JP6031175B2 - Titanium dioxide pigment, method for producing the same, and printing ink composition - Google Patents

Description

  The present invention relates to a titanium dioxide pigment for a printing ink composition that is excellent in concealment property and printability and exhibits a bluish color tone, and a method for producing the same.

  Since gravure printing is suitable for photographic printing, it is widely used for packaging materials, publications, building materials and the like. Since an ink composition used for gravure printing is required to have a high concealment property, a rutile type titanium dioxide pigment having a high refractive index of visible light is generally blended. However, the rutile type titanium dioxide pigment has a high hardness, and the doctor blade is rubbed to cause printing defects such as plate fog and doctor streaks, and wear of an expensive printing cylinder is promoted. In particular, in recent years, the doctor blade has been increasingly loaded with higher printing speed and water-solubility of the ink composition. For this reason, a technique for improving printing suitability by using anatase-type titanium dioxide pigment having low hardness for gravure printing has been proposed. (See Patent Document 1) Since the anatase type has a smaller refractive index of visible light than the rutile type, in this technique, the particle diameter of the pigment is in a range of 0.2 to 0.4 μm which is optimal for obtaining a concealment property. It is said.

JP 2004-83904 A

  However, even with the titanium dioxide pigment described in Patent Document 1, the hiding property does not reach that of the rutile type, and in order to obtain the hiding property equivalent to the rutile type, if the pigment concentration of the ink composition is increased, a doctor blade or printing The metal wear of the cylinder increased, and the difference from the conventional rutile type was hardly recognized. In addition, the coating film of the ink composition having a high pigment concentration has a problem that the color tone becomes yellow and the vivid white of the blue color tone of the titanium dioxide pigment is impaired.

  As a result of intensive studies to solve these problems, the present inventors have obtained a gravure coating of a titanium dioxide pigment coated with a specific inorganic compound on the surface of porous titanium dioxide particles having a specific average particle diameter. When used in a printing ink composition, high concealment is obtained, metal wear, particularly doctor blade wear, is reduced and printing suitability is improved, and this has a remarkable bluish hue. The headline and the present invention were completed.

  That is, the present invention is for a printing ink composition in which the surface of titanium dioxide porous particles having an average particle size in the range of 0.2 to 1.0 μm is coated with silicon oxide and / or aluminum oxide. It is a titanium dioxide pigment.

  According to the present invention, a printing ink composition having excellent concealment properties and excellent printability can be obtained.

1 is a transmission electron micrograph of titanium dioxide porous particles (sample a) obtained in Example 1. FIG. (Magnification 16,000 times) FIG. 2 is a transmission electron micrograph of the titanium dioxide pigment (sample A) obtained in Example 1. (Magnification 16,000 times) FIG. 3 is a transmission electron micrograph of the titanium dioxide particles (sample b) obtained in Comparative Example 1. (Magnification 16,000 times) FIG. 4 is a transmission electron micrograph of the titanium dioxide pigment (sample B) obtained in Comparative Example 1. (Magnification 16,000 times) FIG. 5 is a scanning electron micrograph of the titanium dioxide pigment (sample A) obtained in Example 1. (Magnification 24,000 times) FIG. 6 is a scanning electron micrograph of the titanium dioxide pigment (sample A) obtained in Example 1. (Magnification 130,000 times)

  The present invention relates to a titanium dioxide pigment for a printing ink composition, wherein silicon oxide and / or aluminum oxide is formed on the surface of titanium dioxide porous particles having an average particle diameter in the range of 0.2 to 1.0 μm. The object is covered. In the present invention, the average diameter of the porous particles is in the above-described range where the reflectance of visible light is the highest, so even if the particles are not dense and have a smooth surface, the excellent concealment property of titanium dioxide is impaired. Thus, the surface of the porous particles is coated with silicon oxide and / or aluminum oxide, thereby making the titanium dioxide pigment more suitable for printing ink. In general, titanium dioxide pigments exhibit a bluish color tone because the refractive power in the visible light region is higher on the short wavelength side, but in the present invention, they are more bluish than conventional ones. The color tone is exhibited. It is presumed that because the porous particles have pores, long-wavelength light easily reaches the inside of the particles, and the refractive power on the particle surface is significantly reduced. For this reason, even if it mix | blends the titanium dioxide pigment of this invention with an ink composition by high concentration, it is hard to become a yellowish color tone. Furthermore, when it is used for an ink composition for gravure printing, excellent printing suitability is obtained. This is presumably because the hardness of the titanium dioxide and the doctor blade are difficult to come into contact with each other due to the irregularities on the surface of the porous particles, and wear of the doctor blade is reduced. More preferably, the average particle diameter of the porous particles is 0.2 to 0.5 μm.

