Note: Descriptions are shown in the official language in which they were submitted.
20~'~l.~.r
HOECHST ARTIEPIGESELLSCHAFT HOE 90/F 364 Dr.ICI/1
Description
Water-containing organophilic phyllosilicates
It is widely known that organophilically modified
phyllosilicates can be employed as Theological additives
in organic media. Examples of these are the commercial
products marketed under the names ~Tixogel (manufacturer:
Sudchemie AG) and ~Bentone. These theological additives
have the effect of the build-up of a thixotropic struc- '
tuts in organic media, for example in paints and var-
nishes. As a result of this thixotropic structure, such
organic media are easier to process . The organophilically
modified phyllosilicates are obtained by treating phyllo-
silicates in aqueous suspension with an aqueous solution
of an onium compound, preferably a quaternary organic
ammonium salt, this organic ammonium salt being embedded
between the layers of the phyllosilicate. The phyllo-
silicate organophilically modified in this manner is then
separated from the water by filtration and dried under
the action of heat, for example in a drum drier at about
100°C. The modified organophilic phyllosilicates obtained
in this manner are water-insoluble.
Such a drying operation has previously been considered
necessary, since the filtercake obtained when the water
is filtered off contains considerable amounts of water,
and this water content has been said to interfere in the
use of the organophilic phyllosilicates in the organic
media. It has now been found, surprisingly, that this is
not the case and that the filtercake of such organophilic
phyllosilicates can be employed as a Theological additive
in organic media even without being dried.
The invention thus relates to the use of water-containing
organophilic phyllosilicates which are obtained by the
reaction of a phyllosilicate, which is completely
delaminated colloidally in water and is capable of ration
exchange, with an organic onium salt in aqueous
- 2 -
suspension and subsequent mechanical removal of the
water, without drying by heating, as a rheological
additive in organic media and for coating paper.
These organophilic phyllosilicates are obtained by
methods which are known per se, which therefore do not
have to be explained in more detail. Possible phyllo-
silicates which are capable of cation exchange and are
completely delaminated colloidally in water are all the
synthetic or naturally occurring smectic phyllosilicates,
preferably bentonite or montmorillonite, which, in
addition to a smectic phyllosilicate, can also contain
25-30~ by weight of impurities in the form of other
minerals. The minerals are treated with an aqueous
solution of onium compounds, such as, for example,
phosphonium compounds, but preferably quaternary organic
ammonium salts, these compounds being embedded between
the layers of these minerals. Possible quaternary organic
ammonium salts are, in particular, compounds of the
formula
R, Rz
2 0 ~ N ~ A°'
R,/ ~Rz
in which Rl is C8-CZZ-alkyl or C8-CZZ-alkenyl, RZ is Cl-Cd-
alkyl and A is an anion, preferably chloride or metho-
sulfate. The compound distearyl-dimethyl-ammonium
chloride is particularly preferred. When the phyllo-
silicate is charged with the quaternary organic ammonium
salt, the water is filtered off or pressed off. This is
done by the customary processes of separation. The
filtercake obtained consists, depending on the purity of
the phyllosilicates, to the extent of about 65 to 83$ of
water and is employed according to the invention in this
form directly as a rheological additive in organic media.
Examples of organic media in the sense of this invention
- 3 -
are paints, varnishes, coatings, putties, lubricating
greases, cosmetics, paint removers, filler compositions
and similar formulations containing organic solvents. The
water-containing organophilically modified phyllo-
silicates according to the invention have a thixotroping
effect in all these systems. As a result of this effect, .
the formulations mentioned are easier to process. In
addition, these phyllosilicates also prevent settling of
the insoluble components, for example the pigments within
these media. As another surprising effect of these water
containing organophilic phyllosilicates it has been found
that the thickening action here is significantly higher
in comparison with the analogous commercially available
products having the same solids content, but from which
the water has been removed by drying by heating.
These water-containing organophilically modified phyllo-
silicates are added to the organic media by methods which
are known per se. The amount of these rheological addi-
tives also lies within the range known to the expert in
this field (about 0.5 to 3% by weight).
The water-containing organophilic phyllosilicates accord-
ing to the invention are particularly suitable for
coating paper. From economic considerations, efforts are
made to use thin printing papers for printed products
with a high circulation, for example newspapers or mail-
order catalogs. However, problems arise here in respect
of opacity, i.e. in the case of printing the print shows
through in an interfering manner on the other side of the
paper. To prevent this effect, it is already known
(EP 192 252) that paper can be coated with an organo-
philic complex of a smectic phyllosilicate and a
quaternary organic ammonium compound from a suspension in
organic solvents. The starting material is present here
in a form from which as much of the water as possible has
been removed by heating. In the context of the present
invention, it has now been found that drying of the
organophilically modified phyllosilicate can be dispensed
- 4 -
with in this process (solvent coating) and the water-
containing presscake of this organophilically modified
phyllosilicate can be employed directly. It is surprising
here that the water in the presscake does not interfere
with the homogeneity of the overall organic system. The
water remains in the inner phase, and no swelling of the
paper fibers occurs, as would be the case with an aqueous
coating. This finding is therefore of relatively great
importance, since in future such "solvent coating"
processes based on toluene or white spirit will gain
increasing importance. The solids content (i.e. without
the content of water from the presscake) of such suspen-
sions is about 3 to 9% by weight. These "solvent coating"
suspensions can furthermore also contain white pigments
(TiOz). As a result of the ability of the organo-
philically modified phyllosilicates to form films, these
white pigments are bonded firmly to the paper by the
phyllosilicates; no additional binder is therefore
needed. A good hold-out effect is obtained in this
manner, i.e. print-through on the printed paper is
prevented.
Examples
A commercially available, non-purified Na bentonite
(exchange capacity 80 milliequivalents/100 g) was stirred
in a hot solution of distearyl-dimethyl-ammonium chloride
at a ratio of the two products of 69% by weight of Na
bentonite and 31% by weight of quaternary organic
ammonium salt. When the reaction had ended, the mixture
was filtered and the now organophilically modified
bentonite was pressed off to a solids content of about
31% by weight. This filtercake was dispersed in toluene
and the dispersion was applied in a thin layer to a sheet
of paper and dried. The details of the examples and the
particular evaluation of the hold-out effect can be seen
from the following Tables 1 and 2.
As the examples show, a very good hold-out effect is
- 5 -
obtained with the water-containing organophilic
phyllosilicates according to the present invention. The
examples in the table show that customary white pigments
can also be applied to the paper and firmly anchored
there by means of the dispersion of the organophilically
modified phyllosilicate in toluene; no additional binder
is required here.
Table 1
1 2 3
Toluene 87.5 g 85 g 82.5 g
Filtercake 12.5 g 15 g 17.5 g
Brookfield viscosity
in mPas at 100
rpm
after 2 days 308 528 720
Weight applied 1.5-1.8 1.6-1.7 1.4-1.6
(g/m2)
Hold-out good good good
Weight applied
(g/mz) 2.3-2.5 2.8-3.0 2.5-2.7
Hold-out very goo best very good
- 6 -
Table 2
3 4 5
Toluene to 100 to 100 to 100
Filtercake 15 g 15 g 15 g
Titanium dioxide 0.4 g
China clay 0.4 g
Optical 0.1 g
brightener
Brookfield viscosity
in mPas at 100 rpm
after 2 days 29g 324 216
Weight applied
g/mz~ 1.3 1.4 1.5
Hold-out good good good
