Note: Descriptions are shown in the official language in which they were submitted.
:~2~ 3
The present invention relates to the ex-foliation of
vermiculite ore and more particularly to a method whereby the
volume increase upon exEoliatlon of the vermiculite ore can be
increased.
Vermiculite ore is well known for its capacity to
undergo expansion to several times its original volume when
subjected to elevated temperatures. The process of expanding
vermiculite ore by heating is reEerred to as thermal exfoliation.
This process is generall.y a continuous proceclure in which vermi-
culite ore particles are fed into an expansion kiln or oven,heated rapidly to temperatures in the range of 1100F to 1900F,
ana the resultant expanded vermiculite proauct removed from the
heating zone as additional unexpanded material is introduced.
The expanded vermiculite has a wide variety of well known uses,
including use as an aggregate in plaster and concrete
formulations, a thermal insulator, an extender in fertilizers
and soil mixes, an inert carrier for chemlcals, a packaging
material, and as roughage or filler in animal feeds.
In reference to thermal exfoliation of vermiculite,
it is common in the art to refer to the "yield" obtained by
exfoliation, this being the volume of expanded vermiculite,
when loosely accumulated without compression of the expanded
particules, obtained Erom an lnitial weight of unexpanded ore.
Since expanded vermiculi-te is generally sold on a volume basis,
it proves economically advantageous to the producer to maximize
the yield.
The present invention provides a method Eor increasing
the volume yield of expanded vermiculite obtained from exfo:Lia-
tion of unexpanded vermiculite ore particles comprising the
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sequential steps of applying a vegetable oil to said particles
at a temperature below that at which said ore particles undergo
exfoliation, and thermally exfoliating said ore particles in an
expansion oven or an expansion furnace.
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66925-295
The present invention is directed toward a method for
significantly increasing the yield of expanded vermiculite
obtained by exfoliation of vermiculite ore. The method o~ this
invention comprises the steps of applying a vegetable oil to
unexpanded vermiculite ore particles and thermally exfoliating
the ore to which the oil has been applied. It has been
discovered that volume yield increases of up to about 9% can
be attained with the present method. Vol~1me yield increases
in the range of about 4% to 7~ are normally attained, although
this range may vary as a function of the particular oil, water
content of the vermiculite, and the origin of the vermiculite
ore. As specified hereinafter, the yield increases are obtained
with the application of relatively small quantities of
vegetable oil, thus making -the present method economically
attractive.
In accordance with the present method, the vegetable
oil should be uniformly applied to the vermiculite ore so as
to provide an approximately equal amount of oil on each particle.
This can be conveniently and accurately controlled by spraying
the oil onto the ore particles and agitating or tu~bling the
particles as the oil is applied. Spraying a fine mist of the oil
onto the particles as they are tumbled in a rotating mixer such
as a cannister, drum or paddle blender is the preferred
method. Spray application also facilitakes modulation of the
quantity of oil applied, so as to provide the desired uniform
application using a minimal quantity of oil.
The oil is normally applied at ambient temperature,
although it may be applied at elevated temperatures, e.g., bv
pre-heating the oil or by applying the oil to the vermiculite in
a heated environment. Elevated temperatures may be advantageous,
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3 66925-295
for example, for purposes of lowering the viscosity of the oil
and thereby facilitating the
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spraying process or the distribution of the oil on the ore particles.
The elevated temperature should, however, be substantially below that
at which the vermiculite undergoes exfoliation, inasmuch as the oil or,
more specifically, the oil temperature is not used to expand or promote
expansion of the vermiculite.
The vegetable oil can be applied to the vermiculite in any amount
which affords a volume yield increase. In the general, the oil is
applied in a weight percentage amount of at least about 0.196, based on
the weight of vermiculite ore. Typically, the oil is applied in a weight
percentage range of about 0.196 to about 1%, based on the weight of
vermiculite ore. This relatively small quantity of oil helps minimize any
additional cost incurred by use of the present method and, t~us,
contributes significantly to the economic feasibility of employing the
present method.
