Note: Descriptions are shown in the official language in which they were submitted.
Le A 31 523-US / Eck/ngb/S-P 2 2 0 0 1 4 4
MOISTURE CURING. ONE-COMPONENT COATING COMPOSITIONS
AND TIIEIR USE FOR COATING SUBSTRATES
Back~round of the Invention
Field of the Invention
The present invention relates to moisture curing, one-component coating
compositions based on a polyisocyanate component cont~ining a mixture of
selected aromatic polyisocyanates and plasticizers or high-boiling solvents, and the
10 use of these coating compositions for producing coatings, in particular primer
and/or intermediate coatings for preventing corrosion.
Description of the Prior Art
Coating compositions which cure under the influence of moisture and contain
binders in the form of organic polyisocyanates, particularly higher-molecular NCO
15 prepolymers, are known (see e.g. H. Kittel, Lehrbuch der Lacke und
Beschichtungen, 1973, Verlag W. A. Coulomb; Volume 1, Part 2, pages 573 to
576 or Houben Weyl, Methoden der organischen Chemie, Volume E 20, page
1646, Georg Thieme Verlag 1987). The main disadvantage of moisture curing,
one-component polyurethane lacquers is that these lacquer systems can be applied20 only up to a certain layer thickness. If thicker layers are applied, the carbon
dioxide liberated during the curing reaction cannot escape from the coating and
forms bubbles. Therefore, to obtain thick layers, a moisture curing, one-component
polyurethane coating composition must be applied to the substrate in a number ofthin coats, which is not economically feasible.
25 Maximum layer thicknesses of up to 300 ,~m may be obtained from solvent-free,one-component polyurethane coating compositions. These solvent-free one-
component polyurethane lacquers, however, are too highly viscous for many
applications and uses. To avoid sagg during application and to obtain bubble-free
coatings with good adhesion, conventional lacquer coating formulations contain
30 considerable quantities of volatile solvents. This is becoming less and less
acceptable, in view of worldwide efforts to preserve the environment from
hazardous emissions and to make economic use of resources. Solvent-containing
aromatic polyisocyanates currently in use in one-component polyurethane anti-
Le A 31 523-US 22001 44
corrosive coating compositions can usually only form bubble-free dry films when
applied at a maximum thickness of about 80 ~m.
Admittedly there are also special low viscosity, solvent-free aromatic
polyisocyanates which give thicker films after drying, but the resulting coatings
5 are brittle and easily crack. In addition, anti-corrosion polyurethane coatings must
be capable of being coated with a second layer of the same coating composition or
with a different polyurethane anti-corrosion coating composition, i.e., there must
be adequate intercoat adhesion between layers even after a prolonged interveningperiod (after the time of application), as is the case with prior art solvent-
1O cont~ining coating compositions.
An obj ect of the present invention is to provide binders for one-component,
polyurethane coating compositions which 1) have the same viscosity on
application, the same surface protection efficiency (i.e., anti-corrosive effect) as
known coating compositions without the need for additional volatile lacquer
15 solvents, 2) may be applied in appreciably greater coating thicknesses with
forming bubbles and 3) may be coated with an additional layer of one-component
coating compositions even after long intervals.
These objects may be achieved with the coating compositions according to the
present invention that are described hereinafter.
SUMMARY OF THE INVENTION
The present invention relates to moisture curing, one-component coating
compositions in which the binders are based on polyisocyanate components
containing
A) 100 parts by weight of a polyisocyanate or polyisocyanate mixture of the
diphenyl methane series which has an NCO content of 20 to 33 wt.% and
may optionally be modified with carbodiimide and/or uretonimine groups,
and
B) 40 to 150 parts by weight of NCO prepolymers having an NCO content of
1.5 to 12 wt.% and prepared by reacting
LeA31 523-US 220(~1 44
a) at least one aromatic polyisocyanate having an NCO content of 20
to 34 wt.% with
b) a less than stoichiometric quantity of a polyhydroxyl component
contalnlng
bl) at least one polyol having a number average molecular
weight of 134 to 6,000 and cont~ining ether, ester, thioether
and/or carbonate groups and
b2) up to 40 wt.%, based on the total weight of component b),
of one or more monohydric to hexahydric alcohols, which
have a molecular weight of 32 to 300 and do not conform to
the definition of bl),
and the coating composition additionally contains
C) 0.2 to 250 wt.% of a non-hydrolyzable or difficultly-hydrolyzable
plasticizer having a flash point above 150~C and/or a high boiling solvent
having a flash point above 120~C and a boiling point (at atmospheric
pressure) above 230~C.
