Titanium oxide dispersion

Abstract

To provide a titanium oxide dispersion that has high antifoamability, comprises reduced coarse particles, has excellent sedimentation stability, and expresses excellent coating properties when used as aqueous white ink raw material.SOLUTION: A titanium oxide dispersion comprises rutile titanium oxide (A), a dispersant (B), and water. The rutile titanium oxide (A) comprises one or more elements selected from aluminum, silicon, and zirconium, with its mass ratio satisfying the following formula (1): 0.8<Si / (Al+Zr)<4.0 (1). The dispersant (B) has an acid value of 150 mgKOH / g or less. The content of the dispersant (B) is 1-8 pts.mass relative to 100 pts.mass of the rutile titanium oxide (A).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a titanium oxide dispersion. The titanium oxide dispersion of the present invention can be suitably used, in particular, as a raw material for a water-based white inkjet ink. [Background technology]

[0002] Inks are broadly classified into two types: organic solvent inks, which use an organic solvent as the main component of the solvent, and water-based inks, which use water as the main component of the solvent. Organic solvent-based inks are not safe for humans and emit an odor due to the organic solvent, so in recent years, attention has been focused on aqueous inks that use aqueous solvents. Furthermore, in recent years, inkjet recording apparatuses, which are digital printing systems that do not require plate making, have come into use in order to accommodate high-mix, small-lot printing. Rutile titanium dioxide, an inorganic pigment, is often used as the colorant for water-based white inkjet inks. A common method for producing white ink involves preparing a titanium dioxide dispersion (also called a titanium dioxide paste or titanium dioxide slurry) containing a high concentration of rutile titanium dioxide, and then mixing this titanium dioxide dispersion with a water-soluble organic solvent, a resin dispersion, additives, water, etc. In both water-based inkjet white ink and its raw material, titanium dioxide dispersion, rutile titanium dioxide tends to settle due to its high specific gravity, and once the sediment forms a hard deposit (hard cake), it becomes impossible to redisperse. For this reason, both water-based inkjet white ink and its raw material, titanium dioxide dispersion, need to have good redispersibility that allows the composition to easily become uniform during the redispersion process, such as circulation, shaking, and stirring, during use. Additionally, there is a risk that air bubbles generated during redispersion may have an adverse effect on the ejection head, and that air bubbles may fill the container, preventing sufficient redispersion and causing uneven solids concentration between the top and bottom of the container. For these two reasons, high foam suppression is required for both the water-based white ink for inkjet use and the titanium dioxide dispersion that is its raw material.

[0003] For example, Patent Document 1 shows that in a water-based ink containing rutile titanium oxide and a polymer dispersant, by using a high acid value dispersant containing 72% by mass or more of a component derived from an anionic group-containing monomer, it is possible to obtain a water-based white ink with excellent foam-suppressing properties that is less likely to foam when redispersed. Furthermore, for example, Patent Document 2 discloses that an aqueous ink is prepared from a titanium oxide dispersion in which titanium oxides with various surface treatments are dispersed in a dispersant with an acid value of 10 mgKOH / g, and that by using titanium oxide that is only alumina-treated and does not contain silica as the surface treatment, a white ink with excellent redispersibility can be obtained. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6881836 [Patent Document 2] Patent Publication No. 2014-185236 Summary of the Invention [Problem to be solved by the invention]

[0005] The water-based white ink and its raw material, the titanium oxide dispersion, described in Patent Document 1 are an invention related to a type of dispersant with low foaming properties. However, the aforementioned hard cake formation is likely to occur. Even if excessive redispersion is possible due to the low foaming properties, the hard cake prevents the internal solids concentration from being uniform. Furthermore, only water-based white inks have been shown to have good redispersibility, and the redispersibility and sedimentation stability of titanium oxide dispersions with high pigment concentrations are also problematic. Furthermore, the high acid value of the dispersant used results in the ink containing excessive electrolyte components. When water evaporates due to localized drying, increasing the concentration of the water-soluble organic solvent, precipitation of the electrolyte components occurs, resulting in a lack of satisfactory organic solvent resistance for a water-based white ink. The titanium oxide dispersion in Patent Document 2 has a low titanium oxide concentration of 20% by mass, which makes it difficult to blend in the amount of resin dispersion required to provide abrasion resistance when used as a raw material for white inkjet ink. Furthermore, redispersibility was only evaluated using white ink, leaving issues with the sedimentation stability of the titanium oxide dispersion used as a raw material.

[0006] Increasing the amount of dispersant is one possible measure to prevent the formation of hard cakes and to provide good redispersibility; however, an excessive amount of dispersant will cause the viscosity of the water-based white inkjet ink to increase over time, reduce the strength of the coating film, cause the coating film to become sticky, and reduce blocking resistance and foam suppression properties. Therefore, it is necessary to provide redispersibility with a small amount of dispersant. Furthermore, in order to reduce the amount of plastic used, water-based white inkjet inks are required to be compatible with printing methods that do not require a lamination process, and this requires high abrasion resistance of the ink coating film after the ink has dried.To achieve high abrasion resistance while maintaining hiding power, it is necessary to include a higher concentration of resin dispersion as a binder component in the water-based white inkjet ink, and a high concentration of titanium oxide in the titanium oxide dispersion, which is the raw material, is desired. Furthermore, when the water in the ink evaporates locally, for example, near the head nozzles, and the concentration of the water-soluble organic solvent contained in the ink increases, there is a risk of nozzle clogging due to precipitation of electrolyte components. Therefore, water-based white inks for inkjet printing are required to have high resistance to organic solvents.

