Recycled Titanium Dioxide

Abstract

To provide a method for producing recycled titanium oxide capable of obtaining recycled titanium oxide which has a good powder hue, has a certain range of a primary particle diameter, has a small content of transition metal as impurity, has a good coating hue and has a high hiding rate, from a resin composition containing titanium oxide.SOLUTION: A method for producing recycled titanium oxide subjects a resin composition containing titanium oxide to overheat steam treatment at 550 to 1,000°C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing recycled titanium oxide by treating a resin composition containing titanium oxide, and to the recycled titanium oxide obtained thereby. [Background technology]

[0002] In recent years, driven by environmental and waste problems, there has been a worldwide increase in demand for the recovery and recycling of products consumed on the market. Here, because titanium oxide is used in many products as a white pigment, attempts have been made to recover this titanium oxide and recycle it as recycled titanium oxide.

[0003] For example, Patent Document 1 describes a method for producing recycled titanium dioxide pigment for ink, which comprises Step 1 of preparing raw materials for the pigment, and Step 2 of calcining the raw materials at a temperature of 400 to 800°C and preparing the recycled titanium dioxide pigment from the resulting calcined product. The raw materials in Step 1 are waste plastic film prints containing titanium dioxide pigment. The plastic film prints are plastic film substrates with an ink coating formed on at least one side. The ink coating has a white ink layer formed with a white ink containing a white pigment made of titanium dioxide and a colored ink layer formed with a colored ink containing a colored pigment other than the white ink. The mass ratio of titanium dioxide to solids other than titanium dioxide in the white ink layer is 0.1 to 6.0, and the plastic film substrate has a thickness of 10 to 60 μm.

[0004] Patent Document 2 describes a method for recovering titanium oxide from titanium oxide-containing plastics, which comprises heating a titanium oxide-containing plastic at 800 to 1000°C in an oxygen-containing atmosphere to combust the organic components contained in the titanium oxide-containing plastic and converting the titanium oxide components contained in the titanium oxide-containing plastic to anatase type, and reusing the resulting combustion residue containing anatase type titanium oxide as a raw material for producing titanium oxide using a sulfuric acid method to recover titanium oxide.

[0005] Furthermore, Patent Document 3 describes a method for recovering titanium dioxide, which comprises crushing waste vinyl chloride resin materials containing calcium carbonate and titanium dioxide, heating and dehydrochlorinating the resulting residue, washing the residue with an aqueous liquid, burning and treating the residue, and recovering the resulting residue as titanium dioxide. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 7232375 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-253713 [Patent Document 3] Patent No. 4628721 Summary of the Invention [Problem to be solved by the invention]

[0007] Although Patent Documents 1 to 3 aim to recover titanium oxide, all of them are methods of recovering titanium oxide after calcining in an air atmosphere. The inventors' investigations revealed that in such methods of calcining in an air atmosphere, even if a constant temperature is set, the combustion reaction generates reaction heat, which may sinter and enlarge the titanium oxide. Enlarged titanium oxide has reduced light scattering, and reduced opacity and whiteness, posing quality issues for recycling as recycled titanium oxide.

[0008] The present invention has been made to solve the above-mentioned problems, and has as its object to provide a method for producing recycled titanium oxide that can obtain, from a resin composition containing titanium oxide, recycled titanium oxide that has a good powder color tone, a primary particle size within a certain range, a low content of transition metal impurities, a good paint color tone, and a high hiding power. [Means for solving the problem]

[0009] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by a method for producing recycled titanium oxide, in which a resin composition containing titanium oxide is treated with superheated steam within a certain temperature range, and have completed the present invention.

[0010] That is, the present invention provides: [1] A method for producing recycled titanium oxide, comprising treating a resin composition containing titanium oxide with superheated steam at 550 to 1000°C; [2] The method for producing recycled titanium oxide according to [1], wherein the titanium oxide is washed with an acid before or after the superheated steam treatment; [3] The method for producing recycled titanium oxide according to [1] or [2], wherein the titanium oxide is pulverized after the superheated steam treatment; [4] Recycled titanium oxide obtained by recycling a resin composition containing titanium oxide, wherein the L value of the powder color tone is 50 or more and the D50 measured by TEM is 0.18 μm or more and 0.31 μm or less; [5] Recycled titanium oxide according to [4], having a total acid-insoluble transition metal content of 1.0 mass% or less; [6] The recycled titanium oxide according to [4] or [5], wherein the recycled titanium oxide is molded into a pellet form into powder pellets having a reflectance of 85% or more at a wavelength of 420 nm; [7] The recycled titanium oxide according to any one of [4] to [6], wherein the L value of the paint color tone in the Lab color system of a coating film containing the recycled titanium oxide and boiled linseed oil is 85 or more and the b value is 4.3 or less; [8] A recycled titanium dioxide according to any one of [4] to [7], wherein the L value of the paint color tone in the Lab color system of a coating film containing the recycled titanium dioxide and boiled linseed oil is 93.5 or more, and the hiding rate in a hiding rate test is 99.5% or more; [9] Recycled titanium oxide obtained by recycling a resin composition containing titanium oxide, wherein the L value of the powder color tone is 50 or more and the D10 measured by TEM is 0.29 μm or less;

[10] Recycled titanium oxide obtained by recycling a resin composition containing titanium oxide, wherein the L value of the powder color tone is 50 or more and the D90 measured by TEM is 0.71 μm or less;

[11] Recycled titanium oxide obtained by recycling a resin composition containing titanium oxide, wherein the L value of the powder color tone is 50 or more and the difference between D90 and D10 measured by TEM is 0.46 μm or less;

[12] [4]~

[11] Ink containing recycled titanium dioxide; Regarding. [Effects of the Invention]

[0011] The production method of the present invention makes it possible to obtain recycled titanium oxide from a resin composition containing titanium oxide, which has a good powder color tone, a primary particle size within a certain range, a low content of transition metal impurities, a good paint color tone, and a high hiding power. The recycled titanium oxide thus obtained is of excellent quality and is suitable for use as a white pigment. DETAILED DESCRIPTION OF THE INVENTION

[0012] The method for producing recycled titanium oxide of the present invention is characterized by treating a resin composition containing titanium oxide with superheated steam at 550 to 1000°C (sometimes referred to as the "superheated steam treatment step"). The inventors focused on the fact that the chemical reaction between hydrocarbons such as CH4 and superheated steam is an endothermic reaction, and as a result of extensive research, they discovered that treating a resin composition containing titanium oxide with superheated steam within a fixed temperature range can prevent titanium oxide from sintering and becoming enlarged, while also improving the powder color. As can be seen from a comparison between the Examples and Comparative Examples described below, in the Comparative Example in which the reaction was carried out in air, even when the reaction temperature was set to a constant value, reaction heat was generated due to the combustion reaction. As a result, the primary particle size (D50) of the resulting titanium oxide exceeded a certain value, confirming enlargement. Furthermore, in the Comparative Example in which the reaction was carried out in an inert atmosphere, the color of the resulting titanium oxide powder was not good. In contrast, in the examples in which a resin composition containing titanium oxide was treated with superheated steam within a fixed temperature range, recycled titanium oxide was obtained that had a good powder color tone, a primary particle diameter (D50) within a fixed range, a low content of transition metal impurities, a good paint color tone, and a high hiding power. Therefore, it is clear that there is great significance in adopting the method for producing recycled titanium oxide of the present invention. Furthermore, if a resin composition containing titanium oxide is treated with superheated steam within a fixed temperature range, a reaction under an inert atmosphere may be combined with the superheated steam treatment.

