US3704187A - Pyrotechnic disseminating composition - Google Patents

Abstract

A PYROTECHNIC DISSEMINATING FORMULATION COMPRISING AN INORGANIC OXIDIZER WHICH READILY IS COMBUSTIBLE AT ATMOSPHERIC PRESSURE, AN EPOXY RESIN BINDER AS FUEL AND AN EFFECTIVE QUANTITY OF AN AGENT TO BE DISSEMINATED.

Description

United States Patent 3 704,187 PYROTECHNIC DISSI IMINATING COMPOSITION Alan C. Kott, Mount Pleasant, and Erwin M. Jankowiak and George A. Lane, Midland, Mich., assignors to The Dow Chemical Company, Midland, Mich. No Drawing. Filed Sept. 1, 1967, Ser. No. 667,043 Int. Cl. C06!) 1/04 US. Cl. 149-60 6 Claims ABSTRACT OF THE DISCLOSURE A pyrotechnic disseminating formulation comprising an inorganic oxidizer which readily is combustible at atmospheric pressure, an epoxy resin binder as fuel and an effective quantity of an agent to be disseminated.

BACKGROUND OF THE INVENTION This invention relates to pyrotechnic dissemination and more particularly is concerned with a novel system for the thermal dissemination of chemical agents.

Pyrotechnic disseminating formulations are widely employed for colored smoke production used as a signal or screen, for the distribution of plant growth regulating agents such as pesticides, fumigants, herbicides and the like and for the release and distribution of chemicals used in warfare and law enforcement such as tear gas, psychotomimetic incapacitating agents and the like.

The primary problem in disseminating such signalling and treating materials, hereinafter referred to as agents, by pyrotechnic means is in providing a combustible mixture evolving large quantities of gaseous combustion products which burns at a sufliciently low temperature such that the agent being disseminated is not detrimentally degraded or destroyed. In general, such compositions should provide large volumes of gaseous combustion products while undergoing complete burning at a low burning pressure, e.g. a maximum of about two atmospheres, and a maximum burning temperature of about 800 C. and preferably from about 300 to about 600 C. It is another criterion of operation that the agent to be disseminated must be compatible with the pyrotechnic composition to assure reliability of burning after storage as well as storageability without mix degradation,

Heretofore, pyrotechnic dissemination of smoke dyes, herbicides, chemical warfare materials, tear gas and other like agents has been carried out using compositions wherein substantial amounts of the agent to be disseminated are mixed with "cool burning fuel-oxidizer combinations which provide copious quantities of water vapor and carbon dioxide as the principal gaseous exhaust products. In these formulations, many times undesirable high percentages of the agent are lost through degradation during the combustion dissemination process.

Empirically, it has been found that a mixture of carbohydrates or sulfur with potassium chlorate in the presence of minor amounts of certain additives, e.g. sodium bicarbonate with sulfur or kaolin with sugar, can be used as a pyrotechnic system for dissemination of colored smoke and chemical warfare agents. These systems can be classified as cool burning only because of. the flame quenching additives employed therein. Polyvinyl acetate in dilute solutions has been used with these conventional pyrotechnic compositions to increase their physical strength and ease of consolidation. Such solutions reduce the amount of pressure needed to compact the formulation into a grain. This is of interest especially with those formulations containing sulfur as compaction of such formulations at high pressure is hazardous in that these compositions during fabrication are prone to ignition.

Patented Nov. 28, 1972 Even when partially compacted, the resulting defiagration borders on detonation with respect to velocity. Oil, as a diluent, has been used to moisten and reduce friction sensitivity in such mixtures. This material, however, undesirably degrades the composition from the standpoint of elficiency of dissemination.

Dissemination of agents of the type set forth herein also has been realized using pyrochemical gas producers as the high volume gas source. To illustrate, self-sustained gas producing reactions as realized by the relatively low temperature catalytic decomposition of ammonium nitrate, guanidine nitrate and nitroguanidine utilizing chromates and dichromates as catalysts have been used to disperse benzene hexachloride, DDT and other pesticides. These formulations suffer from the disadvantage that they exhibit relatively low efiiciency of dissemination and are not universally applicable.

