TW202045124A - White pigment having high masking performance for use in low-viscosity dispersion mediums, and method for producing same - Google Patents

Abstract

Provided is a surface-coated calcination pigment which is less likely to precipitate in a low-viscosity dispersion medium such as a water-based dispersion medium, and contains, as the main component, titanium oxide that has excellent masking performance. The surface-coated calcination pigment containing titanium oxide as the main component according to the present disclosure is composed of secondary structural particles each having a surface-protruding shape, wherein each of the secondary structural particles is composed of a plurality of primary structures connected to each other, the surface of each of the secondary structural particles is coated with an inorganic material other than titanium oxide, and the each of the secondary structural particles has an equivalent circular area particle diameter of 150 to 500 nm inclusive.

Description

High concealment white pigment for low-viscosity dispersion medium and manufacturing method thereof

The present invention relates to a surface-coated calcined pigment suitable for use in a low-viscosity dispersion medium, with titanium oxide as the main component, and a manufacturing method thereof.

In recent years, pigments with various particle shapes of titanium oxide as the main component have been blended into various dispersion media and used in various applications.

For example, Patent Document 1 discloses a technique for using concealed unbaked rutile-type titanium oxide aggregate particles in high-viscosity cosmetics. The size of the rutile-type titanium oxide aggregate particles is 0.05. ～0.2 μm, the thickness direction of rod-shaped particles having a size of 0.02～0.1 μm is assembled and/or formed by further agglomeration of fan-shaped rutile type titanium oxide particles, and the particle size of the agglomerated particles is 0.1～5.0 μm , The average friction coefficient (MIU value) is 0.2 or more and less than 0.7.

Patent Document 2 to Patent Document 4 disclose techniques for using titanium oxide with particle shapes such as straw bundles and short strips in high-viscosity cosmetics.

Titanium oxide is widely used in fields centered on cosmetics, but because the Hamaker constant, which is an indicator of the strength of interaction, is relatively large, it is usually easy to aggregate and precipitate.

…式1 此處，V_s 意指沈澱速度，D_p 意指粒徑，ρ_p 意指粒子密度，ρ_f 意指介質密度，g意指重力加速度，η意指介質黏度。Under normal circumstances, for the index of the precipitation of particles in the liquid medium, the Stokes formula shown in the following formula 1 can be used: [Number 1]

…Equation 1 Here, V _s means precipitation speed, D _p means particle size, ρ _p means particle density, ρ _f means medium density, g means gravitational acceleration, and η means medium viscosity.

The average particle size of pigment-grade titanium oxide is about 0.3 μm. In cosmetics, the refractive index of the crystal system of pigment-grade titanium oxide is relatively high, and it is used in rutile systems that are advantageous in terms of hiding power. The density of the rutile series is 4.27 g/mL (Kingye Science, Titanium Oxide, 1991). In addition, since the precipitation rate is proportional to the square of the particle size and the density difference, and inversely proportional to the viscosity of the medium, high-density pigment-grade titanium oxide particles are easy to precipitate in low-viscosity media such as aqueous dispersion media. Therefore, when this kind of pigment-grade titanium oxide is formulated in a medium used in a higher viscosity cosmetics, etc., it cannot be formulated in a low-viscosity medium such as an aqueous dispersion medium without using physical dispersion methods such as stirring and shaking. in.

In addition, in order to express the concealment required for general pigment-grade titanium oxide, baking is carried out in many cases. However, the density of calcined titanium oxide increases as the porosity decreases, so it is easier to precipitate than uncalcined titanium oxide.

In a low-viscosity dispersion medium, reducing the particle size of titanium oxide is an effective way to improve the precipitation resistance. However, if the particle size of titanium oxide becomes smaller, the concealment property decreases, and therefore there are cases where the performance required as a cosmetic material cannot be satisfied. It is required to have both precipitation resistance and concealment in a low-viscosity dispersion medium. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 4684970 [Patent Document 2] Japanese Patent No. 6258462 [Patent Document 3] Japanese Patent No. 5096383 [Patent Document 4] Japanese Patent Laid-Open No. 2014-84251

The main purpose of the present invention is to provide a surface-coated calcined pigment, which is not easy to precipitate in a low-viscosity dispersion medium such as an aqueous dispersion medium, and has excellent concealability and uses titanium oxide as the main component. [Technical means to solve the problem]

The inventors of the present case have conducted intensive research on the dispersion of titanium oxide and found that the titanium oxide having a protruding shape as shown in Fig. 1 is treated by the inorganic salt aqueous solution as the raw material of the coating agent, and then roasted. This can obtain a surface-coated calcined pigment with titanium oxide as the main component, which has excellent precipitation resistance and concealability in a low-viscosity dispersion medium.

