Modified bentonite is disclosed, comprising modified bentonite
which can be dispersed in water to perform a function of adjusting
rheology of an aqueous liquid.
What is claimed is:
1. Modified bentonite which can be dispersed in water to perform
a function of adjusting rheology of an aqueous liquid, which is
adding at least one alkyltrialkoxysilane represented by formula
wherein R.sup.1 represents a saturated alkyl group having from
1 to 22 carbon atoms; and R represents a methyl group, an ethyl
group, a propyl group or a butyl group, to bentonite in such an
amount that the resulting product can retain an excellent water-dispersibility,
stirring and pulverizing the mixture in a water-free atmosphere
to add an alkylsilyl group to a part of the surface of bentonite
2. Modified bentonite as claimed in claim 1, wherein said bentonite
is purified water-free bentonite prepared by removing non-clay substances
from a bentonite aqueous suspension using spontaneous sedimentation
or centrifugal separation and drying the resulting purified bentonite
3. Modified bentonite as claimed in claim 1, wherein said alkyltrialkoxysilane
is used in an amount of from 0.5 to 15 parts by weight per 100 parts
by weight of bentonite.
FIELD OF THE INVENTION
This invention relates to surface-modified bentonite which is dispersible
in water or organic liquids to exhibit an excellent function of
BACKGROUND OF THE INVENTION
Bentonite deposit has a complicated composition mainly formed of
smectites and containing free silica minerals, such as quartz, .alpha.-cristobalite,
and opal; silicate minerals, such as feldspar, mica, and zeolite;
carbonates or sulfates of alkaline earth metals, such as calcite,
dolomite, and gypsum; and, in addition, iron compounds and humus.
Since bentonite ore mined from bentonite deposit usually has a water
content of 15 to 35%, it is primarily broken and dried in the sun
or hot air to obtain bentonite ore having a water content of 5 to
10%. The dried bentonite ore is pulverized by means of an attrition
grinding machine, such as a centrifugal roller mill, or an impact
mill, such as a hammer mill. The resulting bentonite powder is widely
used in various industrial fields, for example, as a binder for
foundry sand, a main ingredient for a drilling fluid used in oil
well drilling, geothermal well drilling, or hot spring boring, or
a main agent of a stabilizing liquid used in continuous diaphragm
wall construction or earth drilling in engineering works. As stated
above, bentonite for these uses basically has a composition based
on the natural bentonite deposit, containing much non-clay substances.
On the other hand, liquid fine chemicals widely used in various
industrial fields, such as coatings, printing inks, and cosmetics,
contain various natural or chemical substances for rheological adjustment.
Purified bentonite powder, which is obtained by dispersing bentonite
in water, removing unfavorable non-clay substances by spontaneous
sedimentation or centrifugal separation, and drying the resulting
purified bentonite sol by evaporation, is used as a rheological
adjuster for aqueous coatings, aqueous emulsions, or the like aqueous
colloidal dispersion products.
Because the bentonite powder which is merely purified can not be
dispersed in organic-solvents, it is not suitable as a rheological
adjuster for liquid products containing an organic solvent, such
as alkyd resin coatings or other synthetic resin coatings, printing
inks, and sealants. Hence, the purified bentonite is rendered organophilic
by combining with a quaternary ammonium cation (see U.S. Pat. No.
2,531,427), a composite of a quaternary ammonium cation and a nonionic
organic compound (see Japanese Patent 244306 corresponding to JP-B-3018
(The term "JP-B" as used herein means an examined Japanese
patent publication), or a combination of a quaternary ammonium cation
and an organic anion (see JP-A-57-111371), (the term "JP-A"
as used herein means an "unexamined published Japanese patent
applications") to be used as a rheological adjuster which can
be dispersed in organic liquids.
However, the above-mentioned purified bentonite or organophilic
modified bentonite has disadvantages as described below.
Purified bentonite exhibits unique rheological characteristics
which differ from that of organic (high) polymers, e.g., carboxymethyl
cellulose, poly(sodium acrylate), and polyacrylamide. However, because
its function in increasing viscosity is generally insufficient,
it must be added in a considerable proportion to obtain a sufficient
effect in increasing viscosity, which leads to generation of various
undesired side effects, such as impairment of the color tone of
products. Accordingly, the amount of the purified bentonite incorporated
Organophilic modified bentonite has insufficient dispersibility
in a solvent system comprising hydrocarbons only, and it is necessary
to add to the dispersion system an adequate amount of a highly polar
organic compound having a low molecular weight, such as methanol,
ethanol, or acetone, to obtain organophilic modified bentonite which
is sufficiently dispersed. However, such usage is not only complicated
but involves a problem that an unfavorable polar compound should
be introduced into the system.
