Patent Description:
The practice of protecting pyrethroids from an incompatible environment by encapsulation is well known. Encapsulation may be employed for a variety of reasons, including protecting pyrethroids from oxidation, preventing volatile losses, preventing chemical reaction or improving the handling characteristics of pyrethroids. The protective coating or shell is ruptured at the time of desired action of the ingredient. The rupturing of the protective shell is typically brought about through the application of chemical or physical stimuli such as pressure, shear, melting, response solvent action, enzyme attack, chemical reaction or physical disintegration.

A number of companies have worked on improvements in encapsulation materials, including Revolymer Limited (U. ) as disclosed in their published international patent applications <CIT>, <CIT>, <CIT> and <CIT>; and Novozymes A/S (Denmark) as disclosed in <CIT>. <CIT> discloses a method and composition which is obtainable by dispersing an aggregate in aqueous solvent, wherein the aggregate comprises a chemical agent contained within an amphiphilic substance. <CIT> discloses a pesticidal composition comprising a) a first amphiphilic compound and b) a second compound, which may comprise a bifenthrin.

There is still a need for further improvements in encapsulation materials, particularly in regards to the releasable encapsulation of pyrethroids.

The present invention relates to an encapsulation composition comprising a plurality of capsules, each capsule comprising an amphiphilic material encapsulating a pyrethroid. The pyrethroid has a release rate less than a release rate of the unencapsulated pyrethroid.

In a particular embodiment, the encapsulating materials have well-balanced hydrophilic and hydrophobic chemical moieties that are useful for encapsulating pyrethroid.

The addition of materials with well-balanced hydrophilic and hydrophobic moieties to a pyrethroid results in the encapsulation of the pyrethroid via association of the amphiphilic materials onto the pyrethroid. The association of the material onto the pyrethroid may be driven by one or a combination of noncovalent forces such as dipole, hydrogen bonding, van der Waals, electrostatic, cation-pi electron interaction, or hydrophobic effects.

The amphiphilic material is a material composed of hydrophilic and hydrophobic portions or parts, which in certain embodiments are hydrophilic and hydrophobic sections or blocks. The amphiphilic material has a hydrophilic-lipophilic balance (HLB) within a range of <NUM> to <NUM>, or from <NUM> to <NUM>.

The hydrophilic portion anchors the encapsulated pyrethroid, and the hydrophobic portion forms a shell wall of the capsule.

In certain embodiments, the amphiphilic material is a polymer, and more particularly, a copolymer such as a graft copolymer or a block copolymer.

The amphiphilic material a graft copolymer, a modified N,N,N',N'-Tetrakis(<NUM>-hydroxypropyl)ethylenediamine, a cationic nanoparticle, a diblock or triblock copolymer, an ionic or nonionic surfactant, a low surface energy silica, a Guerbet ester, or a poly(stearyl methacrylate -co- acrylic acid).

For example, the amphiphilic material may be one or more of the following:.

By cationic non-bio accumulating fluoropolymer, we mean a fluoropolymer with less than a <NUM> fluorocarbon chain. By low surface energy, we mean the surface energy is less than about <NUM> dynes/cm.

The encapsulated pyrethroid can be liquid, or solid, or combinations thereof. Some non-limiting examples of pyrethroids are allethrin, permethrin, transfluthrin, tefluthrin, metofluthrin, fenfluthrin, kadethrin, neopynamins, prallethrin, vapothrin, esbiothrin, dichlovos, deltamethrin, and cypermethrin.

The pyrethroid is dissolved in a water-immiscible solvent (such as hexane, nonane, dodecane, toluene, xylene) before being mixed into the aqueous solution of amphiphilic material. For example, if the pyrethroid to be encapsulated is soluble in an organic solvent (e.g., transfluthrin), then water is used to dissolve the amphiphilic material, and organic solvent to dissolve the pyrethroid.

Solid or liquid pyrethroids should be sparingly soluble in the liquid used for the solution of the amphiphilic material (water). By sparingly soluble, we mean the solubility of the solute is less than about <NUM> in <NUM> of the liquid. The capsules can be nanocapsules and/or microcapsules. The capsules are typically in the range of about <NUM> to about <NUM>, or about <NUM> to about <NUM>, or about <NUM> to about <NUM>.

In some embodiments, the capsules are stable at alkaline pH.