Furthermore, the surface-coated calcined pigment containing titanium oxide as the main component of the present invention can be used as a composition mixed with a dispersion medium.

<Aspect 1> A pigment with titanium oxide as the main component, which contains secondary structure particles with a surface protruding shape. The secondary structure particles are formed by connecting a plurality of primary structures on the surface of the secondary structure particles. It is coated with an inorganic material other than titanium oxide, and the diameter of the equal-area round particles is 150 nm to 500 nm. <Aspect 2> The pigment of aspect 1, wherein the above-mentioned inorganic material is one or more of oxides selected from the elements of aluminum, silicon, zinc, titanium, zirconium, iron, cerium and tin. <Aspect 3> The pigment as in aspect 1, wherein the inorganic material is at least one selected from silica and alumina. <Aspect 4> The pigment of any of the aspects 1 to 3, wherein the shape of the primary structure is selected from the group consisting of needle-like, granular, spindle-like, short-striped, straw bundle-like, rod-like, and At least one of the cocoon-shaped. <Aspect 5> The pigment of any of the aspects 1 to 4, wherein the apparent bulk density of the above-mentioned pigment is 600 kg/m ³ or less. <Aspect 6> The pigment of any one of aspects 1 to 5, wherein the specific surface area of the above-mentioned pigment is 80 m ² /g or less. <Aspect 7> The pigment of any of the aspects 1 to 6 has a concealment difference of 2.0 or more in the concealment test. <Aspect 8> The pigment of any one of the aspects 1 to 7, the titanium oxide component of which is rutile. <Aspect 9> The pigment of any of the aspects 1 to 8, which is used in cosmetics. <Aspect 10> A pigment having an equal-area round particle diameter of 150 nm or more and 500 nm or less, and at least one selected from an apparent bulk density of 600 kg/m ³ or less and a specific surface area of 80 m ² /g or less One type, and the surface is covered with an oxide layer of inorganic materials other than titanium oxide. <Aspect 11> A composition containing the pigment and dispersing medium of any of the aspects 1 to 10, and the viscosity at a shear rate of 1000/s is 100 mPa·s or less. <Pattern 12> A method for producing a pigment of any one of Aspects 1 to 10, which uses titanium oxide to form a solution to prepare secondary structure particles with surface protruding shapes formed by connecting a plurality of primary structures To the slurry, add an inorganic material coating solution containing an inorganic salt aqueous solution used as a raw material for the coating agent, and coat the surface with an oxide layer of inorganic material secondary structure particles in the air at 550°C above 750°C Perform roasting. [Effects of Invention]

According to the present invention, it is possible to provide a surface-coated calcined pigment containing titanium oxide as a main component, which is not easy to precipitate in a low-viscosity dispersion medium such as an aqueous dispersion medium, and has excellent concealment properties.

Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be implemented with various modifications within the scope of the gist of the invention.

One embodiment of the present invention is a surface-coated calcined pigment containing titanium oxide as the main component, which contains secondary structure particles having a surface protruding shape as shown in FIG. 3, and the secondary structure particles are formed by connecting a plurality of primary structures. , The surface of the secondary structure particles is coated with inorganic materials other than titanium oxide, and the diameter of the equal area round particles is 150 nm or more and 500 nm or less.

In the pigment of the present invention, it is important that the secondary structure particles have a plurality of surface protrusion shapes. The pigment of the present invention has voids due to the protruding shape shown in Fig. 3, so the apparent bulk density becomes smaller. Therefore, it is believed that even in a low-viscosity dispersion medium such as an aqueous dispersion medium, the precipitation rate becomes lower, and it is less likely to precipitate than general pigment-grade titanium oxide.

This kind of pigment has a special apparent bulk density or specific surface area that is different from general pigment grade titanium oxide. It is believed that as long as it is a pigment with such a special apparent bulk density or specific surface area, it can exhibit the same effect.

Furthermore, regarding the pigment of the present invention, a surface coating treatment is applied to the unbaked titanium oxide having the special form shown in FIG. 1, and then the baking treatment is performed. As a result, unlike the pigment described in Patent Document 2 where the titanium oxide (Figure 2) whose surface shape has changed after firing is surface-coated, the surface-coated calcined pigment of the present invention can maintain the surface coating shown in Figures 3 and 4 Special form, that is, the form of secondary structure particles formed by connecting multiple primary structures. It is thought that the reason is that a coating layer containing an inorganic material different from titanium oxide is formed on the surface of the primary structure containing titanium oxide, and therefore the sintering between the primary structures is suppressed.

Furthermore, the coating layer on the surface of the pigment contains inorganic materials other than titanium oxide. It is believed that the hydroxyl group is easily arranged on the surface of the coating layer containing the inorganic material, and therefore the compatibility between the aqueous dispersion medium and titanium oxide is improved, and the dispersion in the aqueous dispersion medium becomes easier.

