CA1122747A - Method for the suspension polymerization of vinyl chloride with a high process yield - Google Patents
Method for the suspension polymerization of vinyl chloride with a high process yieldInfo
- Publication number
- CA1122747A CA1122747A CA306,729A CA306729A CA1122747A CA 1122747 A CA1122747 A CA 1122747A CA 306729 A CA306729 A CA 306729A CA 1122747 A CA1122747 A CA 1122747A
- Authority
- CA
- Canada
- Prior art keywords
- tube
- suspension
- reactor
- vinyl chloride
- reflow
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/18—Stationary reactors having moving elements inside
- B01J19/1868—Stationary reactors having moving elements inside resulting in a loop-type movement
- B01J19/1881—Stationary reactors having moving elements inside resulting in a loop-type movement externally, i.e. the mixture leaving the vessel and subsequently re-entering it
-
- C—CHEMISTRY; METALLURGY
- 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
- C08F14/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
- C08F14/02—Monomers containing chlorine
- C08F14/04—Monomers containing two carbon atoms
- C08F14/06—Vinyl chloride
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Polymerisation Methods In General (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE :
A method for the suspension polymerization of vinyl chloride is disclosed, according to which the suspension is drawn from the reactor prior to attaining 70% conversion and caused to reflow in an external tube which is externally cooled and whereafter the thus reflow is recycled to the reactor. By properly modifying the internal profile of such a tube, the results can further be improved.
A method for the suspension polymerization of vinyl chloride is disclosed, according to which the suspension is drawn from the reactor prior to attaining 70% conversion and caused to reflow in an external tube which is externally cooled and whereafter the thus reflow is recycled to the reactor. By properly modifying the internal profile of such a tube, the results can further be improved.
Description
1~2~.~47 C~SE tO90 This invcntion relates to a method -Eor the polymeri~ation in suspension of vinyl chl.oride.
More particularly, the present invention relates to a method for improving the specific output capacity of the reactors whi.ch are most commonly used in the suspension poly-merization of vinyl chloride.
It is known that the velocit.y of polymeri~ation of vinyl chloride is considerably increased as the reaction proceeds, and that the initiators having a low decomposition velocity . (at the industriallyadopted temperatures of from 50C to 600C) make this phenomenon especially conspicuous so that, nea,rly always, the maximum reaction velocities exceed the average values by 50%-This quite particular kinetic behaviour and the decrease in time of the overall heat exc11ange coefficient (due to soiling of the reactor walls and the increase of the viscosity of the reacting mass) prevent a complete exploitation of the heat exchange capacity of the reactor at least for three qUarte1S of the overa].l reaction time.
At present, the use of initiators having a half-conversion time of one hour or less, such as ace-tylcyclohexanesulphonyl peroxide and peroxidi carbonates, of incrustation-preventing methods and of water to dilute the reacting mass, has considerably reduced these problems, so that kinetics and exchange capacities nearly constant in time can be obtained.
The recent trend towards reactors having considerable dimensions (over 100 cubic metres) has been made possible by virtue of the combined adoption of such technologies and of ad-ditional heat exchanging contrivances, such as reflux condensers, 3 cooled wave-breaking studs, cooling fluids at low temperatures, ~F
l~Z~7~
so that tlle ratio of the irst costs to the prodl1ction capacity per cubic metre has become favollrable to the large si~e rcactors, even though the specific produetion capacity has become as low as 190 tons/cu.metre per year in the reactors having a volume S of 130 cubic metres as compared with 250 tons/cu.metre a year of the 20 cu.metre reactors.
This notwithstanding, the general trend towards large size reactors is hindered at present by a number of shortcomings, viz.:
- The installations based on large reactors require, in general, additional costs to secure a great constancy of quality from a batch to another and to minimize the error hazards (alkaline washings and distillations of vinyl chloride, computerized automatic controls on the ingredient batches, on the cooling systems and others).
- The development of such polymerization procedures requires a considerable investment in terms of both time and money since it is virtually impossible to use theoretical scale extrapolations on account of the morphological properties of the product: tests are usually conducted in industr:ial units which are properly equipped, such as with stirring units with variable number of blades and rpm, movable wave-brea~ers and others .
- The running costs are overburdened by the operations of treatment of the vinyl chloride, cooling of the coolant fluids, upkeep of the reflux condensers.
- The trend towards more sophisticated marketing requires a production flexibility which is not possessed by the large reactors.
It is thus apparent from the foregoing how important a significant increase of the specific production capacity of reactors having a smaller size (from 25 to 70 cu.metres) can be, since these are the reactors which are being most commonly ~2~74~
employed, so as to go near the yearly outputs of the large reactors by without suffering from the troubles outlined above.
It is likewise known the stirring in a reactor to produce polyvinyl chloride (PVC) in suspension CannOt exceed certain limits (defined by the geometric fipecifications of the stirrer), beyond which there are uncontrollable lumping phenomena. On the other hand, the adoption of low stirring speeds makes it extremely difficult to achieve a quick and thorough solubilization of the ingredients at the outset (for example the dispersion of the catalyst in the vinyl chloride) while main-taining a homogeneous dispersion of both the phases and the heat during progress of the reaction wherein the physical properties of the phases are continuously changed. Especially after that the 70% of conversion has been achieved, the viscosity increase of the mass causes localized overheatings which have a greatly detrimental bearing on the quality of the product, due to the presence of gels and degraded particles. Such phenomena tend to be exalted as the reaction time is reduced so that~ in reactions lasting less than 8 hours, the quality of the end product imposes a Z0 heavy limitation to an increase of the potential output.
