Packaged Chemiluminescent Material

Abstract

This invention relates to a packaged luminescent material, and more particularly to a combined package of a chemiluminescent agent as the "fuel," and an activating agent therefor, wherein the fuel and activating agent are maintained in close association but separated from each other by a barrier medium to prevent interaction before the same is desired. When the barrier medium is ruptured, or otherwise broken down, either deliberately or unintentionally, a reaction occurs between the chemiluminescent agent and the activating agent with the emission of visible light, without, however, the generation of any appreciable amount of heat.

Description

The term "chemiluminescence," is used herein to indicate the ability to produce light as a direct result of chemical changes. Since the process of light emission is purely an energy transformation, it is deemed proper to apply the term chemiluminescence to the luminescent phenomenon that originates from chemical energy, viz., the transformation of the free energy of a chemical reaction into light energy. Thus, if as a result of a chemical reaction there is a shift of an electron to a higher energy level of an atom or molecule, and this is accompanied by the emission of light during the return of the electron to the ground state level, this phenomenon may be regarded as due to a chemical change, and in that case chemiluminescence is the only mechanism by which the light has been emitted.

Chemiluminescence this differs from fluorescence in that the former is excited by chemical energy while the latter is excited by radiant energy. The demonstration of the validity of this point of view is due mostly to Kautsky and his co-workers (Kautsky, H., et al., Z. Physik, 9, 267 (1922); 31, 60 (1923); Trans. Faraday Soc., 21, 591 (1926), who studied the phenomenon of chemiluminescence caused by the rapid oxidation of "silikon," a mixture of siloxene (Si.sub.6 H.sub.6 O.sub.3).sub.n and its reaction products. The authors showed that in this system, the chemiluminescence was attributable to the absorption of the reaction energy by the unchanged molecules of the silikon which emitted this energy as light. Fluorescence of the silikon could be induced under conditions where chemiluminescence was completely absent. The two sets of spectra were identical.

We have now found that the phenomenon of chemiluminescence can be put to practical uses by so packaging the components, or reactants, of a chemiluminescent system as to make it feasible to produce chemiluminescent light, either deliberately by unskilled personnel, or, for the purpose of detection inadvertently by hostile personnel or equipment. In its simplest aspect, this invention relates to packaged luminescent material comprising a chemiluminescent agent and an activating agent associated in a system, but separated by barrier means that prevent reaction between the components of the system prior to the time desired for such reaction to occur, the barrier means being capable of being broken down under such circumstances as to cause an admixture of the components with a resultant chemical reaction therebetween and an emission of chemiluminescent light. The chemiluminescent agent can be in the form of a liquid, a powder, or a dispersion of a powder in a fluid or gel matrix. It is protected from chemical reaction with the air or with extraneous constituents by its enclosure, or encapsulation, in a protective material that serves as a part of the barrier means between the chemiluminescent agent and the activating agent of the two-component system is also contained within or protected by barrier means in such manner that a prescribed quantity of the activating agent can, on demand, be made to mix and react with the chemiluminescent agent to produce light. Such light can be reactivated if only partial reaction initially takes place between the chemiluminescent agent and the activator, so long as means for subsequent mixing are provided.

According to the prior art, chemiluminescent light cannot be produced efficiently from systems which require two components unless the components are mixed in controlled proportions and handled by technically trained or experienced personnel. We have now discovered means for utilizing a two-component chemiluminescent system which requires controlled proportions of the two components to be mixed for maximum efficiency in the production of emitted light, but which does not require experienced or trained personnel to effectuate the activation of the system. We have also discovered a method for preparing and packaging chemiluminescent materials in forms which have high utility, both for civilian and military purposes.

In the preparation of packaged chemiluminescent material in accordance with our invention, the following steps are employed in combination:

1. Preparing the chemiluminescent agent and the activator separately in the preferred or desired form for the intended use;

2. Preparing aliquot portions of said forms of the chmiluminescent agent and the activator;

3. Packaging the chemiluminescent agent and the activator in such aliquot proportions and in association with each other but so separated from one another that premature reaction therebetween cannot occur, yet upon their reaction, or interaction, there is produced a reaction product of a preferred composition for the emission of chemiluminescent light; and

4. Actuating the release of chemiluminescent light by causing the luminescent agent and the activator in said packaged form of the system to become mixed.

In the practice of our invention, the package of the chemiluminescent agent and of the activator can take various forms both as to construction and design, including the following:

1. Coating either the chemiluminescent agent or the activator in a desired form and packaging such coated material inside a second coating or envelope which contains the other component of the two-component system.

