The "Unsung Hero" of Papermaking: How Calcium Carbonate Makes Paper Whiter and Smoother

In the paper industry, calcium carbonate (CaCO₃) is a vital raw material that significantly improves paper whiteness, smoothness, and printability. Abundant, cost-effective, and finely particulate, it boosts opacity, ink absorption, softness, and gloss while minimally affecting paper strength.

Two Key Roles of Calcium Carbonate in Papermaking

1. Filler

   • Dispersed among pulp fibers to fill gaps, enhancing opacity and brightness.

   • Ground Calcium Carbonate (GCC): Used in printing/writing/office papers (excluding cigarette/filter/specialty papers). Specifications:

     • Coated paper: 325 mesh, brightness ≥92%, CaCO₃ ≥98%.

     • Whiteboard: 1250+ mesh, brightness ≥92%, CaCO₃ ≥98%.

     • Technical Specification Requirements for Filler-Grade Calcium Carbonate (QB/T2811-2019 Calcium Carbonate for Papermaking)
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   • Precipitated Calcium Carbonate (PCC): Preferred for premium papers (e.g., cigarette, fax, inkjet papers).

2. Coating Pigment

   • Improves print quality and uniformity. GCC suits base/top coatings; PCC complements kaolin/GCC in high-gloss/matte papers.

   • Technical Specification Requirements for Coating-Grade Calcium Carbonate (QB/T2811-2019 Calcium Carbonate for Papermaking)
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   • Advantages: High brightness, low binder demand, excellent ink absorption.

   • China Industry Standard (QB/T 2811-2019): Governs purity, brightness (D65), pH, viscosity, and particle distribution.

   • Wet-processed GCC dominates coatings:

     • Base coat: ≥75% particles <2μm.

     • Top coat: ≥90% particles <2μm for gloss.

Secrets to Whiter & Smoother Paper

1. Brightness: CaCO₃’s inherent whiteness elevates paper’s visual appeal.

2. Smoothness/Gloss: Fine, uniform particles create a smooth coating, reducing linting and enhancing print quality.

Technical Specification Requirements for Coating-Grade Calcium Carbonate (QB/T2811-2019 Paper-Use Calcium Carbonate)

Choosing the Right CaCO₃ for Papermaking

• GCC vs. PCC: Select based on paper grade, pulp type, and machine conditions.

• Filler Dosage: Optimize to reduce fiber use while maintaining paper performance.

Beyond Whiteness: CaCO₃’s Advantages

1. Cost Savings: Reduces fiber consumption.

2. Ink Absorption: Improves print sharpness.

3. Strength: Modified CaCO₃ enhances tensile/burst strength.

Modifying CaCO₃ for Papermaking

Untreated CaCO₃ has poor fiber compatibility and retention. Key methods:

1. Chemical Coating Modification

   • GCC: Nano-coating in Ca(OH)₂-H₂O-CO₂ systems improves dispersion and strengthens fiber networks, boosting tensile/burst indices.

   • PCC: Cationic chitosan/carboxymethyl cellulose treatment increases particle size uniformity and retention via mechanical/adsorptive effects.

2. Surface Modification

   • Silane Coupling (KH570): Forms Ca–O–Si bonds on nano-CaCO₃, enhancing hydrophobicity and coating performance.

   • Sodium Stearate: Reduces agglomeration; blends with polyurethane for anti-slip packaging paper.

Applications

From office paper to coated board, CaCO₃ is indispensable—especially in hygiene products (diapers, sanitary pads) and photo papers. Truly the paper industry’s "unsung hero."

Source: Compiled from industry references. Contact us for technical inquiries.

Why Our Vibrating Screens Matter

For GCC/PCC producers, precise particle sizing is critical. Our vibrating screens ensure:

• High-precision grading (325–1250+ mesh).

• Optimal brightness retention by removing oversized impurities.

• Efficient coating prep with tight particle distribution control.

Let’s optimize your CaCO₃ process—screen smarter, produce better.