Melamine-urea-formaldehyde resin

Breyer, R.A., Hollis, S.G. and Jural, J.J., United States patent USP 5,681,917. Low mole ratio melamine-urea-formaldehyde resin. Assigned to Georgia-Pacific Resins, Inc., 1997. 

The release of semivolatile compounds from a variety of nitrogen containing polymers, including ABS, PA 6 PU and melamine/urea formaldehyde resins can be found in the literature (52). The temperature of treatment runs from 70°C to 300°C, i.e., low temperature pyrolysis, if pyrolysis at all. 

Other rapid setting adhesive systems not containing resorcinol are those based on melamine-urea-formaldehyde resins and on one-component polyurethanes, described in Chap. 32 and Chap. 34, respectively [28,29]. 

In general, rigid plastics are superior to elastomers in radiation resistance but are inferior to metals and ceramics. Examples of materials, which will respond satisfactorily in the range of 10 and 10 erg per gram, are fluoroplastics, glass fiber-filled phenolics, certain epoxies, polyurethane, polystyrene, mineral-filled polyesters, silicone, and fiirane resins. The next group of resins in order of radiation resistance includes polyethylene, melamine, urea formaldehyde resins, unfilled phenolic, and silicone resins. Those materials, which have poor radiation resistance, include methyl methacrylate, imfilled polyesters, cellulosics, polyamides, and fluorocarbons (Tables 9.16 and 9.17). 

A. T. Mercer, NMR analysis of strength and emission of melamine and melamine-urea-formaldehyde resins for synthesis optimisation, PhD thesis. University of the Witwatersrand, Johannesburg, South Africa (1996). 

X. Cai, B. Riedl, S.Y. Zhang, and H. Wan, Effects of nanofillers on water resistance and dimensional stability of solid wood modified by melamine-urea-formaldehyde resin. Wood Fiber Sci. 39(2), 307-318 (2007). 

MF/MUF melamine-and melamine-urea-formaldehyde resins MF resins ate used only mixed/coreacted with UF resins MUFF melamine-urea-phenol-formaldehyde resin PF/PUF phenol-and phenol-urea-formaldehyde resin (P)RF resorcinol-(phenol-) formaldehyde resin PMDI polymethylenediisocyanate PVAc polyvinylacetate adhesive... 

Melamine is also employed in condensation reactions with urea, thiourea, phenol, or other amino resin starting materials to give resins with particular properties [61]. The addition of acetaldehyde to melamine-formaldehyde or melamine-urea-formaldehyde resins has been shown to improve the storage... 

Stable Aqueous Melamine-Urea-Formaldehyde Resins [62]... 

Urea is also used as feed supplement for mminants, where it assists in the utilization of protein. Urea is one of the raw materials for urea—formaldehyde resins. Urea (with ammonia) pyrolyzes at high temperature and pressure to form melamine plastics (see also Cyanamides). Urea is used in the preparation of lysine, an amino acid widely used in poultry feed (see Amino acids Feeds and feed additives, petfoods). It also is used in some pesticides. 

Both melamine—formaldehyde (MF) and resorcinol—formaldehyde (RF) foUowed the eadier developments of phenol—, and urea—formaldehyde. Melamine has a more complex stmcture than urea and is also more expensive. Melamine-base resins requite heat to cure, produce colorless gluelines, and are much more water-resistant than urea resins but stiU are not quite waterproof. Because of melamine s similarity to urea, it is often used in fairly small amounts with urea to produce melamine—urea—formaldehyde (MUF) resins. Thus, the improved characteristics of melamine can be combined with the economy of urea to provide an improved adhesive at a moderate increase in cost. The improvement is roughly proportional to the amount of melamine used the range of addition may be from 5 to 35%, with 5—10% most common. 

Melamine resins are included in urea—formaldehyde resins. 

Amino and Phenolic Resins. The largest use of formaldehyde is in the manufacture of urea—formaldehyde, phenol—formaldehyde, and melamine—formaldehyde resins, accounting for over one-half (51%) of the total demand (115). These resins find use as adhesives for binding wood products that comprise particle board, fiber board, and plywood. Plywood is the largest market for phenol—formaldehyde resins particle board is the largest for urea—formaldehyde resins. Under certain conditions, urea—formaldehyde resins may release formaldehyde that has been alleged to create health or environmental problems (see Amino RESINS AND PLASTICS). 

Urea—formaldehyde resins are also used as mol ding compounds and as wet strength additives for paper products. Melamine—formaldehyde resins find use in decorative laminates, thermoset surface coatings, and mol ding compounds such as dinnerware. 

In the eady 1920s, experimentation with urea—formaldehyde resins [9011-05-6] in Germany (4) and Austria (5,6) led to the discovery that these resins might be cast into beautiful clear transparent sheets, and it was proposed that this new synthetic material might serve as an organic glass (5,6). In fact, an experimental product called PoUopas was introduced, but lack of sufficient water resistance prevented commercialization. Melamine—formaldehyde resin [9003-08-1] does have better water resistance but the market for synthetic glass was taken over by new thermoplastic materials such as polystyrene and poly(methyl methacrylate) (see Methacrylic polya rs Styrene plastics). 

Uron Resins. In the textile industry, the term uron resin usually refers to the mixture of a minor amount of melamine resin and so-called uron, which in turn is predorninantly N,]S -bis(methoxymethyl)uron [7388-44-5] plus 15—25% methylated urea—formaldehyde resins, a by-product. 

Miscellaneous Resins. Much less important than the melamine—formaldehyde and urea—formaldehyde resins are the methylo1 carbamates. They are urea derivatives since they are made from urea and an alcohol (R can vary from methyl to a monoalkyl ether of ethylene glycol). 

The term aminoplastics has been coined to cover a range of resinous polymers produced by interaction of amines or amides with aldehydes. Of the various polymers of this type that have been produced there are two of current commercial importance in the field of plastics, the urea-formaldehyde and the melamine-formaldehyde resins. There has in the past also been some commercial interest in aniline-formaldehyde resins and in systems containing thiourea but today these are of little or no importance. Melamine-phenol-formaldehyde resins have also been introduced for use in moulding powders, and benzoguanamine-based resins are used for surface coating applications. 

By the mid-1990s world production of aminoplastics was estimated at about 6 000 000 t.p.a. of which more than 5 000 000 t.p.a. were urea-formaldehyde resins. The bulk of the rest were melamine-formaldehyde. Such bald statistics, however, disguise the fact that a considerable amount of aminoplastics used are actually co-condensates of urea, melamine and formaldehyde. 

Modified melamine resins are also employed commercially. Alkylated resins analogous to the alkylated urea-formaldehyde resins provide superior coatings but are more expensive than the urea-based products. 

At one time thiourea-urea-formaldehyde resins were of importance for moulding powders and laminating resins because of their improved water resistance. They have now been almost completely superseded by melamine-formaldehyde resins with their superior water resistance. It is, however, understood that a small amount of thiourea-containing resin is still used in the manufacture of decorative laminates. 

A variety of methylols are possible due to the availability of six hydrogens in melamine. As with urea formaldehyde resins, polymerization occurs by a condensation reaction and the release of water. 

Aminoplastics In this group, melamine-formaldehyde resins with their good heat resistance, scratch resistance and stain resistance, are usually preferred to urea-formaldehyde resins where chemical resistance is important. Unlike the phenolics these materials are not restricted to dark colours. 

Variation of Reaction Stages And Mole Composition Effect on Melamine-Urea-Formaldehyde (MUF) Resin Properties... 

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