IL32606A - Device emitting vapors of insecticidal substances,and its manufacture - Google Patents

Description

2)©v±ce" ml l^ substances, and its manufacture CIBA-GEIGY AG C.30867 2-2876/AO PROCESS FOR THE MANUFACTURE OF APPARATUS FOR EMITTING OF INSECTICIDAL VAPORS The present invention concerns a process of manufacture of devices designed to emit, at room temperature, insecticidal vapors, or products such as insect repellants, which will make it possible to combat insects in enclosed spaces.

The process of fabrication envisaged by the invention is intended to facilitate the industrial production of devices which will assure a prolonged diffusion and substantially constant discharge of at least one insecticidal agent, devices which can be stocked without alteration before use, and which assure, when put to use, a lasting protection against insects, notably flies, mosquitoes and mites.

It is interesting to produce industrially devices which are permanent diffusers of insecticidal vapors, particularly where the latter is constituted by dimethyl dichloro-vinyl phosphate (or DDVP) . This phosphoric ester possesses remarkable insecticidal properties, particularly against flies in domestic quarters.

Compositions of homogeneous structure have already been produced in which DDVP is used in the form of a solid solution in various substances to provide blocks, cakes or analogous masses of homogeneous structure, for example, the French Patent No .1 , 343 , 700. However, such compositions are often sensitive to heat, with consequent risk of partial are liable to flow. Further, when the retention of the DDVP i not strong, there is always some exudation of the active material, even without a rise in temperature. If, in order to avoid this risk, one uses a solid mass with a strong retention for DDVP, the evaporation decreases rapidly with time, and the yield is poor since unused DDVP remains.

Evaporative devices of heterogeneous structure are also known, consisting of a reservoir of liquid insecticide, preferably DDVP, which feeds a diffusing panel permeable to this agent, preferably of plasticised polyvinyl chloride or a thin sheet of polyethylene (example French patent No .1 , 310 , 86 In evaporators of this kind, the presence of a relatively large quantity of liquid DDVP in the reservoir means serious risks of poisoning during storage, transport or use if the reservoir is inadequately sealed or deteriorates. This danger creates a serious problem in selecting material for the reservoir, and necessitates the provision of a protective exterior for the evaporative device against the deterioration of the reservoir and/ or the diffusion panel.

The French patent 1,535,792 concerns evaporative devices consisting of the application on to a substance containing DDVP in the form of a solid solution in a thermoplastic material, of an exterior diffusion panel permeable by DDVP consisting of a thin layer of a thermoplastic material such as polyethylene. The methods for producing such evaporators are of two types: (a) the exterior diffusion panel is a film, separated from the substance containing the insecticide} (b) the exterior diffusion panel is a laminated product attached to the substance containing the insecticide.

The evaporators made according to process (a) have the drawback that they require a relatively large evaporation surface for two reasons s (1) it is very difficult to use industrially very- thin plastic panels without support? (2) the transmission of the DBYP between the solid solution and the exterior diffusion panel is bad following the non-adherence of these t^o constituents· The method according to type (b) present great technological difficulties, for it is very difficult to brine about close adherence between a thin film of polymer with a mass of another polymer permanently diffusing gas or exuding liquid. ( here is no example given of this type of procedure in the French patent 1,535»792). e process followed in the invention envisages the industrial manufacture of apparatus for the emission of vapors of insecticidal substances, particularly of phosphoric esters such as 3>DVP. The method of manufacture is characterised by the impregnation of at least one pure active insecticide substance, or a substance in solution, in a fibrous absorbent plate, which is provided on at least one of its wo principal external faces, wi h 32606/2, Insecticidal substance to diffuse without being permeable to the surrounding humidity, said layer being so deposited as to adhere intimately to the fibrous plate; and by a system of joins between the elements of polymeric material of the evaporation device and those of the packing of the device for storage before use* It has been found that the fibrous mass was capable of feeding the diffusion layer continuously by close contact, the layer being advantageously constituted by a film of plastic material such as polyethylene, polypropylene or a copolymer with a high content of vinylidene chloride.

The phosphoric ester migrates across this polymeric diffusion layer which strongly limits the atmospheric humidity*s penetration of the fibrous ma†s serving es a reserve for the ester. It is very important \o limit as far as possible penetration of the mass by humidity, 3b r it is well-known that phosphoric esters, and particularly D.0YP hydrolyae easily.

