CA1109193A - Method of degassing polymers and copolymers prepared by mass polymerizing a monomeric composition based on vinyl chloride - Google Patents
Method of degassing polymers and copolymers prepared by mass polymerizing a monomeric composition based on vinyl chlorideInfo
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- CA1109193A CA1109193A CA248,892A CA248892A CA1109193A CA 1109193 A CA1109193 A CA 1109193A CA 248892 A CA248892 A CA 248892A CA 1109193 A CA1109193 A CA 1109193A
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F6/00—Post-polymerisation treatments
- C08F6/001—Removal of residual monomers by physical means
- C08F6/005—Removal of residual monomers by physical means from solid polymers
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Abstract
AN IMPROVED METHOD OF DEGASSING POLYMERS AND
COPOLYMERS PREPARED BY MASS POLYMERIZING A MONOMERIC
COMPOSITION BASED ON VINYL CHLORIDE
ABSTRACT OF THE DISCLOSURE
An improved method of degassing polymers and co-polymers prepared by mass polymerizing a monomeric composi-tion, based on vinyl chloride.
The polymer is kept under agitation, the monomeric composition to be eliminated is brought from polymerization pressure to a pressure below 120 mm of mercury, the polymer is brought to or kept at a temperature of at least 70°C. and below the temperature at which degradation of the polymer or copolymer commences, and these conditions of pressure and temperature are maintained substantially until the degassing process stops, the polymer being put into contact with a quantity of water representing 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.
The polymers and copolymers obtained, before be-ing placed in open air, have a residual monomeric vinyl chloride content which is less than 50 ppm, generally less than 20 ppm and may be as little as 1 ppm.
COPOLYMERS PREPARED BY MASS POLYMERIZING A MONOMERIC
COMPOSITION BASED ON VINYL CHLORIDE
ABSTRACT OF THE DISCLOSURE
An improved method of degassing polymers and co-polymers prepared by mass polymerizing a monomeric composi-tion, based on vinyl chloride.
The polymer is kept under agitation, the monomeric composition to be eliminated is brought from polymerization pressure to a pressure below 120 mm of mercury, the polymer is brought to or kept at a temperature of at least 70°C. and below the temperature at which degradation of the polymer or copolymer commences, and these conditions of pressure and temperature are maintained substantially until the degassing process stops, the polymer being put into contact with a quantity of water representing 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.
The polymers and copolymers obtained, before be-ing placed in open air, have a residual monomeric vinyl chloride content which is less than 50 ppm, generally less than 20 ppm and may be as little as 1 ppm.
Description
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
.
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
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 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 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_ 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 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 11~9193 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 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:
- 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.
~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 -
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 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 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_ 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 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 11~9193 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 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:
- 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.
~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 -
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of degassing polymers and copolymers prepared by poly-merizing a monomeric composition based on vinyl chloride in a mass, agitat-ing the formed polymer, bringing the monomeric composition to be eliminated from polymerization pressure to a pressure below 120 mm of mercury, bring-ing the polymer to a temperature of at least 70°C. but below the temper-ature at which degradation of the polymer or copolymer commences, maintain-ing these conditions of pressure and temperature substantially until the de-gassing process stops, contacting the polymer with a quantity of water rep-resenting 0.01% to 0.8% by weight after the residual monomeric vinyl chlor-ide content of the polymer or copolymer has been reduced below 2000 ppm.
2. The method as claimed in Claim 1 in which the amount of water is 0.05% to 0.5% by weight of the polymer or copolymer.
3. The method as claimed in Claim l which includes the step of con-tacting the polymer with an inert gas during the degassing process and after the monomeric composition to be eliminated has been brought to a pressure below 120 mm of mercury.
4. The method as claimed in Claim 3 in which the inert gas is nitrogen gas.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7509798A FR2305446A1 (en) | 1975-03-28 | 1975-03-28 | IMPROVED PROCESS FOR DEGASING POLYMERS AND COPOLYMERS PREPARED BY MASS POLYMERIZATION OF A MONOMERIC COMPOSITION BASED ON VINYL CHLORIDE |
