US3855373A

US3855373A - New process for making nitrocellulose base propellants

Info

Publication number: US3855373A
Application number: US00419828A
Authority: US
Inventors: J Swotinsky; O Colitti; J Confides
Original assignee: United States Department of the Army
Current assignee: United States Department of the Army
Priority date: 1972-09-19
Filing date: 1973-11-28
Publication date: 1974-12-17
Anticipated expiration: 1991-12-17

Abstract

A new process for fabricating mitrocellulose base propellants which possesses the unique burning rate characteristics associated with propellants produced by the known solventless process but having superior physical strength characteristics. The invention combines selected steps of both the solventless and solvent processes.

Description

United States Patent [191 Swotinsky et a1.

[ Dec. 17, 1974 NEW PROCESS FOR MAKING NITROCELLULOSE BASE PROPELLANTS Inventors: Jacob M. Swotinsky, Morris Plains; ()lindo A. Colitti, Parsippany, both of N.J.; James ,1. Confides, Chambersburg, Pa.

Assignee: The United States of America as represented by the Secretary of the Army, Washington, DC.

Filed: Nov. 28, 1973 Appl. No.: 419,828

Related US. Application Data 3,093,523 6/1963 Besser 149/100 X 3,103,458 9/1963 Besser et al 149/98 X 3,280,746 10/1966 Brown 149/98 3,422,170 1/1969 Brooks et a1... 149/18 x 3,447,983 1/1969 Camp et a1. 149/18 X 3,450,583 6/1969 Chaille et al i i v 149/18 3,673,286 6/1972 Remaly et al. 264/3 B X Primary Examiner-Leland A. Sebastian Assistant Examiner-P. A. Nelson Attorney, Agent, or Firm-Edward J. Kelly; Herbert Berl; A. Victor ERkkila [57] ABSTRACT A new process for fabricating mitrocellulose base propellants which possesses the unique burning rate characteristics associated with propellants produced by the known solventless process but having superior physical strength characteristics. The invention combines selected steps of both the solventless and solvent processes.

4 Claims, 3 Drawing Figures PROPELLANT PREPARED BY SOLVENTLESS SOLVENT PROCESS BURNING RATE IN/ SEC wow- PRESSURE I000 PSI Pmmnznnt 71914 $108,373

PROPELLANT PREPARED BY 0 STANDARD SOLVENTLESS PROCESS 5, 1.5 E u; 145 F F OF FIG. 1 i 1.0 7

D 9 E 2 II 3 .7 m 1 2 s 4 PRESSURE, 1000 PSI PROPELLANT PREPARED BY STANDARD SOLVENT PROCESS 3 1 5 140F or g 70F 0 -40 F FIG. 2 E 1.0 I v .9 g .s I 5 z: .7 D .6

PRESSURE, 1000 PSI PROPELLANT PREPARED BY U SOLVENTLESS -SOLVENT PROCESS w 1.5 In

145F FIG 3 5 9 40F 5 z .8 g .7 m 1 2 3 '4 NEW PROCESS FOR MAKING NITROCELLULOSE BASE PROPELLANTS This is Continuation of application Ser. No. 290,286, filed 19 Sept. 1972, now abandoned, which was a continuation of application Ser. No. 80,611, filed 14 Oct. 1970, now abandoned.

The invention described herein maybe manufactured, used and licensed by or for the Government for Governmental purposes without the payment to us of any royalty thereon.

This invention relates to a new process of producing propellants which may be employed in the specialized propulsion equipment in use today.

Since World War ll, extruded nitrocellulose base propellants have been widely used in small diameter solid-rocket propulsion systems. There are basically two methods employed to manufacture this family of propellants.

The first of these methods utilized is a solvent process. In this method, the nitrocellulose is combined with both explosive and fuel type plasticizers and treated with solvents to produce a colloided mass. Ballistic modifiers and stabilizers are added and the mixture is consolidated in a hydraulic press. The resultant mass is then extruded into solid, single perforated or multi-perforated strands and cut to a prescribed grain length. The green grains are then cured at elevated temperature to remove the solvents.

