Method of removing foam during polymerization of vinyl chloride polymers

The present invention provides a method of producing vinyl chloride polymers, including the steps of subjecting vinyl chloride monomer or a mixture of monomers containing vinyl chloride monomer to suspension polymerization reaction in an aqueous medium within a polymerization vessel equipped with a reflux condenser, and subsequently, after the completion of the polymerization reaction, recovering any unreacted monomer, wherein foam generated on the surface of the liquid phase inside the polymerization vessel is eliminated by discharging a high pressure water having a pressure of 20 kg/cm.sup.2 or more substantially linearly to the surface of the liquid phase. The high pressure water discharging is carried out at the polymerization step, particularly from the time when operation of the reflux condenser begins, and/or at the recovery step. A vinyl chloride polymer is thus obtained without the splashing of foam over the gaseous phase section of the polymerization vessel, regardless of whether the heat removal rate of the reflux condenser, or the recovery rate per unit time for the unreacted monomer are increased.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method for producing vinyl chloride 
polymers. 
2. Description of the Prior Art 
Utilizing the currently available methods of producing vinyl chloride 
polymers, tests have been conducted on removing the heat generated at the 
polymerization reaction to reduce the polymerization time, in an attempt 
to improve efficiency of production of the polymer. Known methods for 
removal of this heat of reaction rely on the use of cooling jackets, 
cooling baffles, and a reflux condenser fitted inside the polymerization 
vessel. Of these methods, the use of a reflux condenser is favorable in as 
far as it ensures a large heat transmission surface area without affecting 
the stirring and mixing of a content (reaction mass) in the polymerization 
vessel. However, with this reflux condenser method, if the amount of heat 
to be removed is large, a marked amount of the monomer in the content 
inside the polymerization vessel vaporizes, forming a layer of gaseous 
monomer-containing foam on the surface of the content. Furthermore, as 
this foam includes low density polymers, if large amounts of foam are 
generated, it can cause a build up of scale in the gaseous phase section 
of the polymerization vessel. A further problem arises due to the fact 
that this foam is splashed over the inside of the polymerization vessel, 
and can generate scale in areas which are difficult to clean by standard 
cleaning operations, such as on the very inside of the reflux condenser. 
The scale thus generated becomes mixed with the polymer being produced, 
generating the problem of fish eyes appearing on products formed from the 
polymer. Consequently, with the reflux condenser method, it is necessary 
to first remove the foam generated inside the polymerization vessel in 
order to reduce the polymerization time. 
On the other hand, in addition to the above methods which rely on 
shortening the polymerization time, there have also been tests done on 
improving the efficiency of production of the polymer by shortening the 
polymerization cycle. An example of a method for reducing the 
polymerization cycle involves reducing the time spent recovering unreacted 
monomer. However this method, when the amount of unreacted monomer to be 
recovered in a specified time period is increased, generates the same 
problems as the previously mentioned reflux condenser method, as it too 
results in the generation of large amounts of foam in the polymerization 
vessel. Furthermore it suffers from an additional problem in that the foam 
can clog the monomer recovery line. 
In order to effect the removal of the foam from the gaseous phase section 
of the polymerization vessel, methods involving stirring the gaseous phase 
section of the polymerization vessel with a rotary vane (refer to Japanese 
Patent Publication (Kokoku) No. 60-42804), and methods involving spraying 
either water, or an aqueous solution of a foam inhibitor, with a spray 
nozzle such as a flat nozzle or a full cone nozzle have been 
proposed.(refer to Japanese Patent Publication (Kokoku) No. 50-30106) 
However, the former method, although it has the effect of breaking up the 
foam, still results in the splashing of spray, which includes some of the 
polymer, over the inside of the polymerization vessel, and as such does 
not solve the fundamental problem of preventing scale, and allowing 
production of a high quality polymer. Furthermore, the latter method 
although resulting in some inhibition of foam formation, still displays 
insufficient foam breaking effect. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a method of producing 
vinyl chloride polymers, where production of the vinyl chloride polymer is 
carried out using a polymerization vessel equipped with a reflux 
condenser, and where foam is not splashed over the gaseous phase section 
of the polymerization vessel at polymerization, nor at recovery of the 
unreacted monomer, regardless of whether the amount of heat to be removed 
by the reflux condenser is increased, and regardless of whether the amount 
of unreacted monomer to be recovered is increased, thus resulting in a 
high yield of a high quality vinyl chloride polymer. 
The inventors have developed this invention when, in an attempt to remove 
the layer of foam covering the surface of the content (liquid phase) in 
the polymerization vessel, they discharged high pressure water linearly to 
the surface of the liquid phase, and noted that not only did the 
discharged water penetrate the foam layer, reaching the liquid phase 
underneath, where the discharged water caused vibration of the surface of 
the liquid phase allowing for simpler destruction of the foam bridging, 
but also that the discharged water facilitated foam-breaking by diluting 
and reducing the concentration of low density polymers contained in the 
foam around the place where the discharged water penetrated, and by 
providing a path through the foam for the gaseous monomer trapped in the 
foam to escape. 
The present invention provides a method of producing vinyl chloride 
polymers, which comprises the steps of subjecting vinyl chloride monomer 
or a mixture of monomers containing vinyl chloride monomer to suspension 
polymerization reaction in an aqueous medium in the presence of a 
suspending agent within a polymerization vessel equipped with a reflux 
condenser, and subsequently, after the completion of the polymerization 
reaction, recovering unreacted monomer, said method comprising discharging 
a high pressure water having a pressure of 20 kg/cm.sup.2 or more 
substantially linearly to the surface of a liquid phase inside the 
polymerization vessel from a nozzle provided in a gaseous phase section of 
the polymerization vessel at said polymerization step, at said recovery 
step or at both these steps, whereby foam generated on the surface of the 
liquid phase is eliminated. 
The high pressure water discharging of this invention is preferably carried 
out at operation of the reflux condenser in the polymerization step, and 
at the monomer recovery step. 
With the method of producing vinyl chloride polymers according to the 
present invention, the production of the vinyl chloride polymer is carried 
out using a polymerization vessel equipped with a reflux condenser, and 
foam is not splashed over the gaseous phase section of the polymerization 
vessel at polymerization, nor at recovery of the unreacted monomer, 
regardless of whether the amount of heat to be removed by the reflux 
condenser is increased, and regardless of whether the amount of unreacted 
monomer to be recovered is increased, and consequently a high quality 
vinyl chloride polymer with few fish eyes or other imperfections can be 
produced at a good level of productivity by appropriate reduction in the 
polymerization time and the polymerization cycle. These effects are most 
pronounced if the high pressure water is discharged at operation of the 
reflux condenser in the polymerization step, and at the recovery step.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention is described in more detail below. 
The water pressure of the high pressure water used in the production method 
of this invention should be 20 kg/cm.sup.2 or more (all pressures refer to 
the gauge pressure in piping attached to the nozzle), with 20-500 
kg/cm.sup.2 being preferable, 30-300 kg/cm.sup.2 being even more 
preferable, 50-200 kg/cm.sup.2 being even more preferable again, and 
80-150 kg/cm.sup.2 being the most preferred. If the pressure is too low, 
then the foam breaking effect can be insufficient, while if too high, the 
discharged water turns to a mist and the linearity of the discharged water 
deteriorates, resulting in an insufficient foam breaking effect. 
The nozzle capable of linearly discharging a high pressure water (hereafter 
referred to as the linearly discharging nozzle) used in the present 
invention can be any nozzle which will produce a discharged water with 
good linearity when high pressure water is discharged therethrough. With 
reference to, for example, the numerals in FIG. 7, good linearity here 
refers to a nozzle 13, which satisfies the requirement that, when high 
pressure water is discharged through the nozzle 13 under atmospheric 
conditions, the ratio (Y/X) of the diameter Y of the discharge circle 12 
to the distance X discharged, of the discharged water 11, is 0.15 or less, 
with 0.1 or less being preferable. In these situations an X value of 
between 100 cm and 200 cm is preferable. 
For the linearly discharging nozzle used in the present invention, an 
orifice diameter of 0.5-7.0 mm is preferable, with 1.0-5.0 mm being even 
more preferable. If this orifice diameter is too small, the volume of 
water to be discharged decreases, resulting in a fall in the kinetic 
energy of the discharged water. If the discharge pressure is then 
increased to try and increase the volume of water to be discharged, the 
discharged water turns to a mist which is undesirable. In contrast, if the 
orifice diameter is too large, then as there is a limit to the total 
volume of water which can be discharged into the polymerization vessel, it 
may be necessary to reduce the discharge pressure, which will result in an 
undesirable lowering of the foam breaking effect. 
