US3637444A

US3637444A - Process of making deterrent-coated and graphite-glazed smokeless powder

Info

Publication number: US3637444A
Application number: US816023A
Authority: US
Inventors: John O Bonyata; Lynn G Rohrbaugh
Original assignee: Hercules LLC
Current assignee: Hercules LLC
Priority date: 1969-04-14
Filing date: 1969-04-14
Publication date: 1972-01-25
Anticipated expiration: 1989-01-25

Abstract

An improved process for manufacture of deterrent-coated and graphite-glazed smokeless powder is provided with deterrent coating and graphite glazing being done in an aqueous slurry at elevated temperatures.

Description

United States Patent 1151 3,637,444

Bonyata et a1. [45] Jan. 25, 1972 54] PROCESS OF MAKING DETERRENT- 32 333 172/195; Woodbridge 149 9 19 Wagner 149/10 2,113,418 4/1938 Woodbridge ....149 10 SMOKELESS POWDER 2,152,509 3/1939 Troxler ....149/10 [72] inventors: John 0. Bonyata, Mountain Lakes; Lynn 11791312 11/1939 Allison Rohrbaugh Lake Hopatcong, both of 2,346,125 4/1944 Goodyear. ....149/ 10 I N1 2,440,267 4/1948 Hale ..l49/l0 2,407,967 9/1946 Thomson.. ..149/9 [73] Assigneez Hercules Incorporated, Wilmington, Dei. 2 3 5 723 2 195 Cook 149 10 [22] Filed: AP 14, 1969 3,506,505 4/1970 Herzog et a1 ..149/9 [21] Appi. No; 816,023 Primary Examiner-Car! D. Quarforth Assistant Examiner-Stephen J. Lechert, Jr. [521 11.5.0 ..149/10,149/9, 149/11, Gramswwa" 51 1111.01. ..C06b 19/02 [57] ABSTRACT [58] Field of Search 14 /100, 7, ll, An improved process for manufacture of deterrent-coated 1 /1 264/3 and graphite-glazed smokeless powder is provided with deterrent coating and graphite glazing being done in an aqueous [56] References Cited slurry at elevated temperatures.

UNITED STATES PATENTS 20 Claims, No Drawings 1,393,623 1 0 1 921 Henning 149/9 PROCESS OF MAKING DETERRENT-COATED AND GRAPHITE-GLAZED SMOKELESS POWDER This invention relates to a process for manufacture of smokeless powder in which each of the processing steps of nitrocellulose densification, deterrent coating, and graphite glazing can be performed in an aqueous slurry. More particularly this invention relates to an aqueous slurry process for rapidly deterrent coating and graphite glazing of granulated nitrocellulose particles. In still another aspect, this invention relates to an aqueous slurry process for manufacture of deterrent-coated and graphite-glazed double-base smokeless powder from a single-base type of granulated nitrocellulose in which all of the processing steps are conducted in an aqueous slurry.

The conventional process for manufacture of smokeless powder involves as a first step the granulation of nitrocellulose. In this process water-wet nitrocellulose is dehydrated with denatured alcohol in a blocking press. The resulting dehydrated nitrocellulose is broken up in the blocking press and subsequently masticated in a large mixer by the addition of solvents such as denatured ethyl alcohol and acetone to form a homogeneous stiff dough. Energetic plasticizers such as nitroglycerin are admixed with the dough if a double-base composition comprised of nitroglycerin and nitrocellulose is to be made. The stiff dough is blocked in large hydraulic presses and subsequently extruded at high pressure into strands of powder. The strands of powder are cut into a desired length. These particles are then dried for several days to remove processing solvents and water. The particles of powder produced are referred to herein as smokeless powder. Some of these dried particles can be coated with various buming rate deterrents if desired in order to obtain progressive burning smokeless powder. The coated smokeless powder particles or granules are dried and then glazed with graphite to prevent the build up of a static charge on the granules and to increase ease of handling.

The foregoing process is tedious, requires considerable amounts of massive and expensive equipment and requires much skilled labor in order to produce a quality product. Over the years numerous attempts have been made to develop processes to obviate one or more of the processing difficulties encountered in this process for manufacture of smokeless powder. Many of these processes, sometimes referred to as nitrocellulose densification processes, are directed to alternative methods for granulation of nitrocellulose which eliminate long mixing times, extrusion of doughs, and cutting of strands of powder. One such process is the Ball Powder Process and is disclosed in U.S. Pat. No. 2,027,114. A modification of this process is disclosed in U.S. Pat. No. 2,885,736.

Other processes have been developed for granulation of nitrocellulose in which water wet nitrocellulose is agitated in a slurry to which solvents for the nitrocellulose are added to partially gelatinize the nitrocellulose without dissolution thereof. The solvent is then removed from the slurry producing smooth, hardened, densified nitrocellulose particles. Such processes are described in U.S. Pat. Nos. 2,946,673 and 2,948,601. A recent patent disclosing both a granulation method for fibrous nitrocellulose by a nitrocellulose densification process and a process for manufacture of double base smokeless powder therefrom is U.S. Pat. No. 3,346,675 to J. Sapiego. With the exception of the conventional process all of the foregoing processes have one basic step in common, i.e., that nitrocellulose is granulated through the action on nitrocellulose of one or more solvents for nitrocellulose dispersed in the presence of a nonsolvent for nitrocellulose, such as water.

