Different morphologies and particle sizes of silica for new visual properties
Benefits at a Glance
- Appearance of waterborne leather coatings in viewing angles (sheen) can be adjusted
- SPHERILEX® DP-0111 combined with ACEMATT® TS 100 or ACEMATT® OK 520 shows excellent results
- Easy to incorporate into the liquid coating by stirring in with a dissolver
Materials and Methodes
ACEMATT® OK 520 (precipitated silica) and ACEMATT® TS 100 (pyrogenic silica) are mainly responsible for direct matting, measured at 60 degree angle with a glossmeter. But often the impression in the 85 degree angle shows a more glossy impression, i.e. a high sheen value.
A novel approach to address the issue of high sheen is to incorporate spherical silica, SPHERILEX®, alongside the previously mentioned state-of-the-art silica matting agents. Spherical silica has a lower efficiency in matting compared to the irregular shaped traditional silica matting agents. Especially at 60 degree angle the surface shows very little impact to gloss reduction properties within liquid coatings.
A comparison in shape of irregular precipitated, pyrogenic and spherical precipitated silica is shown in figure 1.
Figure 1: Comparison of microscopic images of ACEMATT® OK 520, ACEMATT® TS 100, SPHERILEX® DP-0110 resp. SPHERILEX® DP-0111
In these tests the usage of different silica ACEMATT® OK 520 (Ꝋ 6.5 µm), ACEMATT® TS 100 (Ꝋ 9.5 µm) and SPHERILEX® DP-0110 resp. DP-0111 (Ꝋ 4.4 and 5.5 µm) had been tested in a one-component waterborne leather coatings system based on a polycarbonate containing polyurethane dispersion.
The silica based matting agents were dispersed by a dissolver approximately 10 minutes at a speed of 5 m/s. This procedure is sufficient to incorporate the particles properly but without any damage to the fragile structures. Too high shear forces will lead to degradation of the particles and matting efficiency will be reduced dramatically.
By ratio variation of ACEMATT® OK 520 resp. ACEMATT® TS 100 and as well SPHERILEX® DP-0110 resp. DP-0111 in the test formulation the aim of the experiments was to achieve a synergistic effect for the reduction of the sheen.
To measure the gloss, the test formulations had been applied to LENETA cards to minimize the influence of different substrates with a wire bar of 24 µm. Drying was done 72 hours at room temperature.
| Dosage SPHERILEX® DP-0110 [% by weight] | Dosage ACEMATT® OK 520 [% by weight] | Sheen (Gloss 85° - 60°) | Dosage SPHERILEX® DP-0111 [% by weight] | Dosage ACEMATT® OK 520 [% by weight] | Sheen (Gloss 85° - 60°) |
|---|---|---|---|---|---|
| 0 % | 5,5 % | 17,2 | 0 % | 5,5 % | 17,2 |
| 2 % | 5,5 % | 13,2 | 2 % | 5,5 % | 11,0 |
| 4 % | 5,5 % | 11,5 | 4 % | 5,5 % | 8,1 |
| 6 % | 5,5 % | 10,5 | 6 % | 5,5 % | 6,1 |
| 8 % | 5,5 % | 9,0 | 8 % | 5,5 % | 4,6 |
| 10 % | 5,5 % | 8,6 | 10 % | 5,5 % | 4,0 |
| Dosage SPHERILEX® DP-0110 [% by weight] | Dosage ACEMATT® TS 100 [% by weight] |
| Dosage SPHERILEX® DP-0111[% by weight] | Dosage ACEMATT® TS 100 [% by weight] | Sheen (Gloss 85° - 60°) |
| 0 % | 7,0 % | 23,7 | 0 % | 7,0 % | 25,0 |
| 2 % | 7,0 % | 13,0 | 2 % | 7,0 % | 12,7 |
| 4 % | 7,0 % | 9,8 | 4 % | 7,0 % | 7,4 |
| 6 % | 7,0 % | 7,3 | 6 % | 7,0 % | 4,5 |
| 8 % | 7,0 % | 5,6 | 8 % | 7,0 % | 2,7 |
| 10 % | 7,0 % | 5,6 | 10 % | 7,0 % | 2,1 |
Table 2: content of ACEMATT® OK 520, ACEMATT® TS 100, SPHERILEX® DP-0110 resp. SPHERILEX® DP-0111 in waterborne formulation.
Conclusion
In the tested waterborne one-component formulation, optimal results were achieved using a high content (10%) of SPHERILEX® DP-0111 combined with ACEMATT® TS 100 or ACEMATT® OK 520. Beyond visual sheen reduction, the coatings also provide a desirable tactile experience, reminiscent of premium leather, due to the smooth distribution of silica particles,
Different morphologies of silica particles allow to adjust the visual properties of the high-class water-borne leather coating accordingly to the whole premium market needs and give more freedom of formulation to the coatings manufacturer.