Note: Descriptions are shown in the official language in which they were submitted.
207~23~
Field of the Invention
The present invention relates to a controlled release
device, in particular, a controlled release device for
volatile materials and a m~thod of making the same.
Backqround of the Invention
Insect sex pheromones are attractive chemical scents
released in minute quantities by one sex to attract the other
for mating. For example, many male moths can detect and
follow minute quantities of pheromone carried by air
currents, sometimes over long distances.
Researchers have identified over 600 different insect
pheromone components. The natural pheromone released by the
female may be composed of ~ust one component while other
species may release several or more different chemicals.
After identification the pheromone components are chemically
~ynthesized and suitably attractive mixe~ can then be
formulated. Formulation i8 concerned with putting the
pheromone into suitable controlled release devices so that
they can be released at given rates over long periods of
time. This is extremely important since several pheromones
cost over $10,000 per kilo.
The two ma~or uses for synthetic pheromones are in the
monitoring and control of insect populations. Monitoring
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involves the use of traps or other devices baited with
pheromone in a controlled relea~e device to attract and trap
adult insects, usually the males. A common application is
for monitoring for the presence and density of newly emerged
adults so that appropriate control measures can be taken.
Traps are also used for detection of new introduced pest
species.
The second ma~or use of insect pheromones is control of
insects through mating disruption. Pheromone is loaded into
slow-release dispensers that are then distributed evenly over
wide areas. The males of the target insect species living
within the treated area are unable to locate females, hence a
measure of control is attained since unmated females do not
lay fertile eggs. Several modes of action may be involved in
mating disruption including adaptation~habituation of the
males sensor system; false trail following, where males are
preferentially attracted to, and follow pheromone plumes
emanating from the release devices, and camouflage where the
pheromone being relea~ed by the devices overpowers and
camouflages the plumes from the live females.
The ma~or requirement for monitoring and mating
disruption i8 the controlled release of pheromone. To obtain
suitable control it is necessary to release the pheromone at
a constant level over several wee~ or even months. The
2~7~231
pheromone must also be protected from external factors such
as air, water and ultraviolet light so ~hat it does not
degrade.
There are several c~mmercial relea e devices presently
being developed or sold for mating disrup~ion. The Scen~ry
Celcon hollow fiber and the Scentry sprayable
microencapsulated particle, the Hercon chip or trilaminate
and the Mitsubishi rope are a few. Scentry and others have
used polyvinyl chloride (pvc) release sy~tems in the past.
These are commonly prepared by mixing the pheromone in a
plastisol and then exposing the plasti~ol to heat to cure and
harden it. Scentry and others have used dip molding, pan
molds, extru~ions of PVC with heat to make dispensers. A
ma~or defect of these formulations is that a significant
amount of pheromone may be lost during the heating or curing
process. These techniques tend to be both wa~teful and
inaccurate since loss of pheromone may vary from batch to
batch or product to product. Loss of pheromone during this
process also effects the active ingredient specifications.
It is critical to deliver the specified amount of technical
pheromone in each dispenser since it i8 unlawful to deliver
less than label rates.
The need for effectiva release devices for volatile
materials, in particular pheromones, which release an active
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ingredient at a constant rate, tend to be in ~reat demand.
Since some active ingredients, such as pheromones, may cost
from $1,500.00 up to $12,000.00 per kilo, there is a demand
for release devices which are less expensive to produce and
are more effective in releasing a volatile material at a
constant rate.
The production of pre~ent release de~ice~ can be
exemplified as follows, the active ingredient is generally
placed into a molten substrate, e.g., polymer contained in a
heated vessel. A mandrel is heated in a furnace, then on
exiting the furnace is lowered into the molten substrate
which adheres to the "fingers". The mandrel is raised clear
of the molten pheromone con~aining substrate and the adhering
polymer cured by passage through a second furnace. Air
cooling follows and the pheromone containing devices are
separated from the mandrel by blasts of compressed air.
However, during such a procedure, there exists the problem of
the active ingredient vaporizing and releasing from the
molten substrate and during curLng. Industry estimates place
losses of the active ingredient at 26% of the total amount
initially in the molten ~ubqtrate. Obviou~ly, such losses
are economically impractical and greatly increase production
and hence product costs.
With existing methods of producing release devices for
volatile materials, there tends to be no way to accurately
2~7~2~
formulate dispensers for monitoring lures or for regi~tered
products for control of pests in the field. Also, with
present release devices, many pheromones contained therein
degrade quickly when exposed to ultraviolet light or oxygen.