The product produced from the foregoing granulation processes which are intended to represent the basic prior art process is particles of granulated nitrocellulose. These particles can be deterrent coated, graphite glazed, and converted from single-base particles to double-base particles, (where applicable) with each step performed in an aqueous slurry in accordance with the process of this invention. The process of this invention is particularly suitable for manufacture of smokeless powder from granulated nitrocellulose prepared by a process such as is described in U.S. Pat. No. 3,346,675, so that each step of the process including granulation is performed in an aqueous slurry. However, granulated nitrocellulose in particle form manufactured by the conventional solvent process can be employed. The process of this invention provides a highly safe method for deterrent coating, graphite glazing, and nitroglycerin absorption of granulated nitrocellulose particles since the granulated nitrocellulose is processed in an aqueous slurry in each step.

Broadly, the process of this invention comprises (a) forming a slurry of granulated nitrocellulose particles and water, (b) admixing in the slurry of step (a) a burning rate deterrent or finely divided graphite to form a slurry comprising a continuous phase of water and a dispersed phase of burning rate deterrent or finely divided graphite, (c) heating the slurry to a temperature at which the burning rate deterrent, when present, melts but to at least 150 F. until substantially all of the burning rate deterrent or finely divided graphite adheres to the granulated nitrocellulose particles, and (d) separating smokeless powder from the slurry.

In the deterrent-coating and graphite-glazing steps heretofore described, it has been found that if energetic plasticizers are employed in manufacture of the granulated nitrocellulose particles some of these plasticizers are extracted out of the particles into the water phase of the slurry causing a change in the composition of the resulting coated and glazed smokeless powder. In the process of this invention temperatures of at least 150 F. are required in order to achieve rapid and suitable deterrent coating and glazing. At these temperatures plasticizer extraction rates increase. While powder can be manufactured with an amount of excess plasticizer equivalent to that which would be extracted under a particular set of processing conditions for aqueous slurry deterrent coating and graphite glazing, it is in general undesirable from an economic and process standpoint to do so. To eliminate loss of explosive plasticizer from a powder composition where composition is critical as is often times required, it is necessary to employ in the water in the aqueous slurry an equilibrium concentration of plasticizer. This equilibrium concentration of plasticizer is dependent upon the slurry composition, and the slurry temperature; the equilibrium concentration of nitroglycerin as an energetic plasticizer being preferably from about 0.1 to about 0.3 percent by weight based on the weight of the water in the aqueous slurry. The term equilibrium concentration" is used herein with reference to energetic plasticizer is defined as a concentration of energetic plasticizer in the aqueous slurry at which there is substantially no tendency for the plasticizer to be either absorbed into or extracted from the granulated nitrocellulose particles during the processing cycle. If the granulated nitrocellulose contains no plasticizers, then no extraction problem exists.

In the aqueous slurry process of this invention it may be desired to manufacture a double-base-type smokeless powder from granulated nitrocellulose of the single-base type. In this case, prior to addition of deterrent to the slurry of granulated nitrocellulose and water, an energetic plasticizer is slowly admixed in the slurry at ambient temperature in an amount of from about 5 to about 40 percent by weight, based on the weight of the granulated nitrocellulose. The slurry is then heated to a temperature of from about F. to about F. and is maintained in this temperature range for from onehalf hour to about 4 hours. During this period the energetic plasticizer completely penetrates the granulated nitrocellulose. The quantity of energetic plasticizer that remains in the water phase of the slurry after complete penetration of the plasticizer into the granulated nitrocellulose is the equilibrium concentration of plasticizer. The deterrent coating and graphite glazing steps heretofore described are then performed. The deterrent-coated and graphite-glazed smokeless powder is separated from the aqueous slurry by any suitable means such as decantation or centrifugation and dried.

The following examples will more fully illustrate the aqueous slurry process of this invention. All parts and percentages are by weight unless otherwise specified.

Example 1 illustrates granulation of fibrous nitrocellulose in an aqueous slurry to produce granulated nitrocellulose of the single base type.

EXAMPLE 1 A slurry is prepared in a vessel by admixing 72.5 parts of water and 8.08 parts of fibrous nitrocellulose in the vessel and agitating the admixture with a Cowels high shear agitator having a 12-inch diameter blade operating at 900 r.p.m. To this admixture is added 0.074 part of diphenyl amine and 0.098 part of barium nitrate. The slurry is heated from ambient temperature (68 F.) to 130 F. To the warmed slurry is added 19.42 parts of methyl isobutyl ketone over a period of 19 minutes. About 0.074 part of methyl cellulose is added to the warmed slurry after about one-fourth of the total methyl isobutyl ketone has been added. After all the MIBK is added, the temperature of the slurry is progressively increased to remove methyl-isobutyl ketone as a water azeotrope. Agitation is maintained during solvent removal but is reduced to 500 r.p.m. after the temperature of the slurry has reached 180 F. and been held at that temperature for 75 minutes. Following removal of the solvent, the slurry is cooled to at least 125 F. and centrifuged at 1,400 r.p.m. in a 12-inch diameter basket centrifuge to remove the major portion of the process water. Water-wet densified nitrocellulose particles are recovered having a particle size distribution as set forth in table 1.