In addition to the amphiphilic material, an additional surfactant (or co-surfactant) can be added to the mixture. Examples of co-surfactants include, but are not limited to, Sodium dodecyl sulfate, Sodium dodecylbenzenesulfonate, Sodium laureth sulfate, Sodium lauroyl sarcosinate, Sodium myreth sulfate, Sodium nonanoyloxybenzenesulfonate, Sodium stearate, Sulfolipid, Benzalkonium chloride, Benzyldodecyldimethylammonium bromide, Cetylpyridinium chloride, Dimethyldioctadecylammonium bromide, Dodecyltrimethylammonium bromide, Hexadecylpyridinium chloride, Tridodecylmethylammonium chloride.

<FIG> is a flow chart of the encapsulation of a pyrethroid with an amphiphilic material. In step <NUM>, the pyrethroid, such as TAED, is suspended in a solvent, such as hexane. In step <NUM>, amphiphilic material is added. In step <NUM>, in some cases, the amphiphilic material forms micelles. In step <NUM>, if micelles are formed, the micelles are deposited onto the pyrethroid with the amphiphilic material. Otherwise, the amphiphilic material encapsulates the pyrethroid without forming micelles. The product can then be isolated in step <NUM>.

In certain embodiments, the amphiphilic material is an amphiphilic polymer capable of forming a micelle around the pyrethroid when the capsule is dispersed in a liquid.

Micelles form only when the concentration of the polymer is greater than the critical micelle concentration (CMC). In certain embodiments, capsules have a CMC within a range of from about <NUM> wt% to about <NUM> wt%. In addition, micelles only form when the temperature is above the critical micelle temperature (CMT) (also known as the cloud point or Krafft temperature). The CMT depends on a number of factors including the molecular weight of the polymer, the ratio of the hydrophobic portion to the hydrophilic portion, and functionality of the hydrophilic moiety. In general, the higher the amount of the hydrophobic portion, the higher the critical micelle temperature.

In general, block copolymers having a number average molecular weight less than <NUM>,<NUM> kD will form micelles. Examples of amphiphilic polymers forming micelles include, but are not limited to, PEO-PPO-PEO, PEO-PPO, PDMS-PEO-PDMS, PDMS-PEO, C19-diPEG, diblock copolymer prepared by reacting mono hydroxy polyethylene oxide with <NUM>-bromo octadecane, nonionic triblock copolymer prepared by reacting di hydroxy polyethylene oxide with <NUM>-bromo octadecane, C19 dicarboxylic acid salts, tert-octyl phenol derivative of sulfonated dichloro diphenyl sulfone, nonyl phenol derivative of sulfonated dichloro diphenyl sulfone, and poly(dimethyl siloxane) derivative of sulfonated dichloro diphenyl sulfone.

<FIG> is a schematic representation of the encapsulation of a pyrethroid in amphiphilic micelles. As shown, in the first step <NUM>, an amphiphilic material <NUM> is dispersed in a solvent, such as water. The amphiphilic material <NUM> has a hydrophilic segment <NUM> and a hydrophobic segment <NUM>. The hydrophobic segment <NUM> of the amphiphilic material is adsorbed onto the pyrethroid <NUM>.

Above the CMC and CMT of the amphiphilic material <NUM> as shown in the second step <NUM>, the amphiphilic material <NUM> forms micelles <NUM> around the pyrethroid <NUM>. The pyrethroid <NUM> is encapsulated inside a hydrophobic core of the micelle <NUM> formed by the hydrophobic segment <NUM> of the amphiphilic material <NUM>. The hydrophilic segment <NUM> of the amphiphilic material <NUM> extends radially outward and forms the shell of the micelle <NUM>.

<FIG> illustrates the disintegration of micelles by dilution with water in graphical form. The amphiphilic material was a non-ionic diblock copolymer prepared by reacting mono hydroxy polyethylene oxide with <NUM>-bromo octadecane. When the copolymer was dissolved in water at a concentration of <NUM> wt%, the surface tension of the water was <NUM> dynes/cm (bar <NUM>). When the copolymer was dissolved in water at a concentration of <NUM> wt% and exposed to <NUM> pH aqueous solution, the surface tension of the water was <NUM> dynes/cm (bar <NUM>). When the copolymer was dissolved in water at a concentration of <NUM> wt% the surface tension of the water was <NUM> dynes/cm (bar <NUM>). When the copolymer was dissolved in water at a concentration of <NUM> wt% and exposed to <NUM> pH aqueous solution, the surface tension of the water was <NUM> dynes/cm (bar <NUM>). For reference purposes, the surface tension of water is <NUM> dynes/cm. When more water was added to the micelles, the surface tension increased and approached the value of water, which suggests that the non-ionic diblock copolymer prepared by reacting mono hydroxy polyethylene oxide with <NUM>-bromo octadecane disintegrates on dilution.

When the pyrethroid is transfluthrin, a preferred amphiphilic material is PEO-PPO-PEO.

