CH618846A5 - Device for controlling insects - Google Patents

Abstract

The device comprises a formed solid material having a porous surface capable of releasing 1,2-dibromo-2,2-dichloroethyldimethyl phosphate in a quantity sufficient to give an effective concentration of the insecticide for a prolonged period. It comprises a matrix of synthetic resin, 15 to 35% by weight of insecticide, finely divided silica particles in a quantity sufficient to retard the sweating of the insecticide and at least one C14-C20 saturated carboxylic acid or one of its salts or esters. It consists of a mixture of the compounds mentioned above and of a surface-porosity regulating agent non-reactive in the mixture and having a boiling point equal to or less than the hardening temperature of the mixture. The device is particularly useful for controlling houseflies, fruit flies and mosquitoes.

Description

The present invention relates to a device for controlling insects such as the house fly (Musca domestica), the fruit fly (Drosophila melanogaster), the mosquito (Culex pipiens), and other similar insects.

Insect control devices such as insect ribbons and the like have been widely used to date, comprising a PVC resin containing a dispersion of dimethyl 2,2-dichlorovinylphosphate, well known as DDVP or under its brand name Vapona, in order to combat flying insects such as house flies, mosquitoes and the like in the vicinity of the device. However, DDVP has been reported to have a deleterious depressant effect on the cholinesterase content of plasma and erythrocytes, at least in animals, this effect being particularly acute at the high concentrations that are produced during the very first days, when exposed to the atmosphere, for the first time, an insect-proof tape. This is believed to be due to the fact that the release rate of DDVP from currently available DDVP-containing insect ribbons is not uniform, but is rather higher during the first days after activation, that is, that is, when you removed the insect tape from its packaging and exposed it to the atmosphere. There are also indications that DDVP can be harmful to humans. Anti-insect tapes containing DDVP have been banned in the Netherlands. In addition, the above mentioned high initial release rate represents too rapid loss of insecticide and creates an upper limit on the release time of DDVP at a rate sufficient to effectively control the insects. DDVP has also been found to have a high degree of residual toxicity in the area of the device, apparently due to the absorption of DDVP vapors by walls, floors, ceilings, curtains, blankets, etc. Even after removing a DDVP insect control tape from a room, residual DDVP fumes can often be detected for several more days.

It has also been suggested to use other insecticides such as Naled or 1,2-dibromo-2,2-dichloroethyldimethylphosphate

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in an insect control device, such as an insect control tape. The preparation of Naled is described in United States patent No. 2971882. PVC / Naled resin combinations have been proposed for use as a general insecticide, in French patent No. 1568198 and in the patent application. No. 85445, filed January 30, 1961 (discontinued, but available to the public) and corresponding to British Patent No. 995350. The published Dutch patent application No. 6610279 describes fly ribbons made from PVC / Naled or PVC / DDVP combinations and having insecticide release rates high enough to require an outer laminate to delay the release of the insecticide. U.S. Patent No. 3,344,021 describes PVC / Naled combinations for use as an anthelmintic composition.

A number of problems have been encountered in the development of commercially satisfactory PVC / Naled resin combinations for use in an insect control device. First you need a sufficient amount of Naled to effectively fight insects in the vicinity of the device. Contrary to indications in the prior art, it has been found that the release rates for Naled are much lower than for DDVP. Naled has a low vapor pressure of about 2-10 ~ 4 mm Hg at 20 ° C, instead of 1.2.10-2 mm Hg for DDVP, i.e. only about 1.7% of the vapor pressure of the DDVP.

It has also been found that incorporating an insecticide such as Naled into a synthetic resin matrix in amounts sufficient to control the insects in a commercially acceptable period of time leads to the exudation of the insecticide liquid on the surface of the device. These droplets of liquid pose serious environmental and aesthetic problems, as well as a significant reduction in the effective service life of the device.

Another unexpected problem encountered with a PVC / Naled composition is the tendency of the resin to decompose during the forming process. For example, unsatisfactory results were obtained in the preliminary tests where DDVP was replaced by Naled in PVC combinations used in the extrusion machine used to make PVC / DDVP collars for pets , known in the art. Burning and charring of the extruded product was observed during curing of the collars, and the finished collars experienced an inexplicable decrease in the concentration of Naled compared to the concentration of Naled in the initial mixture.

The subject of the invention is therefore an insect control device, this device making it possible to reduce or eliminate the problems encountered in the prior art.

The new insect control device can contain a relatively high charge of insecticide without undesirable formation of droplets of liquid insecticide on the surface of the device. It can be used to fight insects in the vicinity of the device, by prolonged release of the insecticide, while minimizing the undesirable adsorption of the insecticide by neighboring solid objects.

