GB2057884A

GB2057884A - A method of thermally volatilizing a chemical agent

Info

Publication number: GB2057884A
Application number: GB8022157A
Authority: GB
Original assignee: Earth Chemical Co Ltd
Current assignee: Earth Corp
Priority date: 1979-08-10
Filing date: 1980-07-07
Publication date: 1981-04-08
Also published as: IT1200979B; AR222880A1; FR2465416A1; DE3029933C2; GR69685B; FR2465416B1; GB2057884B; DE3029933A1

Abstract

A method of volatilizing a thermally vaporizable chemical agent by heating a volatilizing plate (2) with its volatilizing surface at least partially covered with a thin metal sheet (1) permeable to the vapor of the chemical agent; and a volatilizing plate, an attachment and a device useful for practicing the method. The method is useful for controlling insects and fungi, for repelling insects, for incensing and other purposes. <IMAGE>

Description

SPECIFICATION A method of thermally volatilizing a chemical agent This invention relates to a method of thermally volatilizing chemical agents, and more particularly to a method of volatilizing chemical agents by heating a volatilizing plate and to attachments, plates and devices useful for this method.

Volatilizing plates, typical of which are electric mosquito controlling mats, are heated on a heat plate which is heated electrically to volatilize chemical agents, for example, for controlling insects and fungi or repelling insects. Such volatilizing plates are prepared by coating or impregnating a substrate, such as a plate composed mainly of pulp or asbestos fiber, with a solution or like ofathermallyvaporiz- able chemical agent and drying the resulting substrate. However, the volatilizing plates heretofore known have the drawback that the chemical agent incorporated in the plate is not fully effectively voi- atilizable by heating but remains in the substrate in a large amount.Stated more specifically, the known volatilizing plate, when adapted to be heated at a low temperature, is unable to cause the chemical agent to volatilize at a sufficient rate per unit time, failing to produce the desired insecticidal or like effect and permitting a large amount of the effective agent to remain in the substrate as a loss. When set for heating at a high temperature, the plate involves an increased loss of the effective component due to thermal decomposition, similarly failing to achieve a high effective volatilization ratio. Especially when a small heat source is used to renderthe heating device compacter and less expensive, a greatly reduced volatilization ratio will result from an increase in the thermal decomposition ratio of the chemical agent and scorching of the plate due to local heating.

An object of the invention is to provide a method of thermally volatilizing chemical agents with a remarkably improved efficiency and with greatly reduced thermal decomposition ratio and residual ratio.

Another object of the invention is to provide volatilizing plates suitabledfor practicing the above method.

Another object of the invention is to provide attachments useful for the method.

Another object of the invention is to provide devices for practicing the method.

These and other objects and features of the invention will become apparent from the following description.

The present invention provides a method of volatilizing a thermally vaporizable chemical agent by heating a plate having the chemical agent incorporated therein, the method being characterized in that the plate is heated with its volatilizing surface at least partially covered with a thin metal sheet permeable to the vapor of the chemical agent.

The invention also provides a volatilizing plate comprising a substrate and a thermally vaporizable chemical agent retained by the substrate, the plate being characterized in that the substrate has a volatilizing surface at least partially formed with a thin metal sheet permeable to the vapor of the chemical agent.

The invention further provides an attachment for a volatilizing plate having a thermally vaporizable chemical agent incorporated therein, the attachment being characterized in that it comprises a thin metal sheet for at least partially covering the volatilizing surface of the plate in contact therewith, the thin metal sheet being permeable to the vapor of the chemical agent, and means provided at the metal sheet for attaching the metal sheet to the plate.

The invention further provides a device for volatilizing a chemical agent from a volatilizing plate by heating the volatilizing plate on a heat plate, the device being characterized in that it comprises means for at least partially covering the volatilizing surface of the volatilizing plate with a thin metal sheet in contact therewith when the volatilizing plate is heated, the metal sheet being permeable to the vapor of the chemical agent.

Throughout the specification and appended claims, the term "thin metal sheet" means a foil or sheet made from a metal alone, or a film or sheet prepared from a finely divided metal with use of a film forming resin. Examples of useful thin metal sheets are foils or sheets of metal produced by rolling, films of metal formed by vacuum evaporation, platings and films prepared from a coating composition containing a metal powder. Of these examples, films prepared by coating or vacuum evaporation are usually permeable to vapors of chemical agents, while metal foils or sheets must be perforated by suitable means as by punching and thereby made permeable to such vapors. The term "to cover" a surface with such a thin metal sheet refers to the usual mode of covering and also to the formation of a thin metal sheet on the surface concerned by affixing, vacuum evaporation, plating or coating.

We have found that when the volatilizing plate is heated as covered with a thin metal sheet, the chemical agent contained in the plate can be effectively volatilized at a remarkably improved ratio with greatly reduced thermal decomposition and residual ratios.

The substrates to be used for the volatilizing plates of this invention can be any of various materials which are usually used for the plates of this type.

Examples of useful materials are papers, nonwoven fabrics, woven fabrics orthe like of organic fibers, such as natural fibers, animal or vegetable fibers, regenerated fibers, synthetic fibers, etc., foamed bodies of resins, plates molded from ceramics, inorganic powders, such as pearlite, diatomaceous earth, silica, alumina, alumina-silica, calcium carbonate and titania, etc. The thickness, shape and area of the substrate are not particularly limited but can be determined suitably in accordance with the contemplated use, the type of the heating device, etc.

insofar as the substrate can be placed on the heat plate to volatilize the chemical agent therefrom by heating. Usually the substrate is in the form of a plate having a thickness of about 0.5 to 4 mm, preferably about 1.0 to 3.0 mm. For use with usual electric mosquito controlling devices, for example, the area is in the range of about 1 to about 100 cm2. In view of ease of manufacture and use, the substrate is preferably rectangular, square, triangular, rhombic, circular or oval in plan view. In section, the substrate is basically rectangular but can be L-shaped, trapezoidal, concave, convex or otherwise curved or bent. The substrate is usually smooth-surfaced on its front side (volatilizing surface) as well as on its rear side (surface to be heated) but can be somewhat rough-surfaced. The substrate may be in the form of a hollow cylinder, for example.In this case, the cylindrical substrate is heated from inside or outside to cause the chemical agentto volatilize from its outer or inner side. The substrate may then have approximately the same thickness as above. The substrate may be provided with a projection on its volatilizing surface so that the user can easily move the volatilizing plate with his finger or nail in engagement with the projection when fitting the plate in the heating device or removing the plate therefrom. Preferably the projection is projected by at least about 0.1 mm, more advantageously about 0.1 to about 2 mm, from the volatilizing surface. The projection can be provided at any desired location in the desired shape and size. Generally it is formed along the entire, or part of, the periphery of volatilizing plate.In the case of a rectangular volatilizing plate, for example, it is preferable to provide the projection at least at one of its long edges or short edges. The projection can be formed on a planar substrate by a press work, by affixing a projection piece to a planar substrate, by shaping the projection simultaneously with the substrate with use of a suitable mold, or by any other desired method. When the substrate has such a projection, the resulting volatilizing plate, which is of course easilyfittable in an removable from the heating device, can be as thin as about 0.5 mm. The plate can then be heated uniformly rapidly and achieves a greater increase in effective volatilization ratio and a further decrease in thermal decomposition and residual ratios.

The thermally vaporizable chemical agents to be retained by the substrate are various active agents heretofore used for controlling and repelling vermin, fungi, etc., for incensing and other purposes. Typical of such chemicals are given below.

