Note: Descriptions are shown in the official language in which they were submitted.
CA 02429743 2003-05-23
WO 02/43487 PCT/USO1/45830
BARRIER PREVENTING WOOD PEST ACCESS TO
WOODEN STRUCTURES
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the effective filing date of U.S. Provisional
Application
Serial No. 60/251,112 which was filed on December 3, 2000 and U.S. Provisional
Application Serial No. 60/251,141 which was filed on December 4, 2000.
This application also claims the effective filing date of U.S. Application
Serial
No. 09/353,494 which was filed on July 13, 1999 which is a continuation of
U.S.
Application Serial No. 09/030,690 which was filed on February 25, 1998 and
issued on
November 16, 1999 as U.S. Patent No. 5,985,304.
The disclosures of the aforementioned provisional applications and regular
applications are incorporated by reference in their entirety herein.
FIELD OF INVENTION
The present invention relates to barriers for preventing access by pests
(e.g.,
termites and boring insects) to protected areas and/or structures, such as,
homes,
buildings and wooden structures for the long-term protection of these areas
and/or
structures. More particularly, the present invention relates to long-lasting
protective
barriers and methods which prevent pests from entering protected areas and/or
structures, especially areas which contain wooden objects and structures which
contain
wood. The present invention also relates to methods of making the protective
barrier
and methods for incorporating them around the areas and/or structures.
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 one or more wood pests including, but not limited to, termites, ants
and other
boring insects. Insecticides are available to protect wood from the action of
such
pests.
1
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Commercial methods which are currently used for controlling pests such as
wood boring insects include spraying with insecticides, fumigation with
insecticides
such as by sealing an entire structure and releasing an insecticide therein,
and placing
insecticides in spaced discrete locations in the soil beneath the foundation
and by
treating the soil under the building foundation, before and after
construction, with
long-residual insecticides in order to repel and/or exterminate insects such
as termites.
These present commercial methods have a variety of shortcomings.
For example, a common method involves treating the soil underlying the
foundation of newly constructed buildings be pre-treated with an insecticide
to prevent
termite infestation. Insecticide is typically sprayed over and into the soil
prior to
construction. Because of the lack of communication between pesticide
applicator and
construction workers, the treated soil often loses its continuity during the
construction.
Moreover, the currently available soil insecticides tend to lose their
biological activity
after a period of time to the extent that the treated soil is no longer
effective against
termite invasion.
The use of insecticides in sprays and fumigation may be damaging to the
environment and to human and animal occupants of a home. In addition,
significant
release of insecticides by spraying and from devices provides the quick
release a
relatively short lifetime for protection against ingress of pests. Due to the
quick
release, the insecticides must be repeatedly applied at intervals of from a
few days to a
' few months or a year to remain effective.
Where insecticides are placed in the soil, significant amounts of the
insecticides
are generally released into the surroundings. Such releases can be harmful to
the
insecticide applicators, persons who reside at or visit the site of the
insecticide
application and can be harmful to the environment.
Applying insecticides in a sufficient quantity to be elective over a prolonged
period of time is also undesirable. Applying large quantities of insecticides
poses
ecological and health concerns and may cause unpleasant odors, soil leaching,
and
volatility of the insecticide. Even where large quantities of insecticide are
applied, the
insecticides dissipate within a relatively short time and need to be
reapplied. Another
disadvantage of applying large quantities of insecticide is that the
concentration starts
out well above the minimum level necessary for effectiveness, decreases
rapidly, and
drops below the minimal e~'ective level necessary to maintain a barrier within
a short
2
CA 02429743 2003-05-23
period of time relative to the lifetime of the building. Accordingly,
established termite
colonies in the soil may then invade the structure if additional chemical is
not applied
beneath and around the structure.
A common method of applying additional insecticide is to introduce it around a
building foundation by injection into soil underlying concrete foundations,
drenching
the soil surrounding the building perimeter, or a combination of both. This
type of
post-construction treatment is labor-intensive and may not adequately produce
a
continuous protection.
There is, therefore, a need for providing and maintaining a long-lasting
protection for areas and structures such as wooden structures using methods
and
devices which do not super from the aforementioned disadvantages.
SUMMARY OF THE INVENTION
The present invention provides a multi-layer wood pest barrier having a
prolonged lifetime that can be as long as the life of a building or structure
to be
protected. The lifetime protection is achieved by binding at least one
pesticide within a
continuous or discontinuous polymer matrix layer thereby substantially
reducing
release of the pesticide from the matrix. The release rate of the pesticide
from the
matrix can be controlled by the use of a carrier such as carbon black or gas
black. The
release of the pesticide from the barrier can be further controlled by
inclusion of
additional layers which can make the barrier substantially non-releasing.
In addition, the barrier can include layer(s), such as for example, scrim,
mesh,
sheet, and combinations thereof. The additional layers) also may contain one
or more
pesticides that are the same or different compared to the pesticides in the
polymer
matrix layer of the multi-layer barrier. The pesticides 'may be permitted to
release from
the additional layers) for enhanced short term protection.
The barrier and/or additional layers) are made with a polymer selected from
the group consisting of thermoplastic polymers, thermoset polymers,
elastomeric
polymers and copolymers thereof. By incorporating the pesticides) into the
polymers,
the pesticides) can be held or released at such a rate that they will continue
to be
ei~ective as toxicants or repellents for insect pests capable of damaging wood
3
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structures for a prolonged period of time while at the same time maintaining
sufficient
concentrations within the barrier to prevent insect penetration through the
barrier.
According to one aspect of this invention, there is provided a polymeric-
carrier
system wherein the pesticide is bound to the carrier as a bound friable mix. A
polymeric matrix formed from the mix is made into a thin polymeric sheet or
film. The
sheet with the bound friable mix is then placed near a wooden structure to
provide a
barrier that wood pests do not penetrate. An additional layer may provide
means for a
slow and relatively constant release of the volatile insecticide in order to
create a
barrier zone beyond the barrier itself 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 which includes a carrier capable of controlled
release of the
insecticide. The 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 insecticides 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 a further aspect of the invention, temperature driven controlled
release devices are used to provide the exclusion zones.
4
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According to another aspect of this invention, the controlled release device
is
used to fumigate structures. It is desirable to place a barrier or 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.
In a further aspect of the present invention a high density polymer having a
low
volatility insecticide providing a low release rate of insecticide is combined
with a low
density (soft) polymer having a more volatile insecticide to provide a
reliable exclusion
zone.
In accordance with another aspect of the invention, a mufti-layer barrier
prevents penetration of pests such as crawling wood boring insects and
termites into
protected areas or structures for a prolonged period of time while avoiding
harmful
effects on installers of the barrier, persons who visit or occupy the
protected areas or
structures, and on the environment. The barrier includes an inner active layer
(i.e., the
pesticide-releasing layer) which contains and releases a pesticide. The
barrier also
includes two pesticide-retaining layers which allow only minute quantities of
the
pesticide to release out of the barrier. The inner active layer is sandwiched
between
the two pesticide-retaining layers such that substantially no pesticide is
released from
the barrier. One or more additional layers can be included between the
pesticide
retaining layers and the pesticide-releasing layer.
In accordance with one aspect of the invention, the barrier comprises a
plurality
of polymeric layers which are bonded together to form a thin flexible film.
The film
can be placed to surround areas (such as foundations for houses) which need to
be
protected from crawling insects such as termites and other pests. In
accordance with
another aspect of the present invention, the barrier film is pre-shaped off
site to fit in
its intended location prior to placing it in its intended location such as in
the excavation
for the foundation of a house.
In accordance with a further aspect of the present invention, the mufti-layer
barrier is in form of a thin sheet or film which includes at least one layer
which
provides strength and puncture resistance to the sheet or film. In accordance
with yet
another aspect of the present invention, the mufti-layer barner includes outer
protective layers which protect the barrier from ultraviolet (UV) rays during
installation and when the barrier is exposed to sunlight thereafter.
5
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In accordance with a still further aspect of the present invention, the
pesticide is
released from the active layer in a controlled manner to help in achieving
substantially
non-releasing barrier. In other words, the release of only minute amounts of
the
pesticide from the barrier can be assisted by controlling the release from the
active
layer.
The present invention also provides efficient methods for making the multi-
layer barrier using conventional, commercially available equipment. In
accordance
with one aspect of the present invention, lamp black or gas black is used in a
premix
for making the active layer. Lamp black achieves the desired flowability of
the premix
but unlike a number of other types of carbon black, lamp black does not have
detrimental effects on the activity of the pesticide. Lamp black has been
found not to
deactivate or decompose pesticides.
In accordance with another aspect of the present invention, to make the
premix, all or at least a major portion of the carbon black is mixed with
polymer
particles before adding the pesticide. This approach minimizes detrimental
effect of the
carbon black on the activity of the pesticide.
In accordance with a further aspect of the present invention, one or more
bonding layers are used to secure the layers of the barrier to each other. One
advantage of using a bonding layer or layers is that the active layer can be
made from a
polymer which need not be bondable to the pesticide-retaining layer or
additional
layers. This allows for the use of active layer polymers which have low
melting points.
The lower processing temperatures reduce losses of pesticide in the process of
making
the active layer.
Therefore, in view of the above, it is an object of this invention to provide
a
barrier or zone of insecticide to protect wooden structures.
It is a further object of the present invention to provide a barrier and an
exclusion zone having 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 a barrier for relatively
long
periods of time or about 10 to 20 years.
It is a further object of this invention to maintain an exclusion zone for
relatively long periods of time of about 10 to 20 years.
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The present invention, together with attendant objects and advantages, will be
best understood with reference to the detailed description below read in
conjunction
with the accompanying drawing. Other aspects and advantages of the present
invention will become apparent to those skilled in the art upon studying this
specification and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a first embodiment of the invention, comprising spun-bonded
polymeric sheeting, and a physical melt-bonded mixture of polymer and
insecticide,
wherein the mixture of polymer and insecticide is bonded in spots to the
polymeric
sheeting.
FIG. 2 illustrates a second embodiment of the invention, comprising spun-
bonded polymeric sheeting, and a physical melt-bonded mixture of polymer and
insecticide, wherein the mixture of polymer and insecticide is bonded in
stripes to the
polymeric sheeting.
FIG. 3 illustrates a first manner of using the embodiments of the invention
shown in FIGS. 1 and 2 and the exclusion zone created by the release of
insecticide.
FIG. 4 illustrates a second manner of using the first and second embodiments
of
the invention to create an exclusion zone.
FIG. 5 illustrates a third manner of using the embodiments of the invention
shown in FIGS. 1 and 2 creating an exclusion zone.
FIG. 6 illustrates a third embodiment of the invention, in the form of a
cylindrical extrusion.
FIG. 7 illustrates a fourth embodiment of the invention, in the form of a flat
strip extrusion.
FIG. 8 illustrates a manner of creating an exclusion zone using the embodiment
of the invention shown in FIG. 6.
FIG. 9 illustrates a manner of using the embodiment of the invention shown in
FIG. 7 to create an exclusion zone.
FIG. 10 illustrates another embodiment of the invention in the form of pellets
wherein the pellets are being inserted into the ground near a wooden
structure.
FIG. 11 illustrates a cross-sectional view of pellets placed on a surface.
CA 02429743 2003-05-23
FIG. 12 illustrates the application of pellets to a concrete structure ~
utilizing
foam.
FIG. 13 illustrates a cross-sectional view of a concrete foundation after foam
has been applied.
FIG. 14 illustrates pellets set on a board.
FIG. 15 illustrates a board containing pellets being applied to a concrete
foundation.
FIG. 16 illustrates a hot-melt injection.
FIG. 17 illustrates the spacing of the hot-melt injection.
FIG. 18 illustrates a plug fumigating cement blocks.
FIG. 19 illustrates a mode of applying plugs to fumigate cement blocks.
FIG. 20 shows a layered device of the present invention.
