Sustained-release insect repellent sheet

Abstract

[Problem] To provide a sustained-release insect repellent sheet facilitating the adjustment of the release period of a pyrethroid-based agent. [Solution] A sustained-release insect repellent sheet which is liquid-component-containing sheet in which a liquid component is carried in voids formed around a filler dispersed in a thermoplastic resin, wherein the carried liquid component contains a pyrethroid-based agent as a medicinal component and contains a surfactant and / or liquid paraffin.

Description

Slow-release insect repellent sheet

[0001] The present invention relates to a sustained-release insect repellent sheet.

[0002] Conventionally, insect repellents, insecticides, repellents, and other insect repellents have been used to prevent small animals, insects, and other pests from invading various objects, such as buildings and auxiliary facilities such as houses and stores, installed equipment such as vending machines, and containers such as grain bags and rice bins. Pyrethroid-based chemicals are commonly used as these insect repellents, and they are used, for example, by spraying them in a sprayer. However, when spraying insect repellents, the insect repellents easily run off, making it difficult to maintain their effectiveness over a long period of time. There is also a concern that spraying insect repellents may pollute the surrounding environment.

[0003] Another known method involves supporting an insect repellent or the like on a sheet and slowly releasing the insect repellent or the like from the sheet. This method can maintain its effectiveness longer than spraying. For example, Patent Document 1 describes a sustained-release sheet in which a resin composition containing a filler is stretched to create voids around the filler, and these voids are filled with a functional liquid component such as an insecticide. This sustained-release sheet can release the liquid component over a long period of time while maintaining a constant release amount.

[0004] JP 2019-130729 A

[0005] Although sustained-release sheets that slowly release insect repellents and the like can release liquid ingredients over a long period of time, insect activity is seasonal, and continuous release during periods when insects are not active is ineffective. It is not enough to simply say that a long effective period is good; in some cases, it is better to shorten the effective period, reduce the amount of insect repellent used, and reduce manufacturing costs. In other words, insect repellent sheets that support insect repellents and the like are required to be able to optimally control the release period of the liquid ingredients.

[0006] In the sustained-release sheet of Patent Document 1, in order to incorporate a large amount of liquid ingredient into the voids formed around the filler by stretching, the voids must be open to allow the liquid ingredient to penetrate deep into the sheet. To open the voids, a large amount of filler had to be added and the sheet had to be stretched at a high stretch ratio. As a result, in addition to the constraints on the stretch ratio and the amount of filler added, there were also natural limitations on the sheet thickness, making it difficult to change the content of the liquid ingredient inside the sheet under these conditions. As a result, the effect lasted longer than necessary, and the addition of a large amount of insect repellent, etc., led to increased costs.

[0007] The present invention aims to facilitate the adjustment of the content of insect repellent and the like when applying such a sustained-release sheet to an insect repellent sheet, thereby facilitating the adjustment of the release period.

[0008] The above-mentioned problems are solved by a sustained-release insect repellent sheet that is a liquid component-containing sheet made of a thermoplastic resin having a filler dispersed therein, and in which a liquid component is carried in voids formed around the filler, the voids being interconnected, and the carried liquid component containing a pyrethroid drug as a medicinal component, as well as a surfactant and / or liquid paraffin.

[0009] The pyrethroid agent is preferably transfluthrin, and in this case, it preferably contains a fatty acid ester as a surfactant.

[0010] A sustained-release insect repellent sheet that solves the above-mentioned problems is a method for producing a liquid component-containing sheet by stretching an unstretched sheet in which a filler is dispersed in a thermoplastic resin, and causing a liquid component to be carried in voids formed around the filler, wherein the liquid component contains a pyrethroid drug as an active ingredient, and the sustained-release insect repellent sheet may be produced by impregnating the unstretched sheet with a mixed liquid in which a volatile component is mixed with the liquid component during or after stretching, causing the mixed liquid to be carried in the voids, and then performing a heat-relaxing treatment while volatilizing the volatile component.

[0011] According to the present invention, when a pyrethroid-based agent is used as the medicinal ingredient, the release period can be easily adjusted, and a sustained-release insect repellent sheet can be provided according to the intended use.