It has now been surprisingly found, and this is the subject matter of the present invention, that the production capacity of a reactor for the suspension polymerization of vinyl chloride can considerably be improved, at least by 20%, while concur-rently obtaining products which are devoid of any melted particles and have an extremely low porosity (invisible occlusions), if, prior to attaining 70% conversion, the suspension is caused to flow through an external tube which is equipped with a cooling jacket.
Tube soiling and tube clogging problems are offset by adopting well-known incrustation preventing methods, such as specific formulations, passivation and pickling, coating and 1~2Z~7~L7 other fol stainless stecl tub:ings, enamel coatings having out-standing an-tiadhesiveness characteristics and o-ther expcdicnts and by impressing to the suspension a velocity over one metre per second.
The composLtion of the organic phase entering the tube can be varied from 100% to 5% by wt of vinyl chloride~ this statement being intended to say that the flow in the external tube can be started at any instant of the polymerization run provided that it is before attaining 70% conversion and that such flow is to be protracted up to the completion of the reaction, and that the external tube can also beused for feeding to the reactor a suspension of vinyl chloride in water, said suspension having previously been prepared in an appropriate vessel, it being also possible to use the tube as a feeding device for a partially pre-polymerized suspension.
It has been surprisingly been found, moreover, that if the reflow rate of flow is such as to ensure a stay time in the reactor shorter than 30 mins., it becomes possible consi-derably to reduce, or even to dispense with, the stirring during the reflow without any appreciable effects on the quality of the product, apart from the necessity of a small enrichment of the suspension agents in the formulation.
Another subject matter of the present invention is the apparatus for the production of PVC in suspension, said ap-as paratus comprising a reactor for the polymerization of vinyl chloride, to which a cylindrical tube is applied for the reflow of the suspension, a loop closed on the reactor with a pump adapted to transfer the suspensions.
The modified-profile shown in Figure 1 has proven to be especially suitable for non-stirred systems since it ensures, for equal rate of flow and average velocity, an improved heat exchange together with a reduced consumption of suspension 1~22747 agents over thc smooth tubings.
The modification of the profile is obtained by forming on the inside wall of the tube a set of solid elements, each of which is obtained by imagining to cut a conical surface with a plane and with the surface of the tube, such plane forming an angle ~ , with the axis of the cone, so that is equal to, or wider than 3 d t, wherein ~ ' is one half of the apex angle of the cone. The axis of the cone is parallel to the axis of the tube and lies on the tube wall, or is external of it. Such elements are consecutively arranged along a helix along the tube with an angular shift of ~0 from each other on the transversal cross-section of the tube.
In the Figure of the drawings, the numeral 1 is for the tube wall, whereas 2 is the conical surface of the element, 3 is the planar surface of theelement at an angle ~ : appreciable results can be obtained with the following geometrical specifications:
d ~ 3 ~ 10, b~DT /6 ; R~DT/6; d ~L
wherein d ' is one half of the apical angle of the cone, DT is the tube inside diameter, L is the length of the element which modifies the cylindrical surface of the tube, d is the distance between two consecutive elements, ~ is the maximum radius of curvature of the conical element and b is the maximum thickness of the element.
The present invention is applicable to suspensions of vinyl chloride in water, formulated according to criteria which are well known to the technicians and such criteria are based on the use of the following components which are indicated by way of example only and without any intended limitation to them:
- Primary suspension agents such as water-soluble cellulose ethers and hydroxyethers, polyvinyl alcohols having a saponification number below 270, polyvinylpirrolidone, copolymers llZ~7~L7 of maleic anhvdride, gclatin and others.
- Secondary suspcnsion agents, sucl as ionic suri`ace active agents of the types of the sulphonates and the long-chain alkyl sulfates, non:ionic surface active agents of the class of the derivatives of polyoxyethylene, polyvinyl alcohols having a saponification number comprised between 270 and 550, and others.
- Buffers such as sodium bicarbona-te.
- Additives having a specific incrustation-preYenting action such as natural substances of the type of clay or bentonite, hydroxides of alkali metal- and alkaline earth metals, mono-and polycarboxylic acids and their salts (citric acid, oxalic acid and others), inorganic oxidizing agents such as permanganates, bichromates, nitric acid and others strongly polar organic substances such as aniline and others.
- Peroxide initiators such as alkyl peresters, diacylperoxides, peroxidicarbonates, acylperoxides of alkyls or of cycloalkyl-sulphonyl and diazoic initiators. Such initiators can be introduced into the reaction mass as such or they can be directly produced in the polymerization reactor.
- Molecular-weight adjusters such as alpha-olefines, chlorinated derivatives of alkyls or alkenes, mercaptans and others.
This invention is applied to the production of homopolymers of vinyl chloride in powder form, or of copolymers of vinyl chloride with all the monomers which are known as being capable of copolymerizing with vinyl chloride and for initial composi-tions which contain up to 20% by wt of comonomers: among these and without limitation to them, vinylidene chloride, vinyl acetate and butyrate, methyl-, but~l- and iso-octyl acrylates, methyl- and hexyl metacrylates, diethylmaleate, dipropyl fumarate, diallyl phthalate, diallyl maleate, styrene, ethylene, propylene, l'lZ~ 7 butene, acrylonitri]~, n~etacrylonitrilc, vinyl ethyl ether and others.
