WO2005065604A1

WO2005065604A1 - Wound dressing

Info

Publication number: WO2005065604A1
Application number: PCT/KR2004/003201
Authority: WO
Inventors: Myung-Hwan Park; Chul-Ho Eo; Pil-Eun Lee; Hyun-Jung Kim; Duk-Hee Ryu
Original assignee: Biopol Co., Ltd.
Priority date: 2004-01-07
Filing date: 2004-12-07
Publication date: 2005-07-21

Abstract

Disclosed is a wound dressing protecting wounds through direct contact with wounds. The dressing includes a wound contacting layer that is made of a microporous polyurethane film, contains a plurality of micropores with an average diameter of 5-80 gm and a means for absorbing highly viscous wound exudates, and is 10-200 µm thick, and a supporting layer that is combined with an upper surface of the wound contacting layer. The supporting layer is composed of a base sheet layer and/or a fibrous absorbent sheet layer with high absorptivity. The means for absorbing highly viscous wound exudates is a plurality of macropores 100 1,000 µm in diameter and/or slits 0.1-10 mm long. The dressing preferably further includes an outer protective film layer that is combined with an upper surface of the supporting layer. Due to its structural properties, the dressing has excellent non-adherence to wounds and high absorptivity to exudates, prevents the infiltration of external bacteria and impurities and provides a suitably moist environment to wounds, thereby promoting wound healing.

Description

[DESCRIPTION]

WUND DRESSING

[Technical Field] The present invention relates, in general, to an occlusive wound dressing for use in covering and protecting wounds and promoting wound healing through direct contact with wounds. More particularly, the present invention relates to a wound dressing which is excellent in absorptivity, waterproofing ability, moisture permeability, non-adherence to wounds and an ability to create an appropriate moist environment.

[Background Art] The skin is an organ that protects the body against external stimuli and microbial invasion and functions to prevent water loss from the body and control body temperature. Wounds, whether the skin is damaged, burned or otherwise traumatized, cause the skin to lose its full function, at least in the wound area, resulting in several side effects caused by water loss and microbial infection. In severe cases, the wound area is difficult to cure, or secondary functional disorder or damage occurs . In the worst case, wounds may be fatal to the patient. Therefore, it is essential to dress wounds using proper dressings in order to help wounds heal more quickly and minimize secondary side effects . Major factors involved in wound healing include moisture environment, microbial infection, debris, necrotized tissues, temperature, oxygen concentration and pH. Accordingly, ideal dressings are those which meet the following requirements: maintenance of an appropriate moist environment at the face contacting the wound, rapid absorption of exudates from the wound, easy attachment to and removal from the wound, gas/moisture vapor permeability, heat insulation against the exterior, defense against bacterial infection, harmlessness to the body, and economic benefits . Conventional gauze and non-woven dressings can absorb exudates from wounds well, but can neither defend against bacterial infection nor create moist conditions at wound sites, thus retarding wound healing. In addition, because gauze and non-woven dressings are apt to hold fast to wounds, they may damage newly generated tissue with accompaniment of discomfort upon their removal. Further, lints removed from the surface of the dressings remain on the wounds. Among these problems, the attachment to the wound area and generation of the bits of the projected fiber can be prevented by preparing non-woven and gauze dressings using a polyethylene film. However, these dressings still have the disadvantage of not providing moist conditions to wounds . Thus far, a variety of occlusive dressings that are capable of providing moist conditions to wounds have been developed. However, occlusive dressings in current use are very expensive and are difficult to control their absorption capacity and moisture permeability. With these problems, occlusive dressings are not applied to a broad spectrum of wounds, but mainly to specific wounds. Occlusive dressings in current use may be broken down into the following five types: film, foam, hydrocolloid, hydrogel, and non-woven using sodium alginate. In particular, film-type dressings are convenient in use and easy to be manufactured, but have poor absorptivity, and is thus limited in use. Also, the other dressings have significant problems with respect to convenience in use, easiness in manufacture and economic benefits . U.S. Pat. Nos. 4,202,800, 4,367,327 and 4,686,137 disclose polyurethane films prepared using hydrophilic polyols, which can be used as dressings. The film-type dressings are useful for slight wounds, such as abrasions or erosions, and skin graft donor sites, but not suitable for wounds generating a large quantity of exudates due to their properties of poor moisture permeability and absorptivity. In addition, the film-type dressings are convenient to use and easy to manufacture, but can be used only on very slight wounds due to their poor exudate absorptivity and moisture permeability.

