US443105A - Method of preparing nitro-cellu lose - Google Patents

Description

. UNITED STATES PATENT rFicE.

GEORGE M. MOIVBRAY, OF NORTH ADAMS, MASSACHUSETTS.

METHOD OF PREPARING NlTRO-CELLULOSE.

SPECIFICATION forming part of Letters Patent No. 443,105, dated December 23, 1890.

Application filed October 10, 1889. Serial No. 326,609. (No specimens.)

' To all whom it may concern:

Beit known that I, GEORGE M. MOVVBRAY, a citizen of the United States, residing at North Adams,in the county of Berkshire and State of Massachusetts, have invented new and useful Improvements in the Art, Process, or Method of Manufacturing Nitro-Oellulose or Pyroxyline, of which the following is a specification. 1

The present method of manufacturing pyroxyhne on alarge scale is to select very line pure cotton tissue-paper, unsized, of a thicknessless than one five-hundredth of an inch, and nnmerse the same in a bath of sulphuric and nitric acids of certain strength at a given temperature-say about 85 Fahrenheitrfor about thirty minutes, to remove from the acid bath, expel the adherent acid, plungebeneath cold water, and wash out all trace of acids by systematic flow of water. Fine pure thin tissue-paper is selected because the instant the paper touches the acid bath it takes on a glutinous or colloid surface, which impedes the thorough conversion of the paper, thin as it is, and thus requires some thirty minutes, or thereabout to enable the conversion to take place through only one five-hundredth of an inch thickness. IVith thicker paper treated in like manner only the surfaces of a sheet could be nitrated, as the body of the paper would be unacted upon. During immersion the paper has assimilated some forty per cent. of nitric acid, yet at the end of the operation it occupies less bulk than before immersion, so dense and parchment-like has it become. It is this property of the thin film of converted nitro-cellulose protecting the paper beneath from chemical action that has led to selecting so fine a paper and demanded so long immersion, each of these factors adding to the cost of the pyroxyline or gun-cotton.

My invention has for its object the reduction of cost of the crude materials used by substituting a waste product-such as cotton rags, cottonseed lint from the hulls, &c. in lieu of high-priced unsized tissue-paper now in use, lessening time now required for conversion, and withal producing a better, because a more uniform, product. These re sults I attain by availing myself of a phys ical effect in crystallizing a salt (preferring nitrates) in the cells of the fiber as a preliminary step to nitration, which opens up these cells to the action of the acid loath, whereby on immersion in the acid bath the sulphuric acid sets free from the salt (if nitrate) nitric acid in a nascent state, which instantly acts chemically 011 the adjacent walls of each cell wherein the nitrate has crystallized, and thus I effectnitration more rapidly, with less costly material, than is possible by the present method of immersing uusized tissue-paper in the usual mixed-acid bath, where the process of nitration is obstructed by the superficial glutinous film of pyroXyline, which forms on the surface of the fibrous sheet of unsized tissue-paperthe'instant it touches the acid bath.

I do not confine myself to the use of any particular form of cellulose, whether unsized paper, baled cotton, cotton yarn, or textile fabric, as in cotton rags, or even the cottonlint from cotton-seed hulls obtainedby digester process, whether by treatment with sulphurous acid or by caustic soda, or by simple cotton-lint from cotton hulls, as with any one of these forms of cellulose fiber properly cleansed, bleached, and washed, if impregnated with a salt not necessarily, but preferably, a nitrate, a manufacturer can, by adopting my devices, make pyroxyline with less costly cellulose and overcome the inconvenience of that superficial glutinoushinderance to nitration hereinbefore described.

I have said it was not absolutely necessary to use a nitrate. I wish to be understood by this assertion that any salt crystallized, or even water crystallized by freezing in the cells of fibrous cellulose, facilitates nitration by rendering the inner walls of cellular tissue more readily accessible to the acids of the immersion-bath. Some salts it might be necessary to remove after crystallization by washing, while nitrates sodic nitrate, for i11- stance, for its low price, for its ready crystallization and yield of nitric acid evolved in the acid bath in contact with its sulphuric acid-I prefer to other salts.

To enable others skilled in the art to avail of my invention, I describe it for two varic- ICC) ties of pyroxylincvix., gun-cotton, and soluble pyroxyline for plastic purposes, respectively.

For preparing textile cotton for explosive purposes use for one hundred parts of clean dry bleached rags three hundred parts of boiling water and twenty-five to fifty parts sodic nitrate. l irst dissolve the sodic nitrate in pure clean water,heat to a boiling-point,and gradually introduce the rags, keeping up a moderate circulation of the mass until no more air-bubbles leave the solution. Pass the rags through rollers to remove excess of saline solution. The operator may estimate that rags as theyleave the rollers in their wet condition will retain twice their weight of sol ution. Thereforeeitherby weighing or deducting the proportion of liquid left in the tank he can calculate about the quantity of sodic nitrate taken up by the textile fiber. The rags from the impregnatingtank, having passed through the rollers, are now thrown onto frames protected from dust and allowed to dry gradually, in order to enable the salt to penetrate by the action termed osmose into the cells of the fiber and there crystallize. They are then to be thoroughly dried and are ready for the mixed-acids-bath conversion into nitrocellulose.

The acids immersion-bath for gun cotton, (trinitro-cellulose,) as is known in the art, should be as COl'lCOlltl'ZttQti as possible say for sulphuric acid, specific gravity 1.8;; for nitric acid, specific gravity 1.5;, and in the proportion of sulphuric acid two parts, nitric acid one part, both by weight.

For preparing soluble pyroxyline, (dinitrocellulosez) use of clean dry bleached rags, one hundred parts; water, three hundred parts; sodic nitrate, from ten to twenty-five parts. The directions given for impregnating, hereinbefore described, are to be observed here. The proportions, however, of acids an d the strength of the acids immersion-bath differ; for example,sulphuricaeid,specific gravityl.8i5,sixtyseven parts; nitric acid, specific gravity 1.520, seventeen parts: Water, sixteen parts.

It is hardly necessary to remind one skilled in the artthat if line tissue-paper be used, because it is desired to avoid the fine opaque specks found therein by the present process, a weak saline bath, consisting of ten parts of sodic nitrate to one hundred parts of paper, will snttiee, and that the drying of the paper should not be too rapid, so as to give time for &

the osmose action to take place.

llaving thus explained my process as I conceive the action to take place and given a full, clear, and explicit description of the mode of proceeding to obtain the advantageous results sought, what I claim in the application, and desire to secure by Letters Patent, is

In the manufacture of the various grades of nitro-cclluloseorpyroxyline,the followingprocess, consisting of three steps: first, a preliminary impregnation ot' the cellulose material, whether simply fibrous, felted, or textile, by

crystallizing a salt, preferably sodic nitrate,

in the interstices of the cellulose material; second, immersing this dry saline impregnated cellulose material in a suitable bath of sulphuric and nitric acids, and, third, removing the intro-cellulose from the saline-acids bath, washing outthe adherent acids, and drying the intro-cellulose, substantially as described, and for the purposes set forth. In testimony whereof I have affixed my nature in presence of two Witnesses.

GEORGE M. MOWBRAY. Witnesses:

EDWARD Bnosson, J one CAnv.