In the present invention, if the particles contained in the porous particles have pores having a longest diameter of 10 nm or more as measured from a scanning electron micrograph on the particle surface, it is advantageous for bluish color tone and printing suitability. This is preferable. It is more preferable if the longest diameter is a pore of 50 nm or more, and further preferable if it is 80 nm or more. The upper limit of the longest diameter is limited by the average particle diameter of the porous particles, but is usually less than 300 nm. Further, assuming that the average particle diameter by electron microscopy is D ₁ , and the particle diameter calculated from the specific surface area with the particle shape being a true sphere is D ₂ , the conventional spherical dense titanium dioxide particles have a substantially smooth surface. There is no significant difference between the values of ₁ and D ₂ , and the ratio D ₁ / D ₂ is approximated to 1. On the other hand, porous particles used in the present invention because it has an uneven surface, towards _{D 1} is larger than _{D 2, D} 1 / _{D 2} becomes 1.50 or more. The shape of the porous particles is preferably an isotropic shape. As long as the particles are isotropic, any of non-spherical particles, substantially spherical particles and the like may be used. Furthermore, if the porous particles are aggregates of primary particles, it is preferable because the pitch of the irregularities on the surface of the porous particles is large and the depth of the holes tends to be deep. These primary particles are not agglomerated by the interaction between particles such as van der Waals force, or are mechanically consolidated, but are firmly bonded, and are usually used for industrial mixing and crushing industries. Operation does not disintegrate easily and most remains as porous particles. If the average particle diameter of the primary particles is in the range of 0.01 μm or more and less than 0.2 μm, it is preferable that desired porous particles are easily formed.

  The crystal form may be either anatase type or rutile type, but it is preferable to use an anatase type whose hardness is smaller than that of the rutile type in order to obtain better printing suitability. When the anatase type is used, the hiding property is lower than that of the rutile type, but in the present invention, the metal wear is very small, so the influence of the pigment concentration on the metal wear is small. However, the printability is hardly deteriorated. Moreover, since the blue tint is strong, even if it is a high pigment density | concentration for the same reason, it is hard to exhibit a yellow tint. Anatase-type titanium dioxide particles contain anatase-type crystals in the range of 98 to 100%, and the content (R%) of rutile-type crystals is determined by X-ray diffraction, and 100-R (%) is converted to anatase-type. The content of crystals.

The form of the silicon oxide or aluminum oxide coating layer may be porous or dense, and can be selected as appropriate. Each of them can be coated alone, or can be used in combination by laminating or mixing them. In particular, if the surface of the porous particles is coated with silicon oxide and then further coated with aluminum oxide, the surface is suitable for back-printing gravure printing, and the aluminum is not coated with silicon oxide. When the oxide is coated, the gloss suitable for surface printing and gravure printing becomes high. These preferable coating amounts are in the range of 0 to 10% by weight of silicon oxide in terms of SiO ₂ and 1 to 10% by weight of aluminum oxide in terms of Al ₂ O _{3 with} respect to porous particles in terms of TiO _2. Range. More preferably, it is in the range of 2 to 5% by weight and 1 to 6% by weight, respectively, for back printing, and is in the range of 0% by weight and 1 to 6% by weight, respectively, for surface printing. In the present invention, the silicon oxide and aluminum oxide include silicon, an anhydrous oxide of aluminum, a hydrous oxide, and a hydrated oxide.