The following example illustrates nitroglycerin absorption by granulated nitrocellulose in an aqueous slurry to provide double base type smokeless powder.

EXAMPLE 2 Nitroglycerin Absorption About 8.33 parts of granulated nitrocellulose particles prepared in example 1 are admixed in 100 parts of water at ambient temperature. This admixture is agitated mildly with a propeller agitator to fonn a slurry comprised of a continuous aqueous phase of water and a dispersed phase of densified nitrocellulose. To this slurry is added 2.36 parts of nitroglycerin. The nitroglycerin is dispersed in the slurry and at no time is this dispersion of nitroglycerin in water or the dispersed granulated nitrocellulose particles allowed to settle. Following addition of the nitroglycerin to the slurry, the slurry temperature is rapidly increased to 115 F. and held at that temperature for about 2 hours. During this heating period the nitroglycerin completely penetrates the densified nitrocellulose. The resulting slurry is dewatered in a 12-inch diameter basket centrifuge operating at 1,000 r.p.m. The nitroglycerin content of the water is measured and is about 0.2 percent by weight based on the weight of the water. This represents the equilibrium concentration of nitroglycerin in this slurry. Substantially all nitroglycerin admixed in the slurry is absorbed by and penetrates the granulated nitrocellulose.

The following example illustrates deterrent coating of double base type smokeless powder in an aqueous slurry.

EXAMPLE 3 Deterrent Coating About 10.7 parts (dry bases) of the double-base smokeless powder prepared in example 2 is admixed with 131 parts of water at 68 F. The admixture is mildly agitated in a vessel equipped with a propeller-type agitator. To the resulting slurry is added 0.562 parts of symmetrical diethyl-diphenyl urea (ethyl centralite) in flake powder form corresponding to (MIL-E-ZSS-class 2). The slurry is heated to 175 F. and maintained at this temperature for about 15 minutes. This temperature is slightly above the melting point of the ethyl centralite. Substantially quantitative deposition of the ethyl centralite on the surface of the smokeless powder is achieved during this heating period. The temperature of the slurry is then reduced to 120 F. following the deterrent coating of the granulated nitrocellulose and the slurry is centrifuged. Water wet deterrent coated smokeless powder is recovered containing about 30 weight percent water based on the weight of the water wet powder. The total deterrent-coating operation is completed in less than minutes. The deterrent-coated particles are dried. There is substantially no particle agglomeration in the dried deterrent-coated powder.

The following example illustrates graphite glazing in an aqueous slurry of smokeless powder particles in which granulation, nitroglycerin absorption and deterrent coating are each conducted in an aqueous slurry.

EXAMPLE 4 Smokeless powder is prepared by granulating fibrous nitrocellulose (13.25 percent N) following the procedure of example 1. The granulated nitrocellulose particles are admixed in an aqueous slurry of nitroglycerin following the procedure of example 2 and absorb 16 percent nitroglycerin from the slurry. The resulting double-base granulated nitrocellulose is centrifuged. The wet particles are reslurried in water so that 13.4 parts granulated double-base nitrocellulose particles are dispersed in about 125 parts of water. The slurry is agitated at about 70 F. and 0.53 parts ethyl centralite are admixed therewith. Agitation is maintained to keep the granulated nitrocellulose and ethyl centralite dispersed in the slurry. The aqueous slurry is heated to about 175 F. After 5 minutes of heating at this temperature 0.25 part of colloidal graphite (type GPW, an aqueous paste containing 22 percent by weight solids and sold by Graphite Products Corporation) is added to the slurry. Agitation of the slurry and heating at about 175 F. are continued for an additional 10 minutes. Substantially quantitative deposition of colloidal graphite on the particles is achieved. The resulting slurry of deterrent coated and graphite glazed smokeless powder is cooled to F., centrifuged and dried.

The following example illustrates incomplete nitroglycerin absorption from an aqueous slurry by a singlebase type granulated nitrocellulose manufactured by a solvent densification process.