1. Insecticides 1-A. Pyrethroids (1) 3 - Allyl - 2 - methylcyclopenta - 2 - ene - 4 one - 1 - yl dl - cis/trans - chrysanthemate (generally called allethrin, available under the trademark "Pynamin", product of SUMITOMO CHEMICAL CO., LTD., Japan, hereinafter referred to as "allethrin"); (2) An optical-isomer of allethrin (available under the trademark "Pynamin-forte", product of SUMITOMO CHEMICAL CO., LTD., Japan, hereinafter referred to as "Pynamin-forte"); (3) A stereo and optical-isomer of allethrin (available under the trademark "Exrin", product of SUMITOMO CHEMICAL CO., LTD., Japan); (4) A stereo and optical-isomer of allethrin (available under the trademark "Bioallethrin", product of Society' Roussel-Uclaf, France);; (5) N - (3,4, 5,6 -tetrahydrophthalimide) - methyl dl - cis/trans - chrysanthemate (generally called phthalthrin, available under the trademark "Neopynamin", product of SUMITOMO CHEMICAL CO., LTD., Japan, hereinafter referred to as "phthalthrin"); (6) ct - Cyano - 3' - phenoxybenzyl dl - cis/trans - a - isopropyl - 4 - chlorophenylacetate (generally called fenvalerate, available under the trademark "Sumici- din", product of SUMITOMO CHEMICAL CO., LTD., Japan);; (7) 5 - BenzyI - 3 - furylmethyl dl - cisitrans - chrysanthemate (generally called resmethrin, available under the trademark "Chrysron", product of SUMITOMO CHEMICAL CO., LTD., Japan); (8) An optical-isomer of resmethrin (available under the trademark "Chrysron-forte", product of SUMITOMO CHEMICAL CO., LTD., Japan); (9) 5 - Propargyl - 3 - furylmethyl chrysanthemate (generally called furamethrin); (10) 2 - Methyl - 5 - propargyl - 3 - furylmethyl chrysanthemate (generally called proparthrin);; (11) 3 - Phenoxybenzyl dl - cis/trans - 3 - (2,2 dichlorovinyl) - 2,2 - dimethyl - 1 - cyclo - propanecarboxylate (generally called permethrin, available underthetrademark"Exmin", product of SUMITOMO CHEMICAL CO., LTD., Japan, hereinafter referred to as "permethrin"); (12) 3 - Phenoxybenzyl d - cis/trans - chrysanthemate (generally called phenothrin, available under the trademark "Sumithrin", product of SUMITOMO CHEMICAL CO., LTD., Japan, hereinafter referred to as "Sumithrin"); 1-B.Organophosphorus insecticides (1) O, Dimethyl 0- (2,2 - dichlorovinyl)phosphate (generally called DDVP, hereinafter referred to as "DDVP"); (2) O, O - Dimethyl S - (1,2 - dicarbethoxyethyl)phosphorodithioate (generally called Malathion); (3) O,O-Dimethyl O - (3 - methyl - 4 - nit- rophenyl)phosphorothioate (generally called Sumithion); (4) 0, O - Diethyl 0-2- isopropyl - 4 - methylpyrimidyl - 6 - phosphorothionate (generally called Diazinon); 1-C. Carbamates (1) 1 - Naphthyl N - metbylcarbamate; (2) 2 - Isopropoxyphenyl N - methylcarbamate; 2. Industrial fungicides (1) 2,4,4' - Trichloro 2' - hydroxydiphenyl ether (available underthetrademark"lrgasan DP300", product of Ciba-Geigy Ltd., Switzerland, hereinafter referred to as "Irgasan DP300"); (2) Alkylbenzyl dimethylammonium chloride (generally called benzalkonium chloride, hereinafter referred to as "benzalkonium chloride"); (3) 2 - (4'-Thiazolyl)benzimidazole (hereinafter referred to as "TBZ"); (4) p - Chloro - m - xylenol (PCMX); (5) Benzyidimethylt2 -[2 - (p - 1,1,3,3 -tet- ramethylbutylphenoxy)ethoxy]ethyl} ammonium chloride; (6) Salicylic acid; (7) N - (3',5' - Dichlorophenyl) -1,2 - dimethylcyc- lopropanecarboximide (available under the trademark "Sumilex", product of SUMITOMO chemical co., Itd., Japan);; (8) S-n-BuPyl S' -p-tert- butylbenzbrlN-3- pyridyldithiocarbonimidate (available under the trademark "Denmert", product of SUMITOMO CHEMICAL CO., LTD., Japan); 3. Antiseptics (1) eY - Bromo - cinnamaldehyde; (2) N,N - Dimethyl - N - phenyl - N' - (fluorodichloromethylthio) - sulfamide; 4. Agricultural fungicides (1) Tetrachloroisophthalonitrile; (2) 2,4 - Dichloro - 6 - (o - chloroanilino) - 1,3,5 - triazine; (3) Ethyl p,p' - dichlorobenzylate; 5. Plant growth regulants (1) 4 - Chiorophenoxy acetic acid; (2) Gibberellin; (3) N - (Dimethylamino) succinamide; (4) - Naphthylacetamide; 6. Herbicides (1) Sodium 2,4 - dichlomphenoxyacetate; (2) 3,4- Dichloropropionanilide; 7.Repellents (1) N,N - Diethyl - m -toluamide (D.E.T.); (2) Di - n - propyl isocinchomeronate (3) Di - n - butyl succinate Among the above thermally vaporizable chemicals, insecticides are more suited for use in this invention. These chemicals can buzz be used conjointly with any oFsynergists, deodorants, perfumes, etc.

which are usually used. Preferable examples of the synergists are piperonyl butoxide, N-propyl isome, "MGK-264" (product of MCLAUGHLIN GOPMLEY KING CO., U.S.A., "Cynepirin-222" (product of YOSHlTOMl PHARMACEUTICAL INDUSTRIES LTD., Japan), "Cynepirin-500" (product ofYOSHITOMI PHARMACEUTICAL INDUSTRIES LTD., Japan), "Lethane 384" (product of ROHM AND HAAS COM PANY, U.S.A.), "IOTA" (product of NIPPON FINE CHEMICAL CO., LTD., Japan), "S421 " (product of SANYO CHEMICAL INDUSTRIES, LTD., Japan). Pre ferred deodorants are lauryl methacrylate (LMA), etc.Citral and citronellal are preferably usable as perfumes.

The substrate is caused to retain the thermally vaporizable chemical agent before or simultaneouslywith or afterthe formation ofthethin metal sheet to be described later. The chemical agent is applied to the substrate by a usual method, for example, by impregnation, dropwise application, spraying or printing. The chemical agent and the material for preparing the substrate may be kneaded and then formed into the volatilizing plate. Preferably the chemical agent is applied to the substrate by dissolving the agent in petroleum ether, n-hexane or like organic solvent in about 10 times the amount by weight of the agent together with the desired additives, impregnating the substrate with the solution and removing the solvent from the substrate by drying. The substrate may be impregnated with the chemical agent up to the saturated amount.The amount of the chemical agent in the substrate is preferably about one half of the saturation amount.

The volatilizing plate ofthis invention is characterized in that a thin metal sheet which is permeable to the vapor of the chemical agent retained by the plate is formed over the volatilizing surface of the substrate. Useful for forming the thin metal sheet are metals or alloys having ductility and higher heat conductivity than the substrate, such as Al, Fe, Cu, Zn, Ni, Cr, Sn, Pb, Au, Ag, etc. These metals are usable singly or in the form of an alloy of at least two metals, and may contain C, O, Si or the like. More preferable among these metals are metals having good heat reflectivity, such as Al, Cu, Ag, etc. The thin metal sheet may be suitably processed to impart good heat reflectivity to the sheet. The thin metal sheet can be formed on the volatilizing surface of the substrate typically by the following methods.

(1) Affixing method in which a foil or sheet of metal formed by rolling is affixed to the substrate with adhesive.

(2) Direct method in which a sheet of metal is formed without using any adhesive directly on the substrate, for example, by vacuum evaporation or plating.

(3) Transfer method in which a thin metal sheet formed on plastics of like sheet as by vacuum evaporation or plating is transferred onto the substrate with use of adhesive.

(4) Printing or coating method in which a composition prepared by admixing a finely divided metal with an aqueous or oily solution of film forming resin is applied to the substrate by photogravure, lithography, relief printing, screen printing orflexog- raphic printing, or by roll, reverse, spray, knife or like coating process, or by electrostatic coating.

