Method for manufacturing a water-containing paste-like composition

Abstract

To solve the problem in which when porous silica added to cosmetics or the like contains ionic impurities, lowering of oil absorption and the like may occur, which requires washing with water, etc. to reduce the amount of ionic impurities and yet a large amount of washing water is required and this increases waste liquid accordingly.SOLUTION: An aqueous dispersion of silica gel is prepared using silica sol as a starting material by an emulsion method. After hydrophobization treatment, a water-soluble organic solvent is added to separate the aqueous dispersion of silica gel into a water-soluble organic solvent layer having silica gel dispersed therein and an aqueous layer, and the aqueous layer is removed. Since most ionic impurities are dissolved in the aqueous layer, subsequent steps of reducing ionic impurities can be greatly made efficient by removing the aqueous layer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a novel method for producing a paste-like composition containing hydrophobic silica and water. More specifically, it relates to a production method that can reduce the amount of water used for washing to reduce the content of ionic impurities compared to conventional methods. [Background technology]

[0002] Aerogels are materials with a high porosity and excellent oil absorption properties. Here, aerogel refers to a solid material with a porous structure and containing gas as a dispersion medium, and specifically refers to a solid material with a porosity of 60% or more. Porosity is the amount of gas contained in the apparent volume, expressed as a volume percentage. Due to its high porosity, aerogels possess excellent oil absorption properties.

[0003] Silica aerogel has a variety of uses, but it is particularly useful as a cosmetic ingredient. Taking foundation as an example, it is used as an additive to improve the longevity of its appearance when applied to the skin. More specifically, the porous structure of silica aerogel absorbs sebum well, preventing the skin from becoming wet with sebum, which increases the specular reflectivity of light and causes shininess. Moreover, if silica aerogel is manufactured using a hydrophobic process, it has better affinity with the organic components of cosmetic ingredients such as foundation and disperses uniformly, further enhancing the aforementioned effect of preventing shininess and improving the longevity of the appearance.

[0004] For example, when used in powder form as an ingredient in foundation, silica aerogel, which has a high oil absorption capacity, can absorb a large amount of sebum that causes shine, thus allowing the appearance of the finished makeup to last for a long time (see Patent Document 1).

[0005] Furthermore, when these silica aerogels are incorporated into cosmetics, it is desirable that their particle size be between 1 and several tens of micrometers in order to obtain a smooth texture, and that their shape be spherical in order to improve their rolling properties on the skin.

[0006] As a method for producing spherical silica aerogels having such appropriate particle sizes, the following method has been proposed, for example.

[0007] Patent Document 2 discloses a method for producing spherical silica aerogel, comprising the steps of preparing an aqueous silica sol, dispersing the aqueous silica sol in a hydrophobic solvent to form a W / O emulsion, gelling the silica sol to convert the W / O emulsion into a dispersion of the gelled body, replacing the water in the gelled body with a solvent having a surface tension of 30 mN / m or less at 20°C, hydrophobizing (silylation) the gelled body with a hydrophobic agent (silylation agent), and removing the substituted solvent, in the order described above.

[0008] Patent Document 3 discloses a method for producing spherical silica aerogel, which sequentially includes the steps of: separating the dispersion of the gelled substance obtained in the step of converting the W / O type emulsion into a dispersion of the gelled substance into two layers, an O phase and a W phase; adding a basic substance to the W phase to mature the gelled substance dispersed in the W phase; silylation treatment of the gelled substance dispersed in the W phase; extracting the gelled substance with a hydrophobic organic solvent; and recovering the gelled substance to obtain a powder consisting of hydrophobic spherical silica aerogel. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2014-88307 [Patent Document 2] International Publication No. 2012 / 057086 [Patent Document 3] Japanese Patent Publication No. 2018-177620 [Overview of the project] [Problems that the invention aims to solve]

[0010] The hydrophobic silica aerogel powder obtained as described in the aforementioned patent document has the problem of being difficult to disperse in water due to its hydrophobic nature. To solve this problem, the present inventors have already proposed (Japanese Patent Application No. 2021-014785) to produce a paste-like composition containing hydrophobic silica and water by adjusting the amount of water directly from an aqueous dispersion in which a hydrophobic gelled material, produced as an intermediate in the manufacturing method described in Patent Document No. 2, is dispersed, and using this paste-like composition. That is, by reducing the water content in the W phase in which the hydrophobic gelled material is dispersed to an extent that the gelled material does not dry out, a paste-like composition can be made. By making it a paste-like composition, it becomes possible to disperse it in water or a water-based medium, which was difficult with hydrophobic silica aerogel powder.

[0011] Aqueous dispersions containing hydrophobized gels contain salts derived from the raw materials used in the preparation and hydrophobization of the aqueous silica sol, which tend to remain in the gel. When salts remain in the gel, the pores become filled with salts, preventing the gel from maintaining a high oil absorption capacity and thus preventing it from absorbing large amounts of sebum. Therefore, in the production of paste-like compositions (Japanese Patent Application No. 2021-014785), salts are removed by performing a washing process in which water is continuously (or intermittently) added and removed while taking care to prevent the gel from drying out.

[0012] One problem with this washing process was that it required the use of large amounts of deionized water to adequately remove chlorides, sulfates, and other salts. Furthermore, this washing process generated a large amount of wastewater, making it uneconomical.

[0013] Therefore, the present invention aims to provide an economically superior method for producing a paste-like composition containing hydrophobic silica with a sufficiently low salt content and water. [Means for solving the problem]

[0014] As a result of intensive research to solve the above problems, the inventors of the present invention have found that, in a method for producing a paste-like composition containing water, by adding a water-soluble organic solvent to a solution containing a large amount of salt, it is possible to phase-separate into an organic layer in which an aerogel is dispersed and an aqueous layer containing salt. Therefore, in the step of removing the aqueous layer, the salt can be removed, and furthermore, the amount of water required for washing can be reduced, making it possible to produce more economically, and thus the present invention has been completed.

