US3024143A - Solid propellant compositions - Google Patents

Description

United States atent 3,9Z4,l43 Patented Mar. 6, 1952 fitice 3,024,143 SSLHD PRGRELLANT CQMPOSHTIONS George D. Sammons and Richard C. Doss, Bartlesviile,

Qida, assignors to Phillips letroleurn Company, a corporation of Delaware N Drawing. Filed May 16, 1958, Ser. No. 735,07 Claims. (Cl. 149-19) This invention relates to solid propellant compositions. In one aspect this invention relates to processing aids which can be used in the manufacture of solid propellants. In another aspect this invention relates to additives which can be incorporated in a propellant mix to facilitate the manufacture and/or ballistic properties of the finished solid propellant. In another aspect this invention relates to incorporating certain selected diamine dinitrates in solid propellants.

Solid propellants can be classified with respect to composition as double base type, single base type, and composite type. An example of a double base propellant is ballistite which comprises essentially nitroglycerine and nitrocellulose. Examples of single base propellants are nitrocellulose and trinitrotoluene. Composite type propellants are generally composed of an oxidizer, and a binder or fuel. They may contain other materials to facilitate manufacture or increase ballistic performance such as a burning rate catalyst.

Rocket propellants have achieved considerable commercial importance as well as military importance. Jet propulsion motors of the type in which the propellants of this invention are applicable can be employed to aid a heavily loaded plane in take off. Said motors can also be employed as an auxiliary to the conventional power plant when an extra surge of power is required. Said motors can also be employed to propel projectiles and land vehicles. Said propellants can also be used for uses other than propulsion. For example, they can be used as gas generators in starting devices, power units where a fluid is employed as a motive force, and other applications where a comparatively large volume of gas is required in a relatively short period of time.

Recently, it has been discovered that superior solid propellant materials are obtained comprising a solid oxidant such as ammonium nitrate or ammonium perchlorate, and a rubbery material such as a copolymer of butadiene and a vinylpyridine or other substituted heterocyclic nitrogen base compound, which after incorporation is cured by a quaternization reaction or a vulcanization reaction. Solid propellant mixtures of this nature and a process for their production are disclosed and claimed in copending application Serial No. 284,447, filed April 25, 1952, by W. B. Reynolds and J. E. Pritchard.

Some solid propellant compositions are very difficult, if not impossible, to mix by a dry mix method. Even if other mixing procedures are successful, such as a solvent mixing technique, it is not always possible to extrude the material. It has now been found that when certain selected diamine dinitrates of the type described hereinafter are employed as additives in solid propellant compositions both the mixing and extruding operations are greatly facilitated. In some instances the propellant ingredients can be mixed by a dry mix method and the resulting mix can be extruded if these additives are present, whereas such procedures cannot always be employed in the absence of the addtives. An additional advantage is the increase in burning rate when diamine dinitrates are present Thus, broadly speaking, the present invention resides in propellant compositions comprising an oxidant compopent, a binder component, and a selected diamine dinitrate as defined further hereinafter.

An object of this invention is to provide an improved propellant composition. Another object of this invention is to provide a processing aid for use in the manufacture of solid propellants. Still another object of this invention is to provide a solid propellant having an additive incorporated therein to facilitate the manufacture of, and/or improve the ballistic properties of said propellant. Other aspects, objects, and advantages of the invention will be apparent to those skilled in the art in view of this disclosure.

Thus, according to the invention there is provided a propellant composition comprised of: a base propellant comprising an oxidant component selected from the group consisting of ammonium nitrate and alkali metal nitrates, a binder component comprising a rubbery material selected from the group consisting of natural rubber and synthetic rubbery polymers and mixtures thereof; and from 2 to 20 parts by weight per parts by weight of said base propellant of a diamine dinitrate characterized by the structural formula wherein: R is an alkylene group containing from 4 to 18 carbon atoms wherein at least 2 of said carbon atoms are in a chain between the nitrogen atoms; R is an alkyl group containing from 1 to 4 carbon atoms, which alkyl groups can be alike and unlike; and wherein the total number of carbon atoms in the molecule does not exceed 24.

All diamine dinitrates and similar types of compounds are not operable in the practice of the invention. It has been found, for example, that ethylene diamine dinitrate, N,N,N,N'-tetramethyl1,Z-diaminoethane dinitrate, N,N, N,N-tetramethyl-1,2-diaminopropane dinitrate, and N,N, N',N'-tetramethyl-l,4-diaminobutene dinitrate show very little, if any, improvement in processing when employed in propellant composition of the type herein described. Likewise, diethylenetriamine trinitrate gives very little, if any, effect.