SUMMARY OF THE INVENTION
An object of the present invention is to provide modified bentonite
which can be dispersed in an aqueous system to provide an excellent
effect in increasing viscosity which has not been achieved with
conventional purified bentonite products.
Another object of the present invention is to provide organophilic
modified bentonite which can easily be dispersed in a hydrocarbon
solvent system to provide an excellent effect in increasing viscosity
without use of a highly polar organic compound.
The inventors have found that the above objects of the present
invention are accomplished by purified bentonite treated with an
The present invention relates to modified bentonite which can be
dispersed in water to perform a function of adjusting rheology of
an aqueous liquid, which is obtained by
adding at least one alkyltrialkoxysilane represented by formula
wherein R.sup.1 represents a saturated alkyl group having from
1 to 22 carbon atoms; and R.sup.2 represents a methyl group, an
ethyl group, a propyl group or a butyl group, to bentonite in such
an amount that the resulting product can retain an excellent water-dispersibility,
stirring and grinding the mixture in a water-free atmosphere to
add an alkylsilyl group to a part of the surface of bentonite particles.
The present invention also relates to modified bentonite which
can be easily dispersed in an organic liquid to perform a function
of adjusting rheology of an organic liquid, which is obtained by
adding to bentonite (1) from 1 to 1.5 equivalent of a quaternary
ammonium cation represented by formula (II):
wherein R.sup.3 represents a long-chain alkyl group having from
12 to 22 carbon atoms; R.sup.4 represents a methyl group, a benzyl
group or a long-chain alkyl group having from 12 to 22 carbon atoms;
and R.sup.5 represents a methyl group, based on the cation exchange
capacity of said bentonite and (2) from 0.5 to 15 parts by weight
of at least one alkyltrialkoxysilane represented by formula (I):
wherein R.sup.1 and R.sup.2 each has the same meaning as defined
above, per 100 parts by weight of said bentonite to render said
bentonite hydrophobic .
DETAILED DESCRIPTION OF THE INVENTION
Bentonite which can be used as a raw material in the present invention
is substantially water-free purified bentonite which is obtained
by removing non-clay substances from a crude bentonite suspension
using spontaneous sedimentation or centrifugal separation to recover
a purified bentonite sol, evaporating the resulting purified bentonite
sol, and finally drying at a temperature of from 150 to 200.degree.
The modified bentonite which can provide an excellent effect in
increasing viscosity in an aqueous dispersion system according to
the present-invention can be prepared by adding to purified bentonite
in a water-free atmosphere an alkyltrialkoxysilane of the above
formula in such an amount that does not cause the resulting product
to exhibit water repellency, and, after stirring, grinding the mixture
to thereby add an alkylsilyl group to a part of the surface of bentonite
Specific examples of the alkyltrialkoxysilane represented by formula
(I) which can be used in the present invention include methyltrimethoxysilane,
methyltriethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane,
hexyltrimethoxysilane, octyltriethoxysilane, dodecyltriethoxysilane,
and octadecyltriethoxysilane. Among these, hexyltrimethoxysilane,
octyltriethoxysilane, dodecyltriethoxysilane, and octadecyltriethoxysilane
The amount of the alkyltrialkoxysilane to be added to purified
bentonite is experimentally decided from the degree of non-water
repellency, wetting with water, and waterdispersibility of the finally
obtained modified bentonite. In most cases, while not limiting,
such an amount ranges generally from 0.5 to 15 parts by weight,
preferably from 1 to 10 parts by weight, and most preferably from
1 to 7 parts by weight, per 100 parts by weight of bentonite.
By the treatment with the alkyltrialkoxysilane, an alkylsilyl group
is added to hydrophilic hydroxyl groups present on the surface of
bentonite particles, such as a silanol group, to render the part
of the bentonite surface hydrophobic. The thus modified bentonite
particles, when dispersed in an aqueous system, form a plastic structure
due to association of the hydrophobic groups thereof and, as a result,
considerably increase the apparent viscosity of the aqueous system
and endow the aqueous system with favorable thixotropic properties.
