Paper making and fiber liberation – Processes and products – Safety – identification and fraud preventing paper
Patent
1996-05-23
1998-04-28
Chin, Peter
Paper making and fiber liberation
Processes and products
Safety, identification and fraud preventing paper
162103, 283 70, 283 72, D21H 1310
Patent
active
057440000
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to filaments or fibers which are treated to give them a recognisable "signature" (encoding) and more particularly, a signature which is machine-readable. The invention is realized in both the method of producing the filaments or fibers and in the filaments or fibers themselves.
SUMMARY OF THE INVENTION
Fibers having a machine-readable signature can be used, for example, to identify security papers, such as paper used for currency.
According to a first aspect of the invention, a method of manufacturing an encoded filament or fiber comprises: providing a film, applying a bar code directly onto the film across the effective width of the film, and then dividing the film substantially at right angles to the bar code into longitudinal filaments. It will be appreciated that it is not feasible to apply a bar code to a very narrow filament or fiber, but a bar code can be readily applied across the effective width of a film, and when the film is divided longitudinally, each of the strips or filaments so produced has the bar code applied to it. Even if the filaments are narrow enough to constitute fibers, each of those fibers will still carry the bar code, in very narrow form, and hence has the same "signature" or encoding as that applied to the film.
The film is preferably made of plastics material. Preferred materials include polyolefin, polyvinylchloride, polyester, polyamide, polyethersulphone, or polyetheretherketone (PEEK). A preferred polymer is polyolefin, especially a propylene polymer (which may be a homopolymer or an ethylene-propylene co-polymer with a minor proportion of ethylene). The polyolefin is preferably polypropylene with a melt flow index of approximately 8 to 10 grammes per ten minutes, according to ASTM D1238.
According to a preferred feature of the invention, the film is divided longitudinally by fibrillation. If relatively wide filaments (say, over 1 mm in width) are required, it might be possible to employ slitters, but where the requirement is for narrower filaments, which can properly be described as fibers, then slitters are not suitable, but fibrillation can be used.
The deformation in the fibrillation unit may be twisting (for example, as described in British Patent Specification 1 040 663) or surface striation (for example, as described in "Fibre Technology: From Film to Fibre" by Hans A. Krassig, published by Dekker (1984)). Such surface striation typically involves passing the film under tension against needles or pins provided on a rotating roller, to cause rupture of the film longitudinally (in the machine direction), but without lateral separation or splitting until after the film has passed downstream of the roller. Such fibrillation is well known for polymer films where the film is fed in a continuous production run from the extruder to the fibrillation unit and it is one of the perceived advantages of the fibrillation process that it can be operated as an integral part of a continuous operation.
The fibrillation process causes the film to break up into long parallel filaments. In practice these long filaments may be cut to a "staple" length longer than the bar code repeat. It will also be appreciated that the film can be fed continuously past a bar code applicator, the arrangement providing repeats of the bar code along the length of the film.
According to another preferred feature of the invention, the two colour effect required to produce the code bars and spaces is not readily visible to the naked eye. If the fibers produced by the invention are of small size, then the bar code will be difficult to detect with the naked eye in any event. (By way of illustration, 20 microns width will give a fiber approximately 5 decitex.) However, it is preferred that at least one of the two colours is outside the visible spectrum, and in the preferred method, the said one colour is fluorescent. In practice, it may only be necessary to apply one colour, since the other colour may be the natural colour of the film.
The use of encoding not visi
REFERENCES:
patent: 4761205 (1988-08-01), Crane
patent: 4891254 (1990-01-01), Bianco
patent: 4997875 (1991-03-01), Geddes et al.
patent: 5239902 (1993-08-01), Kaule
patent: 5573639 (1996-11-01), Schmitz et al.
Athey Graham
Zorab James
Chin Peter
Leavitt Steven B.
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