Jann.` 29, 1946. L. H. DAwsl_-:Y_ Erm. 2,393,391 ‘ PRODUCTION oF METAL PERoxIDEs Filed June 8, 1943 INVENTORS NEYS Patented Jan. 29,1946 2,393,891 UNITED .STATES PATENT olf-FICE 2,393,891 PRODUCTION OF METAL PEROXIDES Lynn H. Dawsey, Kenmore, and Hans A. Rudolph, Buiîalo, N. Y., assignors to Bull'alo Electro Chexnical Company, Inc., Tonawanda, N. Y. Application June 8, 1943, Serial No. 490,040 3 Claims. (Cl. 23­­187) Thisl invention relates to the stabilization of ing a very real combustion hazard. Another dis alkaline earth metal peroxides stabilized against advantage resides in using stabilizers containing deterioration due to absorptionof atmospheric magnesium, aluminum, or zinc, as large propor water andfcarbon- dioxide. It is especially appli tions of foreign metals are lintroduced into the cable in the manufacture of calcium and stron-Y product, which are, of course, undesirable when tium peroxides‘. _ ' i ' the product is to be utilized in special chemical It' is alwell-known fact that the anhydrous syntheses involving polymerization reactions and alkaline earth metal peroxides are hygroscopic, the like. A further disadvantage of the products and when exposed to I.the atmosphere rapidly take of the prior art is their tendency to cake or ball up moisture and/ carbon dioxide with the forma .up when manipulated rather .than remain free tion of crystalline peroxide‘hydrates, hydroxides iiowing. Y y ' and carbonates. The absorption of water and It is an object of the present invention to over l carbon dioxide by the alkaline earth metal per come the previous disadvantages of the prior art. oxides is accompanied by deterioration dueto It is a further object of the invention to produce ’ loss of V active oxygen from the product, Special stabilized alkaline earth metal peroxides in which precautions in handling have been found neces the amount of stabilizer is only a small percent sary heretofore to prevent this type of deteriora of the peroxide, thereby producing a stabilized tion, such 4as the use in storage of hermetically peroxide having an active oxygen content sub sealed» metal containers, and the avoidance of stantially the same as that of the unstabilized prolonged exposure to the air, When the prod 20 product~ The product of the present invention ucts have been exposed too long, they become having-only a small additive material therewith worthless for pyrotechnical uses such as in ñre does not possess the fire hazardA of previous prod works, flares and other burning compositions due ucts having a high content of organic material. both to the water absorption and the loss of As a‘ iinal advantage, the stabilized product is oxygen. .When the peroxides are transported on free flowing even when exposed to air and so seagoing vessels, or are stored in tropical climates, may be readily handled and transported. deterioration, ,due to the above factors, becomes According to the present invention, an im especially objectionable.A » . pervious, protective filmv is formed about _each ' It has been suggested heretofore that water particle of metal peroxide. In a copending ap-l repellents, such as solid magnesium laurate and 30 plication for patent, the desired alkaline earth aluminum stearate be incorporated with the cal metal peroxide is precipitated from a solution of cium peroxide for the purpose of stabilizing a soluble salt oi’ the metal by adding calculated ' against moisture absorption, but this method has a amounts of alkali and hydrogen peroxide or by a number of disadvantages. One disadvantage is adding hydrated sodium peroxide, followed by that the water repellent is dry mixed into the 36 filtration, washing of the wet metal peroxide peroxide and is, therefore, ineffective in com cake and driving the remaining moisture from pletely sealing up the surfaces of the metal per the cake at a temperature above 100° C. to give oxide particles; another disadvantage is the rela the usual products which are initially dry, free tively large quantity of the agent which must be flowing powders. According to this invention, a added to the peroxide to become _even partly 40 stabilized product is formed in the above outlined effective. Thus, 50 to 100 parts of magnesium process during the regular course of manufacture. laurate must be mixed with 100 parts of calcium simply by impregnatlng thev moist metal peroxide peroxide to obtain only indiiferent results. The . cake, before drying. with _solutions of certain highest strength calcium peroxide sold commer stabilizing agents. After impregnation, the moist cially heretofore has been 80% CaOz so that the 45 cake is dried in the usual way. The stabilized mixing of the water repellent therewith acts as product obtained resembles the regular product a diluent reducing the final product to a. 40% to in every way. ‘ ' 53% CaOz content, at best. Such a low active vThe agents applicable in the invention are oxygen content renders the product, even though water soluble fatty acid soaps and the like, ì stabilized, unfit for many special applications 50 water soluble’caseinates, soluble silicates, and . requiring a composition capable of giving ofl'~a soluble carbonates, having the property of be maximum amount of oxygen. Another objection ing able to react with alkaline earth metal to this type of stabilized product is that appre peroxldes to form water-impervious films.