The examples tabulated in Tables 1 and 2 are intended to illustrate the directions for the use of the external exchanger but without limiting the field of application.
Table 1 re~orts the conditions of use of the external exchanger, the working conditions of the polymerization and the yearly output per cubic metre of installation.
Table 2 indicates the formulations which are used and the morphological properties of the powder and the analytical data as to gels and impurities.
The tests have been carried out using reactors having an - effective volume of from 23 cubic metres to 50 cubic metres with their inner wall surfaces being plated with stainless steel and enameled.
For each type of reactor a comparison has been instituted between the polymerization conditions without the exchanging tube (tests Nos. 1, 2 and 11) and with the exchanging tube.
A fraction of the heat is removed with water at 5C
injected directly in the reacting mass as soon as the other heat exchange systems attain their own limits.
Test No. 2 has been conducted with a reflux condenser in order that a shorter reaction time might be adopted.
The minimum temperature of the coolant fluid (water from a water tower) is 25C and the polymerization temperature has been maintained on 54C to obtain a K = 70, as measured on a solution of 1 g of polyvinyl chloride in 100 mls of cyclohexa~ne at 25~C.
~n a few tests, stirring has been either reduced or even dispensed with during the operation of the exchanger (tests Nos.
6, 7, 8, 9 and 10). Table 1 reports the conversion at the start of the reflow and the time of stay in the reactor at the instant of the change of the stirring. The tests Nos. 1, 2 and 3 have beet~ carried out with no anti.-sc)i1.ing agents being present, so that at the end of the reaction the autoclave and the tube were coated by a PVC film which strongly stuck to the walls, whereas from -test No. ~ onwards anti-incrustation agents had been adopted so that the tube was clean and ready to be used. for the subsequent polymerization run after having been shortly washed with demineralized water.
It has been seen, in practice, that, in the presence of anti-incrustation agents, the exchanger can be used for a very high number of batches (more than 100~ without any cleaning operations. In thi.s set, only in the test No. 5 local PVC
buildups have been experienced due to the too low reflow velocity of the suspension.
In the tests on reactors having 50 effective cub;c metres capacity, enameled tubes have been uSed, which have given results similar to those which have obtained with tubings plated with stainless steel, even if no incrustation-preventers had been used.
1~227~q O ~1 u~o oo,~ o o 1~
o o ~~ ~n In o ~ o o ~D In r-1-- n ~ o~ In r~
~o o o ~ o o a~
u~ o o o u~ In o ~In 'n o ~
~ ~ o a~ oo In .~ U~ O o ~ In o ~ ~ o ~D ~ ~ ~
o H * o o~ o O o ~ H ~ ~ ~ ~~ .--1 co ,--I
~J H O In p O O Or~l H ~ `N oO In ~ 1-- In ~
a~ H O In ~ ~ cx7 'n O O O a~ H ~1 2 ~ In n In ~ co In ~ ~D
o~ H O In m ~ In t o--I ~ I` ~
O O O ~ H ~1 o ~ n ~
1-- H O O ~r ~ 1:4 ~, ~ ~ ~ ~ ~ ~ 'n O O O~I H ~ ot~ ') o o o c)~
~D H o In ~
O O O ~ H ~) O 1` ~ ~ ~1 In ~
u~ H O In a~
~ o ~~ . ~ o co ~
O O Ot~ H ~ O1~~ In m ~H O u~ 'n ~:C o o o H r~ o ~ oo 11~ ~ ~ In r--E~ ~ H O In ~ ~ P~
~ In ~J o~ ~ In H ~ O
1:4 <'`I ~ O O~) ~ ~ ~ .
H r~) o ~ ~ ~ o o ~1 ~
O O
~ ~ ~ v ~ ~ o~o u~
V n~ I g ~d~ h -' 2 ~i3 s~ ~ ~ ~V
O v ~ 3~) h v O v ~ 3 v 0 ~) ~1 1-l ~ v ~
Z JJ ~ ~ ~ 1 0 ~ ~ O rl ~J ~ O trl Ou~ 41 ~1 ~ ~1 ~ O
O O ~ ~ O
~ O V O ~ o Q) (I~
C Q) ~ t ~) a) o O :~ h a~
X ~ a ~ 3 3 ~13N~H~X~ SNOI;[ IaNO;~ NOIL~Z I~ lOa .s -- 10 --~lf~7g!t7 Notes t;o Table 1 _ _ I stainless s-~eel PI plated with stainless steel S enameled PM modificd profile (*) a~erage values along the tube Example 2 with re~lux condenser.
