Note: Descriptions are shown in the official language in which they were submitted.
1~91~3
S P E C I ~ I C ~ T I 0 N
.
The inverltion relates to a method of dega~sin~
polymers and copolymers prepared by mass polymerizincJ a
monomeric composition based on vinyl chloride and to pol~ers
and copolymers containing a small proportion of residual
monomeric vinyl chloride obtained ~y the method.
The presence of residual monomeric vinyl chloride in
polymers and copolymers based on vinyl chloride has disadvan-
tages, including the following: the danger of producing
mixtures which explode with ambient air, the danger of contam-
inating the air in workshops where the polymers and copolymers
are handled, and the danger of microbubbles being present in
finished articles prepared from the polymers or copolymers.
Thus attempts are being made to minimize the content of residual
monomeric vinyl chloride.
In the preparation of ~olymers and copo~ymers based
on ~inyl chloride in a mass, when the conversion of the mono-
meric composition has reached the desired degree, a polymer is
obtained which then undergoes degassification designed to re-
move the unreacted monomer from the poly~ers or copolymers.
The degassing treatment is carried out with agita-
tion. The monomeric composition to be eliminated is brough.
~rom polymerization pressure to a pressure generally within the
range of 50 to 180 mm of mercury; the polymer is brought to or
kept at a temperature of at least 70C. and below ths temper-
ature at which degradation of the polymer or copolymer com-
m~nces, and these pressure and temperature conditivns are
maintained until the end of the degassing process.
The degassing time varies generally from 60 to 120
minutes. It is obviously longer, the lower the degassing rate
3 of~tlle monomeric composition. The degassing rate is controlled
-1- ~
11`09~93
so that the monomeric composition to he eliminatcd cnn bc bro~lght from
polymerization pressure to a pressure of about 4 bars in 2n to 60 minutcs.
Below this approximate pressure level the degassing rate of the monomeric
composition is higher - all other things being equal - the higher the
temperature of the polymer. In practice, the polymer is heated as soon as
the degassing process starts, so that it can, where appropriate, be brought
rapidly to the temperature stipulated or so that it can be kept there.
When the degassing process has stopped, the polymers or copolymers
are brought to atmospheric pressure by means of nitrogen before being placed
in open air. This step is generally followed by a screening operation
designed to eliminate coarse particles.
The polymers and copolymers obtained contain at least 80 ppm
and generally from 100 to 500 ppm of residual monomeric vinyl chloride.
There is known a method of degassing polymers and copolymers,
prepared by mass polymerizing a monomeric composition based on vinyl
chloride. The products obtained from this process have a residual monomeric
vinyl chloride content which is less than 50 ppm, generally less than 20
ppm and which may be as little as 1 ppm. The process, during which the
polymer is kept under agitation, comprises bringing the monomeric composition
to be eliminated from polymerization pressure to a pressure below 120 mm
of mercury, bringing the polymer to or keeping it at a temperature of at
least 70C. and below the temperature at which degradation of the polymer
or copolymer commences, and maintaining these
- 2 -
~ ~ .
11~91~3
conditions o~ pressure and temperature suhstantic:lly un~ h~
degassing process stops; the degassing rate of the ~nonomcric
composition is controlled so that the time taken to brin~ t~c
monomeric composition to be eliminated from polyr~lerization
pressure to a p essure of 4 bars is less than 10 minutes.
When the degassing process has stopped, the polymers
or copolymers are brought to atmospheric pressure by means of
an inert gas such as nitrogen, before being placed in open air.
This step is generally followed by a screening operation de-
signed to eliminate coarse particles.
Applicants have now disco~ered that polymers or co-
polymers degassed by the methods described above have a resid-
ual monomeric vinyl chloride content of over 300 ppm, after
the degassing process has stopped but before they are placed
i~ open air. With the described method, the drop in the
content of residual monomeric vinyl chloride to levels below
300 ppm or even to 50 ppm or as little as 1 ppm, which risks
contaminating ambient air, thus takes place when the polymers
or copolymers have been placed in open air and particularly
during the conveying and screening operations.
