Process and apparatus for the continuous production of vinyl chloride polymers in aqueous emulsion

A continuous process and an apparatus for the polymerization of vinyl chloride in aqueous emulsion wherein the liquid reaction mixture is fed into the lower part of a vertical, cylindrical vessel, the liquid level in the vessel is adjusted to at most 97% of the total interior height of the vessel, the reaction mixture is stirred with a stirrer which is totally immersed in the liquid and extends over 15 to 60% of the total interior height of the vessel and the produced polymer emulsion is laterally discharged from the upper part of the vessel.

The invention relates to a process and apparatus for the continuous 
production of vinyl chloride homo-, co- and graft polymers in aqueous 
dispersion in the presence of radical-forming catalysts, surface-active 
substances and optionally other polymerisation auxiliaries in upright, 
preferably cylindrical vessels, wherein the reaction mixture is introduced 
from below, removed from above at the side and stirred with a stirrer 
which is completely immersed in the liquid and extends over 15 to 60% of 
the total internal height of the vessel. 
It is known to produce vinyl chloride polymers in aqueous emulsion in 
upright cylindrical vessels, wherein there is constantly added to the 
reaction mixture, in the upper part of the vessel, vinyl chloride, 
possibly comonomers, an aqueous solution of the emulsifier and optionally 
other polymerisation auxiliaries, as well as a solution of the 
radical-forming catalyst, and a volume of the polymer-containing emulsion 
equivalent to the quantity of substances added is drawn off at the base of 
the vessel and conducted away for further processing. The emulsion to be 
polymerised is in general moved by a stirrer which dips into the upper 
region of the emulsion and chiefly effects the emulsification of the 
monomer or monomers introduced. The resulting reaction heat is usually 
removed by a double jacket, charged with a coolant, of the vessel or 
sometimes also by special members fitted into the vessel (cooling fingers) 
or onto the vessel (return flow coolers). 
It is furthermore known to emulsify monomers and aqueous emulsifier first, 
and to charge the reaction vessel with this emulsion and add the initiator 
either simultaneously or later. 
Although the afore-described process has been employed for a long time on a 
large industrial scale it has certain deficiencies. For example, after 
operating for some time, crusts form in particular in the upper part of 
the reaction vessel in the region of the surface of the liquid, and these 
make continuation of polymerisation difficult and, if they crumble away 
partially the polymer emulsion drawn off becomes contaminated. If the 
crust growth is too great the apparatus must be shut down and cleaned, and 
this involves considerable expenditure on labour, loss of production and 
undesirable emission of vinyl chloride when the container is opened. In 
addition, in the course of the polymerisation process coarse polymer 
particles are constantly formed, that is particles of a diameter of more 
than 0.1 mm (referred to hereinafter as "grit"), which in some cases can 
grow to diameters of up to several centimeters. This grit is drawn off 
with the polymer emulsion and leads to difficulties in further processing. 
Although it is possible to keep back some of this grit by means of filter 
sieves, these filters are quickly blocked if there is relatively extensive 
grit formation. Changing and cleaning the filters entails undesirable 
expenditure. In addition, finer grit is often not held back completely, 
contaminates the end product, and on further processing of the polymer 
into moulded articles results in the formation of spots or fish eyes. 
The hitherto customary blade stirrers, especially in vessels having a large 
ratio of height to diameter, for example 3 or more, operate substantially 
in the upper part of the container, whereas the liquid is mixed only 
slightly in the zones beneath. 
A process is furthermore known for the continuous production of aqueous 
polymer dispersions by polymerisation of the monomers, pre-emulsified in 
water, with initiators and emulsifiers as they pass through a tube 
reactor, in which by damming in the reactor the polymer emulsion flowing 
off, a pressure is produced which is sufficient to prevent dissociation as 
a result of evaporation of the monomers at the polymerisation temperature 
applied, wherein, further, the reactor content is mixed perpendicular to 
the direction of flow by a stirring device, of which the faces inside the 
polymerisation zone are parallel to the direction of flow and are cleaned 
periodically or continuously, without interrupting the stirring action, by 
strippers displaceable in the direction of flow. In this process at least 
a part of the edge of the stirring device or of the stripper brushes over 
the reactor wall within the polymerisation zone at the smallest possible 
distance from this wall. 
This process has the disadvantage that as a result of stirrer parts or 
strippers running along the reactor wall at the smallest possible distance 
therefrom, there is a high shear rate especially at high stirrer speeds, 
which result in coagulation in the case of shear-sensitive emulsions. In 
addition, the stirring devices extend over the whole length of the 
polymerisation vessel, which causes construction difficulties in the case 
of relatively tall vessels. This design of the stirring devices effects 
mixing of the liquid only in the direction perpendicular to the axis of 
the vessel. Consequently relatively pronounced differences in 
concentration of the layers of liquid lying one above the other arise 
which, especially in the case of emulsion polymerisation where reaction 
mixture is introduced from below, may result in the formation of grit, for 
example if, as a result of sudden fluctuations in the supply or removal or 
liquid, uncontrolled mixing occurs between the liquid layers of different 
concentration. The coatings deposited on the stirring devices are removed 
by a mechanical stripping device which is awkward to handle especially in 
the case of relatively large vessels, and its movable carrier acting 
through the vessel wall causes sealing problems. In addition, the 
stripped-off coating mixes with the polymer dispersion and contaminates 
it. To avoid the deposition of crusts which are formed on the stirring 
device and to a greater extent at the boundary surface between liquid and 
gas space, the reaction tube must be absolutely full. Consequently an 
additional buffer vessel is required in the withdrawal pipe for the 
polymer emulsion. 