Preferably the fibrous mass is constituted by a porous plate formed of agglomerated fibres, while the insecticidal agent is constituted by a solution of phosphoric ester in a non-volatile hydrophobic diluent such as a dialkyl phthalate .

The general process of industrial manufacture, according to the invention, includes the following operations: 1 - (a) coating, preferably continuous, of a fibrous absorbent plate with a thin layer of polymeric material destined to act as diffusion layer, followed by cutting the coated fibrous plate in plates of any shape or slze^ 1 - (b) sealing along the periphery of the coated face of the 32606/2 thermoplastic material preferably of the sane nature as the coating of polymeric substance on the fibrous plate; l-(c) dessication of the ensemble according to l-(b); l-(d) impregnation by a determined quantity of phosphoric ester, either pure or in solution, of the ensemble produced by operations l-(b) and l-(c)j l-(e) joining¾y sealing the frames of the two impregnated elements resulting from the previous operations in such a way that the two fibrous faces are applied one against the other and that the tvo coated faces constitute the external faces of the evaporation apparatus; l-(f) sealing along the periphery of each of the two faces of the e^oration device of an impervious sealing sheet designed to prevent evaporation before being put to use# l-(c), Preferably, operations -(d) f l-(e) and l-(f) are carried out in a dry atmosphere, and wh manual movements are necessary for these operations they should be made in a protective ©nclosure such as a glove-box.

In certain variants of general procedure, the order of different operations can be changed. In particular, In placing a rigid frame, the operation l-(f) is performed preferably before operation l-(b) , thus allowing control to be exercised by pressure of the quality of the sealing of the impervious sheet on the frame.

We will now detail the characteristics of the constituent elements necessary for the general process: She substance constituting the absorbent fibrous plate must have a good absorbent capacity and good power of retention of the chosen Insecticide (preferably DDVP) to which it must pre 32606 2^ In view of the above, the absorbent plate is constituted preferably by one of the following substances: a strong non-sized paper, a card of non-sized cellulose, a wool felt, a felt card, a cardboard of old papers, a pack of glass fibre, a felt of glass fibre or a non-woven fabric.

On the other hand, the thin coating of polymeric material is constituted preferably by one of the following substances: a polyethylene, a polypropylene, a mixture of polyethylene and polypropylene, a copolymer of ethylene and propylene, or a copolymer with a high content of chloride of vinylidene · When a copolymer of chloride of vinylidene is used its content of chloride of vinylidene is generally between 75 an 97$ and preferably between 87 and 95$· ¾e copolymerisefi substances can be in particular of chloride of vinyl , of acrylic esters, of acrylonitrile.

The diffusion layer does not possess micropores which* if they existed, would lead to a permeability by flo¾, thus being non-selective. The slow passage of the DDVP occurs by activated diffusion, that is to say, by a movement molecule by molecule froa one free space to another, with substantial engaging of interaction between the membrane and the diffusing molecules. She quantity of product traversing the membrane perHinit of time increases with the temperature, and the diffusion is selective. The diffusion of the diluent is practically fail, and the absorption of humidity is very weak, even though the DDVP is hygroscopic.

•She thickness of the layer of polymeric material is generally between 10 and 80 microns, and preferably between 20 and 40 microns. 32606/2 > the same nature as that of the diffusion layer but of a thickness that is from 4 to 20 times as great. In the case of a semi-rigid or rigid frame, it is preferably obtained by moulding from a thermoplastic substance of the same nature as the diffusion layer. She rigidity of the frames obtained by moulding coses from their shape and thickness. Frames obtained by moulding are advantageously ©quipped with bars constituting a grille for the protection of the evaporation surfaces. This grille prevents contacts with the evaporation surfaces, and prevents young children from tearing or sucking them.

The insecticide destined to impregnate the fibrous absorbent plate is generally a liquid phosphoric ester, preferably BBTP; in any case, the BMP or the active substance derived should be as pure as possible, at least equal to 95%· Its acidity should be as weak as possible. The active agent is advantageously put in solution in a non-volatile diluent hydrophobe, fhis should not be susceptible to react with DDVP, nor to provoke its decomposition in time. It should be liquid at ordinary temperature. It should be miscible with DDVP at ordinary temperature and at the concentration for use. Preferably, the tension of vapour of the diluent at 20°C should be less than Q.C3 mm of mercury. In these conditions the diluent is advantageously a high molecular weight dialkyl phthalate, for example dioctyle phthalate; a silicon oil miscible with DBTP, for example oil SI 555 of BOVJ C0R1II8; a fatty acid ester, for example isopropyl myristate; a fatty alcohol, for example lauryl alcohol; a vegetable oil, for example castor oil, linseed oil, soya oil.