Before they are placed in open air, polymers and co-
polymers degassed by the method of the invention have a resid-
ual monomeric vinyl chloride content which is less than 50
ppm, generally less than 20 ppm and may be as little as l ppm.
The method or the invention, for degassing polymers
ar.d copolyme~s prepared by polymerizing a monomeric composi
tion based on ~inyl chloride in a mass, comprises keeping the
polymer under agitation, bringing the monomeric composition i:o
be eliminated ~rom polymeri~ation pressure to a press-lre below
3 1~0 mm of mercurv, bringing the polymer to or keeping it at a
~:109~93
.emperature of at least 70C. and beJow the temp~at:tlrc ~t
which degradation of the polymer or copolymer comm~nces, cln~
maintaining these conditions of pressure and tcmpcrature sub-
stantially until the degassing process stops, the ~olymer be-
ing put into contact with a quantity of water representirlg
0.01 to 0.8% and preferably 0.05 to 0.5% of its weight, after
the residual monomeric vinyl chloride content of the polymer or
copolymer has been reduced below 2000 ppm.
Applicants have in fact made the surprising discovery
that a small quantity of water put into contact with the
polymer, under the conditions according to the invention, made
the degassing process more efficient. The water may be added
to the polymer in one or more stages.
In a modified embodiment of the invention, the
pol~mer is put into contact with an inert gas such as nitrog2n
during the degassing process and after the monomeric composi-
tion to be eliminated has been brought to a pressure below 120
mm of mercury. The inert gas may be added to the polymer in
one or more stages.
In order to reduce the degassing time, it is obvious-
ly advantageous to heat the polymer right from the beginning
of the degassing process. Degassing then generally takes from
60 to 120 minutes. When the process has stopped, the polymers
or copolymers are brought to atmospheric pressure by introduc-
ing an inert gas, such as nitrogen, before placing them in
open air.
Some exc~mPles will now be given of the preparation
of polymers and copolymers based on vinyl chlori~e in 2 mass,
and of the application of the degassing procecs according to
the invention. The AF~OR viscosity index of t,he polymers and
c
--4
ll~91g3
copolymers is aetermined in accordance witll NFT ~t:~n~l~rd SL ~l3.
ExamPle 1
This example is given as a comparison.
2200 kg of vinyl chloride is placed in a pre-poly-
merizer having a capacity of 3.5 m3, made of stainless steeland e~uipped with a tur~ine agitator, and the apparatus is
purged by degassing 200 kg of vinyl chloride. 41.7 g of
acetylcyclohexane sulphonyl peroxide, corresponding to 3 g of
active oxygen, and 189 g of ethyl peroxydicarbonate~ corres-
ponding to 17 g of active oxygen, are also fed in. The agitat-
ing speed is set to l~0 R.P.M.
q~e temperatuxe of the reaction medium in the pre-
polymerizer is brought to and kept at 69C., corresponding to
a relative pressure of 11.5 bars in the pre-polymerizer.
After 25 ninutes of pre-polymerizatio~, the conver
BiOn rate being approximately 12%, the pre-polymer is transfer-
red to a vertical polymerizer with a capacity of 8 m3, made of
J stainless steel and equipped with a double jacket. It has
been purged, at a preliminary stage, by degassing 200 kg of
vinyl chloride and now contains 2000 ~g of viny' chloride,
3.33.5 y cf ethyl peroxydicarbonate, corresponding to 12 g of
active oxygen, and 1368 g of lauroyl peroxide, corresponding
to 55 g of active oxygen. The polymerizer is equipped with a
helical ribbon agitator. Agitating speed is set to 30 R.P.M.
The temperature of the reaction medium is brought rapidly to
69C. and kept there; this corresponds to a relative pressure
of 11.5 bars in the pol~nerizer.
After 3.5 hours of pol~nerization at 69C.~ the tem-
perature of the watex circulating in the double jacket of the
3~ pol~ erizer is brought to 75C. arld the polymer is deyassed.