In the present invention, in addition to silicon oxide and aluminum oxide, inorganic compounds other than these and organic compounds may be coated. Examples of the inorganic compound include oxides such as zirconium, tin, titanium, and antimony, and phosphates. Examples of organic compounds include polyol compounds (trimethylolpropane, trimethylolethane, ditrimethylolpropane, trimethylolpropane ethoxylate, pentaerythritol, etc.), alkanolamine compounds (monoethanolamine, monopropanolamine, diethanolamine, dipropanolamine). , Triethanolamine, tripropanolamine and the like) and derivatives thereof (acetate, oxalate, tartrate, formate, benzoate, etc.). Among these, a polyol compound is preferable because it has a high effect of improving dispersibility, and trimethylolpropane and trimethylolethane are more preferable. The organic compound is preferably coated on a silicon oxide or aluminum oxide coating, and the coating amount is preferably in the range of 0.1 to 5% by weight with respect to the porous particles in terms of TiO ₂ . The range of 1 to 2% by weight is more preferable.

  Next, the present invention is a method for producing a titanium oxide pigment for printing ink, the step of obtaining porous particles of titanium dioxide having an average particle diameter in the range of 0.2 to 1.0 μm, and the obtained porous The surface of the conductive particles is covered with silicon oxide and / or aluminum oxide.

In order to obtain porous particles, titanium dioxide particles having an appropriate size may be granulated by spray drying, compaction treatment or the like. However, in the present invention, the hydrolyzable titanium compound solution is hydrolyzed at a temperature in the range of 200 to 400 ° C. and a pressure in the range of 30 to 200 kg / cm ² to generate hydrous titanium oxide. When the method of calcining the obtained hydrous titanium oxide at a temperature in the range of 400 to 1200 ° C. is used, it is preferable that porous particles having pores in the above range are easily obtained.

Hydrolysis can be carried out in a known pressure vessel such as an autoclave, and a preferable temperature by hydrolysis is in the range of 200 to 350 ° C., and a more preferable pressure is in the range of 30 to 150 kg / cm ² . In order to accelerate the reaction, the hydrolysis may be performed in the presence of a nucleating agent for hydrolysis. The nucleating agent for hydrolysis can be obtained, for example, by aging hydrous titanium oxide. As the hydrolyzable titanium compound, for example, titanyl sulfate (TiOSO ₄ ), titanium tetrachloride (TiCl ₄ ), titanium alkoxide (Ti (OR) ₄ : R is an alkyl group), and the like can be used. It is preferable to use titanyl sulfate or titanium tetrachloride. In particular, when titanyl sulfate is hydrolyzed, cauliflower-like porous particles are more easily obtained. Therefore, it is preferable to use titanyl sulfate. Titanyl sulfate is obtained, for example, by reacting a titanium component and sulfuric acid while dissolving a titanium-containing ore such as illuminite ore and titanium slag with sulfuric acid.

Known devices such as a rotary kiln and a tunnel kiln can be used for firing the hydrous titanium oxide. The firing temperature is preferably in the range of 400 to 900 ° C. if an anatase type crystal is obtained, and is preferably in the range of 900 to 1200 ° C. if a rutile type crystal is obtained. Baking can also be performed in the presence of various baking treatment agents such as a phosphoric acid compound, a potassium compound, an aluminum compound, and a zinc compound. In particular, since a phosphoric acid compound and a potassium compound have an effect of adjusting the particle shape, it is preferable to use them together as a baking treatment agent. The amount of these used is preferably in the range of 0.1 to 0.4% by weight as the phosphoric acid compound as P ₂ O _{5 with} respect to the hydrous titanium oxide in terms of TiO ₂ , and the potassium compound is 0.05 to as the K ₂ O. A range of 0.4% by weight is preferred. Examples of the phosphoric acid compound include orthophosphoric acid, pyrophosphoric acid, and salts thereof. Examples of the potassium compound include potassium hydroxide and potassium chloride.

