US3420874A

US3420874A - Amine addition salts of nitro-carboxyalkali metal phenolates

Info

Publication number: US3420874A
Application number: US227048A
Authority: US
Inventors: Lionel A Henderson
Original assignee: Standard Oil Co
Current assignee: Standard Oil Co
Priority date: 1962-09-28
Filing date: 1962-09-28
Publication date: 1969-01-07
Anticipated expiration: 1986-01-07

Description

United States Patent 3,420,874 AMINE ADDITION SALTS 0F NITRO-CARBOXY- ALKALI METAL PHENOLATES Lionel A. Henderson, Columbus, Ind., assignor to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Filed Sept. 28, 1962, Ser. No. 227,048 US. Cl. 260501.14 3 Claims Int. Cl. C07c 101/44; C06 9/02 This invention relates to the novel compounds nitroaminocarboxy-alkali metal phenolates and to ammonium nitrate propellant compositions utilizing these compounds as a combustion catalyst.

In ammonium nitrate compositions formed from an oxidizable organic binder material which functions as a matrix for ammonium nitrate particles, it is necessary to promote the combustion of the mixture by means of a catalyst. Many catalysts are known for this purpose ranging from the very old inorganic chromium compounds such as ammonium dichromate to recently discovered alkali metal salts of certain organic acids and even completely organic compounds. The Prussian blues are of interest in high burning rate propellants, but these like the chromium compounds, produce reaction products which are solid materials which cause severe nozzle erosion. The alkali metal catalysts react to form alkali metal carbonates which, while not particularly erosive, do result in an objectionable accumulation of ash in certain uses such as in gas generator use in connection with auxiliary power systems.

For propellant purposes, it is very desirable that the burning rate of the propellant show a minimum effect with variation in combustion chamber pressure. This effect of pressure on burning rate is commonly spoken of as the pressure exponent having the symbol n. The smaller the size of n, the less effect of pressure on the burning rate. The burning rate is aifected by the temperature of the propellant mass. In general, the lower the temperature of the mass, the lower the burning rate. It is desirable that this temperature coefficient, like the pressure exponent, be low. The ultimate would be a situation in which the burning rate would be independent of pressure and temperature.

In general, the better known combustion catalysts have no influence on the characteristics of the propellant and function solely with respect to the rate of burning. Dependent upon the oxidizable organic binder material present, there commonly exists a problem with respect to ignition of the propellant at lower atmospheric temperatures. Frequently, it is necessary to introduce additives into the propellant composition to improve ignitabilit at these lower atmospheric temperatures which may be 20 to -75 F. For some installations, it is necessary that the propellant deliver gas smoothly and uniformly for a long period of time. It is common to use low burning rate propellants in these situations. Unfortunately, -with the prior art catalysts at low burning rates, it is difficult to maintain smooth, uniform burning. Still more unfortunately, it is very difiicult to overcome this problem by the addition of other compounds which improve burning smoothness without simultaneously harming the other characteristics of the propellant composition.

A novel class of compounds has been discovered. These compounds act as combustion catalysts for ammonium nitrate propellant compositions. Compositions containing these compounds have superior ignitability characteristics at even the lowest of atmospheric temperatures. Propellant compositions containing these compounds have superior, smooth, uniform burning characteristics at low burning rates. Propellant compositions containing these Patented Jan. 7, 1969 compounds give much less ash formation at a given burning rate than do the best previously known alkali metal containing organic compounds which function as combustion catalysts.

The novel class of chemical compounds of the invention may be broadly described as mixed salts of nitrocarboxyhydroxybenzene (nitromonocarboxylphenol or nitromonohydroxylbenzoic acid). In the compounds of the invention, the carboxyl group is reacted with an organic compound containing an amino group; the hydroxyl group is reacted with an alkali metal. The nitrosalicylic acids are especially suitable for the preparation of ammonium nitrate combustion catalysts. In addition to one or more nitro groups, the benzene nucleus may include alkyl substituents. It is to be understood that the novel class of compounds of the invention includes not only the compounds containing a single substituted benzene nucleus, but also two such nuclei which are joined by an alkylene bridge. Illustrative of such a compound which can be used to produce an exceptional ammonium nitrate combustion catalyst is dinitromethylene disalicylic acid.