The content of diluent in the active solution is generally 32606/2 may also contain other ingredients such as stabilisers, synergistic compounds, perfumes and dyes.

The quantity of insecticide per apparatus depends on the nature of the insecticide, the space to be treated, the length of time for which it is required and the residual retention of the BDYP in the fibrous absorbent plate. The quantity will be about 15 to 25 g of DDVP for an apparatus in-tended for a space of 30 m during three months.

The impervious sealing sheet is constituted of a thermoplastic material of the same nature as that of the frame, with sufficient thickness (for example 0.5 mm of high density polyethylene) to ensure that the diffusion of the phosphoric ester shall be negligible during storage. Preferably the impervious sealing sheet is made by a multilayer ensemble, heat-sealable on one face, of the type known in the packing field under the name of "complex", fhe complexes known are very numerous; the number end nature of their layers are variable. Orse finds in the different complexes the following layers! paper, aluminium, low-density polyethylene, high-density polyethylene, pol amide, polyester, copolymer of vinylidene acetate of cellulose, etc. According to the method of laanufacture in accordance with the invention, it is necessary to choose a "complex" the layers of which villi not de-laminate on contact with the vapours of the phosphoric ester, and it is preferable to choose a "complex" of which the internal layer is made of a thermoplastic substance of the same nature as that of the frame of the diffusion apparatus* The following procedural operations are necessary: The deposition and adherence of the diffusion layer on the fibrous absor 32606/2 , position can be made in one or more successive layers (or coats). In the case of polyethylene, the deposition can be effected either by the technique known as extrusion-lamination, or by coating with an aqueous or organic dispersion of very fine polyethylene powderj this last technique, described by FicSHAERY, HOVJELL and HEMERIHO in "ELastiques Hodernes et Blastomeres", April, 1968, has the advantage of giving a highly superior bonding of the polyethylene on the plate. In the case of vinylidene copolymer, the deposit is preferably obtained by coating from an aqueous dispersion, for example, the product IXA WA of the S0L?AY company. One can also use a solution of the plastic substance in a volatile solvent which is uniformly sprayed on one of the faces of the plate. The adherent deposit is also obtained by "sticking" that is to say by heat-lamination of a film on the fibrous plate. Shis technique ia generally less successful as it does not give good adherence* The cutting in plates is carried out by known methods, for example with a paper-cutter for square and rectangular forms or with a punch-press for the other shapes.

The sealing along the periphery of the coated face of the plates on the frame of thermoplastic material is effected on a width of about 2 to 5 mm by heat sealing with the aid of a metal heating block of the same shape as the absorbent plate. She temperature of the heating block depends on the nature and thickness of the thermoplastic substance. This temperature should be controllable to a precise degree. Further, the heating block should exercise a certain pressure between the pack of absorbent plates and diffusion layer or layers, and the frame in order to assure 52606/2 ^ or of its stage is preferably controlled by a pneumatic screw with a delay mechanism. In the case of a flexible frame, that is, a fairly thin frame, the heating block is applied to the frame. In the case of a rigid frame, that is, a relatively thick one, the heating block is applied to the non-coated face of the pack, the heat necessary for the fusion of the diffusion layer being transmitted through the fibrous plate.

The dessication of the packrahen mounted on the frame is carried out by known methods, for example by submitting the pieces to infra-red rays in a tunnel, taking care to turn the non-coated face of the pack towards the rays. The temperature in the dessication area should be regulated in such a way that it does not induce the deterioration or deformation of the thermoplastic parts permanently. The duration of time in the dessication area depends on the temperature in the cavity and on the degree of humidity in the fibrous plate.

The impregnation of the fibrous plates, coated and mounted on the frame, by the phosphoric ester, pure or in solution, is effected, for example, by distribution of the liquid with the use of a titrating apparatus on the plates in a horizontal position. The speed of distribution should be regulated according to the speed of absorption of the liquid by the plate, in such a w that the liquid does not soil the frame. Different methods of impregnation can be preferable in different general procedures.