~1it)9193
The monomer is recovered in a tan~ set asidc for ~lc yurpos~
containing monomer at an absolute pressure of 4 bars.
The monomer to be eliminated is first brought to an
absolute pressure of 4 bars by direct degassing in 50 minutes,
then a compressor is used to bring it to a pressure of 1]0 mm
of mercury, and that pressure is maintained until the degassing
process has stopped.
The temperature of the polymer had risen to 75C.
five minutes after the water had been put into circulation at
75C. in the double jacket of the polymerizer. It is now kept
at 75C~ until degassing is over. The degassing process takes
120 minutes.
After the polymer has been degassed and the vacuum
broken by the introduction of nitrogen, the polyvinyl chloride
present in the polymerizer is found to contain 350 ppm of
residual monomeric vinyl chloride.
2760 kg of polyvinyl chloride with an AFNOR viscosity
index of 78 is collected. The proportion of polymer passing
through a screen, with a mesh size of 630 microns, represents
97% by weight, has an apparent weight per unit volume of 0.59
g/cm3 and has a grain-size distribution with an average dia-
~eter of 110 microns.
Example 2
Polymerization conditions are identical with those in
example 1.
After 3.5 hours o~ polymerization at 69C., the tem-
pexature of the water circulating in the double jacket of the
polynlerizer is brought to 75C. and the polymer is degassed.
The monomer is recovered in the tanX set aside for the purpose,
3 con~aining monomer at an absolute pressure oE 4 bars.
11C~9193
The moncm~r to be eliminated is ~irst IJLOU~J~It ~0 an
absolute pressure of 4 bars by direct degassing in 50 minutes,
then it is brought to a pressure of llO mm of mercury with the
compressor used in example l.
When the residual monomeric vinyl chloride content
of the polymer present in the polymerizer drops below 2000 ppm,
30 minutes after the compressor has been set in operation, 0.5
kg of water is fed into the polymerizer. The pressure in the
polymerizer is returned to llO mm of mercury and kept at that
level until the degassing process has stopped.
The temperature of the polymer, which had risen to
75C. five minutes after the water was put into circulation at
75C. in the double jacket of the polymerizer, is now kept at
75~C. until degassing is over. The degassing process takes 120
minutes.
When the polymer has been degassed and the vacuum
broken by the introduction of nitrogen, the polyvinyl chloride
present in the polymerizer is found to contain 3 ppm of resid-
ual monomeric vinyl chloride.
2800 kg of polyvinyl chloride, with an AF~oæ viscos-
ity index of 78, is collected. The proportion of polymer
passing through a screen, with a mesh size of 630 microns,
represents 97% by weight and has an apparent weight per unit
volume of 0.60 g/cm3 and a grain size distribution with an
average diameter of 108 microns.
Example 3
This ex-ample is given as a comparison.
8250 kg of vinyl chloride is fed into a pre-poly-
merizer with a capacity of 14 m3, made of stainless steel 3nd
equipped with a turhine agitacor, and the apparatus is purged
1~9193
by degassing 1000 kg of vinyl chloride. 417 g of ace~ylc~c~
hexane sulphonyl peroxide, corresponding to 30 g o actl~
oxygen, and 779 g of ethyl pero~ydicarbonate, correspondin~ o
70 g of active oxygen, are also introduced. The a~itating
speed is set to 75 R.P.M.
The temperature of the reaction medium in the pre-
polymerizer is brought to 70C~ and kept there; thi3 corres-
ponds to a relative pressure of 11.5 bars in the pre-pol~ner-
izer.
After 10 minutes of pre-polymerization, the conver-
sion rate being approximately 10%, the pre-polymer is trans-
ferred to a horizontal polymerizer with a capacity of 25 m3,
made of stainless steel and equipped with a double jacket. The
polymerizer has been purged at a previous stage by degassing
1000 kg of vinyl chloride and now contains 5750 kg of vinyl
chloride, 1931 g of acetylcyclohexane sulphonyl peroxide, cor-
responding to 139 g of active oxygen, and 1524 g of ethyl
peroxydicarbonate, corresponding to 137 g of active oxygen.
