BREATHABLE, NON-LIQUID-PERMEABLE COMPOSITE SHEET

Abstract: A breathable liquid-impervious composite sheet of a comfortable touch which is free from generation of fibrous waste. The composite sheet includes opposite surfaces of a breathable liquid-impervious sheet made of thermoplastic synthetic resin which are covered with continuous fibers.

Description: This invention relates to breathable liquid-impervious composite sheets as stock material for disposable garments such as disposable working clothes. A breathable liquid-impervious composite sheet is well known, which comprises a breathable liquid-impervious film of thermoplastic synthetic resin and a nonwoven fabric of thermoplastic synthetic fiber laminated on one surface of the film. Such a sheet has been used, for example, as a backsheet of a disposable diaper. The film makes this backsheet breathable and liquid-impervious and the nonwoven fabric gives this backsheet a cloth-like soft touch. In the composite sheet of the prior art, the nonwoven fabric comprises staple fibers, each having a length of 50 mm, which may sometimes fall off from the composite sheet. In view of this, this composite sheet of the prior art is not suitable as stock material for gowns or working clothes used in a medical site or food plant wherein generation of dust, dirt and fibrous waste are prohibited. This composite sheet of the prior art is disadvantageous also in that its one surface is defined by the film destined to come directly in contact with the wearer's skin. Some of the wearers have antipathy to a touch peculiar to the film and, also in view of this, it is not preferable to use the composite sheet of the prior art as stock material for gowns or the like which inevitably comes in direct contact with the wearer's skin. The present invention is directed to a breathable liquid-impervious composite sheet generally of the type disclosed in W097/45259 and defined in the preamble of claim 1, comprising a breathable liquid-impervious sheet made of thermoplastic synthetic resin and having its opposite surfaces covered with layers of continuous thermoplastic synthetic fibers which are bonded to the sheet of thermoplastic synthetic resin. It is a principal object of this invention to improve the composite sheet of the prior art and provide a composite sheet being free from generation of fibrous waste and offering a comfortable touch. The breathable liquid impervious composite sheet according to the present invention, as defined in the characterising clause of claim 1, is characterised in that the sheet made of thermoplastic synthetic resin is nonwoven fabric and has its opposite surfaces bonded intermittently to the layers of continuous fibers. In a preferred embodiment of the invention, the air-permeable, liquid-impervious composite sheet has a maximum breathability of 200 sec/100 cc as measured in accordance with the method B of JIS (Japanese Industrial Standards) L 1096 and a water resistance of at least 300 mm as measured in accordance with the method A of JIS L 1092. Reference will now be made to the accompanying drawings, in which:- Fig. 1 is a perspective view of a composite sheet embodying this invention; and Fig. 2 is an exploded perspective view of the composite sheet. Fig. 1 is a perspective view of a breathable liquid-impervious composite sheet according to a preferred embodiment of this invention and Fig. 2 is an exploded perspective view of the composite sheet. A composite sheet 1 has upper and lower layers 2, 4 and an intermediate layer 3 disposed between these upper and lower layers 2, 4. The upper and lower layers 2, 4 have a breathability equal to or higher than that of the intermediate layer 3. The upper and lower layers 2, 4 respectively comprise a plurality of continuous fibers 6, 7 extending to describe irregular curves on upper and lower surfaces of the intermediate layer 3. The continuous fibers 6 of the upper layer 2 and the continuous fibers 7 of the lower layer 4 respectively have a basis weight of 10-100 g/m 2 and may be respectively sealed together at their intersections. The continuous fibers 6, 7 may be selected from a group including polypropylene fiber and conjugated fiber comprising polypropylene or polyester as a core and polyethylene as a sheath. The intermediate layer 3 is formed by a breathable liquid-impervious sheet made of thermoplastic synthetic resin. In particular, the intermediate layer 3 is formed by a fibrous assembly, namely a nonwoven fabric such as a melt blown nonwoven fabric made of polypropylene or the like. The breathable liquid-impervious nature of the intermediate layer 3 can be quantitatively expressed by breathability and water resistance. Preferably, the intermediate layer 3 has a maximum breathability of 200 sec/100 cc as measured in accordance with the method B of JIS L 1096 and a water resistance of at least 300 mm as measured in accordance with the method A of JIS L 1092. The upper and lower layers 2, 4 and the intermediate layer 3 are bonded together in bond regions 11 (See Fig. 1) intermittently formed over the composite sheet 1. It should be understood that such bond regions are not shown in Fig. 2 showing the composite sheet in an exploded perspective view. While it is not critical how the bond regions 11 are configured, each of these bond regions 11 has an area of 0.5 ∼ 10 mm 2 and their total area occupies 1 ∼ 30 % of the composite sheet's surface area. Bonding of the respective layers 2 - 4 may be carried out not only by means of a sealing technique but also by means of a suitable adhesive such as a hot melt adhesive. The composite sheet formed in the manner as has been described above is advantageously free from an undesirable generation of fibrous waste when this composite sheet is used as stock material for working clothes or gowns for surgical operations. This is for the reason that the upper and lower layers comprise continuous fibers. Additionally, the upper and lower layers present a cloth-like touch and therefore the wearer does not experience a feeling of incompatibility possibly presented by a film of thermoplastic synthetic resin even when the working clothes come in direct contact with the wearer's skin. Accordingly, this composite sheet is suitable as the surface material of disposable garments for which the breathable and liquid-impervious nature is required, for example, disposable working clothes, disposable gowns for surgical operation, disposable trousers, disposable shorts or disposable diapers.

Claims: A breathable liquid-impervious composite sheet (1) comprising a breathable liquid-impervious sheet (3) made of thermoplastic synthetic resin and having its opposite surfaces covered with layers (2,4) of continuous thermoplastic synthetic fibers which are bonded to said sheet of thermoplastic synthetic resin, said breathable liquid-impervious composite sheet being characterized in that said sheet (3) made of thermoplastic synthetic resin is nonwoven fabric and has its opposite surfaces bonded intermittently to said layers (2,4) of continuous fibers. A breathable liquid-impervious composite sheet according to Claim 1, wherein said nonwoven fabric sheet (3) has a maximum breathability of 200 sec/100 cc as measured in accordance with the method B of JIS L 1096 and a water resistance of at least 300 mm as measured in accordance with the method A of JIS L 1092.

Inventors: HANAJIRI TAKESHI, MATSUSHITA MICHIYO, HANAJIRI, TAKESHI, MATSUSHITA, MICHIYO, Hanajiri, Takeshi Technical Center, MATSUSHITA, Michiyo Technical Center
Applicants: UNI CHARM CORP, UNI-CHARM CO., LTD.
Application year: 2000
Main classification: B32B5
IPC codes: B32B5, D04H3, D04H13, B32B27