For melamine

Urea. Urea (carbamide) CH4N2O, is the most important building block for amino resins because urea—formaldehyde is the largest selling amino resin, and urea is the raw material for melamine, the amino compound used in the next largest selling type of amino resin. Urea is also used to make a variety of other amino compounds, such as ethyleneurea, and other cyclic derivatives used for amino resins for treating textiles. They are discussed later. 

As with the U-F moulding powders the relative importance of M-F moulding powders for other plastics materials and also in other uses for melamine-formaldehyde resins has declined. 

Dicyandiamide forms white, non-hygroscopic crystals which melt with decomposition at 209°. Its most important reaction is conversion to melamine (Fig. 8.25) by pyrolysis above the mp under a pressure of NH3 to counteract the tendency to deammonation. Melamine is mainly used for melamine-formaldehyde plastics. Total annual production of both H2NCN and NCNC(NH2)2 is on the 30 000 tonne scale. 

In the past, the term high-pressure laminates was reserved for melamine and phenolic impregnated papers or fabrics compressed under high pressures (about 13.8 to 34.5 MPa, or 2,000 to 5,000 psi). They were heated to form either decorative laminates (for example Formica and Micarta) or industrial lami-... 

Figure 6. TG, DTG curves and rate of ammonia evolution (arbitrary units) for melamine hydrobromide. Conditions as Figure 2.

However, the decomposition of organic compounds does not always lead to nontoxic solutions. Mineralization of melamine (2,4,6-triamino-l,3,5-triazine) and other chemicals was accomplished on Ti02 Degussa P-25. The formation of cyanuric acid prevents the complete mineralization of melamine as observed for atrazine and other. v-tria/incs on Ti02 photocatalysts, and the toxicity of the photocatalyzed solutions was higher than initially found for melamine [199],... 

Pigments that are intended for use in inks for melamine resin sheets are chosen primarily with respect to the particular process characteristics. The list of pos-... 

The list of applications also includes decorative printing inks for melamine based laminated plastic sheets. It should be noted, however, that P.B.15 1 may not be used in decorative printing inks for polyester-based sheets, because the pigment... 

The list of applications also includes printing inks, in which P.Gr.36 is tinctori-ally weaker than its copper phthalocyanine counterparts. For comparison, 1/3 SD letterpress proof prints containing P.Gr.36, printed at standardized film thickness, require approximately 26% pigment, while only 17% of P.Gr.7 suffice for the same purpose. The fastness properties exhibited by P.Gr.36 in prints, as in paints, closely resemble those of P.Gr.7, including the phototropic behavior of decorative printing inks for melamine-based laminated plastics sheets. 

In contrast to the fairly simple crosslinking chemistry in urethane coatings, crosslinking in melamine-formaldehyde coatings can be quite complex. The following crosslinking reactions can be written for melamine coatings (29) ... 

In 2001 the worldwide nameplate capacity for melamine was estimated to be about 1.1 million tons per year. Between 1997 and 2001 worldwide melamine capacity increased at annual rate of 13% per year. However demand growth was only 5% to 7% per year. Therefore worldwide melamine capacity will probably be in surplus after 2005234. In 1998, Western Europe accounted for 35% of world capacity, followed by Asia (excluding Japan) with 24% and both the United States and Japan with 16% each114. 

Broad range catalyst best suited for melamine and UF resins also used with fluorochemical finishes--organic salt. 

Mineral fillers find application for melamine-formaldehyde resins, thus enabling compositions to be obtained with heat resistance in excess of 200 °C. 

For the manufacture of a diverse range of articles, the following properties of aminoplasts are very important possibility of being coloured, absence of small, superior hardness, good dielectric properties, a satisfactory resistance to the impact of water in the case of urea-formaldehyde aminoplasts and an excellent one for melamine-formaldehyde aminoplasts. 

The expression (29) points to the existence of proportionality between the reciprocal value of the gelation time and the rate constant Figure 33 presents the interrelation between 1/t and the rate constant determined from the rheokinetic equation for the curing of melamine-formaldehyde oligomer. The value of the proportionality factor determined from the data of Fig. 33 coincides with the value calculated from Eq. (29). In particular, for melamine-formaldehyde resin investigated in Ref. [81], Eq. (29) assumes the form ... 

Cyanamide is used in the production of synthetic rubber, cyanide, fumigants, and metal cleaners. It has also found use as an intermediate for pesticides, herbicides, detergents, medicines (e.g., antihistamines, hypertension, sedatives), in the photography industry, as an additive for fuels, lubricants, and cements, and as a paper preservative. The dimer (dicyandiamide) is a raw material for melamine and guanidine. 

Properties Crystalline solid. Mp (decomposes). Insoluble in alcohol slightly soluble in hot water. Similar to melamine and suggested for melamine-type (amino) resins. 

Resimene [Solutia]. TM for melamine and ureaformaldehyde resins. Supplied in organic liquid solutions. The melamine is also available in water-alcohol and soluble, spray-dry powders. 

Tanak MRX [Cytec]. TM for melamine-formaldehyde resin tanning agent used to make pure-white leather and for bleaching and filling chrome leather. 

Urea and Melamine Resins. In the urea class, modifications with melamine are excluded. In the melamine class, modifications with urea are included. Annual figures on total urea and melamine resins are shown specifically from 1994 on (11), Prior to 1944, figures for melamine are small, and the urea figure is really most of the total. 

Yang and Suspene (1991) and Malkin and Kulichikin (1991) showed that for melamine formaldehyde and polyester-styrene systems prone to microgel formation the following chemoviscosity models were relevant ... 

FIGURE 1 An F0 Fourier synthesis for melamine that shows series termination error. Maximum sind/X is 1.0 A 1. 

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). 

MAJOR USES Solvent and wetting agent for many organic compounds alcohol dena-turant plasticizer stabilizer cryoscopic agent intermediate for melamine, thioacetamide, pesticides, pharmaceuticals, rubber chemicals and plastics. 

---