Representative diamine dinitrates which are operable in the practice of the invention include, among others, the following:

N,N,N,N'-tetramethyl-2,3-diaminobutane dinitrate; N,N,N,N-tetramethyl-3,4-diaminohexane dinitrate; N,N,N',N' tetramethyl-l,3-diamino-2-ethylpropane dinitrate; N,N,N',N'-tetramethyl-Z,4-diaminooctane dinitrate; N,N,N,N-tetramethyl-1,3-diaminobutane dinitrate; N,N,N',N'-tetramethyl-1,4-diaminobutane dinitrate; N,N,N',N'-tetramethyl-2,S-diaminohexane dinitrate; N,N,N',N'-tetraethy1-l,S-diaminobutane dinitrate; N,N-dimethyl-N',N-diethyl-1,3-diaminobutane dinitrate; N,N,N,N-tetramethyl-1,5-diamino-octadecane dinitrate; N,N,N',N'-tetra-n-propyl-1,3-diaminobutane dinitrate; N,N,N',N'-tetran-butyl-1,8-diaminooctane dinitrate; N,N,N,N' tetramethyl-1,S-diamino-2,4-dimethylpentane dinitrate; N,N dimethyl N,N diethyl-1,8-diamino-3,6-dipentyloctane dinitrate; N,N dimethyl-N',N-dipropyl-l,10-diamino-2,4,6,8-tetramethyldecane dinitrate; and N,N,N,N'-tetramethyl-1,8-diaminooctane dinitrate.

The amine nitrates employed in the practice of the invention can be prepared by several methods. One method is to react a suitable amine with nitric acid. Another method which can be employed is to form a salt of the amine such as a hydrochloride or an acetate, and then react the amine salt with nitric acid.

The quantity of the diamine dinitrate employed is usually in the range of about 2 to about 20 parts by weight per 100 parts by weight of the base propellant. As used herein and in the claims unless otherwise specified, the term base propellant is defined as the binder component plus the oxidant component.

The rubbery material employed in the binder component of the propellant compositions of the invention can be a natural rubber, a synthetic rubbery polymer, or a mixture of natural rubber and said rubbery polymer. The term rubbery polymer as used herein and in the claims, unless otherwise specified is defined as including all rubbery polymers of olefins and diolefins which are prepared by either mass or emulsion polymerization. Some examples of suitable rubbery polymers are polybutadiene, polyisobutylene, polyisoprene, copolymers of isobutylene and isopreue, copolymers of conjugated dienes with comonomers such as styrene, and copolymers of conjugated dienes with polymerizable heterocyclic nitrogen bases. Said copolymers of conjugated dienes with polymerizable heterocyclic bases comprise a pre* ferred class of rubbery polymers for use in the binder component of the propellants of the invention. A presently preferred rubbery polymer is a copolymer of 1,3- butadiene with Z-methyl-S-vinylpyridine.

Said preferred class of rubbery polymers prepared by copolymcrizing a conjugated diene with a heterocyclic nitrogen base can vary in consistency from very soft rubbers, i.e., materials which are soft at room temperature but will how retraction when relaxed, to those having a Mooney value (ML4) up to 100. The rubbery copolymers most frequently preferred have Mooney values in the range between 5 and 50. The may be prepared by any polymerization methods known to the art, e.g., mass or emulsion polymerization. One convenient method for preparing these copolymers is by emulsion polymerization at temperatures in the range between 0 and 140 F. Recipes such as the iron pyrophosphate-hydroperoxide, either sugar-free or containing sugar, the sulfoxylate, and the persulfate recipes are among those which are applicable. It is advantageous to polymerize to high conversion as the unreacted vinylpyridine monomer is difficult to remove by stripping.

The conjugated dienes employed are those containing from 4 to carbon atoms per molecule and include 1,3-butadiene, isoprene, 2methyl-1,3-butadiene, and the like. Various alkoxy, such as methoxy and ethoxy and cyano derivatives of these conjugated dienes, are also applicable. Thus, other dienes, such as phenylbutadiene, 2,3-dimethyl-1,3-hexadiene, 2-methoxy-3-ethylbutadiene, 2-ethoxy-3-ethyl-1,3-hexadiene, Z-CyanQ-LS-butadiene, are also applicable.