The encapsulated product is coated on a fabric. The coating can be accomplished using any suitable coating process including, but not limited to, immersion, spraying, knife coating, direct roll coating, pad-dry coating, calender coating, hot melt extrusion coating, foam finishing, and gravure printing.

The fabric can be derived from polymeric fibers such as polyester, polyamide, polyester amide, polyimide, poly ester imide, polybenzimidazole, polybenzoxazole, polythiazole, polydimethyl siloxane-polyether amide copolymer, and the blends thereof. The fibers can be derived from natural materials such as cotton, soybeans, corn, sorghum, sugarcane, coconut, animal proteins and sea weed.

One or more additional ingredients useful for formulating the product can be included. Additional ingredients include, but are not limited to, thickening agents (e.g., polyvinyl alcohol, poly vinyl pyrrolidone, and carboxyl methyl cellulose), and co-solvents (e.g., glycerol, and <NUM>,<NUM>-propylene glycol).

The release rate of active ingredient from the encapsulation composition of the present invention was determined by gravimetric analysis. A fabric (1sq. inch) was coated with the encapsulation composition and dried at room temperature to remove excess water and toluene. The coated fabric was kept under a controlled atmosphere (<NUM> degree F and <NUM>% relative humidity), and its weight was monitored and recorded as a function of time. The release rate was calculated using the following equation: <MAT>.

Where, K is the release rate, Δm is difference in mass and Δt is the difference in time.

In the first step, the amphiphilic material is dissolved in water. The amphiphilic materials were commercially available products (Pluronic®) from BASF, asn shown below.

In the second step, the pyrethroid, transfluthrin, was dissolved in a large amount in toluene.

In the third step, the mixture obtained from second step was added to the mixture obtained from first step to form the pyrethroid encapsulated in the amphiphilic material.

The release rate of the pyrethroid from the capsules is controlled by a number of factors. One is the amount of amphiphilic material used in step <NUM>. Higher amounts of amphiphilic material in step 1result in decreased release rates of the pyrethroid. The release rate of the pyrethroid from the capsules is further controlled by the CMC of the amphiphilic material used in step <NUM>. The higher the CMC of the amphiphilic material in step <NUM>, the lower the release rate of the pyrethroid. The release rate of the pyrethroid from the capsules is further controlled by the ratio of organic solvents to the pyrethroid in step <NUM>. The higher the ratio of organic solvents to the pyrethroid in step <NUM>, the lower the release rate of the pyrethroid.

In the first step, an aqueous solution of <NUM> wt% poly(ethylene oxide) - block-poly(propylene oxide) -block-poly(ethylene oxide) (PEO-PPO-PEO) (Pluronic® L64 (BASF)) was prepared by mixing <NUM> of the block co-polymer in <NUM> water. The solution was mixed for <NUM> hr using a magnetic stirrer at <NUM> rpm.

In the second step, <NUM> of transfluthrin (TF) was dissolved in <NUM> of toluene.

In the third step, the mixture obtained from the second step was added to the mixture obtained from the first step at room temperature to form the pyrethroid encapsulated in the amphiphilic material.

The product obtained from third step was characterized for particle size using dynamic-light-scattering (DLS, Master sizer <NUM>, Malvern). Formation of <NUM> droplet size with uniform drop-size-distribution was observed, as shown in <FIG>.

The release rate of the transfluthrin as determined by the gravimetric method was found to be ≤<NUM>/day.

In the third step, the mixture obtained from the second step is added to the mixture obtained from the first step at room temperature to form the pyrethroid encapsulated in the amphiphilic material.

The product obtained from third step, was characterized for particle size using dynamic-light-scattering (DLS, Master sizer <NUM>, Malvern). Formation of <NUM> droplet size with uniform drop-size-distribution was observed, as shown in <FIG>.

Claim 1:
An encapsulated composition comprising:
a plurality of capsules each comprising an amphiphilic material encapsulating a pyrethroid, the encapsulated pyrethroid having a release rate less than a release rate of unencapsulated pyrethroid,
wherein the amphiphilic material has a hydrophilic-lipophilic balance within a range of from <NUM> to <NUM> and wherein the amphiphilic material is a graft copolymer, a modified N,N,N',N'-Tetrakis(<NUM>- hydroxypropyl)ethylenediamine, a cationic nanoparticle, a diblock or triblock copolymer, a low surface energy silica, a Guerbet ester, or a poly(stearyl methacrylate-co-acrylic acid), and
wherein the composition is formable from a method that involves dissolving the pyrethroid in a first solvent, and then mixing the pyrethroid and first solvent in an aqueous solution of amphiphilic material comprising water and the amphiphilic material, wherein the water is immiscible in the first solvent.