Method for producing spherical silica particles for cosmetics and spherical silica particles for cosmetics derived from organic waste

Abstract

To provide a method for producing spherical silica particles for cosmetics which are suitable for cosmetic applications and have a low content of nanoparticles even when organic waste is used as a starting raw material, and to provide spherical silica particles for cosmetics derived from organic waste.SOLUTION: Provided is a method for producing spherical silica particles for cosmetics, including: preparing silica-containing organic wastes as a starting material; immersing the organic wastes in a liquid to increase the purity of silica; firing the organic wastes to obtain silica powder; pulverizing the silica powder to obtain silica fine particles; and melting and spheroidizing the silica fine particles in a flame to obtain spherical silica particles, wherein the silica fine particles have a specific surface area of 100 m2 / g or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing spherical silica particles for cosmetics and spherical silica particles for cosmetics derived from organic waste. [Background technology]

[0002] In recent years, attention has been focused on a method for obtaining silica particles using organic waste as a starting material. For example, Patent Document 1 discloses a method for producing spherical silica particles, which includes the steps of preparing organic waste containing silica as a starting material, immersing the organic waste in a liquid (particularly an acid solution) to increase the purity of the silica, calcining the organic waste to obtain silica powder, pulverizing the silica powder to obtain silica microparticles, and melting and spheroidizing the silica microparticles in a flame to obtain spherical silica particles. According to this production method, it is possible to obtain high-purity spherical silica that is suitable as a sealing material for semiconductor devices, which require particularly high electrical insulation properties. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5703428 Summary of the Invention [Problem to be solved by the invention]

[0004] Silica is used in a variety of fields other than electronic components, including cosmetics. When using silica in cosmetics, it is usually desirable to use silica with a small number of nanoparticles (especially fine particles of 100 nm or less).

[0005] On the other hand, the spherical silica particles obtained by the method of Patent Document 1 contain a very large amount of nanoparticles, which is problematic in that they are not suitable for use in cosmetics.

[0006] Therefore, an object of the present disclosure is to provide a method for producing spherical silica particles for cosmetics that have a low content of nanoparticles and are suitable for cosmetic applications, even when organic waste is used as a starting material, and to provide spherical silica particles for cosmetics derived from organic waste. [Means for solving the problem]

[0007] [1] Prepare organic waste containing silica as a starting material; After the organic waste is immersed in a liquid to increase the purity of silica, calcining the organic waste to obtain silica powder; The silica powder is pulverized to obtain silica fine particles, The silica fine particles are melted and spheroidized in a flame to obtain spherical silica particles, The specific surface area of ​​the silica particles is 100m 2 / g or less. [2] Using organic waste containing silica as the starting material, the specific surface area is 100 m 2 / g or less, and these silica particles are melted and spheroidized in a flame to obtain spherical silica particles for cosmetics derived from organic waste. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a method for producing spherical silica particles for cosmetics that have a low content of nanoparticles and are suitable for cosmetic applications, even when organic waste is used as a starting material, and to provide spherical silica particles for cosmetics derived from organic waste. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present disclosure will be described in detail below. However, the scope of the present disclosure is not limited to the embodiment described herein, and various modifications can be made without departing from the spirit of the present disclosure. Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. In this disclosure, a combination of preferred aspects is a more preferred aspect. Furthermore, when multiple upper and lower limit values ​​are described for a specific parameter, any of these upper and lower limit values ​​can be combined to form a suitable numerical range. Furthermore, the lower and / or upper limit values ​​of a numerical range described in this disclosure are numerical values ​​within that numerical range and may be replaced with numerical values ​​shown in the examples. The expression "X to Y" indicating a numerical range means "X or more and Y or less." If a specific description described for one embodiment also applies to other embodiments, that description may be omitted in other embodiments.

[0010] [Manufacturing method of spherical silica particles for cosmetics] The method for producing spherical silica particles for cosmetics according to the present disclosure includes preparing organic waste containing silica as a starting material, immersing the organic waste in a liquid to increase the purity of the silica, calcining the organic waste to obtain silica powder, pulverizing the silica powder to obtain silica microparticles, and melting and spheroidizing the silica microparticles in a flame to obtain spherical silica particles, wherein the silica microparticles have a specific surface area of ​​100 m 2 / g or less.

[0011] With the above-described configuration, even when organic waste is used as the starting material, spherical silica particles for cosmetics with a low content of nanoparticles, which are suitable for use in cosmetics, can be obtained.

