WO2010117191A2

WO2010117191A2 - Absorbent article comprising an encapsulated plant extract exhibiting an insecticidal effect

Info

Publication number: WO2010117191A2
Application number: PCT/KR2010/002100
Authority: WO
Inventors: Soo Yong Cho; Jik Hwan Park; Jin Hee Lee; Won Young Lee
Original assignee: Yuhan-Kimberly, Limited
Priority date: 2009-04-06
Filing date: 2010-04-06
Publication date: 2010-10-14
Also published as: HK1166027A1; JP5411349B2; CN102387819B; WO2010117191A3; KR101105574B1; KR20100110919A; CN102387819A; JP2012522618A

Abstract

The present invention relates to a disposable absorbent article in which an encapsulated natural plant extract exhibiting an insecticidal effect is applied thereto. In particular, the present invention relates to a disposable absorbent article comprising a liquid permeable top sheet, an absorbent core, and a liquid impermeable back sheet, characterized in that insecticidal microcapsules prepared by microencapsulating an extract of natural plants providing an insecticidal effect are applied thereto, where the plant is selected from the group consisting of cinnamon, rosemary, lavender, mint, eucalyptus, and mixtures thereof. Since the disposable absorbent article according to the present invention comprises an extract of natural plants in an encapsulated form that naturally provide an insecticidal effect while being nontoxic to the human body, it can effectively and consistently prevent harmful insects from invading the article during distribution and storage.

Description

[DESCRIPTION]

[Invention Title]

ABSORBENTARTICLE COMPRISING AN ENCAPSULATED PLANT EXTRACT

EXHIBITING AN INSECTICIDAL EFFECT [Technical Field]

The present invention relates to a disposable absorbent article comprising an insecticidal microcapsule, wherein the extract of at least one natural plant selected from the group consisting of cinnamon, rosemary, lavender, mint and eucalyptus is microencapsulated. [Background Art]

Disposable absorbent articles refer to products that absorb body fluids excreted by various physiological reactions, such as diapers, toilet training underpants, adult incontinence garments, absorbent underwear, feminine care products, nursing pads, etc. With respect to the performance characteristics of these disposable absorbent articles, the degree of absorption and the absorption rate of body fluids excreted by physiological reactions are primarily considered as important. Significant improvements have been made in the areas of absorbency and absorption rate due to the development of super absorbent polymers and the like.

Another performance characteristic required for disposable absorbent articles, in addition to absorbency, is the capability to prevent skin problems that may be caused by the use of these articles during the excretion of body fluids. Further, since the body fluids that are absorbed to the absorbent articles normally produce undesirable odors, methods of applying aromatic agents or deodorizing agents to the absorbent articles in order to remove such odors have been actively studied. Increasingly, there has also been a need to develop methods to effectively prevent larvae or adult insects from invading the disposable absorbent articles, because the invasion of insect pests into the absorbent articles during distribution and storage may cause deterioration in the quality of the absorbent articles, as well as hygienic problems.

The most common insect pests that invade absorbent articles during distribution and storage generally include mosquitoes, rice weevils, cadelle beetles, Indian meal moth larvae, fungi or bacteria such as Penicillium islandicum, and the like. These insect pests grow rapidly on the surface or the inside of the absorbent articles after infiltration and discharge excretions, thereby deteriorating the quality of the absorbent article product.

In order to control the insect pests mentioned above, fumigants such as methyl bromide, aluminum phosphide, chloropicrin, etc. can be used as pesticides, but these are synthetic organic pesticides which have a number of problems including toxicity, adverse effects on the human body, increased resistance to various types of insect pests, etc. As a way to solve these problems associated with synthetic organic pesticides, various attempts have recently been made to use vegetable oils extracted from natural substances as a repellent. It has been reported that many plant extracts and vegetable oils exhibit ovicidal, repellent, and insecticidal effects against various kinds of insect pests in stored grain. For example, the oil of sweet flag has been reported to have a bactericidal effect against red bean weevils, rice weevils, cadelle beetles, and lesser grain borers (Rhyzopertha dominica). Representative technologies relating to compositions for controlling insect pests mainly consisting of vegetable ingredients include U.S. Patent No. 4,455,304 which discloses a composition for repelling animals comprising, as an active ingredient, a vegetable oil extracted from pepper and garlic, and a method of using the same. In addition, U.S. Patent No. 4,440,783 discloses a composition for repelling animals comprising, as an effective ingredient, isothiocyanate and lemon oil. Further, WO 99/22751 discloses a method of using a combination of pepper extract, allyl isothiocyanate, and lemon oil in place of methyl bromide as a soil treatment, insecticide, commodity fumigant, and structural fumigant. In addition, technologies relating to food preservatives, films, etc. utilizing the antimicrobial effect of allyl isothiocyanate, which is the main ingredient of horseradish oil and mustard oil, are disclosed.