[Disclosure] [Technical Problem] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a wound dressing including a microporous polyurethane film layer that contacts wounds and contains micropores, and a means for absorbing highly viscous wound exudates on a wound-contacting surface, with which excellent absorptivity to wound exudates and non-adherence to wounds are provided. It is another object of the present invention to provide a wound dressing which includes a highly-absorptive fibrous absorbent sheet that provides an appropriate moist environment to wounds and is applicable to a variety of wounds, from slight wounds to wounds generating large amounts of exudate, such as ulcerations or burns. It is a further object of the present invention to provide a wound dressing including an outer protective film with excellent air permeability, moisture permeability and waterproofing ability, for defending against the infiltration of bacteria and other external impurities, protecting against the leakage of wound exudates and providing an appropriate moist environment. [Technical Solution] In order to accomplish the above objects, the present invention provides a wound dressing, including a wound contacting layer that is made of a microporous polyurethane film, contains a plurality of micropores with an average diameter of 5-80 μm and a means for absorbing highly viscous wound exudates, and is 10-200 μm thick, and a supporting layer that is combined with an upper surface of the wound contacting layer. The supporting layer is composed of a base sheet layer and/or a fibrous absorbent sheet layer with high absorptivity. The means for absorbing highly viscous wound exudates is a plurality of macropores 100-1,000 μm in diameter and/or slits 0.1-10 mm long. The dressing according to the present invention preferably has an outer protective film layer that is combined with an upper surface of the supporting layer. That is, the wound dressing according to the present invention has a multi-layered structure including a wound contacting layer that is made of a microporous polyurethane film having absorptivity to wound exudates and non-adherence to wounds, a base sheet layer (or a fibrous absorbent layer) that supports the wound contacting layer and holds absorbed wound exudates, and preferably an outer protective film layer that prevents the infiltration of external bacteria and impurities and maintains suitable moisture permeability. The thickness and form of the wound dressing may vary depending on the intended purpose. The wound dressing has, but is not limited to, a thickness ranging from 0.1 mm to 10 mm.

[Advantageous Effects] Due to its properties of non-adherence to wounds, high exudate absorptivity, formation of a suitable moist environment, defense against infiltration of external impurities, etc., the dressing of the present invention has excellent wound healing effect, is applicable to diverse wounds from slight wounds to severe wounds generating a large quantity of exudates, and causes no discomfort upon changing by no adherence to wounds .

[Description of Drawings] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a schematic cross sectional view of a dressing according to a first embodiment of the present invention; Fig. 2 is a schematic cross sectional view of a dressing according to a second embodiment of the present invention; Fig. 3 is a schematic sectional view of a surface of a wound contacting layer of the dressing of Fig. 1 or Fig. 2; Fig. 4 is a scanning electron microphotograph (SEM) showing a surface of a microporous polyurethane film prepared in a Preparation Example of the present invention; Fig. 5 is a schematic cross sectional view of a dressing according to a third embodiment of the present invention; Fig. 6 is a schematic cross sectional view of a dressing according to a fourth embodiment of the present invention; and Fig. 7 is a schematic cross sectional view of a dressing according to a fifth embodiment of the present invention.

[Best Mode] As used herein, the term "combined" refers to all of states at which components (layers) of a dressing are bound to each other by a binding means, such as an adhesive, thermal compression or microwaves, which one component (first layer) is bound to another component (second layer) by coating a solution comprising the first layer onto the second layer, and which layers are simply layered without this binding. Referring to Figs. 1 and 2, the dressing according to the present invention includes at least a wound contacting layer 10 that directly contacts wounds and a supporting layer to support the wound contacting layer 10. Useful supporting layers in the present invention include any that is able to support a wound contacting layer 10 in a state of being combined with an upper surface of the wound contacting layer 10 and is able to hold absorbed wound exudates. In detail, the supporting layer is a base sheet layer 20, or preferably a fibrous absorbent layer 30 having high absorptivity. Fig. 1 is a schematic cross sectional view of a dressing according to a first embodiment of the present invention, in which the dressing has a double-layered structure consisting of the wound contacting layer 10 and the base sheet layer 20. Fig. 2 is a schematic cross sectional view of a dressing according