Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Merck Patent Gesellschaft
mit beschrànkter Haftung
6100 Darmstadt
Polymer-encapsulated platelet-like substrates
The in~ention rQlates to polymer-encapsulated platelet-
like substrates obtainable by polymerization of an
organic monomer system which contains platelet-like
substrates which have been surface-modified using organic
coupling agents.
Platelet-like substrates i.e. materials having a rela-
tively small thickness in relation to length and width
are u~ed in many fields of technology. For in~tance,
platelet-like minerals such as, for example, kaolin, mica
or talc are used in finely divided form as fillers for
plastics. Platelet-like pigments such as, for example,
metal oxide-coated mica platelets or platelet-like iron
oxide or bismuth oxychloride are used not only in the
pigmenting of, for example, paints, colorants, plastics
and the like but al~o in cQsmetic preparations.
The ever increasing utility of platelet-like substrates
in different industrial fields increasingly requires the
development of surface-modified ~ubstrates to ultimately
ensure the compatibility of the substrate~ with further
components present in industrial compositions.
A fundamental problem is the strong tendency of platelet-
like substrates of this type to form agglomerates in
which the substrates are present lying on top of one
another like a deck or house of cards and can only bs
separated again with difficulty owing to strong adhesion.
This is all the more troublesome since on incorporating
platelet-like sub~trates in formulations, high shear
forces cannot be applied owing to the fragility of the
thin substrates.
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Numerous methods have therefore been developed, inter
alia, to solve the problem of incorporating platelet-like
pigments, in particular, into thermoplastic materials
(DE-A-2,603,211, DE-A-3,221,044, DE-A-3,627,329).
Furthermore, coatings have been disclosed which contain
polysiloxanes for improved weather resistance
(DE 3,334,598) or silicones (EP 0,224,978). However,
these processes are either too expensive or the coated
pigments have only a restricted use.
The treatment of platelet-like substrates with coupling
agentssuch as organotitanates for improved dispersibility
in cosmetic preparations and with organosilanes for
improved water resistance hasbe2n disclosed (EP 0,306,056
or EP 0,268,918), but polymer-encapsulated substrates
have not been disclosed.
Ths ob~ect of the present invention was to provide im-
proved processes for the polymer coating of platelet-like
substrates. In particular, the substrates must be com-
patible in a great many different industrial formulations
without losing the typical properties of platelet-like
substrates. There is a need, inter alia, for platelet-
like, ~urface-modified pigment~ which can be incorporated
without Io8s of their pigment properties into formu-
lation~. ~xamples of frequently occurring disadvantages
with pigment incorporation are pigment shock, i.e. the
formation of agglomerates on incorporation owing to
incompatibilities, and pigment migration.
This ob~ect is achieved by the present invention. In
particular, it has been found that platelet-like ~ub-
strates can be readily encapsulated with polymer systemsif they have previously been treated with organic cou-
pling agents.
The present invention accordingly provides polymer-
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encapsulated platelet-like ~ubstrates obtainable by
polymerization of an organic monomer system which con-
tains platelet-like subRtrates which have been surface-
modified using organic coupling agents.
In particular, the invention provide~ latex systems which
contain the substrates according to the invention.
The invention also provides a procass for the preparation
of latex sy3tems of this type, which is characterized in
that platelet-like substrate~ are treated with organic
coupling agents which ara suitable for hydrophobizing the
substrate particles, and tho substrates which have been
modified in this manner are finely distributed in an
aqueous solution with the addition of an emulsifier, this
giving micelle-like structures, and to this dispersion is
added a monomer and optionally an initiator, and the
monomer system is polymerized.
Finally, the invention provides the use of the platelet-
like substrates which have been surface-modified using
or~anic coupling agents or of the latex systems which
contain substrates of this type, in paints, dye compo-
sitions and plastics.
The invention ultimately provides formulations which
contain the substrates or latex systems according to the
inv~ntion.
