Continuous process for producing a finely divided aqueous disperson of a homogeneous phase of at least one fusible solid ingredient

Continuous process for producing a finely divided aqueous dispersion of a homogeneous phase of at least one fusible solid ingredient and possibly of at least one liquid ingredient in which an aqueous solution of dispersion additive with a melted homogeneous phase is continuously subjected to a high velocity gradient in an agitation zone. The respective temperatures and flow rates of the aqueous solution and the homogeneous phase are regulated so that the homogeneous phase of the dispersion thusly produced reaches its solidification temperature after the dispersion has been evacuated from the agitation zone and before thermal equilibrium between the aqueous solution and the homogeneous phase is reached.

The present invention relates to a continuous process for producing a 
finely divided aqueous dispersion of a homogeneous phase consisting of at 
least one fusible solid ingredient, and to the aqueous dispersions 
prepared by said process. 
French Pat. No. 2,216,311 covers the preparation of vinyl chloride base 
polymer and copolymer pulverulent compositions for immediate use by a 
process according to which vinyl chloride base polymers and copolymers and 
the various additives necessary for their implementation such as 
stabilizers, plasticizers, lubricants, pigments, colorants, loads, polymer 
modifying agents are mixed in an aqueous medium, after which the 
compositions are separated from the aqueous medium and dried. In 
accordance with the described process, the liquid additives and at least a 
part of the fusible solid additives are introduced into the mixing zone, 
and maintained with agitation in the form of at least one finely divided 
aqueous dispersion of a homogeneous phase. This homogeneous phase is 
obtained by mixing the ingredients heated to a temperature higher than the 
solidification temperature of said mixture. The length of time during 
which such a dispersion can be stored at ambient temperature under 
agitation is very limited and generally does not exceed 5 hours because, 
most often, the dispersion coagulates when, during cooling, the dispersed 
homogeneous phase reaches its solidification temperature. Furthermore, its 
storage at a temperature higher than the solidification temperature of the 
homogeneous phase would require permanent vigorous agitation in order to 
avoid coalescence of the particles; it would also cause hydrolysis 
reactions detrimental to its properties. 
In accordance with the process of this invention, it is possible to obtain 
a finely divided aqueous dispersion, which remains stable during storage 
at ambiant temperature under agitation, of a homogeneous phase containing 
at least one solid fusible ingredient and possibly at least one liquid 
ingredient. The term, ambiant temperature, as used herein, is meant to 
refer to a temperature generally comprised between 5.degree. and 
30.degree. C., without it being necessary to consider this interval as 
limitative. The above-mentioned ingredients are especially selected from 
those usable for the preparation of vinyl chloride base polymer and 
copolymer pulverulent compositions, such as stabilizers, plasticizers, 
lubricants, pigments, colorants, loads. 
According to the process of this invention, an extemporaneous mixture 
obtained by contact of an aqueous solution of dispersion additive and a 
melted homogeneous phase is subjected continuously to a high velocity 
gradient, in an agitation zone. By "extemporaneous", it is meant that the 
mixture has been prepared in less than a second, and preferably, in less 
than 0.2 second, before its arrival in the agitation zone. 
According to the process of this invention, the respective temperatures and 
flow rates of the aqueous solution and the homogeneous phase are regulated 
so that the homogeneous phase of the dispersion thusly produced reaches 
its solidification temperature after the dispersion has been evacuated 
from the agitation zone and before thermal equilibrium between the aqueous 
solution and the homogeneous phase is reached. 
It has been noted that by operating so that the dispersed homogeneous phase 
passes from melted state to solid state outside the agitation zone and, 
while the aqueous phase of the dispersion is at a temperature lower than 
the solidification temperature of the homogeneous phase, no coagulation of 
the dispersion is observed during cooling and a dispersion which remains 
stable during storage at ambient temperature under agitation is obtained. 
In the opposite case, where the dispersed homogeneous phase passes from 
melted state to solid state in the agitation zone and/or when the aqueous 
phase of the dispersion is at a temperature equal to the solidification 
temperature of the homogeneous phase, coagulation of the dispersion is 
observed during cooling. The solidification temperature of the homogeneous 
phase is generally between 40.degree. and 80.degree. C. 
As fusible solid ingredients, we can cite lubricants such an ester waxes, 
natural waxes, polyethylene waxes, paraffin waxes, fatty acids, fatty 
alcohols, amines of fatty acids; vinyl chloride base polymer and copolymer 
stabilizers such as alphaphenylindol, calcium hydroxystearate, zinc 
stearate, calcium stearate. 