FIG. 21 is a cross sectional side view showing the layers of a mufti-layer
barrier
made according to another embodiment of the invention.
FIG. 22 is a perspective view of a pre-shaped barrier made of a mufti-layer
polymeric film in accordance with the present invention.
FIG. 23 is a perspective view of a pre-shaped barrier made of a mufti-layer
polymeric film in accordance with the present invention.
FIG. 24 is a cross sectional side view showing the layers of a mufti-layer
barrier
made according to another embodiment of the invention.
FIG. 25 shows repellency of Eastern subterranean termites.
FIG. 26 shows repellency of Formosan subterranean termites.
DETAILED DESCRIPTION OF THE INVENTION
It has been found that a significant reduction or elimination of insects
capable
of damaging wood structures can be achieved when a barrier alone or in
combination
with an exclusion zone of insecticide is maintained for a prolonged time in
the soil
surrounding such structures. An exclusion zone is a zone having a sui~icient
amount of
chemical agent to deter fauna. In the present invention, the chemical agent is
a
pesticide and the fauna are insects especially boring insects, for example
termites and
ants. According to one embodiment of the present invention, the insecticide is
held in a
s
CA 02429743 2003-05-23
barrier and/or is released from a controlled release device comprising a
polymer matrix
system which will last for at least 6 years and often as long as 10 or even 30
years.
It has also been discovered that long-lasting protection from pests can be
achieved by sandwiching a pesticide-releasing layer between two substantially
non
releasing layers. The substantially non-releasing layers control the release
of the
pesticide such that only minute amounts of the pesticide release therethrough.
These
minute amounts of pesticide are sufficient to repel at least most pests and
the barrier
prevents pests from crossing it. The pesticide is exhausted very slowly and,
as a result,
the barrier of the present invention can be used to prevent pests from
entering a
protected area and/or structure for a prolonged period of time, as long as 10
or even
30 years. The use of the layers surrounding the pesticide-releasing layer to
substantially prevent the release of the pesticide allows the inner pesticide-
releasing
layer to release pesticide at a rate that is higher than that of the barrier.
This allows the
active layer (i. e., the pesticide-releasing layer) to be made using materials
and
1 S processing conditions that could not be used for making a substantially
non-releasing
active layer. The release from the pesticide-releasing layer can also be
controlled by
incorporating a pesticide in a polymer matrix and additional using a carrier
such as
carbon black (including lamp black and gas black).
As used herein, the term "controlled release device" refers to a device that
results in controlled and sustained release of a bioactive chemical to its
surface and
from its surface into a surrounding medium, for example soil. As used herein,
the term
"bioactive" means stimulating an organism, usually in a negative way up to and
including death for purposes of a deterrent. The term "pesticide" as used
herein means
and includes any bioactive chemical which controls, repels, reduces and/or
prevents
pests from penetrating the barrier. A "pest," as used herein, is~~meant to
include any
unwanted plant, animal or microorganism such as arthropods, arachnids,
triatomes,
insects (such as ants, termites and other wood boring insects), and fungi for
example.
Included among pesticides are in particular insecticides, herbicides,
biocides, e.g.
bactericides, viruscides, fungicides and nematicides, and other biological
control agents
or management materials. The barrier of the present invention is, therefore,
intended
to be used against all pests which succumb to the lethal and/or repellent
properties
thereof. The terms "pesticidally effective amount", "insecticidally effective
amount" or
9
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"fungicidally effective amount" means the dosage of active substance
sufficient to exert
the desired pesticidal, insecticidal or fungicidal activity.
In accordance with another aspect of the invention, the device of the present
invention provides a method for controlled release of the bioactive chemical
into the
surrounding environment. The controlled release device releases insecticide at
a high
rate initially and a lower, steady rate thereafter. Moreover, the initial
pesticide can be
different from that which is released for a prolonged period of time. This
release
profile assures that the protected areas and/or structures such as wooden
objects or
structures containing wood become protected in a relatively short period of
time and
that, subsequent to reaching the minimum effective level, only the amount of
insecticide necessary to replace the degraded insecticide is released. This
release profile
diminishes potential environmental and health problems of the treatment and
reduces
the cost of the treatment. The device release rate is dependent only upon the
device
construction and composition of the device and is independent of external
elements
such as water.
In accordance with another aspect of the invention, the controlled release
device releases the insecticide into the soil at a desired rate to create a
zone having the
"minimal effective level" of insecticide necessary to prevent insect
intrusion. As used
herein, the term "minimal effective level" is defined to mean the level of
insecticide
needed in the zone to prevent insects from entering the zone, the specific
level depends
on the specific insect and the specific insecticide. When placed adjacent to a
foundation
or below-grade structural portion, the exclusion zone is created in the soil
near the
controlled release device. When placed between a non-wood structural portion
and an
attached wood structural portion, the exclusion zone is created at the
interface
between the non-wood structural portion and the attached wood structural
portion.
When used commercially, the insecticides used generally are approved by a
national regulatory body such as the IJ.S. Environmental Protection Agency
(EPA) or
other equivalent regulatory body as insecticides suitable to kill or repel
termites, ants
and other boring insects. The insecticides which are presently preferred for
use in the
present invention are pyrethrins, including tefluthrin, lambda cyhalothrin,
cyfluthrin,
and deltamethrin. It will, however, be recognized by those skilled in the art
that other
effective insecticides such as isofenphos, fenvalerate, cypermethrin,
permethrin and
natural pyrethrin can also be used. These are available from a number of
commercial
to
CA 02429743 2003-05-23
sources, such as, The Dow Chemical Company, Mobay, Syngenta Crop Protection,
Inc., Velsicol and FMC. A combination of insecticides or one or more
insecticides in
combination with other bioactive ingredients such as fungicides is also in
accord with
this invention.
Referring now to the drawings, a first controlled release embodiment of the
invention as illustrated in FIG. 1 utilizes a polymeric-carrier device for the
controlled
release of insecticide to generate an exclusion zone. The embodiment comprises
spun-
bonded polymeric sheeting 20 and a physical melt-bonded mixture of polymer and
insecticide (shown as spots 21 in FIGS. 1 and 3-5). The spun-bonded polymeric
sheeting 20 can be either a woven or non-woven textile or it can be a
polymeric sheet.
Such textiles can be obtained from a number of manufacturers such as Reemay,
Exxon
Fibers, and Phillips Fibers. Preferably, the textile is woven or non-woven
polypropylene.
The polymer in the melt-bonded mixture can comprise any number of
thermoplastic polymers, thermoset polymers, elastomeric polymers or copolymers
thereof. The selection of the polymers depends upon the desired release rate,
the
compatibility of the polymer with insecticide and upon environmental
conditions. By
way of example and not intending to limit the scope of this invention, the
following
polymers can be used: high density polyethylene, low density polyethylene,
vinyl
acetate, urethane, polyester, santoprene, silicone, or neoprene. However, the
preferred
polymers are high density and low density polyethylene. In some embodiments,
chlorpyrifos is the preferred pesticide although other pesticides described
herein may
also be used.
The mixture of polymer and insecticide may be placed on the spun-bonded
polymeric sheeting in spots. These spots should be spaced so as to adequately
maintain
the amount of insecticide above the minimal effective level in an exclusion
zone. The
minimal effective level is the least amount of insecticide needed in a zone so
as to
prevent intrusion by insects. Spots 21 in FIGS. 1 and 3-5 are preferably about
0.5 to
1.5 centimeters in diameter, and about 0.5 to 1.5 centimeters in height. The
size and
shape of the spots will depend upon the user's preference and can be tailored
to the job
contemplated by the buyer. The spots 21 can be configured in rows with the
spacing of
the spots preferably being from about 1.5 to 4 centimeters from adjacent
spots. It will
be recognized by those skilled in the art that other configurations of spots
can also be
11
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used depending on the particular application. The insecticide releasing
polymeric sheet
is placed near or around the wooden structure to create an exclusion zone by
the
controlled release of insecticide.
A second controlled release embodiment of the invention also utilizes a
polymeric-carrier delivery system for the controlled release of insecticide
comprising
spun-bonded polymeric sheeting 20 and a physical melt-bonded mixture of
polymer
and insecticide. The polymeric sheeting 20 as in the first embodiment can be
either
woven or non-woven polypropylene upon which is bonded the physical melt-bonded
mixture (shown as stripes 22 in FIG. 2). Similarly, the polymers and
insecticide
described above with respect to the first embodiment may also be used in the
embodiment described in this section.
The mixture of polymer and insecticide of the second embodiment may
alternatively be placed on spun-bonded polymeric sheeting using extruder
systems
which provide stripes, e.g., as shown in FIG. 2. The stripes 22 can be about 1
centimeter in height and about 5 to 15 centimeters apart. Optimally, the
stripes should
be placed about 10 centimeters apart. It is desirable that the stripes should
be
configured in such an arrangement so as to permit a steady state concentration
of
insecticide in the exclusion zone after an initial burst of insecticide. After
the stripes are
applied to the polymeric sheet, the sheet is placed on or near the wooden
structure to
be protected from insects.
Binding filler and/or carriers may also be included in all of the embodiments
of
the invention. The inclusion of the binding filler and/or carrier permits
greater amounts
of insecticide for a given release rate or permits a lower release rate for a
given amount
of pesticide. The binding carrier binds the pesticide. Binding carriers found
to bind the
pesticide include carbon based carriers for example carbon black~~(including
lamp black
and gas black), activated carbon and combinations thereof. It is believed that
alumina,
silicoaluminate, hydroxyapatite and combinations thereof may be comparable to
carbon
for binding bioactive chemicals.
When a carbon based carrier is utilized, the first step is to insure dryness
of the
carbon followed by mixing the insecticide in a liquid form with the carbon.
Only
sufficient carbon black (filler) is used to produce a friable mixture. The
term "friable"
means substantially dry or non-sticky flowable particles. Certain pesticides
may have to
be heated to achieve a liquid form. The liquid insecticide adheres or binds to
the
is
CA 02429743 2003-05-23
extremely large surface area of the finely divided carbon black and the
mixture is
cooled for incorporation in the polymer. Polymers which may be used in a
carbon
application are a polyethylene (including low and high density polyethylene),
polypropylene, copolymers or blends of polyethylene and polypropylene,
polybutylene,
S epoxy polymers, polyamides, acrylate-styrene-acrylonitrile, aromatic or
unsaturated
polyesters, polyurethanes, silicones, or any other suitable polymers or
copolymers
thereof.
The carbon-insecticide mixture in the first and second embodiments (or just
insecticide if carbon is not used) is then mixed with the polymer, preferably
polyurethane, in either the molten, powder or liquid stage. Next, this mixture
is bonded
to the polymeric sheeting. In the first and second embodiments of the
invention, the
polymer and insecticide are melt-bonded to the polymeric sheeting.
Another mode of bonding the mixture of polymer and insecticide to the
polymeric sheeting is by "through-injection molding." In "through-injection
molding",
molten material is injected from a heated nozzle through a porous web and into
a mold.
The molten material flows through the web under pressure and is solidified in
the
mold. While the molten material is being injected, the porous web allows air
to escape,
but it also retains the molten mass under pressure until it has cooled.
A different method of bonding the mixture of polymer and insecticide to the
polymeric sheeting is by placing a melted mixture of polymer and insecticide
on the
spun-bonded polymeric sheeting. If the mixture is melted, it must be allowed
to cool,
cure and solidify. As used hereinafter, "a melted mixture of polymer and
insecticide" is
intended to indicate that the polymer is either melted or already in the
liquid stage. The
insecticide may also be melted or contained in a slurry solution depending on
its
melting point. A "melted mixture of polymer and insecticide" can also contain
carbon
or other additives which do not melt but flow with the melted
polymer/insecticide
mass.
The first and second embodiments of the invention should provide release rates
sufficient to maintain an effective insecticide concentration in the exclusion
zone to kill
or repel insects but at sui~ciently slow rates to maintain an effective
concentration for
an extended period of time.
