Pest repellent polymer composition

Abstract

This invention relates to a polymer composition for insect repellents, comprising a thermoplastic polymer and a silica carrier thereon on which the active insect repellent substance is absorbed. In the presence of a surfactant, the active insect repellent substance is absorbed onto the silica carrier. This invention also relates to articles prepared from the polymer composition for insect repellents.

Description

[0001] This invention relates to a polymer composition for insect repellents, comprising a thermoplastic polymer and a silica carrier dispersed in the thermoplastic polymer. The silica carrier comprises the active substance of the insect repellent.

[0002] It is known that active substances can be integrated into a polymer matrix to provide the desired functionality. However, the controlled release of the active substance from the polymer is important for long-lasting performance. For example, too rapid a release causes the polymer to rapidly expel the active substance, while too slow a release does not achieve the desired efficiency.

[0003] Long-lasting insecticidal nets (LLINs) have been proven effective in reducing mosquito populations and malaria incidence. For LLINs, the dosage of insecticide or repellent on the surface of the net material should be sufficiently high to kill and / or repel insects. Secondly, the release should persist for several years and remain throughout multiple flushing cycles. The total concentration of insecticide and / or repellent should be low to minimize the likelihood of end-user exposure to the active ingredients. The largest market for LLINs is in low-income regions, so cost is a factor to consider when developing the technology.

[0004] US-2009 / 0041820 discloses a functional polymer composition comprising at least 50% by weight of one or more polymer components, 0.1 to 50% by weight of one or more fluids, and 1-50% by weight of one or more active substrates. The active substrates include insect repellent active substances. The fluid components in US-2009 / 0041820 are those that impart specific functionality and / or facilitate the transport of one or more active substrates to the surface of a polymer matrix.

[0005] WO-2011040252 discloses an insect repellent resin composition comprising N,N-diethyl-3-methylbenzamide, wherein the insect repellent active substance is loaded on a specific layered silicate.

[0006] CN-1709957 discloses a plastic cap for repelling flies. The cap contains an active substance for repelling flies, an adsorbent, and a thermoplastic resin. The adsorbent includes silica.

[0007] There is a need to develop polymer compositions for insect repellents that exhibit long-lasting performance while maintaining cost-effectiveness compared to existing solutions. This invention provides polymer compositions comprising at least 50 wt% of a thermoplastic polymer based on the total weight of the composition, and 0.1 wt% to 50 wt% of a silica carrier comprising the active substance based on the total weight of the composition. In the presence of a surfactant, the active substance is absorbed onto the silica carrier. The polymer compositions of this invention provide long-lasting performance and are effective in repelling insects.

[0008] As used in this article, the term "long-lasting" means more than 6 months, preferably more than one year.

[0009] As used in this article, the term "pests" refers to mosquitoes, ticks, cockroaches, bedbugs, mites, fleas, lice, leeches, houseflies, termites, ants, moths, spiders, locusts, crickets, black flies, and silverfish.

[0010] Preferred thermoplastic polymers include polyamides, polystyrene, polyvinyl chloride, polyolefins, or any copolymers thereof. Examples of polyolefins include polyethylene (PE), preferably selected from: high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), metallocene low-density polyethylene (mLDPE), and metallocene linear low-density polyethylene (mLLDPE); polypropylene (PP), preferably selected from: polypropylene homopolymer (PPH), polypropylene random copolymer (PP-R), and polypropylene block copolymer (PP-block-COPO); PE copolymers, preferably selected from: ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA), ethylene-butyl acrylate copolymer (EBA), ethylene-ethyl acrylate copolymer (EEA), and cyclic olefin copolymer (COC), general-purpose polystyrene (GPPS), and high-impact polystyrene (HIPS).

[0011] The insect repellent composition comprises at least 50% by weight, preferably at least 70% by weight, and more preferably at least 90% by weight of a thermoplastic polymer based on the total weight of the composition.

[0012] Preferred silica supports include commercially available precipitated silica. Preferred silica supports are hydrophilic in nature. In one embodiment, the silica support is a mixture of precipitated silica supports having both hydrophilic and hydrophobic properties. Precipitated silica is commercially prepared using a wet process. In the wet process, an alkali metal silicate, preferably sodium silicate, is precipitated by adding an acid such as sulfuric acid. The precipitated silica is then filtered, rinsed, and dried. Preferred supports have a silica or silicon dioxide (SiO2) content of at least 97%. Precipitated silica has a macroporous pore structure, which makes them particularly suitable for liquid absorption. According to the International Union of Pure and Applied Chemistry (IUPAC), a support is considered macroporous if the average pore size is greater than 50 nanometers.