[0013] The type of resin constituting the resin composition is not particularly limited, but examples include polyolefins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymers; polyamides; polyesters; polystyrenes; polyurethanes; polyvinyl chloride; polycarbonates; acrylic resins; epoxy resins; and silicone resins.

[0014] In the present invention, the reaction temperature in the superheated steam treatment step is 550 to 1000°C. If the reaction temperature in the superheated steam treatment step is less than 550°C, the reaction will not proceed sufficiently, and titanium oxide with a good powder color tone will not be obtained. The reaction temperature in the superheated steam treatment step is preferably 580°C or higher, more preferably 600°C or higher, even more preferably 680°C or higher, particularly preferably 750°C or higher, and most preferably 780°C or higher. On the other hand, if the reaction temperature in the superheated steam treatment step exceeds 1000°C, there is a risk of sintering and enlargement of the titanium oxide. The reaction temperature in the superheated steam treatment step is preferably 980°C or lower, more preferably 920°C or lower, and even more preferably 820°C or lower.

[0015] In the present invention, the reaction time of the superheated steam treatment step is not particularly limited. The reaction time in the present invention refers to the time from the start of the superheated steam treatment while maintaining the reaction temperature in the superheated steam treatment step to the completion of the reaction. The reaction time is preferably 0.1 to 10 hours, more preferably 0.2 to 6 hours, and even more preferably 0.5 to 4 hours. Furthermore, the means for maintaining the reaction temperature in the superheated steam treatment step is not particularly limited, and a method of raising the temperature to the desired reaction temperature using superheated steam is preferably employed. That is, a preferred embodiment of the present invention is to raise the temperature to the desired reaction temperature and then perform the superheated steam treatment while maintaining the reaction temperature. The time required for the temperature increase is not particularly limited, and is preferably 0.1 to 4 hours, more preferably 0.2 to 3 hours, and even more preferably 0.5 to 2 hours.

[0016] In the present invention, a preferred embodiment involves washing with an acid before or after the superheated steam treatment (sometimes referred to as an "acid washing step"). This allows the metal oxides and metal salts remaining after the superheated steam treatment to be removed with the acid, making it possible to obtain recycled titanium oxide with high purity and a good powder color tone. Among these, washing with an acid after the superheated steam treatment is a more preferred embodiment. The acid used is not particularly limited, and any water-soluble inorganic or organic acid may be used. Suitable inorganic acids include at least one selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and hydrofluoric acid, and suitable organic acids include at least one selected from the group consisting of acetic acid, oxalic acid, and citric acid. Among these, at least one acid selected from the group consisting of sulfuric acid, hydrochloric acid, and nitric acid is more preferred. A preferred method for washing with an acid involves adding an aqueous solution of the aforementioned acid to the titanium oxide after the superheated steam treatment and mixing it. A preferred embodiment involves performing a filtration and water washing step after the acid washing step. Known methods can be used for the filtration and water washing step. In a preferred embodiment, a drying step is carried out after the filtration and washing step, and the drying temperature is preferably 100 to 130°C, and more preferably 105 to 115°C.

[0017] In the present invention, pulverization (sometimes referred to as the "pulverization step") after the superheated steam treatment is a preferred embodiment. As a pulverization method, pulverization is preferably performed using a known pulverizer or the like. The pulverizer is not particularly limited, and an ultracentrifugal pulverizer, ball mill, airflow mill, hammer mill, Raikai mill, or the like can be used. By this pulverization, recycled titanium oxide having a primary particle size (D50) within a certain range can be obtained. The pulverization is preferably performed as the final step for obtaining recycled titanium oxide. Therefore, it is a preferred embodiment that the acid washing step is performed before the pulverization step.

[0018] The recycled titanium oxide obtained by the present invention has an L value of powder color tone of 50 or more, and a D50 measured by TEM of 0.18 μm or more and 0.31 μm or less. Since the L value of powder color tone is a certain level or more and the D50 measured by TEM is within a certain range, it can be recycled as high-quality recycled titanium oxide. The L value of powder color tone is preferably 50 or more, more preferably 70 or more, even more preferably 85 or more, particularly preferably 92 or more, and most preferably 95 or more. The L value of powder color tone indicates the L value in the Lab color system measured using a colorimeter.

[0019] Furthermore, the D50 measured by TEM is preferably 0.18 μm or more, more preferably 0.21 μm or more, even more preferably 0.22 μm or more, and most preferably 0.23 μm or more. On the other hand, the D50 measured by TEM is preferably 0.31 μm or less, preferably 0.30 μm or less, and even more preferably 0.29 μm or less. The D50 measured by TEM refers to the particle diameter at 50% of the cumulative total in the volume-based particle size distribution, which is obtained by photographing a certain number of primary particles of titanium oxide using a transmission electron microscope and measuring the particle size distribution using image analysis particle size distribution measurement software.

[0020] Furthermore, the recycled titanium oxide obtained by the present invention has a powder color L value of 50 or more and a D10 measured by TEM of 0.29 μm or less. Because the powder color L value is above a certain level and the D10 measured by TEM is within a certain range, it can be recycled as high-quality recycled titanium oxide.

[0021] The D10 measured by TEM is preferably 0.29 μm or less, more preferably 0.27 μm or less, even more preferably 0.25 μm or less, and most preferably 0.24 μm or less. The D10 measured by TEM is preferably 0.12 μm or more, more preferably 0.16 μm or more, and even more preferably 0.20 μm or more. The D10 measured by TEM refers to the particle size at 10% of the cumulative particle size in the volume-based particle size distribution obtained by photographing a certain number of primary particles of titanium oxide using a transmission electron microscope and measuring the particle size distribution using image analysis particle size distribution measurement software.

[0022] Furthermore, the recycled titanium oxide obtained by the present invention has a powder color L value of 50 or more and a D90 measured by TEM of 0.71 μm or less. Because the powder color L value is above a certain level and the D90 measured by TEM is within a certain range, it can be recycled as high-quality recycled titanium oxide.