The present invention also relates to the use of one-component coating
compositions for coating any substrates, preferably metallic substrates. The present
invention also relates to the use of the one-component coating compositions for
producing primer and/or intermediate coating (" coats") for preventing
corroslon.
DETAILED DESCRIPTION OF T~E INVENTION
The coating compositions according to the invention contain a mixture of
100 parts by weight of component A), 40 to 150, preferably 50 to 120 parts by
weight of component B) and 0.2 to 250, preferably 10 to 100, parts by weight of
component C).
Component A) is selected from polyisocyanates or polyisocyanate mixtures of the
diphenyl methane series which have an NCO content of 20 to 33, preferably 27 to
LeA31 523-US 22001 44
- 4 -
33 wt.% and may optionally be modified with carbodiimide and/or uretonimine.
These polyisocyanates include 4,4'-diisocyanatodiphenyl methane or mixtures
thereof with 2,4'- and optionally 2,2'-diisocyanatodiphenyl methane. Also suitable
are mixtures of these isomers with their higher homologs, which may be obtained
S in known manner by the phosgenation of aniline-formaldehyde condensation
products. In addition, polyisocyanates containing carbodiimide and/or uretonimine
groups may be used. They may be obtained by forming carbodiimide and/or
uretonimine groups in known manner from a portion of the isocyanate groups of
the preceding polyisocyanates or polyisocyanate mixtures, provided their NCO
content is within the limits stated hereinbefore. Preferably component A) is a
polyisocyanate mixture that is liquid at room temperature (20~C).
Component B) is based on NCO prepolymers having an NCO content of 1.5 to 12,
preferably 2 to 8 wt.% and prepared from aromatic polyisocyanates a) and organicpolyhydroxyl compounds b).
"NCO prepolymers" are understood to mean the monomer free reaction products
obtained from starting components a) and b). This means that after the preparation
of NCO prepolymers B) from readily-volatile starting polyisocyanates a), such asthe diisocyanatotoluene isomers (TDI), excess unreacted component a) is removed
by thin film distillation to a residual content of less than 1.0 wt.%, preferably less
20. than 0.5 wt.%. When the NCO prepolymers B) are prepared from polyisocyanates
or polyisocyanate mixtures of the diphenyl methane series as starting component
a), any excess present in the reaction product results in the in-situ formation of a
mixture of polyisocyanate A) and (monomer-free) NCO prepolymer B).
Component B) is prepared by the known reaction of polyisocyanates a) with
polyhydroxyl component b) at a temperature of 20 to 140~C, preferably 40 to
100~C. If component a) is a readily-volatile diisocyanate, such as TDI, the reaction
between components a) and b) is preferably carried out at an NCO/OH equivalent
ratio of up to 40:1, preferably up to 20:1 and more preferably 5:1 to 12:1,
followed by removal of unreacted excess isocyanate by distillation as previouslydescribed.
If polyisocyanates a) for producing component B) are from the dipheyl methane
series, a large excess of component a) can also be used as previously described
and remain in the product, resulting in an in-situ mixture of components A) and
LeA31 523-US 22001 44
B). Preferably, when polyisocyanates from the diphenyl methane series that are
suitable as component A) are used for producing NCO prepolymer B), the
polyisocyanates are used in an amount sufficient to provide an NCO/OH
equivalent ratio of 3:1 to 40:1, preferably 5:1 to 25:1, so that the resulting mixture
5 of component A) and NCO prepolymer B) conforms to the required amounts of
these components. Alternatively, the mixture of components A) and B) produced
in-situ can be mixed with an additional quantity of a polyisocyanate or
polyisocyanate mixture of the diphenyl methane series that is suitable for use as
component A) to obtain the required amounts of these components.