to a second embodiment of the present invention, in which the dressing has a double-layered structure consisting of the wound contacting layer 10 and the fibrous absorbent layer 30 with high absorptivity. The wound contacting layer 10 is made of a microporous polyurethane film that is 10-200 μm thick and has a microporous structure. In detail, the wound contacting layer 10 is a microporous structure having a plularity of micropores 12 with an average diameter of 5-80 μm. In addition to the plurality of micropores 12, the wound contacting layer 10 includes a small amount of a means for absorbing highly viscous wound exudates . The means for absorbing highly viscous wound exudates, which effectively absorbs highly viscous wound exudates, is a plurality of micropores 14 having a diameter of 100-1,000 μm and/or a plurality of slits 15 having a length of 0.1-10 mm. Fig. 3 is a schematic sectional view of the wound contacting layer 10 of the dressing of Fig. 1 or Fig. 2. As shown in Fig. 3, the wound contacting layer 10 may have a structure containing a plurality of micropores 12 with an average diameter of 5-80 μm and a plurality of macropores 14 with a diameter of 100-1,000 μm, a structure containing a plurality of micropores 12 with an average diameter of 5-80 μm and a plurality of slits 15 0.1-10 mm long, or a structure containing a plurality of micropores 12 with an average diameter of 5-80 μm, a plurality of macropores 14 with a diameter of 100-1,000 μm and a plurality of slits 15 0.1-10 mm long. Fig. 3 shows a structure containing micropores 12, macropores 14 and slits 15. Due to this structure, the wound contacting layer 10 has excellent absorptivity to wound exudates and non-adherence to wounds. Also, this surface of the wound contacting layer 10 does not adhere to wounds, thereby preventing regenerated tissues from being damaged and reducing the discomfort of patients when being exchanged with a new dressing. The wound contacting layer 10 is prepared by coating the supporting layer (i.e., base sheet layer or fibrous absorbent layer) with a polyurethane solution and allowing the polyurethane solution to coagulate to lead to conjugation with the surface of the supporting layer. Alternatively, the wound contacting layer 10 is prepared by coating the polyurethane solution on a release paper, allowing the polyurethane solution to coagulate to generate a film and conjugating the film to the supporting layer. During coagulation of the polyurethane solution, a plurality of micropores 12 with an average diameter of 5-80 μm are generated. A plurality of macropores 14 with an average diameter of 100-1,000 μm or slits 15 as a means for absorbing highly viscous wound exudates may be formed by a mechanical method. The preparation of the wound contacting layer 10 will be described in detail, as follows. The polyurethane solution used in the preparation of the wound contacting layer 10 is a mixture prepared by mixing a polyurethane resin synthesized using isocyanate, polyols and a chain extender with a solvent. The polyurethane solution may further include a hydrophilic agent and an antifungal agent. The polyurethane resin is prepared as follows. A polyol and a chain extender are added to a reactor and mixed with each other with sufficient stirring. After the reactor is heated to 70-80°C, isocyanate is added over several times to the reactor to increase the viscosity of the mixture. When the viscosity of the mixture increases, a solvent is added over several times to control the viscosity of the mixture. When the viscosity reaches a desired value, the presence of residual NCO (isocyanate) is investigated, and the reaction is then terminated. The isocyante used in the synthesis of the polyurethane resin is one or more selected from among isoporone diisocyanate, hexamethylenediisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, 2,2-bis- 4' -propaneisocyanate, 2, 4-toluenediisocyanate and its isomers, 4, 4' -biphenylenediisocyanate, 4,4- dicyclohexylmethanediisocyanate, 1, 4-xylenediisocyanate, 1, 3-xylenediisocyanate. Preferably, the isocyanate is selected from among 4, 4' -biphenylenediisocyanate, isoporone diisocyanate and hexamethylenediisocyanate. Examples of the polyols include a polypropylene glycol which contains at least two hydroxyl groups and ranges in a molecular weight from 200 to 3,000, an ethylene oxide/propylene oxide random copolymer which contains at least two hydroxyl groups and ranges in molecular weight from 3,000 to 6,000, a polyetherpolyol such as polytetramethylglycol which contains at least two hydroxyl groups and ranges in molecular weight from 1,000 to 3,000, a polyesterpolyol ranging in molecular weight from 500 to 3,500, and mixtures thereof. To function as the chain extender, at least two intramolecular hydroxyl groups are required. Examples of the chain extender include 1, 3-butanediol, 1, 4-butanediol, 1,5- pentanediol, 1, 6-hexanediol, neophentylglycol, propyleneglycol, ethylene glycol, glycerol, trimethylolethane, trimethylolpropane, esterglycol, and mixtures thereof. Preferred are 1, 3-butanediol, 1,4- butanediol, ethylglycol and 1, 6-hexanediol . The solvent used as a viscosity controller of the polyurethane resin should have high hydrophilicity. Examples of the viscosity controller include dimethylacetamide

