25  us 6,946,538 B2  26  Trimerization from Benzimidinate or "Siam" (Examples 17,  18)  Study of the Influence of the Experimental Parameters  Influence of the Nature of the Metal Center  Comparison Between Samarium and Na  The handling operations were carried out according to the  same procedures above.  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)  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.  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  19  EXAMPLE  18  EXAMPLE  17  Trimer  Entities present  Appearance  bands  and their amounts  Tin°  C.  of the RM  in cm- 1  (GPC/Ff!R analysis)  DC  60  Yellowish  1686.5  Bis- Trimer  +  biuret  HD!  Ov: 8%  viscous  1465  trimer  6.3%  liquid  0.7%  100  Yellowish  1689  Heavy  Tris- Bis- Trimer  viscous  1464.5  products  trimer  trimer  13%  liquid  0.8%  0.4%  2.1%  83.3%  T  +  B: 7%  HD!  Ov: 25%  64.3%  T: 20%  Metal Appear- Trimer  cen- ance  bands  Entities present  ter  of the RM  in cm- 1  (GPC/Ff!R analysis)  Sm  Opaque  1688.5  Heavy  Tris- Bis- Trim- HD!  paste  1464  products  trimer  trimer  er  Yb  Opaque  1688.5  Heavy  Tris- Bis- Trim- HD!  paste  1463  products  trimer  trimer  er  y  Off-white  1688.5  Heavy  Tris- Bis- Trim- HD!  paste  1463  products  trimer  trimer  er  Percentage by Appearance of  Trimer bands  Catalyst  mass  the crude product  observed in cm- 1  Sm(Siam)$_{3}$PhCN  1%  Opaque paste  1688.5  1464  NaSiam  1%  Opaque solid  1686  1465.5  LiSiam  1%  Opaque solid  1689  1465  Trimer  Entities present  Content as  Appearance  bands in  and their amounts  % by mass of the RM  cm- 1  (GPC/Ff!R analysis)  DC  1%  Off-white  1688.5  Heavy  Tris- Bis- Trimer  HD!  paste  1463  products  trimer  trimer  0.2%  Yellowish  1686  Heavy  Tris- Bis- Trimer  +  biuret  HD!  Ov: 35%  viscous  1460  products  trimer  trimer  13.4%  41.3%  T  +  B: 21%  liquid  2.7%  1.7%  4.3% 