10 In another embodiment the in-situ production of mixtures of component A) and B)
can be prepared by reacting a portion polyisocyanate of polyisocyanate mixture a)
with a sub-stoichiometric quantity of a polyhydroxyl compound b 1) and an
additional quantity of a polyisocyanate or polyisocyanate mixture a) with a sub-stoichiometric quantity of an alcohol b2), and subsequently mixing the two
15 reaction products together. It is only necessary to ensure that the proportions of
starting components A), bl) and b2) result in product mixture that contain the
required amounts of these components.
Monomeric polyisocyanates a) that are suitable for producing component B) are
selected from aromatic polyisocyanates having an NCO content of 25 to
20 48.3 wt.%. Preferred are aromatic polyisocyanates that are known from
polyurethane chemistry, such as 2,4-diisocyanatotoluene or commercial mixtures
thereof containing up to 35 wt.%, based on the weight of the mixture, of 2,6-
diisocyanatotoluene, or polyisocyanates or polyisocyanate mixtures of the diphenyl
methane series that are also suitable as component A). If component B) is
25 produced separately, the polyisocyanate component A) and the polyisocyanate a)
used for producing NCO prepolymers B) may be different.
Polyhydroxyl component b) is selected from polyhydroxyl compounds having a
number average molecular weight (determined by end group analysis) of 134 to
6,000, preferably 500 to 6,000 and cont~ining ether, ester, thioether and/or
30 carbonate groups, preferably ether andlor ester groups. Polyhydroxyl compounds
bl) may be present in admixture with up to 40, preferably up to 20 wt.%, based
on the total weight of component b), of monohydric to hexadydric alcohols that
have a molecular weight of 32 to 300 and do not conform to the definition of bl).
Preferably, component b) exclusively contains polyhydroxyl compounds bl).
LeA31 523-US 22001 44
_ -- 6 --
Polyhydroxyl component bl) preferably has an average hydroxyl functionality of 2to 4, more preferably 2 to 3.
Polyhydroxyl compounds bl) are known from polyurethane chemistry, have the
required number average molecular weight and contain ether, ester, thioether
5 and/or carbonate groups. As previously discussed all molecular weights are
calculated from the content of hydroxyl groups and the hydroxyl functionality, i.e.,
by end group analysis.
Preferred polyhydroxyl compounds b 1) include the known polyether polyols,
which may be obtained in known manner by the alkoxylation of suitable starter
10 molecules, preferably using ethylene oxide and/or propylene oxide. The starter
molecules can be monomeric polyhydric alcohols of the kind described in detail
hereinafter as component b2), amines (such as ethylene diamine, hexamethylene
diamine or aniline) or amino alcohols (such as ethanolamine or propanolamine).
Any mixtures of the starter molecules can also be used.
15 Optional alcohols b2) are selected from monohydric to hexahydric alcohols which
have a number average molecular weight of 32 to 300 and are different from
alcohols bl). Examples include monomeric monohydric or polyhydric alkanols
such as methanol, ethanol, n-hexanol, 2-ethyl hexanol, ethylene glycol, propylene
glycol, glycerol, trimethylol propane, pentaerythritol and/or sorbitol; amino
20 alcohols such as ethanolamine or N,N-dimethyl ethanolamine; and diethylene
glycol. If amino alcohols containing tertiary nitrogen atoms, such as N,N-dimethyl
ethanolamine, are used as component b2), nitrogen atoms serving as catalysts arealso incorporated into the binders.
Component C) is selected from non-hydrolyzable or difficultly-hydrolyzable
25 plasticizers having a flash point above 150~C and/or high boiling solvents having
a flash point above 120~C and a boiling point (at atmospheric pressure) above
230~C. Suitable plasticizers include commercial phenyl alkyl sulphonates
(Mesamoll, Bayer) and phosphoric acid esters (e.g. Disflamoll TOF or Disflamoll
DPK, Bayer). Suitable high boiling solvents include cyclic carbonate esters such30 as ethylene carbonate or 1,2-propylene carbonate (Texacar EC, Texacar PC,
Texaco Chemicals).