11 .
llZ~7a~7 O o o ~ ~r ~ ~ o ~ In O O O I I O O O O 00 0 ~
o o o ~o ~o ~
,~ o. o o o o o o r-- Lli ,J c~ ~ ~ O
~ O ,~ O o o ~ ~ ~ o ~D O
o o o o o o ,, ~ ~ ~
~ ~` ~ ~ ~ ~D ~ ~ ~ 1-- o o o I o I o o o o o j a~
CO o o o o o o o o ~ ~i ~I ~ O O O ~ ~ D O~ -o , o O O I O O O O O d' ~ ~ O ~ O ~
_ o o o o 8~, 1 o o m u~ O O ~ O~ ~ O~ O~ o` a~
E~~ o ~ o o o ~r ~ ~ ~ ~ o Ln ,1 4 o o I I o o o o o ~ u~
o o I I o o ~ oo ~ ~ ~
~ ~o aO ~o o o ~ ~ ~ ~ o o O ~ fi ~
O O O O O O
~1 0 0 ~ I ~ o O O o~ O ~ U~ N ~ ~1 0 00 ~
UU~ 0 8 8 8 8 8 ~ , Y
NOI~tn~IO~ :~IZIS
More particularly, the present invention relates to a method for improving the specific output capacity of the reactors whi.ch are most commonly used in the suspension poly-merization of vinyl chloride.
It is known that the velocit.y of polymeri~ation of vinyl chloride is considerably increased as the reaction proceeds, and that the initiators having a low decomposition velocity . (at the industriallyadopted temperatures of from 50C to 600C) make this phenomenon especially conspicuous so that, nea,rly always, the maximum reaction velocities exceed the average values by 50%-This quite particular kinetic behaviour and the decrease in time of the overall heat exc11ange coefficient (due to soiling of the reactor walls and the increase of the viscosity of the reacting mass) prevent a complete exploitation of the heat exchange capacity of the reactor at least for three qUarte1S of the overa].l reaction time.
At present, the use of initiators having a half-conversion time of one hour or less, such as ace-tylcyclohexanesulphonyl peroxide and peroxidi carbonates, of incrustation-preventing methods and of water to dilute the reacting mass, has considerably reduced these problems, so that kinetics and exchange capacities nearly constant in time can be obtained.
The recent trend towards reactors having considerable dimensions (over 100 cubic metres) has been made possible by virtue of the combined adoption of such technologies and of ad-ditional heat exchanging contrivances, such as reflux condensers, 3 cooled wave-breaking studs, cooling fluids at low temperatures, ~F
l~Z~7~
so that tlle ratio of the irst costs to the prodl1ction capacity per cubic metre has become favollrable to the large si~e rcactors, even though the specific produetion capacity has become as low as 190 tons/cu.metre per year in the reactors having a volume S of 130 cubic metres as compared with 250 tons/cu.metre a year of the 20 cu.metre reactors.
This notwithstanding, the general trend towards large size reactors is hindered at present by a number of shortcomings, viz.:
- The installations based on large reactors require, in general, additional costs to secure a great constancy of quality from a batch to another and to minimize the error hazards (alkaline washings and distillations of vinyl chloride, computerized automatic controls on the ingredient batches, on the cooling systems and others).
- The development of such polymerization procedures requires a considerable investment in terms of both time and money since it is virtually impossible to use theoretical scale extrapolations on account of the morphological properties of the product: tests are usually conducted in industr:ial units which are properly equipped, such as with stirring units with variable number of blades and rpm, movable wave-brea~ers and others .
- The running costs are overburdened by the operations of treatment of the vinyl chloride, cooling of the coolant fluids, upkeep of the reflux condensers.
- The trend towards more sophisticated marketing requires a production flexibility which is not possessed by the large reactors.
It is thus apparent from the foregoing how important a significant increase of the specific production capacity of reactors having a smaller size (from 25 to 70 cu.metres) can be, since these are the reactors which are being most commonly ~2~74~
employed, so as to go near the yearly outputs of the large reactors by without suffering from the troubles outlined above.
It is likewise known the stirring in a reactor to produce polyvinyl chloride (PVC) in suspension CannOt exceed certain limits (defined by the geometric fipecifications of the stirrer), beyond which there are uncontrollable lumping phenomena. On the other hand, the adoption of low stirring speeds makes it extremely difficult to achieve a quick and thorough solubilization of the ingredients at the outset (for example the dispersion of the catalyst in the vinyl chloride) while main-taining a homogeneous dispersion of both the phases and the heat during progress of the reaction wherein the physical properties of the phases are continuously changed. Especially after that the 70% of conversion has been achieved, the viscosity increase of the mass causes localized overheatings which have a greatly detrimental bearing on the quality of the product, due to the presence of gels and degraded particles. Such phenomena tend to be exalted as the reaction time is reduced so that~ in reactions lasting less than 8 hours, the quality of the end product imposes a Z0 heavy limitation to an increase of the potential output.
It has now been surprisingly found, and this is the subject matter of the present invention, that the production capacity of a reactor for the suspension polymerization of vinyl chloride can considerably be improved, at least by 20%, while concur-rently obtaining products which are devoid of any melted particles and have an extremely low porosity (invisible occlusions), if, prior to attaining 70% conversion, the suspension is caused to flow through an external tube which is equipped with a cooling jacket.
Tube soiling and tube clogging problems are offset by adopting well-known incrustation preventing methods, such as specific formulations, passivation and pickling, coating and 1~2Z~7~L7 other fol stainless stecl tub:ings, enamel coatings having out-standing an-tiadhesiveness characteristics and o-ther expcdicnts and by impressing to the suspension a velocity over one metre per second.