The invention also relates to a method for manufacturing such a device.

The insect repellent device comprises a molded solid body having a porous surface capable of gradually and continuously releasing 1,2-dibromo-2,2-dichloroethyldimethylphosphate in an amount sufficient to give an active concentration of the insecticide, said device comprising a matrix of synthetic resin, 15 to 35% by weight of the insecticide, an amount effective to delay the seepage of the insecticide, of finely divided silica particles and at least one aliphatic carboxylic acid saturated with C14-C20 or one of its salts or esters, said device being formed of a mixture of said insecticide resin of said silica particles of said carboxylic acid or its salt or

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ester and a surface porosity adjusting agent which is not reactive in the mixture and which has a boiling point equal to or less than the curing temperature to produce surface openings in communication with the pores of said 5 body, by spraying said porosity regulating agent, to give the release of the gaseous insecticide at a speed effective in combating insects in the vicinity of said body, but insufficient to produce oozing on the device.

In a preferred embodiment, the device contains 20 to 10 30% by weight of Naled and an amount effective to delay the seepage by 15 to 25% by weight, of finely divided silica particles and 0.5 to 1.5 % by weight of at least one aliphatic carboxylic acid saturated with C14-C20 or one of its salts or esters, the said device being molded in a mixture of Naled synthetic resin, of finely divided silica particles and of approximately 1 to 3 % by weight of the agent for controlling the surface porosity.

The method of manufacturing the device is to produce an article comprising a mixture of a synthetic resin of 15 to 35% by weight of the insecticide and an amount effective to retard the seepage of the insecticide, particles of finely divided silica, at least one aliphatic carboxylic acid saturated with C14-C20 or one of its salts or esters and an amount of an agent for adjusting the surface porosity which is not reactive in the mixture and which has a boiling point equal to or less than the curing temperature of said mixture, said mixture being formed into said article at curing temperature to vaporize said porosity adjusting agent and to produce surface porosity in said article to provide an effective insecticide release rate to control insects in the vicinity of said article, but insufficient to form droplets on the article.

The invention is described in more detail below with reference to the figure of the accompanying drawing which represents a typical device suitable for combating insects.

As indicated in the figure, this device can be in the form of a molded body 1 having a regular symmetrical matrix comprising cavities, generally designated by 2, which extend along a dimension of the body. The cavities have substantially parallel axes and walls 3 which define a substantially straight line along a dimension. In this way, the molded device has good dimensional stability and is easy to manufacture and also has a relatively high specific surface from which the insecticide is released. It is understood by those skilled in the art that other forms can also be used.

The constituents of a satisfactory insecticide-containing insecticide device include a synthetic resin which is, for example, compatible with relatively high amounts of insecticide and strong enough to maintain the cohesion of the molded device throughout the release time of the mold. insecticide in effective amounts to control insects, such as flies or mosquitoes. The molded anti-insect device should comprise the synthetic resin in sufficient concentration to give the device physical properties such as strength, flexibility and lack of tack, making it suitable for use as an insect control device. Generally, the molded device contains from about 20 to 80% by weight, preferably from about 25 to 50% by weight of the synthetic resin.

The various known synthetic resins which can be used in the insect repellent device include substances such as polyethylene, polypropylene, ethylene / propylene copolymers, nylon, cellophane, polyacrylates such as polymers and copolymers of methyl acrylate, ethyl acrylate, methyl methacrylate 65 and ethyl methacrylate; polymers of vinyl compounds such as polystyrenes, polymerized divinylbenzene; polyvinyl halides such as polyvinyl chloride; polyvi-nylacetals, such as polyvinylbutyral; polyvinylidene compounds,

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such as polyvinylidene chloride; polyvinyl acetate; ethyl acetate / vinyl acetate copolymers; chloride / vinyl acetate copolymers; polyurethanes, polyaldehydes and thermoplastics.

Polyvinyl chloride (PVC) homopolymers and copolymers with other polymers such as polyvinyl acetate (PVA) are preferred synthetic resins. Suitable PVC resins are commercially available and include, for example, the dispersion of Diamond PVC-7502 ™ homopoly mother resin and Diamond PVC-7-446 ™ homopolymer / thinner PVC resin both by The Diamond Shamrock Co., and mixtures thereof. Other suitable commercial PVC resins are known in the art. Suitable PVC / PVA copolymers are also commercially available and include, for example, the following products: Geon 135 from Goodrich Corp., PVC-74 from Diamond Alkali Co. and XR-6338 from Exxon-Firestone. Other PVC / PVA copolymers are also known in the art.