Overall, a preferred composition for the first and second embodiments of the
invention comprises from about 70 to 95 parts by weight of carrier polymer,
from
13
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about 0 to 15 parts by weight of carbon, and from about 5 to 30 parts by
weight of
insecticide. The design considerations of the controlled release devices vary
according
to such factors as user preference and geographic conditions. The steady state
release
rate of the polymeric delivery system of these two embodiments after the
initial burst
of insecticide can be maintained for at least 6 years as a barrier to insects
such as ants
and termites. However, the equilibrium concentration of this embodiment can
easily be
adjusted to meet the specific needs of each user.
Optionally, the embodiments shown in FIGS. 1-5 may comprise a pesticide
impervious sheet (not shown) such as a metallized foil. The metallized foil or
an
extruded sheet of a polymer is laminated to one side of the spun-bonded
polymeric
sheeting in order to direct the flow of insecticide.
A further embodiment of the present invention is a barrier of a pest-
impervious
sheet wherein a bound friable mix of the bioactive chemical or pesticide with
a carbon
carrier is placed within a polymer and exhibits substantially no release of
the bioactive
chemical. The phrases "substantially no release" and "releasing only minute
amounts"
are intended to define a release rate less than 0.4 ~,g/cm2/day, preferably
less than 0.1
p,g/cmz/day, and most preferably less than 0.05 p.g/cm2/day. This embodiment
encompasses a release rate of below detectable limits. In this embodiment,
pests are
deterred upon "sniffing" or "scratching" a polymer surface and detecting the
presence
of the pest harmfixl bioactive chemical. The lifetime of the barrier is much
longer than
a barrier with a higher release rate. Moreover, a flaw or tear in the polymer
will be less
prone to "leak" bioactive chemical. Hence, two or more ,layers of this
embodiment may
be preferred to maintain a complete barrier. Multiple layers would permit a
tear or hole
in one layer, but a pest would not pass a second or subsequent untorn layer.
It may
further be desirable to place a protective layer, for ex~.mple scrim, on one
or both sides
of a barrier layer to avoid tearing.
Once made, the polymeric-carrier delivery systems of the first and second
embodiments are placed near the structure desired to be protected from
insects. FIGS.
3-5 illustrate various applications of either the spotted or striped sheet
embodiments of
the invention. The FIG. 1 configuration is shown in FTGS. 3-S, but it is
understood that
the FIG. 2 configuration or other configurations can work as well.
14
CA 02429743 2003-05-23
In FIG. 3, the polymeric-carrier delivery system 1 is placed under and
alongside
a concrete foundation 23 of a wooden structure 100 creating an exclusion zone
10 to
protect the structure from termites, ants and other boring insects.
In FIG. 4, the polymeric-carrier delivery system 2 is placed under a
structural
member 24, such as a porch, patio, sidewalk, or under a basement foundation
beside
the wooden structure 101 to provide an exclusion zone 10.
In FIG. 5, the polymeric-carrier delivery system 3 is placed over and on the
sides of the concrete foundation 23 of a wooden structure 102, but under the
wooden
portion 25 of the structure to create an exclusion zone 10.
Another embodiment of the invention is illustrated in FIGS. 6 and 7. This
embodiment pertains to extrusions such as extruded flexible cylinders 26 and
extruded
flexible flat strips 27 shown respectively in FIGS. 6 and 7. A wide variety of
polymers
which can be classified into four broad subgroups can be utilized. The groups
include
thermoplastic polymers, thermoset polymers, elastomeric polymers and
copolymers of
the three groups named above. By way of example, some polymers which can be
used
from the four groups are high density polyethylene, low density polyethylene,
ethyl
vinyl acetate (EVA), vinyl acetate, urethane, polyester, santoprene, silicone,
neoprene
and polyisoprene. In some embodiments, the preferred insecticide is
chlorpyrifos
although other insecticides described herein can be used. A filler may also be
added.
The cylinders preferably have a size ranging from about 5 to 15 millimeters in
diameter, but most preferably about 10 millimeters in diameter for the optimal
steady
state delivery of insecticide into the exclusion zone. Flat strips should
preferably have a
thickness of from about 1 to 6 millimeters and a width of from about 5 to 15
millimeters. It, however, should be noted that both cylinders and flat strips
can be
designed to meet the varying conditions encountered by the user.~~
Overall, in order to maintain an equilibrium concentration of pesticide in the
exclusion zone for an extended period of time, the composition of this
embodiment of
the invention should comprise from about 70 to about 95 parts by weight of
polymer,
from about 0 to about 30 parts by weight of carbon, and from about 5 to about
30
parts by weight of pesticide. The composition of the extrusion can, however,
be
tailored to the specific needs of the user. It is estimated that the exclusion
zone can be
maintained for at least 6 years for a cylinder and likewise for flat strips.
CA 02429743 2003-05-23
The extrusions can be positioned in a variety of positions to create exclusion
zones. FIG. 8 illustrates a manner of using the extrusion shown in FIG. 6. One
or more
flexible cylinders 26 are placed between the concrete foundation 23' and the
wooden
portion 25' of the structure. The flexible cylinders 26 release insecticide at
a controlled
rate to create an exclusion zone. An advantage of this configuration is that
flexible
cylinders 26 can be placed under a structure that has already been built.
Similarly, in a
manner not shown, the flexible cylinders can be placed vertically into the
ground as
opposed to horizontally. As will be recognized by those skilled in the art,
the
extrusions may have other suitable shapes and be placed in any suitable
position
depending upon the particular use contemplated.
FIG. 9 illustrates a manner of using the flexible flat strip extrusion shown
in
FIG. 7. One or more flexible flat strips 27 create an exclusion zone by being
placed
between or alongside the concrete foundation 23" and the wooden portion 25" of
the
structure. The flexible flat strips 27 can also be placed vertically alongside
a wall in an
embodiment not illustrated in the drawings. Again, any suitable placement of
the flat
strips is considered as being within the scope of the invention.
The controlled release of insecticide can also be conveniently achieved by
using
pellets as illustrated in the embodiments shown in FIGS. 10-13. The pellet 13
comprises polymer, insecticide and preferably also includes a filler. Various
polymers
can be used in this embodiment. They can comprise polymers of four subgroups
consisting of thermoplastic polymers, thermoset polymers, elastomeric polymers
and
copolymers thereof. Polymer selection from these four subgroups depends upon
design considerations with the preferable polymer being either high density
polyethylene or low density polyethylene. In turn, the insecticide preferable
comprises
tefluthrin, but the following insecticides can also be used: isofenphos,
fenvalerate,
cypermethrin, permethrin and other pyrethrins. For optimal results, a carrier
such as
carbon can also be incorporated into the mixture.
The pellet 31 releases insecticide at a controlled rate for an extended period
of
time in order to establish an exclusion zone. The composition for such a
pellet needed
for the maintenance of a zone in the soil is from about 70 to about 95 parts
by weight
of polymer, from about 0 to about 30 parts by weight of carbon black, and from
about
5 to about 30 parts by weight of insecticide. Ultimately, the compositions of
the pellet
depend upon user preference.
16
CA 02429743 2003-05-23
The pellets can be any convenient size depending upon the intended use, such
as 1 to 25 millimeters in diameter (or width and thickness, if rectangular) by
2 to 20
centimeters or more in length. Furthermore, in order to fit specific user
needs, the
dimension of the pellets and the concentrations of the insecticide can easily
be
adjusted. However, an exclusion zone can be maintained for at least 6 years.
Additionally, pellets 31 have the advantage that they can be conveniently
placed almost anywhere. The pellets of this embodiment of the invention are
shown in
FIG. 10. A pellet 31 is inserted near a wooden structure 25. The pellets as
illustrated in
FIG. 10 can be placed under a cement foundation 23 "' or they can be placed
directly
under the wood structure (not illustrated) so as to permit the creation of a
zone 10
surrounding the wooden structure 25"' to exclude insects capable of damaging
such
structures. FIG. 11 shows a cross-sectional view of pellets 31 inserted on a
surface 40.
Pellets are easily applied to a wide variety of uses. FIG. 12 illustrates
pellets
sprayed 50 onto a concrete structure surface 40. FIG. 15 illustrates treating
a surface
by placing pellets 33 on preformed boards 300.
Pellets 32 are applied onto a surface 40 such as soil or concrete via a foam
41
as illustrated in FIG. 13. The pellets are first incorporated into a foam in a
manner
known in the art. The foam 41 containing the fine pellets is then sprayed 50
as
illustrated onto the surface 41 via a motorized sprayer 70 in FIG. 12 so as to
provide a
protective coating for the surface. The pellets 32 then release the
insecticide to create a
protective barrier in the soil to protect the wood from harmful insects. For
best results,
the foam 50 is comprised of polyurethane. It is also possible to use silicone,
polyester,
or polyvinyl acetate. The pellets 32 can vary in size depending upon the foam
thickness
and the desired concentration of insecticide in the exclusion zone. The
thickness of the
foam to be applied to a surface can vary according to the user's preference.
The
exclusion zone can be maintained for at least 6 years. In addition to being
used as a
carrier for insecticide, the foam also cures cement and acts as an insulator.
A preformed board with embedded pellets 33 can also be utilized as an
embodiment of this invention as illustrated in FIG. 14. This board 300 can be
made of
any type of material which can suitably hold the pellets 33. Preferably, the
board is
comprised of Styrofoam which is registered as a trademark of The Dow Chemical
Company. The board can be applied in any variety of fashions and can also work
as an
insulating device. One manner of application is illustrated in FIG. 15, where
the board
17
CA 02429743 2003-05-23
300 with pellets 33 is placed above a concrete surface 42. The embedded
pellets are
regularly spaced with the spacing being specified by the devised amount of
insecticide.
In another embodiment as shown in FIGS. 16 and 17, the controlled release
device comprising the polymer matrix and insecticide can be applied via a hot
melt.
This embodiment is designed to meet the needs of structures already in place.
As stated
above, the polymer matrix can comprise any of the four above-named polymer
groups.
Similarly, any of the above-named insecticides can be utilized. However, it is
preferable
to use high or low density polyethylene with either a pyrethrin. Although
tailored to
the user, the concentrations of the various substances in the hot-melt
application
should range from about 70 to about 95 for the polymer, from about 5 to about
30 for
the insecticide and from about 0 to about 30 for filler/carrier for optimal
results.
FIG. 16 shows hot melt 50 being injected by a syringe 400 into the ground near
a concrete foundation 43. The concrete structure 43 supports a wooden
structure 250.
FIG. 17 shows the spacing between the hot melt 50 which has already been
injected
into the ground.
In another embodiment, FIGS. 18 and 19 illustrate the use of insecticide to
fumigate a structure 500. By injecting or placing the controlled release
device in or
near a structure which can be fumigated, the insecticide released from the
controlled
release device can vaporize, thereby fumigating the structure. FIG. 18
illustrates the
use of plugs 34 to fumigate a structure 500 made of building blocks 502.
Similarly,
FIG. 19 illustrates a mode of applying the controlled release device by using
a drill 800
to bore a hole 700 into a cement slab 900. Once inserted, the plug is able to
fumigate
the structure.
Another embodiment of the device of the present invention is shown in FIG.
20. A first polymer 200 of medium or high density polymer, having a low vapor
pressure insecticide is combined with a second polymer 202 of low density
having a
more volatile, vis higher vapor pressure insecticide. High, medium and low
density are
terms well known in the polymer art refernng to the degree of cross linking
within a
polymer. High vapor pressure is defined as vapor pressure in excess of about 1
millipascal and preferably ranges from about 10 millipascals to about 100
millipascals.