Although studies have been conducted to apply folk remedies for controlling insect pests where whole garlic bulbs, pepper, charcoal, etc. are put in storage containers, such as rice containers, for the purpose of preserving the quality of the stored grains, the effects of controlling insects were not excellent. Japanese Patent Publication No. (Hei)6-38678 discloses an exemplary product containing a formulation based on vegetable oil components as an improvement to the above folk remedies, i.e., an air-permeable container made of synthetic resin which comprises an allicin component extracted from garlic and a capcycin component extracted from pepper to be used as a rice preservative. However, the above vegetable oils are volatile and exhibit an insecticidal effect mostly via the fumigation of the volatilized insecticidal components. Due to the drastic volatilization of the active ingredients that occurs within a very short period of time, vegetable oils have problems of exhibiting inconsistent insecticidal effects. Thus, formulations that are capable of retaining a consistent insecticidal effect by inhibiting the rapid volatilization of the above vegetable oils and modulating the release rate are in high demand.

Previously, pest control has been focused on agricultural products in distribution and storage, and there has no report yet on absorbent articles to be used in direct contact with the human body which additionally have an insecticidal effect for the purpose of pest control. [Disclosure] [Technical Problem] Thus, there is a need to develop a formulation that can effectively prevent insect pests from invading disposable absorbent articles while continuously maintaining the insecticidal effect of the natural plant extract that has human- friendly and eco-friendly advantages. [Technical Solution] The inventors of the present invention have endeavored to develop a human-friendly and eco-friendly method that can prevent larvae or adult insects from invading disposable absorbent articles during distribution and storage. As a result, the inventors have found that disposable absorbent articles comprising a microcapsule in which the extract of a natural plant such as cinnamon, rosemary, lavender, mint, eucalyptus, and the like exhibiting an insecticidal effect that is microencapsulated can effectively and continuously prevent the infiltration of larvae, e.g., Indian meal moth, into the disposable absorbent articles during distribution and storage, while being nontoxic to the human body.

Thus, the objective of the present invention is to provide a disposable absorbent article comprising an encapsulated natural plant extract which is harmless to the human body while continuously exhibiting an insecticidal effect that can effectively prevent larvae or adult insects from invading the article during distribution and storage.

In order to achieve the above objective, a disposable absorbent article comprising a liquid permeable top sheet, an absorbent core, and a liquid impermeable back sheet is provided, characterized in that an insecticidal microcapsule in which the extract of at least one natural plant selected from the group consisting of cinnamon, rosemary, lavender, mint and eucalyptus is microencapsulated and applied to the absorbent article.

[Advantageous Effects]

The disposable absorbent article according to the present invention comprising a microencapsulated plant extract which naturally exhibits an insecticidal effect and is nontoxic to the human body is capable of continuously providing a superior insecticidal effect and can thus effectively prevent the invasion of insect pests into the absorbent article that may occur during distribution and storage.

[ Description of Drawings ]

Fig. 1 shows photographs of the experimental results illustrating the insecticidal effect of disposable diapers comprising a microencapsulated natural plant extract according to the present invention.

[Best Mode] The present invention provides a disposable absorbent article comprising an encapsulated natural plant extract exhibiting an insecticidal effect.

Specifically, the present invention provides a disposable absorbent article comprising a liquid permeable top sheet, an absorbent core, and a liquid impermeable back sheet, characterized in that an insecticidal microcapsule in which the extract of at least one natural plant selected from the group consisting of cinnamon, rosemary, lavender, mint, and eucalyptus is microencapsulated and applied thereto.

Natural plants having an insecticidal effect that are suitable for the present invention include, e.g., cinnamon, rosemary, lavender, peppermint, and eucalyptus.

Cinnamomum cassia bark is the bark of an evergreen tree belonging to the family Lauraceae, native to Southern China and Vietnam. Cinnamon bark refers to the bark of the tree, while Cinnamomi ramulus is the twig of the tree, Cinnamomi cortex spissus is the thick bark, and Cassiae cortex interior is the spread dried thick bark of an old tree. Cinnamon bark includes from 1 to 3.4% of essential oil such as cinamic aldehyde, cinnamyl aldehyde, etc., from 2 to 3% of tannic acid, a mucilaginous juice, a carbohydrate and the like, and has been reported to contain higher levels of essential oil at the age of 5 to 6 years. Cinnamon bark has been adapted for various applications, ranging from a diaphoretic, an antipyretic, a pain killer to spices for foodstuff. In addition, cinnamon bark has been known to stimulate intestinal peristalsis, while having a preservative effect of inhibiting intestinal abnormal fermentation. Furthermore, cinnamon bark has been traditionally used as an ingredient in oriental medicine for those who have a delicate constitution and weak vital energy, based on the expectation that it has an immune-stimulating effect, but its accurate mechanism is unknown.