EXAMPLE 5 About 10.3 parts of nitrocellulose (13.2 percent N) is slurried in gt.68 parts of water. The slurry is subjected to high shear agitation with a Cowels high shear agitator having a 12- inch diameter blade operating at 800 r.p.m. To this admixture is added 0.09 part diphenylamine, 0.113 part barium nitrate, and 0.1 13 part of triphenyl phosphate. The slurry is heated to F. and 21.6 parts of methyl isobutyl ketone is added to the slurry over a 20-minute period. About 0.09 part of methyl cellulose is added to the slurry after addition of one-fourth of the methyl isobutyl ketone. The methyl isobutyl ketone is removed from the slurry as a water azeotrope. The resulting water-wet granulated nitrocellulose is centrifuged. The waterwet granulated nitrocellulose is reslurried in water to form a slurry comprised of 10.7 parts granulated nitrocellulose and 124 parts water. While the slurry is vigorously agitated 1.8 parts of nitroglycerin is added to the slurry. The temperature of the slurry is increased from ambient temperature to 80 F. and held at this temperature for 15 minutes. The resulting mixture is centrifuged at low r.p.m. The water from the centrifuge is sent to a decanter and unabsorbed nitroglycerin recovered. About 55 percent of the nitroglycerin added to the slurry is absorbed by the granulated nitrocellulose. The granulated nitrocellulose recovered has a particle size distribution as set forth in table I.

The following example illustrates complete absorption of nitroglycerin from an aqueous slurry by a single-base type granulated nitrocellulose prepared by a solvent densification process.

EXAMPLE 6 About 8.33 parts of granulated nitrocellulose is prepared following the general procedure as set forth in example 1 with some variations in processing conditions. The resultant granulated nitrocellulose has a particle size distribution and bulk density as set forth in table I. The resulting granulated nitrocellulose, about 8.33 parts, is slurried in 100 parts of water. About 2.36 parts of nitroglycerin is added to the slurry. The slurry is heated to 80 F. and maintained at that temperature for about 15 minutes. After 15 minutes of heating the aqueous slurry becomes substantially clear indicating complete absorption of the nitroglycerin by the granulated nitrocellulose. The slurry is divided into two portions. The water is carefully drained from one portion of the granulated nitrocellulose particles. Only an equilibrium concentration of nitroglycerin is in the decanted water. The second portion of the slurry is mildly centrifuged. The resultant water is very cloudy indicating removal of nitroglycerin from the surface of the granulated nitrocellulose particles.

TABLE I Particle Size Distribution Granulated Nitrocellulose The following example illustrates graphite glazing and deterrent coating of smokeless powder in which the granulated nitrocellulose is made by the conventional solvent process.

EXAMPLE 7 Granulated nitrocellulose in the form of base grain and manufactured by the solvent process in which it is extruded through a 0.065-inch O.D. X 0.0l5-inch [.D. die and curs at 300 cuts per lineal inch is dried and is slurried in water at ambient temperature (65 F.). About 12.6 parts of the granulated nitrocellulose is combined with 153 parts of water. About 0.65 part of Vinsol resin, fully defined hereinafter, is dispersed in the slurry. The slurry which is comprised of a dispersed phase of granulated nitrocellulose and finely powdered Vinsol and continuous phase of water is heated above the melting point of the Vinsol and held at 190 F. for 15 minutes. After this heating cycle the slurry is cooled, filtered and dried in a conventional dry house. The resulting deterrent coated powder is blended with base grain of the same powder composition. Ballistic results for the powder blend are set forth in table II below. Comparison is made with a conventionally deterred powder of the same powder composition.

EXAMPLE 8 Example 7 is repeated with the exception that the cut granulated nitrocellulose (base grain) is not dried but is slurried in water while still water wet and containing about 10 percent by weight of processing solvent based on the weight of dry base grain. About 12.6 parts of the powder (dry basis) are dispersed in 153 parts of water, and 0.65 part of finely powdered Vinsol resin is dispersed in the slurry. The slurry is heated to 190 F. and maintained at that temperature for minutes. The Vinsol resin melts and is deposited on the surface of the granulated nitrocellulose. During this heating period processing solvents in the granulated nitrocellulose are extracted into the water phase of the slurry. The powder is separated from the slurry dried and blended with nondeterred granulated nitrocellulose (base grain) and ballistically tested. Results are set forth in table ll below.

TABLE II [Ballistics aqueous slurry deterred powder] Standard Aqueous slurry deterrent deterrent coating coating Powder process (control) Ex. 7 Ex. 8

Percent Vinsol on base grain 6. 0 5. 0 5. 0 Blend ratio, deterred/base grain 70/30 40/60 40/60 Coating tlme at 190 F. (minutes) 30 15 15 Stability; German test (minutes) 35 50 45 Charge weight in shell, grains 20 20 20 Ballistics:

Velocity, feet/second 1, 206 l, 294 1, 139 Pressure, p.s.i 9, 820 9, 600 9,100

Ballistics on Federal 12 gauge shell 1% ounee#7} shot.

As can be seen from table II the powder blends employing the aqueous slurry deterrent coated powder, examples 7 and 8, require less of the deterrent-coated powder in the blend in order to achieve ballistics substantially the same as a powder blend employing standard deterrent-coated powder. A more uniform coating of powder by the deterrent in the aqueous process of this invention is attributed to this result. Higher German stability values are also obtained with powder obtained by blending deterrent coated powder manufactured by the aqueous slurry process of this invention probably due to increased coating uniformity of the deterrent coated powder.

