US3759444A

US3759444A - Process and apparatus for the production of aerosols

Info

Publication number: US3759444A
Application number: US00158671A
Authority: US
Inventors: S Tanaka
Original assignee: Showa Denko KK; Sanko Kagaku Kogyo KK
Current assignee: Sanko Kagaku Kogyo KK; Resonac Holdings Corp
Priority date: 1968-02-28
Filing date: 1971-06-21
Publication date: 1973-09-18
Anticipated expiration: 1990-09-18
Also published as: NL6903100A; NL142338B

Abstract

A process and apparatus for production of aerosols which comprise charging a chemical in an aerosol forming apparatus equipped with a heating means and a fluid jet nozzle, and ejecting a fluid from the fluid jet nozzle, whereby a chemical vapor is drawn in the reduced pressure area formed by jetting of the fluid, as well as rapidly ejected into the atmosphere.

Description

United States Patent 1191 Tanaka [11] 3,759,444 1451 Sept. 18,1973

[ PROCESS AND APPARATUS FOR THE PRODUCTION OF AEROSOLS Inventor: Seizo Tanaka, Kanagawa, Japan Assignees: Showa Denko Kabushlki Kaisha,

Shiba-Tokyo; Sanko Kagaku Kogyo Kabushiki Kaisha, Tokyo, Japan Filed: June 21, 1971 Appl. No.: 158,671

Related U.S. Application Data Continuaiionbf Ser. No. 802,457, Feb. 26, 1989, abandoned.

Feb. 28, 1968 Japan 43/13121 U.S. Cl. 239/138, 239/338 Int. Cl B05b 1/24 Field of Search 239/138, 338

References Cited UNITED STATES PATENTS 3,511,236 5/1970 Conlin et a1. 128/187 Foreign Application 1 W 3,097,645 7/1963 Lester 239/338 1,999,265 4/1935 Tiscornia 239/138 2,181,650 11/1939 Briggs 239/138 2,696,548 12/1954 Bencetti 239/138 X 3,398,897 8/1968 Urbanowicz.. 239/338 3,584,792 6/1971 Johnson 239/338 Primary Examiner-Lloyd L. King Attorhey-Sughrue, Rothwell, Mion, Zinn & Macpeak [5 7] ABSTRACT 9 Claims, 3 Drawing Figures HEATING MEANS Pmminszmma 5.759.444

FIG. 3

PROCESS AND APPARATUS FOR THE PRODUCTION OF AEROSOLS CROSS-REFERENCE TO RELATED APPLICATION BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for the formation of chemical containing aerosols and an apparatus for the same. More particularly, it relates to a process and apparatus suited for the formation of aerosols of fungicides or insecticides.

The process of the present invention may be applied to a wide variety of chemicals so long as they can be formed into aerosols. However, the process will be hereinafter explained in more detail with reference to its application to fungicides and insecticides which are the preferred embodiments.

2. Description of the Prior Art Recently, the application of fungicides or insecticides in the form of aerosols thereof has received increasing interest in the art and has been used with a wide variety of chemicals as an effective means for controlling fungi and insects not only in enclosable rooms, such as warehouses and greenhouses, but also in open fields.

In general, processes for the application of insecticides or fungicides in the form of aerosols, or atomized particles, can be classified as follows:

A. Spraying a solution of active ingredients (e.g. fungicides, insecticides or both) which have been dissolved in a liquefied gas enclosed in a vessel utilizing the vapor pressure of the liquefied gas;

B. Spraying the solution of active ingredients using mechanical atomization;

C. Vaporizing the active ingredients with a mixture combustible material using the heat of combustion; and

D. Vaporizing the active ingredients by indirect heating.

However, none of these known processes is completely satisfactory. Process (A) for instance, has drawbacks in (1) use of a liquefied gas in which the active ingredient is dissolved, (2) compression in a confined container, (3) the high cost of the liquefied gas as well as difficult handling, etc. Process (B), though being rather widely used, still finds limited utility since it not only requires a particular solvent which must be.(1) inexpensive and (2) easily handled, but also the resulting aerosols are unstableand lack diffusibility and penetration into fine spaces.

