Hexafunctional polyols

Melamine is soluble only in water and has low solubility in dimethylsulfoxide (DMSO) and in other aprotic dipolar solvents (9% at 120 °C), in glycerol or ethylene glycol (10% at 140 °C). In the majority of other usual solvents it is insoluble. Kucharski and Lubczak discovered a new class of reactive solvents for melamine [36] poly (hydroxymethyl) derivatives of cyclohexanone, acetone, nitromethane which are able to dissolve 50-60% melamine. Melamine can be totally propoxylated or ethoxylated at lower temperatures (70-90 °C), in aprotic dipolar solvents (for example DMSO, dimethylformamide, N-methyl pyrrolidone and so on), in the presence of quaternary ammonium hydroxides as catalysts [for example tetrabutyl ammonium hydroxide (TBAH)], at a low reaction rate (reaction 15.35), for a very long reaction time (40-50 hours) [31, 37]. The resulting hexafunctional polyols give very thermostable rigid PU (up 200 °C). 

By the hydrogenation of D-glucose, a hexafunctional polyol, sorbitol is obtained, one of the most important starters to initiate the polymerisation of propylene oxide (PO) to hexafunctional rigid polyether polyols. 

Thus, by the reaction of TMP with 3 mols of glycidol a hexafunctional polyol is obtained (first generation) and by the reaction of this with 9 mols of PO, a polyol with 12 hydroxyl groups/mol is obtained (second generation) as shown in reaction 19.8. 

By the propoxylation of the synthesised melamine derived Mannich base, without catalyst, a hexafunctional polyether polyol is obtained (reaction 15.40). 

Flexible polyether polyols based on high functionality starters (chain initiators) (for example a hexafunctional polyether polyol of equivalent weight 1000-2000, based on alkoxylation of sorbitol instead of glycerol), produces flexible PU foams with higher load bearing properties, but with a decrease in tensile strength and elongation. These polyols were used in carpet underlay [18]. 

Chem. Descrip. Hexafunctional aliphatic urethane acrylate containing acrylated polyol diluent Uses Urethane-acrylic in coatings and inks Features Exceptional cure speed and scratch/abrasion resist, in combination with nonyellowing props. fast cure with exc. hardness, solv. resist. 

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