Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~2570~4
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The invention reIates to coating compos~tions
which due to their content of polyurethane-forming
isocyanate harden chemically. More particularly,
the invention relates to one-component coating
compositions of this kind which in ready mixed form
are stable on storage under exclusion of moisture,
but harden on exposure to moisture. Moreover, the
invention relates to a method of producing a protective
coating using such coating compositions and various
applications thereof. The coating compositions are
particularly suitable for the protection of building
structures such as the protection of roofs of any kind,
the sealing of flat roofs covered with tar board or tar
paper, for the coating of concrete and/or for the corrosion
protection of steel concrete.
Coating compositions for the protection of
building structures are known. The known preparations
include, for example, water-dilutable acrylates. How-
ever, these acrylates had to be applied in several
layers and, in practice, did not afford satisfactory
protection. A further known coating composition
consists of a two-component epoxy resin system. How-
ever, this system was only workable under specific
temperature and humidity conditions and difficulties
occurred with regard to the pot time. Moreover,
coating compositions based on combinations of coal tar
and polyurethanes are known (see "Farbe und Lack", 83,
p. 701-705 (1977)). Coal tar is typically character-
i~ed by its black color and viscous consistency and
consists practically exclusively of aromatic compounds
which, besides carbon and hydrogen, contain a certain
percentage of other atoms such as oxygen, nitrogen and
sulphur. A portion of these heteroatoms are present in
hydroxyl and amino groups. Accordingly, such tar con-
tains active hydrogen atoms which can react with
~257034
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isocyanate groups. T~pically, thexefore~ mixture$ of
coal tar and polyurethane forming isocyanate are not
one-component coating compositions.
In general, it can be said that processing of the
known coating compositions requires an air temperature
of about 10C and a relative humidity of below 80~
To achieve useful protection, the known coating composi-
tions have to be applied in an amount of 170 g/m2 per
coat. Even when complying with these conditions the
known coating compositions were not fully satisfactory.
In their practical applications the following diffi-
culties became particularly apparent:
- the diffusability of the coating composition
was insufficient;
- the coating composition had to be applied at
least twice;
- the hardened protective coating had only a low
elasticity;
- due to strong weathering reworkability of the
protective coating was poor;
- with time strong chalking occurred (for this
reason the respective directions for those known
systems provide for renewal after at least five
years);
- the coating composition can only be applied in
good, dry weather;
- the finished protective coating exhibits only
slight pore sealing;
- the known coal tar/polyurethane-forming isocyan-
ate mixtures necessarily have the disadvantages
connected with coal tar such as the black color,
the bleeding of tar through covering coatings,
and the decomposition of coal tar components
by W-radiation.
Accordingly it is an object of the present inven-
tion to provide a one-component coating composition
1257034
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for the protection of building structures which shows
improvements over at least some, preferably all, of
the disadvantages of the known systems.
The coating composition according to the in-
vention is a one-component coating composition which
hardens under exposure to moisture and which comprises:
15 to 70% by weight polyurethane-forming iso-
cyanate,
5 to 25~ by weight light-liquid, OH-grou~s-con-
taining, low molecular,
aromatic hydrocarbon resin,
0.2 to 2% by weight anti-settling agent,
10 to 35% by weight flake-shaped extender,
2 to 25% by weight coloring pigment,
1 to 5~ by weight moisture-absorbing agent, and
the remainder,at least however 5% by weight,resin
solvent.
In contrast to the known coal tar the hydrocarbon
resin according to the invention is a colorless or
lightly yellow oil so that the inventive composition
results in a clear and light, even white, coating
which nevertheless exhibits the advantageous properties
of the polyurethane/coal tar coating. When exposed to the
sunlight, the light coatings according to the invention
compose, due to UV-radiation, to a lesser extend than the
known coal tar containing coatings.
