0075] <Evaluation of High-Temperature Salt Tolerance> 65 g of the brine test sample was placed in a 120 ml sealable Teflon (trade name) container and sealed. The Teflon (trade name) container was placed in a dryer at 100° C. After maintaining the container at 100° C. for a predetermined time (10 hours), the brine test sample was evaluated for its appearance, pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the sample. The salt tolerance was evaluated by judging the salt tolerance (see <Judgment of Salt Tolerance> below) based on the measurement results of the DLS average particle size of the aqueous silica sol (silica particles) in the sample after maintaining the container at 100° C. for a predetermined time (10 hours) and by evaluating the appearance.

[0076] <Judgment of Salt Tolerance> A: The ratio of the DLS average particle size after the salt tolerance test to the DLS average particle size before the test is 1.1 or less. B: The ratio of the DLS average particle size after the salt tolerance test to the DLS average particle size before the test is more than 1.1 but not more than 1.5. C: The ratio of the DLS average particle size after the salt tolerance test to the DLS average particle size before the test is more than 1.5 but not more than 2.4. D: The ratio of the DLS average particle size after the salt tolerance test to the DLS average particle size before the test is more than 2.4 but not more than 20.0. E: The ratio of the DLS average particle size after the salt tolerance test to the DLS average particle size before the test is more than 20.0 or the sample is cloudy and exhibits solid-liquid separation. A is the most preferable salt tolerance test result, followed by B, C, D, and E. If the salt tolerance test results are A, B, or C, the sample's salt tolerance can be determined to be good.

[0077] Example 2-1 A 120 ml polystyrene bottle was charged with a stirrer, and 6.4 g of pure water and 85.3 g of the aqueous silica sol surface-treated with a silane compound prepared in Synthesis Example 1 were added and stirred with a magnetic stirrer. Subsequently, while stirring with the magnetic stirrer, 2.3 g of anionic surfactant sodium α-olefin sulfonate (Lipolan (trade name) LB-440, manufactured by Lion Specialty Chemicals Co., Ltd., active ingredient 36.3% by weight) was added and stirred until completely dissolved. Subsequently, 0.9 g of anionic surfactant sodium dodecyl sulfate (Shinoline (trade name) 90TK-T, manufactured by New Japan Chemical Co., Ltd., active ingredient 100% by weight) was added and stirred until completely dissolved. Subsequently, 5.1 g of a nonionic surfactant, polyoxyethylene styrenated phenyl ether with an HLB of 14.3 (Noigen (trade name) EA-157, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., active ingredient 100% by mass), diluted with pure water to 70% by mass of active ingredient, was added and stirred until completely dissolved. By the above procedure, a composition of Example 2-1, which is a mixture of the aqueous silica sol of Synthesis Example 1 and three surfactants (corresponding to Surfactant Solution-6), was produced. The pH, electrical conductivity, viscosity, and DLS average particle size of the composition of Example 2-1 were evaluated. The evaluation results are shown in Table 3, along with the silica solid content (% by mass) and free silane amount (% by mass) in the composition of Example 2-1. The free silane amount (% by mass) is the amount of bound silane (number of silanes / nm ) relative to the amount (g) of silane compound added for surface modification in each aqueous silica sol.２ ) and free silane amount (particles / nm ２ ) was calculated from the ratio of the salt content of the test specimens. In addition, according to the salt tolerance evaluation, brine test samples were prepared and their physical properties were evaluated, and their physical properties after being kept at high temperatures were evaluated, and then the salt tolerance was evaluated. The results are shown in Table 3.

[0078] Example 2-2 A composition of Example 2-2, which is a mixture of the aqueous silica sol of Synthesis Example 2 and three surfactants (corresponding to Surfactant Solution-6), was produced in the same manner as in Example 2-1, except that the aqueous silica sol surface-treated with the silane compound prepared in Synthesis Example 2 was used instead of Synthesis Example 1. The pH, electrical conductivity, viscosity, and DLS average particle size of the composition of Example 2-2 were evaluated. The evaluation results, along with the silica solid content (mass%) and free silane content (mass%) in the composition of Example 2-2, are shown in Table 3. In addition, according to (Salt Tolerance Evaluation), a brine test sample was prepared and its physical properties were evaluated, and its physical properties after high-temperature storage were evaluated, and a <Determination of Salt Tolerance> was performed. The obtained results are shown in Table 3.