The composLtion of the organic phase entering the tube can be varied from 100% to 5% by wt of vinyl chloride~ this statement being intended to say that the flow in the external tube can be started at any instant of the polymerization run provided that it is before attaining 70% conversion and that such flow is to be protracted up to the completion of the reaction, and that the external tube can also beused for feeding to the reactor a suspension of vinyl chloride in water, said suspension having previously been prepared in an appropriate vessel, it being also possible to use the tube as a feeding device for a partially pre-polymerized suspension.
It has been surprisingly been found, moreover, that if the reflow rate of flow is such as to ensure a stay time in the reactor shorter than 30 mins., it becomes possible consi-derably to reduce, or even to dispense with, the stirring during the reflow without any appreciable effects on the quality of the product, apart from the necessity of a small enrichment of the suspension agents in the formulation.
Another subject matter of the present invention is the apparatus for the production of PVC in suspension, said ap-as paratus comprising a reactor for the polymerization of vinyl chloride, to which a cylindrical tube is applied for the reflow of the suspension, a loop closed on the reactor with a pump adapted to transfer the suspensions.
The modified-profile shown in Figure 1 has proven to be especially suitable for non-stirred systems since it ensures, for equal rate of flow and average velocity, an improved heat exchange together with a reduced consumption of suspension 1~22747 agents over thc smooth tubings.
The modification of the profile is obtained by forming on the inside wall of the tube a set of solid elements, each of which is obtained by imagining to cut a conical surface with a plane and with the surface of the tube, such plane forming an angle ~ , with the axis of the cone, so that is equal to, or wider than 3 d t, wherein ~ ' is one half of the apex angle of the cone. The axis of the cone is parallel to the axis of the tube and lies on the tube wall, or is external of it. Such elements are consecutively arranged along a helix along the tube with an angular shift of ~0 from each other on the transversal cross-section of the tube.
In the Figure of the drawings, the numeral 1 is for the tube wall, whereas 2 is the conical surface of the element, 3 is the planar surface of theelement at an angle ~ : appreciable results can be obtained with the following geometrical specifications:
d ~ 3 ~ 10, b~DT /6 ; R~DT/6; d ~L
wherein d ' is one half of the apical angle of the cone, DT is the tube inside diameter, L is the length of the element which modifies the cylindrical surface of the tube, d is the distance between two consecutive elements, ~ is the maximum radius of curvature of the conical element and b is the maximum thickness of the element.
The present invention is applicable to suspensions of vinyl chloride in water, formulated according to criteria which are well known to the technicians and such criteria are based on the use of the following components which are indicated by way of example only and without any intended limitation to them:
- Primary suspension agents such as water-soluble cellulose ethers and hydroxyethers, polyvinyl alcohols having a saponification number below 270, polyvinylpirrolidone, copolymers llZ~7~L7 of maleic anhvdride, gclatin and others.
- Secondary suspcnsion agents, sucl as ionic suri`ace active agents of the types of the sulphonates and the long-chain alkyl sulfates, non:ionic surface active agents of the class of the derivatives of polyoxyethylene, polyvinyl alcohols having a saponification number comprised between 270 and 550, and others.
- Buffers such as sodium bicarbona-te.
- Additives having a specific incrustation-preYenting action such as natural substances of the type of clay or bentonite, hydroxides of alkali metal- and alkaline earth metals, mono-and polycarboxylic acids and their salts (citric acid, oxalic acid and others), inorganic oxidizing agents such as permanganates, bichromates, nitric acid and others strongly polar organic substances such as aniline and others.
- Peroxide initiators such as alkyl peresters, diacylperoxides, peroxidicarbonates, acylperoxides of alkyls or of cycloalkyl-sulphonyl and diazoic initiators. Such initiators can be introduced into the reaction mass as such or they can be directly produced in the polymerization reactor.
- Molecular-weight adjusters such as alpha-olefines, chlorinated derivatives of alkyls or alkenes, mercaptans and others.
This invention is applied to the production of homopolymers of vinyl chloride in powder form, or of copolymers of vinyl chloride with all the monomers which are known as being capable of copolymerizing with vinyl chloride and for initial composi-tions which contain up to 20% by wt of comonomers: among these and without limitation to them, vinylidene chloride, vinyl acetate and butyrate, methyl-, but~l- and iso-octyl acrylates, methyl- and hexyl metacrylates, diethylmaleate, dipropyl fumarate, diallyl phthalate, diallyl maleate, styrene, ethylene, propylene, l'lZ~ 7 butene, acrylonitri]~, n~etacrylonitrilc, vinyl ethyl ether and others.
The examples tabulated in Tables 1 and 2 are intended to illustrate the directions for the use of the external exchanger but without limiting the field of application.
Table 1 re~orts the conditions of use of the external exchanger, the working conditions of the polymerization and the yearly output per cubic metre of installation.
Table 2 indicates the formulations which are used and the morphological properties of the powder and the analytical data as to gels and impurities.
The tests have been carried out using reactors having an - effective volume of from 23 cubic metres to 50 cubic metres with their inner wall surfaces being plated with stainless steel and enameled.
For each type of reactor a comparison has been instituted between the polymerization conditions without the exchanging tube (tests Nos. 1, 2 and 11) and with the exchanging tube.
A fraction of the heat is removed with water at 5C
injected directly in the reacting mass as soon as the other heat exchange systems attain their own limits.
Test No. 2 has been conducted with a reflux condenser in order that a shorter reaction time might be adopted.