[0013] The precipitated silica support has an average particle size of no more than 50 micrometers (μm), preferably no more than 35 μm, and more preferably no more than 20 μm. The average particle size of the silica can be measured using laser diffraction (ISO 13320). Preferred silica is a free-flowing, non-agglomerated powder that retains its shape upon absorption of active materials and exhibits minimal pulverization, making it attractive for further processing with polymers using standard polymer processing techniques.

[0014] The active insect repellent of the present invention comprises N,N-diethyl-3-methylbenzamide (DEET), 1-piperidinic acid-2-(2-hydroxyethyl)-1-methylpropyl ester (picaridin), 3-[N-butyl-N-acetyl]-aminopropionic acid, ethyl esters, dimethyl carbate, and any combination thereof. Other insect repellents include natural insect repellents such as essential oil of Corymbiacitriodora, nepetalactone, citronella oil, neem oil, and extracts of Bog Myrtle (Myrica Gale). In a preferred embodiment, the active insect repellent is DEET. DEET may contain a substituted isomer, such as p-toluamide or an isomer in which the N-ethyl group is replaced by another alkyl group having 1-3 carbons. The active ingredient of the pest repellent of the present invention exhibits excellent pest repellency against mosquitoes, and it can additionally repel ticks, termites, moths, spiders, locusts, woodlice, crickets, houseflies, ants, cockroaches, black flies, mites, lice, stable flies, bedbugs, fleas, trombiculid mite, and land leeches.

[0015] Additionally, insecticides can be incorporated into the insect repellent polymer composition. Exemplary insecticides that can be used include pyrethroid insecticides such as permethrin, deltamethrin, cypermethrin, deltamethrin, α-cypermethrin, β-cypermethrin, etofenprox, lambda-cyhalothrin, and combinations thereof. Other insecticides that can be used alone or in combination include carbamate compounds such as alanycarb, cypermethrin, carbaryl, isopropcarb, carbofuran, fenoxycarb, indoxacarb, propoxur, pirimicarb, thiocarb, methomyl, ethiofencarb, fenitrothion, xylylcarb, and pyrrole compounds such as bromfenac. Another group of insecticides such as organophosphates can be used. Such compounds include fenitrothion, diazinon, pyridaphenthion, pirimiphos-ethyl, pirimiphos-methyl, etrimphos, fenthion, phorate, chloropyrifos, fenitrothion, pyrazophos, methylpyridinium, malathion, dithion, dimethoate, fenthion, and inofengsan.

[0016] In the presence of a surfactant, the active ingredient of an insect repellent is mixed with a silica carrier to form an insect repellent silica carrier. Exemplary surfactants include nonionic surfactants. Examples of nonionic surfactants include fatty alcohol polyethylene glycol ethers, alkylphenol polyethylene glycol ethers, fatty acid polyethylene glycol esters, fatty amide polyethylene glycol ethers, fatty amine polyethylene glycol ethers, alkoxylated triglycerides, mixed ethers, alkenyl oligoglycosides, fatty acid N-alkyl glucosamides, protein hydrolysates, polyol fatty acid esters, glycol esters, dehydrated sorbitan esters, polysorbate esters, amine oxides, and any combination thereof. Non-limiting examples of nonionic surfactants include sorbitan monostearate, polyoxyethylene esters of rosin, polyoxyethylene dodecyl monoether, polyoxyethylene-polyoxypropylene block copolymers, polyoxyethylene monolaurate, polyoxyethylene monohexadecyl ether, polyoxyethylene monooleate, polyoxyethylene mono(cis-9-octadecenyl) ether, polyoxyethylene monostearate, polyoxyethylene monooctadecyl ether, polyoxyethylene dioleate, polyoxyethylene distearate, and polyoxyethylene sorbitan monostearate. Alcohol monolaurate, polyoxyethylene dehydrated sorbitan monooleate, polyoxyethylene dehydrated sorbitan monopalmitate, polyoxyethylene dehydrated sorbitan monostearate, polyoxyethylene dehydrated sorbitan trioleate, polyoxyethylene dehydrated sorbitan tristearate, polyglycerol esters of oleic acid, polyoxyethylene sorbitan hexastearate, polyoxyethylene monotetradecyl ether, polyoxyethylene sorbitan hexaoleate, fatty acids, tall oil, sorbitan hexaester, castor oil ethoxylate, soybean oil ethoxylate, rapeseed oil ethoxylate, ethoxylated fatty acids, ethoxylated fatty alcohols, ethoxylated polyoxyethylene sorbitan tetraoleate, mixed esters of glycerol and polyethylene glycol, alcohols, polyglycerol esters, monoglycerol esters, sucrose esters, alkyl polyglycosides, polysorbate esters, fatty chain alkanolamides, polyethylene glycol ethers, any derivatives thereof, and any combination thereof. In a preferred embodiment, the nonionic surfactant is castor oil ethoxylate. The castor oil ethoxylate may have an average degree of ethoxylation of 2-50, preferably 10-45, and more preferably 20-40. The average degree of ethoxylation is defined as the number of moles of ethylene oxide required per mole of oil.