[0023] The D90 measured by TEM is preferably 0.71 μm or less, more preferably 0.68 μm or less, even more preferably 0.65 μm or less, and most preferably 0.64 μm or less. The D90 measured by TEM is preferably 0.23 μm or more, more preferably 0.27 μm or more, and even more preferably 0.32 μm or more. The D90 measured by TEM refers to the particle size at 90% of the cumulative particle size in the volume-based particle size distribution obtained by photographing a certain number of primary particles of titanium oxide using a transmission electron microscope and measuring the particle size distribution using image analysis particle size distribution measurement software.

[0024] Furthermore, the recycled titanium oxide obtained by the present invention has a powder color L value of 50 or more, and the difference between D90 and D10 measured by TEM (sometimes referred to as "D90-D10") is 0.46 μm or less. Because the powder color L value is a certain level or more and the difference between D90 and D10 measured by TEM is within a certain range, it can be recycled as high-quality recycled titanium oxide.

[0025] The difference between D90 and D10 measured by TEM is preferably 0.46 μm or less, more preferably 0.41 μm or less, and even more preferably 0.36 μm or less.The difference between D90 and D10 measured by TEM is preferably 0.06 μm or more.

[0026] The recycled titanium oxide obtained by the present invention preferably has a total acid-insoluble transition metal content of 1.0% by mass or less. The total acid-insoluble transition metal content refers to the total transition metal content remaining after the acid washing step, and the transition metals are derived from metal oxides, metal salts, etc. contained in the resin composition. Specifically, it refers to the total content of transition metals derived from CuO and Fe2O3. If the transition metal content exceeds 1.0% by mass, the whiteness may decrease, potentially making the quality insufficient for recycling. The transition metal content is more preferably 0.8% by mass or less, even more preferably 0.6% by mass or less, particularly preferably 0.4% by mass or less, and most preferably 0.3% by mass or less. On the other hand, the transition metal content is 0% by mass or more, and may be 0.005% by mass or more, 0.01% by mass or more, or 0.05% by mass or more.

[0027] The powder pellets obtained by molding the recycled titanium oxide obtained by the present invention into pellets preferably have a reflectance at a wavelength of 420 nm of 85% or more. Having a reflectance of at least a certain level allows the powder to be recycled as high-quality recycled titanium oxide. The reflectance is more preferably 87% or more, even more preferably 88% or more, and particularly preferably 94% or more. The reflectance is usually 100% or less.

[0028] The recycled titanium oxide obtained by the present invention preferably has a paint color tone in the Lab color system of a coating film containing the recycled titanium oxide and boiled linseed oil, with an L value of 85 or more and a b value of 4.3 or less. If the L value of the paint color tone is less than 85, the quality may be insufficient for recycling, and the L value is more preferably 88 or more, more preferably 90 or more, even more preferably 92 or more, particularly preferably 93.5 or more, and most preferably 94 or more. The L value of the paint color tone is usually 99 or less. Furthermore, if the b value of the paint color tone exceeds 4.3, the quality may be insufficient for recycling, and the L value is more preferably 4.2 or less, even more preferably 4.1 or less, particularly preferably 4.0 or less, and most preferably 3.9 or less. The L value and b value of the paint color tone respectively represent the L value and b value in the Lab color system measured using a colorimetric color difference meter.

[0029] Furthermore, the recycled titanium oxide obtained by the present invention preferably has a hiding rate of 99.5% or more in a coating film containing the recycled titanium oxide and boiled linseed oil in a hiding rate test. If the hiding rate is less than 99.5%, the quality may be insufficient when used as a paint, so a hiding rate of 99.6% or more is more preferable, 99.7% or more is even more preferable, and 99.8% or more is particularly preferable. The hiding rate is usually 100% or less. The hiding rate is calculated according to JIS K5600 (general testing method for paints) by measuring the L value in the Lab color system using a colorimeter for coating films painted on a white board and a blackboard, respectively, and using the following formula:

number

[0030] The recycled titanium oxide obtained by the present invention has a good powder color tone, a primary particle size within a certain range, a low content of transition metal impurities, a good paint color tone, and a high hiding power. Therefore, it is suitable for use as a white pigment in paints, inks, paper, molding resin compounds, and the like. Among these, ink containing the recycled titanium oxide obtained by the present invention is a more preferred embodiment. The recycled titanium oxide obtained by the present invention is obtained by recovering it from a resin composition containing titanium oxide. Therefore, a method for recovering recycled titanium oxide from a resin composition containing titanium oxide is a preferred embodiment, and a resin composition containing recycled titanium oxide obtained by the present invention is also a preferred embodiment. [Example]

[0031] The present invention will be explained in more detail below using examples.

[0032] Preparation example 1 90g of titanium oxide, 3.3g of phthalocyanine blue (0.5% by mass of CuO relative to 100% by mass of titanium oxide), 100g of polyurethane resin, and 73.3g of solvent were mixed together in a 400mL mayonnaise bottle together with 180g of 1.5mm glass beads, and dispersed for 1 hour using a paint conditioner (manufactured by Red Devil) to prepare an ink. The following ingredients were used: Titanium oxide: "Titanix JR-707" (manufactured by Teika Co., Ltd.) Phthalocyanine Blue: "Phthalocyanine Blue" (Fujifilm Wako Pure Chemical Industries, Ltd.) Polyurethane resin: "Sanprene IB-422" (manufactured by Sanyo Chemical Industries, Ltd.) Solvent: A mixed solvent of methyl ethyl ketone, isopropyl alcohol, and toluene (1:1:1 by mass) This procedure was repeated several times to prepare a total of 13 kg of ink. The resulting 13 kg of ink was spread thinly and dried at 120°C for 12 hours to obtain 6 kg of a titanium oxide resin composition containing 0.5 mass% of CuO.

[0033] Preparation example 2 90g of titanium oxide, 6.6g of phthalocyanine blue (1.0% by mass of CuO relative to 100% by mass of titanium oxide), 100g of polyurethane resin, and 73.3g of solvent were mixed together in a 400mL mayonnaise bottle together with 180g of 1.5mm glass beads, and dispersed for 1 hour using a paint conditioner (manufactured by Red Devil) to prepare an ink. The following ingredients were used: Titanium oxide: "Titanix JR-707" (manufactured by Teika Co., Ltd.) Phthalocyanine Blue: "Phthalocyanine Blue" (Fujifilm Wako Pure Chemical Industries, Ltd.) Polyurethane resin: "Sanprene IB-422" (manufactured by Sanyo Chemical Industries, Ltd.) Solvent: A mixed solvent of methyl ethyl ketone, isopropyl alcohol, and toluene (1:1:1 by mass) This procedure was repeated several times to prepare a total of 13 kg of ink. The resulting 13 kg of ink was spread thinly and dried at 120°C for 12 hours to obtain 6 kg of a titanium oxide resin composition containing 1.0 mass% of CuO.