The junction of the frames of two impregnated Rlements is effected by a sealing method which differs according to whether 32606/2 rigid frame which is relatively thick.

In the case of a flexible frame the junction is made on a width of about 2 to 5 mm by heat sealing between two heating blocks similar to one another, adapted to the frame, such as to grip it* The two heating blocks are either identical metallic blocks to those used for the sealing of the coated sheets on the frames, or rigid armatures furnished with a heating ribbon. The temperature, the time nd the pressure of the pincer grip, and eventually the cooling time under pressure in the case of a heating-ribbon device are determined by the nature and thickness of the thermoplastic material of the flexible frame. The joining of flexible frames can also be effected by heat welding ¾ith the use of a heating wire.

In the case of a rigid frame the junction is made on a width of 1 to 3 mm (approx.) preferably with the use of the thermic procedure known by the name of "heated tool welding".

The sealing of the impervious sealing sheet on the frame is effected on a width of about 1 to 10 mm* preferably by heat welding, with the use of a metallic heating .block similar to that used for the sealing of the coated plates on the frames· When the impervious sealing sheet is a "complex" including a sheet of aluminium, one can also use a high-frequency soldering technique using the heat energy developed by a high-frequency current* In certain other varieties of procedure, well-known soldering techniques, different from those indicated in the detai.¾ of assembly operations may be preferred, There follow certain variants of the constituent elements 32606/2 surface or any other system allowing the diffuser to be attached; - (b) when the frame is rigid or serai-rigid it has feet or any other system for maintaining the diffuser in a vertical position on a horizontal surface. - (c) The capacity of absorption of the emission apparatus of pure phosphoric ester or of a solution s increased by the insertion of one or more plates of absorbent material, non-coated, between the two coated absorbent fibrous plates. The non-coated plates inserted are of the same nature or of a different nature from those coated. - (d) Only one fibrous absorbent plate is used, relatively thick and coated on its two sides instead of the assembly of two plates coated on one side, - (e) Only one fibrous absorbent plate is used, coated on one side, the device only diffusing on one side. In this case the assembly has only one frame. - (f) In the case of a single diffusion surface the non- diffusing surface of the assembly consists of the bottom of a tight reservoir, preferably moulded from a thermoplastic substance of the same nature as that of the frame supporting the diffusion layer. - (g) The impregnation liquid containing the phosphoric ester is absorbed on a holder or is jellified to make a paste or cream. - (h) The frame is metallic, for example, of galvanised hoop iron or aluminium with anti-corrosive varnish on the inside The followin variants of e e al rocedure can be used 32606/2 - (a) The adherent coating of the polymeric material (diffusion layer) is deposited on a thin sheet of non-absorbent paper, non-woven fabric or similar material, Instead of being deposited on a fibrous absorbent plate. One cuts this thin coated plate to the required shape. By pressure, with heat, the coated face of the thin sheet is made to adhere to a fibrous absorbent non-coated plate previously cut to a slightly smaller size, so that the thin coated sheet projects beyond the perimeter of the fibrous absorbent plate. Impregnation is carried out, then the two coated elements are joined in such a way that the two fibrous surfaces are applied one against the other. The edges of the two elements are then sealed, thanks to the coating of polymeric material. Thus is produced a watertight asuembly without frame* - (b) If the cut or moulded thermoplastic frame is suppressed, the sealing of the edges and eventually the assemblage in the case of a device with multiple plates occurs by treatin the edge with a coating of plastic substance in concentrated solution, which is then dried, or a coating of melted plastic substance which is later solidifed by cooling, - (c) ¥hen the absorption capacity is increased with the aid of inserted absorbent plates (case 2-(c)) these latter can be held on the coated plates by one or several spots of glue to facilitate the subsequent 32606/2 (d) When using a single fibrous absorbent plate coated on both sides (case 2-(d)) the active liquid is injected into the absorbent fibrous mass by the use of a hollow needle introduced at the edge of the plate* (e) In the case of a flexible frame one effects the Joining of the frames by sealing their edges before impregnation, one edge remaining non-sealed thus forming a kind of sachet with an opening through which one introduces the active liquid between the two fibrous absorbent plates, after which said opening is sealed. (f) In the case of semi-rigid or rigid frames of thermoplastic material, the frames are joined by sealing before impregnation. A hole is pierced in the side of the frames and the active liquid is injected between the two fibrous absorbent plates by means of a hollow needle inserted through the hole. Then the hole is sealed up by fusion of the thermoplastic material, possibly with the addition of a little more of the material* (g) When the absorption capacity is increased with the aid of inserted absorbent plates (case 2-(c)) impregnation is limited to these plates, and is effected by dipping them into the active solution. ( h) When the frame is metallic (case 2-(h)) it is sealed hermetically on the diffusion layer by crimping in lieu of heat-welding* (i) In a case where one of the diffusion surfaces is re- 32606/2 placed by a, the bottomof a tight reservoir (case 2-(f)) the active solution is introduced directly into the reservoir, which then receives the coated fibrous absorbent plate and is mounted on its frame. 3 - (j) In the case where the active solution is absorbed or jellified (case 2-(g)) impregnation is effected by the deposition of a paste or cream on the absorbent fibrous plate. The diffusion of the active solution in the fibrous absorbent plate occurs slowly and of its own accord after the frames have been sealed* 3 - (k) In the case of flexible frames, or in the absence of a frame (eases 3 - (a) and 3 - (b) ) the insecticide! agent without absorbent plate is placed in a gridded or perforated cavity. 3 - (1) Instead of impervious sealing sheets sealed onto the frame an impervious sachet is used, with thermo-sealed edges into which the insecticidal agent has been introduced. 3 - (m) Instead of impervious sealing sheets sealed onto the frame an airtight metallic box is used, designed to be opened by hand.