[0012] 1A and 1B are schematic cross-sectional views of unstretched films according to Comparative Examples and Examples, and schematic cross-sectional views of stretched sheets according to Comparative Examples and Examples.

[0013] Preferred embodiments for carrying out the present invention will now be described.

[0014] The sustained-release insect repellent sheet of the present invention comprises a liquid-component-containing sheet in which a filler is dispersed in a thermoplastic resin and a liquid component is supported in voids formed around the filler. The sheet before the liquid component is incorporated is preferably composed of a thermoplastic resin. The thermoplastic resin is not particularly limited, but is preferably a resin that is easily stretchable, and polyolefin, polyamide, polyester, polyvinylidene fluoride, etc. can be selected. Since the sheet contains the liquid component, a polyolefin that has excellent chemical resistance and is not easily reactive with the liquid component is preferred. If the crystallinity is too high, the medicinal ingredient of the liquid component may not be able to pass through the thermoplastic resin, resulting in an excessively low release rate. For this reason, among polyolefins, low-crystalline ones such as low-density polyethylene and low-stereoregularity polypropylene are preferred. When using low-density polyethylene, the lower the density, the lower the crystallinity tends to be, and its density should be 0.895 to 0.925 g / cm. ３ It is preferable that the low-density polyethylene contains one of the following: From the viewpoint that the sheet involves stretching, the low-density polyethylene is preferably linear low-density polyethylene. The melting point of the low-density polyethylene is preferably 80 to 135°C. The softening point of the low-density polyethylene is preferably 45 to 90°C. Between linear low-density polyethylene and branched low-density polyethylene, branched low-density polyethylene tends to be less likely to crystallize, and from the viewpoint of gradually releasing the liquid component contained inside the sheet, it is also preferable to mix branched low-density polyethylene to a degree that does not inhibit stretchability in order to lower the crystallinity. By partially containing branched low-density polyethylene, voids tend to be more easily formed between the filler and the sheet, making it easier to obtain interconnected pores.

[0015] The filler is primarily an inorganic filler such as calcium carbonate, talc, silica, mica, zinc oxide, barium sulfate, titanium oxide, or aluminum. However, organic fillers may also be used as long as they are incompatible with the thermoplastic resin that constitutes the raw material of the sheet and exhibit hard properties at room temperature. Numerous voids are formed around the filler, particularly through stretching, and liquid components are supported within these voids. Fillers that are resistant to liquid components are preferred, with inorganic fillers being relatively more stable. Filler shapes that are closer to spherical are easier to disperse and tend to regulate the size of the voids. Therefore, calcium carbonate is preferred. The particle size of the filler used here is not particularly limited and can be selected appropriately depending on the thickness of the sheet and the state of the interconnected pores. However, an average particle diameter of 0.1 to 10.0 μm as measured by the air permeability method is preferred. The average particle diameter can be calculated from the specific surface area measured by the Blaine air permeability test. The more fillers with a smaller average particle size are dispersed, the longer the liquid component can be released at a given volatilization rate, but if the average particle size is too small, the voids become smaller and it becomes difficult to support the liquid component due to the influence of surface tension, etc. From the viewpoint of supporting liquid components containing surfactants and liquid paraffin together with pyrethroid agents, the average particle size is more preferably in the range of 0.5 to 3 μm.

[0016] To obtain interconnected pores in which the voids around the filler are connected, it is preferable to use a relatively high amount and uniformly disperse the filler. The filler is preferably added in an amount that accounts for 40% by mass or more of the mass of the sheet before the liquid component is added. A range of 40 to 70% by mass is more preferable. Adding a filler in this range connects the multiple voids formed by stretching, allowing the liquid component to be absorbed deep into the sheet, thereby enabling a large amount of liquid component to be supported. If the filler content is less than 40% by mass of the sheet, the voids may be sparsely generated, potentially limiting the liquid component to support near the surface of the sheet. Furthermore, if the filler content exceeds 70% by mass of the sheet, the mass of the thermoplastic resin will be less than 30% by mass, which may result in the sheet becoming brittle and difficult to handle.