[0034] Preparation example 3 90g of titanium oxide, 3.3g of phthalocyanine blue (0.5% by mass of CuO relative to 100% by mass of titanium oxide), 0.45g of iron(III) oxide (0.5% by mass of Fe2O3 relative to 100% by mass of titanium oxide), 100g of polyurethane resin, and 73.3g of solvent were mixed together in a ratio of 1:1, placed in a 400mL mayonnaise bottle with 180g of 1.5mm glass beads, and dispersed for 1 hour using a paint conditioner (manufactured by Red Devil) to prepare an ink. The following ingredients were used: Titanium oxide: "Titanix JR-707" (manufactured by Teika Co., Ltd.) Phthalocyanine Blue: "Phthalocyanine Blue" (Fujifilm Wako Pure Chemical Industries, Ltd.) Iron (III) oxide: "Iron (III) oxide" (Fujifilm Wako Pure Chemical Industries, Ltd.) Polyurethane resin: "Sanprene IB-422" (manufactured by Sanyo Chemical Industries, Ltd.) Solvent: A mixed solvent of methyl ethyl ketone, isopropyl alcohol, and toluene (1:1:1 by mass) This procedure was repeated several times to prepare a total of 13 kg of ink. The resulting 13 kg of ink was spread thinly and dried at 120°C for 12 hours to obtain 6 kg of a titanium oxide resin composition containing 0.5 mass% CuO and 0.5 mass% Fe2O3.

[0035] Preparation example 4 90g of titanium oxide, 3.3g of phthalocyanine blue (0.5% by mass of CuO relative to 100% by mass of titanium oxide), 100g of polyurethane resin, and 73.3g of solvent were mixed together in a 400mL mayonnaise bottle together with 180g of 1.5mm glass beads, and dispersed for 1 hour using a paint conditioner (manufactured by Red Devil) to prepare an ink. The following ingredients were used: Titanium oxide: "Titanix JR-809" (manufactured by Teika Co., Ltd.) Phthalocyanine Blue: "Phthalocyanine Blue" (Fujifilm Wako Pure Chemical Industries, Ltd.) Polyurethane resin: "Sanprene IB-422" (manufactured by Sanyo Chemical Industries, Ltd.) Solvent: A mixed solvent of methyl ethyl ketone, isopropyl alcohol, and toluene (1:1:1 by mass) This procedure was repeated several times to prepare a total of 13 kg of ink. The resulting 13 kg of ink was spread thinly and dried at 120°C for 12 hours to obtain 6 kg of a titanium oxide resin composition containing 0.5 mass% of CuO.

[0036] Preparation example 5 6 kg of the resin composition prepared in Preparation Example 1 was cut into 1 cm cubes and immersed in 30 kg of 1 mass % sodium hydroxide solution for 1 hour. 100 L of water was added to 20 kg of the immersed material (water content 70 mass %), stirred for 30 minutes, and the sample collected by filtration was washed with twice the amount of water. It was then dried in a dryer at 110°C for 24 hours, yielding 6 kg of an alkali-cleaning titanium oxide resin composition containing 0.5 mass % CuO.

[0037] Example 1 1 kg of the resin composition of Preparation Example 1 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.), and the temperature was raised from room temperature to 150°C over 1 hour. Superheated steam (600°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 600°C over 1 hour, and the temperature was maintained for 1 hour, allowing the contents to undergo steam pyrolysis. The resulting powder was pulverized to obtain recycled titanium oxide.

[0038] Example 2 1 kg of the resin composition of Preparation Example 5 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.), and the temperature was raised from room temperature to 150°C over 1 hour. Superheated steam (700°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 700°C over 1 hour, and the temperature was maintained for 1 hour, allowing the contents to undergo steam pyrolysis. The resulting powder was pulverized to obtain recycled titanium oxide.

[0039] Example 3 1 kg of the resin composition of Preparation Example 1 was placed in a batch-type superheated steam furnace (manufactured by Takasago Industrial Co., Ltd.), and the temperature was raised from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour, and the temperature was maintained for 1 hour to allow steam pyrolysis of the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0040] Example 4 1 kg of the resin composition of Preparation Example 1 was placed in a batch-type superheated steam furnace (manufactured by Takasago Industrial Co., Ltd.), and the temperature was raised from room temperature to 150°C over 1 hour. Superheated steam (900°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 900°C over 1 hour, and the temperature was maintained for 1 hour, allowing the contents to undergo steam pyrolysis. The resulting powder was pulverized to obtain recycled titanium oxide.

[0041] Example 5 1 kg of the resin composition of Preparation Example 1 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.), and the temperature was raised from room temperature to 150°C over 1 hour. Superheated steam (1000°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 1000°C over 1 hour, and the temperature was maintained for 1 hour, allowing the contents to undergo steam pyrolysis. The resulting powder was pulverized to obtain recycled titanium oxide.

[0042] Example 6 1 kg of the resin composition of Preparation Example 1 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.), and the temperature was raised from room temperature to 150°C over 1 hour. Superheated steam (550°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 550°C over 1 hour, and the temperature was maintained for 1 hour to allow steam pyrolysis of the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0043] Example 7 1 kg of the resin composition of Preparation Example 1 was placed in a batch-type superheated steam furnace (manufactured by Takasago Industrial Co., Ltd.), and the temperature was raised from room temperature to 150°C over 1 hour. Superheated steam (580°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 580°C over 1 hour, and the temperature was maintained for 1 hour to allow steam pyrolysis of the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0044] Example 8 1 kg of the resin composition of Preparation Example 1 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.) and heated from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour and maintained at that temperature for 1 hour, allowing the contents to undergo steam pyrolysis. 650 mL of 50% by mass sulfuric acid was added to 500 g of the resulting titanium dioxide pigment, and water was added to make a 5 L volume while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The resulting powder was pulverized to obtain recycled titanium dioxide.

[0045] Example 9 1 kg of the resin composition of Preparation Example 1 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.) and heated from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour and maintained at that temperature for 1 hour, allowing the contents to undergo steam pyrolysis. 650 mL of 50% by mass nitric acid was added to 500 g of the resulting titanium oxide pigment, and water was added to make a 5 L volume while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The resulting powder was pulverized to obtain recycled titanium oxide.

[0046] Example 10 1 kg of the resin composition of Preparation Example 5 was placed in a batch-type superheated steam furnace (manufactured by Takasago Industrial Co., Ltd.) and heated from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour and maintained at that temperature for 1 hour, allowing the contents to undergo steam pyrolysis. 650 mL of 50% by mass hydrochloric acid was added to 500 g of the resulting titanium dioxide pigment, and water was added to the resulting solution to 5 L while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The resulting powder was pulverized to obtain recycled titanium dioxide.