In addition, the coating layer on the surface of the pigment increases the bonding force with the titanium oxide by firing and prevents the peeling of the coating layer. Therefore, the durability is improved compared with the unfired coating layer.

If the equal-area round particle diameter of the pigment of the present invention is 150 nm or more and 500 nm or less, it is equivalent to the general pigment-grade titanium oxide, and is calcined after the surface coating treatment. As a result, as compared with the unfired surface-coated titanium oxide described in Patent Document 1, Patent Document 3, and Patent Document 4, the porosity of the pigment, especially the inside of the pigment that is not easily coated on the surface, can be improved. The void ratio near the core is reduced, so the concealment performance can be further improved.

<<Surface-coated calcined pigment with titanium oxide as the main component>> As the surface-coated calcined pigment with the titanium oxide of the present invention as the main component (sometimes referred to as "pigment"), it is possible to use oxidized pigments with surface protrusions. Titanium as the main component of the pigment of secondary structure particles, the surface of the secondary structure particles is coated with an inorganic material other than titanium oxide, has an equal area round particle diameter of 150 nm to 500 nm, and is connected by a plurality of primary structures And constitute; and/or use a pigment with titanium oxide as the main component, the titanium oxide having at least one selected from an apparent bulk density of 600 kg/m ³ or less and a specific surface area of 80 m ² /g or less.

The type of the titanium oxide component in the pigment may be any of anatase type, rutile type, and brookite type. From the viewpoint of concealability, rutile type titanium oxide is preferred.

＜Characteristics of pigments＞ (Equal area round particle diameter) The so-called equal-area round particle diameter of the pigment can mean, for example, the particle diameter when converted to a round particle having the same area as the projected area of the pigment observed by a transmission electron microscope. The diameter of the related equal-area round particles can be specified as the average value of more than 10 particles. Regarding the equal-area round particle diameter of titanium oxide particles, for example, in order to improve the scattering effect of visible light and enhance concealment, it is preferably a size near 1/2 wavelength of visible light, more preferably 150 nm or more and 450 nm or less. It is above 200 nm and below 400 nm.

(Apparent Bulk Density) In order to reduce the precipitation rate of the pigment of the present invention, the apparent bulk density is preferably 600 kg/m ³ or less. There is no particular limitation on the lower limit of the apparent bulk density, and for example, it can be set to 100 kg/m ³ or more. The apparent bulk density can be obtained in the following manner using a specific volume tester, for example.

(Specific surface area) The specific surface area of the pigment of the present invention is desirably 80 m ² /g or less from the viewpoint of concealment and precipitation resistance. The specific surface area of titanium oxide can be obtained by, for example, the BET (Brunauer-Emmett-Teller, Buert) method.

(Concealment) In the following concealability test of the pigment of the present invention, the color difference (ΔE) as an index of concealment can be, for example, 30.0 or less, 27.0 or less, 25.0 or less, 24.0 or less, or 23.0 or less. There is no particular limitation on the lower limit of the color difference, and for example, it may be 10.0 or more, 12.0 or more, or 15.0 or more.

In the following concealment test, the pigment of the present invention can be evaluated based on the color difference of titanium oxide without surface coating and baking treatment based on the difference in chromaticity with other titanium oxides (bad concealment power). The difference in hiding power can be specified to be 2.0 or more. There is no particular limitation on the upper limit of the difference in concealment power, and it can be set to 20.0 or less, for example.

(Crystal diameter) The pigment of the present invention desirably has a crystallite diameter of 8.0 nm or more, and desirably has a crystallite diameter of 25.0 nm or less. The crystallite diameter of titanium oxide can be measured by a general X-ray diffraction method.

(shape) As the pigment of the present invention, the secondary particles can be formed by connecting a plurality of primary structures and having a surface protrusion shape.

The shape of the primary structure can be any shape as long as precipitation resistance and concealment performance can be obtained. It is not limited to the following shapes. For example, it can be selected from needle-shaped, granular, spindle-shaped, short-shaped, and straw-shaped At least one of, rod-shaped, and cocoon-shaped. Among them, a needle-like or rod-like shape as shown in FIGS. 3 and 4 is preferred.

The primary structure can be connected in a way that can exhibit a protruding shape on the surface of the secondary structure particle. The connection structure is not particularly limited. For example, the primary structure can be connected in a fan shape, a radial shape, or an irregular shape. From the standpoint of precipitation resistance and concealment properties, the connection is preferably radial.