Low vapor pressure is defined as less than 1 millipascal and preferably ranges
from
about 0.05 millipascals to about 0.5 millipascals. The first polymer 200
preferably has a
thickness in the range from about 1/32 to 1/8 inches. The low vapor pressure
18
CA 02429743 2003-05-23
insecticide is preferably permethrin or lambda cyhalothrin. The preferred
material of
the first polymer 200 is selected from among polyurethane, high density
polyethylene
and polypropylene. The second polymer 202 is placed adjacent to and preferably
attached to the first polymer 200. It is preferred that the first polymer 200
be water and
radon impermeable. Hence, the first polymer 200 is preferably a sheet that may
be a
film or spun bonded. According to the present invention, the first polymer 200
may be
in two sub-parts with one sub-part 204 a permeable medium or high density
polymer
containing the low vapor pressure insecticide and another sub-part 206 an
impermeable
layer having no insecticide within. The impermeable layer has an advantage for
handling of preventing or reducing exposure/contact of the installer with the
bioactive
chemical. The impermeable layer may be, for example, Mylar, saran or Saranax.
The second polymer 202 is a low density polymer, preferably an ethylene vinyl
acetate, a low density polyethylene or blend thereof. The more volatile or
higher vapor
pressure insecticide placed within the second polymer is preferably a
synthetic
pyrethroid, for example tefluthrin.
The second polymer 202 may be in the form of pellets as previously described
and the first and second polymers deployed with the first polymer under a sill
plate on
a foundation and the second polymer scattered in the soil adjacent the
foundation.
More preferably, the second polymer 202 is in the form of an open mesh, either
woven
or non-woven as shown. Mesh openings may range from touching but not sealed to
about 1 to four inches square and ribs 208 having a cross section width of
from about
1 mil to about 1/8 inch. A scrim that can be made from polyethylene,
polypropylene, or
polyester may be used as the mesh. With a first polymer 200 sheet and a second
polymer 202 open mesh, the device of the combination of. the first and second
polymers 200, 202 is preferably placed below grade. The first copolymer sheet
200 is
placed adjacent the second polymer 202 open mesh with the first polymer 200
sheet in
contact or near a foundation 43 and between the foundation and the second
polymer
202 open mesh. The mesh material may absorb bioactive chemical and contribute
to
the reservoir of bioactive material.
In operation, the first polymer 200 maintains a physical/chemical barrier
against
insect intrusion. However, because of the slow release of the first polymer
200, very
little insecticide is released that would be available to create an exclusion
zone within
about the first year after installation. In addition, it is impossible to
install a defect free
19
CA 02429743 2003-05-23
barrier because of penetrations, for example electrical and plumbing, and
because of
punctures or tears during construction. Accordingly, the second polymer 202 is
deployed to create exclusion zones within a few days of installation thereby
preventing
insect access through the imperfections of the first polymer 200. The first
polymer 200,
therefore, has three functions: insect barrier, vapor/moisture barrier, and
radon barrier.
The first polymer 200 is designed to last at least 10 years and preferably up
to and in
excess of 20 years. The second polymer 202 is designed to last at least 5
years and
preferably up to about 10 years. By the time that the second polymer 202 is
depleted
and no longer effective against insects, the first polymer 200 will have
developed a
concentration of released insecticide sufficient to maintain the exclusion
zone.
The Preferred Mufti-Layer Barrier
Yet another embodiment of the present invention is a mufti-layer barrier which
includes at least three layers: a pesticide-releasing layer and two pesticide-
retaining
layers. The pesticide-retaining layers are on either side of a pesticide-
releasing layer.
The pesticide-releasing layer (i.e., the "active" or pesticidal active-
ingredient
containing layer) contains at least one pesticide. The pesticide-releasing
layer releases
the at least one pesticide. The pesticide-retaining layers allow only a minute
amount of
the pesticide to be released out of the barrier. The inner, active layer is
sandwiched
between the two pesticide-retaining layers so that substantially no pesticide
is released
from the barrier. The thickness of the barrier is generally in the range of
from about
0.010 inch (10 mil) to about 0.030 inch (30 mil) and preferably about 0.014
(14 mil) to
about 0.016 inch (16 mil). The mufti-layer barrier can be formed into a sheet
or film
and placed to surround areas such as foundations for houses which need to be
protected from crawling insects such as termites and other pests.
This mufti-layer barrier protects areas and/or structures by preventing pests
such as crawling wood-boring insects and termites from entering into protected
areas
and/or structures and by repelling and/or preventing pests from crossing the
barrier.
The mufti-layer barrier protects areas and/or structures for a prolonged
period of time
while avoiding harmful effects on installers of the barrier, persons who visit
or occupy
the protected areas and/or structures and on the environment. The release of
pesticide
from the barrier is minimal so that the barrier can be handled by installers
without
adverse consequences. The minimal release of pesticide provides minimum impact
on
the environment and allows the barrier to last for a prolonged period of time,
generally
CA 02429743 2003-05-23
up to 10 or even 30 years. The mufti-layer barrier can be installed beneath
the
foundation of buildings prior to construction so as to offer new-construction
property
owners long-term protection against pests such as crawling wood-boring insects
and
termites. In addition to keeping pests out of protected areas andlor
structures, the
mufti-layer barrier assists in preventing moisture and harmful gases such as
radon from
penetrating the protected area and/or structure.
The barrier of this embodiment of the invention may include one or more
additional layer or layers. The additional layer or layers can be placed in
any desirable
location with respect to the pesticide-releasing layer and the pesticide-
retaining layers
but an additional layer is preferably placed between the pesticide-releasing
layer and
the pesticide-retaining layer.
The barrier of this embodiment of the invention can include an additional
layer
or layers which add strength and puncture resistance to the barrier. This
additional
layer or layers can be placed in any desirable location with respect to the
required
layers but an additional layer is preferably placed between the pesticide-
releasing layer
and the pesticide-retaining layer. The mufti-layer barrier may be in the form
of a thin
sheet or film which includes at least one layer which provides strength and
puncture
resistance to the sheet or film. The thickness of the strength and puncture
resistance
layer generally ranges from about 0.002 inch (2 mil) to about 0.006 inch (6
mil),
preferably about 0.004 inch (4 mil).
The barrier of this embodiment of the invention can also include one or more
additional protective layers to protect the barrier from environmental factors
such as
ultraviolet rays. The additional protective layers) protect the barrier from
UV rays
during installation and when the barrier is exposed to sunlight thereafter.
The
additional protective layers) can be placed in any location with respect to
the other
layers but are generally placed outside the other layers of the barrier. The
protective
layers) can be made of heat sealable polymers to facilitate heat sealability
of the
barrier. The thickness of the protective layers generally ranges from about
0.0005 inch
(0.5 mil) to about 0.003 inch (3 mil), preferably about 0.001 inch (1 mil).
The
protective layers generally range from about 15% by weight to about 30% by
weight
of the barrier, preferably about 22% by weight of the barrier. The area
densities of the
protective layers generally range from about 13 grams of material per square
meter to
21
CA 02429743 2003-05-23
about 78 grams of material per square meter, preferably about 26 grams of
material per
square meter.
The layers of the barrier are held together or bonded to each other to form a
unitary mufti-layer product. The layers can be bonded to each other either
directly or
by the use of bonding layers. For example, a strength and puncture resistance
layer
can be bonded to the active layer (i.e., the pesticide-releasing layer) and to
the
pesticide-retaining layers) using a bonding layer. Similarly, the strength and
puncture
resistance layer can be bonded to the pesticide-releasing layer using a
bonding layer.
One advantage of using one or more bonding layers to secure the layers of the
barrier
to each other is that the active layer can be made from a polymer which need
not be
bondable to the pesticide-retaining layer or additional layers. This allows
for the use of
polymers in the active layer (i.e., the pesticide-releasing layer) that have
low melting
points. The lower processing temperatures reduce losses of pesticide in the
process of
making the active layer.
The pesticide-retaining layers are preferably made of a polymeric material
which allows only minute amounts of the pesticide to pass through such that
substantially no pesticide is released from the barrier. The preferred polymer
is
Saranex~ available from The Dow Chemical Company of Midland, Michigan. The
thickness of each of the pesticide-retaining layers generally ranges from
about 0.001
inch (1 mil) to about 0.005 inch (5 mil), preferably about 0.002 inch (2 mil).
The
pesticide-retaining layers generally range from about 20% by weight to about
40% by
weight of the barrier, preferably from about 25% to about 35% by weight of the
barrier, more preferably about 30% by weight of the barrier. The area
densities of the
pesticide-retaining layers generally range from about 26 grams of material per
square
meter to about 130 grams of material per square meter, preferably about 60
grams of
material per square meter. In this embodiment of the present invention, the
pesticide-
retaining layers) rather than the pesticide-releasing layer control the
release of the
pesticide from the barrier. However, the pesticide-releasing layer can assist
in assuring
that only minute amounts of the pesticide are released by controlling the
release of the
pesticide from the pesticide-releasing layer. The release rate from the
barrier can, in
some cases, be below detectable limits.
The pesticide-releasing layer can be made of a polymeric matrix and a
pesticide
which is dispersed throughout the polymeric matrix. The polymeric matrix may
be a
22
CA 02429743 2003-05-23
controlled-release polymeric matrix which is formed into a film. In one
embodiment of
the present invention, the polymeric matrix is made from low density
polyethylene.
Linear low density polyethylene is currently preferred as the polymeric matrix
material
because it has a lower melting point than other polyethylenes. The low density
polyethylene may be a metallocene-catalyzed low density polyethylene. Other
suitable
polymers for use in the polymeric matrix include, but are not limited to,
urethane,
polyurethane, epoxy, silicone, polyethylene + wax (PE + wax), aromatic
polyesters,
pellethane, ethylvinyl acetate (EVA), polyethylene, high density polyethylene,
low
density polyethylene, vinyl acetate, polyester, santoprene, neoprene,
polyisoprene,
polypropylene, copolymers or blends of polyethylene and polypropylene,
polybutylene,
epoxy polymers, polyamides, acrylate-styrene-acrylonitrile, unsaturated
polyesters,
silicones, and combinations thereof. The polymer for use in the polymeric
matrix may
be hydrophobic.
Examples of suitable pesticides for use in the pesticide-releasing layer
include,
but are not limited to, pyrethroids, neonicotinoids, isofenphos, fenvalerate,
pyrethrins,
and combinations of these types of compounds. The preferred pesticides for use
in
the pesticide-releasing layer include tefluthrin, permethrin, lambda
cyhalothrin,
resmethrin, deltamethrin, cypermethrin, cyphenothrin, cyfluthrin,
deltamethrin,
chlorpyrifos, fenoxycarb, diazinon, dichlorophen, methyl isothiocyanate,
pentachlorophenol, tralomethrin, chlorfenapyr, fipronil, neonicotinoids and
combinations of these compounds. Examples of suitable neonicotinoids include,
but
are not limited to, thiamethoxam, nitenpyram, imidacloprid, clothianidin,
acetamiprid,
and thiacloprid. One preferred pesticide for use in the pesticide-releasing
layer is
lambda cyhalothrin. Lambda cyhalothrin is a highly potent termiticide with a
lethal
concentration that kills 99 percent of test termites (LC99) of 0.0001
p,g/termite for the
most important United States termite species, Reticulitermes fZavipes. In some
embodiments, at least one of the pesticides in the pesticide-releasing layer
is present in
an amount of at least 5% of the pesticide-releasing layer by weight. In other
embodiments, at least one of the pesticides in the pesticide-releasing layer
is present in
an amount of at least 10% of the pesticide-releasing layer by weight.
The mufti-layer barrier provides several modes of action against termites. The
mufti-layer barrier provides lethal insecticidal protection by using pesticide
such as
lambda cyhalothrin in the barrier to deliver a lethal dose of pesticide which
may be
23
CA 02429743 2003-05-23
transferred to termites following transient contact with the barrier. The
multi-layer
barrier also provides repellant protection against termites. The multi-layer
barrier
further provides physical protection against termites because the barrier
preferably has
external pesticide-retaining layers which are smooth and tough so that
termites cannot
S initiate feeding on the barrier.