Broadly, the compounds of the invention fall into two subclasses: nitro-aminocarboxy-alkali metal phenolate or alkylene di(nitro-aminocarboxy-alkali metal phenolate) where the alkylene group has 1-3 carbon atoms, i.e., methylene, ethylene or propylene. Any of the alkali metals may be used in forming the compounds of the invention. For use as a combustion catalyst, a sodium salt is especially suitable. Any organic compound containing an.

amino group may be used in forming the compound of the invention. The amines which contain carbon, hydrogen and nitrogen atoms and the amines containing carbon, hydrogen, oxygen and nitrogen atoms are especially suitable. The amines which are strongly basic are preferred when the composition needs exceptionable storage sta bility. Illustrative of especially suitable amines for the preparation of the catalyst used in the composition of the invention are ethylene diamine, monoethanolamine, diethylene diamine (piperazine) and guanidine.

Illustrative compounds of the invention based upon the reaction products of 3,5-dinitrosalicylic acid where the carboxyl group is in the 1 position are: the reaction product with guanidine and sodium methoxide is 3,5-dinitro-1- guanidiniumcarboxy-2-sodium phenolate. The reaction product with 1 mole of ethylene diamine, 2 moles of sodium methoxide and 2 moles of acid is diethylene diamino bis(carboxy-3,5-dinitro-2-sodium phenolate). The reaction product with 1 mole of ethylene diamine, 2 moles of sodium methoxide and 2 moles of acid is ethylene diamino bis(carboxy-3,5-dinitro-2-sodium phenolate). The reaction product of 5,5-methylene-di(3,5-dinitrosalicylic acid) with guanidine and sodium methoxide is 5,5- methylene di(3,3' nitro 1,1guanidiniumcarboxy-2,2- sodium phenolate). It is to be understood that the scope of the compounds of the invention are not limited to the illustrative compounds set forth above, but include the class as broadly defined above.

When a compound of the invention is utilized as a catalyst for promoting the burning rate of ammonium nitrate propellant compositions, enough must be introduced into the composition to obtain a burning rate promotion. The amount of catalyst used is also influenced by the rate of burning desired. The more catalyst present, to a degree, the faster the rate of combustion of the composition. (It is to be understood that the burning rate is also affected by the particular oxidizable organic binder material present.) In general, the composition will contain between about 0.1 and 15 Weight percent of the catalyst. (Hereinafter all percentages are to be understood as weight percent.) With the thermoplastic matrix formers or binders obtained from cellulose esters and plasticizers therefor, between about 1 and 7% of catalyst produces satisfactory burning rates for typical military gas generation and rocketry usages.

The ammonium nitrate propellant composition utilizes as a catalyst broadly about 0.ll weight percent of the above defined mixed salt; about 1()4O weight percent of oxidizable organic binder material; and ammonium nitrate as the major component. Other catalysts and additives may also be present.

The ammonium nitrate may be the high purity material commonly produced by synthetic plants today, or it may be technical grade containing small amounts of inorganic impurities. In addition to the ammonium nitrate, for special purposes, sodium nitrate or potassium nitrate maybe present in an appreciable amount. The decomposition rate of the ammonium nitrate is influenced by the particle size. For gas generation purposes, the ammonium nitrate is finely divided. Particularly suitable ammonium nitrate will contain about 80 weight percent of material having a screen size greater than 80 mesh and smaller than 30 mesh. The more finely powdered ammonium nitrate is used where higher burning rates are desired. Usually the propellant composition will contain between about 60 and about 80% of ammonium nitrate. In all cases, the major component present in the composition is ammonium nitrate.