[0047] Example 11 1 kg of the resin composition of Preparation Example 2 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.) and heated from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour and maintained at that temperature for 1 hour, allowing the contents to undergo steam pyrolysis. 650 mL of 50% by mass sulfuric acid was added to 500 g of the resulting titanium dioxide pigment, and water was added to make a 5 L volume while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The resulting powder was pulverized to obtain recycled titanium dioxide.

[0048] Example 12 1 kg of the resin composition of Preparation Example 2 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.) and heated from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour and maintained at that temperature for 1 hour, allowing the contents to undergo steam pyrolysis. 650 mL of 50% by mass nitric acid was added to 500 g of the resulting titanium oxide pigment, and water was added to the resulting solution to 5 L while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The resulting powder was pulverized to obtain recycled titanium oxide.

[0049] Example 13 1 kg of the resin composition of Preparation Example 2 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.) and heated from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour and maintained at that temperature for 1 hour, allowing the contents to undergo steam pyrolysis. 650 mL of 50% by mass hydrochloric acid was added to 500 g of the resulting titanium dioxide pigment, and water was added to the resulting solution to 5 L while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The resulting powder was pulverized to obtain recycled titanium dioxide.

[0050] Example 14 1 kg of the resin composition of Preparation Example 3 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.) and heated from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour and maintained at that temperature for 1 hour, allowing the contents to undergo steam pyrolysis. 650 mL of 50% by mass sulfuric acid was added to 500 g of the resulting titanium oxide pigment, and water was added to make a 5 L volume while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The resulting powder was pulverized to obtain recycled titanium oxide.

[0051] Example 15 1 kg of the resin composition of Preparation Example 3 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.) and heated from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour and maintained at that temperature for 1 hour, allowing the contents to undergo steam pyrolysis. 650 mL of 50% by mass nitric acid was added to 500 g of the resulting titanium oxide pigment, and water was added to the resulting solution to 5 L while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The resulting powder was pulverized to obtain recycled titanium oxide.

[0052] Example 16 1 kg of the resin composition of Preparation Example 3 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.) and heated from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour and maintained at that temperature for 1 hour, allowing the contents to undergo steam pyrolysis. 650 mL of 50% by mass hydrochloric acid was added to 500 g of the resulting titanium dioxide pigment, and water was added to the resulting solution to 5 L while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The resulting powder was pulverized to obtain recycled titanium dioxide.

[0053] Example 17 1 kg of the resin composition of Preparation Example 1 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermosystems Corporation), heated from room temperature to 800°C in 1 hour under a nitrogen atmosphere, and held at that temperature for 6 hours to pyrolyze the contents. The resulting pyrolysis product was then placed in a batch-type superheated steam furnace (trade name: manufactured by Takasago Kogyo Co., Ltd.), heated from room temperature to 150°C in 1 hour, and then heated to 800°C in 1 hour by introducing superheated steam (800°C x 5 kg / hr) into the furnace. The temperature was held for 1 hour to pyrolyze the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0054] Example 18 1 kg of the resin composition of Preparation Example 4 was placed in a batch-type superheated steam furnace (manufactured by Takasago Industrial Co., Ltd.), and the temperature was raised from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour, and the temperature was maintained for 1 hour to allow steam pyrolysis of the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0055] Comparative Example 1 1 kg of the resin composition of Preparation Example 1 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corp.), heated from room temperature to 500°C over 1 hour, and then held at that temperature for 12 hours to calcinate the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0056] Comparative Example 2 1 kg of the resin composition of Preparation Example 1 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corp.), heated from room temperature to 600°C over 1 hour, and then held at that temperature for 12 hours to calcinate the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0057] Comparative Example 3 1 kg of the resin composition of Preparation Example 5 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corp.), heated from room temperature to 700°C over 1 hour, and then held at that temperature for 12 hours to calcinate the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0058] Comparative Example 4 1 kg of the resin composition of Preparation Example 1 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corp.), heated from room temperature to 800°C over 1 hour, and then held at that temperature for 12 hours to calcinate the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0059] Comparative Example 5 1 kg of the resin composition of Preparation Example 1 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corporation), heated from room temperature to 900°C over 1 hour, and then held at that temperature for 12 hours to calcinate the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0060] Comparative Example 6 1 kg of the resin composition of Preparation Example 1 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corporation), heated from room temperature to 1000°C over 1 hour, and then held at that temperature for 12 hours to calcinate the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0061] Comparative Example 7 1 kg of the resin composition of Preparation Example 1 was placed in a batch-type superheated steam furnace (manufactured by Takasago Industrial Co., Ltd.), and the temperature was raised from room temperature to 150°C over 1 hour. Superheated steam (500°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 500°C over 1 hour, and the temperature was maintained for 1 hour to allow steam pyrolysis of the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0062] Comparative Example 8 1 kg of the resin composition of Preparation Example 1 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corporation), heated from room temperature to 800°C over 1 hour, and then maintained at that temperature for 12 hours to calcinate the contents. 650 mL of 50% by mass sulfuric acid was added to 500 g of the obtained titanium oxide pigment, and water was added to make a total volume of 5 L while stirring well. The obtained liquid was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The obtained powder was pulverized to obtain recycled titanium oxide.

[0063] Comparative Example 9 1 kg of the resin composition of Preparation Example 1 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corporation), heated from room temperature to 800°C over 1 hour, and then maintained at that temperature for 12 hours to calcinate the contents. 650 mL of 50% by mass nitric acid was added to 500 g of the obtained titanium oxide pigment, and water was added to make a total volume of 5 L while stirring well. The obtained liquid was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The obtained powder was pulverized to obtain recycled titanium oxide.

[0064] Comparative Example 10 1 kg of the resin composition of Preparation Example 5 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermosystems Corporation), heated from room temperature to 800°C over 1 hour, and then maintained at that temperature for 12 hours to calcinate the contents. 650 mL of 50% by mass hydrochloric acid was added to 500 g of the obtained titanium oxide pigment, and water was added to make a total volume of 5 L while stirring well. The resulting liquid was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The obtained powder was pulverized to obtain recycled titanium oxide.