Examples of adhesives useful for the affixing method (1) and the transfer method (3) are of starch, protein, polyvinyl acetate, ethylene-vinyl acetate copolymer, acrylic resin, polyacrylate, polyac rylamide, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, amino resin, polyurethane, polyester, fluorine-containing resin, epoxy resin, phenolic resin, polyaromatic resin, wax, polyethylene, ionomer, polypropylene and like types. These adhesives are usable in the form of an aqueous solution, emulsion, film, hot-melt composition or pressure sensitive tape. The thickness of the thin metal sheet to be formed on the substrate by the affixing method (1) is not particularly limited but is preferably about 10 to about 3000 ,u m in view of economy.Thinner or thicker metal sheets, although capable of producing the effect contemplated by this invention, are costly to make. When a thin metal sheet is to be formed directly on the substrate by the direct method (2), the substrate can be surfacetreated suitably in the usual manner, if desired, before the formation of the sheet. Usually the method (2) affords a film about 300 A to about 10 ,um in thickness. Films as thin as about 300 A also produce the desired effect according to the invention.

Film forming resins useful forthe printing or coating method (4) are vehicle or binder resins generally used for inks and coating compositions, such as phenol resin, nitrocellulose, acetylcellulose, methylcellulose, hydroxypropylcellulose, acetylbutyrylcel- lulose, ethylcellulose, acetylpropionylcellulose, benzylcellulose, carboxymethylcellulose and like cellulose derivatives, melamine resin, polyester resin, acrylic resin, alkyd resin, vinyl resin, aminoalkyd resin, epoxy resin, polyurethane resin and like resins which are oxidation-polymerizable or thermosetting or which can be dried by evaporation. Starchs are also usable.The finely divided metal is not particu- larly limited in particle size and can be in the form of fine particles which are usually available, for exam ple, about 1 to about 500 ,u m in particle size. The ratio of the finely divided metal to the film forming resin varies with the kind of each of these ingredients, the particle size of metal powder, etc. Usually the metal is used in an amount of about 1 to about 40% by weight of the resin.It is desired that the thin metal film prepared from the finely divided metal andfilmforniing resin be formed in an amountofat least 0.01 mg/cm2, usually 0.05 to 10 mg/cm2, preferably 0.1 to 3 mg/cm2, by dry weight relative to a unit area of the substrate. The thickness of the metal film is usually within the range of about 10 to about 200 szm.

Thin metal sheets usually about 300Ato about 3 mm are formed as contemplated by the above methods. Although the thin metal sheets formed by the printing or coating method (4) are permeable to the vapors of chemical agents, the metal sheets produced by the other methods, especially by the method (1), are substantially impermeable to such vapors and must therefore be made permeable. This can be done, for example, by forming a multiplicity of perforations for passing vapors of chemical agents in the thin metal sheet Such perforations can be formed by any desired method, typically by punching the sheet before or after the sheet is formed on the substrate.When the metal sheet is formed on the substrate and thereafter punched for perforation, the substrate can be punched at the same time so as to form perforations extending through the volatilizing plate. When a plurality of volatilizing plates of suitable size are produced by preparing a large shaped plate serving as a substrate material, forming a thin metal sheet over the shaped plate and blanking the resulting plate into small pieces of volatilizing plates, the metal sheet bearing plate is preferably punched for perforation simul- taneously with the blanking procedure. Although the thin metal sheet formed by the printing or coating method (4) need not be perforated, perforations can be formed therein.In this case, it is advantageous to print the composition on a substrate having suitable indentations orto apply the composition to a substrate with a roller having suitable indentations. The number and size of the vapor passing perforations and the combined area of the perforations are so determined that the chemical agent retained by the substrate will be released through the peribrations to the atmosphere when heated for vaporization.

Usually it is desirable that the perforations be arranged uniformly over the entire volatilizing surface of the substrate. Further preferably the com bined area of the perforations is at least about 3.3 mm2, usually about 3.3 to 75 mm2 (about 1/30 to about 3/4 of the volatilizing surface area of the substrate), more preferably about 5 to about 50 mm2 (about 1/20 to about 1/2 of the same), per 100 mm2 of the area of the volatilizing surface of the substrate to be covered with the metal sheet.

The thin metal sheet may be formed overthe entire volatilizing surface of the substrate on one side thereof opposite to the side (the surface to be heated) to be brought into contact with a heat plate when the volatilizing plate is heated on the heat plate. Alternatively the metal sheet can be formed only over a portion ofthe volatilizing surface, for example, along its periphery.When the volatilizing surface is partly covered with a thin metal sheet which itself is permeable to the vapor of the chemical agent, preferably at least 1/4, more preferably at least 1/2 of the area of the volatilizing surface is covered with the metal sheet When the metal sheet has perforations, the overall area of the sheet minus the combined area of the perforations, namely the substantial area of the sheet, is also preferably at least 114, more preferably at least 1/2 of the area of the volatilizing surface.The thin metal sheet can be formed also on the other surface of the substrate to be heated, in which case the sheet gives a smooth surface for heating, thus assuring effective contact between the volatilizing plate and the heat plate so that the plate can be heated uniY' rmlV- The attachment according to the invention comprises a thin metal sheet for at least partially covering a volatilizing surface of a volatilizing plate in contact therewith, the thin metal sheet being permeable to the vapor of a chemical agent and means provided at the metal sheet for attaching the metal sheet to the plate having the chemical agent incorporated therein. The vapor-permeable thin metal sheet may be substantially the same as those already described and formed on the volatilizing plate.Depending on the material and thickness of the thin metal sheet and on the processing method therefor, the thin metal sheet is subject to warping, deformation or breaking. In such a case, it is advantageous that the attachment be provided with a reinforcement, such as a frame for retaining the metal sheet thereon or a heat insulating plate or metal net for affixing the metal sheetthereto. The attaching means to be provided on the thin metal sheet is not particularly limited insofar as it is capable of fixing the sheet to the volatilizing plate. For example, a layer of usual pressure sensitive adhesive is useful when formed on the surface of the metal sheet to be brought into contact with the volatilizing plate.However, removable attaching means is usually preferable so that the attachment can be used repeatedly. Examples of preferable means are: an engaging portion provided continuously or discontinuously on a peripheral portion of the metal sheet and engageable with a side shoulder portion of the volatilizing plate; and a piern- ing portion adapted to penetrate the volatilizing plate. With the latter means, the thin metal sheet need not always be in conformity with the volatilizing plate in shape as seen in plan view. When the thin metal sheet is retained on a frame, the attaching means can be provided on the retaining frame.

The attachment of the invention is used as fixed to a specified portion of a usual volatilizing plate by the attaching means. The volatilizing plate having the attachment fixed thereto can be used in the same manner as the volatilizing plate of the invention already described to produce the same effect.

The present invention further provides a device for volatilizing a chemical agent from a volatilizing plate by heating the plate on a heat plate. The device is characterized in that it comprises means for at least partially covering the volatilizing surface of the plate with a thin metal sheet in contact therewith when the plate is heated and that the metal sheet is permeable to the vapor of the chemical agent. The main body of the device basically comprises a heat plate for placing the volatilizing plate thereon for heating and a heat source for heating the heat plate. The main body substantially has the same construction as conventional fumigators typical of which are usual electric mosquito controlling devices and which comprise a heat plate for heating a volatilizing plate thereon to thermally volatilize the vaporizable chemical agent retained in the plate.The covering means provided on the main body is so constructed that the volatilizing plate to be heated on the heat plate can be covered, over the volatilizing surface (upper surface) thereof, with a thin metal sheet which is permeable to the vapor of the chemical agent retained by the volatilizing plate. The thin metal sheet, a component of the covering means, may be the same as the thin metal sheet formed on the volatilizing plate of the invention and the thin metal sheet component of the attachment of the invention.

When the thin metal sheet is likely to warp, deform or break depending on the material and thickness thereof, the method of manufacture thereof, etc. the sheet can be provided with a suitable reinforcement as is the case with the attachment.

The present invention will be described below with reference to the accompanying drawings, in which: Figs. 1 to 4 are perspective views each showing a preferred embodiment of the volatilizing plate of the invention; Fig. 5 is a fragmentary sectional view on an enlarged scale showing the volatilizing plate of Fig.