[0012] The reason why the method for producing spherical silica particles for cosmetics according to the present disclosure exhibits the above-mentioned effects is not clear, but one possible reason is as follows. In the manufacturing method of Patent Document 1, in order to increase the purity of silica, the organic waste material, in particular, is subjected to acid washing and calcination in two heating stages. It is believed that the resulting silica powder is porous silica with many voids. Porous silica is more brittle than mineral-derived silica, making it easier to pulverize, but the silica microparticles obtained by pulverization have a larger specific surface area than mineral-derived silica. Silica microparticles with a large specific surface area have a larger surface area exposed to high temperatures during melting and spheroidization, making the silica more likely to sublimate in the flame. As a result, the sublimated silica resolidifies in the furnace and becomes microparticles with a particle diameter of approximately 10 to 100 nm (hereinafter referred to as "fumes"). In other words, the spherical silica particles obtained by this manufacturing method contain a large amount of fumes.

[0013] On the other hand, silica particles suitable for cosmetic applications should preferably contain a small amount of nanoparticles (especially fine particles with a particle diameter of 100 nm or less). Therefore, when obtaining spherical silica particles from organic waste as a starting material, it is particularly important to suppress the generation of fumes. Therefore, the inventors of the present invention have conducted extensive research and have found that the specific surface area of ​​the silica particles to be fed into the flame in the melting and spheroidizing process should be set to 100 m 2 / g or less, and it was found that this can suppress the generation of a large amount of fumes during the melt-spheroidizing process.

[0014] That is, the method for producing spherical silica particles for cosmetics according to the present disclosure controls the specific surface area of ​​the silica microparticles supplied into the flame during the melt-spheroidization process within a predetermined range, thereby preventing silica microparticles with a large specific surface area from being supplied into the flame. As a result, sublimation of silica in the flame can be suppressed, thereby suppressing the generation of fumes. The spherical silica particles obtained by this production method contain a reduced content of nanoparticles such as fumes (particularly those with a particle diameter of 100 nm or less, and even 50 nm or less), making them suitable for use in cosmetics.

[0015] In this specification, the following terms are defined as follows: "Silica" is another name for silicon dioxide (SiO2). "Silica powder" refers to powdered silica, and in this specification it particularly refers to silica obtained by burning organic waste and composed of particles before being crushed. "Fine silica particles" refers to finely divided silica, and in this specification it particularly refers to silica obtained by pulverizing silica powder obtained by burning organic waste, before being melted and sphericalized. "Fume" refers to silica that sublimes in the flame during melting and spheroidization, resolidifies in the furnace, and becomes fine particles that float and settle. In this specification, "fumes" refers particularly to fine particles with a primary particle diameter of about 10 to 100 nm. The term "spherical silica particles" refers to spherical silica particles, and in this specification particularly refers to particles obtained by melting and spheroidizing fine silica particles in a flame.

[0016] The manufacturing method of the present disclosure will be described in detail below. <Process 1> In this process, organic waste containing silica is prepared as a starting material.

[0017] The silica-containing organic waste is not particularly limited as long as it is an organic material containing silica, but is preferably one or more selected from the group consisting of rice husks, rice straw, rice bran, wheat straw, wood, thinned wood, construction waste, sawdust, bark, bagasse, corn, sugarcane, sweet potato, soybean, peanuts, cassava, eucalyptus, fern, pineapple, bamboo, rubber, and waste paper. Unlike silica stone, these are available in a wide range of regions. The inventors preferably used rice husks for the experiments of the present disclosure because of their ease of availability and handling, but similar effects can be expected even if other organic wastes are used.

[0018] Prior to immersion in the liquid, the organic waste may be crushed to a minute size.

[0019] <Process 2> In this process, the organic waste is immersed in a liquid to increase the purity of the silica.

[0020] By immersing the organic waste material as the starting material in liquid and stirring it, impurities are removed from the starting material and the silica purity is increased. The liquid in which the organic material is immersed is not particularly limited as long as it can remove impurities from the starting material and increase the purity of silica. Examples include an acid solution and warm water, and an acid solution is preferred.

[0021] When an acid solution is used as the liquid for soaking the organic waste, the acid used is preferably a hydroxycarboxylic acid (e.g., lactic acid, tartaric acid, citric acid, glycolic acid, malic acid, tropic acid, benzilic acid, etc.), more preferably citric acid. When an acid solution is used, it is preferable to subsequently carry out a water washing treatment, which allows metal impurities such as potassium, calcium, and aluminum contained in the raw material to be discharged and removed from the raw material to the outside of the system through a chelate reaction and a dehydration reaction.

[0022] When citric acid is used as the acid of the acid solution, the concentration of the citric acid solution is preferably 5% by mass or more and 20% by mass or less, more preferably 10% by mass or more and 18% by mass or less. Within the above range, a sufficient chelating effect is exhibited, and the number of times of washing with water is not increased, which is economical.

