EN ISO 4629-1:2016 PDF

Overview

EN ISO 4629-1:2016 - "Binders for paints and varnishes - Determination of hydroxyl value - Part 1: Titrimetric method without using a catalyst (ISO 4629-1:2016)" specifies a laboratory titrimetric procedure to measure the hydroxyl value of binders and binder solutions used in paints and varnishes. The method quantifies free hydroxyl groups (e.g., polyhydric alcohols, partial esters, polyester end groups, hydroxylated fatty acids) by acetylation with acetic anhydride followed by hydrolysis and back-titration of the produced acetic acid with a standard potassium hydroxide solution.

Key topics and requirements

• Scope and limitations
  • Applicable to binders and binder solutions for paints and varnishes.
  • Not applicable to resins that contain both hydroxyl and epoxy groups (epoxy contributes to the result), nor to cellulose nitrate or phenolic resins.
  • For binder solutions, users must account for hydroxyl-bearing constituents other than the binder.
• Principle
  • Acetylation of hydroxyl groups → hydrolysis of excess acetic anhydride → titration of acetic acid with KOH (indicator or potentiometric).
  • Primary/secondary amines, if present, are also acetylated and must be considered in calculations.
• Reagents & typical preparations
  • Standard KOH volumetric solution, approx. 0.5 mol/L in methanol (preparation and standardization specified).
  • Acetylating reagent prepared from acetic anhydride and p-toluenesulfonic acid in ethyl acetate.
  • Solvents and indicators: ethyl acetate, toluene/butanol mix, pyridine/water, phenolphthalein or mixed indicator; water of at least ISO 3696 grade 3.
• Apparatus & procedure essentials
  • Ordinary lab glassware, reflux setup, burette, class A pipettes (5 mL for acetylating reagent), heating bath (50 ±1 °C).
  • Determination is carried out in duplicate; test portion mass is chosen according to expected hydroxyl value (guidance table provided in the standard).
  • Potentiometric titration is an optional alternative to visual end-point.

Applications and users

• Primary users: paint and varnish formulators, QC laboratories, raw material suppliers, R&D teams, and contract testing labs.
• Typical uses:
  • Quality control and batch release of binders.
  • Raw-material verification and supplier qualification.
  • Formulation development and troubleshooting where hydroxyl content affects crosslinking, curing, viscosity or film properties.
  • Comparative testing against specifications in procurement and regulatory contexts.

Related standards

• ISO 4629-2 (Part 2): titrimetric method using a catalyst.
• ISO 7142: method for hydroxyl value determination of epoxy resins (referenced when epoxy groups are present).
• Normative references used in EN ISO 4629-1: ISO 385, ISO 648, ISO 2114, ISO 3696, ISO 15528.

Keywords: hydroxyl value, binders for paints and varnishes, titrimetric method, ISO 4629-1, acetylation, paint binder testing, quality control.