4; Fig. 6 is a perspective view showing an attachment according to a preferred embodiment of the invention; Fig. 7 is a view in section taken along the line I-I in Fig. 6; Fig. 8 is a perspective view showing an attachment having a retaining frame and according to a preferred embodiment of the invention; Fig. 9 is a view in section taken along the line ll-ll in Fig. 8; Fig. 10 to 12 are sectional views each showing an attachment provided with another reinforcement and according to a preferred embodiment of the invention; Fig. 13 is a sectional view showing a volatilizing device having pivotable covering means and according to a preferred embodiment of the invention; Fig. 14 is a sectional view showing a volatilizing device having lid-type covering means and according to a preferred embodiment of the invention;; Fig. 15 is a sectional side elevation showing a volatilizing device having slidable covering means and according to a preferred embodiment of the invention; Fig. 16 is a plan view of the device shown in Fig.

15; and Fig. 17 is a front view showing the same.

Throughout the accompanying drawings, like parts are referred to by like reference numerals.

With reference to Fig. 1, a thin metal sheet 1 permeable to the vapor of a chemical agent is formed over the entire volatilizing surface of a substrate 2. The metal sheet 1 can be formed easily, for example, by the printing or coating method (4) orthe direct method (2) already described. Fig. 2 shows a thin metal sheets 1,1 which are permeable to the vapor of a chemical agent and which, however, are formed partially over the volatilizing surface of a substrate 2. Fig. 3 shows another embodiment of the thin metal sheet 1. The metal sheets 1, 1 in Fig. 2 cover 2/3 of the surface, while the sheet 1 in Fig. 3 covers about 3/5 of the surface. According to the embodiments of this invention shown in Fig. 1 through Fig. 3, the metal sheet preferably covers at least about 1/4 of the volatilizing surface of the plate.

With reference to Figs. 4 and 5, a thin metal sheet 1 having a multiplicity of perforations 3 arranged uniformly for passing the vapor of a chemical agent is formed over the volatilizing surface of a substrate 2. The metal sheet 1 is produced by the affixing method (1) described above but can be formed by some other method. The combined area of the perforations 3 in the sheet 1 can be so determined that the portions of the substrate volatilizing surface exposed by the perforations will be in the range of 1/30 to 3/4 of the entire volatilizing surface in area.

The metal sheet can be formed partially over the surface as seen in Figs. 2 and 3.

The volatilizing plates of this invention shown in Figs. 1 to 5 are used as placed in a volatilizing device having suitable heat source and heat plate, such as a known electric mosquito controlling device.

Thus the method of this invention is practiced by heating the volatilizing plate with a suitable heating device. The heating temperature, although optionally variable insofar as the chemical agent contained in the plate is thermally volatilizable, is usually up to about 450"C, preferably about 70 to about 350 C.

While the volatilizing plate can be heated with a heat source, such as a heating wire, sheet-like heater or heater including a thermistor or like semiconductor, which emits heat when electrically energized, any other heat source or heating device is usable provided that the plate can be heated to a temperature in the foregoing range. Examples of other useful heat sources are calcium oxide or like substances which gives off heat upon contact with water; iron powder or like metal powder which gives off heat on contact with an oxidizing agent; a material which generates heat when reacted with oxygen, such as a mixture of sodium sulfide, and iron carbide and/or carbon black; electric lamp; alcohol lamp; gas burner; and the combination of such a heat source and a fan for producing hot air.When the substance which emits heat when reacted with oxygen is to be used as the heat source, the heat emitting substance is shaped to a plate, which is fitted to the heating surface of the volatilizing plate in contact therewith in an inert gas atmosphere, and the assembly is hermetically enclosed in an air-impermeable bag.

The volatilizing plate is usable merely by opening the bag. The heat emitting substance then comes into contact with air, giving off heatto heat the volatilizing plate to a specified temperature. Thus the present method can be practiced with extreme ease as contemplated.

Figs. 6 and 7 show an attachment of the invention comprising a thin metal sheet 1 made from a metal of relatively high hardness by rolling. To renderthe sheet 1 permeable to the vapor of a chemical agent, the sheet has perforations 3 as uniformly distributed over the entire area thereof. The metal sheet 1 is provided at each corner with an engaging portion 4 engageable with a side shoulder portion of a volatilizing plate a. When the thin metal is made of relatively hard metal and is therefore unlikely to warp or break as in the present embodiment, there is no need to use a frame for retaining the metal sheet 1.

Figs. 8 and 9 show another attachment of the invention comprising a thin metal sheet 1 in the form of a film in which a film-forming resin has dispersed therein a finely divided metal and which itself is permeable to the vapor of a chemical agent. In this case, therefore, there is no need to perforate the sheet 1 for passing the vapor therethrough. The metal sheet 1, which is very likely to have low strength, is advantageously usable when retained on a frame 5 which is provided with engaging portions 4.

Figs. 10 to 12 each show an awachment compris- ing a thin metal plate 1 and another example of rein forcement. Fig. 10 shows a perforated reinforcing plate 6 affixed to the thin metal sheet 1. Fig. 11 shows a metal net 7 affixed to the sheet 1. The thin metal sheet 1 shown in Fig. 12 is folded in two. With this embodiment, a volatilizing plate can be sandwiched between the upper and lower leaves 1 a, 1 a of the metal sheet 1, so that the sheet need not be provided with any engaging portion unlike the other embodiments.Perforations 3 may be formed only in the metal leaf 1 a covering the volatilizing surface of the plate a, but when both the leaves 1 a, 1 a are perforated as at 3 as seen in Fig. 12, the plate a can be covered over both surfaces thereof with the vaporpermeable metal leaves la, 1a in contact therewith.

The volatilizing plate a is then usable either side up, while the chemical agent can be volatilized more effectively than when only one side ofthe plate covered.

As indicated with phantom lines in Figs. 7 and 9, the attachment of the invention is used with its thin metal sheet 1 attached to the plate a and covering the volatilizing surface thereof in contact therewith.

The thin metal sheet 1 covering and in contact with the volatilizing surface of the volatilizing plate a enables the plate to volatilize the chemical agent at a remarkably improved ratio with a great reduction in decomposition ratio as well as in residual ratio.

Figs. 13 to 17 show volatilizing devices ofthis invention. Indicated at A is the main body of the device which comprises a case 11, a heat plate 12 disposed approximately in the center of the case 11 and a thermistor 13 for heating the heat plate 12. The main body A is provided with means B for covering the volatilizing plate with a thin metal sheet The covering means shown in Fig. 13 is pivotable, while that shown in Fig. 14 is in the form of a lid fittable in the case. The covering means shown in Fig. 15 is slidable.

The pivotable covering means B of Fig. 13 comprises a cover 15 disposed on the case 11 and pivotably connected at its one end to the case 11 buy a hinge 14, and a thin metal sheet 17 attached to the cover 15 by bars 16 extending downward from the lower side of a top plate 1 5a of the cover 15. When the cover 15 is closed, the metal sheet 17 is brought into face-to-face contact with the volatilizing surface (upper surface) ofthe volatilizing plate a on the heat plate 12. To hold the metal sheet 17 in covering contact with the plate a properly with good stability, the cover 15 can be made holdable in its closed position on the case 11 by suitable engaging means (not shown) which basically comprises, for example, the combination of a projection and an indentation engageable with each other.As seen in Fig. 13, the top plate 15a of the cover 15 has a volatilizing aperture 18. With the embodiment shown in Fig. 13, retaining portions 19 for the plate a are provided on the lower side of the metal sheet 17 along edges thereof. Alternatively with the plate a held to the retaining portions 19,thecover15 is closed to place the plate a on the heat plate 12.

The lid-type covering means B shown in Fig. 14 comprises a lid 20 and athin metal sheet 22 attached to the lid 20 by bars 21 extending downward from the lower side of the lid 20. The lid 20 is fittable in an upperopening 11a of the case 11, whereby the thin metal sheet 22 can be brought into covering contact with the volatilizing surface of the volatilizing plate a placed on the heat plate 12. The lid 20 has a volatilizing aperture 23. With the embodiment shown in Fig.

14, the lid 20 can be made holdable in its closed position as fitted in the case 11 by suitable engaging means (not shown) which basically comprises, for example, engageable projection and indentation in combination.