The second method utilized to prepare this class .of propellants is called the solventless process. In this process, all constituents are combined in a water slurry. Ballistic modifiers and stabilizers are initially suspended or dissolved in a fuel type plasticizer and this mixture, along with the explosive plasticizers, is combined with the nitrocellulose that has previously been dispersed in water. A partial colloid is achieved during wringing and drying processes that reduce the moisture content to about percent. A colloid is subsequently formed, when the moist part is worked and cured first on a heated differential roll mill and then on a heated even speed roll mill. The resulting homogeneous propellant sheet is then consolidated and extruded to the required rocket charge geometry in a hdyraulic extrusion press. A final machining operation is performed to reduce the charge to the desired grain-length.

, Propellants produced by the above processes offer a wide variety of physical and ballistic properties. Although there is some flexibility in tailoring the physical properties of the propellants produced with each method, by varying the ratio of nitrocellulose binder to plasticizer, the solvent process inherently produces the stronger propellant. On the other hand, a unique phenomenon associated with extruded nitrocellulose base propellants, which has been produced by the solventless process, as opposed to the solvent process, is the ability to accurately control their burning rate characteristics by the homogeneous incorporation of certain metallic salts in the propellant matrix. These additives alter the normally exponential burning rate versus pressure relationship so that the burning rate of the propellants will remain nearly constant, or may even decrease, as the pressure increases over a finite pressure range. This also results in a decrease in the variation of burning rate with temperature. This phenomenon has been successfully exploited by the rocket propulsion industry during the past two decades.

Through the years, certain rocket propulsion applications have required the ballistic properties offered by propellants manufactured by the solventless process but, because of the environment to which the propulsion system is exposed, including; internal pressure, ac-

celeration, rough handling and temperature cycling, 3

the physical properties offered by a solvent processed formulation were found to be necessary. Furthermore, a solvent extruded propellant was needed because the ballistic performance requirements of the rocket system called for a small diameter, thin web, propellant charge. One specific system that has such specialized requirements is the propulsion system for a missile of a certain new antitank weapon. This propulsion system requires a propellant with the ballistic properties achieved through preparation by the solventless process in conjunction with the increased physical strength normally associated-with a propellant produced by the solvent process. In addition, when specific ballistic properties were required to be produced and accurately controlled through the use of certain organometallic, salts, prior art processes could not employ any solvent because of the detrimental effect of solvents on the ballistic properties.

The subject invention answers the needs of the art as described above, with special emphasis on the production of a propellant having the properties desired for the high performance necessary in specialized propulsion equipment.

It is, therefore, an object of this invention to provide a process of making a nitrocellulose base propellant for use in the specialized propulsion equipment employed today.

Another object is to provide a'process for making a propellant having the physical strength and ballistic characteristics generally desired by propulsion systems designers.

A further object is to provide a process for use in making a propellant having a combination of properties not available in propellants produced by prior art processes.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same become better understood by reference to the following description.

In conformity with the above stated objects, in the process of this invention, a propellant having the advantages heretofore described may be produced by first dispersing in water, in proper sequence, the following ingredients; viz., nitrocellulose, stabilizer, plasticizer, additives and extrusion lubricant. This latter step should be followed by removing a portion of the water and blending in ballistic modifiers. The resultant mass is then partially colloided by rolling into a thin sheet.

This initial part of the process produces a homogene ous distribution of the ballistic modifiers which in turn results in superior ballistic properties in the propellant. The next part of the process is accomplished by cutting the sheet into small pieces, saturating the pieces with a volatile organic solvent or solvent mixture to effect complete gelatinization and mixing until a mass of semi-dry, crumbly, discrete particles are produced, at which time the resulting mass is extruded into the desired shape and cut when dry.

