TiO2 pigment is used to provide whiteness and opacity in a range of applications, including paint and coatings. TiO2 pigment is produced from titanium feedstocks. The two dominant processes for producing TiO2 suitable for pigment are the sulfate and chloride processes. TiO2 pigment has two crystal forms: rutile and anatase. Anatase grade pigment is only made by the sulfate route, while rutile grade pigment can be manufactured using both processes.
Sulfate process and Chloride process
Initially TiO2 was only manufactured using the sulfate process which was independently developed by two different companies: one in Norway and another in the US.
This was the only commercial means of manufacturing TiO2 until 1958, when DuPont built a large-scale plant to create TiO2 using the chloride process.
The intellectual property and proprietary knowledge required to operate a chloride plant is vigorously protected by the select few companies that own this technology. Chloride TiO2 pigment generally has a superior whiteness to sulfate products and there is often less waste per tonne of finished TiO2. Also, chloride TiO2 tends to be bluer, while sulfate TiO2 can have a yellow tinge. A primary advantage of the chloride system is it is a continuous process, compared to the batch procedure on the sulfate route. The downside of the chloride process is it necessitates a larger initial capital outlay and the technology is not as readily available.