A process and an apparatus have now been found that do not have the 
above-described disadvantages. 
This process for the continuous production of vinyl chloride homo-, co- or 
graft polymers in aqueous emulsion in the presence of radical-forming 
catalysts, surface-active substances and, optionally, other polymerisation 
auxiliaries in an upright, preferably cylindrical vessel with a ratio of 
height to diameter (both values measured internally) of at least 3 and a 
capacity of at least 5 m.sup.3, whilst moving the polymerisation mixture 
and regulating the level of the liquid in the vessel is characterised in 
that the polymer dispersion is discharged from the vessel at the side at a 
level which is situated 30 to 90% of the total internal height of the 
vessel above the inlet for the starting substances and at least 15 cm 
below the surface of the liquid, the standing level of the liquid is 
regulated to a maximum of 97% of the total internal height of the vessel 
and the content of the vessel is moved by at least one stirring device 
which extends in the liquid over 15 to 60% of the total internal height of 
the vessel, ends at least 20 cm below the surface of the liquid and stays 
at a distance of at least 15 cm from the vessel wall. 
There is to be understood by "total internal height of the vessel", the 
distance of the lowest point of the vessel base from the highest point of 
the vessel cover measured internally, openings and bulges of 
cross-sections of less than 1/5 of the internal diameter of the vessel 
being discounted. 
The standing level of the liquid in the vessel is measured according to 
known methods and the discharge of liquid is advantageously so controlled 
by the measurement signal that the surface of the liquid in the vessel is 
at least 15 cm above the upper edge of the discharge opening. 
The starting substances for the polymerisation are introduced in liquid, 
dissolved or dispersed form at the bottom, or advantageously laterally 
with respect to the wall of the vessel, in the lower third of the vessel. 
The starting substances, for example monomers, aqueous solution of the 
surface-active substances and solution of the radical-forming catalysts, 
may be introduced into the vessel separately or mixed or pre-emulsified 
shortly before introducing into the polymerisation vessel. Tuyeres, 
rapid-rotation or oscillation stirrers, ultrasonic devices or colloid 
mills, for example, are suitable for mixing. 
It may be advantageous to provide a second stirrer, acting essentially only 
in the region of the inlet openings for the starting substances, to ensure 
thorough mixing of these starting substances. This second stirrer may be 
operated independently of the main stirrer, but should run in the same 
direction in order to avoid excessive turbulence. The second stirrer 
should stay at least 15 cm from the inner wall of the vessel and extend, 
at most, over 10% of the total internal height of the vessel. 
The polymer emulsion is removed from the vessel at the side at a level 
situated at 30 to 90% of the total internal height of the vessel above the 
inlet for the starting substances. If the emulsion is removed at a point 
below 30% of the height of the vessel, the dispersion contains too much 
unreacted starting substances, and if it is removed at a point above 90% 
of the height of the vessel the gas space in the upper part of the vessel 
is generally not large enough and this may lead to difficulties in 
regulating the pressure. Preferably, the polymer emulsion is removed at a 
level which is situated 50 to 90%, especially advantageously at a level 
situated 70 to 85%, of the total internal height of the vessel above the 
inlet for the starting substances. 
The standing level of the liquid in the vessel should be at least 15 cm 
above the discharge opening, so as to ensure that no gas is simultaneously 
drawn off with the liquid, but principally so that the discharge opening 
is substantially kept free of crusts and coatings which form predominantly 
at the areas of the inner walls of the vessel close to the surface of the 
liquid. Advantageously the distance of the surface of the liquid from the 
discharge opening is 8 to 25% of the total internal height of the vessel, 
but must be at least 40 cm. 
The content of the vessel is stirred by at least one stirring device, which 
is totally immersed in the liquid. The stirring device should end at least 
20 cm below the lowest point of the surface of the liquid, it being 
necessary to take into consideration the formation of a so-called 
whirlpool especially when the stirrer is operated at relatively high 
speeds. If the surface of the liquid is less than 20 cm away from the 
stirring device, an undesirable crust formation can occur in the areas of 
the stirring device close to the surface. 
The outer edges of the stirring device should stay at a minimum distance of 
15 cm from the vessel wall so that, especially at relatively high speeds, 
too large a shearing rate, which leads to coagulation in sensitive 
emulsions, does not occur. The minimum distance from the wall is 
preferably 25 cm. 
The stirring device should extend over 15 to 60% of the internal height of 
the polymerisation vessel. Below 15% adequate mixing of the total liquid 
content of the vessel is not achieved; above 60% adequate axial mixing of 
the vessel content no longer occurs. Preferably a stirring device is used 
that extends over 20 to 40% of the internal height of the vessel and that 
ends approximately 25 cm below the surface of the liquid. 
