US2690964A - Process for gelling liquid nitroparaffins - Google Patents

Description

Patented Oct. 5, 1954 UNITED STATES ATENT OFFICE PROCESS FOR GELLING LIQUID NITROPARAFFIN S Herman Maisner, Los Angeles, Calif., assignor,

by mesne assignments, to Aerojet-General Corporation, Cincinnati, Ohio, a corporation of Ohio 3 Claims. 1

This invention relates to nitroparamn-containing substances, and has for its principal object to provide a gel containing nitroparaffin, and a process of forming it.

This is a division of my copending application Serial No. 725,977, filed February 1, 1947.

Liquid nitroparafiins have heretofore been employed as propellants in jet propulsion devices, and they have also been used in explosives. It is desirable for some types of operating conditions to employ the liquid nitroparaffins in a solid or semi-solid form, or gel, for these purposes. Up to the present time, difficulty has been encountered when it was attempted to produce gels from the various liquid nitroparaflins without seriously afiecting their oxygen balance and otherwise changing their properties.

By the present invention I have discovered a method for thickening, gelling, or solidifying liquid nitroparafiins and forming semi-solid or solid gels which retain their consistency for a period of time without undergoing any marked change.

This invention is, in general, directed to solidifying or gelling any of the liquid nitroparaflins including the mono, and poly nitromethanes, mononitroethane, mononitropropane, mononitroisopropane, mononitrobutanes, mononitroisobutanes, mononitropentanes and the like which are normally liquid compounds at room temperatures. Thus, I may employ any of the liquid nitroparaffins, such as mononitromethane (commonly called nitromethane, and so designated hereinafter), dim'tromethane, nitroethane, nitro- .propane, nitrobutane, and the like or any mixany of the normally solid polynitroparaffins having sufficient oxygen to sustain self-combustion in nitromethane. [Nitromethane is usually the preferred nitroparaifin for propellant and explosive purposes, in that it forms a very satisfactory self-combustible propellant when gelled with nitrocellulose and employed in the manner in which such propellants are usually used; and a very satisfactory explosive when gelled in combination with a sensitizer or otherwise treated and handled in the manner of an explosive.

I have discovered that it is possible to produce a homogeneous semi-solid or solid gel from liquid nitroparafiins by dissolving or adding to the liquid nitroparaifins, such as nitromethane, nitroethane and the like, a quantity of nitrocellulose. Various commercial forms in which nitrocellulose suitable for the purpose, may be obtained are: Pyrocellulose, pyroxylin, guncotton, etc., all of which are trade names for such nitrocelluloses. Y

til

The gelling of the nitroparaffins is preferably conducted at room temperatures, or temperatures not more than slightly above room temperatures, since both nitroparafiin and nitrocellulose become explosive when confined and sub jected to more elevated pressures and temperatures. This is particularly true when a sensitizing agent has been added to nitromethane to assure its action as an explosive. At elevated temperatures, that is, above 350 F., nitromethane, for example, becomes extremely sensitive to shocks and at still higher temperatures may explode without subjecting the liquid to any shock whatsoever.

The gels produced from nitrocellulose and a liquid nitroparaffin may be compounded, by adjusting th proportions to give gels having varying degrees of viscosity. These range from syrupy materials to solid gels. For practical purposes the gels employed vary from between about 5% to nitrocellulose by weight based on the weight of nitroparafiin used. Gels may be made to contain any amount above 75% nitrocellulose by weight based on the weight of the total mixture, but even 75% nitrocellulose gels are practically solid, therefore, there is little advantage from this standpoint in using a higher percentage of nitrocellulose.

Since nitroparaflins of the type of nitromethane, and nitrocellulose both have sufficient oxygen in their molecules to insure their complete combustion, these substances are capable of burning to completion at ambient conditions without requiring the addition of oxidizers. Gelled nitroparafiins such as nitromethane are particularly useful where it is desired to employ these substances as solid or semi-solid explosives or as self-combustible solid propellant fuels such as are used in self-contained rocket motors.

The nitroparafiin gels prepared according to my invention may be employed either as explosives or as self-combustible propellants, depend ing upon the manner of use. The gels are explosive when detonated with sufiicient force but may readily be adapted to be burned as fuels, particularly in jet propulsion motors, in the absence of detonation. If it is desired to prepare a nitroparafin gel to be used as an explosive I may incorporate in the liquid nitroparafiin, prior to gelling, a sensitizer. Such sensitizers as the organic amines disclosed by Laurence in patent application Ser. No. 605,747, filed July 18, 1945, are highly satisfactory, including the aromatic amines such as aniline, diphenylethylenediamine and the like and the aliphatic amines such as diethylamine, tetraethylene pentamine and the like. A nitroparafiln gel in which a sensitizer such as one of the organic amines is incorporated is much more sensitive to detonation than is the gel. in ,the absence of the sensitizer, although it is to be understood that the use of a sensitizer is optional; and the gels may be em ployed as explosives either with or without a sensitizer.

Thus mixtures of nitromethane or other 2111- troparaifins and nitrocellulose containing from about 75% to about 85% by weight of nitroparafiin based on the total weight maybe satisfactorily used as explosives in conjunction with a suitable detonator. Higher proportions of nitrocellulose may be employed; ,this tends to decrease the explosive strength.

Mixtures of 'nitroparaifin and. nitrocellulose containing from 79% to 83% by weight .of hitroparafiin such as nitromethane based on the total weight of the mixture are easily exploded by the shock of a No. 8 fulminate type of blasting cap, yet in the absence of shock, such mixtures (containing as high as 74% to 84% by weight of nitromethane in combination with nitrocellulose) may be confined and burned satisfactorily as restricted propellant charges without exploding. A restricted propellant charge defined as one in which the burning occurs over a predetermined face of limited area and does not take place simultaneously over the entire outside surface of the propellant mass. Restriction may be accomplished by coating all surfaces except the burning surface with a liner which is adhesive to the propellant mass and has a slower burning rate than the material forming the principal charge. Examples of adhesive liners suitable for confining the burning are ethylcellulose, cellulose acetate, cellulose butyrate, cellulose acetate butyrate, etc.

The burning properties .of solid propellant charges compounded by gelling nitromethane with nitrocellulose may be greatly improved by adding suitable catalysts to the nitromethane before gelling. A particularly desirable catalyst for assisting the easy ignition of nitromethane is chrome acetyl acetonate. Small amounts of this substance ranging between a trace up to approximately 3% by weight maybe used to improve the burning of nitromethane.

The ratio of nitroparafiin to nitrocellulose may, as stated, be varied over a wide range of proportions ranging from a trace of nitrocellulose in liquid nitroprafin to a trace of nitroparafiin in nitrocellulose. The amount of nitrocellulose which may be incorporated into the liquid .nitroparaflin by stirring or agitation alone will not appreciably exceed 45% based on the weight of the nitroparafiin employed.

A fairly substantial gel may be formed by dissolving in nitroparafiin as low as 10% nitrocellulose by weight based on the weight of the nitroparafiin while a reasonably stiff gel is obtained when the amount of nitrocellulose employed is increased .to or by weight based on the weight of the nitroparaffin employed. Particularly stifi gels are formed when to by weight of nitrocellulose based on the weight of nitroparaffln present is employed.

If it is desired to incorporate amounts of nitrocellulose in excess of 45% by weight, it is preferable to mill or knead the mixtures of nitrocellulose and a liquid nitroparaflin to insure a more homogeneous mixture.

The process herein described possesses the ad.- vantage that any desired consistency. of gel may be easily produced from nitroparamns. Sensitized nitroparaifin such as nitromethane may, by careful selection of the proportions of nitromethane to nitrocellulose, be used .either as a solid or semi-solid explosive. Non-sensitized nitromethane and other self-combustible nitroparaffins may be made into selfcombustible solid propellants, or may be used as explosives when detonated with sufficient force.

The following examples of gels made according to my invention serve to illustrate the application of the invention.

Example 1.--A gel consisting of 30% by weight of nitromethane and 20% by weight of nitrocellulose has been prepared by dissolving the nitrocellulose in the nitromethane at 75 F. The gel thus formed was very stable and fairly rigid. Additional gels consisting of nitromethane and nitrocellulose were made-in similar manner and contained nitrocellulose varying in proportions from about 10% to 50%.

Example 2.Numerous other gels have been prepared by dissolving nitrocellulose in nitropropane and nitroethane at temperatures ranging from approximately F. to 90 F. These gels consisted of from about 50% to 90% by weight of therespective nitroparaffin and from about 10% to 50% by weight of nitrocellulose.

Example ;3.-A gel consisting of 14.6% by weight of nitrocellulose dissolved in 85.4% of nitromethane formed a thick fluid gel.

Example 4.-.A gel consisting of 25% nitrocellulose and nitromethane was prepared by dissolving the nitrocellulose in the nitromethane at approximately 75 F. This produced a fairly stiff gel.

Example 5.-A solution of 50% nitromethane into which has been dissolved 50% .of nitrocellulose produced a very stiff gel having substantially solid properties.

Example 6.A sample of a gel consisting of 75.3% nitromethane which had dissolved therein 22.9% nitrocellulose was made more active by the addition of 1.8% of chrome acetyl acetonate.

- This formed a fairly stiff gel having suitable Other gels'which may be satisfactorily formed due to the fact that nitrocellulose is a good gelling agent for nitromethane and similar nitroparaffins are those which are made from solutions of solid organic polynitrocompounds in nitromethane. Examples of these substances are trinitrotoluene, polynitrobenzene, dinitropropane, dinitroethane and other higher polynitroparafiins which possess sumcient oxygen in their molecules to sustain their self -combus.tion. These are selected to produce propellants having the required properties such as hardness, temperature coeflicient and freedom from detonation.

An additional advantage of my process apparent from the foregoing examples, is that the ingredients may be compounded at ambient temperatures and require little or no heating, thus eliminating the hazard present when propellants are subjected to temperatures greatly in excess of ambient. This is particularly desirable in view of the fact that nitro-paraflins, such as nitro-methane, become more sensitive to shocks at elevated temperatures.

A particularly desirable feature, inherent in restricted burning propellant charges formed from solid gels of the above ingredients, is that the gases produced when these charges are burned in a jet motor are substantially smokeless, noncorrosive and nontoxic. The specific impulse obtained by burning nitro-methane, or any other of the nitroparaffins having sufiicient oxygen in the molecule to support their own combustion, in combination with nitrocellulose is not appreciably lower than that developed by the nitroparailin alone.

Gels compounded from sensitized nitromethane and nitrocellulose may be formed into sticks similar to dynamite and may be substituted for dynamite since sensitized nitromethane when exploded compares favorably with nitroglycerin in shattering properties and power. The addition of nitrocellulose does not appear to affect the ease with which sensitized nitromethane can be exploded when subjected to shocks.

I claim:

1. A composition of matter comprising from about to 50% by weight of nitrocellulose, 50% to 90% by weight of nitromethane, and a sensitizer from the group consisting of aniline, diphenylethylenediamine, diethylamine and tetraethylene pentamine.

6 2. A composition of matter consisting of a mixture of a liquid nitroparafiin, nitrocellulose and a sensitizer consisting of organic amine from the group consisting of aniline, diphenylethylenediethylamine and tetraethylene pentamine, the

weight of the nitromethane being between and by weight based on the weight of the total mixture, and the weight of the nitrocellulose ,being between 15% and 50% by weight based on the weight of the total mixture.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,985,968 Wyler Jan. 1, 1935 2,325,064 Lawrence July 27, 1943 FOREIGN PATENTS Number Country Date 24,839 Great Britain of A. D. 1913

Claims (1)

1. A COMPOSITION OF MATTER COMPRISING FROM ABOUT 10% TO 50% BY WEIGHT OF NITROCELLULOSE, 50% TO 90% BY WEIGHT OF NITROMETHANE, AND A SENSITIZER FROM THE GROUP CONSISTING OF ANILINE, DIPHENYLETHYLENEDIAMINE, DIETHYLAMINE AND TETRAETHYLENE PENTAMINE.