Le A 31 523-US 220~ l 44
-- 7 --
The polyisocyanate mixtures according to the invention have a low viscosity and
cure under the influence of atmospheric moisture without bubbles7 even in layersup to 150 ,um thick. They also have a zero content or a much smaller content of
volatile solvents than the coating compositions of the prior art. In addition,
5 coatings obtained therefrom can be covered without difficulty, even after a
prolonged period, with a second layer of a moisture curing, one-component
coating composition according to the invention.
Because they may be cured in thick layers to obtain bubble-free coatings, the
polyisocyanate mixtures according to the invention are exellent binders for
10 moisture curing, one-component coating compositions on a wide variety of
subskates~ preferably metal substrates, and especially as priming coatings and/or
intermediate coatings (also called "base coats") for preventing corrosion. In
addition, the polyisocyanate mixtures according to the invention can be used as
clear lacquers, either without additives or after mixing with conventional lacquer
1 5 additives.
Suitable additives include fillers, pigmets, solvents, drying agents, catalysts and
levelling agents. One particularly advantageous fact is that due to the preferred
low viscosity of the plasticizer component or high-boiling solvent component C),it is possible to produce extremely low-solvent coating compositions (<10-4 wt.%20 of volatile solvent).
When the coating compositions are prepared for use, it is possible and often
advantageous to make a prelimin~ry mixture of the additives or a portion thereofand a portion of binder components A) to C), and to subsequently mix this
preliminary mixture with the other constituents of the lacquer. The only
25 requirement is that in the finally-obtained coating compositions must contain individual binder components A) to C) in the required amounts.
Le A 31 523-US 22 ~ O 1 44
EXAMPLES
In the following examples, all parts and percentages are by weight, unless
otherwise indicated.
The statements regarding the quantitative composition of the polyisocyanate
5 mixtures mentioned in the examples are calculated approximate values, which are
only intended to confirm that the mixtures in the examples have compositions
within the essential limits according to the invention. Since a large excess of
isocyanate component 1 was always used in the in-situ production of mixtures of
components A) and B), the calculation was based on the assumption that no chain-
10 lengthening reaction occurred during production of the mixtures. Anotherassumption in the calculation was that the remaining, unreacted excess of
isocyanate component 1 exclusively contained diisocyanates (molecular weight =
250). The quantitative composition can be determined exactly, e.g., by gel
permeation chromatography.
15 The following starting components were used in the examples:
lsocvanate component 1
2,025 parts by weight of a commercial, crude MDI mixture having an NCO
content of 31.5% and a viscosity of 120 mPa s (Desmodur VL, Bayer) were
reacted with a mixture of 935 parts by weight of a polyether produced by the
20 propoxylation of ethylene diamine and having a molecular weight of 3,740 and
500 parts by weight of a polyether produced by the propoxylation of propylene
glycol and having a molecular weight of 2,000 at 60~C, until the NCO content
was 16.0%. The NCO prepolymer had a viscosity of 6,500 mPa s (23~C).
Isocvanate component 2
2,000 parts by weight of a distilled MDI mixture containing 65 wt.% of 2,4'-MDI
and 35 wt.% of 4,4'-MDI were reacted at 60~C with 748 parts by weight of a
polyether produced by the propoxylation of ethylene diamine and having a
molecular weight of 3,740 and 800 parts by weight of a polyether produced by thepropoxylation of propylene glycol and having a molecular weight of 1,000, until
Le A 31 523-US 2 2 0 0 1 4 4
g
the NCO content was 16.0%. The NCO prepolymer had a viscosity of 1,800 mPa s
(23 ~C).
Isoc~anate component 3
1,000 parts by weight of the isocyanate component 2 were mixed with 1,000 parts
5 by weight of a commercial MDI mixture having an NCO content of 32.5% and a
viscosity of 23 mPa s (23~C) (Desmodur VL 50, Bayer). The mixture had an NCO
content of 23.7% and a viscotiy of 300 mPa s (23~C).