| FR75.09798 | 1975-03-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1109193A true CA1109193A (en) | 1981-09-15 |
Family
ID=9153250
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA248,892A Expired CA1109193A (en) | 1975-03-28 | 1976-03-26 | Method of degassing polymers and copolymers prepared by mass polymerizing a monomeric composition based on vinyl chloride |
Country Status (22)
| Country | Link |
|---|---|
| JP (1) | JPS51119784A (en) |
| AR (1) | AR207812A1 (en) |
| AT (1) | AT348255B (en) |
| BE (1) | BE840031A (en) |
| BR (1) | BR7601836A (en) |
| CA (1) | CA1109193A (en) |
| CH (1) | CH609990A5 (en) |
| DE (1) | DE2612748C3 (en) |
| DK (1) | DK131576A (en) |
| ES (1) | ES446382A1 (en) |
| FI (1) | FI61035C (en) |
| FR (1) | FR2305446A1 (en) |
| GB (1) | GB1506981A (en) |
| IE (1) | IE42533B1 (en) |
| IN (1) | IN144657B (en) |
| IT (1) | IT1057398B (en) |
| LU (1) | LU74649A1 (en) |
| NL (1) | NL165758C (en) |
| NO (1) | NO144968C (en) |
| SE (1) | SE426493B (en) |
| SU (1) | SU656530A3 (en) |
| TR (1) | TR19439A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1547614A (en) * | 1975-09-15 | 1979-06-27 | Tenneco Chem | Removing residual monomer from vinyl chloryde polymers |
| DE2653256C2 (en) * | 1976-11-24 | 1983-02-17 | Hoechst Ag, 6000 Frankfurt | Process for lowering the residual monomer content of vinyl chloride polymers |
| FR2489826A1 (en) * | 1980-09-08 | 1982-03-12 | Rhone Poulenc Ind | PROCESS FOR DEGASSING MASS-PREPARED VINYL CHLORIDE POLYMERS AND COPOLYMERS AND POLYMERS AND COPOLYMERS HAVING IMPROVED IMPROVED SCREENABILITY |
| FR2516521A1 (en) * | 1981-11-13 | 1983-05-20 | Chloe Chemie | Removing residual vinyl chloride monomer from polymerisation system - followed by adding water contg. nonionic surfactant to polymer |
| CN117957289A (en) * | 2021-10-21 | 2024-04-30 | Dnp精细化工股份有限公司 | Ink composition, ink set, recording method, method for producing recorded matter, and recorded matter |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1096973A (en) * | 1966-05-16 | 1967-12-29 | Shell Int Research | The manufacture of styrene polymers, and the resulting polymers |
| DE1816350A1 (en) * | 1967-12-26 | 1969-10-16 | Union Carbide Corp | Removal of volatiles from a viscous polymer solution |
| US3668161A (en) * | 1969-06-09 | 1972-06-06 | Union Carbide Corp | Devolatilization of liquid polymer compositions |
| IT989178B (en) * | 1972-07-19 | 1975-05-20 | Solvay | PROCEDURE TO ELIMINATE RESIDUAL VINYL CHLORIDE PRESENT IN POLI MERI |
| NO752264L (en) * | 1974-08-29 | 1976-03-02 | Huels Chemische Werke Ag |
-
1975
- 1975-03-28 FR FR7509798A patent/FR2305446A1/en active Granted
-
1976
- 1976-01-01 AR AR262672A patent/AR207812A1/en active
- 1976-02-27 SE SE7602693A patent/SE426493B/en not_active IP Right Cessation
- 1976-03-24 FI FI760782A patent/FI61035C/en not_active IP Right Cessation
- 1976-03-24 JP JP51032370A patent/JPS51119784A/en active Granted
- 1976-03-25 BE BE165561A patent/BE840031A/en not_active IP Right Cessation
- 1976-03-25 DK DK131576A patent/DK131576A/en not_active Application Discontinuation
- 1976-03-25 DE DE2612748A patent/DE2612748C3/en not_active Expired
- 1976-03-25 NO NO761043A patent/NO144968C/en unknown
- 1976-03-26 IE IE640/76A patent/IE42533B1/en unknown
- 1976-03-26 TR TR19439A patent/TR19439A/en unknown
- 1976-03-26 AT AT224976A patent/AT348255B/en not_active IP Right Cessation
- 1976-03-26 SU SU762338311A patent/SU656530A3/en active
- 1976-03-26 CH CH384476A patent/CH609990A5/en not_active IP Right Cessation
- 1976-03-26 GB GB12310/76A patent/GB1506981A/en not_active Expired
- 1976-03-26 IT IT48739/76A patent/IT1057398B/en active
- 1976-03-26 CA CA248,892A patent/CA1109193A/en not_active Expired
- 1976-03-26 LU LU74649A patent/LU74649A1/xx unknown
- 1976-03-26 NL NL7603198.A patent/NL165758C/en not_active IP Right Cessation
- 1976-03-26 BR BR7601836A patent/BR7601836A/en unknown
- 1976-03-26 ES ES446382A patent/ES446382A1/en not_active Expired
- 1976-03-27 IN IN532/CAL/1976A patent/IN144657B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| GB1506981A (en) | 1978-04-12 |
| SE7602693L (en) | 1976-09-29 |
| TR19439A (en) | 1979-03-20 |
| NL165758B (en) | 1980-12-15 |
| NO144968B (en) | 1981-09-07 |
| DE2612748C3 (en) | 1980-11-13 |
| FI61035C (en) | 1982-05-10 |
| DE2612748B2 (en) | 1980-03-20 |
| FI760782A (en) | 1976-09-29 |
| IE42533L (en) | 1976-09-28 |
| CH609990A5 (en) | 1979-03-30 |
| IN144657B (en) | 1978-06-03 |
| AT348255B (en) | 1979-02-12 |
| DE2612748A1 (en) | 1976-10-07 |
| JPS51119784A (en) | 1976-10-20 |
| NO144968C (en) | 1981-12-16 |
| NL165758C (en) | 1981-05-15 |
| LU74649A1 (en) | 1977-01-28 |
| IE42533B1 (en) | 1980-08-27 |
| NO761043L (en) | 1976-09-29 |
| AR207812A1 (en) | 1976-10-29 |
| BR7601836A (en) | 1976-09-28 |
| ATA224976A (en) | 1978-06-15 |
| IT1057398B (en) | 1982-03-10 |
| NL7603198A (en) | 1976-09-30 |
| JPS558007B2 (en) | 1980-03-01 |
| DK131576A (en) | 1976-09-29 |
| FI61035B (en) | 1982-01-29 |
| SE426493B (en) | 1983-01-24 |
| SU656530A3 (en) | 1979-04-05 |
| FR2305446A1 (en) | 1976-10-22 |
| ES446382A1 (en) | 1977-06-16 |
| FR2305446B1 (en) | 1979-02-16 |
| BE840031A (en) | 1976-09-27 |
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