ISO 4629-2:2016 PDF

Binders for paints and varnishes — Determination of hydroxyl value — Part 2: Titrimetric method using a catalyst

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Title (English):

ISO 4629-2:2016

Binders for paints and varnishes — Determination of hydroxyl value — Part 2: Titrimetric method using a catalyst

Document status:: Active
Format:: Electronic (PDF)
Number of pages:: 6
Publication date:: June 2, 2016
Edition:: ISO IS 4629 edition 1 version 1
ICS:: 87.060.20

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Description (English):

ISO 4629-2:2016 specifies a titrimetric method for determining the hydroxyl value of resins, binders for paints and varnishes, primary alcohols, glycols and fats. Whether it can be applied for hydro carboxylic acids, phenolic hydroxyl groups, polyols such as trimethyl propane and substances containing aromatic groups have been activated for Friedel-Crafts acylation shall be decided on case-to-case basis. Under the right conditions, the method is also applicable for determining the hydroxyl value of castor oil and its derivatives.

Technical details

Technical committee: ISO/TC 35 - Paints and varnishes
SKU: ISO 4629-2:2016

Abstract

Overview

ISO 4629-2:2016 specifies a titrimetric method using a catalyst to determine the hydroxyl value (hydroxyl number) of resins and binders for paints and varnishes. The method measures milligrams of KOH equivalent per gram of sample by acetylating hydroxyl groups with acetic anhydride and titrating the excess reagent with alcoholic KOH. It applies to resins, paint and varnish binders, primary alcohols, glycols and fats; applicability to certain polyols, phenolic OH, hydroxycarboxylic acids or aromatics is decided case-by-case. Under suitable conditions the method can be used for castor oil and derivatives.

Key topics and technical requirements

Principle: Acetylation of OH groups with acetic anhydride; titration of excess anhydride with alcoholic KOH; hydroxyl value calculated from titrant volumes and concentration, corrected for acid value.
Catalyst and solvents: Uses a catalyst solution of 4‑N‑dimethylaminopyridine (DMAP, 1% in NMP) and acylating reagent as 10% acetic anhydride in N‑methylpyrrolidone (NMP). NMP improves solubility and reduces hazardous solvent use versus pyridine methods.
Reagents and quality: Analytical-grade reagents; water meeting ISO 3696 quality. Methanolic (or ethanolic) KOH standard (~0.5 mol/L) is prepared and calibrated against potassium hydrogen phthalate.
Apparatus: Standard laboratory glassware plus titrimeter or automatic burette, analytical balance, magnetic stirrer and heating plate.
Procedure highlights:
- Sample mass calculated from expected hydroxyl value.
- Reaction times: typically ≥15 min at 23 ± 2 °C; products with secondary OH require longer acetylation (≥60 min) and hydrolysis times (≥30 min).
- Endpoint detection potentiometrically or with indicators (thymolphthalein or phenolphthalein).
- Daily blank determination required.
Results & precision: Hydroxyl value reported in mg KOH/g (individual values and mean, rounded to 1 mg KOH/g). Repeatability and reproducibility limits are specified (examples: repeatability ≤0.84 mg KOH/g for HV

Related standards

Mentioned in the description and other ISO standards

Abstract

Overview

Key topics and technical requirements

Principle: Acetylation of OH groups with acetic anhydride; titration of excess anhydride with alcoholic KOH; hydroxyl value calculated from titrant volumes and concentration, corrected for acid value.
Catalyst and solvents: Uses a catalyst solution of 4‑N‑dimethylaminopyridine (DMAP, 1% in NMP) and acylating reagent as 10% acetic anhydride in N‑methylpyrrolidone (NMP). NMP improves solubility and reduces hazardous solvent use versus pyridine methods.
Reagents and quality: Analytical-grade reagents; water meeting ISO 3696 quality. Methanolic (or ethanolic) KOH standard (~0.5 mol/L) is prepared and calibrated against potassium hydrogen phthalate.
Apparatus: Standard laboratory glassware plus titrimeter or automatic burette, analytical balance, magnetic stirrer and heating plate.
Procedure highlights:
- Sample mass calculated from expected hydroxyl value.
- Reaction times: typically ≥15 min at 23 ± 2 °C; products with secondary OH require longer acetylation (≥60 min) and hydrolysis times (≥30 min).
- Endpoint detection potentiometrically or with indicators (thymolphthalein or phenolphthalein).
- Daily blank determination required.
Results & precision: Hydroxyl value reported in mg KOH/g (individual values and mean, rounded to 1 mg KOH/g). Repeatability and reproducibility limits are specified (examples: repeatability ≤0.84 mg KOH/g for HV

ISO 4629-2:2016 PDF

Technical details

Abstract

Overview

Key topics and technical requirements

Related standards

Abstract

Overview

Key topics and technical requirements

Related standards

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