Note: Descriptions are shown in the official language in which they were submitted.
CA 0220~88~ 1997-0~-23
9238-EWG
ag\fo\f: \428\9238\~pec\9238 . ewg
RT.~Nn.~ OF CARBOXYLIC ACIDS AND ORGANIC
AMINES IN ORE FLOTATION
The present invention relates to compositions
of matter which are blends of amines, particularly alkyl
amines, alkyl diamines, alkyl polyamines, ether amines,
and ether polyamines, with acids selected from a certain
carefully defined class of medium-chain linear or
branched carboxylic acids, including any reaction
products of such amines and acids that may be present.
The present invention also relates to
compositions of matter comprising the aforementioned
blends of acids and amines which are useful as surface
active agents. The present invention further relates to
processes using these novel compositions of matter in
applications taking advantage of their superior surface
active properties in water, particularly in their use in
mineral flotation such as the beneficiation of iron
ores. The present invention also relates to the
improved physical handling characteristics of these
novel compositions especially as compared to
corresponding blends with shorter chain carboxylic
acids, particularly acetic acid.
Amine compounds such as alkyl amines,
alkyldiamines, ether amines, ether diamines, and
polyamines, exhibit surface active properties
particularly in aqueous media which make such compounds
useful in a host of applications.
One such application is the beneficiation of
ores by froth flotation, particularly the removal of
CA 0220~88~ 1997-0~-23
silica from iron ores or phosphate ores, the recovery of
potash from sylvite, and the purification of calcite.
In the froth flotation of silica from e.g.
iron ore hydrophobic amine compounds are added to a pulp
of finely ground ore causing the silica particles to
become hydrophobic by selectively adsorbing on them.
The hydrophobic silica particles are then removed from
the slurry by attachment to air bubbles rising through
the pulp. The relatively more hydrophilic iron ore
particles are unaffected by the air bubbles and remain
in the pulp.
The hydrophobic nature of the amine is
critical to the froth flotation process, but it causes
problems in obtaining a uniform mixture of amine in the
ore pulp due to its immiscibility in water. The small
amount of amine used (0.02 - 2 pounds per ton of ore
treated) requires a uniform dilute dispersion of amine
in the pulp in order to obtain optimum coverage of the
silica particles. Two methods are generally used to
effectively deliver the amine to the silica surface.
One method used is to disperse the amine in
water and then meter the dispersion into the froth
flotation slurry. The use of a dilute amine dispersion
improves amine consumption and eases the metering
problems associated with the small amount of amine used.
It is convenient to store the dispersion for 8 to 12
hours while metering it into the flotation cell. A
storage stable dispersion is one that remains dispersed
for 12 hours without agitation. The hydrophobic amine
products used in silica flotation will not form storage
CA 0220~88~ 1997-0~-23
-
stable dispersions in water unless a dispersant is used.
The choice of dispersing aids is limited due to the need
to disperse the amine without forming an emulsion or
interfering with the attachment of amine to the silica
surface. The dispersing aid generally used heretofore
has been acetic acid either directly in the dispersion
water, or as amine products partially neutralized or
blended with acetic acid. The need to handle a
corrosive acid in the flotation plant environment is a
drawback to this method. Directly adding the acid to
the amine to form an amine salt as a dispersing aid at
the point of manufacture solves the problem of acid
handling. However, for lower molecular weight amines,
such as C8 - C10 ether primary amines, the by-products of
the amine and acetic acid reaction can be very
odoriferous and unpleasant to work with.
Also, acetic acid-neutralized ether primary
amines can form very stable foams if air is mixed in
(even inadvertently) such as can occur during packaging,
transporting and/or unloading. Further, the acetic
acid-neutralized amines and diamines are higher melting
and more viscous which makes handling more difficult
and, in some cases, leads to the formation of amides at
the temperatures necessary to maintain liquidity. In
some cases, amine-acetate dispersions become nonuniform
with an oily layer or creamy layer at the top in 24-48
hours, even in as little as 8 hours, and thus cannot be
viewed as being long term stable.
The second method meters the amine directly
into the flotation slurry relying on the shear generated
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by the agitated slurry to disperse the amine. While
this method solves the potential odor problem, it
requires accurate metering pumps to deliver the proper
amount of amine and relies on perfect mixing in the
flotation cell in order to obtain satisfactory amine
usage levels and selectivity.