[0015] That is, the present invention provides (1) A step of preparing an aqueous silica sol; (2) A step of dispersing the aqueous silica sol in a hydrophobic solvent to form a W / O type emulsion; (3) A step of gelling the silica sol to convert the W / O type emulsion into a dispersion of silica gel; (4) A step of phase-separating into an organic phase and an aqueous phase in which the silica gel is dispersed, and then removing the organic phase; (5) A step of adding a hydrophobizing agent to the aqueous phase in which the silica gel is dispersed to hydrophobize the silica gel; (6) A step of adding a water-soluble organic solvent to phase-separate into an organic phase in which the silica gel is dispersed and an aqueous phase; (7) A step of removing the aqueous phase, and (8) A step of de-liquoring the organic phase in which the silica gel is dispersed to form a paste A method for producing a paste-like composition containing hydrophobic silica and water, comprising the above steps.

Advantages of the Invention

[0016] In the production method of the present invention, by adding a water-soluble organic solvent, performing the step of phase-separating into an organic phase in which silica gel is dispersed and an aqueous phase, and the step of removing the aqueous phase, it is possible to produce a paste-like composition containing hydrophobic silica and water by a method that is more economical than conventional methods and suppresses the amount of washing water used. Conversely, if the amount of water used is the same, the content of ionic impurities can be relatively reduced.

Embodiments for Carrying Out the Invention

[0017] The method for producing the water-containing paste-like composition of the present invention includes the following steps: (1) Steps to prepare aqueous silica sol, (2) A step of dispersing the aqueous silica sol in a hydrophobic solvent to form a W / O type emulsion. (3) A step of gelling the silica sol to convert the W / O type emulsion into a silica gel dispersion, (4) A step of separating the phases into an organic phase and an aqueous phase in which the silica gel is dispersed, and then removing the organic phase. (5) A step of adding a hydrophobic agent to an aqueous phase in which silica gel is dispersed to make the silica gel hydrophobic, (6) A step in which a water-soluble organic solvent is added to separate the organic phase in which silica gel is dispersed into an aqueous phase. (7) A step of removing the aqueous phase, and (8) A step of deliquing the organic phase in which silica gel is dispersed to form a paste, This involves performing the following steps in order.

[0018] The above manufacturing method will be described in detail below, in a step-by-step manner.

[0019] (1) Steps to prepare aqueous silica sol As a raw material for silica sol, a method using alkali metal silicates, etc., can be suitably adopted because it is inexpensive. Examples of alkali metal silicates include potassium silicate and sodium silicate, and their compositional formula is shown in the following formula (1).

[0020] m(M2O)·n(SiO2) (1) [In equation (1), m and n each represent independent positive integers, and M represents an alkali metal atom.] Among the raw materials for preparing silica sol as described above, sodium silicate is particularly preferred because it is readily available.

[0021] The following explanation will use alkali metal silicate salts as a raw material as an example.

[0022] When using an alkali metal silicate as a raw material for preparing the aqueous silica sol of the present invention, it is preferable to prepare the silica sol by neutralizing it with a mineral acid such as hydrochloric acid or sulfuric acid. Specifically, this can be done by adding an aqueous solution of the alkali metal silicate to an aqueous solution of the acid while stirring the solution, or by causing a collision mix of the aqueous solution of the acid and the aqueous solution of the alkali metal silicate in a pipe (see, for example, Japanese Patent Publication No. 4-54619).

[0023] In this invention, the pH of the prepared silica sol is set to be in the acidic range. Specifically, the amount of acid used when preparing the aqueous silica sol is preferably such that the molar ratio of hydrogen ions to alkali metal content in the alkali metal silicate salt is 1.05 to 1.2. When the amount of acid is within this range, the pH of the prepared silica sol will be approximately 1 to 5. More preferably, the amount of acid is adjusted so that the pH of the prepared silica sol is 2.5 to 3.5.

[0024] The silica sol prepared by the above method is preferably concentrated at 50 g / L or more in terms of silica content (SiO2 equivalent concentration), as this allows gelation to be completed in a relatively short time, sufficiently forms a skeletal structure of silica particles to suppress shrinkage during drying, and makes it easier to obtain a large pore volume. On the other hand, it is preferable to have a silica concentration of 160 g / L or less, and more preferably 100 g / L or less, as this allows for a relatively low density of silica particles, resulting in a good pore volume and easier oil absorption. Even more preferably, it is 90 to 100 g / L.

[0025] By setting the concentration of aqueous silica sol to above the lower limit, it becomes easier to set the pore volume of the aerogel by the BJH method to 8 mL / g or less, and also to set the peak of the pore radius of the aerogel by the BJH method to 50 nm or less. Furthermore, by setting the concentration of aqueous silica gel to below the upper limit, it becomes easier to set the pore volume of the aerogel by the BJH method described in the above patent document to 2 mL / g or more, and also to set the peak of the pore radius of the aerogel by the BJH method to 10 nm or more.

[0026] (2) A step of dispersing the aqueous silica sol in a hydrophobic solvent to form a W / O type emulsion. In the manufacturing method of the present invention, the aqueous silica sol obtained by the method described above is dispersed in a hydrophobic solvent to form a W / O emulsion. By forming such a W / O emulsion, the silica sol becomes spherical due to surface tension, etc., and by gelling the silica sol dispersed in the hydrophobic solvent in this spherical shape, a spherical gel can be obtained. In this way, by going through the emulsion formation step of forming a W / O emulsion, it becomes possible to produce aerogels that usually have a high circularity of 0.8 or more.

