Performance Index Requirements Of Paper Coating Anti-stick Wax Emulsion

The performance index of paper coating anti-stick wax emulsion needs to be optimized according to the specific application scenario (such as packaging paper, label paper, heat-sealing paper, etc.) and production process (coating method, drying conditions, etc.). The following are general core performance index requirements and suggestions:

1. Basic physical and chemical indicators

Solid content (solid content):

Usually 30-50% is required, and the coating efficiency and drying energy consumption need to be balanced. Too low solid content may cause the coating to be too thin and the anti-stick effect is insufficient; too high may affect the emulsion stability and coating uniformity.

pH value:

Recommended range 7.5-9.0 (weak alkaline) to avoid reaction with other components in paper coating (such as starch, adhesive).

Viscosity:

Adjusted according to the coating process, typical range 50-500mPa·s (25℃). For example:
Scraper coating: 200-400mPa·s
Spraying/dip coating: 50-150mPa·s

2. Emulsion stability
Mechanical stability:
No stratification or flocculation after centrifugal test (such as 3000rpm, 30 minutes).
Storage stability:
No precipitation or stratification for at least 6 months at room temperature (25℃).
Stay stable after high temperature (50℃)/low temperature (-5℃) cycle test (7 days).
Electrolyte resistance:
Compatible with common ions in coatings (such as Ca²⁺, Na⁺), no demulsification.

3. Particle size and dispersibility
Average particle size:
Nanoscale dispersion, typical range 50-200nm (laser particle size analyzer detection).
Narrow particle size distribution (PDI＜0.3) to ensure coating uniformity.
Dispersibility:
No visible particles after dilution, no agglomeration under microscope.

4. Functional indicators
Anti-stick performance:
Peel force test: Peel force with sticky materials (such as tape, heat seal layer) ≤1.0N/cm (can be adjusted according to application).
Test after heat sealing: Still effective anti-stick at heat sealing temperature (such as 120-180℃).
Temperature resistance:
High temperature stability: The wax emulsion coating does not melt or migrate at the target temperature (such as 150℃).
Low temperature crack resistance: The coating has no cracks at -20℃.
Surface performance:
Contact angle (hydrophobicity): ＞100° (if waterproof and oil-proof is required).
Gloss: Adjust according to paper requirements (such as high gloss packaging paper needs to be compatible with wax emulsion).

5. Compatibility and environmental protection
Compatibility with coating components:
No flocculation, thickening and other problems after mixing with common coating components (such as acrylic resin, calcium carbonate, defoamer).
Environmental protection and safety:
No harmful substances such as APEO and formaldehyde, in compliance with REACH/ROHS regulations.
VOC content <50ppm (if used for food contact grade paper).
6. Process adaptability
Drying speed:
After coating, it can form a film quickly, for example, it can be cured within 1-2 minutes under hot air drying conditions of 100-120℃.
Coating amount:
According to the requirements of the anti-sticking grade, the typical coating amount is 0.5-3.0g/m² (needs to be optimized through experiments).
Test methods and standards
Anti-sticking test: refer to TAPPIT549 (peeling force) and ASTMF88 (heat sealing strength).
Stability test: refer to ISO2555 (viscosity), GB/T11543 (storage stability).

Environmental testing: certified by a third-party organization (such as SGS, Intertek).

Notes

The wax emulsion formula needs to be adjusted according to the paper substrate (such as coated paper, leather paper) (such as PE wax, stone wax or silicone wax).

If used for food packaging, it is necessary to ensure that the wax emulsion complies with FDA21CFR175.105 and other standards.

It is recommended to conduct a small test before production to verify the compatibility with the existing coating production line (such as roller coating, air knife coating).

If further optimization is required, specific application scenarios (such as high-speed coating machine, food grade requirements) can be provided to adjust the index parameters in a targeted manner.