[0017] The thermoplastic resin and filler, along with any other additives, are kneaded in an extruder and molded into a sheet to form an unstretched sheet. A known extruder may be used, and the unstretched sheet may be produced by either a tubular method or a T-die method. In the present invention, the liquid component-containing sheet is preferably finished to a thickness of 50 to 1000 μm, so that it can be easily stretched, the liquid component can be easily and sufficiently supported in the voids within the sheet, and the medicinal component can be sustainedly released over a sufficiently long period of time. When finishing to this thickness, it is preferable to use a T-die method, which makes it easy to form a thick unstretched sheet.

[0018] The voids around the filler can be obtained by cooling and solidifying the unstretched sheet and then stretching it. This stretching may be a known method of stretching at a speed ratio between rolls. When an unstretched sheet containing a filler dispersed in a thermoplastic resin is stretched, voids are formed around the filler. The voids formed here are formed in a vacuum state, and when stretched while exposed to a liquid component, they can absorb the liquid component and support the liquid component around the filler. If stretching is performed in air, air will enter around the filler. The voids around the filler are fine, and once air enters the voids, the liquid component will be less likely to enter the voids due to influences such as surface tension. By utilizing the absorbing force that occurs when the voids are formed, a large amount of liquid component can be supported within the sheet. If the liquid component can be supported in the fine voids around the filler, the liquid component will be less likely to leak out of the sheet.

[0019] The force that attracts the liquid component is generated by deforming the unstretched sheet, and when the suction force is increased by stretching, it is preferable to increase the stretching ratio. The interconnection of voids is also generated by deforming the unstretched sheet, and can be achieved by stretching at a relatively high stretching ratio. If the voids are not interconnected, the liquid component will not penetrate to the interior of the sheet. Therefore, it is preferable to stretch the unstretched sheet at a stretching ratio of 3 or more. On the other hand, from the viewpoint that if the stretching ratio is too high, the sheet is more likely to break during production, and if the voids become too large due to stretching, the sustained release properties may be impaired, it is preferable to set the stretching ratio to 10 or less.

[0020] The liquid component contained in the liquid component-containing sheet uses a pyrethroid-based pesticide as a medicinal ingredient. Pyrethroid-based pesticides have a pest control effect, and examples thereof include metofluthrin, transfluthrin, profluthrin, empenthrin, cyfluthrin, fenothrin, cyphenothrin, permethrin, tralomethrin, fenpropathrin, and etofenprox. These may be used alone or in combination in the present invention.

[0021] By supporting the liquid component in the fine voids, an excellent sustained release effect is achieved. The vapor pressure at 30°C is 1 x 10 －４ ~1 x 10 －２ Suitable pyrethroid agents that are volatile at room temperature include metofluthrin, transfluthrin, profluthrin, and empenthrin.

[0022] The liquid component contains a pyrethroid agent as well as a surfactant and / or liquid paraffin. The surfactant and liquid paraffin act as extenders for diluting the pyrethroid agent in the liquid component, and adjusting the content of the pyrethroid agent in the liquid component allows for adjustment of the volatilization amount and effective period of the final insect repellent sheet. Furthermore, surfactants and liquid paraffin do not increase the surface tension of the entire liquid component, making it easier for the liquid component to spread throughout the fine voids formed in the sheet. Furthermore, surfactants and liquid paraffins that are almost non-volatile at room temperature are preferred. If a volatile surfactant or liquid paraffin is used and volatilizes during the impregnation process, the dilution rate of the pyrethroid agent is likely to change, leading to uneven content. Furthermore, if the surfactant or liquid paraffin is released together with the pyrethroid agent during use, it becomes difficult to determine the amount of pyrethroid agent volatilized, making it difficult to determine the expiration date.

