Pressed powder product and its manufacturing method

Abstract

To provide a pressed powder product and a method for manufacturing the product.SOLUTION: A pressed powder product includes a basic pressed powder layer, an ink absorption layer, and a pattern layer. The pattern layer is formed by printing ink, the ink absorption layer is formed by blowing ink absorption coating onto the basic pressed powder layer, the ink absorption coating contains oil control agent, developer, solvent and stabilizer, and the oil control agent consists of hydroxyapatite and kaolin with a mass ratio of (5 to 6):(1 to 2). A method for manufacturing the pressed powder product includes the steps of: uniformly mixing the oil control agent, developer, solvent and stabilizer to obtain a mixture; blowing the mixture onto the basic pressed powder layer, and drying the mixture to obtain a semi-pressed powder product; and printing a pattern on the semi-pressed powder product to obtain a pressed powder product.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] <Cross-reference to related patent applications> This application claims priority to a Chinese patent application filed on November 15, 2022, bearing application number 202211423577.4 and entitled "Pressed powder product with a complete surface pattern and method for manufacturing the same," the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to the technical field of pressed powder product manufacturing, and more particularly to pressed powder products and methods for manufacturing the same. [Background technology]

[0003] Pressed powder products such as powder cake, blush rouge, and eye shadow are made by pressing. Powder cakes are made by mixing the raw materials for making the powder cake and then pressing them in a powder compactor.

[0004] In order to improve the functionality of powder cakes and further increase sales of powder cakes, people usually apply some patterns to the surface of the powder cakes to attract consumers' attention. Currently, pressed powder products with patterns on the surface are mainly produced by spraying a white slurry onto the surface of pressed powder products, which creates a few simple patterns locally.

[0005] Currently, pressed powder products with patterns on their surfaces have only a single color pattern, and only simple patterns can be sprayed on, and the sprayed patterns are incomplete.

[0006] To enhance the surface pattern integrity of a pressed powder product, the present invention provides a pressed powder product and a method for making the same.

[0007] On the one hand, the present invention provides a pressed powder product, which adopts the following technical content:

[0008] The pressed powder product includes a base pressed powder layer, an ink-absorbing layer, and a pattern layer, the pattern layer being formed by printing ink, and the ink-absorbing layer being formed by spraying an ink-absorbing coating onto the base pressed powder layer, the ink-absorbing coating including an oil control agent having a weight percentage of 0.5 to 10%, a color developer having a weight percentage of 0.5 to 20%, a solvent having a weight percentage of 55 to 98.5%, and a stabilizer having a weight percentage of 0.5 to 10%, and the oil control agent being composed of hydroxyapatite and kaolin in a mass ratio of (5 to 6):(1 to 2).

[0009] The developer is titanium dioxide.

[0010] The stabilizer is calcium carbonate.

[0011] The solvent is either an alcohol or isopropanol, and preferably the solvent is an alcohol.

[0012] The oil control agent is composed of hydroxyapatite and kaolin in a mass ratio of (5-6):(1:2). Preferably, the oil control agent is composed of hydroxyapatite and kaolin in a mass ratio of 5:1.

[0013] The kaolin is calcined kaolin.

[0014] By adopting the above technical content, the present invention provides a pattern layer on the surface of a pressed powder product, which is formed by printing ink, to enhance the integrity of the pattern on the surface of the pressed powder product. To reduce ink penetration into the pressed powder product during the printing process, an ink-absorbing layer is provided between the pattern layer and the pressed powder layer, thereby reducing the risk of ink from the pattern layer penetrating into the pressed powder layer and affecting the use of the pressed powder product. The oil-controlling agent in the ink-absorbing layer is a blend of kaolin and hydroxyapatite. Kaolin has a fluffy, porous structure, which is convenient for increasing the volume and thickness of the gaps in the ink-absorbing layer and absorbing ink. The hydroxyapatite reduces ink penetration into the pressed powder layer, while the developer enhances the integrity of the pattern layer. The oil-controlling agent and the developer work together to enhance the integrity and variety of the pattern on the surface of the pressed powder product and reduce the risk of ink penetrating into the pressed powder layer and affecting the use of the pressed powder product.

