Stock material or miscellaneous articles – Composite – Of polyamidoester
Patent
1998-03-20
2000-04-11
Krynski, William
Stock material or miscellaneous articles
Composite
Of polyamidoester
428195, 156 60, 1563317, 4274121, 4274124, 427369, B32B 2700, B32B 2740
Patent
active
060486198
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of attaching a bicomponent polyurethane surface to a polymer substrate. This method applies to the domain of bonding two polymers, particularly for manufacturing smart cards with and/or without projecting contacts.
Current methods of bonding bicomponent polyurethane (PU) to a polymer substrate consist of placing a resin on the substrate, said resin comprising the two components necessary for forming the PU, namely a polyol and a diisocyanate, and pressing them for several minutes.
However, the bonds obtained by these methods are not of very good quality. This is because molecular water layers present at the substrate surface create a screen between the substrate and the polyurethane. This screen prevents formation of hydrogen and/or Van der Walls bonds between the polyurethane and the substrate, which are necessary for obtaining a good-quality bond. The polyurethane hardening agent, i.e. the diisocyanate, tends to react both with the polyol of the polyurethane composition and with the surface moisture.
The first solution that immediately comes to mind to allow good bonding of the polyurethane on the substrate without interference by the surface moisture consists of using a resin wherein the diisocyanate is in excess relative to the polyol. In this way, the polyol can be made to react fully with the diisocyanate and the surface moisture to react with the excess diisocyanate. However, secondary reaction products form in this case, such as urea or biuret bridges, which also form a screen at the interface between the PU and the substrate and are thus detrimental to a good-quality bond.
A second solution, in current use, consists of using a specific catalyst to avoid over-reactivity of the surface moisture of the substrate with the diisocyanate and on the contrary to increase the kinetics of the reaction between the polyol and the diisocyanate. Thus, the reaction between the polyol and the diisocyanate is favored over the reaction between the moisture and the diisocyanate. The specific catalyst used is dibutyltin dilaurate. However, this solution is unsatisfactory since some moisture still remains at the substrate surface, forming a screen between the polyurethane and the substrate, so that it is impossible to obtain a good-quality bond.
The present invention overcomes all the disadvantages listed above since it provides a method for bonding a bicomponent polyurethane surface to a polymer substrate, consisting of placing on the substrate a resin comprising a polyol and a diisocyanate, which are necessary for forming polyurethane, and pressing them, wherein a specific catalyst able simultaneously to catalyze the reaction between the polyol and the diisocyanate and the reaction between the surface moisture and the diisocyanate is used.
For this purpose, one characteristic of the method according to the invention consists of using a catalyst chosen from the tertiary amines.
According to another characteristic of the invention, the catalyst used is diazobicyclo[2.2.2]octane (Dabco).
According to another characteristic of the invention, the substrate material is chosen from the polymers that have hydrogen bonds with the PU.
The method according to the present invention overcomes all the disadvantages linked to the surface moisture of the substrate. Hence, it eliminates the screen formed by the water molecules at the interface between the substrate and the polyurethane, thus considerably improving the quality of the bond.
Dabco is generally used as a foaming agent to make polyurethane foams. On the other hand, it has never been used in areas other than foams, such as bonding two polymers for example.
Other features and advantages of the invention will emerge from reading the description provided as an illustrative and nonlimiting example.
One embodiment of the method according to the invention consists, first, of placing a resin on a polymer substrate, said resin comprising a catalyst and the two components necessary for forming the polyurethane network by polycondensation, namely a
REFERENCES:
patent: 3813380 (1974-05-01), Bock
patent: 4373081 (1983-02-01), Nachtkamp et al.
patent: 4424834 (1984-01-01), Sumi et al.
patent: 4436784 (1984-03-01), Ehrhart
patent: 5356717 (1994-10-01), Choki et al.
Leriche Christian Gustave Alain
Turin Joel Alain Jerome
Gemplus S.C.A.
Krynski William
Plottel Roland
Shewareged B.
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