[0023] When transfluthrin is used as a pyrethroid drug, it is preferable to use a fatty acid ester among surfactants. Examples of fatty acid esters include diisobutyl adipate, diethylhexyl succinate, cetyl 2-ethylhexanoate, glyceryl tri-2-ethylhexanoate, hexyldecyl ethylhexanoate, triethylhexanoin, neopentyl glycol diethylhexanoate, trimethylolpropane triethylhexanoate, pentaerythrityl tetraethylhexanoate, neopentyl glycol dicaprate, ethylhexyl isononanoate, isononyl isononanoate, isodecyl isononanoate, isotridecyl isononanoate, hexyl laurate, isopropyl myristate, octyldodecyl myristate, and myristate. Examples of suitable transfluthrin include isocetyl palmitate, isopropyl palmitate, ethylhexyl palmitate, octyl palmitate, ethyl stearate, octyl stearate, isocetyl stearate, ethyl isostearate, isopropyl isostearate, hexyldecyl isostearate, isostearyl isostearate, glyceryl triisostearate, polyglyceryl triisostearate, trimethylolpropane triisostearate, pentaerythrityl tetraisostearate, ethyl oleate, caprylic / capric triglyceride, and octyldodecyl 12-stearoyl stearate. Transfluthrin has a melting point of approximately 33°C and exists in a mixture of solid and liquid forms at room temperature. When a liquid-component-containing sheet is obtained by stretching while exposed to a liquid component, the stretching bath is heated, so transfluthrin remains in a liquid state. However, after stretching, the liquid-component-containing sheet solidifies at room temperature. When transfluthrin solidifies, the texture, hardness, and other properties of the liquid component-containing sheet change at room temperature, and the solidification can also clog or deform the pores, making it more likely to change volatility.By thoroughly mixing transfluthrin with a fatty acid ester, its crystallization can be adjusted, allowing it to remain in a liquid state even when used at room temperature.

[0024] Since liquid paraffin contains a large amount of olefin hydrocarbons, when the thermoplastic resin forming the sheet is polyolefin, the liquid component containing liquid paraffin has a good affinity with the sheet and easily penetrates into the voids. Therefore, unless there are special circumstances such as the above-mentioned transfluthrin, it is preferable to add liquid paraffin to the liquid component, and a surfactant and liquid paraffin may be mixed together to the extent that it does not affect dispersion.

[0025] The blending ratio (mass ratio) of the pyrethroid agent to the surfactant and / or liquid paraffin in the liquid component is appropriately selected taking into consideration the target effective period, etc. If a longer effective period is desired, it is preferable to blend a higher pyrethroid agent. When mixing transfluthrin with a surfactant to prevent coagulation of transfluthrin, it is preferable to mix them in a mass ratio of transfluthrin:surfactant = 1:0.1 to 10.

[0026] The liquid component content in the liquid component-containing sheet is selected as appropriate, but is preferably 10 to 60% by mass. Because the pyrethroid content can be adjusted using surfactants or liquid paraffin, reducing the pyrethroid content does not require reducing the liquid component content itself; the sheet can be manufactured under manufacturing conditions that facilitate ensuring voids in the sheet. Increasing the liquid component content requires forming many large voids. Therefore, increasing the liquid component content too much not only reduces the strength of the sheet, but also makes the void shape unstable and makes it difficult to ensure sustained release.

[0027] A volatile component having a higher volatility than the medicinal component may be mixed with the liquid component. The volatile component is liquid at room temperature, and in particular, has a vapor pressure of 1×10 at 30° C. ２ However, if the volatility is too high, it is difficult to handle as a liquid, so the vapor pressure at 30°C is 1 x 10 ５It is preferable that the viscosity of the solvent is not more than Pa. Specific examples include n-hexane, toluene, o-xylene, etc., and those which are easily mixed with the liquid components, pyrethroid-based agents, surfactants, and liquid paraffin, and have low reactivity with these are preferred, and n-hexane is more preferred among them.

[0028] When a sheet is stretched in a liquid mixture containing a liquid component and a readily volatile component, both the liquid component and the readily volatile component are retained in the voids. After retained in the voids, the readily volatile component volatilizes immediately. However, when the readily volatile component volatilizes in the voids, a force is generated that draws the liquid component into the voids, filling the space previously occupied by the readily volatile component. By utilizing this force, the liquid component that has seeped out onto the sheet surface due to sheet shrinkage can be re-removed into the voids. For example, if a sheet is subjected to a heat relaxation (annealing) treatment immediately after stretching in the liquid component, in which the sheet is subjected to heat to forcibly shrink, the liquid component will seep out onto the sheet surface. However, by incorporating a readily volatile component, this seepage can be prevented. Heat relaxation can also suppress sheet shrinkage over time, thereby preventing deformation and seepage of the liquid component even during use of the insect repellent sheet.

