Melamine aldehyde condensations

Details patent for manufacture of melamine aldehyde condensation products ... 

Reaction of dehydrated melamine-aldehyde condensate with fatty acid in the presence of a lower molecular weight alcohol [95]. 

Uses of Formaldehyde. Formaldehyde is the simplest and most reactive aldehyde. Condensation polymerization of formaldehyde with phenol, urea, or melamine produces phenol-formaldehyde, urea formaldehyde, and melamine formaldehyde resins, respectively. These are important glues used in producing particle hoard and plywood. 

This volume continues in the tradition of Volume I in presenting detailed laboratory instructions for the preparation of various types of polymers such as urea, melamine, benzoguanamine/aldehyde resins (amino resins-amino-plasts), phenol/aldehyde condensates, epoxy resins, silicone resins, alkyd resins, polyacetyls/polyvinyl acetals, polyvinyl ethers, polyvinyl pyrroli-dones, polyacrylic acids, and polyvinyl chloride. Polyvinyl acetate and related vinyl esters, allyl polymers, acetylene polymers, maleate and fumarate polymers, and several other addition-condensation polymer types will be covered at a later date in Volume III. 

Group of plastics generated by the condensation of amines (e.g., urea and melamine with aldehydes). 

Group of plastics whose resins are formed by the condensation of melamine and aldehydes. 

In far too many instances trade-name polymer nomenclature conveys very little meaning regarding the structure of a polymer. Many condensation polymers, in fact, seem not to have names. Thus the polymer obtained by the step polymerization of formaldehyde and phenol is variously referred to a phenol-formaldehyde polymer, phenol-formaldehyde resin, phenolic, phenolic resin, and phenoplast. Polymers of formaldehyde or other aldehydes with urea or melamine are generally referred to as amino resins or aminoplasts without any more specific names. It is often extremely difficult to determine which aldehyde and which amino monomers have been used to synthesize a particular polymer being referred to as an amino resin. More specific nomenclature, if it can be called that, is afforded by indicating the two reactants as in names such as urea-formaldehyde resin or melamine-formaldehyde resin. 

A recent innovation in in-situ microencapsulation is the development of acid-triggered release of pesticide from the microcapsules [12]. Diols and aldehydes are reacted to form an acid labile acetal moiety. The acetal is then reacted with isocyanate to create a prepolymer. The prepolymer is a polyisocyanate cmitaining the acid labile moiety and suitable for in-situ shellwall polymerization. The prepolymer is dissolved into a pesticide, emulsified into water, and shellwall formed in-situ. Under alkaline or neutral pH conditions in a container, the insecticide is safely contained in the microcapsules. Acid could be added to the spray tank to rapidly release capsule contents prior to application. Alternate shellwall chemistry for in-situ microencapsulation utilizes etherified urea-formaldehyde prepolymers in the oil phase that are self-condensed with acid catalyst to produce encapsulating aminoplast shellwalls [13]. This process does not have the problem of continuing CO2 evolution. Water-soluble urea-formaldehyde and melamine-formaldehyde prepolymers can be selected to microencapsulate water or aqueous solutions [14]. 

The polyols for rigid foams (referred to as rigid polyols) discussed before (Chapters 13 and 14), are based on the alkoxylation of different polyols or polyamines, commercialised in a relatively high purity form. Some important starters for rigid polyols are obtained by the synthesis of the starter in situ, before the alkoxylation reaction, by the condensation reaction of some aromatic compounds (phenols, melamine and so on) with aldehydes (mainly formaldehyde), followed by the reaction of the resulting condensate with alkylene oxides. Some important rigid polyols based on the condensates mentioned are ... 

C3N3(NH2)3) a white solid organic compound whose molecules consist of a six-membered heterocyclic ring of alternate carbon and nitrogen atoms with three amino groups attached to the carbons. Condensation polymerization with methanal or other aldehydes produces melamine resins, which are important thermosetting plastics. 

Aminoresins or aminoplastics cover a range of resinous polymers produced by reaction of amines or amides with aldehydes [14,46,47]. Two such polymers of commercial importance in the field of plastics are the urea-formaldehyde and melamine-formaldehyde resins. Formaldehyde reacts with the amino groups to form aminomethylol derivatives which undergo further condensation to form resinous products. In contras to phenolic resins, products derived from urea and melamine are colorless. 

Aldehyde resin n. Synthetic resin made by treating various aldehydes with condensation agents. Phenol, urea, aniline, and melamine react readily with aldehydes, such as formaldehyde, which are also called Aldehyde Resins G Aldehydharz n, F resine... 

Amino plastics Plastics based on resins made by the condensation of amines, such as urea and melamine, with aldehydes. 

Amino Rosins. Amino resins are the reaction product of an aldehyde with a compound containing an amino (—NH2) group (see Amino Resins). Both urea and melamine react with formaldehyde, first by addition to form methy-lol compounds, and then by condensation to form cross-linked polymers through methylene bridge and methylene ether formation. The cross-linking reactions are exothermic and produce water and formaldehyde as volatile products in reactions similar to resole phenolics, illustrated in equation 3. Urea-formaldehyde and melamine-formaldehyde account for the bulk of the amino resins. Their characteristics include water solubility and unlimited colorability with dyes and pigments. Applications include decorative high pressure phenolic laminates, adhesives in the laminated wood and furniture industries, and as an additive to textile fabrics to impart wash and wear properties. 

Aldehydes are organic compounds that have a carbonyl group (-CHO) on the terminal carbon atom of a hydrocarbon chain or attached to an aromatic or heterocyclic ring. The aliphatic aldehydes are useful as chemical intermediates in synthetic chemistry where oxidation produces the corresponding acid and reduction yields the alcohol structure. Condensation reactions of the aldehydes with phenol, urea, or melamine yields useful resinous products. A useful heterocyclic aldehyde, furfural or 2-furaldehyde (the aldehyde group attached to the 2 position on the furan ring), is both a reactant in synthetic chemistry and has several specialized uses as a solvent. 

Other aldehydes reported to condense with melamine are furfural [74], terephthalic aldehyde [74], cinnamaldehyde [74], cyclohexane, carboxalde-hyde [74], buten-2-al [75], and butyraldehyde [75]. 

Water-soluble melamine-formaldehyde oligomers are produced in two stages The former takes place in alkaline medium (pH = 7.5—9.0) and yields melamine hydroxymethylene derivatives. At the same time, oligomer formation is avoided. The latter stage achieves hydroxymethylene derivative condensation in acidic medium. A large excess of aldehyde (formaldehyde melamine molar ratio = 8-9) is used. 

---