Pigment dispersion

Abstract

To provide a vapor-deposited aluminum pigment dispersion, which satisfies both specular gloss and water resistance which enables use as a water-based paint.SOLUTION: Provided is a pigment dispersion, comprising a vapor-deposited aluminum pigment, an organic phosphoric acid compound having a C8 or more linear alkyl group, and a solvent. The vapor-deposited aluminum pigment is coated at least partially with at least a part of the organic phosphoric acid compound. The pigment dispersion has a viscosity of less than 1 Pa s when measured by a Brookfield RVT DV2T HB-type viscometer (20°C, CPA-40Z cone spindle, and 20 rpm).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention generally relates to pigment dispersions, and more particularly to pigment dispersions containing vapor-deposited aluminum pigments.

Background Art

[0002] Conventionally, specular gloss has been required for printing and painting.

[0003] For example, Japanese Patent Application Publication No. 2018-534403 (Patent Document 1) describes an offset printing ink containing a PVD aluminum pigment coated with a leafing additive, a binder, and an oil-type solvent such as mineral oil, vegetable oil, and fatty acid ester or a mixture thereof.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the method described in Patent Document 1 is an offset printing ink that is difficult to be made aqueous, and does not meet the recent demand for aqueousness in general paints and inks.

[0006] Therefore, an object of the present invention is to provide a vapor-deposited aluminum pigment dispersion that achieves both specular gloss and water resistance that can be used as an aqueous paint.

Means for Solving the Problems

[0007] As a result of intensive research, the present inventors have found that by using a vapor-deposited aluminum pigment as an aluminum pigment, coating the vapor-deposited aluminum pigment with an organic phosphoric acid compound having a linear alkyl group with a specific number of carbon atoms, and suppressing the viscosity of the pigment dispersion to less than a specific viscosity, it is possible to improve the water resistance while maintaining the specular gloss by the vapor-deposited aluminum pigment, and further improve the leafing property.

[0008] Based on the above findings, the pigment dispersion according to the present invention contains a vapor-deposited aluminum pigment, an organic phosphoric acid compound having a linear alkyl group with 8 or more carbon atoms, and a solvent. The vapor-deposited aluminum pigment is at least partially coated with at least a part of the organic phosphoric acid compound and has a viscosity of less than 1 Pa·s when measured with a Brookfield RVT DV2T HB viscometer (at 20 °C, CPA-40Z cone spindle, 20 rpm).

[0009] By doing so, it is possible to provide a vapor-deposited aluminum pigment dispersion that achieves both specular gloss and water resistance that can be used as an aqueous paint.

Embodiments for Carrying Out the Invention

[0010] The pigment dispersion according to the present invention contains a vapor-deposited aluminum pigment, an organic phosphoric acid compound having a linear alkyl group with 8 or more carbon atoms, and a solvent. The vapor-deposited aluminum pigment is at least partially coated with at least a part of the organic phosphoric acid compound and has a viscosity of less than 1 Pa·s when measured with a Brookfield RVT DV2T HB viscometer (at 20 °C, CPA-40Z cone spindle, 20 rpm).

[0011] Known vapor-deposited aluminum pigments can be used without particular limitation.

[0012] The average particle diameter of the vapor-deposited aluminum pigment is not particularly limited, but the volume-average median diameter (D 50) is preferably from 0.1 μm to 50 μm, more preferably from 1 μm to 20 μm. The volume-average median diameter (D 50 ) is less than 0.1 μm, the overlap of particles on the object to be coated may increase, and the specular gloss may decrease. On the other hand, when the volume-average median diameter (D 50 ) exceeds 50 μm, for example, when spraying a pigment dispersion, the spray nozzle is likely to be clogged, and coating unevenness on the object to be coated may occur. The volume-average median diameter (D 50 ) of the vapor-deposited aluminum pigment can be measured, for example, using a laser scattering particle size distribution measuring device. In the case of the small particle region where the volume-average median diameter (D 50 ) is 0.1 μm, ultrasonic dispersion is required immediately before measurement.

[0013] The thickness of the vapor-deposited aluminum pigment is not particularly limited, but is preferably from 5 nm to 100 nm, more preferably from 10 nm to 50 nm. When the thickness of the vapor-deposited aluminum pigment is less than 5 nm, the production of the vapor-deposited aluminum pigment may be difficult. On the other hand, when the thickness of the vapor-deposited aluminum pigment exceeds 100 nm, the specular gloss, which is a characteristic of the vapor-deposited aluminum pigment, may be significantly reduced. The thickness of the vapor-deposited aluminum pigment can be measured, for example, from an image of a cross-section taken using an electron microscope.