[0007] The present inventors have considered that the adsorption behavior of the dispersant on the titanium oxide surface is important for maintaining good dispersion stability, and therefore, the balance between the dispersant's acid value and the acid-base content on the titanium oxide surface is important. Titanium oxide is generally coated with a metal oxide to adjust its surface acid-base content. It is known that alumina treatment increases the base content, while silica treatment decreases it. When using a dispersant with an acid value of 150 mg KOH / g or less, which can suppress an increase in electrolyte content, no research has been conducted to date on the balance of silicon and aluminum elements contained in titanium oxide to achieve a surface acid-base content of titanium oxide that exhibits good properties with a small amount of dispersant. For this reason, many studies have been conducted to solve various problems related to titanium oxide dispersions and water-based white inkjet inks made therefrom, but none have been successful in solving these problems. An object of the present invention is to provide a titanium oxide dispersion that has high foam-inhibiting properties, contains few coarse particles, has excellent sedimentation stability, and exhibits excellent coating properties when used as an ink raw material, and that exhibits excellent sedimentation stability and organic solvent resistance when used in an aqueous white ink. [Means for solving the problem]

[0008] The inventors have conducted research in consideration of the above-mentioned problems and have discovered a titanium oxide dispersion containing rutile-type titanium oxide (A), a dispersant (B), and water, wherein the rutile-type titanium oxide (A) contains at least one element selected from the group consisting of aluminum element, silicon element, and zirconium element, and the ratio of the parts by mass thereof satisfies the following formula (1): 0.8 < Si / (Al+Zr) < 4.0 (1) The present inventors have found that a titanium oxide dispersion characterized in that the acid value of the dispersant (B) is 150 mgKOH / g or less and the content of the dispersant (B) is 1 to 8 parts by mass per 100 parts by mass of the rutile titanium oxide (A) has few coarse particles and excellent sedimentation stability, and that the aqueous white ink used as an ink raw material has excellent sedimentation stability and organic solvent resistance, thereby completing the present invention. [Effects of the Invention]

[0009] According to the present invention, there is provided a titanium oxide dispersion which has few coarse particles and excellent sedimentation stability, and which provides an aqueous white ink used as an ink raw material with excellent sedimentation stability and organic solvent resistance. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram in which the amount of silicon element per 100 parts by mass of titanium element contained in rutile-type titanium oxide, determined by XRF measurement in Examples 1 to 6 and Comparative Examples 1 to 9, is plotted against the sum of the amount of aluminum element and the amount of zirconium element per 100 parts by mass of titanium element. DETAILED DESCRIPTION OF THE INVENTION

[0011] The titanium oxide dispersion of the present invention is a titanium oxide dispersion containing rutile-type titanium oxide (A), a dispersant (B), and water, wherein the rutile-type titanium oxide (A) contains at least one element selected from the group consisting of aluminum element, silicon element, and zirconium element, and the ratio of the parts by mass thereof satisfies the following formula (1): 0.8 < Si / (Al+Zr) < 4.0 (1) The titanium oxide dispersion is characterized in that the acid value of the dispersant (B) is 150 mgKOH / g or less, and the content of the dispersant (B) is 1 to 8 parts by mass per 100 parts by mass of the rutile-type titanium oxide (A).

[0012] <Titanium oxide> The titanium oxide dispersion of the present disclosure comprises titanium oxide. Titanium oxide of the present disclosure has three crystalline forms: anatase type, rutile type, and brookite type, and from the viewpoint of hiding power, it is preferable to use rutile type titanium oxide (A). The content of rutile titanium oxide (A) in 100 parts by mass of titanium oxide of the present disclosure is preferably 80 parts by mass or more, more preferably 90 parts by mass or more, even more preferably 95 parts by mass or more, and particularly preferably 100 parts by mass.

[0013] The primary particle size of the titanium oxide of the present disclosure is preferably 0.1 μm or more, more preferably 0.15 μm or more, even more preferably 0.2 μm or more, and is preferably 1 μm or less, more preferably 0.4 μm or less, and even more preferably 0.3 μm or less. The primary particle size of titanium oxide can be measured by observation with a scanning electron microscope or a transmission electron microscope. The titanium oxide of the present disclosure contains at least one element selected from the group consisting of aluminum, silicon, and zirconium.

[0014] The content of aluminum element in the titanium oxide of the present disclosure is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more, per 100 parts by mass of titanium element, and is preferably 5.0 parts by mass or less, more preferably 4.5 parts by mass or less, and even more preferably 4.0 parts by mass or less. The content of silicon element in the titanium oxide of the present disclosure is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more, per 100 parts by mass of titanium element, and is preferably 5.0 parts by mass or less, more preferably 4.5 parts by mass or less, and even more preferably 4.0 parts by mass or less. The content of zirconium element in the titanium oxide of the present disclosure is preferably 0.01 parts by mass or more, more preferably 0.03 parts by mass or more, and even more preferably 0.05 parts by mass or more, per 100 parts by mass of titanium element, and is preferably 1.0 part by mass or less, more preferably 0.75 parts by mass or less, and even more preferably 0.5 parts by mass or less.

[0015] The ratio of parts by mass of aluminum element, silicon element, and zirconium element in the titanium oxide of the present disclosure preferably satisfies the following formula (1), from the viewpoints of suppressing coarse particles and improving sedimentation stability. 0.8 < Si / (Al+Zr) < 4.0 (1) In the present disclosure, the total amount of aluminum element and zirconium element in parts by mass per 100 parts by mass of titanium element is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more, and is preferably 5.0 parts by mass or less, more preferably 4.5 parts by mass or less, and even more preferably 4.0 parts by mass or less.

[0016] The amounts of silicon, aluminum, and zirconium contained in the titanium oxide of the present disclosure can be measured using fluorescent X-rays. For quantitative determination using fluorescent X-rays, an analytical method using a calibration curve with a standard sample has been established. Examples of rutile titanium oxide of the present disclosure include JR-403, JR-806, JR-708, JR-805, JR-809 (manufactured by Teika Corporation), and R-62N (manufactured by Sakai Chemical Industry Co., Ltd.).

[0017] The titanium oxide of the present disclosure is preferably surface-treated, and examples of surface treatment methods include those using aluminum oxide, silicon dioxide, zinc oxide, a silane coupling agent, a polyhydric alcohol, an amine, etc., but from the viewpoint of productivity, surface treatment methods using aluminum oxide, silicon dioxide, or zinc oxide are preferred.

[0018] If the titanium oxide content per 100 parts by mass of the titanium oxide dispersion of the present disclosure is too low, productivity will decrease, and when an aqueous white ink is prepared using the titanium oxide dispersion as a raw material, it will be difficult to blend in a sufficient amount of water-dispersible resin as a binder, resulting in reduced physical properties such as abrasion resistance of the coating film. If the content is too high, the viscosity will increase, making dispersion treatment using a bead mill or the like difficult. From these perspectives, the content is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 40 parts by mass or more, and preferably 70 parts by mass or less, more preferably 65 parts by mass or less, and even more preferably 60 parts by mass or less.

