US1945101A - Manufacture of nitro-cellulose - Google Patents

Description

Patented Jan. 30, 1934 UNITED STATES PA'FET OFFICE Ernest Tschudin, Reinach, near Basel, Switzerland No Drawing. Application June 25, 1930, Serial No. 463,830, and in Great Britain June 16,

1 Claims.

This invention relates to improved processes for the manufacture of nitro-cellulose and is a continuation in part of my application Serial No. 348,368 filed March 19, 1929.

In the more generally used processes the cellulose employed for nitration is either in the form of fine fibres such as cotton linters, or of fine powders. If linters are used they are voluminous, and require a large weight of acid in proportion to the weight of the linters effectually to nitrate them, are difiicult to drain, and generally require to be reduced to the form of powder for the purposes of stabilization, which powder is of bulky form. In the case of fine powders they are also difficult to drain and handle, and in some of the forms proposed the process of reducing the cellulose to powder leaves it in a form where direct nitration is difiicult, if not impossible.

The present invention consists in a process for the preparation of nitro-cellulose which is characterized by treating wood pulp with soda lye and carbon-bi-sulphide so as to form a slightly gelatinous paste, pressing such gelatinous paste through dies to produce forms such as strings or pellets which are then immersed in a hardening solution, and where strings are formed, cutting the strings into pellets either before or after the hardening and nitrating the cellulose so prepared. For nitrating I prefer to use a mixture of acids in which the proportion of nitric acid considerably exceeds that of sulphuric acid. The process may be modified by carrying out the nitration and, if desired, subsequent processes, on the substance in the form of strings which may be cut into pellets after nitration.

According to the preferred form of this invention the cellulose is formed into a gelatinous paste and prepared or treated as hereinafter described so as to form comparatively dense pellets of such a size as can be easily handled and drained, and of such a nature that they are easily nitratable and capable of retaining their form throughout the nitration and subsequent operations, and of being efiectively stabilized in that form.

The raw material employed is wood-pulp, and this, preferably bleached, is stirred up with 70% of water, and treated with from about ten to fifteen per cent of caustic soda reckoned on the weight of the cellulose. After half-an-hour 5 to 10% of carbon-bi-sulphide is added, and the mixture left to stand for an hour. Care must be taken not to carry the gelatinization too far, or nitration will be impeded. This operation is performed at room temperature. With the lower quantities of chemicals a less dense but more easily nitratable body is produced. If in place of stirring, grinding apparatus is used, the amount of chemicals in some cases can be even further reduced.

The best form of wood pulp is that which is supplied for paper making in which the wood cellu-' lose'has been subjected to treatment in a hollander or the like.

This results in forming a slightly gelatinous paste which can be pressed through dies forming continuous strings, and these can be cut into suitable lengths, or by using the smaller quantity of soda, the paste may be exuded in the form of short pellets which do not require to be out. A convenient diameter for the strings is from one to two millimetres, and these may be cut into lengths of about a centimetre, but in some cases a finer or coarser division may be v adopted.

These strings or pellets are then immersed in a hardening solution e. g. an acid or acid salt, for example sulphurous acid or sodium bi-sulphite and after the required degree of hardness has been obtained the material is washed and dried.

In some cases there is a tendency to too great shrinking. This may be prevented by immersing the material in a glycerine bath before drying. The glycerine can be recovered by any convenient method, or, where explosives containing intro-glycerine are to be made, the mixture can be nitrated directly.

These pellets, in an air-dried state, are then nitrated, preferably in a centrifugal nitrator. For nitrating we use a mixture of nitric and sulphuric acids in which the proportions employed differ substantially from those ordinarily used. For example to get a high nitration a mixture of 81% nitric acid, 16% sulphuric acid, and 3% water, the parts being by weight, may be used. This normally produces a nitrated body containing about 13.2% nitrogen.

With the cellulose in the form of pellets, an a mixture of acids such as described, very much less acid is necessary than with known methods, a kilogramme of the mixed acids being sufficient to nitrate from to 130 grammes of pellets.