In the aqueous slurry process heretofore described granulated nitrocellulose to be deterrent coated is slurried in water in an amount to preferably provide a slurry containing from about 8 to about 20 percent granulated nitrocellulose. The slurry is agitated sufficiently to fully disperse the granulated nitrocellulose throughout the water phase of the slurry. The deterrent-coating agent is then admixed with the slurry at a temperature below the melting point of the coating agent. The deterrent-coating agents are employed in powdered or finely divided form and are admixed into the slurry at a temperature below their melting point. The slurry is then heated to a temperature slightly above the melting point of the deterrent but to at least 150 F. The slurry is held at a temperature slightly above the melting point of the deterrent until substantially all the deterrent adheres to the surface of the granulated nitrocellulose, which generally requires about 15 minutes.

Suitable deterrent-coating materials which can be employed include materials which will penetrate the smokeless base grain on prolonged heating such as symmetrical diethyl diphenyl urea (ethyl centralite), symmetrical dimethyl diphenyl urea, solid dinitrotoluene, triphenyl phosphate, and the like.

Other deterrent coatings which can be employed which do not penetrate into the smokeless base grain particle but which are absorbed on to the surface of the particle include Vinsol resin, a dark thermoplastic resin having an acid number of about a softening point of about C.; insoluble in hydrocarbon solvent; soluble in polar solvents, and available commercially under the trademark Vinsol from Hercules lncorporated. This resin is preferably employed in pulverized form. Still other deterrent coating materials which can be employed include glyceryl l2-hydroxy'stearate having an acid number of 2, an iodine value (WIJS) of 29, and a hydroxyl number of about 158; and glyceryl monohydrostearate having an acid number of 3, and iodine value (WUS) of 5, and a hydroxyl number of 320. These materials are available commercially as Castorwax MP-80 and Paracin 13 respectively.

Mixtures of two or more of any of the deterrent coating materials can be employed if desired.

The amount of deterrent coating material which is admixed and dispersed in the aqueous slurry deterrent coating step in the process of this invention will vary depending on the ballistic result desired from a particular powder. In general the amount of deterrent will vary from about 3 lzto about 8 percent by weight, based on the weight of the granulated nitrocellulose. The smokeless powder resulting from deterrent coating of granulated nitrocellulose is referred to as progressive buming smokeless powder.

Graphite glazing of granulated nitrocellulose is accomplished in the same vessel in which deterrent coating is performed. In the glazing step of this process colloidal graphite, granulated nitrocellulose (either deterred or nondeterred) and water are slurried. The slurry is agitated so that it is comprised of a dispersed phase of colloidal graphite and densified nitrocellulose particles and a continuous phase comprised of water. The slurry is heated to a temperature of at least 150 F. and heating and agitation of the slurry is maintained until substantially all of the graphite has adhered to the surface of the smokeless powder.

A preferable procedure of graphite glazing is readily accomplished by simply admixing the graphite in the aqueous slurry during the deterrent coating step. The graphite is preferably added after a substantial amount of deterrent has adhered to the surface of the smokeless powder. This occurs after about the first 5 minutes of heating at a temperature of 150 F. or above. The granulated nitrocellulose to be glazed is slurried in water in an amount to provide a slurry containing from about 8 to about 20 percent densified nitrocellulose. The slurry temperature must be at least 150 F. to obtain a rapid glazing rate. Time required for completion of graphite glazing will vary depending on the temperature of the slurry, glazing rate being faster at higher slurry temperatures. Time required to achieve essentially quantitative deposition of graphite on the granulated nitrocellulose at a slurry temperature of 175 F. is about 10 minutes.

The amount of graphite applied to either deterred or nondeterred smokeless powder is from about 0.1 to about 2.0 percent by weight based on the weight of the granulated nitrocellulose.

In the process of this invention double-base powder can be readily manufactured from granulated nitrocellulose by adding energetic plasticizer to the aqueous slurry of granulated nitrocellulose and water. Nonenergetic plasticizers can be admixed with the energetic plasticizer if desired. The energetic plasticizer is added to the slurry at any rate permissible with respect to safety. Agitation of the slurry must be maintained at a level sufficient to keep the plasticizer and granulated nitrocellulose particles fully dispersed in the water phase of the slurry at all times in order to obtain uniform absorption of the plasticizer by the granulated nitrocellulose. Mild agitation with a propeller or paddle-type agitator is sufficient. The slurry to which the energetic plasticizer is admixed will contain from about 8 to about percent by weight of granulated nitrocellulose and from about 80 to about 92 percent by weight of water.