[0023] When an acid solution is used, the acid solution may be heated to further enhance the impurity removal effect, and the temperature of the acid solution is preferably room temperature (20°C ± 5°C, the same applies hereinafter) or higher, more preferably room temperature or higher and 80°C or lower, and even more preferably 50°C or higher and 80°C or lower. Within the above range, the impurity removal effect is enhanced without deteriorating the economic efficiency due to heating.

[0024] Furthermore, when hot water is used as the liquid for soaking the organic waste, the water temperature is preferably room temperature or higher, more preferably room temperature or higher and 80° C. or lower, and even more preferably 50° C. or higher and 80° C. or lower. Even when hot water is used, the impurity removal effect can be expected.

[0025] The time for immersion in the liquid is not particularly limited as long as it is a time sufficient to remove impurities, but from the viewpoint of further enhancing the effect of removing impurities, it is preferably 1 hour or more, more preferably 4 hours or more, and from the viewpoint of productivity, the upper limit is preferably 24 hours or less, more preferably 12 hours or less.

[0026] After immersion in the liquid, the organic waste is separated from the liquid and dried in air or at room temperature or with hot air. If necessary, the organic waste separated from the liquid may be subjected to a dehydration treatment before drying.

[0027] <Process 3> In this process, organic waste is calcined to obtain silica powder.

[0028] The calcination is preferably carried out in a manner that sufficiently burns the carbohydrates in the organic waste to reduce the amount of residual carbon, and more preferably under conditions that suppress the generation of porous silica and increase the hardness of the particles.

[0029] Generally, organic waste contains many impurities, and the silica powder obtained by firing it tends to be porous silica with many voids. In particular, Patent Document 1 discloses that in order to increase the purity of silica, the organic waste as the starting material is subjected to acid washing and firing in two stages, and the resulting silica powder is porous. However, compared with dense silica, when porous silica is pulverized, it produces a large amount of silica particles smaller than the desired particle size. Furthermore, nanoparticle-sized silica particles tend to aggregate together, and even when pulverized to the same average particle size (D50 diameter), the specific surface area tends to be large.

[0030] As mentioned above, when silica fine particles with a large specific surface area are melted and spheroidized in a flame, there is a problem of generating a large amount of fumes. Therefore, in the manufacturing method disclosed herein, by adjusting the firing conditions of the organic waste in particular, the generation of porous silica is suppressed at the stage of the obtained silica powder, and the hardness of the silica particles is also increased. This is thought to prevent the generation of excessively fine silica particles even when the silica powder obtained after firing is pulverized, and to reduce the specific surface area of ​​the resulting silica particles. As a result, in the subsequent pulverization step, it is possible to reduce the specific surface area of ​​the silica particles to 100 m 2 / g or less.

[0031] In the manufacturing method of the present disclosure, the calcination conditions are set so that the carbohydrates in the organic waste can be sufficiently burned, and further, the silica powder obtained by pulverizing the calcined silica powder has a specific surface area of ​​100 m 2 / g or less, but it is preferable to appropriately combine the following firing conditions, from the viewpoint of suppressing the generation of porous silica in the silica powder obtained after firing and further increasing the hardness of the particles.

[0032] The calcination is preferably carried out in the atmosphere, and more preferably with a sufficient supply of air (oxygen), which allows the carbohydrates in the organic waste to be sufficiently combusted.

[0033] The firing temperature is preferably 750° C. or higher and 1100° C. or lower, more preferably 800° C. or higher and 1100° C. or lower, and even more preferably 800° C. or higher and 1000° C. or lower. By setting the temperature within the above range, carbohydrates in the organic waste can be sufficiently burned, the generation of porous silica can be suppressed, and the hardness of the particles can be increased.

[0034] The calcination time is preferably 3 to 8 hours, more preferably 3 to 6 hours, and even more preferably 4 to 6 hours. By setting the calcination time within the above range, carbohydrates in the organic waste can be sufficiently burned, the generation of porous silica can be suppressed, and the hardness of the silica particles can be further increased.

[0035] The firing may be performed by multi-stage heating, but from the viewpoint of suppressing the formation of porous silica, single-stage heating is preferred. Single-stage heating refers to a heating process in which heating is continuously performed from room temperature to a target temperature (firing temperature), and the target temperature is maintained for a certain period of time, and does not refer to a heating process in which two or more temperatures are maintained for a certain period of time. On the other hand, multi-stage heating refers to a heating process in which two or more temperatures are maintained for a certain period of time, and the material is heated from room temperature to a first maintenance temperature, maintained for a certain period of time, and then heated to each maintenance temperature in a stepwise manner, while maintaining the temperature until the target temperature is reached.

[0036] <Step 4> In this step, silica powder is pulverized to obtain silica fine particles. At this time, the specific surface area of ​​the silica particles is 100m 2 Adjust to / g or less.

