Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2001-04-27
2003-03-18
Moore, Margaret G. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C528S033000, C528S025000, C528S012000, C524S430000, C106S287160, C106S287120, C106S287170, C525S474000, C427S493000
Reexamination Certificate
active
06534187
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for the production of functional coatings of organofunctional silanes and a coating material for producing coated substrates.
2. Description of the Prior Art
Thermally curable coating materials for plastic surfaces based on polysiloxane, which lead to improved mechanical characteristics such as scratch resistance and abrasion resistance, have already been used commercially for a considerable time (cf. J. Hennig “Kratzfest beschichtete Kunststoffe” in Kunststoffe 71, 1981, p.103). However, the use of the coating materials described therein is partly limited by the low thermal stability of organic polymeric materials, so that for thermally less stressable thermoplastics, such as e.g. ABS, PS PVC, PUR, PE, PP, etc., UV-curable coating materials have been developed (cf. K. Greiwe in “Better Ceramics through chemistry V” published by M. J. Hampden-Smith, W. G. Klemperer and C. J. Brinker, “Characterisation of hydrolysed Alkoxysilanes and Zirconiumalkoxides for the development of UV-curable scratch-resistant coatings” in Mat. Res. Soc. Symp. Proc. Vol. 271, 1992, p.725). These polysiloxane-based, UV-curable materials are completely suitable for the above-indicated plastics in certain use cases as a result of their faster curing and lower thermal stressing, but fail to completely cover the use range of polysiloxane-based functional protective coatings.
DE 4,025,215 describes an alkali-stable and abrasion-resistant polysiloxane-based coating. The material is obtained by reacting organic epoxides with aminofunctional alkoxy silanes. However, the coating material only has a limited pot life and must therefore be used relatively quickly following its manufacture. DE 3,828,098 A1 describes a lacquer and a process for the production of scratch-proof coatings. Although this process leads to coatings, which offer satisfactory results with respect to numerous characteristics (e.g. scratch resistance, transparency, good primary adhesion to substrates), improvements are necessary to such coatings for numerous applications.
The main disadvantages of these systems are the lack of permanent adhesion of the thus produced coatings to substrates, as well as an inadequate pot life of the lacquers.
In the case of different corrosive stresses (particularly in alkaline aqueous solutions), the adhesion of such coatings deteriorates down to the complete detachment of the coating and consequently the protection (e.g. abrasion and corrosion protection) for the particular substrate is no longer guaranteed. The lacquers according to DE 3,828,098 A1 have such a short pot life that, if the described good characteristics are to be obtained, must be processed within a few hours (max. 8 h) and must therefore be directly produced in situ.
The problem of the present invention, based on DE 3,828,098, is to provide a coating material and a process for the production of functional coatings on substrates, which compared with the known coating materials has a permanent adhesion even under unfavourable corrosive conditions, whereby simultaneously good stratch and abrasion resistances are required. In addition, the coating material must have an increased pot life, so that it can be processed over a longer period of time extending to several weeks.
SUMMARY OF THE INVENTION
With respect to the process, this problem is solved, for example, by a process for the production of abrasion resistant functional coatings utilizing organofunctional silanes, a metal compound and difficultly volatile oxides, comprising the steps of:
a) performing a hydrolytic condensation, optionally in the presence of a condensation catalyst and/or additives, of the following components
1) at least one crosslinkable, organofunctional silane of formula (II)
R′″
m
SiX
(4−m)
(II)
in which the groups X, being the same or different, stand for hydrogen, halogen, alkoxy, acyloxy, alkylcarbonyl, alkoxycarbonyl or —NR″
2
(R″=H and/or alkyl) and the radicals R′″, being the same or different, stand for alkyl, alkenyl, alkynyl, aryl, arylalkyl, alkylaryl, arylalkenyl, alkenylaryl, arylalkynyl or alkynylaryl, in which the R′″ radicals can be interrupted by O or S-atoms or the group —NR″, the R′″ radicals can carry one or more substituents from the group of halogens and optionally substituted amino, amide, aldehyde, keto, alkylcarbonyl, carboxy, mercapto, cyano, hydroxy, alkoxy, alkoxycarbonyl, sulphonic group, phosphoric group, acryloxy, methacryloxy, epoxy or vinyl groups and m has the value 1,2 or 3 and/or an oligomer derived therefrom, in which the radical R′″ and/or the substituent is a crosslinkable radical or substituent, in a quantity of 10 to 95 mole %, based on the total number of moles of the monomeric starting component;
2) at least one metal compound of general formula III
MeR
y
(III)
in which Me is a metal selected from Al, Zr, or Ti, in which y in the case of Al aluminium is 3 and zirconium and titanium is 4 and the radicals R, which can be the same or different, stand for halogen, alkyl, alkoxy, acyloxy or hydroxy, in which said groups can be wholly or partly replaced by chelating ligands or an oligomer derived therefrom or an optionally complexed metal salt of an inorganic or organic acid, in a quantity of 5 to 75 mole %, based on the total number of moles of the monomeric starting component;
3) optionally at least one non-crosslinkable organofunctional silane of formula I
R′
m
SiX
(4−m)
(I)
in which the groups X, which can be the same or different, stand for hydrogen, halogen, hydroxy, alkoxy, acyloxy, alkylcarbonyl, alkoxycarbonyl or —NR″
2
(R″=H and/or alkyl) and the radicals R′, which can be the same or different, stand for alkyl, aryl, arylalkyl or alkylaryl, in which said R′ radicals can be interrupted by O or S-atoms or the group —NR″, the R′ radicals also can carry one or more substituents from the group of halogens and optionally substituted amide, aldehyde, keto, alkylcarbonyl, carboxy, cyano, alkoxy or alkoxycarbonyl groups and m has the value 1,2 or 3 and/or an oligomer derived therefrom, in a quantity of 0 to 60 mole %, based on the total number of moles of the monomeric starting components; and
4) optionally one or more difficultly volatile oxides, soluble in the reaction medium, of an element of the main group Ia to Va or the auxiliary groups IIb, IIIb, Vb to VIIb of the periodic system, with the exception of Al, and/or one or more compounds of one of these elements soluble in the reaction medium and forming a difficultly volatile oxide under the reaction conditions, in a quantity of 0 to 70 mole %, based on the total number of moles of the monomeric starting component;
b) adding to said hydrolytic condensate an organic, crosslinkable prepolymer, said crosslinkable prepolymer being completely an unblocked prepolymer, the reacting, crosslinkable groups of radical R′″ or the crosslinkable substituent at the radical R′″ being crosslinkable with identical reaction groups at the prepolymer and the prepolymer is added in a quantity of 2 to 70 mole %, based on the total number of moles of the monomeric starting component, thereby resulting in a coating solution; and
c) applying and subsequently curing the coating solution on a substrate. Advantageous further developments are described herein.
It is essential to the invention that through the use of the crosslinkable, organic silane of general formula II (component 1) in conjunction with the crosslinkable prepolymer, an additional, organic crosslinking occurs. It has surprisingly been found that the latter crosslinking is responsible for obtaining an excellent permanent adhesion, even when there is simultaneously a corrosive action. At the same time a greatly extended pot life is obtained. According to the preferred embodiment of claim
2
, it is particularly advantageous if the metal compound of genera
Greiwe Klaus
Kron Johanna
Schottner Gerhard
Fraunhofer-Gesellschaft zur Foerderung der Angewandten Forschung
Marshall & Melhorn LLC
Moore Margaret G.
Peng Kuo Liang
LandOfFree
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