Time and temperature are important factors in obtaining complete penetration of energetic plasticizers into the granulated nitrocellulose particles. The term complete penetration" as used herein is defined to mean that the energetic plasticizer is not displaced or removed from the densified nitrocellulose following absorption from an aqueous slurry when subjected to vigorous forces such as in centrifugation. This term is contrasted with complete absorption of energetic plasticizer which is defined herein to mean that densified nitrocellulose has absorbed all the energetic plasticizer from the slurry on to its surface, but when subjected to vigorous forces such as centrifugation, a substantial amount of the energetic plasticizer can be removed from the surface of the densified nitrocellulose into the water phase of the slurry. Example 1 illustrates a set of process conditions at which complete penetration of nitroglycerin into the nitrocellulose particles occurs since only an equilibrium concentration of nitroglycerin can be detected in the water resulting from centrifugation of the slurry. It is preferred and critical to processing of large amounts of smokeless powder having specified compositions to have complete penetration of the nitrocellulose by the plasticizer. While absorption of energetic plasticizer by the nitrocellulose will take place in the aqueous slurry at ambient temperature, the rate of absorption is too slow to be practical. Absorption temperatures of from about to about F. for from about one-half hour for the lowest concentration of energetic plasticizer to about 4 hours for the highest concentration of energetic plasticizer will result in complete penetration of the nitrocellulose particles by the plasticizer in accordance with this invention.

Energetic plasticizers which can be absorbed on densified nitrocellulose include nitroglycerin, the nitrate esters of polyhydric alcohols including diethylene glycol dinitrate, ethylene glycol dinitrate, triethylene glycol dinitrate, and the like. Nonexplosive plasticizers can also be employed separately or in admixture with the explosive plasticizers for nitrocellulose. Illustrative of nonexplosive plasticizers which can be employed are triacetin, dibutyl phthalate, tricresyl phosphate, and the like.

The term granulated nitrocellulose as used herein is meant to encompass all types of colloided nitrocellulose particles, the nitrocellulose in all events being characterized by a nitrogen content of at least about 11.3 weight percent, generally in the range of from about l2-13.5 percent, and being in colloided form. As is well known, the single-base particles contain colloided nitrocellulose as the chief component, on the order of from about 85 to 99 weight percent and the double-base particles contain the same colloided nitrocellulose component but together with an energetic plasticizer, usually nitroglycerin, or an equivalent energetic liquid nitric ester. Double-base particles contain generally at least one-half colloided nitrocellulose and substantially the remainder nitroglycerin with other supplemental ingredients. Granulated nitrocellulose particles of the triple-base type contain nitroguanidine in addition to colloided nitrocellulose, and nitroglycerin in proportions generally at least about 40 to 50 percent nitroguanidine and substantially the remainder colloided nitrocellulose and nitroglycerin, the latter two being in any suitable relative proportions, for example 1:1 to 4:1 of nitrocellulose to nitroglycerin.

Minor amounts of supplemental ingredients are utilized in these particles, particularly stabilizing agents, gelation agents, and the like, all of which are well known in the art.

What we claim and desire to protect by Letters Patent is:

1. In the process of manufacture of burning rate deterrentcoated or graphite-glazed smokeless powder from at least granulated nitrocellulose the improvement comprising:

a. forming a slurry of at least granulated nitrocellulose particles and water,

b. admixing in the slurry of step (a) a burning rate deterrent or finely divided graphite to form a slurry comprising a continuous phase comprising water, and a dispersed phase comprising burning rate deterrent or finely divided graphite and granulated nitrocellulose,

c. heating the slurry to a temperature at which the burning rate deterrent, when present, melts but to at least F. until substantially all of the burning rate deterrent or finely divided graphite adheres to the granulated nitrocellulose particles, and

d. separating burning rate deterrent-coated or graphiteglazed smokeless powder from the slurry.

2. The process of claim 1 wherein the slurry of step (a) is comprised of from about 8 to about 20 percent by weight of granulated nitrocellulose and from about 92 to about 80 percent by weight of water.

3. The process of claim 2 wherein the granulated nitrocellulose is double-base smokeless powder particles.

4. The process of claim 2 wherein the granulated nitrocellulose is densified nitrocellulose particles.

5. The process of claim 3 wherein the water in the slurry has dissolved therein in equilibrium concentration of energetic plasticizer, said energetic plasticizer being of the same composition as the energetic plasticizer in the double-base smokeless powder.

6. The process of claim 5 wherein the energetic plasticizer is nitroglycerin.

7. The process of claim 6 wherein the water contains from about 0.1 to about 0.3 percent by weight of nitroglycerin based on the weight of the water.

8. The process of claim 2 wherein a burning rate deterrent is admixed in the slurry of step (b) in an amount of from about 3% to about 8 percent by weight, based on the weight of the granulated nitrocellulose.

9. The process of claim 8 wherein the burning rate deterrent is symmetrical diethyl diphenyl urea.

10. The process of claim 9 wherein the slurry of step (c) is heated to a temperature of about 175 F.

11. The process of claim 8 wherein the burning rate deterrent is a hydrocarbon insoluble, dark thermoplastic resin which is soluble in polar solvents and having an acid number of about 95 and a drop softening point of about 120 C.