Processes (C) and (D) have been used in practical fields, for example, as formulations comprising a suitable mixture of active ingredients and combustible materials such as sugars, zinc dust, aluminum dust, wood powder, celluloid and similar organic materials, and optionally, with an added oxygen-carrier such as salts or'esters of nitric acid, perchlorate salts, chlorate salts, bichromates, peroxides, etc. The processes are also utilized by heating only the active ingredients by the heat of the combustion. This is done by separating the combustible materials and oxygen-carrier, as illustrated above, from the active ingredients, and then burning the separated combustibles. These two latter processes,

although advantageous in simple operation, also suffer from drawbacks. For examle, the effect of the active ingredient is considerably lower during the combustion or heating in an oxidative atmosphere, such as air, heating mixture, or hot combustion gas, due to the oxidative decomposition of the active ingredient. Also, the by-products formed during the combustion or heating of the active ingredient oftend have hazardous influences on humans, animals and plants.

Therefore, an improved process for the formation of aerosols of chemical substances has long been desired in the art.

SUMMARY OF THE INVENTION It is an object of this invention to provide a process by which aerosols of chemicals, especially of fungicides, insecticides or mixtures thereof are formed in much more active states than those attained by prior processes.

Another object of this invention is to provide a process by which aerosols of fungicides, insecticides or mixtures thereof are produced at a lower cost than in conventional processes.

A further object of this invention is to provide a process by which aerosols of fungicides, insecticides or mixtures thereof are produced in a form containing much less decomposition by-prodlucts than prior processes which'are often hazardous-to humans, animals and plants.

Additionally, it is an outstanding advantage of this invention to provide a high dispersion of pesticidal aerosols in an enclosed room resultingin excellent control'of fungi and insects.

These objects have now been accomplished by the process of this invention, in which a pesticidal vapor is drawn into a reduced pressure area formed around a jet nozzle by means of a fluid ejected at a high speed into the atmosphere, virorouslymixed with air by the speed of jet stream, and rapidly cooled to cause formation of fine aerosols.

' BRIEF DESCRIPTION OF THE DRAWINGS The present-invention will be explained in the followingby appended drawings,

The apparatus shown in FIG. 1 is an aerosol forming apparatus which is used in the case of the chemicals to be formed in aerosols being comparatively unstable in an oxidative atmosphere.

FIG. 2 shows an apparatus for use when the chemicals'utilized in theae'rosol are apt to decompose or dea grade in an oxidative atmosphere, or the chemicals have low vapor pressures.

FIG. 3 shows a suitable apparatus for high vapor pressure, oxidation stable chemicals.

DESCRIPTION OF THE INVENTION This apparatus of FIG. 1 comprises a container 1 equipped with a heating device (which is shown schematically in the Figure) a cover 11 having a jet opening 12 and a bottom plate (13) of the container equipped with a fluid jet pipe 2 having a nozzle 21. The chemicals to be formed in aerosols are charged in the bottom plate and heated to a prescribed temperature by means of the heating device 14 of any suitable type. vaporized chemicals are drawn into the reduced pressure area formed by jetting the fluid from the nozzle and are immediately thrown out in the atmosphere to form aerosols.

In the apparatus of FIG. 2, the heating container is isolated from the open air except for a gas suction opening which communicates with the reduced pressure area being opened to the container, in order to reduce the pressure of whole interior of the container, which accelerates vaporization of ingredients and reduces the evaporation temperature to as low as possible. It will be easily understood that a nozzle is not always directed upwards on the bottom of a heating plate, but a gas suction opening may open anywhere inside the container, in order to attain said object. By using this apparatus, vapor of chemicals is also drawn into the reduced pressure area, mixed rapidly with a jet stream, and further mixed strongly with the open air and cooled rapidly when the chemicals come out of the jet opening. Thus, it is possible to remarkably lower decomposition and deterioration by oxidation.

The apparatus of FIG. 3 has a simple structure, and is inexpensive and easily handled, since the cover part is excluded from the apparatus as shown in FIG. 1.