[0027] The hydrophobic solvent can be any solvent that is hydrophobic enough to form a W / O emulsion with aqueous silica sol. Suitable solvents include, for example, organic solvents such as hydrocarbons and halogenated hydrocarbons. More specifically, examples include hexane, heptane, octane, nonane, decane, dichloromethane, chloroform, carbon tetrachloride, and dichloropropane. Among these, heptane, which has a suitable viscosity, is particularly preferable. Multiple solvents may be mixed and used as needed. Furthermore, water-soluble solvents such as lower alcohols can be used in combination (as a mixed solvent), as long as they can form a W / O emulsion with aqueous silica sol.

[0028] The amount of hydrophobic solvent used is not particularly limited, as long as it is enough to form a w / o emulsion. However, generally, an amount of hydrophobic solvent of about 1 to 10 parts by volume is used per 1 part by volume of aqueous silica sol.

[0029] When forming the above W / O emulsion, it is preferable to add a surfactant. Any of anionic surfactants, cationic surfactants, or nonionic surfactants can be used. Among these, nonionic surfactants are preferred because they readily form a W / O emulsion. In the present invention, since the silica sol is aqueous, a surfactant with an HLB value of 3 or more and 6 or less, which indicates the degree of water solubility and hydrophobicity of the surfactant, can be suitably used. In the present invention, "HLB value" refers to the HLB value by the Griffin method.

[0030] As described above, in the present invention, the shape of the aerogel particles is largely determined by the shape of the droplets of the W / O emulsion. The shape of the droplets depends on the surfactant used. As stated above, the shape of the aerogel particles is preferably spherical, and from this viewpoint, specific surfactants that can be suitably used include sorbitan monooleate, sorbitan monostearate, and sorbitan monosesquiolate.

[0031] The amount of surfactant used is no different from the typical amount used to form a W / O emulsion. Specifically, a range of 0.05 g to 10 g per 100 ml of aqueous silica sol is preferably used. If the amount of surfactant used is high, the droplets of the W / O emulsion tend to become finer, and conversely, if the amount of surfactant used is low, the droplets of the W / O emulsion tend to become larger. Therefore, the average particle size of the aerogel can be adjusted by increasing or decreasing the amount of surfactant used.

[0032] When forming a W / O emulsion, known methods for forming W / O emulsions can be used to disperse the aqueous silica sol in a hydrophobic solvent. From the viewpoint of ease of industrial production, emulsion formation by mechanical emulsification is preferred, and specific examples include methods using a mixer, homogenizer, etc. A homogenizer can preferably be used.

[0033] Since the average particle size of silica sol droplets in a W / O emulsion generally corresponds to the average particle size of aerogel, the average particle size of aerogel can be controlled by controlling the droplet diameter.

[0034] Furthermore, by making the particle size of the silica sol droplets in the emulsion sufficiently small, the shape of the silica sol droplets becomes less likely to be disturbed, making it even easier to obtain spherical aerogels with higher circularity (however, the average particle size of the aerogel also becomes smaller).

[0035] (3) the above Water-based A process of gelling the silica sol to convert the W / O type emulsion into a silica gel dispersion. In this process, after forming an emulsion by the aforementioned operation, the aqueous silica sol is gelled. Any known gelling method can be used without particular limitation, as long as the emulsion state is not disrupted.

[0036] One preferred method is to adjust the pH during aqueous silica sol formation so that the time until gelation is sufficiently extended. In other words, the pH is adjusted so that gelation does not occur during emulsion formation of the silica sol, but then occurs after being held at a certain temperature for a certain period of time.

[0037] After adjusting to the gelation temperature, the time it takes for gelation to begin depends on the pH, gelation temperature, and silica sol concentration. Generally, the lower the pH, the lower the gelation temperature, and the lower the silica sol concentration, the longer the time tends to be. For example, at pH 5, a temperature of 50°C, and a silica concentration (SiO2 equivalent) of 80 g / L in the silica sol, it takes a few minutes. At pH 3, a temperature of 70°C, and a silica concentration (SiO2 equivalent) of 80 g / L in the silica sol, it takes about 60 minutes.

[0038] Another preferred method involves adding a basic substance to the emulsion to raise the pH of the W phase, making it weakly acidic or basic. In this case, it is preferable to prepare the metal oxide sol at a relatively stable low pH (around 0.5 to 2.5) when preparing it. A specific method for raising the pH of the W phase is to predetermine the amount of base needed to raise the W phase to the desired pH and then add that amount of base to the emulsion. The amount of base needed to achieve the desired pH can be determined by taking a fixed amount of the metal oxide sol used in the emulsion, measuring the pH of the taken metal oxide sol with a pH meter, adding the base used for gelation to the taken metal oxide sol, and measuring the amount of base needed to achieve the desired pH.

[0039] When adding a basic substance to an emulsion, it is preferable to prevent localized increases in pH by stirring with a mixer or similar device. Examples of basic substances include ammonia, caustic soda, and alkali metal silicates.

[0040] (4) A step of separating the phases into an organic phase and an aqueous phase in which the silica gel is dispersed, and then removing the organic phase. In the manufacturing method of the present invention, the dispersion of the gelled material prepared as described above is separated into an O phase and a W phase. After separation, the gelled material obtained in the above step is dispersed in the W phase.

[0041] As for the separation method, known methods for dissolving emulsions can be used, but specifically, one or more methods selected from the following can be used: addition of a water-soluble organic solvent, addition of a salt, application of centrifugal force, addition of an acid, and change in volume ratio (addition of water or a hydrophobic solvent). Preferably, a certain amount of water-soluble organic solvent can be added to the emulsion along with water as needed to separate it into the O phase and the W phase. After the separation step, generally the upper layer is the O phase (organic layer) and the lower layer is the W phase (aqueous layer). Examples of the above-mentioned water-soluble organic solvents include acetone, methanol, ethanol, and isopropyl alcohol. Of these, isopropyl alcohol can be preferably used because it is effective in improving the efficiency of the hydrophobic treatment described later.