Compositions comprising a cinnamon extract have been disclosed in Korean Patent Laid-open Publication No. 2000-1280 (composition for preventing and treating atherosclerosis comprising extract of cinnamon bark), Korean Patent Laid-open Publication No. 2001-18668 (cosmetic composition containing Cinnamomi Cortex extracts), and Korean Patent Laid-open Publication No. 2004-46309 (oral care composition comprising nanoparticulated cinnamon extract), but none of the above describes the insecticidal effect of cinnamon.

Rosmarinus officinalis L. is an evergreen woody plant belonging to the family Labiatae, native to the Mediterranean region, and is an herb used for all kinds of applications, including food, medicine, beauty products, spice, and ornaments. The stems, flowers, and leaves of rosemary are all useable. In particular, the essential oil extracted from rosemary is excellent for treating inertia or fatigue recovery. Rosemary is believed to prevent the generation of edema and scurf and to stimulate hair growth. Its pungent odor provides a vital spark to brain cells, thereby enhancing memory and concentration to effectively prevent dementia. Due to its function in stimulating digestion, it is ideal for the treatment of dyspepsia, stomach ache, etc. Further, it is used for antibacterial life goods. Rosemary contains an essential oil consisting mainly of 1,8-cineole, camphor, etc. and a bitter component such as a rosmarinic acid and the like. Thus, it has been used for medicinal purposes, e.g., a stomachic, a carminative, an anti-inflammatory agent, etc. (Bisset NG, Herbal drugs CRC press, London, 428-430, 2000; Duke JA, et al., Handbook of Medicinal Herbs CRC press, London, 630-632, 2002). Rosemary is now cultivated as a potted herb even in Korea. The oil of rosemary is used for aroma therapy in various types of formulations, in combination with other different types of aromas. Meanwhile, a number of studies are being conducted to develop a food preservative using the antioxidant properties of rosemary. (Choo JJ et al., Korean J. Food Culture 16: 34-138, 2003; Koleva II et al., Phytochem Anal. 13: 8-17, 2002). However, the insecticidal effect of rosemary is not disclosed anywhere in the above references.

Lavendula angustifolia Mill is a subshrub and known to grow about 60 cm long. Its native terrain extends across the Canary Islands, the Mediterranean, and India. Its principle components particularly include an essential oil distilled from its aerial parts (mainly, monoterpenes), while caffeic acid and depsides are obtained from its leaves. The essential oil obtained from lavender has been traditionally used for cosmetics and therapy applications, such as aroma therapy. For example, the antibacterial, antifungal, spasmolytic, sedative, and antidepressant properties of lavender oil are disclosed in HMA Cavanagh et al., Phytother. Res. 16: 301-308, 2002. In Germany, formulations using the lavender flower extract are being positively studied for restlessness, sleep disorders, functional ailment of the abdomen and meteorism, and as a bath additive for spa treatments. It has recently been found that the oral administration of lavender oil brings considerable improvements to various disease-related symptoms in patients suffering from neurasthenia, somatization disorder, and/or post-traumatic stress disorder. Animal tests also show that the oral administration of lavender oil significantly inhibits stress-induced behavioral changes. However, the insecticidal effect of lavender has not yet been reported.

Peppermint is a perennial plant of dicortyledon, order Lamiales, and family Lamiaceae. Since it has a cooling effect on the skin and mucous membranes and is effective as an antibacterial agent and a pain relief agent, it has been used in food and medicine, as an aromatic, a cordial, and a bath additive. Peppermint oil is known to eliminate toxic substances, to be effective in treating dermatitis, used as a vaccine, to treat dry tinea, and to ease pruritus, etc. It is also used to expand capillaries and exert a cooling effect and known to be effective in itch relief, inflammation, sun burns and the like. Further, peppermint oil is known to be effective in softening the skin and removing acne while being good for psychic fatigue, depression, nervous breakdown, etc. However, special attention is required with respect to the dosage of peppermint oil because it can cause a strong and intoxicating feeling. In particular, extreme caution must be exercised when applying peppermint oil to sensitive skin areas, e.g., around the eyes, because it may aggravate the skin and mucous membranes. The use of peppermint oil by pregnant or breastfeeding women should be restricted. Eucalyptus globulus is an aromatic plant that is indigenous to Australia. There are more than 300 species of eucalyptus, most of which are cultivated throughout the tropics. The leaves of eucalyptus contain from about 2 to 7% essential oil, which is a colorless or straw-colored fluid with a characteristic stinging odor and a pungent but refreshing taste. Eucalyptus is used in soap, liquor, fragrances, medicine and the like - in particular, in antiseptics, expectorants, gargles, antitussives, disinfectants, etc.

The extracts of the above natural plants can be obtained via conventional extraction methods using water or a lower alcohol, or commercially available extracts of each natural plant can be purchased.