The anti-insect device according to the invention contains Naled or 1,2-dibromo-2-dichloroethyldimethylphosphate in an amount sufficient to give an active concentration of the insecticide for a long time, for example approximately 120 days or more,

this amount can vary between about 15 and 35% by weight, preferably about 20 to 30% by weight of insecticide. With insecticide concentrations in this range, the insect control device can release approximately 1.5 to 5 mg of insecticide per 6.5 cm2 of surface and per day. Although the insect control device according to the invention can be used in any environment containing insects, maximum efficiency can be obtained when the device is used in an enclosed space containing these insects.

In general, the use of Naled in an amount of about 15 to 35% by weight in a synthetic resin matrix leads to the formation of droplets of liquid Naled or oozing on the surface of the insect repellent device. Liquid droplets of Naled forming on the surface of the molded device pose a significant health and safety risk and also decrease the effectiveness of the insecticide. The anti-insect device according to the invention comprises an effective amount, for delaying the seepage of the insecticide, of finely divided silica particles and at least one aliphatic carboxylic acid saturated with C14-C20 or one of its salts or esters and present a markedly reduced tendency to form liquid droplets of Naled on its surface.

Although silica is known in the art, together with other minerals and glasses, as a filler for various synthetic resins, the licensee has unexpectedly discovered that finely divided silica particles generally have a dimension of about 1 to 50 n, preferably about 2 to 10 n, have a relatively high efficacy in delaying the seepage of the insecticide, if used in sufficient amounts, these amounts delaying the seepage being generally about 10 to 35% by weight, preferably about 15 to 25% by weight of the anti-insect device. The use of finely divided silica particles in an amount of less than about 10% by weight is generally ineffective in providing a substantial delay in the seepage of the insecticide, while the use of finely divided silica particles in an amount of more than 35% by weight does not lead to an additional reduction in oozing.

Although the addition of finely divided silica particles is relatively effective in delaying the oozing of Naled, a small amount of Naled may nevertheless sometimes exude from the device containing the insecticide. The incorporation into the device of a small amount of at least one aliphatic carboxylic acid saturated with C14-C20 or one of its salts or esters (for example magnesium stearate) is effective in significantly delaying the oozing of Naled. The C14-C20 saturated aliphatic carboxylic acid, which may be a mixture of such acids, is generally used in an amount of about 0.25 to 3% by weight, preferably about 0.5 to 1.5% by weight, in the device. Preference is given to stearic acid and palmitic acid.

Although German Democratic Republic patent No. 91898 describes the addition of a C14-C20 saturated aliphatic carboxylic acid together with a particular mixture of primary and secondary plasticizers, for a polyvinyl chloride / DDVP mixture, the acid mixture / plasticizers being added to delay the seepage of DDVP, the licensee found that the use of the aliphatic carboxylic acid saturated with C14-C20 alone (that is to say without the finely divided silica particles), with the resin and insecticide in the insect repellent is insufficient to effectively delay the oozing of Naled out of the device. Similarly, the use of finely divided silica particles alone, i.e. without the aliphatic carboxylic acid saturated with C14-C20, is insufficient to effectively delay the seepage of the insecticide out of the device. However, the use of a small amount of both finely divided silica particles and C14-C20 saturated aliphatic carboxylic acid has been shown to be highly effective in delaying seepage of the insecticide and retaining the surface of the device free of liquid droplets of insecticide.

The licensee has verified that when the release rate drops to approximately 0.4 to 0.6 mg of Naled per 6.5 cm2 of surface area per day, the effectiveness of the insect control device is reduced to the point that it must be replaced. The use of Naled in the device in amounts less than about 15% by weight leads to a release rate at an ineffective value in too short a period (for example of about 90 d or less). The use of Naled in amounts greater than about 35% by weight causes seepage and the accumulation of droplets on the surface of the device.

The preparation of synthetic resin / insecticide combinations can be carried out by conventional techniques. Because of the compatibility of the insecticide in the resin dispersions, the compositions can be prepared simply by mechanical mixing of the insecticide with the sprayed resin. Dry mixtures, flowable pastes or plastisol dispersions can be prepared which, as is known, can be molded, extruded, cast or otherwise formed into a strip or ribbon. When the prepolymerized resin exists in liquid form, as is the case with monomers such as styrene or methyl methacrylate, the insecticide can be incorporated into the liquid before it is polymerized or hardened. The term dispersion used in the present description is intended to denote the mixtures of a solid with a liquid, of a liquid with a liquid and of a solid with a solid.

In the embodiments of the invention where a polyvinyl resin is used, the plasticizers and other additives commonly used to give the flexibility, the resistance and the surface characteristics desired for an insect repellent device are well known in the art. skilled in the art and further discussion is not necessary. In addition, it is possible to use, in the devices according to the invention, dyes and odor adjusting agents, to facilitate acceptance by the consumer.