Instead of using a single conjugated diene, a mixture of conjugated dienes can be employed. Thus, a mixture of 1,3-butadiene and isoprene can be employed as the conjugated diene portion of the monomer system.

The polymerizable heterocyclic nitrogen bases which are applicable for the production of the polymeric materials are those of the pyridine, quinoline, and isoquinoline series which are copolymen'zable with a conjugated diene and contain one, and only one,

substituent wherein R is either hydrogen or a methyl group. That is, the substituent is either a vinyl or an alpha-methylviny=l (isopropenyl) group. Of these, the compounds of the pyridine series are of the greatest interest commercially at present. Various substituted derivatives are also applicable but the total number of carbon atoms in the groups attached to the carbon atoms of the heterocyclic nucleus should not be greater than because the polymerization rate decreases somewhat with increasing size of the alkyl group. Compounds where the alkyl substituents are methyl and/or ethyl are available commercially.

4 These heterocyclic nitrogen bases have the formula where R is selected from the group consisting of hydrogen, alkyl, vinyl, alpha-methylvinyl, alkoxy, halo, hydroxy, cyano, aryloxy, aryl, and combinations of these groups such as haloalkyl, alkylaryl, hydroxyaryl, and the like; one and only one of said groups being selected from the group consisting of vinyl and alpha-rnethylvinyl; and the total number of carbon atoms in the nuclear substituted groups being not greater than 15. Examples of such compounds are Z-Vinylpyridine;

2-vinyl-5 -ethylpyridine; Z-methyl-S-vinylpy-ridine; 4-vinylpyridine;

2,3 ,4-trimethyl-5 -vinylpyridine;

3 ,4,5 ,6-tetramethyl-2-vinylpyridine; 3-ethyl-5 -viny] pyridine; 2,6-diethyl-4-vinylpyridine; 2-isopropyl-4-nonyl-5-vinylpyridine; 2meth yl-5 -undecyl3 -vinylpyridine; 2,4-dirnethyl-5 ,6-dipentyl-3 -viuylpyridine; 2-decyl-5-( alpha'methylvinyl) pyridine; 2-vinyl-3 -methyl-5 -ethylpyridine; 2-methoxy-4-chloro-6-vinylpyridine;

3 -vinyl-5-ethoxypyridine;

2-vinyl-4,5-dichloropyridine;

2' alph a-methylvinyl) -4-hydroxy-6-cyanopyridine; 2-vinyl-4-phenoxy-5 -methylpyridine;

2-cyano'5- alpha-methylvinyl) pyridine; 3-vinyl-5-phenylpyridine;

Z-(para-methyl-phenyl -3-vi-nyl-4-methylpyridine;

0 3-vinyl-5-(hydroxyphenyl) pyridine;

2-vinylquinolineg 2-vinyi-4-ethyl quinoline; 3-vinyl-6,7-di-n-propylquinoline;

, 2-methyl-4-nonyl-6-vinylpyridine;

4 alph a-m ethylvinyl -8- do decyl quinoline;

3-vinylisoquinoline;

1,6-dimethyl-3-vinylisoquinoline;

2-vinyl-4-benzylquinoline;

3 -vinyl-5-chloroethylquinoline-3-vinyl-5 ,6-dichloroisoquinoline;

2-vinyl-6-ethoxy-7-methylquinoline;

3 -vinyl-6-hydroxymethylisoquinoline;

any of the well known methods employing well known recipes. Any of the well known GR-S rubbers containing from 1 to 2 and up to about 25 parts of styrene can be used in the practice of the invention. The GR-S rubber designated as 1505 is one preferred copolymer for use in the practice of the invention. GR-S 1505 can be pretax,

pared by copolymerizing 1,3-butadiene with styrene at 41 F. using a sugar free, iron activated, rosin-acid emulsified system. A charge weight ratio of butadiene to styrene is 90/10 and the polymerization is allowed to go to approximately 52 percent completion. The copolymer is then salt acid coagulated and usually has a mean raw Mooney value (ML-4) of about 40. Said copolymers usually have a bound styrene content of about 8 weight percent. Further details regarding the preparation of GR-S rubbers can be found in Industrial and Engineering Chemistry, 40, pages 769-777 (1948), and United States Patents 2,583,277; 2,595,892; 2,609,362; 2,614,100; 2,647,109; and 2,665,269.