[0065] Comparative Example 11 1 kg of the resin composition of Preparation Example 1 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corporation), and the temperature was raised from room temperature to 800°C in 1 hour under a nitrogen atmosphere and maintained at that temperature for 6 hours to pyrolyze the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0066] Comparative Example 12 1 kg of the resin composition of Preparation Example 1 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corporation), and the temperature was raised from room temperature to 800°C over 1 hour in a nitrogen atmosphere and maintained at that temperature for 6 hours to pyrolyze the contents. The resulting pyrolysis product was then placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corporation), and the temperature was raised from room temperature to 500°C over 1 hour in air and maintained at that temperature for 6 hours to calcinate the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0067] Comparative Example 13 1 kg of the resin composition of Preparation Example 1 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corporation), and the temperature was raised from room temperature to 800°C over 1 hour in a nitrogen atmosphere and maintained at that temperature for 6 hours to pyrolyze the contents. The resulting pyrolysis product was then placed in a small electric furnace KBF828N2 (trade name: manufactured by JTEKT Thermo Systems Corporation), and the temperature was raised from room temperature to 800°C over 1 hour in air and maintained at that temperature for 6 hours to calcinate the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0068] Comparative Example 14 1 kg of the resin composition of Preparation Example 4 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corp.), heated from room temperature to 800°C over 1 hour, and then held at that temperature for 12 hours to calcinate the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0069] Preparation Example 6 120g of titanium dioxide, 4.4g of phthalocyanine blue (0.5% by mass of CuO relative to 100% by mass of titanium dioxide), 28.8g of alkyd resin, and 28.8g of solvent were mixed together and placed in a 400mL mayonnaise bottle along with 300g of 1.5mm glass beads. The mixture was dispersed for 1 hour using a paint conditioner (manufactured by Red Devil). 111.2g of alkyd resin and 60.0g of butylated melamine resin were then added to prepare the paint. The following ingredients were used: Titanium oxide: "Titanix JR-600A" (manufactured by Teika Co., Ltd.) Phthalocyanine Blue: "Phthalocyanine Blue" (Fujifilm Wako Pure Chemical Industries, Ltd.) Alkyd resin: "Alkidia J-524-A" (DIC Corporation) Butylated melamine resin: "Amidia J-820-60" (DIC Corporation) Solvent: Mixed solvent of xylene / n-butanol = 4 / 1 by mass This procedure was repeated several times to prepare a total of 18 kg of paint. The resulting 18 kg of paint was spread thinly and dried at 120°C for 12 hours to obtain 6 kg of a titanium oxide resin composition containing 0.5 mass% of CuO.

[0070] Example 19 1 kg of the resin composition of Preparation Example 6 was placed in a batch-type superheated steam furnace (manufactured by Takasago Industrial Co., Ltd.), and the temperature was raised from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour, and the temperature was maintained for 1 hour, allowing the contents to undergo steam pyrolysis. The resulting powder was pulverized to obtain recycled titanium oxide.

[0071] Example 20 1 kg of the resin composition of Preparation Example 6 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.) and heated from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour and maintained at that temperature for 1 hour, allowing the contents to undergo steam pyrolysis. 650 mL of 50% by mass sulfuric acid was added to 500 g of the resulting titanium dioxide pigment, and water was added to make a 5 L volume while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The resulting powder was pulverized to obtain recycled titanium dioxide.

[0072] Example 21 1 kg of the resin composition of Preparation Example 6 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.) and heated from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour and maintained at that temperature for 1 hour, allowing the contents to undergo steam pyrolysis. 650 mL of 50% by mass nitric acid was added to 500 g of the resulting titanium oxide pigment, and water was added to the resulting solution to 5 L while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The resulting powder was pulverized to obtain recycled titanium oxide.

[0073] Example 22 1 kg of the resin composition of Preparation Example 6 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.) and heated from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour and maintained at that temperature for 1 hour, allowing the contents to undergo steam pyrolysis. 650 mL of 50% by mass hydrochloric acid was added to 500 g of the resulting titanium dioxide pigment, and water was added to the resulting solution to 5 L while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The resulting powder was pulverized to obtain recycled titanium dioxide.

[0074] Comparative Example 15 1 kg of the resin composition of Preparation Example 6 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corporation), heated from room temperature to 800°C over 1 hour, and then held at that temperature for 12 hours to calcinate the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0075] Comparative Example 16 1 kg of the resin composition of Preparation Example 6 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermosystems Corporation), heated from room temperature to 800°C over 1 hour, and then maintained at that temperature for 12 hours to calcinate the contents. 650 mL of 50% by mass sulfuric acid was added to 500 g of the obtained titanium oxide pigment, and water was added to make a total volume of 5 L while stirring well. The resulting liquid was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The obtained powder was pulverized to obtain recycled titanium oxide.

[0076] Comparative Example 17 1 kg of the resin composition of Preparation Example 6 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corporation), heated from room temperature to 800°C over 1 hour, and then maintained at that temperature for 12 hours to calcinate the contents. 650 mL of 50% by mass nitric acid was added to 500 g of the obtained titanium oxide pigment, and water was added to make a total volume of 5 L while stirring well. The resulting liquid was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The obtained powder was pulverized to obtain recycled titanium oxide.

[0077] Comparative Example 18 1 kg of the resin composition of Preparation Example 6 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermosystems Corporation), heated from room temperature to 800°C over 1 hour, and then maintained at that temperature for 12 hours to calcinate the contents. 650 mL of 50% by mass hydrochloric acid was added to 500 g of the obtained titanium oxide pigment, and water was added to make a total volume of 5 L while stirring well. The resulting liquid was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The obtained powder was pulverized to obtain recycled titanium oxide.

[0078] Preparation Example 7 120g of titanium dioxide, 4.4g of phthalocyanine blue (0.5% by mass of CuO relative to 100% by mass of titanium dioxide), 28.8g of alkyd resin, and 28.8g of solvent were mixed together and placed in a 400mL mayonnaise bottle along with 300g of 1.5mm glass beads. The mixture was dispersed for 1 hour using a paint conditioner (manufactured by Red Devil). 111.2g of alkyd resin and 60.0g of butylated melamine resin were then added to prepare the paint. The following ingredients were used: Titanium oxide: "Titanix JR-805" (manufactured by Teika Co., Ltd.) Phthalocyanine Blue: "Phthalocyanine Blue" (Fujifilm Wako Pure Chemical Industries, Ltd.) Alkyd resin: "Alkidia J-524-A" (DIC Corporation) Butylated melamine resin: "Amidia J-820-60" (DIC Corporation) Solvent: Mixed solvent of xylene / n-butanol = 4 / 1 by mass This procedure was repeated several times to prepare a total of 18 kg of paint. The resulting 18 kg of paint was spread thinly and dried at 120°C for 12 hours to obtain 6 kg of a titanium oxide resin composition containing 0.5 mass% of CuO.

[0079] Example 23 1 kg of the resin composition of Preparation Example 7 was placed in a batch-type superheated steam furnace (manufactured by Takasago Industrial Co., Ltd.), and the temperature was raised from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour, and the temperature was maintained for 1 hour, allowing the contents to undergo steam pyrolysis. The resulting powder was pulverized to obtain recycled titanium oxide.

[0080] Example 24 1 kg of the resin composition of Preparation Example 7 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.) and heated from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour and maintained at that temperature for 1 hour, allowing the contents to undergo steam pyrolysis. 650 mL of 50% by mass sulfuric acid was added to 500 g of the resulting titanium dioxide pigment, and water was added to make a 5 L volume while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The resulting powder was pulverized to obtain recycled titanium dioxide.