As noted above, Naled has a low vapor pressure. The release rate from a PVC / Naled device is relatively low and may be inadequate for a commercial insect control device. The use of an additive in the mixture is very useful for increasing the rate of release of Naled and allows both an effective fight against insects at lower initial concentrations of Naled and the obtaining of an anti- insects with an increased effective service life.

The additive, also known as a surface porosity control agent, is present in the final dispersion of plastisol or the final mixture used to mold the device and must therefore not be reactive with the other constituents of the dispersion or mixture. The main function of this additive is to provide a surface porosity which preferably comprises distributed pores.

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fogging in the body of the device. The desired surface characteristics are obtained by spraying the additive during the curing period. The additive must therefore comprise one or more compounds having a boiling point equal to or lower than the curing temperature of the resin. ''

Compounds suitable as surface porosity adjusting agents in resins such as PVC, which are cured at a temperature in the range of about 127 to 204 ° C, include aldehydes and their lower alkyl acetals containing bromine or chlorine, generally having a boiling weight of about 77 to 204 ° C, preferably about 85 to 177 ° C.

The porosity control agent can therefore comprise one or more of the following compounds which have approximately the following boiling temperatures:

chloroacetaldehyde 85 ° C

dichloroacetaldehyde 90 ° C

chloral 103 ° C

bromoacetaldehyde 80-104 ° C

dibromoacetaldehyde 174 ° C

bromodichloroacetaldehyde 125 ° C

chlorodibromoacetaldehyde 149 ° C

bromochloroacetaldehyde '111.7 ° C

2-bromopropanol 110 ° C

The surface porosity adjusting agent is incorporated in the synthetic resin / Naled combination in sufficient quantity to give a satisfactory surface porosity by its vaporization during the hardening of the dispersion, effectively increasing the rate of release of the Naled gas, to from the molded device. Although the amount of porosity adjuster to be used depends on the desired density of the surface openings, and somewhat on the particular technique used for curing the resin, it is generally about 0.8 to 5% by weight, preferably about 1 to 3% by weight of the dispersion.

Example 1:

A mixture of the following composition is vigorously triturated:

30 parts by weight of polyvinyl chloride homopolymer resin dispersion

16 parts by weight of bis-2-ethylhexyl phthalate (DOP)

2 parts by weight of epoxidized octyl tallate (EPO)

1 part by weight of bentone

27 parts by weight of Naled or 1,2-dibromo-2,2-dichloro-ethyldimethylphosphate

3 parts by weight of bromodichloroacetaldehyde

20 parts by weight of amorphous silica particles with an average particle size of 2.35 n

1 part by weight of palmitic acid to form a dispersion of plastisol having a viscosity at 25 ° C of 16,000 cPo, measured with the Brookfield viscometer at 20 rpm, from 12,000 cPo at 2 rpm. A portion of the plastisol is measured in a closed cast aluminum mold having a honeycomb cavity, as shown in the attached figure. The temperature in the mold at the time of filling, indicated by a thermocouple located immediately below the surface of the cavity, is 199 ° C. The temperature of the mold is maintained at 199 ° for 2.5 min to maintain the dispersion at least at the hardening temperature, after which the mold temperature is quickly lowered to room temperature. The color of the device is brownish bronze. There is a strong odor of drug from the final resin.

Analysis of the device after hardening and cooling shows that the Naled content of the collar is 26% by weight.

The polyvinyl chloride dispersion used is sold by the company Diamond Shamrock Co. under the name of PVC 7502:

it is a dispersion of homopolymer resin, of high molecular weight, having a particle size less than 2 n, a specific viscosity 1.62 to 1.68, measured in 1% solution in cyclohexane at 30 ° C, according to ASTM standard technique.

DOP is a plasticizer for PVC and EPO is a stabilizer. Bentone is added to adjust the viscosity of the plastisol.

The above resin and thinner dispersions are as easy to handle in producing a satisfactory device as any of those commonly used. However, as is well known to those skilled in the art, a large number of other substances, as discussed above, can be used. As far as is known, Naled does not react chemically with any synthetic resin and large variations in both ingredients and their proportions can be successfully used.

Example 2:

The procedure of Example 1 is repeated, with the same quantities, except that an open face mold is used. The upper face of the device is rounded due to the meniscus formed during the filling of the mold, this shape being retained during hardening. The resulting device is brownish bronze and contains 25% Naled. It appears that a small portion of Naled was lost by vaporization or caused by vaporization of the surface porosity control agent during curing. We detect the same smell of medicine.