Vegetable oils constitute a well known and widely used class of
materials. As used herein, the term "vegetable oil" includes all oils
derived from vegetable seeds, fruits, and other vegetable matter. The
vegetable oil can be refined or unrefined, unsaturated, or partially or
completely hydrogenated. Examples of vegetable oils which can be used
herein are soybean oil, castor oil, corn oil, sunflower oil, palm oil,
cottonseed oil, peanut oil, and olive oil. Vegetable oils contain
substantial levels of fatty acids and the present invention includes the
use of fatty acids, per se, derived from or extracted out of ve~3etable
oils. The term "vegetable oil", as used herein, thus also includes fatty
acids, per se, derived from vegetable oil, examples of which are oleic
acid, linoleic acid, lauric acid, ricinoleic acid, stearic acid, and palmitic
acid .
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The vermiculite ore to which the oil is applied
should be dry to the touch and free flowing. Most preferably,
the ore should be dried to remove essentially all of the ~mbound
or surface water which is initially present on the ore sample.
The ore should, however, retain its bound interlayer water,
generally constituting 5% to 10~ by weight of the ore, this
water being generally recognized in the art as necessary for
optimal thermal expansion of the ore.
The vegetable oil is believed to form a coating on at
least the exterior major surfaces of the vermiculite ore
particles. Although notwishing to be bound by any particular
theory, it is speculated that this coating, due primarily toits
hydrophobicity, inhibits the liberation of the interlayer water
from the particles during exfoliation and thereby provides a
greater degree of expansion of the individual particles and
an overall increase in volume yield.
The ore particles used in the present process can be
of any convenient dimension or size. As a general rule,
vermiculite ore particles are obtained, either by milling or as
naturally occuring materials, in particle sizes measuring from
a~out 0.005 in. up to a~out 0.4 in. across their maior surfaces.
These particles can be seg~egated according to size by screening,
with arbitrary maximum and minimum sizes being set to define a
given size range or grade of ore particles. After being
separated into the various size grades, the ore particles are
thermally exfoliated to yleld an expanded product of substant-
ially uniform particle size. In accordance with the practice in
the art, the present method is also normally conducted employing
ore particles which fall within a relatively narrow size range,
as opposed to a mixture of particles which vary widely in size.
As illustrated in the following Example, volume yield increases
were obtained in the
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exEoliation of all of the various commercial grades of
vermiculite ore which were expanded in accordance with the
present method.
The oil treatment step of the present method provides
an additional advantage in that it substantially reduces the
dust which is often generated in the -transport and handling of
vermiculite ore, i.e., the oil which is applied to the ore is
able to bind substantially the dust and fibrous particles
present in the ore and thus suppress the liberation of same
during the handling of the ore. It has been found that the
application of as little as 0.1% of oil can provide substantial
decreases in dust and fiber liberation and that the effecti~e-
ness of the oil in this respect increases with increasing
dosage. From the standpoint of health and safety, this dust
suppression aspect of the invention can be particularly advan-
tageous and beneficial.
The oil treated vermiculite ore particles of this
invention can be thermally exfoliated utilizing any of those
procedures heretofore known in the art. Any suitable
vermiculite expansion oven or furnace may be used. Thermal
exfoliation procedures generally involve the continuous
introduction of vermiculate ore particles into the upper end of
a high temperature oven or furnace, at which point the ore is
exposed to tempexatures in the range oE about llOO~ to 1900F
and undergoes rapid expansion. The expanded ore is allowed to
fall to a lower zone within the oven under the action of
gravity, at which point the particles may continue to expand
due, at least in part, to residual heat acquired in the upper
zone and retained in the particle. The particles are withdrawn
from the lower end of the furnace at a rate approximately equal
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to the introduction of new particles into the furnace.
Vermiculite exfoliation procedures and furnace apparatus for
use in exfoliation are disclosed in United States Patent Nos.
2,203,821; 3,010,911 and 3,533,610.
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The present invention is further illustrated ln the
following Example which is intended as illustrative only and
not in any limiting sense.