[0017] The inventors surprisingly discovered that when the absorption of the active substance of an insect repellent is performed on a silica carrier in the presence of a surfactant, the retention of the active substance is enhanced compared to absorption on a silica carrier without a surfactant. This is especially true for volatile active substances such as DEET. The enhanced retention of the active substance on the silica carrier manifests as a more prolonged release of the active substance from the insect repellent composition.

[0018] The insect repellent silica carrier may include an active substance in an amount of 0.1% to 50% by weight, more preferably 10% to 40% by weight, based on the total weight of the insect repellent silica carrier. It is preferred to mix the silica carrier, the insect repellent active substance, and the surfactant at room temperature. However, mixing at a temperature above room temperature but below the degradation temperature of the insect repellent active substance is contemplated. The mixing time is preferably 5 seconds to 36 hours, more preferably 5 seconds to 24 hours.

[0019] The insect repellent polymer composition of the present invention is prepared by dispersing an insect repellent silica carrier in a thermoplastic polymer. The insect repellent silica carrier is added in powder form to, for example, polyethylene or polypropylene granules or mixtures thereof. The resulting mixture is then melt-extruded from an extruder in strip form by applying heat. The extruded material is then cut into short lengths and ultimately formed into small granules to form insect repellent granules. The weight of the insect repellent granules obtained after the heating and melting step is not significantly different from the total weight of the insect repellent silica carrier and polymer material before heating and melting, indicating that the volatile insect repellent activator is well protected and retained in the composition. Concentrated insect repellent granules are also known as insect repellent masterbatches.

[0020] The insect repellent masterbatch may contain up to 25% by weight, preferably 0.1% to 20% by weight, and more preferably 1% to 16% by weight of the insect repellent masterbatch, based on the total weight of the insect repellent masterbatch.

[0021] Pesticide masterbatches may also include other additives to improve or enhance functionality, processability, or effect properties. Non-limiting examples of additives include UV absorbers, fragrances, sterically hindered amine-based light stabilizers, flame retardants, quenchers, antioxidants, pigments, acid scavengers, fillers, flame retardant additives, antioxidants, light stabilizers, colorants, antistatic agents, dispersants, release agents, copper inhibitors, nucleating agents, plasticizers, lubricants, emulsifiers, optical brighteners, rheology modifiers, catalysts, flow control agents, slip agents, crosslinking agents, crosslinking accelerators, halogen scavengers, smoke suppressants, clarifying agents, or foaming agents.

[0022] The insect repellent masterbatch can then be processed with the second polymer to form articles with the desired color, shape, or form. These articles can be molded or extruded. As molding methods, conventional methods such as extrusion molding, injection molding, blow molding, calendering, and compression molding are used to obtain molded products with the desired shape. The second polymer is a thermoplastic polymer as discussed previously.

[0023] In one embodiment, the insect repellent masterbatch is blended with a polyolefin such as polypropylene or high-density polyethylene and used to produce films, filaments, fibers, sheets, thermoformed or injection-molded articles, woven or nonwoven materials, yarns, or meshes such as mosquito nets. In one embodiment, the invention provides fibers with insect-repellent properties. These fibers can be manufactured according to methods known in the art. The fibers can have desired softness and physical-mechanical properties and can be used in various applications such as continuous filament yarns, bulk continuous filament yarns, chopped strands, meltblown fibers, and spunbond fibers. In one embodiment, the invention provides fabrics made from the fibers of the invention. The fabrics can be manufactured using any known process for producing nonwoven or woven fabrics.