The pesticide-releasing layer which is made of a polymeric matrix and a
pesticide dispersed through the matrix may also include a carrier such as
carbon black
(including lamp black and gas black). Carbon black in the form of lamp black
has been
found to provide an advantage of not deactivating or decomposing the
pesticide, being
easier to extrude and easier to keep from agglomerating. The use of carbon
black in
the form of lamp black assists in producing a friable mixture of substantially
dry or
non-sticky flowable particles and in preventing evaporation of the pesticide
during
extrusion. The thickness of the pesticide-releasing layer is generally in the
range from
about 0.001 inch (1 mil) to about 0.020 inch (20 mil), preferably from about
0.001 inch
(1 mil) to about 0.005 inch (5 mil), more preferably about 0.002 inch (2 mil)
or 0.0037
inch (3.7 inch). The pesticide-releasing layer generally ranges from about 15%
by
weight to about 30% by weight of the barrier, preferably from about 22% by
weight to
about 25% by weight of the barrier, more preferably about 24% by weight of the
barrier. The area density of the pesticide-releasing layer generally ranges
from about
22 grams of material per square meter to about 115 grams of material per
square
meter, preferably about 45 grams of material per square meter.
The pesticide-releasing layer preferably releases the pesticide in a
controlled
manner. This controlled release assists the pesticide-retaining layer in
releasing only
minute amounts of the pesticide from the barrier to help in achieving a
substantially
non-releasing barrier. In other words, the release ~ of only minute amounts of
the
pesticide from the barrier can be assisted by controlling the release from the
active
layer (i.e., the pesticide-releasing layer).
In addition to pesticides which repel and prevent penetration by insects, it
may
be desirable to include one or more fungicides in the barrier. 'The
fungicides) can be
included in the pesticide-releasing layer containing an insecticide or in a
separate
fungicide-releasing layer. The separate fungicide-releasing layer may be
located inside
the pesticide-retaining layers. One or more fungicides can be included to
prevent
deterioration of the integrity of the barrier by fungi.
24
CA 02429743 2003-05-23
The term "fungicide" as utilized herein is intended to cover compounds active
against phytopathogenic fungi that may belong to a very wide range of compound
classes. Examples of compound classes to which the suitable fungicidally
active
compound may belong include both room temperature (25°C) solid and room
temperature liquid fungicides including, but not limited to, triazole
derivatives,
strobilurins, carbamates (including thio and dithiocarbamates), benzimidazoles
(such as
thiabendazoles), N-trihalomethylthio compounds (such as captan), substituted
benzenes, carboxamides, phenylamides, phenylpyrroles, and mixtures thereof.
Suitable
fungicides also include trichloronitromethane, a mixture of
methylisothiocyanate and
1,3-dichloropropane, sodium N-methyl dithiocarbonate, 2,3,5,6-tetrachloro-1,9-
benzoquinone, calcium cyanamide, biphenyl, copper naphthenate, dichlorophen,
fentin
hydroxide, and combinations of these compounds.
The fungicidally active compounds) are employed in a fungicidally effective
amount in the active layer of the mufti-layer barrier. Mixtures of one or more
of the
foregoing fungicidally active compounds also are usable as an active component
in the
practice of the present invention.
Where the barrier of this embodiment of the invention includes one or more
strength and puncture resistance layers, the strength and puncture resistance
layers)
are preferably made out of scrim. The strength and puncture resistance layers)
assist
in preventing tears and punctures and in providing tensile strength to the
barrier. The
preferred scrim is made out of a woven polymer. Especially preferred are woven
polymers made of high density polyethylene. The thickness of the scrim is
generally in
the range from about 0.002 inch (2 mil) to about 0.006 inch (6 mil),
preferably about
0.004 inch (4 mil). The scrim layer generally ranges from about 11% by weight
to
about 24% by weight of the barrier, preferably from about 17% by weight to
about
18% by weight of the barrier. The area density of the scrim layer generally
ranges
from about 30 grams of material per square meter to about 95 grams of material
per
square meter, preferably about 62 grams of material per square meter.
To reduce the release of pesticide from the pesticide-releasing layer at the
edges of the barrier, the pesticide-retaining layers can be made wider and
longer than
the corresponding pesticide-releasing layers) and the pesticide-retaining
layers
advantageously can be bonded to each other either directly or by a bonding
layer.
CA 02429743 2003-05-23
Placing one or more additional layers (i. e., the layers other than the
pesticide-
releasing layer) inside the pesticide-retaining layers offers an advantage if
the barrier
becomes penetrated by a pest. As pesticide is released, the additional layers)
become
impregnated with the pesticide. Accordingly, the additional layers) offer
additional
physical and pesticidal protection against the pests going through the
barrier.
One advantage of the mufti-layer barrier according to this embodiment of the
present invention is that the barrier can prevent termites, wood boring ants,
and other
pests from entering a structure built in whole or in part of wood. Another
advantage is
that the barrier can prevent pests from crossing it for a prolonged time, as
long as 10
or even 30 years. Yet another advantage is that the outside surfaces of the
barrier are
substantially free of pesticide when the barrier is installed. This leads to
increased
safety for handlers and installers of the barrier. A still further advantage
of this
embodiment of the invention is that the process manufacture of the barrier is
effcient,
and the barrier can be produced in large quantities using conventional
commercially
available equipment. In addition to keeping the pest out of a protected area
and/or
structure, the barrier according to this embodiment of the present invention
prevents
moisture and harmful gases from penetrating the protected area and/or
structure.
In accordance with one aspect of the invention, the barrier comprises a
plurality
of polymeric layers which are bonded together to form a thin flexible film.
The film
can be placed to surround areas such as foundations for houses which need to
be
protected from crawling insects such as termites and other pests.
The currently preferred mufti-layer barrier of the present invention is
composed
of a thin eight-layer polymeric film. The layers are bonded together to form a
flexible
film. The thickness of the currently preferred barrier film ranges from about
0.01 S inch
(15 mil) to about 0.016 inch (16 mil). The width of the currently preferred
barrier film
ranges from about 81 inch to about 83 inch. The weight of the currently
preferred
barrier film is approximately 327 grams per square meter. The eight layers of
the
currently preferred film are schematically shown in cross-section in FIG. 21.
Referring now to FIG. 21, a barrier film 110 includes outside layers 112 and
114. The outside layers 112, 114 are made of blends of an extrusion-coating
grade
polyolefin plastomer (sold under the brand name and model number of Affinity~
PT1450 by The Dow Chemical Company), a color concentrate (a blend produced by
Colortech Inc. of Brampton, Ontario, Canada of the carbon black Vulcan~ 9
26
CA 02429743 2003-05-23
manufactured by the Cabot Corporation and LDPE), and extrusion-coating grade
polyethylene (Novapol~ LC-0522-A available from Nova Chemicals Canada Ltd.).
The materials used to make the outside layers 112, 144 are also referred to
below as
the "New Generation Resin" or "NGR". The materials used to make the outside
layers
112, 114 assist in providing ultraviolet protection and heat sealability to
the barrier.
The melting point of the outside layers 112, 114 is approximately
110°C. The life
expectancy of the outside layers 112, 114 is expected to be comparable to
moisture
barriers currently being used during construction, and the material is
expected to last
indefinitely when applied underground. The outside layers 112, 114 have a
thickness
of approximately 0.0011 inch ( 1.1 mil) and have approximately 26 grams of
material
per square meter in the preferred embodiment.
Inside the outside layers 112, 114 are the pesticide-retaining layers 116,
118.
The pesticide-retaining layers 116, 118 are made of Saranex~ 14, a product of
The
Dow Chemical Company. Saranex~ 14 has a melting point above 143°C and
is not
believed to be biodegradable or photodegradable. Saranex~ 14 is a five-layer
coextruded product which consists of low density polyethylene, vinylidene
chloride/vinyl chloride copolymer (i.e., Saran), ethylene/vinyl acetate
copolymer, and
silicon dioxide. The layers made of Saranex~ 14 (i.e., layers 116 and 118)
have a
thickness of approximately 0.002 inch (2 mil) and have area densities of
approximately
53 grams of material per square meter in the preferred embodiment.
To the inside of pesticide-retaining layer 116, there is a bonding layer 120
which bonds the pesticide-retaining layer 116 to a scrim layer 122. The
bonding layer
120 is made of the same material as the pesticide-retaining layers 112, 114.
The
bonding layer 120 has a thickness of approximately 0.0011 inch (1.1 mil) and
an area
density of approximately 26 grams of LDPE per square meter in the preferred
embodiment.
The scrim layer 122 is made of high density polyethylene, specifically Sclair~
HDPE No. 99G available from Nova Chemicals Corporation. The scrim layer is
preferably a woven HDPE. The HDPE used to make the scrim layer 122 is extruded
into a sheet and slit into tapes. The tapes are then pre-stressed and woven
into a sheet,
which is incorporated into the barrier film 110 to provide tensile strength
and
resistance to puncture. The HDPE used to make the scrim layer 122 is very
similar to
the resin used to make common water piping and is expected to have a
comparable
27
CA 02429743 2003-05-23
lifetime. The scrim layer 122 has a thickness of approximately 0.004 inch (4
mils) and
an area density of approximately 63 grams of material per square meter in the
preferred
embodiment.
A bonding layer 126 bonds the scrim layer 122 to an active layer 128. The
bonding layer 126 is an extrusion-coating grade low density polyethylene
available
from Nova Chemicals Canada Ltd. such as Novapol~ LC-0522-A. The bonding layer
126 has a melting point of approximately 165°C. The bonding layer 126
has a
thickness of approximately 0.001 inch (1 mil) and an area density of
approximately 25
grams of material per square meter in the preferred embodiment.
Between the bonding layer 126 and pesticide-retaining layer 118 is the active
layer 128. In some embodiments of the invention, the active layer 128 is made
from
about 0.82% by weight to about 1% by weight lambda cyhalothrin technical (85%
w/w), from about 0.85% by weight to about 1.05% by weight carbon black, Lamp
black #6 (which is also known as Lamp black Superfine #6) available from
General
Carbon Company, and from about 20.9% by weight to about 23.1% by weight low
density (LDPE) polyethylene resin. In another embodiment, the active layer 128
is
made from 11.74 weight percent lambda cyhalothrin in a 85.2 weight percent
technical
solution, 10.87 weight percent Lamp black #6, and 77.39 weight percent low
density
polyethylene (LDPE) resin. The LDPE resin is preferably PE XU59400.00 (which
is
also known as PE XU59400) available from The Dow Chemical Company, a
metallocene-catalyzed extrusion coating grade LDPE. This particular LDPE was
chosen for its low melting point of approximately 80°C and its
extrusion coating
ability. The active layer 128 is about 23% by weight of the barrier film 110,
has a
thickness of approximately 0.002 inch (2 mil), and an area density of
approximately 45
grams of material per square meter in the preferred embodiment. ~a
In the eight-layered barrier film described above, the outside layers 112 and
114 and the bonding layer 120 together comprise approximately 22.2% by weight
of
the barrier film 110. The pesticide-retaining layers 116, 118 together
comprise
approximately 29.7% by weight of the barrier film 110. The scrim layer 122
comprises
approximately 17.8% by weight of the barrier film 110. The bonding layer 126
comprises approximately 6.4% by weight of the barrier film 110. The active
layer 128
is about 23.9% by weight of the barrier film 110.
28
CA 02429743 2003-05-23
The release rate of bioactive chemicals from the bonding layer 126 to the
other
layers is greater than the release rate of bioactive chemicals from the
barrier film 110 to
the exterior of the barrier film 110. The release rates of lambda cyhalothrin
in the
preferred eight-layer embodiment were measured to be less than 0.002 p.g per
square
centimeter of film per day. The barrier film 110 serves to prevent the
entrance of
wood deteriorating organisms into a structure while resulting in a negligible
concentration of lambda cyhalothrin in the soil and other surroundings.