[0015] The hydroxyapatite is a modified hydroxyapatite, and the method for preparing the modified hydroxyapatite includes the following steps: immersing a chitosan quaternary ammonium salt in a styrene-butadiene emulsion to obtain a pre-treated chitosan quaternary ammonium salt, and mixing the pre-treated chitosan quaternary ammonium salt with the hydroxyapatite to obtain the modified hydroxyapatite.

[0016] The mass ratio of the chitosan quaternary ammonium salt to the hydroxyapatite is 1:(4 to 6).

[0017] By adopting the above technical content, the chitosan quaternary ammonium salt has typical properties of quaternary ammonium salts, such as antibacterial properties, bacteriostatic properties, hygroscopic properties, and moisture retention properties, while maintaining chitosan's inherent good film-forming properties and biocompatibility. Hydroxyapatite is attached to the outer layer of the chitosan quaternary ammonium salt, and the hydroxyapatite forms an oil-controlling layer on the outer layer of the chitosan quaternary ammonium salt. Therefore, while adjusting the ink penetration power of the ink absorbing layer, a certain level of antibacterial properties can be imparted to the ink absorbing layer, thereby enhancing the antibacterial properties when pressed powder products are used.

[0018] The chitosan quaternary ammonium salt is a modified chitosan quaternary ammonium salt, and the modified chitosan quaternary ammonium salt is the chitosan quaternary ammonium salt that has been surface-treated with triethoxyoctylsilane.

[0019] The particle size of the modified chitosan quaternary ammonium salt is 50 nm to 100 nm.

[0020] By adopting the above technical content, after the chitosan quaternary ammonium salt is surface-treated with triethoxyoctylsilane, its surface becomes lipophilic, and therefore has a certain degree of hydrophobicity, making it easy to improve the hydrophobicity of the ink absorbing layer.

[0021] The chitosan quaternary ammonium salt is etched with an organic solvent.

[0022] By adopting the above-mentioned technology, after the chitosan quaternary ammonium salt is etched with an organic solvent, the specific surface area of ​​the chitosan quaternary ammonium salt increases, and the surface roughness of the chitosan quaternary ammonium salt also increases, so that the chitosan quaternary ammonium salt can adhere more styrene-butadiene emulsion and more hydroxyapatite during the immersion process, thereby increasing the density of the oil-control layer, improving the oil control of the oil-control layer, and further reducing the penetration of ink into the pressed powder product.

[0023] In the kaolin, the mass proportion of kaolin in the particle size distribution of 0.5 to 0.8 μm accounts for 20% to 25%, the mass proportion of kaolin in the particle size distribution of 0.8 to 1.5 μm accounts for 30% to 35%, the mass proportion of kaolin in the particle size distribution of 1.5 to 2.0 μm accounts for 25% to 30%, and the mass proportion of kaolin in the particle size distribution of 2.0 to 2.5 μm accounts for 15% to 20%.

[0024] By adopting the above technical content, the present invention adds kaolin with different particle sizes, so that the kaolin is alternately distributed in the ink absorbing layer and fills the gaps in the ink absorbing layer, thereby improving the density of the ink absorbing layer, reducing the penetration of ink into the pressed powder product, and improving the integrity of the pattern.

[0025] The ink absorbing coating further contains 1% to 2% of an adhesive, and the adhesive contains at least both of silicon dioxide, polyvinyl alcohol, and ethylene vinyl acetate copolymer.

[0026] By adopting the above technical content, the addition of an adhesive is convenient for increasing the adhesion between the components of the ink absorbing layer, and the oil control effect of the hydroxyapatite and the color development effect of the color developer are better exerted, thereby improving the integrity of the pattern, and at the same time, increasing the density of the ink absorbing layer and reducing the penetration of ink into the pressed powder product.

[0027] The adhesive is made of silicon dioxide, polyvinyl alcohol, and ethylene vinyl acetate copolymer in a mass ratio of (5-6):(3-4):(1-2).

[0028] By adopting the above technical content, the three components of silicon dioxide, polyvinyl alcohol, and ethylene vinyl acetate copolymer cooperate with each other to produce a good synergistic effect, and polyvinyl alcohol is useful for improving the dispersibility of silicon dioxide and ethylene vinyl acetate in the ink absorbing layer, improving the uniformity of the ink absorbing layer and making the ink spread more uniformly on the surface of the ink absorbing layer. Polyvinyl alcohol and ethylene vinyl acetate have well-matched particle sizes and shapes, and the two can work together to effectively adjust the diffusion and penetration of ink, reduce the penetration of ink into the pressed powder layer, and at the same time improve the stability of the pattern layer.