Moreover, it is an object of the present invention
to provide a method of producing a protective coating by
applying the inventive one-ccmponent coating composition
to a clean base and allowing the composition to harden
under exposure to moisture in the surrounding atmos-
phere.
Due to the fact that the inventive coating compo-
sition is a one-com~onent system, the composition can,on
exclusion of moisture, be stored for substantially
,~P .~ i'
~25~034
- 4
unlimited time while hardening w-ithin about lO to 30
minutes after application to a base a~d on expos~re bo
moisture in the surrounding atmosphere so that, if
desired, already after about 30 minutes one or more
additional coating(s) can be applied. After about
15 to 20 hours the total protective coating is
completely hardened and can be exposed to the intended
load.
The coating composition according to the invention
is suited for producing protective coatings for the
protection of building structures in general. Preferred
applications include the protection of roofs of all kinds
including the sealing of flat roofs covered with tar
board or tar paper, the coating of concrete and the
corrosion protection of steel concrete.
Further object and advantages of the invention
will become apparent from the following description
and claims.
In the following the advantages and characteris-
tics of the coating composition according to the
invention are listed in abbreviated form:
- the coating composition is still workable at
temperatures of less than 5C;
- the coating composition is workable even at
relatively high atmospheric humidity, for
example, at humidities of more than 90~;
- the coating composition is self-spreading;
- the coating produced with the coating composi-
tion affords excellent protection against
ultrava let radiation;
- the finished protective coat exhibits good
reflection values in respect of radiation of
light and heat;
- even when the protective coat is thin, for ex-
ample in the magnitude of only 50 ym, the
finished coat exhibits high pore sealing;
~257034
- the finished protecti~e coat shows good
elasticity and high adhesive strengths
- even after weather~ng the protective coat
is reworkable without problem;
- prior to application of the coating composition
only the usual simple pre-treatme~t of the base
is required;
- the protective coat is flame-resistant; and
- even when the protective coat is thick, for
example thicker than 200 ~m, no cracking of
the coat occurs during hardening.
In the following the invention is described in
more detail with reference to preferred embodiments.
The coating composition according to the inven-
tion comprises the following ingredients in the given
proportions:
15 to 70% by weight polyurethane-forming iso-
cyanate;
5 to 25% by weight light, liquid, OH-groups-c~n-
taining, low molecular,
aromatic hydrocarbon resin;
0.2 to 2% by weight anti-settling agent;
10 to 35% by weight flake-shaped extender;
2 to 25% by weight coloring pigments;
1 to 5% by weight moisture absorbing agent; and
at least 5% by weight resin
solvent.
In addition to the listed nec~ssary ingredients
the coating composition according to the invention can
contain additives and supplements commonly used in the
resin, varnish, lac~uer or related technologies such as,
anti-bacterial or anti-fungal agents, additives inhibit-
ing decomposition ~y light, heat and/or corrosive
influences, and other commonly used additives adapted
for specific requirements (for example to suppress
blister formation) or anti-drip agents.
12570~4
- 6 .
As pol~ureth~ne~forming isocyanates kno~n di-~
isocyanates, triisocyanates and low ~olecular poly
isocyanatesmay be used such as, for ex~le, the grouP of
~socyanates available under the trademark "Desmodur".
Good results were obtained with toluylene diisocyanates,
whereby 2,4- as well as 2,6- toluylene diisocvanate or
the commercially available isomer mixture may be used.
Furthe~more, diphenylmethane-4,4'-diisocyanate or
hexamethylene-1,6-diisocyanate can be used as poly-
urethane-forming isocyanate.
As further essential ingredients the coating
composition according to the invention contains a
liquid OH-groups-containing aromatic hydrocarbon resin.
In contrast to the known tar, in particular, coal tar,
the hydrocarbon resin according to the invention is a
light, i.e. colorless to light yellow, material with
a brightness according to Barrett of between about 0.5
and 2.
The hydrocarbon res;n is liquid and has at 25C
a viscosity of between about 700 and 2,000 cP.
