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Kaolin: The answer to TiO2 price hikes?

By Cameron Perks
Published: Friday, 23 March 2018

Pigment buyers have begun cutting costs and increasing end prices in response to rising TiO2 pigment prices, but what else can be done?

Industrial Minerals reported in February that pigment buyers had already began cutting costs and increasing end prices in response to titanium dioxide (TiO2) pigment price inflation, with warnings that further inflation was to come.

TiO2 prices rose in 2017 due to rising demand and the suspension or closure of Chinese production capacity in the wake of an anti-pollution drive. 

Now, prices are set to continue rising alongside their raw-material counterparts; ilmenite and rutile.

While it is not a complete replacement for TiO2, kaolin producers and their marketing teams are pushing hard for coatings, plastics and paper end-user’s business. Imerys Kaolin, the global leader in the supply of high quality white pigments into the paper industry, recently stated that "the decision to optimize TiO2 usage using Imerys Kaolin’s advanced TiO2 extenders" is "the most logical choice" in the current TiO2 market.

Imerys says its Opacilite product "has been proven to reduce TiO2 by up to 20%", relieving pigment costs and TiO2 availability issues for coatings and inks producers. More specifically, it is fine kaolin minerals that can be used to extend the TiO2 used in paints, coatings, inks, paper, adhesives, cosmetics, and thermoplastics by optimal and mechanical properties.

TiO2 Distribution – Crowding of Pigment Particles April 2018 
 Figure 1: TiO2 Distribution – Crowding of Pigment Particles
According to Imerys Mineral’s Helen Dollani, today’s coatings "typically contain 3-30% TiO2 depending on the pigment volume concentration (PVC) of the coating and end performance requirements."

"Opacity is a fundamental property for all paints. Use of high refractive index pigment such as titanium dioxide generates opacity and/or the inclusion of air voids creates dry hiding in the film. As shown in Figure 1, materials can become opaque/white when there are a large number of 'small’ particles of an ideal size scattering light efficiently within a given volume. 

"To be effective, pigment particles also require optimal spacing and low crowding within both the wet and dry paint. 

Figure 1 illustrates crowding of titanium dioxide particles. The use of coarse mineral extenders tends to crowd TiO2 pushing the pigment particles together and lowering overall paint opacity. Extenders that are finer, however, improve the scattering efficiency of titanium dioxide in matt paints (high PVC) due to the physical separation of pigment particles. Fine platy particles are ideal to 'space’ TiO2 when pigment levels are high, typically in gloss and semi-gloss coatings.

"Opacity in white paints can be achieved by using two different mechanisms. In high gloss paints, opacity is achieved primarily by the titanium dioxide pigment with the high refractive index giving good wet and dry opacity properties but it is expensive with paints typically containing 15-30% TiO2. 

"Opacity in white paints can be achieved by using two different mechanisms. In high gloss paints, opacity is achieved primarily by the titanium dioxide pigment with the high refractive index giving good wet and dry opacity properties but it is expensive with paints typically containing 15-30% TiO2.

 Imerys kaolin recommendations for decorative paints depending on PVC April 2018
 Figure 2: Summary of Imerys’ kaolin recommendatons for decorative paints depending on PVC.

 Here mineral additions can improve opacity and allow the reduction of the high cost pigment.

"The second mechanism is dry hiding and comes from the inclusion of air voids. In this instance the opacity is achieved in the dry film only and is the dominant mechanism used in matt paints (medium to high PVC). Mineral fillers are used in higher amounts in matt finishes and enable the incorporation of air into the coating."

Imerys has a wide range of products suitable for various decorative paints, depending on the PVC, as shown in Figure 2.

Other applications

TiO2 extenders may also be found in plastic formulations, however, applications should be thick, (sheet or molded), in which case marginal extension/substitution is possible. Extenders need to be highly concentrated to have an impact, due to the crowding effect, something that is difficult in plastic applications, and especially in thin-film applications.

Helen Dollani notes that Imerys’ kaolins may also be employed for TiO2 reduction and/or as opacifiers in "flexographic printing inks".



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