(DMAc) , dimethylformamide (DMF) , tetrahydrofuran (THF) and acetone. Preferred are DMAc and DMF. The polyurethane resin synthesized as described above is combined in a film form to the supporting layer by a coagulation process through precipitation or selective evaporation. The coagulation precipitation is carried out, as follows. The polyurethane resin is dissolved in a highly water-miscible solvent to generate a low viscosity polyurethane solution. The polyurethane solution is coated onto the supporting layer. The supporting layer is then immersed in a coagulation bath to coagulate the polyurethane resin. In the coagulation bath, the highly water-miscible solvent contained in the polyurethane solution gets out to water while the polyurethane resin is coagulated, resulting in the generation of a film containing a plurality of micropores 12 on a surface of the supporting layer in an adherent state. By the selective evaporation coagulation, the polyurethane resin is dissolved in a mixture of a nonsolvent that is for the polyurethane resin and has a high boiling point and a solvent that is for the polyurethane resin and has a low boiling point. The resulting polyurethane solution is coated onto the supporting layer, and the supporting layer is then heat-dried. In this dry step, the low boiling point solvent is evaporated while the polyurethane is coagulated, resulting in generation of a film containing a plurality of micropores 12 on a surface of the supporting layer in an adherent state. Fig. 4 is a scanning electron microphotograph (SEM) showing a surface of a microporous polyurethane film prepared in a Preparational Example of the present invention, in which a plurality of micropores 12 is formed by the precipitation coagulation process. As described above, simultaneously with its generation, the wound contacting layer 10 is combined with the supporting layer. Alternatively, the wound contacting layer 10 is primarily prepared on a release paper, as follows: the polyurethane resin is coated on the release paper, and the polyurethane resin is then coagulated to develop a film containing a plurality of micropores 12, that is, the wound contacting layer 10. The wound contacting layer 10 is detached from the release paper and combined with a surface of the supporting layer, for example, by a thermal compression method. On the wound contacting layer 10, combined with a surface of the supporting layer as described above, a plurality of macropores 14 of 100-1,000 μm and/or a plurality of slits 15 of 0.1-10 mm are formed by a mechanical method such as perforation or cutting. In addition, the polyurethane solution used in the preparation of the wound contacting layer 10 may further include a highly absorbable resin as a hydrophilic agent to increase the absorptivity of the dressing according to the present invention. The highly absorbable resin is one or more selected from the group consisting of L-62, L-64, P-84, P-85, P-105, F-68, F-87, F-88, F-108, and F-127, all of which are kinds of ethylene oxide/propylene oxide block copolymers, manufactured by BASF, Germany, hyaluronic acid, carboxymethylcellulose, pectin, Guar gum, sodium alginate, chitin, chitosan, gelatin, starch, hydroxyethylcellulose, xanthan gum, and karaya gum. The polyurethane solution may further include an anitfungal agent to improve the antifungal activity of the dressing. The anitfungal agent is one or more selected from among silver sulfur diazine, chlorohexidin, povidone iodine, idocaine, ginosolt, vibriocin, hexachlorophene, chlorotetracycline, neomycin, penicillin, gentamycin, acrinol, etc. As described above, the supporting layer consists of a base sheet layer 20 and/or a fibrous absorbent sheet layer 30 with high absorptivity. The base sheet layer 20 is composed of one or more base sheets. The base sheet is selected from among non-woven fabrics, woven fabrics and clothes, which all are prepared by using natural fibers or synthetic fibers, such as polyester, polyethylene, polypropylene, nylon, acryl, rayon, silk and cotton. Preferred are those which has proper supporting ability and high absorptivity. In addition, the fibrous absorbent sheet layer 30 is composed of one or more absorbent sheets with high absorptivity. The absorbent sheet is prepared by gathering a synthetic fiber or a natural fiber into a cotton wool form and processing the cotton wool into a sheet. Also, the absorbent layer is made of any one with high absorptivity among base sheets such as non-woven fabrics, woven fabrics and clothes, which all are prepared using natural fibers or sythetic fibers, or a highly absorbable sheet that is prepared by conjugating a highly absorbable fiber, polymer or natural material to such a base sheet, for example, by a dispersion method. Preferably, the fibrous absorbent layer is composed of a base sheet such as non-woven fabrics, woven fabrics and clothes, which all are prepared using natural fibers or sythetic fibers, and a highly absorbable polymer or natural material to be mixed with the base sheet. In detail, the fibrous absorbent layer 30 is composed of a base sheet that is mixed, for example, by dispersion or impregnation, with one or more selected from the group consisting of highly absorbable polymers and natural materials, which are exemplified by polyacrylic acid, polysulfonates, polyacrylates, polyvinylalcohol, polyoxyethylene, polyethyleneoxide, polysaccharides, polymetacrylate, polyacrylamide and cellulose, carboxymethylcellulose, pectin, Guar gum, sodium alginate, chitin, chitosan, gelatin, starch, hydroxyethylcellulose, xanthan gum, pulp and karaya gum. The fibrous absorbent layer 30 may form a proper moist environment and has a proper absorptivity, which are determined depending on the kind and amount of the highly absorbable polymer and natural material . In particular, the fibrous absorbent layer 30 may have a high exudate absorptivity to absorb over 400% by weight based on the weight thereof and an excellent retention ability to prevent leakage of wound exudates. Fig. 5 is a schematic cross sectional view of a dressing according to a third embodiment of the present invention. As shown in Fig. 5, the dressing according to the third embodiment has a three-ply structure consisting of a wound contacting layer 10, a base sheet layer 20 and a fibrous absorbent layer 30, which are combined in the sequence starting from the bottom contacting wounds of the dressing. This three-ply structure provides sufficient supporting ability, in particular, and excellent absorptivity and retention ability for wound exudates, and thus, allows the dressing to be applied to diverse wounds generating a large quantity of exudates, and is useful when the relatively frequent exchange of dressing is required. Fig. 6 is a schematic cross sectional view of a dressing according to a fourth embodiment of the present invention. As shown in Fig. 6, the dressing according to the fourth embodiment has a three-ply structure consisting of a wound contacting layer 10, a base sheet layer 20 or a fibrous absorbent layer 30, and an outer protective film layer 40, which are combined in the sequence starting from the bottom contacting wounds of the dressing. This three-ply structure contains the base sheet layer 20 or the fibrous absorbent layer 30 between the wound contacting layer 10 and the outer protective film layer 40. Fig. 7 is a schematic cross sectional view of a dressing according to a fifth embodiment of the present invention. As shown in Fig. 6, the dressing according to the fifth embodiment has a four-ply structure consisting of a wound contacting layer 10, a base sheet layer 20, a fibrous absorbent layer 30 and an outer protective film layer 40, which are combined in the sequence starting from the bottom contacting wounds of the dressing. The outer protective film layer 40 of the dressings according to the fourth embodiment (Fig. 6) and the fifth embodiment (Fig. 7) is a moist permeable film 10-200 μm thick. In detail, the outer protective film layer 40 is a non-porous film and has high moisture permeability and waterproofing ability. This outer protective film layer 40 functions to defense against invasion of bacteria and impurities, prevent leakage of wound exudates and maintain an appropriate moisture permeability. In particular, the outer protective film layer 40 stimulates wound healing by providing an appropriate moist environment to wounds. The outer protective film layer 40 may be made of a polymer film which is prepared using polyurethane, polyethylene, polypropylene, polyvinylchloride, etc. Preferred is a film with a moisture permeability of 300- 2,000 g/m²/24 hrs. [Mode for Invention] A better understanding of the present invention may be obtained through the following examples which are set forth to illustrate, but are not to be construed as the limit of the present invention.