[0014] The organic phosphoric acid compound is preferably at least one selected from the group consisting of phosphoric acid esters, acidic phosphoric acid esters, chlorinated phosphoric acid esters, phosphorous acid esters, and their condensed phosphoric acid esters. When the organic phosphoric acid compound adsorbs on the surface of the vapor-deposited aluminum pigment and coats at least a part of the vapor-deposited aluminum pigment, water is prevented from approaching the vapor-deposited aluminum pigment by the organic group, and the water resistance of the vapor-deposited aluminum pigment is improved. Among them, the acidic phosphoric acid ester is preferable because it can strongly adsorb on the surface of the vapor-deposited aluminum pigment and has high water resistance.

[0015] The organic phosphate compound used in the pigment dispersion according to the present invention is an organic phosphate compound having a linear alkyl group as an organic group. When the organic group of the organic phosphate compound has a branch or a double bond, the leafing property may decrease. This is because the organic groups interfere with each other due to the bending of the carbon chain caused by the branch or double bond, so that sufficient organic phosphate compound cannot be adsorbed on the surface of the vapor-deposited aluminum pigment.

[0016] The number of carbon atoms of the linear alkyl group of the organic phosphate compound is 8 or more and 30 or less, preferably 10 or more and 20 or less. If the number of carbon atoms is less than 8, sufficient water resistance and leafing property cannot be obtained. On the other hand, even if the number of carbon atoms exceeds 30, no further improvement effect of the leafing property can be obtained.

[0017] As the organic phosphate compound, it is preferable to use one that is in a solid state at 25°C. In this way, the water resistance and leafing value tend to be high.

[0018] The amount of the organic phosphate compound is preferably 10 parts by mass or more and 100 parts by mass or less, more preferably 20 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the vapor-deposited aluminum pigment. If the amount of the organic phosphate compound is less than 10 parts by mass with respect to 100 parts by mass of the vapor-deposited aluminum pigment, the surface of the vapor-deposited aluminum pigment may not be sufficiently coated, and the water resistance and leafing property may be insufficient. If the amount of the organic phosphate compound exceeds 100 parts by mass with respect to 100 parts by mass of the vapor-deposited aluminum pigment, the organic phosphate compound may precipitate during storage at room temperature.

[0019] The solvent is not particularly limited, but for the purpose of making the pigment dispersion aqueous, it is preferably a hydrophilic solvent. As the hydrophilic solvent, alcohols, glycols, glycol ethers, acetone, etc. may be used.

[0020] The pigment dispersion may contain, in addition to the vapor-deposited aluminum pigment, the organic phosphoric acid compound, and the solvent, additives and the like. The additives are not particularly limited, and a dispersant, a surfactant, an anti-settling agent, a leveling agent, a thixotropic modifier, or the like may be used.

[0021] The pigment dispersion contains an aqueous resin composition and can also be made into an aqueous paint. As the aqueous resin composition, known ones such as emulsion resins and dispersions can be used according to the application.

[0022] When the pigment dispersion is made into an aqueous paint, the amount of the vapor-deposited aluminum pigment varies depending on applications such as inks and paints, but it is preferably 1 part by mass or more and 500 parts by mass or less with respect to 100 parts by mass of the aqueous resin composition.

[0023] Next, a method for producing the pigment dispersion according to the present invention will be described.

[0024] The pigment dispersion can be prepared by a known method using the above-described raw materials. For example, while stirring the vapor-deposited aluminum pigment and the solvent, the organic phosphoric acid compound is added, and further stirred to coat at least part of the vapor-deposited aluminum pigment with at least part of the organic phosphoric acid compound, thereby preparing a slurry-like pigment composition.

[0025] The pigment dispersion thus produced has a viscosity of less than 1 Pa·s when measured with a Brookfield RVT DV2T HB type viscometer (at 20°C, CPA-40Z cone spindle, 20 rpm). The viscosity is preferably 0.1 or more and 0.6 or less.

[0026] The present invention is summarized as follows.

[0027] [1] The pigment dispersion according to the present invention contains a vapor-deposited aluminum pigment, an organic phosphoric acid compound having a linear alkyl group with 8 or more carbon atoms, and a solvent. The vapor-deposited aluminum pigment is at least partially coated with at least a part of the organic phosphoric acid compound and has a viscosity of less than 1 Pa·s when measured with a Brookfield RVT DV2T HB viscometer (at 20°C, CPA-40Z cone spindle, 20 rpm).