As indicated hereinbefore, conventional munitions used for the thermal dissemination of various agents generally consist of dry powders which are intimately mixed and compacted into grains under high pressure using expensive, slow processes and equipment. Such fabrication techniques are hazardous in that the dry powders are susceptible to shock and friction. Further, with a number of the agents, particularly the tear gas and psychotomimetic incapacitating agents, the dust associated with the manufacture in itself is toxic or at least a temporary health hazard or inconvenience to operators. Additionally, such pressed, dry grains are porous and have an undesirable low density.

It is a principal object of the present invention to provide a novel pyrotechnic composition for thermal dissemination of chemical agents.

It is also an object of the present invention to provide a pyrotechnic formulation which is safe to handle during mixing and other production operations when in admixture with an agent to be disseminated.

It is a further object of the present invention to provide a pyrotechnic formulation containing a tear gas chemical agent to be disseminated which exhibits compatibility dur ing mixing and curing and wherein the resultant composition remains stable under prolonged storage even at relatively elevated temperatures of 70 C. or more and which gives high efficiencies of gaseous combustion production and agent dissemination upon use.

It is a further object of the present invention to provide munitions for the thermal dissemination of agents which have a high density, good structural integrity and are substantially pore free.

It is another object of the present invention to provide a novel thermal disseminating system which before curing is readily castable or easily compactable without requiring high forming pressures.

These and other objects and advantages readily will become apparent from the detailed description of the invention presented hereinafter.

SUMMARY The present invention comprises a pyrotechnic disseminating formulation employing inorganic oxidizers which readily are combustible at atmospheric pressure, nonhalogenated epoxy based resins with an organic acid or organic acid anhydride curing agent as binder-fuel, and effective quantities of a chemical agent to be disseminated.

More particularly the present invention comprises from about 15 to about 50 weight percent of an alkali metal or ammonium nitrate, -chlorate, -perchlorate or mixtures thereof as oxidizer, from about 20 to about 30 weight percent cured epoxy resin binder-fuel and balance agent to be disseminated.

By effective quantities of an agent to be disseminated is meant those amounts whereby a predetermined level of treatment or activity is realized as is understood by one skilled in the art of pyrotechnic dissemination.

The fluid formulations can be fabricated into compacts or grains using casting procedures and low pressure compacting techniques. Blends usually are made by mixing the components, placing as by casting, for example, the resulting substantially homogeneous mix into a container and curing the so-formed mass into a grain. Ignition of the grain is achieved by contacting the formulation with an ignition system and igniter as conventionally employed in thermal disseminating munitions.

Both end burning and internal burning grains can be fabricated using the present novel system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention comprises from about to about weight percent potash sium chlorate oxidizer, from about 20 to about 30 weight percent of an epoxy resin-organic acid anhydride curing agent binder system and from about to about weight percent of an agent to be disseminated.

This composition has been found to be particularly effective in the fabrication of a munition wherein the lachrymator o-chlorobenzal malononitrile (hereinafter referred to as CS) is the chemical agent to be disseminated. With the present formulation, castability, mix stability, and compatibility, long term storageability and good yields and efiiciencies of agent dissemination upon burning are realized.

In the preferred embodiment usually the binder is comprised of a fluid aromatic disulfide containing epoxy resin or an epoxy-polysulfide copolymer resin system employing an acid anhydride such as, for example, Methyl Nadic Anhydride, pyromellitic dianhydride, cyclopentanoic dianhydride or maleic anhydride as a curing agent. Maleic anhydride is preferred since it has a low equivalent weight and a melting point (5355 C.) such that it is a liquid at the temperature ordinarily employed in the munition casting operations. The quantities of curing agent to epoxy resin to be employed are those conventionally employed in resin curing operations. Preferably the quantities of curing agent used range from about 110 to about 200 weight percent of that required stoichiometrically for reaction with the active groups of the epoxy resin.