SYNTHESIS EXAMPLE 1

A polyurethane resin was prepared, as follows. To a 3- L flask filled with nitrogen gas, 0.2 mole of polyethylene glycol with a molecular weight of 2,000, 0.8 mole of polytetramethylene glycol with a molecular weight of 2,000, 0.4 mole of polyesterpolyol with a molecular weight of 3,000, 3 mole of 1, 4-butanediol and dimethylformamide (DMF) were added. After sufficient mixing with stirring, the reactor was heated to 70-80°C, diphenylmethanediisocyanate was added over several times to increase viscosity of the mixture. When the viscosity of the mixture increased, a solvent was added over several times to control the viscosity of the mixture. When the viscosity reached a solid content of 30%, the presence of residual isocyanate was investigated, and the reaction was then terminated, thus generating a polyurethane resin. DMF was mixed with the polyurethane resin in an amount of 200 parts by weight based on the amount of 100 parts by weight of the polyurethane resin, thus yielding a polyurethane solution. SYNTHESIS EXAMPLE 2

A polyurethane resin was prepared, as follows. To a 3- L flask filled with nitrogen gas, 0.2 mole of polyethylene glycol with a molecular weight of 2,000, 0.8 mole of polytetramethylene glycol with a molecular weight of 2,000, 0.4 mole of polyesterpolyol with a molecular weight of 3,000, 3 mole of 1, 4-butanediol and dimethylformamide (DMF) were added. After sufficient mixing with stirring, the reactor was heated to 70-80°C, diphenylmethanediisocyanate was added over several times to increase viscosity of the mixture. When the viscosity of the mixture increased, a solvent was added over several times to control the viscosity of the mixture. When the viscosity reached a solid content of 30%, the presence of residual isocyanate was investigated, and the reaction was then terminated, thus generating a polyurethane resin. To the polyurethane resin, F-127 of 50 parts by weight, silver sulfur diazine of 1.0 parts by weight and DMF of 200 parts by weight, based on the amount of 100 parts by weight of the polyurethane resin, were added. A hydrophilic agent and an antifungal agent were added to the mixture and dispersed in the mixture by stirring for 30 min for room temperature, thus generating a polyurethane solution.

PREPARATION EXAMPLE: Preparation of outer protective film An outer protective film layer was prepared, as follows. 20 g of polyurethane elastomer was added to a solvent mixture of dimethylformamide (DMF) and methylethylketone (MEK) (DMF:MEK = 30:70), and the mixture was then heated to 60°C with stirring, resulting in a polyurethane solution in a viscous liquid state. A release paper, treated with silicon, was fixed at both surfaces with a Gauge Bar with a constant thickness, and was uniformly coated with the polyurethane solution using a film coater, following by drying in an oven at 100°C for over 1 hour. The obtained polyurethane films were 20 μm thick.

EXAMPLE 1

The polyurethane solution prepared in Synthesis Example 1 was coated on a non-woven fabric (Vilen Co. Ltd., Korea) into a thickness of 500 μm. The non-woven fabric was then immersed in a coagulation bath containing a 30% DMF solution and maintained at 30°C. The coagulation was carried out for 30 min. The polyurethane was coagulated while forming a white microporous membrane containing micropores 12. The coagulated specimen was fixed on a dry support by squeezing and subjected to hot air drying in a dry oven at 100°C for 20 min. The dried specimen was mechanically perforated into a diameter of 1,000 μm to generate fifteen macropores 14 per cm². Fig. 1 shows the structure of the dressing prepared in this Example. The dressing was evaluated for physical properties in the following processes and the measured results are given in Table 1, below.

(1) Thickness Thickness of the dressing was measured at three regions using a dial micrometer, and a mean value was calculated using the measured values .

(2) Mechanical properties (Tensile Strength, Elongation) Measurements were made by use of a tensile tester, such as that manufactured by Instron Corporation, identified as Universal Test Machine, according to JIS-K-6401.

(3) % Absorptivity The dressing was cut to a size of 3 cm x 3 cm. The sample pieces were dried in an oven at 70° for 24 hrs and weighed (A) . It was immersed in distilled water at 25 °C for 48 hours, followed by the removal of moisture from the surface with dust-free paper. Its wet weight was measured (B). % Absorptivity of the dressing was calculated according to the following equation.

B - A % Absorptivity = x 100 A

(4) Moisture permeability Using an incubator, the dressing was measured according to the desiccant method of ASTM E96-94. In this regard, the incubator was kept at a temperature of 40°C at a relative humidity of 90%. Moisture permeability was calculated according to the following equation:

P = A/S A = ( (aι-a₀) + (a₂-aι) + (a₃-a₂) )/3 wherein, P is moisture permeability (g/m²/24hr) A is an average increment for 1 hour (g) S is a specimen area through which moisture permeation occurs (m²) ao is the specimen weight measured after 1 hour A ai, a₂ and a₃ are the specimen weights measured after 2, 3 and 4 hours, respectively.

(5) Pore size The dressing was measured for pore size using a scanning electron microscope.

(6) Animal test Rats, 6-8 weeks old, weighing 250-300 g were used to observe the wound healing effects of the dressing. To this end, a dermal lesion with a size of 4 cm x 4 cm was made on the back of each rat which had been anesthetized by abdominal injection with Rembutal, and then subjected to dressing. At 1, 2 and 3 weeks after the dressing, the wound was examined for size change, tissue separation upon changing of dressing, and histochemistry, to determine the wound healing effect of the dressing.