A further problem in the indu~try is known as the ~burst
effect.~ The ~burst effectll occurs when the active
ingredient is released initially at a considerably higher
than desired rate. In some cases, the llburst ef~ect~ can
release 20% of the active ingredient in the first 1-3 days.
U.S. Patent No. 4,639,393 is said to disclose dispensers
for the controlled release of pest-controlling agents,
wherein laminated articles are provided which comprise one or
more layer~ containing active pest control and pest
attractant substances and which allow the controlled release
of the pest controlling substance from within the laminate to
the surface of the laminate.
U.S. Patent No. 4,445,641 i~ said to disclose a
controlled-release dispenser which comprise a rate-
controlling membrane and a solid microporous polymeric
reservoir having interconnected or continuous pores capable
of retaining the active ingredient by capillar~ forces.
U.K. Patent Application No. GB 2 141 932 A is said to
disclose compositions for pest control which comprises a
pheromone or a pheromone inhibitor in liquid or ~emi-liquid
207~231
form, in a polymeric water-resistant matrix which provides W
protection and which allows an adequate rate of diffusion of
the active material over a prolonged period of time. The
composition is then applied in the form of large globules or
spots.
European Patent Application No. 0 243 007 is said to
disclose a tubular sustained-relea~e dispenser of insect sex
pheromones wherein the pheromone permeates through a barrier
wall made of a polymeric material.
European Patent Application No. 0 233 lO9 is said to
disclose a tubular plastic vapor dispenser for sustained
releasing vapor of a sex pheromone which has a deformed
configuration forming at least one loop.
U.S. Patent No. 4,600,146 is said to disclose a vapor-
releasing body of an elongated form capable of sustainedly
releasing vapor of a vaporizable ~ubstance such as a sex
pheromone. The integrated structure i9 composed of a
capillary tubing of a polymeric material filled with the
vaporizable substance.
The article by Weatherston, "Alternative Dispensers for
Trapping and Disruption", Insect Pheromones in Plant
Protection, lg89, disclose~ a method for preparation by
mixing a resin and plasticizer together (with the addition of
an antioxidant) and removing air bubbles by vacuum
`~ 2~023~
evacuation, wherein a pheromone is then added and air bubbles
removed again by vacuum evaporation. The mixture iq then
placed in a glass t~be and the mix~ure fused at 145C for
2-5 minutes or until it becomes translucent. The mold is
then broken and the plastic rod slid out and cut into the
desired lengths. Fitzgerald et al., ~'Slow Release Plastic
Formulation of the Cabbage Looper Pheromone cis-7-Dodecenyl
Acetate: Release Rate and Biological Activity~ discloses a
similar method of preparation.
None of the above dispensers (and methods of making the
dispensers) overcome all of the problems described above.
Thu~, there is a need for a more stable release device
for volatile materials and a method of making the same which
overcome the problems and disadvantages described above.
SUMMARY OF THF INVFNTION
One ob~ect of the present invention is to provide a
release device which provides a constant and regulated rate
of release over the entire ~urface area of the device for an
extended period of time.
Another ob~ect is to provide a release device which can
be configured 80 as to be used both as a monitoring lure and
also as a disruption formulation for dirsct control of pest
species when pheromone is used as an active ingredient.
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A further object i~ to provide a release device which
greatly reduces the ~'burst effect~.
A still further ob~ect is to provide a method of making
a release device which greatly conserves the active
ingredient from loss during the preparation process.
An ~dditional ob~ect is to provide a method of making a
release device which allows accurate formulation of the
volatile material in the release device.
Additional objects and advantages of the invention will
be set forth in part in the description which follows, and in
part will be obvious from the description, or may be learned
by practice of the invention. The ob~ects and advantages of
the invention will be realized and attained by means of the
elements and combinations particularly pointed out in the
appended claims.
To achieve the ob~ects and in accordance with the
purpose of the invention, as embodied and broadly described
herein, the present invention is directed to a controlled
release device for a volatile material comprising a polymeric
container having enclosed therein a cured matrix containing
an active ingredient capable of permeating the matrix and the
wall of the container.
The present invention i al~o directed to a method of
making a controlled release device for a volatile material
~07~23~
comprising mixing a volatile active inqredient with a
polymeric resin and placing the mixture into a polymeric
container.
The present invention is further direct~d to a method of
making a controlled release device for a volatile material
comprising mixing a polymeric resin and a plasticizer to form
a plastisol matrix; mixing a volatile active ingredient into
the plastisol matrix; placing the resultant mixture into a
polymeric container; and then curing the plastisol matrix
containing the volatile active ingredient.