[0037] As described above, when porous silica is pulverized, a large amount of silica fine particles having a particle size smaller than the desired particle size are usually produced, and the specific surface area of ​​the resulting silica fine particles tends to be large. In contrast, in the manufacturing method of the present disclosure, for example, the generation of porous silica in the obtained silica powder is suppressed, and the hardness of the silica particles is further increased. As a result, even when the silica powder is pulverized, the generation of excessively fine silica microparticles can be suppressed, and the specific surface area of ​​the obtained silica microparticles can be kept small. As a result, the specific surface area of ​​the silica microparticles can be reduced to 100 m 2 / g or less.

[0038] The pulverization can be carried out by any known method as long as it can control the average particle size of the resulting silica fine particles to a desired range and does not excessively increase the specific surface area. The pulverization may be carried out in multiple stages, including coarse pulverization and fine pulverization. The pulverization can be carried out using a vibrating sieve or a pulverizer, and may be, for example, dry pulverization using a jet mill, hammer mill, vibration mill, etc., or wet pulverization using a ball mill, etc. The pulverization conditions may be appropriately adjusted depending on the target average particle size, specific surface area, etc. After pulverization, classification may be carried out to adjust the average particle size and specific surface area to the desired values.

[0039] The specific surface area of ​​silica particles is 100m 2 / g or less, preferably 98m 2 / g or less, more preferably 80m 2 / g or less. The lower limit is, for example, 1 m 2 By setting the content within the above range, generation of fumes can be effectively suppressed during melting and spheroidizing. The specific surface area of ​​the silica fine particles can be measured by the method described in the Examples section of the present disclosure or a method that will be understood by those skilled in the art to be equivalent thereto.

[0040] The specific surface area of ​​silica particles is 100m 2 / g or less, for example, by adjusting the firing conditions in the firing step, the generation of porous silica in the obtained silica powder can be suppressed and the hardness of the silica particles can be increased, and excessive grinding can be avoided in the grinding step.

[0041] The average particle size (D50) of the silica fine particles is preferably 3 μm or more and 8 μm or less, more preferably 4 μm or more and 7 μm or less, and even more preferably 4 μm or more and 6 μm or less. By setting the average particle size within this range, it is easy to melt and spheroidize the silica into spherical silica having a particle size suitable for cosmetics, and the specific surface area does not become excessively large. The average particle size (D50) of the silica fine particles can be measured by the method described in the Examples section of the present disclosure or a method that will be understood by those skilled in the art to be equivalent thereto.

[0042] <Process 5> In this step, fine silica particles are melted and spheroidized in a flame to obtain spherical silica particles. At this time, the specific surface area of ​​the silica particles is 100m 2 / g or less.

[0043] In the method for producing spherical silica particles for cosmetics of the present disclosure, the specific surface area of ​​the silica fine particles supplied into the flame is set within a predetermined range (100 m 2 / g or less), it is possible to prevent silica fine particles with a large specific surface area from being supplied to the flame. As a result, it is possible to suppress the sublimation of silica in the flame, and to prevent the generation of large amounts of fumes. The spherical silica particles obtained by this production method are thought to have a low content of nanoparticles such as fumes (particularly those with a particle diameter of 100 nm or less, and even 50 nm or less), and are therefore thought to be suitable for use in cosmetics.

[0044] The melting and spheroidizing equipment preferably comprises a powder supply device, a burner, a melting zone, a cooling zone, a powder recovery device, and a suction fan. The silica fine particles processed in the above-mentioned pulverization process are fed into a burner, spheroidized in the high-temperature flame of the melting zone, removed from the heat by the combustion exhaust gas in the cooling zone, and recovered in the powder recovery device. The silica fine particles fed into the high-temperature flame reach a temperature above their melting point, and are spheroidized by the surface tension of the particles themselves during the melting and liquefaction process. The processing temperature in the flame is preferably 1750°C to 2500°C.

[0045] The spherical silica particles obtained by the production method of the present disclosure have, for example, the following properties. The specific surface area of ​​the spherical silica particles is preferably 25 m 2 / g or less, more preferably 23m 2 / g or less, more preferably 22m 2 / g or less. The lower limit is, for example, 1 m 2 If the content is within the above range, the cosmetic product will have a good feel on the skin. The specific surface area of ​​the spherical silica particles can be measured by the method described in the Examples section of the present disclosure or a method that will be understood by those skilled in the art to be equivalent thereto.

[0046] The spherical silica particles have an average particle size (D50) of preferably 1 μm or more and 20 μm or less, more preferably 4 μm or more and 15 μm or less, and even more preferably 4 μm or more and 10 μm or less. When the average particle size is within the above range, the spherical silica rolls easily when made into a cosmetic product, without causing roughness, and the cosmetic product feels good on the skin. The average particle size (D50) of the spherical silica particles can be measured by the method described in the Examples section of the present disclosure or a method that will be understood by those skilled in the art to be equivalent thereto.