It is preferable in any case that the jet pipe and the nozzle or the suction opening of the pressure reduction device is positioned near the evaporation surface of heated chemicals. The chemicals do not stay on the heating plate for long periods since the chemical vapor is drawn into the reduced pressure area formed by jetting fluid from the nozzle and forced therefrom and into the atmosphere. Accordingly, not only stable aerosols in which deterioration of ingredient is very low are produced, but, also it is possible to treat a large variety of chemicals, as compared with those treated by a prior direct heating or pyrotechnic method. Further this process can be used for ingredients which are easily decomposable by controlling the reduced pressure in the heating container to low grade.

These facts will be apparent from the following description of various processes for the formation of an aerosol of 6-methylquinoxaline-2,B-dithiocarbonate (Morestane) useful as an agricultural fungicide.

EXAMPLE A An aerosol forming apparatus was set on the center of a greenhouse of 300m". Disinfection of cucumbers, on which powdery mildew was parasitic, cultivated in the house was effected by natural diffusion of Morestane aerosols. The aerosol forming apparatus was a steel tray (container) having a diameter of 10 cm, without a cover, and was equipped with a heating device. 30g of Morestane were charged into the apparatus, and the container was heated to 300C to form aerosols. As the result, the germination control ratio for powdery mildew was only 73 percent at the center of the house and the germination controlling effect was hardly observed at outlying areas of the house.

' As the result of experiments on thermal decomposition of Morestane when forming aerosols, it was found that 47 percent by weight, based on the Morestand used, was decomposed and remained in the apparatus. The Morestane content in the aerosols product was only 34.5 percent, based on weight of said collected aerosols.

EXAMPLE B Using a steel plate equipped with a heating device instead of the aerosol forming apparatus as described EXAMPLE C In another experiment, cucumbers planted in a greenhouse of m, were disinfected by aerosols formed by burning a mixture comprising 20g of Morestane, 17g of potassium perchlorate, 30g of sucrose, 19g of charcoal powder, and 14 g of diatomaceous earth. As the result, there was no elimination of powdery parasitic mildew on the cucumbers, but also the cucumbers were injured by the decomposed chemicals.

EXAMPLE D On the contrary, according to the process of this invention, an aerosol forming apparatus as in FIG. 1 was placed on the center of a greenhouse of 300m? The apparatus comprised a steel open container 1 having a diameter of 10 cm, a cover 11 having a jet opening (3cm/diameter) 12 in the center thereof, and a jet pipe 2 having a nozzle 21 with an inner diameter of 0.8 mm disposed on the center of a bottom plate 13 of the container. The jet pipe was inserted to a height of 2 cm in the bottom plate, and the bottom plate can be heated by electric heating. 30g of Morestane (M) was charged in container 1 and the bottom plate 13 was heated to 300C, thus evaporating the Morestane. The vapor was drawn into the reduced pressure area formed by jetting air at a rate of 13 L./min. from the nozzle and thus rapidly ejected into the atmosphere from the jet opening to form an aerosol, thus effecting disinfection of cucumbers'planted in the house. The aerosol was scattered throughout the whole of the house, and the germination control ratio for powdery mildew on the cumcumbers was 97 percent. In this case, the amount of Morestane decomposition products that remained in the container was 14 percent by weight, based on the Morestane used, and the Morestane content in the aerosol was as high as 71 percent by weight.

Reasons for noxious insect and fungus extermination effect in the process of this invention as described above, can be explained as follows: first, stable and diffusible aerosols are produced by the acceleration of fine atomizing since the vapor is drawn into the reduced pressure area produced near the nozzle, mixed violently with a jet fluid and ejectedinto and rapidly cooled by air; second, inactivation by thermal decomposition is restrained since the evaporation rate is accelerated in accordance with the pressure reduction effect because the supersaturated vapor at the heating surface is continuously drawn into the reduced pressure area formed by a jet fluid; and third, diffusion areas are remarkably enlarged, as compared with the case when a jet fluid is not used since the aerosols are strongly ejected into and diffused in the atmosphere together with the jet fluid.