Example 3:

The procedure of Example 1 is repeated using a dispersion of plastisol of the following composition:

20 parts by weight of PVC homopolymer resin dispersion

10 parts by weight of PVC homopolymer diluent resin 18 parts by weight of bis-2-ethylhexyl phthalate (DOP)

2 parts by weight of epoxidized octyl tallate (EPO)

22 parts by weight of Naled

2 parts by weight of surface porosity adjusting agent, for example bromodichloroacetaldehyde

25 parts by weight of amorphous silica particles, average particle size 2.35 | i

1 part by weight of stearic acid, a bronze-colored resin body is obtained, suitable as insect repellant tape and containing, according to the analysis, 22% by weight of Naled after hardening and cooling. There is a smell of medicine.

Example 4:

Following the procedure of Example 1, a plastisol dispersion of the following composition is used:

20 parts by weight of PVC homopolymer resin dispersion

11 parts by weight of PVC homopolymer diluent resin 9 parts by weight of bis-2-ethylhexyl phthalate (DOP) 2.5 parts by weight of epoxidized octyl tallate (EPO)

1 part by weight of bentone 28 parts by weight of Naled

2 parts by weight of surface porosity adjusting agent, for example bromodichloroacetaldehyde

25 parts by weight of amorphous silica particles, average particle size 2.35 n

1.5 parts by weight of palmitic acid, a bronze-colored resin body is obtained, suitable as an insect repellant tape after hardening and cooling and which contains, according to the analysis, 26% by weight of Naled. There is a smell of medicine.

Example 5:

The procedure of Example 1 is repeated using the same mixture, except that 30% by weight of technical grade Naled sold by the company Chevron Chemical Co. is used.

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knows that this product contains certain impurities such as bromodichloroacetaldehyde, chloral, carbon tetrachloride and various forms of phosphates. These impurities constitute approximately 9% by weight of the product and are largely volatile enough to be released from the collar during hardening or shortly after and therefore do not interfere with the effectiveness of the collar.

The device molded and hardened as indicated in Example 1 is brownish bronze and contains approximately 26% by weight of Naled.

Example 6:

A homogeneous mixture of the following composition is prepared: 29.0 parts by weight of polyvinyl chloride homopolymer resin for general use

15.3 parts by weight of bis-2-ethylhexyl phthalate (DOP) 2.0 parts by weight of epoxidized octyl phthalate (EPO) 25.7 parts by weight of Naled 3.0 parts by weight of bromodichloroacetaldehyde 20, 0 parts by weight of amorphous silica particles, average particle size 2.35 | i 1.0 part by weight of stearic acid 4.0 parts by weight of thermal stabilizer and lubricant The thermal stabilizer and lubricant is a mixture of 3.3 parts by weight of dibasic lead phosphate and 0.7 parts by weight of dibasic lead stearate. The mixture is introduced into an injection molding machine and is molded by injection, in the form indicated in the appended figure, at the temperature of 129 ° C, under a pressure of 700 to 1540 kg / cm2. The color of the device is brownish bronze and there is a strong odor of drug from the molded device.

Analysis of the device after cooling indicates a Naled content of approximately 25% by weight.

Naled release speed

The speed of release of Naled from the compositions which can be used according to the invention, for a certain specific surface of a device of given thickness and surface, varies not only according to the initial concentration of Naled, but more significantly, depending on whether the The volatile additive which is used for the adjustment of the porosity has or has not been used as indicated above. A molded device according to the invention contains an amount sufficient to combat insects in the region of the device for several months.

A notable advantage of the Naled device according to the invention, compared to the DDVP device of the prior art, in current commercial use, is found in the release curve of the insecticide in the gaseous state during the first days activation, from the moment when said device is removed from a sealed container. The initial rate of release of Naled during the first few days is only a fraction of the initial rate of release of DDVP from comparable devices, mainly due to the difference in vapor pressure. For Naled with the porosity control additive, the release rate does not decrease significantly for a period of about ten weeks; thereafter, the release rate gradually decreases to about 50% of the maximum at the end of a period of about twenty weeks. The release rate curve for Naled from a PVC device without the porosity adjuster is generally parallel. However, the total amount of Naled released from the device made from a formulation containing the porosity control agent was significantly higher, for example 10% or more, than that released from a device made with a formulation similar without the porosity adjuster, indicating that more Naled is released at any time during the 20 week period for the first device than for the second.

Comparative example A:

The procedure of Example 2 is followed using a plastisol dispersion of the following composition:

20 parts by weight of homopolymer PVC resin dispersion

12 parts by weight of homopolymer PVC thinner resin

15 parts by weight of bis-2-ethylhexyl phthalate (DOP)

2 parts by weight of epoxidized octyl tallate (EPO)

30 parts by weight of Naled

20 parts by weight of amorphous silica particles, average particle size 2.35 n

1 part by weight of stearic acid

The cured insect tape contains approximately 25% by weight of Naled, which indicates that a greater proportion of the Naled initially present in this dispersion was lost during the curing process than in the case of Example 2.

