Composite particles and cosmetics containing the same

Abstract

To provide composite particles with excellent smoothness when touching the skin.SOLUTION: Composite particles include base particles and a plurality of UV-shielding fine particles adhering to the base particles. The base particles include starch. The UV-shielding fine particles contain at least one selected from titanium oxide, zinc oxide, and cerium oxide. The starch is, for example, cornstarch. The composite particles have an average friction coefficient (MIU) of, for example, 0.23 or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to composite particles containing a base particle and fine particles attached to the surface thereof, and further to a cosmetic containing the composite particles. [Background technology]

[0002] A technique for forming composite particles by attaching multiple microparticles to the surface of base particles that are relatively larger than the microparticles is known. Patent Document 1 discloses composite particles that use resin particles such as nylon or PMMA as the base particles and ultraviolet-shielding microparticles with an average particle size of 175 nm or less as the microparticles. Titanium oxide microparticles, zinc oxide microparticles, etc. are disclosed as ultraviolet-shielding microparticles. In the composite particles, the base particles support the microparticles and prevent the microparticles from aggregating. Preventing aggregation suppresses unevenness in the ultraviolet-shielding effect of the ultraviolet-shielding microparticles.

[0003] Particles used in cosmetics intended for use in contact with the skin are required to contribute to a smooth feel. Smoothness when in contact with the skin can be indicated by the mean coefficient of friction (MIU), which can be measured using a friction tester. Patent Document 2 discloses that spherical titanium oxide agglomerated particles obtained by agglomerating rod-shaped titanium oxide particles have a low MIU. According to the examples in Patent Document 2, the MIU of the spherical titanium oxide agglomerated particles is 0.26 to 0.65. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-221148 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-56535 Summary of the Invention [Problem to be solved by the invention]

[0005] As far as the inventors know, no studies have been conducted to date on improving the smoothness of composite particles when they come into contact with the skin. Therefore, an object of the present invention is to provide composite particles with excellent smoothness. [Means for solving the problem]

[0006] The comparative example in Patent Document 2 also reports that the average coefficient of friction (MIU) of insufficiently aggregated, fan-shaped, i.e., non-spherical, titanium oxide aggregate particles was 0.72. Comparing the examples suggests that the smoothness of composite particles would also be improved if they were spherical. In fact, the smoothness of composite particles was improved when spherical resin particles were used as the base particles of the composite particles. However, during the course of research, it was discovered that the smoothness of composite particles could also be improved by using starch particles. Because the shape of starch particles is not spherical, this effect is thought to result from the combination of starch and UV-blocking microparticles.

[0007] That is, the present invention provides: The ink jet recording medium comprises a base particle and a plurality of ultraviolet-shielding fine particles attached to the base particle, the substrate particles comprise starch; the ultraviolet-shielding fine particles contain at least one selected from titanium oxide, zinc oxide, and cerium oxide; Composite particles are provided. [Effects of the Invention]

[0008] The composite particles of the present invention can provide a smooth feel to the skin. Furthermore, since starch, a biodegradable material, is used, they are also highly biodegradable. The present invention can also contribute to the reduction of microplastics, which have been identified as a cause of environmental pollution. Furthermore, because the aggregation of the UV-absorbing microparticles is suppressed by the base particles, they also have excellent UV-blocking effects. [Brief explanation of the drawings]

[0009] [Figure 1]This is a scanning electron microscope (SEM) photograph of starch (corn starch) particles. [Figure 2] 2 is an SEM photograph of composite particles obtained by combining the particles of FIG. 1 with titanium oxide fine particles. [Figure 3] This is an SEM photograph of spherical nylon particles. [Figure 4] 4 is an SEM photograph of composite particles obtained by combining the particles of FIG. 3 with titanium oxide fine particles. [Figure 5] 1 is an SEM photograph of non-spherical nylon particles. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described, but the following description is not intended to limit the present invention to any particular embodiment.

