Boiling under pressure Kiering in autoclaves

According to the stabilization method used in German factories, after primary stabilization in boilers, the nitrocellulose was subjected to a short kiering in autoclaves made from acid-resistant steel with a hot-water circulation (Fig. 153). 

At Aschau [5] autoclaves of 5 m3 capacity were used, loaded with 400 kg nitrocellulose and 4 m3 of water. The autoclave was equipped with a stirrer, and was heated by means of both direct and external heat, under a pressure of 12 atm until the desired temperature of 140°C was reached, after which the temperature was maintained exclusively by means of external heating. Kiering took about 15 min. 

After kiering, the contents of the autoclave were transported by means of a pump or in a water conveyer to the beaters, where the fibres were broken down. 

Treatment in autoclaves was also used in earlier years to reduce the viscosity of collodion cotton intended for the manufacture of varnishes. For the same purpose, a water slurry of nitrocellulose may be boiled under hydrostatic pressure in tubes, as a continuous process. These methods are discussed in detail in the chapter devoted to the manufacture of collodion cotton for varnish production. 

According to Miles [7] at Ardeer, rotary autoclaves, spherical in shape, made from stainless steel are used. A pressure of about 3.5 kg/cm3 and a temperature of ca. 142°C are maintained inside the autoclave. The nitrocellulose to water ratio is 1 10, and since the nitrocellulose contains less than 0.25% of acids (as H2S04), the acidity of the water in which the kiering is performed is less than 0.03%. 

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Stabilization of Nitrocellulose Primary washing and boiling in kiers Boiling under pressure (kiering in autoclaves) Pulping... 

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