In the attached drawings the various methods of procedur are shown for the production of an insecticidal system such as intended in the invention.

Fig. 1 is a partial schematic view in perspective, with^bransverse section of an apparatus according to the invention. Figure 1 is in conformity with the variants 2-(d), 3-(b), 3-(d) of the general procedure. In this figure, 1 is the fibrous 32606/2 absorbent plate, rectangular in shape, of which the two large surfaces are covered by two diffusion layers 2 which are attached to said surfaces. The slice of the sandwich plate thus constituted is sealed on its periphery by means of a thermoplastic substance, 3· Figure 2 is a transverse section view of a variant of the previous scheme. igure 2 is in conformity with the 3-(b) variant of method. ~ In this figure l-(a) and 1(b) the fibrous absorbent plates- f rectangular shape are juxtaposed and pressed against one another. Each absorbent plate is covered by a diffusion layer 2, to which it is adhering* The plate thus constituted is sealed by a cordon of plastic substance 3.

Figure 3 is like Pig. 1» but of another apparatus made according to the 2-(a), 2-(d), 2-(h) , 3-(d), 3-(h) variants.

In this figure 1 is the fibrous absorbent plate of rectangular shape, of which the two large surfaces are covered by two diffusion layers 2 which adhere to theai. The mounting consists of a metallic frame 3a of which the edges 4 provide a mechanical seal. She emission apparatus also comprises an apertured tab 5 and bosses 6, designed to maintain the layer 2 facing the wallet a certain distance therefrom, to allow the free circulation of air anc a good diffusion of the insecticidal vapours.

Figure 4 is a view analogous to that of Figure 2 of another embodiment made according to variant 2-(c) ♦ In this figure la and lc are fibrous absorbent plates, rectangular in shape, covered by two diffusion layers 2 which adhere to them; one is a non-coated inserted absorbent plate. Assembly by sealing (6) of the two frames 3a and 3b in thermoplastic substance holds the three sheets pressed one against the other. The diffusion layers 2are 32606/2 The two impervious sealing sheets, 5 and 5b are soldered 6nto the outside of the rim of the frame.

Figure 5 is a partial scheme in perspective, with right section of another dispenser made according to variant 3-(a). In this figure la and lb are fibrous absorbent plates of rectangular shape on which, with pressure under heat, the polymer-treated surfaces 2a and 2b of sheets of paper 7a and 7b have been made adherent, this paper having dimensions slightly larger than those of the fibrous absorbent plates la e d lb.

After impregnation, these two assemblages formed respectively by la, 2a, 7a and lb, 2b and 7b are joined by heat soldering on the whole perimeter following the margin 10 of the coated paper 7· This dispenser thus includes two sheets of paper 7 as exterior surfaces.