2. Packaging the chemiluminescent agent and the activator separately within barrier means, or by the use of a barrier medium therebetween, and associating together the separately packaged agents, as by physical union of the separately packaged agents, or by enclosure within a common barrier means; and

3. Packaging the chemiluminescent agent and the activator, respectively, in a suitable form in relatively large containers or tanks so arranged that the chemiluminescent agent and the activator are in the proper proportions and/or can be metered in the proper proportions for admixture and resultant emission of light.

In general, the barrier means above referred to are most suitably in the form of films or membranes that envelop or encapsulate the luminescent agent and activator, respectively, and that are not only inert towards these components, but are, relatively water- and moisture-impervious and are either fragile, frangible or of such character as to be easily ruptured or broken down. In some cases, as when the package takes the form of a grenade, the same explosive force that disintegrates the enclosing shell also ruptures the barrier media separating the chemiluminescent agent from the activator and thus brings about a mixing of the reactants of the two-component system that results in the emission of chemiluminescent light.

The ehcmiluminescent agent preferably used in the package of our invention is a polysiloxene (sometimes in the literature spelled "siloxen"). When calcium silicide (CaSi.sub.2) is treated with dilute hydrochloric acid (HCl), a "polymerized siloxane" of the composition (Si.sub.6 O.sub.3 H.sub.6).sub.n is formed. This compound, known as a polysiloxene is the parent substance for a group of compounds of unusual properties.

Siloxene, itself, is not chemiluminescent, but it is a component of silikon, which is herein used as the generic term for any chemiluminescent mixture of siloxene, polysiloxenes and substitution products of polysiloxenes. The term "Silicone" has been used in the literature (Analytical Chemistry, Vol. 22, No. 5, May 1950 (pp. 693-697) but since that is a commonly used term denoting a now well-known series of polymeric R.sub.2 Si=O compounds, we shall use the term silikon here.

The following example will serve to illustrate a preferred method of making substituted polysiloxenes:

EXAMPLE

Two grams of powdered calcium silicide were mixed with 20 ml of concentrated hydrochloric acid with stirring. When the temperature subsided, an additional 10 ml of concentrated hydrochloric acid were added with stirring and the resulting mixture was boiled for 5 minutes. The suspension of the product was diluted with 60 ml of water and boiled for 5 minutes. The crude polysiloxene was separated from the liquid on a funnel and washed successively with approximately 5 ml each of water, ethyl alcohol and ether. This procedure can be varied by those skilled in the art to cover a wide range of conditions. The preparation is acceptable so long as the product has the desired properties and the preparation can be carried out safely.

Activating agents for activating the various polysiloxenes and their substitution products are, in general, oxidizing agents, such as the following:

Hydrogen peroxide

Potassium permanganate

Manganese peroxide

Chromic acid

Persulfuric acid

Mercurous nitrate

Mercuric nitrate

Ferric chloride

Ceric ammonium sulfate

Ceric ammonium nitrate

Ceric sulfate

Ceric oxide

Cerium nitrate

Potassium hexanitrate cerate

Uranyl nitrate

Uranyl acetate

Potassium ruthenate

Vanadium pentoxide

Chromium trioxide

Magnesium perchlorate

Most per- acids, such as perchloric acid, perboric acid, persulfuric acid and the like can be employed, but we have found that organic oxidizers, generally speaking, cannot be successfully used to produce chemiluminescence from silikon.

In order to activate the chemiluminescent agent, water should be added, or should be furnished by the chemiluminescent agent, the inorganic oxidizing agent, or by both. An aqueous-type liquid, such as a C.sub.1 to C.sub.5 alcohol, preferably methanol or ethanol can be used in order to provide a medium in which the oxidizing agents can diffuse rapidly into the siloxene particles, but water is preferred. The water or other solvent appears not to enter into the reaction, but only to make the reaction proceed.

While the chemiluminescent agent and/or the oxidizing agent can be used in a solid state, we have found it advantageous to incorporate either or both of the agents into a gel system. A gelling medium which has been found suitable is Cab-o-sil M-5, manufactured by the Cabot Corporation, but other types of gel-forming silicas than Cab-o-sil can be used satisfactorily. Cab-o-sil is a fire-dry pyrogenic silica with a particle size of 0.015 microns, a surface area of 200 m.sup.2 /gm, and bulk density of 2.2 lb/ft.sup.3. If a water gel is made up from any of these active silicas, the gel is thixotropic, i.e., it thins down and flows when agitated, beaten or otherwise submitted to a shearing action. Thus, although the gel sets after mixing, the degree of set and the time after mixing at which set occurs (both of which are functions of the percent solids and the percent silica gel), the application of a shearing force will cause the gel to flow. These properties are considered advantageous for storage and application.