The polymerizer is equipped with an agitator of the frame type.
Agitating speed is set to 8 R.P.M. The temperature or the re-
action medium is brought rapidly to 55C. and kept there; this
corresponds to a relative pressure of 8.1 bars in the poly-
merlzer .
After 4.25 hours of polymerization at 55C. the te~-
perature of the water circulating ir. the double jacket of thepolymerizer is brought to 80C. and the polyrer is degassed.
The monomer is recovered in a tank set aside for the purpose,
containing the monomer at an absGlute pressure of 4 bars.
The monomer to be eliminated is first brought to a
3 pre~sure of 4 bars by direct degassing in 50 minutes, then
-8-
193
brought to a pressure of 100 mm of merc~lr~ with a comprcssor
The absolute pressure in the polymeriz~r is brought
to 1 bar by a first introduction of nitrogcn, then a vacuum
pump with its output directed to an adjoining tank is used to
bring the absolute pressure in the polymerizer to 60 mm of
mercury.
The absolute pressure in the polymerizer is restored
to 1 bar by a second introduction of nitrogen, and is then re-
turned to 60 mm of mercury by means of the vacuum pump.
The temperature of the pol~ner rose to 80C. ten
minutes after water at 80C. had been put into circulation in
the double jacket of the polymerizer. It is now kept at 80C.
until degassing is over. The degassing process lasts 120
minutes.
~5 When the pol~ner has ~een de~assed and the vacuum
broken by the introduction of nitrogen, the polyvinyl chloride
present in the polymerizer is found to contain 320 ppm of rcsi~
ual monomeric vinyl chloride.
11200 kg of polyvinyl chloride, with an AFNOR vis-
cosity index of 109, is collected~ The proportion of polymer
passing through a screen with a mesh size of 630 microns rep-
resents 99% by weight and has an apparent weight per unit
volume of 0.60 g/cm3 and a grain siæe distribution with an
average diameter of 145 microns.
_x n~ple 4
.
Polymerization conditions are identical with those
in example 3.
After 4.25 hours of polymerization at 55C., the tem-
perature of the water circulating in the double jacket of tne
3C pol~meri~er i5 brought to 80C. and the polymer is degassed.
_g_
9193
The monomer is recovered irl the tarlk ~t aside Ço~ th~ purpose,
containing monomer at an absolute pressure of 4 bars.
The monomer to be eliminated is first brollght to ~n
absolute pressure of 4 bars by direct degassing in 50 minutcs,
and is then brought to a pressure of 100 mm of mercury with
the compressor used in example 3.
When the residual monomeric vinyl chloride content o~
the polymer in the polymerizer drops below 2000 ppm (this hap-
pens 30 minutes after the compressor has been set in action),
80 kg of water is fed into the polymerizer.
Absolute pressure in the polymerizer is brought to 1
bar with a first introduction of nitrogen~ then to 60 mm of
mercury by means of the vacuum pump used in example 3, with its
output directed to an adjoining tank.
Pbsolute pressure in the polymerizer is brought to 1
bar by a second introduction of nitrogen, then returned to 60
mm of mercury by means of the vacuum pump.
The temperature of the polymer, which rose to 80C.
ten minutes after water at 80C. had been put into circulation
in the double jacket of the polymerizer, is now kept at 80C.
until degassing is over. The degassing process takes 120
minutes.
After the polymer has been degassed and the vacuum
broken by the introduction of nitrogen, the polyvinyl chloride
in the polymerizer is found to contain 1 ppm of residual mono-
meric vinyl chloride.
11200 Xg of polyvinyl chloride3 with an A~NOR vis-
cosit~ index of 109, is collected. The proportion of polymer
passing through a screen with a mesh size of 630 microns rep-
3 resents 99~/O ~y weight and has an apparent weight per unit
--10--
91~3
volume of 0.60 g/cm3 and a grain size distribution with an
average diameter of 145 microns.