Preferred platelet-like substrates for surface modifica-
tion according to the invention are, in particular,
layer-structured silicates and oxides or oxide-coated
materials, since these have reactive OH groups on their
surface. Example~ of these are, on the one hand, mica,
talc, kaolin or other comparable minerals and, on the
other hand, also platelst-like iron oxide, bismuth
oxychloride and the metal oxide-coated micas known as
pearl lustre pigments, and also aluminium platelets and
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oxide-coated aluminium platelets. All conventional pearl
lustre pigments can be used, for example mica coatings
containing coloured or colourless met~l oxides such as
rio2, Fe2O3, SnO2, CrzO3, ZnO and other metal oxides as ~uch
or mixed in a uniform layer or in succes~ive layers.
These pigments have been di~closed, for example, in the
German Patents and Patent Applications 1,467,468,
1,959,998, 2,009,566, 2,214,545, 2,215,191, 2,244,298,
2,313,331, 2,522,572, 3,137,808, 3,137,809, 3,151,343,
3,151,354, 3,151,355, 3,211,602 and 3,235,017. Further-
more, the abovementioned platelet-like substrates may
also be coated with organic dye compositions or pigment
molecules.
The coupling agents used can be appropriate compounds as
described, for example in the following publications:
Edwin P. Plueddemann; Silane Coupling Agents; Plenum
Press; New York, London (1982) and the literature
referred to therein. Salvatore J. Monte, Gerald Sugerman;
Ken-React Reference Nanual - Titanate, Zirconate and
Aluminate Coupling Agents (1987~ and the literature
referred to therein. Dynasilan Haftvermittler, Organo-
funktionelle Silane, Technische Information Dynamit Nobel
(1985). Lawrence B. Cohen, The Chemistry of Zirson-
aluminate Coupling Agents and their Application in HIgh
Solids Coatings, ~ater-borne and Higher-Solids Coatings
Sympoaium, New Orleans 1986. Lawrence B. Cohen, Corro~ion
Reduction in High Solids an Water-borne Coating~ using
Zirconaluminate Adhesion Promoters, Water-borne and
Higher-Solids Coatings Symposium, New Orleans, 1988.
Peter Z. Moles, The Application of Zirconium Compounds in
Surface Coatings, Water-borne and Higher-Solids Coatings
Symposium, New Orleans, 1987.
As a rule, cuitable compounds contain one or more metal
centre~ such as Si, Ti, Zr or Al to which functional
organic group~ are bonded. Examples of suitable silanes
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are the commercially available DYNASYLAN~ agents (Dynamit
Nobel)~ These are alkoxysilane derivatives having two or
three alkoxy radicals and one or two alkyl radicals to
which additional functional groups may also be bonded,
for example amino, mercapto~me~cryloxy or a nitrile group or a
halogen radical such as chlorine. Examples of ~uitable
titanate coupling agents are the commercially available
"RR~ or "~ICA~ materials (Renrich Petrochemicals, Inc.).
Like the abovementioned silanes, these agents are com-
pounds having alkoxy radical~ and, optionally, additionalradicals ~ubstituted by functional groups, the radicals
of the said compounds being bonded via oxygen to the
metal centre. Examples of the functional groups are
amino, mercapto or hydroxyl groups.
Examples of suitable zirconate coupling agents are the
compounds obtainable from Renrich Petrochemicals, Inc.
under the designation "RZ n or ~LZ n agents, these com-
pounds, if appropriate, having amino or mercapto groups.
Furthermore, the substrates according to the invention
can be prepared using zirconium aluminates ~uch as, for
example, the appropriate "Cavco Mod~ agents obtainable
from Cavedon Chemical Co., Inc. Polymer encapsulations
according to the invention using zirconium aluminates as
coupling agents can, in particular, also be suitably
carried out using platelet-like metal substrates, for
example platelets of Al, Cu or Zn or alloys.
The coupling agents are applied either directly or by
intensive mixing of substrate and coupling agent, prefer-
ably, however in organic solvents or in aqueous medium.
The concentration of the coupling agent in these procedu-
res is in the range from about 0.01 to 20, preferably 0.1
to 10% by weight. Furthermore, it is also possiblQ to use
mixtures of coupling agents.