Preferably, the gels prepared from any of the suitable chemiluminescent agents have a pH of about 1, due to traces of HCl in the chemiluminescent agent, while the activator, or oxidizing agent gels have a pH of about 6. Inasmuch as the chemiluminescent agent works best in a specific environment, the ability of silica gels, such as Cab-o-sil, to gel in an acid environment is an important characteristic.

The principle which underlies the obtaining of the optimum results from both agents in activated gels thereof is that of obtaining the greatest intensity of chemiluminescent activity per unit weight of gel that is consistent with the maintenance of suitable gel characteristics. Thus, although the highest possible concentration of active ingredients per unit weight of gel would seem to be most advisable, a high percentage of solid material renders the gel highly viscous and results in an attendant decrease in the diffusion-controlled chemiluminescent reaction rate. The result is a trade-off between brightness and light-emitting lifetime. Our studies thus far have shown that the optimum activator-to-agent ratio, considering only the weights of active ingredients, is approximately 5:1 when ceric ammonium sulphate is the activator. Since there is no evidence of internal quenching of the chemiluminescent process by an excess of the oxidizing agent, any mixture ratio of activator (oxidizer) to luminescent agent will emit some light and such light will be made available for use provided it is not absorbed before it can be detected.

In the following tables showing in percentages by weight various compositions of suitable luminescent agent gels, termed "Agent Gel," and oxidizing agent gels, termed "Activator Gel," the luminescent agent used was a silikon in the form of a solid, yellow mixture which, as previously stated, does not have a definite composition but which was in this case a mixture of polysiloxenes (Si.sub.6 H.sub.6 O.sub.3).sub.n, and substituted polysiloxenes, the latter in possibly various states of oxidation but still capable of luminescence.

TABLE NO. 1

Agent Gels

No. of Gel % silikon % active silica % water Agent Gel No. 1 7.6 16.4 76.0 Agent Gel No. 2 14.5 13.4 72.1 Agent Gel No. 3 26.3 13.2 60.5

TABLE NO. 2

Activator Gels

No. of Gel % oxidizer* % active silica % water Activator Gel No. 1 14.6 15.2 70.2 Activator Gel No. 2 30.2 20.0 48.8 Activator Gel No. 3 10.8 2.4 86.0** * The oxidizer was ceric ammonium sulfate. This can be replaced by any of the above listed oxidizing agents ** In place of water as such, 1M-H.sub.2 SO.sub.4 was used

It should also be understood that in place of the particular silikon mixture used in the foregoing tables any other silikon mixture could be used, or any individual chemiluminescent polysiloxenes or their substitution products as above set forth.

The following tables show the performance of various mixtures of Agent and Activator Gels of the compositions given in Tables 1 and 2 in terms of chemiluminescent activity. The headings above the performance data show the proportions and actual weights of Gel, Agent and Activator used:

TABLE NO. 3

1 gram agent gel No. 1 (0.263 grams of agent) + 3 grams of activator gel No. 1 ( 0.437 grams of activator)

RUN 1

Time (seconds) Brightness (ft. lamberts) 10 1.2 35 0.6.sup.2 60 0.1.sup.3 85 0.1.sup.6 125 -- still visible 145 -- but beyond range of 180 -- instrument

RUN 2

Time (seconds) Brightness (ft. lamberts) 15 1.3 32 0.7.sup.5 60 0.2.sup.5 100 0.1.sup.8 115 0.1.sup.1 still visible 145 -- but beyond range of instrument

RUN 3

1 gram agent gel No. 1 + 4.4 grams activator gel No. 2

Time (seconds) Brightness (ft. lamberts) 10 1.0 23 0.8.sup.2 38 0.4.sup.3 54 0.1.sup.8 77 0.1.sup.2 111* 0.4.sup.8 128 0.2.sup.3 147 0.1.sup.2 still visible 177 -- but beyond range of instru- ment * At 111 seconds the gelled system was agitated, whereupon it gave an additional pulse of emitted light, thereby showing that the system was capable of further activation

The significant parameter, which characterizes the total available light energy, is the integral of the brightness over the light emitting lifetime. This integrated birghtness averages about 58 ft. lambert seconds over Runs -1, 2 and 3.

