Dextrins manufacture

Dextrins. Dextrine, White Farina 30, the dextrin manufactured by the British firm of Elliot and Crabtree and used in the preparation of RD 1352, was supplied by Liang National Ltd. as Dextrine, White Farina required for manufacture of lead azide. There is no specification for this dextrin, and as received it contained 10.73% moisture. A portion was air-dried and was used to prepare the solutions for the three batches of dextrinated azide. 

In various countries, the ratio of the amount of dextrins used for nutritional purposes to the total amount of dextrins available is, of course, different. In the Federal Republic of Germany, —40% of the dextrins manufactured per annum is consumed by the food industry, and the rest is utilized for... 

Commercially, lead azide is usually manufactured by precipitation in the presence of dextrine, which considerably modifies the crystalline nature of the product. The procedure adopted is to add a solution of dextrine to the reaction vessel, often with a proportion of the lead nitrate or lead acetate required in the reaction. The bulk solutions of lead nitrate and of sodium azide are, for safety reasons, usually in vessels on the opposite sides of a blast barrier. They are run into the reaction vessel at a controlled rate, the whole process being conducted remotely under conditions of safety for the operator. When precipitation is complete, the stirring is stopped and the precipitate allowed to settle the mother liquor is then decanted. The precipitate is washed several times with water until pure. The product contains about 95% lead azide and consists of rounded granules composed of small lead azide crystals it is as safe as most initiating explosives and can readily be handled with due care. 

The original initiating explosive used by Nobel and all manufacturers for many years was mercury fulminate. This had the disadvantage of decomposing slowly in hot climates, particularly under moist conditions. For this reason mercury fulminate is no longer widely used. In most countries it has been replaced by a mixture of dextrinated lead azide and lead styphnate. In the U.S.A. some detonators are made containing diazodinitrophenol. 

The introduction of LA into commercial detonators resulted in an unacceptably high level of explosions during manufacture and use and hence its use was discontinued until it could be prepared in less sensitive form. A number of methods have been used to prepare LA in a less sensitive form. The main control of properties is by synthesis rather than by any other approach. Lead azide compositions RD 1343 (improved CMC co-precipitated LA), RD 1352 (improved dextrinated LA) and Service lead azide (SLA) illustrate some modified LAs which are used depending on the requirements. Different processes developed for the modification of LA may be summarized as follows ... 

Considerable progress in the manufacture and application of lead azide was achieved by the addition of dextrin to the solution in which it was produced, as mentioned above. 

Lead azide is manufactured on a technical scale by the action of sodium azide on an aqueous solution of lead nitrate. According to a description of manufacture in the Wolfratshausen factory in Germany [109], the reaction is conducted in an open reactor of stainless steel, provided with a jacket warmed by hot water and a stirrer which may be lifted out of the reactor (Fig. 49). The reactor is emptied by tilting. Its upper edge is therefore fitted with a spout so that the contents pour easily. The size of the reactor is such that 4.5 kg of lead nitrate in the form of a 9-10% solution can be used in each batch. This solution is poured into the reactor, warmed to 50°C and neutralized with sodium hydroxide to a pH of about 4.0 (in the presence of methyl orange) and 150 g of dextrin mixed with a small amount of water, is added. The suspension or solution of dextrin in water should be decanted before use to separate mechanical impurities, such as sand. 

Pure lead azide may be produced in the same equipment, but instead of lead nitrate and dextrin lead acetate is employed. The precipitation temperature is lower than in the manufacture of technical-grade lead azide (having a purity of less than 95%). All other operations are the same as already described. 

Plant Manufacture of Dextrinated LA by the duPont Method. The procedure briefly described below is essentially the same as... 

Bulk powders are made in considerable variety, but they consist always of nitrocellulose fibers which are stuck together but are not completely colloided. Some contain little else but nitrocellulose others contain, in addition to potassium and barium nitrates, camphor, vaseline, paraffin, lampblack, starch, dextrine, potassium dichromate or other oxidizing or deterrent salts, and diphenylamine for stabilization, and are colored in a variety of brilliant hues by means of coal-tar dyes. In the United States bulk powders are manufactured by one or the other of two processes, either one of which, however, may be modified considerably the materials are incorporated under wooden wheels, grained, and partially gelatinized, or the grains arc formed in a still where a water suspension of ptdped nitrocellulose is stirred and heated with a second liquid, a solvent for nitrocellulose which is volatile and immiscible with water. 

As a rule, dextrins are almost completely soluble in hot water, the insoluble matter being composed of a few organic impurities (cellulose, gluten) together with a little sand. Sometimes, however, they contain untransformed starch, which is due to faulty manufacture or is added intentionally and is found in the residue insoluble in hot water. 

These cocoa substitutes are of two kinds. First, they consist of otherwise unprocessed bulking agents with added flavor and color. The bulking agents employed are soybean flour, modified food starches, dextrins, or mixtures thereof. They are definitely offered as extenders none of the manufacturers recommend that they be used as a total replacement for cocoa. Manufacturers include Cargill, Inc., Minneapolis, Minnesota (Cocoa-Max), McCormick Company, Inc., Hunt Valley, Maryland, (McCormick Cocoa Extenders), and National Starch Chemical Corp., Bridgewater, New Jersey (N-Liven Cocoa). A.E. Staley Mfg. Co., Decatur, Illinois, entered the field but quickly dropped out. 

Dextrinization of tapioca starch is well-known. The difficulty in dextrinizing corn starch,64 and the relative ease of tapioca starch conversion,65 have been described. The near-absence of lipids, which interfere with the dextrinization process, has given tapioca dextrins an advantage in stability and color because of their ease of manufacture and control. However, the economics of base starch supply have resulted in a significant shift to waxy com starch as a base for industrial dextrins, even though... 

Alpha amylase—Converts starch into dextrin used in the manufacture of glucose syrup. 

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