[0047] The average sphericity of the spherical silica particles is preferably 0.84 or more, more preferably 0.84 or more, and even more preferably 0.85 or more. The upper limit may be, for example, 0.90 or less. Within this range, when the spherical silica particles are used in cosmetics, they roll easily, do not become rough, and have a good feel on the skin. The average sphericity of the spherical silica particles can be measured by the method described in the Examples section of the present disclosure or a method that will be understood by those skilled in the art to be equivalent thereto.

[0048] The higher the silica purity of the spherical silica particles, the better, but the SiO2 content by mass is preferably 95.0 mass% or more, more preferably 96.5 mass% or more, and even more preferably 97.0 mass% or more. The upper limit may be, for example, 99.99 mass% or less.

[0049] As mentioned above, spherical silica particles derived from organic waste undergo processing to increase the purity of the silica during the manufacturing process. However, compared to silica derived from minerals (e.g., silica stone), the purity of the silica is lower and the content of impurities is higher. For example, in the case of spherical silica particles derived from silica stone, the SiO2 content by mass is typically 99.80 mass% or more, which means that the silica purity is very high and the content of impurities is very low. Therefore, spherical silica particles derived from organic waste can be distinguished from spherical silica particles derived from minerals in terms of the content of impurities.

[0050] For example, the spherical silica particles may contain calcium oxide (CaO) as an impurity component. The CaO content by mass is preferably 0.10% by mass or more and 0.80% by mass or less, more preferably 0.20% by mass or more and 0.70% by mass or less, and even more preferably 0.30% by mass or more and 0.50% by mass or less. The spherical silica particles may also contain trace amounts of impurities other than CaO, such as magnesium oxide (MgO), potassium oxide (K2O), phosphoric acid (P2O5), and manganese oxide (MnO).

[0051] The content of each component in the spherical silica particles can be measured by the method described in the Examples section of the present disclosure or a method that will be understood by those skilled in the art to be equivalent thereto.

[0052] The spherical silica particles also have an oil absorption measured in accordance with JIS K 5101-13-1:2004 of preferably 3.70 mL / 10 g or less, more preferably 3.50 mL / 10 g or less. The lower limit may be, for example, 1.00 mL / 10 g or more. If the oil absorption falls within the above range, it means that the content of nanoparticles in the spherical silica particles is effectively suppressed, making them suitable for use in cosmetics.

[0053] [Spherical silica particles for cosmetics] The spherical silica particles for cosmetics of the present disclosure are obtained by the above-described production method, and even when organic waste containing silica is used as the starting material, they have a low content of nanoparticles and are suitable for use in cosmetics.

[0054] In other words, the spherical silica particles for cosmetics of the present disclosure are produced by using organic waste containing silica as a starting material, and then processing the particles to produce spherical silica particles having a specific surface area of ​​100 m 2 The silica particles are prepared by melting and spheroidizing them in a flame.

[0055] In addition, the spherical silica particles for cosmetics of the present disclosure preferably have a specific surface area of ​​25 m 2 / g or less. For example, in the manufacturing method described in Patent Document 1, the specific surface area is already large at the stage of silica fine particles, and further, when the silica fine particles are melted and spherically formed in a flame, a large amount of fumes is generated, so the resulting spherical silica particles contain a large amount of nanoparticles. As described above, nanoparticles tend to aggregate with each other, and even if they have the same average particle diameter (D50), the specific surface area tends to be large. Therefore, in the manufacturing method described in Patent Document 1, when organic waste is used as the starting material, it is necessary to use a material with a relatively small specific surface area (preferably a specific surface area of ​​25 m 2 / g or less) is unlikely to be obtained.

[0056] In other words, the specific surface area is 25m 2 It can be said that the spherical silica particles for cosmetics derived from organic waste, having a particle size of 1 / g or less, can be obtained for the first time by the manufacturing method of the present disclosure.

[0057] Examples of cosmetics in which the silica particles of the present disclosure can be suitably used include makeup powder, lip balm, hand cream, sunscreen cream, cologne, antiperspirant, hair styling product, and body gel. It should be noted that the cosmetics in the present disclosure are not particularly restricted by classification under the Pharmaceutical Affairs Law, such as cosmetics, quasi-drugs, and pharmaceuticals.

