Patent GB-513633-A (GB)
Title: Improvements in or relating to explosives
IPC: C08J9/40
Filed: 1938-03-03
Abstract: 513,633. Urea aldehyde condensation products. AMERICAN CYANAMID CO. March 3, 1938, No. 6693. Convention date, March 4, 1937. [Class 2 (iii)] [Also in Group XXI] An explosive comprises a solid and/or liquid active explosive substance carried within the pores of a porous carrier consisting of a condensation product of a urea and formaldehyde. The carrier may be produced by condensing urea and an aqueous solution of formaldehyde in a ration of 1 mcl. of urea to 2 mols. of formaldehyde in a reflux apparatus. At the beginning of the condensation process the solution is maintained at a pH value of 7 or higher. After fifteen minutes, formic acid is added in such an amount as to bring the pH to the value of about 4.5 and the condensation continued for about an hour. After the condensation is complete, the solution is diluted to a degree dependent upon the degree of porosity desired and the diluted solution is then acidified by further additions of formic acid to a pH value of about 2-3 and subsequently allowed to solidify in closed containers. Where a particular shape is desired in the final mass, the container may take this shape. After the desired degree of hardness has been obtained, the gel is removed from the container, allowed to solidify and then dried. If desired,. the gel may be washed with diluted ammonia solution in order to remove free acids or traces of formaldehyde. The production of products where the absorption varies can be effected either by heating the jelly to a higher temperature during the production, before the structure is solidified thoroughly, in which case the outer layer will collapse more or less dependent upon temperature and humidity, or the finally hardened jelly is impregnated with water or aqueous solutions and quickly heated to a high temperature whereby the outer layer collapses whereas the inner part remains unchanged. The porous material may be impregnated with any explosive salt and/or oxygen carrier such as ammonium, sodium or potassium nitrates or the alkali chlorates or perchlorates, and/or such liquid explosives as nitroglycerine, nitroglycols or mixtures thereof with or without additions of aromatic nitro bodies. The impregnation with salts may be effected by making a solution of the latter, absorbing this solution in the porous material and then removing the solvent whereupon the salts are permanently retained in the pores of the absorbent in the solid state. Where liquid explosive materials are used, these may be absorbed directly in the porous material. If desired, the final porous material may be ground to a desired state of fineness, so long as the grinding is not carried to such an extent that the porosity is destroyed, and then impregnated with the above salts, or liquid explosives in the desired proportions. Suitable fillers, such as wood meal, or kieselguhr, may be added to the ground porous material prior to carrying out the impregnation. When it is desired to mould the impregnated material into a shaped mass, a small quantity of comparatively long fibres, such as bagasse or sisal, may be incorporated in the material to be moulded to act as a binding agent. Specification 261,409, [Class 2 (iii)], is referred to.