[0011] The composite particle of this embodiment comprises a base particle and a plurality of ultraviolet-shielding microparticles attached to the surface of the base particle. The base particle contains starch. The ultraviolet-shielding microparticles contain at least one selected from titanium oxide, zinc oxide, and cerium oxide. The composite particle typically has a so-called core-shell structure, with the base particle as the core and the ultraviolet-shielding microparticles as the shell. The ultraviolet-shielding microparticles are supported on the surface of the base particle, and the base particle inhibits their aggregation. In this way, changes in the apparent particle size of the ultraviolet-shielding microparticles are suppressed, and the ultraviolet-shielding effect of the ultraviolet-shielding microparticles is exerted without being inhibited by aggregation. Below, the base particle and ultraviolet-shielding microparticles that constitute the composite particle are described, followed by a method for combining them, the properties of the obtained composite particle, and cosmetics containing the composite particle.

[0012] (base material particles) The base particle contains starch. The starch is, for example, at least one type selected from corn starch (cornstarch), potato starch, sugarcane starch, tapioca starch, sago starch, wheat starch, and rice starch, and is preferably cornstarch. The average particle size of the base particle is not particularly limited, but may be, for example, 3 to 100 μm, preferably 5 to 60 μm, more preferably 5 to 50 μm, and in some cases, may be in the range of 5 to 20 μm, or even 5 to 18 μm. In this specification, the average particle size is defined as the particle size at 50% volumetric penetration measured using a laser diffraction method.

[0013] Resin particles such as nylon, polystyrene, polyethylene, and PMMA have been used as base particles for composite particles. These resin particles can be easily produced by controlling their shape and surface undulations, and can even be made into particles with extremely smooth, spherical surfaces. Spherical particles with highly smooth surfaces have a sufficiently low mean coefficient of friction (MIU), which contributes to a lower MIU of composite particles. In contrast, starch particles have shapes such as polyhedrons and lenses and are not spherical. However, when compared as composite particles, starch particles can serve as base particles that can provide a lower MIU than spherical resin particles, which have a lower MIU.

[0014] Starch particles are biodegradable materials that are rapidly decomposed in nature, and are therefore superior to petroleum-derived resin particles from the standpoint of environmental protection.

[0015] (UV shielding fine particles) The ultraviolet-shielding microparticles contain at least one selected from titanium oxide, zinc oxide, and cerium oxide, and preferably contain titanium oxide. The ultraviolet-shielding microparticles do not need to be composed of a single type of inorganic material. For example, titanium oxide microparticles can be used as ultraviolet-absorbing microparticles without any problems even if they contain trace amounts of iron oxide and other impurities. The crystal type of titanium oxide is preferably other than the anatase type, which has high catalytic activity, specifically the rutile type. Fine particles such as titanium oxide are sold by Croda Japan Co., Ltd., Sakai Chemical Industry Co., Ltd., Titan Kogyo Co., Ltd., Teika Corporation, Ishihara Sangyo Co., Ltd., etc.

[0016] The average particle size of the ultraviolet-shielding microparticles is preferably 10 to 200 nm. The lower limit of this average particle size may be 15 nm or more, and in some cases 20 nm or more. The upper limit may be 175 nm or less, and in some cases 160 nm or less. The ultraviolet-shielding properties of the ultraviolet-shielding microparticles depend on the particle size of the microparticles, and generally, the smaller the particle size, the more the absorption wavelength range shifts to the short wavelength side. For example, for blocking ultraviolet B rays (UVB), ultraviolet-shielding microparticles with an average particle size of about 15 to 60 nm are suitable. For example, for blocking ultraviolet A rays (UVA), ultraviolet-shielding microparticles with an average particle size of about 70 to 175 nm are suitable.

[0017] (Method of compounding) The base particles and the ultraviolet-shielding microparticles can be combined by mixing the base particles and the microparticles using a mixer such as an automatic mortar, a ball mill, a Henschel mixer, a Nauta mixer, a Loedige mixer, a V-type mixer, a hammer mill, or a pin mill.

[0018] This composite can be achieved by referring to the method described in Patent Document 1. This method includes an attachment step in which fine particles are attached to the surface of base particles (resin particles) by electrostatic forces generated between the base particles and the fine particles due to frictional charging between the base particles and the fine particles, and a strength enhancement step, which is performed after the attachment step, in which the base particles with the attached fine particles collide with each other to increase the adhesion strength of the fine particles to the base particles. The attachment step utilizes the phenomenon in which different substances are charged according to a triboelectric series when they come into contact and separate. Base particles and fine particles repel each other because they have the same charge due to charging, while base particles and fine particles with different charges attract each other. This electrostatic attraction results in the fine particles being densely supported on the surface of the base particles. In the strength enhancement step, the adhesion strength between the base particles and the fine particles is improved by the impact force associated with the collision. By performing the above-mentioned attachment step and strength enhancement step, it is possible to produce composite particles with improved adhesion strength of UV fine particles compared to conventional methods.

