The Initial Stage of the Reaction of Melamine with Formaldehyde

Homogeneous methylolation of melamine: Mathematical modeling

“…(4). In Figure 1 and Table I, any ringed molecule is represented by P A 0 ;A 1 ;A 2 , where A 0 , A 1 , and A 2 are, respectively, the number of unreacted amines À ÀNH 2 ; of generated monohydroxymethylamine groups (or primary methylols) À ÀNH(CH 2 OH); and of dihydroxymethylamine groups (or secondary methylols) À ÀN(CH 2 OH) 2 .…”

“…Even though not shown in Figure 1, all forward reactions consume a CH 2 O molecule, and all backward reactions regenerate such a molecule. Figure 1 also includes the nomenclature adopted in this work for representing M and each of its nine methylolated species.…”

“…In this work, the condensation reactions of eqs. (2) and (3) are avoided by operating at a low temperature and in alkaline conditions. 19,20 The solubility of M in water is relatively low (0.32 g/ 100 mL H 2 O at 208C and 5 g/100 mL H 2 O at 1008C).…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] First, the hydroxymethylation (or ''methylolation'') is represented by 1,2 ÀÀH þ CH 2 O Ð À ÀCH 2 OH (1) where À ÀH is any reactive H of any amine group contained in M or its derived products. Then, a hydroxymethyl group can either react with another reactive H to produce a methylene bridge:…”

Physical gelation of melamine formaldehyde resin solutions. II. A combined light‐scattering and low‐resolution relaxation proton NMR study

“…At relatively low pH (7)(8), methylene bridges are formed [reaction 2(a)], whereas at pH values above 9, the formation of ether bridges is favored [reaction 2(b)]. 3 According to previous studies, chemical changes during the storage time at RT are largely negligible. 1 Depending on the molecular structure of MF resins (reaction times), the storage stability of MF solutions is affected by three different physical processes: solid-liquid phase separation of (methylol)melamines for infinitely water-dilutable MF solutions (short reaction times), physical gelation for samples with the highest storage stability (medium reaction times), and liquid-liquid phase separation for MF solutions with a relatively high degree of condensation (long reaction times).…”