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98% High Whiteness Ground Calcium Carbonate (GCC, CAS: 471-34-1) is a premium mineral filler derived from ultra-pure limestone deposits, processed through multi-stage grinding and classification to achieve a calcium carbonate content ≥98% and whiteness (L*) ≥98. With a median particle size of 5–20μm and low iron (Fe₂O₃ ≤0.03%), this off-white powder is optimized for use in paper manufacturing, enhancing opacity, brightness, and printability in both 填料 (filler) and 涂布 (coating) applications. Its natural origin and chemical inertness make it a sustainable choice for eco-friendly paper production, compliant with FSC and PEFC chain-of-custody standards.
Exceptional Whiteness and Purity:
*L ≥98 (ISO 2470)**: The highest available whiteness for GCC, reflecting over 98% of incident light to enhance paper brightness (ISO 2471: ≥95%) and reduce reliance on optical brightening agents (OBAs) by 20%.
98% Purity: MgCO₃ ≤1%, SiO₂ ≤0.5%, ensuring minimal interference with papermaking chemicals (e.g., rosin sizes, wet-strength resins).
Controlled Particle Morphology:
Scalenohedral Crystal Structure: Platelet-shaped particles (aspect ratio 2–3) improve packing density in paper webs, increasing opacity (ISO 2471: +5% vs. calcite GCC) and reducing paper thickness by 5–8%.
Narrow Particle Distribution: D90 ≤3x D50 ensures uniform filler retention on wire sections (retention rate ≥70% in 200 mesh screens), minimizing machine deposits and sheet defects.
Process Optimization:
Low Abrasivity: Mohs hardness 3, reducing wear on paper machine wires and rolls (maintenance costs -15% vs. talc fillers).
pH Neutrality: 10% slurry pH 8–9, compatible with both acidic (pH 4–5) and neutral (pH 6–7) papermaking systems without altering sizing chemistry.
Paper Filler Applications:
Wood-Free Paper: Fills cellulose fibers in office paper (15–25% loading), improving brightness (ISO 2471: ≥95%) and ink hold-out (IGT AIC2-5: ≤15% ink spread).
Corrugated Linerboard: Increases stiffness (ECT +10%) and moisture resistance (Cobb value -12%) at 20% loading, critical for heavy-duty packaging.
Paper Coating Applications:
Art Paper Coating: Fine-grade GCC (D50 5μm) enhances surface smoothness (Bekk smoothness +20%) and print gloss (60° gloss ≥80) in topcoat layers of magazines and catalogs.
Food Packaging Paper: Compliant with FDA 21 CFR 176.170, it improves grease resistance (TAPPI T559: ≤5 seconds for paraffin oil penetration) in sandwich wraps and bakery papers.
Specialty Papers:
Bible Paper: Ultra-fine GCC (D50 3μm) reduces paper weight (60–70 g/m²) while maintaining opacity (≥90%), enabling thin, lightweight printed materials.
Security Paper: Used in banknote paper to enhance watermark clarity and tactile feel, with particle size D90 ≤10μm to prevent screen plugging during formation.
Q: How does GCC compare to precipitated calcium carbonate (PCC) in paper?
A: GCC offers better cost-efficiency and lower oil absorption, while PCC provides higher surface area; GCC is ideal for filler applications, PCC for coatings.
Q: Can this GCC be used in recycled paper?
A: Yes, it improves brightness and filler retention in OCC (old corrugated containers) pulps, even with 30% recycled fiber content.
Q: What is the optimal loading level for improving printability?
A: 15–20% loading in the furnish and 30–40% in coatings balance print quality and cost, as higher loads may reduce tensile strength.
Q: Does high whiteness GCC yellow over time?
A: No, the low iron and manganese content (Mn <5ppm) prevent photochemical yellowing (ΔE ≤2 after 1000 hours of xenon arc exposure).
