US3323958A - Smoke grenade filling containing encapsulated oil and pyrotechnic materials - Google Patents

Description

United States Patent 3,323,958 SMOKE GRENADE FHLLING CONTAINING ENCAPSULATED OIL AND PYROTECHNIC MATERIALS Mitchell Penn and Julius Miller, Baltimore, Md., assignors to the United States of America as represented by the Secretary of the Army No Drawing. Filed Aug. 3, 1965, Ser. No. 477,041 7 Claims. (Cl. 149-11) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to us of any royalty there- This invention relates to a novel smoke-generatingcomposition and more particularly to an improved mixture which may be used as a filling for smoke grenades and and other smoke-producing munitions.

Various methods for generating screening and signaling smokes have a serious drawback in that dense clouds or smoke are more or less toxic. In addition, highly corrosive acid fumes render such smoke producers as oleum, sulfur trioxide and chlorosulfonic acid less desirable for use on concealing friendly troops and their military equipment.

A more suitable source of smoke, one which provides a substantially nontoxic white smoke, is the liquid hydrocarbon called fog oil, which is vaporized in various generators and the vapor condenses immediately in the air as minute oil droplets. Various smoke generators have been devised to evaporate the oil, but they are handicapped by complexity of design and by weight. An mportant consideration in designing the smoke generating equipment is the requirement for separate compartments for the oil and for the pyrotechnic which supplies the heat for vaporization. Thus, previous approaches for generating oil smoke or fog were directed toward oil-vaporizing equipment in which liquid oil was fed into a vaporizing region heated externally by a pyrotechnic composition.

The present invention is based on a novel composition which is capable of generating oil smoke in a simplified manner, said smoke being more eflectively utilized by troops in the field for screening or signaling purposes, The present composition is capable of autocombustion, nate an inclosed oil as a screening fog. The composition of this invention may be conveniently employed as a filling for conventional smoke grenades, smoke pots, shells, motor rounds or bombs, thus obviating the previous requirement for maintaining a separate heat source to vaporize the oil.

It is therefore an object of the invention to provide a novel smoke agent and a heat source in a homogeneous composition for generating smoke more conveniently.

Another object of the invention is to provide an oilbearing ingredient in an intimate mixture with one or more pyrotechnic ingredients to produce an oil fog.

A further object of the invention is to provide the combination of a novel filling in a conventional chemical munition whereby oil smoke may be generated by ignition of said filling.

Other objects and advantages will become apparent from the following detailed description of the invention.

According to the invention, an oil-bearing smoke agent is intimately mixed with pyrotechnic ingredients to form a solid mixture which can be readily ignited to generate oil smoke. The smoke agent consists of solid particles containing therein oil as the central nucleus and surroundin the oil is an encapsulating wall which is substantially impermeable to the oil. The encapsulating wall may be formed of a gelled colloid, i.e. gelatin or calcium algi- 3,323,958 Patented June 6, 1967 nate, or it may be formed of an artificial polymer as a dense oil-impermeable capsule. The solid particles may be of microscopic size measurable in microns, or they may be of macroscopic droplets visible to the unaided eye. Thus, encapsulated oil, as an apparently dry entity, may form intimate mixtures with solid pyrotechnic ingredients, and said mixtures are considerably easier to handle and load into various munitions.

The encapsulation of oil according to the invention provides a dense coating around each droplet of oil; the inclosed oil is unreactive toward the coating and is retained indefinitely without loss due to leakage or chemical action. Thus, a fluid oil which is encapsulated may be handled and stored in the manner of any solid material. The fluid oil may constitute as much as of volume of the particle, yet the oil contained therein is protected from contact with the surrounding environment. The encapsulating material is preferably formed by methods that assure a continuous, uniformly thick capsular wall. Gellable substances, such a gelatin or calcium alginate, may be effectively deposited as a colloidal gel which remains impermeable to the passage of oil. A solid polymer may also be formed into a capsular material by polymerization reactions that solidify a liquid monomer around each oil droplet. Monomers which may be mentioned in connection with polymer formation are methacrylates, methylmethacrylates and vinyl acetate.

Processes for encapsulating oil are well known in the art and various suitable reactions are provided to form a solid coating on oil droplets. Oil-containing capsules may be formed by methods disclosed in US Patent 2,969,330, 2,969,331 and Re. 24,899. Other prior art practices provide spray drying for convenient preparation of encapsulated oil in a substantially dry form.

The oil which is utilized for smoke formation and which is encapsulated in accordance wtih the teachings of this invention is a petroleum hydrocarbon with a high flash point and high ignition temperature in order to resist burning. Oil which is suitable for this purpose is essentially a lubricant base stock, one which is preferably deasphalted and dewaxed. Lubricant oil fractions can be vaporized by a burning pyrotechnic, and the vapor is rapidly condensed on hitting the air.

