Stock material or miscellaneous articles – Structurally defined web or sheet – Including aperture
Reexamination Certificate
2000-12-06
2004-06-15
Pyon, Harold (Department: 1772)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including aperture
C442S062000, C604S367000
Reexamination Certificate
active
06749923
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to liquid impermeable moisture vapour permeable composite structures comprising a specific thermoplastic film which is thinly coated onto a support layer. The composite structures of the present invention can find a variety of applications, wherein moisture vapour permeability is desirable for example within absorbent articles such as diapers, sanitary napkins, panty liners and incontinence products, protective bedding covers, protective clothing and the like.
BACKGROUND OF THE INVENTION
Thermoplastic films which provide a liquid barrier in addition to providing moisture vapour permeability are known in the art. Particularly preferred are hydrophilic continuous films that do not allow the flow of moisture vapour through open pores or apertures in the material, but do transfer substantial amounts of moisture vapour through the film by absorbing water on one side of the film where the moisture vapour concentration is higher, and desorbing or evaporating it on the opposite side of the film where the moisture vapour concentration is lower. Compositions used to form hydrophilic continuous, moisture vapour permeable, liquid impervious films are also said to be moisture vapour permeable, liquid impervious.
For example WO 95/16746 discloses films prepared from mixtures of a) block copolyether ester, block copolyether amides (e.g. Pebax™) and or polyurethane and b) thermoplastic polymer which is incompatible with a, and c) a compatibiliser. The films are liquid impermeable and have moisture vapour permeability of about 700 g/m
2
/day. Also, U.S. Pat. No. 5,447,783 discloses a vapour permeable water resistant multi component film structure having at least three layers. The outer layers are hydrophobic copolyetherester elastomers having a thickness of 1.3-7.6 micrometers and a WVTR of 400-2500 g/m
2
/24 hrs. and the inner layer is a hydrophilic copolyetherester elastomer having a thickness of 7.6-152 micrometers and a WVTR of at least 3500 g/m
2
/24 hrs.
U.S. Pat. No. 5,445,875 discloses a waterproof, bloodproof and virusproof breathable laminate. The laminate comprises a woven
onwoven fabric and an extruded film such as Hytrel™ having a thickness of about 1 mil.
However, whilst these films are desirable in so far as their moisture vapour transport rate is concerned, these films tend to lack other desirable physical characteristics such as tear strength and flexibility depending on the end usage envisioned.
Attempts to address this problem have resided in providing the polymers on a supportive substrate which provides the required physical attributes. Such composites are described for example in U.S. Pat. No. 5,599,610 which discloses tri-laminated fabric for surgical gowns comprising outer layers of woven fabric and an inner layer of a microporous polyurethane membrane. The microporous film has a thickness of 12-55 micrometers and a MVTR of 1100 g/m
2
/24 hrs. upright and 5500 g/m
2
/24 hrs. inverted (ASTM E96-B). Polyether-polyurethane adhesive is used to join the layers.
Similarly, U.S. Pat. No. 5,532,053 discloses a high moisture transmission medical film which can be laminated onto a nonwoven material. The laminate film comprises a first layer of polyetherester copolymer and second and third layers selected from a specified group of polymers. The film has a MVTR of greater than 750 g/m
2
/24 hrs. (ASTM F1249) and a thickness of less than 1 mil (25.4 micrometer) preferably 0.6 mm to 0.75 mm (15-19 micrometers).
U.S. Pat. No. 4,938,752 discloses absorbent articles comprising films of copolyether esters which have reduced water permeability, a water vapour permeability of 500 g/m
2
/24 hrs. (as measured in a specified described test) and a thickness of 5-35 micrometers. There is no disclosure of a supportive substrate.
U.S. Pat. No. 4,493,870 discloses a flexible layered waterproof product comprising a textile material covered with a film of a copolyetherester having an MVTR of at least 1000 g/m
2
/24 hrs. (ASTM E96-66) having a thickness of 5 to 35 micrometers.
GB 2 024 100 discloses a flexible layered water resistant article comprising a microporous hydrophobic outer layer which is moisture vapour permeable but resist liquids and a hydrophilic inner layer of polyetherpolyurethane having a MVRR of above 1000/m
2
/24 hrs.
However a problem with the films disclosed in the prior art is that the thickness at which the films can be readily extruded onto a support substrate is severely limited using standard extrusion techniques. Furthermore such films often require the addition of an adhesive in order to ensure permanent fixation of the coating to the substrate. However, this in turn detrimentally affects the overall moisture vapour permeability of the resulting composite.
Hence, there is a need to provide a composite structure which is liquid impermeable and moisture vapour permeable and which is readily processable so as to provide a thin film coating.
SUMMARY OF THE INVENTION
The present invention relates to a moisture vapour permeable liquid impervious composite substrate.
Said substrate comprises:
(a) a thermoplastic film made form a moisture vapour permeable thermoplastic composition having a complex viscosity of from 50 poise to 4000 poise at a frequency of 1 rad/s, at a temperature of 210° C. or less, and a complex viscosity of less than 2000 poise at a frequency of 1000 rad/s and at a temperature of 210° C. or less, said film having a thickness of less than 10 micrometers to 0.5 micrometers and
(b) a support layer, said support layer being moisture vapour permeable.
REFERENCES:
patent: 4758239 (1988-07-01), Yeo et al.
patent: 4857393 (1989-08-01), Kato et al.
patent: 5683815 (1997-11-01), Leiss
patent: 5827252 (1998-10-01), Werenicz et al.
patent: 6071450 (2000-06-01), Topolkaraev et al.
patent: 6495612 (2002-12-01), Corzani et al.
patent: 6498201 (2002-12-01), Corzani et al.
patent: 6534561 (2003-03-01), Palumbo et al.
patent: 0 295 694 (1988-12-01), None
patent: 0 539 604 (1993-05-01), None
patent: 1 341 605 (1973-12-01), None
patent: WO 96/25902 (1996-08-01), None
Corzani Italo
Palumbo Gianfranco
Johnson Kevin C.
Lewis Leonard W.
Nordmeyer Patricia L.
Pyon Harold
Taffy Frank
LandOfFree
Moisture vapor permeable composite structure and the... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Moisture vapor permeable composite structure and the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Moisture vapor permeable composite structure and the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3346449