The minimum temperature of the coolant fluid (water from a water tower) is 25C and the polymerization temperature has been maintained on 54C to obtain a K = 70, as measured on a solution of 1 g of polyvinyl chloride in 100 mls of cyclohexa~ne at 25~C.
~n a few tests, stirring has been either reduced or even dispensed with during the operation of the exchanger (tests Nos.
6, 7, 8, 9 and 10). Table 1 reports the conversion at the start of the reflow and the time of stay in the reactor at the instant of the change of the stirring. The tests Nos. 1, 2 and 3 have beet~ carried out with no anti.-sc)i1.ing agents being present, so that at the end of the reaction the autoclave and the tube were coated by a PVC film which strongly stuck to the walls, whereas from -test No. ~ onwards anti-incrustation agents had been adopted so that the tube was clean and ready to be used. for the subsequent polymerization run after having been shortly washed with demineralized water.
It has been seen, in practice, that, in the presence of anti-incrustation agents, the exchanger can be used for a very high number of batches (more than 100~ without any cleaning operations. In thi.s set, only in the test No. 5 local PVC
buildups have been experienced due to the too low reflow velocity of the suspension.
In the tests on reactors having 50 effective cub;c metres capacity, enameled tubes have been uSed, which have given results similar to those which have obtained with tubings plated with stainless steel, even if no incrustation-preventers had been used.
1~227~q O ~1 u~o oo,~ o o 1~
o o ~~ ~n In o ~ o o ~D In r-1-- n ~ o~ In r~
~o o o ~ o o a~
u~ o o o u~ In o ~In 'n o ~
~ ~ o a~ oo In .~ U~ O o ~ In o ~ ~ o ~D ~ ~ ~
o H * o o~ o O o ~ H ~ ~ ~ ~~ .--1 co ,--I
~J H O In p O O Or~l H ~ `N oO In ~ 1-- In ~
a~ H O In ~ ~ cx7 'n O O O a~ H ~1 2 ~ In n In ~ co In ~ ~D
o~ H O In m ~ In t o--I ~ I` ~
O O O ~ H ~1 o ~ n ~
1-- H O O ~r ~ 1:4 ~, ~ ~ ~ ~ ~ ~ 'n O O O~I H ~ ot~ ') o o o c)~
~D H o In ~
O O O ~ H ~) O 1` ~ ~ ~1 In ~
u~ H O In a~
~ o ~~ . ~ o co ~
O O Ot~ H ~ O1~~ In m ~H O u~ 'n ~:C o o o H r~ o ~ oo 11~ ~ ~ In r--E~ ~ H O In ~ ~ P~
~ In ~J o~ ~ In H ~ O
1:4 <'`I ~ O O~) ~ ~ ~ .
H r~) o ~ ~ ~ o o ~1 ~
O O
~ ~ ~ v ~ ~ o~o u~
V n~ I g ~d~ h -' 2 ~i3 s~ ~ ~ ~V
O v ~ 3~) h v O v ~ 3 v 0 ~) ~1 1-l ~ v ~
Z JJ ~ ~ ~ 1 0 ~ ~ O rl ~J ~ O trl Ou~ 41 ~1 ~ ~1 ~ O
O O ~ ~ O
~ O V O ~ o Q) (I~
C Q) ~ t ~) a) o O :~ h a~
X ~ a ~ 3 3 ~13N~H~X~ SNOI;[ IaNO;~ NOIL~Z I~ lOa .s -- 10 --~lf~7g!t7 Notes t;o Table 1 _ _ I stainless s-~eel PI plated with stainless steel S enameled PM modificd profile (*) a~erage values along the tube Example 2 with re~lux condenser.
11 .
llZ~7a~7 O o o ~ ~r ~ ~ o ~ In O O O I I O O O O 00 0 ~
o o o ~o ~o ~
,~ o. o o o o o o r-- Lli ,J c~ ~ ~ O
~ O ,~ O o o ~ ~ ~ o ~D O
o o o o o o ,, ~ ~ ~
~ ~` ~ ~ ~ ~D ~ ~ ~ 1-- o o o I o I o o o o o j a~
CO o o o o o o o o ~ ~i ~I ~ O O O ~ ~ D O~ -o , o O O I O O O O O d' ~ ~ O ~ O ~
_ o o o o 8~, 1 o o m u~ O O ~ O~ ~ O~ O~ o` a~
E~~ o ~ o o o ~r ~ ~ ~ ~ o Ln ,1 4 o o I I o o o o o ~ u~
o o I I o o ~ oo ~ ~ ~
~ ~o aO ~o o o ~ ~ ~ ~ o o O ~ fi ~
O O O O O O
~1 0 0 ~ I ~ o O O o~ O ~ U~ N ~ ~1 0 00 ~
UU~ 0 8 8 8 8 8 ~ , Y
NOI~tn~IO~ :~IZIS
Claims (6)
1. A method for the suspension polymerization of vinyl chloride with a high process yield characterized in that, when stirring is discontinued, the suspension exiting the polymerization reactor is caused to reflow to the reactor through an external tubular section equipped with a cooling system thus originating the whirling of the suspension stream, the reflow being started prior to attaining 70% conversion.
2. A method according to claim 1, characterized in that the stirring in the reactor is either reduced or stopped during reflow if the reflow rate of flow is such as to afford a time of stay in the reaction not exceeding 30 minutes.