Figs. 15 to 17 show slidable covering means B comprising a pair of rectangular holder frames 30, 30 and athin metal sheet 31 provided between and supported by the lower ends of the holder frames 30, 30. A support plate 11 b is disposed in a central top portion of the case 11 of the main body A and is supported by the case in a cantilever fashion. The holder frames 30, 30 of the covering means B are suspended from the support plate 11 b to render the covering means B slidable along the support plate 11 b. The covering means B is removable from the support plate 11 b at the free end of the plate 11 b through a side opening 1 1c (on the left-hand side in Fig. 15) of the case 11. With the covering means B removed from the case 11, a volatilizing plate a is held to the lower side of the metal sheet 31 by retaining portions 32, and the means B is then placed on the support plate 11 b in suspension and slidingly brought to a position above the heat plate 12. The volatilizing plate a is ready for use. To bring the plate a into proper contact with the heat plate 12, it is desirable to place the plate a in position relative to the heat plate 12 while slightly lifting the frames 30, 30, so that when the frames 30, 30 are released, the entire weight of the covering means B will force the plate a against the heat plate 12. With the present embodiment, the thin metal sheet 31 of the covering means B may be placed into covering contact with the pirate a afterthe plate a has been placed on the heat plate 12.The case 11 shown in Figs. 15 to 17 has a volatilizing aperture 11d in atop portion thereof.

With the devices of thins invention shown in Figs.

13 to 17, the volatilizing surface of the plate a can be covered at least partially with the thin metal sheet of the covering means B in contact therewith while the plate a is in use. The metal sheet thus directly covering the volatilizing surface enables the plate a to volatilize the chemical agent at a remarkably improved ratio with a great reduction in decomposition ratio as well as in residual ratio.

The process and devices of the invention described above are very useful for controlling and repelling vermin, such as mosquitoes, cockroaches, mites, lice, fleas, bedbugs, etc., for controlling insects noxious for agriculture and horticulture, such as those inhabiting greenhouses and further for volatilizing fungicides, incenses, inhalants, antiseptics, dermatitherapy and other chemical agents.

The invention will be described below in greater detail with reference to examples.

Example 1 A plate of pulp measuring 2.2 cm x 3.5 cm x 0.30 cm and serving as a substrate is coated, over the entire surface of its on side, with a mixture of resin and finely divided metal dispersed therein listed in Table 1 below, and then dried in airto form a thin metal film on the substrate. The substrate is impregnated with a mixture of a specified quantity of chemical agent indicated in Table 1 and 40 mg of piperonyl butoxide (PB, efficacy enhancing agent) to prepare a volatilizing plate as shown in Fig. 1. The same procedure as above is repeated with use ofthe other mixtures of resin and finely divided metal as well as chemical agents shown in Table 1.

Comparison Example 1 For comparison, volatilizing plates are prepared with forming resin film and without forming any film as shown in Table 1.

Table 1 Specimen ChemicalAgent Finely divided metal Resin Weight of Amount dryedcoat based on Particle (mg/cm2) Kind Amount Kind resin size (mg) (wit%) {/lm) This invention 1-A Allethrin (90) Al 15 90 (a) 0.2 1-B Pynamin-forte (40) Al 15 45 (b) 0.05 1-C " (40) Al 15 45 (c) 0.1 1-D " (40) Al 15 45 (d) 0.2 1-E ,, (40) Al 15 45 (e) 0.5 1-F " (40) Al 15 45 (f) 1.0 1-G " (40) Cu 20 90 (a) 1.0 1-H " (40) Cu/Ni 20 90 (a) 2.0 (1/1) 1-I " (40) Ag 20 45 (a) 2.0 1-J " (40) Ag 20 90 (a) 1.0 1-K " (40) Iron 20 90 (a) 1.0 oxide 1-L " (40) Sn 20 90 (a) 2.0 1-M " (40) Zn 20 90 (a) 2.0 1-N " (40) Al 15 90 (9) 2.0 1-0 " (40) Al 15 45 (h) 2.0 1-P Benzalkonium chloride (90) Al 15 45 (a) 2.0 1-Q Irgasan DP300 (90) Cu 15 45 (a) 2.0 1-R TBZ (90) Ag 15 45 (a) 2.0 Comparison 1-a Pynamin-forte (40) - - - (f) 1.0 1-b " (40) - - - - 1-c Allethrin (90) - - - (a) 1.0 1-d " (90) - - 1-e Benzalkonium chloride (90) - - - - 1-f Irgasan DP300 (90) - - - 1-g TBZ (90) - - - - The resins (a) to (h) listed in Table 1 are as follows:: (a)... Phenolic resin underthetrademark"TOYO KING ULTRA Medium," product of TOYO INK MFG. CO., LTD., Japan.

(b) . . Alkyd resin under the trademark "SS 5-510 Medium," product of the same company.

(c) ... Nitrocellulose-melamine resin under the trademark "SS 3-300," product of the same company.

(d)... Polyester resin under the trademark "SS 6K-600," product of the same company.

(e) . Acryl-vinyl resin under the trademark "SS 8-800," product of the same company.

(f) . . . Phenolic resin (heat-settable type) underthe trademark "Webking LTD. Victoria," product of the same company.

(g). ..a-Starch (h)... Carboxymethyl cellulose The volatilizing plates (Specimens Nos. 1-A to 1-R) thus prepared according to the invention each have a thin metal sheet permeable to the vapors of chemicals. The specimens are subjected to the following tests I, II and Ill.

Test I The specimen is placed on a heat plate of stainless steel having its surface (2.7 cm x 3.7 cm) maintained at a temperature of 166 t 2"C by electric heating. The specimen is heated in this manner for 12 hours within a hollow cylinder (18.0cm in in diameter and 30.0 cm in height) of paper having an upper opening.

A silica gel trap is prepared which is in the form of a glass tube (2.4 cm in inside diameter and 12 cm in length) filled with 20 g of silica gel (drying agent for packages, JIS grade 1, A type, up to 40 in grain size).

The trap has one end packed with absorbent cotton and connected by a rubber stopper two a funnel (0.7 cm in the inside diameter of its leg, 9 cm in length and 10 cm in the diameter of its opening) and the other end similarly packed with absorbent cotton and connected by a rubber stopper to a glass pipe.

The opening of the funnel is fitted to the opening of the paper cylinder, and the glass pipe is connected to a vacuum pump. The vapor of chemical released from the specimen is collected in the silia gel trap by suction at a suction rate of about 2.0 liters/min. The trap is replaced by a fresh one every hour. Each of the silica gel traps thus used is treated by the following procedure for the extraction and analysis of the trapped component (effective component).

1) The funnel is removed from the trap, the inner surface of the funnel is washed with ethyl ether, and the washing is placed into a flat-bottomed flask (hereinafter referred to as a "container") for Soxhlet's extractor. A boiling stone is placed into the container, and about 100 ml of ethyl ether is further added to the washing.

2) The container and a condenser tube are attached to Soxhlet's extractor with the glass tube of the silica gel trap placed in the extractor. The trapped component is subjected to extraction under reflux on a water bath at50"Cforabout2 hours.

3) Afterthe completion of extraction, the container is removed from the extractor and placed in a water bath at 50"C to distill off the ether for recovery.

4) A 1 ml quantity of standard solution (prepared by dissolving 600 mg of ethyl stearate in acetone to obtain 100 mi of solution) is added to the residue in the container, and the mixture is thoroughly shaken.

A 1 zl portion ofthe mixture is collected in a microsyringe and analyzed by gas chromatograph to measure the amount (mg) of the volatilized chemical agent per unit time.

The specimen, heated for 12 hours as above, is also subjected to extraction with ethyl ether. The same standard solution as above is added to the resulting extract and the mixture is analyzed by gas chromatography to measure the amount (mg) of the chemical agent remaining in the specimen.

The effective volatilization ratio (%) and residual ratio (%) of the chemical agent are determined from the following equations: B Effective volatilization ratio (%) = -x 100 A C Residual ratio (%) = -x 100 A in which A is the amount (mg) of the chemical agent impregnating the specimen, B is the amount (mg) of volatilized chemical agent per unit time, and C is the amount (mg) of the chemical agent remaining in the specimen after the test.

Table 2 below shows the results.