[0081] Example 25 1 kg of the resin composition of Preparation Example 7 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.) and heated from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour and maintained at that temperature for 1 hour, allowing the contents to undergo steam pyrolysis. 650 mL of 50% by mass nitric acid was added to 500 g of the resulting titanium dioxide pigment, and water was added to the resulting solution to 5 L while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The resulting powder was pulverized to obtain recycled titanium dioxide.

[0082] Example 26 1 kg of the resin composition of Preparation Example 7 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.) and heated from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour and maintained at that temperature for 1 hour, allowing the contents to undergo steam pyrolysis. 650 mL of 50% by mass hydrochloric acid was added to 500 g of the resulting titanium dioxide pigment, and water was added to the resulting solution to 5 L while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The resulting powder was pulverized to obtain recycled titanium dioxide.

[0083] Comparative Example 19 1 kg of the resin composition of Preparation Example 7 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corp.), heated from room temperature to 800°C over 1 hour, and then held at that temperature for 12 hours to calcinate the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0084] Comparative Example 20 1 kg of the resin composition of Preparation Example 7 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corporation), heated from room temperature to 800°C over 1 hour, and then maintained at that temperature for 12 hours to calcinate the contents. 650 mL of 50% by mass sulfuric acid was added to 500 g of the obtained titanium oxide pigment, and water was added to make a total volume of 5 L while stirring well. The resulting liquid was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The obtained powder was pulverized to obtain recycled titanium oxide.

[0085] Comparative Example 21 1 kg of the resin composition of Preparation Example 7 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermosystems Corporation), heated from room temperature to 800°C over 1 hour, and then maintained at that temperature for 12 hours to calcinate the contents. 650 mL of 50% by mass nitric acid was added to 500 g of the obtained titanium oxide pigment, and water was added to make a total volume of 5 L while stirring well. The resulting liquid was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The obtained powder was pulverized to obtain recycled titanium oxide.

[0086] Comparative Example 22 1 kg of the resin composition of Preparation Example 7 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermosystems Corporation), heated from room temperature to 800°C over 1 hour, and then maintained at that temperature for 12 hours to calcinate the contents. 650 mL of 50% by mass hydrochloric acid was added to 500 g of the obtained titanium oxide pigment, and water was added to make a total volume of 5 L while stirring well. The resulting liquid was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The obtained powder was pulverized to obtain recycled titanium oxide.

[0087] Preparation Example 8 90g of titanium oxide, 3.3g of phthalocyanine blue (0.5% by mass of CuO relative to 100% by mass of titanium oxide), 100g of polyurethane resin, and 73.3g of solvent were mixed together in a 400mL mayonnaise bottle together with 180g of 1.5mm glass beads, and dispersed for 1 hour using a paint conditioner (manufactured by Red Devil) to prepare an ink. The following ingredients were used: Titanium oxide: "Titanix JR-405" (manufactured by Teika Co., Ltd.) Phthalocyanine Blue: "Phthalocyanine Blue" (Fujifilm Wako Pure Chemical Industries, Ltd.) Polyurethane resin: "Sanprene IB-422" (manufactured by Sanyo Chemical Industries, Ltd.) Solvent: A mixed solvent of methyl ethyl ketone, isopropyl alcohol, and toluene (1:1:1 by mass) This procedure was repeated several times to prepare a total of 13 kg of ink. The resulting 13 kg of ink was spread thinly and dried at 120°C for 12 hours to obtain 6 kg of a titanium oxide resin composition containing 0.5 mass% of CuO.

[0088] Example 27 1 kg of the resin composition of Preparation Example 8 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.), and the temperature was raised from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour, and the temperature was maintained for 1 hour to allow steam pyrolysis of the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0089] Example 28 1 kg of the resin composition of Preparation Example 8 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.) and heated from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour and maintained at that temperature for 1 hour, allowing the contents to undergo steam pyrolysis. 650 mL of 50% by mass sulfuric acid was added to 500 g of the resulting titanium dioxide pigment, and water was added to the resulting solution to 5 L while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The resulting powder was pulverized to obtain recycled titanium dioxide.

[0090] Example 29 1 kg of the resin composition of Preparation Example 8 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.) and heated from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour and maintained at that temperature for 1 hour, allowing the contents to undergo steam pyrolysis. 650 mL of 50% by mass nitric acid was added to 500 g of the resulting titanium dioxide pigment, and water was added to the resulting solution to 5 L while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The resulting powder was pulverized to obtain recycled titanium dioxide.

[0091] Example 30 1 kg of the resin composition of Preparation Example 8 was placed in a batch-type superheated steam furnace (manufactured by Takasago Kogyo Co., Ltd.) and heated from room temperature to 150°C over 1 hour. Superheated steam (800°C x 5 kg / hr) was then introduced into the furnace to raise the temperature to 800°C over 1 hour and maintained at that temperature for 1 hour, allowing the contents to undergo steam pyrolysis. 650 mL of 50% by mass hydrochloric acid was added to 500 g of the resulting titanium dioxide pigment, and water was added to the resulting solution to 5 L while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The resulting powder was pulverized to obtain recycled titanium dioxide.

[0092] Comparative Example 23 1 kg of the resin composition of Preparation Example 8 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corp.), heated from room temperature to 800°C over 1 hour, and then held at that temperature for 12 hours to calcinate the contents. The resulting powder was pulverized to obtain recycled titanium oxide.

[0093] Comparative Example 24 1 kg of the resin composition of Preparation Example 8 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermosystems Corporation), heated from room temperature to 800°C over 1 hour, and then maintained at that temperature for 12 hours to calcinate the contents. 650 mL of 50% by mass sulfuric acid was added to 500 g of the obtained titanium oxide pigment, and water was added to make a total volume of 5 L while stirring well. The resulting liquid was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The obtained powder was pulverized to obtain recycled titanium oxide.

[0094] Comparative Example 25 1 kg of the resin composition of Preparation Example 8 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermo Systems Corporation), heated from room temperature to 800°C over 1 hour, and then maintained at that temperature for 12 hours to calcinate the contents. 650 mL of 50% by mass nitric acid was added to 500 g of the obtained titanium oxide pigment, and water was added to make a total volume of 5 L while stirring well. The resulting liquid was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The obtained powder was pulverized to obtain recycled titanium oxide.

[0095] Comparative Example 26 1 kg of the resin composition of Preparation Example 8 was placed in a small electric furnace KBF828N2 (manufactured by JTEKT Thermosystems Corporation), heated from room temperature to 800°C over 1 hour, and then maintained at that temperature for 12 hours to calcinate the contents. 650 mL of 50% by mass hydrochloric acid was added to 500 g of the obtained titanium oxide pigment, and water was added to make a total volume of 5 L while stirring well. The resulting liquid was boiled for 5 minutes while stirring and then cooled to room temperature. The filtered sample was washed with 5 L of water and dried in a dryer at 110°C for 5 hours. The obtained powder was pulverized to obtain recycled titanium oxide.