ON THE DRAWINGS

Various methods of packaging the luminescent agent and the oxidizing agent, or activator, are illustrated in the accomapnying drawings, which are diagrammatic in nature, and in which:

FIG. 1 is an elevational view, partly broken away, of an encapsulated system;

FIG. 2 is an alevational view, partly broken away, of a modified encapsulated system;

FIG. 3 is an elevational view, partly borken away, of a gel dispenser system;

FIG. 4 is a perspective view of a package intended primarily as a hand signalling device; and

Fig. 5 is an elevational view, partly broken away, of a wave-off grenade utilizing capsules of the luminescent agent and oxidizing agnet of our invention.

AS SHOWN ON THE DRAWINGS

In FIG. 1, the reference numeral 10 indicates an outer spherical container, preferably formed of a transparent plastic film or membrane 11. Plastics such as polyethylene, ethyl cellulose, vinylidene chloride and other plastics can be used, or glass can be employed. The material used should be impermeable to water, moisture vapor and air, and should be capable of being easily ruptured by compressive forces exerted thereagainst. While the thickness of the container wall 11 has been exaggerated for purposes of illustration, the membrane wall should be relatively thin, in the neighborhood of 2 to 20 mils, in thickness, although thicker container walls may be employed so long as they can be ruptured or broken under the desired conditions of use.

An inner, generally concentric sphere 12, having a wall 13 also formed of plastic material or glass or other ceramic material, is positioned within the outer sphere 10. Prior to assembly, said sphere 12 is filled with a "fuel" 14, viz., a silikon. The silikon used may be in a dry powdered form or in the form of a water gel.

An oxidizing agent, indicated by the reference numeral 15, is positioned in the space between the inner and outer spheres 12 and 10, and, as in the case of the luminescent agent, the oxidizing agent, or activator, can be in powdered or liquid form, or can be distributed throughout a water gel.

The proportions of luminescent agent to oxidizing agent, or activator, are preferably those that will give optimum performance in use. The concentric method of packaging illustrated by FIG. 1 results in maximum mixing and maximum light output upon rupture of the walls 11 and 13, or of the wall 13 only, where this can be accomplished. If only the inner wall 13 is to be ruptured, it should be of a thin, frangible material, while the outer wall 11 should be stronger, flexible and less easily rupturable so that forces exerted against the outer wall 11 can be transmitted through the oxidizing agent 15 to rupture the inner wall 13. Where the outer container wall 11 is intended to withstand rupturing forces, it should, of course, be of transparent or transluscent material, so that the light emitted upon the mixing of the oxidizing agent, or activator, with the chemiluminescent material 14 can pass through the unbroken outer wall 11.

In FIG. 2, instead of concentric spheres, there is diagrammatically illustrated a pair of spherical containers 20 and 21 joined together in side by side relationship by means of an adhesive, indicated at 22. Either of the spherical containers 20 or 21 may contain the luminescent agent, composition 14 and the other contain the oxidizing agent composition, or activator, 15. As before, the proportions of the active components of the compositions are such that upon mixing of the two, satisfactory performance will be realized. The side-by-side arrangement shown in FIG. 2, while not resulting in so complete mixing as would give best results, in nevertheless suitable for applications in which a reactivation of the chemiluminescent activity is desired.

In FIG. 3, there are illustrated diagrammatically a pair of pressurized tanks 25 and 26, which may be cylindrical in form and have walls 27 and 28 of sufficient strength to withstand the gas pressure, usually from 25 to 100 psi in the spaces 29 and 30 above the contents 31 and 32, respectively, of said vessels 25 and 26. Vessel 25, for instance, may contain the chemiluminescent material 14, preferably in the form of a water gel, while vessel 26 contains the oxidizing agent, or activator 15, also in the form of a water gel. Delivery tubes 33 and 34, extending in the respective vessels 25 and 26 to points near the bottoms thereof, serve for the discharge of the contents of these vessels into a common tube 35 provided with a suitable mixing valve 36 and terminating in a nozzle 37. As shown, the agent and activator gels are discharged in a single premixed stream from the nozzle 37, but the discharge could be in unmixed streams, side by side, if that type of valve were employed.

In the case of the gel dispensers of FIG. 3, the containers would be filled, or partially filled, with the agent and activator gels of such concentration as to give satisfactory or optimum performance, or, if a mixing valve is used, the mixing may be in such proportions as to give optimum performance. While the gel dispenser system of FIg. 3 is shown for manual operation, it can, of course, be provided with a timing device for the timed operation of a power-actuated valve in place of the valve 36.

