Dicyandiamide product

It is manufactured by heating dicyandiamide, H2N C(NH) NH CN, either alone or in the presence of ammonia or other alkalis, in various organic solvents. Melamine is an important material in the plastics industry. Condensed with melhanal and other substances it gives thermosetting resins that are remarkably stable to heat and light. U.S. production 1980 80 000 tonnes. 

Uses. The principal use of adiponitrile is for hydrogenation to hexamethylene diamine leading to nylon-6,6. However, as a result of BASE s new adiponitrile-to-caprolactam process, a significant fraction of ADN produced may find its way into nylon-6 production. Adipoquanamine, which is prepared by the reaction of adiponitrile with dicyandiamide [461-58-5] (cyanoguanidine), may have uses in melamine—urea amino resins (qv) (see "Benzonitrile, Uses"). Its typical Hquid nitrile properties suggest its use as an extractant for aromatic hydrocarbons. 

Phosphoric Acid-Based Systems for Cellulosics. Semidurable flame-retardant treatments for cotton (qv) or wood (qv) can be attained by phosphorylation of cellulose, preferably in the presence of a nitrogenous compound. Commercial leach-resistant flame-retardant treatments for wood have been developed based on a reaction product of phosphoric acid with urea—formaldehyde and dicyandiamide resins (59,60). 

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... 

Dimerization involves addition of the cyanamide anion to the nitnle group of an undissociated molecule to give the anion of cyanoguanidine, or dicyandiamide. This reaction takes place most readily at pH 8—10 where the reactants are present in favorable proportion. The product is a weaker acid than cyanamide and is protonated at once with generation of a new cyanamide anion. 

For production of commercial 50% solution and for recovery of crystalline cyanamide, this process is modified to improve purity and concentration. Calcium and iron may be removed by ion-exchange treatment. The commercial 50% solution is stabilized at pH 4.5—5.0 with 2% monosodium phosphate and contains less than 1.5% dicyandiamide and 0.2% urea. Such solutions are expected to show less than 1% change ia cyanamide content per month of storage below 10°C. It is advisable, however, to adjust the pH periodically duriag extended storage. Organic esters may be used iastead for improved stabihty (23). 

Manufacture. Dicyandiamide is converted into melamine by heating. Simple pyrolysis above the melting point leads to an exothermic reaction however, deammoniation occurs, forming products containing two or three triazine rings as well as melamine. After it was discovered in 1940 that deammoniation can be counteracted by conducting the reaction under ammonia pressure, various methods were developed to control the exothermic reaction on an industrial scale. 

CaNCN is used as a direct application fertilizer, weed killer, and cotton defoliant it is also used for producing cyanamide, dicyandiamide and melamine plastics. Production formerly exceeded 1.3 million tonnes pa, but this has fallen considerably in the last few years, particularly in the USA where the use of CaNCN as a nitrogenous fertilizer has been replaced by other materials. In 1990 most of the world s supply was made in Japan, Gennany and Canada. 

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. 

Thorough washing with hot water serves to remove any dicyandiamide or melamine which may be present in the crude product. Benzoguanamine is slightly soluble in hot water. 

Five grams of potassium hydroxide (85% KOH) is dissolved in 100 ml. of Methyl Cellosolve (Note 1) in a 500-ml. flask (Note 2) fitted with a mechanical stirrer, reflux condenser, and a heating mantle. Dicyandiamide (50.4 g. 0.6 mole) (Note 3) and benzo-nitrile (50 g. 0.485 mole) are added, and the mixture is stirred and heated. A solution is formed, and, when the temperature reaches 90-110°, an exothermic reaction begins and the product separates as a finely divided white solid. The vigor of the reaction is kept under control by the refluxing of the solvent (Note 4). 

The earliest polymeric cationic aftertreatments stemmed from the development of crease-resist finishes for cellulosic fibres. One such, promoted specifically for its colour fastness improvements when applied as an aftertreatment to direct dyeings, was a condensation product of formaldehyde with dicyandiamide (Scheme 10.82). Many similar compounds followed, such as condensation products of formaldehyde with melamine (10.212), polyethylene imine) with cyanuric chloride (10.213) and alkyl chlorides with polyethylene imine) (10.214 R = alkyl). 

In summary, it has been established that all NMPs and NDPs are phosphorylated in reactions where calcium phosphate is present. However, no phosphorylation products are obtained when diphosphate (PP0 or tripolyphosphate (PPPi) is used instead of phosphate (Pi). Neither cyanamide nor dicyandiamide can be used instead of cyanate. 