Conventional methods for extracting a natural plant, for example, involve: drying a natural raw material followed by powder grinding; adding, based on the dry weight, about 1- to 10-fold, specifically about 2- to 6-fold amount of water or lower alcohol to the powder; subjecting the mixture to ultrasonic extraction for about 1-5 hours, specifically about 2-4 hours, while heating the mixture at about 20-60 "C, specifically about 30-50 ^°C, and then cooling and subjecting to filtration; and concentrating the filtered products using a rotating evaporator under reduced pressure, where the residue left after filtration may be subjected to repeated filtration for at least two times. Suitable lower alcohols that can be used as an extraction solvent include methanol, a methanol aqueous solution, ethanol, an ethanol aqueous solution, normal propanol, isopropanol, normal butanol, or a solvent mixture thereof. Specifically, water or ethanol can be used.

In addition, a non-polar solvent-soluble natural extract, specifically a dichloromethane soluble extract, suitable for the present invention, can be obtained by suspending the natural extract obtained above in distilled water and then subjecting the suspension to hot water extraction or fractional extraction using a non-polar solvent such as dichloromethane, n-hexane, chloroform, or ethyl acetate.

Moreover, the natural extracts according to the present invention can be prepared by other essential oil extraction methods such as steam distillation, compression, adsorption, exudation, super-critical gas extraction and the like.

The natural plant extracts mentioned above can be used alone or in combination as a mixture of two or more. The substrate solvents for dissolving at least one natural plant extract mentioned above and for enhancing the compatibility and scent duration thereof include dipropylene glycol, dioctyl adipate (DOA), isopropyl myristate (IPM), propylene glycol (PG), floralyn, etc.

The natural plant extract according to the present invention exhibits an insecticidal effect against adult pests or the larvae of various types of pests. The pests include, but are not limited to, hygiene pests, stored product/food pests, agricultural pests, wood pests, and forest pests. Examples of hygiene pests include, but are not limited to, mosquitoes, flies, cockroaches, ticks, and ants. Examples of stored product/food pests include, but are not limited to, the Indian meal moth {Plodia interpunctella), red bean weevil, rice weevil, Cardia cautella, Paralipia gularis, angoumois grain moth (Sitotroga cerealellά), Tribolium castaneum, Cigarette beetle (Lasioderma serricorne), Oryzaephilus surinamensis, Phraortes illepidus Brunner von Wattenwy, black carpet beetle (Attagenus unicolor), Dermestes maculates, and varied carpet beetle (Anthrenus verbasci). Examples of wood pests include, but are not limited to, termites (white ants), and examples of forest pests include, but are not limited to, the Pine needle gall midge (Thecodiplosis japonensis), Fall webworm moth {Hyphantria cunea), Lackey moth (Malacosoma neustria), Gypsy moth (Lymantria dispar), Cicada moth (Lymantria dispar), gold beetles (Mimela splendens), aphid, mites, Matsurocus thunbergianae, Acantholyda parki, Dioryctria abietella, Common pine shoot beetle (Tomicus piniperda), and the like. Examples of agricultural pests include, but are not limited to, Trialeurodes vaporariorum, brown planthopper (Nilaparvata lugens Stal), small brown planthopper {Laodelphax striatellus Fallen), White backed plant hopper (Sogatella furcifera), rice green leafhopper, zigzag-striped leafhopper, etc.

The natural plant extracts prepared above are subjected to microencapsulation in order to make them exhibit a continuous insecticidal effect. The term "encapsulation" used herein refers to a process of preparing a particle comprising an active ingredient inside and a shell outside, where the active ingredient contained inside the shell and the ingredient of the shell can be determined differently depending on the purpose of the encapsulation. The encapsulation may be carried out, for example, 1) to make a change in state from a liquid to a solid for ease in handling or storing, 2) to separate substances which react to one another, 3) to modulate the release rate of the active ingredient inside the capsule, 4) to mask an unpalatable taste or smell, or 5) to protect an unstable substance. The microcapsule of a natural plant extract exhibiting an insecticidal effect prepared according to the present invention can exhibit a continuous insecticidal effect by modulating the release rate of the natural plant extract encapsulated in the capsule and at the same time protecting the safety of the natural plant extracts against the external environment. The term "insecticidal microcapsule" used herein refers to a microcapsule comprising a natural plant extract exhibiting an insecticidal effect microencapsulated within a shell, thereby ensuring the controlled release and safety of the natural plant extract to continuously exhibit a superior insecticidal effect.