The platelet-like substrates which have been surface-
modified in this way have a number of advantages in
comparison with untreated sub~trates.
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For instance, in humidity and adhe~ion tests, far better
results are obtained from pearl lustre pigments which
have been treated with silanes such as aminoalkylalkoxy-
silanes or 3-glycidyloxypropyl~ilane, than with untreated
pigments.
Preferred titanate and zirconate agents are the mono-
alkoxy titanates (RR) such as KR TTS, RR 6, RR 7, gR 12,
RR 26 S, KR 38 S and RR 44, the so-called quat titanates
and quat zirconates such as KR 138 D, XR 158 D, RR 238 T,
RR 238 M, XR 238 A, RR 238 J, KR 262 A, LICA 38 J, LZ 38
J, the coordinated titanates and zirconates such as RR 41
B, RR 46 B, RR 55, RZ 55, the neoalko~y titanates such as
LICA 01, LICA 09, ~ICA 12, LICA 38, LICA 44, LICA 97,
LICA 99 and the neoalkoxy zirconates such as LZ 01, LZ
09, L2 12, LZ 33, LZ 38, L~ 39, LZ 44, LZ 49, LZ 89 and
LZ 97.
Some of the pigments treated with quat titanates or
zirconates have a very long settling time in water. This
is advantageous on i~corporating the pigments in water-
borne paints. Some neoalkoxy zirconate-cQated pigments
have considerably les~ photoactivity than untreated
pigments.
Furthermore, it is also possible to use oxyacetate-
chelate titanates, A,B-ethylene-chelate titanates and
cycloheteroato-titanates and -zirconates.
Particular preference is given to the quat titanates and
quat zirconates, the coordinated titanates and zirconates
and the neoalkoxy titanates and zirconates.
Of tho abovementioned compounds, RR TTS, ~R 6, RR 7, RR
41 B and RR 55 ar~ known for coating pigments and other
cosmetic material (EP 0,306,056).
The present invention aecordingly al~o provides coatings
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of platelet-like sub~trates containing all of the other
abovementioned coupling agents, in particular the quat
titanates and quat zirconates and also coordinated
zirconates and neoalkoxy zirconates, owing to the surpri-
sing and advantageous properties of the coated sub-
strates, for example of the pigments.
In particular, the invention also provides zirconium
aluminate-coated platelet-like substrates, for example
pigments. With these pigments also, the settling time of
the treated pigments in water is significantly greater
than that of the untreated pigments. Particularly suit-
able coupling agents are the abovementioned ~Cavco Mod~
agents such as Cavco Mod APG, Cavco Mod CPG, Cavco Mod
F, Cavco Mod C, Cavco Mod A, Cavco Mod CPM, Cavco ~od C-
lP~, Cavco Mod M, Cavco Mod SPM, Cavco Mod APG-2, Cavco
Mod MPM, Cavco Mod A PG-l and Cavco Mod APG-3.
The platelet-like substrates which have been coated with
the abovementioned coupling agents can be advantageously
encapsulated with polymer sy~tems. On the one hand, owing
to improved dispersibility, the substrate~ can ba readily
incorporated in various polymer systems. On the other
hand, stable latex systems can be prepared using pro-
cesses such as emulsion polymerization.
The modified platelet-like substrate~ for example a
pigment, iB finely di~persed in an aqueou~ ~olution which
contains an emulsifier. The emulsifier molecule~ then
become prefarentially attached to the hydrophobic pigment
particles so that ultimately the hydrophilic functions of
the emulsifier molecules are directed into the agueou~
phase. Thi~ gives micelle-like structures which fill up
with monomer if the critical micelle concentration is not
exceeded or is only ~lightly exceeded. Polymerization
then takes place, optionally after adding an initiator,
almost exclusively in the pigment micelles. In principle,
the amount of monomer to be added can be varied a~
.