The peripheral speed of the stirring device may vary within wide limits 
depending on the type of polymerisation process used, especially on the 
type and quantity of the surface-active substances used, and on the 
desired particle size and shape. Generally, peripheral speeds of 0.2 to 
approximately 10 m/sec are used. 
The process according to the invention is suitable for homo-, co- and graft 
polymerisation of vinyl chloride in aqueous emulsion. The polymerisation 
is carried out at 10.degree. to 90.degree. C., preferably at 30.degree. to 
80.degree. C., especially at 40.degree. to 75.degree. C. For the 
copolymerisation of vinyl chloride, a total of 0.1 to 99% by weight 
(calculated on vinyl chloride) for example, of one or more of the 
following monomers, can be used: olefins, such as ethylene or propylene, 
vinyl esters of straight-chained or branched carboxylic acids having 2 to 
20, preferably 2 to 4 carbon atoms, such as vinyl acetate, -propionate, 
-butyrate, -2-ethylhexoate, and vinylisotridecanoic acid esters; vinyl 
halides, such as vinyl fluoride, vinylidene fluoride, vinylidene chloride, 
vinyl ether, vinyl pyridine, unsaturated acids, such as maleic, fumaric, 
acrylic and methacrylic acids and their mono- or diesters with mono- or 
dialcohols having 1 to 10 carbon atoms; maleic acid imide and its 
N-substitution products with aromatic, cycloaliphatic and optionally 
branched, aliphatic substituents; acrylonitrile and styrene. 
There may be used for graft polymerisation, for example, elastomeric 
polymers that have been obtained by the polymerisation of one or more of 
the following monomers: dienes, such as butadiene and cyclopentadiene; 
olefins, such as ethylene and propylene; styrene, unsaturated acids, such 
as acrylic or methacrylic acid and the esters of such acids with mono or 
dialcohols having 1 to 10 carbon atoms; acrylonitrile, vinyl compounds, 
such as vinyl esters of straight-chained or branched carboxylic acids 
having 2 to 20, preferably 2 to 4, carbon atoms, vinyl halides, such as 
vinyl chloride and vinylidene chloride. 
The polymerisation can be carried out with or without the use of a seed 
prepolymer. Polymerisation is carried out in aqueous emulsion in the 
presence of 0.001 to 3% by weight, preferably 0.01 to 0.3% by weight, 
calculated on the monomers of radidal-forming catalysts, such as, for 
example, peroxydisulfates, peroxydiphosphates, perborates of potassium, 
sodium or ammonium, hydrogen peroxide, tert.-butylhydroperoxide or other 
water-soluble peroxides, as well as mixtures of various catalysts, wherein 
catalysts may be used also in the presence of 0.01 to 1% by weight, 
calculated on the monomers, of one or more reducing substances that are 
suitable for making up a redox catalyst system, such as, for example, 
sulfites, bisulfites, dithionites, thiosulfates, aldehyde sulfoxylates, 
for example, Na-formaldehyde sulfoxylate. Optionally, the polymerisation 
may be carried out in the presence of 0.05 to 10 ppm, calculated as metal 
per monomer, of soluble to sparingly soluble metal salts, for example, of 
copper, silver or iron. 
Furthermore, the polymerisation may be carried out in the persence of 0.01 
to 5% by weight, calculated on the monomer, of one or more emulsifiers. 
Anionic, amphoteric, cationic and non-ionic emulsifiers may be used. 
Suitable anionic emulsifiers are, for example, alkali metal salts, 
alkaline earth metal salts and ammonium salts of fatty acids, such as 
lauric acid, palmitic acid or stearic acid, of acid fatty alcohol sulfuric 
acid esters, of paraffinsulfo acids, of alkylarylsulfo acids, such as 
dodecylbenzenesulfo acid or dibutylnaphthalenesulfo acid, of sulfosuccinic 
acid dialkyl esters, and the alkali metal and ammonium salts of epoxy 
group-containing fatty acids, such as epoxystearic acid with unsaturated 
fatty acids such as oleic acid or linoleic acid, or unsaturated hydroxy 
fatty acids, such as ricinoleic aicd. Suitable amphoteric or cation-active 
emulsifiers are, for example: alkyl betaines, such as dodecyl betaine and 
alkylpyridinium salts, such as laurylpryidinium hydrochloride, also 
alkylammonium salts, such as hydroxyethyldodecylammonium chloride. 
Suitable non-ionic emulsifiers are, for example: partial fatty acid esters 
of polyhydric alcohols, such as glycerylmonostearate, sorbitol 
monolaurate, oleate or palmitate, polyoxyethylene ethers of fatty alcohols 
or aromatic hydroxy compounds; polyoxyethylene esters of fatty acids as 
well as polypropylene oxide-polyethylene oxide condensation products. 
In addition to catalysts and emulsifiers, the polymerisation can be carried 
out in the presence of buffer substances, for example alkali metal 
acetates, borax; alkali metal phosphates, alkali metal carbonates, alkali 
metal bicarbonates, ammonia or ammonium salts of carboxylic acids, as well 
as in the presence of molecular weight regulators, such as, for example, 
aliphatic alkehydes having 2 to 4 carbon atoms, chlorohydrocarbons or 
bromohydrocarbons, such as, for example, dichloroethylene and 
trichloroethylene, chloroform, bromoform, methylene chloride as well as 
mercaptans. 
