Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Woven fabric
Reexamination Certificate
2002-03-11
2004-08-03
Juska, Cheryl A. (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Woven fabric
C428S131000, C428S132000, C428S133000, C428S134000, C428S135000, C428S136000, C428S137000
Reexamination Certificate
active
06770579
ABSTRACT:
The present invention relates to smart films and materials particularly those which can modify their porous properties and can be used in clothing.
When covering objects with a protective film or material it is often desirable for the film or material to be capable of allowing fluids, such as liquids and gases, to pass from the object through the film or material to the surrounding environment.
Examples of this requirement can be found particularly in clothing where a variety of Moisture Vapour Permeable (MVP) materials are known which allow water vapour to pass through the garment thus removing a proportion of the sweat generated by a wearer. These materials are also widely used in the medical field in the form of bandages and dressings. Also known are materials such as Stomatex (RTM) which is a rubber material having a number of perforations spread throughout the material. The material has pockets below each perforation configured so as to allow a local build up of vapour pressure before allowing the gases through. In both the clothing and medical uses these materials perform their specific function but are limited in that they can only remove gases and vapours and have a limited performance which is constant and does not change in response to environmental changes. Thus under extreme conditions the material will not be able to function satisfactorily. Clothing includes gloves, hats and footwear.
An aim of the present invention is to provide a smart porous film or material which automatically controls its porous properties in relation to changes in its local environment thus allowing fluids to pass through the film or material in a controlled fashion.
Accordingly, the present invention provides a smart film or material comprising at least two layers having different fluid absorption properties wherein all the layers are cut so as to provide a plurality of close fitting flaps through the film or material such that any strain differences between the layers caused by their different fluid absorption properties will cause the flaps to bend providing a plurality of openings in the layer.
As an alternative, the present invention also provides a smart film or material comprising a layer, a surface of which has discrete areas which have fluid absorption properties different to the rest of the layer wherein the discrete areas and the layer which they cover are cut so as to provide a plurality of close fitting flaps through the film or material such that any strain difference between the discrete areas and the layer which they cover, caused by their different fluid absorption properties, will cause the flaps to bend thus providing an opening in the layer.
The bending of the flaps is a result of the layers having different affinities for a fluid in the local atmosphere or the discrete areas having a different affinity for a fluid than layer which they cover.
One example of this effect is where a discrete area has different hydrophilic properties to the layer it covers or the layers have different hydrophilic properties to each other.
In a more specific example a discrete area could be arranged to take in more water or water vapour from the local atmosphere than the layer which it covers it then expands causing a strain difference between it and the layer which it covers. This strain difference causes the flaps to bend in the most energetically favourable direction.
The advantage of the above is that a film or material whose porosity can change in a controlled manner in response to changes in its local environment is provided.
In use the layer or one of the layers can be substantially impermeable such that fluids cannot pass through the film or material except via the openings caused through the film or material. Alternatively the layer or one of the layers can be permeable, in such an embodiment the amount of fluid which can pass through the film or material is increased or decreased by the opening or closing of the flaps through the film or material.
Advantageously one of the layers can be made of a polymer fibre with increased fluid absorption properties such as a polyethylene oxide macromolecular polymer covered by nylon such as Hygra™.
The discrete areas can be produced in the form of materials individually deposited on a surface of the layer, possibly using some form of chemical bond, by a printing process such as dot printing, by transfer coating or spread coating or by any other means which is capable of accurately depositing small amounts of a material on a surface. Alternatively the discrete areas can be produced by an etching process whereby a further layer is attached to the surface of the layer and areas of the further layer are etched away to leave the discrete areas.
The discrete areas deposited on a surface of the layer can be a hydrophilic gel or gel mixture or other suitable material. Such materials may contain, singly or in combination, polyvinyl alcohol, partially hydrolysed polyvinyl acetate, poly(vinylpyrrolidone), polyethylene glycol, ethoxylated polyethylene glycol, polysiloxane, ethoxylated polysiloxane, poly(acrylic acid),copolymers of acrylic acid, poly(N-isopropylacrylamide), poly(2-acrylamide-2-methylpropanesulphonic acid), collagen, gelatin, pectin, starch, in each case optionally cross-linked by incorporation of an appropriate physical cross-linking agent, e.g. borax, or chemical cross-linking agent, e.g. ethylene-bis-acrylamide, and suitable catalysts, e.g. lactic acid, or free radical initiators, e.g. azo-bis-isobutyronitrile, and compatible vegetable or mineral fillers, as has all been described in literature regarding such materials.
The discrete areas can also be formed by locally modifying the layer's fluid absorption properties thus avoiding the need to bond the discrete areas to the layer this can be done by plasma treating a surface of the layer or by treating a surface of the layer with chemicals or radiation. For example, exposing a material composed of an uncrosslinked polymer to a source of high energy radiation (such as UV light or gamma rays) or ionic particles (such as a plasma) it is possible to form crosslinks between the polymer molecules. If the initial starting material is hydrophilic it will be made more hydrophobic by this treatment and the material may also become stiffer.
Advantageously the discrete areas can be only a few millimeters in diameter and can be dispersed over the entire layer, or in specific locations of the layer, in a density defined by the level of porosity required of the film or material. The size of the discrete areas will in practice be limited by manufacturing techniques and the ability to make accurate, small cuts through the film or material.
Obviously larger discrete areas can be provided should large openings be required such as would be needed to allow liquids instead of gases to pass through the film or material.
The cutting of the flaps is preferably done so as to form a plurality of flaps which are located in a close fitting arrangement, i.e. the amount of material removed during cutting should be kept to a minimum. This is advantageous as it aims to maintain as much of the properties of the uncut film or material as is possible. Usefully this can be done using laser, water jet or punching techniques.
Any number of close fitting flaps can be provided at a single location in the film or material however a minimum of 3 flaps will allow the flaps to bend easily providing an opening. Further flaps would increase the size of opening produced at each location, however, the cutting procedure increases in complexity, and the amount of material removed will be increased, as more cuts are needed. The removal of more material will increasingly affect the overall properties of the film or material when the flaps are closed.
An additional improvement of the invention can be obtained by causing a further discrete area which has fluid absorption properties different to the rest of the layer to be formed, which individually surrounds some or all of the discrete areas and is disposed from the discrete area it surr
Dawson Colin
Vincent Julian
Juska Cheryl A.
Kilpatrick & Stockton LLP
Russell Dean W.
Salvatore Lynda
The Secretary of State for Defense
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