[0029] When the thermoplastic resin of the sheet is polyolefin and n-hexane is used as the volatile component, n-hexane is compatible with polyolefin and penetrates to some extent into small voids formed by stretching. Even if a certain amount of the mixture of the liquid component and n-hexane penetrates the voids, the evaporation of n-hexane generates a force that draws the liquid component into the voids. Therefore, even without stretching in a mixture of the liquid component and the volatile component, it is possible to support the liquid component in the voids formed around the filler by applying a mixture of the liquid component and n-hexane to a sheet in which voids have already been formed around the filler. When laminating a barrier layer or adhesive layer on a sheet containing a liquid component, the liquid component can inhibit interlayer adhesion, resulting in insufficient adhesion and the risk of the liquid component volatilizing during processing. However, if the liquid component can be supported in the voids around the filler by application, the liquid component can be supported after laminating the barrier layer, adhesive layer, etc., on the stretched sheet, facilitating lamination of the barrier layer or adhesive layer. In this specification, "impregnation" refers to the process of soaking a liquid component into voids. Impregnation includes a method of immersing a sheet in a liquid, and a method of contacting a sheet with a mixed liquid in air by coating.

[0030] The mixing ratio (mass ratio) of the liquid component to the readily volatile component is not particularly limited, but in both cases where the sheet is stretched in the mixed liquid and where the mixed liquid is applied and supported, the mixing ratio (mass ratio) is preferably liquid component: readily volatile component = 1:0.1 to 10. The readily volatile component is likely to volatilize during the impregnation process, which can lead to unevenness in the liquid component content, and if the readily volatile component remains in the sheet, it can lead to excessive odor components. Therefore, it is preferable to avoid incorporating an excess amount of the liquid component and to volatilize it during the manufacturing process so that as little remains in the sheet as possible. From this perspective, the mixing ratio (mass ratio) is more preferably in the range of liquid component: readily volatile component = 1:0.1 to 1.

[0031] The liquid component-containing sheet obtained as described above contains a pyrethroid-based drug as a medicinal component, and serves as a sustained-release insect repellent sheet that sustains the release of the drug.

[0032] Examples of pests that the sustained-release insect repellent sheet targets include, but are not limited to, flying pests such as mosquitoes, flies, horseflies, midges, moth flies, leaf beetles, stink bugs, leafhoppers, and crane flies, as well as crawling pests such as ants, pill bugs, woodlice, spiders, millipedes, centipedes, house centipedes, and caterpillars.

[0033] When a sustained-release insect repellent sheet is soaked in liquid ingredients, it gradually becomes cloudy as the ingredients evaporate. Therefore, the degree of cloudiness can be used to gauge the extent of evaporation of the liquid ingredients. When used in an insect repellent sheet, this serves as a so-called indicator display to show the end of the effective period. This cloudiness gradually progresses once a certain amount of the liquid ingredients have evaporated, and the change in cloudiness diminishes after a certain point. Therefore, the sheet approaches the color indicating the end of the effective period sooner than when all the liquid ingredients have evaporated. In the present invention, the liquid ingredients contain a surfactant and / or liquid paraffin that is less likely to volatilize, so that it remains in the sheet even after the pyrethroid pesticide has completely evaporated. Therefore, the end of the effective period can be displayed at a time when the change in cloudiness is easily noticeable.

[0034] The sustained-release insect repellent sheet may be laminated with other layers, such as a barrier layer or an adhesive layer, depending on the purpose. For example, by laminating a resin with gas barrier properties as a barrier layer, the amount of pyrethroid pesticide volatilized can be adjusted. Furthermore, by laminating an adhesive layer on top of the barrier layer, the sheet can be attached to various locations for use. As described above, a liquid component can be carried in the voids around the filler by application, so lamination can be performed using various methods without having to consider constraints such as the ability to stretch in the liquid component or the inhibition of adhesiveness by the liquid component.

[0035] In the sustained-release insect repellent sheet, various additives other than those mentioned above can be appropriately blended with the thermoplastic resin or liquid component, such as ultraviolet absorbers, antioxidants, surfactants, colorants, pigments, dyes, natural essential oils, fragrances, lubricants, etc., to the extent that they do not interfere with the intended purpose.