[0019] <Dispersant> The titanium oxide dispersion of the present disclosure contains a dispersant (B) (hereinafter also referred to as a dispersant). The acid value of the dispersant (B) of the present disclosure is preferably 150 mgKOH / g or less, more preferably 100 mgKOH / g or less, and even more preferably 50 mgKOH / g or less, from the viewpoints of dispersion stability and suppression of an increase in electrical conductivity. The lower limit of the dispersant (B) of the present disclosure is not particularly limited, but may be 5 mgKOH / g or more, 6 mgKOH / g or more, or 7 mgKOH / g or more.

[0020] The pH of the dispersant of the present disclosure is preferably an acidic dispersant of less than 7 from the viewpoint of dispersion stability. The dispersant of the present disclosure may be a polymer having anionic groups. The anionic group contained in the dispersant of the present disclosure is preferably a carboxyl group, a sulfo group, or a phosphate group, and among these, a carboxyl group is more preferred.

[0021] The dispersant used in the present invention is not particularly limited as long as it has an acid value of 150 mgKOH / g or less, and examples thereof include acrylic polymers, styrene-acrylic polymers, maleic acid polymers, styrene-maleic acid polymers, α-olefin-maleic acid polymers, urethane polymers, ester resin polymers, sulfonic acid polymers, phosphoric acid polymers, etc. Among these, acrylic polymers and styrene-acrylic polymers are preferred from the viewpoint of preventing the formation of hard cakes.

[0022] Furthermore, the introduction of polyalkylene glycol groups into the dispersant is expected to improve the effect of preventing hard cake formation. As the polyalkylene glycol group, it is preferable that the dispersant contains a polypropylene glycol group or a polyethylene glycol group.

[0023] Dispersants with an acid value of 150 mg KOH / g or less as described above can be obtained by known techniques, but any of these commercially available products can be used. Commercially available products include, but are not limited to, Disperbyk-102, Disperbyk-111, Disperbyk-190, Disperbyk-191, Disperbyk-194N, Disperbyk-2010, Disperbyk-2012, and Disperbyk-2015 manufactured by BYK Japan; TEGO Dispers-715N, TEGO Dispers-750W, and TEGO Dispers-755W manufactured by Evonik Japan; and Efka 6230 manufactured by BASF. Furthermore, dispersants containing polyalkylene glycol groups and having an acid value of 150 mg KOH / g or less include, but are not limited to, Disperbyk-190 and Disperbyk-2015 manufactured by BYK Japan.

[0024] The content of the dispersant per 100 parts by mass of titanium oxide of the present disclosure is 2% by mass or more, preferably 2.2 parts by mass or more, more preferably 2.5% by mass or more, and even more preferably 2.8% by mass or more, from the viewpoint of dispersion stability, and is preferably 8% by mass or less, more preferably 7% by mass or less, and even more preferably 6.5% by mass or less, from the viewpoint of foam-suppressing properties and the physical properties of the coating film after being made into an ink.

[0025] <Water> The titanium oxide dispersion of the present disclosure contains water. The water content per 100 parts by mass of the liquid phase component in the titanium oxide dispersion of the present disclosure is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, from the viewpoint of safety during production of the titanium oxide dispersion. The titanium oxide dispersion of the present disclosure may contain a water-soluble organic solvent in addition to water, and ethylene glycol or propylene glycol is preferred as the water-soluble organic solvent. The boiling point of the water-soluble organic solvent is preferably 240°C or lower, more preferably 220°C or lower, and even more preferably 200°C or lower, from the viewpoint of the drying property of the ink when the ink is produced using the titanium oxide dispersion as a raw material.

[0026] From the viewpoints of safety when made into a water-based ink and drying property of the ink, the amount of the water-soluble organic solvent having a lactam ring structure is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 2 parts by mass or less per 100 parts by mass of the titanium dioxide dispersion, and may be zero. Examples of the water-soluble organic solvent having a lactam ring structure include 2-pyrrolidone, N-methylpyrrolidone, and N-ethylpyrrolidone.

[0027] The boiling point of the water-soluble organic solvent is preferably 240°C or lower, more preferably 220°C or lower, and even more preferably 200°C or lower, from the viewpoint of the drying property of the ink when the ink is produced using the titanium oxide dispersion as a raw material. The water content per 100 parts by mass of the liquid phase component in the titanium oxide dispersion of the present disclosure is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, from the viewpoint of safety during production of the titanium oxide dispersion.

[0028] <Other additives> Other additives that can be appropriately blended include antifoaming agents, plasticizers, leveling agents, mildew inhibitors, rust inhibitors, matting agents, flame retardants, thixotropic agents, tackifiers, thickeners, lubricants, antistatic agents, surfactants, reaction retarders, antioxidants, ultraviolet absorbers, hydrolysis inhibitors, weather stabilizers, anti-tack agents, etc. The blending ratios of various additives are appropriately selected depending on the purpose and application.

[0029] The defoaming agents of the present disclosure include silicone-based defoaming agents, polyether-based defoaming agents, fatty acid ester-based defoaming agents, and acetylene glycol-based defoaming agents. Among these, silicone-based defoaming agents and acetylene glycol-based defoaming agents are preferred because they have excellent ability to properly maintain surface tension and interfacial tension and hardly generate foam. The content of the antifoaming agent per 100 parts by mass of the titanium oxide dispersion of the present disclosure is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and even more preferably 0.05 parts by mass or more, from the viewpoint of foam suppression, and is preferably 0.5 parts by mass or less, more preferably 0.4 parts by mass or less, and even more preferably 0.3 parts by mass or less, from the viewpoint of suppressing floating on the oil film.

[0030] <Physical properties of titanium oxide dispersion> The pH of the titanium oxide dispersion of the present disclosure is preferably 5 to 10, more preferably 5.5 to 8, and even more preferably 5.5 to 7, from the viewpoint of dispersion stability. If the viscosity of the titanium oxide dispersion of the present disclosure is too high, the efficiency of dispersion treatment using a bead mill or the like will decrease, and when used as a raw material for an aqueous white ink, the viscosity of the aqueous white ink will increase, reducing printability. If the viscosity is too low, the settling rate of titanium oxide, which has a high specific gravity, will increase, raising concerns about the formation of a hard cake. From these perspectives, the viscosity of the titanium oxide dispersion is preferably 1 to 200 mPa·s or less, more preferably 2 to 100 mPa·s or more, more preferably 5 to 50 mPa·s or more, and even more preferably 10 to 20 mPa·s or more. The viscosity of the titanium oxide dispersion of the present disclosure at 25°C can be measured by a known method, specifically, using a B-type viscometer or E-type viscometer.

