Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
This invention relates to 'A process for making
high polymeric dispersants suitable for effecting separation
of clays and other materials containing active hydroxyl groups
on the surfaces present in ores and minerals'. More
particularly, the present invention is directed to methods for
synthesising a number of polymeric dispersants, using raw~
materials such as phenol, acetaldehyde, formaldehyde,
paraformaldehyde, chloral hydrate, sodium sulphite, potassium
sulphite, sodium and potassium metabisulphite, and the like.
In the mineral processing industries beneficiation
of low-grade ores and minerals is an essential step to upgrade
the same for effective commercial utilization. The technique
adopted for beneficiation differs from material to material.
The conventional techniques are mainly:-
1. Ma~netic separation, 2. Flotation,
3. Heavy media separation, 4~ El~ctrostatic separ~tion "
S. Elutriation and 6. Hydrocyclone.
No single technique is suitable for all kinds of
minerals and ores. Concentration by a dispersion technique
is yet another method being followed in clay beneficiation.
The common agents utilized for effecting dispersion are
sodium carbonate, sodium pyrophosphate and modified
polyacrylamide type polymers. While these are effective in
dispersion in certain cases,in many others these are not
suitable. For instance, beneficiation of Indian iron ore 7
fines needs removal of not only the clay materials associated
as impurities but also alumina hydrate as well as alumina
present in lateritic minerals. Indian iron ore fines are
characterised by the presence of a higher percentage of
alumina than silica. For utiliæation of the fines through a
process of agglomeration it is of the utmost importance
that in the final agglomerates the alumina:silica ratio should
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preferably be 1 or less than 1. The polymeric dispersants
prepared following the invented process as described
hereinunder may be utilized more effectively for upgrading ores
and minerals where impurities like clay and other aluminous
materials create problems for their industrial utili~ation.
The present invention provides a process for the
preparation of high polymeric dispersants suitable for effect-
ing the separation of clays and other materials containing
active hydroxy groups on the surface of ores and minerals
which comprises the steps of (1) reacting a water-soluble
aliphatic aldehyde with an equimolecular proportion o an
alkali metal sulphite or metabisulfite, (2) then reacting
with an equimolecular proportion of phenol or sodium or
potassium phenate; and (3) reacting the product of step (2)
with an equimolecular proportion of a water-soluble
aliphatic aldehyde.
The present invention, more particularly, provides
a method of preparing a number of polymeric dispersants as
herein described which comprises reacting equimolecular
proportions of water-soluble aliphatic aldehydes, for example
~ormaldehyde or acetaldehyde or chloral hydrate, with sodium
or potassium sulphite; sodium or potassium metabisulphite and
the like in water solution at room temperature and
preferably between 30 and 50C and or a period of 1 2~ hours
depending on the level of concentration of the reactants in
solution; reacting further with equimolecular proportions
of phenol or sodium phenate in the case where sodium or
potassium metabisulphite is used, gradually added to the
first step reaction product at ambient to room temperature,
gradually raising the temperature to 95 + 2C. over a period
of 4-24 hours and allowing the reaction mixture to stand for
a further 2-4 hours at 95 + 2C; finally reacting with a
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further amount of formaldehyde,at ambient to room temperature,
gradually raised to 95 + 2C. and maintained at that
temperature for a period up to 47 hours or until such time
as the reaction resulting in the formation of the polymeric
dispersant is complete.
In accordance with the present invention there is
also provided a method as herein described wherein all the
three step reactions as described earlier can be carried out
in a single operation using the same reactants except for the
formaldeh~de solution and maintaining the same ingredient molar
proportions but mixing the ingredients in dry condition and ~
adding a molar proportion of water, and warming to initiate ?
the reaction.
In another embodiment the invention is directed to a
process of synthesising polymeric dispersants using the same
reactants and in molar proportions as described earlier,
excepting that in the inal step o the reaction the
formaLdehyde molar ratio was increased up to three mole~ per
mole of phenol, thus resulting in the formation of polymeric
dispersants with better compatibility towards electrolytes
concentration in efecting a stable dispersion.