Example 5
This example is given as a comparison.
The pre-polymerîzer used has a capacity of 200 liters
and is made of stainless steel and equipped with an agitator,
comprising a turbine of the "Lightnin" type with 6 flat blades
- 215 mm in diameter. 133 kg of vinyl chloride is placed in the
polymerizer and the apparatus is purged by degassing 10 kg of
vinyl chloride. 2 kg of vinyl acetate, 11.1 g of acetylcyclo-
hexane sulphonyl peroxide, corresponding to 0.8 g of active
oxygen, and 7.8 g of ethyl peroxydicarbonate, corresponding to
0.7 g of active oxygen, are also introduced. The agitating
speed is set to 400 R.P.M.
The temperature of the reaction medium in the pre-
polymerizer is brought to 70C. and kept there; this corres-
ponds to a relative pressure of 11.3 bars in the pre-polymer-
izer.
After 20 minutes of pre-polymerization~ the conver-
sion rate being approximately 10%~ the pre-polymer is transfer-
red to a vertical polymerizer with a capacity of 400 liters,
made of stainless steel and equipped with a double jacket. The
polymerizer had been purged at a preliminary stage by degas-
sing 18 kg of vinyl chloride and now contains 127 kg of vin~l
2~ chloride, 3 kg of vinyl acetate, 33.3 g of acetylcyclohexane
sulphonyl peroxide, corresponding to 2.4 g of active oxygen,
and 50 g of ethyl peroxydicarbonate, corresponding to 4.5 g of
active oxygen. The polymerizer is equipped with two indepen-
dently controlled agitators: one A comprises a ribbon coiled
3 in ~elical windings on a rotary shaft extending across the
--11--
11~9193
upper part of the polymeriæ~r ~lon~ i~s a~is, ancl th~ oth~r B
comprises two arms which correspond in shape to the hottom of
the autoclave and wllich are connected to a pivot ~xtending
across the bottom of the pol~nerizer along its axi~. The
agitating speed of agitator A is set to 50 R.P.M. and that of
agitator B to 5 R.P.M. The temperature of the reaction medium
is rapidly brought to 55C. and kept there; this corresponds
to a relative pressure of 7.8 bars in the polymerizer.
After 4.20 hours of polymerization at 55C., the tem-
perature of the water circulating in the double jacket of thepolymerizer is brought to 75C. and the copolymer is degassed.
The monomeric composition to be eliminated is first
brought to an absolute pressure of ~ bars by direct degassing
in 30 minutes. A compressor is then used to bring it to 90 mm
~5 of mercury, and it is kept at that pressure until degassing is
overO
The temperature of the polymer, which rose to 75C.
seven minutes after water at 75C. had been put in circulation
in the double jacket of the polymerizer, is kept at 75C.
until degassing is over. The degassing process takes 100
minutes.
When the polymer has been degassed and the vacuum
broken by the introduction of nitrogen, the vinyl chloride/
vinyl acetate copolymer in the polymerizer is found to contain
400 ppm of residual monomeric vinyl chloride.
206 kg of the copol~me. is collected, made up of 99%
by weight of vinyl chloride and 1% by weight of vinyl acetate,
with an AFNOR viscosity index of 103. The proportion of co-
polymer passing through a screen with a mesh size of 630
3~ microns represents 98% by weight and has an apparent weight
-12-
11;~9i~3
per unit volume of 0.63 g/cm3 and a grain siz~ clistrib~tion
with an average diameter of 140 microns.
Example 6
Polymerization conditions ar~ identical with those
in example S.
After 4.20 hours of polymerization at 55C., the tem-
perature of the water circulating in the double jacket of the
polymerizer is brought to 75C. and the copolymer is degassed.
The monomeric composition to be eliminated is first
brought to an absolute pressure of 4 bars by direct degassing
in 30 minutes, then to a pressure of 90 mm of mercury with the
aid of the compressor used in example 5.