[0031] With regard to the titanium oxide-containing particles (C) in the titanium oxide dispersion of the present disclosure, when the particle diameter of the cumulative 99% from the finest particle side of the volume-based cumulative particle size distribution is taken as the D99 particle diameter, the upper limit of the D99 particle diameter is preferably 800 nm or less, more preferably 775 nm or less, and even more preferably 750 nm or less, from the viewpoints of the sedimentation stability of the titanium oxide dispersion and the ejection stability when used as an aqueous white ink for inkjet printing. The lower limit of the D99 particle diameter is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more, from the viewpoints of preventing overdispersion and thickening due to detachment of the surface-treated metal oxide due to excessive bead milling.

[0032] Regarding the titanium oxide-containing particles (C) in the titanium oxide dispersion of the present disclosure, when the particle diameter D50 is defined as the cumulative 50% particle diameter from the finest particle side of the volume-based cumulative particle size distribution, if the D50 particle diameter is too large, it can cause nozzle clogging when used as an inkjet ink raw material, while if it is too small, it can reduce hiding power when used as an inkjet ink raw material. From these perspectives, the upper limit of the D50 particle diameter is preferably 500 nm or less, more preferably 450 nm or less, and even more preferably 380 nm or less, and the lower limit of the D50 particle diameter is preferably 150 nm or more, more preferably 200 nm or more, and even more preferably 250 nm or more.

[0033] The particle size distribution of the titanium oxide dispersion of the present disclosure can be measured by known methods, specifically, by dynamic scattering methods, Coulter counter methods, or the like, and a particle size distribution measurement method conforming to ISO 13319 or the like may also be used. Regarding the titanium oxide-containing particles (C) in the titanium oxide dispersion of the present disclosure, if the concentration of particles with a diameter of 1.0 μm or more is too high, it can cause nozzle clogging when used as a raw material for inkjet ink, and if it is too low, the productivity of the titanium oxide dispersion decreases. 6 ~200×10 6 μm3 / ml is preferred, and 3×10 6 ~100×10 6 μm 3 / ml, more preferably 5 × 10 6 ~50×10 6 It is more preferably μm 3 / ml.

[0034] The concentration of particles having a diameter of 1.0 μm or more in the titanium oxide dispersion of the present disclosure can be measured by a known method, specifically, by the Coulter counter method or the like.

[0035] The amount of nonvolatile matter in the titanium oxide dispersion of the present disclosure is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and particularly preferably 50% by mass or more, from the viewpoint of hiding power and processing efficiency when made into a printed matter. Also, from the viewpoint of suppressing the viscosity of the titanium oxide dispersion, the amount is preferably 80% by mass or less, more preferably 70% by mass or less.

[0036] The nonvolatile content of the titanium oxide dispersion liquid of the present disclosure is the amount of water and various additives based on the total mass of the titanium oxide dispersion liquid. Alternatively, 1 g of titanium oxide dispersion may be weighed, dried in a hot air dryer at 150°C for 1 hour, and the resulting residue may be used as the non-volatile content, and the mass may be calculated by the formula: [Non-volatile content (mass%) in titanium oxide dispersion liquid] = ([mass of residue] ÷ [1 g of titanium oxide dispersion]) × 100 It may be determined based on the following.

[0037] <Method of manufacturing titanium oxide dispersion> The titanium oxide dispersion of the present disclosure can be dispersed using titanium oxide, a dispersant, and water by a known method. As a dispersion method, a media-based dispersion device such as a ball mill, a sand mill, or a bead mill may be used, or a media-less dispersion device may be used, but a media-based dispersion device is preferred from the viewpoint of dispersion treatment efficiency. In terms of dispersibility and dispersion efficiency, it is preferable to use zirconia beads as the dispersion medium in the dispersion device using media. Two or more of these dispersion methods may be used in combination. If the diameter of the beads in the bead mill is too small, the cost of the beads increases and handling becomes difficult, while if it is too large, the efficiency of the bead mill processing decreases. From these viewpoints, the diameter of the beads is preferably 0.01 mm or more, more preferably 0.05 mm or more, and even more preferably 0.07 mm or more, and is preferably 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less.

[0038] The dispersion method for the titanium oxide dispersion of the present disclosure may be a circulation method or a multi-pass method. The circulation method includes a method in which a tank and a media-type disperser are installed and a circulation system is formed with piping to allow circulation and passing. The multi-pass method includes a method in which a mother tank, a receiving tank, and a media-type disperser are installed and the dispersion is returned from the receiving tank to the mother tank and passed, or a method in which two tanks and a media-type disperser are installed and passed using a catch-ball method. However, the circulation method is preferred from the viewpoint of simplicity of the equipment. The required number of media-type dispersers may be installed in series. The circulation system of the present disclosure is preferably a circulation system in which a titanium oxide dispersion containing titanium oxide, a dispersant, and water is repeatedly circulated through a media disperser.

[0039] <Water-based white ink using titanium dioxide dispersion> If the amount of rutile titanium oxide contained in the water-based white ink using the titanium oxide dispersion of the present disclosure as a raw material is too low, the hiding power will decrease, and if it is too high, the ink viscosity will increase and the printability will decrease. From these perspectives, the amount of rutile titanium oxide contained in 100 parts by mass of the water-based white ink is preferably 1 to 25 parts by mass, more preferably 3 to 20 parts by mass, and even more preferably 6 to 12 parts by mass.

[0040] The water-based white ink using the titanium oxide dispersion of the present disclosure contains a binder resin. In aqueous white inks using the titanium dioxide dispersion of the present disclosure as a raw material, the ratio of binder resin to rutile titanium dioxide (mass of rutile titanium dioxide / mass of non-volatile content of binder resin) is preferably 2 / 10 to 6 / 1, more preferably 5 / 10 to 2 / 1, and even more preferably 6 / 10 to 1 / 1, because too low a ratio reduces hiding power, while too high a ratio reduces the abrasion resistance and gloss of the coating film.

[0041] The nonvolatile content of the binder resin may be determined by referring to the value listed in a catalog or the like, or by calculating the mass excluding the mass of the volatile components contained in the binder resin and various additives, or by weighing 1 g of a water-dispersible resin containing a binder resin, drying it in a hot air dryer at a temperature of 110°C for 1 hour, and calculating the nonvolatile content by the formula: [Non-volatile content (mass%) in water-dispersible resin] = ([mass of residue] ÷ [1 g of water-dispersible resin]) × 100 It may be determined based on the following.