[0079] (Example 2-3) A stirrer was placed in a 120 ml polystyrene bottle, and 12.0 g of pure water and 84.9 g of the surface-treated aqueous silica sol prepared in Synthesis Example 3 were added thereto and stirred with a magnetic stirrer. Subsequently, while stirring with the magnetic stirrer, 0.8 g of anionic surfactant sodium α-olefin sulfonate (Lipolan (trade name) LB-440, manufactured by Lion Specialty Chemicals Co., Ltd., active ingredient 36.3% by mass) was added and stirred until completely dissolved. Subsequently, 0.30 g of anionic surfactant sodium dodecyl sulfate (Shinoline (trade name) 90TK-T, manufactured by New Japan Chemical Co., Ltd., active ingredient 100% by mass) was added and stirred until completely dissolved. Subsequently, 1.7 g of a nonionic surfactant, polyoxyethylene styrenated phenyl ether with an HLB of 14.3 (Noigen (trade name) EA-157, active ingredient 100% by mass, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), diluted with pure water to 70% by mass of active ingredient, was added and stirred until completely dissolved. By the above procedure, the composition of Example 2-3, which is a mixture of the aqueous silica sol of Synthesis Example 3 and three surfactants (corresponding to surfactant solution-0), was produced. The pH, electrical conductivity, viscosity, and DLS average particle size of the composition of Example 2-3 were evaluated. The evaluation results, along with the silica solid content (mass %) and free silane content (mass %) in the composition of Example 2-3, are shown in Table 3. Furthermore, according to (Salt Tolerance Evaluation), a brine test sample was prepared and its physical properties were evaluated, and its physical properties after high-temperature storage were evaluated, and then a <Determination of Salt Tolerance> was performed. The obtained results are shown in Table 3.

[0080] Example 2-4 A composition of Example 2-4, which is a mixture of the aqueous silica sol of Synthesis Example 4 and three surfactants (corresponding to surfactant solution-0), was produced in the same manner as in Example 2-3, except that the amount of pure water used was 26.6 g and 70.6 g of the surface-treated aqueous silica sol prepared in Synthesis Example 4 was used instead of Synthesis Example 3. The pH, electrical conductivity, viscosity, and DLS average particle size of the composition of Example 2-4 were evaluated. The evaluation results, along with the silica solid content (mass%) and free silane content (mass%) in the composition of Example 2-4, are shown in Table 3. In addition, according to (Salt Tolerance Evaluation), a brine test sample was prepared and its physical properties were evaluated, and its physical properties after high-temperature storage were evaluated, and a <Determination of Salt Tolerance> was performed. The obtained results are shown in Table 3.

[0081] Example 2-5 A composition of Example 2-5, which is a mixture of the aqueous silica sol of Synthesis Example 6 and three surfactants (corresponding to surfactant solution-0), was produced in the same manner as in Example 3, except that the surface-treated aqueous sol prepared in Synthesis Example 6 was used instead of Synthesis Example 3. The pH, electrical conductivity, viscosity, and DLS average particle size of the composition of Example 2-5 were evaluated. The evaluation results are shown in Table 3, along with the silica solid content (mass %) in the composition of Example 2-5 (free silane: 0 mass %). In addition, according to (Salt Tolerance Evaluation), a brine test sample was prepared and its physical properties were evaluated, and its physical properties after high-temperature storage were evaluated, and an <Assessment of Salt Tolerance> was performed. The obtained results are shown in Table 3.

[0082] Example 2-6 A stirring bar was placed in a 120 ml polystyrene bottle, and 13.9 g of pure water and 85.3 g of the surface-treated aqueous silica sol prepared in Synthesis Example 3 were added thereto and stirred with a magnetic stirrer. Subsequently, while stirring with the magnetic stirrer, 0.8 g of anionic surfactant sodium α-olefin sulfonate (Liporan (trade name) LB-440, manufactured by Lion Specialty Chemicals Co., Ltd., active ingredient 36.3% by mass) was added and stirred until completely dissolved. This procedure produced the composition of Example 2-6, which was a mixture of the aqueous silica sol of Synthesis Example 3 and one surfactant (corresponding to Surfactant Solution-1). The pH, electrical conductivity, viscosity, and DLS average particle size of the composition of Example 2-6 were evaluated. The evaluation results, along with the silica solids content (mass%) and free silane content (mass%) in the composition of Example 2-6, are shown in Table 3. In addition, according to (Salt Tolerance Evaluation), brine test samples were prepared and their physical properties were evaluated, and their physical properties after being kept at high temperatures were evaluated, and <Salt Tolerance Determination> was carried out. The obtained results are shown in Table 3.