Other additives suitable for polymerisation are listed in H. Kainer 
"Polyvinylchloride and Vinylchlorid-Mischpolymerisate", 1965 edition, 
pages 34 to 59. 
The process according to the invention is suitable especially for the 
continuous emulsion polymerisation of vinyl chloride polymers having a 
content of at least 80% by weight (calculated on pure polymer) of 
polymerisable vinyl chloride units. 
The heat produced during the reaction can be removed by cooling the vessel 
wall by means of cooled built-in fitments or by reflux cooling, wherein 
the intensity of the cooling can be controlled by measuring the 
temperature of the reaction mixture. 
To prevent the formation of coatings, special substances may be added to 
the polymerisation mixture, or the internal walls of the vessel and of the 
built-in fitments may be chemically pretreated, coated or lacquered. 
Further, the polymerisation may be carried out by producing an electrical 
potential difference between mutually insulated inner parts of the vessel 
and of the built-in fitments, optionally with, in addition, spraying of 
the vessel walls not covered by liquid with water or aqueous solutions. 
As a result of the process according to the invention, substantially less 
extensive formation of grit (undesired large polymer particles) and crusts 
on the vessel parts and the built-in fitments in the region of the surface 
of the liquid is established than in the case of the usual procedure with 
starting substances introduced from above and polymer emulsion removed 
from below. Blockages of the emulsion outlet, which occur repeatedly with 
the conventional process, are substantially fewer in number in the process 
according to the invention. The grit filters (sieves), which in the 
conventional process are customarily arranged in the polymer emulsion 
discharge pipe, may be dispensed with. The running time of the 
polymerisation are significantly prolonged, as a result of which there is 
a considerable reduction in labour and an increase in capacity. 
Furthermore, the VC-emission associated with cleaning operations is 
markedly reduced. 
The new process can also be used for shear-sensitive emulsions. A further 
advantage in comparison with the conventional processes is the greater 
reliability of operation: if the standing level measurement and control 
means break down, the polymerisation vessel retains the standing level of 
the liquid with only slight losses, whereas in the case of the 
conventional process it can empty to such an extent that the stirrer is no 
longer immersed or no longer sufficiently immersed in the liquid. As a 
result of poor mixing and too small a cooling surface, the temperature and 
pressure can quickly increase in the polymerisation vessel, which results 
in acute danger to the operating personnel and total loss of the 
polymerised product. 
The subject matter of the invention is furthermore an apparatus, consisting 
of an upright, cylindrical vessel having a ratio of height to diameter, 
measured inside the vessel, of at least 3, and a total capacity of at 
least 5 m.sup.3, which contains at least one stirring device, and, in the 
lower part of the vessel, at least one opening for introducing liquid, in 
the upper part of the vessel at least one opening each for removing liquid 
and gas, a control means for the standing level of the liquid and a double 
jacket optionally subdivided into several zones, which apparatus is 
characterised in that the opening for removing liquid is arranged 
laterally in the wall of the cylindrical vessel at a distance situated 30 
to 90% of the total internal height of the vessel above the opening(s) for 
introducing liquid provided in the lower third of the vessel, and a 
stirring device is provided inside the vessel which reaches upwards as far 
as, at a maximum, the level of the opening for removing the liquid, 
extends over 15 to 60% of the total internal height of the vessel, and 
stays a minimum distance of 15 cm from the vessel wall. 
Advantageously, the apparatus according to the invention contains a 
measuring device for the standing level of the liquid, the measurement 
signal of which controls the quantity of dispersion removed, as well as, 
if desired, other measuring devices, for example for temperature and 
pressure. 
The supply pipes in the lower part of the vessel may be arranged at the 
bottom or, advantageously, laterally in the jacket of the vessel at a 
maximum distance of 33% of the total internal height of the vessel from 
the bottom, and a cleaning opening may advantageously be arranged at the 
base. These supply lines advantageously contain means, for example, 
non-return valves or non-return flap valves, which, when there is excess 
pressure in the polymerisation vessel, prevent the mixture being 
polymerised from flowing back out of the vessel into the supply lines. 
The opening arranged laterally in the wall of the vessel for discharging 
liquid should generally have a free cross-section at least 1.5 times the 
sum of all the free cross-sections of the inlet openings in the lower part 
of the vessel. This discharge opening is advantageously arranged at a 
distance situated 50 to 90%, especially 70 to 85% of the total internal 
height of the vessel from the liquid inlet opening or openings. 
The apparatus furthermore contains at least one opening for the supply and 
discharge of gas, which is advantageously arranged in the cover of the 
cylindrical vessel in the vicinity of its highest point. Inert gas, for 
example nitrogen, can be supplied through this opening when the vessel is 
being emptied or before it is filled, or optionally for the purpose of 
pressure regulation. 
The apparatus also contains at least one stirring device, for example a 
blade stirrer, of which the blade may be of varying geometrical shape. It 
may, for example, be square, rectangular, triangular, trapezoid or oval, 
or may be composed of several geometric figures, for example two triangles 
or trapeziums; it may have openings over its area and/or recesses of 
different shape at the edge. The stirring device may also consist of 
several blades with parallel axes, arranged at an angle with respect to 
one another. It is also possible to use other stirring devices, for 
example those having curved surfaces. 