12. The process of claim 11 wherein the slurry of step (c) is heated to a temperature of about 190 F 13. In the process of manufacture of burning rate deterrentcoated and graphite-glazed smokeless powder from at least granulated nitrocellulose, the improvement comprising:

a. fonning a slurry of at least granulated nitrocellulose particles and water,

b. admixing in a burning rate deterrent to the slurry of step (a) forming a continuous phase comprising water and a dispersed phase comprising granulated nitrocellulose particles and burning rate deterrent,

c. heating the slurry to a temperature at which the burning rate deterrent melts but to at least 150 F.,

d. admixing finely divided graphite to the heated slurry of step (c) said graphite being dispersed throughout the slurry and maintaining a slurry temperature of at least 150 F. until substantially all the burning rate deterrent and finely divided graphite have adhered to the granulated nitrocellulose, and

e. separating burning rate deterrent-coated and graphiteglazed smokeless powder from the slurry.

14. The process of claim 13 in which the finely divided graphite is admixed in the slurry in an amount of from about 0.1 to about 2 percent by weight based on the weight of the granulated nitrocellulose.

15. The process of claim 13 wherein the burning rate deterrent is symmetrical diethyl diphenyl urea.

16. The process of claim 13 wherein nitroglycerin is admixed in the slurry of step (a) in an amount of from about 5 to about 40 percent by weight based on the weight of the granulated nitrocellulose forming a slurry comprising a continuous phase comprising water and a dispersed phase comprising granulated nitrocellulose and nitroglycerin and admixing this slurry until substantially all the nitroglycerin but an equilibrium concentration of nitroglycerin in water has been absorbed by the granulated nitrocellulose.

17. The process of claim 16 in which the slurry of water, granulated nitrocellulose, and nitroglycerin is heated to a temperature of from about F. to about F. for from about 30 to about 240 minutes to permit complete penetration of the nitroglycerin into the granulated nitrocellulose.

18. The process of claim 4 wherein nitroglycerin is admixed in the slurry of step (a) in an amount of from about 5 to about 40 percent by weight based on the weight of the densified nitrocellulose particles forming a slurry comprising a continuous phase of water and a dispersed phase of densified nitrocellulose particles and nitroglycerin and admixing this slurry until substantially all the nitroglycerin, but an equilibrium concentration of nitroglycerin in water, has been absorbed by the densified nitrocellulose particles.

19. The process of claim 19 in which the slurry of water,

densified nitrocellulose particles and nitrogl cerin is heated to a temperature of from about 100 to abou 140 F. for from about 30 minutes to about 250 minutes to permit complete penetration of the nitroglycerin into the densified nitrocellulose particles.

20. In a process for the manufacture of a smokeless powder selected from the group consisting of burning rate deterrentcoated, graphite-glazed, and buming-rate-deterrent-coated and graphite-glazed smokeless powders, from at least granulated nitrocellulose, the improvement comprising:

a. forming a slurry of at least granulated nitrocellulose particles and water,

b. admixing in the slurry of step (a) at least one member selected from the group consisting of a burning rate deterrent and finely divided graphite, to form a resulting slurry comprising a continuous phase comprising water and a dispersed phase comprising granulated nitrocellulose and each member of said group of burning rate deterrent and finely divided graphite admixed with the slurry of step (a) as described,

c. heating the resulting slurry of step (b) at a temperature at which the burning rate deterrent, when present, melts but at at least F. until substantially all of each member of said group of burning rate deterrent and finely divided graphite dispersed therein adheres to the granulated nitrocellulose particles, and

. separating from the slurry of step (c), as product of the process, a smokeless powder selected from said group of burning rate deterrent-coated, graphite-glazed, and buming rate deterrent-coated and graphite-glazed smokeless powders.

mg UNTTED STATES PATENT OFFICE CEHHCA'E @EF I EQ'TWN Patent No. 3,637,444 Dated January 25, 1972 InVentO1(S) Bonyata and Rohrbauqh Case 2 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

- "T Q01. 5, Line 49 of p.p.

"curs" should be "cut" Col. 6, Line 20 (approx.) of p.p.

"1294 should be 1194" Col. 9, Line 22 of p.p.;

"95" should be "95" Col. 10, Line 21 of p.p.;

"Claim 19" should be "Claim 18" Signed and sealed this 3rd day of October- 1972.

(SEAL) Attest:

EDWARD P LFLETCHERJR, ROBERT GUT'ISCHALK Attesting Officer Commissioner of Patents @2 3 UNTTED STATES PATENT OFFICE CERTIFICATE Gd CORRECTWN Patent No. 3,637,444 Dated n ry 25, 1972 Inventor(s) Bonyata and Rohrbauqh Case 2 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 5, Line 49 of p.p.