＜Surface coating layer＞ The pigment of the present invention is coated with more than one inorganic material other than titanium oxide on its surface. The related inorganic materials are not limited to the following materials. Examples include components containing elements selected from aluminum, silicon, zinc, zirconium, iron, cerium, and tin. Examples include oxides of the aforementioned elements. Among them, silicon oxide and aluminum oxide are preferred, and silicon oxide is more preferred. From the viewpoint of self-concealability of the pigment having a surface coating layer, it is preferable to use titanium oxide as the main component, that is, 800 g/kg or more is the titanium oxide component. The ratio of the surface coating layer of the related titanium oxide can be set to 200 g/kg or less and 10 g/kg or more based on the mass of the pigment.

By coating the surface of the pigment of the present invention with an inorganic material other than titanium oxide, the shape change caused by the sintering of the primary structure can be reduced, and the dispersibility in a dispersion medium, especially an aqueous dispersion medium, can be improved.

＜＜Composition containing surface-coated roasted titanium oxide＞＞ The pigment with titanium oxide as the main component of the present invention can form a composition together with a low-viscosity dispersion medium, especially an aqueous dispersion medium.

＜Characteristics of the composition＞ (Viscosity) The pigment-containing composition of the present invention can have a viscosity of 100 mPa·s or less at a shear rate of 1000/s. The relative viscosity can be measured, for example, using a rheometer such as MCR-302 (manufactured by Anton-Paar). When measured at 32°C and 1 atmosphere, the viscosity of the measured object at a shear rate of 1000/s can be specified as 100 mPa・S or less, 50 mPa·s or less, or 10 mPa·s or less, and can be specified as 1 mPa·s or more, 2 mPa·s or more, or 3 mPa·s or more.

When the static viscosity of the composition of the present invention, that is, the shear rate is infinitely close to 0 s ^-1 , for example, the viscosity at a shear rate of 1/s can be specified as 1000 mPa·s or less, and can be specified as 10 mPa· s above. The static viscosity can also be measured using the above rheometer under the conditions of 32°C and 1 atmosphere.

(Precipitation resistance) In the following precipitation resistance test, the composition of the present invention can achieve 90.0% or more, 93.0% or more, or 95.0% or more, and can achieve 100% or less, less than 100%, or 99.0% or less after 24 hours .

(Precipitation resistance) In the following precipitation resistance test, the composition of the present invention can achieve more than 90.0% after 24 hours, and more than 85.0% after 90 hours.

＜The amount of pigment blending＞ The amount of pigment in the composition can be appropriately adjusted according to the intended use, and is not limited to the following amounts. For example, in the composition, it can be set to 50 g/kg or more, 100 g/kg or more, or 200 g /kg or more, and can be set to 300 g/kg or less, 270 g/kg or less, or 250 g/kg or less.

＜Dispersion medium＞ The dispersing medium is not particularly limited as long as it can disperse the pigment, and one or more kinds of well-known dispersing media such as organic dispersing media and aqueous dispersing media can be used. Among them, it is preferable to use an aqueous dispersion medium. As an aqueous dispersion medium, for example, various alcohols such as water, lower alcohols and polyhydric alcohols, or mixtures of these can be cited.

Examples of lower alcohols include ethanol, propanol, isopropanol, isobutanol, and tert-butanol.

Examples of polyhydric alcohols include diols (e.g., ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 2-butene-1,4-diol, hexanediol, octanediol, etc.); triol (for example: glycerin, trimethylol Propane, etc.); Tetrahydric alcohols (e.g., pentaerythritol, such as 1,2,6-hexanetriol, etc.); Pentahydric alcohols (e.g., xylitol, etc.); Hexahydric alcohols (e.g., sorbitol, mannitol, etc.); Polyol polymers (for example: diethylene glycol, dipropylene glycol, triethylene glycol, polypropylene glycol, tetraethylene glycol, diglycerin, polyethylene glycol, triglycerin, tetraglycerin, polyglycerin, etc.); glycol Alkyl ethers (for example: ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monohexyl ether, ethylene glycol mono-2-methylhexyl Ether, ethylene glycol isoamyl ether, ethylene glycol benzyl ether, ethylene glycol isopropyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, etc.); glycol alkyl ether Class (for example: diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol butyl ether, two Ethylene glycol methyl ethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol isopropyl ether, dipropylene glycol methyl ether, dipropylene glycol Diethyl ether, dipropylene glycol butyl ether, etc.); glycol ether esters (for example: ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol mono Phenyl ether acetate, ethylene glycol diadipate, ethylene glycol disuccinate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether ethyl Acid esters, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol monophenyl ether acetate, etc.); glycerol monoalkyl ethers (for example: mackerel alcohol, salitolol, squalyl alcohol, etc.); Sugar alcohol (for example: sorbitol, maltitol, maltotriose, mannitol, sucrose, erythritol, glucose, fructose, amylolytic sugar, maltose, xylitol, amylolytic sugar reducing alcohol, etc.); GLYSOLID; tetrahydrofuran Methanol; POE-tetrahydrofuran methanol; POP-butyl ether; POP•POE-butyl ether; tripolyoxypropylene glycerol ether; POP-glyceryl ether; POP-glyceryl ether phosphoric acid; POP•POE-pentaerythritol ether, polyglycerol, etc.