[0024] A particular advantage of this invention is that the active insect repellent substance is preserved through two intense heating cycles involved in the manufacture of woven fabrics such as mosquito nets. It is believed that the active insect repellent substance is well protected within the pores of the silica carrier, and the presence of a nonionic surfactant further contributes to this good protection. The mesh may include an active substance content depending on the desired safety and recommended dosage of the active substance. In one embodiment, the mesh comprising the insect repellent composition may have an active substance content of up to 2% by weight, preferably 0.1-1.5% by weight, and more preferably 0.5-1% by weight based on the total weight of the mesh.

[0025] While the primary objective of this invention is to provide protection against mosquitoes, it also includes the control and / or prevention of various pests such as ticks, cockroaches, bedbugs, mites, fleas, lice, leeches, houseflies, termites, ants, moths, spiders, locusts, crickets, silverfish, and other flying and crawling insects. Besides mosquito nets, other applications include netting or fabrics used in agriculture, such as fences, animal enclosures, greenhouse nets, or crop fencing, especially for hanging fruits or vegetables from trees or shrubs; examples include cocoa pods or bananas. Other examples include bedding, mattresses, pillows, comforters, mats, curtains, wall coverings, carpets and windows, cabinets and door curtains, geotextiles, tents, shoe insoles, clothing such as socks, trousers, shirts, uniforms, horse blankets, pet collars and bedding, coverings in agriculture and the wine industry; fabrics or nets for packaging, bags, and outdoor equipment; containers for food, seeds, and feed; building materials; and furniture. Depending on the insecticidal efficacy of the active ingredient in the insect repellent, the typical amount of the active ingredient in these applications can be 0.001-5% of the weight of the fabric or mesh.

[0026] Without further detailed description, it is believed that those skilled in the art can use the invention to its fullest extent using the description herein. The following examples are provided to offer additional guidance to those skilled in the art in practicing the protected invention. The provided examples are merely illustrative of work that aids the teachings of this application. Therefore, the examples are not intended to limit the invention in any way, as the invention is defined by the appended claims. Example

[0027] Comparative Example 1

[0028] Preparation of the insect repellent silica carrier: The insect repellent silica carrier was prepared by mixing DEET and precipitated silica (Sipernat 22S from Evonik Industries) in different proportions (g) as shown in Table 1. Samples 1a and 1b were kept in an oven at 105 ± 1 °C for 5 days, and the weight of the samples was measured at the end of this period. Sample 1a lost approximately 3.6% by weight and sample 1b lost approximately 9.9% by weight, respectively, indicating the loss of volatile DEET from the insect repellent silica carrier.

[0029] Table 1: Composition of silica carrier for insect repellents

[0030] 1a 1b DEET(g) 10 40 Silicon dioxide (g) 90 60 Approximate weight loss (%) 3.6 9.9

[0031] Comparative Example 2

[0032] Preparation of insect repellent masterbatch: Approximately 40 g of Comparative Example 1's insect repellent silica carrier sample 1b was melt-extruded with 40 g of LDPE powder (HD50MA180), 0.5 g of wax PE 520, 0.1 g of mineral oil, and 19.4 g of HDPE granules to form insect repellent masterbatch sample 2. Sample 2 was maintained in an oven at 105 ± 1 °C for 5 days, and its weight was measured at the end of this period. The weight loss of sample 2 was found to be approximately 8.7%.

[0033] Example 1

[0034] Preparation of Insect Repellent Silica Carriers: Three samples, 3a, 3b, and 3c, containing different amounts of DEET, castor oil ethoxylate, and silica as shown in Table 2, were prepared. First, DEET was mixed with castor oil ethoxylate (Emulsogen 360EL from Clariant International), and the resulting DEET solution was absorbed onto a precipitated silica carrier (Sipernat 22S from Evonik Industries) to form insect repellent silica carrier samples 3a, 3b, and 3c, respectively. The insect repellent silica carrier samples thus prepared were free-flowing, non-clumping powders with minimal pulverization. The prepared samples were kept in an oven at 105 ± 1 °C for 5 days, and the approximate percentage weight loss of these samples was measured at the end of this period. The weight loss of sample 3a was found to be approximately 2.6%. In contrast, sample 1a of Comparative Example 1 had a percentage weight loss of approximately 3.6%. This example demonstrates that absorption of DEET in the presence of castor oil ethoxylate reduces weight loss. From sample 3b to sample 3c, increasing the amount of surfactant further reduces weight loss, thus demonstrating that DEET retention is enhanced when absorbed onto silica in the presence of a surfactant.