  Next, the obtained porous particles are subjected to a step of coating silicon oxide or aluminum oxide. First, porous particles are dispersed in water, and wet pulverization is preferably performed using a vertical sand mill, a horizontal sand mill, or the like to prepare an aqueous slurry. At this time, it is preferable to adjust the pH of the aqueous slurry to 9 or more because the porous particles are stably dispersed in water. Moreover, you may use dispersing agents, such as phosphoric acid compounds, such as sodium hexametaphosphate and sodium pyrophosphate, and silicic acid compounds, such as sodium silicate and potassium silicate, as needed. The solid content concentration of the porous particles in the aqueous slurry is in the range of 50 to 800 g / liter, and preferably in the range of 100 to 500 g / liter.

  Then, after adding a salt of a silicon compound, a salt of an aluminum compound, etc. to an aqueous slurry, a neutralizing agent is added, or a salt of a silicon compound, a salt of an aluminum compound and the neutralizing agent are added simultaneously. By doing so, the silicon oxide and the aluminum compound are coated. Examples of the silicon compound salt used include sodium silicate and potassium silicate. Examples of the aluminum compound salt include sodium aluminate, aluminum sulfate, and aluminum nitrate. Further, as the neutralizing agent, if it is a basic compound, hydroxides or carbonates such as alkali metals and alkaline earth metals, ammonium compounds such as ammonia, amines, etc., if acidic compounds, sulfuric acid And inorganic acids such as hydrochloric acid, and organic acids such as acetic acid and formic acid.

  As for the silicon oxide coated on the porous particles, porous treatment and dense treatment are known, and the porous silicon oxide coating can be obtained by the above-described method. If the dense silicon oxide is coated, a known method described in JP-A-53-33228 can be applied. If the method described in JP-A-53-33228 is used, the slurry pH is preferably in the range of 9 to 10.5 while maintaining the slurry in the range of 80 to 100 ° C. of the porous particle slurry. The sodium silicate is rapidly added while being maintained at, and then neutralized at a pH of 9-10.5, after which a temperature in the range of 80-100 ° C. is held for 50-60 minutes. Or the method of neutralizing the salt of a silicic acid compound over 30 minutes can also be used. In this method, the neutralization is more preferably performed over 1 hour. If the neutralization pH is in the range of 4 to 7.5 and the pH of the aqueous slurry at the time of neutralization is 80 ° C. or higher, it is preferable because a denser coating is easily formed. The range of more preferable neutralization pH is 4.5-7, and the neutralization temperature is 90 degreeC or more.

  Porous particles coated with silicon oxide, aluminum oxide or the like are dehydrated, solid-liquid separated from the slurry, dried, and then subjected to dry pulverization as required to obtain a titanium dioxide pigment. For dehydration, for example, a filter press, a roll press, or the like can be used. For example, a band heater, a batch heater, or the like can be used for drying. For the dry pulverization, for example, an impact pulverizer such as a hammer mill or a pin mill, a pulverizer or the like, a grinding pulverizer, an airflow pulverizer such as a jet mill, or a spray dryer such as a spray dryer can be used.

  As an organic compound, for example, if a polyol compound is coated, the porous particles coated with silicon oxide or aluminum oxide are coated by using a dry pulverizer or a high-speed stirrer, and stirring and mixing them. Can be done. In particular, a method using a dry pulverizer is preferable because pulverization of porous particles and coating with an organic compound can be performed simultaneously. As the dry pulverizer, an airflow pulverizer such as a jet mill having good pulverization efficiency and excellent mixing properties is preferably used.

  Furthermore, this invention is a printing ink composition, Comprising: The said titanium dioxide pigment and the resin for ink are characterized by the above-mentioned. In particular, the present invention reduces metal wear in gravure printing such as back printing and surface printing, so that the friction of the doctor blade is suppressed, printing defects such as plate fog and doctor streaks are unlikely to occur, and excellent printing suitability is achieved. Have. For this reason, it is possible to cope with high-speed printing and water-solubilization of the ink composition, in which a load is easily applied to the doctor blade. In addition, an expensive printing cylinder is less likely to be worn, which is economically advantageous. In addition, it has a high concealment property and a vivid white color with a blue tint. Moreover, it can be used not only for gravure printing but also for other intaglio printing, letterpress printing, flat printing, stencil printing, and the like. The substrate to be printed can be selected without limitation, such as plastics, paper, and metal foil. The printing ink composition includes intermediate products of printing inks such as toning inks and color chips in addition to the final printing ink.