"curs" should be "cut" Col. 6, Line 20 (approx.) of p.p.;

"1294" should be "1194" Col. 9, Line 22 of p.p.;

"95" should be 95" Col. 10, Line 21 of p.p.;

fClaim l9 should be "Claim 18" Signed and sealed this 3rd day of October 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GUTTSCHALK Attesting Officer Commissioner of Patents

Claims

2. The process of claim 1 wherein the slurry of step (a) is comprised of from about 8 to about 20 percent by weight of granulated nitrocellulose and from about 92 to about 80 percent by weight of water.
3. The process of claim 2 wherein the granulated nitrocellulose is double-base smokeless powder particles.
4. The process of claim 2 wherein the granulated nitrocellulose is densified nitrocellulose particles.
5. The process of claim 3 wherein the water in the slurry has dissolved therein in equilibrium concentration of energetic plasticizer, said energetic plasticizer being of the same composition as the energetic plasticizer in the double-base smokeless powder.
6. The process of claim 5 wherein the energetic plasticizer is nitroglycerin.
7. The process of claim 6 wherein the water contains from about 0.1 to about 0.3 percent by weight of nitroglycerin based on the weight of the water.
8. The process of claim 2 wherein a burning rate deterrent is admixed in the slurry of step (b) in an amount of from about 3 1/2 to about 8 percent by weight, based on the weight of the granulated nitrocellulose.
9. The process of claim 8 wherein the burning rate deterrent is symmetrical diethyl diphenyl urea.
10. The process of claim 9 wherein the slurry of step (c) is heated to a temperature of about 175* F.
11. The process of claim 8 wherein the burning rate deterrent is a hydrocarbon insoluble, dark thermoplastic resin which is soluble in polar solvents and having an acid number of about 95* and a drop softening point of about 120* C.
12. The process of claim 11 wherein the slurry of step (c) is heated to a temperature of about 190* F.
13. In the process of manufacture of burning-rate-deterrent-coated and graphite-glazed smokeless powder from at least granulated nitrocellulose, the improvement comprising: a. forming a slurry of at least granulated nitrocellulose particles and water, b. admixing in a burning rate deterrent to the slurry of step (a) forming a continuous phase comprising water and a dispersed phase comprising granulated nitrocellulose particles and burning rate deterrent, c. heating the slurry to a temperature at which the burning rate deterrent melts but to at least 150* F., d. admixing finely divided graphite to the heated slurry of step (c) said graphite being dispersed throughout the slurry and maintaining a slurrY temperature of at least 150* F. until substantially all the burning rate deterrent and finely divided graphite have adhered to the granulated nitrocellulose, and e. separating burning-rate-deterrent-coated and graphite-glazed smokeless powder from the slurry.
14. The process of claim 13 in which the finely divided graphite is admixed in the slurry in an amount of from about 0.1 to about 2 percent by weight based on the weight of the granulated nitrocellulose.
15. The process of claim 13 wherein the burning rate deterrent is symmetrical diethyl diphenyl urea.
16. The process of claim 13 wherein nitroglycerin is admixed in the slurry of step (a) in an amount of from about 5 to about 40 percent by weight based on the weight of the granulated nitrocellulose forming a slurry comprising a continuous phase comprising water and a dispersed phase comprising granulated nitrocellulose and nitroglycerin and admixing this slurry until substantially all the nitroglycerin but an equilibrium concentration of nitroglycerin in water has been absorbed by the granulated nitrocellulose.
17. The process of claim 16 in which the slurry of water, granulated nitrocellulose, and nitroglycerin is heated to a temperature of from about 100* F. to about 140* F. for from about 30 to about 240 minutes to permit complete penetration of the nitroglycerin into the granulated nitrocellulose.
18. The process of claim 4 wherein nitroglycerin is admixed in the slurry of step (a) in an amount of from about 5 to about 40 percent by weight based on the weight of the densified nitrocellulose particles forming a slurry comprising a continuous phase of water and a dispersed phase of densified nitrocellulose particles and nitroglycerin and admixing this slurry until substantially all the nitroglycerin, but an equilibrium concentration of nitroglycerin in water, has been absorbed by the densified nitrocellulose particles.
19. The process of claim 19 in which the slurry of water, densified nitrocellulose particles and nitroglycerin is heated to a temperature of from about 100* to about 140* F. for from about 30 minutes to about 250 minutes to permit complete penetration of the nitroglycerin into the densified nitrocellulose particles.
20. In a process for the manufacture of a smokeless powder selected from the group consisting of burning-rate-deterrent-coated, graphite-glazed, and burning-rate-deterrent-coated and graphite-glazed smokeless powders, from at least granulated nitrocellulose, the improvement comprising: a. forming a slurry of at least granulated nitrocellulose particles and water, b. admixing in the slurry of step (a) at least one member selected from the group consisting of a burning rate deterrent and finely divided graphite, to form a resulting slurry comprising a continuous phase comprising water and a dispersed phase comprising granulated nitrocellulose and each member of said group of burning rate deterrent and finely divided graphite admixed with the slurry of step (a) as described, c. heating the resulting slurry of step (b) at a temperature at which the burning rate deterrent, when present, melts but at at least 150* F. until substantially all of each member of said group of burning rate deterrent and finely divided graphite dispersed therein adheres to the granulated nitrocellulose particles, and d. separating from the slurry of step (c), as product of the process, a smokeless powder selected from said group of burning-rate-deterrent-coated, graphite-glazed, and burning-rate-deterrent-coated and graphite-glazed smokeless powders.