[0042] Furthermore, the addition of water is not necessarily required to form the W phase in this process. A method can be employed in which a sufficient amount of water from the water used as a raw material is discharged from the gelled material to allow for its dispersion. Specifically, this method can be implemented by selecting a water-soluble organic solvent that penetrates the pores of the gelled material and has the function of displacing water.

[0043] The amount of water-soluble organic solvent added is preferably adjusted according to the type and amount of surfactant used during emulsion formation. For example, when sorbitan monooleate is used as the surfactant for a W / O type emulsion, the O phase and W phase can be separated by adding a water-soluble organic solvent in an amount of about 0.1 to 0.4 times the mass of the O phase, stirring as necessary, and then allowing it to stand. However, in this case, it is preferable to add water along with the water-soluble organic solvent in an amount of about 0.6 to 0.9 times the mass of the O phase. Furthermore, the temperature during this separation operation is not particularly limited, but it can usually be carried out at around 20 to 70°C.

[0044] In carrying out the manufacturing method of the present invention, it is preferable to perform aging thereafter. This aging is carried out by adding a basic substance to the W phase (where the gelled material is dispersed) that has been separated from the O phase, and adjusting the pH of the W phase to weakly acidic or basic.

[0045] By adding a basic substance, the pH of the W phase, which is in an acidic range, rises, resulting in a weakly acidic or basic state. Specifically, the pH of the W phase is preferably 4.5 to 10, more preferably 5.5 to 8.5, and particularly preferably 6.0 to 8.0.

[0046] In the present invention, the basic substance used is a basic substance containing sodium. While inorganic bases such as sodium hydroxide, sodium bicarbonate, and sodium carbonate, and sodium salts of organic acids such as sodium acetate can be used as the basic substance, inorganic bases are preferred because organic acids may be undesirable impurities. Among these, sodium hydroxide is preferred because it allows for easy pH adjustment.

[0047] Furthermore, the gelled material can be matured by maintaining the maturation temperature at room temperature to approximately 80°C. The maturation time can be appropriately set depending on the pH of the W phase and the maturation temperature, but it is generally between 0.5 and 12 hours.

[0048] In the manufacturing method of the present invention, the separated O phase is then removed. This is to improve the processing efficiency in the subsequent step of hydrophobic treatment of the gelled body. The removal method is not particularly limited, but it can be easily achieved by removing the O phase from the two phases, the O phase and the W phase, for example by decantation, and recovering the W phase.

[0049] Here, it is not necessary to completely separate and remove the O phase, but in order to efficiently perform the hydrophobic treatment in the step of hydrophobicating the gelled body contained in the W phase, it is preferable that the proportion of the O phase that remains unremoved be as small as possible. It is preferable that it be 20% by mass or less relative to the amount of W phase (including the mass of the gelled body), and more preferably 10% by mass or less.

[0050] (5) A step of adding a hydrophobic agent to an aqueous phase in which silica gel is dispersed to make the silica gel hydrophobic. As the hydrophobic agent, any compound that reacts with Si-OH to form a Si-O-Si bond can be used, and known hydrophobic agents used in the production of hydrophobic silica aerogels can be employed.

[0051] More specifically, hydrophobic agents usable in the present invention include silanol groups: M-OH (2) [In the formulas, M represents the Si atoms forming the gel. In formula (2), the remaining valence of M is omitted. The same applies to all the following formulas.] And reacted to this (MOw) (4-n) SiR n (3) As an example, a silylating agent that can be converted to [In formula (3), n is an integer from 1 to 3, R is a hydrocarbon group, and if n is 2 or greater, multiple Rs may be the same or different from each other] can be given.

[0052] By performing a hydrophobic treatment using such a hydrophobic agent, the hydroxyl groups on the surface of the aerogel powder are end-capped and deactivated by hydrophobic silyl groups, thereby suppressing dehydration condensation reactions between surface hydroxyl groups. Therefore, drying shrinkage can be suppressed even when drying is performed under conditions below the critical point, making it possible to obtain hydrophobic silica aerogel powder with a BJH pore volume of 2 mL / g or more.

[0053] The following compounds represented by general formulas (4) to (6) are known as hydrophobic agents.

[0054] R n SiX (4-n) (4) [In formula (4), n represents an integer between 1 and 3; R represents a hydrophobic group such as a hydrocarbon group; and X represents a group that can be removed from the molecule by cleaving its bond with the Si atom in a reaction with a compound having a hydroxyl group (a leaving group). When n is 2 or greater, multiple Rs may be the same or different. Also, when n is 2 or less, multiple Xs may be the same or different.]

[0055]

Chem.

[0056] [In formula (5), R 1 represents an alkylene group; R 2 and R 3 each independently represent a hydrocarbon group; R 4 and R 5 each independently represent a hydrogen atom or a hydrocarbon group.]

[0057]

Chem.

[0058] [In formula (6), R 6 and R 7 each independently represent a hydrocarbon group, and m represents an integer from 3 to 6. The plurality of R 6 may be the same or different. Also, the plurality of R 7 may be the same or different.] In the above formula (4), R is a hydrocarbon group, preferably a hydrocarbon group having 1 to 10 carbon atoms, more preferably a hydrocarbon group having 1 to 4 carbon atoms, and particularly preferably a methyl group.