[0058] A non-limiting list of exemplary embodiments and combinations of exemplary embodiments of the present disclosure are disclosed below. [1] Prepare organic waste containing silica as a starting material; After the organic waste is immersed in a liquid to increase the purity of silica, calcining the organic waste to obtain silica powder; The silica powder is pulverized to obtain silica fine particles, The silica fine particles are melted and spheroidized in a flame to obtain spherical silica particles, The specific surface area of ​​the silica particles is 100m 2 / g or less. [2] The method for producing spherical silica particles for cosmetics according to the above [1], wherein the average particle diameter (D50) of the silica fine particles is 3 μm or more and 8 μm or less. [3] The specific surface area of ​​the spherical silica particles is 25 m 2 The method for producing spherical silica particles for cosmetics according to the above [1] or [2], wherein the particle size is 1 / g or less. [4] The method for producing spherical silica particles for cosmetics according to any one of the above [1] to [3], wherein the spherical silica particles have an average particle size (D50) of 1 μm or more and 20 μm or less. [5] The method for producing spherical silica particles for cosmetics according to any one of the above [1] to [4], wherein the spherical silica particles have an average sphericity of 0.84 or more. [6] The method for producing spherical silica particles for cosmetics according to any one of [1] to [5] above, wherein the organic waste is one or more selected from the group consisting of rice husks, rice straw, rice bran, wheat straw, wood, thinned wood, construction waste, sawdust, bark, bagasse, corn, sugarcane, sweet potato, soybean, peanut, cassava, eucalyptus, fern, pineapple, bamboo, rubber, and waste paper. [7] The method for producing spherical silica particles for cosmetics according to any one of the above [1] to [6], wherein the liquid in which the organic waste is immersed is an acid solution. [8] The method for producing spherical silica particles for cosmetics according to any one of the above [1] to [7], wherein the firing temperature of the organic waste is 750°C or higher and 1100°C or lower. [9] The method for producing spherical silica particles for cosmetics according to any one of the above [1] to [8], wherein the treatment temperature in the flame is 1750°C or higher and 2500°C or lower.

[10] Using organic waste containing silica as the starting material, a 100m2 specific surface area 2 / g or less, and these silica particles are melted and spheroidized in a flame to obtain spherical silica particles for cosmetics derived from organic waste.

[11] Specific surface area is 25m 2 The spherical silica particles for cosmetics derived from organic waste according to

[10] above, having a molecular weight of 1 / g or less.

[12] Spherical silica particles for cosmetics derived from organic waste according to

[10] or

[11] above, having an average particle diameter (D50) of 1 μm or more and 20 μm or less.

[13] Contains CaO as a component, The spherical silica particles for cosmetics derived from organic waste according to any one of the above

[10] to

[12] , wherein the CaO content by mass is 0.10% by mass or more and 0.80% by mass or less.

[14] The organic waste-derived spherical silica particles for cosmetics according to any one of

[10] to

[13] above, wherein the organic waste is one or more selected from the group consisting of rice husks, rice straw, rice bran, wheat straw, wood, thinned wood, construction waste, sawdust, bark, bagasse, corn, sugarcane, sweet potato, soybean, peanut, cassava, eucalyptus, fern, pineapple, bamboo, rubber, and waste paper.

[0059] Although the embodiments of the present disclosure have been described above, the configurations and combinations thereof in each embodiment are merely examples, and the configurations can be added, omitted, substituted, and otherwise modified as appropriate within the scope of the gist of the present disclosure. The present disclosure is not limited by the embodiments. Each feature disclosed herein may be combined with any other feature disclosed herein. [Example]

[0060] The present disclosure will be explained in more detail below by showing examples, but interpretation of the present disclosure is not limited to these examples.

[0061] [1] Manufacturing of spherical silica particles for cosmetics (Examples 1 to 5 and Comparative Examples 2 to 7) In Examples 1 to 5 and Comparative Examples 2 to 7, spherical silica particles were obtained by the following procedure. <Process 1> As a starting material, 50 kg of rice husks (produced in Fukushima Prefecture) were prepared and crushed to an average particle size (D50) of approximately 20 μm. The crushed rice husks were placed in a plastic litter bag. <Process 2> Next, citric acid was dissolved in 300 L of water to prepare a citric acid solution (concentration: 15% by mass). Next, the crushed rice husks prepared in step 1 were immersed together with the bag in the above citric acid solution at room temperature for 6 hours. After the soaking treatment, the rice husks were taken out of the citric acid solution together with the bag, rinsed with water using a household washing machine, then spun out, taken out of the washing machine, and air-dried. <Process 3> The air-dried rice husks were calcined in the atmosphere under the conditions of the calcination temperature and calcination time shown in Table 1 to obtain silica powder. <Step 4> First, the obtained silica powder was coarsely pulverized using a vibrating sieve (manufactured by Kowa Kogyosho Co., Ltd., product name: "Circular Vibrating Sieve"). The mixture was then placed in the grinding chamber (SiC lining) of a jet mill (Seishin Enterprise Co., Ltd., product name "STJ-315") and ground at a feed rate of 10 kg / h and an air pressure of 0.55 MPa to obtain silica microparticles. The specific surface area (BET) and average particle size (D50) of the obtained silica microparticles are shown in Table 1. <Process 5> The obtained silica microparticles were melted and spheroidized in a flame to obtain spherical silica particles. The treatment temperature in the flame was 2000°C. The specific surface area (BET), average particle size (D50), average sphericity, SiO2 content, and CaO content of the obtained spherical silica particles are shown in Table 1.