Amines lose their surfactant nature and their
utility as flotation reagents at pH above about 10.5 and
act as oils. Flotation of siliceous material from iron
ore carried out at these high pH levels is marked by
higher consumption and lower yield due to the lack of
surface active amine in the system. Flotation of fine
grained hematite ores is generally carried out at pH
10.5 - 11 and would benefit by having a more surface
active amine reagent.
Accordingly, there is still a need for
compositions of matter and particularly aqueous systems
containing amines of the aforementioned types whose
efficacy, as may be influenced by their dispersability,
is enhanced by suitable acidic agents without the
generation of undesirable odors, or by-products, and
without suffering loss of desired properties of the
amine components. Also, there is a need for amine based
flotation reagents that do not lose effectiveness when
used at pH 10 or above.
The present invention satisfies these objects
and avoids the drawbacks of prior approaches, and also
provides the additional advantages enumerated herein.
The present invention relates to compositions
of matter comprising a blend of (a) an amine component
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which is one or more compounds selected from the group
consisting of alkyl amines, alkyl diamines, alkyl
polyamines, ether amines, ether polyamines, and mixtures
thereof; and (b) an acid component selected from the
group consisting of linear, branched and cyclic,
alkenoic, alkanoic and aromatic carboxylic acids
containing 3 to 24 and preferably 6 to 13 carbon atoms;
wherein the amount of the acid component corresponds to
about 1 to 100 mole percent, and preferably about 3 to
about 70 mole percent, of the number of nitrogen atoms
of the amine component.
In addition to the above-noted blends, the
present invention is also directed to products which are
dispersions in water of any of such blends. Such
dispersions, especially when the acid component
comprises linear acids, form readily and remain stable,
and exhibit the other advantages described herein.
Thus, the present invention is further
directed to a method of forming an aqueous homogeneous
storage-stable dispersion of one or more of said amines
(a) as defined hereinabove, the method comprising
dispersing said one or more amines with one or more of
said acids (b) as defined hereinabove and adding the
resulting dispersed blend to water while mixing with
mild agitation.
Still even further, the present invention is
directed to a method of removing impurities from ore,
such as iron ore, potash ore, phosphate ore, or calcite,
comprising subjecting a slurry of said ore in water to
froth flotation, wherein the water contains dispersed
CA 0220~88~ 1997-0~-23
therein a composition of matter as set forth herein, in
an amount of said composition in said slurry effective
to promote flotation of said impurities.
Amines with which this invention is useful
include alkyl amines, alkyl diamines, alkyl polyamines,
ether amines, and ether polyamines. Said amines can be
primary, secondary or tertiary amines.
Alkyl amines with which the present invention
is useful include those of the formula RnNH3n wherein R
is linear or branched alkyl or alkenyl (i.e. containing
a carbon-carbon double bond) of 4 to 24 carbon atoms,
and n is 1, 2 or 3.
Ether amines with which this invention is
useful include those having the formula R1-O-R2NH2,
wherein R1 is branched or linear alkyl or alkenyl
containing 4 to 36 carbon atoms and R2 is alkyl
containing 2 to 5 carbon atoms. Preferably, R1 is alkyl
containing 6 to 15 carbon atoms, and more preferably 8
to 13 carbon atoms and yet more preferably 8 to 10
carbon atoms. R2 is preferably alkyl containing 3 carbon
atoms, as would result from Michael addition reactions
using acrylonitrile.
Ether diamines or ether polyamines with which
the present invention is useful include those having the
formula R3-o-(R4NH)l6-RsNH2 wherein R3 is linear or
branched alkyl or alkenyl containing 4 to 36 carbon
atoms, each R4 is independently alkyl containing 2 to 5
carbon atoms, and each Rs is alkyl containing 2 to 5
carbon atoms. Preferably, R3 is alkyl containing 6 to 15
carbon atoms, and yet more preferably 8 to 12 carbon
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atoms. R4 is preferably alkyl containing 2 to 3 carbon
atoms, and R5 is preferably alkyl containing 2 to 3
carbon atoms.
Alkyl polyamines useful in the present
invention include those having the formula X-(Alk-
N(Rl~))p-Y wherein X is -NH2 or -H, p is 2 to 10, each Alk
group is independently alkylene containing 1 to 6 carbon
atoms, each R10 is independently -H or alkyl containing 1
to 22 carbon atoms, and Y is -H, alkyl containing 1 to
22 carbon atoms, or alkenyl containing 2 to 22 carbon
atoms. In preferred polyamines of this formula, p is 3
to 5, each Alk is ethylene or 1- or 2-propylene, each Rl~
is -H, methyl or ethyl, and Y is -H or alkyl containing
1 to 6 carbon atoms.