[0059] Examples of the leaving group represented by X include halogen atoms such as chlorine and bromine; alkoxy groups such as methoxy group and ethoxy group; a group represented by -NH-SiR3 (where R has the same meaning as R in formula (4)), etc.

[0060] Specific examples of silylating agents represented by formula (4) above include chlorotrimethylsilane, dichlorodimethylsilane, trichloromethylsilane, monomethyltrimethoxysilane, monomethyltriethoxysilane, hexamethyldisilazane, octamethylcyclotetrasiloxane, and hexamethyldisiloxane. Chlorotrimethylsilane, dichlorodimethylsilane, trichloromethylsilane, octamethylcyclotetrasiloxane and / or hexamethyldisilazane and hexamethyldisiloxane are particularly preferred due to their good reactivity.

[0061] The number of hydroxyl groups bonded to the aerogel powder skeleton changes depending on the number of leaving groups X (4-n). For example, if n is 2: (MO-)2SiR2(7) This will result in the following combination.

[0062] Also, if n is 3: MO-SiR3(8) This results in the formation of a bond. The silylation of the hydroxyl group thus performs a hydrophobic treatment.

[0063] In equation (5) above, R 1 is an alkylene group, preferably an alkylene group having 2 to 8 carbon atoms, and particularly preferably an alkylene group having 2 to 3 carbon atoms.

[0064] In equation (5) above, R 2 and R 3 Each of these is independently a hydrocarbon group, and preferred groups include those similar to R in formula (4) above. 4 and R 5 represents a hydrogen atom or a hydrocarbon group, and if it is a hydrocarbon group, a preferred group is one similar to R in formula (4). When the gelled product is treated with the compound represented by formula (5) (cyclic silazane), the Si-N bond is cleaved by reaction with the hydroxyl group, so on the surface of the aerogel powder skeleton in the gelled product (MO-)2SiR 2R 3 (9) This results in the formation of a bond. Thus, the hydroxyl group is silylated and hydrophobized by the cyclic silazanes of formula (7) above.

[0065] Examples of cyclic silazanes represented by formula (5) above include hexamethylcyclotrisilazane and octamethylcyclotetrasilazane.

[0066] In the above equation (6), R 6 and R 7 Each of these is an independent hydrocarbon group, and preferred groups include those similar to R in formula (4). m is an integer from 3 to 6. When the gelled body is treated with the compound represented by formula (6) (cyclic siloxane), the aerogel powder skeleton surface in the gelled body is formed as follows: (MO-)2SiR 6 R 7 (10) This results in the formation of a bond. Thus, the hydroxyl group is silylated and hydrophobized by the cyclic siloxanes of formula (6) above.

[0067] Examples of cyclic siloxanes represented by formula (6) above include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and decamethylcyclopentasiloxane.

[0068] The amount of hydrophobic agent used in the above hydrophobic treatment depends on the type of treatment agent, but when hexamethyldisiloxane is used as the hydrophobic agent, 10 to 150 parts by mass per 100 parts by mass of silica (amount of SiO2 calculated from the amount of silica sol used) is preferable. More preferably, it is 20 to 130 parts by mass, and even more preferably, 30 to 120 parts by mass.

[0069] The above hydrophobic treatment conditions can be met by adding a hydrophobic agent to the W phase and allowing it to react for a certain period of time. For example, if hexamethyldisiloxane is used as the hydrophobic agent and the treatment temperature is 50°C, the treatment can be carried out by holding it for 6 to 12 hours or more, and if the treatment temperature is 70°C, the treatment can be carried out by holding it for 3 to 12 hours or more.

[0070] Furthermore, when using cyclic siloxanes such as octamethylsiloctetrasiloxane as a silylation agent, it is preferable to add mineral acid to adjust the pH of the solution to 0.3 to 1.0 in order to improve the efficiency of the reaction.

[0071] The mineral acids mentioned above are preferably sulfuric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, thiocyanic acid, and phosphoric acid, with sulfuric acid being the most preferred among them.

[0072] In the hydrophobic treatment step, it is preferable to add a water-soluble organic solvent to increase the solubility of the hydrophobic agent in the W phase and thereby improve the efficiency of the reaction. Examples of water-soluble organic solvents include acetone, methanol, ethanol, and isopropyl alcohol. Of these, isopropyl alcohol can be suitably used. The amount added should be approximately 15 to 80 wt% in the W phase containing the gelled product.

[0073] (6) A step in which a water-soluble organic solvent is added to separate the organic phase in which silica gel is dispersed from the aqueous phase. After hydrophobizing the silica gel, a water-soluble organic solvent is added to the W phase to separate the liquid phase into an O phase and a W phase. This is due to salting out, where the salt produced in the previous steps is dissolved in the W phase, reducing the solubility of the water-soluble organic solvent, and the water-soluble organic solvent that cannot be dissolved in the W phase is released as the O phase. Since the silica gel is hydrophobized, it disperses in the O phase, and most of the salt dissolves in the W phase. The separated O phase also contains water, and its proportion is about 30-50% by mass, depending on the water-soluble organic solvent. The amount of water-soluble organic solvent used should be set appropriately, with a guideline of 1 to 10 times the amount of the W phase. There are no restrictions on the water-soluble organic solvent used, but isopropyl alcohol, n-propyl alcohol, tert-butyl alcohol, n-butyl alcohol, ethanol, methanol, acetone, and tetrahydrofuran are preferred. Among these, isopropyl alcohol is particularly preferred.

[0074] In order to obtain a state in which the liquid phase of this process is separated, it is preferable that sulfate ions, carbonate ions, dihydrogen phosphate ions, and chloride ions are present in the aqueous solution, with sulfate ions being more preferable among them.

[0075] Furthermore, while there are no limitations on the temperature at which the phase separation state is formed, it is preferable to heat to approximately 30°C to 70°C.