[0029] On the one hand, the present invention provides a method for producing a pressed powder product.

[0030] The method for producing a pressed powder product includes the following steps: Preparation of the mixture: The oil control agent, the color developer, the solvent, and the stabilizer are uniformly mixed to obtain a mixture containing 0.5-10% by weight of the oil control agent, 0.5-20% by weight of the color developer, 55-98.5% by weight of the solvent, and 0.5-10% by weight of the stabilizer, and the oil control agent is composed of hydroxyapatite and kaolin in a mass ratio of (5-6):(1-2). Preparation of ink-absorbing layer: The mixture is sprayed onto the base pressed powder layer and dried to obtain a semi-pressed powder product. Manufacture of pressed powder product: A pattern is printed on the semi-pressed powder product to obtain a pressed powder product.

[0031] The mixture further comprises an adhesive.

[0032] The mixture further contains 1% to 2% of an adhesive, and the adhesive contains at least both of silicon dioxide, polyvinyl alcohol, and ethylene vinyl acetate copolymer.

[0033] The base pressed powder layer of the present invention is the surface of a pressed powder product such as a powder cake, blush rouge, or eye shadow, which is produced by pressing.

[0034] The drying is carried out in an oven at a drying temperature of 40°C to 50°C for a drying time of 1 to 2 hours.

[0035] By adopting the above technical content, the present invention is convenient for improving the completeness and diversity of the pattern on the surface of the basic pressed powder layer by spraying an ink absorbing layer on the basic pressed powder layer, and at the same time, by adding an oil control agent to the ink absorbing layer, it can reduce the penetration of the ink in the pattern into the basic pressed powder layer.

[0036] The present invention has the following effects.

[0037] 1. The pressed powder product of the present invention comprises a base pressed powder layer, an ink-absorbing layer, and a pattern layer. The pattern layer is convenient for printing the required pattern with ink, and the ink-absorbing layer is convenient as an intermediate layer connecting the pattern layer and the base pressed powder layer. The ink-absorbing layer adjusts the degree of ink absorption and penetration, thereby reducing the direct penetration of ink into the base pressed powder layer and further reducing the impact of the printed pattern on the pressed powder product.

[0038] The ink-absorbing layer of the pressed powder product of the present invention may contain an adhesive, which can enhance the adhesion between the components of the ink-absorbing layer, better exert the oil-controlling effect of the hydroxyapatite and the color-developing effect of the color developer, improve the integrity of the pattern, and at the same time, increase the density of the ink-absorbing layer and reduce the penetration of ink into the pressed powder product. [Brief explanation of the drawings]

[0039] [Figure 1] 1 is a diagram showing the overall structure of a pressed powder product according to an embodiment of the present invention (1, pattern layer; 2, ink absorbing layer; 3, base pressed powder layer). FIG. [Figure 2] FIG. 1 shows the overall structure of a pressed powder product in a comparative example of the present application (1′, pattern layer; 3′, base pressed powder layer). DETAILED DESCRIPTION OF THE INVENTION

[0040] The present invention will be described in further detail below in conjunction with the embodiments.

[0041] Embodiment 1 The pressed powder product is composed of, from bottom to top, a base pressed powder layer 3, an ink-absorbing layer 2, and a pattern layer 1. In this embodiment, the base pressed powder layer 3 is a powder cake, and the ink-absorbing layer 2 is formed by spraying ink-absorbing paint onto the base pressed powder layer 3. The ingredients of the ink-absorbing paint are listed in Table 1. The oil control agent is composed of hydroxyapatite and kaolin in a mass ratio of 5:1, the developer is titanium dioxide, the stabilizer is calcium carbonate, and the solvent is alcohol.

[0042] The method for manufacturing the aforementioned pressed powder product comprises the following steps: (1) Preparation of the mixture: The oil control agent, the color developer, the solvent, and the stabilizer are mixed uniformly to obtain a mixture. (2) Preparation of ink absorbing layer: The mixture prepared in step (1) is sprayed onto the basic pressed powder layer, and dried in an oven at a drying temperature of 50°C for 1 hour to obtain a semi-pressed powder product. (3) Manufacturing of pressed powder product: A pattern is printed on the semi-pressed powder product prepared in step (2) to obtain a pressed powder product. Table 1: Amount of raw materials for ink-absorbing slurry in the ink-absorbing layer of the pressed powder products of embodiments 1 to 6 JPEG0007777564000001.jpg45170

[0043] The pressed powder products of Embodiments 2 to 4 differ from the pressed powder product of Embodiment 1 in that the amounts of raw materials are as shown in Table 1.