Table 2 Specimen Effective volatilization Residual No. ratio per unit time { /0) ratio in 12 hours.

0-1 hr. 4-5hr. ii- 12 hr. l"/ol This invention 1-A 9.9 8.6 7.1 5.1 1-B 9.3 8.2 7.3 6.8 1-C 9.5 8.3 7.4 5.9 1-D 9.6 8.5 7.2 4.8 1-E 10.1 8.8 7.1 4.3 1-F 10.4 9.1 7.0 3.4 1-G 9.8 8.7 7.2 4.2 1-H 10.2 8.6 7.0 3.6 1-l 9.9 8.6 7.1 3.5 1-J 9.6 8.3 7.5 4.1 1-K 9.7 8.4 7.3 4.5 1-L 9.8 8.5 7.1 3.7 1-M 10.0 8.7 7.2 3.8 1-N 10.2 8.8 7.0 3.2 1-0 10.1 9.0 7.0 3.5 1-P 8.0 7.5 6.4 6.8 1-Q 8.2 7.3 6.1 9.2 1-R 8.3 7.4 6.3 9.8 Comparison 1-a 4.1 3.7 3.5 32.4 1-b 6.1 6.0 4.8 14.7 1-c 3.9 3.5 3.2 31.6 1-d 6.0 5.8 5.1 15.1 1-e 4.2 3.5 3.0 27.5 14 4.2 3.3 2.8 28.7 1-g 4.0 3.2 2.5 32.8 Table 2 reveals that the volatilizing plates of this invention enable chemical agents to volatilize effec timely at remarkably improved ratio per unit time with greatly reduced residual ratios, whereas the comparison specimens are all low in effective volatilization ratio and high in residual ratio. Comparison Specimens 1-a and 1-c which are coated with resin film are further inferior to Comparison Specimens 1-b and 1-d which have no film coating in effective volatilization ratio and in residual ratio.

Test II Specimens Nos. 1 -C and 1 -F of the invention and Comparison Specimen No. 1-a are tested in a room 13.2 m2 in area.

An electric fumigator is placed in the center of the room with the specimen held in intimate contact with a heat plate. Thirty minutes afterthe start of supply of current to the fumigator, a 25 cm3 cage of plastics net having released therein about 25 adults of Culer pipiens pallens is placed at each of the four corners of the room 1.5 m above the floor as equidistantly spaced from the fumigator. The number of insects incapacitated (the number of knockdown) by contact with the vapour from the specimen is counted with the lapse oftime. One hour afterthe termination of fumigation, the insects are placed into a clean polyethylene container, given a 1% aqueous solution of sugar and allowed to stand in a room at about 25"C for 24 hours. The number of insects killed is thereafter counted.

To test the specimen for its efficacy with the lapse of time, the same procedure as above is repeated 4, 8 and 12 hours after the start of heating of the specimen.

The same procedure as above is repeated three times to obtain average values, which are listed in Table 3.

Table 3 knockdown (%) Time* Specimen No. Death (Lapse of time in min) rate 1 2 3 5 7 10 15 30 45 60 1%1 Invention No.1-C 1.9 11.6 34.2 65.8 97.7 100.0 100.0 30 min. " No.1-F 2.1 12.4 32.9 67.3 99.0 100.0 100.0 Comparison No.1-a 0 1.8 2.7 20.0 51.8 71.8 94.5 100.0 95.7 Invention No.1-C 3.5 20.9 64.2 89.5 98.7 100.0 100.0 4 hrs. " No.1-F 3.5 21.8 66.7 94.0 99.5 100.0 100.0 Comparison No.1-a 0 4.1 15.5 37.1 59.8 81.4 99.6 100.0 99.1 Invention No.1-C 3.6 16.9 40.2 74.3 93.1 97.8 100.0 100.0 8 hrs. " No.1-F 3.8 17.2 43.5 76.4 95.2 98.6 100.0 100.0 Comparison No.1-a 0 0 4.6 21.2 48.3 70.6 82.5 95.6 100.0 97.3 Invention No.1-C 1.0 4.8 9.7 37.6 67.8 89.2 91.6 97.4 100.0 98.2 12 hrs. " No.1-F 0 4.1 9.3 35.0 65.6 86.9 90.1 95.3 99.2 100.0 97.9 Comparison No.1-a 0 1.0 1.0 2.1 10.8 20.6 40.2 67.0 80.0 85.6 53.2 * Lapse of time before the cages are placed in the room afterthe start of heating of the specimen.

Test l// Specimen No.1 -E of the invention and Comparison Specimen No.1-b are tested forthe distribution of the effective component remaining in the specimens.

The specimen is heated for 10 hours on a heater having its surface heated to a maximum temperature of 1650C in the center and comprising a thermis torof positive characteristics 12 mm in diameter The substrate 3 mm in thicknes of the specimen is thereafter divided into three equal portions, namely, to upper, middle and lower portions, and the residual ratios (%) or Pynamin-forte in these portions are determined. The same procedure as above is repeated except that the length of the substrate is divided into three equal portions, namely, to left, center and right portions. Tables 4-1 and 4-2 below show the results.

Table 4-1 Portions Specimen No. 1-E Comparison Specimen No. 1-b Upper 5.4 12.0 Middle 2.6 4.0 Lower 1.1 1.2 Total 9.1 17.2 Table 4-2 Portions Specimen No. 1-E Comparison Specimen No. 1-b Left 3.3 7.4 Center 2.1 2.6 Right 3.4 7.2 Total 8.8 17.2 Example 2 A mixture of the resin (f) and finely divided aluminum as dispersed therein is applied to the entire surface of one side of a pearlite plate or diatomaceous earth plate (3 cm x 5 cm x 0.20 cm) serving as a substrate and prepared by adding 30% by weight of wood flour and 20% by weight of starch to 50% by weight of finely divided pearlite or diatomaceous earth, kneading the mixture with water, extruding the mixture and drying the shaped mixture. The coated plate is dried in air and then impregnated with 200 mg of a specified chemical agent to obtain Specimen No.2-A of the invention listed in Table 5.The same procedure as above is repeated with the exception of using different chemicals to obtain Specimens Nos.2-B and 2-C as listed in Table 5.

Comparison Example 2 The same procedure as in Example 2 is repeated with the use of the resin (f) instead of the mixture of resin (f) and aluminium, and without the use of the mixture to obtain Comparison Specimens Nos.1 -a and 1-b as listed in Table 5.

Table 5 Specimen Chemical agent Finely divided Al Resin Weight of No. Amount Particle dryer coat based on size Kind Amount resin (mug) (wit.%) (pom) (mg/cm2) This invention 2-A Permethrin (200) 15 45 (f) 1.0 2-B Sumithrin (200) 15 45 (f) 1.0 2-C Chrysronforte (200) 15 45 (f) 1.0 Comparison 2-a Permethrin )200) - - (f) 1.0 2-b Permethrin (200) - - - - The specimens are tested in the same manner as in Test I in Example 1 except that each of the specimens is placed on a heat plate having its surface maintained at a temperature of 350"C to determine the effective volatilization ratio in 20 minutes. Table 6 shows the results.

Table 6 Specimen No. Effective volatilization ratio (%) This invention 2-A 93 2-B 90 2-C 92 Comparison 2-a 51 2-b 67 Like Table 2, Table 6 shows that the specimens of the invention permit the chemical agents to volatilize effectively at improved ratios.

Example 3 Specimens of volatilizing plate according to the invention and as shown in Fig. 2 are prepared in the same manner as in Example 1 except that the mixture of resin and finely divided metal is applied to one side of the substrate over the longitudinally opposite end portions of equal area other than the 1/3 midportion thereof to form a thin metal film.

When tested in the same manner as in Test 1 in Example 1, the specimens are found to achieve remarkably improved effective volatization ratios comparable to those of the specimens of the invention in Example 1.

Example 4 Specimens of volatilizing plates according to the invention and as shown in Fig. 3 are prepared in the same manner as in Example 1 exceptthatthe mixture of resin and finely divided metal is applied to one side of the substrate over a width of 5 mm along all the edges of the substrate other than the center portion the reof to cover about 60% of the volatilizing surface of the substrate with a thin metal film.