[0076] In the step of adding a hydrophobic agent to the W phase in which silica gel is dispersed to hydrophobize the silica gel, if a mineral acid such as sulfuric acid is added to increase the efficiency of the reaction, the liquid phase can be separated more easily. Therefore, it is preferable to add a basic substance to neutralize the mineral acid before adding a water-soluble organic solvent in this step. That is, it is preferable to change (5) the step of adding a hydrophobic agent to the aqueous phase in which silica gel is dispersed to hydrophobize the silica gel to a step of adding a hydrophobic agent and a mineral acid to the aqueous phase in which silica gel is dispersed to hydrophobize the silica gel, and then adding a basic substance.

[0077] By adding a basic substance, the pH of the W phase becomes neutral to weakly acidic. Specifically, the pH of the W phase is preferably 1.0 to 7.5, and more preferably 1.5 to 7.0.

[0078] As the basic substance, inorganic bases such as hydroxide salts, carbonates, bicarbonates, and aqueous ammonia, and organic salts such as acetates can be used.

[0079] Furthermore, this process can be carried out by maintaining a temperature of approximately 35°C to 80°C. Since an exothermic acid-base neutralization reaction occurs during this process, this temperature range can be maintained without additional heating. The time required to add the basic substance can be set appropriately depending on the temperature of the W phase, but it is approximately 0.5 to 1 hour.

[0080] (7) Step to remove the aqueous phase As mentioned above, the W phase contains most of the salt generated during the manufacturing process; therefore, this step of removing the W phase makes it possible to remove almost all of the salt from the manufacturing process. The simplest method of removal is to transfer the liquid to a separatory funnel and extract it from the bottom by gravity.

[0081] (8) A process of deliquing the organic phase in which silica gel is dispersed to form a paste. The O phase, after the W phase has been removed by the aforementioned W phase removal process, is a slurry (with self-flowing properties) in which the gelled body is dispersed in a mixture of a water-soluble organic solvent and water. Therefore, by removing a portion of the solution contained in the slurry, a paste-like composition (with virtually no self-flowing properties) can be obtained.

[0082] The deliquidation method involves passing the slurry through a filter with a mesh size (opening diameter) that prevents the gel from passing through. The slurry described above has poor filterability, and even when filtered, it undergoes clean solid-liquid separation. The gel is not recovered as a wet powder, but rather as a paste (gel + water + water-soluble organic solvent) that adheres to the filter. Even after it becomes a paste, the solution volume will gradually decrease if filtration continues on the filter, so it can be collected when the desired solution volume is reached.

[0083] (9) Reduction of ionic substances by adding and removing water to an organic phase in which silica gel is dispersed. In the manufacturing method of the present invention, since the salt is removed at the same time as step (7) removing the aqueous phase, the content of ionic impurities in the paste-like composition is relatively low. However, in order to further reduce the amount and improve physical properties such as oil absorption, it is preferable to perform an operation to reduce ionic substances at this stage.

[0084] To reduce ionic substances, washing with water is preferable. One method of washing with water is to introduce the O-phase containing the gel into a filter and then pass water through it; that is, to wash by simultaneously adding and removing water. During this process, the balance between the water being added and the water being discharged can be adjusted by applying pressure or suction. Furthermore, raising the temperature to a range that does not exceed the boiling point of the water-soluble organic solvent remaining in the gel is preferable for improving washing efficiency. Typically, this can be done in the range of 20 to 60°C. This washing also removes reaction residues of organic solvents and silylation agents used in each step. The addition and removal of water may also be performed alternately.

[0085] It is preferable to use water with a low content of ionic impurities, such as deionized water or pure water.

[0086] The timing for ending the water washing process can be determined by measuring the electrical conductivity of the discharged water. The electrical conductivity of the discharged water is preferably 100 μS / cm or less, more preferably 70 μS / cm, and even more preferably 40 μS / cm. Achieving an electrical conductivity of 100 μS / cm in the discharged water results in the final hydrophobic silica having a high oil absorption capacity.

[0087] A paste-like composition can be obtained by adjusting the water content as described above after the electrical conductivity of the discharged water falls below a predetermined value.

[0088] The composition ratio of the paste-like composition produced by the above method is not particularly limited, but considering ease of handling as a paste, it is preferable that it contains 300 to 1900 parts by mass of water per 100 parts by mass of hydrophobic silica. A larger amount of water in the paste-like composition means that the silica voids in the paste-like composition are larger.

[0089] The paste-like composition produced as described above contains hydrophobic silica and water. Although a water-soluble organic solvent remains, it is a liquid and does not clog the silica voids, so the remaining water-soluble organic solvent does not significantly affect the oil absorption. If it is necessary to reduce the water-soluble organic solvent, this can be adjusted by (9) reducing ionic substances by adding and removing water. Here, silica refers to silicon dioxide, and is a general term for substances composed of silicon dioxide, with a chemical composition represented by SiO2.

[0090] The hydrophobic silica is porous due to its manufacturing method, and if the water content in the residue is reduced to 1% by mass or less by placing it in an atmosphere with a temperature of 60°C to 150°C and a gauge pressure of -100kPaG to -20kPaG, and the water is evaporated, it will have physical properties equivalent to hydrophobic silica aerogel powder manufactured by the methods described in Patent Documents 1 to 3, except that it has a small pore volume and oil absorption capacity and a small peak in pore radius.

[0091] The difference in peaks for pore volume, oil absorption, and pore radius is due to the fact that in the production of hydrophobic silica aerogel powder, the dispersion medium is first replaced with a hydrophobic organic solvent with low surface tension before drying, whereas in the above method, drying is carried out directly from water, resulting in drying shrinkage.