＜Optional ingredients＞ The composition of the present invention can be appropriately blended with other ingredients as needed within the range that does not hinder the effect of the present invention, such as: pigments other than titanium oxide, dyes, esters, humectants, water-soluble polymers, oils, higher alcohols, and adhesives , Dispersants, various salt ingredients, tackifiers, various surfactants and other surface tension reducing agents, coating agents, ultraviolet absorbers, ultraviolet scattering agents, metal ion blocking agents, amino acids, organic amines, polymer emulsions, pH adjusters, skin nutrients, vitamins, antioxidants, antioxidant additives, fragrances, preservatives, anti-inflammatory agents, anti-inflammatory agents, whitening agents, activators, anti-seborrhoeic agents, various natural medicine extracts, pharmaceuticals, etc. . Since the pigment of the present invention has excellent precipitation resistance, it is not necessary to use a dispersant, but when a dispersant such as a polymer electrolyte is used, the precipitation resistance can be further improved.

＜＜Use＞＞ The surface-coated calcined pigment containing titanium oxide as the main component of the present invention and the pigment-containing composition of the present invention can be suitably used in a wide range of applications such as cosmetics, paints, and inks.

<<The manufacturing method of the surface-coated calcined pigment containing titanium oxide as a main component>> There is no particular limitation on the method of producing the surface-coated calcined pigment containing titanium oxide as the main component of the present invention. Regarding the manufacturing method of the unbaked titanium oxide without surface coating as shown in FIG. 1, the disclosure of Patent Document 1 can be referred to, for example. Specifically, for example, a titanyl sulfate solution is used as a titanium oxide forming solution, and hydrochloric acid is added to orthotitanic acid obtained by alkali neutralization of the related titanyl sulfate solution at a temperature below 10°C, After the orthotitanic acid is completely dissolved, it is heated and hydrolyzed to obtain unbaked titanium oxide without surface coating of secondary structure particles formed by connecting needle-shaped primary structures as shown in FIG. 1. The TiO ₂ concentration at this time is 50 g/L or more and 140 g/L or less, preferably 60 g/L or more and 120 g/L or less, and the hydrochloric acid concentration is 70 g/L or more and 170 g/L or less, preferably 80 Above g/L and below 160 g/L. In addition, the temperature of hydrolysis is 25°C or more and 60°C or less, preferably 30°C or more and 55°C or less.

In addition, the unbaked titanium oxide without surface coating as shown in Figure 1 can be obtained by hydrolyzing titanium tetrachloride solution or the following solution in addition to orthotitanic acid: For treatment, the solution obtained by dissolving the alkali salt of titanic acid with hydrochloric acid.

In addition, with regard to the uncoated, unbaked titanium oxide of the secondary structure particles formed by connecting primary structures such as straw bundles and short strips, for example, as described in Patent Documents 3 and 4 can be suitably used. The method is obtained by heating, roasting, etc. as necessary.

Regarding the surface coating method of unfired titanium oxide without surface coating, there is no particular limitation. For example, the titanium oxide prepared as described above is added to ion exchange water to prepare a slurry. Secondly, keep the slurry at 70℃, and while stirring, slowly add the inorganic material coating solution containing sodium silicate aqueous solution. After stirring for a specific time, add dilute hydrochloric acid, dilute sulfuric acid and other acids to adjust the pH from 5.0 to 8.0. Perform this operation twice or more to adjust the layer composition or coating amount of the surface coating layer. In addition, by adjusting the composition, concentration, and blending amount of the inorganic material coating solution, the amount of coating of the surface coating layer can also be adjusted.

The resulting slurry is filtered, washed with water, dried, and fired in a muffle furnace or rotary kiln, which is a general roasting furnace, to obtain a surface coating with titanium oxide in the shape shown in Figures 3 and 4 as the main component Roasted pigments. Here, the firing temperature can be set to 500°C or higher and 800°C or lower, more preferably 550°C or higher and 750°C or lower, and the firing time can be set to 0.5 hour to 2.0 hours, more preferably 1.0 hour to 1.5 hours.

When firing unfired titanium oxide without surface coating, in general, the shape changes from the shape of FIG. 1 to the shape of FIG. 2. However, when sintering titanium oxide coated with an inorganic material on the surface, the particle shape of titanium oxide can basically maintain the shape of FIG. 1 as shown in FIGS. 3 and 4.