Particularly suitable examples of these linearly discharging nozzles are 
the type of nozzle shown in FIG. 4. This linearly discharging nozzle 
consists of a substantially cylindrical water-inlet portion 1A, and a 
discharge portion 1B with an internal diameter d (in this nozzle, 
equivalent to the orifice diameter) smaller than that of a water inlet 
portion D (hereafter referred to as the nozzle internal diameter), 
connected by a tapered portion 1C. Linearly discharging nozzles where the 
ratio (L/d) of the length L of the discharge portion 1B to the internal 
diameter d of the same dischage portion is between 1.0 and 10.0 are 
particularly preferable. If this ratio is too small, then the linearity of 
the discharged water may deteriorate. In contrast, if the ratio is too 
large, the pressure loss in the nozzle may increase significantly. 
Furthermore, if the length L of the dischage portion 1B is too long (when 
the L/d ratio is too large), then it becomes difficult to polish the 
internal surface of the dischage portion 1B, meaning distortions remain, 
and a smooth surface can not be produced. 
Linearly discharging nozzles in which the internal surfaces have been 
polished and smoothed in order to lower frictional resistance are most 
preferable. The tapered portion 1C has the effect of lowering the amount 
of pressure loss in the nozzle, as well as preventing turbulence in the 
water flow inside the nozzle. 
With the linearly discharging nozzles used in the present invention, 
straighteners such as discharge stabilizers may be connected to the water 
inlet portion 1A. Fitting the linearly discharging nozzle with this type 
of straightener allows continual straightening of the water flowing 
through the nozzle, resulting in a further improvement in the linearity of 
the discharged water. Although there are no particular restrictions on the 
materials used in the linearly discharging nozzle, materials with good 
abrasion resistance properties such as stainless steel are preferable. 
For the production method outlined in the present invention, a linearly 
discharging nozzle which will produce a discharged water with good 
linearity must be used, as the nozzles employed in currently used methods 
such as full cone nozzles, flat nozzles and hollow cone nozzles, will not 
generate a discharged water with sufficient linearity. Furthermore, in 
highly dense atmospheres which contain large amounts of gaseous monomer, 
such as the atmosphere in the gaseous phase section inside a 
polymerization vessel, energy dispersion of the dischaged water from 
currently employed nozzles is large, and consequently, the discharged 
water cannot penetrate the foam layer right through to the liquid phase, 
and thus generates an insufficient foam-breaking effect. 
The linearly discharging nozzle may be located at any point in the gaseous 
phase section of the polymerization vessel which allows water to be 
discharged onto the foam layer which develops. However, the preferred 
location is at a position where it will not interfere with other devices 
located in the gaseous phase section of the polymerization vessel for 
supplying additives into the polymerization vessel. 
The number of linearly discharging nozzles located in the polymerization 
vessel can be determined relative to the total volume of water which can 
be discharged into the polymerization vessel. The total allowable volume 
of water to be discharged can be calculated from the volume of water 
discharged (the volume of the discharged water per hour) and the 
discharging time per linearly discharging nozzle when the nozzle was 
operated at a water pressure sufficient to allow the discharged water to 
penetrate the foam layer right through to the liquid phase beneath. 
Specifically, for polymerization vessels with, for example, volumes 
between 40 and 300 m.sup.3, normally 1-6 nozzles will generate sufficient 
foam-breaking effect. Furthermore, multiple linearly discharging nozzles 
may be fitted to a piping arrangement, such as in FIG. 5, where linearly 
discharging nozzles 1 are attached to a ring-shaped piping 2, or as in 
FIG. 6, where linearly discharging nozzles 1 are attached to a rod-shaped 
piping 2. 
The upper limit for the total volume of water to be discharged can be set 
at a value which maintains the capacity of the gaseous phase section of 
the polymerization vessel at a value of 10% or more of the total volume of 
the polymerization vessel. Polymerization vessels with volumes of 40 
m.sup.3 or more are preferred, with volumes of 80 m.sup.3 or more being 
even more preferable. If water is discharged into the vessel until the 
volume of the gaseous phase section is less than 10%, the distance between 
the linearly discharging nozzles and the upper surface of the foam layer 
becomes too small and can generate problems. For example, there are 
instances where if the foam layer is very thin, the foam cannot be broken 
up, even if the water pressure or the volume of water to be discharged is 
increased. In these instances if the distance between the linearly 
discharging nozzles and the upper surface of the foam layer becomes too 
small, then the situation can arise that by the time the foam layer 
reaches a thickness which can be broken up, the linearly discharging 
nozzles have already been engulfed in the foam layer. If the linearly 
discharging nozzles become engulfed by the foam layer in this way, the 
foam breaking effect diminishes markedly. Consequently due consideration 
must be given to the total volume of water to be discharged. 
The flow rate of water to be discharged from each linearly discharging 
nozzle is determined by the pressure of the high pressure water to be 
discharged and said orifice diameter, and so provided the linearly 
discharging nozzle orifice diameter falls within the range mentioned 
above, the pressure is first fixed within the above mentioned range, and a 
linearly discharging nozzle then chosen with an orifice diameter 
sufficient to allow linear-discharging of water at that pressure. For 
discharge pressures of 20-500 kg/m.sup.3, the flow rate is generally 1-100 
liters/minute, with 3-50 liters/minute being preferable. 
With the production method of the present invention, high pressure water is 
discharged substantially linearly from the linearly discharging nozzles 
mentioned above, to the surface of the liquid phase in the polymerization 
vessel, at the polymerization step, at the unreacted monomer recovering 
step, or at both these steps. 
In those instances where the high pressure water discharging is carried out 
at the polymerization step, it can be carried out, without any particular 
restrictions, at any time from the point of polymerization initiation, 
until the completion of polymerization. However, as there is a tendency 
for foam generation to increase markedly following commencement of heat 
removal with the reflux condenser, it is preferable to continue the high 
pressure water discharging from the time when heat removal using the 
reflux condenser is begun, until the completion of polymerization. Heat 
removal using the reflux condenser is preferably carried out from the 
point where the content inside the polymerization vessel reaches the 
polymerization temperature, until the polymerization reaction is complete. 
There are no restrictions on when, at the unreacted monomer recovery step, 
the high pressure water discharging should be carried out, with the time 
period from the point of monomer recovery initiation, until the completion 
of the recovery step being suitable. 
Methods for recovery of the unreacted (gaseous) monomer from the 
polymerization vessel include the widely employed method shown in, for 
example, FIG. 2, where the unreacted monomer is recovered via an unreacted 
monomer recovery piping arrangement 15 located at the top of a 
polymerization vessel 6. With this method, firstly a sequence valve 16 
fitted part way along the recovery piping 15 is opened, and the flow rate 
of the gaseous monomer through the recovery piping 15 measured with a flow 
rate meter 19. The measured flow rate S.sub.1 from the flow rate meter 19 
is then transmitted to a flow rate controller 18, and this controller 18, 
in order to effect an adjustment in the flow rate to a pre-set value, then 
transmits a flow rate adjustment signal S.sub.2 to a flow rate control 
valve 17. The flow rate control valve 17 then adjusts the flow rate of the 
gaseous monomer in the recovery piping 15 to the pre-set flow rate. The 
value of the pre-set flow rate stored in the controller 18, is a value, 
obtained by experimentation, which will not generate splashing of the 
product polymer over the gaseous phase section 14 of the polymerization 
vessel. The gaseous monomer thus recovered, passes through a gas holder 21 
fitted to an extension of the recovery piping 15, and is then transferred 
to a compressor to complete the recovery step. If required, an unreacted 
monomer recovery blower 20 can be fitted to the recovery piping 15, at a 
point between the flow rate meter 19 and the gas holder 21, and this 
blower then used to effect vacuum recovery of the gaseous monomer. This 
type of vacuum recovery enables a large reduction in the amount of 
residual unreacted monomer contained in the product polymer (typically 
0.1-1% of the polymer). Normally, recovery conditions where the unreacted 
gaseous monomer is recovered at a space linear velocity (the linear 
velocity at which the unreacted gaseous monomer rises up the straight 
cylindrical portion of the polymerization vessel) of 0.01-1 m/sec are 
preferable. Recovery times cannot be fixed unconditionally as they will 
vary with, among other things, the size of the device and the amount of 
polymer splashing which occurs in the gaseous phase section of the 
polymerization vessel, but generally recovery times of between 15 and 120 
minutes are sufficient. From a production efficiency viewpoint, the faster 
the recovery rate and the shorter the recovery time the better, providing 
there is no splashing of the polymer in the gaseous phase section of the 
polymerization vessel. 
In those instances where the high pressure water discharging is carried out 
at the unreacted monomer recovery step in accordance with the present 
invention, the recovery rate of the unreacted monomer is preferably 40 
Nm.sup.3 /min or more, and particularly 50 Nm.sup.3 /min or more, whereby 
splashing of foam over the inner wall of the gaseous phase section of a 
polymerization vessel and the inside of a reflux condenser and into the 
recovery line of the unreacted monomer can be effectively prevented. 
