Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Patent
1994-04-29
1997-07-01
Dean, Ralph H.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
528 10, 528 32, C08G 7724
Patent
active
056440146
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to coating compositions based on fluorine-containing inorganic polycondensates as well as the preparation and the use thereof.
There are already known numerous coating compositions which are based on organically modified inorganic polycondensates, particularly those of Si, Al, Ti and Zr, and after a corresponding curing result in coatings for a wide variety of substrates, said coatings having the most different advantageous properties, e.g. outstanding scratch resistance, flexibility, transparency and/or abrasion resistance. Nevertheless, said known coating systems still leave room for improvement, particularly as regards their anti-adhesion properties towards hydrophilic and oleophilic substances as well as towards dust.
Thus, the problem underlying the present invention was to provide a coating composition which besides the excellent properties of the already known coating systems based on inorganic polycondensates modified with organic groups, particularly transparency, mechanical strength and abrasion resistance, also exhibits outstanding anti-adhesion properties towards the most different substances.
According to the present invention the above problem is solved by a coating composition based on polycondensates of one or more hydrolyzable compounds of elements M of the main groups III to V and the subgroups II to IV of the periodic system of elements, at least part of said compounds having non-hydrolyzable carbon containing groups B in addition to hydrolyzable groups A and the total molar ratio of groups A to groups B in the monomeric starting compounds from which they are derived ranging from 10:1 to 1:2, said coating composition being characterized in that 0.1 (and particularly 0.5) to 100 mol-% of said groups B are groups B' which on the average have 2 to 30 fluorine atoms bonded to one or more aliphatic carbon atoms which carbon atoms are separated from M by at least two atoms.
The preparation of such coating compositions generally cannot be carried out satisfactorily by means of the common methods for the provision of such coating systems, particularly if transparent coatings are to be obtained, as upon the addition of water necessary for the hydrolysis of the starting compounds, the starting compounds having (fluorinated) groups B' tend to separate, thereby resulting in a two-phase system with which a satisfactory homogeneous coating composition cannot be achieved anymore. Thus, another problem underlying the present invention also was to provide a process for the preparation of the above coating composition wherein the just mentioned problems do not occur.
Accordingly, object of the present invention is also a process for the preparation of the coating composition defined above, which process is characterized in that initially all or a part of the starting compounds without groups B' are hydrolyzed and precondensed by the addition of water whereafter the starting compounds having said groups B' are added and after the reaction of the latter with the already present prehydrolyzed starting compound and the precondensates, respectively the hydrolysis and condensation of the species present is continued by adding further water and, optionally, the remainder of the starting compounds without groups B' until an applicable system is obtained, the addition of said starting compounds having groups B' being carried out only after the water content of the system is not higher than 5% by weight, based on the total weight of the system without solvent optionally employed, and not more than 50% of the theoretically possible groups M--OH are present in the system.
Thus, in the preparation process according to the present invention, precondensates are first prepared and only then the fluorinated starting compounds are added, said fluorinated starting compounds being then bonded to said precondensates by hydrolysis and condensation and thereafter do not result in phase separation upon further addition of water anymore, so that a homogeneous coating system cab be obtained.
The hydro
Bruck Stefan
Kasemann Reiner
Schmidt Helmut
Dean Ralph H.
Institut fur Neue Materialien gemeinnutzige GmbH
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