Ureas from cyanamide

Amino resins are condensation thermosetting polymers of formaldehyde with either urea or melamine. Melamine is a condensation product of three urea molecules. It is also prepared from cyanamide at high pressures and temperatures ... 

The two nitrogen atoms may be simultaneously derived from urea or cyanamide as indicated in the following examples (72JHC715, 72JHC1295 73USP374584 81 PS 147). The bicyclic product 67 is reported to explode on rapid heating. 

Urea occurs as a colorless to white, prismatic, crystalline powder or as small, white pellets. It is commonly produced from C02 by ammonolysis or from cyanamide by hydrolysis. It is freely soluble in water and in boiling alcohol, but practi-... 

Most derivatives of carbonic acid are made from one of three industrially available compounds phosgene, urea, or cyanamide. 

Derivation (1) By heating urea and ammonia. The resulting mixture of isocyanic acid and ammonia reacts over a solid catalyst at approximately 400C to form melamine. (2) From cyanamide, dicyanamide, or cyanuric chloride. 

Sodium nitrite hydrogen chloride Amines from cyanamides via ureas... 

The identification of Tris as a potential carcinogen dealt a resounding blow to the flame-retardant finishing industry. From 1977 to 1984, several principal supphers of flame-retardant chemicals either reduced the size of their operations or abandoned the market completely. However, Albright and Wilson Corp. (UK) continues to produce THPC—urea precondensate and market it worldwide, and Westex Corp. (Chicago) continues to apply precondensate—NH finish to millions of yards of goods for various end uses. American Cyanamid reentered the market with a precondensate-type flame retardant based on THPS. 

Melamine. Melamine (cyanurotriamide, 2,4,6-ttiainino-j -triazine) C H N, is a white crystalline soHd, melting at approximately 350°C with vaporization, only slightly soluble in water. The commercial product, recrystallized grade, is at least 99% pure. Melamine was synthesized eady in the development of organic chemistry, but it remained of theoretical interest until it was found to be a usehil constituent of amino resins. Melamine was first made commercially from dicyandiamide [461-58-5] (see Cyanamides), but is now made from urea, a much cheaper starting material (9—12) (see also... 

Ammonia is used in the fibers and plastic industry as the source of nitrogen for the production of caprolactam, the monomer for nylon 6. Oxidation of propylene with ammonia gives acrylonitrile (qv), used for the manufacture of acryHc fibers, resins, and elastomers. Hexamethylenetetramine (HMTA), produced from ammonia and formaldehyde, is used in the manufacture of phenoHc thermosetting resins (see Phenolic resins). Toluene 2,4-cHisocyanate (TDI), employed in the production of polyurethane foam, indirectly consumes ammonia because nitric acid is a raw material in the TDI manufacturing process (see Amines Isocyanates). Urea, which is produced from ammonia, is used in the manufacture of urea—formaldehyde synthetic resins (see Amino resins). Melamine is produced by polymerization of dicyanodiamine and high pressure, high temperature pyrolysis of urea, both in the presence of ammonia (see Cyanamides). 

Urea has been obtained from calcium cyanamide via cyanamide ... 

Guanidine dearranges less readily than urea and yidds ammonia and cyanamide as would be expected from the familiar method for its synthesis. If it is heated with aniline, the cyanamide shows no tendency to combine with that substance but combines with itself, as it does in the absence of aniline, to form melamine. 

The synthesis of the oligomers involved the known reaction of isocyanates and cyanamide (Nl CN). For example, N-cyano-N -phenyl urea has been synthesized from phenyl isocyanate and an aqueous alkaline solution of cyanamide in high yield.(3) Recently, similar reactions were used to prepare various di-N-cyanourea compounds from diisocyanates. ( 1) These monomers were also synthesized directly by reacting diisocyanates with cyanamide at melt temperatures. 

An aqueous solution of amitrole can decompose in the following free radical systems Fenton s reagent, UV irradiation, and riboflavin-sensitized photodecomposition (Plimmer et al, 1967). Amitrole-5- C reacted with Fenton s reagent to give radiolabeled carbon dioxide, unlabeled urea, and unlabeled cyanamide. Significant degradation of amitrole was observed when an aqueous solution was irradiated by a sunlamp (L = 280-310 nm). In addition to ring compounds, it was postulated that other products may have formed from the polymerization of amitrole free radicals (Plimmer et al., 1967). 

If the reaction, say, with cyanogen chloride, is carried out in ether solution, ammonium chloride precipitates and is filtered off, and the cyanamide is procured as a syrup by allowing the ether solution to evaporate spontaneously and later as crystals by allowing the syrup to stand over sulfuric acid in a desiccator. Cyanamide may also be prepared by removing the component atoms of hydrogen sulfide from thiourea by means of mercuric oxide. Thionyl chloride effects the corresponding removal of water from urea. 

Urea, which is also known as carbamide and carbonyldiamide, was discovered in urine by Rouelle in 1773. It was first synthesized from ammonia and cyanic acid by Woehler in 1828 . In the early 1900 s urea was produced on an industrial scale by the hydration of cyanamide, which was obtained from calcium cyanamide109 ... 

Reaction of methyl 2-( 1 -methoxycarbonyl-4-oxo-4//-pyrido[ 1,2-a]-pyrazin-3-yl)acetate (144) with ferf-butoxybis(dimethylamino)methane furnished 3-dimethylaminoacrylate 145 (96JHC639). Urea 146 was obtained from 145 with cyanamide. 

Amino-3-methoxycarbonylpyrazine with urea in the presence of sodium hydride in dimethylformamide at — 15° gave 2-amino-3-ureidocarbonylpyrazine (1152, 1322). The reaction was also applied to the following pyrazines 2-amino-5-chloro-3-methoxy carbonyl (1152) 2,6-diamino-3-chloro-5-methoxycarbonyl (1380) 2-amino-5-chloro-3-methoxycarbonyl-6-methylamino (1380) 2-amino-5-chloro-6-dimethylamino(and other dialkylamino)-3-methoxycarbonyl (1152) and 2-amino-5-chloro-3-methoxycarbonyl-6-methylthio (1152). The preparation of ureidocarbonylpyrazines from A -cyanamides has been described in Section 2C(2)(d). 

Diarock (Nitto Chemical Ind., Japan), marketed internationally for about a decade beginning in the mid-1960s, appears (from the manufacturer s literature) to be basic urea-formaldehyde resin (not a prepolymer). Cyanaloc 62 (American Cyanamid Company, Wayne, New Jersey) is a prepolymer marketed as a concentrated liquid which is diluted with water for field use. Sodium bisulfate is the catalyst normally used, and the relationship between catalyst concentration and setting time is shown in Fig. 

Tertiary aliphatic isocyanates can be made by addition of isocyanic acid (a toxic material) to olefins (2.17). Cytec (formerly American Cyanamid) makes a diisocyanate this way.58 The reaction can be controlled to produce the monoadduct which can be used as a monomer. Tertiary isocyanates of this type react at lower rates than primary ones in addition reactions. The isocyanic acid can be produced by the pyrolysis of cyanuric acid which, in turn, can be prepared from the urea (reaction 2.18). 

The reaction of starch with bis(hydroxymethyl)ethyleneurea condensed with cationic poly(urea amides) and cationic polyamides was used to produce paper sizes, adhesives, and textile-finishing agents.2616 Cationic starch that has been prepared from starch and cyanamide was patented for sizing wood and for synthetic wool fibers and fabrics.2296,2298,2662 Reaction of starch urethanes with alkylene oxides and aldehydes was reported for use as hardenable compounds in waterproof films, coatings, and adhesives.2663... 

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