DIN EN ISO 4629-2:2016-12

There are several different methods standardized for determining the hydroxyl value of resins. The classic method using pyridine without a catalyst is specified in ISO 4629-1. The advantages of the method using a catalyst are the following:
- the solvents used are less hazardous to health; - the solvent consumption is lower; - the method is faster due to shorter reaction times; - the end point of the titration is easier to see; - polyols are more readily soluble.
This part of ISO 4629 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.
The responsible German standardization committee is Working Committee NA 002-00-02 AA "Lackrohstoffe" ("Raw materials for paints and varnishes") at DIN Standards Committee Coatings and Coating Materials (NAB).