[0044] The difference between the pressed powder product of embodiment 5 and the pressed powder product of embodiment 3 is that the dosage of raw materials is as shown in Table 1, and the adhesive is composed of silicon dioxide and polyvinyl alcohol in a mass ratio of 1:1.

[0045] The manufacturing method of the aforementioned pressed powder product includes the following steps: (1) Preparation of the mixture: The oil control agent, the color developer, the solvent, the stabilizer, and the adhesive are mixed uniformly to obtain a mixture. (2) Preparation of ink absorbing layer: The mixture prepared in step (1) is sprayed onto the basic pressed powder layer, and dried in an oven at a drying temperature of 50°C for 1 hour to obtain a semi-pressed powder product. (3) Manufacturing of pressed powder product: A pattern is printed on the semi-pressed powder product prepared in step (2) to obtain a pressed powder product.

[0046] The pressed powder product of embodiment 6 differs from the pressed powder product of embodiment 5 in that the dosage of ingredients is as shown in Table 1.

[0047] The difference between the pressed powder product of embodiment 7 and the pressed powder product of embodiment 5 is that the hydroxyapatite is modified hydroxyapatite. The method for producing the modified hydroxyapatite includes the following steps: immersing chitosan quaternary ammonium salt in a styrene-butadiene emulsion to obtain a pre-treated chitosan quaternary ammonium salt, and mixing the pre-treated chitosan quaternary ammonium salt with hydroxyapatite to obtain a modified hydroxyapatite. The mass ratio of the chitosan quaternary ammonium salt to the hydroxyapatite is 1:6.

[0048] The pressed powder product of embodiment 8 differs from the pressed powder product of embodiment 7 in that the chitosan quaternary ammonium salt used to prepare the modified hydroxyapatite is a modified chitosan quaternary ammonium salt, which is surface-treated with triethoxyoctylsilane. The particle size of the modified chitosan quaternary ammonium salt is 60 nm.

[0049] The difference between the pressed powder product of embodiment 9 and the pressed powder product of embodiment 7 is that the chitosan quaternary ammonium salt used to prepare the modified hydroxyapatite is obtained by etching with an organic solvent to obtain the etched chitosan quaternary ammonium salt, and then surface-treating the etched chitosan quaternary ammonium salt with triethoxyoctylsilane.

[0050] The pressed powder product of embodiment 10 differs from the pressed powder product of embodiment 9 in that the mass proportion of kaolin in the particle size distribution of 0.5 to 0.8 μm is 25%, the mass proportion of kaolin in the particle size distribution of 0.8 to 1.5 μm is 35%, the mass proportion of kaolin in the particle size distribution of 1.5 to 2.0 μm is 25%, and the mass proportion of kaolin in the particle size distribution of 2.0 to 2.5 μm is 15%.

[0051] The pressed powder product of embodiment 11 is different from the pressed powder product of embodiment 10 in that the adhesive is composed of silicon dioxide, polyvinyl alcohol, and ethylene vinyl acetate copolymer in a mass ratio of 5:3:1.

[0052] Embodiment 12: The pressed powder product differs from the pressed powder product of embodiment 10 in that the adhesive is made of silicon dioxide, polyvinyl alcohol, and ethylene vinyl acetate copolymer in a mass ratio of 6:4:2.

[0053] Comparative Example Comparative Example 1: The pressed powder product is, from bottom to top, a base pressed powder layer 3' and a pattern layer 1', and the base pressed powder layer 3 in this comparative example is a powder cake.

[0054] Comparative Example 2: Pressed powder product differs from the pressed powder product of embodiment 1 in that the oil control agent is kaolin.

[0055] Comparative Example 3: Pressed powder product differs from the pressed powder product of Example 1 in that the oil control agent is made of hydroxyapatite and kaolin in a mass ratio of 2:1.

