<p>This International Standard specifies methods for the measurement of the acidity of aromatic isocyanates and</p>
<p>prepolymers used as polyurethane raw materials. Method A is a straightforward titration without a blank and is</p>
<p>primarily applicable to products derived from crude or modified methylene-bis-(4-phenylisocyanate), polymethylene</p>
<p>polyphenylisocyanates and toluene diisocyanate having moderate to high (> 100 mg/g ) levels of acidity. Method B is</p>
<p>applicable to refined, crude or modified isocyanates derived from methylene-bis-(4-phenylisocyanate), polymethylene</p>
<p>polyphenylisocyanate and toluene diisocyanate having low (< 100 mg/g ) levels of acidity, and a blank is employed.</p>
<p>These methods can also be used for isomeric mixtures of toluene diisocyanate, methylene-bis-(4-phenylisocyanate)</p>
<p>and polymethylene polyphenylisocyanate. Other aromatic isocyanates may be analysed by this method if</p>
<p>precautions are taken to verify suitability.</p>
Registration number (WIID)
25886
Scope
<p>This International Standard specifies methods for the measurement of the acidity of aromatic isocyanates and</p>
<p>prepolymers used as polyurethane raw materials. Method A is a straightforward titration without a blank and is</p>
<p>primarily applicable to products derived from crude or modified methylene-bis-(4-phenylisocyanate), polymethylene</p>
<p>polyphenylisocyanates and toluene diisocyanate having moderate to high (> 100 mg/g ) levels of acidity. Method B is</p>
<p>applicable to refined, crude or modified isocyanates derived from methylene-bis-(4-phenylisocyanate), polymethylene</p>
<p>polyphenylisocyanate and toluene diisocyanate having low (< 100 mg/g ) levels of acidity, and a blank is employed.</p>
<p>These methods can also be used for isomeric mixtures of toluene diisocyanate, methylene-bis-(4-phenylisocyanate)</p>
<p>and polymethylene polyphenylisocyanate. Other aromatic isocyanates may be analysed by this method if</p>
<p>precautions are taken to verify suitability.</p>