[0042] The type of water-dispersible resin contained as a binder resin in the water-based white ink using the titanium oxide dispersion of the present disclosure as a raw material to improve the scratch resistance of the coating film and adhesion to the substrate is not particularly limited, but from the viewpoint of improving the scratch resistance of the coating film and adhesion to the substrate, acrylic resin, styrene-acrylic resin, and urethane resin are preferred. Among these, acrylic resin is preferred from the viewpoint of improving adhesion to poorly absorbent substrates such as plastics, and water-dispersible resins containing polymers having structural units derived from cyclic aliphatic group-containing monomers are more preferred from the viewpoint of obtaining good adhesion to poorly adhesive olefin-based substrates such as biaxially oriented polypropylene (OPP) without primer printing or the like.

[0043] The water-dispersible resin of the present disclosure may be a single-layer resin emulsion particle, or may be a resin emulsion particle having multiple layers.

[0044] The cycloaliphatic group-containing monomer of the present disclosure is preferably a monomer having a carbon-carbon double bond, and examples thereof include a (meth)acrylate monomer having a cycloaliphatic hydrocarbon group. The (meth)acrylate monomer having a cycloaliphatic hydrocarbon group is preferably a compound having a monovalent cycloaliphatic hydrocarbon group and a monovalent (meth)acrylate group, and the monovalent cycloaliphatic hydrocarbon group and the monovalent (meth)acrylate group are directly bonded. Examples of the cycloaliphatic hydrocarbon group include monocyclic groups, polycyclic groups, and bridged ring groups. The cycloaliphatic hydrocarbon group preferably has 4 to 20 carbon atoms. The cycloaliphatic hydrocarbon group preferably has 4 to 20 carbon atoms, particularly 5 to 12 carbon atoms. The cycloaliphatic hydrocarbon group preferably has 15 or less carbon atoms, particularly preferably 10 or less carbon atoms. It is preferable that a carbon atom in the ring of the cycloaliphatic hydrocarbon group is directly bonded to an ester group in the (meth)acrylate group. Specific examples of the cycloaliphatic hydrocarbon group include a cyclohexyl group, a t-butylcyclohexyl group, an isobornyl group, a dicyclopentanyl group, and a dicyclopentenyl group. The (meth)acrylate group may be an acrylate group or a methacrylate group, with a methacrylate group being preferred.

[0045] Specific examples of the monomer having a cyclic aliphatic hydrocarbon group include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and the like, of which cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate are preferred, and cyclohexyl (meth)acrylate and isobornyl (meth)acrylate are more preferred. These alicyclic group-containing monomers can be used alone or in combination.

[0046] From the viewpoint of adhesion, the content of the structural units derived from the monomer having a cycloaliphatic hydrocarbon group in 100 parts by mass of the polymer having structural units derived from the cycloaliphatic group-containing monomer of the present disclosure may be 30 parts by mass or more, preferably 35 parts by mass or more, more preferably 40 parts by mass or more, and even more preferably 45 parts by mass or more; and may be 95 parts by mass or less, preferably 90 parts by mass or less, and more preferably 85 parts by mass or less.

[0047] When a water-dispersible resin containing a polymer having structural units derived from a cyclic aliphatic group-containing monomer is used as the binder resin of the present disclosure, the content of the structural units derived from the monomer having a cyclic aliphatic hydrocarbon group in 100 parts by mass of the water-dispersible resin may be 30 parts by mass or more, preferably 35 parts by mass or more, more preferably 40 parts by mass or more, and even more preferably 45 parts by mass or more, from the viewpoint of adhesion, and may be 95 parts by mass or less, preferably 90 parts by mass or less, and more preferably 85 parts by mass or less.

[0048] The polymer of the present disclosure having structural units derived from a cycloaliphatic group-containing monomer may also have structural units derived from other monomers in addition to the structural units derived from the cycloaliphatic group-containing monomer. The structural units derived from other monomers are not limited to structural units formed by polymerizing other monomers described below, but may also be structural units formed by a post-reaction after polymerization, for example.

[0049] Examples of the other monomer include monofunctional monomers and polyfunctional monomers. The monofunctional monomers and polyfunctional monomers may be used alone or in combination. Examples of monofunctional monomers include (meth)acrylic acid esters having a linear alkyl group, (meth)acrylic acid esters having a branched alkyl group, acid group-containing monomers, hydroxyl group-containing (meth)acrylates, oxo group-containing monomers, fluorine atom-containing monomers, nitrogen atom-containing monomers, epoxy group-containing monomers, alkoxyalkyl (meth)acrylates, silane group-containing monomers, carbonyl group-containing monomers, aziridinyl group-containing monomers, styrene-based monomers, aralkyl (meth)acrylates, and addition-polymerizable oxazolines, but are not limited to these examples.

[0050] The water-based white ink of the present disclosure may contain water as well as a water-soluble organic solvent from the viewpoints of ink viscosity, control of wetting and spreading on a recording medium to be printed, improvement of image quality, and ejection stability. Examples of the water-soluble organic solvent include glycols such as propylene glycol, 1,3-propanediol, glycerin, dipropylene glycol, tripropylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol; ethers of monoethylene glycol such as monoethylene glycol monomethyl ether, monoethylene glycol monoethyl ether, monoethylene glycol monopropyl ether, monoethylene glycol monoisopropyl ether, monoethylene glycol monobutyl ether, and monoethylene glycol monoisobutyl ether; monopropylene glycol monomethyl ether, monopropylene glycol monoethyl ether, monopropylene glycol monopropyl ether, monopropylene glycol monoisopropyl ether, monoethylene ...butyl ether, monoethylene glycol monomethyl ether, monopropylene glycol monopropyl ether, monopropylene glycol monoisopropyl ether, monoethylene glycol monomethyl ether, monopropylene glycol monoethyl ether, monopropylene glycol monopropyl ether, ethers of monopropylene glycol such as propylene glycol monobutyl ether and monopropylene glycol monoisobutyl ether; ethers of polyethylene glycol such as monomethyl ether of polyethylene glycol (number of moles of EO added=2 to 10, preferably 2 to 4), monoethyl ether of polyethylene glycol (number of moles of EO added=2 to 10, preferably 2 to 4), monopropyl ether of polyethylene glycol (number of moles of EO added=2 to 10, preferably 2 to 4), monoisopropyl ether of polyethylene glycol (number of moles of EO added=2 to 10, preferably 2 to 4), monobutyl ether of polyethylene glycol (number of moles of EO added=2 to 10, preferably 2 to 4), and monoisobutyl ether of polyethylene glycol (number of moles of EO added=2 to 10, preferably 2 to 4);Examples of suitable organic solvents include monomethyl ether of polypropylene glycol (number of moles of EO added = 2 to 10, preferably 2 to 4), monoethyl ether of polypropylene glycol (number of moles of EO added = 2 to 10, preferably 2 to 4), monopropyl ether of polypropylene glycol (number of moles of EO added = 2 to 10, preferably 2 to 4), monoisopropyl ether of polypropylene glycol (number of moles of EO added = 2 to 10, preferably 2 to 4), monobutyl ether of polypropylene glycol (number of moles of EO added = 2 to 10, preferably 2 to 4), and monoisobutyl ether of polypropylene glycol (number of moles of EO added = 2 to 10, preferably 2 to 4). Among these, preferred are propylene glycol, diethylene glycol, triethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, tripropylene glycol monomethyl ether, monoethylene glycol monoisopropyl ether, and monopropylene glycol monopropyl ether. These organic solvents may be used alone or in combination of two or more. ;