Figure 6 is a view in elevation of a particular embodiment according to variants 2-(c) and 3-(g) · Figure 7 is the sectional view according to YII-VII of Figure 6. In Figure 7 two fibrous absorbent plates la and lb, together with their respective diffusion layers 2a, 2b are lodged in groove 9 of the two elements 8a and 8b destined to be jointed alonf the periphery of the frame. The surface of the diffusion layer 2a, 2b is soldered on the periphery to the contact surface of groove 9· Plate lc is a fibrous material impregnated with the insecticide placed between the two assemblies la, 2a and lb, 2b before the assemblage of the two elements 8a, 8b, T s two elements 8a# 8b are advantageously made of plastic in polyethylene material (for example^) and the periphery of the frames serve as supports for the grids 11, formed by moulding and constituting protective grilles situated at a relatively great distance from th 32606/2 diffusion layers 2a, 2b„ This arrangement avoids any accidental contact with surfaces 2a, 2b, and prevents children from tearing or lickiig them. Safety can thus be assured. At the same time, the two elements 8a and 8b, while sealing the edge, maintain the other elements of the apparatus in contact and give the apparatus rigidity.

After some day*s storage the insecticide solution initially contained in the plate lc has spread uniformly by capillary action between the three fibrous plates la, lc, lb.

Good preservation in storage is ensured by sealing the edges of the impervious sealing sheets onto the edge of the frame t-.s in 10a, 10b.

At the time of use the impervious sheets are easily cut if a groove as 11a, lib has been formed for this purpose in the two lateral faces of the frame.

The emission apparatus according to the invention presents the following notable advantages: - long duration of action (1 to 6 months) - constancy of evaporation with time • good storage quality before and during use - safety during storage, transport and us e - low cost This combination of advantages is peculiar to the combination of methods envisaged by the invention.

There will now be described two detailed examples of diffusion apparatus and the results obtained from tests of these embodiment : 32606/2 2 Grey cardboard of old papers 560 g/m with a coating 2 of 45 g/m of polyethylene. Square format 14x14 cm* b) intermediate card lb Cellulose cardboard, unsized, 1000 g/m « Square format 14x14 cm, c) Active solution DDVP, technical at 96% .76$ diociyl phthalate *.·20 epoxidised soya oil Total quantity impregnated into the three cartons: 51 g, that is 15 g on the intermediate card and 8 grammes on each coated card. d) Assembly The diffusion ayers 2 are heat sealed soldered at their edges onto the interior surface of the rim 4 of the two frames of polyethylene 3a, 3b, of 2 mm thickness. The two frames, 3 , 3b, are sealed together by heated tool welding in 6* The two impervious sealin sheets, 5a and 5 are soldered on the exterior surface of the rim 4* Put into service in a room at 22°C this diffusion appar atus emits the insecticidal vapours of DDVP at a constant level of about 100 mg/day for 130 days. At the end of 65 days of em's ission the diffuser is placed in a closed chamber 30 m free from all products of insecticidal action. The temperature of the room is 25°C and the hygrometric degree is 05$. As soon as the diffuser has been put into the room, 100 domestic flies (Musca b) intermediate card lb 2 Cellulose cardboard, unsized, 1000 gm . Square format 14x1 cm, c) Active solution DDVP, technical at 96 76 dioctyl phthalate ... 20$ epoxidioed soya oil 4 Total quantity impregnated into the three cartons: 51 g, that is 15 g on the intermediate card and 8 grammes on each coated card. d) Assembly The diffusion layers 2 are heat sealed at their edges on to the interior surface of the rim 4 of the two frames of polyethylene 3a, 3b* of 2 mm thickness.

The two frames, 3a, 3b, are sealed together by heated tool welding in 6. The two impervious sealing sheets, 5a and 5b are heat-welded on the exterior surface of the rim 4.

Put into service in a room at 22°0 this diffusion apparatus emits the insecticidal vapours of DD?P at a constant level of about 100 mg/day for 130 days. At the end of 65 days of emission the diffuser is placed in a closed chamber 30 m free from all products of insecticidal action. The temperature of the room is 25°C and the hygrometric degree is 40$· As soon as the diffuser has been put into the room, 100 domestic flies (Musca domestica) are introduced. At the end of 49 minutes it is noted that half these flies are in decubitus dorsal. The figure is 87$ at the end of an hour.