Example 1 - Production of a clear coating composition according to the invention
1,000 parts by weight of isocyanate component 1 were introduced into 150 parts
10 by weight of a plasticizer based on tris(2-ethylhexyl)phosphate (Disflamoll TOF,
Bayer) at room temperature and with agitation.-Agitation was continued for a
further 30 minutes to obtain a homogeneous mixture.
Viscosity at 23~C (Efflux time according to DIN 53211, 4 mm nozzle) 445 s
NCO content 13.9%
15 Example 2 - Production of a clear coating composition according to the invention
1,000 parts by weight of isocyanate component 1 were mixed with 300 parts by
weight of the plasticizer from Example 1 as described therein.
Viscosity at 23~C (Efflux time according to DIN 53211, 4 mm nozzle) 225 s
NCO content 12.3%
20 ExamPles 3 and 4 - Production of clear coating compositions according to the
mventlon
1,000 parts by weight of isocyanate component 2 were mixed with 150 (Example
3) or 300 (Example 4) parts by weight of the plasticizer from Example 1 as
described therein.
Le A 31 523-US 2 2 0 0 1 4 4
1 0 --
Example 3 Example 4
Viscosity at 23~C (see above) 175 s 85 s
NCO content 13.9% 12.3%
Examples 5 and 6 - Production of clear coating compositions according to the
5 invention
1,000 parts by weight of isocyanate component 3 were mixed with 150
(Example 5) or 300 (Example 6) parts by weight of the plasticizer from
Example 1 as described therein.
Example 5 Example 6
Viscosity at 23~C (see above) 43 s 31 s
NCO content 20.6% 18.2%
Comparison Example 1
150 parts by weight of a mixture of 120 parts by weight of solvent naphtha
(Solvesso 100, Exxon) and 30 parts by weight of methoxypropyl acetate were
15 added to 850 parts by weight of isocyanate component 1 and agitated for a further
30 minutes.
Viscosity at 23~C (see above) 124
NCO content 13.5%
Comparison Example 2
20 150 parts by weight of the solvent mixture described in Comparison Example 1
were added to 850 parts by weight of isocyanate component 2 and agitated for 30
minutes.
Viscosity at 23~C (see above) 59 s
NCO content 13.4%
Le A 31 523-US 2 2 0 0 1 4 4
Comparison ExamPle 3 (not according to the invention)
150 parts by weight of the solvent mixture described in Comparison Example 1
were added to 850 parts by weight of isocyanate component 3 and agitated for 30
minutes.
5 Viscosity at 23~C (see above) 22 s
NCO content 19.9%
Tests of coating properties and corrosion protection efficiency
A) Maximum dry film thickness
In order to determine the maximum thickness of the coatings, the clear
coating compositions from Examples 1 to 6, Comparison Examples 1 to 3
and also isocyanate components 1 to 3 were applied to glass plates using a
layer thickness wedge. The thickness of the wet films was up to about
1,000 llm. After the films dried, a layer thickness gauge was used to
determine the thickness at the places where intçn~ified formation of carbon
dioxide gas bubbles was observed in the film. Each of the following values
are averages of five individual measurements.
Maximum dry film thickness [~m]
Example 1 480
Example 2 1,000
Example 3 430
Example 4 480
Example 5 500
Example 6 1,000
Isocyanate component 1 140
Isocyanate component 2 150
Isocyanate component 3 170
Comparison Example 1 140
Comparison Example 2 200
Comparison Example 3 170
LeA31 523-US 22001 44
B) Other properties of the coatings
Other coating properties of the coating compositions according to the
invention or the comparison coating compositions were tested, i . e.,
compatibility, surface stickiness, occurrence of craters and/or bubbles,
curing times before reaching sand or pressure dryness, brushability and
s~gging
The compatibility was judged visually from the appearance of the clear
coatings, i.e., = completely transparent to 5 = completely cloudy. The
surface stickiness was evaluated on the following scale: best value 0 (dry),
worst value 5 (sticky). Bubbles and craters were also evaluated on a scale
extending from 0 to 5 (0 being the best possible value).