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required. Owing to the very much greater surface of the
micelle~, a radical which has been formed in the aqueous
phase much more often encounter~ a micelle filled with
monomer molecules than a monomer droplet ~wLmming in the
suspension. Monomers which have been consumed in the
micelle are renewed from the monomer droplets by dif-
fu~ion 80 that even at high monomer concentration polym-
erization virtually only occurs in the micelle region.
The amount of monomer can be up to 100% by weight,
relative to the ~ubstrate weight, but in individual cases
can be considerably more. ~C.H.M. Caris et al.,
~Polymeriz~tion at tho surface of inorganic submicron
particles", XIX FATIPEX Congress, Aachen 1988). Based on
this process principle, all of the polymer reactions
which can be carried out in emulsion, for example the
polymerization and copolymerization of acrylate, meth-
acrylate, styrene, vinyl acetate, butadiene, isoprene,
acrylonitrile, vinyl chloride and the like, can be
carried out on platelet-like substrates which bear
initiator groups. The reaction conditions are Xnown to a
person skilled in the art and can, for example, be taken
from: D.B. Braun et al.in ~PraXtikum der makromolekularen
organischen Chemie~, published by Huthig-Verlag,
Heidelberg 1979. The polymer which has been formed on the
surface of the pi~ment may be held by physical bonds or
be link~d to the pigment surface by a covalent bond to a
functional group of the coupling agent for example to a
methacrylate group acting as comonomer unit.
;The polymer content of the substrates according to the invention can be
controlled for example by the choice of the emulsifier or by the amount of
¦initiator. The polymer content can be determined by product pyrolysis.
Anionic, ca-tionic and nonionic surfactants can be used as emulsifiers.
Emulsifiers which are Nppropriate are for e~ample sodium doclecyl slllphate
~(SDS), sodium oleate, silicon oil (f.e. ME~ nrt. 77~2) and a polyo~yethylene
sorbitan monolaurate which is known as tween 20 (ME~ art. 82218~). In
individual cases mi~tures of different emulsifiers ar~ acl~alltageous. By
after-coating the initial pigments with bnsic aluminillm suLIlhate, an increase
of the ~olymer colltellt w~s also observed.
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The polymer-encapsulated pigments which have been
prepared in this manner can be significantly better
incorporated in polymer systems and also have improved
weathering resistance. There i~ virtually no los~ of
lustre or formation of agglomerates.
Furthermore, it i8 not necessary to isolate the polymer-
encapsulated substrate particles.-The substrate/polymer
particles formed as pigment latices in the emulsion
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polymerization can be mixed directly with the compon~nts
of a waterborne paint system by latex-intermixing. In
this procedure, the polymer coating of the platelet-like
substrates can be optimally adapted to the paint system
by the appropriate selection of the monomers. The mixing
of the harmonized latices allows any incompatibilities
and any imperfections in the paint system caused by
pigment addition (pigment shock) to be for the greatest
part or even completely eliminated.
The invention is explained with the aid of the following
examples:
ExamPle 1
Coatings containing coupling agents
A) 200 g of Iriodin 504 (iron(III) oxide-coated mica
flake pigment from E. Merck, Darmstadt) are suspen-
ded in 4 1 of completely deionized water. The
reaction suspension is then heated with vigorous
stirring to 75C. The pH is ad~usted to 6.5 using
15% aqueous sodium hydroxide solution. Then a
solution of 2 g of DYNASYIA~ 1110 in 200 ml of
deionized water is added dropwise to the pigment
suspension over a period of 10 minutes. During this
procedure, the pH is maintained at 6.5 using 5%
aqueous sodium hydroxide solution. After the ad-
dition has ceased, the mixture is stirred for a
further 30 min at 75C. Then the pigment is filtered
off under suction through a suction filter, washed
eight times with 2 1 portion~ of deionized water and
dried at 100C for 16 h.
Iriodin 225 (TiO2-coated mica flake pigment from
E. ~erck, Darmstadt) is similarly coated, but at a
pH of 8.
202~ ~ ~ 3
lri()~H~ )225 is simi~nrly~ ~ont-~(l b' it~l D~!;AS~I.A.~IF;MO nt p~l Or 5.5.