The stirring device may either be driven from above or from below. For 
constructional reasons a drive at the top is generally chosen. 
Advantageously, the stirring device used is a blade stirrer, its greatest 
width being 25 to 80% of the internal diameter of the vessel, but it being 
necessary for the stirrer to stay at least 15 cm from the inside wall of 
the vessel; the stirrer extends over 20 to 40% of the total internal 
height of the vessel and ends approximately 5 cm below the discharge 
opening for the liquid. 
Especially when the starting materials for the polymerisation are 
introduced separately through different pipes into the apparatus according 
to the invention, the apparatus advantageously contains, in the region of 
these supply lines, a second stirring device which may be operated 
independently of the stirring device described above but in the same 
direction of rotation. This second stirring device should have a diameter 
which is 25 to 80% of the internal diameter of the vessel, but should stay 
at a distance of at least 15 cm from the inner wall of the vessel and 
extend over a maximum of 10% of the total internal height of the vessel. 
The apparatus according to the invention may be used especially 
advantageously when the ratio of height to diameter of the cylindrical 
vessel (both values measured internally) is from 4 to 16 and when the 
total capacity of the vessel is at least 25 m.sup.3.

The following examples illustrate the invention 
EXAMPLE 1 
An upright, cylindrical polymerisation vessel having a capacity of over 5 
cm.sup.3, is used, which is equipped with a double jacket through which a 
liquid having a certain temperature flows, a blade stirrer, an inlet 
opening arranged in the lower third of the vessel and a discharge opening 
for liquid arranged in the upper third of the vessel, as well as an 
opening for the supply and removal of gas in the vessel cover, and a level 
measuring and regulating means which regulates the discharge of liquid. 
The dimensions are as follows: 
______________________________________ 
Ratio of the height of the 
vessel to the diameter 
(measured inside the vessel 
= 4.7 
Height of the liquid inlet 
= 2% of the total internal height 
of the vessel 
Height of the liquid outlet 
= 80% of the internal height 
of the vessel 
Length of the blade stirrer 
= 37% of the internal height 
of the vessel 
Diameter = 55% of the internal diameter 
of the vessel 
Distance of the vertical 
edges of the stirrer blade 
from the vessel wall 
= 33 cm 
Upper end of the blade 
= at the same level as the 
stirrer liquid outlet 
______________________________________ 
After rinsing the polymerisation vessel with N.sub.2 and heating the vessel 
to 50.degree. C., a mixture of 
______________________________________ 
100 parts by weight/h 
vinyl chloride 
122 parts by weight/h 
water 
0.15 part by weight/h 
potassium persulfate 
0.4 part by weight/h 
E 1 = sodium salt of an 
alkylsulfo acid 
mixture containing 
80% by weight of 
alkylsulfo acids 
having 14 to 16 
carbon atoms 
1.6 parts by weight/h 
E 2 = sodium salt of 
sulfosuccinic acid 
diisodecyl ester 
0.1 part by weight/h 
sodium carbonate 
______________________________________ 
is introduced continuously through the lower opening. The standing level of 
the liquid in the vessel is maintained at 92.6% of the total internal 
height of the vessel by regulating the discharge of liquid through the 
upper opening, and stirring is effected at a peripheral speed of 1.7 
m/sec. The polymer emulsion drawn off is freed of unreacted vinyl chloride 
by relaxing the pressure and dried by spraying in hot air. 
The polymerisation vessel is operated continuously for 840 hours, then shut 
down, emptied and opened. A uniform coating of polymer approximately 2 cm 
thick has formed on the parts of the apparatus covered by liquid. Polymer 
particles of a size of &gt; 0.1 mm have settled on the base of the 
polymerisation vessel, and these are removed, washed, dried at 150.degree. 
C. in a circulating air drying chamber for 21/2 hours and weighed. The 
measured values, and the details of the maintenance work necessary during 
the course of the polymerization process, together with the time expended 
on this in man hours, are compiled in the following table. 
Comparison experiment A 
An upright, cylindrical polymerisation vessel of the same capacity, like 
that used in Example 1, is used, which is provided with a double jacket 
through which a liquid of a certain temperature flows, a blade stirrer, a 
discharge opening arranged in the base of the vessel and an inlet opening 
for the liquid arranged in the vessel cover, as well as a second opening 
in the vessel cover for the supply and removal of gas and a level 
measuring and regulating means which regulates the discharge of liquid, 
and which has the following dimensions: 
______________________________________ 
Ratio of the height of the vessel to 
the diameter (measured inside the vessel) 
= 4.7 
Length of the blade stirrer 
= 12% of the 
total internal 
height of the 
vessel 
Diameter of the blade stirrer 
= 55% of the 
internal diameter 
of the vessel 
Distance of the vertical edges of the 
stirrer blade from the vessel wall 
= 33 cm 
Upper end of the blade stirrer 
= 7.4% of the 
total internal 
height of the 
vessel from the 
highest point 
of the vessel 
cover. 
