Patent Application
20050005504
The present invention relates generally to insect control devices, and more particularly to insect control devices that release a volatile insect control agent.
The release of a volatile ingredient into ambient surroundings has been known for some time. For example, Bishopp et al. European Patent 0670685, assigned to the Beautiful Bouquet Company, discloses a volatile liquid sampler comprising a vapor impermeable base layer and a vapor impermeable cover layer between which a volatile liquid is disposed. An adhesive ring 4 is disposed between the base and cover layers to hold the layers together, thereby inhibiting pre-usage volatilization of the volatile liquid. As an alternative to adhesive, column 9 lines 43-47 disclose that the cover layer may be a polyvinylidene-dichloride cling film that auto-adheres to the base layer. The polymers used to make the base layer are those which absorb the volatile liquid. However, prior to absorbing into the base layer the liquid preferably is retained on the sheet by a surface tension effect, such that the base layer may be immediately handled without undue concern for the liquid volatile spilling off the base layer. To use the sampler, a user separates the base and cover layer, thereby exposing the volatile to the ambient surroundings.
Baker et al. U.S. Pat. No. 4,445,641 (“Baker et al.”) discloses retention of a fluid volatile in the pores of a micro-porous plastic by capillary action. The rate of evaporation is regulated by the nature of the passages in the micro-porous material to give a zero order rate of release. The micro-porous plastic acts as an evaporation regulating membrane. Baker et al. further discloses a reservoir and a release rate controlling membrane. The reservoir is a solid microporous polymeric structure with interconnected or continuous pores of appropriate diameter to retain the active ingredient therein by a capillary action. The active ingredient is essentially insoluble in the polymer material. Further, a membrane is sealed to an impermeable backing material around the microporous reservoir material impregnated with active.
Many species of insects, especially certain flying insects (e.g., mosquitoes), have posed a nuisance to people for many centuries. Numerous techniques to release a volatile ingredient to control such insects have been developed. Such techniques involve releasing a sufficient concentration of a volatile insect control agent within a volume of airspace to repel or terminate nuisance insects within the airspace. One example of this type of technology is disclosed in Feng U.S. Pat. No. 6,239,044, which discloses a mosquito expelling/killing device having a clip to hang the device on a user's body (i.e., clothing). The device includes an electric heater that heats a mosquito incense mat for releasing mosquito killing incense in the vicinity of the user.
Paciorek et al. U.S. Pat. No. 3,685,734 discloses a pest repellent article having a heat sealed outer cover layer 12 that may be removed to expose a repellent material carrier 14 having an absorbent member 16 and holes 20 that allow volatilization of the pest repellent composition from the absorbent member 16.
Commonly assigned Munagavalasa U.S. Pat. No. 6,534,079, incorporated herein by reference, discloses a non-absorbent and inert substrate that is coated with an active insect control ingredient. The active insect control ingredient passively evaporates from the substrate to control flying insects. The active insect control ingredient has a solubility less than 40 micrograms per square centimeter of the substrate, such that the active is not absorbed into the substrate and remains on the surface thereof, thereby promoting volatilization.
Commonly assigned Flashinski et al. U.S. Pat. No. 6,360,477, incorporated herein by reference, discloses an insect control pouch having a volatile insect control ingredient disposed therein. The pouch may be formed by a single sheet that is folded upon itself and then heat sealed, thereby sandwiching the insect control active between opposed faces of the folded sheet to prevent volatilization of the active prior to opening of the pouch. A user may open the pouch to allow passive evaporation of the insect control ingredient into ambient surroundings. The pouch may be hung from a structure such as a clothes bar in a closet.
There will continue to be a need for volatilizing devices that perform effectively but require only a minimal amount of volatile material. Devices that volatilize all or nearly all of the volatile during the useful life of the device are advantageous from a waste avoidance standpoint and in terms of providing a maximum rate of volatilization. In addition, devices capable of minimizing pre-usage volatilization are similarly beneficial.
In accordance with one aspect of the present invention, an insect control device includes a first substantially non-permeable surface having a first critical surface tension value. An insect control volatile agent is disposed on the first surface and has a surface energy at least about 5 dynes/cm2 less than the first critical surface tension value.
