Different treatments of calcium powder in the application of oil-based paint differences
Calcium carbonate is the most widely used physical pigment in coatings. It can not only greatly reduce the production cost of coatings, but also affect many properties of coatings, such as changing the mechanical strength of the coating film, improving the water resistance of the coating film, etc. It is the main functional filler for civil and industrial coatings.
Conventional heavy calcium and light calcium are affected by oil absorption value and particle size, often appear hard precipitation and low filling ratio in use. For this reason, calcium carbonate often appears in different ways and forms such as surface modification and nanocrystalization in the formulation system. Here, the rotational viscosity and thixotropy state of the coating under the same ratio of resin liquid and different filling ratio are controlled.
Table 1 Viscosity comparison of low filling ratio | |||||||||||
Model | 1250 mesh ground calcium carbonate | 1250 mesh light calcium carbonate | 1250 mesh activated calcium carbonate | DXC-10 | |||||||
Filling ratio | 25 copies | 25 copies | 25 copies | 25 copies | 25 copies | ||||||
6RPM（mPa.s） | 169 | 862 | 1534 | 24383 | 918 | ||||||
60RPM（mPa.s） | 229.5 | 826.8 | 722.9 | 4512 | 509 | ||||||
Thixotropic index(TI) | 0.74 | 1.04 | 2.12 | 5.40 | 1.80 | ||||||
Filling ratio | 35 copies | 35 copies | 35 copies | 35 copies | 35 copies | ||||||
6RPM（mPa·s） | 356 | 3984 | 21280 | 65156 | 13212 | ||||||
60RPM（mPa·s） | 479 | 6491 | 4532 | outrange | 2819 | ||||||
Thixotropic index(TI) | 0.74 | 0.61 | 4.70 | - | 4.69 | ||||||
Table 2 Comparison of high filling ratio viscosity | ||||||
Model | 1250 mesh ground calcium carbonate | 1250 mesh light calcium carbonate | 1250 mesh activated calcium carbonate | DXC-10 | ||
Filling ratio | 65 copies | 45 copies | 65 copies | 48 copies | 65 copies | |
6RPM（mPa·s） | 1063 | It's hard to stir, more stirring, the thicker it becomes. | 45412 | 89317 | 24750 | |
60RPM（mPa·s） | 1428 | outrange | outrange | 5377 | ||
Thixotropic index(TI) | 0.74 | - | - | 4.60 | ||
(Note: Many viscosity data are out of range under high shear. This time, low shear viscosity data is used to show the high shear viscosity in general product processing and construction.)
(1) Light calcium and heavy calcium show different rheological states from modified calcium and nano-calcium. There is a situation where the thixotropy index is less than 1, and the more stirring, the thicker it becomes, which is not suitable for processing and use of high filling ratio products.
② Nano calcium, 1250 mesh activated calcium , DXC-10 all have certain thixotropy, holding the characteristic of the more stirred, the thinner it becomes. It can effectively improve the processing efficiency.
③ Nano calcium has excellent thixotropy and processability at low filling ratio; But DXC-10 still has good processability and thixotropy at high filling ratio, while nano calcium and activated calcium both have the problem of high viscosity, which significantly reduces the processability.
Model | 1250 mesh ground calcium carbonate | 1250 mesh light calcium carbonate | 1250 mesh activated calcium carbonate | DXC-10 | |
Oil absorption mL/100g | 30 | 55 | 18 | 25 | 10 |
At the same time, combined with the oil absorption data, it can be found that the oil absorption value of DXC-10 is significantly lower than that of other types of calcium powder, which also means that the same resin can carry more DXC-10. That is, DXC-10 can effectively reduce the use of resin in the formula while ensuring the thixotropy, processability, stability and construction of the product.
The following figure shows the status of high filling ratio of calcium powder with different treatments in oily coatings.
It can be seen that DXC-10 is especially suitable for oily coatings with high filling ratio, solven-free coatings, adhesives, modified plastics and other products that have high demand for product rheology, stability and processability.