> For ciable quantities of organic material have been instance, sodium oleate reacts with calcium per added to the dry metal peroxides thus constitut 55 oxide in the presence of moisture to form water 2 .insoluble calcium oleate, andammonlum case waxy nature whiclnrepe'lled> water when placed inate reacts with strontium peroxide to form on the surface. strontium caseinate which, upon drying, pro The >graphs of Figure 1 are given to illustrate duces a water-proofing iilm. Although the so the effectiveness of the invention in the stabilisa dium and potassium salts of fatty acids may be tion ofvalkaline earth metal peroxides, as applied employed to advantage, it has been found that to calcium peroxide and to strontium'peroxide, ammonium compounds such as ammonium stes using two of the agents from the classes of sta rate, ammonium caseinate and ammonium-car bilizers­ already mentioned. The curves were bonate are ci' special value in practicing the in­_ drawn from data taken from actual tests made vention, because, during the actual process of 10 to determine the comparative amounts of mois film formation ammonia is liberated and driven ture and carbon dioxide absorbed from the air off leaving no foreign metal salt impurities in by the stabilized product of Example l and oi the finished product. correspondingly prepared unstabilized materials. In the practice of the invention, the purified, , . The results shown represent tests carried out un moist, alkaline earth metal peroxide, mentioned 15 der accelerated weathering conditions, that is. above, is treated with an aqueous solution of the 90% humidity and 40° C., which were more severe stabilizing agent. This operation is best carried than anything Vlikely to be encountered durin out in a centrifuge, in which the cake has pre storage or shipment oi the products. , ‘ viously been collected’and washed. The solution I The stability tests were conducted by placing containing the soluble agent is simply poured over 20 20 gram samples of the material in circular weigh- - the cake, at a suitable temperature, with cen ing dishes of 72 mm. diameter and 30 mm. depth ` trifuge running in such a manner as to impreg so as to distribute the materials in thin layers in nate the cake uniformly and allow the excess order to obtain th'e lmaximum possible effect of' soluti n to be whirled through the basket. Dur the atmosphere. The 4 samples were placed in ing itspassage through the peroxide cake, the 25 a circulating atmosphere maintained at 40° C. solubleïstabinzmg agent reacts with the solid and 90%. humidity. The gain in weights due to peroxidelparticles forming in situ a protective absorption ­of moisture and carbon dioxide were ñlm­around each particle which film, upon sub recorded from time to time. e sequent d l g, hardens into an impervious coat In _Figure 1, the percent gain in weight of the ing. A single passage of the stabilizer solution 30 respective samples, .as ordinate, has been plotted through the cake is sufiicient to achieve the de against time, in days exposed, as the abscissa. sired impregnation. In accordance with the _ Examination of the curves shows th'at the sta invention, it has been found that _washing the bilized sample had only gained about 7% in 30 moist cake with yabout twice its volume of a 1% days, after which absorption had practically solution of stabilizer gives satisfactory results. stopped; v .on the other hand, the unstabiliaed 'I‘he following examples illustrate the methods product had absorbed large quantities of moisture employed in eiïecting stabilization of strontium and was continuing to do so at a rapid rate when peroxide and calcium peroxide; they are not to the tests ended. At the end of th'e tests the be deemed limitative of the invention: stabilized products remained free-flowing withv 1. strontium peroxide-Into a centrifuge bas 40 no` apparent change in physical character: ket of 350 cc. ­capacity running at a speed of 3000 whereas, the >unstabilized products had changed R. P. M., containing puriñed moist strontium per into hard cakes. oxide in the shape of an annular cake of inside Had these tests vbeen conducted under normal, radius 5.35 cm.. outside radius 6.35 cm., and vol instead of accelerated weathering conditions, and unie of 198 ce., the temperature of strontium per had th‘e samples been subjected in bulk form to v oxide'cake being maintained at approximately 60° such a normal atmosphere, instead of being spread C., 500 cc.