When tested in the same manner as in Test 1, the specimens are found to achieve results comparable to those listed in Table 2.

Example 5 Specimens Nos.5-Ato 5-0 of volatilizing plates as shown in Figs. 4 and 5 are prepared according to this invention each by forming a thin metal film over the entire surface of one side of a substrate pulp plate, 2.2 cm x 3.5 cm x 0.3 cm, by printing, affixing, transfer or vacuum evaporation according to one of the following methods (1) to (6), then impregnating the substrate with a mixture of a specified amount of chemical agent and 40 mg of piperonyl butoxide (PB, efficacy enhancing agent) and further punching a specified number of uniformly distributed perforations with a specified size in the resulting plate.

When the metal film is formed by printing (Specimens Nos.5-l and 5-N), the perforations are formed in the thin metal portion simultaneously with printing with use of a roller having indentations without performing the subsequent punching step.

Film forming method (1) The substrate is coated with a vinyl acetate adhesive (trademark "Polysol L-111," product of SHOWA HIGH-POLYMER CO., LTD., Japan) by a roll coater in an amount of 40 to 50 g/m2, and a 10-,am-thick metal foil is placed on the coating. The assembly is pressed at 3 kg/cm2 and 100"C for 30 minutes.

Film forming method (2) A30-,um-thickfilm of polyethylene (trademark "Mirason," product of MITSUI POLYCHEMICAL CO., LTD., Japan) is formed by an extruder over a 10- m- thick metal foil with a titanate anchoring agent provided therebetween. The substrate is superposed over the film, and the assembly is pressed at 10 kg/cm2 and 180"Cto melt the polyethylene and affix the film to the foil.

Film forming method (3) A 12-,am-thick biaxially oriented polyester film (trademark "E-5000," product of TOVO SPINNING CO., LTD., Japan) is coated with a release varnish of the chlorinated rubber type (trademark "ABS-HP Release Varnish," product of TOYO INK MFG. CO., LTD., Japan) in an amount of 1 to 2 glum2 calculated as solids. A film of metal 800 A in thickness is formed over the coated surface of the film by vacuum evaporation by heating the metal at 1300 to 1400"C in a vacuum (10 4 mm Hg). An acrylic adhesive varnish (trademark "ABS-HP Adhesive Varnish," product of TOYO INK MFG. CO., LTD., Japan) is applied to the metal film in an amount of 2 to 4 g/m2 calculated as solids to obtain a transfer film, which is placed over the substrate. The assembly is pressed at 3 kg/m2 and 150"C for 15 seconds and the polyester film is pealed off.

Film forming method (4) The substrate is coated with an epoxy adhesive (trademark "Araldite," product of SHOWA HIGH POLYMER CO., LTD., Japan) by a knife coater in an amount of 50 git2. A 10-,um-thick metal foil is placed over the coated surface, and the assembly is pressed at 10 kg/cm2 with use of roll nipand60'Cforone hour.

Film forming method (5) The substrate is placed in a vacuum chamber at 10-4 mm Hg, and a metal is heated (for example, at 1300 to 14000C for Al) and deposited on the substrate to a thickness of about 10 pom under this condition.

Film forming method (6) A solvent solution of printing ink resin containing 20% by weight (based on the resin) of finely divided metal dispersed therein is applied to the substrate with a roller having specified indentations and thereafter dried in air to form a film having a thickness of 10 pom when dried.

Table 7 below shows the kinds and amounts of chemical agents used, the kinds of metals used for forming the thin metal films, the film forming methods and the number and combined area of perforations of each plate. Table 7 also shows volatilizing plates having no metal film for comparison.

Table 7 Specimen Chemical agent Metal Method Combined Number of No. Kind Amount area (mum2) perforations (mug) This invention 5-A Allethrin 90 Al (1) 38 76 5-B Pynamin-forte 40 Al (2) 38 38 5-C " 40 Al (3) 76 38 5-D - Benzalkonium 90 Al (4) 76 18 chloride 5-E Pynamin-forte 40 Al (5) 190 18 5-F " 40 Al (1) 380 18 5-G Irgasan DP300 90 Cu (2) 380 18 5-H Pynamin-forte 40 Cu/Ni (2) 380 18 (1/1) 5-1 " 40 Ag (6) 380 18 5-J TBZ 90 Ag (2) 380 18 5-K Pynamin-forte 40 Iron (2) 380 18 oxide 5-L ,, 40 Sn (3) 380 18 5-M " 40 Zn (4) 380 18 5-N " 40 Al (6) 380 18 5-0 " 40 Al (1) 380 18 Comparison 5-a " 40 - - 5-b Allethrin 90 - - 5-c Benzalkonium 90 - - chloride 5-d Irgasan DP300 90 - - 5-e TBZ 90 - - The specimens obtained are tested in the same manner as in Tests I, II and Ill in Example 1.

Table 8 to 10-2 show the results.

Table8 Effective volatilization Residual Specimen ratio per unit time (%) ratio in No. 0-1 hr. 4-5 hr. 11-12 hr. 12 hrs. (%) This invention 5-A 9.6 8.3 6.9 5.0 5-B 9.0 8.0 7.1 6.6 5-C 9.2 8.0 7.2 5.7 5-D 8.0 7.4 6.3 6.7 5-E 9.8 8.5 6.9 4.2 5-F 10.1 8.8 6.8 3.4 5-G 8.1 7.1 6.0 9.4 5-H 9.9 8.3 6.8 3.5 5-l 9.6 8.3 6.9 3.5 5-J 8.3 7.4 6.3 9.9 5-K 9.4 8.1 7.1 4.4 5-L 9.5 8.2 6.9 3.6 5-M 9.7 8.4 7.0 3.7 5-N 9.9 8.5 6.7 3.2 5-0 9.8 8.7 6.7 3.5 Comparison 5-a 6.1 5.9 4.8 14.7 5-b 5.9 5.7 5.0 15.5 5-c 4.2 3.5 3.1 27.4 5-d 4.1 3.3 2.8 28.6 5-e 3.9 3.2 2.6 33.1 Table9 Knockdown (O/o) Time* Specimen No.Death (Lapse oftime in min) rate 7 2 3 5 7 10 15 30 45 60 {ç/OJ Invention No.5-C 1.9 11.7 34.2 65.8 97.7 100.0 100.0 30 min. " No.5-F 2.1 12.4 32.8 67.3 99.0 100.0 100.0 Comparison No.5-a 0 1.8 2.7 20.0 51.8 71.8 94.5 100.0 95.7 Invention No.5-C 3.5 20.9 64.2 89.5 98.6 100.0 100.0 4 hrs. " No.5-F 3.5 21.8 66.7 93.9 99.5 100.0 100.0 Comparison No.5-a 0 4.1 15.5 37.1 59.8 81.4 99.6 100.0 99.1 Invention No.5-C 3.6 17.0 40.2 74.3 93.1 97.8 100.0 100.0 8 hrs. " No.5-F 3.7 17.2 43.5 76.4 95.2 98.6 100.0 100.0 Comparison No.5-a 0 0 4.6 21.2 48.3 70.6 82.5 95.6 100.0 97.3 Invention No.5-C 1.0 4.8 9.8 37.6 67.9 89.2 91.6 97.4 100.0 98.1 12 hrs " No.5-F 0 4.1 9.3 35.1 65.6 86.9 90.1 95.3 99.2 100.0 97.9 Comparison No.5-a 0 1.0 1.0 2.1 10.8 20.6 40.2 67.0 80.0 85.6 53.2 * Lapse of time before the cages are placed in the room after the start of heating of the specimen.

