Crease-resistant security film
The invention relates to a crease-resistant security film including: fibers; polyurethane aggregates, the proportion of said polyurethane amounting to between 5 and 45 wt. % in relation to the total dry weight of the fibers and the polyurethane, and said polyurethane having a break elongation that is higher than 600%; and a main cationic flocculant in a quantity of between 1 and 5 wt. % in relation to the total dry weight of the fibers and the polyurethane. The invention also relates to the method for the production of said film, and to a security document including said security film.
1. A crease-resistant security sheet comprising:
fibers,
polyurethane aggregates, the polyurethane being in a proportion of between 5% and 45% by dry weight relative to the total dry weight of the fibers and of the polyurethane and having an elongation at break of greater than 600%, and
a main cationic flocculating agent in an amount of between 1% and 5% by dry weight relative to the total dry weight of the fibers and of the polyurethane.
2. The security sheet as claimed in claim 1 , wherein the proportion of said polyurethane is between 10% and 30% by dry weight relative to the total dry weight of the fibers and of the polyurethane.
3. The security sheet as claimed in claim 1 , wherein said polyurethane has an elongation at break of greater than 1000%.
4. The security sheet as claimed in claim 1 , wherein said polyurethane has a glass transition temperature below 0° C.
5. The security sheet as claimed in claim 1 , wherein said polyurethane has a glass transition temperature below −25° C.
6. The security sheet as claimed in claim 1 , wherein said polyurethane has a glass transition temperature below −40° C.
7. The security sheet as claimed in claim 1 , wherein said polyurethane is selected from the group consisting of a polyurethane-polyester, a polyurethane-polyether, and a polyurethane-polycarbonate.
8. The security sheet as claimed in claim 1 , wherein said polyurethane is a polyurethane-polyester.
9. The security sheet as claimed in claim 1 , wherein said main cationic flocculating agent is selected from the group consisting of a cationic resin, polyacrylamides, polyethyleneimines, polyvinylamines, and mixtures thereof.
10. The security sheet as claimed in claim 1 , wherein said main cationic flocculating agent is a polyamide-amine-epichlorohydrin resin.
11. The security sheet as claimed in claim 1 , wherein said fibers comprise cellulosic fibers.
12. The security sheet as claimed in claim 11 , wherein said cellulosic fibers is present in a proportion of greater than 60% by dry weight relative to the total dry weight of the fibers and of the polyurethane.
13. The security sheet as claimed in claim 1 , wherein said fibers comprise synthetic fibers.
14. The security sheet as claimed in claim 13 , wherein said synthetic fibers is present in an amount of between 5% and 30% relative to the total dry weight of the fibers and of the polyurethane.
15. The security sheet as claimed in claim 1 , wherein said sheet comprises a secondary cationic flocculating agent selected from the group consisting of polyacrylamides, polyethyleneimine, polyvinylamines, and mixtures thereof, in an amount which may be between 0.1% and 0.5% by dry weight relative to the total dry weight of the fibers and of the polyurethane.
16. The security sheet as claimed in claim 1 , wherein said sheet comprises at least one security element.
17. The security sheet as claimed in claim 1 , wherein said sheet comprises an RFID device.
18. The security sheet as claimed in claim 1 , wherein said sheet comprises an external surfacing layer.
19. A process for manufacturing a security sheet as described in claim 1 , consisting in forming said sheet via a wet route from an aqueous suspension comprising:
fibers,
an anionic dispersion of a polyurethane, and
a main cationic flocculating agent,
then draining and drying said sheet.
20. A process according to claim 19 , wherein said polyurethane is in a proportion of between 5% and 45% by dry weight relative to the total dry weight of the fibers and of the polyurethane and has an elongation at break of greater than 600.
21. A process according to claim 19 , wherein said main cationic flocculating agent is in an amount of between 1% and 5% by dry weight relative to the total dry weight of the fibers and of the polyurethane.
22. The process as claimed in claim 19 , wherein said fibers, said anionic dispersion of polyurethane, and said main cationic flocculating agent are mixed in bulk.
23. A security document, comprising a security sheet as described in claim 1 .
24. The security document as claimed in claim 23 , wherein said document is a means of payment, an identity document, or a card.
25. The security document as claimed in claim 24 , wherein said document is a banknote, a driving license, or a card.