Preferred alkyl diamines useful in the present
invention include those having the formula
(R6)(R7)N(CH2)23N(R5)(R9) wherein each of R6, R7, R5 and R9
is alkyl containing 1 to 30 carbon atoms, and preferably
alkyl containing 4 to 20 carbon atoms. Also, the groups
R6-9 can be linear, branched, cyclic, or aromatic
(especially phenyl). Moreover, any of R7, R3 and/or R9
can be hydrogen.
The amines, diamines, and polyamines of any of
the foregoing formulas can readily be formulated in
accordance with known synthetic techniques. Indeed,
many of the amines of the foregoing structures are
commercially available.
In all of the foregoing formulas, any or all
alkyl groups can be linear or branched, and saturated or
unsaturated.
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--8--
Acids useful in the present invention include
linear, branched and cyclic alkanoic and alkenoic
carboxylic acids containing 3 to 24 carbon atoms and
preferably 6 to 13 carbon atoms. Useful acids also
include aromatic carboxylic acids containing 7 to 12
carbon atoms, such as benzoic acid. This acid component
can comprise one acid but preferably comprises a mixture
of two or more such acids. Acids corresponding to this
description, as well as mixtures thereof, are readily
synthesized and many are also commercially available.
Preferred examples include the mixtures of branched-
chain carboxylic acids marketed by the Exxon Corporation
under the trade names "NEO 908 " and "NEO 913 ", or the
straight-chain carboxylic acid blend marketed by Witco
Corp. under the name "Industrene 365".
The relative amounts of the amine component
and the acid component can range widely, and accordingly
can be tailored to optimization of the particular
properties and intended applications of the resulting
composition of matter. In general, the amount of acid
corresponds to at least about 2 percent based on the
total number of nitrogen atoms present in the amine
component. More preferably, the amount of acid can
correspond to at least about 10%, up to about 50~ or
even higher, e.g., up to 80~ to 100~ on that basis.
Thus, it should be understood that the term
"neutralization" as used herein is not limited to
situations of complete neutralization of all amine sites
with acid, but extends also to blends wherein the amount
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of acid is only sufficient to partially neutralize the
amine. Even partial neutralization provides improved
performance as described herein.
When neutralization is carried out to improve
the dispersibility in water of the amine, the extent of
neutralization required depends strongly on the
molecular weight of the amine. Short chain amines
require very little neutralization to achieve proper
dispersion whereas longer chain amines require higher
neutralization to disperse as desired in cold water. In
some cases neutralization with middle chain-length acids
does not yield stable dispersions, but nonetheless,
surprisingly, improves ore flotation.
The products useful in this invention are
termed "blends", which can be formed by simply combining
the acid or acids, and the amine or amines, in the
amounts indicated, in any suitable manner that forms a
uniform mixture thereof. The term "blend" used herein
denotes the resulting mixture and encompasses not only
compositions composed entirely of discrete acids and
amines, but also compositions containing one or more
reaction products of acid and amine, typically acid
salts.
The composition of matter is preferably
provided as 100~ active but may be dissolved or
dispersed or emulsified in appropriate organic solvents
water, or aqueous solution.
It has been determined that the compositions
prepared in accordance with the present invention
exhibit enhanced surface active performance in selected
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--10--
applications, coupled with ease of handling as a neat
liquid and freedom from by-products. Especially
advantageous is the freedom of these compositions from
any by-products causing an unpleasant odor. Heating
blends of an amine and short chain carboxylic acid can
cause the formation of by-products that have a very
unpleasant odor. The formation of by-products decreases
the activity of the amine and acid in the blend and thus
leads to a shorter storage life.
Also, the compositions retain desired
liquidity at temperatures lower than has been the case
with prior products that needed to be heated to remain
liquid.
The present invention is illustrated in the
following examples.
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EXAMPLE 1
Three amines, coco fatty primary amine
(commercially available as Adogen 160D, Witco Chemical),
n-dodecyl ether primary amine, and isododecyl ether
amine, were 100~ neutralized with three acids (acetic
acid, C8-C10 linear carboxylic acid and branched Cg-Cl3
carboxylic acid). The samples were placed in an 80~C
oven for two weeks. Total amine value (or TAV --a
measure of the active amine in the sample) was taken on
each sample before and during oven storage to determine
the stability.
