阅读说明：本技术 一种二氧化钛颜料及其制备方法 (Titanium dioxide pigment and preparation method thereof ) 是由 陈建立 王永珊 王莉萍 周文静 冯亚阳 赵姗姗 曹青喜 张健 赵丁 王欢欢 于 2019-09-17 设计创作，主要内容包括：本发明公开了一种二氧化钛颜料,其包括作为基材的TiO<Sub>2</Sub>粒子,以及其表面包覆的包覆层；所述包覆层为磷酸钙、磷酸钛、磷酸铝或氢氧化铝中的一种或几种,并且所述包覆层至少有一层为磷酸钙包覆层,其是在柠檬酸化合物存在下使磷酸化合物与钙化合物进行反应形成的。本发明所述二氧化钛颜料可抑制二氧化钛本身所具有的光催化活性,具有优秀的耐光稳定性。(The invention discloses a titanium dioxide pigment which comprises TiO as a base material 2 Particles and a coating layer coated on the surface thereof; the coating layer is one or more of calcium phosphate, titanium phosphate, aluminum phosphate or aluminum hydroxide, and at least one layer of the coating layer is a calcium phosphate coating layer which is formed by reacting a phosphoric acid compound with a calcium compound in the presence of a citric acid compound. The titanium dioxide pigment can inhibit the photocatalytic activity of titanium dioxide and has excellent light-resistant stability.)

1. A titanium dioxide pigment characterized by: the titanium dioxide pigment comprises TiO as a substrate₂Particles and a coating layer coated on the surface thereof; the coating layer is one or more of calcium phosphate, titanium phosphate, aluminum phosphate or aluminum hydroxide, and at least one layer of the coating layer is a calcium phosphate coating layer which is formed by reacting a phosphoric acid compound with a calcium compound in the presence of a citric acid compound.

2. The titanium dioxide pigment of claim 1, wherein: when the TiO is₂When the surface of the particle is only coated with the calcium phosphate, the citric acid compound is added in TiO₂The weight percentage is 0.1-3%.

3. The titanium dioxide pigment of claim 1, wherein: when the TiO is₂When the surface of the particle is only coated with the calcium phosphate, the calcium compound is added in an amount of CaO accounting for TiO₂The weight percentage is 0.5-5%.

4. The titanium dioxide pigment of claim 1, wherein: when the TiO is₂When the surface of the particle is only coated with the calcium phosphate, the phosphoric acid compound is added in an amount of P₂O₅Is TiO 2₂The weight percentage is 0.5-5%.

5. A titanium dioxide pigment according to any one of claims 1 to 4, wherein: when the TiO is₂When the surface of the particle is coated with multiple layers, the total amount of the coating compound added in each layer of the coating layer is the oxide thereofTiO₂The weight percentage is 2-15%.

6. A titanium dioxide pigment according to any one of claims 1 to 4, wherein: when the TiO is₂The amount of the phosphoric acid compound used for forming the titanium phosphate coating layer, the calcium phosphate coating layer and the aluminum phosphate coating layer when the particle surface is coated with a plurality of layers is P₂O₅Is TiO 2₂The weight percentage is 2-10%.

7. A titanium dioxide pigment according to any one of claims 1 to 4, wherein: when the TiO is₂When the surface of the particle is coated with a plurality of layers, the aluminum compound for forming the aluminum phosphate and/or aluminum hydroxide coating layer is added in an amount of Al₂O₃Is TiO 2₂The weight percentage is 2-8%.

8. A titanium dioxide pigment according to any one of claims 1 to 4, wherein: when the TiO is₂When the surface of the particle is coated with a plurality of layers, the titanium compound used for forming the titanium phosphate coating layer is added in TiO₂The weight percentage is 0.1-3%.

9. The titanium dioxide pigment of claim 1, wherein: the citric acid compound is citric acid, sodium citrate or potassium citrate; the calcium compound is calcium hydroxide, calcium chloride, calcium nitrate or calcium acetate; the titanium compound used for forming the titanium hydroxide coating layer is titanium chloride or titanium sulfate; the aluminum compound used to form the aluminum phosphate and/or the aluminum hydroxide coating layer is aluminum sulfate or sodium aluminate.

10. The titanium dioxide pigment of claim 1, wherein: the phosphoric acid compound is one or more of orthophosphoric acid, orthophosphate, polyphosphate, metaphosphate or perphosphate, and is preferably sodium metaphosphate.