The first step of the present process comprises
dissolution of sodium or potassium sulphite or metabisulphite
in water, preerably a saturated solution under conditions
of substantially atmospheric pressure and at room temperature ~
and adding gradually an equimolecular proportion of the ~''
aldehyde in water solution with constant agitation. ~he
duration of reaction is dependent on the concentration of ~'
the reactants in solution and may extend from instantaneous '
reaction to several hours. The reaction rate is also
dependent on the temperature employed. ~;
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In the second step of the process phenol or sodium
phenate in e~uimolecular proportion to sodium or potassium
sulphite or metabisulphite is gradually added to the product of the
first step reaction with constant agitation. The reaction between
phenol and the ~irst step reaction product leading to the formation
of monomer is dependent largely on the temperature employed
and may extend from about 4 h~s. at 95 + 2C. to more than
24 hours at ~0C.
In the third step reaction the monomer from the
second step is cooled to below 50C., and an equimolecular
proportion or more of formaldehyde solution is gradually
added, depending upon the el~ctrolyte compatibility level to
be achieved by the polymeric dispersant~ with constant
stirring. The rate of reaction leading to the formation of
polymeric dispersant is again dependent on the concentration
of the reactant in solution and to the temperature during
reaction. For a particular reactant concentration the rate
of reaction is a function of temperature. Using reactants
in the solid state, all the three steps of the reaction
leading to the formation of polymeric dispersant can be
merged into a single step and can be completed in 10 minutes.
The following examples will serve to illustrate
the method of this invention, without limitin~ it.
Example 1
To a solution of 66.3 gms. of sodium sulphite in
220 ml water, 25.7 ml of acetaldehyde was added with stirring
at room temperature. A~ter allowing the reaction to continue
for two hours 65.2 ml of phenol was added. Gradually the
temperature was raised to 95 + 2C. and stirred at that
temperature for 3-4 hrs. At the end the contents were cooled
to below 50C and 45.2 ml formaldehyde solution was added.
The temperature of the reaction mixture was raised to 95 + 2C.
and maintalned at that temperature for a period of 32 hrs. to
obtain the polymeric dispersant.
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Example 2
The product oE this example was made in essentially
the same manner as in Example 1 except tha~ the proportioned
amount of phenol was added simultaneously along with sodium
sulphite and ace-taldehyde at room temperature.
Example 3
The product of this example was made in essentially
the same manner as in Example 1 except that instead of
sodium sulphite an equimolecular amount of potassium sulphite
was used~
Example 4
. .
The product of the Example was made essentially in
the same manner as in Example 1 except that an equivalent
amount of potassium metabisulphite, formaldehyde solution and
sodium phenate were used at the appropriate stages instead of
sodium sulphite, formaldehyde and phenol and also the reaction
was carried out for 38 hours ater the second addition of
formaldehyde solution.
Example 5
.
The product of this example was made essentially
in the same manner as in Example 4 except that the final
reaction was prolonged to 100 hours after the second addition
of formaldehyde solution with successive addition of a half
molecular proportion of formaldehyde every 24 hours.
Example 6
: :
The product of this example was made essentially
in the same manner as in Example 1 except that an equimolecular
amount of sodium metabisulphite was used and the reaction
was prolonged to 47 hours at 9S + 2C. after the second
addition of formaldehyde solution.
Example 7
The products of this example were made essentially
in the same manner as in Example 1 except that sodium sulphite
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solutions of 33~, 50~ and 100~ concentrations were used and
were reacted with an equimolecular amount of formaldehyde
solution, and the reaction was prolonged to 26-30 hours ater
the second addition of formaldehyde solution.
Example 8
The products of this example was made essentially
in the same manner as in Example 1 except that all the
ingredients, namely sodium or potassiunl sulphite, para-
formaldehyde and phenol in equimolecular amount in the
dry state were added together, and equimolecular quantity
of water was then added, the mixture was warmed to initiate
the reaction which was completed in about 5-10 minutes.
Example 9
The product o this example was made essentially
in the same manner as in Example 1 except that sodium or
potassium metabisulphite was used and the reaction was
carried out exactly in the same manner as described under
Example 8 after the addition of the requisite amount of
sodium hydroxide to neutralise the acidity due to phenol.
Example 10
The produc-t of this example was made essentially
in the same manner as in Example 1 except that chloral hydrate
and sodium phenate were used in equivalent amount. The
addition of sodium sulphite solution was made slowly to
chloral hydrate solution with stirring and the reaction was
prolonged after the addition of chloral hydrate to 24 hours.
After standing for a while the top layer was separated and
used for the final reaction. The bottom layer was discarded.
Final reaction was carried out for 9 hours with an
equimolecular amount of formaldehyde solution and sodium
hydroxide in an amount sufficient to raise the pH to 8 9.
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