______________________________________ 
The polymerisation vessel is, as in Example 1, charged through the opening 
in the cover of the vessel with the same quantity/h of the same reaction 
mixture and polymerisation is effect at 50.degree. C. (same temperature as 
in Example 1). The standing level of the liquid in the vessel is 
maintained, by regulating the discharge of liquid at the bottom of the 
vessel, at 92.6% of the total internal height of the vessel and the liquid 
is stirred at a peripheral speed of 1.7 m/sec. The polymer emulsion drawn 
off is filtered through a sieve with a mesh width of 6 mm, freed of 
unreacted vinyl chloride by relaxing the pressure and dried by spraying in 
hot air. 
The polymerisation vessel can be operated continuously for a period of 372 
hours only, then it must be shut down, emptied and opened for the purpose 
of cleaning. 
In addition to a polymer coating approximately 4 cm thick on the parts of 
the apparatus covered by liquid, a thick deposit of polymer has formed on 
the stirrer and the vessel wall in the region of the surface of the 
liquid, and this has grown so thick that the covering on the stirrer, on 
rotation, grinds against the covering established on the vessel wall. 
The sieve arranged in the outlet for the polymer emulsion has to be cleaned 
frequently during the operating time; the coarse polymer particles 
retained there are collected, washed, dried at 150.degree. C. for 
approximately 21/2 hours in a circulating air drying chamber and weighed. 
The measured values, and the details of the maintenance work necessary 
during the course of the polymerisation process, together with the time 
expended on this in man hours, are compiled in the following table. 
EXAMPLE 2 
An upright, cylindrical polymerisation vessel with a capacity of over 5 
m.sup.3 is used, which is provided with a double jacket through which a 
liquid of a certain temperature flows, a blade stirrer, a discharge 
opening for liquid arranged in the lower third of the vessel, as well as 
an opening for the supply and removal of gas in the vessel cover and a 
level measuring and regulating means which regulates the discharge of the 
liquid; the vessel has the following dimensions: 
______________________________________ 
Ratio of the height of the vessel to 
the diameter (measured inside the 
vessel) = 4.7 
Level of the liquid inlet 
= 2.9% of the 
total internal 
height of the 
vessel 
Level of the liquid outlet 
= 81% of the 
total internal 
height of the 
vessel 
Length of the blade stirrer 
= 20% of the 
total internal 
height of the 
vessel 
Diameter of the blade stirrer 
= 28% of the 
internal diameter 
of the vessel 
Distance of the vertical edges of the 
stirrer blade from the vessel wall 
= 52 cm 
Upper end of the blade stirrer 
= 20 cm below the 
outlet for the 
liquid. 
______________________________________ 
After rinsing the polymerisation vessel with N.sub.2 and heating the vessel 
to 54.degree. C., a mixture of 
______________________________________ 
4.4 parts by weight/h 
vinyl acetate 
87.5 parts by weight/h 
vinyl chloride 
115 parts by weight/h 
water 
0.1 part by weight/h 
potassium persulfate 
0.4 part by weight/h 
E 1 (see Example 1) 
1.4 parts by weight/h 
E 2 (see Example 1) 
0.1 part by weight/h 
sodium carbonate 
______________________________________ 
is introduced continuously into the polymerisation vessel through the lower 
opening. The standing level of the liquid in the vessel is maintained at 
92.6% of the total internal height of the vessel by regulating the 
discharge of liquid through the upper opening, and the liquid is stirred 
at a peripheral speed of 1.6 m/sec. The polymer emulsion is freed of 
unreacted vinyl chloride by relaxing the pressure, and dried by spraying 
in hot air. 
The polymerisation vessel is operated continuously for 768 hours, then shut 
down, emptied and opened. A uniform coating of polymer approximately 2.5 
cm thick has formed on the parts of the apparatus covered by the liquid. 
Polymer particles of a size of &gt; 0.1 mm have settled on the base of the 
polymerisation vessel, and these are removed, washed, dried at 150.degree. 
C. for 21/2 hours in a circulating air drying chamber and weighed. The 
measured values, and the details of the maintenance work necessary during 
the course of the polymerisation process, together with the time expended 
on this in man hours, are compiled in the following table. 
Comparison experiment B 
An upright, cylindrical polymerisation vessel of the same capacity, like 
that used in Example 1, is used, which is provided with a double jacket 
through which a liquid having a certain temperature flows, a blade 
stirrer, a discharge opening arranged in the base of the vessel and an 
inlet opening for the liquid arranged in the vessel cover, as well as a 
second opening in the vessel cover for the supply and removal of gas and a 
level measuring and regulating means which regulates the discharge of 
liquid: the vessel has the following dimensions: 
______________________________________ 
Ratio of the height of the 
vessel to the diameter (measured 
internally) = 4.7 
Length of the blade stirrer 
= 12% of the 
total internal height 
of the vessel 
Diameter of the blade stirrer 
= 28% of the 
internal diameter 
of the vessel 
Distance of the vertical edges of 
the stirrer blade from the vessel 
wall = 52 cm 
Upper end of the blade stirrer 
= 7.4% of the 
total internal height 
of the vessel 
from the highest 
point of the 
vessel cover. 