When the residual monomeric vinyl chloride content of
the copolymer in the polymerizer drops below 2000 ppm (this
happens 20 minutes after the compressor has been set in opera-
tion), 325 g of water is fed into the polymerizer. The pres-
sure in the polymerizer is restored to 90 mm of mercury and
kept at that level until degassing is over.
The ~emperature of the polymer, which rose to 75C.
seven minutes after water at 75C. had been put into circula-
tion in the double jacket of the polymerizer, is kept at 75C.
until degassing is over. The degassing process takes 100
minutes.
When the polymer has been degassed and the vacuum
~5 broken by the introduction of nitrogen, the vinyl chloride/
vinyl acetate copolymer in the polymerizer is found to contain
5 ppm of residual monomeric vinyl chloride.
206 kg of the copol-ymer is collec~ed, made up or q9
by weight of vinyl chloride and 1/~ by weight of vinyl acetate,
3 with an AFNOR viscosity index of 103. The proportion of
11~9193
copolymer passing tllrough a screen with a mesh ~i2e o~ G30
microns represents 98% by weight and has an apparen~ weight per
unit volume of 0.63 g/cm3 and a grain size distribution with an
average dic~meter of 142 microns.
Example 7
This example is given as a comparison.
The apparatus is the same as that used in example 5.
135 kg of vinyl chloride is intxoduced in the pre-
polymerizer and the apparatus is purged by degassing 10 kg of
vinyl chloride. 1.875 kg of isobutene, 6.9 g of acetylcyclo-
hexane sulphonyl peroxide, corresponding to 0.5 g of active
oxygen, and 16.7 g of ethyl peroxydicarbonate, corresponding 'o
1.5 g of active oxygen, are also introduced. The agitating
speed is set to 400 R.P.M.
The temperature of the reaction medium in the pre-
polymerizer is brought to 6~C. and kept at that level, this
corresponds to a relative pressure of 11.2 bars in the pre-
polymerizer.
After 30 minutes of pre-polymerization, ~he conver-
sion rate being approximately 10%, the pre-polymer is transfer-
red to the polymerizer, which has been purged at a prelimina7ystage by degassing 20 kg of vinyl chloride. It now contains
130 kg of vinyl chloride~ 1.9 kg of isobutene, 41.7 g of acetyl-
cyclohexane sulphonyl peroxide, corresponding to 3.0 g of
active oxygen, ard 66.7 g of ethyl peroxydicarbonate, corres
ponding to-6.0 g of active oxygen. The agitating speed of
agitator A is set to 50 R.P.M and that of agitator B to 5
R.P.M. The temoerature of the reaction medium is brought
rapidly to 55~C. and kept at that level, this corresponds to a
3 relative p7essure of 8 bars in the polymerizer.
11~9193
After 5 hours of po~ym~riza~ion at 55C., th~ co-
polymer obtained is degassed under the conditions dcscribed in
ex~mple 5.
When it has been degassed and the vacuum broken ~y
the introduction of niirogen, the vinyl chloride/isobutene co-
polymer in the polymerizer is found to contain 380 ppm of
residual monomeric vinyl chloride.
200 kg of the copolymer is collected, made up of 99%
by weight of vinyl chloride and 1% by weight of isobutene, with
an AF~OR viscosity index of 99. The proportion of copolymer
passing through a screen with a mesh size of 630 microns rep-
resents 97% by weight and has an apparent weight per unit
volume of 0.62 g/cm3 and a grain size distribution with an
average diameter of 139 microns.
Example 8
Polymerization conditions are identical with ~hose
in example 7 and degassing conditions identical with those in
e~ample 6.
When the polymer has been degassed and the vacuum
broken by the introduction of nitrogen, the vinyl chloride/
isobutene copolymer in the polymerizer is found to contain 3
ppm of residual monomeric vinyl chloride.