With the present invention, the high pressure water discharging is 
preferably carried out at both the polymerization step and the recovery 
step. As described above, the high pressure water discharging at the 
polymerization step is preferably carried out at operation of the reflux 
condenser. That is, with the present invention, the high pressure water 
discharging is best carried out at operation of the reflux condenser and 
at the recovery step of the unreacted monomer. Specifically, this means 
that discharging could be carried out both during the whole period of 
reflux condenser operation and during the whole unreacted monomer recovery 
step; both during part of the period of reflux condenser operation and 
during the whole unreacted monomer recovery step; both during the whole 
period of reflux condenser operation and during part of the unreacted 
monomer recovery step; or both during part of the period of reflux 
condenser operation and during part of the unreacted monomer recovery 
step. 
Regardless of at which step discharging is conducted, provided it is 
carried out at the discharging times mentioned above, the high pressure 
water discharging can be carried out either continuously, with no 
interruption from the beginning of discharging until its completion 
(continuous discharging), or alternatively, as intermittent discharging, 
with the discharging being started, interrupted at some point, and then 
recommenced. Multiple interruptions in the discharging sequence are also 
possible. 
Regardless of whether the high pressure water discharging is to be carried 
out at the polymerization step or the unreacted monomer recovery step, it 
is preferable to commence discharging once confirmation is obtained of 
foam generation inside the polymerization vessel. Methods for confirming 
foam generation inside the polymerization vessel include, for example, 
confirmation via a foam sensor located in the gaseous phase section of the 
polymerization vessel; and confirmation by use of a simple foam sampling 
pipe, consisting of a pipe with one end inside the gaseous phase section 
of the polymerization vessel, the other end outside the vessel and 
containing an open-close valve and a sight glass, where confirmation is 
carried out by opening the valve, and then checking, via the sight glass, 
whether or not foam is being forced up into the pipe from the gaseous 
phase section of the polymerization vessel. 
Examples of the foam sensor mentioned above, include electrostatic capacity 
sensors, ultra sound sensors, radiation sensors, infrared sensors, and 
conductivity cells. 
These type of foam sensors can be installed at any position which takes 
into consideration the velocity with which the foam layer moves up the 
inside of the polymerization vessel, although they should preferably be 
installed at a point at least 10 vertical cm below the outlet of the 
linearly discharging nozzle. Furthermore, if two or more foam sensors are 
installed, the vertical distance between individual sensor locations 
should preferably be 10 cm or more. 
An example of an apparatus which uses this type of foam sensor to confirm 
foam generation, and which discharges high pressure water from linearly 
discharging nozzles is shown in, for example, FIG. 3. This apparatus 
comprises: foam sensors 3A, 3B located in a gaseous phase section 14 of a 
polymerization vessel 6, linearly discharging nozzles 1, piping 2 for 
supplying high pressure water to the linearly discharging nozzles 1, a 
solenoid valve 4 for adjusting the flow rate of high pressure water in the 
piping 2, and a valve opening controller 5 (for example, a CPU) for 
controlling the opening and closing of the solenoid valve 4. With this 
type of apparatus, when a foam layer is formed either at the time of 
operation of the reflux condenser or at the unreacted monomer recovery 
step, and the upper surface of that foam layer starts rising up the 
interior of the polymerization vessel 6, the foam is detected by the foam 
sensors (3A, 3B) which then transmit a foam detection signal h to the 
valve opening controller 5. The valve opening controller 5, on receipt of 
this foam detection signal h, transmits a valve opening signal j to the 
solenoid valve 4. The solenoid valve 4 then lets water flow through the 
piping 2, in accordance with the valve opening signal j, and high pressure 
water is discharged out through the nozzles 1. The foam generated inside 
the polymerization vessel 6 is broken down by the linear discharge of high 
pressure water, and the upper surface of the foam layer drops back down 
the inside of the vessel 6. At this point, the foam sensors (3A, 3B) 
detect the falling of the upper surface of foam layer, and transmit a loss 
of foam detection signal i to the valve opening controller 5. The valve 
opening controller 5, on receipt of this loss of foam detection signal i, 
transmits a valve closing signal k to the solenoid valve 4, and the 
solenoid valve 4 then closes the valve in accordance with this signal k, 
and the discharging of high pressure water from the linearly discharging 
nozzles 1 is interrupted. When the upper surface of the foam layer starts 
rising up the interior of the polymerization vessel 6 again, the cycle 
consisting of the high pressure water discharging and the discharging 
interruption, as described above, is repeated. 
With the production method outlined in the present invention, if the high 
pressure water discharging is conducted only at the polymerization step, 
or alternatively only at the monomer recovery step, then either the 
polymerization step is preferably carried out in the presence of an 
anti-foaming agent, or the unreacted monomer recovery step is preferably 
carried out in the state of an anti-foaming agent being present in the 
content of the polymerization vessel. Of course, such anti-foaming agents 
can also be used when the high pressure water discharging is conducted at 
both the polymerization and monomer recovery steps. 
When the polymerization is carried out in the presence of an anti-foaming 
agent, the only requirement is that the agent is present in the content of 
the polymerization vessel at the time of polymerization. Thus, the 
anti-foaming agent may be placed in the polymerization vessel before the 
polymerization reaction, or alternatively, introduced into the 
polymerization vessel between the time of polymerization initiation and 
the time of polymerization completion. It is particularly preferable to 
conduct this introduction between commencement of heat removal using the 
reflux condenser and completion of polymerization. 
Furthermore, when the unreacted monomer recovery is carried out in the 
state of an anti-foaming agent being present in the content inside the 
polymerization vessel, the only requirement is that the agent is present 
in the content in the vessel at the time of recovery. The anti-foaming 
agent may be placed in the polymerization vessel before initiation of the 
polymerization reaction, introduced into the polymerization vessel between 
the time of polymerization initiation and the time of polymerization 
completion, or alternatively, introduced into the polymerization vessel 
between the time of initiation of the recovery of unreacted monomer and 
the time of completion of this monomer recovery. It is particularly 
preferable to conduct this introduction at the period between commencement 
of unreacted monomer recovery and completion of this recovery. 
Examples of methods for introducing an anti-foaming agent into the 
polymerization vessel include; placing the anti-foaming agent, together 
with deionized water, in the polymerization vessel prior to the 
polymerization step; using high pressure water which contains an 
anti-foaming agent; and introduction of the anti-foaming agent into the 
polymerization vessel through a separate anti-foaming agent addition pipe 
10, comprising a pipe fitted with an open-close valve, one end of which 
opens inside the gaseous phase section 14 of the polymerization vessel 6, 
and the other end of which remains outside the vessel 6, as shown in, for 
example, FIGS. 1 and 2. The anti-foaming agent can either be introduced 
into the polymerization vessel without any addition of the agent to the 
high pressure water, by either placing the agent in the polymerization 
vessel prior to reaction, or adding it to the vessel via the separate 
addition pipe, or alternatively it can be introduced by both methods, so 
that it is placed in the polymerization vessel prior to reaction or added 
via the separate addition pipe, in addition to being added with the high 
pressure water. Furthermore, in those instances where the anti-foaming 
agent is added via the separate addition pipe described above, the 
addition can be carried out either continuously or intermittently. 
Examples of the anti-foaming agents discussed above include widely used 
foam inhibiting agents and foam breaking agents such as silicones such as 
organopolysiloxane, alcohols such as methyl alcohol, ethyl alcohol, octyl 
alcohol, and acetylene alcohol, and nonionic surface active agents such as 
Span (tradename of sorbitan fatty acid ester-based nonionic surface active 
agent) and polyether. 
The amount of anti-foaming agent should preferably be maintained between 
0.0001 and 1 part by weight per 100 parts by weight of the monomer, or 
monomer mixture. If the amount of anti-foaming agent used is too large, it 
can have a deleterious influence on the quality of the product polymer. 
Consequently, the total amount of anti-foaming agent added, including that 
added with the high pressure water and that added through the separate 
addition pipe (and any added prior to the commencement of polymerization) 
should be adjusted so that it falls within the range listed above. 
The method of producing vinyl chloride polymers described in this invention 
involves reaction under the same conditions as typical vinyl chloride 
polymer production methods, with the exception that, as described above, 
the high pressure water is discharged from linearly discharging nozzles 
into the polymerization vessel to break up the foam layer generated on the 
upper surface of the content inside the vessel (sometimes with the use of 
an anti-foaming agent), at the polymerization step, at the unreacted 
monomer recovery step, or at both of these steps. That is, the 
introduction to the polymerization vessel, of the vinyl chloride monomer, 
or the mixture of monomers containing vinyl chloride monomer, a suspending 
agent, a polymerization initiator, and an aqueous medium, is conducted in 
the standard way, with the polymerization conditions also being the same 
as those for current polymerization reactions. 
