New TiO2 Requirements


by Marc Giersemehl, Christian Begass and Fabian Mertens published in "Farbe und Lack 10/2020"

Up to now, powder coatings have been considered to be solvent-free, eco-efficient and the risk of fire and explosion is significantly lower than with solvent-based liquid coatings. Now many experts in the paint and coatings industry fear that most paints and coatings will lose their environmental label. [1]

A process has been developed that reduces the content of titanium dioxide particles with a particle size ≤ 10 μm in the powder coating to below 1%. The new titanium dioxide reduction system was investigated in detail.

In October 2019, the European Commission classified titanium dioxide (TiO2) as a substance suspected of being carcinogenic by inhalation, and in February 2020 the official regulation controlling TiO2 was published. This classifies powdered TiO2 as a class 2 carcinogen.

As of October 1, 2021, it will thus become legally binding that powdered mixtures containing at least 1% TiO2 particles with a particle size ≤ 10 μm (hereinafter referred to as "TiO2 fine dust") must be labeled with a warning notice informing users of the possible formation of respiratory dusts or droplets (EUH211/EUH212). Powdery and solid mixtures containing at least 1% TiO2 must have the following warning: "EUH 212: Warning! During use, dangerous respiratory dust may be generated. Do not inhale dust." Additionally, the mixtures must have the warning EUH 210.

The advantages of powder coatings are that they are solvent-free, eco-efficient and the risk of fire and explosion are significantly lower than with solvent-based liquid coatings. The loss of the environmental label [1] through the new regulation would therefore be a decisive Disadvantage.

In addition, powder paint residues with a TiO2 fine dust content are treated as "hazardous waste", which will increase disposal costs. [2]

In the powder coatings sector, will this discourage customers from buying and processing TiO2-containing powder coatings, thereby reducing the demand for powder coatings?

The largest application area of TiO2 is as a white pigment in the paint and coatings industry. [3] From the powder coating manufacturers point of view, there is no technical substitute for TiO2 in the production of light and white powder coatings. TiO2 has the best hiding power, weather resistance and color brilliance, and so far there is no alternative without sacrificing quality or environmental compatibility. Only 119 (5%) of the 2,328 color shades of the RAL system are produced without titanium dioxide. [4] Therefore, TiO2 must continue to be used for certain color formulations in powder coating production.

In the course of this, an engineering process was developed to guarantee a TiO2 fine dust content of less than 1% in powder coatings and to ensure the supply of the post-blend additives in the final powder coating product. [5]

In TiO2 reduction, the properties of the powder coating after the comminution and classifying process in the impact classifier mill are changed in such a way that the content of TiO2 particles is reduced. At the end of the process, the powder coating has a TiO2 fine dust content of less than 1%.

At the same time, the process ensures that the additive content in the powder coating remains unchanged despite the changed particle size distribution. The TiO2 reduction system can be used both inline in a powder coating grinding system and offline in a separate process step.

The TiO2 fine dust is granulated in a process directly downstream for further use within the value chain. This reduces costs, as the loss of raw materials is kept low and compaction produces very little "hazardous waste". [2]

TiO2 reduction system

The target during development was to realize a compact system with high throughput rates and low energy consumption that reduces the content of TiO2 fine dust to below 1% while maintaining and even further improving the quality of the powder coating.

In Fig. 1 the TiO2 reduction reduction process is described by means of a flow chart of a plant operated offline.

In the offline TiO2 reduction system, the ground powder coating is first added to the TiO2 reduction system via a rotary valve. In the further course within the system the transport is done pneumatically. The temperature of the intake air can be lowered to 2 °C via an upstream air cooler. In the TiO2 reduction system, a specially developed separation process reduces the content of TiO2 fine dust in the powder coating. This principle is based on mechanical separation based on density gradients.

The TiO2 fine dust and the TiO2 reduced powder coating are finally discharged separately from each other by means of double flaps. The air required for transport flows out of the system filtered. In addition, there is the possibility of conveying the exhaust air back into the system.

Due to the mechanical separation within the TiO2 reduction system, post-blend additives such as aluminum oxide and silicon dioxide are added after TiO2 reduction. For this purpose, a new additive dosing and dispersing system is used, which feeds the additive into big bags or the usual powder coating boxes before filling. In a further process, the TiO2 fine dust is compressed in the compacting unit.

Development process of the reduction system

The TiO2 reduction system was developed using Computational Fluid Dynamics (CFD). A concept was used as input geometry, which was then analyzed and improved with focus on flow control and energy efficiency. The idea is to achieve a high particle Reynolds number ReParticles during mechanical separation. The particle Reynolds number is proportional to the difference between the air velocity vair and the particle velocity vparticle.

ReParticles ∝ vAir - vParticles

Fig. 2 shows the result of a CFD simulation of the mechanical separation unit of the TiO2 reduction process.

The high particle Reynolds numbers are achieved by means of built-in components. These internals for flow control extend over the entire transport zone.

High particle Reynolds numbers in combination with the internals facilitate the mechanical separation of particles with different densities. In addition, this process is influenced by the flow velocity of the particles, the dust load and the temperature. The influence of these parameters is investigated in more detailed tests.

Results of the reduction system

Two powder coatings with different particle size distributions, already ground, were available for the tests. Both powder coatings were whites with a titanium dioxide content of approximately 60%. Fig. 3 shows the particle size distributions of the feed material.