[0092] (Physical properties and applications) The paste-like composition produced by this invention disperses easily in water when mixed with water, despite the hydrophobic nature of the silica it contains. Furthermore, by selecting manufacturing conditions to achieve an appropriate particle size distribution and specific surface area for use as a cosmetic additive, it exhibits excellent appearance retention and a smooth texture when used as an additive in liquid cosmetics. In addition, if the hydrophobic silica is porous silica, it has a high oil absorption capacity, efficiently absorbing oil from the skin and scalp surface, and also exhibits hydrophobic properties that repel sweat. Therefore, it can be suitably used in cosmetics other than the liquid cosmetics mentioned above, such as paste and cream-type makeup and skincare products, as well as deodorants and hair styling products.

[0093] Of course, since the water-containing paste composition has the aforementioned appropriate particle properties, it can be suitably used as a material for various applications such as heat insulating agents and matting agents. [Examples]

[0094] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The examples and comparative examples were evaluated using the following method.

[0095] <Evaluation Method> The paste-like compositions prepared in Example 1 and Comparative Example 5 were tested for the following items.

[0096] Furthermore, "hydrophobic silica contained in the paste-like composition" refers to the silica remaining after the water has been removed by drying the paste-like composition in a vacuum dryer at 150°C and -100kPaG (gauge pressure) for 16 hours until the moisture content of the paste-like composition is 1% by mass or less.

[0097] (Electrical conductivity) Electrical conductivity was measured using a COND METER ES-51 manufactured by Horiba, Ltd.

[0098] The electrical conductivity of the water (washing solution) discharged during the washing process to remove salt was measured directly.

[0099] The electrical conductivity of the hydrophobic silica contained in the dried paste-like composition was measured for a mixture obtained by adding 1 g of the hydrophobic silica contained in the paste-like composition, 7 g of isopropyl alcohol, and 30 g of deionized water to a 50 ml screw-cap bottle, and then dispersing the mixture using ultrasound for 30 minutes.

[0100] (moisture content) The moisture content of the paste-like composition was measured using an Ohaus halogen moisture meter (MB25) in the following manner.

[0101] 3.0 g of a paste-like composition containing hydrophobic silica was placed on a dedicated aluminum dish, set in a moisture meter, and analyzed. The measurement conditions were 160°C for 30 minutes.

[0102] (Chloride ion content) A dispersion was prepared by adding 6.7 g of a paste-like composition containing hydrophobic silica and 100 ml of ultrapure water to a 200 ml beaker and stirring with a stirring bar for 15 minutes. This dispersion was filtered through a 0.45 μm syringe filter, and the chloride ion content was measured using an ion chromatography (ICS-2100) manufactured by Thermo Fisher SCIENTIFIC. The results are presented as chloride ion content relative to silica mass.

[0103] (Volume-based cumulative 50% diameter (D50)) A paste-like composition containing the manufactured hydrophobic silica was added to ethanol and ultrasonically dispersed for 30 minutes. The resulting ethanol dispersion was measured using a Beckman Coulter Multisizer 3 precision particle size distribution analyzer, with a 100 μm aperture tube to determine the cumulative 50% diameter (D50) by volume.

[0104] (Specific surface area, pore volume, peak pore radius, and oil absorption) The specific surface area of ​​the hydrophobic silica contained in the paste-like composition was calculated using the BET method, and the peaks of pore volume and pore radius were calculated using the BJH method. The adsorption isotherms used in these calculations were measured using a BELSORP-max manufactured by Microtrac-Bell Corporation.

[0105] The specific surface area obtained by the BET method is calculated by drying the sample powder under a vacuum of 1 kPa or less at a temperature of 150°C for 2 hours or more, then obtaining the adsorption isotherm only on the nitrogen adsorption side at liquid nitrogen temperature, and analyzing it using the BET method. The partial pressure (P / P0) range during the analysis is 0.1 to 0.25.

[0106] The BJH pore volume is obtained by acquiring adsorption isotherms in the same manner as in the BET specific surface area measurement described above, and analyzing them using the BJH method (Barrett, EP; Joyner, LG; Halenda, PP, J. Am. Chem. Soc. 73, 373 (1951)). The pores measured by this method are pores with a radius of 1 to 100 nm, and the integrated value of the volume of pores in this range is the pore volume in this invention.

[0107] The peak pore radius was obtained by acquiring adsorption isotherms, similar to the BET specific surface area measurement described above, and analyzing them using the BJH method. It represents the pore radius value at which the cumulative pore volume (volume distribution curve) on the logarithmic scale of the pore radius yields the largest peak value.

[0108] The amount of oil absorbed was measured according to JIS K6217-4 "Method for determining the amount of oil absorbed".

[0109] (M value) Hydrophobic silica floats in water but completely suspends in methanol. Utilizing this property, the degree of modified hydrophobicity, measured by the following method, was defined as the M value and used as an indicator of the degree of hydrophobicity.

[0110] 0.2 g of hydrophobic silica contained in the paste-like composition was added to 50 ml of water in a 200 mL beaker and stirred with a magnetic stirrer. Methanol was then added using a burette, and the mixture was dropped down until the entire amount of hydrophobic silica contained in the paste-like composition was wetted and suspended in the solvent in the beaker. During this process, methanol was introduced into the solution via a tube to prevent direct contact with the sample. The volume percentage of methanol in the methanol-water mixed solvent at the endpoint was defined as the hydrophobicity (M value).

[0111] M value = methanol drop volume / (methanol drop volume + 50 ml) (Carbon content) The carbon content of the hydrophobic silica contained in the paste-like composition was measured using an elemental analyzer (vario MICRO cube) manufactured by Elementor Japan Co., Ltd.

