White TiO2 Pigments: Is a New Revolution Possible?

3-5 October 2017 the RD Titan Group participated in TiO2 World Summit 2017. The conference took place in Alicante, Spain and had a huge success. Covering trend topics including market outlooks, nano TiO2 applications, safety, feedstock minerals and development of the alternative TiO2 process that was presented by Andriy Gonchar. Ahead of RD Titan Group represented VELTA RD TITAN company, founded by Velta Group Global and RD Titan Group, that working on the development of i-TiO₂ process, an innovative method for the production of titanium dioxide i-TiO2, and on new technologies for processing titanium raw materials.

VELTA RD TITAN sees the potential of pigment dioxide as one of the important materials for the Forth TiO2 revolution.  Referring to the VELTA website:

"During rapid technological development, more and more innovators pay attention to the TiO2 products, but for the explosive growth of this material, a significant reduction in cost of production is required. Our developments will reduce the cost, and thus increase the use of titanium products, both in the classical and in the innovative markets", said Andriy Gonchar, Deputy CEO-Technical Director of VELTA RD TITAN.

The topic of  VELTA RD TITAN presentation on the TiO2 World Summit 2017 is ‘i-TiO₂ Process: Emerging Technology for i-TiO₂ Pigments Production’.

 

 

Three TiO₂ Revolutions in the 20th Century

The invention of sulfate TiO₂ production and start of titanium dioxide (anatase) use as a white pigment at the beginning of the 20^th century^[1]  became a real revolution for the world of paints and coatings (in fact, this was the first TiO₂ revolution when titanium dioxide was first produced on industrial scale). This unrivaled pigment with superior hiding power and brightness, excellent physical and chemical properties such as thermal resistance and resistance to acids and alkalis, was also safe for human health and living beings, as opposed to the pigments which had been used before, and the deposits of raw material for its production were some of the most abundant in nature and almost limitless (at least such were the thoughts of the man of the first half of the last century).

Another industry breakthrough (the second TiO₂ revolution) happened in 1939, when Kronos marketed the first rutile pigment. The rutile modification is preferred for its superior pigmentary properties. It has replaced the anatase modification completely in paints and coatings and plastics.

The next revolutionary milestone was the development and commercialization of the chloride technology for titanium dioxide production in the 1940s (the third TiO₂ revolution). The sulfate technology was replaced by a more ‘green’ technology which allowed obtaining brighter and less yellow pigments with a narrower particle size distribution range. Since that time this technology has spread, expanding around the world and forcing sulfate producers to improve and optimize their production so as not to lose out in the competitive struggle with the new technology. It should be noted that some sulfate producers have successfully done this, and today it can be stated that the sulfate technology, with certain optimization, can compete with the chloride one in terms of production costs, quality of finished products and environmental safety. Actually, today for 85-90% of titanium dioxide applications it does not matter whether a sulfate or chloride pigment is used; the most important thing is that its characteristics should meet the requirements for this application. Only 10-15% of applications require the exclusive use of chloride pigments as they are brighter and less yellow in comparison to sulfate pigments.

 

End of the 20^th Century - Beginning of the 21^st Century: the Fourth TiO₂ Revolution Attempted

 As is known, in the past three decades attempts have been made to find an alternative method of titanium dioxide production, which would be competitive with respect to the classical sulfate and chloride technologies from the production point of view. Thus, it is worth noting the efforts of a number of companies such as BHP-Billiton/Altair Nanotechnologies/AlSher/5iTech in 1990-2010^[2], as well as Argex Titanium^[3]in 2000-2010, to develop a new hydrochloride process with organic extraction. Considerable physical resources and time have been spent on these studies, but by now none of these technologies have yet been commercialized, although from time to time there appear encouraging reports about the plans of these companies to build a fully functional titanium dioxide production using the new technology.

 

^{VELTA RD TITAN and the Fourth TiO₂ Revolution}

VELTA RD TITAN is a collaboration of two companies: Velta Group Global Limited and RD Titan Group.

VELTA is located in the United Kingdom with ilmenite deposits in Ukraine. The total production is 270 thousand tons per year and Company plans to increase production by 120 thousand tons per year and to develop the production of goods with high added value. 

Our team has long been deeply involved in the development of technologies for titanium dioxide production. There are years of experience in the sulfate and chloride industries under our and our associate partners’ belts. And we have long been wrestling with questions about how to make titanium dioxide even more effective, while making the process of its production cheaper and avoiding the known problem of waste generation. We achieved certain success in the sulfate production, as well as in some segments of the chloride process. However, these are the improvements in the framework of already existing processes. But we are thinking about a new process that could make the fourth TiO₂ revolution in the first third of the 21st century. We call it innovative TiO₂ process or i-TiO₂ process for short. By now we have worked out the general concept of this process and we are preparing to start a 3-year program for the development of i-TiO₂ process.

 

Main Features of i-TiO₂ Process:
Decomposition of Titanium-Containing Raw Materials

What are the main problems of the existing industrial processes of titanium dioxide production?

For example, one of them is waste generation.

Thus, the sulfate process produces about 2 tons of iron sulfate per one ton of TiO₂ and about 5 tons of 20-25% weak acid with high iron content per one ton of TiO₂. And if in recent years iron sulfate has turned into a commodity and has been widely used by industry^[4], then the situation with hydrolysis acid is somewhat more complicated as it requires significant costs for recycling (for example, evaporation^[5] for reuse in the titanium dioxide production or other needs).