[0083] Example 2-7 A stirring bar was placed in a 120 ml polystyrene bottle, and 11.4 g of pure water and 85.3 g of the surface-treated aqueous silica sol prepared in Synthesis Example 3 were added thereto and stirred with a magnetic stirrer. Subsequently, while stirring with the magnetic stirrer, 3.3 g of anionic surfactant sodium α-olefin sulfonate (Lipolan (trade name) LB-440, manufactured by Lion Specialty Chemicals Co., Ltd., active ingredient 36.3% by mass) was added and stirred until completely dissolved. This procedure produced the composition of Example 2-7, which was a mixture of the aqueous silica sol of Synthesis Example 3 and one surfactant (corresponding to Surfactant Solution-2). The pH, electrical conductivity, viscosity, and DLS average particle size of the composition of Example 2-7 were evaluated. The evaluation results, along with the silica solids content (mass%) and free silane content (mass%) in the composition of Example 2-7, are shown in Table 3. In addition, according to (Salt Tolerance Evaluation), brine test samples were prepared and their physical properties were evaluated, and their physical properties after being kept at high temperatures were evaluated, and <Salt Tolerance Determination> was carried out. The obtained results are shown in Table 3.

[0084] Example 2-8 A stirrer was placed in a 120 ml polystyrene bottle, and 13.0 g of pure water and 85.3 g of the surface-treated aqueous silica sol prepared in Synthesis Example 3 were added thereto and stirred with a magnetic stirrer. Subsequently, while stirring with the magnetic stirrer, 1.7 g of a nonionic surfactant, polyoxyethylene styrenated phenyl ether with an HLB of 14.3 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., Noigen (trade name) EA-157, active ingredient 100% by mass) diluted with pure water to 70% by mass of active ingredient, was added and stirred until completely dissolved. Using the above procedure, a composition of Example 2-8 was produced, which was a mixture of the aqueous silica sol of Synthesis Example 3 and one surfactant (corresponding to surfactant solution-3). The pH, electrical conductivity, viscosity, and DLS average particle size of the composition of Example 2-8 were evaluated. The evaluation results, along with the silica solids content (mass%) and free silane content (mass%) in the composition of Example 2-8, are shown in Table 3. In addition, according to (Salt Tolerance Evaluation), brine test samples were prepared and their physical properties were evaluated, and their physical properties after being kept at high temperatures were evaluated, and <Salt Tolerance Determination> was carried out. The obtained results are shown in Table 3.

[0085] (Example 2-9) A stirrer was placed in a 120 ml polystyrene bottle, and 12.2 g of pure water and 85.3 g of the surface-treated aqueous silica sol prepared in Synthesis Example 3 were added thereto and stirred with a magnetic stirrer. Subsequently, while stirring with the magnetic stirrer, 0.8 g of anionic surfactant sodium α-olefin sulfonate (Lipolan (trade name) LB-440, manufactured by Lion Specialty Chemicals Co., Ltd., active ingredient 36.3% by mass) was added and stirred until completely dissolved. Subsequently, while stirring with the magnetic stirrer, 1.7 g of a nonionic surfactant polyoxyethylene styrenated phenyl ether with an HLB of 14.3 (Noigen (trade name) EA-157, active ingredient 100% by mass, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., diluted with pure water to 70% by mass of active ingredient) was added and stirred until completely dissolved. By the above-mentioned procedure, a composition of Example 2-9 was produced, which was a mixture of the aqueous silica sol of Synthesis Example 3 and two surfactants (corresponding to Surfactant Solution-4). The pH, electrical conductivity, viscosity, and DLS average particle size of the composition of Example 2-9 were evaluated. The evaluation results, along with the silica solid content (mass%) and free silane amount (mass%) in the composition of Example 2-9, are shown in Table 3. In addition, according to (Salt Tolerance Evaluation), a brine test sample was prepared and its physical properties were evaluated, and its physical properties after being kept at high temperatures were evaluated, and <Determination of Salt Tolerance> was performed. The obtained results are shown in Table 3.