Table 10-1 Portions Specimen No. 5-E Comparison Specimen No.5-a Upper 5.6 12.1 Middle 2.7 4.0 Lower 1.1 1.2 Total 9.4 17.3 Table 10-2 Portions Specimen No. 5-E Comparison Specimen No.5-a Left 3.4 7.4 Center 2.1 2.7 Right 3.5 7.2 Total 9.0 17.3 Example 6 A 1O1Lm-thick perforated film of aluminum, silver or copper is affixed by the film forming method (2) or (4) in Example 5 to the entire surface of one side of a pearlite plate or diatomaceous earth plate (3 cm x 5 cm x 0.20 cm) serving as a substrate and prepared by adding 30% by weight of wood flour and 20% by weight of starch to 50% by weight of finely divided pearlite or diatomaceous earth, kneading the mixture with water, extruding the mixture and drying the shaped mixture.The substrate is impregnated with 200 mg of a specified chemical agent by placing the assembly into an air-impermeable bag, injecting the chemical agent into the bag and sealing the bag, whereby Specimen No.6-A of this invention is obtained. The same procedure as above is repeated to prepare Specimens Nos.6-B to 6-D according to the invention. These specimens are listed in Table 11 below, which also shows comparison specimens Nos.6-a to 6-c having no metal film.

Table 11 Metal film Specimen No. Chemical agent (mg) Substrate Metal Method Combined Number of area (mum2) perforation invention 6-A Permethrin (200) Pearlite Al (2) 380 18 6-B Benzalkonium (200) Diatomaceous Ag (4) 380 18 chloride earth 6-C Sumithrin (200) Pearlite Cu (4) 380 18 6-D Chrysron-forte (200) Diatomaceous Cu (2) 380 18 earth Comparison 6-a Permethrin (200) Diatomaceous - - - - earth 6-b Chrysron-forte (200) Pearlite - - - - 6-c Benzalkonium (200) Diatomaceous - - - - chloride earth The specimens are tested in the same manner as in Test I in Example 1 exceptthatthe specimens are placed on a heat plate having its surface maintained at a temperature of 350"C to determine the effective volatilization ratios 20 minutes after the start of heating of the specimens. Table 12 shows the results.

Table 12 Specimen No. Effective volatilization ratio ( /OJ This invention 6-A 91 6-B 85 6-C 90 6-D 90 Comparison 6-a 51 6-b 67 6-c 56 Example 7 An attachment of this invention as seen in Figs. 6 and 7 is prepared which comprises a thin metal sheet (about 10- m-thick rolled sheet), the sheet having perforations uniformly distributed therein.

The number and combined area (mama) of the perfo- - rations are listed in Table 13. The attachment is affixed to a volatilizing plate in the form of a pulp plate 2.2 cm x 3.5 cm x 0.3 cm and impregnated with 40 mg of Pynamin-forte and 40 mg of piperonyl butoxide. Specimens according to this invention are also prepared by repeating the same procedure as above except that the perforated thin metal sheets of various metals listed in Table 13 are used. These specimens and a volatilizing plate the same as above having no attachment for comparison are tested in the same manner as in Test I in Example 1. Table 14 shows the results.

Table 13 Specimen No. Kind of thin Perforations metal sheet Combined area Number (mm2) Invention 7-A Al 38 76 7-B " 76 38 7-C " 76 18 7-D " 190 18 7-E " 380 18 7-F Ag 380 18 7-G Fe 380 18 7-H Pb 380 18 7-l Sn 380 18 7-J Cu 380 18 Comparison 7-a - - Table 14 Specimen Effective volatilization Residual No. ratio per unit time (%) ratio in 12hrs.

0-1hr. 4-5hr. 11-12 hr. (%) This invention 7-A 9.5 8.2 6.7 4.9 7-B 9.2 8.1 7.1 5.6 7-C 8.0 7.4 6.3 6.7 7-D 9.8 8.6 7.0 4.0 7-E 10.0 8.5 6.7 3.5 7-F 9.5 8.2 6.8 3.6 7-G 9.4 8.1 7.0 4.3 7-H 9.5 8.2 6.9 3.7 7-1 9.7 8.4 7.1 3.8 7-J 9.8 8.7 6.9 3.5 Comparison 7-a 6.0 5.9 4.7 14.9 Example 8 A volatilizing plate of pulp (2.2 cm x 3.5 cm x 0.3 cm) impregnated with 40 mg of Pynamin-forte and 40 mg of piperonyl butoxide is placed on the heat plate 12 of a device of the invention (made of stainless steel) as shown in Fig. 13 while the heat plate is being heated electrically at 166 + 2 C. The volatilizing plate is thus heated for 12 hours with the lid 15 closed.The covering means B of the device used has thin metal sheet (0.01 -mm-thick rolled sheet) having perforations in the number and combined area listed in Table 15. The same procedure as above is repeated with use of similar devices except that the cov ering metal sheets listed in Table 15 are used.

Table 15 Perforations Specimen No. Kind of metal sheet Combined Number area (mm2) Invention 8-A Al 38 38 8-B " 38 76 8-C " 76 38 8-D " 76 18 8-E " 190 18 8-F " 380 18 8-G Cu 380 18 8-H Cu/Ni (1/1) 380 18 8-l Ag 380 18 8-J Fe 380 18 8-K Pb 380 18 8-L Sn 380 18 Table 16 shows the effective volatilization ratios and residual ratios of the chemical agent (Pynaminforte) resulting from heating the volatilizing plates as determined in the same manner as in Test I in Example 1. For comparison, Table 16 shows the test result achieved with use of a device having no covering means B.

Table 16 Specimen Effective volatilization Residual No. ratio per unit time ( /0) ratio in 12 hours.

O-lhr. 4-5 hr. 11-12hr ( /O) This invention 8-A 9.1 8.0 7.2 6.5 8-B 9.5 8.2 7.0 5.1 8-C 9.3 8.1 7.1 5.5 8-D 8.5 7.6 6.4 6.0 8-E 9.8 8.6 7.0 4.0 8-F 9.8 8.7 6.8 3.6 8-G 8.5 7.6 6.5 6.5 8-H 9.9 8.2 6.9 3.5 8-l 9.7 8.5 7.0 3.7 8-J 9.4 8.2 7.1 4.4 8-K 9.4 8.2 6.9 3.8 8-L 9.7 8.3 7.0 3.9 Comparison 8-a 6.0 5.9 4.8 14.8

Claims

1. A method of volatilizing a thermally vaporizable chemical agent by heating a plate having the chemical agent incorporated therein, the method being characterized in that the plate is heated with its volatilizing surface at least partially covered with a thin metal sheet permeable to the vapor of the chemical agent.

2. A method as defined in claim 1 wherein the thin metal sheet is a coating film comprising a finely divided metal and a film-forming resin.

3. A method as defined in claim 1 wherein the thin metal sheet is formed with a multiplicity of performations for passing the vapor of the chemical agent therethrough.

4. A method as defined in claim 1 wherein at least 1/4 portion of the volatilizing surface is covered with the thin metal sheet.

5. A method as defined in claim 4 wherein at least 1/2 portion of the volatilizing surface is covered with the thin metal sheet.

6. A method as defined in claim 1 wherein the plate is heated at a temperature of about 70 to about 450"C.

7. Avolatilizing plate comprising a substrate and a thermally vaporizable chemical agent retained by the substrate, the plate being characterized in that the substrate has a volatilizing surface at least partially formed with a thin metal sheet permeable to the vapor of the chemical agent.

8. A plate as defined in claim 7 wherein the thin metal sheet is a coating film comprising a finely divided metal and a film-forming resin.

9. A plate as defined in claim 7 wherein the metal sheet is formed with a multiplicity of perforations for passing the vapor of the chemical agent therethrough.

10. A plate as defined in any one of claims 7 to 9 wherein the volatilizing surface has a projection.

11. An attachmentforavolatilizing plate having a thermally vaporizable chemical agent incorporated therein, the attachment being characterized in that it comprises a thin metal sheet for at least partially covering the volatilizing surface of the plate in contact therewith, the thin metal sheet being permeable to the vapor of the chemical agent, and means provided at the metal sheet for attaching the metal sheet to the plate.

12. An attachment as defined in claim 11 wherein the thin metal sheet is held by a retaining frame having attaching means.

13. An attachment as defined in claim 11 or 12 wherein the attaching means is capable of removably fixing the metal sheet to the plate.

14. A device for volatilizing a chemical agent from a volatilizing plate by heating the volatilizing plate on a heat plate, the device being characterized in that it comprises means for at least partially covering the volatilizing surface of the volatilizing.plate with a thin metal sheet in contact therewith when the volatilizing plate is heated, the metal sheet being permeable to the vapor of the chemical agent.