In this respect the chloride process is more ‘green’, since it works with more concentrated titanium raw material (rutile, synthetic rutile, or slags^[6]), most of the decomposing agent (chlorine) returns to the process after TiCl₄ oxidation stage, however, this process also generates wastes, for example, iron (III) chlorides, which require disposal. In addition, raw materials used for the chloride process (chloride slag, natural rutile, synthetic rutile) are more expensive than raw materials used in the sulfate process (ilmenite).

Knowing the peculiarities mentioned above, we couldn’t help but wonder what if we invent the technology that would enable:

• Effective decomposition of titanium-containing raw materials (ilmenite);

• Cheap regeneration of the decomposing agent for reuse;

• No waste generation (stretch goal) or minimization of waste generation (primary goal), turning all waste or most of it into marketable products.

As a result, within several years that have passed since the task was set, we managed to work out a self-consistent concept of such process and even to test experimentally individual elements of this process.

 

Main Features of i-TiO₂ Process:
Production of TiO₂

It is well known that one of the most important titanium dioxide properties, which makes it the leading and unrivaled white pigment, is its high refractive index (2.7 - for rutile, 2.55 - for anatase^[7]). It is even difficult to imagine what other material could be compared with titanium dioxide or surpass it in this regard. For example, its closest competitors are white materials - zinc oxide (2.0), zirconium oxide (2.13), diamond (2.4). As you can see, the first material is far behind, on top of that it is toxic to some extent; zirconium oxide also poorly compares to titanium dioxide (and its cost is slightly higher), and even the diamond does not reach the required level, besides it is obvious that the diamond could not compete with titanium dioxide in view of its incredibly high cost, insufficient reserves in nature to provide the market, as well as the complicated process of fine diamond powder production because of the diamond hardness. There are other materials that have a close or even higher refractive index than titanium dioxide has, but they are either not white (for example, red iron oxide with a refractive index of 3.0), or not only not white, but also and, moreover, enough expensive (for example, orange-yellow gallium phosphide with a refractive index of 3.45).

Thus, it all looks like there simply won’t be any alternatives to the use of titanium dioxide as the main white pigment in the coming decades (and maybe even in the coming centuries, because it has already been popular for one whole century, defeating all other ‘white’ competitors).

But since there are no alternatives to titanium dioxide, can one find any methods that would significantly increase hiding power of titanium dioxide without increasing the cost of production or, perhaps, even reducing it? If this was possible, obviously, wouldn’t it be a game-changing technology for the market?

 

These questions began to bother us several years ago and we undertook to check various options. Our studies and calculations showed that under certain conditions such problem can be solved and hiding power of titanium dioxide can be increased by 20-50% in comparison with the current titanium dioxide grades. The cost of titanium dioxide production will then be significantly reduced. Though, the technical implementation of this solution poses a serious challenge from the technological point of view and with respect to necessary industrial equipment. Nevertheless, the most important conclusion from our research is that, in principle, this task has a solution, albeit difficult. And it should be noted that we have recently made significant progress in the elaboration of the concept for this technology.

 

Main Features of i-TiO₂ Process:
Increasing TiO₂ Durability without Loss of Key Pigment Properties

Titanium dioxide is a semiconductor which exhibits extremely undesirable photocatalytic activity for most applications, when absorbing ultraviolet radiation. This leads to deterioration in the quality of coatings and materials and reduction in their durability. All companies producing titanium dioxide are struggling to solve this problem regardless of the process they use (sulfate, chloride or emerging processes) and, it should be noted, they have achieved significant success in this regard. Our team is no exception: at the moment we possess world-class technologies and technical solutions for the production of high and superior durable TiO₂ grades for all applications (Paints & Coatings, Plastics, Décor Paper). One of our ambitions is the development of a new generation of titanium dioxide pigments with Super+ durability without loss of pigment properties (for classical processes - sulfate and chloride), as we reported at the World TiO₂ Summit in Cleveland, Ohio 4-6 October 2016^[8].

We will use the existing projects to study and develop i-TiO₂ pigments. Our ultimate goal is to make the end consumer of i-TiO₂ pigments simply forget about such titanium dioxide property as photocatalytic activity.

In fact, achieving almost zero effect of photocatalytic activity on systems using titanium dioxide should lead to the reduction in the types of titanium dioxide that exist now. The existing classification subdivides pigments not only according to their use, but also according to their durability^[9]. i-TiO₂ pigments will all be super+ durable and will be classified only according to their main application: Paint & Coatings, Plastics or Décor Paper. And of course, the subclassification according to undertones will probably remain the same: neutral, blue and super-blue undertones of the same type of pigments. Of course, if some of the consumers want to use pigments with a yellow undertone, it will also be possible, since it will not be difficult to produce such a pigment.

Thus, the concept of a new i-TiO₂ pigment is:

• Extremely low production costs;
• Almost non-waste production;
• Extremely high level of hiding power;
• Almost absolute durability.

 

Summary

We see new opportunities in the titanium dioxide industry and in the development of new technologies for its production. Taking part in the fourth TiO₂ revolution is a real challenge for us. Besides, we can see that this is not an infinite process and that it is quite feasible after about three years of research to enter the stage of pilot production with subsequent commercialization of the new technology.