The monomer employed in the method of producing vinyl chloride polymers 
described in this invention can be either vinyl chloride monomer, or 
alternatively, a mixture of monomers containing vinyl chloride monomer as 
the main constituent (50% by weight or more) but also containing one or 
more other vinyl monomers (comonomers) which are capable of 
copolymerization with the vinyl chloride monomer. Examples of suitable 
comonomers include vinyl esters such as vinyl acetate and vinyl 
propanoate; acrylic acid esters and methacrylic acid esters such as methyl 
acrylate and ethyl acrylate; olefins such as ethylene and propylene; vinyl 
ethers such as lauryl vinyl ether and isobutyl vinyl ether; maleic 
anhydride; acrylonitrile; styrene; vinylidene chloride; and other monomers 
which can copolymerize with vinyl chloride, and these comonomers can be 
used individually or in mixtures of two or more thereof. 
There are no particular restrictions on the suspending agent mentioned 
above, provided it is one of those suspending agents normally used in 
polymerization reactions of vinyl chloride monomer in an aqueous medium, 
and suitable examples include water-soluble cellulose ethers such as 
methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl 
cellulose and hydroxypropyl methyl cellulose; acrylic acid polymer; 
water-soluble polymers such as gelatin; water- or oil-soluble partially 
saponified polyvinyl alcohols; oil-soluble emulsifiers such as sorbitan 
monolaurate, sorbitan trioleate, sorbitan monostearate, glycerin 
tristearate and ethylene oxidepropylene oxide block copolymer; 
water-soluble emulsifiers such as polyoxyethylene sorbitan monolaurate, 
polyoxyethylene glycerin oleate and sodium lauryl sulfate; calcium 
carbonate; calcium phosphate; and sodium dodecyl benzenesulfonate, and 
these suspending agents can be used individually or in mixtures of two or 
more thereof. 
The amount of suspending agent added is normally 0.01 to 0.3 part by 
weight, per 100 parts by weight of the monomer (or monomer mixture) in the 
polymerization vessel, with 0.02 to 0.2 part by weight being preferable. 
The polymerization initiator employed can be any of the water-soluble or 
oil-soluble polymerization initiators currently used in the production of 
vinyl chloride polymers. Examples of suitable oil-soluble polymerization 
initiators include percarbonate compounds such as diisopropyl 
peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate and diethoxyethyl 
peroxydicarbonate; perester compounds such as t-butyl peroxyneodecanoate, 
t-butyl peroxypivalate, t-hexyl peroxypivalate, .alpha.-cumyl 
peroxyneodecanoate, and 2,4,4-trimethylpentyl-2-peroxy-2-neodecanoate; 
peroxide compounds such as acetylcyclohexylsulfonyl peroxide, 
2,4,4-trimethylpentyl-2-peroxyphenoxy acetate, 3,5,5-trimethylhexanoyl 
peroxide, and lauroyl peroxide; and azo compounds such as azo 
bis-2,4-dimethyl valeronitrile, and 
azobis(4-methoxy-2,4-dimethylvaleronitrile). Examples of suitable 
water-soluble polymerization initiators include potassium persulfate, 
hydrogen peroxide, and cumene hydroperoxide. These polymerization 
initiators can be used individually or in mixtures of 2 or more thereof. 
The amount of polymerization initiator added is normally 0.01 to 0.5 part 
by weight per 100 parts by weight of the monomer (or monomer mixture) in 
the polymerization vessel, with 0.02 to 0.3 parts by weight being 
preferable. 
An example of a suitable aqueous medium is deionized water, and this is 
normally added into the polymerization vessel in an amount of 80 to 300 
parts by weight per 100 parts by weight of the monomer (or monomer 
mixture), with 110 to 200 parts by weight being preferable. 
With the method of producing vinyl chloride polymers described in the 
present invention, polymerization-degree adjusters, chain transfer agents, 
pH regulators, gelling improvers, anti-static agents, crosslinking agents, 
stabilizers, fillers, anti-oxidants, buffers, and scale preventive agents 
which are suitable for use in the production of vinyl chloride polymers 
may also be added into the polymerization vessel as required. 
With regard to the polymerization conditions, the polymerization 
temperature is normally in the range of 30.degree. to 70.degree. C., the 
polymerization pressure normally in the range of 3 to 12 kg/cm.sup.2, and 
the polymerization time normally in the range of about 3 to 6 hours. 
EXAMPLES 
The present invention is outlined in more detail below with reference to 
working examples and comparative examples. It should be noted however that 
the present invention is in no way limited to the working examples given 
below. 
Examples 1-5! 
These examples employed, as shown in FIG. 1, a polymerization vessel 6 made 
of a stainless steel having a 2 m.sup.3 internal capacity, equipped with a 
reflux condenser 7, a stirrer 8, and a jacket 9, and with a linearly 
discharging nozzle 1 internal diameter (d) of the discharge portion (1B) 
of the nozzle: shown in Table 1, ratio of the length L of the discharge 
portion 1B to the internal diameter d of the nozzle: shown in Table 1, 
number of nozzles: 1! fitted in the gaseous phase section 14 of the 
vessel. In this polymerization vessel was placed 900 kg of deionized 
water, 390 g of partially saponified polyvinyl alcohol and 420 g of 
t-butyl peroxyneodecanoate. Following evacuation of the polymerization 
vessel, 600 kg of vinyl chloride monomer was then added. Next, with the 
content inside the polymerization being stirred constantly, heated water 
was passed through the jacket, and the temperature of the content was 
raised to initiate polymerization. After a period of 60 minutes 
(temperature of the content: 57.degree. C.) the reflux condenser was 
operated, and heat removal from the content was initiated (heat removal 
rate: 150 Mcal/hour). 
Simultaneously with the operation of the reflux condenser, high pressure 
water was discharged to the content from the nozzle located in the gaseous 
phase section of the polymerization vessel, under the conditions shown in 
Table 1. The intermittent discharging method referred to in Table 1, 
refers to a method whereby discharging of high pressure water was 
commenced at the same time as the reflux condenser was operated, and 
discharging was then continued for one minute, and then halted for 9 
minutes, with this 1 minute discharging--9 minute halt cycle being 
repeated until the polymerization reaction was stopped. 
When the internal pressure of the polymerization vessel dropped to 6.0 
kg/cm.sup.2 (gauge pressure), the polymerization reaction was halted, any 
unreacted monomer recovered, and the vinyl chloride polymer removed from 
the polymerization vessel as a slurry. The water was then removed from 
this polymer slurry, and subsequent drying yielded a powdered vinyl 
chloride polymer. 
Comparative Example 1! 
Polymerization was carried out in the same way as that described in Example 
1, with the exception that no high pressure water discharging was 
conducted, and a powdered vinyl chloride polymer was obtained. 
Comparative Example 2! 
Polymerization was carried out in the same way as that described in Example 
1, with the exception that the pressure of the high pressure water was 
reduced from 300 kg/cm.sup.2 to 10 kg/cm.sup.2, and a powdered vinyl 
chloride polymer was obtained. 
Examples 6-8! 
Polymerization was carried out in the same way as that described in Example 
5, with the exceptions that the anti-foaming agents listed in Table 2 were 
added to the high pressure water, and the internal diameter of the 
discharge portion of the linearly discharging nozzle was reduced to 0.6 
mm, and a powdered vinyl chloride polymer was obtained. 
Example 9! 
Polymerization was carried out in the same way as that described in Example 
6, with the exception that no anti-foaming agents were added to the high 
pressure water, and a powdered vinyl chloride polymer was obtained. 
Examples 10-12! 
Polymerization was carried out in the same way as that described in Example 
6, with the exception that the anti-foaming agents listed in Table 3 were 
not added to the high pressure water, but were instead added directly to 
the inside of the polymerization vessel via the anti-foaming agent 
addition pipe 10 shown in FIG. 1, at the same time as the high pressure 
water discharging (intermittent addition), and in the amounts shown in 
Table 3, and a powdered vinyl chloride polymer was obtained. 
In Examples 1-12 and Comparative Examples 1 and 2 described above, 
following removal of the polymer slurry from the polymerization vessel, 
the internal section of the polymerization vessel which corresponds to the 
gaseous phase section at the polymerization reaction was investigated for 
the remains of splashed polymer, and evaluated by the following judgment 
criteria. The results are shown in Tables 1, 2 and 3. 
Judgment Criteria 
.smallcircle. . . . No splashing of polymer was observed on the inner wall 
of the gaseous phase section of the polymerization vessel. 
.DELTA. . . . A small amount of splashed polymer was observed on the inner 
wall of the gaseous phase section of the polymerization vessel. 
.times. . . . Large amounts of splashed polymer was observed on the inner 
wall of the gaseous phase section of the polymerization vessel, and also 
on the inner wall of the reflux condenser. 