In addition to the fusible solid ingredient(s), the homogeneous phase may 
also contain pure liquid ingredients or solutions of solid ingredients in 
solvents. In this category, are vinyl chloride base polymer end copolymer 
stabilizers, such as organic salts of tin, short chain metallic soaps; 
lubricants such as esters of glycerol and oleic acid, esters of glycerol 
and ricinoleic acid; antioxidizers such as trinonylphenylphosphite; 
plasticizers such as dioctyl phthalate, epoxidized soya oil. The quantity 
of liquid ingredients used for the preparation of the homogeneous phase 
can vary from 0 to 70 parts by weight per 100 parts by weight of the 
homogeneous phase. 
Depending on the composition of the homogeneous phase to be treated and the 
fineness of the dispersion desired, the scientist has at his disposal the 
technology needed to satisfy the required conditions in order to implement 
the process in the invention by working within the following parameters. 
Respective temperatures and flow rates of the aqueous solution and 
homogeneous phase: The respective flow rates of the aqueous solution and 
homogeneous phase must be sufficiently high with respect to the volume of 
the agitation zone so that the dispersion is evacuated from the agitation 
zone before the homogeneous phase has reached its solidification 
temperature and before thermal equilibrium between the aqueous solution 
and the homogeneous phase is reached. For example, for an agitation zone 
with a volume of 100 cm.sup.3, the flow rates are generally between 1000 
and 10000 l/h (liters per hour) for the aqueous solution and 700 and 7000 
l/h for the homogeneous phase. The ponderal ratio of the flow rates of the 
aqueous solution and the homogeneous phase is determined by the ponderal 
concentration in dry material of the dispersion desired. The temperature 
of the homogeneous phase, during contact with the aqueous solution, must 
be sufficiently high, all thing being equal, so that the dispersion is 
evacuated from the agitation zone before the homogeneous phase reaches its 
solidification temperature. The temperature of the aqueous solution, 
during contact with the homogeneous phase, must obviously be lower than 
the solidification temperature of the homogeneous phase; all things being 
equal, the temperature of the aqueous solution must be sufficiently low so 
that the thermal equilibrium between the aqueous solution and the 
homogeneous phase is reached after the homogeneous phase has reached its 
solidification temperature. When the aqueous solution and the homogeneous 
phase are put in contact, the temperatures of the aqueous solution and the 
homogeneous phase are generally between 0.degree. and 50.degree. C. and 
80.degree. and 150.degree. C., respectively. 
Velocity gradient in the agitation zone: This depends on the fineness of 
the dispersion desired. To obtain a dispersion with particle diameters 
between 1 and 40 microns, the velocity gradient applied, calculated for a 
laminar flow, is generally between 10,000 and 100,000 seconds - l. 
Although the velocity gradient is calculated on the presumption of a 
laminar flow in the agitation zone, it must be noted that for the velocity 
gradients actually applied, the type of flow is highly turbulent. 
Nature and ratio of dispersion additive: A dispersion additive, which is 
chemically inert with respect to the ingredients to be dispersed, is used. 
As dispersion additives, use can be made of non-ionic emulsifying agents 
such as alkylphenolpolyoxyethylenes, protector colloids such as 
methylcelluloses, polyvinyl alcohol, copolymers of maleic anhydride and 
styrene partially neutralized by potash or soda. These are generally used 
in a ratio of 0.2 to 20% by weight with respect to the homogeneous phase 
to be dispersed. 
To implement the process according to the invention, it is better to use a 
homogenizer apparatus of the type consisting of a stator and a rotor. The 
stator, in the form of a casing, is equipped with a supply device (inlet) 
with two concentric pipes and with a single pipe evacuation device 
(outlet); the rotor has one or more moving bodies, the surfaces of which 
are located a short distance from the interior surface of the stator. An 
apparatus excellently suited to the desired objective is a cylindrical 
casing containing a cylindrical body capable of rotating at high speed and 
having a diameter slightly less than the interior diameter of the casing, 
for example by 1 mm or less. Through each of the supply pipes 
respectively, each one equipped with a valve permitting flow regulation, 
the aqueous solution of dispersion additive and the homogeneous phase are 
fed into the apparatus, its rotor rotating at high speed, for example 
between 2,000 and 10,000 r.p.m. In the narrow space provided between 
stator and rotor, the aqueous solution - homogeneous phase mixture 
obtained when the apparatus is fed, is immediately subjected to a high 
velocity gradient caused by rotation of the rotor, and this produces the 
desired dispersion and its evacuation from the apparatus through the 
outlet pipe furnished for this purpose in which only thermal equilibrium 
between the aqueous solution and the homogeneous phase is reached. 
With the process of the invention, it is possible to obtain aqueous 
dispersions, with average particle size generally between 1 and 40 
microns, stable for storage at ambiant temperature under agitation and 
having ponderal concentrations in dry material of 10 to 40% and up to 50%. 