In order to permit the shaping of the ammonium nitrate composition into definite configurations, a matrix former or binder material is present. When ammonium nitrate decomposes, free-oxygen is released. The existence of this free-oxygen permits oxidizable organic materials to be used as the binders and thereby obtain additional gas production. These oxidizable organic materials may contain only carbon and hydrogen, for example, high molecular weight hydrocarbons such as asphalts or residuums, and rubbers, either natural or synthetic. Or, it may contain other elements in addition to carbon and hydrogen, for example, as in Thiokol rubber and neoprene. The stoichiometry of the composition is improved, with respect to smoke production, by the use of organic materials containing combined oxygen as the binders. The binder or matrix former may be a single compound such as a rubber or asphalt or it may be a mixture of compounds. The mixtures are particularly suitable when special characteristics are to be imparted to the propellant which cannot be obtained by the use of a single compound.

Multi-component binder, or matrix former, consists of a polymeric base material and a plasticizer therefor. Particularly suitable polymeric base materials are cellulose esters of alkanoic acids containing from 2 to 4 carbon atoms such as cellulose acetate, cellulose acetate butynate and cellulose propionate. The polyvinyl resins such as polyvinylchloride and polyvinyl acetate are good bases. Styreneacrylonitrile is an example of a copolymer which forms a good base material. Polyacrylonitrile is another suitable base material.

The plasticizer component of the binder also, preferably, contains combined oxygen. The oxygen may be present in the plasticizer as an ether linkage and/or hydroxyl and/or carboxyl; also the oxygen may be present as a part of an inorganic suhstituent, particularly, a nitro group. In general, any plasticizer which is adapted to plasticize the particular polymer may be used in the invention. A single plasticizing compound may be used; more usually two or more compounds are used in conjunction. Exemplary classes of plasticizers which are suitable are set out below. (It is to be understood that these classes are illustrative only and do not limit the types of organic compounds which may be used to plasticize the polymer.)

Di-lower alkyl-phthalates, e.g., dimethyl phthalate, dibutyl phthalate dioctyl phthalate and dimethyl nitrophthalate.

Nitrobenzenes, e.g., nitrobenzene, dinitrobenzene, nitrotoluene, dinitrotoluene, nitroxylene, and nitrodiphenyl.

Nitrodiphenyl ethers( e.g., nitrodiphenyl ether and 2,4-

dinitrodiphenyl ether.

Tri-lower alkyl-citrates, e.g., triethyl citrate, tributyl citrate and triamyl citrate.

Acyl tri-lower alkyl-citrates where the acyl group contains 24 carbon atoms, e.g., acetyl triethyl citrate and acetyl tributyl citrate.

Glycerol-lower alkanoates, e.g., monoacetin, triacetin,

glycerol tripropionate and glycerol tributyrate.

Lower alkylene-glycol-lower alkanoates wherein the glycol portion has a molecular weight below about 200, e.g., ethylene glycol diacetate, triethylene glycol dihexoate, triethylene glycol. dioctoate, polyethylene glycol dioctoate, dipropylene glycol diacetate, nitromethyl propanediol diacetate, hydroxyethyl acetate and hydroxy propyl acetate (propylene glycol monoacetate).

Dinitrophenyl-lower alkyl-lower alkanoates, e.g., dinitrophenyl ethylacetate, and dinitrophenyl amyloctoate.

Lower alkylene-glycols wherein the molecular weight is below about 2.00, e.g., diethylene glycol, polyethylene glycol (200), and tetrapropylene glycol.

Lower alkylene-glycol oxalates, e.g., diethylene glycol oxalate and polyethylene glycol (200) oxalate.

Lower alkylene-glycol maleates, e.g., ethylene glycol m aleate and Bis-(diethylene glycol monoethyl ether) maleate.

Lower alkylene-glycol diglycolates, e.g., ethylene glycol diglycolate and diethylene glycol diglycolate.

Miscellaneous diglycollates, e.g., dibutyl diglycollate, dimethylalkyl diglycollate and methylcarbitol diglycollate.

Lower alkyl-phth-alyl-lower alkyl-glycollate, e.g., methyl phthalyl ethyl glycollate, ethyl phthalyl ethyl glycollate and butyl phthalyl butyl glycollate.

Di-lower alkyloxy-tetraglycol, e.g., dimethoxy tetra glycol and dibutoxy tetra glycol.

Nitrophenylether of lower alkylene glycols, e.g., dinitrophenyl ether of triethylene glycol and nitrophenyl ether of polypropylene glycol.