[0019] Details of this preferred method are described in Patent Document 1. That is, the above-mentioned adhesion step and preferred strength-improving step can be carried out using, for example, a Henschel mixer. Specifically, the adhesion step is carried out by feeding base particles and fine particles into a Henschel mixer and rotating the stirring blades at a first speed for a predetermined time to mix the base particles and fine particles. Subsequently, the strength-improving step is carried out by rotating the stirring blades of the Henschel mixer at a second speed, which is faster than the first speed, for a predetermined time. The strength-improving step is carried out by feeding only base particles with UV-absorbing fine particles attached thereto as particles whose surfaces are composed of inorganic or metal into the Henschel mixer. The "predetermined time" mentioned above varies depending on the amount of particles added, but for the adhesion step, for example, 1 minute or more, particularly 2 to 10 minutes, and even if 10 minutes or more is used, the adhesion state is good, but longer production times result in poor cost efficiency. For the strength-improving step, for example, 15 minutes or more, particularly 20 to 60 minutes, are used. Strength improvement is also effective even if the time is longer than 60 minutes, but longer production times result in poor cost efficiency.

[0020] As the treatment time progresses, the compounding progresses, the fine particles enter between the agglomerated starch particles, breaking up the agglomerations, and the fine particles are bombarded onto the surface of the starch particles, promoting compounding.

[0021] According to the above-mentioned method, the ultraviolet-shielding microparticles can be attached to the base particles without relying on the adhesive force of other materials. Therefore, even if an organic material such as wax that encapsulates and integrates the ultraviolet-shielding microparticles and the base particles is not present, the adhesion state between the ultraviolet-shielding microparticles and the base particles is maintained. In this embodiment, the composite particles do not need to contain an organic material that coats both the base particles and the ultraviolet-shielding microparticles and integrates them.

[0022] The mass ratio of the ultraviolet absorbing particles to the total amount of the base particles and the ultraviolet absorbing particles is not particularly limited, but is preferably 50% or more, more preferably 55% or more, particularly preferably 60% or more, and especially preferably 65% ​​or more.

[0023] (Characteristics of composite particles) The mean coefficient of friction (MIU) of the composite particles of this embodiment can be reduced to 0.23 or less, and even 0.22 or less. However, the MIU value differs depending on the type of ultraviolet-shielding microparticles, the ratio of base particles to microparticles, etc., and therefore the MIU of the composite particles of this embodiment is not limited to the above. The composite particles of this embodiment can have a lower MIU than those using conventional resin particles, provided that the type of microparticles, etc., is the same.

[0024] (Cosmetics) The composite particles of this embodiment are suitable for incorporation into cosmetics. Cosmetics containing the composite particles of this embodiment are not particularly limited in type, but include facial cosmetics, makeup cosmetics, and the like. In particular, for facial cosmetics such as foundations and face powders, there is a particularly high demand for materials that block ultraviolet rays. The form of the cosmetics is not particularly limited, but may be powder, cake, pencil, stick, ointment, liquid, emulsion, cream, or the like. [Example]

[0025] The present invention will be further described below with reference to examples, but the present invention is not limited to the following.

[0026] [Composite particles] Example 1 Cornstarch White (see FIG. 1; average particle size 15 μm) manufactured by Nippon Corn Starch Co., Ltd. was used as the starch particles, and MT100TV (average particle size 15 nm) manufactured by Teika Corporation was used as the titanium oxide fine particles.

[0027] 40 parts by mass of starch particles and 60 parts by mass of titanium oxide microparticles were placed in a Henschel mixer and mixed for 3 minutes at a peripheral speed of 40 m / s. The apparent specific volume of the processed product was 1.6 mL / g. The mixture was then mixed for 20 minutes at a peripheral speed of 100 m / s to obtain composite particles (see Figure 2).

[0028] (Comparative Example 1) Composite particles were obtained (see FIG. 4) in the same manner as in Example 1, except that spherical nylon particles SP10 (see FIG. 3; average particle size 10 μm) manufactured by Toray Industries, Inc. were used instead of starch particles.