Liquid epoxy resins which contain sulfide groupings, e.g. aromatic disulfide containing diglycidyl ethers, or such ethers which have been copolymerized with liquid low molecular weight polysulfide resins have been found to give the optimum in castability, efiiciency of combustion and agent dissemination. However, other liquid non-sulfur containing epoxy resins, e.g. aliphatic glycerine glycidyl ethers also can be employed in conjunction with liquid polysulfide resins. The liquid polysulfide polymers serve to reduce the viscosity of the binder blend during mixing and casting operations. Generally, if used, the polysulfide polymer is included up to a maximum of about 10 percent, preferably up to a maximum of about 5 percent, of the total formulation weight.

Particularly effective binder-fuel systems have been prepared using aromatic disulfide containing epoxy resins alone or in combination with a polysulfide polymer produced by the chemical reaction between dichlorodiethylformal and an alkali polysulfide, or the copolymer of a glycerine glycidyl ether with such a polysulfide polymer.

Additional viscosity reducing agents as conventionally employed can be incorporated into the mix if desired.

The amount of curing agent and total quantities of binder components to be employed in preparing a particular munition within the composition range disclosed herein are dependent to a large extent on the type of handling properties desired in the blended munition, temperature of mixing and blending, the length and temperature of cure to be employed and the amount of agent present.

To illustrate, it has been found in formulations containing a binder of an aromatic disulfide containing epoxy resin cured with maleic anhydride that when the binder weight is greater than about 25 percent of the formulation, maleic anhydride curing agent should comprise from about 20 to about 50 percent of the total binder while in formulations containing less than 20 percent binder, the maleic anhydride should be from about 26 to about 50 percent of the binder.

In the actual preparation of a munition utilizing the composition of the present invention, the liquid components of the formulation usually first are mixed followed by addition of the chemical agent. Ordinarily, the chemical agent is added slowly while continuing the mixing operation. After thorough dispersion of the chemical agent in the liquid mixture of binder components, the oxidizer is added with stirring and the final mixture agitated until homogeneity and castability is achieved. Alternatively, if desired, the solid and liquid components can be introduced together into a blender.

The actual mixing operation is carried out over a temperature of from about room temperature up to about 70 C. The temperature to be employed will be determined by the mix composition, i.e. the relative amounts of solid oxidizer and chemical agent and liquid binder concentration. In general, it has been found that the higher the binder concentration, the lower the temperature of blending that can be employed and the lower the agent concentration the lower the temperature of mixing. In the practice of the invention it has been found that munitions containing greater than 50 percent of CS agent and binder of less than about 20 percent by weight of the total composition are at the limit of maximum processable solids level. Beyond this loading level the strength of the cured munition drops and mixing becomes difficult.

The blended composition usually is cast into a mold of predetermined configuration and maintained at a predetermined temperature to etfect curing. The actual cure temperature employed ranges from about room temperature to about C. and preferably at from about 40 to about 60 C. The time of cure ranges from several minutes to 48 hours or more. This time is somewhat dependent on the mix formulation. To illustrate, mixes containing more than 3 percent butyl diglycidyl ether or 6 percent Methyl Nadic Anhydride or less than a total of about 25 percent binder by weight require curing at a temperature of about 45 C. or higher. Formulations having a binder of an aromatic disulfide containing epoxy resin cured with maleic anhydride and containing more than about 25 percent binder readily are cured at room temperature. The addition of polysulfide resins to epoxy resins promotes curing.

The following examples will serve to illustrate the present invention but are not meant to limit it thereto.

