A single-component polyurethane coating mass, applicable in a dry layer up to 2000 microns thick, containing a mixture of 50 to 67 wt. % of an aromatic di- or polyisocyanate as the isocyanate component.

TECHNICAL FIELD 
The invention relates to a moisture-hardening coating mass applicable in a 
dry layer having a thickness up to 2000 microns, i.e. a single-component 
polyurethane coating mass. 
BACKGROUND OF THE INVENTION 
Coating masses, in which aliphatic di- or polyisocyanates are used as the 
isocyanate component, are particularly suitable for the production of 
mechanically and/or climatically resistant coatings on objects made of 
wood, concrete, steel, etc. Compared with two-component polyurethane 
coating masses, they have the advantage that they harden through reaction 
with the moisture contained in the ambient air, i.e., it is not necessary 
to add a separately supplied hardener prior to their use. Up until now, 
however, it has only been possible to apply them to the substrate in 
relatively thin dry layers up to 100 microns thick, because bubbles tended 
to form in thicker layers and/or the coating adhered poorly to the 
substrate and/or the hardened layer exhibited buckling and/or cracking 
and/or opacity. However, the protection provided against mechanical and/or 
atmospheric influences by such thin coatings is often not as good or not 
as durable as desired. 
SUMMARY OF THE INVENTION 
It is the object of the invention to provide a single-component 
polyurethane coating mass which can be applied in one operation to a 
substrate in film thicknesses up to 2000 microns without any of the 
above-mentioned disadvantages occurring. 
Up to now, aliphatic di- or polyisocyanates were used as the isocyanate 
component in the single-component coating masses. 
Surprisingly, it has now been discovered that, using a single component 
polyurethane coating mass containing a mixture of 30 to 70 vol. % 
aliphatic and 70 to 30 vol. % cycloaliphatic polyisocyanate as the 
isocyanate component, it is possible to apply coatings having a dry film 
thickness up to 2000 microns without the above disadvantages occurring.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In accordance with the present invention, there is provided a 
single-component polyurethane coating mass which includes as the 
isocyanate component a mixture of from about 50 wt. % to about 67 wt. % of 
an aliphatic di-of polyisocyanate and from about 33 wt. % to about 50 wt. 
% of an cycloaliphatic di- or polyisocyanate. In other words, in forming 
the coating masses in accordance with the present invention, the 
aforementioned inventive mixture of isocyanates is utilized. 
In one embodiment, a single-component polyurethane coating mass is provided 
which includes about 15 to about 23 wt. % hexamethylene diisocyanate 
prepolymer, where the NCO-content is about 2.7%; about 7 to about 15 wt. % 
isophorone diisocyanate prepolymer, where NCO-content is about 11.5%; 
about 0.0 to about 1.0 wt. % montmorillonites as an anti-settling agent; 
about 0.2 to about 3.0 wt. % highly-dispersed silica as an anti-settling 
agent; about 3 to about 7 wt. % trichloroethyl phosphate; about 0.1 to 
about 1.0 wt. % co-polymer of butyl acrylate/vinylisobutyl ether; about 3 
to about 10 wt. % dioctyl distannous laurate; about 0.1 to about 0.4 wt. % 
magnesium silicate hydrate; about 15 to about 40 wt. % barium sulphate; 
about 2 to about 15 wt. % chromium oxide green; about 0 to about 1.0 wt. % 
salt of unsaturated polyamine amides and high molecular acid esters; and 
about 5 to about 15 wt. % solvent mixture. 
The coating masses according to the invention can be applied in a dry film 
thickness up to 2000 microns at temperatures between -10 degrees C and +45 
degrees C at relative humidities of up to 85% and more. Drying takes place 
rapidly and without any problems so that the coating can be handled within 
a very short time. The applied coating is extremely elastic and possesses 
a high degree of UV-resistance, even while still unhardened, and the 
coating mass does not run on surfaces inclined at up to 30 degrees. The 
surface of the hardened layer is very smooth so that very little 
mechanical abrasion occurs. The resistance to chemicals and solvents as 
well as to light and UV radiation is good, even in the unhardened state. 
EXAMPLES 
The following examples illustrate the coating mass according to the 
invention and are not intended to in any way limit the scope of the 
present invention. 
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Ex- 
ample Example Example 
1 2 3 
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Hexamethylene diisocyanate 
prepolymer (NCO = 2.7%) wt. % 
18.20 17.50 18.70 
Isophorone diisocyanate 
prepolymer (NCO = 11.5%) wt. % 
7.95 7.00 9.70 
Montmorillonites as anti- 
settling agents wt. % 
0.50 -- 0.40 
Highly dispersed silica 
as an anti-settling agent wt. % 
0.25 2.65 2.30 
Trichloroethyl phosphate wt. % 
4.55 3.50 4.70 
Co-polymer of butyl acrylate/ 
vinylisobutyl ether wt. % 
0.50 0.50 0.25 
Urethane bisoxazolidine wt. % 
5.30 5.30 5.20 
Dioctyl distannous 
laurate wt. % 0.20 0.20 0.20 
Magnesium silicate 
hydrate wt. % 6.50 9.40 9.20 
Barium sulphate wt. % 
20.70 36.00 35.00 
Iron oxide red wt. % 
11.50 -- 5.60 
Chromium oxide green wt. % 
-- 5.00 -- 
Calcium ferrite 
(corrosion inhibitor) wt. % 
12.50 -- -- 
Salt of unsaturated 
polyamine amides and high 
molecular acid esters wt. % 
0.25 -- 0.50 
Mixture of solvents* wt. % 
11.10 12.95 8.25 
Total Wt. % 100.00 100.00 100.00 
Analysis 
Hexamethylene diisocyanate 
prepolymer (wt. % of 
isocyanate mixture) 
69.6 71.4 65.9 
Isophorone diisocyanate 
prepolymer (wt. % of 
isocyanate mixture) 
30.4 28.6 34.1 
Solids content, wt. % 
88.9 87.05 91.75 
Binder/pigment ratio 
33.8: 21.7: 36.3: 
66.2 67.3 63.7 
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*The mixture of solvents may consist of aromatic and/or aliphatic 
hydrocarbons and esters, for example: 
"Solvesso 100" 
50 25 70 60 25 
Xylene 50 25 5 10 25 
White Spirit 
-- 25 5 -- -- 
n-butyl acetate 
-- 25 20 30 50 
The formulation given in Example 1 is used, for example, for the outer 
coating of steel; it gives good corrosion protection at dry film 
thicknesses of approximately 350 microns, and it can be applied in only 
one process. In addition, this formulation can also be combined with 
Example 2, e.g.: 
1.times.200 microns coating mass of Example 1 
1.times.150 microns coating mass of Example 2 
The formulation given in Example 2 is suitable for coating concrete 
although before applying this coating the concrete must be pretreated with 
a single-component polyurethane-based penetrating stopper. The dry film 
thicknesses of the formulation according to Example 2 may, for example, be 
600 microns thick, applied in 2 coatings each 300 microns thick. 
The formulation of Example 3 is particularly suitable for the internal 
coating of pipelines (e.g. oil or gas pipelines). In this case, the 
coating can be applied by means of a pig, because the thixotrophic 
characteristics of the coating are such that it will not run.