The resin is a low molecular, aromatic material
with a~ average molecular weight of 600. The density
of the hydrocarbon resin at 20C is between about
1 and 1.2 g/cm3.
The acid number of the hydrocarbon resin is
preferably between about 0.2 and 3.
The hydrocarbon resin necessarily contains a
certain portion of OH-groups. Preferably, these are
aromatic OH-groups which result from a prior "phenol
modification" or "activation". Preferably, the
hydrocarbon resin contains OH-groups,particularly
aromatic OH-groups, in an amount of about 2 to 4%
by weight of the resin.
The hydrocarbon resin is preferably free of water
and solvents. The amount of volatile components in
the hydrocarbon resin ~s less than~l0% and can in
certain commercially available products be between about
~25~03~
~ 7 -
5 and ~% by wei~ht.
Hydrocarbon resins of this kind are known in the
art and are offered by commerc~al establ~shments
specifically for the requirements of the resin and
related industries. To descri~e these materials
terms such as special light resistant tar", "Albino-
tar" etc. are used in the art. For example, materials
available under the tradèmark "aktivierte VFT Spezial-
Flussigharze" from VFT-Vertriebsgesellschaft fur
Teererzeugnisse mbH, Essen,Federal R~Iblic o~ G~Eny,
may be used as hydrocarbon resin according to the
invention.
Anti-settling agentsfor the present kind of
coating compositions are known in the art. Known
anti-settling agents which are useful according to
the invention include, for example,montmorillonite,
silica, hydrogenated castor oil and the like.
Flake-shaped extenders or fillers are also
known. Flake-shaped extenders which are useful ac-
cording to the invention include, for example, talc,barium sulphate, flaked pigments based on Si/Al-oxides
and similar filler materials. The extenders according
to the invention should contain little or, preferably,
no carbonate and/or CO2-releasing components so that
in admixture with polyisocyanate stability on storage
is assured.
Coloring pigments for the present kind of
coating compositions are also known. These pigments
convey to the protective coat the ability to reflect
3Q light and heat and give the coat a certain color.
Suitable coloring pigments are commercially available,
for example, under the trademarks "Sicominp~gment",
"Heliogenpi~ment", "Litholpigment" and the like.
According to a further aspect of the invention
at least a portion of the "coloring" pigments consists
of aluminum powder. Preferably, a flake-shaped alum-
~num powder having an area extension of less than 45 ,um
~Z57034
` 8 .
is used. Prefe~ably, the alum~num component amounts
to about 20 to 80~ hy weight of the coloring pigment.
In a particularly preferred embodiment the coating
composition contains about 1 to 6~ aluminum pigment
relative to the total weight of the coating composition.
Su~table moisture-absorbing or mois~ure-extracting
agents include finely divided natural and synthetic
zeolites (for example "Zeolith l-Paste" (trademark)
available from Bayer AG), and molecular sieves made of
alumina and silica compounds, which may be supplemented
with titanium. Moreover, agents which bind or absorb
water chemically such as monoisocyanate can also be
employed. Such moisture-binding, moisture-absorbent
or moisture-extracting agents are also commercially
available.
As resinsolvents the known solvents and solvent
mixtures are suitable. For example, ~ommonly available
mixtures of aromatics with a molecular weight of
between 100 and 200 proved useful. Furthermore, solvents
commonly used in the resin industry based on aliphatic
esters such as acetates, propionates and/or butylates
can be employed. Higher esters are less suitable,
because the resulting drying time may be too long.
The preparation of the coating composition
according to the invention can be effected according
to techniques commonly used in the resin industry.
Generally, the ingredients are placed into a vessel
in the required proportions and mixed with a speed
stirrer or dissolver. It proved useful to place a
mixture of polyurethane-forming isocyanate and hydro-
carbon resin into the vessel and then successively
add the other ingredients, whereby the moisture-ab-
sorbing agent is added last. Stirring for a period
of 10 to 20 minutes at room temperature was found
to give satisfactory results. A slight rise in tempera-
ture, for example up to about 40C, may occur. This
is probably not attributable to any reaction heat, but
~2S~034
to shearing forces. Finally, the re~uired amount of
solvent is added to ensure workability of the material.