TABLE 1 
______________________________________ 
Internal 
Pressure Flow diameter 
of high rate of Discharging 
of 
pressure high method of discharge 
L/d 
water pressure 
high portion 
ratio 
(kg/ water pressure of nozzle 
of Evalua- 
cm.sup.2) (l/min) water (mm) nozzle 
tion 
______________________________________ 
Exam- 300 10 intermittent 
1.0 3.0 .largecircle. 
ple 1 discharging 
Exam- 200 10 intermittent 
1.1 3.0 .largecircle. 
ple 2 discharging 
Exam- 150 10 intermittent 
1.2 3.0 .largecircle. 
ple 3 discharging 
Exam- 100 10 intermittent 
1.3 3.0 .largecircle. 
ple 4 discharging 
Exam- 50 10 intermittent 
1.5 3.0 .largecircle. 
ple 5 discharging 
Com- -- -- -- -- -- X 
parative 
Exam- 
ple 1 
Com- 10 10 intermittent 
2.2 3.0 X 
parative discharging 
Exam- 
ple 2 
______________________________________ 
TABLE 2 
__________________________________________________________________________ 
Total Total 
Pressure Flow rate 
Discharging 
amount of 
amount 
of high of high 
method of 
high of anti- 
Type of 
pressure pressure 
high pressure 
foaming 
anti- 
water water 
pressure 
water agent foaming 
(kg/cm.sup.2) 
(l/min) 
water discharged(*) 
used(*) 
agent 
Evaluation 
__________________________________________________________________________ 
Example 6 
50 1 intermittent 
3 parts 
1 part 
anti- 
.largecircle. 
discharging 
by weight 
by weight 
foaming 
agent 1 
Example 7 
50 1 intermittent 
3 parts 
0.01 parts 
anti- 
.largecircle. 
discharging 
by weight 
by weight 
foaming 
agent 2 
Example 8 
50 1 intermittent 
3 parts 
0.01 parts 
anti- 
.largecircle. 
discharging 
by weight 
by weight 
foaming 
agent 3 
Example 9 
50 1 intermittent 
3 parts 
none none .DELTA. 
discharging 
by weight 
__________________________________________________________________________ 
In Table 2, (*) refers to the amount of material used by weight, per 100 
parts by weight of monomer. Anti-foaming agent 1 refers to methanol, 
anti-foaming agent 2 to a silicone-based anti-foaming agent KM-72A 
(tradename) produced by Shin-Etsu Chemical Co., Ltd.!, and anti-foaming 
agent 3 to an acetylene alcohol-based anti-foaming agent Surfynol 104 
(tradename) produced by Nisshin Kagaku Co.!. 
TABLE 3 
__________________________________________________________________________ 
Total Total 
Pressure Flow rate 
Discharging 
amount of 
amount 
of high of high 
method of 
high o anti- 
Type of 
pressure pressure 
high pressure 
foaming 
anti- 
water water 
pressure 
water agent foaming 
(kg/cm.sup.2) 
(l/min) 
water discharged(*) 
used(*) 
agent 
Evaluation 
__________________________________________________________________________ 
Example 10 
50 1 intermittent 
3 parts 
0.01 parts 
anti- 
.largecircle. 
discharging 
by weight 
by weight 
foaming 
agent 2 
Example 11 
50 1 intermittent 
3 parts 
0.01 parts 
anti- 
.largecircle. 
discharging 
by weight 
by weight 
foaming 
agent 3 
Example 12 
50 1 intermittent 
3 parts 
0.01 parts 
anti- 
.largecircle. 
discharging 
by weight 
by weight 
foaming 
agent 4 
__________________________________________________________________________ 
In Table 3, (*), anti-foaming agents 2 and 3 are as described above for 
Table 2. Anti-foaming agent 4 is a polyether based anti-foaming agent SN 
defoamer 777 (brand name) produced by Sannopco Co.!. 
Example 13! 
Using the same conditions outlined in Example 1, three consecutive batches 
of polymerization reactions were conducted, and fish eyes in the finally 
obtained polymer powder were measured using the method outlined below. The 
results are shown in Table 4. 
Fish eyes 
A mixture consisting of 100 parts by weight of the product polymer, 1 part 
by weight of tribasic lead sulfate, 1.5 parts by weight of lead stearate, 
0.2 part by weight of titanium dioxide, 0.1 part by weight of carbon 
black, and 50 parts by weight of DOP was kneaded for 3 minutes on a 
145.degree. C. roll. The mixture was then formed into a sheet of thickness 
0.2 mm, and the number of transparent particles per 100 cm.sup.2 of the 
sheet was counted. thickness 0.2 mm, and the number of transparent 
particles per 100 cm.sup.2 of the sheet was counted. 
Examples 14-15, Comparative Example 3! 
The polymer powders were produced in the same manner as that described in 
Example 13, with the exception that the actual polymerization reactions 
were conducted using the same conditions as those outlined in Examples 7 
and 11 and Comparative Example 1 respectively, rather than those of 
Example 1. The polymer powders thus obtained were then measured for fish 
eyes. The results are shown in Table 4. 
TABLE 4 
______________________________________ 
Number of fish 
eyes 
______________________________________ 
Example 13 6 
Example 14 4 
Example 15 7 
Comparative 54 
Example 3 
______________________________________ 
Examples 16-20! 
These Examples employed, as shown in FIG. 2, a polymerization vessel 6 made 
of a stainless steel having a 2 m.sup.3 internal capacity, equipped with a 
reflux condenser 7, a stirrer 8, and a jacket 9, and with a linearly 
discharging nozzle 1 internal diameter (d) of discharge portion (1B): 
shown in Table 5, ratio of the length L of the discharge portion 1B to the 
internal diameter d of the nozzle: shown in Table 5, number of nozzles: 1! 
fitted in the gaseous phase section 14 of the vessel. The polymerization 
vessel 6 was also fitted with an unreacted monomer recovery piping 
arrangement 15 at the top of the gaseous phase section of the vessel. In 
this polymerization vessel was placed 900 kg of deionized water, 390 g of 
partially saponified polyvinyl alcohol and 420 g of t-butyl 
peroxyneodecanoate. Following evacuation of the polymerization vessel, 600 
kg of vinyl chloride monomer was then added. Next, with the content inside 
the polymerization being stirred constantly, heated water was passed 
through the jacket, and the temperature of the reaction mixture was raised 
to 57.degree. C. Polymerization was conducted with the temperature of the 
reaction mixture maintained at a constant 57.degree. C., and when the 
internal pressure of the polymerization vessel dropped to 6.0 kg/cm.sup.2 
(gauge pressure), the polymerization reaction was halted. 
Next, any unreacted monomer was recovered from the polymerization vessel 6 
using the unreacted monomer recovery piping arrangement 15, described 
above. This unreacted monomer recovery was conducted under conditions that 
gave a space linear velocity of 0.15 m/s. Furthermore, high pressure water 
discharging from the nozzle 1 was commenced simultaneously with the start 
of this unreacted monomer recovery, using the conditions outlined in Table 
5. The continuous discharging mentioned in the high pressure water 
discharging method column of Table 5 refers to continuous discharging of 
high pressure water, from the time the unreacted monomer recovery was 
begun, until its completion. Following the recovery of the unreacted 
monomer under these high pressure water discharging conditions, the vinyl 
chloride polymer was removed from the polymerization vessel as a slurry. 
The water was then removed from this polymer slurry, and subsequent drying 
yielded a powdered vinyl chloride polymer. 
Comparative Example 4! 
Polymerization was carried out in the same way as that described in Example 
16, with the exception that no high pressure water discharging was 
conducted at the unreacted monomer recovery step, and a powdered vinyl 
chloride polymer was obtained. 
Comparative Example 5! 
Polymerization was carried out in the same way as that described in Example 
16, with the exception that the pressure of the high pressure water was 
reduced from 300 kg/cm.sup.2 to 10 kg/cm.sup.2, and a powdered vinyl 
chloride polymer was obtained. 
Examples 21-23! 
Polymerization was carried out in the same way as that described in Example 
20, with the exceptions that the anti-foaming agents listed in Table 6 
were added to the high pressure water, the internal diameter of the 
discharge portion of the nozzle was reduced to 0.6 mm, and the discharging 
was conducted intermittently following the method described below, as 
opposed to the previous continuous discharging method, and a powdered 
vinyl chloride polymer was obtained. 
Intermittent discharging 
The high pressure water discharging was commenced simultaneously with the 
commencement of the unreacted monomer recovery step, continued for 1 
minute, and then halted for 1 minute. This 1 minute discharging--1 minute 
rest cycle was continued until the monomer recovery step was completed. 
Example 24! 
Polymerization was carried out in the same way as that described in Example 
21, with the exception that no anti-foaming agent was added to the high 
pressure water, and a powdered vinyl chloride polymer was obtained. 
Examples 25-27! 