  The blending amount of the titanium dioxide pigment is preferably in the range of 0.5 to 10 parts by weight with respect to 1 part by weight of the ink resin, and more preferably in the range of 2 to 10 parts by weight if used for back printing. If it is, the range of 0.5-2 weight part is still more preferable. Examples of the ink resin include urethane resin, vinyl chloride resin, chlorinated propylene resin, polyamide resin, acrylic resin, maleic acid resin, cyclized rubber resin, nitrified cotton, and rosin resin. It can be appropriately selected depending on the situation. These ink resins may be any of a dissolution type, an emulsion type, a colloidal dispersion type, and a curing method such as a room temperature curing type, a thermosetting type, an ultraviolet curing type, and an electron beam curing type can be used without limitation. Furthermore, the ink composition contains an organic solvent such as an alcohol compound, an ester compound, an ether compound, a ketone compound, an aromatic hydrocarbon compound, an aliphatic hydrocarbon compound, water or a mixing agent thereof as a solvent. It may be selected according to the suitability with the ink resin. In addition, colorants such as organic pigments, inorganic pigments, dyes, extenders, surfactants, antistatic agents, plasticizers, curing aids, antifoaming agents, lubricants, antioxidants, UV absorbers, chelating agents Various additives such as these may be contained.

  The printing ink composition of the present invention may be added to the titanium dioxide pigment and the ink resin as necessary, such as a sand mill, attritor, disper, ball mill, paint shaker, two roll mill, three roll mill, etc. It is obtained by mixing and dispersing using a disperser. Various additives may be added at the time of dispersion or after dispersion.

  Examples of the present invention are shown below, but the present invention is not limited thereto.

Example 1
(Preparation of porous particles)
An aqueous solution of titanyl sulfate having a concentration of 150 g / liter in terms of TiO ₂ was charged into an autoclave, a nucleating agent for hydrolysis was added, and hydrolysis was performed at a pressure of 100 kg / cm ² at a temperature of 250 ° C. for 4 hours. Thereafter, filtration and washing were performed to obtain hydrous titanium oxide. Thereafter, 0.2 wt% of orthophosphoric acid as P ₂ O ₅ and 0.2 wt% of potassium hydroxide as K ₂ O are added to 150 g of hydrous titanium oxide in terms of TiO ₂ , and then at 850 ° C. Baked. The obtained baked product is made into an aqueous slurry having a TiO ₂ concentration of 300 g / liter, a sodium hydroxide aqueous solution is added to disperse the pH to 10.5, and then wet pulverized by a sand mill and subjected to stationary classification. The porous particles of titanium dioxide were obtained. (Sample a)

(Preparation of titanium dioxide pigment)
After the classification, 1000 ml of the slurry was taken, and while maintaining the temperature at 60 ° C., 80 ml of an aqueous sodium silicate solution (150 g / liter as SiO ₂ ) was added over 60 minutes with stirring, and aged for 30 minutes. . Next, 80 ml of an aqueous sodium aluminate solution (150 g / liter as Al ₂ O ₃ ) was added over 40 minutes, the pH was adjusted to 7 with sulfuric acid for 30 minutes, and then aged for 60 minutes. After aging, the mixture is filtered with a suction filter, washed with water, dried at 120 ° C. for 20 hours, and then pulverized with a jet mill. The hydrous silicon oxide is 4% by weight in terms of SiO ₂ , and the hydrous aluminum oxide is Al ₂ O _3. A titanium dioxide pigment of the present invention (sample A) coated with 4% by weight in terms of conversion was obtained.

