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US-12617949-B2 - Silica, paint and silica manufacturing method

US12617949B2US 12617949 B2US12617949 B2US 12617949B2US-12617949-B2

Abstract

Provided is a silica that exhibits a high matting property when utilized as a matting agent for a paint, and can also suppress the occurrence of cloudiness. The silica has an aggregated structure in which primary particles are aggregated, has a particle diameter ratio R represented by the following equation (1) of from 4.3 to 5.2, has an absorbance of 0.6 or less for light having a wavelength of 700 nm as an aqueous dispersion having a concentration of 1.48 mass %, and has a particle density measured with a He pycnometer of 2.18 g/cm 3 or more: Equation (1) R= L D50/ C D50 (in the equation (1), L D50 represents a volume-based 50% cumulative particle diameter (μm) of the silica measured based on a laser diffraction/scattering method, and C D50 represents a volume-based 50% cumulative particle diameter (μm) of the silica measured based on a Coulter counter method).

Inventors

  • Masahiro Nakamura

Assignees

  • TOKUYAMA CORPORATION

Dates

Publication Date
20260505
Application Date
20210401
Priority Date
20200402

Claims (7)

  1. 1 . A silica, which has an aggregated structure in which primary particles are aggregated, has a particle diameter ratio R represented by the following equation (1); R= L D 50/ C D 50. equation (1) has an absorbance of 0.6 or less for light having a wavelength of 700 nm as an aqueous dispersion having a concentration of 1.48 mass %, and has a particle density measured with a He pycnometer of 2.18 g/cm 3 or more, wherein the particle diameter ratio R as calculated using equation (1) is from 4.3 to 5.2, and in the equation (1), L D50 represents a volume-based 50% cumulative particle diameter (μm) of the silica measured based on a laser diffraction/scattering method, and C D50 represents a volume-based 50% cumulative particle diameter (μm) of the silica measured based on a Coulter counter method.
  2. 2 . The silica according to claim 1 , wherein the volume-based 50% cumulative particle diameter L D50 is 1.7 μm or more.
  3. 3 . The silica according to claim 1 , wherein the silica has a bulk density of 35 g/L or more.
  4. 4 . A matting agent for a paint comprising the silica according to claim 1 .
  5. 5 . A clear paint or a black-colored paint comprising the matting agent according to claim 4 .
  6. 6 . A paint, comprising at least: a matting agent; and a resin, wherein the matting agent contains a silica, which has a structure in which primary particles are aggregated, has a particle diameter ratio R represented by the following equation (1) of from 4.3 to 5.2, has an absorbance of 0.6 or less for light having a wavelength of 700 nm as an aqueous dispersion having a concentration of 1.48 mass %, and has a particle density measured with a He pycnometer of 2.18 g/cm 3 or more: R= L D 50/ C D 50 Equation (1) in the equation (1), L D50 represents a volume-based 50% cumulative particle diameter (μm) of the silica measured based on a laser diffraction/scattering method, and C D50 represents a volume-based 50% cumulative particle diameter (μm) of the silica measured based on a Coulter counter method.
  7. 7 . The paint according to claim 6 , wherein the paint is any one selected from the group consisting of: a clear paint; and a black-colored paint.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a U.S. National Phase Application under 35 U.S.C. 371 of International Application No. PCT/JP2021/014165, filed on Apr. 1, 2021, which claims priority to Japanese Patent Application No. 2020-066586, filed on Apr. 2, 2020. The entire disclosures of the above applications are expressly incorporated by reference herein. BACKGROUND Technical Field The present invention relates to a silica, a paint, and a method of producing a silica. Related Art Silica produced through flame thermal decomposition of a chlorosilane is fine silica having a specific surface area of from about 50 m2/g to about 500 m2/g, and is generally called fumed silica. The fumed silica is mainly used as a filling/reinforcing material or thickener for a transparent resin, and as a fluidizing agent for powder, and is excellent in dispersibility. Accordingly, the fumed silica is often utilized particularly as a filler for a silicone rubber, a thickener for a polyester resin, a fluidizing agent for toner, or the like. However, when the fumed silica is applied as a matting agent for a paint, the above-mentioned good dispersibility is a disadvantage. That is, the fumed silica is dispersed in a paint to a size equal to or smaller than the wavelength of visible light even by a weak dispersion force. Consequently, in general, the fumed silica cannot be used as it is as a matting agent for a paint. Accordingly, silica obtained by milling and classifying wet process silica (silica produced in a solvent such as water) having a large particle diameter has only been used as a matting agent for a paint. However, even when the silica produced using the wet process silica as a raw material is used as a matting agent, it can hardly be said that sufficient matting performance is necessarily obtained. Meanwhile, there is a proposal of a technology involving utilizing the fumed silica, which cannot be utilized as it is as a matting agent, as a matting agent. For example, in JP 56-44012 B2, there is a proposal of a technology involving utilizing, as a matting agent, a silicic acid having an aerogel-like structure, which is obtained by blending fumed silica with 5 wt % to 50 wt % of water and drying the resultant powdery mixture. In addition, there is also a proposal of a technology adopting an approach significantly different from that of the technology described in JP 56-44012 B2. For example, in JP 4440114 B2, there is a proposal of a technology involving utilizing, as a matting agent, texture-coated silica, which is obtained by spraying fumed silica with water and a thermoplastic elastomer, while mixing in a mixing vessel, and then milling and subsequently drying the mixture. The inventor of the present invention has made further investigations on the technology described in JP 56-44012 B2 out of the technologies described in JP 56-44012 B2 and JP 4440114 B2, which adopt technical approaches significantly different from each other. As a result, the inventor has recognized that, even when the silica obtained utilizing the technology described in JP 56-44012 B2 is utilized as a matting agent for a paint, a sufficient matting property is not necessarily obtained. The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a silica that exhibits a high matting property when utilized as a matting agent for a paint, and can also suppress the occurrence of cloudiness, a paint using the silica, and a method of producing the silica. SUMMARY The above-mentioned object is achieved by embodiments of the present invention to be described below. According to one embodiment of the present invention, there is provided a silica, which has an aggregated structure in which primary particles are aggregated, has a particle diameter ratio R represented by the following equation (1) of from 4.3 to 5.2, has an absorbance of 0.6 or less for light having a wavelength of 700 nm as an aqueous dispersion having a concentration of 1.48 mass %, and has a particle density measured with a He pycnometer of 2.18 g/cm3 or more: R=LD50/CD50  Equation (1) in the equation (1), LD50 represents a volume-based 50% cumulative particle diameter (μm) of the silica measured based on a laser diffraction/scattering method, and CD50 represents a volume-based 50% cumulative particle diameter (μm) of the silica measured based on a Coulter counter method. In the silica according to one embodiment of the present invention, it is preferred that the volume-based 50% cumulative particle diameter LD50 be 1.7 μm or more. In the silica according to another embodiment of the present invention, it is preferred that the silica have a bulk density of 35 g/L or more. In the silica according to another embodiment of the present invention, it is preferred that the silica be for use as a matting agent for a paint. In the silica according to another embodiment of the present invention, it is pr