[0035] Table 2: Composition of silica carrier for insect repellents

[0036] 3a 3b 3c DEET(g) 10 40 40 Silicon dioxide (g) 89 59 55 Castor oil ethoxylate (g) 1 1 5 Approximate weight loss (%) 2.6 7.2 3.2

[0037] Example 2

[0038] Preparation of insect repellent masterbatch: Approximately 40 g of the insect repellent silica carrier sample 3c from Example 1 was melt-extruded with 40 g of LDPE powder (HD50MA180), 0.5 g of wax PE 520, 0.1 g of mineral oil, and 19.4 g of HDPE granules to form insect repellent masterbatch sample 4. Sample 4 was maintained in an oven at 105 ± 1 °C for 5 days, and its weight was measured at the end of this period. It was found that sample 4 had a weight loss of approximately 2.8%. In contrast, sample 2 of Comparative Example 2 had a weight loss of approximately 8.7%. This example demonstrates that the absorption of DEET in the presence of castor oil ethoxylate enhances the retention of DEET in the masterbatch by approximately 32%.

[0039] Quantification of DEET in insect repellent masterbatch: Approximately 5 g of Sample 4 was added to acetonitrile and sonicated for 30 min at room temperature (30°C). This was then refluxed at 80°C for 3–4 h. The sample was removed from this solution and tested using an acetonitrile:methanol (90:10) mobile phase (isocratic system) at a flow rate of 0.5 mL / min on an HPLC column (Eclipse XDB C18 150*4.6 mm, 3.5 μm). The HPLC-quantified DEET content was approximately 14.97 wt%, compared to the theoretical 16 wt%, indicating a loss of approximately 6.5% during masterbatch processing.

Claims

1. A polymer composition for insect repellent, comprising: At least 50% by weight of a thermoplastic polymer based on the total weight of the composition; and Based on 0.1 wt% to 50 wt% of the total weight of the composition, a precipitated silica carrier containing an insect repellent active substance is disposed of on the precipitated silica carrier, wherein the active substance is absorbed on the precipitated silica carrier in the presence of a surfactant, wherein the surfactant comprises a nonionic surfactant, wherein the nonionic surfactant is a castor oil ethoxylate. The active ingredient of the insect repellent is released from the insect repellent polymer composition for more than 6 months. The thermoplastic polymer comprises polyamide, polystyrene, polyvinyl chloride, polyolefin, or any copolymer thereof, and The active substance comprises N,N-diethyl-3-methylbenzamide (DEET), 1-piperidinic acid-2-(2-hydroxyethyl)-1-methylpropyl ester (picaridin), ethyl 3-[N-butyl-N-acetyl]-aminopropionic acid, dimethyl carbamate, or any combination thereof.

2. The polymer composition of claim 1, wherein the active substance is N,N-diethyl-3-methylbenzamide, and wherein the thermoplastic polymer is a polyolefin.

3. The polymer composition according to any one of claims 1-2, wherein the active substance is present in an amount of 0.1 wt% to 25 wt% based on the total weight of the polymer composition.

4. An article prepared from the composition of any one of claims 1-3, wherein the article is a molded article, a film, a nonwoven fabric, a woven fabric, or an extruded article.

5. The article of claim 4, wherein the article is a meltblown fabric.

6. The article of claim 4, wherein the article is a spunbond fabric.

7. The article of claim 4, wherein the woven fabric is a mosquito net.

8. A silica composition for insect repellent, comprising: A precipitated silica carrier, wherein the precipitated silica carrier contains an insect repellent active substance and a surfactant absorbed on the precipitated silica carrier, wherein the surfactant comprises a nonionic surfactant, wherein the nonionic surfactant is a castor oil ethoxylate. The active substance of the insect repellent is released from the insect repellent silica composition for more than 6 months.

9. Use of the insect repellent silica composition of claim 8 for forming an insect repellent polymer composition.