B. Diffusion apparatus of Figure 5: a) Coated paper 2a, 7a or 2b, 7b 2 Bleached kraft paper 40 g/m Coating of copolymer of vinylidene chloride of 2 g/m in two layers Square format 12x12 cm. b) Absorbent sheet la or lb 2 Cellulose card, nonsized, 1000 g/m Square format 10x10 cm. c) Active solution DDVP, technical 96% 76% Dioctyl phthalate 20% Epoxidised soya oil 47o Total quantity impregnated into the two cartons: g.

Put into service in a room at 22°C, this diffusion apparatus emits insecticidal vapours of DDVP at a constant level of 175 mg/day (approx.) for 35 to 40 days. Emission at 60 days is still 125 mg/day. At the end of 50 days of 3 diffusion the diffuser is placed in a closed room of 30 m free from all products with insecticidal action. The temperature of the room is 25 °C and the hygrometric degree is 35%.

Immediately after putting the diffuser in the room, 100 flies (Musca domestica) are introduced. It is noted. that half the flies are in decubitus dorsal after 28 minutes. The mortal- . ity is total at the end of 55 minutes. The same biological tests after 70 days of evaporation gives a decubitus dorsal If one takes as the limit of useful employment the time when the level of evaporation of insecticide is no more than 707o of the initial level, the balance sheet of the active material is as follows in the case of DDVP: DDVP regularly diffused: 65 to 75% DDVP hydrolised in plates of fibrous material 5 to 1570 DDVP remaining in the plates of fibrous material 10 to 307o The duration and consistency of insecticidal effect are, in the two cases, particularly remarkable when one considers the simplicity and the low cost of the means employed . - - t

Claims (8)

1. tances, comprising a support impregnated with liquid insecticidal phosphoric acid ester, a coating layer of thermoplastic material permitting diffusion of the vapors of the insecticide, and optionally an outer protecting sheet preventing loss of insecticide vapors prior to the use of the device characterized in that: a) the support is a fibrous plate or plate assembly comprising one or more plates of strong unsized paper, unsized cellulose board, woolfelt, re-used-paper cardboard, glass fiber board or glass fiber matting, said plate or plate assembly is coated on one or both surfaces with a thin diffusion layer of a polymer of a kind and thickness so chosen as to permit the diffusion of the vapors of liquid insecticidal phosphoric acid ester without becoming permeable to the moisture of the ambient atmosphere, said diffusion layer firmly adheres to the fibrous plate or plate assembly and said plate or, where the device comprises more than one fibrous plate, at least one of the plates of the plate assembly is impregnated with said liquid phosphoric acid ester; b) a frame of metal or thermoplastic material, impervious to the insecticidal vapors, is disposed at the periphery of said coated fibrous plate or plate assembly, and where the device comprises a plate assembly, two fibrous coated .are plates/applied to each other with their uncoaten surfaces directly or with the interposition of one o more uncoated fibrous plates and the frame is tightly joined to, or thermally fused together with, the diffusion layer or layers present and has, in each frame member extending along a diffusion layer, at least one window for the passage of the insecticidal vapors diffusing through such layer; and c) at least one sealing sheet is provided for each such window, which sheet is impervious to the insecticidal vapors and arranged to he easily removed "before the use of the device.
2. 2. A device according to Claim 1, wherein the frame and the diffusion layer or layers are made from the same polymer material*
3. 3. A device according to Claims 1 or 2, wherein the frame is rigid.
4. 4. A device according to Claims 1, 2 or 3» wherein the diffusion layer consists of polyethylene or polypropylene or a mixture of both, or an ethylene-propylene copolymer, or a vinylidene chloride copolymer containing from 75 to 97$ by weight of the vinylidene chloride monomer, the co-monomer being vinyl chloride, an acrylic acid ester or acrylonitrile.
5. 5. A device according to any of Claims 1 to 4, wherein the diffusion layer has a thickness from 10 to 80 microns.
6. 6. A device according to any of Claims 1 to 5, wherein the sealing sheet is made of a thermoplastic material (equal or) similar to that of the frame, and its thickness is sufficient to permit at most a negligible diffusion of insecticidal vapours during storage of the device.
7. 7. A device according to any of Claims 1 to 6, wherein the sealing sheet is a heat-sealable multilayer foilihose - 25 - 32606/2 layers do not beco*i© detached from ©.ch other by contact with the insecticidal vapors.
8. 8. A athod for the manufacture of a device according to Claim 3 p iherein first the sealing e¾ and then the fibrous board or sheet coated with the diffusion layer are welded to the frame. Por the Applicants SR. P vTMS KG/rb