Comparative Example 1
(Preparation of titanium dioxide particles)
A hydrous titanium oxide was obtained in the same manner as in Example 1 except that hydrolysis of titanyl sulfate was performed at 100 ° C. under normal pressure. Subsequently, with respect to TiO ₂ in the hydrous titanium oxide, aluminum sulfate corresponding to 0.1% by weight in terms of Al ₂ O ₃ , potassium hydroxide corresponding to 0.3% by weight in terms of K ₂ O and P ₂ O ₅ Orthophosphoric acid equivalent to 0.15% by weight in terms of conversion is added to the hydrous titanium oxide obtained as a baking treatment agent, and heated and baked at a temperature of 960 ° C. for 1 hour using an electric furnace to obtain anatase-type titanium dioxide particles. Obtained. The obtained titanium dioxide particles were filtered, washed, dried, pulverized, and classified in the same manner as in the Examples to obtain comparative titanium dioxide particles. (Sample b)

(Inorganic compound coating)
1000 ml of the classified slurry was collected, and then surface-coated by the same method as in Example 1. The hydrous silicon oxide was 4% by weight in terms of SiO ₂ and the hydrous aluminum oxide was 4 in terms of Al ₂ O _3. A comparative titanium dioxide pigment coated with a weight percent mixture was obtained. (Sample B)

Comparative Example 2
Using rutile-type titanium dioxide particles (sample c) obtained by the sulfuric acid method, the surface was coated in the same manner as in Example 2, and the hydrous silicon oxide was 4% by weight in terms of SiO ₂ and the hydrous aluminum oxide was Al. A comparative titanium dioxide pigment coated with 4% by weight in terms of ₂ O ₃ was obtained. (Sample C)

Evaluation 1: Evaluation of Particle Shape Transmission electron micrographs of samples a, A, b, and B obtained in Example 1 and Comparative Example 1 are shown in FIGS. Moreover, the scanning electron micrograph of the sample A of Example 1 is shown in FIGS. Samples a and A are found to be porous particles. 5 and 6, it can be seen that the sample A contains particles having pores having a longest diameter of 100 to 150 nm on the surface.

Evaluation 2: Evaluation of average particle diameter and specific surface area Titanium dioxide porous particles obtained in Example 1 (sample a), average particles of titanium dioxide particles obtained in Comparative Examples 1 and 2 (samples b and c) The diameter was measured by electron microscopy using a particle analyzer (TGZ3 type: manufactured by Carl Zeiss). The 50% cumulative particle size was taken as the average particle size. The specific surface area was measured by a simple BET method using a specific surface area measuring device (Monosorb MS-16 type: manufactured by Yuasa Ionics). The particle diameter (D ₂ ) calculated from the specific surface area with the particle shape as a true sphere was calculated by the following formula 1. The specific gravity of anatase titanium dioxide was 3.9. The results are shown in Table 1.
Formula 1: D ₂ = 6 / specific gravity of titanium dioxide × specific surface area

Evaluation 3: Evaluation of content of anatase type The titanium dioxide porous particles (sample a) obtained in Example 1 and the titanium dioxide particles (samples b and c) obtained in Comparative Examples 1 and 2 were placed on the surface of an aluminum cell. After being filled so as to be smooth, using an X-ray diffractometer (RAD-2CV type: manufactured by Rigaku Corporation), the content (R (%)) of the rutile type crystal is obtained, and 100-R (%) is obtained. The content of the anatase type was calculated. The results are shown in Table 1.

Examples 2 and 3, Comparative Examples 3 and 4 (Preparation of ink composition)
The titanium dioxide pigments (samples A to C) obtained in Example 1 and Comparative Examples 1 and 2 were charged into a 220 cc glass container according to the formulation 1 shown in Table 2, and a paint conditioner (manufactured by Red Devil) was used. The dispersion was prepared by dispersing for 30 minutes, and an ink composition of 4 parts by weight of a titanium dioxide pigment was obtained with respect to 1 part by weight of the ink resin according to the formulation 2 formulation shown in Table 3. These are referred to as Example 2 and Comparative Examples 3 and 4 (Samples D, F, and G), respectively. For Sample A, a 220 cc glass container was prepared according to the prescription 3 shown in Table 4 and a dispersion was prepared in the same manner. Then, according to the prescription 4 shown in Table 5 with respect to 1 part by weight of the ink resin. An ink composition containing 5 parts by weight of titanium dioxide pigment was obtained. This is Example 3 (Sample E).