11. A process for producing a titanium dioxide pigment according to any one of claims 1 to 10, wherein: the method comprises the following steps:

adding TiO into the mixture₂Dispersing the particles in water, pulping, and adjusting the concentration of the pulp to 100-600 g/L; adding a citric acid compound, a phosphoric acid compound, a calcium compound alone or in combination with a titanium compound and/or an aluminum compound, and an alkali compound to the slurry; wherein the calcium phosphate coating layer is formed by reacting the phosphoric acid compound with the calcium compound in the presence of the citric acid compound.

Technical Field

The invention discloses a titanium dioxide pigment and a preparation method thereof, belonging to the technical field of titanium dioxide pigments.

Background

The titanium dioxide pigment has a high light scattering ability with a high refractive index, and therefore is widely used as a white pigment for paints, inks, plastics, and the like. However, when the film is irradiated with ultraviolet rays in the presence of moisture and oxygen, TiO is formed₂Holes h generated inside the particles⁺It reacts with moisture to generate hydroxyl radicals, which oxidatively decomposes the resin component of the coating material, so that the gloss of the coating film using the titanium dioxide pigment is reduced when the coating film is exposed outdoors for a long period of time, and the chalkiness is caused. In addition, in the decorative paper using the titanium dioxide pigment, TiO appears₂Photo-excited electrons e generated simultaneously inside the particles^-The titanium dioxide itself is reduced to become blue black. In order to suppress the photocatalytic activity possessed by such titanium dioxide pigment particles themselves, it is common to use TiO pigment particles₂The surface of the particles is coated with a hydroxide of silicon, zirconium, titanium, tin, aluminum, or the like.

TiO₂The surface of the particles may be coated with not only hydroxides such as silicon, titanium, tin, and aluminum but also phosphates such as aluminum phosphate and calcium phosphate. For example, in US patent US5,785,748 it is disclosed to use TiO₂The surface of the particles is formed into a reticular aluminum phosphate film by mutual condensation of molecular chain sides formed by-O-P-O-Al-O-P-generated by the reaction of an aluminum compound and a phosphoric acid compound. US2004/0171484 and US2017/0130055 disclose methods of adding a phosphate such as sodium hexametaphosphate and a calcium compound such as calcium chloride to a titanium dioxide slurry to precipitate calcium phosphate and thereby suppress the photocatalytic activity of titanium dioxide itself.

When the surface of titanium dioxide particles is coated with a hydroxide of silicon, zirconium, titanium, tin, aluminum or the like, a compound of silicon, zirconium, titanium, tin, aluminum or the like is added to a slurry of titanium dioxide, and the slurry is slowly changed in pH to hydrolyze the compound of silicon, zirconium, titanium, tin, aluminum or the like, thereby precipitating the hydroxide of silicon, zirconium, titanium, tin, aluminum or the like into TiO₂The surface of the particles. And phosphoric acid compoundThe reaction with calcium compounds is ionic, and the reactant calcium phosphate is instantaneously precipitated, thereby generating non-adhesion to TiO₂Calcium phosphate on the surface of the particles is difficult to form a uniform calcium phosphate coating, which makes the calcium phosphate coating less light resistant in decorative paper, ink, plastic and other applications.

Disclosure of Invention

The invention provides a titanium dioxide pigment and a preparation method thereof, aiming at solving the problem of TiO pigment₂The surface of the particles is difficult to form a uniform calcium phosphate coating layer. The titanium dioxide pigment can inhibit the photocatalytic activity of titanium dioxide and has excellent light-resistant stability.

One aspect of the present invention relates to a titanium dioxide pigment comprising TiO as a substrate₂Particles and a coating layer coated on the surface thereof; the coating layer is one or more of calcium phosphate, titanium phosphate, aluminum phosphate or aluminum hydroxide, and at least one layer of the coating layer is a calcium phosphate coating layer which is formed by reacting a phosphoric acid compound with a calcium compound in the presence of a citric acid compound.

In a preferred embodiment, when the TiO is₂When the surface of the particle is only coated with the calcium phosphate, the citric acid compound is added in TiO₂The weight percentage is 0.1-3%.

In a preferred embodiment, when the TiO is₂When the surface of the particle is only coated with the calcium phosphate, the calcium compound is added in an amount of CaO accounting for TiO₂The weight percentage is 0.5-5%.

In a preferred embodiment, when the TiO is₂When the surface of the particle is only coated with the calcium phosphate, the phosphoric acid compound is added in an amount of P₂O₅Is TiO 2₂The weight percentage is 0.5-5%.