[0086] (Example 2-10) A stirrer was placed in a 120 ml polystyrene bottle, and 11.3 g of pure water and 85.3 g of the surface-treated aqueous silica sol prepared in Synthesis Example 3 were added thereto and stirred with a magnetic stirrer. Subsequently, while stirring with the magnetic stirrer, 1.7 g of anionic surfactant sodium α-olefin sulfonate (Lipolan (trade name) LB-440, manufactured by Lion Specialty Chemicals Co., Ltd., active ingredient 36.3% by mass) was added and stirred until completely dissolved. Subsequently, while stirring with the magnetic stirrer, 1.7 g of a nonionic surfactant polyoxyethylene styrenated phenyl ether with an HLB of 14.3 (Noigen (trade name) EA-157, active ingredient 100% by mass, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., diluted with pure water to 70% by mass of active ingredient) was added and stirred until completely dissolved. By the above-mentioned procedure, a composition of Example 2-10 was produced, which was a mixture of the aqueous silica sol of Synthesis Example 3 and two surfactants (corresponding to Surfactant Solution-5). The pH, electrical conductivity, viscosity, and DLS average particle size of the composition of Example 2-10 were evaluated. The evaluation results, along with the silica solid content (mass%) and free silane amount (mass%) in the composition of Example 2-10, are shown in Table 3. In addition, according to (Salt Tolerance Evaluation), a brine test sample was prepared and its physical properties were evaluated, and its physical properties after being kept at high temperatures were evaluated, and <Determination of Salt Tolerance> was performed. The obtained results are shown in Table 3.

[0087] (Comparative Example 2-1) An aqueous silica sol (Snowtex (trade name) ST-O, manufactured by Nissan Chemical Industries, Ltd.) was used as the aqueous silica sol of Comparative Example 1. The pH, electrical conductivity, viscosity, and DLS average particle size of the aqueous silica sol (silica particles) of Comparative Example 1 were evaluated. The evaluation results are shown in Table 3, along with the silica solid content (mass%) in the composition of Comparative Example 1. In addition, according to (Salt resistance evaluation), a brine test sample was prepared and its physical properties were evaluated, and the physical properties after being kept at high temperature were evaluated, and <Determination of salt resistance> was performed.> The obtained results are shown in Table 3.

[0088] (Comparative Example 2-2) A stirrer was placed in a 120 ml polystyrene bottle, and 26.6 g of pure water and 70.6 g of the surface-treated aqueous silica sol prepared in Synthesis Example 5 were added thereto and stirred with a magnetic stirrer. Subsequently, while stirring with the magnetic stirrer, 0.8 g of anionic surfactant sodium α-olefin sulfonate (Lipolan (trade name) LB-440, manufactured by Lion Specialty Chemicals Co., Ltd., active ingredient 36.3% by mass) was added and stirred until completely dissolved. Subsequently, 0.30 g of anionic surfactant sodium dodecyl sulfate (Shinoline (trade name) 90TK-T, manufactured by New Japan Chemical Co., Ltd., active ingredient 100% by mass) was added and stirred until completely dissolved. Subsequently, 1.7 g of a nonionic surfactant, polyoxyethylene styrenated phenyl ether with an HLB of 14.3 (Noigen (trade name) EA-157, active ingredient 100% by mass, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) diluted with pure water to 70% by mass of the active ingredient, was added and stirred until completely dissolved. By the above procedure, a composition of Comparative Example 2-2, which is a mixture of the aqueous silica sol of Synthesis Example 5 and three surfactants (corresponding to surfactant solution-0), was produced. The pH, electrical conductivity, viscosity, and DLS average particle size of the composition of Comparative Example 2-2 were evaluated. The evaluation results, along with the silica solid content (% by mass) and free silane content (% by mass) in the composition of Comparative Example 2-2, are shown in Table 3. Furthermore, according to (Salt Tolerance Evaluation), a brine test sample was prepared and its physical properties were evaluated, and its physical properties after high-temperature storage were evaluated, and then a <Determination of Salt Tolerance> was performed. The obtained results are shown in Table 3.