The insecticidal microcapsules according to the present invention can be prepared by various methods known in the art. Processes for encapsulating an oleophilic component generally include interfacial polymerization, spray drying, in-situ polymerization and the like. Particularly, a process for preparing a microcapsule comprising an aromatic component as a core material is disclosed in U.S. Patent Nos.. 5,011,634, 4,965,025, and 4,824,823 and German Patent No. 3,543,803, etc. According to the present invention, an insecticidal microcapsule comprising a natural plant extract may be prepared by: preparing a distillation by dissolving at least one natural plant extract in a hydrocarbon solution; stirring the distillation at 100 to 12,000 rpm with an emulsifier to form a finely dispersed emulsion; preparing a pre-polymerization solution by using urea or melamine, formaldehyde, and water; and then polymerizing the pre-polymerization solution at 50 to 90 ^°C by adding a weak acidic additive, where the emulsion temperature is between 10 and 50 ^°C and the pre-polymerization solution is cooled at from 30 to 60 °C before polymerization.

The insecticidal microcapsule prepared above contains from 5 to 30% by weight of a natural plant extract. When the amount of the natural plant extract within the microcapsule is too low to emit a scent, a sufficient insecticidal effect cannot be expected. On the other hand, when the amount of the natural plant extract is too high, the product may emit too strong an odor and may offend the customers in spite of its superior insecticidal effect.

The thickness of the urea-formaldehyde or melamine-formaldehyde layer of the microcapsule can be adjusted by varying the ratio of the emulsion to the pre-polymerization solution. When the resin layer is too thin, the durability will be poor; when the resin layer is too thick, the microcapsule will not burst, thereby prohibiting the insecticidal effect of the natural plant extract from being exhibited in the disposable absorbent article.

In the disposable absorbent article comprising a liquid permeable top sheet, an absorbent core, and a liquid impermeable back sheet, the insecticidal microcapsules prepared according to the present invention may be applied to the liquid permeable top sheet, the absorbent core, the liquid impermeable back sheet, a flap, a loop, a hook, a packaging material and the like to exhibit their insecticidal effect. The insecticidal microcapsules may specifically be applied to the back sheet to effectively prevent insects from invading the articles. The insecticidal microcapsules according to the present invention are specifically incorporated into the absorbent article at about from 0.006 to 0.03% by weight based on the total weight of the disposable absorbent article. In one embodiment of the present invention, the insecticidal microcapsules according to the invention are applied to the back sheet in a film or nonwoven form to make a disposable absorbent article having an insecticidal effect. The back sheet of absorbent article of the present invention may be in the form of a film, a nonwoven, and a film/nonwoven laminate.

First, the back sheet in a film form comprising an insecticidal microcapsule will be explained. The back sheet in a film form according to the present invention may be prepared by using a molding or expanded film extrusion or other suitable film-forming technologies after preparing a masterbatch by blending insecticidal microcapsules with a thermoplastic polymer forming a back sheet matrix. However, in order to maintain a continuous insecticidal effect, it is desirable to prepare the back sheet by casting the masterbatch at about from 170 to 240 ^°C, specifically about from 180 to 230 ^°C through a T-die. The above back sheet in a film form prepared according to the present invention through a T-die can be prepared as follows:

First, a masterbatch is prepared by mixing insecticidal microcapsules according to the present invention with a thermoplastic polymer in a desired ratio. The masterbatch is incorporated into an extruder and then melted and mixed. A fine dispersion is induced through a Screen Pack device inside the T-die and the impurities are removed. The masterbatch is subsequently cast into a film through the T-die and the casted film passes through a cooling roll. The film is then cut into a desired width and then coiled to prepare a back sheet in a film form according to the present invention. Corona treatment or embossing, which is a typical process for preparing a back sheet, can be added to the above preparation process, if necessary.

The masterbatch comprising insecticidal microcapsules which are used for the preparation of a back sheet in a film form according to the present invention contains from 40 to 50% of a thermoplastic polymer, from 40 to 50% of a filler, from 1 to 10% of insecticidal microcapsules, and from 0.1 to 5% of additives. The additives in the above masterbatch comprising insecticidal microcapsules may vary depending on the desired properties, such as antioxidants, dyes, etc. Suitable thermoplastic polymers used for the masterbatch comprising insecticidal microcapsules include, but are not limited to, VLDPE (very low density polyethylene), LDPE (low density polyethylene), HDPE (high density polyethylene), polypropylene, ethylene and a copolymer of ethylene with C₃-Ci₂ α-olefins, a copolymer of propylene with ethylene and/or C₄-Ci₂ α-olefins, a soluble polyolefin comprising propylene-based polymers comprising all the atactic and isotactic propylene units in the polypropylene main chain, an elastomer such as polyurethane, copolyether ester, and polyester degradable resin, a polyamide polyether block copolymer, an ethylene vinyl acetate copolymer, a block copolymer of the formula A-B-A' or A-B such as copoly(styrene/ethylene-butylene), styrene-poly(ethylene-butylene)-styrene, polystyrene/poly(ethy lene-butylene)/polystyrene, poly(styrene/ethylene-butylene/styrene), and the like.