[0028] [2] In the pigment dispersion according to the present invention, the organic phosphoric acid compound is preferably the organic phosphoric acid compound in a solid state at 25°C.

[0029] [3] In the pigment dispersion according to the present invention, the organic phosphoric acid compound is preferably at least one selected from the group consisting of phosphate esters, acidic phosphate esters, chlorinated phosphate esters, phosphite esters, and their condensed phosphate esters.

[0030] [4] The pigment dispersion according to the present invention preferably contains 15 parts by mass or more and 80 parts by mass or less of the organic phosphoric acid compound with respect to 100 parts by mass of the vapor-deposited aluminum pigment.

[0031] [5] In the pigment dispersion according to the present invention, the organic phosphoric acid compound is preferably an acidic phosphate ester having a linear alkyl group with 8 or more and 30 or less carbon atoms.

[0032] [6] The aqueous paint according to the present invention contains the pigment dispersion according to any one of [1] to [5] above and an aqueous resin.

[0033] [7] The aqueous paint according to the present invention preferably contains 1 part by mass or more and 500 parts by mass or less of the vapor-deposited aluminum pigment with respect to 100 parts by mass of the aqueous resin.

Examples

[0034] The present invention will be described in more detail with reference to Examples and Test Examples, but the present invention is not limited thereto.

[0035] [Example 1] Vapor-deposited aluminum pigment and solvent were used, and TS-710PM (D) manufactured by Toyo Aluminum Co., Ltd. 50 500 g of (N = 10 μm, average thickness 25 nm, non-volatile content 10 mass%, solvent: propylene glycol monomethyl ether) was added to a 1 L reactor and heated to 80°C while stirring with a stirring blade. Next, 15 g of granular stearyl acid phosphate (manufactured by SC Organic Chemical Co., Ltd., product name: Phoslex A-18, melting point 70°C, non-volatile content 100 mass%, linear alkyl group has 18 carbon atoms) was added as an organic phosphoric acid compound and stirred for 30 minutes to obtain a slurry-like evaporated aluminum pigment dispersion with a non-volatile content of 13 mass%. The viscosity of the obtained pigment dispersion was measured with a Brookfield RVT DV2T HB type viscometer (at 20°C, CPA-40Z cone spindle, 20 rpm). The viscosity was 0.2 Pa·s.

[0036] [Example 2] A vapor-deposited aluminum pigment dispersion in slurry form with a nonvolatile content of 13 mass % was obtained in the same manner as in Example 1, except that the organophosphate compound in Example 1 was changed to 15 g of granular lauryl acid phosphate (manufactured by SC Organic Chemical Co., Ltd., product name: Phoslex A-12, melting point 45°C, nonvolatile content 100%, linear alkyl group having 12 carbon atoms). The viscosity was 0.2 Pa s.

[0037] [Comparative Example 1] The vapor-deposited aluminum pigment and the solvent (TS-710PM manufactured by Toyo Aluminum Co., Ltd.) used in Example 1 were used without any treatment to prepare a vapor-deposited aluminum pigment dispersion. The viscosity was 0.4 Pa·s.

[0038] [Comparative Example 2] A vapor-deposited aluminum pigment dispersion in the form of a slurry with a non-volatile content of 13% by mass was obtained in the same manner as in Example 1, except that 15 g of granular stearic acid (manufactured by NOF Corporation, product name: Beads Sakura Stearic Acid, melting point 60°C, non-volatile content 100%) was used instead of the organophosphate compound in Example 1. The viscosity was 0.3 Pa s.

[0039] [Comparative Example 3] A slurry-like vapor-deposited aluminum pigment dispersion with a non-volatile content of 11% by mass was obtained in the same manner as in Example 1, except that the organophosphoric acid compound of Example 1 was changed to 15 g of oleyl acid phosphate (trade name: Phoslex A-18C, manufactured by SC Organic Chemicals Co., Ltd., a linear alkenyl group having 18 carbon atoms and 1 unsaturated bond) which was liquid at 25°C. The viscosity was 0.4 Pa·s.

