Stock material or miscellaneous articles – Structurally defined web or sheet – Including variation in thickness
Reexamination Certificate
2001-05-07
2003-08-19
Loney, Donald J. (Department: 1772)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including variation in thickness
C428S171000, C428S198000, C156S209000, C156S219000, C156S290000, C156S553000
Reexamination Certificate
active
06607810
ABSTRACT:
The invention relates to a multi-layer composite according to the introductory clause to claim 1, and to a procedure for manufacturing a multi-layer composite according to the introductory clause to claim 17.
Numerous multi-layer composites are known, consisting of at least two layers made out of thermoplastics, wherein at least one layer is a knit comprised of thermoplastic fibers. Generally speaking, these involve web structures, in which a knit or several knits can be at least thermally bonded with at least one other web consisting of film, foil, fiber web or another knit, wherein the other web is to have at least one characteristic deviating from the knit. Therefore, an attempt is here made to combine varying characteristics of all kinds in the varying layers, in an effort to integrate varying functional systems of the second layer into fiber composites.
The knit layer is generally used as a carrier material, which ensures a certain mechanical strength and, if needed, must exhibit textile-like properties. Even as fast a flow of liquids, solids and gaseous substances through the knit can play a part in terms of the application.
The second layer is to have at least one property deviating from the first layer comprised of a knit. For example, the second layer can be a waterproof and vapor permeable membrane, a rubbery film (waterproof, if needed), or another knit, wherein the second knit has a property deviating from the first knit, e.g., the second knit can be hydrophobic, difficultly flammable, UV resistant or equipped with larger hole structures relative to the first knit.
These composites consisting of two varying layers can be used in another area of application, e.g., in the textile sector, in the area of hygiene as a component of diapers, feminine products, in medicine, e.g., as a cove, in construction, where such composites are used as support webs, or membranes open to diffusion, as protective clothing, and in agriculture as tarpaulins to protect against insects.
Depending on the requirement profile, the knits here consist of textile fibers comprised of PP, PE, PU, PA, PL, a copolymer or its homologues, isomers, as well as mixtures. of these raw materials.
In turn, the second layer designed as a membrane, for example, can be a plastic film, which is either microporous or enables the transport of water vapor through the membrane chemically via adsorption/desorption. In the latter case, it is conceivable to use a film comprised of PU, a block copolymer, a polyether, polyester or other hydrophilic polymers and copolymers that enable the transport of water vapor.
Also used as the membrane in addition to plastic foils are fiber membranes, preferably consisting of microfibers, which are given the required characteristics by compressing and/or hot sealing the fibers during their manufacture, or in another way.
As mentioned above, the second layer can also be a rubbery foil or rubbery film, as described in DE 42 43 012 C2.
The problem associated with all of these composites is the permanent and damage-free bonding of the second layer with one or two layers of a knit.
In order to bond the layers together, there are primarily three procedures available, namely bonding the layers in a hot-melt procedure, for example, thermal bonding, wherein a combination of both procedures is also possible, along with in situ direct coating, in particular with hydrophilic polymers.
Bonding the layers here poses a problem in that the application of adhesive over all or part of the surface impairs or diminishes air and water vapor permeability, and also results in a significant stiffening of the bonding material, thereby deteriorating the textile character of the composite in terms of softness, flexural rigidity and textile drape. In addition, the application of adhesives increases the manufacturing costs.
In thermal bonding, an attempt is made to non-positively and positively bond the layer over a partial surface based on the engraving pattern on the bonding rolls via pressure, temperature and time. This becomes a problem when the sharp edges of the bonding stubs dipping into the surface of the composite damage the second layer designed as a membrane, foil or film gets in such a way as to significantly diminish or even eliminate imperviousness to liquids. In addition, velocity differences of the web pulled out of the roll pressure nip by a preset tensile stress have a negative impact relative to the circumferential velocity of the bonding rolls itself.
If the second layer is designed as a rubbery foil, the diminished waterproofness is combined with the problem that no non-positive and positive bond can be achieved between the two layers during thermal bonding. The hot and sharp bonding stubs or stamps burn through the rubbery foil at the bonding points, thereby eliminating it. Thermal bonding changes the rubbery foil in such a way that it becomes a mesh-type structure after thermal bonding, which can be removed from the knit with only a slight exertion of force. This because the film is not integrated into the fiber system of the knit homogeneously or over the entire surface after thermal bonding, but rather only bonded with the knit at the bonding points.
The damage to the second layer is caused by the sharp edges of the bonding stubs. As a result of the sharply delineated, flat and small embossed surface, individual or several fibers involved in the bonding process get squeezed, melted or shorn off when the bonding stubs are immersed in the surface of the unbonded fiber structure of the fiber-woven fabric or the knit. Subsequently, this causes the material surrounding the bonding zone to become condensed, bonded and welded, and its properties relative to the textile nature to undergo an undesirable change.
With respect to the second layer, the sharp-edged, flat and punctiform embossed surface leads very easily to a fusing or melt break in this second layer. This results in a loss or decrease in the required properties, e.g., fluid imperviousness, in particular waterproofness, resilience of rubbery systems, imperviousness to bacteria and viruses, antibacterial finish, low flammability, UV resistance, antistatic finish, etc.
The object of the invention is to indicate a composite according to the introductory clause to claim
1
, which has the best possible textile properties, while at the same time not negatively influencing the respectively desired property of the second layer by bonding the varying layers to each other via thermal bonding. Further, the object of the invention is to indicate a procedure with which to fabricate such a composite.
This object is achieved with a multi-layer composite with the features in claim 1, or is achieved with a procedure having the features in claim 17.
According to the invention, the three-dimensional structure has at least one bonding zone in the transverse and longitudinal section resembling a curved cavity without any edges, which is formed by a floor area comprising a bonding center, as well as by seamlessly adjacent lateral areas, wherein the layers are thermally bonded with each other exclusively in the floor area of the cavity.
Such a composite completely satisfies the requirements placed on the textile nature, or retention of required properties for the second layer. Because the bonding zone does not have sharp and distinct edges based on the geometry of the bonding stubs as in conventional solutions, and appears punctiform just by appearance already, the cavity resembling a hemisphere, a body derived from the hemisphere or any other edgeless, rounded body enables a softly rolling thermal bonding process, and therefore a departure from the previously used embossing or stamping thermal bonding.
The lateral areas seamlessly adjacent to the bonding center here ensure a smooth, soft and flowing transition to the surface of the composite.
A visual inspection of a multi-layer composite according to the invention shows in particular that there are no sharp, hard delineated bonding points that impart a waffle-like structure to the composite. Quite the con
Coronor Composites GmbH
Loney Donald J.
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