Nitrophenoxy alkanols wherein the alkanol portion is derived from a glycol having a molecular weight of not more than about 200. These may be pure compounds or admixed with major component bis(nitrophenoxy)alkane.

In addition to the main components, i.e., ammonium nitrate binder and catalyst, the propellant composition may contain other components. For example, materials may be present to improve low temperature ignitability, for instance, oximes or asphalt; surfactants may be present in order to improve the adhesion of the nitrate and the binderalso to improve the shape retention characteristics of the composition; burning rate promoters which are not considered to be true catalysts such as finely divided carbon may be present. Aromatic hydrocarbon amines such as toluene diamine, diphenyl amine, naphthalene diamine, and toluene triamine may be present. In order to improve storage stability, particularly at higher atmospheric temperatures, between about 0.1% and 1% of N-phenylmorpholine will be present.

A particularly good composition consists of cellulose acetate, about 6-12%; acetyltriethylcitrate, about 6-12%; dinitrophenoxyeth'anol, about 612; carbon, about 26%; toluene diamine, about 0.00.5%; N-phenylmorpholine, about 0.5%; catalyst, about 17% and the remainder ammonium nitrate.

It has been observed that propellant compositions containing one of the defined compounds of the invention and also an alkali metal barbiturate have exceptionally low pressure exponents and simultaneously very good temperature coefficients. In general, these results are obtained using about equal weight amounts of the mixed salt of this invention and alkali metal barbiturate with the total amount of the two compounds being between about 2 and 7 weight percent. An especially suitable combination is formed by monosodium barbiturate and the guanidinesodium mixed salt of 3,5-dinitrosalicy1ic acid.

Although the burning rate at equal weight content is somewhat lower than with the mononuclear compounds, the alkylene bridge dinuclear compounds give exceptionally low pressure exponents and very satisfactorily low temperature coeflicients. For these reasons, compositions containing such mixed salts are suitable for military use where the composition will be fired over a wide range of atmospheric temperatures.

Illustrations The mixed salts of the invention are easily prepared by reaction in a common solvent for the particular acid, the particular amine and the alkali metal affording reactant. Methanol is a particularly good solvent reaction medium and a methoxide as the alkali metal afiording reagent. A reaction medium can be readily selected wherein the product precipitates out in crystalline form. Purity of the product can be determined easily by measuring the melting point of the crystals. It has been found by means of infrared inspection, regardless of which agent-amine or alkali metalis used first in the reaction, the final product has the amino group attached to the carboxy group' and the alkali metal attached to the hydroxy group. Compounds were prepared by reacting equal moles of guanidine and sodium methoxide with 3,5-dinitrosalicylic acid; reacting 2 mols of the 3,5-dinitrosalicylic acid with 1 mol of diethylene diamine (piperazine); 2 mols of the 3,5- dinitrosalicylic acid with ethylene diamine; 2 mols of guanidine with 1 mol of 3,3'-dinitro-5,5'-methylene disalicylic acidin each instance the theoretical amount of sodium methoxide was added. In all cases, essentially the theoretical yield of mixed product was obtained in the form of crystalline solids. The position of the sodium and amino group was determined by infrared spectrographic analysis of the crystalline solid.

The compounds were found to be effective burning rate catalysts for ammonium nitrate propellant compositions. Comparative compositions were prepared in a one quart laboratory mixer; each composition was mixed together for one hour at a temperature of about 212 F. Cellulose acetate, analyzing about 55% of acetic acid equivalent, was used in conjunction with essentially pure dinitrophenoxyethanol land acetyl triethyl citrate plasticizers.

After the completion of the mixing, the pasty mass was compression molded into a slab /2" in thickness. The slab was permitted to cool to room temperature and sawed into strips for use in the Crawford Bom'b burning rate tests. Tests were carried out at diiferent pressures in order to determine the pressure exponent n for each composition.

Tests were run to determine the temperature coefiicient r of each composition. Temperature coefiicients were obtained at both constant pressure and constant nozzle size. In these tests, a propellant strand was brought to the desired test temperature by storage at that temperature until the entire mass of propellant was certain to be at the desired temperature. The ease of ignition and the smoothness and the uniformity of burning of the propellants was also observed.

