SMI: Silk Screen Inks

Silk Screen Inks Benefit From Specialty Minerals Precipitated Calcium Carbonates (PCCs)

PVC Plastisol Silk Screen Inks
Specialty Minerals Inc. (SMI) coated ultrafine or nano precipitated calcium carbonates (PCCs) are extremely effective builders of rheology in PVC plastisol systems, making them useful in many silk screen ink applications. The 0.07 micron or 70 nanometer nano PCC particles form a true thixotropic structure in polyvinyl chloride plastisols and plasticizers, building viscosity and yield value, and controlling ink spread after application. The particle’s stearic acid coating improves dispersion and compatibility in the plastisol system, and thus also improves the rheological effectiveness.

The coated ultrafine PCCs serve both as rheological additives and as fillers in PVC plastisol applications. Thus, reformulation to the use of PCC should be a reformulation of both rheological additive and filler. Typically, the final formulation should have a combination of enough PCC to give the desired rheology, plus ground calcium carbonate to bring the solids up to the desired level.

Rheological Effectiveness of Specialty Minerals Ultrafine Precipitated Calcium Carbonates
As an example of the thickening efficiency of SMI’s ultrafine PCCs, 35 percent Ultra-Pflex^® PCC pastes were prepared with a high-speed disperser in DINP (diisononyl phthalate plasticizer), and viscosities measured at 20 and 2.5 rpm with a Brookfield RVF Viscometer, using a #7 spindle.

The high efficiency and shear thinning behavior of this nano PCC can be clearly seen.

High Image Quality With Precipitated Calcium Carbonate
The exceptional brightness of PCCs contributes to high brightness inks. The particle spacing function of PCCs also help maximize opacity and color strength development of the organic pigments and titanium dioxides used in the formula.

Specialty Minerals Coated Ultrafine Precipitated Calcium Carbonates For PVC Plastisol Screen Inks
The SMI coated nano PCCs for PVC plastisol applications are Ultra-Pflex^® PCC and Calofort^® S PCC. Both are true nano particles. By definition, nano particles have a particle size of less than 100 nanometers, or 0.1 micron. SMI’s nano PCCs are 0.07 microns or 70 nanometers in median particle size. The Ultra-Pflex^® PCC is manufactured in the U.S., while the Calofort^® PCC is manufactured in the U.K.

Other Specialty Minerals Products For Silk Screen Inks
Other SMI calcium carbonates are also useful in various silk screen applications. For water-based screen inks, hydrophilic nano PCCs are recommended, which also form thixotropic structures. They are named Multifex-MM^® PCC in the U.S. and Calofort^® U PCC in the U.K.

For general filling of screen inks, SMI has a range of high-brightness, high-purity ground calcium carbonates (GCCs), which are manufactured in the United States. Ranging in size from 3 to 17 microns are the Vicron^® GCC products and the RiverCal^TM 8100 GCC series, and at 325 and 200 mesh are the Marblewhite^® ground limestones.

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