Iriodin- 504 i8 similarly coated with DYNASYLAN~
GLYMO at a pH of 7.
In the humidity test (16 h at 66-C in the ~ingle
coat humidity test) and in the adhe~ion test (cro~s-
hatch adhesion test according to DIN 53 151 using a
Du Pont paint system, all of the coated pigments
give significantly better result~ than the untreated
pigments, by a wide marqin.
B) 61.5 g of LICA 38 J are dissolved in 4500 ml of
deionized water and heated to 30-C. Then 1500 g of
Iriodin 504 are added in portions to the solution.
After the addition ha~ ceased, the mixture is
stirred for a further ~0 min. Then tXe pigment is
filtered off, washed three time~ with 4500 ml
portions of ~eionized water and dried at 120C for
16 h. It is also possible to use dichloromethane,
toluene or isopropanol in the treatment instead of
deionized water. However, in this case the opera-
tions are carried out at room temperature.
A similar procedure was followed to produce coatings
on Iriodin 225 from each of ~R 12, KR 138 1,
RR 238 M, KR 238 J, KR 41 B, RR 46 B and LZ 38. The
last thr~ abovement~onsd titaniu~ coupling agents
are applied dissol~ed in toluene.
The humidity and adhesion test re~ult~ obtained from
the coated pigments are comparable with those given
under A). The LZ 38-coated pi~ment Iriodin 225 has
significantly lower photoactivity (Rronos photo-
activity test) than the untreated pigment.
C) 100 g of Iriodin 504 coated with 1% by weight of
SiO2 and 1.3% by weight of Al(OH)SO~ are suspended in
2 1 of deionized water. To the reaction suspension
which has been ad~usted to a pH of 4 is then added
dropwise over a period of 30 min, a solution of
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8.47 g of Cavco Mod M 1 (= 2% of acti~e component
relative to 100 g of pigment) in 50 ml ~f i~opro-
panol. After the dropwise addition has ceased,
stirring is continued for a further hour. Then the
pigment is filtered off, washed three times with 2 l
portions of deionized water and dried for 16 h at
105C.
The Cavco Mod M l-treated pigment can be screened in
a third of the time compared with the untreated
pigment or commercially available Iriodin 504, the
amount screQned in each case being identical.
A similar procedure is followed for treating
Iriodin 504 which had been coated with SiO2 and
Al(OH)SO~, in accordance with the dirèctions given
above, with the zirconium aluminates Cavco Mod APG,
Cavco Mod CPG, Cavco Nod F, Cavco Mod C, Cavco Mod
A, Cavco Mod CPM, Cavco Mod C-lPM, Cavco Mod M,
Cavco Mod 5PM, Cavco Mod APG-2, Cavco Mod MP~, Cavco
Mod APG-l and Cavco Mod APG-3. Cavco Mod F and Cavco
Mod SPM are added dropwise in the form of isopro-
panol solutions, while all of the other zirconium
aluminates are added dropwise in the form of aqueous
solutions.
The zirconium aluminate-treated pigments ar~ sub-
stantially hydrophobic. In aqueous suspension, they
are present in particularly finely dispersed form
and, in particular, do not form any agglomerates or
aggregates. The settling time of the treated pig-
ments in water is siqnificantly longer than that of
the untreated pigments.
The water used in the examples which follow is in
every case completely deionized and thoroughly
boiled under an atmosphare of nitrogen.
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Example 2
40 g of monoalkoxy titanate (KR 12)-coated Iriodin 225
are suspended in 250 ml of water. Then a ~olution of
0.37 g of sodium dodecyl sulphate (SDS) in 186 ml of
water is added. The initially hydrophobic pigment par-
ticles are now hydrophilic (micelle formation). After
adding 62 ml of methyl methacrylate which ha~ been
distilled under nitrogen, the mixture is heated to 60C
and stirred vigorously. Then a solution of 1.16 g of
potassium peroxodisulphate in 40 ml of water is added.
The viscosity of the solution increases signif$cantly.