The curing time before reaching sand dryness was- determined by applying
the wet film to- a glass plate and scattering sand onto it at intervals of 5
minutes. Sand dryness was obtained as soon as the sand could be
completely removed from the film surface with a dry brush (without
sticking). The curing time until pressure dryness was determined according
to DIN 53150.
The brushability was evaluated by judging the ease with which a wet film
could be applied with a painter's brush to a steel surface (Sa 2l/2). The
highest mark (0) corresponded to very little brushing resistance and good
distribution (without permanent brush furrows in the film), whereas the
worst mark (5) correspond to the high resistance to brushing ("caky
consistency"), very pronounced brush furrows and inadequate distribution.
The sagging on vertical surfaces was marked from 0 (remains on the
vertical surface) to 5 (runs off like water).
B1) Properties of clear coating compositions according to the invention
at wet film thickness of 90 llm
Le A 31 523-US 22001 44
- 13 -
Solids Compatibility Surface Bubbles/
(%)* stickiness craters
Example 1 100 0 0 0
Example 2 100 0 0 - 1 0
Example 3 100 3 - 4 0 0
Example 4 100 3 - 4 1 0
Example 5 100 3 1 0
Example 6 100 3 2 0
*) Content of non-volatile or at least difficultly-volatile constituents
B2) Properties of clear coating compositions according to the invention
and comparison coating compositions at a wet film thickness of
- 10 60 !lm
Sand Pressure Brushability Sagging
dryness dryness
(min) (min)
Example 1 >360 >420 3 1-2
Example 2 >360 >420 1-2
Comparison
example 1 115 145 1-2 0
Example 3 >360 >420 1-2
Example 4 >360 >420
Comparison
example 2 145 195 1-2 0
Example 5 345 >420 2
Example 6 >420 >420 1-2
Comparison
example 3 200 225 1-2 0
C) Evaluation of corrosion resistance properties and adhesion of film. The
following three layers of coating compositions were applied stepwises
to metal plates (three) cleaned from rust by hand:
Le A 31 523-US 22 00 1 4 4
~ 14 -
- Clear coat primer, based on examples 3 and 6 and isocyanate
components 1 to 3,
- Primer coating composition set forth hereinafter and
- Top coat composition set forth hereinafter.
The dry film thickness of each individual layer was 80 llm.
"$tepwise construction" means that the first segment of the metal plate was
only covered with the clear coat, the second segment was covered with the
clear coat and the primer coating and the last segment was covered with all
three layers (in the sequence given above).
10 The formulation of primer coating and top coat were as follows:
Le ~ 31 523-US 22001 44
- 15 -
Component in formulation Primer coating Top coat
(wt.%) (wt.%)
Additive MT (Bayer )I ) 4.55 --
HDI-based water scavenging co-binder2+) Bayer) -- 8.45
P 65 soft resin (Bayer) -- 5.65
Solvesso 100 (Exxon) 22.76 --
Acronal 700 L (10% in ethyl acetate) (BASF) 0.20 0.38
Thixatrol ST (Rheox GmbH) 0.43 0.35
Disperbyk 163 (Byk) -- 0.15
Bentone 34 (Rheox GmbH) 0.54 0.50
Meth~xy~Jropyl acetate/butyl acetate mixture (3:1) -- 2.00
Bayertitan R-KB-3 (Bayer) -- 5.10
- Bayferrox 130 BM (Bayer) 1.26
Bayferrox 415 (Bayer) -- 0.60
Chromium oxide green GN-M (Bayer) -- 3.40
Barium sulphate 4.78 21.90
AT 1 Micro-talc (Norwegian ~alc) 18.47 2.40
3530 Leaf silicate (Mineralwerk Naintsch, Graz) 7.83 --
Stapa 2 nl (Eckart-Werke, Furth) 2.95
Desmodur E 21 (Bayer) 15.13 --
Desmodur Trial Product LS 2823 -- 29.94
Hardener OZ (Bayer)3 ) -- 3.68
Ultra 25 zinc dust (Lindgens, Cologne) 20.06 --
Additive OF (Bayer)4 ) 1.14 2.10
Meth~yplol)yl acetate/butyl acetate mixture (3:1) -- 13.40
) MDI-based prepolymer, NCO-content 16,8%, viscosity (23~C) 900 mPas,
equivalent weight ~250
2 ) HDI-based polyisocyanate, NCO-content 11,5%, viscosity (23~C) 85 mPas
equivalent weight ~365
3 ) Latent hardener based on a urethane-bis(oxazolidine), NH equivalent
weight 243, viscosity (23~C) 7500
4 ) (Trimethyl arthoformiate)
-
Le A 31 523-US 22001 44
- 16 -
The test metal plates were exposed to the weather for 18 months in a Central
European climate (Leverkusen, Germany). Adhesion to the substrate and the
corresponding extent of rusting underneath were checked at regular intervals. The
test for adhesion to the substrate was made with a penknife. An attempt was madeto scrape a portion of the coating off the substrate. Marking: 0 = very diff1cult to
scratch off; 5 = very easy to scratch off. These adhesion ranking values are given
in angular brackets, [...], in order to distingllish them from rusting underneath
ranking, Ri.... The extent of rusting was judged in accordance with the Ri (Rustinternational) scale (according to DIN Standard 53210).