One of the effects of this invention is to provide a new method for producing high impulse, low smoke, low muzzle flash propellants which exhibit modified burning rate ballistic characteristics and which can be extruded into the final shape necessary for a weapon system. Propellants processed in this manner obviate the need for a series of thin discs formed from sheet propellants. The necessity for using either inert spacers between the discs with an attendant weight disadvantage, or embossed discs with their inherent structural weakness has been eliminated. The propellants formed by the process of this invention provide a structurally strong grain much less vulnerable than previous propellants to premature break up prior to burn out. By the use of this invention a weapon system can be made lighter and more reliable, thus increasing its efficiency. Another effect of this invention is to producea very thin web propellant having mesa burning rate ballistic characteristics and high structural strength at a practical extrusion rate.

The stabilizers which can be utilized to advantage with this invention are any compounds or mixture of compounds which prevent the decomposition of nitrocellulose while not interfering with the ballistic or structural properties of the final propellant, for example; diphenylamine, 2-nitrodiphenylamine, ethyl centralite and N-methyl p-nitroaniline.

Plasticizers that may be used to advantage include both explosive types such as nitroglycerin, diethylene glycol dinitrate, triethylene glycol dinitrate, 1,2,4-

'butanetriol trinitrate, trimethylolethane trinitrate and other common polyhydroxylic compounds that form nitrate esters and fuel types such as glycerol triacetate, esters such as dimethyl phthalate, diethyl phthalate, din-butyl phthalate, di-octyl phthalate and analogous adipate and sebacate compounds and nitro compounds such as dinitrotoluene.

Additives may be used in small quantities to produce desired effects, for example, a small amount of carbon black can be used beneficially as an opacifying agent. Any common extrusion lubricant such as candelilla wax can be used.

Ballistic modifiers, to produce the desired mesa or plateau, burning rate vs pressure relationship, will depend on the relationship desired and on the nature and amount of the constituents used in the propellant. For

example n-lead beta resorcylate, monobasic cupric salicylate. lead salicylate, lead 2 ethyl hexoate and lead stearate have been used advantageously with our invention.

The solvent system for use with our invention is governed largely by empirical criteria. It must be capable of final gelatinization of the propellant, principally the nitrocellulose portion of the propellant. The degree of final gelatinization must be balanced between required structural strength, including internal cohesion, in the final propellant grain and required rheological properties necessary for extrusion. In the process of our invention, the solvents used are divided into active and inactive categories based on their relative ability to gelatinize nitrocellulose. Active solvents include: ketones of six carbons or less, for example acetone, methyl ethyl ketone, methyl isobutyl ketone and methyl isoamyl ketone; alcohols of six carbons or less such as methyl. alcohol, ethyl alcohol, isopropyl alcohol and isoamyl alcohol; esters of seven carbons or less such as ethyl acetate, isopropyl acetate, ethyl propionate, ethyl isobutyrate and amyl acetate. Inactive solvents include: lower aromatic hydrocarbons such as benzene, xylene and toluene; short chain liquid alkanes of between six and 10 carbon atoms such as heptane, hexane and isooctane and ethers of four to six carbons such as diethyl ether, dipropyl ether, methyl normal propyl ether and ethyl isopropyl ether. The choice of the solvent system to be used with our invention is governed in part by the amount of nitrocellulose, bythe percentage of nitrogen in the nitrocellulose, by the amount and nature of the plasticizer used and by the chemical and physical properties of the solvent. Certain mixtures of solvents have been used to advantage. in general an active solvent is combined with an inactive solvent to achieve final gelatinization of the propellant. The ratio of active solvent to inactive solvent may be varied to achieve optimum results.

Solvents which may be used advantageously with our invention are listed in Table 1 along with the variable ratios which may be used. The ratios are expressed in integers representing parts by weight.

Table l Solvent Systems Which May be Used for Final Gelatinization The total solvent weight necessary to accomplish final gelatinization of the propellant in the processof our invention is a function of the nature of the solvent system and the nature of the propellant. Generally the total solvent weight which may be used advantageously with our invention varies from about 10 by weight to percent by weight based on the weight of the propellant. For example, if the benzene/acetone system were used in a ratio of 1 to l by weight the total solvent weight based on the propellant weight could be as low as about 10% whereas if the ratio were 6 parts benzene to 1 part acetone by weight, the total solventweight could be as high as 80 percent.