[0051] The amount of the water-soluble organic solvent cannot be determined in general terms because it differs depending on the type and amount of the colorant contained in the water-based white ink. Therefore, it is preferable to determine the amount of the water-soluble organic solvent appropriately depending on the type and amount of the colorant contained in the water-based white ink.

[0052] For example, if the colorant contains a white pigment, the amount of organic solvent in 100 parts by mass of the water-based white ink may be 5 parts by mass or more, preferably 8 parts by mass or more, and more preferably 10 parts by mass or more, from the perspective of controlling the wetting and spreading of the ink onto the recording medium to be printed and improving image quality, and may be 50 parts by mass or less, preferably 45 parts by mass or less, and more preferably 40 parts by mass or less.

[0053] The water-based white ink of the present disclosure contains the resin emulsion for water-based ink and a colorant, but may also contain other resins, such as resin emulsions other than the resin emulsion for water-based ink, water-soluble resins, water-dispersible resins, etc., as long as the object of the present invention is not impaired. Furthermore, the water-based ink of the present invention may also contain appropriate amounts of additives, such as surfactants, film-forming aids, ultraviolet absorbers, ultraviolet protection agents, fillers, leveling agents, dispersants, thickeners, wetting agents, plasticizers, stabilizers, antioxidants, waxes, etc., as long as the object of the present invention is not impaired.

[0054] <Applications and substrates of aqueous white ink using the titanium oxide dispersion of the present disclosure as a raw material> The water-based white ink of the present disclosure obtained as described above has excellent adhesion and scratch resistance, and can therefore be suitably used, for example, as an inkjet water-based ink, an ink for flexographic printing, an ink for offset printing, an ink for lithographic printing, an ink for gravure printing, or an ink for screen printing, and among these, an inkjet water-based ink is particularly suitable.

[0055] The water-based white ink of the present disclosure can form prints or images having a predetermined pattern by ejecting the water-based ink in a predetermined pattern onto a recording medium using, for example, an inkjet recording device.

[0056] Examples of recording media include paper, paper laminated with a resin film such as polyethylene, polypropylene, or polystyrene (coated paper, etc.), metal plates such as aluminum, zinc, or copper, resin films such as cellulose, polyethylene terephthalate, polystyrene, olefin-based resins, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyamide, nylon, and acrylic resins, paper with a metal coating, and resin films with a metal coating. Resin films are preferred as recording media for printing with the aqueous ink of the present disclosure, and polyethylene terephthalate and olefin-based resins are particularly preferred. Examples of olefin resins include polyethylene and polypropylene, and the application to polypropylene, such as biaxially oriented polypropylene film (OPP) and non-oriented polypropylene film (CPP), is particularly preferred.

[0057] The water-based white ink of the present disclosure is preferably formed on a resin film, and in this embodiment, it is a laminate having a printed layer formed from the water-based ink on the resin film. The disclosed laminate may or may not have a primer layer between the resin film and the printed layer, but it is preferable that it does not have one from the viewpoint of productivity, and it is preferable that the printed layer is formed directly on the resin film. The laminate of the present disclosure is formed by laminating the resin film and the printed layer in this order, and may or may not have a protective film (laminate layer) on the printed layer, but it is preferable that it does not have one from the viewpoint of productivity, and by using the aqueous ink of the present disclosure, it is expected that a laminate having excellent adhesion to the substrate and good scratch resistance can be obtained, even without a primer layer or a protective film (laminate layer). [Example]

[0058] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass."

[0059] <Glass transition temperature of polymer component in water-dispersible resin> The glass transition temperature (Tg) of a polymer component can be calculated using the glass transition temperature of a homopolymer of a monomer used in a monomer component constituting the polymer component, using the formula: 1 / Tg=Σ(Wm / Tgm) / 100 (wherein Wm represents the content (mass%) of monomer m in the monomer components constituting the polymer component, and Tgm represents the glass transition temperature (absolute temperature: K) of a homopolymer of monomer m.) The value was calculated based on the Fox equation:

[0060] <Acid value derived from carboxyl groups of polymer components in water-dispersible resin> The acid value derived from the carboxyl groups of the resin emulsion particles was obtained by approximating the acid value as the number of mg of potassium hydroxide required to neutralize the carboxyl groups present in 1 g of the monomer component used. <Minimum film-forming temperature of polymer component in water-dispersible resin> The minimum film-forming temperature is a value measured in accordance with JIS K6828-2:2003. <Average particle size of polymer component in water-dispersible resin> The measurement temperature was 25±0.5°C, and a multi-analyte nanoparticle size measurement system (Otsuka Electronics Co., Ltd., product name: nanoSAQLA), a particle size measurement device using dynamic light scattering, was used to determine the autocorrelation function using the photon correlation method, and the average particle size (hydrodynamic diameter) was calculated using cumulant analysis.

[0061] <Measurement of primary particle size of rutile-type titanium dioxide> Calculated from scanning electron microscope observation. <Measurement of parts by mass of each element contained in rutile-type titanium dioxide> The mass parts of each element contained in the rutile-type titanium oxide were measured by X-ray fluorescence (XRF) measurement using a ZSX Primus II manufactured by RIGAKU Corporation. <D50 particle size, D99 particle size, and particle concentration of 1 μm or larger for titanium dioxide dispersion and water-based white ink> The volumetric particle size was evaluated using a Beckman Coulter Multisizer4e.

