Liaoning Xinda Talc Group Co., LTD. - Yang Yongli

I. Introduction

Talcum powder, as an important inorganic non-metallic mineral material, is a hydrophobic and organic-friendly substance with its unique and stable layered silicate rock chemical structure, chemical stability and lubricity. It has an affinity for viscous components such as vinyl acetate in resins and deinking pastes.

Talcum powder adheres to the resin or wraps the resin, turning it into a solid that flows along with the fibers.

A small portion of talcum powder sinks together with the adsorbed resin during the water purification process and separates from the water circuit, preventing it from accumulating more and more in the water and thus further controlling the resin obstruction.

It is widely used in the papermaking industry in fields such as fillers, coatings and resin control.

The R&D center of Liaoning Xinda Talc Group focuses on the impact of talc powder with different talc contents (55%, 75%, 90%) and mesh sizes (1250 mesh, 3000 mesh) on the performance of paper. By integrating industry practice and technical standards, it provides a scientific basis for the raw material selection of papermaking enterprises.

Ii. Basic Properties of Talcum Powder and Application Principles in Papermaking

1. Chemical Composition and Structural Characteristics: The main component of talcum powder is hydrated magnesium silicate (3MgO·4SiO₂·H₂O), and its theoretical silicon dioxide content is approximately 63.47%. Its layered crystal structure endows it with lipophilic hydrophobicity and flaky form, which is a key factor affecting the performance of paper.

2. Papermaking application mechanism

• Filler function: Fill the gaps between fibers, enhance the opacity of paper (through light scattering), smoothness and printability.

• Coating function: Improves the gloss of the coating and the ink absorbency, especially suitable for coated paper.

• Resin control: Talcum powder encapsulates the resin, turning it into a solid that flows along with the fibers, adsorbing adhesives and reducing equipment clogging.

Iii. The Influence of Talc Content on Papermaking Performance

1. Low talc content of 55% • Performance characteristics: When the talc content is low, the magnesium content in talc is relatively high, the hardness is low (Mohs hardness 1-1.5), and the whiteness is usually between 85% and 88%.

• Application scenarios:

• Common packaging paper: such as boxboard and corrugated paper, can reduce fiber usage by approximately 8%.

Newsprint: It enhances ink absorbency and reduces the risk of overprinting, but the strength loss is relatively obvious, with the tensile index dropping by approximately 5%. • Limitations: High oil absorption value (25-35g/100g) may increase the viscosity of the coating, and the formula needs to be adjusted.

2. Talc content 75% • Performance characteristics: With an increase in talc content, the whiteness can reach 88%-92%, and the refractive index (1.53-1.59) is higher than that of calcium carbonate (1.49), significantly enhancing opacity.

• Application scenarios with talc content above 90% :

• Food packaging paper: High-purity talc products comply with GB 5009 standards and have high-temperature resistance (decomposition temperature > 800℃), making them suitable for heat-sealing packaging.

• Specialty paper: For instance, capacitor paper, talc powder with a talc content of over 90% can reduce dielectric loss by 30%.

• Advantages: Strong chemical stability, suitable for neutral/alkaline papermaking systems, and can increase the retention rate to 90%.

Iv. The Influence of Mesh Size on Papermaking Performance

1. 1250 mesh talcum powder • Performance characteristics: The particles are relatively coarse, with a specific surface area of approximately 1100m²/Kg. After filling, the porosity of the paper is relatively high, about 40%, and it has good air permeability.

• Application scenarios: • Uncoated printing paper: Such as textbook paper, adding 10%-15% can increase opacity by about 10% or more, but the smoothness is relatively low.

• Notes: The retention rate is relatively low, so retention AIDS (such as cationic starch) should be used in combination.

2. 3000 mesh talcum powder • Performance characteristics: Ultrafine particles, specific surface area approximately 1800m²/Kg, forming a dense coating (porosity < 20%), with a gloss of up to 60-70 Gu.

• Application scenarios:

Specialty paper: such as thermal paper, talcum powder with a particle size D50≤3μm can optimize the thermal stability of the coating and reduce the color development temperature.

• Technical advantages: After surface modification (such as silane coupling agent), the dispersibility is significantly improved, and the retention rate is increased to 85%-90%.

V. Comparative Analysis with Other Fillers

Calcium carbonate

• Advantages: High whiteness (90%-96%), suitable for alkaline or neutral papermaking.

• Disadvantages: It has a relatively high hardness (Mohs hardness 3), a wear index 2 to 3 times that of talcum powder, and a high COD value in the wastewater.

2. Comprehensive advantages of talcum powder

• Environmental friendliness: Replacing part of calcium carbonate can reduce the COD of wastewater by 15% to 20%, which is in line with the requirements of the "dual carbon" policy. • Versatility: Simultaneously enhance smoothness, water resistance (increase sizing degree by 0.5-1.0mm), and printability.

Vi. Industry Standards and Technological Trends

Current standards

• GB/T 15342-2023: Whiteness of talcum powder for papermaking ≥88% (first grade), pH value 8.0-10.0, residue on 45μm sieve ≤2%.

• Food contact standards: SiO₂≥60%, heavy metals (As≤3ppm, Pb≤5ppm) shall comply with GB 5009.75-76.

2. Technological innovation direction

• Surface modification: The bonding force between talcum powder and fibers is increased by 40% after treatment with silane coupling agent, and the retention rate is raised from 60% to 90%.

Nano-sized talcum powder can be used in ultra-thin capacitor paper, with the dielectric constant reduced to 3.5-4.0.

Vii. Conclusions and Suggestions

1. Selection Strategy • Low-cost Demand: Prioritize the use of talcum powder with 55% content and 1250 mesh for ordinary packaging paper and newsprint.

• High-end paper products: 90% content, 3000 mesh talcum powder (modified) is an ideal choice for coated paper and specialty paper.

2. Process optimization

• Dispersion control: For high-mesh talcum powder, a dispersant (such as sodium polyacrylate) should be added to the coating, with a dosage of 0.3%-0.5% (for absolutely dry talcum powder).

• Sizing synergy: When talcum powder is combined with AKD sizing agent, it is recommended to control the pH value at 7.5-8.5 to enhance water resistance.

3. Future trends

• Greening: Develop fluorescent and degradable talcum powder for food packaging that complies with the EU REACH regulation.

• Functionalization: Develop antibacterial (Ag+ loaded) and conductive (composite carbon nanotube) talcum powder to expand the application scenarios of specialty paper.

References

[1] China National Pulp and Paper Research Institute Technical Appraisal Report on the Manufacturing of Ultrafine Talcum Powder for Paper Coating [R]. 2018.

[2] China Non-metallic Minerals Industry Association. White Paper on China's Papermaking Grade Talcum Powder Market in 2025 [R]. 2025.

[3]GB/T 15342-2023 Talcum powder [S]. China National Standards Press, 2023.

[4] Xufeng Powder. Application Technology Manual of Talcum Powder in PP Synthetic Paper [Z]. 2022.

[5] Liming Heavy Industry. A Comparative Study on the Performance of Calcium Carbonate and talcum Powder as fillers [J]. Non-metallic Minerals, 2024 (3): 45-48. (Note: Some data are quoted from industry reports and patented technologies. Specific values can be adjusted according to actual production conditions.)