The organophilic modified bentonite containing an alkylsilyl group
for organic liquids, particularly hydrocarbon solvent systems, according
to the present invention is preferably prepared by dissolving an
alkyltrialkoxysilane in a quaternary ammonium cation solution, immediately
adding the solution to a purified bentonite sol to conduct a reaction,
followed by dehydration, drying, and pulverizing. The organophilic
modified bentonite may also be prepared by re-dispersing in water
the abovementioned alkyltrialkoxysilane-treated bentonite produced
in a water-free atmosphere and then adding thereto a quaternary
ammonium cation. However, the latter method is not practical because
it requires re-dehydration and re-pulverizing, thus increasing cost.
Specific examples of the alkyltrialkoxysilane which can be used
in the preparation of the organophilic modified bentonite are the
same as those enumerated above.
The amount of the alkyltrialkoxysilane added ranges from 0.5 to
15 parts by weight per 100 parts by weight of bentonite.
The quaternary ammonium cation represented by formula (II) shown
above which can be used in the present invention can be added in
the form of a quaternary ammonium chloride. The amount of the quaternary
ammonium cation added (i.e., the amount of the quaternary ammonium
cation added) ranges from 1 to 1.5 equivalent and preferably from
1 to 1.25 quivalent, based on the cation exchange capacity of the
By the above-mentioned treatment with the quaternary ammonium cation
and alkyltrialkoxysilane, the alkyltrialkoxysilane is solubilized
by a quaternary ammonium salt having surface activity and, at the
same time, undergoes partial hydrolysis to form an alkylsilyl polymer,
which is added to the hydrophilic sites on the surface of bentonite
particles together with the quaternary ammonium cation to thereby
accomplish a treatment for rendering the bentonite surface hydrophobic
to such a degree that a quaternary ammonium cation alone cannot
achieve. The resulting modified bentonite particles are easily dispersed
in a hydrocarbon organic liquid to form a plastic structure due
to association of the hydrophobic particles, with which a high apparent
viscosity and favorable thixotropic properties can be imparted to
the organic liquid system.
Bentonite which can be used in the present invention belongs to
phyllosilicate minerals having a dioctahedral structure and/or a
trioctahedral structure and having substantially a cation exchange
capacity, which are selected from the group consisting of montmorillonite,
beidellite, nontronite, hectorite and saponite, and further the
bentonite may be artificial phyllosilicates.
The present invention is now illustrated in greater detail with
reference to Examples, but it should be understood that the present
invention is not deemed to be limited thereto. All the percents
and parts are by weight unless otherwise indicated.
One kilogram of bentonite produced in Wyoming, U.S.A. was poured
into 50 kg of deionized water and allowed to stand overnight to
be swollen. Then the mixture was dispersed in a disper for 1 hour,
and the resulting bentonite suspension was centrifuged at 4,000
rpm for 10 minutes to recover 43.5 kg of the supernatant purified
bentonite sol (solids content: 1.03%). The purified bentonite sol
was dried in a hot air circulator at 100.degree. C. to obtain flaky
purified bentonite having a water content of 6%. The flaky purified
bentonite was ground in Bantam Mill (manufactured by Hosokawa K.K.)
to a size of 250 mesh and dried at 200.degree. C. for 2 hours to
obtain 425 g of water-free bentonite.
Fifty grams of the water-free bentonite were put in a 1000 ml-volume
ceramic pot mill, and 1 g of alkyltrialkoxysilane shown in Table
1 below each was added thereto. After sealing, the mill was rotated
for 30 minutes to prepare alkyltrialkoxysilane-modified bentonite
(Samples 1 to 8).
Each of Samples 1 to 8 and the non-treated purified bentonite as
prepared above was dispersed with water in a Hamilton Beach Mixer
(manufactured by Hamilton Beach Inc.,), and the rheological characteristics
of the aqueous dispersion solution were measured with a Fann Viscometer
(Model 35 SA" manufactured by Fann Instrument Corp.) at 23.degree.