Example 7:

The procedure of Example 1 is repeated with the same quantities. The resulting device having an area of 6.5 cm 2 is called A. Similar devices are manufactured according to the same process and with the same quantities as in Example 1, except that 1% by weight of stearic acid is used instead of palmitic acid (device B), 2% by weight of stearic acid instead of palmitic acid (device C), we remove palmitic acid (device D), we remove silica (device E ) and the silica and palmitic acid are removed (device F).

Each of these devices is suspended in a 0.516 m3 cell measuring 0.61 x 0.61 x 1.5 m. The cells consist of a frame covered at the ends and on three sides with a kraft paper laminate, closed above by a glass plate to facilitate observation. Anti-insect ribbons are hung from the top, in the middle of the cell, so as not to touch the edges or the bottom of the cell. The test is carried out for a period of sixteen weeks.

Visual observations are made of the surfaces of each device to determine the formation of Naled liquid droplets daily. The measurements made include the time after which the surface first appears washed or wet, with the formation of beads or droplets, the time after which run marks are observed for the first time, and the time after which drops actually form at the bottom of the sample. The results are shown in Table I.

As can be seen in Table I, devices which do not contain both the silica component and the aliphatic carboxylic acid component saturated with C14-C20 exhibit the pearling phenomenon in relatively short times. Device E (acid but no silica) and device F (neither silica nor acid) have a washed appearance in about two weeks and beading in about four weeks, while device D (silica but no acid) has beading in about six weeks and forming drops in about ten weeks. All the devices according to the invention (A, B and C) exhibit beading in a considerably longer time and no drop formation.

The biological activity of devices B, C and D is measured against an SRS-susceptible strain of Musca domestica.

25 SRS-susceptible flies are added daily to each cell containing a tested device. TL50 is known in the art as the lethal effect time on 50% of the insects introduced. Table II shows the values obtained for male SRS-susceptible flies. Similar results are also obtained with female flies, although the latter are generally slightly more resistant.

The values obtained indicate that the addition of the acid component does not affect the biological activity of the devices. Similar results are obtained when the tests with Musca domestica CSMA (NAIDM) -susceptible and resistant strains FC, Orlando DDT and Isolan-B are repeated. The latter are pure resistant strains of Musca domestica known to those skilled in the art.

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Example 8:

Biological activity tests are carried out on flies (Musca domestica), both resistant and susceptible strains, and mosquitoes (Culex pipiens) in the cell used in Example 6. The insects are introduced into the cell containing a device manufactured according to Example 1 and containing 25% by weight of Naled. The values of TLso and TL95 are measured at the same time. The results are shown in Table III.

The results show that devices containing Naled slowly and evenly release Naled over a period of twenty weeks. The devices are effective in killing both resistant and susceptible flies, as well as the least resistant mosquitoes. Similar tests with Drosophila melanogaster show that these insects are also killed faster than flies.

Similar devices containing 25% by weight of Naled are hung in the entrance hall of a building for twenty weeks, where they are exposed to ambient temperature. The percentage of Naled remaining in the device (average over five devices) is shown in Table IV.

This new test shows that the devices release Naled uniformly for an extended period of time. Although there is a certain pearling of Naled around sixteen weeks, there are no drops or traces of sagging at the end of the twenty week test.

Example 9:

Samples of various household surfaces are placed (aluminum foil, synthetic fiber screen, particle board, wood, semi-gloss wood varnish, vinyl wall paper, gloss wood varnish, vinyl flooring and annealed cardboard)

in a cell of the type used in Example 4, and they are exposed for 102 days to the devices containing 25% by weight of Naled according to Example 6. The devices are used at a rate of one per 0.566 m 3 (test G) and two by 0.566 m3 (test H). Identical samples are exposed for the same duration to a commercial anti-insect tape containing 20% by weight of DDVP, at the rate of one device per 0.566 m 3 (test I). The adsorption of toxic Naled or DDVP is determined by the biological activity of the exposed material, placed in a closed container of 1.891, in which house flies are introduced. The TL50 values are measured for each sample and the duration in days necessary to reach a TL50 of 300 min is evaluated by ventilating the container. The results obtained are shown in Table V.

These results show that there is a considerably lower amount of Naled adsorbed on the surfaces than DDVP (as indicated by the higher TL50 values for Naled). Naled is desorbed much faster by ventilation than DDVP. Similar tests are carried out with different foods (potato, apple, bread, lettuce, tomato, orange and hamburger) with an exposure time of 24 h. The adsorption of DDVP (compared to Naled) is even higher. DDVP is adsorbed on all foods tested with TL50 values, between 12 min (potato) and 51 min (hamburger). Naled, at the same concentration, is not adsorbed on a certain number of the foods tested and, if there is adsorption, the TL50 values are between 155 min (potato) and 380 min (sliced apple) ).

