ISO 5263-3:2023

Overview

ISO 5263-3:2023 - Pulps - Laboratory wet disintegration - Part 3: Disintegration of mechanical pulps at ≥85°C specifies the apparatus and procedures for laboratory hot wet disintegration of mechanical pulps that exhibit latency. Applicable to mechanical, semi-chemical and chemi‑mechanical pulps, this standard defines how to remove latency by combining mechanical treatment and heat (≥85 °C) so pulps can be prepared reproducibly for downstream tests (e.g., freeness, strength). The procedure can also be used to prepare test portions for other International Standards.

Key technical topics and requirements

• Scope: Applies to mechanical pulps exhibiting latency (except when brightness is measured - see ISO 5263-2 for brightness).
• Temperature: Maintain the fibre–water suspension at ≥85 °C during disintegration.
• Disintegrator types: Use either the standard disintegrator (Annex A) or the circulation (Domtar) disintegrator (Annex C). Report which type was used because treatment differs.
• Test portion mass:
  • Standard disintegrator: (50 ± 5) g oven-dry pulp
  • Circulation disintegrator: (56 ± 1) g oven-dry pulp
• Soaking time (Table 1):
  • Dry matter < 20%: 0 min
  • 20–60%: 30 min

  • 60%: 4 h (flash-dried: minimum 10 min)

• Standard disintegration cycle: heat to ≥85 °C, run propeller for 30 000 revolutions (visual check for complete separation).
• Circulation disintegration: preheat system with 90–95 °C water, run pump cycles of (120 ± 5) s; ensure fibre separation and a final temperature ≥85 °C.
• Immediate cooling/dilution: after hot disintegration dilute rapidly to 0.3–1.5% concentration at (20 ± 2) °C (or (0.30 ± 0.02)% for freeness testing) to avoid re-establishment of latency.
• Reporting requirements: include reference to ISO 5263-3:2023, sample ID, water grade (ISO 14487), soaking time, dry matter (ISO 638-1 / ISO 4119), disintegrator type, any deviations.

Practical applications and users

• Quality control and R&D laboratories in pulp and paper mills
• Independent testing labs performing freeness, drainage, fiber morphology or strength tests
• Instrument manufacturers (disintegrators) and method developers
• Standards committees and auditors verifying test preparation consistency

ISO 5263-3:2023 ensures reproducible latent‑property removal for mechanical pulps, enabling reliable comparison of pulp properties and consistent preparation of test portions across labs.

Related standards

• ISO 5263-2 (hot disintegration for brightness measurements)
• ISO 638-1 (dry matter determination)
• ISO 4119 (stock concentration)
• ISO 14487 (standard water for physical testing)

Keywords: ISO 5263-3:2023, pulps, laboratory wet disintegration, mechanical pulps, latency removal, standard disintegrator, circulation disintegrator, hot disintegration, freeness testing.