Agitation during storage, while being moderate, should be sufficient to 
maintain the particles of the dispersion in suspension. It should not be 
so violent as to result in their reagglomeration. When there is no 
agitation, particle sedimentation is observed, but these can be easily put 
back in suspension by agitation.

Several examples carrying out the process according to the invention are 
hereinafter given for purposes of illustration and not by way of 
limitation. 
EXAMPLE 1 
This example is given for comparison purposes. 
In a 7500 liter useful capacity melting pot, by heating to 110.degree. C. 
and stirring the ingredients constituting the homogeneous phase, a 
homogeneous phase is produced which is composed of 3750 kg epoxidized soya 
oil, 1750 kg hydrogenated castor oil, 400 kg alphaphenylindol and 300 kg 
glycerol trimontanate. This homogeneous phase is poured into a 20 m.sup.3 
capacity vat containing 2250 kg of an aqueous solution having 0.27% by 
weight of cellulose methyl ether, the aforementioned solution having been 
preheated to 75.degree. C. and having undergone agitation in the vat by 
means of a 150 cm diameter helix rotating at 40 r.p.m. and a 20 cm 
diameter turbine rotating at 3000 r.p.m. 
After 2 hours of agitation, an aqueous dispersion is obtained, its ponderal 
concentration in dry material being 40%, its particles having an average 
diameter of 30 microns and its temperature being 85.degree. C. 
After the turbine is stopped, it is noted that this dispersion coagulates 
as soon as its temperature drops below 50.degree. C. 
EXAMPLE 2 
At 110.degree. C., under the same conditions as in example 1, a homogeneous 
phase with the same composition is prepared. Its solidification 
temperature is approximately 50.degree. C. 
At 10.degree. C., an aqueous solution having 0.27% by weight of cellulose 
methyl ether is prepared. 
In a 100 cm.sup.3 useful capacity homogenizer apparatus, of the type with 
rotor, stator, two concentric supply pipes and one evacuation pipe, the 
175 mm diameter rotor rotates at 3000 r.p.m., with the distance between 
rotor and stator being 0.5 mm, the aqueous solution, at a rate of 4700 
kg/h, and the homogeneous phase at a rate of 3150 kg/h, are separately 
introduced. An aqueous dispersion is obtained, its ponderal concentration 
in dry material being 40%, its particles having an average diameter of 22 
microns and its temperature being approximately 45.degree. C. when thermal 
equilibrium is reached between aqueous solution and homogeneous phase. 
This dispersion does not coagulate or separate during storage in a 20 
m.sup.3 capacity vat equipped with a 150 cm in diameter helix rotating at 
40 r.p.m. 
EXAMPLE 3 
This example is given for comparison purposes. 
In a 5000 liter useful capacity melting pot, by heating to 120.degree. C. 
and stirring the ingredients constituting the homogeneous phase, a 
homogeneous phase is produced which is composed of 2000 kg epoxidized soya 
oil, 1750 kg hydrogenated castor oil, 400 kg alphaphenylindol and 300 kg 
glycol diethylene dimontanate. This homogeneous phase is poured into a 15 
m.sup.3 capacity vat containing 6640 kg of an aqueous solution having 0.5% 
by weight of copolymer of maleic anhydride and styrene neutralized with 
potash, said solution having previously been heated to 80.degree. C. and 
having undergone agitation in the vat by means of a 120 cm diameter helix 
rotating at 40 r.p.m. and a 20 cm diameter turbine rotating at 3000 r.p.m. 
After 2 hours of agitation, an aqueous dispersion is obtained, its ponderal 
concentration in dry material being 40%, its particles having an average 
diameter of 10 microns and its temperature being 90.degree. C. 
After the turbine is stopped, it is noted that this dispersion coagulates 
as soon as its temperature drops below 58.degree. C. 
EXAMPLE 4 
At 120.degree. C., under the same conditions as in example 3, a homogeneous 
phase of the same composition is prepared. Its solidification temperature 
is approximately 58.degree. C. 
At 20.degree. C. an aqueous solution having 0.5% by weight of copolymer of 
maleic anhydride and styrene neutralized by potash is prepared. 
In the homogenizer apparatus described in example 2, the rotor of which is 
rotated at 3000 r.p.m., the aqueous solution, at a rate of 4700 kg/h, and 
the homogeneous phase, at a rate of 3150 kg/h, are separately introduced. 
An aqueous dispersion is obtained, its ponderal concentration in dry 
material being 40%, its particles having an average diameter of 8 microns 
and its temperature being approximately 54.degree. C. when thermal 
equilibrium between aqueous solution and homogeneous phase is reached. 