In a preferred embodiment, when the TiO is₂When the particle surface is coated with multiple layers, the total amount of the coating compound added in each layer of the coating layer is that the oxide accounts for TiO₂The weight percentage is 2-15%.

In a preferred embodiment, when saidTiO₂The amount of the phosphoric acid compound used for forming the titanium phosphate coating layer, the calcium phosphate coating layer and the aluminum phosphate coating layer when the particle surface is coated with a plurality of layers is P₂O₅Is TiO 2₂The weight percentage is 2-10%.

In a preferred embodiment, when the TiO is₂When the surface of the particles is coated in multiple layers, the aluminum compound for forming the aluminum phosphate and/or aluminum hydroxide coating layer is added in an amount of Al₂O₃Is TiO 2₂The weight percentage is 2-8%.

In a preferred embodiment, when the TiO is₂When the surface of the particle is coated with a plurality of layers, the titanium compound for forming the titanium phosphate coating layer is added in an amount of TiO₂The weight percentage is 0.1-3%.

In a preferred embodiment, the citric acid compound is citric acid, sodium citrate or potassium citrate.

In a preferred embodiment, the calcium compound is calcium hydroxide, calcium chloride, calcium nitrate, or calcium acetate.

In a preferred embodiment, the phosphate compound is one or more of orthophosphoric acid, orthophosphate, polyphosphate, metaphosphate, or perphosphate; sodium metaphosphate is preferred.

In a preferred embodiment, the aluminum compound is aluminum sulfate or sodium aluminate.

In a preferred embodiment, the titanium compound is titanium chloride or titanium sulfate.

Another aspect of the present invention relates to a method of preparing a titanium dioxide pigment comprising the steps of:

adding TiO into the mixture₂Dispersing the particles in water, pulping, and adjusting the concentration of the pulp to 100-600 g/L;

adding a citric acid compound, a phosphoric acid compound, a calcium compound alone or in combination with a titanium compound and/or an aluminum compound, and an alkali compound to the slurry;

wherein the calcium phosphate coating layer is formed by reacting the phosphoric acid compound with the calcium compound in the presence of the citric acid compound.

Detailed Description

The present invention provides a titanium dioxide pigment comprising TiO as a substrate₂Particles and a coating layer coated on the surface thereof; the coating layer is one or more of calcium phosphate, titanium phosphate, aluminum phosphate or aluminum hydroxide, and at least one layer of the coating layer is a calcium phosphate coating layer which is formed by reacting a phosphoric acid compound with a calcium compound in the presence of a citric acid compound.

Substrate TiO used in the invention₂The particles are obtained by a sulfuric acid process or a chlorination process, and are rutile type crystals. The particle size is preferably 600 or more oriented particle diameters (interval between two parallel lines sandwiching the particle in a predetermined direction) in the field of view of an electron microscope, and the average number of particles is in the range of 0.15 to 0.35. mu.m. The average particle diameters described below were all measured by the present method.

In certain embodiments of the present invention, the titanium dioxide pigment is TiO₂The substrate is coated with a calcium phosphate coating layer on the surface. The calcium phosphate coating layer is formed by reacting a phosphoric acid compound with a calcium compound in the presence of a citric acid compound.

It has been studied to react a phosphoric acid compound with a calcium compound in the presence of a citric acid compound, in TiO₂The calcium phosphate coating layer is coated on the particle surface, so that the photocatalytic activity of titanium dioxide can be obviously inhibited, and the citric acid is considered to form calcium ions and double salts to delay the reaction with phosphoric acid, so that calcium phosphate can be slowly precipitated, and a uniform calcium phosphate layer is formed on the surface of titanium dioxide particles.

The citric acid compound is added in an amount of TiO when forming the calcium phosphate coating layer₂The weight percentage is 0.1-3%. If the weight percentage is 0.1% or less, the effect of adding the citric acid compound is not obtained. If the weight percentage is more than 3%, it is uneconomical.

When the calcium phosphate coating layer is formed, the calcium compound is added in an amount of CaO accounting for TiO₂Weight of hundredThe ratio is 0.5-5%. If the amount is less than 0.5% by weight, sufficient photochemical stability may not be obtained. If the weight percentage is more than 5 percent, the TiO₂The dispersibility of the particles is deteriorated, and sufficient whiteness and hiding power cannot be obtained.

The phosphoric acid compound is added in an amount of P when forming the calcium phosphate coating layer₂O₅Is TiO 2₂The weight percentage is 0.5-5%. If the weight percentage is less than 0.5%, sufficient photochemical stability may not be obtained. If the weight percentage is more than 5%, it is uneconomical.