200 kg of the copolymer is collected, made up of 99%
by weight of vinyl chloride and 1% by weight of isobutene, with
an AFNOR viscosity index of 99. The proportion of copolymer
passing through a screen with a mesh size of 630 microns rep-
resents g7% by weight and has an apparent weight per unit
vol~Ime of 0.62 g/cm3 and a grain size distribution with an
average diameter of 140 microns.
li~9193
ExamPle 9
This example is ~iven as a comparison.
The apparatus is that used in example S.
135 kg of vinyl chloride is placed in the pre-pol~er
and the apparatus is purged by degassing 10 kg of vinyl
chloride. 3.125 kg of propylene, 8.3 g of acetylcyclohexane
sulphonyl peroxide, corresponding to 0.6 g of active oxygen,
and 22.2 g of ethy' peroxydicarbonate, corresponding to 2.0 g
of active oxygen, are also introduced. The agitating speed is
set to 400 R.P.M. The temperature of the reaction medium in
the pre-polymerizer is brought to 69C. and kept at that level;
this corresponds to a relative pressure of 12 bars in the pre-
polymerizer.
After 30 minutes of pre-polymerization, the conver-
sion rate being approximately 10%, the pre-polymer is transfer-
red to the polymerizer, which has been purged at a preliminary
stage by degassing 20 kg of vinyl chloride. It now contains
~`~ 130 kg of vinyl chloride, 3.3 kg of propylene, 69.4 g of acetyl-
cyclohexane sulphonyl peroxide, corresponding to 5.0 g of
active oxygen3 and 100.1 g of ethyl peroxydicarbonate, corres-
ponding to 9.0 g of active oxygen. The agitating speed of
agitator A is set to 50 R.P.M. and that of agitator B to 5
:,
R.P.M. The temperature of the reaction medium is brought
rapidly to 55C. and kept at that level; this corresponds to a
relative pressure of 8.4 bars in the polymerizer.
After 5 hours of polymerization at 55C., the co-
polymer obtained is degassed under the conditions described in
example 5.
When the copolymer has been degassed and ~he vacuum
3 broken by the introduction of nitrogen, the vinyl chloride/
11()9~1~3
propylene copolymer in the polymeriY.~r is foun(l ~o contain 410
ppm of residual monomeric vinyl chloride.
198 kg of the copolymer is collected, made up of 99~0
by weight of vinyl chloride and 1% by weight of propylene,
with an AF~OR viscosity index o 100. The proportion of co-
polymer passing through a screen with a mesh size of 630
microns represents 97% by weight; it has an apparent weight per
unit volume of 0.63 g!cm3 and a grain size distribution with an
average diameter of 142 microns.
lû ExamPle 10
Polymerization conditions are identical with those in
example 9 and degassing conditions identical with those in
ex~nple 6.
~ hen the copolymer has been degassed and the vacuum
broXen by the introduction of nitrogen~ the vinyl chloride/
propylene copolymer in the polyrnerizer is found to contain 4
ppm of residual monomeric vinyl chloride.
198 kg of the copolymer is collec~ed, made up of 99%
by weight of -~inyl chloride and 1% by weight of propylene, with
an AFNOR viscosity index of 100. The proportion of copolvmer
passing through a screen with a mesh size of 630 microns rep-
resents 97% by weight; it has an apparent weight per unit
volurne of 0.63 g/cm3 and a grain size distribution with an
average diameter of 142 microns.
ExamPle 11
This example is given as a comparison.
The apparatus is that used in example 5.
135 kg of vinyl chloride is placed in the pre-
pol~nerizer and the apparatus is purged by degassing 10 kg oî
3~ vinyl chloride. 5 kg of vinyl acetate, 11.1 g of
11091~3
acetylcyclohexane sulphonyl peroxicle, corr~spondincJ to 0.~ y
of active oxy~en, and 7.8 g of ethyl peroxydicarbon~te, cor-
responding to 0 7 g of active o~ygen, are also introduced. The
agitating speed is set to 400 R.P.M.