______________________________________ 
As in Example 1, the polymerisation vessel is charged through the opening 
in the cover of the vessel with the same quantity/h of the same reaction 
mixture and polymerisation is effected at 54.degree. C. (same temperature) 
in the same manner as in Example 1. The standing level of the liquid in 
the vessel is maintained at a distance which is 8% of the internal height 
of the vessel from the highest point of the vessel cover by regulating the 
discharge of liquid at the bottom of the vessel, and the liquid is stirred 
at a peripheral speed of 1.6 m/sec (as in Example 2). The polymer emulsion 
drawn off is filtered through a sieve with a mesh width of 6 mm, freed of 
unreacted vinyl chloride by relaxing the pressure and dried by spraying in 
hot air. 
The polymerisation vessel can be operated continuously for a period of 408 
hours only, then it must be shut down, emptied and opened for the purpose 
of cleaning. 
In addition to a polymer coating approximately 5 cm thick on the parts of 
the apparatus covered by liquid, a thick deposit of polymer has formed on 
the stirrer and the vessel wall in the region of the surface of the 
liquid, and this has grown so thick that the covering on the stirrer, on 
rotation, grinds against the covering established on the vessel wall. 
The sieve arranged in the outlet for the polymer emulsion has to be cleaned 
frequently during the operating time; the coarse polymer particles 
retained there are collected, washed, dried at 150.degree. C. in a 
circulating air drying chamber and weighed. The measured values, and the 
details of the maintenance work necessary during the course of the 
polymerisation process, together with the time expended on this in man 
hours, are compiled in the following table. 
EXAMPLE 3 
An upright, cylindrical polymerisation vessel is used, which is provided 
with a double jacket through which a liquid of a certain temperature 
flows, a blade stirrer, an inlet opening arranged in the lower third of 
the vessel, and a discharge opening for liquid arranged in the upper third 
of the vessel, as well as an opening for the supply and removal of gas in 
the vessel cover and a level measuring and regulating means which 
regulates the discharge of liquid; the vessel has the following 
dimensions: 
______________________________________ 
Ratio of the height of the 
vessel to the diameter (measured 
internally) = 4.5 
Level of the liquid inlet 
= 17% of the 
total internal height 
of the vessel 
Level of the liquid outlet 
= 87% of the 
total internal height 
of the vessel 
Length of the stirrer blade 
= 37% of the 
total internal height 
of the vessel 
Diameter of the stirrer blade 
= 61% of the 
internal diameter 
of the vessel 
Distance of the vertical edges of the 
stirrer blade from the vessel wall 
= 29 cm 
Upper end of the stirrer blade 
= 10 cm below 
the liquid outlet 
______________________________________ 
After rinsing the polymerisation vessel with N.sub.2 and heating the vessel 
to 64.degree. C., a mixture of 
______________________________________ 
100 parts by weight/h 
vinyl chloride 
109 parts by weight/h 
water 
0.08 part by weight/h 
potassium persulfate 
2.1 parts by weight/h 
E 3 = sodium salt of 
dodecylbenzenesulfo 
acid 
0.07 part by weight/h 
secondary sodium phosphate 
______________________________________ 
is introduced continuously into the polymerisation vessel through the lower 
opening. The standing level of the liquid in the vessel is maintained at 
96% of the total internal height of the vessel by regulating the liquid 
discharge through the upper opening, and the liquid is stirred at a 
peripheral speed of 1.6 m/sec. The polymer emulsion drawn off is freed of 
unreacted vinyl chloride by relaxing the pressure, and dried by spraying 
in hot air. 
The polymerisation vessel is operated continuously for 960 hours, then shut 
down, emptied and opened. A uniform polymer coating approximately 2 cm 
thick has formed on the parts of the apparatus covered by liquid. Polymer 
particles of a size of &gt; 0.1 mm have settled on the base of the 
polymerisation vessel, and these are removed, washed, dried at 150.degree. 
C. for 21/2 hours in a circulating air drying chamber and weighed. The 
measured values, and the details of the maintenance work necessary during 
the course of the polymerisation process, together with the time expended 
on this in man hours, are compiled in the following table. 
Comparison Experiment C 
An upright, cylindrical polymerisation vessel of the same capacity, like 
that used in Example 1, is used, which is provided with a double jacket 
through which a liquid of a certain temperature flows, a blade stirrer, an 
inlet opening for liquid arranged in the vessel base as well as a second 
opening in the vessel cover for the supply or removal of gas and a level 
measuring and regulating means which regulates the discharge of liquid, 
and has the following dimensions 
______________________________________ 
Ratio of the height of the 
vessel to the diameter 
(measured internally) = 4.5 
Length of the blade stirrer 
= 12% of the 
total internal height 
of the vessel 
Diameter of the blade stirrer 
= 61% of the 
internal diameter 
of the vessel 
Distance of the vertical edges 
of the stirrer blade from the 
vessel wall = 29 cm 
Upper end of the blade stirrer 
= 8.8% of the 
total internal height 
of the vessel 
from the highest 
point of the 
vessel cover. 
______________________________________ 
As in Example 1, the polymerisation vessel is charged through the opening 
in the cover of the vessel with the same quantity/h of the same reaction 
mixture and polymerisation is effected at 64.degree. C. (same temperature) 
in the same manner as in Example 1. The standing level of the liquid in 
the vessel is maintained at a distance which is 10.3% of the total 
internal height of the vessel from the highest point of the vessel cover 
by regulating the discharge of liquid at the bottom of the vessel, and the 
liquid is stirred at a peripheral speed of 1.6 m/sec. (as in Example 1). 