[0056] Comparative Example 4: Pressed powder product differs from the pressed powder product of Example 1 in that the oil control agent is made of hydroxyapatite and kaolin in a mass ratio of 8:1.

[0057] Detection Method Stability test: The pressed powder products manufactured in embodiments 1 to 12 were stored at 50°C and -18°C for one month, and compared with products stored in an incubator at 25°C to observe the stability of the pressed powder products in terms of appearance, color, pattern integrity, practical smear, etc. The test results are shown in Table 2.

[0058] Detection of ink penetration: The pressed powder products manufactured in embodiments 1 to 12 and comparative examples 1 to 4 were taken out, the moisture content of the pressed powder layer was measured using a moisture meter, and the ink penetration thickness of the basic pressed powder layer was calculated. The detection results are shown in Table 2.

[0059] Pattern completeness detection: The pressed powder products manufactured in Examples 1 to 12 and Comparative Examples 1 to 4 were taken out, and the pattern completeness was observed and scored. The scores were divided into 1 to 4, 5 to 7, and 8 to 10. The higher the score, the more complete the pattern. The pattern scoring results are shown in Table 2. Table 2: Performance test results of pressed powder products of Embodiments 1 to 12 and Comparative Examples 1 to 4 JPEG0007777564000002.jpg100170

[0060] Combining the data in Examples 1 to 4 with those in Table 2, it can be seen that the pattern integrity of the pressed powder products prepared in Examples 1 to 4 is relatively high, and remains relatively normal after being stored at 50°C and -18°C for one month. This indicates that the prepared ink-absorbing layer is relatively stable, and the ink that penetrates into the pressed powder layer is less than 2 μm thick, causing little impact on the pressed powder product. The inventors of the present invention speculate that by placing an ink-absorbing layer between the pattern layer and the base pressed powder layer, on the one hand, it is possible to improve the pattern integrity of the pattern layer, and on the other hand, the ink-absorbing layer can act as a buffer layer to reduce ink penetration into the base pressed powder layer, thereby reducing the impact of ink on the pressed powder product and improving the aesthetics of the pressed powder product.

[0061] Combining the data in Table 2 with those in Examples 4 to 6, it can be seen that the pressed powder products produced in Examples 5 and 6 have relatively high pattern integrity, and are relatively normal after being stored at 50°C and -18°C for one month, with the thickness of the ink penetrating into the pressed powder layer being less than 1 μm. The inventors of the present invention speculate that the difference between Examples 5 and 6 and Example 4 is that an adhesive is added to the ink-absorbing coating in Examples 5 and 6, and the adhesive is a blend of silicon dioxide and polyvinyl alcohol. The adhesive strengthens the bonds between the other components of the ink-absorbing coating, improving the density of the ink-absorbing layer. This reduces the size of the gaps between adjacent components of the ink-absorbing layer, allowing for better adjustment of the ink absorption and penetration, improving the stability of the pressed powder product pattern, and reducing the impact of ink penetration on the pressed powder product.

[0062] Combining the data from Examples 5, 7, and Table 2, it can be seen that the pressed powder product produced in Example 7 has relatively high pattern integrity, is relatively normal after storage at 50°C and -18°C for one month, and the thickness of the ink that has penetrated into the pressed powder layer is less than 1 μm. Compared to Example 5, the inventors of the present invention speculate that in Example 7, by encapsulating hydroxyapatite on the surface of the chitosan quaternary ammonium salt, the chitosan quaternary ammonium salt possesses the typical properties of quaternary ammonium salts, such as antibacterial, bacteriostatic, hygroscopic, and moisturizing properties, while maintaining chitosan's inherent good film-forming properties and biocompatibility. The hydroxyapatite is attached to the outer layer of the chitosan quaternary ammonium salt, and the hydroxyapatite forms an oil-control layer on the outer layer of the chitosan quaternary ammonium salt, thereby imparting a certain antibacterial property to the ink absorbing layer by adjusting the ink penetration of the ink absorbing layer.

[0063] Combining the data in Examples 7 and 8 with those in Table 2, it can be seen that the pressed powder product produced in Example 8 has relatively high pattern integrity, is relatively normal after being stored at 50°C and -18°C for one month, and the thickness of the ink that has penetrated into the pressed powder layer is less than 0.7 μm. The inventors of the present invention speculate that the chitosan quaternary ammonium salt of Example 8 is hydrophobized, thereby reducing the water absorption and hygroscopicity of the chitosan quaternary ammonium salt, and at the same time, the hydroxyapatite attached to the surface of the chitosan quaternary ammonium salt can better absorb ink, thereby reducing the thickness of the ink that has penetrated into the basic pressed powder layer.

