Significant improvement of stain resistances with Gloxil WW SL in water-based clear coats

Rising environmental awareness and legal conditions lead to an increased demand for water-based clear coats for wood. These are, e.g., low VOC emissions, efficiency and versatility of such coatings. As a result, challenges for optimization arise, i.e. matting, and maintaining excellent optical properties combined with very good resistance characteristics. Particularly in binder emulsions with higher film formation and glass transition temperature. As well as the mostly insufficient handling properties of matting agents, majorly fumed and precipitated silica, must be optimized. Here, the functional matting agent slurry Gloxil WW SL, a HOFFMANN MINERAL Tailored Filler Solution, can be the product of choice.

The product at a glance

Gloxil WW SL is a 15% aqueous silica dispersion modified with specific additives adapted to the matting agent and the intended application. It is used as a pre-dispersed matting agent slurry in water-based coatings, in particular clear coats for wood.  During film formation of dispersions, the inclusion of matting agent particles will, therefore, be improved. As a result, despite and along with a matting action, films with good water resistance and stain resistance will be obtained. This includes very often dispersions with a higher minimum film formation temperature based on polymers with a higher glass transition temperature. 

Technical study of Gloxil WW SL in water-based clear coats

The performance of Gloxil WW SL versus established powdery silica matting agents in a standard water-based clear coat for wood is assessed concerning the following criteria: matting effect and optical appearance, resistance against water, alcohol and ink as well as optimized processing properties. The Gloxil WW SL slurry is compared to a common fumed and precipitated silica, both with a loading of 2.5 pbw (2.5%) , with a varying loading of 7.7 pbw (7.7%), 15.4 pbw (14.3%) and 23.1 pbw (20.0%).

Results

First, the performance as a matting agent is presented in comparison to both silica alternatives. While with a low loading the Gloxil WW SL can already provide good matting, by increasing the loading up to 14.3% a similar potential matting effect can be observed. By increasing the loading to 20.0%, in particular at gloss 85°, the best performance can be achieved and both competitors can be overcome.

Second, with regard to water resistance, all formulations have been tested at different drying times and duration of exposure. Compared to the Gloxil WW SL at all loadings, both silica formulations show a blushing effect at drying/exposure stages of 1h/1h and 15h/16h (h = hours). Especially at early drying stages Gloxil WW SL shows the best performance.

Third, the resistance to ink was tested, which followed the same trend as for water resistance. The early stages can be mostly influenced positively by a higher loading of Gloxil WW SL. Significant is also that with 14.3% and 20.0% loading of Gloxil WW SL, no stain can be observed after a drying time of 28 days with an exposure time of 16 hours. Also here, the best performance is illustrated at the highest loading of Gloxil WW SL in the formulation.

In the following diagram, the overall performance of Gloxil WW SL in this formulation for a water-based clear coat for wood is presented. While similar results can be achieved with both silica types concerning drying time, blocking resistance and storage stability, significant advantages were found at most other properties, e.g. dispersing/mixing time, resistances to alcohol, ink and water as well as dust prevention.

Summary

• No dust formation
• Highly improved metering and incorporation
• Easier and time-reduced mixing without high shear dispersion process
• Foam-supressing effect
• Better early blocking resistance
• Very high transparency with good long term stability
• Strong matting effect
• Good wood grain enhancement, particularly on dark wood
• Superior early water and stain resistance
• Easy matting level adjustment via post-addition

Want to know more about Gloxil WW SL in water-based clear coats?

• Overview page of Gloxil WW SL
• Technical datasheet of Gloxil WW SL
• Technical study of Gloxil WW SL in water-based clear coats
• Video of dispersing Gloxil WW SL vs. silica

Stay tuned for future posts regarding the Tailored Filler Solutions to receive a better understanding of the products and where to use them! 

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