The results are listed in Table 1. They show
that the present invention exhibits greatly reduced loss
of the amine to by-products, even over time, which means
that the present invention makes a higher proportion of
the amine available for its desired function.
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Table 1
TAV of amine acid blends stored at 80~c
amine/acid Start 1 day 7 day 14 day ~ drop
coco/acetic 218 205 138 102 53
isododecyl/ 171 162 103 65 62
acetic
n-dodecyl acetic 181 163 99 67 63
COCO/CB-1O 159 148 111 80 50
isododecyl/ 135 123 84 54 60
8 -10
n-dodecyl/ 138 130 79 54 61
B-10
COCO/C9-l3 158 162 161 154 3
isododecyl/ C9l3 138 140 142 133 4
n-dodecyl/ 143 142 143 140 2
C9 _ 13
EXAMPLE 2
The viscosity vs. temperature properties of the samples
tested in Example 1 were determined. Each sample
viscosity was measured in the Brookfield viscometer
small sample cell that was temperature controlled by a
programmable hot bath. The temperature was raised to
45~C and slowly lowered to 10~C. Viscosity measurements
were made at 2 minute intervals. The linear amines and
salts were marked by a sharp solidification point
(arbitrarily set at cP of 200,000) while the branched
amines and salts generally remained below the pour point
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-13-
(arbitrarily set at cP 10,000). The viscosity data is
summarized below:
Amine Salt Solid Pour
Cocoamine 10~C 15~C
("Adogen 160")
Acetate 30 45
C913 <10 25
C810 20 25
Isododecyl ether ~10 clO
amine
Acetate ~10 clO
C913 <10 20
C8_l0 clO <10
n-dodecyl ether <10 <10
amine
Acetate 45 55
C913 <10 15
C810 10 15
Typically acetic acid is used as the
dispersant for amine in water dispersions. Many of the
longer chain carboxylic acids can also act as
dispersants for amine in water systems. This aspect of
the invention is illustrated in the following example.
EXAMPLE 3
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An ether amine corresponding to the general
formula (C8-ClO alkyl)-O-CH2-CH2-CH2-NH2 (commercially
available from Witco Corporation as "Arosurf MG 98") was
neutralized 50~ with various chain length carboxylic
acids. The neutralized MG 98 was used to make
dispersions of 6~ amine in room temperature tap water.
The dispersions were allowed to sit undisturbed to
determine the stability of the dispersion formed. A
dispersion was considered stable if there was no
evidence of separation in 2 hours. The results are
indicated as stable or unstable dispersions:
Acid Dispersion
Acetic Stable
Propionic Stable
Butyric Unstable
Hexanoic Stable
2-Ethyl hexanoic Unstable
2-Methyl valeric Stable
C8-C10 Acid Stable
Tall oil Unstable
Neo 913 Unstable
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-15--
In particular, compositions in accordance with
the present invention have been found to be unexpectedly
highly beneficial in the froth flotation of impurities,
particularly siliceous impurities, from ore such as iron
ore, potash ore, phosphate ore, and calcite. Such
impurities generally comprise silica, inorganic
silicates, and mixed silicates such as aluminosilicates.
This advantageous application will now be described in
further detail.
Most of the particulars of the froth flotation
are carried out in accordance with conventional, well-
known apparatus and conditions familiar to those of
ordinary skill in this art. Finely divided ore is
slurried in water (at a solids content on the order of
25 wt.% to 50 wt.%) in a flotation cell equipped to
inject air (or gas) into the slurry at a rate sufficient
to form a froth of bubbles at the top of the cell. The
froth is removed by skimmers, paddles or other
conventional techniques. Additives can be added, and
usually are added, to the slurry to improve the
separation provided by the flotation cell. Such
additives can include frothers, which promote the
formation of the froth, activators, promoters, and
collectors, which improve the separation by increasing
the affinity of the floated material for the froth, or,
optionally, depressants for decreasing the affinity for
the froth of the material which is desired to remain
unfloated in the flotation cell, and pH regulators for
adjusting the pH of the ore slurry to the desired level
to obtain optimum utility from the additives mentioned.
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--16-
In iron ore processing, because of the relative weights
involved and because of the details of the surface
chemistry, it is desired to float the impurities in the
froth, leaving the ore thus beneficiated in the pulp in
the slurry.
