Core process of Titanium dioxide post treatment: coating process

2019-09-24

In order to make the properties of titanium dioxide more perfect, both the sulfate process and the chloride process are subjected to surface treatment to weaken the photochemical activity (enhanced weather resistance) of the titanium dioxide and improve the dispersibility thereof.


1. Titanium dioxide post-treatment core process - envelope


The coating of titanium dioxide is a core part of the post-treatment process. The coating is also known as surface treatment. Its purpose is to improve the application performance of titanium dioxide, especially rutile titanium dioxide, so that it has excellent use in different applications.


The coating film can be classified into an inorganic coating film and an organic coating film according to the properties of the desired material coated on the surface of the titanium dioxide; according to the coating method, it can be further divided into a dry coating film and a wet coating film. In general, the film formed by the inorganic oxide is made of a wet coating, that is, an inorganic coating; for the addition of an organic surfactant to improve the performance of the product, generally, a dry coating is used, and the individual uses a wet coating. membrane.


Second, titanium white powder post-treatment process


1. Inorganic treatment process


Mechanism of action: A uniform colorless or white inorganic oxide film is formed on the surface of the titanium oxide particles to block the photoactivation point of TiO2 and improve weather resistance.


Treatment process: the inorganic coating is after the titanium dioxide is beaten, the soluble salt is added in the environment of the slurry, and then the pH of the slurry is adjusted to deposit the soluble salt on the surface of the titanium dioxide particles to form an oxide film package. The coating not only isolates the contact of titanium dioxide with air, but also makes the pigment properties of titanium dioxide preserved because of the thinness and transparency of the film.


Treatment purpose: mainly to improve weather resistance.


Inorganic surface treatment agents: aluminum sulfate, sodium metaaluminate, sodium silicate, etc.; for high weathering products, there are zirconium sulfate, titanium oxysulfate (increasing the oil absorption value, gradually eliminated), zinc sulfate and antimony, tin and the like.


The hydrated oxide film layer is coated with primary particles as a core, and generally has a thickness of several nanometers. The most widely used inorganic coating is aluminum coating, and there are many products treated with single aluminum, and many treatments are combined with silicon and titanium.


2. Organic treatment process


Mechanism of action: an organic oxide film or surfactant is coated on the surface of TiO2. After the organic coating agent is added to the surface of the pigment particles, the van der Waals force of the pigment particles is not enough to cause them to adsorb again. The pigment is imparted with good dispersibility; at the same time, the exposed groups of the organic coating agent impart good compatibility with the pigment system and the solution system.


Treatment process: the method of adding the organic surface treatment agent can be generally added after the inorganic surface treatment, before the drying, or at the last air flow pulverization, and the addition amount generally accounts for 0.1% to 1% (mass) of the titanium dioxide. The amount is 0.2%~0.6%. It is common in the industry to add an organic surface treatment agent during the final pulverization stage of titanium dioxide production, that is, during air flow pulverization.


Treatment purposes: to improve the dispersion and compatibility of titanium dioxide in different media, and to improve gloss, rheology and wettability.


Organic surface treatment agents: three types, namely, polyols such as neopentyl glycol and trimethylolpropane, organic amines such as triethanolamine and trimethylamine, and silicones such as silicone.


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