In certain embodiments of the present invention, the titanium dioxide pigment is TiO₂And a calcium phosphate coating layer coated on the surface of the substrate, wherein the titanium dioxide pigment further comprises an aluminum phosphate and/or aluminum hydroxide coating layer formed by adding an aluminum compound when reacting a phosphoric acid compound with a calcium compound in the presence of a citric acid compound to form a coating layer.

In certain embodiments of the present invention, the titanium dioxide pigment is TiO₂The titanium dioxide pigment also comprises a titanium phosphate coating layer, an aluminum phosphate and/or aluminum hydroxide coating layer which is formed by adding a titanium compound and an aluminum compound when a phosphoric acid compound reacts with a calcium compound in the presence of a citric acid compound to form the coating layer.

It was found that coating titanium phosphate before coating calcium phosphate can further suppress the photocatalytic activity of titanium dioxide, and this is considered to be because the titanium phosphate precipitation buffers the pH at the time of the subsequent calcium phosphate precipitation.

When forming the titanium phosphate coating layer, the amount of the titanium compound added is TiO₂The weight percentage is 0.1-3%. If the content is 0.1% by weight or less, sufficient photochemical stability may not be obtained. If the weight percentage is more than 3%, it is uneconomical.

When the aluminum phosphate coating layer and/or the aluminum hydroxide coating layer are formed, the amount of the aluminum compound added is Al₂O₃Is TiO 2₂The weight percentage is 2-8%. If the weight percentage is below 2 percent, the TiO₂The dispersibility of the particles may be deteriorated. If the weight percentage is more than 8 percent, the TiO is₂The light scattering of the particles becomes weak, and sufficient hiding power cannot be obtained.

In certain embodiments of the invention, when the TiO is₂When the particle surface is coated with multiple layers, the total amount of the coating compound added in each layer of the coating layer is that the oxide accounts for TiO₂The weight percentage is 2-15%. If the amount is less than 2% by weight, sufficient photochemical stability cannot be obtained. If the weight percentage is more than 15 percent, the TiO is₂The light scattering of the particles becomes weak and sufficient hiding power is not obtained.

In certain embodiments of the invention, when the TiO is₂The amount of the phosphoric acid compound used for forming the titanium phosphate coating layer, the calcium phosphate coating layer and the aluminum phosphate coating layer is P₂O₅Is TiO 2₂The weight percentage is 2-10%. If the amount is less than 2% by weight, sufficient photochemical stability may not be obtained. If the weight percentage is more than 10%, the light scattering of the titanium dioxide particles becomes weak, and sufficient hiding power cannot be obtained.

The invention also provides a preparation method of the titanium dioxide pigment, which comprises the following steps:

adding TiO into the mixture₂Dispersing the particles in water, pulping, and adjusting the concentration of the pulp to 100-600 g/L;

adding a citric acid compound, a phosphoric acid compound, a calcium compound alone or in combination with a titanium compound and/or an aluminum compound, and an alkali compound to the slurry to form a titanium dioxide pigment;

wherein the calcium phosphate coating layer is formed by reacting a phosphoric acid compound with a calcium compound in the presence of a citric acid compound.

In certain embodiments of the invention, a citric acid compound, a phosphoric acid compound, a calcium compound, and an alkali compound are added to the slurryFormation of TiO₂Titanium dioxide pigment with calcium phosphate coating layer on the particle surface.

In certain embodiments of the invention, a citric acid compound, a phosphoric acid compound, a calcium compound, and an aluminum compound, and a base compound are added to the slurry to form TiO₂Titanium dioxide pigment with calcium phosphate coating, aluminum phosphate coating and/or aluminum hydroxide coating on the surface of the particles.

In certain embodiments of the present invention, a citric acid compound, a phosphoric acid compound, a calcium compound, and a titanium compound, and an alkali compound are added to the slurry to form TiO₂Titanium dioxide pigment with titanium phosphate coating layer and calcium phosphate coating layer on the surface of the particles.

In certain embodiments of the present invention, a citric acid compound, a phosphoric acid compound, a calcium compound, a titanium compound, and an aluminum compound, and an alkali compound are added to the slurry to form TiO₂Titanium dioxide pigment with titanium phosphate coating, calcium phosphate coating and/or aluminum hydroxide coating on the surface of the particles.

Compared with the prior art, the titanium dioxide pigment can greatly inhibit the photocatalytic activity of the titanium dioxide while maintaining the performance of the titanium dioxide pigment as a white pigment.