Comparative example B:

A study is being carried out to determine the effects of various materials on the release rates and efficacy of polyvinyl chloride formulations containing about 25% by weight of Naled, about 3% by weight of a porosity control agent and small amounts of plasticizer and PVC stabilizer.

Based on an initial selection, calcium carbonate, medium quality aluminum oxide and various liquid silicones and resins appear to be unsuitable, either because of their reactivity with Naled, or with the agent porosity adjustment, either because of the high incompatibility with PVC formulations, even at relatively low contents, of approximately 5 to 15% by weight in the formulation. Various qualities of powdered polyethylene and ethylene / vinyl acetate resin are also tested, and it is determined that these products are unsuitable due to their extremely high absorption of plasticizer as well as their cost price.

Various qualities of solid glass microspheres are also tested (average particle sizes from 6 to 50 µi). All the qualities of solid glass microspheres pose relatively significant sedimentation problems (increasing with the particle size). In addition, the devices prepared according to Example 1 and containing 25% by weight of Naled and 45% by weight of the solid glass microspheres show surface oozing after only two to three weeks. Similar samples prepared with incorporation of 45% by weight of silica particles (all particles passing through a sieve of 44 (i and 95% of particles under 40 (J., and, in another case, all particles passing sieve 74 n and 95% less than 70 (i) show oozing in 5 to 6 weeks.

The insect control device according to the invention contains relatively high amounts of Naled which are released uniformly over a long period of time. Naled has reduced toxicity compared to prior art devices containing DDVP and exhibits a significantly lower tendency for adsorption by surfaces adjacent to the device.

Although Naled has been known and marketed for a number of years, and there has been considerable research into the use of Naled as an insecticide, it has not been considered possible to substitute it for DDVP in an anti-insect device. Attempts to form a collar containing Naled as an insecticide have failed in previous research, making trials of the effectiveness of Naled for flea control very difficult. In addition, Naled was not considered to be a likely substitute for DDVP since it is known that its vapor pressure is less than 2% of that of DDVP. In addition, the problem of seepage with Naled concentrations greater than about 25% by weight set upper limits on the amount of Naled that can be used in an article. The device according to the invention containing for delaying the seepage effective quantities of finely divided silica and at least one aliphatic carboxylic acid saturated with C14-C20 or one of its salts or esters allows the use of Naled even above 25%, without any seepage on the device.

By incorporating volatile additives into the mixture used to form the device, it has been possible to increase the release rate of Naled to a value that allows mass production of an appropriate insect repellant.

The device according to the invention is produced so as to have a porous external surface which makes it possible not only to release the Naled at a speed greater than that which was otherwise possible and in greater gross quantity, but also to release the Naled at a speed effective for combating insects for a significantly longer time than was otherwise possible.

5

10

15

20

25

30

35

40

45

50

55

60

618 846

8

Table I

Device Time

A B C D E F

First appearance

"Washed" (without "pearling") 7-8 weeks 10 weeks 10 weeks 4-5 weeks 2 weeks 2 weeks Pearling actually observed 12-13 weeks 15-16 weeks 15-16 weeks 6 weeks 4 weeks 4 weeks Observable sag marks , no drops yet 7-8 weeks Effective drop formation at the bottom of the sample 10 weeks

Age

Table II

TLso for SRS-susceptible flies, minutes B C

Table IV:

20

30 34 37

49

50

51 55

68 76

86

54 79

77 83

D Duration of exposure

62 69

62 66

81,

35

Naled residual (% by weight)

of the device

(weeks)

in the exposed devices

(days)

25

0

25.25

1

50

51

48

1

24.66

2

45

44

47

2

23.22

13

55

54

55

4

21.22

14

55

61

59 30

8

17.38

21

53

-

54

12

15.98

23

-

66

■ -

16

13.28

29

-

57

-

20

12.34

Device age

Ü)

1 3

28 30 56 59 84 87 112 115 140 143

Table III: TL, minutes, at 21 ° C

Table V:

