GB545410A - Improvements in or relating to gelatin dynamites - Google Patents

Abstract

545,410. Explosives. HERCULES POWDER CO. June 4, 1940, No. 9789. Convention date, April 13. [Class 9 (ii)] Cellular carbonaceous material which has been treated with synthetic heat hardening resin to stiffen the cell walls is used in the preparation of gelatine dynamites whereby the resultant explosive offers increased resistance to high pressures so as to preserve its sensitivity and plasticity after prolonged immersion at great depths in water or other liquid. The carbonaceous material may consist of ground cork, balsa, bagasse, bongo wood, hemp hurds, and the like. The general method of treatment consists in impregnating the material with a synthetic resin such as the urea aldehyde, phenol aldehyde, or thiourea aldehyde type, and then heathardening. In a typical method, a mixture of cork and urea in aqueous formaldehyde solution is heated to condense the formaldehyde resin and dry the cork at a temperature of 70-100‹C. The resin-impregnated cork is then submitted to further heating at 100‹C. for ¢ to 1 hour, or for shorter periods at temperatures up 150‹C. to harden the resin. The urea may be mixed with the cork before adding the formaldehyde, or the urea-formaldehyde solution may be sprayed on the hot cork. As a further alternative, the carbonaceous material may be treated with a partial condensation product of urea and formaldehyde in aqueous or organic solvent (e.g. ethyl alcohol), the solvent evaporated, and the resin heathardened, other suitable hardening-agents mentioned include a formaldehyde solution of cresol with a catalyst such as hydrochloric acid, and a combustion of chlorinated rubber and a heat-hardening phenol formaldehyde resin. The Specification includes numerous comparative tables setting out the effect of the cell-hardening on the relative immunity to density-change resulting from external pressure, resistance to water penetration, and the consequential larger range of sensitivity of the improved explosive. The Specification also describes a method of testing which is exemplified as follaws. Three sticks of dynamite are placed end to end in a steel tube having end-closures in which a water filling is subjected to pressure for any described period, one end-stick being fitted with a standard blasting cap. The tube is laid on the ends of a spaced series of lead cylinders each covered by a steel disc of corresponding diameter, the completion (or otherwise) of the detonation-effect being registered by the extent of the resultant compression in the lead cylinders along the line of the tube. The low-density carbonaceous materials may be prepared as described in Specification 546,382, [Group IV].