Another suitable mufti-layer barrier may be composed of a thin six-layer
polymeric film where the layers are bonded together to form a flexible film.
In one
embodiment, the thickness of the six-layer polymeric film is about 0.012 inch
(12 mil),
the width ranges from about 81 inch to about 83 inch, and the weight is about
263
grams per square meter. The layers of one suitable six-layered film are
schematically
shown in cross-section in FIG. 24 and are described below.
Referring now to FIG. 24, a barrier film 210 includes outside layers 212, 214.
The barrier film 210 serves to prevent the entrance of wood deteriorating
organisms
into a structure while resulting in a negligible concentration of lambda
cyhalothrin in
the soil and other surroundings. In one embodiment, the outside layers 212,
214 are
made of blends of an extrusion-coating grade polyolefin plastomer, a color
concentrate, and extrusion-coating grade polyethylene as described above with
respect
to the eight-layer film and referred to as the "New Generation Resin" or
"NGR". The
outside layers 212, 214 may have a thickness ranging from approximately 0.0005
inch
(0.5 mil) to about 0.003 inch (3 mil) and may have from approximately 13 grams
to 78
grams of material per square meter.
Inside the outside layers 212, 214 are the pesticide-retaining layers 216,
218.
In one embodiment, the pesticide-retaining layers 216, 218 are made of
Saranex~ 14
as described above. Layers 216 and 218 may have a thickness ranging from
approximately 0.0005 inch (0.5 mil) to about 0.003 inch (3 mil) and have from
approximately 26 grams to 130 grams of material per square meter.
To the inside of pesticide-retaining layer 216, there is structural layer 222.
In
one embodiment, the structural layer 222 is made of HDPE as described above.
The
structural layer 216 may have a thickness ranging from approximately 0.002
inch (2
mil) to about 0.006 inch (6 mil) and may have from approximately 31 grams to
93
grams of material per square meter.
29
CA 02429743 2003-05-23
Between the structural layer 222 and pesticide-retaining layer 218 is the
active
layer 228. In one embodiment, the active layer 216 is made from 0.91 weight
percent
lambda cyhalothrin in an 85 weight percent technical solution, 0.95 weight
percent
Lamp black #6, and 22 weight percent LDPE resin. The active layer 216 may have
a
thickness ranging from approximately 0.002 inch (2 mil) to about 0.005 inch (5
mil)
and may have from approximately 22 grams to 115 grams of material per square
meter.
The release rate of lambda cyhalothrin in the six-layer embodiment was
measured to be less than 0.002 p.g per square centimeter of film per day. The
barrier
film 210 serves to prevent the entrance of wood deteriorating organisms into a
structure while resulting in a negligible concentration of lambda cyhalothrin
in the soil
and other surroundings.
The present invention also provides eff=icient methods for making the multi
layer barrier using conventional, commercially available equipment. In
accordance
with one aspect of the present invention, lamp black or gas black is used in a
premix
for making the active layer. Lamp black achieves the desired flowability of
the premix
but unlike a number of other types of carbon black, lamp black does not have
detrimental effects on the activity of the pesticide such as deactivating the
pesticide.
Method of Making the Barrier Film
The mufti-layer barrier film described above may be formed by a variety of
methods. In one method, the carrier such as carbon black is mixed with
particles of a
polymer to form a mixture.. One or more pesticides are added in a liquid form
to the
mixture while maintaining the mixture at a temperature below the temperature
at which
the pesticide decomposes but above the melting temperature of the pesticide to
form a
friable premix. The premix is melt extruded to form a thin active layer. The
premix is
extruded along with the desired additional layer or layers to form a barrier
film. The
desired number of layers, the type of layers selected, the order of the
layers, and the
materials used in making the layers depend upon a variety of factors
including, but not
limited to, the end application of the barrier film, the desired length of
protection
against pest intrusion, the type of area and/or structure being protected, the
specific
types of pests, manufacturing costs and capabilities, and the like.
The active layer may be prepared by combining the pesticide or bioactive
chemical with the carrier to form a bound friable mix and adding the bound
friable mix
CA 02429743 2003-05-23
to the polymeric matrix. The active layer may also be prepared by mixing the
polymer
and the carrier to form polymer-carrier mixture followed by the addition of
the
pesticide or bioactive chemical.
The eight-layer barrier film 110 described above may be formed by the
following preferred method. To produce the active layer 128, the polyethylene
resin
and carbon black in form of lamp black are combined and mixed. A suitable
mixer is a
Marion-type mixer. Where a Marion-type mixer is used, the mixer is sealed and
an
agitator is activated. The polyethylene resin and carbon black are mixed until
they are
well blended and carbon agglomerates are reduced in size. The polyethylene
resin is
preferably in pellet form and cryogenically ground to a 35 mesh powder. The
bulk
temperature of the mixture is preferably kept below 60°C.
Next, lambda cyhalothrin is gradually added as a molten spray while
maintaining the mixing of the polyethylene resin-carbon black mixture. In the
preferred embodiment, an 85.2% weight percent solution of technical grade of
lambda
cyhalothrin is used. The mixing is continued until contents are uniformly
blended. The
mixture may then be stored, for example in plastic-lined drums.
The mixture is next pelletized by being fed into an extruder/pelletizer fitted
with a die. In the preferred embodiment, an extruder/pelletizer fitted with a
1/8 inch
strand die is used and the extruder temperature is maintained at approximately
85°C
along the length of the extruder barrel and die. The extruder strand may
require water
cooling before pelletizing. Pellets are made approximately 1/8 inch long in
the
preferred embodiment. The pellets are next dried. The pellets are dried in a
hot air
cyclone drier or, if necessary to achieve more complete drying, placed in flat
trays and
put into a 60°C forced-air oven to dry.
The premix pellets are extruded and laminated between~~two mufti-layer films
via a lamination process. Specifically, the premix pellets are extruded and
laminated
between two mufti-layer films designed to hold the bioactive premix material
within a
final barrier film 110. A conventional extruder such as a single screw or
double screw
exturder may be used to extrude the layer 128.
The two mufti-layer films used in the lamination step are pre-fabricated. The
first mufti-layer film comprises layers 114 and 118 described above (i. e.,
the pesticide
retaining layer made of Saranex~ 14 and the adjacent NGR layer). The second
multi
layer film comprises layers 112, 116, 120, 122, 126 114 and 118 described
above (i.e.,
31
CA 02429743 2003-05-23
the NGR layer, the adjacent pesticide-retaining layer made of Saranex~ 14, the
adjacent NGR layer, the adjacent HDPE layer, and the adjacent LDPE layer). The
layers of the second mufti-layer film are oriented so the first NGR layer (i.
e., layer 112)
is on the outer surface of the final product.
The premix pellets are diluted with virgin polyethylene resin to a desired
concentration of lambda cyhalothrin and fed to an extruder to be directly
laminated
between the first and second mufti-layer films to form the barrier film 110.
The lambda
cyhalothrin concentration of the barrier film 110 is 0.77 wt.%, or 2.75 grams
per
square meter of barrier film 110 in the preferred method. The barrier film 110
is then
rolled into bolts and packaged for sale or delivery for sizing and seaming.
Moisture in the premix, particularly from the carbon black, can cause problems
during manufacture such as bubbling in the active layer 128 as that layer
exits an
extruder die. This may be solved by drying the premix in an incubator set at
approximately 54°C for a period of approximately 12 hours, which has
been found to
substantially dry the premix so that bubbling does not occur. Care must also
be taken
to reduce atmospheric moisture contact with the premix concentrate.
Further, carbon agglomerates can form a highly textured surface in the barrier
film 110. Carbon agglomeration is a problem because this results in
heterogeneous
distribution of the bioactive ingredients (lambda cyhalothrin for example) in
the active
layer 128. This problem may be reduced by sieving the carbon black component
of the
scrim layer 122 through a 100 mesh screen prior to use. Proper carbon black
dispersion may also be achieved through the use of high energy mixers such as
Henschel-type mixers and twin screw extruders, or the use of masterbatching
whereby
high carbon loading is used to increase polymer melt viscosity, thereby
increasing shear
stress in an extruder to result in carbon dispersion. A lower extruder
temperature or
the use of an extruder screw having a high shear mixing section may also
effect better
carbon distribution. One example of an extruder screw having a shear mixing
section
is a screw design having a fluted barrier flight built into the screw. When
such a screw
is used, the polymer melt is forced to flow over the barrier flight, which is
close to an
extruder barrel. This subjects the polymer melt to a high shear rate and
thereby
increases carbon distribution through the mixture.
Thermal decomposition and volatilization of lambda cyhalothrin occurs in the
manufacturing process at temperatures above approximately 160°C, with a
breakpoint
32
CA 02429743 2003-05-23
between approximately 160°C and approximately 170°C where lambda
cyhalothrin
losses become significant. To have a safety cushion for operating conditions,
it is
beneficial to have a processing temperature of approximately 150°C.
Preferred Method of Ofd Site Pre-Forming the Barrier Film
The currently preferred use of the barrier film is in protecting houses from
invasion of termites and other wood boring crawling insects. In order to
prevent
insects from entering the house through the soil, the barrier film of the
present
invention should be placed between the soil and foundation of the house that
is in
contact and in the proximity of the soil.
It is currently preferred to make the barrier film of the present invention
commercially in sheets which are smaller than the foundation of a house.
Accordingly,
it is necessary to combine a number of sheets to line the entire foundation
with the
barrier film. In order to avoid gaps between adjacent sheets, the sheets can
be sealed,
bonded or otherwise attached to each other.
In accordance with another aspect of the present invention, the barrier film
is
pre-shaped or pre-formed oil site to fit in its intended location prior to
placing the
barrier film in its intended location such as in the excavation for the
foundation of a
house. It is beneficial to combine the sheets of the barrier material to form
a pre-
shaped barrier which will envelop the entire foundation of a house off site
and then
transport it and install it in the excavation for the foundation. The off site
combination
of sheets into the shape of the foundation reduces the chances that the sheets
will be
torn or improperly sealed together so as to leave gaps.
FIG. 22 shows a pre-shaped barrier made of a mufti-layer polymeric film. The
pre-shaped barrier may be formed by sealing various segments of the barrier.
Preferably, the thermoplastic sheets used for sealing the various segments of
the barrier
are the outside layers of the mufti-layer barrier. However, the segments of
the barrier
can be formed into desired sheets using any other means including overlaying
segments
of thermoplastic materials on the adjacent barrier sheets. The segments, for
example,
may be in the form of patches or strips of thermoplastic material. FIG. 23
shows an
excavation for a foundation adapted to receive the pre-shaped barrier of FIG.
22.
In an embodiment of the barrier film having a loading of 2.75 ~,g of lambda
cyhalothrin per mm2, each mm2 of the~barrier film contains enough lambda
cyhalothrin
to kill at least 24,000 individuals ofR. fZavipes. Resistance to termites and
other wood
33
CA 02429743 2003-05-23
boring pests is preserved by the barner film even in the event that holes or
tears
develop in the barrier film. For example, with holes or tears having a size of
2 mm or
less, R. fZavipes' contact with the exposed active ingredient as they pass
through the
hole results in high termite mortality.
Not every embodiment of the present invention provides every named
advantage. Moreover, additional advantages of the present invention will
become
apparent upon studying of this specification.
EXAMPLES
The following examples are provided by way of explanation and to further
illustrate the various aspects of the present invention. As such, these
examples are
provided for illustrative purposes only and are not viewed as limiting the
scope of the
invention in any manner.
EXAMPLE 1
Experiments were conducted to determine the release rate of chlorpyrifos.
Loading rates for the insecticide were either 5 wt.% (weight percent) or 10
wt.%
depending on the polymer. Release rates were determined for all devices at
50°C.
