Cyanamide polymerization

If it is warmed in aqueous solution, the nitrosoamide breaks down into water and nitrogen, and the cyanamide polymerizes to dicy-andiamide. The evaporation of the solution yields crystals of the latter substance. A cold aqueous solution of nitrosoguanidine acidified with hydrochloric acid yields nitrous acid, and may be used for the introduction of a nitroso group into dimethylaniline or some similar. substance which is soluble in the acidified aqueous liquid. 

Pinck and Hetherington showed that the maximum conversion of cyan-amide to dicyandiamide is obtained when the starting solution contains at least 20 per cent cyanamide and 2 per cent ammonia (Table 8-6). Cyan-amide is quantitatively pol3rmerized to the dimer in liquid ammonia solution upon spontaneous evaporation of the solvent. The use of ammonia is, however, not essential inasmuch as cyanamide polymerizes readily in alkaline solution and in commercial practice, the batch is set at the optimum pH (viz., about 9.2 at 180 C). 

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). 

Handling and Storage. Cyanamide solution dimerizes to dicyandiamide and urea with the evolution of heat and a gradual increase in alkalinity accelerating the reaction. Storage above 30°C without pH stabilizer leads to excessive dimerization and can result in violent exothermic polymerization. Cyanamide should be stored under refrigeration and the pH tested periodically. Stabilized cyanamide can be kept at ambient temperature for a few weeks. 

Polymers Polyacrylamide and hydrolyzed polyacrylamide were prepared by the American Cyanamid Company specifically for this project, starting with l C labelled monomer. The radioactivity level of the monomer was kept below 0.20 mC /g in order to avoid significant spontaneous polymerization, utilizing a copper inhibitor. The homopolymer was synthesized by free radical solution polymerization in water at 40°C, using monomer recrystallized from chloroform, an ammonium persulfate-sodium metabisulfite catalyst system, and isopropanol as a chain transfer agent. Sodium... 

The difunctional N-cyanourea compounds were found to polymerize into different polymeric materials at different temperatures. At room temperature, a linear polymer was obtained either from the polymerization of a di-N-cyanourea monomer or directly from the mixture containing a diisocyanate and cyanamide. At elevated temperature (>100°C), the di-N-cyanourea monomer, or the mixture of a diisocyanate and cyanamide, cross-linked to a rigid foam or flexible material, depending on the structure of the monomer. 

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). 

Mino, G., and S. Kaizerman, American Cyanamid Company Process for polymerization of a vinylidene monomer in the presence of a ceric salt and an organic reducing agent. U. S. 2,922,768 (January 26, 1960). 

Segro, N. R., and J. H. Daniel, American Cyanamid Company Graft polymerization of certain esters of acrylic acid with cellulose substrate. U. S. 2,955,015 (October 4, 1960). 

Moore, S. T., American Cyanamid Company Pellicules de cellulose regeneree non fibreuse modifiees par de revetements des polymeres vinyliques. French Pat. 1,221,901 (June 7, 1960). 

Salsbury, J. M., S. Kaizerman, and G. Mino, American Cyanamid Company Graft polymerization process, U. S. 3,046,078 (July 24, 1962). 

Cryst cyanamide slowly polymerizes on standing to dicyandiamide reacts with Amm... 

Cyanamide itself is not a suitable raw material for the preparation of guanidine salts, for it is difficult to prepare and to purify, and it polymerizes on keeping. The evaporation of an aqueous solution of cyanamide yields the dimer, dicyandiamide, and the heating, or even the long keeping, of the dry substance produces the trimer, melamine. 

Stirring for one hour in the cold permits the relatively insoluble calcium cyanamide to react with sodium hydroxide and go into solution as sodium cyanamide. If the temperature is not kept below 250 during this time, there is some tendency for polymerization to dicyanodiamide. 

Mallison, W. C. Continuous process for the polymerization of acrylonitrile. United States Patent 2,777,832, (to American Cyanamid Company), January 15, 1957. 

Materials. The PMMA used was Acrylite H-12 molding compound (American Cyanamid Co.). This material was available as pellets. PVdF was Kynar 401 (Pennwalt Chemicals Co.), a powder of high but unspecified molecular weight. PEMA was polymerized in bulk in the laboratory from ethyl methacrylate (Rohm Haas) by a laboratory scale adaptation of the PMMA process (22). 

In benzene solution or in the solid state, a-chlorophenyl-cyanamide does not polymerize on storage for several months at 20-30°. 

It is made by dimerizing cyanamide in basic aqueous solution, and is a colorless solid melting at 208°C. Dicyandiamide is soluble in polar solvents, but at room temperature is insoluble in bisphenol A epoxy resins. It can be made into a very fine powder and milled into epoxy resins to form stable dispersions. Because the dicy is insoluble in the epoxy, the only possible reaction sites are at the particle surfaces. Although some reaction certainly occurs over a short time, the adhesives easily can have a useful shelf life of six months. On heating to about 150°C, the dicyandiamide becomes soluble in the epoxy resin, and the adhesive polymerizes rapidly. Cure can be accelerated by incorporation of tertiary aromatic amines or substituted ureas. 

The lime nitrogen used in this preparation should be the crude, untreated, product sold as fertilizer under the name Cyanamid. It contains approximately 55 per cent calcium cyanamide, 20 per cent calcium oxide, 12 per cent graphite, and small amounts of various impurities. Lime nitrogen should be protected from moisture when stored, in order to prevent slow polymerization to dicyanodiamide. It is advisable to use a fresh supply of lime nitrogen for this synthesis. 

Heating of N-trimethylsilyltetrazole 24 to 135 °C affords bis(trimethylsilyl)carbodiimide, nitrogen and polymeric cyanamide. ... 

The phosphoryl bis-carbodiimide 17 polymerizes in the solid state when stored for one week at 30 °C. A thiophosphoryl bis-carbodiimide 19 is also obtained from the bis-cyanamide precursor 18 and bis(diisopropylamino)chlorophosphane with subsequent oxidation with elemental sulfur. 

Oligomeric and polymeric silylcarbodiimides are synthesised reacting dichlorodiorganylsilanes with cyanamide and pyridine in THF as solvent [4]. 

National Starch 78-6121, poly[methyl acrylate-co-(3-hydroxy-4-benzoylphenyl) acrylate] [82] and Cyasorb UV 2126, poly[4-(2-acryloyloxy)-2-hydroxybenzo-phenone] (71, American Cyanamide) are representatives of polymeric benzo-phenones designed for polyolefins. Some very impottant oligomeric LS from the HALS group are available on the market Chimassorb 944 (161 a, Ciba-Geigy), Cyasorb UV 3346 (161b, American Cyanamide), MARK LA-63 (167, Asahi Denka), Spinuvex A-36 (160, Montefluos) and Tinuvin622 (166, Ciba-Geigy). 

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