Polymerization was carried out in the same way as that described in Example 
21, with the exception that the anti-foaming agents listed in Table 7 were 
not added to the high pressure water, but were instead added directly to 
the inside of the polymerization vessel via the anti-foaming agent 
addition pipe 10 shown in FIG. 2, at the same time as the high pressure 
water discharging (intermittent addition), and in the amounts shown in 
Table 7, and a powdered vinyl chloride polymer was obtained. 
In Examples 16-27 and Comparative Examples 4 and 5 described above, 
following removal of the polymer slurry from the polymerization vessel, 
the internal section of the polymerization vessel which corresponds to the 
gaseous phase section at the polymerization reaction was investigated for 
the remains of splashed polymer, and the splashed polymer was evaluated 
using the judgment criteria described for Examples 1-12. The results are 
shown in Tables 6-8. 
TABLE 5 
______________________________________ 
Internal 
Pressure Flow diameter 
of high rate of Discharging 
of 
pressure high method of discharge 
L/d 
water pressure 
high portion 
ratio 
(kg/ water pressure of nozzle 
of Evalua- 
cm.sup.2) (l/min) water (mm) nozzle 
tion 
______________________________________ 
Exam- 300 10 continuous 
1.0 3.0 .largecircle. 
ple 16 discharging 
Exam- 200 10 continuous 
1.1 3.0 .largecircle. 
ple 17 discharging 
Exam- 150 10 continuous 
1.2 3.0 .largecircle. 
ple 18 discharging 
Exam- 100 10 continuous 
1.3 3.0 .largecircle. 
ple 19 discharging 
Exam- 50 10 continuous 
1.5 3.0 .largecircle. 
ple 20 discharging 
Com- -- -- -- -- -- X 
parative 
Exam- 
ple 4 
Com- 10 10 continuous 
2.2 3.0 X 
parative discharging 
Exam- 
ple 5 
______________________________________ 
TABLE 6 
__________________________________________________________________________ 
Total Total 
Pressure Flow rate 
Discharging 
amount of 
amount 
of high of high 
method of 
high of anti- 
Type of 
pressure pressure 
high pressure 
foaming 
anti- 
water water 
pressure 
water agent foaming 
(kg/cm.sup.2) 
(l/min) 
water discharged(*) 
used(*) 
agent 
Evaluation 
__________________________________________________________________________ 
Example 21 
50 1 intermittent 
0.5 parts 
0.5 part 
anti- 
.largecircle. 
discharging 
by weight 
by weight 
foaming 
agent 1 
Example 22 
50 1 intermittent 
0.5 parts 
0.01 parts 
anti- 
.largecircle. 
discharging 
by weight 
by weight 
foaming 
agent 2 
Example 23 
50 1 intermittent 
0.5 parts 
0.01 parts 
anti- 
.largecircle. 
discharging 
by weight 
by weight 
foaming 
agent 3 
Example 24 
50 1 intermittent 
0.5 parts 
none none .DELTA. 
discharging 
by weight 
__________________________________________________________________________ 
In Table 6, (*) refers to the amount of material used by weight per 100 
parts by weight of monomer. Anti-foaming agent 1 refers to methanol, 
anti-foaming agent 2 to a silicone-based anti-foaming agent KM-72A 
(tradename) produced by Shin-Etsu Chemical Co. Ltd.!, and anti-foaming 
agent 3 to an acetylene alcohol-based anti-foaming agent Surfynol 104 
(tradename) produced by Nisshin Kagaku Co.!. 
TABLE 7 
__________________________________________________________________________ 
Total Total 
Pressure Flow rate 
Discharging 
amount of 
amount 
of high of high 
method of 
high of anti- 
Type of 
pressure pressure 
high pressure 
foaming 
anti- 
water water 
pressure 
water agent foaming 
(kg/cm.sup.2) 
(l/min) 
water discharged(*) 
used(*) 
agent 
Evaluation 
__________________________________________________________________________ 
Example 25 
50 1 intermittent 
0.5 part 
0.01 part 
anti- 
.largecircle. 
discharging 
by weight 
by weight 
foaming 
agent 2 
Example 26 
50 1 intermittent 
0.5 part 
0.01 part 
anti- 
.largecircle. 
discharging 
by weight 
by weight 
foaming 
agent 3 
Example 27 
50 1 intermittent 
0.5 part 
0.01 part 
anti- 
.largecircle. 
discharging 
by weight 
by weight 
foaming 
agent 4 
__________________________________________________________________________ 
In Table 7, (*), anti-foaming agents 2 and 3 are as described above for 
Table 6. Anti-foaming agent 4 is a polyether-based anti-foaming agent SN 
defoamer 777 (tradename) produced by Sannopco Co.!. 
Example 28! 
Using the same conditions outlined in example 16, three consecutive batches 
of polymerization reactions were conducted, and the number of fish eyes in 
the finally obtained polymer powder measured using the method outlined for 
Example 13. The results are shown in Table 8. 
Examples 29-30, Comparative Example 6! 
The polymer powders were produced in the same manner as that described in 
Example 28, with the exception that the actual polymerization reactions 
were conducted using the same conditions as those outlined in Examples 22 
and 26 and Comparative Example 4 respectively, rather than those of 
Example 16. The polymer powders thus obtained were then measured for fish 
eyes. The results are shown in Table 8. 
______________________________________ 
Number of fish 
eyes 
______________________________________ 
Example 28 8 
Example 29 5 
Example 30 6 
Comparative 40 
Example 6 
______________________________________ 
Example 31! 
This Example employed, as shown in FIG. 3, a polymerization vessel 6 made 
of a stainless steel (80 m.sup.3 internal capacity), equipped with a 
reflux condenser 7, a stirrer 8, and a jacket 9, and with a foam sensor 
3A, a foam sensor 3B located 10 cm above the sensor 3A, and a ring pipe 
arrangement 2 to which were fitted linearly discharging nozzles 1 (number 
of nozzles: 4), all fitted in the gaseous phase section of the vessel. The 
linearly discharging nozzles 1 were a linearly discharging nozzle as shown 
in FIG. 4, with an orifice diameter d (here, corresponding to the internal 
diameter d of the discharge portion 1B) of 2.08 mm, and with a ratio of 
the length L of the discharge portion 1B to the orifice diameter d (L/d) 
of 3.0. Furthermore, the foam sensors 3A and 3B were electrostatic 
capacity sensors. 
In this stainless steel polymerization vessel 6 was placed 39 t of 
deionized water, 10.1 kg of partially saponified polyvinyl alcohol and a 
6% by weight aqueous solution of hydroxypropyl methyl cellulose 
(equivalent to 6.7 kg of hydroxypropyl methyl cellulose). Following 
evacuation of the polymerization vessel until the pressure inside had 
fallen to 50 mmHg (absolute pressure), 28 t of the vinyl chloride monomer 
was added. Next, with the content inside the polymerization vessel being 
stirred constantly, the polymerization reaction was initiated by 
introducing 12.6 kg of t-butyl peroxyneodecanoate and 7.0 kg of cumyl 
peroxydecanoate into the polymerization vessel under pressure, and 
simultaneously passing heated water through the jacket to raise the 
temperature of the content. When the temperature of the content reached 
the pre-set polymerization temperature of 56.degree. C., cooling of the 
content was commenced by passing cooling water through the jacket. 
(1) High pressure water discharging at operation of the reflux condenser 
When the polymerization conversion reached 5%, cooling water was passed 
through the reflux condenser, commencing the process of heat removal from 
the content of the polymerization vessel. The rate of heat removal by the 
reflux condenser was increased as the polymerization reaction proceeded, 
to a maximum of 1600 Mkal/hr. At the point where the polymerization 
conversion reached 65%, the sensor 3A detected the presence of foam. One 
minute after this detection of foam by the sensor 3A, high pressure water 
discharging pressure: 100 kg/cm.sup.2 ! from the linearly discharging 
nozzles 1 was commenced (In Table 9, the pressure of the high pressure 
water is listed as the discharge pressure. Hereafter all tables follow 
this labeling convention). Within 1 minute of the commencement of high 
pressure water discharging, the foam had broken up, and even sensor 3A 
could no longer detect the presence of any foam. The high pressure water 
discharging was continued from this point, without interruption until the 
polymerization was completed (In Table 9 this is referred to as continuous 
discharging. This labeling convention is also followed in Table 11 below). 
(2) High pressure water discharging at recovery of the unreacted monomer 
When the pressure inside the polymerization vessel had fallen to 6.0 mmHg 
(absolute pressure) a polymerization stopper was introduced into the 
vessel under pressure, to terminate the polymerization reaction. Recovery 
of the unreacted monomer was then commenced via the polymerization vessel 
recovery pipe 15 (recovery rate: 60 Nm.sup.3 /min). Ten minutes after the 
commencement of monomer recovery, the foam sensor 3A detected the presence 
of foam. One minute after this detection of foam by the sensor 3A, high 
pressure water discharging pressure: 100 kg/cm.sup.2 ! from the linearly 
discharging nozzles 1 was commenced. Within 30 seconds of the commencement 
of high pressure water discharging, the foam had broken up, and even 
sensor 3A could no longer detect the presence of any foam. The high 
pressure water discharging was continued from this point, without 
interruption until the recovery of unreacted monomer was completed (In 
Table 9 this is referred to as continuous discharging. The same labeling 
convention is also used in Table 12 below). 