Addition of a composition of matter comprising
an amine component and an acid component, in accordance
with the description herein, when added to a slurry of
hematite ore at pH 10.5 containing siliceous impurities,
is effective in promoting flotation of the siliceous
impurity from the iron ore. Typical amounts of this
promoter to add range from about 0.001 wt.~ to about
0 . 06 wt.~, and preferably 0.0025 wt.~ to about 0.025
wt.~ of the ore. This advantageous result is described
further in the following specific examples.
CA 0220~88~ l997-0~-23
--17-
EXAMPLE 4
An ether amine corresponding to the general
formula (C8-C10 alkyl)-O-CH2CH2CH2NH2 ~commercially
available from Witco Corporation as "Arosurf MG 98") was
neutralized 40~ with a commercially available carboxylic
acid product comprised predominantly of branched
carboxylic acids with 9 to 13 carbon atoms, commercially
available from Exxon Corp. as "NEO 913". This amine-
acid blend was compared, for effectiveness in removing
siliceous impurities from magnetite iron ore
concentrate, to unneutralized "Arosurf MG-98". One
test series was carried out with the iron ore slurry at
pH 8.5 and another with the slurry at pH 11Ø In both
cases the slurry was 35 wt.% iron ore, and equal amounts
of amine sample were used.
The following table sets forth the iron
recovery in the froth flotation step, as a function of
the iron grade of the magnetite concentrate produced,
for the flotation runs made with unneutralized "Arosurf
MG-98" and with "Arosurf MG-98" blended 40% with "NEO
913". The results for pH 8.5 and pH 11.0 are shown in
Table 2.
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-18-
TABLE 2
Comparison of Magnetite Iron Ore Flotation with AROSURF
MG-98, and AROSURF MG-98 Neutralized 40~ with NEO 913
At pH=8.5
With MG-98
Iron Grade (~) Iron Recovery (~)
68.5 59.8
68.4 68.9
68.1 79.3
67.6 86.0
With MG-98/40~ Neutralized
Iron Grade (%) Iron Recovery (%)
68.3 71.2
68.2 75.1
68.0 82.7
67.5 90.0
At pH=11.0
With MG-98
Iron Grade(~) Iron Recovery (~)
67.7 80.5
67.67 82.0
67.43 86.5
67.01 91.0
CA 0220~88~ 1997-0~-23
-19--
With MG-98/40~ Neutralized
Iron Grade (~) Iron Recovery (~)
67.7 81.0
67.52 84.8
67.2 88.7
66.74 92.9
The results of flotation at pH 8.5 are
expected due to the fact that the 40~ neutralized
material is only 77% by weight amine and should be less
effective than 100~ active amine. The especially
surprising result is the quality of the neutralized
reagent when flotation was done at pH ll.o. At this pH
the amine in the neutralized product is being utilized
more efficiently than the unneutralized amine to obtain
the equivalent results noted.
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-20--
EXAMPLE 5
"Arosurf MG-98" and a sample of "Arosurf MG-
98" that was 30~ neutralized with a mixture of linear C~-
C10 carboxylic acids were compared for flotation
effectiveness on a nonmagnetic ore. The slurry that was
tested comprised about 35 wt.~ hematite iron ore and had
a pH of 10.5. A comparison was made of the effect of
the ether amine compared to an equal amount of ether
amine that had been neutralized with the carboxylic acid
mixture. The amount of amine employed was about 0. 02
wt.~ of the amount of iron ore in the slurry. The
following Table 3 sets forth the iron recovery in the
froth flotation step, as a function of the iron grade of
the hematite material left in the flotation bowl, for
the flotation runs made with the unneutralized ether
amine and with the same ether amine neutralized with the
carboxylic acid mixture.
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-21-
TABLE 3
Hematite Iron Ore, Tilden, Michigan
Unneutralized MG-98 Ether amine
Iron Grade(~) Iron Recovery(~)
61.3 53.3
61.2 64.8
60.9 69.2
59.3 75.5
MG-98 Neutralized 30~ with
C8 Clo Acids
Iron Grade(~) Iron Recovery(~)
61.5 58.8
61.4 69.2
61.1 73.3
60.0 77.7
These results, demonstrate that for any given
grade of iron ore the recovery of the iron ore is
superior when the froth flotation is carried out with
partially neutralized ether amine as described
hereinabove in this application.