EXAMPLE 2

The polyurethane solution prepared in Synthesis Example 2 was coated on a non-woven fabric (Vilen Co. Ltd., Korea) into a thickness of 500 μm. The non-woven fabric was then immersed in a coagulation bath containing a 30% DMF solution and maintained at 30°C. The coagulation was carried out for 30 min. The polyurethane was coagulated while forming a white microporous membrane containing micropores 12. The coagulated specimen was fixed on a dry support by squeezing and subjected to hot air drying in a dry oven at 100°C for 20 min. The dried specimen was mechanically perforated into a diameter of 1,000 μm to generate fifteen macropores 14 per cm². Fig. 1 shows the structure of the dressing prepared in this Example. The dressing was evaluated for physical properties according to the same processes as in Example 1, and the measured results are given in Table 1, below.

EXAMPLE 3

The polyurethane solution prepared in Synthesis Example 2 was coated on a non-woven fabric (Vilen Co. Ltd., Korea) into a thickness of 500 μm. The non-woven fabric was then immersed in a coagulation bath containing a 30% DMF solution and maintained at 30°C. The coagulation was carried out for 30 min. The polyurethane was coagulated while forming a white microporous membrane containing micropores 12. The was fixed on a dry support by squeezing and subjected to hot air drying in a dry oven at 100°C for 20 min. The dried specimen was mechanically perforated into a diameter of 1,000 μm to generate fifteen macropores 14 per cm². On the perforated polyurethane film sheet, a non-woven fabric absorbent sheet (0.3 mm thick, Baiksan T&S Co. Ltd., Korea) was layered. Then, the moisture permeable polyurethane film, prepared in Preparation Example of an outer protective film, was layered on the non-woven fabric absorbent sheet. Fig. 6 shows the structure of the resulting dressing. The dressing was evaluated for physical properties according to the same processes as in Example 1, and the measured results are given in Table 1, below.

EXAMPLE 4 The polyurethane solution prepared in Synthesis

Example 2 was coated on a non-woven fabric (Vilen Co. Ltd.,

Korea) into a thickness of 500 μm. The non-woven fabric was then immersed in a coagulation bath containing a 30% DMF solution and maintained at 30°C. The coagulation was carried out for 30 min. The polyurethane was coagulated while forming a white microporous membrane containing micropores 12. The coagulated specimen was fixed on a dry support by squeezing and subjected to hot air drying in a dry oven at 100°C for 20 min. The dried specimen was mechanically perforated into a diameter of 1,000 μm to generate fifteen macropores 14 per cm². On the perforated polyurethane film sheet, a non-woven fabric absorbent sheet (0.3 mm thick, Baiksan T&S Co. Ltd., Korea) was layered. Then, a highly absorbable polymer (GE- 600, Kolon Industries, Inc., Korea) was dispersed to be laminated on the non-woven fabric absorbent sheet at an amount 10 g/m². Then, the moisture permeable polyurethane film, prepared in Preparation Example of the outer protective film, was layered on the highly absorbable polymer. Fig. 6 shows the structure of the resulting dressing. The dressing was evaluated for physical properties according to the same processes as in Example 1, and the measured results are given in Table 1, below.

EXAMPLE 5 The polyurethane solution prepared in Synthesis

Example 2 was coated on a non-woven fabric (Vilen Co. Ltd.,

Korea) into a thickness of 500 μm. The non-woven fabric was then immersed in a coagulation bath containing a 30% DMF solution and maintained at 30°C. The coagulation was carried out for 30 min. The polyurethane was coagulated while forming a white microporous membrane containing micropores 12. The coagulated specimen was fixed on a dry support by squeezing and subjected to hot air drying in a dry oven at 100°C for 20 min. The dried specimen was mechanically perforated into a diameter of 1,000 μm to generate fifteen macropores 14 per cm². On the perforated polyurethane film sheet, a non-woven fabric absorbent sheet (0.3 mm thick, Baiksan T&S Co. Ltd., Korea) was layered. Then, a highly absorbable polymer (GE- 600, Kolon Industries, Inc., Korea) was dispersed to be laminated on the non-woven fabric absorbent sheet at an amount 20 g/m². Then, the moisture permeable polyurethane film, prepared in Preparation Example of the outer protective film, was layered on the highly absorbable polymer. Fig. 6 shows the structure of the resulting dressing. The dressing was evaluated for physical properties according to the same processes as in Example 1, and the measured results are given in Table 1, below.

EXAMPLE 6 The polyurethane solution prepared in Synthesis

Example 2 was coated on a non-woven fabric (Vilen Co. Ltd.,

Korea) into a thickness of 500 μm. The non-woven fabric was then immersed in a coagulation bath containing a 30% DMF solution and maintained at 30°C. The coagulation was carried out for 30 min. The polyurethane was coagulated while forming a white microporous membrane containing micropores 12. The coagulated specimen was fixed on a dry support by squeezing and subjected to hot air drying in a dry oven at 100°C for 20 min. The dried specimen was mechanically perforated into a diameter of 1,000 μm to generate fifteen macropores 14 per cm². On the perforated polyurethane film sheet, a non-woven fabric absorbent sheet (1.0 mm thick, Baiksan T&S Co. Ltd., Korea) was layered. Then, a highly absorbable polymer (GE- 600, Kolon Industries, Inc., Korea) was dispersed to be laminated on the non-woven fabric absorbent sheet at an amount 20 g/m². Then, the moisture permeable polyurethane film, prepared in Preparation Example of the outer protective film, was layered on the highly absorbable polymer. Fig. 6 shows the structure of the resulting dressing. The dressing was evaluated for physical properties according to the same processes as in Example 1, and the measured results are given in Table 1, below.