3. A method according to claim 1 or 2, characterized in that the tubular section used for the reflow of the suspension is a cylindrical tube having a modified profile.
4. A method according to claim 1, characterized in that the organic phase (vinyl chloride plus polyvinyl chloride) entering the tube may contain from 100% to 5%
of vinyl chloride by weight.
of vinyl chloride by weight.
5. A method according to claim 1, characterized in that the external tubular section can be used to feed to the reactor a suspension of vinyl chloride in water, previously prepared in an appropriate vessel, or to feed a partially prepolymerized suspension.
6. An apparatus for the suspension polymerization of vinyl chloride comprising a polymerization reactor and characterized in that to the reactor a cylindrical tube having a modified internal profile is applied, through which the suspension is caused to reflow in a loop closed by the reactor, said modified profile being obtained by forming on the internal tube wall a set of solid elements each of which is obtained by imagining to cut a cone with the tube surface and with a plane forming an angle a with the cone axis, which is maintained parallel to the tube axis and lying on the tube wall or externally thereof, such elements being arranged in succession along a helix on the tube with an angular shift of 90° from each other on the transversal cross-section of the tube and by observing the following geometrical specifications:
b?DT/6; R?DT/6; d?L; .alpha.?3 .alpha.'; .alpha.'?10°
wherein DT is the tube inside diameter, L is the length of the element which modifies the cylindrical surface of the tube, d is the distance between two consecutively arranged elements, R is the maximum radius of curvature of the conical element, b is the maximum thickness of the element, and .alpha.' is one half the apical angle of the cone.
b?DT/6; R?DT/6; d?L; .alpha.?3 .alpha.'; .alpha.'?10°
wherein DT is the tube inside diameter, L is the length of the element which modifies the cylindrical surface of the tube, d is the distance between two consecutively arranged elements, R is the maximum radius of curvature of the conical element, b is the maximum thickness of the element, and .alpha.' is one half the apical angle of the cone.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT26192/77A IT1082250B (en) | 1977-07-27 | 1977-07-27 | METHOD FOR HIGH-PRODUCTIVITY VINYL CHLORIDE SUSPENSION POLYMERIZATION |
| IT26192A/77 | 1977-07-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1122747A true CA1122747A (en) | 1982-04-27 |
Family
ID=11218890
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA306,729A Expired CA1122747A (en) | 1977-07-27 | 1978-07-04 | Method for the suspension polymerization of vinyl chloride with a high process yield |
Country Status (31)
| Country | Link |
|---|---|
| JP (1) | JPS5424991A (en) |
| AR (1) | AR218677A1 (en) |
| AT (1) | AT367434B (en) |
| AU (1) | AU519510B2 (en) |
| BE (1) | BE869324A (en) |
| CA (1) | CA1122747A (en) |
| CH (1) | CH636629A5 (en) |
| CS (1) | CS207638B2 (en) |
| DD (1) | DD137237A5 (en) |
| DE (1) | DE2832628C2 (en) |
| DK (1) | DK333578A (en) |
| EG (1) | EG13559A (en) |
| ES (1) | ES472622A1 (en) |
| FR (1) | FR2398760A1 (en) |
| GB (1) | GB2001659B (en) |
| GR (1) | GR64798B (en) |
| HU (1) | HU180652B (en) |
| IL (1) | IL55081A (en) |
| IN (1) | IN150429B (en) |
| IT (1) | IT1082250B (en) |
| LU (1) | LU80032A1 (en) |
| NL (1) | NL171365B (en) |
| NO (1) | NO782563L (en) |
| PH (1) | PH14899A (en) |
| PL (1) | PL111635B1 (en) |
| PT (1) | PT68351A (en) |
| RO (1) | RO76798A (en) |
| SE (1) | SE7808195L (en) |
| TR (1) | TR20015A (en) |
| YU (1) | YU171878A (en) |
| ZA (1) | ZA783989B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS55157607A (en) * | 1979-05-25 | 1980-12-08 | Ryonichi Kk | Suspension polymerization of vinyl chloride |
| JPS5882127A (en) * | 1981-11-10 | 1983-05-17 | Ishida Scales Mfg Co Ltd | Method for measuring mixed and combined articles of a plurality of kinds |
| US5169918A (en) * | 1989-09-18 | 1992-12-08 | Kanegafuchi Kagaku Kogyo Kabushiki Kaisha | Polymerization apparatus having an effective height/effective inner diameter ratio of at least 4 and a circumferential agitative diameter/effective inner ratio diameter of from 0.7 to 0.9 |
| TW200630385A (en) | 2005-02-09 | 2006-09-01 | Vinnolit Gmbh & Co Kg | Process for the polymerisation of vinyl-containing monomers |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2528469A (en) * | 1948-02-24 | 1950-10-31 | Shell Dev | Granular polymerization of vinyl chloride |
| DE2118542A1 (en) * | 1971-04-16 | 1972-10-26 | Dserschinskij filial nautschno lssledowatelskowo i konstruktorskowo in stituta chimitscheskowo maschinostrojem ja, SSSR, Dserschinsk (Sowjetunion) | Polymeriser with external coolers - permitting high throughput having recirculation line(s) with pumps and cooling jackets |