The suitable amount of the insecticidal microcapsule of the present invention to be applied in accordance with the above process may be between about 0.01 and 0.5% by weight, specifically between about 0.01 to 0.3% by weight, based on the total weight of the back sheet. When the amount of the above insecticidal microcapsule is less than 0.01% by weight, the desired level of insecticidal effect cannot be attained. However, when the amount of the above insecticidal microcapsule is greater than 0.5% by weight, the odor reaches a detectable level and is thus undesirable.

In another embodiment, a film imparted with permeability may also be used as a back sheet in the present invention by extending a film monoaxially or biaxially through a number of steps, e.g., preheating, extending, and heat-fixing, where the film is prepared by casting a masterbatch containing insecticidal microcapsules additionally comprising a filler particle such as CaCO_3,, and where the extension process is conducted twice, the suitable extension temperature being set in consideration of the evaporation and decomposition of the insecticidal microcapsules at from about 20 to 70 ^°C , specifically from about 40 to 45 ^°C , and the suitable extension ratio being about 160 to 350%, specifically about 180 to 220%. The heat-fixing process is carried out between 20 and 100^°C , specifically at about 70 ^°C or less, in consideration of the evaporation and decomposition of insecticidal microcapsules.

The above extended film has a thickness that allows structural integration and liquid impermeability. The film after extension has a thickness of about 50 to 300 microns, specifically about 100 microns.

In addition, the back sheet of the present invention may be formed from spunbond, meltblown, thermal-bonded carded web, thru-air bonded carded web, spunlace, spunbond-meltblown-spunbond (SMS), or spunbond-meltblown-meltblown-spunbond (SMMS), specifically a nonwoven of SMS or SMMS prepared by conventional methods using a masterbatch comprising the insecticidal microcapsules.

The nonwoven comprising the insecticidal microcapsules may be prepared, for example, by using impregnation, from a yarn comprising insecticidal microcapsules obtained by mixing insecticidal microcapsules with a masterbatch, or by using a printing method. Specifically, the nonwoven obtained by using impregnation may be prepared by carrying out the following steps:

1) preparing a nonwoven by an ordinary process;

2) passing the prepared nonwoven through a sedimentation tank having insecticidal microcapsules according to the present invention incorporated therein; and 3) drying the nonwoven that has passed through the sedimentation tank with hot air at a set temperature.

In one embodiment of the present invention, after preparing an ordinary nonwoven, the nonwoven is treated with insecticidal microcapsules by a post-treatment process, e.g., unwinding the nonwoven that is wound around an unwinding roller and passing the nonwoven through a sedimentation tank having insecticidal microcapsules and adhesives mixed therein, and after drying the nonwoven by using a hot-air dryer set at a constant temperature to adhere insecticidal microcapsules to the nonwoven, winding the nonwoven around a winding roller to obtain a nonwoven coated with insecticidal microcapsules.

The nonwoven obtained by using a printing method may be prepared by carrying out the following steps: 1) preparing a nonwoven by an ordinary process; and

2) passing the prepared nonwoven through a printing plate as well as a printing solution, in which the insecticidal microcapsules according to the present invention are dispersed to adhere to the solution in which the insecticidal microcapsules are dispersed to the nonwoven. In another embodiment of the invention, after a nonwoven is ordinarily prepared, the nonwoven that is wound around an unwinding roller is unwound and passed through a printing plate as well as a printing solution in which the insecticidal microcapsules are dispersed. The solution comprising insecticidal microcapsules dispersed therein is adhered to the nonwoven like printing and accordingly a nonwoven comprising insecticidal microcapsules attached thereto in a desired shape at a desired site through printing is obtained.

The nonwoven obtained by using a masterbatch can be prepared by carrying out the following steps in a consecutive manner:

1 ) preparing a masterbatch by mixing a thermoplastic polymer for the preparation of a nonwoven and the insecticidal microcapsules according to the present invention in a specific ratio;

2) preparing a yarn comprising insecticidal microcapsules through a fiber spinning device using said masterbatch; and