Small samples are withdrawn at 10 min intervals and
observed under the interference contrast micrascope. No
agglomeration of the pigment particles can be observed.
After about one hour, the solution is diluted using
700 ml of water.
This give~ a ~table latex system which can be readily
latex-intermixed with various acrylate and methacrylate
waterborne paint systems.
A similar procedure is used to obtain latex systems which
have good to very good compatibility with the above-
mentioned waterborne paint systems, using the pigments
Iriodin 504 and Iriodin 225, each modified according to
LA, lB ad lC.
Example 3
A procedure similar to that of Example 2 is used to
encapsulate 40 g of the Iriodin 504, coated according to
Example lB (LICA 38 J), with 40 g of polystyrene.
~efore adding styrene, 50 mg of sodium dihydrogen phos-
phate are added to the reaction suspansion, since styrenepolymerizes best in a weakly alkaline medium. The mixture
is stirred vigorously for a total of 6 h at 60C. This
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gives a stable latex sy~tem which i~ very compatible with
other ~tyrene-ba~ed latex sy~tem~.
A sLmilar procedure i~ used to prepare polystyrene-
encapsulated modified pigment~ using pigments coated
according to lA, lB and lC, and the~e can likewise be
well to very well mixed in the form of stable latices
with comparable waterborne paint systems.
Example 4
10 g of Iriodin 504, coated according to lC (Cavco Mod
M 1), are suspended in 50 ml of water. Then a solution of
O.S g of sodium dodecyl sulphate in 2~ ml of water is
added followed by 125 mg (0.32 mmol) of iron(II)ammonium
sulphate and 125 mg of sodium pyrophosphate in 5 ml of
water for buffering purposes. The buffer solution was
preheated for about 15 min at 60-70C. The mixture is
allowed to cool to room temperature and 20 ml (O.2 mol)
of isoprene which has been distilled under nitrogen are
added, followed after 15 min o$ vigorous stirring by
50 mg (0.21 mmol) of potassium peroxodisulphate. The
mixture is stirred for about 6 h at room temperature.
This give~ a latex system which iY readily compatible
with comparable latices.
A s~milar procedure i8 used to prepare likewise readily
compatible latex systemY using pigments coated according
to LA, lB and lC.
Exam~le 5
30g of Iriodin ~ 225 coated with 1,3Z by weight of Al(OH)SO~ and 2,3% by
weight of Dynasyla~ ~1EMO are added at room temperature to a solution of
0.56~ of sns in 260 ml of water. Then the mixture is heated at 60C. Then 3.2
ml of methyl methacrylate are added dropwise followed by a solution of 0.45g
of potassium peroxodisulphate in lO ml of water. The mixtl1re is heated at 60C
and stirred for 90 minutes. Then the mixture is allowed to cool to room
temperature, the non-reacted monomer is removed in vaclllIm, the product is
f;ltered off, w~shed with water and dried At. 120C.
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Tl~ls ~ s a ~m(~ tl~ til~ (tt~ mr!lt ~illl flvery s]o~ pignle~ positioll bella~iollr ill hater, a(et()rle~ ethallol arl(l toluene~
The pol~mer contellt amounts to l.6~% by weight.
EY am~Q 6
A procedure similar to that of example 5 is carried Ollt but only hith 0.09~ of
potassium peroxodisulphate. The polymer content amounts to about 0.5X by
weight.
Example 7
A procedure similar to that of example 6 is carried out, but 2 ml of silicon
oil (MEK art. 7742) are added before adding the monomer. The polymer content
amounts to 3.65% by weight.
ExamPIe 8
A procedure similar to that of example 6 is carried out but with 0.93g of
sodium oleate as emulsifier. The polymer content amounts to about 1,55 by
weight.
Example 9
A procedure similar to that of example 6 is carried out but with 0.56g of the
nonionic surfactant tween 20 as emulsifier. The polymer content amounts to
about 1.16% by wei~ht.
Exam~le 10
A procedure similar to that of example 5 is carried out but with 0.93g of
sodium oleate as emulsifier. The polymer content amounts to about 2.12% by
weight.
