Stock material or miscellaneous articles – Composite – Of polycarbonate
Patent
1997-02-27
1998-12-15
Hoke, Veronica P.
Stock material or miscellaneous articles
Composite
Of polycarbonate
B32B 2736
Patent
active
058494146
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Moulded parts made from polycarbonates are distinguished by transparency, high impact strength, high heat deflection temperature and dimensional stability. However their susceptibility to scratching often detracts from these qualities. In order to remedy this, the moulded parts can be provided beforehand with a scratch-resistant layer. The scratch-resistant coatings or coating methods used hitherto are still not completely satisfactory particularly as regards scratch resistance and adhesion of the layer to the substrate with the lowest possible layer thickness or curing time of the scratch-resistant layers.
The invention relates to a method for coating particular polycarbonates having a high heat deflection temperature using particular siloxane-containing coatings, wherein the resulting coating has a particularly high scratch resistance and good adhesion to the substrate and the coating cures within a short period and exhibits a particular transparency.
SUMMARY OF THE INVENTION
The invention provides a method for coating polycarbonate moulded parts, which is characterised in that to the surface of a moulded body composed of a polycarbonate based on a diphenol of formula (Ia) ##STR2## wherein R.sup.1 and R.sup.2 independently of one another signify hydrogen, halogen, preferably chlorine or bromine, C.sub.1 -C.sub.8 alkyl, C.sub.5 -C.sub.6 cycloalkyl, C.sub.6 -C.sub.10 aryl, preferably phenyl, and C.sub.7 -C.sub.12 aralkyl, preferably phenyl-C.sub.1 -C.sub.4 alkyl, in particular benzyl, independently of one another signify hydrogen or C.sub.1 -C.sub.6 alkyl and simultaneously signify alkyl, an aluminium compound of an organofunctional silane and an oxide component, is applied in a thickness of from 2 to 200 .mu.m and the material is cured at a temperature of from 135.degree. to 180.degree. C.
The invention also provides the scratch-resistant polycarbonate moulded bodies thus obtained.
The polycarbonates A are high-molecular, thermoplastic, aromatic polycarbonates having molecular weights M.sub.w (weight average) of at least 10,000, preferably of from 20,000 to 300,000, which contain the bifunctional carbonate structural units of formula (I) ##STR3## wherein R.sup.1 and R.sup.2 independently of one another signify hydrogen, halogen, preferably chlorine or bromine, C.sub.1 -C.sub.8 alkyl, C.sub.5 -C.sub.6 cycloalkyl, C.sub.6 -C.sub.10 aryl, preferably phenyl, and C.sub.7 -C.sub.12 aralkyl, preferably phenyl-C.sub.1 -C.sub.4 alkyl, in particular benzyl, independently of one another signify hydrogen or C.sub.1 -C.sub.6 alkyl and simultaneously signify alkyl.
PREFERRED EMBODIMENTS
These polycarbonates and the underlying dihydroxydiphenylcycloalkanes of formula (Ia) and the preparation of both products are described in detail in EP 395 953. The dihydroxydiphenylcycloalkanes of formula (Ia) are starting materials for the polycarbonates A. In this formula (Ia) the preferred alkyl radical is methyl; the X atoms in the .alpha.-position to the diphenyl-substituted C atom (Cl) are preferably not dialkyl-substituted, whereas alkyl disubstitution in the .beta.-position to Cl is preferred.
Dihydroxydiphenylcycloalkanes having rings of 5 and 6 C atoms in the cycloaliphatic radical (m=4 or 5 in formula Ia) are preferred, for example the diphenols of formulae (Ib) to (Id) ##STR4## with the 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (formula Ib having R.sup.1 and R.sup.2 equal to H) being particularly preferred.
One diphenol of formula (Ia) may be used, with the formation of homopolycarbonates, or several diphenols of formula (Ia) may be used, with the formation of copolycarbonates.
Furthermore the diphenols of formula (Ia) may also be used mixed with other diphenols, for example with those of formula (Ie) polycarbonates.
Other suitable diphenols of formula (Ie) are those wherein Z is an aromatic radical having 6 to 30 C atoms, which can contain one or more aromatic rings, can be substituted and can contain as bridges aliphatic radicals or cycloaliphatic radicals different from those
REFERENCES:
patent: 4746366 (1988-05-01), Phillip et al.
patent: 5126428 (1992-06-01), Freitag et al.
patent: 5298477 (1994-03-01), Wehrmann et al.
patent: 5316855 (1994-05-01), Wang et al.
patent: 5401579 (1995-03-01), Basil et al.
Bier Peter
Freitag Dieter
Schottner Gerhard
Bayer AG
Hoke Veronica P.
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