3) preparing a nonwoven through a nonwoven molding device using said yarn. The nonwoven specifically comprises from 0.01 to 0.5% by weight of insecticidal microcapsules according to the present invention based on the weight of the thermoplastic polymer constituting the nonwoven. In another embodiment of the invention, before preparation of the nonwoven, insecticidal microcapsules are incorporated into the yarn used for the preparation of a nonwoven to prepare a nonwoven comprising insecticidal microcapsules. The yarn is prepared by incorporating insecticidal microcapsules into a masterbatch. That is, a masterbatch is prepared by mixing a thermoplastic polymer with insecticidal microcapsules in a specific ratio; the yarn comprising insecticidal microcapsules is prepared by using a fiber spinning device; then, the yarn comprising insecticidal microcapsules is put into a nonwoven molding device so that insecticidal microcapsules are included in the nonwoven. The process for preparing a nonwoven from yarn prepared by incorporating insecticidal microcapsules into a masterbatch for the preparation of a nonwoven can overcome the shortcomings of insecticidal microcapsules being stuck to the disposable absorbent article user's skin or washed off by secretion, etc. after falling out of the nonwoven. In addition, the back sheet according to the present invention may be prepared by laminating the insecticidal microcapsule-containing film with an ordinary nonwoven by using adhesives, such as a solvent type glue, hot melt adhesive, or cold glue, by heat sealing or laminating the insecticidal microcapsule-containing nonwoven with an ordinary film, or can be a film/nonwoven laminate in which the insecticidal microcapsule-containing film and the insecticidal microcapsule-containing nonwoven are laminated, where the amount of the insecticidal microcapsule to be applied is between about 0.01 to 0.5% by weight based on the weight of the film/nonwoven laminate

The liquid impermeable back sheet prepared above in the form of a film or nonwoven comprising insecticidal microcapsules containing at least one natural plant extract according to the present invention can be applied to a conventional disposable absorbent article together with a liquid permeable top sheet and an absorbent core known in the art.

Accordingly, a disposable absorbent article comprising a liquid permeable top sheet that is in contact with the user's skin when used, an absorbent core that is disposed under the top sheet and absorbs and spreads the body fluids, and a liquid impermeable back sheet that is disposed under the absorbent core, where the liquid impermeable back sheet comprises insecticidal microcapsules containing at least one natural plant extract, falls within the scope of the present invention.

The disposable absorbent article comprising insecticidal microcapsules according to the present invention includes, but is not limited to, baby diapers, adult diapers, sanitary napkins, toilet training underpants, panty liners, and the like.

The top sheet used in the present invention can be prepared with a wide variety of materials including porous foam, networked foam, perforated plastic film, nonwoven, natural fabric, synthetic fabric, or a combination of natural and synthetic fabrics. For example, the top sheet can be composed of a spunlace nonwoven, spunbonded fϊberweb of polyolefin fiber, or bonded carded web made from natural fabric and/or synthetic fabric. In this regard, the top sheet may be of a hydrophobic material treated with a surfactant or can be treated in different ways so as to be imparted with a desired level of wettability and liquid permeability. Examples of the top sheet are disclosed in U.S. Patent Nos. 5,879,343, 5,490,846, and 5,364,382 and U.S. Patent Application No. 09/209,177, etc.

The absorbent core applicable to the present invention may comprise at least one absorbing agent, such as a super absorbent particle, wood pulp fluff fabric, synthetic weed pulp fabric, synthetic fabric, or a mixture thereof. The absorbent core may exist in various forms and its sizes may differ depending on the target absorbent amount, the target use of the absorbent article, and other factors known to those skilled in the art.

Hereinafter, the present invention will be explained in more detail with reference to the following examples. The following examples are provided in order to more specifically explain the present invention, but it will be appreciated by those with ordinary knowledge in the art that this invention is not limited by these examples.

EXAMPLES

Example 1: Preparation of insecticidal microcapsules

In order to prepare insecticidal microcapsules comprising cinnamon extract and rosemary extract, each of cinnamon extract (CAS No 8015-91-6; Cinnamon Bark Oil, Trinity Company), rosemary extract (CAS No. 8000-25-7; Rosemary Oil, Trinity Company), and a mixture thereof were dissolved in and diluted with a hydrocarbon solvent. The diluted solution was then stirred using a homogenous mixer at 2,000-3,000 rpm for 5-10 minutes with a cationic surfactant as an emulsifier to prepare a micronized emulsion in a certain size. Melamine, formaldehyde, and water were mixed together in a certain ratio and adjusted to have a neutral pH. The mixture was stirred at a suitable temperature to prepare a pre-polymerization solution. To the pre-polymerization solution and the finely dispersed emulsion, from 0.1 to 5% of an acetic acid, which is a weak acidic additive, based on the emulsion, was added. While stirring the mixture at a suitable temperature for 100 to 300 minutes, a polymerization reaction was carried out. After cooling to room temperature, ammonia was added to the mixture to remove residual formaldehyde and then stirred for at least one hour. Subsequently, insecticidal microcapsules comprising a cinnamon extract, rosemary extract, and a mixture thereof having a mean particle diameter of from 1 to 10 μm were obtained.

Example 2: Preparation of a disposable absorbent article comprising insecticidal microcapsules having a backsheet in the form of a film

10% of the insecticidal microcapsules comprising a cinnamon extract, rosemary extract, and a mixture thereof prepared in Example 1, 40% low-density polyethylene, and 50% filler (calcium carbonate) were mixed together to prepare a masterbatch comprising insecticidal microcapsules. The prepared masterbatch was cast through T-die at about 200 ^°C to prepare a film. The prepared film was monoaxially extended with an extension ratio of about from 200% to 300% at an extension temperature of about 40 ^°C to prepare a film for an air-permeable back sheet. A disposable diaper was prepared by conventional methods using the above prepared film as a back sheet.