[0064] Combining the data from Examples 7, 9, and Table 2, it can be seen that the pressed powder product produced in Example 9 has relatively high pattern integrity, and after storage at 50°C and -18°C for one month, it is relatively normal, and the thickness of ink penetration into the pressed powder layer is less than 0.5 μm. The inventors of the present invention believe that in Example 9, the chitosan quaternary ammonium salt is first subjected to an organic solvent etching treatment to increase the specific surface area of ​​the chitosan quaternary ammonium salt and roughen the surface of the chitosan quaternary ammonium salt. The pretreated chitosan quaternary ammonium salt is then subjected to a hydrophobic treatment, which reduces the water absorption of the chitosan quaternary ammonium salt and further reduces the thickness of ink penetration into the basic pressed powder layer.

[0065] Combining the data in Examples 9 and 10 with those in Table 2, it can be seen that the pressed powder product produced in Example 10 has relatively high pattern integrity, and is relatively normal after being stored at 50°C and -18°C for one month, and the thickness of the ink that has penetrated into the pressed powder layer is less than 0.5 μm. The inventors of the present invention speculate that the kaolin in the oil control agent used in the ink-absorbing coating of Example 10 has different particle sizes, and the kaolin with different particle sizes is alternately distributed in the ink-absorbing layer and fills the gaps in the ink-absorbing layer, thereby improving the density of the ink-absorbing layer, reducing the penetration of ink into the pressed powder product, and improving the pattern integrity.

[0066] Combining the data in Examples 10-12 with Table 2, it can be seen that the pressed powder products produced in Examples 11-12 have relatively high pattern integrity, are relatively normal after being stored at 50°C and -18°C for one month, and the thickness of the ink that has penetrated into the pressed powder layer is less than 0.5 μm. The inventors of the present invention speculate that the adhesive in the ink-absorbing coating in Examples 11-12 is a combination of three components: silicon dioxide, polyvinyl alcohol, and ethylene vinyl acetate copolymer, which interacts with the other components in the ink-absorbing coating to reduce ink penetration into the basic pressed powder layer and simultaneously improve the variety and stability of the pattern layer.

[0067] The technical features of the above-described embodiments can be combined in any manner. For the sake of brevity, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as the combinations of these technical features are not contradictory, they should all be considered to be within the scope of the present specification.

[0068] The above-mentioned embodiments only represent some embodiments of the present invention, and although the description is relatively specific and detailed, it should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make some variations and modifications without departing from the spirit and scope of the present invention, and they all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the appended claims. [Explanation of symbols]

[0069] 1 pattern layer 2. Ink absorption layer 3. Pressed powder foundation 1' Pattern layer 3' Basic pressed powder layer

Claims

1. preparing a mixture by uniformly mixing an oil control agent, titanium dioxide, a solvent, and a stabilizer to obtain a mixture, the mixture comprising 0.5-10% by weight of the oil control agent, 0.5-20% by weight of the titanium dioxide, 55-98.5% by weight of the solvent, and 0.5-10% by weight of the stabilizer, the oil control agent being comprised of hydroxyapatite and kaolin in a mass ratio of (5-6):(1-2), and the stabilizer being calcium carbonate; creating an ink-absorbing layer by spraying said mixture onto a base pressed powder layer and drying to obtain a semi-pressed powder product; a step of producing a pressed powder product by printing a pattern on the semi-pressed powder product to obtain a pressed powder product; A method for producing a pressed powder product, comprising:

2. 10. The method of claim 1, wherein the mixture further comprises an adhesive.

3. 2. The method for producing a pressed powder product according to claim 1, wherein the kaolin contains 20% to 25% by mass of kaolin having a particle size distribution of 0.5 to 0.8 μm, 30% to 35% by mass of kaolin having a particle size distribution of 0.8 to 1.5 μm, 25% to 30% by mass of kaolin having a particle size distribution of 1.5 to 2.0 μm, and 15% to 20% by mass of kaolin having a particle size distribution of 2.0 to 2.5 μm.

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