Evaluation 4: Evaluation of Hidden Payability and Color Tone after Lamination The ink compositions (samples D to G) obtained in Examples 2 and 3 and Comparative Examples 3 and 4 were treated with toluene / It was diluted and adjusted with a mixed solvent of isopropyl alcohol / methyl ethyl ketone = 3/2/5 so that the # 3 Zahn cup viscosity was 15 to 16 seconds. This diluted ink was applied onto a PET film using a # 3 bar coater and allowed to air dry for 30 minutes to form a coating film. Then, a urethane resin (IB-422: manufactured by Sanyo Chemical Industries, solid content) 30 wt%) was applied with a # 16 bar coater, and an OPP film was bonded to the coating film from above. The reflectivity (Y value) of the film on black paper and the b value by the Hunter color system were measured using a color computer (SM-7 type: manufactured by Suga Test Instruments). The results are shown in Table 6. The higher the Y value, the higher the hidden payability, and the smaller the b value, the bluish color tone.

Evaluation 5: Evaluation of metal abrasion resistance 500 g of the ink composition used in Evaluation 1 was tested at 500,000 revolutions using an ablation tester (ATII type: manufactured by Carl Shredder). The weight of the test plate before and after the test was measured, and the weight loss was evaluated as the metal wear resistance. The results are shown in Table 4.

  The titanium dioxide pigment of the present invention has a higher hiding property than a conventional anatase-type titanium dioxide pigment, has a bluish color tone, and is excellent in metal abrasion resistance. Moreover, even if the pigment concentration is increased so as to have the same hiding property as that of the rutile titanium dioxide pigment, the bluish color tone and the metal wear resistance are hardly impaired.

  With the titanium dioxide pigment of the present invention, a printing ink composition excellent in printing suitability can be obtained particularly in gravure printing, so that it is possible to cope with high-speed printing and water-solubilization.

Claims (10)

For printing ink compositions in which silicon oxide and / or aluminum oxide is coated on the surface of titanium dioxide porous particles having an average particle diameter D1 of 0.2 to 1.0 μm by electron microscopy Titanium dioxide pigment. On the surface of titanium dioxide porous particles (excluding secondary particles in which primary particles are aggregated) whose average particle diameter D1 by electron microscopy is in the range of 0.2 to 1.0 μm, silicon oxide and / or The titanium dioxide pigment according to claim 1, which is coated with aluminum oxide. The average particle diameter D1 measured by electron microscopy is in the range of 0.2 to 1.0 μm, and the surface of titanium dioxide porous particles, which are primary particles having pores, is coated with silicon oxide and / or aluminum oxide. The titanium dioxide pigment according to claim 1 or 2. The titanium dioxide pigment according to any one of claims 1 to 3, wherein particles contained in the porous particles have pores having a longest diameter of 10 nm or more measured from a scanning electron micrograph on the particle surface. D1 / D2 is 1.50 or more, where D1 is an average particle diameter by electron microscopy of porous particles, and D2 is a particle diameter calculated from a specific surface area with the particle shape being a true sphere. Item 5. The titanium dioxide pigment according to any one of Items 1 to 4. The titanium dioxide pigment according to any one of claims 1 to 5, wherein the average particle diameter D1 of the porous particles of titanium dioxide by electron microscopy is in the range of 0.2 to 0.5 µm. The titanium dioxide pigment according to any one of claims 1 to 6, wherein the crystalline form of the porous particles is anatase type. To porous particles of the terms of TiO _2, coating amount of hydrated silicon oxide is in the range of 0 wt% in terms of SiO _2, 1-10 wt coverage of hydrous aluminum oxide in terms _{of Al} 2 _{O 3} The titanium dioxide pigment according to claim 1, wherein the titanium dioxide pigment is in the range of%. A printing ink composition comprising the titanium dioxide pigment according to claim 1 and an ink resin. The printing ink composition according to claim 9, which is used for gravure printing.

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