Previous use of oil in smoke generators was limited to very specific fractions based on their liquid flow characteristics and being free of constituents that would shorten the life of the generator. Smoke generators have utilized low viscosity oils, referred to as Smoke Generator Fog Oils, SGF #1 and SGF #2 (MILF1207OA) based on viscosity and pour point at specified temperatures. The present use of oil in the form of oil-bearing particles is no longer dependent on liquid fiow properties of the oil. Consequently, the present encapsulation of fog oil extends the effective range of hydrocarbons which may be utilized in producing a smoke screen. Ordinary motor oil may be encapsulated and used as a smoke agent, as well as crude oil and other hydrocarbons. Oils with flash points of about 300 or more and ignition temperatures over 380 F. may now form smoke agents for the present invention.

In a particular application of encapsulated oil, a lubricant oil identified as 500 pale oil was encapsulated with a high quality pigskin gelatin. An aqueous solution containing 20 grams of gelatin in grams of water was stirred with 80 grams of the oil at 55 C. to form an emulsion. A 20% solution of sodium sulphate was then added slowly keeping the temperature at about 55 C. until a definite cloudiness was observed in the mixture. At this point gelatin molecules were deposited around each oil droplet. The mixture was then cooled rapidly by pouring it into a large quantity of 10% sodium sulphate solution at room temperature causing the gelatin 3 to solidify rapidly. The solid material was then separated, washed and dried. I

The following examples are illustrative of suitable" solid mixtures containing encapsulated oil:

In the examples given above, the encapsulated oil is combined with a combustible material (sucrose), an oxidant (potassium chlorate) and a stabilizer that controls the burning rate (magnesium'carbonate). The burning time can be regulated by adjusting the proportions of oxidant and combustible materials. The above mixtures contain oxygen for supporting combustionand burn progressively, the burning being a surface phen'OmenOnLOt'her ingredients may be substituted to vary the pyrotechnic properties, as known by these skilled in the art. The

I utilized in a solid filling for smoke grenades and other amount of encapsulated oil which may be used with ipyrotechnic mixtures may vary within certain limits,

suitably between -50 percent by weight.

Mixtures of encapsulated oil and pyroteehnic'rnay be. used as a filling in various burning-type munitions; for example, smoke grenades smoke pots, candles or vfioating boxes in naval use. When the pyrotechnic'is ignited, the heat released is sufficient to volatilize the encapsulated oil, which then condenses outside the munition to form portable type smoke munitions for the generation of nontoxic smoke screen.

Since many modifications and variations may be made from the foregoing, we intend to be limited only as inclicated by the following claims.

We claim:

1. A'smoke-generating composition comprising:

an encapsulated oil, gelled colloid forming the capsular material of said oil, pyrotechnic consisting'of a fuel material, oxidant and stabilizer for vaporizing said oil,

said encapsulated oil, and said pyrotechnic forming a homogeneous solid mixture.

2. A smoke-generating composition accordingto claim l'wherein said hydrocarbon consists of a lubricant motor oil- I 3. A smoke-generating composition according to claim 1 wherein said capsular material consists of an artificial polymer.

4. A smoke-generating composition according to claim '1 wherein said colloid is composed of gelatin.

5. A smoke-generating composition according to claim v ;1 wherein said colloid is composed of calcium alginate.

. chlorate and magnesium carbonate.-

7. A smoke-generatingcomposition according to claim 1 wherein said encapsulated oilis present in said compo smoke. The entire process depends upon a high tempera- 3,117,521 3,143,446 8/1964 Berman s l49-2 BENJAMIN R. PADGETT, Primary Examil elx,

1/1964 Reaves 102-'65 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,323;9S8" un 6, 1967 Mitchell Penn et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as show below:

Column l, line l6, cancel'nate an inclosed oil as a screening fog. and insert the heat released being sufficient 1E0 vaporlze and disseminate an inclosed oil as a screening Signed and sealed this 29th day of July 1969.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, Jr. Attesting Officer Commissioner of Patents

Claims (1)

1. SMOKE-GENERATING COMPOSITION COMPRISING: AN ENCAPSULATED OIL, A GELLED COLLOID FORMING THE CAPSULAR MATERIAL OF SAID OIL, A PYROTECHNIC CONSISTING OF A FUEL MATERIAL, OXIDANT AND STABILIZER FOR VAPORIZING SAID OIL, SAID ENCAPSULATED OIL AND SAID PYROTECHNIC FORMING A HOMOGENEOUS SOLID MIXTURE.