In the context of preparing potential inhibitors of dihydrofolate reductase (DHFR), the group of Organ has developed a rapid microwave-assisted method for the preparation of biguanide libraries (Scheme 6.174) [330]. Initial optimization work was centered around the acid-catalyzed addition of amines to dicyandiamide. It was discovered that 150 °C was the optimum temperature for reaction rate and product recovery, as heating beyond this point led to decomposition. While the use of hydrochloric acid as catalyst led to varying yields of product, evaluation of trimethylsilyl chloride in acetonitrile as solvent led to improved results. As compared to the protic... 

An alternative mechanism [8] entails reaction of cyanamide (or dicyandiamide) with the dye phosphonate to give an O-acylisourea derivative (7.47). This is able to react directly with cellulose to form dye-fibre bonds, urea being released as the anticipated by-product (Scheme 7.31). In support of this mechanism, it is known that O-acylisourea derivatives of arylcarboxylic acids react readily with alcohols and this constitutes an efficient route for the preparation of carboxylic esters [44]. 

Dicyandiamide itself is claimed to react with hydroxylamine to yield the 3,5-diamino-oxadiazole [88), but the structure of the product has not been proven unequivocally ... 

The formula of 3,5-diamino-oxadiazole has been attributed to the product resulting from the action of hydroxylamine on dicyandiamide 88) (see p. 826). No proof of the proposed structure was given but in the light of some novel work 18a) it appears to be extremely doubtful. In fact, it could be shown that the product forms a monohydrochloride and reacts with only one mole of nitrous acid therefore the structure of a hydroxyaminotriazole (L) which is isomeric with the proposed formula cannot be ruled out. 

Jousselin [26] prepared nitroguanidine by the action of anhydrous nitric acid or sulphuric acid on guanidine nitrate. The preparation of this substance by the action of sulphuric acid has been developed as an industrial method for the production of nitroguanidine. The method described by Marqueyrol and Loriette [27] follows somewhat different principles. It consists in acting with anhydrous nitric acid on guanidine sulphate which, in turn, is obtained on treating dicyandiamide with sulphuric acid. 

Urea, melamine, cyanamide, dicyandiamide, and guanidine react at elevated temperatures with sulfur tetrafluoride to give (trifluoromethyl)iminosulfur difluoride (7) in 6-25% yield.172 In the presence of sodium fluoride at 25"C, urea is converted into fluorocarbonyliminosulfur difluoride (8), but at 50°C thiazyl fluoride (9) is the main product, both formed in ca. 60% yield. At higher temperatures, carbonyl difluoride (carbonic difluoride) and sulfur hexafluoride are the sole products of the reaction of urea with sulfur tetrafluoride.173... 

Other proposals have also been published, e.g. the suggestion of Westphalisch-Anhaltische factory [13] to add 0.02-0.05% of talc. Another way of hastening the separation is found in a patent of Carbonit A.G. in Hamburg [14], wherein additions of about 1% urea, acetamide or dicyandiamide (calculated in relation to glycerine) to the mixed acid are recommended. In contact with acid these substances decompose to form gaseous products which hasten separation in the same way as silicon fluoride. 

Dicyandiamide, which is readily obtainable from calcium cyanamide and is a stable commercial product, may be converted into guanidine nitrate by the action of ammonium nitrate, either in concentrated aqueous solution under pressure12,13 or by a fusion reaction.13-16 The latter procedure gives a very pure product and is to be preferred for laboratory practice. Directions for its use are given under procedure A. 

The Eastern Forest Products Laboratory (12,71) at Ottawa, Ontario, has been active in development of leach-resistant treatments using melamine or urea with dicyandiamide, formaldehyde, and phosphoric acid. Decay resistance is also shown for a urea-based treatment (72). One stystem has met the requirements for Class C wood roofing under ASTM El08 by Underwriters Laboratories of Canada (12,73). This treatment, or one similar, is expected to be introduced into the United States within the year as an approved exterior-type leach-resistant treatment. 

Melamine can be produced from urea, dicyandiamide (a derivative of calcium cyanide) or hydrogen cyanide. In 2001 all world production was based on urea. The dicyandiamide process was the original melamine process from the 1930 s, but it was phased out in the 1980 s. Production of melamine from hydrogen cyanide was never commercialized114. 

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