[0036] The sustained-release insect repellent sheet can be processed into a desired shape depending on the purpose. It can be enclosed in a molded frame and hung on a doorknob, or enclosed in a frame with a hook-and-loop fastener and attached to a screen door. It can also be enclosed in a perforated box and placed under a vending machine or in a rice chest. An adhesive layer can also be formed on the sheet and attached to a desired location such as a window sash or window frame.

[0037] The present invention will be explained in more detail below with reference to examples, but the technical scope of the present invention is not limited to the following examples.

[0038] [Comparative Example 1] Linear low-density polyethylene (density 0.932 g / cm ３ , melting point 123 ° C, MFR 3.0 g / 10 min (190 ° C, 2160 g load)) 16 mass%, low density polyethylene (density 0.923 g / cm ３ , melting point 112 ° C, MFR 1.5 g / 10 min (190 ° C, 2160 g load)) 16 mass%, ultra-low density polyethylene (density 0.900 g / cm ３ Mixture 1 was prepared by mixing 8% by mass of 100% polyethylene terephthalate (190°C, melting point 115°C, MFR 2.0g / 10min (190°C, 2160g load)) and 60% by mass of calcium carbonate (average particle size 1.2µm by air permeability method), and high-density polyethylene (density 0.956g / cm ３ , melting point 135 ° C, MFR 0.8 g / 10 min (190 ° C, 2160 g load) 70 mass%, low density polyethylene (density 0.926 g / cm ３ A mixture 2 was prepared by mixing 30% by mass of a cellulose ester copolymer having a melting point of 124°C and an MFR of 0.8 g / 10 min (190°C, 2160 g load), and the mixtures were co-extruded using a T-die to form a laminate structure of a layer of mixture 1 and a layer of mixture 2, and cooled with a chill roll to obtain unstretched film 1. The layer of mixture 1 was approximately 300 μm thick, and the layer of mixture 2 was approximately 150 μm thick. FIG. 1 shows a schematic diagram of the cross section of unstretched film 1.

[0039] The unstretched film 1 was passed through nip rolls, then through a first stretching roll, a constant temperature liquid bath (liquid bath temperature: 60°C), and a second stretching roll in the order listed, and then passed through a third roll consisting of a group of heat-relaxing rolls (temperature: 80°C) and wound up to obtain a sheet body A1. At this time, the constant temperature liquid bath contained empenthrin (vapor pressure (30°C) 1.4 × 10) as the chemical A. －４ Pa) was stored in the sheet, and the sheet was stretched while exposed to chemical A. The speed ratio (stretching ratio) between the first roll and the second roll was 5 times, and the final speed ratio between the second roll and the third roll was 0.9 times, resulting in a 10% relaxation. The resulting sheet A1 was designated Comparative Example 1. Figure 2 shows a schematic diagram of the cross section of the sheet after stretching.

[0040] Example 1 A sheet body A2 was obtained in the same manner as in Comparative Example 1, except that liquid paraffin was mixed with the chemical A stored in the constant-temperature liquid bath of Comparative Example 1 to form liquid component A. The obtained sheet body A2 was used as Example 1. The liquid component A was a mixture of 40 mass % chemical A (empenthrin) and 60 mass % liquid paraffin (empenthrin:liquid paraffin=1:1.5).

[0041] [Example 2] The liquid component A stored in the constant temperature liquid bath of Example 1 was mixed with n-hexane (vapor pressure (30°C) 1.6 x 10 ４ A sheet A3 was obtained in the same manner as in Example 1, except that liquid component A (a mixed liquid of empenthrin and liquid paraffin) was mixed to form mixed liquid A. The obtained sheet A3 was designated as Example 2. Mixed liquid B was prepared by mixing 70 mass % of liquid component A (a mixed liquid of empenthrin and liquid paraffin) and 30 mass % of n-hexane (liquid component A:n-hexane=1:0.4).

[0042] Comparative Example 2 Instead of the drug A stored in the constant temperature liquid bath in Comparative Example 1, transfluthrin (vapor pressure (30°C) 4 x 10) was used as drug B. －４ A sheet B1 was obtained in the same manner as in Comparative Example 1, except that the sheet B1 was used.