The binder contains rubbery polymers of the type hereinbefore described and, in addition, there can be present one or more reinforcing agents, plasticizers, wetting agents, and antioxidants. Other ingredients which are employed for sulfur vulcanization include a vulcanization accelerator, a vulcanizing agent, such as sulfur, and an accelerator activator, such as zinc oxide. The finished binder usually contains various compounding ingredients. Thus, it will be understood that herein and in the claims, unless otherwise specified, the term binder is employed generically and includes various conventional compounding ingredients. The binder content of the propellant composition will usually range from 6 to 40 percent by weight.

A general formulation for the binder component of the propellant composition of the invention is as follows:

Parts by weight Rubber 100 Reinforcing agent 0-50 Plasticizer 0-100 Wetting agent 0-10 Antioxidant 0-3 Vulcanization accelerator 0-5 Sulfur 0-2 Metal oxide 0-5 Reinforcing agents which can be employed include carbon black, wood flour, lignin, and various reinforcing resins such as styrene-divinylbenzene, methyl acrylatedivinylbenzene, acrylic acid-styrene-divinylbenzene, and methyl acrylate-acrylic acid-divinylbenzene resins.

In general, any rubber plasticizer can be employed in the binder compositions. Materials such as Pentaryl A (amylbiphenyl), Paraflux (saturated polymerized hydrocarbon), Circosol-ZXH (petroleum hydrocarbon softener having a specific gravity of 0.940 and a Saybolt Universal viscosity at 100 F. of about 2000 seconds), di(l,4,7- trioxaundecyl) methane, and dioctyl phthalate are suit able plasticizers. Materials which provide a rubber having good low temperature properties are preferred. It is also frequently preferred that the plasticizers be oxygen-containing materials.

Wetting agents aid in deflocculating or dispersing the oxidizer. Aerosol OT (dioctyl ester of sodium sulfosuccinic acid), lecithin, and Duomeen C diacetate (the diacetate of trimethylenediamine substituted by a coconut oil product) are among the materials which are applicable.

Antioxidants which can be employed include Flexamine (physical mixture containing 65 percent of a complex diarylamine-ketone reaction product and 35 percent of N,N'-diphenyl-p-phenylenediamine), phenyl-beta-naphthylamine, 2,2-methylene bis(4-methyl-6-tert-butylphenol), and the like. Rubber antioxidants, in general, can be mployed or if desired can be omitted.

Examples of vulcanization accelerators are those of the carbamate type, such as N,N-dimethyl-S-tert-butylsulfenyl dithiocarbamate and Butyl-Eight. Butyl-Eight is a rubber accelerator of the dithiocarbamate type supplied by the R. F. Vanderbilt Company and described in Handbook of Material Trade Names by Zimmerman and Levine,

1953 edition, as a brown liquid; specific gravity 1.01; partially soluble in water and gasoline; and soluble in acetone, alcohol, benzol, carbon disulfide and chloroform.

It is to be understood that each of the various types of compounding ingredients can be used singly or mixtures of various ingredients performing a certain function can be employed. It is sometimes preferred, for example, to use mixtures of plasticizers rather than a single material.

Oxidizers which are applicable in the solid propellant compositions of the invention are ammonium nitrate and the alkali" metal nitrates. As used herein the term alkali metal nitrates includes sodium nitrate, potassium nitrate, lithium nitrate, caesium nitrate, and rubidium nitrate. Ammonium nitrate is the presently preferred oxidizer. Mixtures of said oxidizers are also applicable. In the preparation of the solid rocket propellant compositions the oxidizers are ground to a particle size preferably within the range between 20' and 200 microns average particle size. The most preferred particle size is from about 40 to about 60 microns. The amount of oxidizer used is a major amount of the total composition and is usually within the range of about 60 to about 94 weight percent of the base propellant, i.e., binder plus oxidizer. When ammonium nitrate is used as the oxidant component it is frequently preferred to use a phase stabilized ammonium nitrate. One method of phase stabilizing ammonium nitrate comprises mixing about 10 parts by weight of-a potassium salt (usually potassium nitrate) with about parts by weight of ammonium nitrate along with some water, heating the mixture to about F., drying, and then grinding the mixture to the desired particle size.

Burning rate catalysts applicable in the invention include ammonium dichromate and metal ferrocyanides and ferricyanides. Ferric ferrocyanides, such as Prussian, Berlin, Hamburg, Chinese, Paris, and milori blue, soluble ferric ferrocyanide, such as soluble Berlin or Prussian blue which contains potassium ferric ferrocyanide, and ferric ferrocyanide which has been treated with ammonia, are among the materials which can be used. Ferrous ferricyanide, Turnbullss blue is also applicable. A particularly effective burning rate catalyst is milori blue, which is pigment similar to Prussian blue but having a red tint and is prepared by the oxidation of a paste of potassium ferrocyanide and ferrous sulfate. Other metal compounds such as nickel and copper ferrocyanides can also be employed. The amount of burning rate catalyst used, in the propellant compositions of this invention is usually in the range of 0 to 15 parts by weight per 100 parts by weight of the base propellant, i.e., oxidant plus binder.