More specifically, the process of this invention, which may be used to produce a propellant having the properties desired, is set forth in the following examples.

EXAMPLE 1 245 lbs. of nitrocellulose containing about 12.6 per cent nitrogen are added to a slurry mix tank containing 300 gallons of water preheated to about F'. The conventional slurry mix tank contains a double inverted-cone agitator and sufficient agitation is maintained therein during the addition of the desired ingredients to obtain a uniform suspension of the ingredients in water. Ten pounds of 2-nitrodiphenylamine is then added while agitation is continued until suspension is complete, which usually requires about 10 minutes, at which time 208 lbs. of nitroglycerine and 16.5 lbs. of di-n-propyladipate are added to the tank. The speed of agitation during this period is increased and continued for approximately 10 minutes to maintain the suspension in water.

At this point in the process, one-half lb. of candelilla wax, which has been dissolved in 1 pound of methanol and homogenized with water, is then added to the slurry above and mixed for an additional 30 minutes. The final slurry resulting from the above stage of the process is then pumped into a centrifuge, and water is removed until a moisture content of approximately 20 per cent is achieved.

The wet paste is removed from the centrifuge, transferred to canvas bags which are then placed on racks in a forced air dry house and dried at about 130F. for 48 hours to a moisture content of between 8 and 12 per cent. The semi-dried paste resulting from the above procedure is then added to a blender and 12.5 lbs. of each of the ballistic modifiers desired, in this example, monobasic cupric salicylate and n-lead beta resorcylate, are added to the mass. The mix is then blended for about 15 minutes to insure a uniform dispersion of the ballistic modifiers throughout the mass. The resulting blended mass is then transferredto a differential-speed roll mill in 8 pound increments and milled-for approximately 3 to 4 minutes on rolls heated to about 210F.,

producing a colloided propellant sheet which is then cut and removed from the mill. At this point, 3 sheets resulting from the differential-speed roll mill are combined on an even-speed roll mill operating at about 11 rpm speed and heated to about 150F. Three to five passes through the mill are generally required to produce a wholly formed, blister free sheet of 0.060 to 0.090 inches thickness.

The sheet, as it is produced by the latter mill, is then cut into approximately 2-inch squares and placed in containers equipped with air-tight lids. A solvent mixture of 3 parts by weight of benzene and 1 part by weight of acetone is then added to the containers, and the containers are sealed to prevent evaporation. The solvent mixture is added to each container in an amount of about 30 percent by weight of the propellant contained. A sufficient number of propellant squares are added to each container in the above stage to insure a uniform solvent wetting throughout each of the propellant squares. This avoids formation of a single mass of propellant which is excessively wet on the surface, but is not wet internally. Uniform wetting of the propellant is critical for the preparation of a mix of the proper consistency for extrusion. The propellant should be allowed to soften in solvent for 16 to 24 hours accompanied with manual mixing to promote wetting of thepropellant by the solvent. Care should be exercised in opening and resealing each of the containers during these periods of mixing to minimize loss of solvent.

The wetted propellant squares, which have been softened, are added in increments to a standardhorizontal Baker-Perkins sigma-blade mixer and mixed until the entire batch of propellant reaches a proper consistency for extrusion. This generally requires 6 to 8 hours of mixing and during this period the mixer should be stopped at intervals of l to 2 hours in order to scrape down th sides of the mixer and to examine the propellant consistency. The water temperature in the jacket of the mixer should normally be between 70 and 80F. At the end of the mixing stageof the process, the propellant should appear dry and crumbly but pliable to the touch. In any case, the mix cycle should not be terminated until the propellant reaches a dry consistency to minimze shrinkage and distortion during the drying cycle. Additional solvent mixture may be added, in the ratio described, at any time if the mix becomes too dry.

The propellant is then screened and reconsolidated into a solid slug in a solvent extrusion press assembled with a suitable adapter. The slug is then cut to the appropriate length and extruded in a solvent extrusion press equipped with an appropriate die and pin assembly. The pressure of extrusion is generally between 1,000 and 1,500 psi with an extrusion rate of 15 to 25 inches per minute for a thin-walled tubular propellant grain having an outside diameter of 0.240 inches and web of 0.040 inches.