To investigate the influence of the dust load on the process, the mass flow of the ground powder coating and the feed volume flow were varied at process temperatures of 35 °C and 5 °C, respectively. Tests with dust loading of between 155 g/m³ - 1009 g/m³ were performed. Fig. 4 shows the TiO2 fine dust content of the treated powder coating end product. On the primary ordinate, the dust load in gpowder coat/m³ air is plotted as columns, and on the secondary ordinate the TiO2 fine dust content in the powder coating end product is shown as a graph in percent. The aim is to achieve a TiO2 fine dust content of less than 1%.

From the results presented, it is clear that the final content of TiO2 fine dust depends on both the dust load and the process temperature. The higher the dust loading of the product stream, the lower the TiO2 fine dust content in the powder coating final product. At a process temperature of 35 °C, the TiO2 fine dust content is approximately 43% lower with a dust load of 1009 g/m³ than with a dust load of 155 g/m³.

The temperature also has a great influence on the TiO2 reduction process. At a process temperature of 35 °C, the maximum limit of 1% of the TiO2 fine dust content in the powder coating end product is not reached. In contrast, at the process temperature of 5 °C, the TiO2 fine dust content in product A is between 0.6% and 0.99% with a dust load of 329 g/m³ to 1009 g/m³. For product B, the limit of 1% TiO2 fine dust content is also met at a process temperature of 5 °C with dust loads between 416 g/m³ and 878 g/m³.

Fig. 4 // TiO2 fine dust content in the powder coating end product based on the dust load at a process temperature of 35 °C and 5 °C.

Fig. 5 shows the specific energy demand for specialty products as a function of the dust load at the process temperature of 5 °C. The efficient operating range of the TiO2 reduction system is at a dust load of approx. 840 g/m³ - 1,050 g/m³. The specific energy requirement - depending on the product specification - lies in this range between 2 kWh/t and 9 kWh/t. To reduce TiO2 fine dust, the specific energy requirement for product B is twice as high as for product A. In conclusion, mechanical separation can be operated more efficiently with coarser particle size distributions than with finer powder coatings.

Successful test summary

The process engineering system for reducing TiO2 fine dust to less than 1% was successfully tested. The tests showed that the process temperature and dust loading have a great influence on the mechanical separation in the TiO2 reduction system. The higher the dust load and the lower the process temperature, the higher the reduction of the TiO2 fine dust content in the powder coating.

The presented TiO2 reduction process can reduce the TiO2 fine dust content to below 1% with a low energy input of 2 kWh/t to 9 kWh/t and high throughputs of up to 1,000 kg/h. The material loss in the preparation of white powder coatings is a maximum of 5%- 9%. With light, non-white powder coatings, the material loss will be less than 5%. With the downstream compacting process, discharged fine dust can be reused in the powder coating value-added chain. The TiO2 reduction system has dimensions of only L = 3m x W = 3m x H = 5m at a throughput of up to 1,000 kg/h.

Due to the small size of the system, it can easily be installed in existing powder coating production facilities. In case of color changes the system can be cleaned easily and quickly due to the good accessibility and the compact design. In combination with the additive dosing and dispersing system, the additive consumption is reduced by more than 60% and the powder coating quality is increased. [5]


[1] J. Gesthuizen: Farbe und Lack, February 18 2020. [Online]: Titandioxid/(cpg)/LA0094?cpg=LA0094&utm_source=newsletter&utm_medium=email&utm_campa gn=FL-NL-2020-02-20&utm_content=EU veroeffentlicht-offiziel. [April 24 2020]

[2] B. S. u.: Entsorgung. Bundesverband Sekundärrohstoffe und Entsorgung. April 9 2019.[Online]: [May 13 2020]

[3] F. &. Lack, „Farbe & Lack,“ Oktober 11 2017. [Online]: [May 13 2020]

[4] Verband der deutschen Lack- und Druckfarbenindustrie e.V.: Position on the proposal for a substance-legal classification of titanium dioxide. Association of the German Paint and Printing Ink Industry, Frankfurt am Main 2018

[5] C. B. F. M. Marc Giersemehl: Dosing and dispersing: A dosing and dispersing system in tests under real conditions, that the amount of additive required is reduced by up to 60%. Farbe & Lack, February 2020


Born in 1970, he studied Process Technology at the university Hochschule Niederrhein in Krefeld. He wrote his diploma thesis about the Cyclone Classifier CSF at NEUMAN & ESSER in 1995 and has worked there continuously since then. Today, as the Technical Managing Director, he is responsible for the technical area including research & development.


Born in 1982, he took his Master’s Degree in Development Management at the FH Aachen. He wrote his Bachelor’s thesis at NEUMAN & ESSER in 2010. He then wrote his Master’s thesis at FEV Europe in 2012. Since 2013, he has been the ICM powder coating Product Manager at NEUMAN & ESSER Process Technology.


Born in 1991, he took his Master’s Degree in Process Technology at the RWTH Aachen. He wrote his Bachelor’s and Master’s theses at NEUMAN & ESSER in 2014 and 2016. He has worked there in the Research & Development Department since 2014. Prior to this, he completed an integrated degree program in connection with industrial training as an Industrial Mechanic at NEUMAN & ESSER Compressors.

Christian Begass

Christian Begass

Product Specialist Powder Coating


NEUMAN & ESSER Process Technology
Werkstr. o. Nr., 52531 Übach-Palenberg