The various ingredients in the propellant composition can be mixed on a roll mill or an internal mixer such as a Banbury or a Baker-Perkins dispersion blade mixer can be employed. The binder forms a continuous phase in the propellant with the oxidant as the discontinuous phase. One procedure for blending the propellant in gredients utilizes a stepwise addition of oxidant ingredient. The binder ingredients are mixed to form a binder mixture and the oxidizer ingredient, having the diamine dinitrate and burning rate catalyst (if one is used) dry blended therewith, is then added to said binder mixture in increments, usually 3 to 5 but more can be used.

After the propellant composition has been formulated as indicated above, or by any other suitable mixing technique, rocket grains can be formed by extrusion.

The curing temperature will generally be in the range between 70 and 250 F., preferably between and 200 F.

The curing time must be long enough to give required creep resistance and other mechanical properties in the propellant. The time will generally range from around three hours, when the higher curing temperatures are employed, to seven days when curing is effected at lower temperatures.

The following examples will serve to further illustrate the invention:

Example I A l,3-butadiene-2-methyl-S-vinylpyridine rubbery copolymer was prepared by emulsion polymerization at 41 F. in accordance with the following recipe:

Parts by weight 1,3 -butadiene 90 1 Fifty-five runs were made using the above polymerization recipe. The latex was masterbatched with 19.5 parts of Philblack A (a trademark of Phillips Petroleum Company for a low abrasion furnace carbon black) per 100 parts of rubber. The black masterbatch was then acid coagulated, washed with water, and dried. The average conversion for these 55 runs was 85 percent in 17.0 hours. The amount of modifier used in each run was in the range of 0.60 to 0.80 part by weight.

Based on 100 parts by weight of rubber. v

Two and one-half parts by weight per 100 parts of rubber of said low-abrasion furnace carbon black was milled into the rubber prepared as described above. This increased the amount of carbon black present to 22 parts/100 parts of rubber.

The above-described composition was then placed in a 0.7 gallon Baker-Perkins mixer and 48 parts per 100 parts of rubber present of liquid polybutadiene was added. Mixing was continued until a uniform binder composition was obtained.

The liquid polybutadiene employed in said binder composition was prepared by mass polymerization using finely divided sodium as the catalyst. Said polybutadiene had the following properties:

Specific gravity, 60/60 F. 0.9059 Density at 60 F., lbs/gal. 7.5 Refractive index, u 1.5174 Iodine number 365-385 Ash, wt. percent 0.05 Color, Gardner 11 Volatile material, wt. percent 1.0 Saybolt Furol viscosity at 100 F 2500 Ingredients employed in two propellant compositions prepared using the above-described binder were as follows:

Parts by weight Composition No Binder (as described above) 7 7 Ammonium nitrate, commercial grade-- 92 88 Ammonium dichromate 1 1 N,N,N,N-tetramethyl-l,3-diaminobutane dinitrate- 4 Total 100 100 was continued 10 minutes after consolidation of each increment and finally 10 minutes under vacuum.

Said propellant compositions were extruded into strands approximately /2" in diameter employing various extrusion pressures. The following extrusion data were obtained:

Extrusion Extrusion rate, pressure on inches/min. propellant,

p.s.i.

Composition N o. 1 (without N,N,N,N-tetramethyl-1,3-diarninobutane dinitrate additive) O. 12, 100 1. 25 14, 500 2 9, 080 Composition N o. 2 (with said additive) 9 12, 100 16 14, 500

Composition No. 1 which did not contain the N,N,N,N-tetramethyl-1,3-diaminobutane dinitrate additive would not extrude at a pressure of 9,680 p.s.i. The data show that at said pressure of 9,680 p.s.i., composition No. 2 containing said additive extruded at the rate of two inches per minute. Composition No. 1 without said additive extruded at a slow rate of 0.75 inch per minute when the pressure was 12,100 p.s.i. while the extrusion rate was nine inches per minute at this pressure for composition No. 2 containing said additive.