The propellant, which is wet with solvent, is now placed in flat trays and dried in air for about 2 days at about 20C. and about 3 days at about 45C. At this point, should the volatile content of the propellant exceed 1.2 percent, the propellant should be further dried at about 45C. until an acceptable volatile content is obtained.

The cured propellant is then removed from the controlled atmosphere and allowed to cool to room temperature, at which time the propellant is cut to the desired length.

EXAMPLE 2 The process steps were performed in a manner similar to those of Example 1 except for the propellant composition and the solvent system which were varied.

PROPELLANT COMPOSITION percent by weight nitrocellulose (approximately 12.6%N) 50.0% nitroglycerin 34.9% diethyl phthalate 10.5% 2-nitr0diphenylamine 2.0% lead salicylate 1.2% lead Z'ethyl hexoate 1.2% candelilla wax 0.2%

SOLVENT SYSTEM 3 parts by weight of benzene to l .part by weight of ace tone. Total solvent weight to propellant weight was approximately 30 percent.-

EXAMPLE 3 The process steps were performed in a manner similar to those of Example 1, the propellant composition remaining the same and the solvent system being varied.

SOLVENT SYSTEM Referring now to the drawings, FIGS. 1 through 3 illustrate the burning rate vs. pressure relationship of the propellant composition described in Example 1 using three different methods of preparation. All measurements were done with a Crawford bomb using standard procedures.

More specifically, FIG. 1 shows the pressure versus burning rate relationship associated with the solventless processed propellant of the prior art.

FIG. 2 shows the pressure versus burning rate relationship associated with a propellant of the prior art prepared by the solvent process.

FIG. 3 illustrates the burning rate-pressure relationship for the propellant prepared by the new process of this invention as described in Example 1.

Although the solvent processed propellant in FIG. 2 is formed from the same ingredients as that illustrated in FIGS. 1 and 3, it can be seen that'there is no constancy in burning rate between 2,000 and 3,500 p.s.i. and the variation of burning rate with temperature is more substantial than the variation with both the solventless processed propellant and the new process of our invention.

In the propellant formed by the process of our invention (FIG. 3), the burning rate is relatively constant at different temperatures and shows the same decrease above about 2500 p.s.i. with increasing pressure that is' shown by the solventless process of the art as illustrated in FIG. 1. The unique feature of this propellant is the relatively constant burning rate that occurs between 2000 and 3500 p.s.i. and the small variation of burning rate with temperature even though a solvent system has been used to prepare it.

The physical characteristics of this newly processed propellant are set forth in Table 2, column 2. The strength is equivalent to that which can be provided by conventional solvent processed propellants. These characteristics show a marked increase over similar properties of a solventless processed propellant as shown in Table 2, column 1 prepared with the same components. The solventless processed'propellant, although having desirable ballistic-burning rate characteristics, does not have the necessary physical strength to withstand the forces imposed by new technology.

Table 2 COMPARISON OF PHYSICAL PROPERTIES OF PROSEHSANFS Temperature, "F 145 145 Max. Stress, psi. 478 726 Compression*-% 40.0 56.7 Temperature, F 70 70 Max. Stress, psi. 994 2533 Compression*-% 40.6 50. l Temperature, F 40 -40 Max. Stress, psi. 1 L000 l6,900 Compression*-7( 30.9 41.9

under a maximum load "propellant processed by conventional solventless procedure. "'propcllant processed by process of this invention.

The data which appear in Table 2 above were obtained on a Baldwin-Emery SR-4 Tester. The loading rate for all tests was 1.0 inches/inch/minute on a uniform test sample having an outside diameter of 0.240 inches, a web of 0.04 inches and a length of 0.375 inches.

Thus, it has clearly been demonstrated from a comparison of the reported results that a new propellant processing procedure has been developed which produces a nitrocellulose base propellant of high physical strength while maintaining the unique burning rate characteristics associated with propellants produced by the solventless process.