C. Thixotropy was expressed in terms of a ratio of apparent viscosity
at 300 rpm (V.sub.300) to apparent viscosity at 600 rpm (V.sub.600)
(i.e., V.sub.300 /V.sub.600). The results obtained are shown in
TABLE 1 __________________________________________________________________________
Concen- Apparent Viscosity Plastic Yield Silane tration V.sub.300
V.sub.600 Viscosity Value Thixotropy Sample No. Treating Agent (part*)
(cps) (cps) (cps) (lb/1000 ft.sup.2) V.sub.300 /V.sub.600 __________________________________________________________________________
Purified bentonite 2 3.5 3.0 2.5 1.0 1.17 (non-treated) 3 6.5 5.5
4.5 2.0 1.18 5 33.0 23.8 14.5 18.5 1.39 Commercially available 1
3.0 2.5 2.0 1.0 1.20 purified bentonite ("Kunipia G" 2
6.0 5.3 4.5 1.5 1.13 produced by Kunimine Kogyo K.K.) 3 16.0 13.8
11.5 4.5 1.16 Sample 1 methyltri- 2 9.0 7.0 5.0 4.0 1.29 methoxysilane
3 33.5 22.5 11.5 22.0 1.49 5 74.0 55.3 36.5 37.5 1.34 Sample 2 methyltri-
2 8.5 6.8 5.0 3.5 1.25 ethoxysilane 3 17.0 12.8 8.5 8.5 1.33 5 70.0
55.0 40.0 30.0 1.27 Sample 3 propyltri- 2 8.5 6.3 4.0 4.5 1.35 methoxysilane
3 24.5 16.0 7.5 17.0 1.53 Sample 4 butyltri- 2 14.0 9.5 5.0 9.0
1.47 methoxysilane 3 42.0 24.0 6.0 36.0 1.75 Sample 5 hexyltri-
1 6.5 4.8 3.0 3.5 1.35 methoxysilane 2 38.5 22.0 5.5 33.0 1.75 3
105.0 57.8 10.5 94.5 1.82 Sample 6 octyltri- 1 5.0 3.8 2.5 2.5 1.32
ethoxysilane 2 31.5 19.0 6.5 25.0 1.66 3 83.5 46.8 10.0 73.5 1.78
Sample 7 dodecyltri- 1 7.0 5.0 3.0 4.0 1.40 ethoxysilane 2 40.0
23.3 6.5 33.5 1.72 3 123.0 67.5 12.0 111.0 1.82 Sample 8 octadecyltri-
1 6.5 5.0 3.5 3.0 1.30 ethoxysilane 2 29.5 18.0 6.5 23.0 1.64 3
82.5 44.5 6.5 76.0 1.85 __________________________________________________________________________
Note: *Part by weight per 100 parts by weight of water
As is apparent from the results of Table 1, the aqueous dispersion
solutions of Samples 1 to 8 are markedly superior to the non-treated
purified bentonite or the commercially available purified bentonite
in apparent viscosity, yield value, and thixotropy, and further
the alkyltrialkoxysilane-modified bentonite according to the present
invention exhibits an excellent function in rheological adjustment
of an aqueous liquid system.
In 20 kg of deionized water was poured 400 g of bentonite produced
in Wyoming, U.S.A. and allowed to stand overnight to be swollen.
The mixture was dispersed with a disper for 1 hour. The resulting
bentonite suspension was allowed to stand for 3 days to sediment
non-clay substances. The purified bentonite sol (16 kg; solids content:
1.39%) of the upper phase was obtained by decantation.
In a 5000 ml-volume stainless steel beaker was put 1,440 g of the
purified bentonite sol (corresponding to 20 g of water-free bentonite)
and heated to 60.degree. C. while stirring with a disper. Separately,
7.0 g of dimethyloctadecylbenzylammonium chloride was dissolved
in 70 ml of deionized water at 60.degree. C., and 2.0 parts of octadecyltriethoxysilane
or methyltrimethoxysilane per 100 parts of bentonite was further
dissolved therein by stirring. The solution was added to the bentonite
sol, and the mixture was stirred for 30 minutes, followed by filtration.
The filter cake was washed with water, dehydrated, dried to a water
content of 5%, and ground in Bantam Mill (manufactured by Hosokawa
K.K.) (Samples 201 and 202). The cation exchange capacity of the
purified bentonite was 72 milliequivalents per 100 g. The quaternary
ammonium cation was added in an amount of 83 milliequivalents per
100 g of bentonite (i.e., water-free bentonite).