The polymers evaluated included low melt polyethylene, polyurethane, two
epoxies, silicone rubber, and a low melt polyethylene high in waxes to reduce
thermal
decomposition of the chlorpyrifos. Studies indicated that excessive thermal
decomposition of the chlorpyrifos occurred at temperatures in excess of
approximately
240°C; thus, polymer selection was restricted to formulations not
requiring excessive
heat processing.
Table 1 provides a summary of the results from these studies. Overall, polymer
compatibility with chlorpyrifos did not appear to present a problem with the
loading
rates employed. There was some loss bf physical integrity of the polyurethane
polymer
employed, however, the other polymer systems exhibited no visible degradation
at
50°C. Release rates ranged from 10 p.g/cm2/day for the silicone rubber
to 0.3
p.g/cm2/day for Epoxy B.
Using the data provided in Table 1, an estimated product longevity can be
approximated. Assuming a device wt. of 0.5 g, with 10% load, then SO mg of
34
CA 02429743 2003-05-23
chlorpyrifos is available for release. Thus, for a polymer system having an
area of 4
cma, and a release rate of 1 p,g/cm2/da, there is sufficient insecticide to
last 30 years at
elevated temperature. These calculations indicate that a variety of
insecticidal products
are possible.
TABLE 1
Polymer Formulations and Release Rates for
Candidate Systems Employing Chlorpyrifos
Polymer Class ChlorpyrifosRelease Rate
Content (p, cm2/da)a
(%)
Pol rethane 5 2.1 ~ 1.4b
E ox A 5 <0.1
Silicone 5 10.3 ~ 3.5
Urethane 10 1.0 ~ 0.3
E ox B 10 0.3 ~ 0.1
PE+Wax 10 1.9+0.3
aRelease rates performed at 50°C.
bMaterial exhibited excessive cracking at elevated temperature
EXAMPLE 2
Studies were also conducted with similar polymer systems as in Example 1 but
with 80% pure pyrethrin. The release rates at 40°C are provided in
Table 2.
TABLE 2
Polymer Formulations and Release Rates for
Candidate Systems Employing Pyrethrin I
Polymer Class Pyrethrin I Release Rate
Content (%) ~ (p, cm2/da)a
E o A 10 0.50.2
Silicone 10 21.2 ~ 5.4
Urethane ~ 10 15.7 ~ 7.1
E o B 10 0.20.1
aRelease rates performed at 40°C.
The release rates were highest for urethane and silicone and lowest for the
epoxies. Substantial variability in release rates were encountered and
appropriate
binders will need to be evaluated.
CA 02429743 2003-05-23
From the data in Table 2, simple calculations can be performed to determine
the possible life of the insecticide systems. As stated in Example 1, there
are many
variables which can alter the lifetime of an exclusion zone.
EXAMPLE 3
Controlled release devices were made and tested to obtain their release rates.
All thermoplastic polymers were formulated with 10 percent pesticide, 3 or 7
percent
carbon black to absorb liquid pesticide, and 83 to 87 percent by weight of
polymer and
injection molded into thin sheets about 1/8 inch thick. Specifically, devices
made from
thermoplastic polymers and deltamethrin and lambda cyhalothrin contained 3
percent
of carbon black. The devices made from the remaining pesticides and
thermoplastic
polymers contained 7 percent of carbon black.
The devices made from S-113 urethane (a thermoset polymer) were made from
a polymer mix containing 60% S-113, 40% castor oil and 5% of TIPA catalyst by
weight. The polymer mix comprised 90% of the total weight of the device. The
pesticide, deltamethrin, comprised the remaining 10% of the device. No carbon
black
was used in this device. The polymer/pesticide mixture was cast into a 1/8
inch thick
sheet and heated at about 60°C for about 40 to 60 minutes to cure the
cast sheet.
One inch squares were then cut from the thin sheets that were injection molded
or cast and the squares were tested for release rates. The following release
rates were
obtained:
TABLE 3
Pesticide Polymer Release Rate
Deltamethrin S-113 urethane 25.2 ~,g/cm2/day
Aromatic 80A 16.8 ~,g/cma/day
Pellethane 2102-80A 8.8 p,g/cm2/day
Pellethane 2102-SSD 8.0 ~.g/cm2/day
Alipmtic PS-49-100 7.2 ~.g/cmalday
Cypermethrin Polyurethane 3100 0.4 ~.g/cm2/day
Polyurethane 2200 0.7 ~,g/cm2/day
EVA 763 27.3 p,g/cma/day
Polyethylene MA 778-000 4.6 p.g/cm2/day
36
CA 02429743 2003-05-23
Lambda cyhalothrin Polyurethane 0.4 p.g/cm2/day
3100
Polyurethane 2200 0.7 p,g/cm2/day
EVA 763 27.3 p,g/cma/day
Polyethylene MA 778-000 4.6 p,g/cma/day
Tefluthrin Polyurethane 3100 6.4 p.g/cm2/day
Polyurethane 2200 25.0 p.g/cm2/day
EVA 763 40.4 p,g/cm2/day
Polyethylene MA 778-000 27.0 p,g/cma/day
Permethrin Polyurethane 3100 1.4 p,g/cmz/day
Polyurethane 2200 1.3 p,g/cm2/day
EVA 763 28.5 ~g/cm2/day
Polyethylene MA 778-000 4.0 p,g/cma/day
EXAMPLE 4
An experiment was conducted to determine the effect of lambda cyhalothrin
(pyrethroid) concentration and insecticide/polymer combination on release rate
of
insecticide from the polymer. The data are summarized in Table 4.
TABLE 4
Release Rate for Polymer/Pyrethroid Concentration Combinations
Polymer Pyrethroid Pyrethroid Release
Concentration Rate (mg/cm2/da)
(Wt.%)
Ethylvinyl Acetate 1 0.3
(EVA)
5 2.2
10 ~ ~~~ 2.5
Polyurethane 1 0.9
5 4.4
10 8.3
Polyurethane/EVA (50150)1 2.6
5 7.2
10 9.1
EXAMPLE 5
An experiment was conducted to determine the effectiveness of the exclusion
zone against termites. Two species of termites were selected for the tests:
Eastern
37
CA 02429743 2003-05-23
subterranean termite because it is the most common and Formosan subterranean
termite because it is the most aggressive.
Test cells were assembled with glass containers. Wood shavings were placed in
the bottom of the containers. Insecticide impregnated polymer was placed over
the
wood chips in a manner that no path or opening existed from above the
impregnated
polymer to the wood chips. A nutrient free auger was placed above the
impregnated
polymer. The surface of the auger was the zero datum and the impregnated
polymer
was mounted at a distance of 5 cm below the surface of the auger. Termites
were
placed on the surface of the auger and their progress through the auger toward
the
impregnated polymer noted each day.
The impregnated polymer combinations are shown in Table 5.
TABLE 5
Release Rate for 10 wt.% Pyrethroid
Polymer Pyrethroid Release Rate
(m cm2/da
Eth lvin 1 acetate Permethrin 3.9
Eth loin 1 acetate Tefluthrin 4.3
Eth lvin 1 acetate Tefluthrin (2 wt.% 3.2
fatt acid
Pol eth lene Permethrin 1.4
Pol eth lene Tefluthrin 2.2
Pol eth lene Tefluthrin (2 wt.% 2.0
fatt acid
Controls having no pyrethroid in a polymer barrier were also used. The results
are shown in FIG. 25 and FIG. 26. In all controls, the termites ate through
the
polymer and obtained access to the wood chips. The rate of access through
ethylvinyl
acetate was slower than for polyethylene. For all impregnated polymers, there
was no
penetration. Because the Formosan subterranean termites are so aggressive,
they came
closer to the impregnated polymer than the less aggressive Eastern
subterranean
termites. In fact, the polyethylene with permethrin suffered mandible marks
from the
Formosan termites, but no holes or penetration. After about 12-14 days, even
the
Formosan termites were discouraged by the release of insecticide and retreated
from
impregnated polymer.
38
CA 02429743 2003-05-23
EXAMPLE 6
An experiment was conducted to demonstrate the effect of a binding carrier on
release rate. The active chemicals were tefluthrin and lambda cyhalothrin in
an amount
of 5 wt.%, the binding carrier was carbon black in amounts of 0 wt.% and 10
wt.%,
with the balance high density polyethylene (MA 778-000). Release rates were
measured at 6 weeks after fabrication wherein samples were wiped weekly to
remove
surface accumulation of released active chemical.
The results are shown in Table 6 below.
TABLE 6
Release Rates for 0 wt.% and 10 wt.% Carbon Black
Active Chemical Carbon Black Release Rate
(wt.%) p cm2/da
Tefluthrin 0 3.13
Tefluthrin 10 0.71
Lambda c halothrin 0 1.78
Lambda c halothrin 10 0.81
Lambda cyhalothrin 20 0.61
EXAMPLE 7
This example illustrates one method of making a premix which is subsequently
used in making an active layer (i.e., the pesticide-releasing layer) of the
barrier of the
present invention.
Low density polyethylene (PE XU59400 or PE XU59400.00 available from
The Dow Chemical Company) is cryogenically ground to form particles having
about
35 mesh particle size. The polyethylene particles are then blended with the
lamp black
carbon (Lamp black Superfine #6 available from General Carbon Company) in a
Marion-type paddle until the carbon is dispersed throughout the polyethylene
forming
a homogeneous mixture having a dry, flowable consistency. Then, with the
blender
operating with an internal bulk temperature of about 50°C, lambda
cyhalothrin
available from Syngenta, Inc. is added to the mixture a molten spray. The
blender
agitation is maintained following the application of lambda cyhalothrin to
achieve a
homogeneous mixture. The premix contains about 3.2 wt.% of lambda cyhalothrin,
about 4 wt.% of lamp black carbon and about 92.8 wt.% of low density
polyethylene.
39
CA 02429743 2003-05-23
The premix can be placed in a forced air oven at about 60-70°C to
reduce its moisture
content.
EXAMPLE 8
A homogeneous premix having about 10.0 wt.% of lambda cyhalothrin and
about 11.3 wt.% of lamp black carbon is prepared using the procedures as
described in
Example 7.
EXAMPLE 9
A premix is prepared using the procedure described in Example 8 except that
molten lambda cyhalothrin is applied to the lamp black carbon as a first step,
and the
mixture is then well blended to form a homogeneously mixed powder. The ground
low density polyethylene is then added and further blending takes place until
a
uniformly dispersed mixture is obtained having a dry, flowable consistency.
EXAMPLE 10
A premix is prepared with about 7.9 wt.% of gas black carbon (Colour Black
FW200 available from Degussa Corporation) and about 9.5 wt.% of lambda
cyhalothrin using the procedure as described in Example 7 except that an
Eirich-type
mixer utilizing a high-speed agitator was used to blend the components.
EXAMPLE 11
Premixes are prepared in accordance with Example 7, Example 8, and Example
10 except that premixes are not dried. The premixes are melt-extruded into a
strand
and then the strand is cut into pellets.
EXAMPLE 12
A premix is prepared having about 7 wt.% of lambda cyhalothrin, about 5 wt.%
of a conductive grade carbon black (Vulcan~ XC-72R available from Cabot
Corporation), and the balance of a low density polyethylene (Novapol~ LC-0522-
A
available from Nova Chemicals Canada Ltd.) using the procedure described in
Example 7. '
CA 02429743 2003-05-23
EXAMPLE 13
A premix prepared in accordance with Example 12 is injection molded to form
thin, circular disks. The molded disks are then chopped into shards using a
rotating
knife regrinder.
EXAMPLE 14
A premix is prepared having about 6 wt.% of lambda cyhalothrin and about 94
wt.% of low density polyethylene in accordance with the procedure of Example
7. The
resulting premix had a tacky consistency.
EXAMPLE 15
A sheet is prepared having a uniform composition of about 2 wt.% of lambda
cyhalothrin (available from Zeneca, Inc.), about 1 wt.% of conductive grade
carbon
black (Vulcan~ XC72R available from Cabot Corporation), and the balance of a
high
density polyethylene (Microthene~ MA77800 available from Quantum Chemical
Company).