Example 11 A /10 butadiene/Z-methyl-5-vinylpyridine rubbercarbon black master-batch was prepared as described in Example I to give a composition containing 22 parts of carbon black per parts of rubber. This composition was placed in a 0.7 gallon Baker-Perkins mixer and 30 parts of di(3,6-dioxadecyl)formal, 5 parts of magnesium oxide, and 3 parts of a physical mixture containing 65 percent of a complex diarylamine-ketone reaction product and 35 percent of N,N'-diphenyl-p-pheylenediamine, based on 100 parts of the rubber, were added. Mixing was continued until a uniform binder composition was obtained.

The binder described above was employed for the preparation of two propellant compositions as follows:

Mixing of the propellant compositions was the same as described for composition No. 2 in Example I. Said compositions were extruded into strands approximately /2 in diameter. The extrusion pressure employed for composition No. 3 was 14,500 p.s.i. For composition No. 4, which contained less dinitrate than composition No. 3, the extrusion pressure was 16,950 p.s.i.

Past experience has shown that propellant compositions like compositions 3 and 4 above, cannot be properly mixed by dry mixing techniques in the absence of the diamino dinitrates of the invention. Such compositions can be mixed (in the absence of said dinitrates) by employing a solvent mixing technique which comprises dissolving the rubbery material of the binder in a suitable solvent such as methylcyclohexane, incorporating the dry ingredients, and then removing the solvent by evaporation. However, the resulting mixtures cannot be extruded but Example III A binder composition, prepared in the manner described in Example II, contained the following ingredients:

Parts by weight Butadiene/2-methyl-5-vinylpyridine copolymer 100 PhilblackA 22 Di(3,6-dioxadecyl)formal 20 Flexamine 2 3 Magnesium oxide 5 Total 150 1 As in Example I.

2 Physical mixture containing 65 percent of a complex diarylamineletone reaction product and 35 percent of N,N-diplienyl-p-phenyleneiamme.

The above-described binder was employed for the preparation of two propellant compositions as follows:

Parts by weight Composition No 5 6 Binder 16. 5 16.5 Ammonium nitrate, commercial grade- 83. 5 83. 5 Ammonium dichromate 4 4 Milori blue 1 2 2 N,N,N,N-tetramethyl-1,3-diaminobutane dinitrate 4 Tom] 110. 0 106. 0

1 A burning rate catalyst widely used in propellants. It is a pigment similar to Prussian blue but having a red tint and is prepared by the oxidation of a paste of potassium ferrocyamde and ferrous sulfate.

Extrusion pressure on propellant, p.s.1. Composition strand 346" strand 3" grain Example IV A binder composition contained the following ingredients:

Parts by weight Butadiene/Z-methyl-5-vinylpyridine copolymer 1 100 Philblack A 22 Di(3,6-dioxadecyl) formal 2O Magnesium oxide 5 Total 147 I As in Example I.

The copolymer was put on a roll mill and the other binder ingredients were added. Milling was continued until a homogeneous composition was obtained. This 19 binder was employed in the following propellant formulations:

Parts by weight Composition No 7 8 Binder 16. 5 16. 5 Ammonium nitrate, commercial grade 83. 5 83. 5 Ammonium dichromate 4 4 Copper chromite 1 4 4 N,N,N,N-tetramethyl-1,3-diaminobutane dinitrate 4 10 Total 112. 0 118.0

1 Harshaw Chemical Company commercial catalyst Cu0202.

Each composition was mixed as follows. The ammonium nitrate, ground to 40 micron average particle size, was dry blended with the ammonium dichromate and copper chromite and this blend was added in increments to the binder on a roll mill. After all of said dry blend had been added, the mixture was cut off the mill, folded, and run through the mill again. The removing from the mill and folding process was repeated five times after which the N,N,N',N'-tetramethyl-1,3- diaminobutane dinitrate was added. After being cut 01? and run through the mill three times (after the addition of the dinitrate) a composition wherein the dry blend ingredients were uniformly dispersed in the binder was obtained.

Strands 7 in diameter were extruded from each of the propellant compositions 7 and 8 and from a control composition prepared in the same manner but without incorporating any N,N,N',N'-tetramethyl-1,3-diamino butane dinitrate. The strands were cured 24 hours at 180 F. and burning rate tests were made. Results were as follows:

Pressure exponent in r=aP where a is a constant, Fe is average chamber pressure, and r is burning rate.