According to a further aspect of the present invention, an insect control device includes first and second substantially non-permeable surfaces. A volatile insect control agent is disposed between the surfaces. An attractive property of the agent substantially solely maintains the first surface in releasable contact with the second surface, thereby inhibiting vaporization of the agent.
In accordance with another aspect of the present invention, a method of producing an insect control device includes the steps of providing at least one substantially non-permeable surface and wetting the surface with an insect control volatile agent. The agent forms a thin substantially uniform film on the surface.
Other aspects and advantages of the present invention will become apparent upon consideration of the following detailed description.
A volatile liquid insect control agent is disposed on a substantially non-permeable surface 20 of a sheet 23. The control agent has a surface energy at least about 5 dynes/cm2 less than a critical surface tension value of the surface 20 (i.e., a dyne level differential). In addition, the control agent could also have a surface energy at least about 10 dynes/cm2 less than the critical surface tension value. The dyne level differential promotes effective wetting of the surface 20 such that the control agent wets all available surface area of the surface 20 in a uniform manner. This effective wetting creates a uniform, thin, continuous film, which promotes maximum volatilization per unit area when the control agent is exposed to ambient surroundings. In a less effectively wetted surface, without the dyne level differential, non-uniformities or pooling in localized areas might occur, which could inhibit optimal volatilization. The rate of volatilization of the control agent remains almost constant until all of the control agent volatilizes.
The material of the surface 20 is not particularly important so long as the dyne level differential is satisfied for a control agent of a given surface energy. Any suitable material may be used for the surface 20 such as polymeric or non-polymeric materials including nylon, polyester, or glass. The surface 20 is optimally inert to the volatile liquid. The sheet 23 may have any suitable thickness such as 0.002 inches (0.05 mm). The sheet 23 may be a transparent OPET (oriented polyethylene terepthalate) and may have a surface energy or critical surface tension value greater than about 50 dynes/cm2. The sheet 23 may have any suitable size such as 10.5 inches (26.67 cm) by 14.5 inches (36.83 cm). The sheet 23 may be folded along a fold line 24, as seen in
As noted above, the surfaces 33a, 36a may be formed of different types of materials. In this regard, the material of the surfaces 33a, 36a is not particularly important so long as a given volatile liquid disposed thereon is at least about 5 dynes/cm2 less than the critical surface tension value of the surfaces 33a, 36a to confer the above-described wetting. The critical surface tension value of the surfaces 20, 33a, 36a is determined using a marker pen sold by Diversified Enterprises 91-N Main Street, Claremont, N.H. 03743, USA. Typical dyne levels of volatile liquids discussed herein are about 35 dynes/cm2, thereby requiring the surface 20 to have a surface tension value of about 40 dynes/cm2 or greater to achieve the at least about 5 dynes/cm2 differential. Polyester and nylon films tend to be suitable materials for the sheet 23 because these materials typically have surface tension values much greater than 40 dynes/cm2. There are many suppliers of suitable polyester and nylon films such as MS packaging of Chicago, Ill. Untreated polypropylene and polyethylene films might not be suitable for 35 dynes/cm2 liquids because such films tend to have surface energies lower than 40 dynes/cm2. However, treating films with corona, flame, or other treatments may increase the surface energy sufficiently to establish the requisite dyne level differential. It follows that the present invention encompasses polypropylene, polyethylene, other polymers, or other materials or laminations of the above materials so long as such materials, in combination with a given volatile liquid, satisfy the requisite at least about 5 dynes/cm2 differential. It should also be noted that even an untreated polyethylene or polypropylene might be suitable where a volatile liquid is selected having a sufficiently low surface energy to satisfy the differential.
An attractive property of the control agent can be used to hold the opposed faces 26, 29, or separate sheets 33, 36, together in a releasable sealing manner to inhibit pre-usage volatilization of the control agent without the need for separate adhesives, heat seals, or other sealing structure. The attractive property could comprise a capillary force derived from the above-described dyne level differential. Alternatively, the attractive property could be derived from a stickiness or tackiness property of the control agent wherein the insect control agent could comprise solids and could even be paste-like and may or may not satisfy the dyne level differential. Avoiding the need for adhesives or heat seals may be advantageous, especially where end users require a device having only a short storage life.