[0062] [Production example 1] Water-dispersible resin A flask equipped with a dropping funnel, stirrer, nitrogen gas inlet, thermometer, and reflux condenser was charged with 520 parts of deionized water. A first-stage pre-emulsion was prepared in the dropping funnel. The pre-emulsion consisted of 163 parts of deionized water, 80 parts of a 25% aqueous solution of emulsifier (ADEKA Corporation, trade name: ADEKA REASORB SR-10), 322 parts of cyclohexyl methacrylate, 103 parts of 2-ethylhexyl acrylate, and 75 parts of 2-hydroxyethyl methacrylate. 74 parts of this pre-emulsion, equivalent to 5% of the total amount of all monomer components, was added to the flask. The temperature was raised to 70°C while slowly blowing in nitrogen gas. 30 parts of a 5% aqueous solution of ammonium persulfate was added to initiate polymerization. The remainder of the pre-emulsion was then added dropwise uniformly to the flask over 120 minutes.

[0063] After the dropwise addition was completed, the contents of the flask were maintained at 70°C for 60 minutes, and then a pre-emulsion for second-stage dropping, consisting of 163 parts of deionized water, 80 parts of a 25% aqueous solution of an emulsifier (manufactured by ADEKA Corporation, trade name: ADEKA REASORB SR-10), 310 parts of cyclohexyl methacrylate, 105 parts of 2-ethylhexyl acrylate, 75 parts of 2-hydroxyethyl methacrylate, and 10 parts of 4-(meth)acryloyloxy-1,2,2,6,6-pentamethylpiperidine (manufactured by ADEKA Corporation, trade name: Adeka STAB LA-82), and 30 parts of a 5% aqueous solution of ammonium persulfate, was uniformly added dropwise to the flask over a period of 120 minutes.

[0064] After the dropwise addition was completed, the contents of the flask were maintained at 70°C for 60 minutes, and the pH was adjusted to 8 by adding 25% aqueous ammonia to terminate the polymerization. The resulting reaction solution was cooled to room temperature and then filtered through a 300-mesh wire mesh to prepare an aqueous dispersion. The resulting aqueous dispersion contained a polymer, which was a resin emulsion and consisted of emulsion particles with a two-layer structure having an inner layer and an outer layer. The nonvolatile content of this aqueous dispersion was 50%, the acid value derived from the carboxyl groups of the polymer was 0 mg KOH / g, and the glass transition temperatures of the inner layer resin and outer layer resin constituting the resin emulsion particles contained in the emulsion were 32°C and 32°C, respectively. The minimum film-growth temperature was 40°C, and the average particle size was 150 nm.

[0065] <Effect of rutile titanium dioxide type (Si / (Al+Zr) ratio)> [Example 1] A 250 mL plastic container was charged with 40.77 parts of pure water, 4.13 parts of Disperbyk-190 (BYK Japan, polyalkylene glycol group-containing acrylic water-soluble resin, acid value 10 mg KOH / g, active ingredient concentration 40%) as a dispersant, 55.00 parts of titanium dioxide A (primary particle diameter 210-290 nm) as rutile-type titanium dioxide, and 0.10 parts of Olfine D10-PG (Nissin Chemical Industry Co., Ltd., acetylene-based surfactant) as an antifoaming agent. Next, 100 g of 0.1 mm diameter zirconia beads were added as dispersion media. The container was sealed and subjected to a paint shaker treatment for 300 minutes. The zirconia beads were then suction filtered through a 7 μm mesh paper filter to obtain a titanium dioxide dispersion with a rutile-type titanium dioxide concentration of 55% by mass. Next, 24.5 parts of pure water, 15.0 parts of propylene glycol and 5.0 parts of tripropylene glycol monobutyl ether as water-soluble organic solvents, 20.0 parts of the titanium oxide dispersion described above, 35 parts of the water-dispersible resin obtained in Production Example 1 as a binder resin, and 0.5 parts of KF-6011 (manufactured by Shin-Etsu Chemical Co., Ltd., PEG-11 methyl ether dimethicone (a polyether-modified silicone surfactant) as a surfactant) were mixed in a Homodisper at 1000 rpm, and the mixture was filtered through a 3 μm filter [manufactured by Advantec Co., Ltd., MCP-3-C10S] to obtain a water-based white ink.

[0066] [Examples 2 to 6, Comparative Examples 1 to 9] A titanium oxide dispersion and a water-based white ink were prepared in the same manner as in Example 1, except that the type of rutile titanium oxide having a primary particle diameter of 210 to 290 nm was changed according to Table 1. The physical properties of the titanium oxides used in Examples 1 to 6 and Comparative Examples 1 to 9 and the amounts of dispersants added are shown in Table 1.

[0067] [Table 1]

[0068] Table 2 shows the evaluation results of the titanium oxide dispersants and water-based white inks obtained in Examples 1 to 6 and Comparative Examples 1 to 9. <Evaluation criteria> Sedimentation stability: 50g of sample was placed in a 100cc plastic container and left at 50℃ for 3 months. 〇: When the container is gently shaken, the difference in non-volatile concentration between the supernatant liquid and the bottom of the container is less than 0.1% △: When the container is gently shaken, the difference in non-volatile content between the supernatant and the bottom of the container is 0.1% or more but less than 1% ×: A hard cake is formed, and when the container is gently shaken, the difference in non-volatile concentration between the supernatant liquid and the bottom of the container is 1% or more.

[0069] Foaming: 50g of titanium dioxide dispersion was placed in a 100cc plastic container and shaken well for 5 minutes. The bubbles that were generated 〇: Disappears within 4 seconds △: Disappears within 4 to 5 seconds ×: Takes more than 5 seconds to disappear The bubbles that appear when 50g of water-based ink is placed in a 100cc plastic container and shaken well for 5 minutes Yes: Disappears within 40 seconds △: Disappears within 40 to 50 seconds ×: Takes more than 50 seconds to disappear

[0070] Resistant to organic solvents; 10 parts of propylene glycol and 90 parts of tripropylene glycol monobutyl ether were mixed thoroughly to create a liquid phase component simulation liquid when water evaporates due to localized drying. When 1 part by mass of water-based white ink was dropped onto 99 parts by mass of this simulation liquid, 〇: Disperses evenly to form a uniform white dispersion △: A very small amount of white precipitate occurs ×: A lot of white precipitates are generated

[0071] Coating strength The water-based white ink was applied to an OPP film (FOR-AQ) manufactured by Futamura Chemical Co., Ltd. using a #3 bar coater and dried at 110°C for 2 minutes to obtain a white coating film. When the coating film was strongly rubbed with a Kimwipe, 〇: The white coating does not peel off at all ×: The white coating peels off even slightly.

