Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Biocides; animal or insect repellents or attractants
Reexamination Certificate
1999-07-30
2001-11-20
Clardy, S. Mark (Department: 1616)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Biocides; animal or insect repellents or attractants
C514S521000, C514S531000, C514S772300, C514S953000
Reexamination Certificate
active
06319511
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to termite and boring insect barriers for the long-term protection of wooden structures. More particularly, it relates to a composition and method which creates and maintains an exclusion zone for insect pests such as termites, ants and other boring insects.
BACKGROUND OF THE INVENTION
Wood which is in contact with concrete, such as in wooden building construction and wood which is in contact with soil for example fence posts, utility poles, railroad cross-ties and wooden supports, can be structurally degraded by the action of termites, ants and other boring insects. Insecticides are available to protect wood from the action of such pests. Although insecticides are somewhat effective against the action of the boring insects, if insecticides are applied by themselves in sufficient quantity tD be effective over a period of time, they pose ecological concerns, human health, and may present unpleasant odors, soil leaching and volatility of the insecticide. Furthermore, even the greatest amounts of insecticides applied by themselves dissipate within a relatively short time and need to be reapplied.
A further disadvantage of conventional application methods is that the concentration of active ingredients resulting from a single application of insecticide starts out well above the minimum level necessary for effectiveness, but decreases rapidly and within a relatively short period of time drops below the minimal effective level necessary for a barrier.
To this end, a number of techniques for the controlled release of chemicals such as insecticides have become common in recent years. These methods employ polymer matrices and microcapsules to release insecticide.
Cardarelli U.S. Pat. No. 4,400,374 discloses the use of polymer matrices generally made of polyethylene, polypropylene, ethylene vinyl acetate, polyamide, polystyrene, polyvinyl acetate, or polyurethane to control the release of insecticides such as the insecticide commercially available under the tradename Dursban. The polymer matrices disclosed in U.S. Pat. No. 4,400,374, incorporate porosigen and a porosity reducing agent which upon contact with soil moisture or an aqueous environment dissolves the matrix.
Similarly, Cardarelli U.S. Pat. No. 4,405,360 relates to a polymer release matrix which can be composed of polyamide, polyurethane, polyethylene, polypropylene, polystyrenes and other polymers. The control release mechanism works in combination with a porosigen to release a herbicide in a moist environment.
In addition, Wysong U.S. Pat. No. 4,435,383 teaches the use of a controlled release mechanism for insecticides including carbamates, organothiophosphates, organophosphates, perchlorinated organics and synthetic pyrethroids. The release mechanism comprises a hydrophobic barrier monomer namely styrene and/or methyl styrene in combination with a monomer selected from one or more unsaturated mono- or di-carboxylic acids.
Another reference, Tocker U.S. Pat. No. 4,282,209 discusses a process for the preparation of insecticide-polymer particles. The insecticide, methomyl, is used to control insects which attack a tobacco, cotton or agricultural crops. Methomyl is dissolved with polymers such as polyamides, urethanes and epoxies to provide long-term residual insecticidal activity.
A second Tocker patent, U.S. Pat. No. 4,235,872, discloses the use of slow-release insecticide microcapsules having a core of methomyl surrounded by a cover of allaromatic, uncrosslinked polyurea. In the arrangement disclosed in this patent, methomyl is used to protect vegetables, field crops and fruit crops.
A sixth reference, Young et al. U.S. Pat. No. 4,198,441, discloses the use of insecticides such as Dursban in a controlled release matrix comprising an organopolysiloxane, a hydrolyzable silane and a hydrolyzable organic titanium.
Additionally, Young et al. U.S. Pat. No. 4,160,335 discloses a mode of dispersing insect control substances by applying stripes to sheets of cellophane. The insect control substance which can include Dursban is placed in a polymer as well.
Although the prior art does disclose the use of controlled release agents, none of the references teach the creation of a completely effective exclusion zone. It is desirable to create a zone so as to prevent any contact between the wood structure and insects capable of damaging such structures. An exclusion zone is necessary to protect wood structures for extended periods of time.
Therefore, in view of the above, it is an object of this invention to provide a zone of insecticide to protect wooden structures. Such zone consisting of a long term low volatility barrier and a high volatility short term barrier to protect adjacent soil.
It is a further object of this invention to maintain an exclusion zone for relatively great lengths of time or about 10 to 20 years.
SUMMARY OF THE INVENTION
The present invention provides a delivery system and method for the controlled release of insecticide which lasts for a predetermined period of time at a minimal effective level creating a zone in order to prevent an intrusion of insects such as termites, ants and other boring insects into wooden structures. The method utilizes a controlled release device which comprises a polymer selected from the group consisting of thermoplastic polymers, thermoset polymers, elastomeric polymers and copolymers thereof. By incorporating the insecticides into the polymers, the insecticides can be released at such a rate that they will continue to be effective as toxicants or repellents for insects capable of damaging wood structures for a prolonged period of time while at the same time maintaining sufficient concentrations to prevent insect penetration through the exclusion zone.
According to one aspect of this invention, there is provided a polymeric-carrier delivery system for the controlled release of insecticide comprising spun-bonded polymeric sheeting, and a bonded mixture of polymer and insecticide. The mixture of polymer and insecticide is next bonded to the polymeric sheeting. The sheeting with the bonded mixture of polymer and insecticide is then placed near a wooden structure to provide a means for a slow and relatively constant release of the volatile insecticide in order to create a barrier zone for insects in the soil around a wood structure. The polymers include thermoplastic polymers, thermoset polymers, elastomeric polymers as well as copolymers thereof and the insecticide comprises the family of insecticides known as pyrethrins.
According to another aspect of this invention, an exclusion zone is created by placing an extrusion near the wooden structure to be protected. The extrusion has a polymeric delivery system capable of controlled release of the insecticide. The carrier system maintains a steady and effective concentration of insecticide in the exclusion zone for great lengths of time.
According to another aspect of this invention, a pellet comprising a polymer and insecticide is provided to create and maintain an equilibrium concentration of insecticide for ants, termites and other wood boring insects in an exclusion zone for the wooden structure. The pellet is placed near a wooden structure to treat the soil in order to shield the wooden structure from termites, ants and other boring insects. The pellet can be placed near the structure by a variety of means. Additionally, the pellet can be embedded in a board or even included in a foam. In preferred embodiments the polymers include thermoplastic polymers, thermoset polymers, elastomeric polymers as well as copolymers thereof and the insecticide are pyrethrins.
According to another aspect of this invention, an exclusion zone is created by injecting a hot melt polymeric mixture. The controlled release device comprises one or more pyrethrins and the polymer is selected from the group consisting of thermoplastic polymer, elastomeric polymers and copolymers thereof.
According to further aspects of the invention, temperature driven controlled release devices are used to provide the exclusion zo
Cataldo Dominic A.
Van Voris Peter
Battelle (Memorial Institute)
Clardy S. Mark
Jenkens & Gilchrist
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