[0062] The specific surface area (BET), average particle size (D50), average sphericity, SiO2 content, and CaO content were measured by the following methods. The measurement samples were the respective measurement targets. <Measurement of specific surface area (BET)> First, 4 g of the measurement sample was filled into an empty cell and degassed at 300°C. After degassing, the cell filled with the measurement sample was placed in a fully automatic specific surface area measuring device (Mountec Co., Ltd., product name "Macsorb Model 1208"), and the specific surface area was measured. He-N2 mixed gas was used as the measurement gas, and measurements were made using the BET multipoint method at a main flow rate of 25 mL / min.

[0063] <Measurement of average particle size (D50)> First, fill a glass beaker with 80cm 3 1 g of pure water and 0.1 g of a measurement sample were added, and dispersion treatment was carried out for 1 minute using an ultrasonic homogenizer (manufactured by SMT Corporation, product name "UH-600S" (homogenizer tip diameter: 20 mmφ)). The dispersion liquid of the measurement sample that had been subjected to the dispersion treatment was added drop by drop using a dropper to a laser diffraction / scattering particle size distribution analyzer (product name "MT3300EXII" manufactured by Microtrackbell Co., Ltd.) The average particle size was measured 30 seconds after the specified amount was added. The particle size distribution was calculated from the data on the light intensity distribution of diffracted / scattered light from the measurement sample detected by the sensor in the laser diffraction / scattering particle size distribution analyzer. D50 was calculated from the particle size corresponding to the cumulative value of 50% in the cumulative particle size distribution based on volume of the particle size being measured.

[0064] <Measurement of average sphericity> First, 300 mL of 15 g of propylene aqueous solution (a mixture of 0.5 L of propylene glycol (Kanto Chemical Co., Ltd.) and 1.5 L of ion-exchanged water) and 0.01 g of a measurement sample were placed in a glass beaker, and the mixture was dispersed for 1 minute using an ultrasonic homogenizer (same as above). The dispersion of the measurement sample subjected to dispersion treatment was flowed into the planar extensional flow cell of a powder image analyzer (manufactured by Spectris Co., Ltd., product name "FPIA-3000"), and 200 or more target particles moving in the cell were recorded as images using an objective lens. The average sphericity was calculated from this recorded image and the following formula (1). Average sphericity = (π × HD / PM) 2 ···(1) In the above formula (1), HD represents the equivalent circle diameter of the particle, which is obtained from the area ratio between the projected area of the target particle and a perfect circle. PM represents the projected perimeter length of the target particle. In this example, the "average circularity" was calculated from the average value of the circularity (π × HD / PM) of 200 target particles, and further, the average circularity was squared to obtain the average sphericity.

[0065] <Measurement of SiO2 content and CaO content> The SiO2 content and CaO content in the spherical silica particles were measured by the fluorescence X-ray method. For the measurement, a fluorescence X-ray analyzer (manufactured by Rigaku Corporation, product name "ZSX-PrimusIV") was used.[[ID=第十五]] [[ID=第十六]]

[0066] [[ID=第十七]] (Comparative Example 1) In Comparative Example 1, spherical silica particles were obtained in the same manner as in Example 1, except that the silica powder was not pulverized in Step 4 and the silica powder was melted and spheroidized in a flame in Step 5. In Comparative Example 1, since silica fine particles were not obtained, instead of the silica fine particles, the specific surface area (BET) and average particle diameter (D50) of the silica powder were measured. The results are shown in the items of silica fine particles in Table 1 with ( ).

[0067] [2] Evaluation of spherical silica particles For the spherical silica particles obtained in [1] above, the oil absorption amount was measured and evaluated by the following method. The results are shown in Table 1.

[0068] <Measurement and evaluation of oil absorption amount> The measurement of the oil absorption amount was carried out in accordance with JIS K 5101-13-1:2004. First, 10 g of the spherical silica particles obtained in [1] above was kneaded while adding dropwise linseed oil (manufactured by Kanto Chemical Co., Ltd., product name "Linseed Oil"). When the kneaded product of the spherical silica particles and linseed oil became a single hard lump, the addition of the linseed oil was stopped, and the total amount of the linseed oil added up to that point was measured as the oil absorption (mL / 10 g). The higher the oil absorption value, the more oil is absorbed. Usually, the higher the content of nanoparticles in spherical silica particles, especially the content of fumes, the higher the oil absorption. Therefore, it is possible to estimate the content of nanoparticles such as fumes using the oil absorption as an indicator. In this example, 3.70 mL / 10 g or less was evaluated as good, and 3.50 mL / 10 g or less was evaluated as better.