Following recovery of the unreacted monomer, the vinyl chloride polymer was 
removed from the polymerization vessel as a slurry. The internal surface 
of the polymerization vessel was then visually inspected, and the amount 
of splashed polymer on the inner wall of the vessel was evaluated using 
the following criteria. The results are shown in Table 9. 
Evaluation criteria 
.smallcircle. . . . No splashing of polymer was observed on the inner wall 
of the gaseous phase section of the polymerization vessel. 
.times. . . . Large amounts of splashed polymer was observed on the inner 
wall of the gaseous phase section of the polymerization vessel, and also 
on the inner wall of the reflux condenser. 
.times..times. . . . Large amounts of splashed polymer was observed on the 
inner wall of the gaseous phase section of the polymerization vessel and 
the inner wall of the reflux condenser, and also inside the unreacted 
monomer recovery line. 
The water was then removed from the polymer slurry, and the slurry was 
dried to give a powdered vinyl chloride polymer. The number of fish eyes 
in the polymer product thus obtained was counted via the method outlined 
in Example 13. The results are shown in Table 9. 
Next, a batch polymerization was carried out, in exactly the same way as 
the polymerization above, with the exception that the polymerization 
vessel was used immediately following the removal of the product polymer 
above. The number of imperfections in 100 g of the powdered vinyl chloride 
polymer obtained from the batch polymerization was then measured. The 
results are shown in Table 9. 
Examples 32 and 33! 
Polymerization was carried out in the same way as that described in Example 
31, with the exceptions that the nozzles used, the number of nozzles, the 
pressure of the high pressure water, the total volume of water discharged, 
and the discharging times for (1) the high pressure water discharging 
conducted at the reflux condenser operation, and (2) the high pressure 
water discharging conducted at the unreacted monomer recovery, were set as 
shown in Table 9. Following removal of the polymer, the amount of polymer 
splashed over the inner wall of the polymerization vessel, the number of 
imperfections in the product polymer, and the number of fish eyes present 
in formed items manufactured from the polymer were evaluated in the same 
manner as described in Example 31. The results are shown in Table 9. 
TABLE 9 
______________________________________ 
Example 31 
Example 32 
Example 33 
______________________________________ 
Nozzle 
Type Linearly Linearly Linearly 
discharging 
dischargimg 
discharging 
nozzle nozzle nozzle 
Orifice diameter (mm) 
2.08 3.30 1.70 
Number of nozzles 
4 2 6 
L/d ratio 3.0 3.0 3.0 
Discharging at condenser 
operation 
Maximum heat removal rate 
1600 1600 1600 
(Mcal/hr) 
Polymerization conversion 
65 65 65 
(%) at foam detection 
(sensor 3A) 
Discharge pressure (kg/cm.sup.2) 
100 80 140 
Discharging method 
continuous 
continuous 
continuous 
discharging 
discharging 
discharging 
Total volume of water 
3.7 3.9 4.3 
discharged (m.sup.3) 
Discharging time 
35 min 34 min 34 min 
Discharging at unreacted 
monomer recovery 
Monomer recovery rate 
60 60 60 
(Nm.sup.3 /min) 
Time elapsed since monomer 
5 min 5 min 5 min 
recovery commencement at 
foam detection (sensor 3A) 
Discharge pressure (kg/cm.sup.2) 
100 80 140 
Discharging method 
continuous 
continuous 
continuous 
(discharging repetitions) 
discharging 
discharging 
discharging 
Total volume of water 
2.2 2.3 2.5 
discharged (m.sup.3) 
Discharging time 
20 min 20 min 20 min 
Splashing of polymer over 
the gaseous phas section etc., 
.largecircle. 
.largecircle. 
.largecircle. 
of the vessel 
Fish eyes (number) 
3 2 4 
Imperfections (number) 
6 8 6 
______________________________________ 
In Table 9, the discharge pressure refers to the gauge pressure measured at 
the pump discharge outlet. 
Examples 34-39! 
Polymerization was carried out in the same way as that described in Example 
31, with the exceptions that the discharging processes were conducted as 
described in (1) and (2) below. 
(1) High pressure water discharging at operation of the reflux condenser 
This discharging process was carried out in the same way as that described 
in Example 31 with the exceptions that the nozzles used, the number of 
nozzles, the pressure of the high pressure water, the total volume of 
water discharged, and the discharging times were set as shown in Table 10, 
and that instead of continuous discharging, the intermittent discharging 
method detailed below was used. In Example 37, forty five seconds after 
commencing the first discharging of this discharging process, the foam 
sensor 3A could no longer detect any foam. In Example 38, seventy five 
seconds after commencing the first discharging, the foam sensor 3A could 
no longer detect any foam. In Example 39, two minutes after commencing the 
first discharging, the foam sensor 3A could no longer detect any foam. 
Intermittent discharging 
High pressure water discharging was commenced one minute after the foam 
sensor 3A detected foam, and even if foam detection by the foam sensor 3A 
ceased, the discharging was continued for a period of two minutes and then 
halted. When the foam sensor 3A re-detected the presence of foam, the 
above procedure was repeated with discharging commencing one minute after 
the detection. This cycle of discharging--halt of discharging was repeated 
until the polymerization was completed. 
(2) High pressure water discharging at the unreacted monomer recovery step 
This discharging process was carried out in the same way as that described 
in Example 31 with the exceptions that the pressure of the water, the 
total volume of water discharged, and the discharging times were set as 
shown in Table 10, and that instead of continuous discharging, the 
intermittent discharging method detailed above was used. In Example 37, 
twenty seconds after commencing the first discharging of this discharging 
process, the foam the sensor 3A could no longer detect any foam. In 
Example 38, forty seconds after commencing the first discharging of this 
process, the foam sensor 3A could no longer detect any foam. In Example 
39, one minute after commencing the first discharging of this process, the 
foam sensor 3A could no longer detect any foam. 
Following recovery of the unreacted monomer, the polymer was removed from 
the polymerization vessel, and the amount of polymer splashed over the 
inner wall of the polymerization vessel, the number of imperfections in 
the product polymer, and the number of fish eyes present in formed items 
manufactured from the polymer were evaluated in the same manner as 
described in Example 31. The results are shown in Table 10. 
TABLE 10 
__________________________________________________________________________ 
Example 34 
Example 35 
Example 36 
Example 37 
Example 38 
Example 39 
__________________________________________________________________________ 
Nozzle 
Type Linearly 
Linearly 
Linearly 
Linearly 
Linearly 
Linearly 
discharging 
discharging 
discharging 
discharging 
discharging 
discharging 
nozzl nozzle 
nozzle 
nozzle 
nozzle 
nozzle 
Orifice diameter (mm) 
2.08 330 1.70 2.08 2.08 2.08 
Number of nozzles 
4 2 6 4 4 4 
L/d ratio 3.0 3.0 3.0 5.0 1.5 3.0 
Discharging at condenser 
operation 
Maximum heat removal 
1600 1600 1600 1600 1600 1600 
rate (Mcal/hr) 
Polymerization 
65 65 65 65 65 65 
conversion (%) at time 
of foam detection 
(sensor 3A) 
Discharge pressure 
100 80 140 100 100 50 
(kg/m.sup.2) 
Discharging method 
intermittent 
intermittent 
intermittent 
intermittent 
intermittent 
intermittent 
(discharging 
discharging 
discharging 
discharging 
discharging 
discharging 
discharging 
repetitions) 
(7 times) 
(8 times) 
(8 times) 
(6 times) 
(8 times) 
(15 times 
Total volume of water 
1.5 1.8 2.0 1.3 1.7 2.3 
discharged (m.sup.3) 
Discharging time 
2 min .times. 7 
2 min .times. 8 
2 min .times. 8 
2 min .times. 6 
2 min .times. 8 
2 min .times. 1 
Monomer recovery rate 
60 60 60 60 60 60 
(Nm.sup.3 /min) 
Discharging at unreacted 
monomer recovery 
Time elapsed since 
5 min 5 min 5 min 5 min 5 min 5 min 
monomer recovery 
commencement at foam 
detection (sensor 3A) 
Discharge pressure 
100 80 140 100 100 50 
(kg/m.sup.2) 
Discharging method 
intermittent 
intermittent 
intermittent 
intermittent 
intermittent 
intermittent 
(discharging 
discharging 
discharging 
discharging 
discharging 
discharging 
discharging 
repetitions) 
(5 times) 
(6 times) 
(6 times) 
(5 times) 
(6 times) 
(8 times) 
Total volume of water 
1.1 1.4 1.5 1.1 1.3 1.2 
discharged (m.sup.3) 
Discharging time 
2 min .times. 5 
2 min .times. 6 
2 min .times. 6 
2 min .times. 5 
2 min .times. 6 
2 min .times. 8 
Splashing of polymer 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
over the gaseous phase 
section etc., of the 
vessel 
Fish eyes (number) 
2 3 2 2 4 6 
Imperfections (number) 
7 8 9 6 9 10 
__________________________________________________________________________ 
In Table 10, the discharge pressure refers to the gauge pressure measured 
at the pump discharge outlet. 
