Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to dispersant systems for talc to be used,
for example, as a coating material in the paper industry. In ma~i:ng such
dispersions, the objective is to disperse in a reasonably short-time, say
1 to 2 hours, as much talc as possi~le in a stable pumpable dispersion.
The smaller the particle size of the talc, the more difficult is this
objective to achieve.
A known dispersant system which is capable of forming a dispersion
of 68.5%7 based on the total dispersion, of talc having the ma~orjty of
particles greater than 5.5~m ~suitable for paper filling~ has the follo~l-
ing composition:
_ . ............ ~ .. ~ .. . _ .
Percent
on dlspersion on talc
As Dispersant: Disodium salt of
copolymer of maleic
anhydride and
di-isobutylene .68 1-
AsThickener: Carboxymethylcellulose .68S
For pHControl:lM NaOH solution .78 1.13
_ _ _ _ ___
However, for paper coating a talc is required having a m~Jority of
particles less than 2.5ym. Known dispersants do not permit the dispersion
of more than about 60% by weight of such particles.
According to our invention, it is possible to obtain a satisfactory
dispersion of coating grade talc, if there are included in the dispersant
system the following constituents:-
(i) an organic polyelectrolyte dispersant
(ii) a nonionic or anionic wetting agent, said system providinga pH of 7 to 11 in the dispersion.
~;. ~,
- 2
The dispersant may, for example, be an alkali metal salt of a poly
carboxylic acid, e.g. a copolymer of maleic anhydride and di-isobutylene
or preferably a homo- or copolymer of acrylic acids. Other dispersants
include carboxymethyl cellulose and naphthalene sulphonate/formaldehyde
condensates.
The dispersant preferably has a weight average molecular weight
less than 100,000 and a number average molecular weight greater than 1,000
.9. 1,000 to lO,OOO.
The wetting agent may be any of the known anionic or nonionic surface
active agents, e.g. nonionic substances such as oxyethylated and/or oxy-
propylated fatty alcohols9 fatty acids, alkylphenols or fatty amines, or
anionic substances such as alkyl ether sulphates, olefin sulphonates,
alkyl benzene sulphonates, alkyl phenol ether sulphates alkyl sulphates
or amine ether sulphates. Particularly preferred are the di-alkyl sulpho-
succinates.
Preferably the wetting agent has one or two alkyl groups having from
6 to 14 carbon atoms e.g. 8 to 10 carbon atoms. A typical example is
di-octyl sulphosucc;nate, with either straight chain or branched chain
alkyl groups.
The composition may optionally contain inorganic dispersants such
as sodium or potassium polyphosphates~ silicates or hexametaphosphates.
It is desirable to avoid or reduce foam;ng, and according to pre-
ferred embodiments of our invention, this may be achieved in one o~ three
ways:-
1. By seléction of a wetting agent (e.g. a dialkyl sulpho-
succinate) which has relatively low foaming character.
2. By inclusion of an antifoam such as a fatty alcohol or
silicone antifoam.
~ 3 -
3. By use of mixing techniques which do not involve a substantial
liquid/gas interface.
According to one embodiment our invention provides a sta~le pumpable
dispersion in water of at least 60% by weight of the dispersion of talc
having a majority of particles less than Z.5~m said dispersion containing
from 0.1% to 2% based on the we;ght of talc of an organic polyelectrolyte
dispersant having a number average molecular weight greater than l,000 and
a weight average molecular weight less than lO0~000 and from 0.1% to 2:5%
based on the weight of talc of a nonionic or anionic wetting agent and
having a pH between 7 and ll.
Preferably the dispersion contains at least 65% by weight of the
talc, e.g. 65%to 75%. The preferred concentration of dispersant is 0.3
to 1% based on the weight of talc.
The preferred concentration of wetting agent is 0.5 to 2% based on
the weight of talc. The preferred pH is 8 to 10.5.
The dispersant system of ~he invention may be manufactured as an
aqueous concentrate containing 20 to 80% total of dispersant and wetting
agent. The purchaser of this concentrate may add a base to adjust the
final pH and then water to the required dilution~ before mixing with the
talc.
The invention is illustrated by the following examples:-
EXAMPLE 1
:
The ta1c to be dispersed, known as Lohjatalc PVlO had the followingspecification:-
99.9% less than 20 ~m.99% less than lO ~m.
85% less than 5 ~m.
60% less than 2 ~.
35% less than l ~m.
The dispersion had the following composition:-
Lt;~ 3
-- 4 --
Lohjatalc PV10: 55% (dry weight)Empicryl APD (sodium salt of di-isobutylene - maleic anhydride
copolymer, 25% so1ids); 0.49%(0.75% on talc)
Empilan KA10/80, a blend of C10-12 fatty alcohol 10 moles ethoxylate5
80%; water 20%; 0.81% (1.25% on talc).
