Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Coated or impregnated woven – knit – or nonwoven fabric which... – Coating or impregnation specified as porous or permeable to...
Reexamination Certificate
1999-04-20
2003-01-14
Morris, Terrel (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Coated or impregnated woven, knit, or nonwoven fabric which...
Coating or impregnation specified as porous or permeable to...
C442S079000, C442S394000, C442S398000, C428S196000, C428S198000
Reexamination Certificate
active
06506695
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to breathable composites comprising film and fibrous nonwoven web layers and to manufacture of such composites.
BACKGROUND OF THE INVENTION
Breathable composites of thermoplastic films and fabrics are well known and are used in many applications, including construction wraps, disposable apparel and hygiene products. Composites of these types are generally characterized by breathability and liquid barrier properties that vary depending on porosity of the film layers and strength that varies with the nature of the fabric layers. For applications calling for low cost and light weight, the composites have been provided in the form of laminates of one or more layers of nonwoven fabric, or web, of thermoplastic filaments and one or more layers of breathable thermoplastic film. Examples of composites in that form and various utilities therefor are reported in commonly assigned U.S. Pat. No. 5,173,356, U.S. Pat. No. 5,208,098, U.S. Pat. No. 5,169,712, U.S. Pat. No. 5,176,953 and U.S. Pat. No. 5,236,963. An example of a strong, heavy-weight, durable composite is housewrap, formerly sold under the trademark Amowrap® by Amoco Foam Products Company, in the form of a laminate of a woven fabric and a permeable, perforated film.
Composites of porous films with uniform basis weight, continuous filament nonwoven fabrics and bonding thereof by means such as calendering, point embossing and needling are known from commonly assigned U.S. Pat. No. 5,173,356. U.S. Pat. No. 5,169,712, also commonly assigned, discloses composites of various materials, including woven fabrics, nonwoven fabrics such as spunbonded and other continuous filament light weight nonwovens, melt blown fabrics and staple fiber nonwovens, with microporous films in which microporosity results from inclusion of low molecular weight polypropylene, an inorganic filler or a beta spherulite nucleating agent in a film-forming resin composition comprising polypropylene and ethylene-propylene copolymer. Various bonding techniques for the layers of the composites and utility thereof in various applications, such as disposable diaper components, housewrap, protective clothing, liners and automobile covers, are disclosed.
Composites of elastic films and nonwoven fabrics are disclosed in U.S. Pat. No. 5,422,172. The composites are prepared by extruding or coating an elastic, film-forming resin composition onto a nonwoven fabric and stretching the result uniformly across the laminate and throughout its depth. Stretching of the laminated film and fabric layers disrupts bonding of the filaments of the fabric such that on release of the stretching force the composite assumes an unstretched state with a multitude of filaments reportedly extending outwardly from a surface of the composite to form a lofty surface. Disclosed utilities for the composites are those in which elasticity, absorbency and softness are desirable; examples are said to include clothing articles, surgical gowns, sheets, dressings, hygienic products, baby diapers, baby training pants and catamenial pads. Typical laminates according to this patent include an impervious, elastic film layer. It is also noted that various degrees of air or vapor permeability may be achieved by providing mechanical microvoids to the films; however, there is no description or example of this concept.
U.S. Pat. Nos. 4,777,073 and 4,929,303 disclose laminates of fabrics and breathable films in which porosity of the film layer is achieved by stretching a particulate-filled film subjected to prior melt embossing so as to form thinner and thicker regions of the film. Stretching of the film results in regions of greater and lesser porosity.
Published International Application WO 97/29909 discloses a method for making microporous, cloth-like laminates of nonwoven fibrous webs and thermoplastic films. The laminates are said to have liquid barrier properties. As disclosed in this application, the laminates are made by laminating, by extrusion or adhesion, a nonwoven fibrous web and a microporous-formable thermoplastic film containing micropore-forming agents and then activating the pore formers by incremental stretching. A difficulty of this method is that the cloth-like surface of the laminate is sometimes achieved at the expense of a good bond between the film-forming and fibrous web layers. In addition, the stretching techniques used according to this publication are quite complex and rely on costly, highly specialized equipment.
There remains a need for improved, breathable laminates and methods for manufacture thereof. More specifically, some of the structures of the patents and publications discussed above suffer from harsh surface textures due to the inherent harshness of plastics from which low cost nonwoven fabrics are typically made. Thermal or adhesive bonding techniques used to laminate films and fabrics, such as bonding with smooth calender rolls, can result in composites with undesirable stiffness. Thermal bonding of microporous films to substrates can also disturb or destroy the films' porosity. It can also lead to formation of pinholes in the films, resulting in loss of strength, liquid barrier properties and other features. In other methods, breathability often is achieved at the expense of liquid barrier properties. Development of porosity in films by stretching after lamination of films and nonwoven webs, on the other hand, can lead to ineffective bonding between layers and nonuniform surfaces or surface textures. Such techniques also can be complicated and costly due to highly specialized equipment needs.
SUMMARY OF THE INVENTION
This invention provides breathable composites of breathable thermoplastic film and fibrous nonwoven web layers having good adhesion between the film and web layers, breathability and liquid barrier properties. The invention also provides a process for manufacture of breathable laminates of breathable film and fibrous nonwoven web layers having a desirable combination of properties.
In one embodiment, there is provided a breathable composite material having a hydrostatic head according to IST 80.4-92 of at least about 4 inches comprising at least one layer of breathable film comprising a thermoplastic resin composition laminated to at least one layer of a nonwoven web comprising filaments of a thermoplastic resin, wherein breathability of the film layer is provided by a plurality of discontinuous point-like deformations of the film layer. Preferred laminates according to this embodiment of the invention have a moisture vapor transmission rate according to ASTM E-96 Method E (“MVTR”) of at least about 500 g/m
2
day.
In another embodiment, the invention provides a process for making breathable composites of films and nonwoven fibrous webs comprising applying to a nonwoven fibrous web comprising thermoplastic filaments a coating of molten, film-forming thermoplastic resin composition capable of developing breathability, cooling the molten resin to form a coated web and applying heat and pressure to the coated web at a plurality of points on a surface thereof to impart breathability to the coated web while substantially maintaining liquid barrier properties thereof.
Also provided is a process for making breathable composites of films and nonwoven fibrous webs comprising contacting a nonwoven fibrous web comprising thermoplastic filaments with a film comprising a thermoplastic resin composition capable of developing breathability and applying heat and pressure to the film in contact with the web at a plurality of points to bond the web and the film and develop breathability of the film at such points.
DETAILED DESCRIPTION OF THE INVENTION
The composites according to this invention are textile- or fabric-like structures in the form of laminates comprising nonwoven web and film layers having a desirable combination of breathability and liquid barrier properties. They have utility in a wide range of applications for both durable and disposable fabrics. Examples include disposable gowns and coveralls for hospital and indu
Gardner Hugh C.
Lui Kam C.
Mumm Jeffrey H.
Befumo Jenna-Leigh
Forman Alexander D.
Gridley Doreen J.
Ice Miller
Morris Terrel
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