EXAMPLE 1 A number of cast munitions were prepared by first weighing the liquid binder components into a container and blending. With continued agitation, the chemical agent CS was slowly added and after thorough dispersion of the agent particulate KClO oxidizer was added to the mixture. This reaction mass was stirred at a temperature within the range of from about 50 to about 70 C. until it appeared to be homogeneous. The so-blended mixture was cast and cured. For those preparations which were mixed and cured at elevated temperatures stirring was continued during the early stages of curing until gelation occurred to assure that no detrimental settling or separation of the solids occurred.

The mix composition, curing condition, and cured product density for a number of compositions are summarized in Table I.

TABLE I Com ition, weight percent p05 Cure Munition Epoxy mp., density, Run No 08 K610; resin MA Additive C g./cc.

1 45 30 16 9 Room 1. 44 2 45 30 16 9 40-60 1.45 3 45 30 1B 5 LP-il, 2 Room 1.49 46 30 12 5 LP-33, 8 Room 1. 46 43 30 14 7 2 MNA, 3 8 Room 1. 38 45 30 16 6 Grill, 4 Room 1. 41 43 30 14 13 40-60 1.49 40 30 24 6 40-60 1. 43 45 30 18 7 40-60 1.50 47 28 20 5 40-60 1.42 50 20 5 40-60 1. 32 El) 10 4 -60 1. 35

adic Anhydride; B G E Butyl glycidyl ether.

EXAMPLE 2 A number of cast 10 gram end burning thermal disthe binder consisted of 18 percent aromatic disulfide containing epoxy resin and 7 percent maleic anhydride curseminating munition grains were prepared and cured fol- 20 mg agfim, these g s be g ba ed on the total cornlowing the general procedure set forth in Example 1. These were ignited and their combustion behavior studied. The results of this study are presented in Table II.

position. Also the size of the munition grain was varied. The results of combustion studies carried out on these grains are summarized in Table IV.

1 Glossary 0! terms: See Glossary for Table I; also GGE Glycerine glyeidyl ether; LP-8= Thiokol Liquid Polymer 01 low molecular weight produced by reaction of dichlorodlethylionnal and an alkali polysultide.

EXAMPLE (3a) A number of 10 gram end burning thermal disseminating munition grains were cast and cured following the procedure set forth in Example 1. These compositions contained on a weight basis CS, 30 percent KClO and 25 percent of a binder-fuel. The binder-fuel composition was comprised of an aromatic disulfide containing epoxy resin liquid polysulfide polymer and maleic anhydride curing agent. The relative amounts of the binder-fuel components were varied within the stated range for various formulations to effect burning rate characteristics of the grains.

The results of representative grains which burned at a substantialy constant rate are summarized in Table III.

A number of grains were prepared using the same composition as for the previously described studies wherein TABLE IV Agent Burning Combustion dissemina- Grain time Burning product tion eitisize, (total), rate, temperature, ciency, Run No. grams sec. sec/gm (2. percent l N o flaming noticed, but good cloud of smoke.

EXAMPLE 4 A number of grains containing 45 weight percent CS, 30 weight percent KClO and 25 percent binder as described in Example (3b) were stored for an extended period of time at 70 C. Other samples wherein a portion of the epoxy binder had been replaced with 5 weight percent (based on total formulation) LP-33 Thiokol Liquid Polymer or wherein the binder comprised (based on total formulation) 13 weight percent of the epoxy binder, 2 weight percent LP-3 Thiokol Liquid Polymer and 10 weight percent maleic anhydride also were put on surveillance at the same temperature. During the surveillance period, the grains were periodically examined and samples taken on a weekly basis for firing.

After 12 weeks storage at the elevated temperature, no visual evidence of any detrimental incompatibility or grain deterioration was noted. Further, the agent disseminating yield upon firing was substantially constant over the entire period.

EXAMPLE About 9.5 parts by weight of LP-8 Thiokol Liquid Polymer, 9.5 parts by weight glycerine glycidyl ether and 7.5 parts by weight of Methyl Nadic Anhydride curing agent were weighed into a container. These liquid components were mixed and about 42 parts by weight of the chemical agent CS added slowly to the agitating mass. After dispersion of the solid agent was complete, about 31.5 parts by weight KClO was added to the agitated mixture. Stirring was continued until a substantially homogeneous, castable mix resulted.