It i~ to be under~tood that both the foregoing general
description and the following detailed description are
exemplary and explanatory only and are not restrictive of the
present invention, as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
Figures 1 and 2 are graphs which illustrate the release
rates from release devices of the pre~ent invention.
Figures 3, 4 and 5 are graphs which illustrate
evaluations of comparisons of the reduction in trap catch of
male tomato pinworm moths using the device of the present
invention with male trap catch in check fields treated
conventionally with insecticides.
2 ~ 3 ~
DETAILED DESCRIPTION OF THE INVENTIQN
The present invention is a device for releasing, over an
extended period of time and at a constant rate, volatile
materials including, but not limited to, insect pheromones
and other behavior modifying chemicals. The device of the
present invention can be used in both the monitoring and
direct control of pest insects by dissemination of synthetic
pheromones within a crop area to either attract one or both
sexes of the pest species to a trap; or to disrupt the sexual
communications between the male and female insects thereby
reducing mating and causing the deposition of unfertilized
eggs with a concomitant reduction in the subsequent
generation.
The release device for volatile materials comprises a
polymeric container having enclosed therein a cured matrix
containing an active ingredient capable of permeating the
matrix and the wall of said container.
Any polymeric container for use in the present invention
is acceptable. In one embodiment, the polymeric container is
a tube made from polyvinylchloride or polyethylene and is of
food grade. One commercially available polymeric tube is
from Rehau Plastics in Leesburg, Virginia. Other suitable
polymeric containers can be made from for example, other
polyolefins such as polypropylene; copolymers of ethylene and
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2~7~2~1
vinyl acetate; cellulose acetate; formalized polyvinyl
alcohol; poly~ers of acrylic and me~hacrylic esters;
polyamide resins; polyester~; and polyorganosiloxanes.
The internal diameter of the polymeric tube can range
from about 30 mil. to about 0.5 inch with a wall thickness in
the range of about 0.016 inch to about 0.25 inch.
The polymeric or plastisol matrix which will contain the
active ingredient is prepared by the polymerization of a
mixture of a polymeric resin with a plasticizer, e.g., of a
plastisol. One typical example of a polymeric resin used in
the present invention is Geon 138 polyvinylchloride
obtainable from Goodrich Inc., Cleveland, Ohio and one
typical example of a plasticizer is benzyl butyl phthalate
obtainable from Monsanto, St. Louis, Missouri. Other
suitable polymeric resins include, for example, esters of
acrylic acid, ester~ of methacrylic acid, vinyl acetate,
vinyl pyrrolidone and styrene. Other suitable plasticizers
include, for example, other organic esters such as
terephthlates, trimellitates, adipates, sebacates, etc.
The range percentage for the polymeric resin can vary,
but preferably, i~ from about 40-60~ by weight of the total
polymeric matrix including the active ingredient. The range
percantage for tha plasticizer can also vary, but is
preferably about 40-60% by weight of the total polymeric
matrix including the active ingredient.
2~23~
Any type of volatile material (active ingredient) which
is desired to be released over an extended period of time and
at a constant rate can be used with the device oP the present
invention, e.g., floral odors, perfumes, scents. In
particular, behavior modifying chemicals are used as the
active ingredient, i.e., pheromones, kairomones, etc.
Specific examples of pheromones include, but are not limited
to, alkanes (e.g., methylnonadecane), alkene aldehydes (e.g.,
Z-11-hexadecenal), al~ene alcohols (e.g., E,E-8-10-
dodecadien-l-ol)/ epoxides (e.g., disparlure), alkene esters
(e.g., gossyplure) and aldehydes derived therefrom, aromatic
compounds (e.g., benzaldehyde) and heterocyclic compounds
(e.g., Japonilure). The pheromones disclosed, for example,
in U.S. Patent No. 4,734,281 and incorporated herein by
reference may be also used. One specific example of a
pheromone is the tomato pinworm pheromone which is sold under
the tradename LYCOPERSILURE.
The range percentage for the active ingredient can also
vary, but preferably i8 from about 5-30% by wei~ht of the
total polymeric matrix including the active ingredient.
Optionally, a dye (e.g., organic pigments such as
pigment scarlet, diarylide orange, indanthrone and carbon
black; ~oluble dyes such as aniline black and anthraquinone;
and inorganic pigments ~uch as titanium dioxide, chrome, iron
20~23~
oxide and chromium oxide - all commercially available) can
be added to the polymeric container or to the polyme~ic
matrix at the time of mixing the polymeric resin and
plasticizer, afterwards, or with the addition of the active
ingredient.
