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AssigneeFraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
InventorsWalter Engel, Herbert Heinisch
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A method of preparing compact nitroguanidine of high bulk density by crystallization from an initially hot nitroguanidine solution. The solution is cooled, while being agitated, at a temperature gradient of at least 3.degree. C./minute, with the crystallization taking place, only at temperatures less than 50.degree. C., from a supersaturated solution. The solvent for the nitroguanidine solution is selected from the group consisting of polyhydric, lower aliphatic alcohols, the mono- or dialkyl ethers of these polyhydric, lower aliphatic alcohols, dimethylformamide, dimethyl sulfoxide, or mixtures thereof. The formed nitroguanidine, in addition to having a high bulk density, has a compact form which makes it possible to prepare a slurry from nitroguanidine and to be able to process nitroguanidine as a composition amenable to casting.
Process for the preparation of nitroguanidine having a high bulk density and a globular form from a hot saturated solution of nitroguanidine in a solvent, said hot saturated solution being at a starting temperatue of 80.degree. C.-150.degree. C., comprising cooling the hot saturated solution of nitroguanidine in a solvent from said starting temperature while being agitated, whereby nitroguanidine, having a high bulk density and a globular form, is crystallized from a strong supersaturation of the solution, wherein the solvent is selected from the group consisting of polyhydric lower aliphatic alcohols, mono- or dialkyl ethers of the polyhydric lower aliphatic alcohols, dimethylformamide, dimethyl sulfoxide, or mixtures thereof, the solution is cooled at a temperature gradient of more than 3.degree. C./minute, and the solvent, the starting temperature, and the coolant temperature are selected such that crystallization of the nitroguanidine from the solution occurs only at temperatures of below 50.degree. C., to provide crystallization from a strong supersaturation of said solution.
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