Comparative Examples 7-11! 
(1) High pressure water discharging at operation of the reflux condenser 
This discharging process was carried out in the same way as that described 
in Example 31 with the exceptions that the nozzles used, the number of 
nozzles, the total volume of water discharged, and the discharging times 
were set as shown in Table 11. The high pressure water discharging angles 
for the full cone nozzles, the flat nozzles and the hollow cone nozzles 
were 30 degrees discharging conditions: discharging at atmospheric 
pressure, discharging pressure 50 kg/cm.sup.2 (guage pressure)!. The 
result for Comparative Example 7 was that three minutes after commencing 
discharging, foam was already detected by the foam sensor 3B, and this 
foam continued to be detected thereafter. Comparative Example 8 gave a 
similar result with foam being continuously detected by the foam sensor 3B 
five minutes after commencing discharging. Comparative Example 9 also gave 
a similar result with foam being continuously detected by the foam sensor 
3B six minutes after commencing discharging. Comparative Example 10 also 
gave a similar result with foam being continuously detected by the foam 
sensor 3B five minutes after commencing discharging. Comparative Example 
11 also gave a similar result with foam being continuously detected by the 
foam sensor 3B three minutes after commencing discharging. 
(2) High pressure water discharging at the unreacted monomer recovery step 
When in Example 31, the recovery rate of the unreacted monomer was changed 
from 60 Nm.sup.3 /min to 30 Nm.sup.3 /min, the foam sensor 3A did not 
detect any foam until after recovery of the unreacted monomer. Hence high 
pressure water discharging was not carried out. 
Following recovery of the unreacted monomer, the polymer was removed from 
the polymerization vessel, and the amount of polymer splashed over the 
inner wall of the polymerization vessel, the number of imperfections in 
the product polymer, and the number of fish eyes present in formed items 
manufactured from the polymer were evaluated in the same manner as 
described in Example 31. The results are shown in Table 11. 
TABLE 11 
__________________________________________________________________________ 
Comparative 
Comparative 
Comparative 
Comparative 
Comparative 
Example 7 
Example 8 
Example 9 
Example 10 
Example 11 
__________________________________________________________________________ 
Nozzle 
Type full cone 
full cone 
flat flat hollow cone 
nozzle 
nozzle 
nozzle 
nozzle 
nozzle 
Orifice diameter (mm) 
2.30 3.60 2.16 3.30 3.60 
Number of nozzles 
4 4 4 2 2 
L/d ratio -- -- -- -- -- 
Discharging at condenser 
operation 
Maximum heat removal 
1600 1600 1600 1600 1600 
rate (Mcal/hr) 
Polymerization 
65 65 65 65 65 
conversion (%) at foam 
detection (sensor 3A) 
Discharge pressure 
100 100 100 100 100 
(kg/cm.sup.2) 
Discharging method 
continuous 
continuous 
continuous 
continuous 
continuous 
discharging 
discharging 
discharging 
discharging 
discharging 
Total volume of water 
3.3 7.4 3.9 4.4 4.2 
discharged (m.sup.3) 
Discharging time 
35 min 
34 min 
35 min 
35 min 
35 min 
Discharging at unreacted 
monomer recovery 
Monomer recovery rate 
30 30 30 30 30 
(Nm.sup.3 /min) 
Time elapsed since 
-- -- -- -- -- 
monomer recovery 
commencement at foam 
detection (sensor 3A) 
Discharge pressure 
-- -- -- -- -- 
(kg/cm.sup.2) 
Discharging method 
-- -- -- -- -- 
(discharging 
repetitions) 
Total volume of water 
0 0 0 0 0 
discharged (m.sup.3) 
Discharging time 
0 0 0 0 0 
Splashing of polymer 
X X X X X 
over the gaseous phase 
section etc., of the 
vessel 
Fish eyes (number) 
50 80 70 60 65 
Imperfections (number) 
30 43 40 35 46 
__________________________________________________________________________ 
In Table 11, the discharge pressure refers to the gauge pressure measured 
at the pump discharge outlet. 
Comparative Examples 12-15! 
(1) High pressure water discharging at operation of the reflux condenser 
With these Comparative Examples, when the maximum heat removal rate of the 
reflux condenser of 1600 Mkal/hr in Example 31 was changed to 1000 
Mkcal/hr, the foam sensor 3A did not detect any foam up until completion 
of polymerization. Hence high pressure water discharging was not carried 
out. 
(2) High pressure water discharging at the unreacted monomer recovery step 
This discharging process was carried out in the same way as that described 
in Example 31 with the exceptions that the pressure of the high pressure 
water, the nozzles used, the number of nozzles, the total volume of water 
discharged, and the discharging times were set as shown in Table 12. The 
full cone nozzles, flat nozzles and hollow cone nozzles used were the same 
as those used in Comparative Examples 7-11. The result for Comparative 
Example 12 was that five minutes after commencing discharging, foam was 
already detected by the foam sensor 3B, and this foam continued to be 
detected thereafter. Comparative Example 13 gave a similar result with 
foam being continuously detected by the foam sensor 3B eight minutes after 
commencing discharging. Comparative Example 14 also gave a similar result 
with foam being continuously detected by the foam sensor 3B five minutes 
after commencing discharging. Moreover with Comparative Example 14, ten 
minutes after commencing discharging the recovery pipe 15 was clogged, so 
that the recovery of unreacted monomer was halted, and the high pressure 
water discharging was also stopped. Comparative Example 15 also gave a 
similar result with foam being continuously detected by the foam sensor 3B 
four minutes after commencing discharging. Moreover with Comparative 
Example 15, eight minutes after commencing discharging the recovery pipe 
15 was clogged, so that the recovery of unreacted monomer was halted, and 
the high pressure water discharging was also stopped. 
Following halting the recovery of the unreacted monomer, the polymer was 
removed from the polymerization vessel, and the amount of polymer splashed 
over the inner wall of the polymerization vessel, the number of 
imperfections in the product polymer, and the number of fish eyes present 
in formed items manufactured from the polymer were evaluated in the same 
manner as described in Example 31. The results are shown in Table 12. 
TABLE 12 
______________________________________ 
Compara- 
Compara- Compara- Compara- 
tive Ex- 
tive Ex- tive Ex- tive Ex- 
ample 12 
ample 13 ample 14 ample 15 
______________________________________ 
Nozzle 
Type full cone 
flat flat flat 
nozzle nozzle nozzle nozzle 
Orifice diameter (mm) 
3.60 2.16 2.16 2.16 
Number of nozzles 
4 4 4 4 
L/d ratio -- -- -- -- 
Discharging at condenser 
operation 
Maximum heat removal 
1000 1000 1000 1000 
rate (Mcal/hr) 
Polymerization 
-- -- -- -- 
conversion (%) at foam 
detection (sensor 3A) 
Discharge pressure 
-- -- -- -- 
(kg/cm.sup.2) 
Discharging method 
-- -- -- -- 
Total volume of water 
0 0 0 0 
discharged (m.sup.3) 
Discharging time 
0 0 0 0 
Discharging at unreacted 
monomer recovery 
Monomer recovery rate 
60 60 60 60 
(Nm.sup.3 /min) 
Time elapsed since 
5 5 5 5 
monomer recovery 
commencement at foam 
detection (sensor 3A) 
Discharge pressure 
100 100 100 100 
(kg/cm.sup.2) 
Discharging method 
continuous 
continuous 
continuous 
continuous 
(discharging discharg- 
discharg- 
discharg- 
dischargin 
repetitions) ing ing ing 
Total volume of water 
4.3 2.2 3.1 0.9 
discharged (m.sup.3) 
Discharging time 
20 min 20 min *15 min 
*12 min 
Splashing of polymer 
XX XX XX XX 
over the gaseous phase 
section etc., of the 
vessel 
Fish eyes (number) 
13 10 9 11 
Imperfections (number) 
40 45 50 47 
______________________________________ 
In Table 12, the discharge pressure refers to the gauge pressure measured 
at the pump discharge outlet. The discharging times with * indicate the 
time at which the recovery operation was stopped due to being unable to 
recover the unreacted monomer.