In the hand signalling device illustrated in FIG. 4, the reference numeral 40 indicates an outer container for the chemiluminescent agent 41, which is suitably in the form of a powder. Within the outer container 40 is an inner container 42, filled or partially filled with the oxidizing agent or activator 43 which may be in a liquid or a flowable pastry state.

In the device of FIG. 4, the shape of the outer container 40 is such that it may be readily held in the hand for manual operation in signalling. The material forming the outer container 40 should be of a transparent, relatively tough material, so that when light is produced by manually rupturing the inner container 42, as by squeezing the outer container 40, the light emitted upon mixing of the contents 41 and 43 can pass through the unruptured outer container wall.

FIG. 5 illustrates a grenade, indicated generally by the reference numeral 45, the form and material of which may be similar to the conventional military hand grenade. Said grenade 45 is in the form of a closed cylinder 46 and is shown as filled with a large number of individual capsules 47 and 48 representing, respectively, capsules of the luminescent agent and of the oxidizing agent, or activator. As in the case of the conventional grenade, the grenade 45 is provided with a detonator 49 and an igniter 50. Consequently, when the igniter 50 is properly set for the grenade to explode, the resulting explosion will effect a mixing of the contents of the capsules 47 and 48 and the generation of luminescent light.

It will be understood that the capsules 47 and 48 can be formed of any suitable easily rupturable plastic, or other suitable encapsulating material, and that the luminescent and oxidizing agents can be in the form of their water gels, or in the form of pellets. In the latter case, the pellets can be coated to provide a continuous inert and impervious film. The size of the capsules 47 and 48 is not critical. The capsules could be one-half inch glass spheres, but whatever the size, the encapsulating film should have a relatively weak wall strength so as to be easily ruptured.

Various colors of chemiluminescent light can be produced by absorbing fluorescent dyes on the surface of the powdered silikon, such as green, red and yellow colors of light. Yellow-orange is the basic color of light emitted by silikon.

Primary uses for our chemical light-producing system include the following:

1. The light-producing materials can be deployed on the boundaries of land areas to detect the movement of animals at night; for example, cattle or sheep on a large open range. 2. The light-producing agent can be used for experimental work requiring night photographing of movement. 3. Others

The generation of light without heat through time release or pressure is, in itself, novel to the general public and, therefore, appears to be of potential interest in the area of tricks, games, toys, etc.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

Claims

We claim as our invention:

1. A packaged chemical light source comprising a constant package

a first mass in said package of a chemiluminescent agent selected from the group consisting of siloxenes, polysiloxenes, substitution products of polysiloxenes and mixtures thereof;

a second mass in said package of an inorganic oxidizing agent, and

a barrier inert to both masses and separating said respective masses,

said barrier being readily breached to effect an admixing of said masses and the resulting admixture when brought into contact with a liquid selected from the group consisting of water, water-miscible C.sub.1 -C.sub.5 alcohols and mixtures thereof reacting to produce chemiluminescent light.

2. A packaged chemical light source as defined by claim 1, wherein,

said oxidizing agent is a tetravalent cerium salt.

3. A source as defined by claim 1, wherein

said barrier is a thin, frangible synthetic plastic membrane.

4. A source as defined by claim 1, wherein

said barrier comprises two associated encapsulating membranes forming separate compartments with the respective masses within the respective compartments.

5. A source as defined by claim 1, wherein

said two membranes form inner and outer walls, one wholly within the other.

6. A source as defined by claim 1, wherein

at least one of said masses includes water, and said barrier being relatively water and moisture impervious.

7. A light source as defined by claim 1, wherein,

said barrier is constituted by plastic membranes separately encapsulating the respective agents, and a rupturable outer casing enclosing a plurality of said membrane encapsulated agents.

8. A light source as defined by claim 1, wherein,

said oxidizing agnet is in the form of a water gel containing an inorganic oxidizing agent.

9. A light source as defined by claim 1, wherein,

the selected chemiluminescent agent is carried in a water gel.

10. A light source as defined by claim 1, wherein,

the selected chemiluminescent agent is distributed in and carried by a water gel, and said oxidizing agent is an inorganic oxidizing agent also distributed in and carried by a water gel.

11. A light source as defined by claim 10, wherein,

both of said water gels are maintained under gas pressure for release and admixture of said gels.

12. A light source as defined by claim 1, wherein,

said package is in the form of a grenade having a detonator and igniter.