Nitration, of cellulose

Nitration of cellulose may result in the addition of from one to three nitrate groups per glucose anhydride unit. The following compounds and their nitrogen content have been postulated ... 

E. Dodgen, "Continuous Nitration of Cellulose SNIA Viscosa Process," in Symposium on Processing Propellants, Explosives and Ingredients, ADPA, Washington, D.C., 1977, p. 4.2-1. 

Fig. 2. Flow diagram of nitration of cellulose by Hercules continuous process.

The nitration of cellulose is unusual in that uniform reaction takes place even though the fibrous structure is retained. This is explained by the fact that nitration is an equilibrium reaction unaffected by fibre structure, the extent of nitration being determined by the strength of the nitrating acid. 

Nitration of cellulose followed by plasticisation of the product with camphor has the effect of reducing the orderly close packing of the cellulose molecules. Hence whereas cellulose is insoluble in solvents, except in certain cases where there is chemical reaction, celluloid is soluble in solvents such as acetone and amyl acetate. In addition the camphor present may be dissolved out by chloroform and similar solvents which do not dissolve the cellulose nitrate. 

Diagram of a Plant for Nitration of Cellulose in Mechanical Nitrators, duPont System... 

Flow Diagram of Nitration of Cellulose by Hercules Continuous Process. . ... 

NC. Although the nitration of cellulose has been described quite extensively in Vol 2,... 

Fig 14 Diagram of a plant for nitration of cellulose in mechanical nitrators, du Pont system (according to du Pont de Nemours (Ref 13)... 

HNOS04+3C02+11H20, and in the nitration of cellulose to NC, or of starch to Nitrostarch ... 

Around the same time, nitration of cellulose to produce nitrocellulose (NC also known as guncotton) was undertaken by different groups and finally the invention of NC was reported by Schonbein (Basel) and Bottger (Frankfurt) independently in 1846. Further, dynamite was invented by Alfred B. Nobel in 1866. 

At the same time as nitroglycerine was being prepared, the nitration of cellulose to produce nitrocellulose (also known as guncotton) was also being undertaken by different workers, notably Schonbein at Basel and Bottger at Frankfurt-am-Main during 1845-47. Earlier in 1833, Braconnot had nitrated starch, and in 1838, Pelouze, continuing the experiments of Braconnot, also nitrated paper, cotton and various other materials but did not realize that he had prepared nitrocellulose. With the announcement by Schonbein in 1846, and in the same year by... 

Bottger that nitrocellulose had been prepared, the names of these two men soon became associated with the discovery and utilization of nitrocellulose. However, the published literature at that time contains papers by several investigators on the nitration of cellulose before the process of Schonbein was known. 

The manufacturing method used today for the nitration of cellulose employs a mixture of sulfuric and nitric acids. During nitration of the... 

When treated with coned HNOj or mixed HNOj-HjS04, adipo cellulose yields products resembling those obtained by nitration of cellulose and fats... 

Nitrocellulose is obtained by esterification of cellulose with nitric acid. This process is described simply as nitration or more exactly O-nitration. The nitration of cellulose can be expressed by means of the following equation ... 

The spatial configuration, extended in consequence of nitration, is retained despite partial denitration. This is why the cell size of a denitrated cellulose is larger than that of nitrocellulose containing the same nitrogen percentage, but obtained by a direct nitration of cellulose. 

Mathieu [18] has shown that X-ray diagrams taken at frequent intervals during nitration of cellulose with N205 vapour indicate that the structure progresses through all the stages from cellulose to cellulose trinitrate. 

Herzog and Londberg [20] have examined the X-ray diagrams of cellulose produced by denitration of a carefully nitrated product. The picture of the regenerated cellulose was in principle identical with that of cellulose before nitration. This observation suggests that a cautious nitration of cellulose that proceeds without oxidation or hydrolysis does not change the microcrystalline structure of the cellulose, i.e. this is a topochemical reaction, in which the product preserves the same... 

Similar observations were also published earlier by Tribot and Marsaudon [16]. Recently, however, Lhoste [17] has questioned the validity of the hypothesis of the formation of sulphuric acid esters during the nitration of cellulose. On the basis of analytical data the author has arrived at the idea that sulphuric acid is bound with nitrocellulose solely by occlusion. He found no evidence to confirm the existence of cellulose sulphates in nitrocotton. 

The rate of nitration of cellulose is dependent both on the rate of the chemical reaction of esterification itself, and on the rate of diffusion of the nitrating add into the cellulose fibres. This is discussed later (p. 356). 

The problem of the rate of nitration of cellulose is discussed in a more detailed way in a special section — p. 355. 

It should be borne in mind that laboratory experiments on the nitration of cellulose on a gramme scale usually using a large excess of acid, do not portray plant conditions in an exact manner. Under laboratory conditions a two hours nitra-... 

Fig. 121. Nitration of cellulose. A modified Sapozhnikov diagram with curves of equal nitrogen content in nitrocellulose. Composition of acid mixtures in weight %.

Fig. 126. Nitration of cellulose as a function of the terminal composition of nitrating mixtures...

Wannow [36] has stated that the nitration of cellulose by means of mixed nitric and phosphoric acid does not reduce the degree of polymerization of the nitrated substance. The stability of nitrocellulose obtained by treatment with H3P04 and HN03 is... 

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