Flies Culex pipiens resistant flies susceptible

TLso TL95 TL50 TL95 TL50 TL95

G

TLso, minutes

H

Estimated ventilation time (d) to reach a TL50 of 300 min

H

I

38 *

90 *

34

60

34 *

89 *

92

198

71

89

55

Aluminum foil

Not

Not

Not

78

129

effect effect effect

-

-

-

95

244

73

112

Fiber mat

112

178

synthetic

185

125

40

<5> 1 <5> 1

13

110

208

104

146

Par sign

30**

184 **

60

tiles - vinyl

135

86

37

6

12

16

144

262

73

114

Wood

104

76

38

5

15

20

149

314

Semi-wood varnish

143

317

83

116

brilliant

125

109

50

9

12

28

107

286

Wall-vinyl paper

110

78

34

11

13

36

65

Glossy wood varnish

125

79

40

24

30

40

Vinyl paving

128

98

35

9

13

42

»Mmpnt fnîKIfts

Annealed cardboard

135

102

50

7

15

46

** Some flies of low viability.

1 sheet of drawings

Claims (10)

618 846 2 1. Anti-insect control device, characterized in that it comprises a solid body formed having a porous surface capable of gradually and continuously releasing 1,2-dibromo-2,2-dichloroethyldimethylphosphate in an amount sufficient to give a concentration effective insecticide, said device comprising: a) a matrix of synthetic resin, b) 15 to 35% by weight of the insecticide, c) an effective amount, to delay the seepage of the insecticide, of finely divided silica particles, and d) at least one aliphatic carboxylic acid saturated with C14-C20 or one of its salts or esters, said device being formed of a mixture of said resin, insecticide, said silica particles, said carboxylic acid or its salt or ester and a surface porosity control agent which is not reactive in the mixture and which has a boiling point equal to or less than the curing temperature to produce surface openings in communication with the pores of said body, by vaporization of said porosity control agent, to give release of the insecticidal gas at an effective rate for fight insects in the vicinity of said body, but insufficient to produce oozing on the device. 2. Device according to claim 1, characterized in that the silica particles are present in an amount of 10 to 35% by weight of said device and said acid is present in an amount of 0.25 to 3% by weight of said device. 3. Device according to claim 2, characterized in that said synthetic resin matrix consists of polyvi-nyl chloride. 4. Device according to claim 1 in the form of a molded article, characterized in that said mixture contains a small amount of a surface porosity adjusting agent having a boiling point between 77 ° C and the temperature of hardening of polyvinyl chloride resin. 5. Device according to claim 4, characterized in that said agent for adjusting the surface porosity is chosen from chloroacetaldehyde, dichloroacetaldehyde, chloral, bro-moacetaldehyde, dibromoacetaldehyde, bramai, bromo-dichloroacetaldehyde, chlorodibromoacetaldehyde, bromo-chloroacetaldehyde, 2-bromopropanol and their mixtures. 6. Device according to claim 1, characterized in that said formed article comprises a regular symmetrical matrix of cavities distributed along a dimension of said body, said cavities having substantially parallel axes and walls which define a substantially straight line along said dimension . 7. A method for manufacturing a device according to claim 1, characterized in that an article is prepared comprising a mixture of a synthetic resin, 15 to 35% by weight of the insecticide and an amount effective in delaying the seepage of the insecticide from finely divided silica particles, at least one aliphatic carboxylic acid saturated with C14-C20 or one of its salts or esters and an amount of a porosity control agent surface, which is not reactive in the mixture and which has a boiling point equal to or less than the curing temperature of said mixture, said mixture being formed into said article at curing temperature to vaporize said setting agent the porosity and to produce the surface porosity in said article to give a rate of release of the insecticide effective in combating insects in the vicinity of said article, but insufficient to form droplets on the article. 8. Method according to claim 7, characterized in that said mixture is formed into said article from a dispersion of liquid plastisol containing polyvinyl chloride by filling a casting mold preheated to a temperature of approximately 143 ° C, by increasing the mold temperature to about 182 ° C in a hot air oven, for about 2 min, and then cooling and separating the article from the mold. 9. Method according to claim 7, characterized in that said mixture is formed into said article by injection molding of said mixture. 10. Method according to one of claims 7 or 9, characterized in that a flexible synthetic resin body is prepared containing between 20 and 30% by weight of the insecticide and an amount effective for delaying the seepage, by 15 to 25% by weight of finely divided silica particles and from 0.5 to 1.5% by weight of at least one C14-C20 saturated carboxylic acid or one of its salts or esters, and from 1 to 3% by weight weight of a surface porosity adjusting agent which is not reactive in the mixture and which has a boiling point equal to or less than the curing temperature of said resin, said mixture being heated to its temperature curing to produce surface openings in communication with the pores in said body by spraying said porosity control agent, to give a release of the insecticidal gas at a rate effective to control insects in the vicinity of said body, and insufficient to form droplets on the body, the synthetic resin being, for example, a polyvinyl chloride resin, the silica particles preferably having less than 74 | x and 90% of the particles less than 70 n, the aliphatic carboxylic acid saturated with C14 -C20 preferably being palmitic acid or stearic acid.