As a first step, the carbon black is dried in a forced air oven at a
temperature of
about 105°C for at least 12 hours or until a constant weight is
achieved. The dried
carbon black is combined with about an equal amount by weight of powdered high
density polyethylene in a Hobart industrial dough mixer and is thoroughly
blended.
Then, while maintaining agitation, molten lambda cyhalothrin in an amount of
about
twice the weight of carbon black is slowly incorporated into the mixture. The
mixture
is then blended with sufficient amount of additional high density polyethylene
to reduce
the concentration of lambda cyhalothrin in the mixture to about 2 wt.%.
The resulting mixture is then melt-extruded at~ about 290°C and cast as
a single
layer film with a thickness of about 0.03 inch (30 mil).
EXAMPLE 16
A sheet is prepared having about 2 wt.% of lambda cyhalothrin, about 1 wt.%
of conductive grade carbon black (such as Vulcan~ XC72R available from Cabot
Corporation), and the balance of a high density polyethylene (Microthene~
MA78000
available from Quantum Chemical Company) in accordance with the procedure of
Example 15.
41
CA 02429743 2003-05-23
EXAMPLE 17
A sheet is prepared having about S% by weight of tefluthrin, about 2.S% by
weight of carbon black and the balance of a high density polyethylene
(Microthene~
S MA77800 available from Quantum Chemical Company) using the procedure of
Example 1S.
EXAMPLE 18
A sheet is prepared having about S% by weight of tefluthrin, about 2.S% by
weight of carbon black and the balance of a ethylene vinyl copolymer (EVA 763
available from Quantum Chemical Company) using the procedure of Example 1 S.
EXAMPLE 19
A sheet is prepared having about 10% by weight of tefluthrin, about S% by
1 S weight of carbon black and the balance of a high density polyethylene
(Microthene~
MA77800 available from Quantum Chemical Company) using the procedure of
Example 1S.
EXAMPLE 20
A sheet is prepared having about 10% by weight of tefluthrin, about S% by
weight of carbon black and the balance of an ethylene vinyl copolymer (EVA 763
available from Quantum Chemical Company) using the procedure of Example 1 S.
EXAMPLE 21
2S A sheet is prepared having about 10% by weight of permethrin, about S% by
weight of carbon black and the balance of an ethylene vinyl copolymer (EVA 763
available from Quantum Chemical Company) using the procedure of Example 1 S.
EXAMPLE 22
A sheet is prepared having about 10% by weight of permethrin, about S% by
weight of carbon black and the balance of a high density polyethylene
(Microthene~
MA78000 available from Quantum Chemical Company) using the procedure of
Example 1S.
42
CA 02429743 2003-05-23
EXAMPLE 23
A sheet is prepared having about 1% by weight of lambda cyhalothrin, about
0.73% by weight of carbon black (Special Black 6 available from Degussa
Corporation), and the balance of a low density polyethylene (Novapol~ LC-0522-
A
available from Nova Chemicals Canada Ltd.) using the procedure of Example 15
except that the melt-extrusion process is conducted at about 130°C and
the cast sheet
has a thickness of about 0.002 inch (2 mil).
EXAMPLE 24
A sheet is prepared using the procedure of Example 23 except with a lambda
cyhalothrin concentration of about 5% by weight and a carbon black
concentration of
about 3.6% by weight.
EXAMPLE 25
A sheet is prepared substantially as described in Example 23 except with a
lambda cyhalothrin concentration of about 10% by weight and a carbon black
concentration of about 7.3% by weight.
EXAMPLE 26
Sheets are prepared in accordance with Example 23, Example 24, and Example
25. The sheets are then laminated on both sides with layers of Saranex~ 14
films
(available from The Dow Chemical Company) using a thermal press.
EXAMPLE 27
A sheet is prepared having about 7.9% by weight of gas black carbon (Colour
Black FW200 available from Degussa Corporation), about 9.5% by weight of
lambda
cyhalothrin, and the balance of a low density polyethylene (PE XU59400 or PE
XU59400.00 available from The Dow Chemical Company) using the procedure of
Example 15, except that the melt-extrusion process is conducted at about
150°C and
the cast sheet has a thickness of about 0.002 inch (2 mil).
43
CA 02429743 2003-05-23
EXAMPLE 28
A sheet is prepared comprising two layers of Saranex~ 14 bonded together by
a melt-extrusion/lamination process. The bonding layer is a comprised of the
component mixture as described in Example 26. As a first step, the components
of the
bonding layer are prepared as a powdered premix. Then, the premix is melt-
extruded
at about 150°C directly between two layers of Saranex~ 14.
EXAMPLE 29
This example describes a method for making an eight-layered sheet. The
composition of each of the layers of the sheet is as follows.
Layer Description
1 New Generation Resin (NGR) (available from Fabrene, Inc.) layer composed of
black resin (Colortech No. 20413-19 available from Colortech Inc.), extrusion
coating grade polyolefin plastomer (A~nity~ PT1450 available from The Dow
~ Chemical Company), and low density polyethylene (Novapol~ LC-0522-A
available from Nova Chemicals Canada Ltd.) having a thickness of about 0.001
inch ( 1 mil);
2 Saranex~ 14 (available from The Dow Chemical Company) layer composed of
vinylidine chloride/vinyl chloride copolymer, low density polyethylene,
ethylene/vinyl acetate copolymer, and silicon dioxide having a thickness of
about 0.002 inch (2 mil);
3 NGR layer as described above;
4 scrim (available from Fabrene Inc.) layer composed of high density
polyethylene (Sclair~ HDPE No. 99G available from Nova Chemicals
Corporation) and carbon black resin (Plasblack~ PE1371. available from Cabot
Corporation) having a thickness of about 0.004 inch (4 mil);
5 low density polyethylene (Novapol~ LC-0522-A available from Nova
Chemicals Canada Ltd.) tie layer containing black resin (Colortech No. 20413-
19 available from Colortech Inc.) having a thickness of about 0.001 inch (1
3 0 mil);
6 active ingredient layer composed of gas black carbon (Colour Black FW200
available from Degussa Corporation), lambda cyhalothrin, and low density
44
CA 02429743 2003-05-23
polyethylene (PE XU59400 or PE XU59400.00 available from The Dow
Chemical Company) having a thickness of about 0.002 inch (2 mil);
7 Saranex~ 14 layer as described above; and
8 NGR layer as described above.
The eight-layered sheet is formed by bonding a layer of NGR (layer 1) to a
sheet of Saranex~ 14 (layer 2) using an extrusion coating method to form a
layer 1-2
composite. Another layer of NGR (layer 3) is melt-extruded to bond the layer 1-
2
composite to a sheet of scrim (layer 4) to form a layer 1-2-3 composite. A
layer of
low density polyethylene (layer 5) is applied to the layer 1-2-3 composite by
an
extrusion coating method to form the first outer layer.
A layer 7-8 composite is prepared by applying a layer of NGR (layer 8) to a
sheet of Saranex~ 14 layer (layer 7) by extrusion coating.
A premix is made using the procedure of Example 10, having about 7.9% by
weight of gas black carbon, 9.5% by weight of lambda cyhalothrin and the
balance
being a low density polyethylene. The premix is formed into active ingredient
pellets
using the procedure of Example 11. The active ingredient pellets are blended
with
low density polyethylene pellets (PE XU59400 or PE XU59400.00 available from
The
Dow Chemical Company) in a ratio of about 2:1 so as to achieve a concentration
of
about 6 wt.% of lambda cyhalothrin in the pellet mixture.
The pellet mixture is fed into an extruder to melt-extrude bond the first
outer
layer (i. e., layers 112, 116, 120, 122 and 126) and the second outer layer
(i. e., layers
118 and 114). A multi-layered laminate sheet having an overall thickness of
about
0.014 inch (14 mil) is formed. The concentration of lambda cyhalothrin in the
formed
laminated sheet is about 0.9 wt.%.
EXAMPLE 30
A sheet is prepared using the procedure described in Example 29 except the
active layer is composed of about 4% by weight of gas black carbon (Colour
Black
FW200 available from Degussa Corporation), about 4.7% percent by weight of
lambda
cyhalothrin, and the balance of a low density polyethylene (PE XU59400 or PE
XU59400 or PE XU59400.00 available from The Dow Chemical Company). The
concentration of lambda cyhalothrin in the formed laminated sheet is about 0.5
wt.%.
CA 02429743 2003-05-23
EXAMPLES 31-3 7
Sheets are prepared from premixes of lamp black carbon (Lamp black
Superfine #6 available from General Carbon Company), lambda cyhalothrin, and
low
density polyethylene (PE XU59400 or PE XU59400.00 available from The Dow
Chemical Company). The sheets are formed into laminates substantially using
the
procedure of Example 29, but having a final concentration of lambda
cyhalothrin in the
formed laminated sheet as provided in Table 7 below.
TABLE 7
Example % By Weight of % By Weight % By Weight of
Lamp Black Carbonof Lambda cyhalothrin
Lambda cyhalothrinin Laminated
Sheet
31 4 3.5 1
32 2 1.8 0.5
33 1 ~ 0.88 0.25
34 0.5 0.44 0.12
3 5 0.25 0.22 0.06
36 0.125 0.11 0.03
I37 1 0.06 -. 1 0.05 -- 1 0.01
EXAMPLE 3 8
A six-layered sheet having the following composition was formed as follows:
Layer Description
1 New Generation Resin (NGR) (available from Fabrene, Inc.) layer composed of
black resin (Colortech No. 20413-19 available from Colortech Inc.), extrusion
coating grade polyolefin plastomer (Affinity~ PT1450 available from The Dow
Chemical Company), and low density polyethylene (Novapol~ LC-0522-A
available from Nova Chemicals Canada Ltd.); w
2 Saranex~ 14 (available from The Dow Chemical Company) layer composed of
vinylidine chloride/vinyl chloride copolymer, low density polyethylene,
ethylene/vinyl acetate copolymer, and silicon dioxide;
3 scrim layer composed of high density polyethylene (Sclair~ HI~PE No. 99G
available from Nova Chemicals Corporation);
4 active ingredient layer composed of 0.91 weight percent lambda cyhalothrin
in
an 85 weight percent technical solution, 0.95 weight percent Lamp black #6,
and 22 weight percent LDPE resin;
46
CA 02429743 2003-05-23
Saranex~ 14 layer as described above; and
6 NGR layer as described above.
The six-layered sheet was subjected to the United States Forest Service
(USFS) concrete slab methods. The concrete-slab method simulates a poured
concrete
5 foundation. To establish a test plot, leaves and debris are removed to
expose soil in a
square area 24 inches on a side. A 21 inch square wooden frame constructed of
one
inch by one inch spruce strips is placed in the center of the cleared area,
and a
triangular trench two inches deep and two directly on the treated soil. The
PVC pipe is
capped to reduce loss of moisture and to preclude rain and sunlight from
affecting the
termiticide.
The results of the concrete slab field trials for the following locations are
shown below in Table 8.
TABLE 8
of Re licates
Not Penetrated
Location Termite Species With Six-LayeredUntreated
Sheet
Florida (USFS) Reticulitermes 100 60
avi es
Arizona (USFS) Reticulitermes 100 50
avi es
Mississippi Reticulitermes 100 100
(USFS)
Zavi es
Malacca (Malaysia)Globitermes 100 30
sul hureus
As shown in Table 8, none of the plots treated with the six-layered sheet were
penetrated by termites.
While the present invention has been described with reference to one or more
particular embodiments, those skilled ,in the art will recognize that many
changes may
be made thereto without departing from the spirit and scope of the present
invention.
Each of these embodiments and variations thereof which fall within the spirit
of the
invention are intended to be included within the scope of the invention
defined by the
following claims.
47
