Stock material or miscellaneous articles – Composite – Of polyamidoester
Reexamination Certificate
1999-07-07
2001-01-23
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of polyamidoester
C428S423100, C428S423300, C428S212000, C428S213000, C428S216000, C428S217000
Reexamination Certificate
active
06177198
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a leather, on the buffed surface of which a finish has been provided, where the finish has an outer layer with a particular surface effect, which has been prefabricated on a hot substrate having a structure corresponding to this surface effect, and comprises a solidified, polyurethane-containing dispersion, and also has an inner layer which has been bonded to the buffed surface of the leather and likewise comprises a solidified, polyurethane-containing dispersion. For the purposes of the invention, th4e term “leather” means either natural leather, the buffed grain side of which has been provided with a finish, or else split leather whose buffed surface has been provided with a finish.
German Patent 32 29 150 discloses a finished split leather in which the finish is composed of two layers. Here, an aqueous polyurethane dispersion is applied to a substrate heated to a temperature of from 70 to 185° C. and solidifies on the substrate to give a film. The film is thereupon bonded, using pressure and suction, to the split-leather surface by a polyurethane dispersion comprising hollow microspheres. This method cannot produce thin finishes.
European Patent 105 046 describes a finished split leather in which the finish is likewise composed of two layers. An inner layer adjacent to the split leather has a thickness of from 0.12 to 0.45 mm, i.e. a substantial thickness. The properties of the leather are thereby adversely affected.
German published patent application 195 10 242 has disclosed a full-grain natural leather whose grain side has been provided with a finish which is applied to shaped pieces cut out from the natural leather. The finish there is composed of two layers formed by solidifying an aqueous, polyurethane-containing polymer dispersion. That finish has a thickness of up to 0.13 mm.
German published patent application 195 10 240 discloses the application of a finish with a varied surface effect and a thickness of up to 0.15 mm to a leather support having a specified margin.
German Utility Model 298 12 075.5 describes a full-grain natural leather provided with a finish and having a specified margin for producing automotive parts and composed of three layers each comprising a polyurethane dispersion. The outermost layer here has a particular surface effect and is prefabricated on a hot substrate having a corresponding structure, and its Shore hardness is greater than those of the intermediate and inner layers. This is claimed to ensure that the leather has the properties required for producing automotive parts.
German published patent application 37 20 776 discloses a leather material provided with a finish which is composed of a relatively thick leveling layer bonded to the leather and, applied thereto, a top layer which forms the visible surface and may be composed of two sublayers arranged one on top of the other, where there may be provision of a primer between the individual layers to improve adhesion, if desired. The leveling layer here is applied to the leather surface as a leveling substrate in the form of granules of leveling material. A finish of this type has substantial thickness, resulting in loss of leather properties.
In prior art leathers provided with a finish, the outer layer with a visible surface is bonded to the split leather by applying the material forming the inner layer in the wet state either to the leather surface or to the solidified outer layer, then laminating while supplying heat, whereupon some of the wet material penetrates into the leather and levels any uneven areas in the leather surface. It is therefore necessary to apply an appropriately large amount of the material forming the inner layer in order to ensure leveling of the uneven areas in the leather surface and reliable bonding, and this entails the thicknesses mentioned. The result is that known finished leathers have only low water-vapor permeability and water-vapor coefficients and therefore do not fulfill the requirements frequently placed upon leather.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a leather with a finish on its buffed surface, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which further improves the properties of a leather of that type, and in particular renders a leather of that type more usable for producing internal trim for conveyances, such as automobiles, aircraft and boats, for example for producing interior trim, trims for door sides, steering-wheel covers and the like, and also for producing shoes, in particular workwear shoes, and also for producing luggage, where the finish can retain the desired low thickness. Another object of the invention is substantially to increase water-vapor permeability and water-vapor coefficient. Another object of the invention is to increase abrasion resistance, lightfastness, heat resistance, chemicals resistance and solvent resistance, and also stability of grain. A further object of the invention is to be able to give a stable shape to the parts produced from the leather provided with a finish so that these parts retain the prescribed form after they have been shaped but surface protection is provided by the finish. A final object of the invention is to produce a leather whose visible side has various surface effects or has been provided with representations which do not have to be applied separately and subsequently, for example by laser treatment.
With the foregoing and other objects in view there is provided, in accordance with the invention, a leather assembly, comprising:
a leather having a buffed surface;
a finish layer on said buffed surface, said finish layer comprising a plurality of layers including
an outer layer with a given hardness and a particular surface effect preformed in a hot substrate having a structure corresponding to the particular surface effect said outer layer being formed of a solidified, cross-linked, hydrolysis-resistant, lightfast, polyurethane-containing dispersion, and having a thickness of between 0.01 and 0.08 mm, and
an inner layer bonded to said buffed surface leather and comprising a solidified, highly crosslinked, hydrolysis-resistant, lightfast, polyurethane-containing dispersion and having a hardness less than a hardness of said outer layer.
Especially if the inner layer is composed of two sublayers comprising a solidified, crosslinked polyurethane dispersion and fused to one another by applying pressure and heat, and is thinner than the outer layer, where the two sublayers forming the inner layer are fused after they have been solidified but before the crosslinking agent becomes effective, the thickness of this inner layer may be less than 0.03 mm since there is no need for the two sublayers forming the inner layer to be exposed before they have solidified, as is the case in known processes, to bonding pressure which requires an appropriate amount of the dispersion material forming the inner layer in order to ensure reliable bonding between the outer layer and the leather surface. This procedure gives undesirable filling of the pores in the outer layer and the cavities in the leather. The invention, in contrast, allows the inner layer to be constructed sufficiently permeably to give the novel leather extremely high water-vapor permeability of more than 3 mg/cm
2
×h and a water-vapor coefficient of more than 25 mg/cm
2
to European Standard EN 344-1, and the leather thus fulfills the requirements placed upon finished parts made from a leather of this type.
The invention allows the inner layer to be constructed in such a way that it does not form a coherent film, and this improves water-vapor permeability.
The outer layer preferably has highly developed elastomeric properties and does not have thermoplastic properties, and recovers completely after elongation at a temperature of from 100 to 120° C., whereas the inner layer, unlike the outer layer, does not have highly developed elastomeric proper
Greenberg Laurence A.
Lerner Herbert L.
Nakarani D. S.
Paulraj Christopher
Stemer Werner H.
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