The amount of dye added can range from about 0.1~ to
2.0% by weight of the release device.
Also, protective materials, such as W protectant~ and
antioxidants, can be added to the polymeric container or to
the polymeric matrix at the time of mixing the polymeric
resin and plasticizer, afterwards, or with the addition of
the active ingredient. Typical example~ of W protectants
include Advastab BC109, Carstab and any of the class of
compounds known as hindered benzophenones. Typical examples
of antioxidants include Sustane, Tenox, Butylated Hydrox-
Toluene, Butylated Hydroxy Anisole.
The amount of the protectLve material added can range
from about 0.01% to 1.0~ by weight of the polymeric matrix
with active ingredient.
In one method for making the controlled release device
for volatile materials, the method comprises the followin~
step3s
(1) mixing a polymeric resin and a plasticizer to form
a pla~tisol matrix;
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(2) mixing a volatile active ingredient into said
plastisol matrix;
(3) placing ~he resultant mixture into a polymeric
container; and
(4) curing the plastisol matrix containing the volatile
active ingredient.
In preparing the matrix, which is preferably polymeric,
a plastici2er is added to a polymeric resin, such as a PVC
powder, and the mixture is stirred with, for example, an
electric stirrer, for approximately 30 minutes until a
homogeneous solution is obtained. The resulting plastisol is
preferably placed under vacuum or other suitable means for a
time sufficient, e.g., approximately 30 minutes, to remove
all air bubbles.
The active ingredient is then added to the plastisol and
the resulting mixture is stirred (as above) for approximately
30 minutes and preferably vacuumed again for a time
sufficient, e.g., 30 minutes, to remove any existing air
bubbles.
The resulting mixture, which i8 the plastisol containing
the active ingredient, is then illed into a container, e.g.,
a polymeric tube. Any suitable filling technique may be
used, preferably vacuum suction. The filled tubing is then
preferably plugged at both ends with plugs. While any type
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2~23~
of plug may be used, plastic lrrigation plugs are preferred.
The filled tubing i6 then heated at a time and temperature
sufficient to cure the plastisol and form the matrix which
also bonds to the tubing, e.g., time: 6 to 12 minutes and
temperature: 250F to 300F.
Besides using heat to cure the plastisol containing the
volatile active ingredient, any other known means may be used
to cure the plastisol containing the volatile active
ingredient.
In one embodiment of the present invention, the filled
tubing can be firmly, but not tightly, wound around rods
(e.g., aluminum rods), wherein the ends of the wound, filled
tubing are taped down leaving enough of the rod ends exposed
to fit into the racks of an oven. The prepared rods are then
heated in the oven for approximately 6-12 minutes at 250-
300F.
Of course, the filled tubing prior to heating does not
have to be wound around rods, but can ~imply be placed in an
elongated ~hape in the heat for the same amount of time.
At the end of the curing period, the filled tubing is
removed from the oven and preferably briefly immerqed in cold
water. At this point, the polymeric matrix containing the
active ingredient inside the polymer tubing will now be solid
and clear and completely bonded with the polymeric tubing
2~7~23~
along its whole length, thus stabilizing and regulating the
release of the active ingredient over the whole surface area
of the device.
The tubing once removed from the water (if used), then
from the rods, if used, can be cut to desired lengths with a
razor blade or any other cutting device, preferably into
approximately 3.25 inch spirals which weigh approximately
1.577 grams, and immediately packaged in foil-lined bagq and
stored at approximately 45-50F.
If rods are used in the curing step, the spiral design
of the cured, filled tubing allows the release device to be
configured in such a way so as to allow easy hanging of the
device in desired locations.
Another method of making the controlled release device
involves a coextrusion process. In one such process, a
plastic extruder is used. In this proces~, plastic powder or
granules of the polymeric resin (e.g., PVC) are converted
into continuous uniform melts and forced through a dLe to
yield a deQired shape (e.g., tube). The coextrusion dies
used are generally of a nested configuration (e.g., a tube of
smaller diameter inside a tube of larger diameter), wherein
individual polymers flow through separate mandrel pas~ages
(e.g., each separate tube). Thus, in this process the matrix
described above will be formed in an inner section of the
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` 2~7~2~
coextrusion die and the polymeric container will be formed in
an outer section of the coextrusion die. Prior to entering
the inner section of the die, the volatile active ingredient
is injected into the matrix, preferably ad~acent the die tip.
The amounts of the active ingredient to be used would be the
same as described above. Once exiting the die, the container
and matrix will bond together to form the controlled release
device and preferably the device then enters a cooling
chamber to harden the resulting device. (Preferably, the
device has the ~ame range of dimensions as described above.)