This new procedure also permits large scale production of thin web, small diameter propellant grains which would not be otherwise feasible due to dangerously high pressures necessary to produce a practical extrusion rate with dry extruded propellants such as those produced by the standard solventless process.

This unique manufacturing process may be applied to any solventless nitrocellulose base propellant formulation to produce a significant increase in physical strength and facilitate fabrication, while retaining the burning rate characteristics of the original solventless processed propellant formulation.

This process can be used to prepare any formulation of nitrocellulose base propellants that encompasses the following range of composition.

4060 percent Nitrocellulose having a nitrogen content of 12.2 to 14.6 percent.

2040 percent Explosive plasticizers 012 percent Fuel type plasticizers 1-8 percent Ballistic modifiers 02 percent Extrusion lubricants 02 percent Stabilizer The solvent mixture defined in Example 1 has been found to be extremely effective however, any solvent mixture which can accomplish final gelatinization of the formulated propellant may be used to advantage with our process. For example; benzene/acetone mixtures may be used in ratios varying from about6 parts by weight of benzene and l part by weight of acetone to about 1 part by weight of benzene and 1 part by weight of acetone. Preferably in our invention the ratios would be between about 4.5 parts by weight of benzene and 1 part by weight of acetone to about 2 parts by weight of benzene and l part by weight of acetone. The optimal ratio for use with our invention is about 3 parts by weight of benzene to 1 part by weight of acetone. Ethyl alcohol/ethyl ether mixtures can be used in ratios varying from about 5 parts by weight of ethyl alcohol and 1 part by weight of ethyl ether to about 1 part by weight of ethyl alcohol and 2 parts by weight of ethyl ether. Preferably in our invention about 4 parts by weight of ethyl alcohol and 1 part byweight of ethyl ether to about 1 part by weight of ethyl alcohol and about 1 part by weight of ethyl ether may be used. The optimum ratio is about 2 parts by weight ofethyl alcohol to 1 part by weight of ethyl ether. Other solvent systems which can be used with our invention include; acetone/ethyl alcohol at a ratio of from about one part by weight of acetone and 2 parts by weight of ethyl alcohol to about 3 parts by weight of acetone and 1 part by weight of ethyl alcohol and ethyl acetate/ethyl alcohol mixtures varying from about 1 part by weight of ethyl acetate and 2 parts by weight of ethyl alcohol to about 3 parts by weight of ethyl acetate and about 1 part by weight of ethyl alcohol. The following solvent systems may also be used to advantage with our invention: methylisobutyl ketone/benzene from about 1 part by weight methyl isobutyl ketone and 2 parts by weight benzene to about 3 parts by weight methyl isobutyl ketone and 1 part by weight benzene. In addition, methyl isoamyl ketone/benzene may be used from about 1 part by weight methyl isoamyl ketone and 2 parts by weight benzene to about 3 parts by weight methyl isoamyl ketone and 1 part by weight benzene.

Process variables can be changed within limits without affecting the final propellant performance. For example; by cutting the finished sheet propellant into smaller pieces the surface area available for softening is increased and the softening time can be reduced from 16 to 24 hours to about 1 to 2 hours. An increase in extrusion pressure increases the rate of extrusion. In our invention, the pressure may be varied between about 500 psi and about 2000 psi, the lower pressure will produce a rate of about inches per minute, the higher pressure a rate of about 100 inches per minute. The extrusion rate also depends on the type and amount of the solvent system used. The method of drying is essentially a slow two step process to prevent solvent entrapment within the finished grains. This procedure encompasses variable times and temperatures depending on the size of the grain and the type and amount of solvent system used. In our invention the first step may be accomplished by drying from about 1 to 4 days at about to 25C, preferably 2 days at C. The second step may be accomplished by drying for 1 to 4 days at 40 to 50C, preferably 3 days at 45C. lfthe temperature is too low the process is not efficient and if the temperature is too high the initial solvent escaping will case harden the outside surface of the grain and entrap the remaining solvent inside of the grain.

We wish it to be understood that we do not desire to be limited to the exact details of construction shown and described, for obvious modification will occur to a person skilled in the art.