Following this the material is again mixed for a
short period yielding a self-spreading, structurally
viscous composition which is ready for use.
If required, the coating composition can be
stored. The storage stability at room temperature is
at least 6 months. Individual samples were stored for
more than 12 months without noticable increase in
viscosity and/or decrease in reactivity.
Since the coating composition according to the
invention is a one-component system, no pot time worth
mentioning is given. After opening of the storage
container the composition should be applied speedily
otherwise film formation and slow through-reaction
takes place due to the presence of atmospheric moisture.
Application of the coating composition to the
intended base can be effected according to conventional
methods such as by way of a roller or by spraying.
For example, the Airles (trademark) spraying method
which employs high pressure was found useful.
The coating composition is applied to the
provided base in a thickness of at least 20,um. Pre-
ferably the thickness of the coating is between about
50 and 70Jum. It is also possible to apply several
coats, each new coat being applied after each previously applied
coat has substantially hardened. For example, a coat which is 45~m
thick dries at the ambient conditions within about
15 minutes and is reworkable after about 30 minutes
so that one or more additional coat(s) can be applied.
After about 18 hours the protective coating is com-
pletely hardened and firm and can be exposed to the
intended load. After weathering and/or aging of the
resulting protective coating,even over a period of
one year or longer, this coating can,without difficulty,
again be coated with the same inventive coating
composition.
i , . ..
257034
~s lQ ~
The preparation of the hase does not call for
special measures. It is sufficient if the base is
free of dirt and dust as can be ach~eved by s~mple
sweeping. No special requirements regarding the dry-
ness of the base has to be met. The coating compositionaccording to the invention can be applied to a moist,
but not quite wet area without effecting either the
hardening and setting or the quality of the finished
protective coating.
After application of the coating composition to
the base,the composition hardens by itself under the
influence of the moisture in the surrounding atmos-
phere without necessitating any special measures.
According to a further aspect of the invention
there is provided a one-ol~onent composition which
hardens under exposure to moisture and which within
the framework of the above described composition
contains a relatively small amount of polyurethane-
forming isocyanate. Preferably, this specific
coating composition comprises:
15 to 40% by weight polyurethane-forming
isocyanate;
5 to 25% by weight of the above described
hydrocarbon resin;
0.5 to 2% by weight anti-settling agent;
15 to 35~ by weight flake-shaped extender;
5 to 25% by weight coloring pigments;
1 to 5% by weight moisture-absorbing agent; and
the remainder, at least however 5% by weight, ~ mon
resin solvent.
In this embodiment, too, the coloring plgments
contain a certain portion of aluminum powder. Prefer-
ably, the portion of aluminum powder amounts to between
20 and 80% by weight of the coloring pigment. In a
particularly preferred embodiment the amount of poly-
urethane-forming isocyanate is 15 to 30% of the total
weight of the coating composition. Toluylene di-
,
~2s7a34
--` 11 ~`
isocyanate containing isocyanate groups in an amount
of about 5.5 to 7.5% of the t~tal weight of isocyanate
is preferred as polyurethane-forming ;socyanate for
this embodiment.
This "reIatively isocyanate-poor" embodiment
of the invention is well suited for the protection of
building structures due to its good elasticity, its
high adhesive strength on various materials and due
to its resistance to UV-radiation. This embodiment
is particularly suitable for the protection of roofs
of all kinds such as, for example, Eternit (trademark)
roofs, roofs insulated with PU-Hartschaum (trademark)
and the like. A further application in the art of
roofs is the foam coating, namely, the roof foam
coating of so-called reverse roofs. Moreover, this
particular coating composition is suitable as protect-
ive coating for engineering constructions, industrial
and energy construction, steel construction, ship
construction, off-shore construction and the like.