[0069] [Table 1]

[0070] As shown in Table 1, when attempting to obtain spherical silica using organic waste containing silica as a starting material, if the silica powder obtained by burning the organic waste is not pulverized but is melted and spheroidized in a flame as is, the average particle size of the obtained spherical silica will be very large (Comparative Example 1).

[0071] On the other hand, when silica powder obtained by calcining organic waste is pulverized to obtain silica fine particles having a desired average particle size (for example, 3 μm or more and 8 μm or less), the specific surface area of ​​the obtained silica fine particles usually becomes large (Comparative Examples 2 to 6). As a result, especially when the specific surface area is 100 m 2 When silica fine particles exceeding 10 ...

[0072] In contrast, according to the manufacturing method of the present disclosure, even when silica-containing organic waste is used as a starting material and the resulting silica powder is pulverized, the specific surface area of ​​the silica fine particles obtained after pulverization can be increased to 100 m 2 / g or less, it was confirmed that when melting and spheroidizing the silica particles in a flame using the silica particles, the generation of a large amount of fumes could be suppressed, and the oil absorption was lower than in the comparative examples (Examples 1 to 5). From this, it can be inferred that the content of nanoparticles is lower than that of the spherical silica particles in the comparative examples. In other words, it was confirmed that the manufacturing method of the present disclosure can obtain spherical silica particles suitable for cosmetic applications that have a low content of nanoparticles, even when organic waste is used as the starting material.

Claims

1. Prepare organic waste containing silica as a starting material, After the organic waste is immersed in a liquid to increase the purity of silica, calcining the organic waste to obtain silica powder; The silica powder is pulverized to obtain silica fine particles, The silica fine particles are melted and spheroidized in a flame to obtain spherical silica particles, The specific surface area of ​​the silica fine particles is 100 m ２ / g or less.

2. 2. The method for producing spherical silica particles for cosmetics according to claim 1, wherein the average particle diameter (D50) of the silica fine particles is 3 μm or more and 8 μm or less.

3. The specific surface area of ​​the spherical silica particles is 25 m ２ The method for producing spherical silica particles for cosmetics according to claim 1 or 2, wherein the surface roughness is 1 / g or less.

4. The method for producing spherical silica particles for cosmetics according to claim 1 or 2, wherein the spherical silica particles have an average particle diameter (D50) of 1 μm or more and 20 μm or less.

5. 3. The method for producing spherical silica particles for cosmetics according to claim 1, wherein the spherical silica particles have an average sphericity of 0.84 or more.

6. 3. The method for producing spherical silica particles for cosmetics according to claim 1 or 2, wherein the organic waste is one or more selected from the group consisting of rice husks, rice straw, rice bran, wheat straw, wood, thinned wood, construction waste, sawdust, bark, bagasse, corn, sugarcane, sweet potato, soybean, peanut, cassava, eucalyptus, fern, pineapple, bamboo, rubber, and waste paper.

7. 3. The method for producing spherical silica particles for cosmetics according to claim 1, wherein the liquid in which the organic waste is immersed is an acid solution.

8. 3. The method for producing spherical silica particles for cosmetics according to claim 1, wherein the organic waste is fired at a temperature of 750°C or higher and 1100°C or lower.

9. 3. The method for producing spherical silica particles for cosmetics according to claim 1, wherein the treatment temperature in the flame is 1750°C or higher and 2500°C or lower.

10. Starting from organic waste containing silica, a specific surface area of ​​100m ２ The spherical silica particles for cosmetics are obtained by preparing silica fine particles having a particle size of 1 / g or less and melting and spheroidizing the silica fine particles in a flame, the spherical silica particles being derived from organic waste.

11. Specific surface area is 25m ２ The spherical silica particles for cosmetics derived from organic waste according to claim 10, wherein the molecular weight of the particles is 1 / g or less.

12. The spherical silica particles for cosmetics derived from organic waste according to claim 10 or 11, having an average particle diameter (D50) of 1 μm or more and 20 μm or less.

13. Contains CaO as a contained component, The spherical silica particles for cosmetics derived from organic waste according to claim 10 or 11, wherein the mass-based CaO content is 0.10 mass% or more and 0.80 mass% or less.

14. The organic waste-derived spherical silica particles for cosmetics according to claim 10 or 11, wherein the organic waste is one or more selected from the group consisting of rice husks, rice straw, rice bran, wheat straw, wood, thinning materials, construction waste, sawdust, bark, bagasse, corn, sugarcane, sweet potato, soybean, peanut, cassava, eucalyptus, fern, pineapple, bamboo, rubber, and waste paper.

Images