The properties of the pigment of the present invention, such as retention of the protruding shape on the surface, precipitation resistance, and concealment, can be controlled by, for example, appropriately adjusting the material of the surface coating layer, the firing temperature, and the firing time. [Example]

Examples are listed below to explain the present invention in more detail, but the present invention is not limited to these. In addition, unless otherwise specified below, the compounding amount is expressed in g/kg.

<<Example 1 to Example 3 and Comparative Example 1 to Comparative Example 5>> For the surface-coated calcined pigment with titanium dioxide as the main component obtained by the manufacturing method shown below, the diameter of the equal-area round particles, Specific surface area, apparent bulk density, crystallite diameter, and concealment. In addition, the viscosity and precipitation resistance were evaluated for the composition obtained by the formula and manufacturing method of Table 1 shown below. In Table 1, the amount of SiO ₂ coated on the unfired titanium dioxide without surface coating is described as the "coating amount", the calcined one is described as "present", and the non-calcined titanium dioxide is described as "no".

＜Evaluation of pigments＞ The various evaluations shown below were performed on the prepared pigments, and the results are summarized in Table 1.

(Evaluation of the diameter of round particles of equal area) Regarding the diameter of the equal-area round particles, the H7100 type (manufactured by Hitachi High-Technology Co., Ltd.), which is a transmission electron microscope, was used to magnify it by 100,000 times and set it as an average value of 10 titanium dioxide particles for evaluation.

(Evaluation of specific surface area) The specific surface area was evaluated by the BET method using Macsorb Hmmodel-1208 (manufactured by Mountech).

(Assessment of apparent bulk density) Add about 10 mL of pigment to a 20 mL specific volume test tube for weighing. Using a specific volume tester TAP-ONE TP01 (manufactured by Yamaguchi Mica Co., Ltd.), the weighed test tube was oscillated 200 times and then the volume was measured to calculate the apparent bulk density. In addition, the apparent bulk density was evaluated according to the following criteria.

A: Apparent bulk density≦500 kg/m ³ B: 500 kg/m ³ ＜apparent bulk density≦600 kg/m ³ C: 600 kg/m ³ ＜apparent bulk density

(Evaluation of crystallite diameter) Regarding the crystallite diameter of titanium dioxide, an X-ray diffraction device (Geigerflex, manufactured by Rigaku Electric Co., Ltd.) was used to measure, and the Scherrer formula was applied to calculate the average crystallite diameter.

…式2 隱蔽力差＝(未經表面被覆及焙燒處理之未焙燒之二氧化鈦之色差)-(其他顏料之色差)              …式3(Evaluation of concealment) In order to make the ratio of the pigment 50 g/kg, titanium dioxide was mixed with the nitrocellulose paint and stirred to prepare a slurry. Then, on the black and white concealment rate test paper described in JIS K5400, the slurry was coated with a 0.101 mm applicator and dried to obtain a test sample. For the obtained test sample, the color measurement of the coating film surface on white and black paper was carried out using CM-2600d (manufactured by Konica Minolta) as a spectrophotometer. Calculate the color difference (ΔE) in the Hunter Lab color space by the following equation 2, and use the color difference of the titanium dioxide without surface coating and baking treatment as the reference, and calculate the color difference with other pigments by the following equation 3 ( Poor concealment), and evaluate concealment according to the following criteria: [Number 2]

…Formula 2 Concealment difference = (color difference of unfired titanium dioxide without surface coating and baking treatment)-(color difference of other pigments) …Formula 3

Furthermore, the larger the difference in concealment power, especially if the difference in concealment power is 2.0 or more, the more the concealment is improved.

A: 4.0≦Hidden power difference B: 2.0≦Hiding force difference＜4.0 C: Concealment difference <2.0

＜Evaluation of composition＞ Various evaluations shown below were performed on the prepared composition, and the results are summarized in Table 1.

(Evaluation of viscosity) Regarding the viscosity, MCR-302 (manufactured by Anton-Paar) was used for evaluation. The relative viscosity is the viscosity at a shear rate of 1000/s of the measured object when the measurement is performed at 32°C and 1 atmosphere.

(Evaluation of resistance to precipitation) Add 0.1 g of pigment to a 50 mL test tube for colorimetry, and then inject ion exchange water to make 30 mL, vigorously shake to disperse the titanium dioxide, and prepare a dispersion for evaluation. For the precipitation state of the pigment after a specific time, the ratio of the height of the precipitation interface to the height of the water surface of the dispersion was calculated by a percentage, and the results are summarized in Table 1. The larger the value, especially if it is 90.0% or more after 24 hours and 85.0% or more after 90 hours, the more it can be said that the precipitation resistance is excellent.