Example V Two additional propellant compositions containing the following ingredients were prepared:

Parts by weight Composition No 9 10 Binder 11 6 Ammonium nitrate 94 N ,N,N 'N -tetramethyl-1,3-diaminobutane dinitrate..- 10

Total 111 The binder compositions were as follows:

Parts by Weight Masterbatch 1 8 6 MgO 1 Di(3,6-dioxadecyl)formal 2 Total 111 6 1 The butadiene/Z-methyl-5-yinylpyridine copolymer. masterbatehed Evith carboin black (22 parts black/100 parts rubber), described in Example was use Composition No. 9 was mixed in the same manner as described in Example I.

Composition No. 10 was prepared as follows. 30 parts by weight of the binder component, cut into approximately A" cubes, was put into 317 parts by weight of methylcyclohexane and the mixture stirred until the binder was dissolved. The resulting solution was placed in a 0.7 gallon Baker-Perkins mixer and the ammonium nitrate was added. Mixing was carried out for approximately minutes at room temperature to disperse the ammonium nitrate in the binder solution. Vacuum was then applied gradually, with continued mixing, until a final vacuum of about 70 mm. of mercury was reached. The temperature was then increased to about 140 F., with continued mixing, and maintained at said temperature for about 25 minutes to complete removal of the solvent. The resulting propellent composition was compression molded.

Burning rate test strands were extruded from composition No. 9 and were cut from composition No. 10. The following results were obtained in burning rate tests on said strands.

The above propellant compositions 9 and 10 show that increased burning rate due to the presence of the dinitrate additives of the invention is not limited to those situations where a burning rate catalyst is present. While the propellant compositions 9 and 10 were not identical, it has been found that the presence of MgO and di(3,6- dioxadecyl)formal makes little, if any, difference in the burning rate of a composition such as the 11/90 and 6/94 base compositions of propellant compositions 9 and 10.

The strand burning tests reported in the above examples were carried out by placing the strands, restricted on all surfaces except one end so as to prevent burning except on said one end, in a bomb and pressuring the bomb to the desired pressure with nitrogen. The bomb was then placed in a temperature bath maintained at 75 F. The strands were then ignited and the time required for the propellant to burn between two fusible wires spaced a known distance apart was recorded. The burning rate was then calculated in inches per second.

As will be apparent to those skilled in the art various other modifications of the invention can be made or followed in view of the above disclosure without departing from the spirit and scope of said invention.

We claim:

1. A solid propellant composition comprising from 60 to 94 weight percent of an oxidant component selected from the group consisting of ammonium nitrate and alkali metal nitrates, and from 6 to 40 Weight percent of a binder component comprising a rubbery material selected from the group consisting of natural rubber, synthetic rubber polymers, and mixtures thereof; and from 2 to parts by weight per 100 parts by weight of the total amount of said binder component plus said oxidant component of a diamine dinitrate characterized by the structural formula wherein: R is an alkylene group containing from 4 to 18 carbon atoms wherein at least 2 of said carbon atoms are in a chain between the nitrogen atoms; R is an alkyl group containing from 1 to 4 carbon atoms, which alkyl groups can be alike and unlike; and wherein the total number of carbon atoms in the molecule does not exceed 24.

2. A propellant composition according to claim 1 wherein said oxidant component is ammonium nitrate.

3. A propellant composition according to claim 1 wherein said rubbery material is natural rubber.

4. A propellant composition according to claim 1 wherein said rubbery material is a copolymer prepared by copolymerizing a conjugated diene containing from 4 to 10 carbon atoms with at least one RI CHZ=C/ substituted heterocyclic nitrogen base selected from the group consisting of pyridine, quinoline, alkyl substituted pyridine and alkyl substituted quinoline wherein the total number of carbon atoms in the nuclear alkyl substituents is not more than 15 and wherein R is selected from the group consisting of a hydrogen atom and a methyl radical.

5. A propellant composition according to claim 4 wherein said copolymer is a copolymer of 1,3-butadiene with 2-methyl-5-vinylpyridine.

6. A propellant composition according to claim 1 wherein said diamine dinitrate is N,N,N,N-tetramethyl- 1,3-diaminobutane dinitrate.

7. A propellant composition according to claim 1 wherein said diamine dinitrate is N,N,-N,N'-tetramethyl- 3,4-diaminohexane dinitrate.

8. A propellant composition according to claim 1 wherein said diamine dinitrate is N,N,N',N-tetramethyl- 1,3-diamino-2-ethylpropane dinitrate.

9. A propellant composition according to claim 1 wherein said diamine dinitrate is N,N,N',N-tetramethyl- 2,3-diaminobutane dinitrate.