The results were as follows [n.c. = no change; m = month; IC = isocyanate
component)
A) Adhesion or extent of rusting for the clear coat layer alone
Ex.3 Ex.4 Ex.5 Ex.6 IC1 IC2 IC3
1 m n.c. n.c. n.c. n.c. n.c. n.c. n.c.
3 m n.c. n.c. n.c. n.c. n.c. n.c. n.c.
6 m Ri 4 Ri 4 n.c. Ri 4 n.c. n.c. n.c.
12 m [5] [5] [4] [4 - 5] [2] n.c. n.c.
18 m [5] [5] [4] [5] [2 - 3] [2 - 3] [2 - 3]
B) Adhesion or extent of rusting for the clear coat covered with the primer
coating
Ex.3 Ex.4 Ex.5 Ex.6 ICl IC2 IC3
1 m n.c. n.c. n.c. n.c. n.c. n.c. n.c.
3 m n.c. n.c. n.c. n.c. nc. n.c. n.c.
6 m n.c. n.c. Ri 3 n.c. n.c. n.c. Ri 3
12 m Ri 3[2 - 3] Ri 3[2] Ri 3 Ri 3[3] n.c. n.c. Ri 3[2 - 3
18 m Ri 3 Ri 3 Ri 3 Ri 3 Ri 3 Ri 3 Ri 3
Le A 31 523-US 22001 44
-- - 17 -
C) Adhesion or extent of rusting for the total three layer structure
Ex.3 Ex.4 Ex.5 Ex.6 ICI IC2 IC3
1 m n.c. n.c. n.c. n.c. n.c. n.c. n.c.
3 m n.c. n.c. n.c. n.c. n.c. n.c. n.c.
6 m n.c. n.c. n.c. n.c. n.c. n.c. n.c.
12 m [2 - 3] [2 - 3] [2] [2 - 3] n.c. n.c. [2]
18 m [2 - 3 ] [2] [2] [2 - 3] Ri 1 Ri 1 [2]
As the Tables clearly show, the one-component polyurethane coating compositions
according to the invention have good anti-corrosion properties and adequate
adhesion when covered with other polyurethane one-component coatings.
The clear coating from Example 3, which was covered with another clear coating
from Example 3 after six months' storage, adhered as firmly as the clear coatingfrom Comparison Example 2 was covered after storage for six months with
another clear coating from Comparison Example 2.
As shown, therefore, in all of the examples, the one-component coating
compositions according to the invention have a low viscosity, do not liberate
polluting solvents, can be processed without difficulty and result in coatings which
are relatively thick and bubble-free, are easy to cover and have good corrosion
resistance.
Although the invention has been described in detail in the foregoing for the
purpose of illustration, it is to be understood that such detail is solely for that
purpose and that variations can be made therein by those skilled in the art without
departing from the spirit and scope of the invention except as it may be limited by
the claims.