Example 3: Preparation of a disposable absorbent article comprising insecticidal microcapsules having a backsheet in the form of a nonwoven

10% of the insecticidal microcapsules comprising cinnamon extract, rosemary extract, and a mixture thereof prepared in Example 1 and 90% polypropylene were mixed together to prepare a masterbatch comprising insecticidal microcapsules. The prepared masterbatch was mixed with polypropylene at a 1 :99 ratio. The mixture was spun through a fiber spinning device to prepare yarn comprising insecticidal microcapsules. A nonwoven was prepared using the prepared yarn through a nonwoven molding device. A disposable diaper was prepared by conventional methods using the above prepared nonwoven as a back sheet.

Example 4: Insecticidal effect of a disposable absorbent article comprising insecticidal microcapsules

In order to identify the insecticidal effect of the disposable diaper prepared in above Examples 2 and 3 comprising insecticidal microcapsules containing cinnamon extract, rosemary extract, or a mixture thereof, the following experiment was carried out.

First, disposable diapers comprising insecticidal microcapsules containing cinnamon extract (CIN), rosemary extract (R), or a mixture thereof (RC) and those without the insecticidal microcapsules serving as a control group were each loaded in four (4) high-density pest spaces (40 x 30 x 40 cm) made of acryl. 500 of 4-week-old Plodia interpunctella larvae were put into the spaces (Fig. 1). The temperature inside the high-density pest spaces was maintained at 28 ^°C and a relative humidity of between 70 and 75%. The number of attracted larvae in each diaper was examined every 24 hours for 30 days, after putting the larvae into the spaces. The results were statistically calculated using the analysis of variance (NOVA test). [Table 1 ]

As seen from Table 1 above, the disposable diapers comprising insecticidal microcapsules containing rosemary extract, cinnamon extract, and a mixture thereof according to the present invention show statistically significant lower numbers of attracted larvae both inside and outside the diaper products compared to the non-treated control group. A, B, AB, C, and BC in the above table represent individual groups categorized as having statistical significance: group A has a lesser number of larvae that enter the disposable absorbent article than group B and B has a lesser number of larvae than group C, while AB group represents an intermediate value between groups A and B and group BC represents an intermediate value between groups B and C.

The above data clearly shows that the disposable absorbent articles according to the present invention comprising microcapsules containing a plant extract which naturally exhibits an insecticidal effect and is nontoxic to the human body continuously exhibit a superior insecticidal effect and can thus effectively block the invasion of insect pests into the products that may occur during distribution and storage of the products. Although specific embodiments of the present invention have been described herein in great detail, it will be appreciated by those with ordinary knowledge in the art that these are merely illustrative embodiments and that the present invention is not limited by these embodiments. Accordingly, it can be said that the substantial scope of the present invention is defined by the claims attached hereto and the equivalents thereof.

Claims

[CLAIMS] [Claim 1 ]

A disposable absorbent article comprising a liquid permeable top sheet, an absorbent core, and a liquid impermeable back sheet, characterized in that an insecticidal microcapsule in which a natural plant extract exhibiting an insecticidal effect is microencapsulated and applied to the absorbent article.

[Claim 2]

A disposable absorbent article according to Claim 1 , wherein a natural plant is selected from the group consisting of cinnamon, rosemary, lavender, mint, eucalyptus, or mixtures thereof.

[Claim 3 ]

A disposable absorbent article according to Claim 1 or 2, wherein the insecticidal microcapsule contains from 5 to 30% by weight of a natural plant extract based on the total weight of the microcapsule.

[Claim 4]

A disposable absorbent article according to Claim 1 or 2, wherein the article comprises from 0.0006 to 0.03% by weight of said insecticidal microcapsule based on the total weight of the disposable absorbent article.

[Claim 5] A disposable absorbent article according to Claim 1 or 2, wherein said insecticidal microcapsule is applied to the liquid impermeable back sheet, the liquid permeable top sheet, the absorbent core, a flap, a loop, a hook, or a packaging material of the absorbent article.

[Claim 6] A disposable absorbent article according to Claim 5, wherein said insecticidal microcapsule is applied to a liquid impermeable back sheet in a film or a nonwoven form. [Claim 7]

A disposable absorbent article according to Claim 6, wherein said back sheet comprises from 0.01 to 0.5% by weight of the insecticidal microcapsule based on the total weight of the back sheet. [Claim 8]

A disposable absorbent article according to Claim 1 or 2, wherein said disposable absorbent article is a baby diaper, adult diaper, sanitary napkin, toilet training underpants, and panty liner.