<Example 1> (Steps for forming unfired titanium dioxide without surface coating) The titanyl sulfate solution obtained by dissolving clean metatitanic acid with sulfuric acid is slowly added dropwise to 160 g/L sodium carbonate solution at a temperature not exceeding 10°C, and the dropwise addition is stopped when the pH becomes 10.0 Titanium oxysulfate. The white precipitate obtained is filtered by a conventional method and thoroughly washed to obtain orthotitanic acid.

Then, it was cooled to below 10° C., and the washed ortho-titanic acid filter cake was added to concentrated hydrochloric acid, and stirred until the ortho-titanic acid was completely dissolved. Thereafter, the concentration in terms of TiO _{2 was} adjusted to 60 g/L, and the concentration of hydrochloric acid was adjusted to 80 g/L, while stirring, the solution was heated so that the liquid temperature was 55° C., and stirred for 20 hours for hydrolysis. The obtained slurry was neutralized, washed by a conventional method, and dried to obtain titanium dioxide A in the form of secondary structure particles formed by connecting needle-shaped primary structures as shown in FIG. 1.

(Formation step of surface-coated calcined pigment with titanium dioxide as the main component) The obtained uncoated titanium dioxide A without surface coating is dispersed in ion-exchange water to prepare a dispersion. Next, for the dispersion liquid containing titanium dioxide A, a sodium silicate aqueous solution of 50 g/kg calculated as SiO _{2 was} added while stirring, and after stirring for 1 hour, dilute hydrochloric acid was slowly added to adjust the pH to 5.0. Here, the amount of sodium silicate solution is based on the mass of titanium dioxide A before coating, and the amount of SiO ₂ coating is 33 g/kg. The obtained dispersion is filtered, washed with water, and dried by a conventional method to obtain an uncalcined titanium dioxide B coated on the surface.

Then, the surface-coated, unfired titanium dioxide B was fired in a muffle furnace at 550°C for 1 hour to obtain a surface-coated rutile-type fired titanium dioxide C. The particle shape of the obtained calcined titanium dioxide C is shown in FIG. 3, and even after calcining, it presents a protruding shape protruding from the surface almost the same as the shape of the unfired titanium dioxide A without surface coating in FIG.

According to the mixing ratio shown in Table 1 below, the obtained calcined titanium dioxide C was added to ion-exchanged water and vigorously shaken to prepare a composition.

<Example 2> Except that the amount of SiO ₂ coating was changed from 33 g/kg to 20 g/kg, the same procedure as in Example 1 was performed to prepare surface-coated calcined titanium dioxide D, and the surface-coated calcined titanium dioxide was used D, in the same manner as in Example 1, the composition of Example 2 was prepared.

<Example 3> Except that the SiO ₂ coating amount was changed from 33 g/kg to 47 g/kg, the same procedure as in Example 1 was carried out to prepare surface-coated rutile-type calcined titanium dioxide E, and using this titanium dioxide E, In the same manner as in Example 1, the composition of Example 3 was prepared.

<Comparative example 1> The titanium dioxide A without surface coating and baking treatment was prepared by the same method as the formation step of titanium dioxide in Example 1. Then, according to the mixing ratio shown in Table 1 below, the obtained titanium dioxide A was added to ion exchange water and vigorously shaken to prepare the composition of Comparative Example 1.

＜Comparative example 2＞ The titanium dioxide A without surface coating and baking treatment prepared by the same method as the formation step of titanium dioxide without surface treatment and baking treatment in Example 1, was baked in a muffle furnace at 550°C for 1 hour , Preparation of roasted titanium dioxide F without surface coating. Then, according to the mixing ratio shown in Table 1 below, titanium dioxide F was added to ion-exchanged water and vigorously shaken to prepare the composition of Comparative Example 2.

<Comparative Example 3> By the same method as the steps of forming titanium dioxide without surface treatment and baking treatment and the steps of forming surface-coated titanium dioxide in Example 1, surface-treated titanium dioxide B without baking after surface coating was prepared. Then, according to the mixing ratio shown in Table 1 below, the obtained titanium dioxide B was added to ion exchange water and vigorously shaken to prepare the composition of Comparative Example 3.

<Comparative Example 4> Add TIPAQUE (trademark) CR-50 (made by Ishihara Sangyo Co., Ltd.) of pigment-grade rutile titanium dioxide whose particle shape is indefinite according to the mixing ratio shown in Table 1 below, and vigorously shake it to prepare comparison The composition of Example 4.

<Comparative Example 5> According to the mixing ratio shown in Table 1 below, TTO-55(A) (manufactured by Ishihara Sangyo Co., Ltd.) of fine-grained rutile titanium dioxide with needle-like particles was added to ion-exchanged water and vigorously shaken to prepare a comparative example Composition of 5.