[0096] Evaluation 1: Evaluation of powder color tone Five grams of the titanium oxides obtained in Examples 1 to 30 and Comparative Examples 1 to 26 were press-molded into pellets at 100 MPa to obtain titanium oxide molded bodies with a diameter of 3 cm and a thickness of 0.3 cm. The powder color tones (L, a, b) of the titanium oxide molded bodies were measured using a colorimeter ZE2000 (manufactured by Nippon Denshoku Industries Co., Ltd.). The results are summarized in Tables 1 and 2.

[0097] Evaluation 2: Evaluation of particle size (D50, D10, D90 by TEM) For the titanium oxides obtained in Examples 1 to 30 and Comparative Examples 1 to 26, 500 or more primary particles of titanium oxide were photographed using a JEM-1230 transmission electron microscope (manufactured by JEOL Ltd.), and the particle size distribution was measured using image analysis particle size distribution measurement software Mac-View (manufactured by Mountec Co., Ltd.), and D50, D10, D90, and the difference between D90 and D10 (D90-D10) were evaluated. The results are summarized in Tables 1 and 2.

[0098] Evaluation 3: Evaluation of the amount of transition metals (CuO, Fe2O3) that are insoluble in acid To 25 g of the titanium oxides obtained in Examples 1 to 30 and Comparative Examples 1 to 26, 32.5 mL of 50% by weight sulfuric acid, 50% by weight hydrochloric acid, or 50% by weight nitric acid was added, and water was added to make a 250 mL solution while stirring well. The resulting solution was boiled for 5 minutes while stirring and then cooled to room temperature. The resulting slurry was filtered, washed with water, and dried to remove acid-soluble transition metals. 5 g of the resulting titanium oxide containing acid-insoluble transition metals was press-molded into pellets at 100 MPa to obtain titanium oxide molded bodies with a diameter of 3 cm and a thickness of 0.3 cm. The elemental composition was measured using a benchtop wavelength-dispersive X-ray fluorescence analyzer, Supermini (manufactured by Rigaku Corporation), and the amount of acid-insoluble transition metals (CuO, Fe2O3) was measured. The results are summarized in Tables 1 and 2.

[0099] Evaluation 4: Evaluation of reflectance (%) at 420 nm by powder pellet molding The titanium oxides obtained in Examples 1 to 30 and Comparative Examples 1 to 26 were press-molded into pellets at 100 MPa to obtain titanium oxide molded bodies with a diameter of 3 cm and a thickness of 0.3 cm. The reflectance curves of the titanium oxide molded bodies were measured in the wavelength range of 300 nm to 700 nm using a spectrophotometer HITACHI U-4100 (manufactured by Hitachi, Ltd.) with a BaSO4 standard tablet as a reference. The reflectance at 420 nm was evaluated from the obtained reflectance curves. The results are summarized in Tables 3 and 4.

[0100] Evaluation 5: Evaluation of paint color tone and hiding rate test (hiding rate) using boiled linseed oil 1.5 mL of boiled linseed oil was added to 1.5 g of the titanium oxide obtained in Examples 1 to 30 and Comparative Examples 1 to 26. The obtained sample was dispersed for 15 seconds using a Huber-Marler. This dispersion was repeated a total of four times. The obtained dispersion paste was applied to a JIS K5600 general paint testing method hiding rate test paper using a 1.5 mil film applicator. The paint color tone on a white board and a black board was measured using a colorimeter ZE2000 (manufactured by Nippon Denshoku Industries Co., Ltd.). The hiding rate was calculated using the following formula. The results are summarized in Tables 3 and 4.

[0101]

number

[0102] [Table 1]

[0103] [Table 2]

[0104] [Table 3]

[0105] [Table 4]

[0106] As shown in Tables 1 to 4, the recycled titanium oxides of Examples 1 to 30, which were obtained by treating a resin composition containing titanium oxide with superheated steam within a certain temperature range, met all of the required qualities for a white pigment of titanium oxide, including: (1) a high L value for the powder color tone and a good powder color tone; (2) the particle size (D50 measured by TEM) was not large and the primary particle size was within a certain range; (3) the content of acid-insoluble transition metals, which are impurities, was low; (4) the L value for the paint color tone (white board) using boiled linseed oil was high, the b value was low, and the paint color tone was good; and (5) the hiding power was also high. On the other hand, the recycled titanium oxides of Comparative Examples 1 to 26, which were obtained by heat-treating a resin composition containing titanium oxide in air or an inert atmosphere or by treating it with superheated steam outside a certain temperature range, did not meet the quality requirements for a white titanium oxide pigment, for example: (1) the L value of the powder color was low; (2) the particle diameter (D50 measured by TEM) was large and the primary particle diameter was enlarged; (3) the content of acid-insoluble transition metals was high; and (4) the L value of the paint color (white board) made from boiled linseed oil was low and the b value was high.

Claims

1. A recycled titanium oxide recycled from a resin composition containing titanium oxide, CuO and Fe contained in the resin composition ２ O ３ the total content of acid-insoluble transition metals derived from the A recycled titanium oxide having a powder color tone L value of 50 or more and a D50 measured by TEM of 0.18 μm or more and 0.31 μm or less.

2. 2. The recycled titanium oxide according to claim 1, wherein the recycled titanium oxide is molded into a powder pellet having a reflectance of 85% or more at a wavelength of 420 nm.

3. 3. The recycled titanium oxide according to claim 1, wherein a coating film containing the recycled titanium oxide and boiled linseed oil has an L value of 85 or more and a b value of 4.3 or less in the Lab color system.

4. 3. The recycled titanium oxide according to claim 1 or 2, wherein a coating film containing the recycled titanium oxide and boiled linseed oil has an L value of 93.5 or more in the paint color tone in the Lab color system and a hiding rate of 99.5% or more in a hiding rate test.

5. A recycled titanium oxide recycled from a resin composition containing titanium oxide, CuO and Fe contained in the resin composition ２ O ３ the total content of acid-insoluble transition metals derived from the A recycled titanium oxide having a powder color tone L value of 50 or more and a D10 measured by TEM of 0.29 μm or less.

6. A recycled titanium oxide recycled from a resin composition containing titanium oxide, CuO and Fe contained in the resin composition ２ O ３ the total content of acid-insoluble transition metals derived from the A recycled titanium oxide having a powder color tone L value of 50 or more and a D90 measured by TEM of 0.71 μm or less.

7. A recycled titanium oxide recycled from a resin composition containing titanium oxide, CuO and Fe contained in the resin composition ２ O ３ the total content of acid-insoluble transition metals derived from the A recycled titanium oxide having a powder color tone L value of 50 or more and a difference between D90 and D10 measured by TEM of 0.46 μm or less.

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