[0072] [Table 2]

[0073] The amount of silicon element per 100 parts by mass of titanium element contained in the rutile-type titanium oxide obtained by XRF measurement in Examples 1 to 6 and Comparative Examples 1 to 9 was plotted against the sum of the amount of aluminum element and the amount of zirconium element per 100 parts by mass of titanium element, and the results are shown in Figure 1. [Examples 7 to 9, Comparative Examples 10 to 22] A titanium oxide dispersion and a water-based white ink were prepared in the same manner as in Example 1, except that the type of rutile titanium oxide having a primary particle diameter of 250 to 260 nm and the type and amount of dispersant were changed according to Table 3. Table 3 shows the physical properties of the titanium oxides and the amounts of dispersants added used in Examples 7 to 9 and Comparative Examples 10 to 22.

[0074] [Table 3]

[0075] The abbreviations in each table have the following meanings: BYK-190; manufactured by BYK Japan, a polyalkylene glycol group-containing acrylic water-soluble resin, acid value 10 mg KOH / g, active ingredient concentration 40% HPD196: BASF acrylic water-soluble polymer dispersant, acid value 200 mg KOH / g, molecular weight (MW) 9200, active ingredient concentration 36% HL415-NH3: A water-soluble polymer dispersant prepared by adjusting the pH of Nippon Shokubai's polyacrylic acid aqueous solution Aqualic HL415 with a 25% ammonia solution manufactured by Wako Pure Chemical Industries, Ltd., to 7.5. The acid value is 750 mg KOH / g, the molecular weight (MW) is 11,700, and the active ingredient concentration is 39%. Table 4 shows the evaluation results of the titanium oxide dispersions and water-based white inks obtained in Examples 7 to 9 and Comparative Examples 10 to 22.

[0076] [Table 4]

[0077] The titanium oxide dispersions having the compositions of Examples 1 to 9 and the water-based white inks using them as raw materials were excellent in terms of sedimentation stability, anti-foaming properties, organic solvent resistance, and coating strength. On the other hand, in the comparative examples outside the scope of the present invention, it was not possible to obtain a titanium oxide dispersion of practical quality that satisfied all evaluation items, and a water-based white ink using the same as a raw material. Tables 1 and 2 and Figure 1 confirm that the mass part ratio of each element contained in rutile titanium dioxide satisfying formula (1) is critical for the titanium dioxide dispersion and water-based white ink to exhibit excellent sedimentation stability. Tables 3 and 4 show that Comparative Examples 10, 12, and 14, in which the dispersant amount was below the lower limit of the present invention, did not provide sufficient sedimentation stability. Comparative Examples 11, 13, and 15, in which the dispersant amount was above the upper limit of the present invention, did not provide sufficient foam suppression and coating strength. Comparative Examples 16, 17, 20, and 21, in which the dispersant acid value was slightly above the upper limit of the present invention, did not provide sufficient sedimentation stability at any dispersant amount, and it was also found that increasing the dispersant amount worsened the foaming properties of the water-based white ink. Comparative Examples 18, 19, 22, and 23, in which the dispersant acid value was significantly above the upper limit of the present invention, provided satisfactory sedimentation stability at a dispersant amount of 3 parts by mass per 100 parts by mass of titanium dioxide, but did not provide satisfactory organic solvent resistance at any dispersant amount.

Claims

1. A titanium oxide dispersion comprising rutile titanium oxide (A), a dispersant (B), and water, The rutile-type titanium oxide (A) contains at least one element selected from the group consisting of aluminum, silicon, and zirconium, The ratio of the mass parts satisfies the following formula (1), 0.8 < Si / (Al+Zr) < 4.0 (1) The content of silicon element per 100 parts by mass of titanium element is 0.5 parts by mass or more, The content of aluminum element per 100 parts by mass of titanium element is 0.5 parts by mass or more, The titanium oxide dispersion is characterized in that the acid value of the dispersant (B) is 50 mgKOH / g or less, and the content of the dispersant (B) is 2.2 parts by mass or more and 6.5 parts by mass or less per 100 parts by mass of the rutile-type titanium oxide (A).

2. 2. The titanium oxide dispersion according to claim 1, wherein the content of the rutile-type titanium oxide (A) is 25 to 70 parts by mass per 100 parts by mass of the titanium oxide dispersion.

3. A titanium oxide dispersion as described in claim 1 or 2, wherein the content of zirconium element per 100 parts by mass of titanium element is 0.01 parts by mass or more.

4. 3. The titanium oxide dispersion according to claim 1, wherein the dispersant (B) contains a polyalkylene glycol group.

5. 5. The titanium oxide dispersion according to claim 1, wherein the content of the water-soluble organic solvent having a lactam ring structure per 100 parts by mass of the titanium oxide dispersion is 10 parts by mass or less.

6. the titanium oxide dispersion contains an antifoaming agent, the defoaming agent comprises a silicone-based defoaming agent and / or an acetylene glycol-based defoaming agent; 6. The titanium oxide dispersion according to claim 1, wherein the content of the antifoaming agent per 100 parts by mass of the titanium oxide dispersion is 0.001 parts by mass or more and 0.5 parts by mass or less.

7. 7. The titanium oxide dispersion according to claim 1, wherein the titanium oxide-containing particles (C) have a D99 particle size of 800 nm or less.

8. 8. The titanium oxide dispersion according to claim 1, wherein the concentration of particles (C) having a size of 1.0 μm or more is 200×10 μm / ml or less.

9. The method for producing the titanium oxide dispersion according to any one of claims 1 to 8, wherein the dispersion is prepared by bead mill treatment using media with a diameter of 0.5 mm or less.

10. A water-based white ink using the titanium oxide dispersion according to any one of claims 1 to 9 as a raw material.

11. The water-based white ink according to claim 10, which is an ink-jet ink.

12. A printed matter obtained using the water-based white ink according to claim 10 or 11.

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