The polymer emulsion drawn off is filtered through a sieve having a mesh 
width of 6 mm, is freed of unreacted vinyl chloride by relaxing the 
pressure, and dried by spraying in hot air. 
The polymerisation vessel can be operated continuously for a period of 528 
hours only, then it has to be shut down, emptied and opened for the 
purpose fo cleaning. 
In addition to a polymer coating approximately 6 cm thick on the parts of 
the apparatus covered by liquid, a thick deposit of polymer has formed on 
the stirrer and the vessel wall in the region of the surface of the 
liquid, and this has grown so thick that the covering on the stirrer, on 
rotation, grinds against the covering established on the vessel wall. 
The sieve in the outlet for the polymer emulsion has to be cleaned 
frequently during the operating time; the polymer particles retained there 
are collected, washed, dried at 150.degree. C. in a circulating air drying 
chamber and weighed. The measured values, and the details of the 
maintenance work necessary during the course of the polymerisation 
process, together with the time expended on this in man hours, are 
compiled in the following table. 
EXAMPLE 4 
An upright, cylindrical polymerisation vessel having a capacity of over 25 
m.sup.3 is used, which is provided with a double jacket through which a 
liquid of a certain temperature flows, a blade stirrer, an inlet opening 
arranged in the lower third of the vessel, and an outlet opening for 
liquid arranged in the upper third of the vessel, as well as an opening 
for the supply and removal of gas in the vessel cover and a level 
measuring and regulating means which regulates the discharge of liquid; 
the vessel has the following dimensions: 
______________________________________ 
Ratio of the height of the 
vessel to the diameter 
(measured internally) = 8.5 
Height of the liquid inlet 
= 11.5% of the 
total internal height 
of the vessel 
Height of the liquid outlet 
= 80% of the 
total internal height 
of the vessel 
Length of the blade stirrer 
= 39% of the 
total internal height 
of the vessel 
Diameter of the blade stirrer 
= 67% of the 
internal diameter 
of the vessel 
Distance of the vertical edges 
of the stirrer blade from the 
vessel wall = 27 cm 
Upper end of the stirrer blade 
= 10 cm below 
the discharge 
of liquid 
______________________________________ 
After the polymerisation vessel has been rinsed with N.sub.2 and heated to 
43.degree. C., a mixture of 
______________________________________ 
166 parts by weight/h 
vinyl chloride 
195 parts by weight/h 
water 
0.13 part by weight/h 
potassium persulfate 
0.035 part by weight/h 
sodium bisulfite 
4.2 parts by weight 
E 1 (see Example 1) 
0.27 part by weight/h 
sodium carbonate 
0.00035 part by weight 
copper sulfate 
______________________________________ 
is introduced continuously into the polymerisation vessel through the lower 
opening. The standing level of the liquid in the vessel is maintained at 
86% of the total internal height of the vessel by regulating the discharge 
of liquid through the upper opening and the liquid is stirred at a 
peripheral speed of 1.5 m/sec. The polymer emulsion drawn off is freed of 
unreacted vinyl chloride by relaxing the pressure and dried by spraying in 
hot air. 
The polymerisation vessel is operated continuously for 840 hours, then shut 
down, emptied and opened. A uniform polymer covering approximately 1 cm 
thick has formed on the parts of the apparatus covered by liquid. Polymer 
particles of a size of 0.1 mm have been deposited on the base of the 
polymerisation vessel, and these are removed, washed, dried at 150.degree. 
C. for 21/2 hours in a circulating air drying chamber and weighed. The 
measured values, and the details of the maintenance work necessary during 
the course of the polymerisation process, together with the time expended 
on this in man hours, are compiled in the following table. 
TABLE 
__________________________________________________________________________ 
Routine maintenance work 
Total 
quantity 
Duration Cleaning 
of coarse 
Stoppage, 
Total 
Polym. 
of Vessel 
of polymer 
cleaning 
maintenance 
Experiment 
Temp. 
Polymer- 
Cleaning 
outlet 
outlet 
particles 
vessel, 
expenditure 
no. .degree. C 
isation h 
6mm sieve 
cleared 
pipe (grit) restarting 
(man 
__________________________________________________________________________ 
hours) 
Example 1 50 840 -- 7 x 2 x 1.20 t -- 3.8 
Comparison A 
50 744 34 x 84 x 8 x 1.8 t 1 x 70.6 
Example 2 54 768 -- 3 x 1 x 0.63 t -- 1.8 
Comparison B 
54 816 38 x 24 x 6 x 1.16 t 1 x 55.6 
Example 3 64 960 -- -- 7 x 0.7 t -- 7 
Comparison C 
64 1056 40 x 68 x 16 x 1.92 t 1 x 77.6 
Example 4 43 840 -- 1 x 3 x 0.85 t -- 3.3 
__________________________________________________________________________ 
Example 1 VC-homopolymer, K = 72, according to DIN 53 726 
Example 2 VC-VAc-copolymer, K = 70 according to DIN 53 726 
Example 3 VC-homopolymer, K = 59, according to DIN 53 726 
Example 4 VC-homopolymer, K = 78 according to DIN 53 726