[0112] (Average circularity) The hydrophobic silica contained in the paste-like composition was observed using a Hitachi High-Technologies SEM (S-5500) with an acceleration voltage of 3.0 kV, secondary electron detection, and a magnification of 1000x. By analyzing the obtained SEM images, the circularity of the hydrophobic silica contained in the paste-like composition was calculated using the following formula. The average circularity was calculated by averaging the circularity of hydrophobic silica contained in more than 2000 paste-like compositions.

[0113] C = 4πS / L² [In the above formula, S represents the area (projected area) occupied by the particle in the image. L represents the length of the outer edge of the particle in the image (perimeter).]

[0114] <Example 1> While stirring 0.8 kg of 9% sulfuric acid with a stirring blade, 1 kg of sodium silicate was gradually added to prepare an aqueous silica sol. At this time, the pH was 2.9.

[0115] To 1.8 kg of the prepared aqueous silica sol, 1.7 kg of heptane was added, and 0.02 kg of sorbitan monooleate was added. This solution was stirred using a homogenizer at 4600 rpm for 2.5 minutes to form a W / O emulsion.

[0116] The obtained W / O emulsion was gelled at 70°C for 1 hour while being stirred with a stirring blade. Subsequently, 1 kg of isopropyl alcohol and 0.7 kg of deionized water were added, and the mixture was separated into an upper layer (O phase) and a lower layer (W phase) while being stirred with a stirring blade. Next, 0.09 kg of 0.5 mol / L sodium hydroxide aqueous solution was added. At this point, the pH of the W phase was 6.8. The gelled mixture was matured at 60°C for 1 hour. The W phase was recovered by removing the O phase by decantation.

[0117] To the obtained W phase, 1.1 kg of 30% sulfuric acid and 0.1 kg of hexamethyldisiloxane were added, and the mixture was kept in a 60°C water bath for 4 hours while stirring to perform silylation treatment.

[0118] After silylation treatment, 1 kg of 24% sodium hydroxide aqueous solution was added while stirring with a stirring blade, and neutralization was performed at 60°C. The pH at this time was 2.3.

[0119] After neutralization, 1 kg of isopropyl alcohol was added, and the mixture was stirred with a stirring blade at 60°C. The mixture was then allowed to stand, resulting in phase separation into an O phase containing hydrophobic silica and a W phase. The water and isopropyl alcohol content of the separated O phase was 43% and 45% by mass, respectively.

[0120] After removing the W phase, the O phase was transferred to a pressure filter, and deionized water was passed through it. Washing was performed until the electrical conductivity of the liquid that passed through the filter was 100 μS / cm or less. 4.2 kg of deionized water was used for washing.

[0121] By using a diaphragm pump to remove some of the moisture, 1.7 kg of a paste-like composition containing hydrophobic silica and water was obtained.

[0122] The paste-like composition contained 89% by mass of water and approximately 0.3% by mass of isopropyl alcohol. The mixture was dried in a vacuum dryer at 150°C and -100 kPaG (gauge pressure) for 16 hours until the water content was 1% by mass or less. The hydrophobic silica remaining after the water was removed (the hydrophobic silica contained in the paste-like composition) was analyzed, and the results are shown in Table 1.

[0123] <Comparative Examples 1-5> The same procedure as in Example 2 was followed, except that (6) the step of adding a water-soluble organic solvent to separate the organic phase in which silica gel is dispersed into an aqueous phase and (7) the step of removing the aqueous phase was omitted. The amount of ion-exchanged water passed through the pressure filter for washing was measured at the point shown in Table 1, and these were designated as Comparative Examples 2 to 5. In Comparative Example 5, when the electrical conductivity of the washing water became the same as in Example 1, a paste-like composition was obtained and evaluated in the same manner as in Example 1.

[0124] [Table 1]

Claims

1. (1) Steps to prepare aqueous silica sol, (2) A step of dispersing the aqueous silica sol in a hydrophobic solvent to form a W / O type emulsion. (3) A step of gelling the aqueous silica sol to convert the W / O type emulsion into a silica gel dispersion, (4) A step of separating the organic phase and the aqueous phase in which the silica gel is dispersed, and then removing the organic phase. (5) A step of adding a hydrophobic agent to an aqueous phase in which silica gel is dispersed to make the silica gel hydrophobic, (6) Add isopropyl alcohol to separate the organic phase in which silica gel is dispersed into an aqueous phase. (7) A step of removing the aqueous phase, and (8) A process of deliquing the organic phase in which silica gel is dispersed to form a paste. A method for producing a paste-like composition containing hydrophobic silica and water, comprising the above.

2. Before or simultaneously with the process of (8) removing the organic phase in which silica gel is dispersed to form a paste, (9) Operation to reduce ionic substances by adding and removing water to an organic phase in which silica gel is dispersed. A method for producing a paste-like composition containing hydrophobic silica and water according to claim 1.

3. (1) The step of preparing aqueous silica sol is Process for preparing aqueous silica sol from metal silicate salt and mineral acid A method for producing a paste-like composition comprising hydrophobic silica and water according to claim 1 or 2.

4. (5) The step of adding a hydrophobic agent to an aqueous phase in which silica gel is dispersed to make the silica gel hydrophobic is The process involves adding a hydrophobic agent and mineral acid to an aqueous phase in which silica gel is dispersed to hydrophobize the silica gel, and then adding a basic substance. A method for producing a paste-like composition comprising hydrophobic silica and water according to claim 1 or 2.

5. (5) The step of adding a hydrophobic agent to an aqueous phase in which silica gel is dispersed to make the silica gel hydrophobic is The process involves adding a hydrophobic agent and mineral acid to an aqueous phase in which silica gel is dispersed to hydrophobize the silica gel, and then adding a basic substance. A method for producing a paste-like composition containing hydrophobic silica and water according to claim 3.

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