EXAMPLE
Five different size commercial grades of vermiculite
ore were each divided into fifty pound batches and each batch
was treated with a predetermined amount of partially hydrogenated
refined soyabean oil. Each oil application was conducted at
ambient temperature by spraying a fine mist of the oil onto the
ore particles as the particles were tumbled in a rotating drum
mixer. The oil was dispensed at a rate of about 300 cc./min.
over a period of 10 to 40 seconds, depending on the total amount
of oil to be applied. After the spray application was completed,
tumbling of the ore was continued for approximately 10 minutes.
The five different grades of vermiculite ore used in
this example, designated herein as Ore Grades A through E, were
all commercial grade ores obtained from a mine in Libby, Montana.
Previous analyses of samples of these commercial grades indicated
the following bulk density and particle size distribution ranges:
~re Grade A:
BUlk density; 45-60 lbs./ft3
Sieve_size Weight Percent Retained
(U.S. Series) Max. Min.
3/8 10 0
4 35 10
6 55 25
8 35 15
16 6 0
6 0
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ase 2776
Ore Grade B:
Bulk density: 55-65 Ibs. /ft.3
Sieve size Wei~ht Percent Retained
~ U . S. Series) Max.hlTn .
6 12 0
8 40 25
16 85 45
0
O re G race C:
- 10~ulk density: 55-65 Ibs./ft.3
Sieve size Weight Percent Retained
(U. ~. Series) Max. Min. ~~ ~
8 1 0
16 38 10
1 5 30 78 40
100 15
,100 9 0
O re G rade D:
2~Bulk density:55-65 Ibs./ft.3
Sieve Size ~Veight Percent Retained
(U. S. Series) l~x. Min.
27 5
L~0
1 00 30 S
~ 100 10 0
?.`'
a se 2 7 7 6 ~2~ 3
O re G rade E:
Bulk density 60 - 70 Ibs. /ft.3
Sieve size Weight Percent Retained
( U . S . Series ) Max .Min .
1 o
18 0
1 00 70 35
,1 00 70 24
Two hundred and fifty grams of each oil treated sample were
expanded in an electrically heated laboratory assay furnace at a
temperature of approximately 1800F. The furnace comprised a four
foot long column equipped with internal baff)es. The vermiculite ore
was introduced at the top of the column and allowed to fall under
gravity through the baffle system, this requiring approximately 10-15
1 5 second5.
The expanded ore was collected at the bottom of the column,
allowed to cool, and poured into a 5 liter graduated cylinder to
determine the final volume. This volume was extrapolated to a "bag
yield" corresponding to the number of 4 cubic foot bags which would be
obtained from one ton of the oil-heated ore sample. For compa~ison
purposes, a "Control" sample of 250 grams of each ore grade, which
was not treated with the oil, was expanded in an identical manner and
the resultant volume or extrapolated bag yield used as a basis for
determining yielcl increases clue to oil application. Table 1 provides the
results for all test and control samples. In Table 1, the "Oil Dosage"
is the amount of oil in ounces applied to each 50 pound ore sample.
se 2776
TABLE 1
Yield % Yield
Ore Grade Oil Dosage(oz. ) Bags/Ton) Increase
A Control 95.5
A 0.8 95.5 0
A 1.6 98.2 2.8
A 2.4 98.2 2.8
A 3.2 100.9 5.6
B Control 84.5
B 0.8 87.3 3.3
B 1.6 87.3 3.3
B 2.4 87.3 3.3
B 3.2 88.7 4.9
C Control 75.8
C 0.8 83.7 10.4
C 1.6 82.3 8.5
C 2.4 82.3 8.
C 3.2 82.3 8.5
D Control 60.5
D 0.8 63.3 4.6
Q 1.6 63.3 4.6
D 2.4 63.3 4.6
E Control 44.9
E 3.2 47.6 6
E 4.0 47.6 6
E 4.8 47.6 6
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se 2776
Each of the above oil-treated samples was observed to generate
substant;ally less dust during handling than did the control samples.
It should be appreciated that the results providèd in Table 1 are
illustrative and that the volume yield increases may vary depending on,
for example, the oil applied to the ore, ore content and origin, and
expansion temperatures and procedures. In addition, since certain
changes, modifications, and substitutions can be made in the
above-described method without departing from the scope of the
invention, it is intended that all matter contained in the above
description shall be interpretecl as illustrative and not limitative.
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