[0029] The average coefficient of friction (MIU) was measured for each composite particle obtained above and each base particle used using a friction tester KES-SE manufactured by Kato Tech Co., Ltd. Silicone was used as the friction probe, the load was 25 g, and the measurement speed was 1 mm / sec. The measurement object was a 24 cm slab of artificial leather, Suplarre (registered trademark; artificial leather) manufactured by Idemitsu Technofine Co., Ltd., where 5 mg of the base particle or composite particle was applied. 2 The results are shown in Table 1.

[0030] [Table 1]

[0031] By compositing, the MIU of the starch particles became lower than that of spherical nylon particles. Among resin particles, SP10 has a particularly low MIU due to its spherical shape. For example, the MIU of non-spherical nylon particles (see FIG. 5; ORGASOL (registered trademark) GREEN TOUCH manufactured by Arkema) was measured and found to be 0.491. Even when composite particles are produced using such resin particles as base particles, the MIU value of the composite particles does not fall below the minimum value of 0.26 obtained by agglomeration of titanium oxide fine particles (see Patent Document 2).

[0032] [Cosmetics] (Examples 2-3 / Comparative Examples 2-3) A sunscreen was prepared according to the formulation shown in Table 2. Specifically, components 1 to 9 (oil phase) and components 10 to 13 (aqueous phase) were mixed by stirring, and then the aqueous phase was added to the oil phase to emulsify. The composite particles were prepared in the same manner as in Example 1, except that "Solabail XTP-1" manufactured by Croda Japan Co., Ltd. was used instead of MT100TV as the titanium oxide microparticles. A powder foundation was also prepared according to the formulation shown in Table 3. Specifically, components 1 to 7 were mixed and pulverized and transferred to a high-speed blender, and a mixture of components 8 to 12 was added, mixed, and pulverized. The resulting mixture was then press-molded into a medium-sized container.

[0033] [Table 2]

[0034] [Table 3]

[0035] The SPF measurement results are shown in Table 4. Evaluation items for cosmetic feel, such as spreadability, roughness, squeaky feeling, and fit (adhesion), were each tested by 10 expert panelists, and the scores given by each panelist were totaled based on the following criteria. The results are shown in Table 5. Evaluation criteria 5 points: Excellent 4 points: Excellent 3 points: Average 2 points: Inferior 1 point: Very poor Evaluation criteria ◎: The total score is 40 points or more. ○: The total score is between 20 and 30 points. △: The total score is between 10 and 20 points. ×: The total score is less than 10 points.

[0036] [Table 4]

[0037] [Table 5]

Claims

1. The ink jet recording medium comprises a base particle and a plurality of ultraviolet-shielding fine particles attached to the base particle, the base particle has a core-shell structure in which the core is made of the base particle and the ultraviolet-shielding fine particles are made of the shell, the substrate particles comprise starch; the ultraviolet-shielding fine particles contain at least one selected from titanium oxide, zinc oxide, and cerium oxide; composite particles. However, this does not include composite particles in which, when the shell is a first coating layer, the first coating layer is at least partially covered with a second coating layer containing a hydrophobic block copolymer.

2. The ink jet recording medium comprises a base particle and a plurality of ultraviolet-shielding fine particles attached to the base particle, the substrate particles comprise starch; the ultraviolet-shielding fine particles contain at least one selected from titanium oxide, zinc oxide, and cerium oxide, The average coefficient of friction (MIU) is 0.23 or less. composite particles.

3. The ink jet recording medium comprises a base particle and a plurality of ultraviolet-shielding fine particles attached to the base particle, the substrate particles comprise starch; the ultraviolet-shielding fine particles are titanium oxide fine particles, the mass ratio of the ultraviolet-shielding microparticles to the total amount of the base particle and the ultraviolet-shielding microparticles is 50% or more; composite particles. However, this does not include composite particles in which, when the layer of the plurality of ultraviolet fine particles is a first coating layer, the first coating layer is at least partially covered with a second coating layer containing a hydrophobic block copolymer.

4. 3. The composite particle according to claim 1, wherein a mass ratio of the ultraviolet-shielding fine particles to the total amount of the base particle and the ultraviolet-shielding fine particles is 50% or more.

5. 4. The composite particles according to claim 1 or 3, having an average coefficient of friction (MIU) of 0.23 or less.

6. A cosmetic comprising the composite particles according to any one of claims 1 to 5.

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