The insect control agent may include any suitable insect control composition that functions as any of insecticides, knock down agents, or repellents. Suitable insect control compositions may include transfluthrin, tefluthrin, vaporthrin. The insect control agent may comprise liquids or solids, and volatilization may include solid to gas or liquid to gas volatilization or combinations thereof.
The insect control agent may include a solvent in which the transfluthrin or other composition may be dissolved. Suitable solvents are those in which the insect control composition solubilizes completely, and can include hydrocarbon solvents, glycol ethers, etc. Examples of suitable hydrocarbon solvents include hydrocarbon solvents commercially available under the trade names ISOPAR® L, ISOPAR® M, and ISOPAR® V, available from the ExxonMobil Chemical Company. Suitable glycol ethers include Dipropylene glycol n-Butyl Ether marketed as DOWANOL® DPnB solvent; Tripropylene glycol Methyl Ether marketed as DOWANOL® TPM solvent; and Dipropylene glycol Dimethyl Ether marketed as PROGLYDE® DMM solvent. All of these glycol ether solvents are available from the Dow Chemical Company.
Colloidal silica particles may also be dispersed within the solvent to function as a use-up cue (discussed hereinbelow), such as those identified by the mark CAB-O-SIL® and supplied by the Cabot Corporation of Boston, Mass.
A peripheral barrier 44 may be provided to one or both of the surfaces 26, 29. The peripheral barrier 44 may be provided to prevent the volatile liquid from migrating off the surface 26 as the liquid spreads thereacross by capillary action or other potential forces during production, storage, or movement of the sheet 23. The peripheral barrier 44 could potentially function as an additional grasping surface, in addition to handling tab portions 45, 46, so that a user might handle the sides of the unfolded sheet 23 without touching the volatile liquid. The handling tab portions 45, 46 may be sized appropriately to serve as an effective gripping surface so that a user need not touch the volatile liquid. The tab portions 45, 46 are pulled apart to expose the faces 26, 29 and initiate volatilization.
A mounting device 56 (
The sheet 23 may further include a use-up cue 76 (
Following application of the liquid to the surface 20 of the sheet 23, the sheet 23 is folded along the fold line 24, thereby bringing opposed faces 26, 29 of the surface 20 into sealing contact as seen in
In accordance with the principles expressed hereinabove and below, a method of producing an insect control device comprises wetting a first surface such as the surface 20 with a control agent to form a thin substantially continuous film on the surface 20. The control agent has a surface energy at least about 5 dynes/cm2 less than the critical surface tension value of the surface. In addition, the surface energy may be at least about 10 dynes/cm2 less than the surface tension value. A second surface may be applied to the first surface. This could involve bringing the opposed face 29 against the face 26 or bringing the separate sheets 33, 36 together. Side edges 85-88 (
Two 10.5 inch (26.7 cm)×14.5 inch (36.8 cm) sheets were coated with 112.6 mg of an insect control agent consisting of 83.5% (by weight) transfluthrin and 16.5% dipropylene glycol dimethyl ether (PROGLYDE®) DMM. The transfluthrin was 95.8% pure technical grade Transfluthrin. Two nylon screened 10 inch (25 cm)×10 inch×10 inch cages each containing twenty 14-day-old female Culex quinquefasciatus mosquitoes were placed in a 20 m3 enclosed square testing room. One of these cages was disposed in a high position, 168 cm above the floor, while the other cage was disposed in a low position, 46 cm above the floor. The high position cage was spaced 1 m from the South wall and 86 cm from the West wall. The low position cage was spaced 1 m from the North wall and 86 cm from the East wall. Unless otherwise specified, prior to placement of the mosquitoes within the cages, the air in the testing room was purged with exhaust apparatus. The sheets were placed on a wall of the testing room 5 feet (1.52 m) above the floor. As seen in Table 1 below, the sheets achieved a mean knockdown of 51% two hours after placement in the room. Unless otherwise specified, the testing procedure for each of the following examples was identical to that of Example 1.