This dispersion does not develop or coagulate during storage in a 15 
m.sup.3 capacity vat equipped with a 120 cm in diameter helix rotating at 
40 r.p.m. 
EXAMPLE 5 
This example is given for comparison purposes. 
In a 4000 liter useful capacity melting pot, by heating to 115.degree. C. 
and stirring the ingredients constituting the homogeneous phase, a 
homogeneous phase is produced which is composed of 1000 kg epoxidized soya 
oil, 1750 kg hydrogenated castor oil, 400 kg alphaphenylindol and 300 kg 
glycol diethylene dimontanate. Said homogeneous phase is poured into a 15 
m.sup.3 capacity vat containing 5150 kg of an aqueous solution having 
0.17% by weight of partially hydrolyzed polyvinyl alcohol, the 
aforementioned solution having previously been heated to 80.degree. C. and 
having undergone agitation in a vat by means of a 120 cm diameter helix 
rotating at 40 r.p.m. and a 20 cm diameter turbine rotating at 3000 r.p.m. 
After 2 hours of agitation, an aqueous dispersion is obtained, its ponderal 
concentration in dry material being 40%, its particles having an average 
diameter of 25 microns and its temperature being 90.degree. C. 
After the turbine is stopped, it is noted that this dispersion coagulates 
as soon as its temperature drops below 64.degree. C. 
EXAMPLE 6 
At 115.degree. C., under the same conditions as in example 5, a homogeneous 
phase with the same composition is prepared. Its solidification 
temperature is approximately 64.degree. C. 
At 20.degree. C. an aqueous solution with 0.17% by weight of partially 
hydrolyzed polyvinyl alcohol is prepared. 
In the homogenizer apparatus described in example 2, the rotor of which 
rotates at 3000 r.p.m., the aqueous solution, at a rate of 4700 kg/h, and 
the homogeneous phase, at a rate of 3150 kg/h, are separately introduced. 
An aqueous dispersion is obtained, its ponderal concentration in dry 
material being 40%, it particles having an average diameter of 17 microns 
and its temperature being approximately 55.degree. C. when thermal 
equilibrium between aqueous solution and homogeneous phase is reached. 
This dispersion does not develop or coagulate during storage in a 15m.sup.3 
capacity vat equipped with a 120 cm diameter helix rotating at 40 r.p.m. 
EXAMPLE 7 
This example is given for comparison purposes. 
In a 130 liter useful capacity melting pot, by heating to 125.degree. C. 
and stirring the ingredients constituting the homogeneous phase, a 
homogeneous phase is produced which is composed of 70 kg hydrogenated 
castor oil, 15 kg glycol diethylene dimontanate, 20 kg alphaphenylindol, 9 
kg zinc stearate, 6 kg calcium stearate. This homogeneous phase is poured 
into a 500 liter capacity vat containing 300 kg of an aqueous solution 
having 0.27% by weight of cellulose methyl ether, the aforementioned 
solution having previously been heated to 80.degree. C. and having 
undergone agitation in the vat by means of a 30 cm diameter helix rotating 
at 100 r.p.m. and a 15 cm diameter turbine rotating at 3000 r.p.m. 
After 15 minutes of agitation, an aqueous dispersion is obtained, its 
ponderal concentration in dry material being 29%, its particles having an 
average diameter of 22 microns and its temperature being 90.degree. C. 
After the turbine is stopped, it is noted that this dispersion coagulates 
as soon as the temperature drops below 60.degree. C. 
EXAMPLE 8 
At 125.degree. C., under the new conditions as in example 7, a homogeneous 
phase with the same composition is prepared. Its solidification 
temperature is approximately 60.degree. C. 
At 35.degree. C., an aqueous solution having 0.27% by weight of cellulose 
methyl ether is prepared. 
In a 50 cm.sup.3 useful capacity homogenizer apparatus, of the type with 
rotor, stator, two concentric supply pipes and one evacuation pipe, the 
rotor of which, having a diameter of 160 mm, rotates at 3000 r.p.m., and 
the distance between stator and rotor is 0.5 mm, an aqueous solution, at a 
rate of 150 kg/mn, and the homogeneous phase, at a rate of 60 kg/mn, are 
separately introduced. An aqueous dispersion is obtained, its ponderal 
concentration in dry material being 29%, its particles having an average 
diameter of 15 microns and its temperature being approximately 55.degree. 
C. when thermal equilibrium between aqueous solution and homogeneous phase 
is reached. 
This dispersion does not develop or coagulate during storage in a 500 liter 
capacity vat equipped with a 30 cm diameter helix rotating at 100 r.p.m. 
It will be understood that changes may be made in the details of the 
compositions and conditions, without departing from the spirit of the 
invention, especially as defined in the following claims.