We claim:

l. A process for preparing a propellant of high structural strength, which comprises:

a. preparing a colloided propellant composition by the solventless process comprising forming a slurry of nitrocellulose double base propellant ingredients in water, drying said aqueous slurry and subjecting the dried slurry to heated differential rolling to produce said colloided propellant composition;

b. contacting said colloided propellant composition with a liquid organic solvent consisting essentially of a mixture of one part by weight of acetone and between about one and six parts by weight of benzene, the amount of said solvent ranging from about 10 to percent by weight of said propellant ingredients, until said propellant composition is essentially completely gelatinized;

c. mixing the gelatinized propellant composition until a mass of semi-dry, crumbly, extrudable particles is obtained;

d. extruding the particles to the desired shape; and

e. drying the extruded propellant to substantially remove the solvent, whereby a propellant of high structural strength is obtained.

2. The process of claim 1, wherein the propellant ingredients consist essentially of 40-60 percent nitrocellulose of 12.2 to 14.6

nitrogen content 2040 percent explosive plasticizer 0-12 percent fuel type plasticizer l-8 percent ballistic modifier 0-2 percent extrusion lubricant 0-2 percent stabilizer 3. The process of claim 2, wherein the nitrocellulose contains approximately 12.6 percent nitrogen and the explosive type plasticizer is nitroglycerin.

percent 4. The process of claim 1, wherein the ratio of benzene to-acetone in the liquid solvent is about 3:1 and the amount of said solvent is about 30 percent by weight of said propellant ingredients.

Claims

1. A PROCESS FOR PREPARING A PROPELLANT OF HIGH STRUCTURAL STRENGTH, WHICH COMPRISES: A. PREPARING A COLLOIDED PROPELLANT COMPOSITION BY THE SOLVENTLESS PROCESS COMPRISING FORMING A SLURRY OF NITROCELLULOSE DOUBLE BASE PROPELLANT INGREDIENTS IN WATER, DRYING SAID AQUEOUS SLURRY AND SUBJECTING THE DRIED SLURRY TO HEATED DIFFERENTIAL ROLLING TO PRODUCE SAID COLLOIDED PROPELLANT COMPOSITION; B. CONTACTING SAID COLLOIDED PROPELLANT COMPOSITION WITH A LIQUID ORGANIC SOLVENT CONSISTING ESSENTIALLY OF A MIXTURE OF ONE PART BY WEIGHT OF ACETONE AND BETWEEN ABOUT ONE AND SIX PARTS BY WEIGHT OF BENZENE, THE AMOUNT OF SAID SOLVENT RANGING FROM ABOUT 10 TO 80 PERCENT BY WEIGHT OF SAID PROPELLANT INGREDIENTS, UNTIL SAID PROPELLANT COMPOSITION IS ESSENTIALLY COMPLETELY GELATINIZED; C. MIXING THE GELATINIZED PROPELLANT COMPOSITION UNTIL A MASS OF SEMI-DRY, CRUMBLY, EXTRUDABLE PARTICLES IS OBTAINED; D. EXTRUDING THE PARTICLES TO THE DESIRED SHAPE; AND E. DRYING THE EXTRUDED PROPELLANT TO SUBSTANTIALLY REMOVE THE SOLVENT, WHEREBY A PROPELLANT OF HIGH STRUCTURAL STRENGTH IS OBTAINED.

2. The process of claim 1, wherein the propellant ingredients consist essentially of 40-60 percent nitrocellulose of 12.2 to 14.6 percent nitrogen content 20-40 percent explosive plasticizer 0-12 percent fuel type plasticizer 1-8 percent ballistic modifier 0-2 percent extrusion lubricant 0-2 percent stabilizer

3. The process of claim 2, wherein the nitrocellulose contains approximately 12.6 percent nitrogen and the explosive type plasticizer is nitroglycerin.

4. The process of claim 1, wherein the ratio of benzene to acetone in the liquid solvent is about 3:1 and the amount of said solvent is about 30 percent by weight of said propellant ingredients.