The resulting blend was cast into a 10 gram grain (1%," diameter) and cured at a temperature of about 70 C. into a firm, solid, substantially pore free grain.

Combustion tests on cured grains indicated a burning time of about 16 seconds with a combustion product temperature of about 600 C. The elficiency of agent dissemination was 63%.

EXAMPLE 6 A number of munition grains were prepared from compositions having 45 to 47 weight percent CS agent, 28 to 30 weight percent KClO and 23 to 25 weight percent binder-fuel, the binder being composed of maleic anhydride/aromatic disulfide containing diglycidyl ether in a weight ratio of 0.28.

For these preparations, the maleic anhydride was ground into a fine powder. All the components were mixed together at about room temperature and the resulting wetted powder formulation pressed into a grain at relatively low pressures, about several hundred pounds per square inch, in a cylindrical mold.

The so-pressed grains were cured at about 60 C. for one to two hours followed by a seven to eight hour postcure at 50 C. The cured grains were found to be free from cracks and substantially pore free.

Combustion studies showed these grains burned satisfactorily. They ignited easily, generated large volumes of smoke and gave good agent yield and efiiciency of dissemination.

Various modifications can be made in the present invention without departing from the spirit or scope thereof for it is understood that we limit ourselves only as defined in the appended claims.

We claim:

I. A pyrotechnic disseminating formulation comprising:

(a) from about to aobut 50 weight percent of a member selected from the group consisting of alkali metalor ammonium nitrates, -chlorates, -perchlorates or mixtures thereof as oxidizer,

(b) from about 20 to about 30 weight percent of a non-halogenated epoxy based resin cured with an organic acid or organic acid anhydride as binder-fuel, and

(c) balance an effective amount of an agent to be disseminated selected from the class consisting of pesticides, fumigants, herbicides and psychotomimetic incapacitating agents.

2. The formulation as defined in claim 1 and comprising fr am about 25 to about 35 weight percent potassium chlorate oxidizer, from about 20 to about 30 weight percent of an epoxy resin-organic acid anhydride curing agent binder-fuel system, and from about 45 to about 55 weight percent agent to be disseminated.

3. The formulation as defined in claim 2 wherein the binder-fuel comprises a fluid aromatic disulfide containing epoxy resin and maleic anhydride as curing agent, the amount of said curing agent ranging from about to about 200 weight percent of that required stoichiometrically for reaction with the active groups of said epoxy resin.

4. The formulation as defined in claim 2 wherein up to a maximum of about 10 weight percent of the binder-fuel component, based on total formulation weight consists of a liquid polymeric sulfide.

5. The formulation as defined in claim 2 wherein the agent is o-chlorobenzol malononitrile.

6. The formulation as defined in claim 2 and comprising about 30 weight percent potassium chlorate, about 25 weight percent of a binder-fuel which on the total formulation weight consists of about 18 percent aromatic disulfide containing epoxy resin and about 7 percent maleic acid curing agent, and about 45 weight percent o-chlorobenzol malononitrile.

References Cited UNITED STATES PATENTS 3,335,039 8/1967 Niles ct al. ...a 149-83 X 3,335,040 8/1967 Niles 149-83 X 3,467,558 9/196'9 Wernettc et a1 149-83 X 3,338,763 8/1967 Kristal et al. 149-85 3,130,096 4/1964 Pruitt et al. 149-19 3,052,577 9/ 1962 Butler et al. 149-84 2,939,779 6/1960 Brock 52-23 2,939,780 6/1960 Brock 52-24 1,886,394 11/1932 GOss l67-47 FOREIGN PATENTS 881,731 3/1958 Great Britain.

BENJAMIN R. PADGETI, Primary Examiner S. J. LECHERT, 1a., Assistant Examiner US. Cl. X.R.