The sheets of Example 2 were identical to those of Example 1 with the exception that the Example 2 sheets were left in the room for two hours (without any air purging) accumulating control agent concentration therein before introducing mosquitoes into the cages. Table 1 shows that two hours after introduction of the mosquitoes, a 78% mean knockdown was achieved.
The sheets of Example 3 were identical to those of Example 1 with the exception that the Example 3 sheets were left in the testing room for 7 days. During this seven day period, the air was purged from the testing room for 15 minutes each day to simulate air exchange in a typical household. After the 7 days, mosquitoes were placed in the cages four hours after purging the air in the testing room, and, as shown in Table 1 below, a mean knockdown of 100% was achieved two hours thereafter.
Two 10 inch (25.4 cm)×14 inch (35.5 cm) polypropylene sheets each having a treated area of 120 in2 (about 774 cm2) were provided. A solution of 104.3 mg pure Transfluthrin, 3 mg of Takasago RD-1436 Instant Release Fragrance, and 7.6 mg of dipropylene glycol dimethyl ether (PROGLYDE®) DMM was applied to the treated area of each sheet. The fragrance is available from Takasago International of New Jersey, USA. As seen in Table 1 below, the sheets of Example 4 achieved a mean knockdown of 96% after two hours.
Two 10 inch (25.4 cm)×22 inch (55.8 cm) ultraclear polyester sheets were employed. Each of these sheets had a polypropylene frame layer bounding a 185 in2 (1193.5 cm2) treated area. A solution of 208.7 mg of transfluthrin and 41.2 mg of dipropylene glycol dimethyl ether (PROGLYDE®) DMM was applied to the treated area. These sheets were tested using the same procedure of Example 1. The sheets of Example 5 achieved a mean knockdown of 78% two hours after placement in the testing room.
The sheets of Example 6 were identical to those of Example 5 except that the Example 6 sheets were left in the testing room for 15 days. During this 15 day period, the air was purged for 15 minutes each day. After the 15 days, mosquitoes were placed in the cages and, as shown in Table 1 below, a mean knockdown of 99% was achieved two hours after placement of the mosquitoes therein.
Comparative Example A is an electric liquid repellent heater having a plug that fits into an electrical outlet, a liquid reservoir containing a 6% Pynamin Forte solution, and a ceramic wick in communication with the liquid reservoir and an electrical heater powered by 220 VAC. Such repellent heaters are advertised as capable of providing effective insect repellency for 45 nights and are available from Zobele Industrie Chimiche of Trento, Italy. The device of Comparative Example A was “aged” 24 hours before introduction of the mosquitoes into the cages meaning the device was operated for 24 hours within the 20 m3 testing room and subjected to one 15 minute air purging during the 24 hour period immediately prior to introduction of mosquitoes into the cages.
Comparative Example B was a mat 2.5 mm thick impregnated with 40 mg Pynamin Forte, 40 mg of piperonyl butoxide (“PBO”), and 20 mg of an m-phthalodinitrile (“IPM”). Such mats are also available from Zobele Industrie Chimiche. The mat was heated with a conventional electric heater identified as a Vape Fumakilla PTC heater and powered by 110 VAC. The mat was disposed on the floor of the testing room. The mosquitoes were placed in the cages at the same time the mat was initially heated.
As seen in Table 1, the control did not exhibit any knockdown of mosquitoes. The control consisted of introducing mosquitoes into the cages after purging of the testing room without any insecticide in the testing room.
As discussed above, the present invention is not limited to folded sheets and may encompass separate sheets or layers constructed of the same or different materials. Also, volatilization performance of a given sheet may vary. In addition, a broad variety of sheet sizes is possible. Numerous modifications to the present invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as merely exemplary of the inventive concepts taught herein and is presented for the purpose of enabling those skilled in the art to make and use the invention and to teach the best mode of carrying out same. The exclusive rights to all modifications which come within the scope of the appended claims are reserved.