| DE2343788C3 (en) * | 1973-08-30 | 1980-07-10 | Wacker-Chemie Gmbh, 8000 Muenchen | Device for the continuous implementation of chemical reactions, in particular polymerizations and processes for the continuous suspension polymerization of vinyl chloride |
| DE2458024B2 (en) * | 1974-12-07 | 1979-10-04 | Hoechst Ag, 6000 Frankfurt | Process for the aqueous suspension polymerization of vinyl chloride |
-
1977
- 1977-07-27 IT IT26192/77A patent/IT1082250B/en active
-
1978
- 1978-06-27 GR GR56609A patent/GR64798B/en unknown
- 1978-06-29 AU AU37589/78A patent/AU519510B2/en not_active Expired
- 1978-07-04 IL IL55081A patent/IL55081A/en unknown
- 1978-07-04 CA CA306,729A patent/CA1122747A/en not_active Expired
- 1978-07-05 PH PH21333A patent/PH14899A/en unknown
- 1978-07-07 GB GB787829113A patent/GB2001659B/en not_active Expired
- 1978-07-12 ZA ZA00783989A patent/ZA783989B/en unknown
- 1978-07-18 YU YU01718/78A patent/YU171878A/en unknown
- 1978-07-18 TR TR20015A patent/TR20015A/en unknown
- 1978-07-21 ES ES472622A patent/ES472622A1/en not_active Expired
- 1978-07-21 AR AR273040A patent/AR218677A1/en active
- 1978-07-22 IN IN807/CAL/78A patent/IN150429B/en unknown
- 1978-07-24 JP JP8952778A patent/JPS5424991A/en active Pending
- 1978-07-24 LU LU80032A patent/LU80032A1/xx unknown
- 1978-07-25 PL PL1978208624A patent/PL111635B1/en unknown
- 1978-07-25 NO NO782563A patent/NO782563L/en unknown
- 1978-07-25 RO RO7894773A patent/RO76798A/en unknown
- 1978-07-25 DE DE2832628A patent/DE2832628C2/en not_active Expired
- 1978-07-25 DD DD78206915A patent/DD137237A5/en unknown
- 1978-07-26 HU HU78AI279A patent/HU180652B/en unknown
- 1978-07-26 CH CH805078A patent/CH636629A5/en not_active IP Right Cessation
- 1978-07-26 FR FR7822105A patent/FR2398760A1/en active Granted
- 1978-07-26 PT PT68351A patent/PT68351A/en unknown
- 1978-07-26 DK DK333578A patent/DK333578A/en not_active Application Discontinuation
- 1978-07-26 CS CS784963A patent/CS207638B2/en unknown
- 1978-07-26 EG EG462/78A patent/EG13559A/en active
- 1978-07-26 AT AT0544178A patent/AT367434B/en not_active IP Right Cessation
- 1978-07-27 SE SE7808195A patent/SE7808195L/en unknown
- 1978-07-27 BE BE189543A patent/BE869324A/en unknown
- 1978-07-27 NL NLAANVRAGE7807990,A patent/NL171365B/en not_active Application Discontinuation
Also Published As
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US6399031B1 (en) | Continuous flow reactor having a plurality of alternating bends | |
| CA1215500A (en) | Continuous process and device for the manufacture of a vinyl chloride polymer in aqueous suspension | |
| CA1333439C (en) | Method for production of hydrophilic polymer | |
| KR19980032518A (en) | Process for preparing emulsion polymerization of homo- and copolymers and apparatus therefor | |
| EP0052421B1 (en) | Vinyl chloride polymerisation process | |
| DE2522473C3 (en) | Polymerization vessel, process for its manufacture and its use | |
| CA1122747A (en) | Method for the suspension polymerization of vinyl chloride with a high process yield | |
| EP3307792B1 (en) | Method for producing vinyl acetate-ethylene copolymers by means of emulsion polymerization | |
| JPS594603A (en) | Continuous manufacture of aqueous plastic dispersion | |
| KR100191378B1 (en) | Process for producing vinyl chloride resin | |
| US3738974A (en) | Liquid phase process for the polymerization of unsaturated monomers | |
| KR860001113B1 (en) | A process for polymerizing vinyl chlovide | |
| JPS6344766B2 (en) | ||
| JPS5838702A (en) | Continuous manufacture of vinyl chloride polymer in aqueous suspension state | |
| US5447999A (en) | Vinyl chloride polymerization with recycle return projecting into gas phase region of reactor | |
| CN113968927A (en) | Method for synthesizing low molecular weight styrene-maleic anhydride resin by tubular reactor | |
| JP2984851B2 (en) | Method for producing emulsion resin | |
| GB2039922A (en) | Apparatus suitable for use in the polymerization in suspension of vinyl chloride | |
| JPS63291905A (en) | Production of olefin-maleic anhydride copolymer particle | |
| KR20010050089A (en) | Process for cleaning reactors | |
| EP0606013A1 (en) | Polymer scale preventive agent | |
| KR830001026B1 (en) | Method of substantially preventing polymer accumulation on the inner surface of the polymerization reactor | |
| EP0051945B1 (en) | Improved suspension process for the polymerization of vinyl chloride monomer | |
| JPS61185502A (en) | Polymerization of vinyl monomer | |
| PL104353B1 (en) | METHOD OF MAKING POLYMERS AND COPOLYMERS OF VINYL CHLORIDE BY SUSPENSIVE POLYMERISATION |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |