US3723207A

US3723207A - Process for preparing stable essentially water-free slurries of nitrocellulose and products thereof

Info

Publication number: US3723207A
Application number: US00083659A
Authority: US
Inventors: A Camp
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1970-10-23
Filing date: 1970-10-23
Publication date: 1973-03-27
Anticipated expiration: 1990-03-27

Abstract

A PROCESS FOR FORMING ESSENTIALLY WATER-FREE STABLE SLURRIES OF PLASTISOL NITROCELLULOSE WHEREIN PLASTISOL GRADE NITROCELLULOSE AND OTHER SOLIDS SUCH AS CYCLOTETRAMETHYLENETETRANITRAMINE, ARE MIXED WITH AN ORGANIC LIQUID DILUENT CAPABLE OF FORMING AN AZEOTROPE WITH WATER, SUCH AS HEPTANE, AND A STABILIZING AMOUNT OF METRIIOL TRINITRATE, AND WHEREIN THE AZEOTROPE IS VOLATILIZED FROM THE MIXTURE TO FORM THE RESULTANT ESSENTIALLY WATER-FREE SLURRY. IN ADDITION, ESSENTIALLY WATER-FREE STABLE SLURRIES CONTAINING PLASTISOL NITROCELLULOSE MADE BY THE ABOVE PROCESS ARE ALSO PROVIDED.

Description

United States Patent M PROCESS FOR PREPARING STABLE ESSENTIALLY WATER-FREE SLURRIES 0F NITROCELLULOSE AND PRODUCTS THEREOF Albert T. Camp, Indian Head, Md., assignor to the United States of America as represented by the Secretary of the Navy No Drawing. Filed Oct. 23, 1970, Ser. No. 83,659

Int. Cl. C06b /02 U.S. Cl. 149--92 8 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates generally to essentially waterfree stable compositions of propellant and explosive ingredients and more particularly "to a process for preparing essentially water-free stable slurries containing plastisol nitrocellulose and the products thereof.

The hazards of handling and processing various propellant and explosive ingredients in a dry condition is well known. Handling materials of this nature, such as cyclotrimethylenetrinitramine (RDX), cyclotetramethylenetetranitramine (HMX), and plastisol nitrocellulose, in a bone dry state is particularly hazardous owing to the likelihood of an electrostatic and deflagration detonation. Thus, in most instances these materials are stored and handled in a liquid medium, usually Water.

However, the Water must be removed from the propellant ingredient, such as plastisol nitrocellulose, before the mixing of the final propellant or explosive composition. Traditionally, for safety reasons, the water is not removed from the plastisol nitrocellulose until immediately prior to the final stages of the mixing. Moreover, past processes to remove residual water have been ineffective and even small quantities (0.10.2 percent) of water react adversely with the other ingredients, such as energetic fuels and oxidizers, high energy cross-linking agents and other additives normally incorporated in propellant and explosive formulations.

Recently, a vast amount of interest has been directed to the development of composite modified double base, as well as strictly double base propellants. A composite modified double base propellant is one in which oxidizers, such as HMX and RDX, are incorporated along with nitrocellulose.

Thus, in view of the present day problems associated with storage of propellant ingredients of this nature in Water and the removal of the water thereof, a need exists for a more convenient and effective way to safely ship and store these ingredients, which will not hinder their reactivity or compatibility in the final propellant formulations.

SUMMARY OF THE INVENTION Accordingly, one object of the present invention is to provide a process for preparing essentially Water-free stable compositions containing plastisol nitrocellulose.

Another object of the present invention is to provide a 3,723,267 Patented Mar. 27, 1973 process for preparing essentially water-free stable compositions containing plastisol nitrocellulose and either cyclotrimethylenetetranitramine or cyclotetramethylenetetranitramine.

Still another object of the instant invention is to provide essentially water-free stable compositions containing plastisol nitrocellulose which can be safely transported and stored and which are compatible and do not render adverse effects upon the final propellant or explosive formulation.

A still further object of this invention is to provide essentially water-free compositions containing plastisol nitrocellulose and either cyclotrimethylenetetranitramine or cyclotetramethylenetetranitramine which can be safely transported and stored and which are compatible and do not render adverse effects upon the final propellant or explosive formulation.

Another object of the instant invention is to provide essentially water-free stable compositions containing plastisol nitrocellulose or compositions containing plastisol nitrocellulose and either cyclotrimethylenetetranitramine or cyclotetramethylenetetranitramine which when mixed therein improve the aging and mechanical properties of the final propellant composition.

These and other objects are achieved by providing a process wherein plastisol nitrocellulose, or plastisol nitrocellulose and cyclotrimethylenetrinitramine or plastisol nitrocellulose and cyclotetramethylenetetranitramine are mixed with metriol trinitrate and a diluent capable of forming an azeotropic mixture with water and upon the evaporation of the azeotrope from the mixture a stable and essentially water-free slurry is formed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with this invention, it has been discovered that it is possible to form stable and essentially Water-free slurries of plastisol nitrocellulose by the admixture of plastisol nitrocellulose and the other solids, if desired, i.e., cyclotrimethylenetrinitramine or cyclotetramethylenetetranitramine and a suitable diluent, which is capable of forming an azeotrope with water, in a conventional propellant mixer. After the addition of the diluent to the solids in the mixer, metriol trinitrate is then added and the complete mixture is thoroughly agitated under vacuum until homogeneity and the complete removal of the azeotrope are achieved.

Although the manner in which the ingredients are added to the mixer and agitated is not critical, the preferred manner is dependent upon several considerations. For example, if the plastisol nitrocellulose and other solids contain a large quantity of water, it is advantageous to add the diluent to the plastisol nitrocellulose and solids and agitate prior to the addition of the metriol trinitrate. If, in turn, large quantities of plastisol nitrocellulose and the other solids are employed and only small quantities of the diluent, then to avoid lumping and non-homogeneity it is preferable to add the metriol trinitrate to the other ingredients before agitation commences. However, in summary, the diluent, plastisol nitrocellulose and other solids should be added and mixed together before the addition thereto of the metriol trinitrate for the most efiicient removal of water.

Plastisol nitrocellulose is a highly densified form of ball nitrocellulose. However, any nitrogen content plastisol nitrocellulose is applicable for the purposes of this invention.

As hereinbefore discussed, all the mixing is performed under vacuum conditions and sufficient heat is supplied to enable the volatilization of the azeotrope from the mixture. If the plastisol nitrocellulose and other solids are mixed with the diluent prior to the addition of the metriol trinitrate, it is essential that the metriol trinitrate be added before all the diluent has evaporated. As the azeotrope is removed, the milky white slurry texture of the mixture becomes thicker until all the azeotrope has been volatilized at which time the slurry is essentially water-free and has a toothpaste constituency. It is then removed from the mixer.

Diluents which are within the scope of the present invention are organic liquids which are immiscible with water and are also capable of forming an azeotrope with water. Specifically some diluents encompassed herein include, for example, heptane, hexane, toluene, benzene and the like.

The amount of diluent employed within the process of this invention is dependent upon the quantity of water present in the plastisol nitrocellulose and other solids which has normally been quantitatively pre-determined. Thus a sufiicient amount of diluent necessary to remove all the water is utilized.

As the azeotrope vapor is removed from the remaining mixture, this vapor is condensed and the water and diluent, being immiscible, are in separate layers and thus are easily separated from one another.

A copending application, Navy Case No. 50,615, by L. Henderson and C. Johnson entitled Azeotropic Removal of Water From Ordnance discloses the concept of forming an azeotrope to remove residual water from propellants and the disclosure is incorporated herein.

The quantities of materials employed in the process of the present invention may vary over a wide range. Actually, any proportion of the plastisol nitrocellulose and other solids may be used perhaps depending upon specific characteristics desired in a final propellant formulation. However, in some instances, the solids may settle out of the slurry. Stable slurries are formed, however, when plastisol nitrocellulose in amounts of from about 50 percent by weight, cyclotrimethylenetrinitramine or cyclotetramethylenetetranitramine in amounts of from about to 70 percent by weight and metriol trinitrate in amounts of from about 30 to about 95 percent by weight are employed.

Accordingly, the resultant stabilized plastisol nitrocellulose and metriol trinitrate slurry or plastisol nitrocellullose, cyclotrimethylenetrinitramine and metriol trinitrate slurry or the plastisol nitrocellulose, cyclotetramethylenetetranitramine and metriol trinitrate slurry formed by the process of this invention are essentially water-free (0.01 percent) and are useful as main intermediates for plastisol nitrocellulose based propellants and explosives. They can be safely and readily shipped in this state and do not harden or cure under normal storage conditions until other ingredients are added.

Obviously, to form the final propellant or explosive, other particulate ingredients and active co-plasticizer, such as triethyleneglycol dinitrate and diethyleneglycol dinitrate along with other energetic plasticizers, stabilizers and conventional cross-linkers are added to the slurry.

Having generally described the invention the following examples are given for purposes of illustration. It will be understood that the invention is not limited to these examples, but is susceptible to different modifications that will be recognized by one of ordinary skill in the art.

EXAMPLE 1 327 grams dry basis of plastisol nitrocellulose containing from about 0.15 to 0.25 percent by weight water and 40 grams of heptane were added to a 60 LP ARC propellant mixer at 120 F. under vacuum and briefly agitated. 510 grams of metriol trinitrate was then added to this mixture with continued agitation for about minutes. After this time an additional 163 grams dry basis of plastisol nitrocellulose was added to the mixture and agitated for another 10 minutes at 120 F. under vacuum. The slurry which had a toothpaste constituency, was then removed from the mixer and stored.