[0040] [Comparative Example 4] A slurry-like vapor-deposited aluminum pigment dispersion with a non-volatile content of 11% by mass was obtained in the same manner as in Example 1, except that the organophosphoric acid compound of Example 1 was changed to 15 g of butyl acid phosphate (trade name: Phoslex A-4, manufactured by SC Organic Chemicals Co., Ltd., the carbon number of the linear alkyl group is 4) which was liquid at 25°C. The viscosity was 0.4 Pa·s.

[0041] [Comparative Example 5] A slurry-like vapor-deposited aluminum pigment dispersion with a non-volatile content of 13% by mass was obtained in the same manner as in Example 1, except that 15 g of 2-ethylhexyl acid phosphate (trade name: JP-508, specific gravity 1.02, an alkyl group having 8 carbon atoms with branches, manufactured by Johoku Chemical Industry Co., Ltd.) which was liquid at 25°C was used instead of the organophosphoric acid compound of Example 1. The viscosity was 0.2 Pa·s.

[0042] [Leafing value test] The leafing values of the pigment dispersions of each Example and Comparative Example were measured according to JIS K 5906:2009. The results are shown in Table 1. [Hydrogen gas generation test] 40 g of the pigment dispersions of each Example and Comparative Example were put into a 200 mL bottle for gas generation measurement, and then 160 g of ion-exchanged water was added. After adding, it was dispersed with a glass rod, and then the gas generation measurement bottle was immersed in a constant temperature water bath at 40°C, and the hydrogen gas generation amount for 48 hours was measured. The results are shown in Table 1.

[0043] [Phosphorus adsorption amount test of vapor-deposited aluminum pigment] After adding aqua regia to 0.1 g of the non-volatile content of the pigment dispersions of each example and comparative example, microwave digestion was performed to solubilize them, and the amount of phosphorus was measured by IPC analysis. The results are shown in Table 1. The phosphorus adsorption amount shown in Table 1 is the mass % of phosphorus with respect to the non-volatile content of each pigment dispersion.

[0044]

Table 1

[0045] As shown in Table 1, the pigment dispersions of Examples 1 and 2 had a leaching value of 60 or more. On the other hand, the pigment dispersions of the comparative examples had a low leaching value not only when the organic phosphoric acid compound was not used (Comparative Examples 1 and 2), but also when the organic phosphoric acid compound was used but the organic phosphoric acid compound did not have a linear alkyl group having 8 or more carbon atoms (Comparative Examples 3 and 4). In particular, when comparing Example 1 and Comparative Example 3, the total number of carbon atoms of the organic phosphoric acid compounds used was the same at 18 for both, but Comparative Example 3 did not have a linear alkyl group having 8 or more carbon atoms. As a result, the phosphorus adsorption amount was less in Comparative Example 3 than in Example 1, and the leaching value was 90 in Example 1 and 0 in Comparative Example 3, showing a large difference. Also, the gas generation amount of the pigment dispersions of Examples 1 and 2 was suppressed.

[0046] The embodiments and examples disclosed above should be considered illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and includes all modifications within the meaning and scope equivalent to the claims.

Claims

Claim 1 A vapor-deposited aluminum pigment, an organic phosphoric acid compound having a linear alkyl group with 8 or more carbon atoms, and a hydrophilic solvent, The vapor-deposited aluminum pigment has a volume-average median diameter (D ５０ ) of 0.1 μm or more and 50 μm or less, and a thickness of 5 nm or more and 50 nm or less, wherein the vapor-deposited aluminum pigment is at least partially coated with at least a part of the organic phosphoric acid compound, and the pigment dispersion contains 15 parts by mass or more and 80 parts by mass or less of the organic phosphoric acid compound with respect to 100 parts by mass of the vapor-deposited aluminum pigment. Claim 2 The pigment dispersion according to claim 1, wherein the organic phosphoric acid compound is an organic phosphoric acid compound in a solid state at 25°C. Claim 3 The pigment dispersion according to claim 1 or 2, wherein the organic phosphoric acid compound is at least one selected from the group consisting of phosphoric acid esters, acidic phosphoric acid esters, chlorinated phosphoric acid esters, phosphorous acid esters, and condensed phosphoric acid esters thereof. Claim 4 The pigment dispersion according to any one of claims 1 to 3, wherein the organic phosphoric acid compound is an acidic phosphoric acid ester having a linear alkyl group with 8 or more and 30 or less carbon atoms. Claim 5 further comprising an aqueous resin, and the pigment dispersion according to any one of claims 1 to 4 contains 1 part by mass or more and 500 parts by mass or less of the vapor-deposited aluminum pigment with respect to 100 parts by mass of the aqueous resin.

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