In practicing the process of the present invention, since the degree of pressure reduction formed by jetting can be easily varied, the evaporation rate of the ingredient can be controlled irrespective of the temperature of the heating area. Consequently, it is easily possible to produce aerosols of chemical substances having poor heat stability by increasing the degree of pressure reduction, although the formation of such aerosols was not possible previously, by heating to a temperature below a decomposition temperature thereof. Furthermore, according to the process of this invention, it is possible to use a heating atmosphere that is oxygen free. Accordingly, it is thus even possible to produce aerosols of chemicals which are easily oxidized at the heating temperature.

As the jet fluid for producing the reduced pressure in the process of this invention, generally gas, liquefied gas, a mixture thereof and smoke can be employable. Inert materials such as steam, carbon dioxide and nitrogen etc. are preferably used when the chemical substances are unstable. When chemical substances are comparatively stable, air or methyl bromide gas can be used as the jet fluid. Although the temperature of the jet fluid is not particularly important, it is generally from about room temperature to 100C. However, tem peratures higher than 100C. may be used, unless deterioration of the chemical substances occurs.

Although the heating temperature of the chemical substances cannot be specified since it depends on heat stability, degree of pressure radiation, and volatility of the used ingredient, 600C. or less is generally used. 300C. or less is preferable when the heat stability is poor.

The degree of pressure reduction used in the process of this invention depends on heat stability, vapor pressure, etc. of the ingredients. However, it is preferred that the degree of pressure reduction be increased by using a closed apparatus if the heat stability of the ingredients is poor, and/or vapor pressure thereof is low. In this manner, it is possible to rapidly form aerosols without elevating the heating temperature. On the other hand, the closed apparatus is not necessary if the vapor pressure is comparatively high and heat stability is good. In this case, increased noxious insect and fungus extermination is obtainable by using an open contion, common heating method by electric heat or fuel may be adapted.

The following examples are included as illustrative of the present invention.

EXAMPLE 1 An apparatus as in FIG. 2, consisting of a stainless steel container 1 of a capacity of 100 cm", equipped with a jet pipe 2 having a nozzle 21 of an inner diameter of 1 mm on a bottom plate of the container and a gas suction opening of reduced pressure device communicating with a jet opening 12 being opened to the container was charged with 1g of sulfur, and was heated to 220C with jetting N at velocity of 20L/min.

As a result, the vapor of sulfur was released in a carrier of N gas through the jet opening to the atmosphere without air flowing into the container, and a stable aerosol was formed.

The amount of sulfur dioxide in the aerosol was only 1 weight percent of the used sulfur. On the contrary, when sulfur is heated on a hot plate at more than 240C, the sulfur was burned by flaming up, and there after only sulfur dioxide was obtained.

In forming aerosols on a heated plate to 220C, it was also confirmed that 45 percent of the used sulfur was oxidized to sulfurous acid gas.

EXAMPLE 2 In an apparatus, as in FIG. 1, consisting of steel container having a diameter of 10 cm and a height of 6 cm equipped with a jet pipe of inner diameter of 1.8 mm and a length of 1 cm at the center of the container and a jet opening diameter of 4 cm at. the center of cover, the bottom plate of the container was heated by a methanol flame of 260280C, and simultaneously steam was jetted through the jet pipe at velocity of 20 L/min., 20g of 2,4-dichloro-d-orthoanilinotriazine mixed with the same weight amount of bentonite were treated, and thereafter produced an aerosol which was scattered to disinfect in a horticultural glass house of 198 m in which cyclarnens were cultivated.

As the result, the percentage control of Botrytis cinerea on the cyclamens fell to 1.8 percent from 88 percent.

EXAMPLE 3 To cover of the apparatus used in Example 2 was removed, the container charged with granule chemicals produced by mixing 30g of y-hexachlorocyclohexane with 1.5g of dextrine, and heated to 250C. The aerosol was then scattered about carnations cultivated in a horticultural glass house of 396 m The air jetting was done at ambient temperature and at a flow rate of 10 L/min.