[0089]

[0090] As shown in the results of the electrical mobility shown in Table 2 and the evaluation of salt tolerance shown in Table 3, when affinity capillary electrophoresis was performed, the compositions of Examples 1-1 to 1-10 had a mobility of −0.014 to −0.0085 cm ２The compositions of Examples 2-1 to 2-10, which had an electrical mobility of 1.0 / V·min and used similar aqueous silica sols and surfactants, showed little change in DLS average particle size even after the salt tolerance test (ratio of DLS average particle size after test / before test was 1.0 to 1.4), and the silica particles were stably dispersed without aggregation even after the salt tolerance test, confirming that these compositions had excellent salt tolerance. On the other hand, the composition of Comparative Example 2-2, which used the same aqueous silica sol and surfactant as Comparative Example 1-2, which had an electrical mobility positioned more toward the uncharged side than the compositions of the Examples, became cloudy after the salt tolerance test, and the ratio of DLS average particle size after test / before test was 7.8, indicating that this composition had poor salt tolerance. As for Comparative Examples 1-1 and 2-1, as described above, mixing of aqueous silica sol (unmodified silica particles) with a surfactant (particularly a nonionic surfactant) resulted in aggregation and gelation, making it impossible to measure electrical mobility (Comparative Example 1-1). Furthermore, a salt-resistant sample containing only aqueous silica sol (unmodified silica particles) (no surfactant) became cloudy after the salt tolerance test, and the DLS average particle size after the test exceeded 1000 nm, suggesting aggregation of silica particles and resulting in a lack of salt tolerance (Comparative Example 2-1).

Claims

1. A composition comprising surface-modified silica particles, a surfactant, and a solvent, the composition being diluted with a 5 mM aqueous solution of sodium tetraborate to a silica concentration of 2 mass% to prepare a test solution, and affinity capillary electrophoresis being performed with the composition under the conditions of a capillary temperature of 25°C, a capillary applied voltage of 30 kV, a capillary inner diameter of 75 μm, a capillary total length of 112.5 cm, and a capillary effective length of 104 cm, using the surface-modified silica particles as a ligand and a surfactant containing an anionic surfactant, a nonionic surfactant, or a mixture of two or more thereof as an analyte. The affinity was -0.017 to -0.0010 cm. ２ / V·min.

2. The composition of claim 1 further comprising a polyorganosiloxane.

3. The composition according to claim 1, wherein the surface silica particles have an average primary particle size of 5 to 100 nm in unmodified silica particles prior to surface modification.

4. The composition according to claim 1, wherein the surface-modified silica particles have an average particle size of 5 to 200 nm as measured by dynamic light scattering.

5. The composition according to claim 1, wherein the surface-modified silica particles are unmodified silica particles, at least a portion of the surface of which is coated with a silane compound having an organic group, and the organic group is a hydrocarbon group-containing organic group, an epoxy group-containing organic group, an amino group-containing organic group, a (meth)acryloyl group-containing organic group, a hydroxyl group-containing organic group, or a carboxyl group-containing organic group.

6. The composition according to claim 1, wherein the surfactant is an α-olefin sulfonate, a polyoxyethylene alkyl phenyl ether, a combination of an α-olefin sulfonate and a polyoxyethylene alkyl phenyl ether, or a combination of an α-olefin sulfonate, a higher alcohol sulfate having 6 to 24 carbon atoms, and a polyoxyethylene alkyl phenyl ether.

7. The composition of claim 1, wherein the solvent comprises water or salt water.

8. The composition of claim 1, wherein the solvent comprises methanol or ethanol.

9. The composition according to claim 1, wherein in a high-temperature salt resistance test in which the composition is stored at 100°C for 10 hours at a silica concentration of 0.1 mass%, 0.5 mass%, or 1.0 mass% in an environment with a salt concentration of 4 mass%, the ratio expressed by DLS average particle size after the high-temperature salt resistance test / DLS average particle size before the test is 1.5 or less (the rate of change in average particle size is 50% or less).

10. A method for producing the composition according to claim 2, comprising the steps of: heating a mixture containing silica particles, a silane compound having an organic group, and a solvent to 10 to 150°C with stirring to obtain a mixture containing silica particles, at least a portion of which is coated with a silane compound having an organic group, a polyorganosiloxane, and a solvent; and mixing the obtained mixture with a surfactant.

11. A method for producing a composition according to claim 10, comprising, after the step of obtaining a mixed solution containing silica particles coated with the silane compound and polyorganosiloxane, a step of maintaining the obtained mixed solution at 10 to 80°C for 1 hour to 1 month before or after the step of mixing the obtained mixed solution with a surfactant.

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