For lower nitrations the amount of water is increased. The relative proportion of sulphuric acid to nitric acid can also be increased, but this tends to slow down nitration, and, if carried too far, to produce parchmentization.

The nitration is effected in about half an hour, and the material is then freed from the acid preferably by means of a centrifugal. Owing to the dense form of the material this can be done with great ease. The pellets are then washed with running Water and stabilized by boiling.

The subsequent treatment varies according to the use for which the nitro-cellulose is required.

Instead of dividing the cellulose prepared or treated as above described into pellets prior to nitration, I may nitrate in the form of strings which can be subsequently divided into pellets, but I consider the first described method as generally preferable, as the pellets pack closer and are more easily handled and drained.

The process is applicable for the production of nitro-cellulose either for explosives or for other industrial purposes.

What I claim is:

1. A process for the preparation of nitro-cellulose starting from wood pulp, which consists in treating said wood pulp with soda lye and carbon-bisulphide so as to form a slightly gelatinous paste, forming said paste into pellets, immersing said pellets in a hardening solution, and nitrating said pellets.

2. A process for the preparation of nitro-cellulose, starting from wood pulp, which consists in treating said wood pulp with soda lye and carbonbisulphide so as to form a slightly gelatinous paste, forming said paste into strings, cutting the strings into pellets, immersing said pellets in a hardening solution, and nitrating said pellets.

3. A process for the preparation of nitro-cellulose, starting from wood pulp, which consists in treating said wood pulp with soda 'lye and carbon-bisulphide so as to form a slightly gelatinous paste, pressing such gelatinous paste to form strings, immersing said strings in a hardening solution, cutting the strings into pellets, and nitrating said pellets.

4. A process for the preparation of nitro-cellulose starting from wood pulp, which consists in treating said wood pulp with soda lye and carbon-bisulphide so as to form a slightly gelatinous paste, forming such paste into pellets, immersing said pellets in a hardening solution, and nitrating said pellets in a nitration mixture in which the proportion of nitric acid considerably exceeds that of sulphuric acid.

5. A process for the preparation of nitro-cellulose starting from wood pulp, which consists in treating said wood pulp with soda lye and carbon-bisulphide so as to form a slightly gelatinous paste, pressing such gelatinous paste to form strings, cutting the strings into pellets, immersing said pellets in a hardening solution, and nitrating said pellets in a nitration mixture in which the proportion of nitric acid considerably exceeds that of sulphuric acid.

6. A process for the preparation of nitro-cellulose starting from wood pulp, which consists in treating said wood pulp with soda lye and carbon-bisulphide so as to form a slightly gelatinous paste, forming said paste into strings, immersing said strings in a hardening solution, cutting the strings into pellets, and nitrating said pellets in a nitration mixture in which the proportion of nitric acid considerably exceeds that of sulphuric acid.

7. A process for the preparation of nitro-cellulose starting from wood pulp, which consists in treating said wood pulp with soda lye and carbon-bisulphide so as to form a slightly gelatinous paste, forming such gelatinous paste into strings, immersing said strings in a hardening solution, nitrating said strings, and cutting said strings into pellets after nitration.

8. A process for the preparation of nitro-cellulose starting from wood pulp, which consists in treating said Wood pulp With soda lye and carbon-bisulphide so as to form a slightly gelatlnous paste, pressing said gelatinous paste into forms having a predetermined shape, immersing said forms in a hardening solution, and nitrating said forms, the forms being out into pellets at some step in the process.

9. A process for the preparation of nitro-cellulose starting from wood pulp, which consists in treating said wood pulp with soda lye and carbon-bisulphide so as to form a slightly gelatinous paste, forming such paste into predetermined forms, immersing said forms in a hardening solution, immersing said forms in a glycerine bath, drying the forms, and nitrating said forms,

the forms being cut into pellets at some step in the process.

10. A process for the preparation of nitrocellulose starting from Wood pulp, which consists in treating said wood pulp with soda lye and carbon-bisulphide so as to form a slightly gelatinous paste, forming such gelatinous paste into predetermined forms, immersing the forms in a hardening solution, and nitrating said forms.

ERNEST TSCHUDIN.