content_image/932836.jpg content_image/932840.jpg content_image/932838.jpg content_image/932839.jpg content_image/932837.jpg
<img src='content_image/932836.jpg'>

Trimerization from Benzimidinate or "Siam" (Examples 17, 18) 

<img src='content_image/932840.jpg'>

The handling operations were carried out according to the same procedures above. 

<img src='content_image/932838.jpg'>

As the 3 reaction mixtures exhibit insoluble materials, the GPC/FTIR analysis was not able to make it possible only to qualify the entities present. It indicates the presence of trimer, of bis-trimer, of tris-trimer and of heavy compounds with isocyanate functional groups predominantly exhibiting at least one isocyanuric ring. The trimerization stage is too advanced to be able to carry out meaningful measurements; catalysis is, however, very strong. 

Comparison Between Samarium and Na 

## EXAMPLE 17 

<img src='content_image/932839.jpg'>

Study of the Influence of the Experimental Parameters Influence of the Nature of the Metal Center 

<img src='content_image/932837.jpg'>

The presence of insoluble materials does not make it possible to quantify the crude products obtained. All the rare earth metal salts constitute powerful trimerization catalysts. 

Influence of the Amount of Catalyst (Yttrium Metal) 

The decrease in the amount of catalyst led to the disap- pearance of the insoluble materials and made it possible to weaken the trimerization stage. 

Cyclotrimerization of the IPDI (Isophorone Diisocyanate) Monomer 

Comparison Between the Yttrium Salt and NaN (SiMe$_{3}$ ) 2 

The tests were carried out under the same operating conditions as for the HDI monomer ( cf. EXAMPLE 12). 

## EXAMPLE 18 

## EXAMPLE 19 