EXAMPLE 2 A slurry of 110 grams of heptane and 500 grams dry basis of Class A cyclotrimethylenetrinitramine containing from about 0.15 to 0.25 percent by weight of water and alcohol was premixed and then added to grams dry basis of plastisol nitrocellulose (about 0.15 to about 0.25 percent water) in a 60 LP ARC propellant mixer. 200 grams of metriol trinitrate was then added to the mixer and the total slurry mixture was further agitated under vacuum at 120 F. for 45 minutes after which time the water-heptane azeotrope was completely evaporated. The slurry which had a white color and of a toothpaste constituency was removed and stored.

EXAMPLE 3 A slurry of 60 grams of heptane and 200 grams of 18 micron size cyclotetramethylenetetranitramine containing from about 0.15 to 0.25 percent by weight of water and alcohol was prepared and then added to 50 grams dry basis of plastisol nitrocellulose (about 0.15 to about 0.25 percent water) in a 60 LP ARC propellant mixer and briefly agitated. 200 grams of metriol trinitrate was then added to the mixer and further agitated under vacuum at 120 F. for 20 minutes. At the end of this time, 50 additional grams of metriol trinitrate was added to the mixture and the resultant slurry was mixed for 30 minutes under vacuum at F.

The slurry compositions of this invention did not decompose or exhibit any phase separation after storage for four months and upon analysis had a water content of only 0.01 percent.

Thus, in accordance with the process of the present invention, plastisol nitrocellulose no longer need be stored and shipped in water, but may be shipped or stored in the stable, safe, and convenient essentially water-free slurry form herein provided. Moreover, the normally present residual Water which would react adversely with energetic fuels and oxidizers is hereby essentially completely eliminated.

It has been found also that the complete removal of the water from the plastisol nitrocellulose and other solids at such an early stage in the final propellant formulation, reduced shrinkage and increased the castable life of the final compositions are provided.

Obviously, numerous modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described herein.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent of the United States is:

1. A process for preparing stable, essentially waterfree slurries of plastisol nitrocellulose consisting of:

mixing moisture wet plastisol nitrocellulose with an organic liquid diluent immiscible with water and capable of forming an azeotrope with water, and selected from the group consisting of heptane, hexane toluene, and benzene, in a sufiicient amount to remove all the water from the plastisol nitrocellulose, whereby an azeotropic mixture of water and said diluent is formed;

adding and mixing a stabilizing amount of metriol trinitrate to the resultant mixture; and

volatilizing the formed water diluent azeotrope from the resultant slurry.

2. A process for preparing stable, essentially waterfree slurries of plastisol nitrocellulose which consists of:

mixing moisture-wet plastisol nitrocellulose and a moisture-wet solid selected from the group consisting of cyclotrimethylenetrinitramine and cyclotetramethylenetetranitramine with an organic diluent immiscible with water and capable of forming an azeotrope with water, and selected from the group consisting of heptane, hexane, toluene and benzene, in a sufficient amount to remove all the water from the plastisol nitrocellulose and other solid, whereby an azeotropic mixture of water andsaid diluent is formed;

volatilizing the formed water-diluent azeotrope from the resultant slurry.

3. The process of claim 1 wherein the organic liquid diluent is selected from the group consisting of heptane and hexane, the plastisol nitrocellulose is mixed in amount which results in an essentially water-free slurry of from about to about 50 percent plastisol nitrocellulose and the remainder being metriol trinitrate.

4. The process of claim 2 wherein the organic liquid diluent is selected from the group consisting of heptane and hexane, the plastisol nitrocellulose is mixed in an amount which results in an essentially water-free slurry of from about 5 to about 50 percent by Weight plastisol nitrocellulose, and the cyclotrimethylenetrinitramine or the cyclotetramethylenetetranitramine is mixed in an amount which results in from about 20 to about 70 percent by weight of the slurry and remainder being metriol trinitrate.

5. A stable, essentially water-free slurry consisting of plastisol nitrocellulose and metriol trinitrate.

6. The slurry of claim 5 wherein the plastisol nitrocellulose is present in an amount of from about 5 to about percent of the total mixture.

7. A stable, essentially water-free slurry consisting of plastisol nitrocellulose, metriol trinitrate and a solid selected from the group consisting of cyclotrimethylenetrinitramine and cyclotetramethylenetetranitramine.

8. The slurry of claim 7 wherein the plastisol nitrocellulose is present in an amount of from about 5 to about 50 percent by weight and the metriol trinitrate is present in an amount of from about 30 to percent by weight of the total mixture.

References Cited UNITED STATES PATENTS 2,852,359 9/1958 Achilles l4996 X 3,222,233 12/1965 Matuszko et al. l4996 X 3,317,361 5/1967 Hopper et a1. l4996 X 3,236,702 2/1966 Sapiego l4996 X 3,284,253 11/ 1966 Enders et a1 1499'6 X 3,325,571 6/1967 Sapiego l4996 X 3,346,675 10/ 1967 Sapiego l4996 X 3,523,841 8/1970 Knight l4996 X STEPHEN J. LECHERT, JR., Primary Examiner U.S. Cl. X.R.