Molar sodium hydroxide solution; 0.73% (1.13% on talc).
Water;balance to 100%.
The dispersion was prepared by dissolving all the water-soluble components
of the formulation in the balance of water required, and then adding the
talc to the solution with the aid of a high-speed mixer over a period of
45/50 minutes.
The viscosity of the dispersion was measured by a Brookfield Viscometerat ambient temperature immediately after processing, and after three
days storage. The slurry tended to thicken and sediment on standing,
but could be readily reconstituted by mild agitation.
Result Time Viscosity
O days 480 cps
3 days 160 cps
EXAMPLE 2
A dispersion was prepared by the method given in examplel. The composi-tion of the dispersion was as foliows:-
Lohjatalc PV10; 65% (dry weight)Dispex N40 (sodium polyacrylate, 40% solids); 0.325% (0.5X on talc)
Empimin OT (60% active di-octyl sulphosuccinate); 0.975% (1.5% on talc).
1 molar sodium hydroxide solution; 0.73% (1.13% on talc).
Water; balance to 100%.
The viscosity was measured as in example 1, with the follow;ng results:-
-- 5 --
Results TimeViscosity
0 days1,200 cps
3 days800 cps
EXAMPLE 3
A dispersion was prepared by the method given in example 1.The composit;on of the dispersion was as follows:-
Lohjatalc PV10; 65% (dry weight)Dispex N40% 0.2% (0.3% on talc)
Empimin KSN70 (sodium C12_18 alkyl 3 mole ether sulphate), 1.17%
(1.8% on talc).
1 molar sodium hydroxide solution; 0.73% (1.13% on talc)
Water, balance to 100%.
The viscosity was measured as in example 1 with the following results:-
Resu_ts TimeViscosity
- O.days2,300 cps
3 days800 cps
EXAMPLE 4
~. ,
A dispersion was prepared by the method given in example 1 except that
instead of Lohjatalc PV10 ~here was used a talc known as Finntalc C10,
having the following specification:-
99% less than 12 ym.75% less than 4 ~m
50% less than 2.3 ~m.
25% less than 1.2 ~m.
-- 6 --
Sodium tripolyphosphate was used as a deflocculating agent.
The dispersion had the following composition:-
Finntalc C10; 65% (dry weight)
Empicryl APD; 0.49% (0.75% on talc)
Emp;lan KA10/80 0.81% (l.Z5% on talc)
Sodium tripolyphosphate; 0.065% (0.1% on talc)
1 molar sodium hydroxide solution; 0.73% (1.13% on talc)
Water; balance to 100%
Results Time Viscosity
~ . . . _ .
0 days 960 cps
3 days 280 cps
EXAMPLE 5
A dispersion was prepared as in example 4 except that the Empicryl APDw~s replaced by an equal weight of Dispex N40.
Results Time Viscosity
O days 300 cps
3 days 5,500 cps
EXAMPLE 6
A dispersion was prepared by the method given in example 1.
The talc used in the dispersion was F;nntalc C10.
Sodium silicate, sold under the trade name
Pyramid Grade No.84 (Crosfields), was used as the optionalingredient.
The dispersion had the following composition:-
Finntalc C10; 65% (dry weight)
3 ~ 3
-- 7 --
Empicryl APD, Q.49% ~0.75% on talc)Empilan KAlO/80; 0.81% (1.25% on talc)
Sodium silicate; 0.33% (0.5% on talc)
l molar sodium hydroxide solution, 0.73% (l.l3% on talc)
Water, balance to 100%.
Results TimeYiscosity
0 days440 cps
3 days400 cps
EXAMPLE 7
= . = = = ~,
The following comparative experiments were performed using the dis-
pers;na system as set out in Page l of the application. That ;s for
a 65% solids talc dispersion:
Polyelectrolyte dispersing agent: 0.65% (l% sn talc)
Carboxymethyl eellulose; 0.65% (1% on talc)
~- molar sodium hydroxide sol'n; 0.73% (l.l3% on talc)
This dispersing system was used to attempt to prepare 65% talc dispersions
from both Finntalc ClO and Lohjatalc PVlO using Empicryl APD as the poly-
electrolyte dispersing agent.
In both experiments it was not possible to disperse all the talc.
EXAMPLE 8
.
The experiment of example 7 was repeated using Lohjatalc PVlO with
Dispex N40 as the polyelectrolyte dispersing agent. It was not possible
to disperse all the talc.