If this particular coating composition is used to coat
steel, prior sand blasting (Sa 2.5) is recommended.
To achieve especially good corrosion protection the
application of the coating composition may be preceded
by priming. Moreover, this particular coating com-
position is suitable for the protection of concrete
and for the corrosion protection of steel concrete.
In all cases excellent resistance to radiation, light,
heat and/or corrosion influences is achieved.
A further specific embodiment of the invention
contains within the framework of the above described
composition a relatively high portion of polyurethane-
forming isocyanate. Preferably, this specific coating
composition comprises:
40 to 70% by weight polyurethane-forming
isocyanate;
5 to 25~ by weight hydrocarbon resin;
0.2 to 1% by weight anti-settling agent;
~ ~5703~i
~ 12 .
10 to 20~ by weight flake-shaped extendex;
2 to 15% by ~eight coloring pigments;
1 to 4~ by weight moisture-absorbing agent; and
the remainder, at least however 5%by weight, resin
solvent.
In the coating composition according to this
particular embodiment at least a portion of the color-
ing pigment consists of aluminum powder. Preferably
the portion of aluminum powder amounts to 20 to 80% of
the total weight of the coloring pigments.
This"relatively isocyanate-rich" coating compo-
sition contains as polyurethane-forming isocyanate
preferably diphenylmethane diisocyanate, especially
a diphenylmethane diisocyanate containing isocyanate
groups in an amount of 9 to 12% of the weight of the
isocyanate. Particularly preferred is a mixture of
different diphenylmethane diisocyanates which differ
in their isocyanate content. In this respect good
results were obta~dwhen the total amount of 40 to 70~
by weight of polyurethane-forming isocyanate (relative
to the total weight of the coating composition) con-
sists of
a) 30 to 50% by weight diphenylmethane diiso-
cyanate containing isocyanate groups in an
amount of 8 to 9% of the total weight of
isocyanate; and
b) 10 to 20~ by weight diphenylmethane diiso-
cyanate containing isocyanate groups in an
amount of 14 to 17% of ~he tota~ weight of
isocyanate.
Such a relatively isocyanate-rich coating com-
position containing different diphenylmethane diiso-
cyanate yields after exposure to moisture a lightly
foaming coating. The latter has a joint-sealing
effect, particularly in coating and sealing of roofs
which are covered with tar board. In spite of this
foam formation the resulting film is highly pore-
57034
- 13 -
sealing and water-impervious. This particular coating
composition is workable at air temperatures o~ from
5 to 40~C and also at high atmospheric moisture, for
example at a relative humidity of over 90~. This
coating composition isi on the one hand,self-spreading
and can, on the other hand, ~e applied in thick layers
so that, for example, in one application coats having
a thickness of up to 200 ~m or more can be achieved.
On hardening the composition forms a lightly foaming
film which evens out roughness of the base and which
seals the joints. The coating resulting from this
particular coating composition also exhibits high
pore-sealing, high elasticity and high adhesive strength.
In view of the preferred application of this particular
coating composition for the sealing of flat roofs
covered with tar board this coating composition pre-
ferably contains resin solvents based on aliphatic
esters such as acetates, propionates and/or butylates
so as to avoid partial and/or complete dissolving of
the tar-constituents in the tar board by aromatic
solvent components.
This particular coating composition can be applied
in one step up to a thickness of 1000 ,um without
encountering adhesivity problems or the like.
As previously indicated, this particular coating
composition is especially adapted to seal flat roofs
covered with tar board. To this effect the coating
composition is applied with a thickness of at least
50 ,um. Preferably, at least 500 g coating composition
are applied per s~uare meter of tar board. Due to the
light foam formation which occurs on hardening this
coating composition enters joints, overlapping areas
and border areas of the tar board sheets and provides
sealing of joints which lasts for many years.