Once the controlled release device is formed and hardened, it
may be cut into any desired length. In determining which
polymers or thermoplastic materials to use in this process,
it is important that ad~acent polymers exhibit similar flow
and adhesion characteristics to form the coextrusion.
Also, dyes and/or protective materials as described
above may be included in the device simply by in~ection into
the desired section, prior to entering the die, i.e. - in~ect
into the matrix extrusion or into the container extrusion.
The amounts to be used would be the same as described above.
The present invention will be further clarified by the
following examples, which are intended to be purely exemplary
of the present invention.
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2~2.3~
EXAMPLE 1
600 g of benzyl butyl phthalate was added to 400 g of
PVC powder and the mixture was stirred with an elec~ric
stirrer for 30 minutes until a homogeneous solution was
obtained. The resulting plastisol was put under vacuum for
30 minutes ~o remove air bubbles. 276 g of Lycopersilure
(the tomato pinworm pheromone) was added to the plastisol and
the mixture was stirred and vacuumed again for 30 minutes.
The mixture was then sucked into a PVC tubing [i.d. 0.125
o.d. 0.188"]. The filled tubing was plugged at both ends
with plastic irrigation plugs. The filled tubing was then
firmly, but not tightly, wound around aluminum rods [o.d.
0.5" by 17.25~' long], the ends of the wound tubing were taped
down with tape, for example, 3M 810, leaving enough of the
rod ends exposed to fit the racks of the oven. The prepared
rods were heated in the oven for 6-12 minutes at 250-300F
(actual oven temperature may reach 310F). At the end of the
curing pexiod, the rods were removed from the oven and
briefly immersed in cold water. The polymeric matrix
(containing the pheromone) inside the PVC tubing was now
solid and clear. The filled tubing was removed from the rods
and cut, with a razor blade, into 3.25" spirals weighing
1.577 g and immediately packaged in foil-lined bags, 500
spirals to a bag, and stored at approximately 45-50F.
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2 ~ J 3 ~
Figures 1 and 2 illustrate the release rate of the
release device constructed. The data indicate that the
device releases the Lycopersilure at a mean rate of
0.98 mg/day (S.D 1.58 mg/day) over a period in excess of
4 months.
EXAMPLE 2
Release devices made in accordance with Example 1 were
used in field tests to determine the efficiency of the
present invention.
In particular, the efficiency of the release devices was
demonstrated in the summer of 1990 on fresh market tomatoes
growing in Ba~a California, Mexico. These tests (three
replicates) were carried out in cooperation with agronomists
from Quimical. The evaluation of the spirals was measured by
the reduction in trap catch of male tomato pinworm moths in
fields treated with the release devices of the present
invention compared to the male trap catch in check fields
treated conventionally with insecticides.
Treatments were made at two rates, 200 devices/acre (LOW
RATE) and 400 devices/acre ~HIGH RATE). The results given in
Figures 3, 4 and 5 clearly demonstrate the effectiveness of
the device. In Figure 3, both the high and low rate were
equally effective in disrupting the mating communication of
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2~ ~23~
the pest species as evidenced by the dramatic reduction in
trap catch over that from the check field. The formulation
proved to be efficacious for a period in excess of 40 days at
which time the test was terminated. In the second replicate
(Figure 4)l both the high and low rates again performed
equally well, being efficacious for a period in exces~ of 110
days.
In the third replicate (Figure 5), both rates performed
excellently as compared to the check over the first 30 days,
at which time the check field was also treated with the
devices. Subsequently, the population of the moths in all
three fields were equally suppressed.
Since virtually all of the active ingredient that is
metered into the plastisol is retained in the cured matrix,
the preparation of this release device conserves all of the
active ingredient so formulated.
In addition, the release device of the present invention
can be configured so as to be used both as a monitoring lure
and also as a disruption formulation for direct control of
pest species. Other release devices, in particular pheromone
dispensers, are not so versatile.
In addition, the release device of the present
invention, whether used for monitoring or direct control,
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2~23~
exhibits a highly controlled and constant release rate as
opposed to other conventional release dispensers which
exhibit a very rapid release of an active ingredient, such as
pheromone, the ~burst effect~ which unnecessarily releases
initially a large amount of active ingredient.
Other embodiments of the present invention will be
apparent to those skilled in the art from consideration of
the specification and practice of the present invention
disclosed herein. It is intended that the specification and
examples be considered as exemplary only, with a true scope
and spirit of the present invention being indicated by the
following claims.
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