In this series of tests, the component analysis of compositions tested was:

Mark 6205 contained the sodium guanidine mixed salt of 3,5-dinitrosalicylic acid. Mark 6206 contained the sodium-piperaz-ine mixed salt of 3,5-dinitrosalicylic acid. Mark 6207 contained the sodium-ethylene diamine mixed Mark Burning rate n 0' 1r 1:

The above data establish that the mixed salt compounds of the invention containing less thanone-hal-f the sodium metal content of sodium barbiturate have as good or better burning rates. These compositions also have better pressure exponents and as good or better temperature 00- eflicients. The three compositions of the invention ignited easily at the lowest temperatures and burned smoothly.

A propellant composition, designated as Mark 6217, was prepared using as the catalyst the reaction product of guanidine, sodium methoxide and 3,3-dinitro-5,5 methylene disalicylic acid in a mole ratio of 212:1. This composition was prepared as described above using a 1 quart mixer with a 40 minute agitation time. The component composition of composition Mark 6217 was:

second with a pressure exponent of 0.487. The temperature coefiiclent, u was 0.075 and the temperature coeflic ent, 'n' was 0.148. By comparison with the characterist1cs shown in an earlier composition, Mark 6217 has a desirably low pressure exponent and desirably low tem perature coeflicient, 1r

Composition Mark 6214 included, as the catalyst, the mixed salt sodium guanidine dinitrosalicylate made as described previously and also monosodium barbiturate. The component formulation of Mark 6214 was:

A Percent mmomum n1trate 61.00 Cellulose acetate 9 79 Acetyl triethyl citrate 11:25 Dinltrophenoxyethanol (28% diether) 990 Carbon 3 00 Sodium guanidine dinitro-salicylate 2 06 Monosodium barbiturate 2 00 N-phenylmorpholine u 0 50 Toluene diamine u 0 50 Composition Mark 6214 gave a burning rate of 0.070 with a pressure exponent of 0.466. The temperature coeflic1ent,a was 0.100 and the temperature coefficient, 1r was 0.19. The pressure exponent was unusually low considering the amount of monosodium barbiturate catalyst present; indeed this pressure exponent is markedly lower than that given by the catalysts set forth earlier. It 1s also evident that this particular composition has a desirably lower temperature coefiicient, 1r than does the composition containing only monosodium barbiturate as a catalyst-Mark 6209.

Thus having described the invention, what is claimed is: 1 1. 3,5-dinitro-1-guanidiniumcarboxy-2-sodium phenoate.

2. Ethylene diamino bis(carboxy-3,S-dinitro-Z-sodium phenolate) 3. 5,5'-methylene-di(3,3'-nitro 1,1 guanidiniumcarboxy-2,2-sodium phenolate) References Cited UNITED STATES PATENTS Erickson 260268 Weston et a1. 260268 Gagliardi 260501 Goldberg 260501 Larrabee 260501 La Font et a1 260501 Mackay 260564 Hageman 260564 Gallaghan 2605 64 8 3,056,702 10/1962 Linsk 149-19 3,056,703 10/ 1962 Korpics 149--19 FOREIGN PATENTS 591,808 4/1931 Germany.

OTHER REFERENCES Graig et 211., Progress in Drug Research, vol. 3, pp. 116-150, p. 116 relied on (1961).

LEON ZITVER, Primary Examiner.

M. W. GLYNN, Assistant Examiner.

U.S. c1. X.R.

zen-501.17, 501.2, 268; 149 19, 55

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,420,874 January 7, 1969 Lionel A. Henderson It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 45, "ethylene diamine" should read piperazine Column 4, line 61, "6-12;" should read 6-l2%; Column 6, lines 24 and 25, "3,3dinitro-S,5 methylene" should read 3,3-dinitro5,5-methylene Signed and sealed this 17th day of March 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Attesting Officer Commissioner of Patents WILLIAM E. SCHUYLER, JR.

Claims

1. 3,5-DINITRO-1-GUANIDINIUMCARBOXY-2-SODIUM PHENOLATE.