EXAMPLE 7 The polyurethane solution prepared in Synthesis

Example 2 was coated on a non-woven fabric (Vilen Co. Ltd., Korea) into a thickness of 500 μm. The non-woven fabric was then immersed in a coagulation bath containing a 30% DMF solution and maintained at 30°C. The coagulation was carried out for 30 min. The polyurethane was coagulated while forming a white microporous membrane containing micropores 12. The coagulated specimen was fixed on a dry support by squeezing and subjected to hot air drying in a dry oven at 100°C for 20 min. The dried specimen was mechanically perforated into a diameter of 1,000 μm to generate fifteen macropores 14 per cm². On the perforated polyurethane film sheet, a non-woven fabric absorbent sheet (2.0 mm thick, Baiksan T&S Co. Ltd., Korea) was layered. Then, a highly absorbable polymer (GE- 600, Kolon Industries, Inc., Korea) was dispersed to be laminated on the non-woven fabric absorbent sheet at an amount 20 g/m². Then, the moisture permeable polyurethane film, prepared in Preparation Example of the outer protective film, was layered on the highly absorbable polymer. Fig. 6 shows the structure of the resulting dressing. The dressing was evaluated for physical properties according to the same processes as in Example 1, and the measured results are given in Table 1, below.

EXAMPLE 8 The polyurethane solution prepared in Synthesis

Example 2 was coated on a non-woven fabric (Vilen Co. Ltd., Korea) into a thickness of 500 μm. The non-woven fabric was then immersed in a coagulation bath containing a 30% DMF solution and maintained at 30°C. The coagulation was carried out for 30 min. The polyurethane was coagulated while forming a white microporous membrane containing micropores 12. The coagulated specimen was fixed on a dry support by squeezing and subjected to hot air drying in a dry oven at 100°C for 20 min. The dried specimen was mechanically perforated into a diameter of 1,000 μm to generate fifteen macropores 14 per cm². On the perforated polyurethane film sheet, a non-woven fabric absorbent sheet (0.5 mm thick, Baiksan T&S Co. Ltd., Korea) was layered. Then, a highly absorbable polymer (KANEBO Ltd., Japan) was dispersed to be laminated on the non-woven fabric absorbent sheet. Then, the moisture permeable polyurethane film, prepared in Preparation Example of the outer protective film, was layered on the highly absorbable polymer. Fig. 7 shows the structure of the resulting dressing. The dressing was evaluated for physical properties according to the same processes as in Example 1, and the measured results are given in Table 1, below.

EXAMPLE 9

The polyurethane solution prepared in Synthesis Example 2 was coated on a non-woven fabric (Vilen Co. Ltd.,

Korea) into a thickness of 500 μm. The non-woven fabric was then immersed in a coagulation bath containing a 30% DMF solution and maintained at 30°C. The coagulation was carried out for 30 min. The polyurethane was coagulated while forming a white microporous membrane containing micropores 12. The coagulated specimen was fixed on a dry support by squeezing and subjected to hot air drying in a dry oven at 100°C for 20 min. The dried specimen was partially cut into a length of 1 mm to generate five slits 15 per cm². On the perforated polyurethane film sheet, a non-woven fabric absorbent sheet (0.5 mm thick, Baiksan T&S Co. Ltd., Korea) was layered. Then, a highly absorbable polymer (KANEBO Ltd., Japan) was dispersed to be laminated on the non-woven fabric absorbent sheet. Then, the moisture permeable polyurethane film, prepared in Preparation Example of the outer protective film, was layered on the highly absorbable polymer. Fig. 7 shows the structure of the resulting dressing. The dressing was evaluated for physical properties according to the same processes as in Example 1, and the measured results are given in Table 1, below.

COMPARATIVE EXAMPLE 1

A commercially available product (Brand Name: Medicsband, non-woven dressing) , manufactured by the N Company in Korea, was used as a comparative sample. This sample was evaluated for physical properties according to the same processes as in Example 1, and the measured results are given in Table 1, below.

COMPARATIVE EXAMPLE 2 A commercially available sterile gauge, manufactured by the D Company in Korea, was used as a comparative sample. This sample was evaluated for physical properties according to the same processes as in Example 1, and the measured results are given in Table 1, below.

COMPARATIVE EXAMPLE 3

A commercially available product (Brand Name: Medilon, non-woven dressing) , manufactured by the P Company in Korea, was used as a comparative sample. This sample was evaluated for physical properties according to the same processes as in Example 1, and the measured results are given in Table 1, below.

TABLE 1 Physical properties of the dressings

^*: Conventional dressings ": g/m²/24 hrs at 40°C, 90% RH Θ: not absorbed; o; very slight; Δ: slight; x: severe