10. A propellant composition according to claim 1 wherein said diamine dinitrate is N,N,N,N'-tetramethyl- 1,4-diaminobutane dinitrate.

11. A propellant composition according to claim 1 wherein said diamine dinitrate is N,N,N,N-tetraethyl- 1,3-diaminobutane dinitrate.

12. A propellant composition according to claim 1 wherein said diamine dinitrate is N,N,N,N-tetra-n-propyl-1,3-diaminobutane dinitrate.

13. A propellant composition according to claim 1 wherein said rubbery material is a copolymer of 1,3- butadiene with styrene.

14. A propellant composition according to claim 1 wherein said oxidant component is ammonium nitrate, said rubbery material is a copolymer prepared by copolymerizing a conjugated diene containing from 4 to 10 carbon atoms with at least one substituted heterocyclic nitrogen base selected from the group consisting of pyridine, quinoline, alkyl substituted pyridine and alkyl substituted quinoline wherein the total number of carbon atoms in the nuclear alkyl substituents is not more than 15 and wherein R is selected from the group consisting of a hydrogen atom and a methyl radical and said amine dinitrate is N,N,N',N-tetramethyl- 1,3-diaminobutane dinitrate.

15. A propellant composition according to claim 14 wherein said copolymer is a copolymer of 1,3-butadiene with 2-methyl-5-vinylpyridine.

16. A propellant composition according to claim 1 wherein said oxidant component is ammonium nitrate and said rubbery material is a copolymer of 1,3-butadiene with 2-methyl-5-vinylpyridine.

17. A propellant composition according to claim 1 wherein said rubbery material is a copolymer of 1,3-butadiene with 2-methyl-5-vinylpyridine and said diamine dinitrate is N,N,NN-tetramethyl-1,B-diaminobutane dinitrate.

18. A propellant composition according to claim 2 13 wherein said ammonium nitrate is a phase stabilized ammonium nitrate.

19. A propellant composition according to claim 15 wherein said ammonium nitrate is a phase stabilized ammonium nitrate.

20. A solid propellant composition comprising from 60 to 94 weight percent of an oxidant component selected from the group consisting of ammonium nitrate and alkali metal nitrates, and from 6 to 40 weight percent of a binder component comprising a rubbery material selected from the group consisting of natural rubber, polybutadiene, polyisobutylene, polyisoprene, copolymers of isobutylene and isoprene, copolymers of conjugated dienes containing from 4 to carbon atoms per molecule with styrene, and copolymers of conjugated dienes contain from 4 to 10 carbon atoms per molecule with at least one B! OHFC substituted heterocyclic nitrogen base selected from the group consisting of pyridine, quinoline, alkyl substituted pyridine and alkyl substituted quinoline wherein the total number of carbon atoms in the nuclear alkyl substituents is not more than and wherein R is selected from the group consisting of a hydrogen atom and a methyl radical; and from 2 to parts by weight per parts by weight of the total amount of said binder component plus said oxidant component of a diamine dinitrate characterized by the structural formula where: R is an alkylene group containing from 4 to 18 carbon atoms wherein at least 2 of said carbon atoms are in a chain between the nitrogen atoms; R is an alkyl group containing from 1 to 4 carbon atoms, which alkyl groups can be alike and unlike; and wherein the total number of carbon atoms in the molecule does not exceed 24.

OTHER REFERENCES Chem. and Eng. News, Oct. 7, 1957, pp. 623. Chemical Engineering, April 21, 1958, pp. 126-9.

Claims (1)

1. A SOLID PROPELLANT COMPOSITION COMPRISING FROM 60 TO 94 WEIGHT PERCENT OF AN OXIDANT COMPONENT SELECTED FROM THE GROUP CONSISTING OF AMMONIUM NITRATE AND ALKALI METAL NITRATES, AND FROM 6 TO 40 WEIGHT PERCENT OF A BINDER COMPONENT COMPRISING A RUBBERY MATERIAL SELECTED FROM THE GROUP CONSISTING OF NATURAL RUBBER, SYNTHETIC RUBBER POLYMERS, AND MIXTURES THEREOF; AND FROM 2 TO 20 PARTS BY WEIGHT PER 100 PARTS BY WEIGHT OF THE TOTAL AMOUNT OF SAID BINDER COMPONENT PLUS SAID OXIDANT COMPONENT OF A DIAMINE DINITRATE CHARACTERIZED BY THE STRUCTURAL FORMULA