As the result, the percentage control of aphides parasitic on the carnations was 96 percent.

EXAMPLE 4 The apparatus of Example 1, consisting of steel container in diameter and 10 cm in height, equipped with jet nozzle of 2 mm in inner diameter, was employed. A mixture of 30g of N-trichloromethylthio-tetrahydrophthalimide with 10g of talc was charged to the container, the cover sealed tightly, and the container heated to 200250,C. Steam was jetted at velocity of 60 L/min. and thereafter cucumbers cultivated in a horticultural vinyl house of m were treated with the aerosol thus produced.

As a result, the percentage control of Erwinia aroideae was reduced to one eighth of that before treatement.

EXAMPLE 5 m Remarkably high prevention of the effect of powdery mildew on cucumbers and nematodes in the soil was obtained.

I claim:

1. Apparatus for the formation of aerosols from a said container opening to create a reduced pressure area adjacent said spraying means and to draw vaporized chemical into the fluid spray, whereby the vaporized chemical is directed toward the container opening and cooled by contact with the surrounding atmosphere to produce aerosols.

2. The apparatus of claim 1 wherein said conveying and spraying means comprise a fluid jet pipe having a nozzle.

3. The apparatus of claim 2 wherein said container has a bottom plate and said jet pipe and nozzle extend substantially upwardly from said bottom plate.

4. The apparatus of claim 2 wherein said nozzle is positioned near the evaporation surface of said heated chemical in said container.

5. The apparatus of' asst;ifivnereiamatasaiaar has a cover with said opening therein. V

6. The apparatus of claim 1 wherein said container has a cover with a jet tube extending into said container and defining said opening.

7. The apparatus of claim 6 wherein a shroud having openings for the vaporized chemical is connectedto the inner end of said jet tube, said shroud surrounding said spraying means.

8. The apparatus of claim 1 wherein said chemical is a pesticide.

9. Apparatus for the formation of aerosols from a solid chemical consisting of a container for the chemical having an opening,

means for heating said container to a temperature sutflcient to "vapb'r'ize the chemical therein,

means for conveying a pressurized fluid into said container, and

means comprising a nozzle for spraying the pressurized fluid directly toward said container opening and directly into the atmosphere to create a reduced pressure area adjacent said nozzle and to draw vaporized chemical into the fluid spray emanating from said nozzle, said nozzle being positioned near the evaporation surface of the heated chemical in said container, whereby the vaporized chemical is directed into the atmosphere in said fluid spray and cooled by contact with the atmosphere to form an aerosol.

Claims

1. Apparatus for the formation of aerosols from a solid state chemical, comprising a container for the chemical, said container having an opening, means for heating said container to a temperature sufficient to vaporize the chemical therein, means for conveying a pressurized fluid into said container and means, including a nozzle, for spraying the pressurized fluid toward said container opening to create a reduced pressure area adjacent said spraying means and to draw vaporized chemical into the fluid spray, whereby the vaporized chemical is directed toward the container opening and cooled by contact with the surrounding atmosphere to produce aerosols.

5. The apparatus of claim 1 wherein said container has a cover with said opening therein.

7. The apparatus of claim 6 wherein a shroud having openings for the vaporized chemical is connected to the inner end of said jet tube, said shroud surrounding said spraying means.

8. The apparatus of claim 1 wherein said chemical is a pesticide.

9. Apparatus for the formation of aerosols from a solid chemical consisting of a container for the chemical having an opening, means for heating said container to a temperature sufficient to vaporize the chemical therein, means for conveying a pressurized fluid into said container, and means comprising a nozzle for spraying the pressurized fluid directly toward said container opening and directly into the atmosphere to create a reduced pressure area adjacent said nozzle and to draw vaporized chemical into the fluid spray emanating from said nozzle, said nozzle being positioned nEar the evaporation surface of the heated chemical in said container, whereby the vaporized chemical is directed into the atmosphere in said fluid spray and cooled by contact with the atmosphere to form an aerosol.