As apparent from the data of Examples 2 to 9 in Table 1, the dressings effectively provided moist environments by its increased absorptivity by the sheet made of the microporous polyurethane film on the non-woven fabric and the fibrous absorbent sheet layer. Also, the employment of the highly absorbable polymer was found to facilitate the control of the absorptivity of the absorbent sheet layer 30. Therefore, through the control of the absorptivity of the absorbent layer, the dressings can be applied to diverse wounds from slight wounds to wounds generating a large quantity of exudates, such as ulcerations or burns. As apparent from the data of Examples 1 and 2, when including the hydrophilic agent, the polyurethane solution was found to form larger pores than the case of not containing the hydrophilic agent. Turning now to the animal test results, when the rats received treatments using the dressings of a control and Examples 1 and 2, due to the poor absorptivity of the dressings, wounds were healed by the contraction of the wounds, accompanied by formation of crusts. However, in these cases, regenerated tissues did not infiltrate the dressings. Also, the dressing of Example 3 was found to have unsatisfactory absorptivity, but to adhere to wounds due to its good moisture permeability. However, when the dressings of Comparative Examples 1 to 3 were applied to the rats, due to generated dry environments, the dressings were adhered to wounds, and regenerated tissues infiltrated the dressings, resulting in bleeding by tissue damage upon changing. When the dressings of Examples 4 to 9 were applied to the rats, re-epithelialization occurred without formation of crusts, and the dressings did not adhere to wounds by providing moist environments. Also, the dressings were found to have excellent absorptivity to wound exudates, caused no injury to regenerated tissues at the wounds upon changing, thereby causing no bleeding upon changing. Further, these dressings displayed over 50% rapider wound healing effects than the dressings of Comparative Examples 1 to 3.

[industrial Applicability]

As described hereinbefore, the present invention greatly improved the disadvantages of the conventional non- woven fabric or gauge dressings, including generation of dry environments, relatively low absorptivity compared to their thickness and adherence to wounds. The dressing of the present invention has excellent wound healing effect when applied to wounds. In detail, since the wound contacting layer contains both micropores and a mean (macropores or slits) for absorbing highly viscous wound exudates, the dressing of the present invention rapidly absorbs low viscosity exudates as well as high viscosity exudates, and has non-adherence to wounds . In particular, since the structure containing the highly absorbable fibrous absorbent sheet layer along with the wound contacting layer maintains an appropriate moist environment and has long-lasting high absorptivity and excellent retention ability for wound exudates, the dressing having this structure can be applied diverse wounds from slight wounds to severe wounds generating a large quantity of exudates . In addition, when having the structure containing the outer protective film layer, the dressing stimulates wound healing by defending against the infiltration of bacteria and other external impurities, preventing the leakage of wound exudates and providing an appropriate moist environment . Therefore, due to its properties of non-adherence to wounds, high absorptivity to wound exudates, formation of a moist environment, defense against infiltration of external impurities, etc., the dressing of the present invention has excellent wound healing effect, is applicable to diverse wounds from slight wounds to severe wounds generating a large quantity of exudates, and causes no discomfort upon changing by no adherence to wounds .

Claims

[CLAIMS] [Claim l] 1. A wound dressing, comprising: a wound contacting layer that is made of a microporous polyurethane film containing a plurality of micropores with an average diameter of 5-80 μm and a means for absorbing highly viscous wound exudates and is 10-200 μm thick; and a supporting layer that is combined with an upper surface of the wound contacting layer.

[Claim 2] The wound dressing as set forth in claim 1, wherein the supporting layer is a base sheet layer, which is combined with an upper surface of the wound contacting layer to form a two-ply structure.

[Claim 3] The wound dressing as set forth in claim 2, further comprising an outer protective film layer 10-200 μm thick and moisture permeable, which is combined with an upper surface of the base sheet layer to form a three-ply structure.

[Claim 4] The wound dressing as set forth in claim 1, wherein the supporting layer is a fibrous absorbent sheet layer with high absorptivity, which is combined with an upper surface of the wound contacting layer to form a two-ply structure.

[Claim 5] The wound dressing as set forth in claim 2, further comprising a fibrous absorbent sheet layer with high absorptivity, which is combined with an upper surface of the base sheet layer to form a three-ply structure.

[Claim 6] The wound dressing as set forth in claim 4, further comprising an outer protective film layer 10-200 μm thick and moisture permeable, which is combined with an upper surface of the fibrous absorbent sheet layer with high absorptivity to form a three-ply structure.

[Claim 7] The wound dressing as set forth in claim 5, further comprising an outer protective film layer 10-200 μm thick and moisture permeable, which is combined with an upper surface of the fibrous absorbent sheet layer with high absorptivity to form a four-ply structure.

[Claim 8] The wound dressing as set forth in any one of claims 1 to 7, wherein the wound contacting layer comprises a plurality of macropores 100-1,000 μm in diameter as the means for absorbing highly viscous wound exudates .

[Claim 9] The wound dressing as set forth in any one of claims 1 to 7, wherein the wound contacting layer comprises a plurality of slits 0.1-10 mm long as the means for absorbing highly viscous wound exudates.

[Claim 10] The wound dressing as set forth in any one of claims 1 to 7, wherein the wound contacting layer comprises a plurality of macropores 100-1,000 μm in diameter and a plurality of slits 0.1-10 mm long as the means for absorbing highly viscous wound exudates.

[Claim 11] The wound dressing as set forth in any one of claims 4 to 7, wherein the fibrous absorbent sheet layer is prepared by mixing a base sheet with one or more selected from the group consisting of polyacrylic acid, polyacrylates, polyvinylalcohol, polysulfonates, polyoxyethylene, polyethyleneoxide, polysaccharides, polymetacrylate, polyacrylamide and cellulose, carboxymethylcellulose, pectin, Guar gum, sodium alginate, chitin, chitosan, gelatin, starch, hydroxyethylcellulose, xanthan gum, pulp and karaya gum.

[Claim 12] The wound dressing as set forth in claim 11, wherein the base sheet comprising the fibrous absorbent sheet layer is a non-woven fabric, a woven fabric or a cloth, all of which are made of synthetic or natural fibers .