Samples 201 and 202 were compared with various commercially available
organophilic modified bentonite products shown in Table 2 below
in terms of swellability in toluene and rheological characteristics
when dispersed in toluene. The swellability was measured by putting
100 ml of toluene in a measuring cylinder, adding 2.0 g of a test
sample, and measuring the total volume after 24 hours at 20.degree.
C. The viscosity was measured by dispersing 3.0 g of a test sample
in 150 g of toluene in a homogenizer at 10,000 rpm for 2 minutes
and immediately measuring the apparent viscosity at 6 rpm or 60
rpm (V.sub.6 or V.sub.60) at 20.degree. C. with a BL type viscometer.
The thixotropy was expressed in terms of a V.sub.6 /V.sub.60 ratio.
The results obtained are shown in Table 2.
TABLE 2 ______________________________________ Silane Apparent
Treating Swella- Viscosity Agent bility V.sub.6 V.sub.60 Thixotropy
Sample (part*.sup.1) (ml/2 g) (cps) (cps) (V.sub.6 /V.sub.60) ______________________________________
Sample 201 octadecyl- 47 580 96 6.40 triethoxy- silane (2.0) Sample
202 methyl- 48 850 168 5.06 trimethoxy- silane (2.0) BENTONE --
38 120 22 5.45 SD-1*.sup.2 BENTONE -- 45 188 21 8.95 SD-2*.sup.2
BENTONE -- 27 108 19 5.68 SD-3*.sup.2 BENTONE -- 20 70 17 4.12 27*.sup.2
BENTONE -- 40 150 36 4.17 34*.sup.2 BENTONE -- 31 150 33 4.55 38*.sup.2
BENTONE -- 32 200 36 5.56 500*.sup.2 NEW D -- 32 120 22 5.45 ORBEN*.sup.3
TIXOGEL -- 37 155 36 4.31 VZ*.sup.4 S BEN*.sup.5 -- 22 80 23 3.48
ORGANITE -- 29 95 28 3.39 T*.sup.5 ORGANITE*.sup.5 -- 32 205 52
3.94 ______________________________________ Note: *.sup.1 Part by
weight per 100 parts by weight of bentonite (i.e. waterfree bentonite).
*.sup.2 Trade name of the product of Rheox Inc., U.S.A. *.sup.3
Trade name of the product of Shiraishi Kogyo K.K. *.sup.4 Trade
name of the product of SudChemie AG, German. *.sup.5 Trade name
of the product of Nihon Yuki Nendo K.K. Note: *1: Part by weight
per 100 parts by weight of bentonite (i.e. water-free bentonite).
*2: Trade name of the product of Rheox Inc., U.S.A.
*3: Trade name of the product of Shiraishi Kogyo K.K.
*4: Trade name of the product of Sud-Chemie AG, German.
*5: Trade name of the product of Nihon Yuki Nendo K.K.
As is apparent from the results of Table 2, the alkyltrialkoxysilane-modified
bentonite according to the present invention has a higher swellability,
a higher apparent viscosity, and sufficient thixotropic properties
in toluene alone as compared with any of the commercially (conventionally)
available organophilic modified bentonite products and therefore
performs excellent functions in adjustment of rheology of a hydrocarbon
As described and demonstrated above, the present invention provides
modified bentonite which is obtained by treating bentonite with
an alkyltrialkoxysilane to make a part of the surface thereof hydrophobic
without causing water repellency and which, when dispersed in an
aqueous liquid, considerably increases the apparent viscosity of
the aqueous liquid to perform excellent rheology adjusting functions.
The present invention further provides organophilic modified bentonite
which is obtained by treating bentonite with a quaternary ammonium
cation and an alkyltrialkoxysilane and which exhibits excellent
dispersibility in a hydrocarbon solvent system, such as toluene,
to perform excellent functions in adjusting rheology of such a system.
The modified bentonite according to the present invention satisfies
the demand of rheological adjustment essential to various industrial
liquid products, either aqueous or organic, such as coatings, printing
inks, ceramic slurries, sealants, and cosmetics.
While the invention has been described in detail and with reference
to specific examples thereof, it will be apparent to one skilled
in the art that various changes and modifications can be made therein
without departing from the spirit and scope thereof.