The temperature of the ~eaction medium in the pre-
polymerizer is brought to 70C. and kept at that level; this
corresponds to a relative pressure of 11.3 bars in the pre-
polymerizer.
After 25 minutes of pre-pol~merization, with a con-
version rate of approximately 10%~ the pre-polymer is transfer-
red to the polymerizer, which has been purged at a preliminary
stage by degassing 20 kg of vinyl chloride. It now contains
113.7 kg of vinyl chloride, ~.3 kg of vinyl acetate, 7 kg of
propylene, 69.4 g of acetylcyclohexane sulphonyl peroxide,
; 15 corresponding to 5.0 g of active oxygen, and 122.4 g of ethyl
peroxydicarbonate, corresponding to 11.0 g of active oxygen.
The agitating speed of agitator A is set to 50 R.P.M. and that
of agitator B to 5 R~P.M. The temperature of the reaction
medium is brought rapidly to 55C. and kept at that level; this
corresponds to a relative pressure of 8.4 bars in the polymer-
izer.
After 6 hours of polymerization at 55C., the co-
polymer obtained is degassed und~r the conditions described in
example 5.
When the copolymer has been degassed and the vacuum
broken by the introduction of nitrogen, the vinyl chloride/
vinyl acetate/propylene copoly~er in the polymerizer is found
to contain 370 ppm of residual monomeric vinyl chloride.
203 kg of the copolymer is obtained; it is of the
3 following composition by weight:
-18-
11119193
- vinyl chloride : 97%
- vinyl acetate : 2%
- propylene : 1%
and has an AFNOR viscosity index of 94. The proportion of co-
polymer passing through a screen with a mesh size of 630
microns represents 96.5% by weight, and has an apparent weight
per unit volume of 0.62 g/cm3 and a grain size distribution
with an average diameter of 140 microns.
Example 12
Polymerization conditions are identical with those in
example 11 and degassing conditions identical with ~hose in
example 6.
When the copolymer has been degassed and the vacuum
broken by the introduction of nitrogen, the vinyl chlorid~/
vinyl acetate/propylene copolymer in the polymerizer is found
to contain 3 ppm of residual monomeric vinyl chloride.
203 kg of the copolymer is collected; it is of the
;~ following composition by weight:
- vinyl chloride : 97%
- vinyl acetate : 2%
- propylene : 1%
and has an AFNOR viscosity index of 34. The proportion of co-
polymer passing through a screen with a mesh size of 630
microns represents 96.5% by weight and has an apparent weight
per unit volume of O.62 g/cm3 and a grain size distribution
with an average diameter of 140 microns.
Example 13
This example is given as a comparison.
Polymerization conditions are identical with those ln
3 example 6.
-19-
~091~3
The apparatus îs that used in exnmple 6,
A~ter 4,20 hours o~ polymerization at 55C " the temperature of
~ ~o ./~r~
the water circulating ilt the double jacket of the p~lroeri~n~i7r is brought
to 85C and the copolymer is degassed under the conditions set forth below.
The monomeric composition to be eliminated is first brought to
an absolute pressure of 4 bars by direct degassing in 7 minutes. It is
then brought to 90 mm of mercury with the aid of the compressor and is
kept at that pressure until degassing is over.
The temperature of the polymer, which rose to 75C ten minutes
after water had been put into circulation at 85~C in the double jacket
of the polymerizer, is kept at 75C. un~il degassing is over The de-
gassing process takes 90 minutes.
When the polymer has been degassed and the vacuum broken by the
introduction of nitrogen, the vinyl chloride/vinyl acetate copolymer in
the polymerizer is found to contain 320 ppm of residual monomeric vinyl
;~ chloride.
206 kg of the copolymer is collected, made up of 99% by weight
of ~inyl chloride and 1% by weight of vinyl acetate, with an AFNOR viscosity
index of 103. The proportion of copolymer passing through a screen with a
mesh size of 630 microns represents 98% by weight and has an apparent
weight per unit volume of 0 63 g/cm3 and a grain size distribution with an
average diameter of 140 microns.
_ 20 -