[Table 1] ingredient Example Comparative example Titanium dioxide (g) The ratio of surface treatment layer (g/kg) Roasting 1 2 3 1 2 3 4 5 Titanium Dioxide A - no - - - 10 - - - - Titanium Dioxide B 33 no - - - - - 10 - - Titanium Dioxide C 33 Have 10 - - - - - - - Titanium Dioxide D 20 Have - 10 - - - - - - Titanium Dioxide E 47 Have - - 10 - - - - - Titanium Dioxide F - Have - - - - 10 - - - TIPAQUE (Trademark) CR-50 - - - - - - 10 - Ishihara Industry TT0-55(A) - 10 Dispersion medium Ion exchange water 90 90 90 90 90 90 90 90 total 100 100 100 100 100 100 100 100 Evaluation Titanium dioxide Equal area round particle diameter (nm) 250 250 250 250 250 250 300 30 Specific surface area (m ² /g) 38 34 51 108 18 100 5 40 Apparent bulk density (kg/m ³ ) 480 470 500 510 640 540 1030 490 A A A B C B C A Crystallite diameter (nm) 12 13 11 10 twenty four 10 55 8.0 Concealment A A A -(Benchmark) A C A C combination Viscosity (mPa·s) 20 or less 20 or less 20 or less 20 or less 20 or less 20 or less 20 or less 20 or less Resistance to precipitation (%) After 24 hours 93.0 94.5 94.3 87.8 84.0 100.0 80.0 70.5 90 hours later 86.7 90.6 87.7 80.5 74.0 95.0 67.3 56.9

＜Results＞ According to the results of Example 1 to Example 3 and Comparative Example 1 to Comparative Example 3 in Table 1, it can be confirmed that if the surface of titanium dioxide is coated with an inorganic material, the precipitation resistance is improved.

In addition, according to the measurement results of Examples 1 to 3 and Comparative Example 3, it is known that in order to achieve a concealment difference of 2.0 or more, it is necessary to calcinate the titanium dioxide coated with an inorganic material on the surface.

By coating the titanium dioxide with an inorganic material and then baking it, it is possible to obtain titanium dioxide having excellent precipitation resistance and poor hiding power of 2.0 or more.

Figure 1 is a transmission electron micrograph of uncoated and unfired titanium oxide. Figure 2 is a transmission electron micrograph of a fired surface without titanium oxide coating. Fig. 3 is a transmission electron microscope photograph of a surface-coated calcined pigment with a silicon oxide-coated surface-coated titanium oxide as a main component after firing in one embodiment of the present invention. Fig. 4 is a transmission electron microscope photograph of a surface-coated calcined pigment with a surface-coated titania coated with silicon oxide and aluminum oxide as the main component in another embodiment of the present invention.

Claims (12)

A pigment with titanium oxide as the main component, which contains secondary structure particles with protruding shapes on the surface, The above-mentioned secondary structure particles are formed by connecting a plurality of primary structures, The surface of the secondary structure particle is coated with an oxide layer of an inorganic material other than titanium oxide, and the diameter of the equal-area round particle is 150 nm or more and 500 nm or less. The pigment of claim 1, wherein the above-mentioned inorganic material is one or two or more selected from oxides of elements of aluminum, silicon, zinc, titanium, zirconium, iron, cerium, and tin. The pigment of claim 1, wherein the above-mentioned inorganic material is at least one selected from silica and alumina. The pigment of any one of claims 1 to 3, wherein the shape of the primary structure is at least one selected from the group consisting of needle-like, granular, spindle-like, short-striped, straw-like, rod-like, and cocoon-like shapes . The pigment of any one of claims 1 to 4, wherein the apparent bulk density of the above-mentioned titanium oxide is 600 kg/m ³ or less. The pigment of any one of claims 1 to 5, wherein the specific surface area of the above-mentioned titanium oxide is 80 m ² /g or less. For example, the pigment of any one of claims 1 to 6 has a concealment difference of 2.0 or more in the concealment test. Such as the pigment of any one of claims 1 to 7, which is rutile type. Such as the pigment of any one of claims 1 to 8, which is used in cosmetics. A pigment having an equal-area round particle diameter of 150 nm or more and 500 nm or less, and at least one selected from the group consisting of an apparent bulk density of 600 kg/m ³ or less and a specific surface area of 80 m ² /g, and a surface coating There are oxide layers of inorganic materials other than titanium oxide. A composition containing the pigment and dispersing medium according to any one of claims 1 to 10, and the viscosity at a shear rate of 1000/s is 100 mPa·s or less. A method for producing a pigment according to any one of claims 1 to 10, which uses titanium oxide to form a solution to prepare a slurry containing secondary structure particles with a surface protruding shape formed by connecting a plurality of primary structures, and The slurry is added with an inorganic material coating solution containing an inorganic salt aqueous solution used as a raw material for the coating agent, and the secondary structure particles coated with the inorganic material on the surface are fired in the air at 550°C or higher and 750°C or lower.

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