[0043] Example 3 A sheet body B2 was obtained in the same manner as in Comparative Example 1, except that isohexyldecyl stearate (2-hexyldecyl stearate) was mixed with the drug B stored in the constant-temperature liquid bath of Comparative Example 2 to form liquid component B. The obtained sheet body B2 was designated Example 3. Liquid component B was a mixture of 40% by mass of drug B (transfluthrin) and 60% by mass of isohexyldecyl stearate (transfluthrin:isohexyldecyl stearate=1:1.5).

[0044] [Example 4] The liquid component B stored in the constant temperature liquid bath of Example 3 was diluted with n-hexane (vapor pressure (30°C) 1.6 x 10 ４ A sheet body B3 was obtained in the same manner as in Example 3, except that liquid component B (a mixture of transfluthrin and isohexyldecyl stearate) was mixed to form mixed liquid B. The obtained sheet body B3 was designated as Example 4. Mixed liquid A was prepared by mixing 70 mass % of liquid component B (a mixture of transfluthrin and isohexyldecyl stearate) and 30 mass % of n-hexane (liquid component A:n-hexane=1:0.4).

[0045] Example 5 An unimpregnated sheet 1 was obtained in the same manner as in Comparative Example 1, except that the constant-temperature liquid bath in Comparative Example 1 was changed to a hot air oven and stretching was performed without exposure to liquid. Next, mixed liquid B (a mixed liquid of transfluthrin, isohexyldecyl stearate, and n-hexane) was applied to the layer of mixed liquid 1 of the unimpregnated sheet using a roll coater, thereby obtaining sheet C. The obtained sheet C was designated Example 5.

[0046] The following evaluation tests were carried out on the sheet bodies of Examples 1 to 5 and Comparative Examples 1 and 2. The results are shown in Table 1. The thickness of each of Examples 1 to 5 and Comparative Examples 1 and 2 was approximately 230 μm.

[0047] [Evaluation Test 1: Appearance] The surface of the sheet was visually inspected and evaluated according to the following criteria: Class 1 (◯): No particular problem in appearance; Class 2 (Δ): Problematic but remediable; Class 3 (×): Clearly problematic.

[0048] [Evaluation Test 2: Content] Each of Examples 1 to 5 and Comparative Example 2 was cut into a 5 cm square, and the initial weight of each test piece was measured. Then, ultrasonic cleaning with toluene was performed for 20 minutes at 60° C., and the weight after cleaning was measured. The difference between the initial weight and the weight after cleaning was calculated as the content of the liquid component, and the content was divided by the initial weight to obtain a percentage, which was the liquid component content.

[0049] Next, the amount of each drug component contained in each liquid component extracted by the washing was determined using a gas chromatograph, and the drug content was calculated as a percentage by dividing the amount of each component by the initial weight.

[0050]

[0051] In Examples 1 and 3 and Comparative Example 1, liquid seepage was observed on the surface of the sheet, but in all cases, the seepage was improved by re-stretching the sheet in air. In Comparative Example 2, liquid seepage was observed, as in Example 1. In Examples 2, 4, and 5, there was no particular seepage or the like, and the sheet appearance was good. In Comparative Example 2, transparent to white crystalline matter adhered to the surface of the sheet, and the shape of the sheet was unstable, making it unusable.

[0052] The relationship between the liquid component content and the drug content in Examples 1 to 5 generally followed the compounding ratio of each liquid component.

Claims

1. A sustained-release insect repellent sheet comprising a liquid component-containing sheet made of a thermoplastic resin having a filler dispersed therein, and a liquid component held in voids formed around the filler, wherein the voids are interconnected, and the held liquid component contains a pyrethroid-based drug as a medicinal ingredient, as well as a surfactant and / or liquid paraffin.

2. The sustained-release insect repellent sheet according to claim 1, wherein the pyrethroid agent is transfluthrin.

3. The sustained-release insect repellent sheet according to claim 2, which contains a fatty acid ester as a surfactant.

4. A method for producing a liquid component-containing sheet by stretching an unstretched sheet in which a filler is dispersed in a thermoplastic resin, and causing a liquid component to be carried in voids formed around the filler, wherein the liquid component contains a pyrethroid drug as an active ingredient, and during or after stretching the unstretched sheet, the sheet is impregnated with a mixed liquid in which a volatile component is mixed with the liquid component, causing the mixed liquid to be carried in the voids, and then performing a heat relaxation treatment while volatilizing the volatile component.

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