JP2003514083A - A continuous process for producing polymers in carbon dioxide. - Google Patents

Abstract

(57) Abstract: (a) preparing an apparatus including a continuous reaction vessel and a separator; and (b) combining a monomer and a carbon dioxide reaction medium in the reaction vessel (preferably, The polymerization reaction step in the reaction vessel, wherein the reaction medium comprises liquid or supercritical carbon dioxide, and the reaction is carried out in the reaction vessel in a solid polymer product. And (c) withdrawing a continuous effluent from the reaction vessel during the polymerization reaction, wherein the continuous effluent is maintained as a liquid or supercritical fluid; and (d) B.) Passing said continuous effluent stream through said separator to separate said solid polymer from said continuous effluent stream, while maintaining said effluent stream as a liquid or supercritical stream; Returning a portion of the serial continuous effluent into the reaction vessel, while the effluent, continuous polymerization process of carbon dioxide reaction medium comprising the step of maintaining a liquid or supercritical fluid. The need to significantly recompress the continuous effluent before returning to the reaction vessel is minimized. An apparatus for performing such a method is also disclosed.

Description

Detailed Description of the Invention

(CROSS REFERENCE TO RELATED APPLICATION) The present invention claims priority to provisional application No. 60 / 165,177 filed on November 12, 1999, the entire disclosure of which is to be incorporated by reference. Shall form part of this specification.

FIELD OF THE INVENTION The present invention relates to a method and apparatus for continuously polymerizing a polymer in a carbon dioxide reaction medium.

BACKGROUND OF THE INVENTION Environmental concerns and regulations on the use of volatile organic compounds (VOCs) have increased since the late 1980s (eg Montreal Protocol 1987 and Cle 1990).
an Air Act Amendment), a great deal of effort has been expended to find environmentally friendly solvents for industrial use (McHugh, MA and VJ Kruonis, Supercritical Flui.
d Extraction: Principles and Practce. Second ed, ed. H. Brenner. 1994, B
oston: Butterworth-Heinemann). University of North Crolina-Chapel Hill
DeSimone et al. Have shown that supercritical carbon dioxide (scCO ₂ ) is a viable and promising alternative solvent (TC = 31.8 ° C, P _C) for conducting free radical cationic and step-growth polymerizations using batch reactors. _c = 76 bar) (DeSimone, JM, Z. Gu
an, and CS Elsbernd, Synthesis of Fluoropolymers in Supercritical Carbo
n Dioxide. Science, 1992. 257: p. 945-947). This work has been summarized in several recent reviews (Kendall, JL, et al., Polymerizations in Supercrit.
ical Carbon Dioxide. Science, Chem. Rev., 1999. 99 (2): p. 543-563; Canel
as, DA and JM DeSimone, Advs. Polym. Sci., 1997. 133: p. 103-140; Sha
ffer, KA and JM DeSimone, Chain Polymerizations in Inert Near and Sup
ercritical Fluids. Trends in Polymer Science, 1995. 3 (5); p. 146-153).
In fact, the CO ₂ technology has been used for production of Teflon® by DuPont at 200
Will be commercially implemented by 6 years (McCoy, M., DuPont, UNC R & D effort
yields results, in Chemical & Engineering News. 1999. p. 10). Reasons interest on strong industrial, CO ₂ is inexpensive (100 to 200 US dollars / ton), low toxicity, non-flammable, it is an environmentally and chemically friendly. CO ₂ technology has several important advantages over existing technologies for producing polymers, because it involves a) an expensive polymer drying step, and (b) a large amount of monomer. Expensive wastewater treatment and disposal steps (Baker, RT
And W. Tumas, Toward Greener Chemistry. Science, 1999. 284; p. 1477-1478.
), (C) disposal of “consumed” organic solvent, and (d) handling of toxic organic solvents,
Storage and transport and (e) chain transfer to solvents, ie reactions that may limit the achievable molecular weight of the polymer, may be eliminated.

Increasing industrial interest in using scCO ₂ as a polymerization medium has led to (1)
Several disadvantages of batch reactors have been recognized, including large reactors, which are expensive at high scCO ₂ pressures, and the difficulty of recycling CO ₂ and unreacted monomer. Therefore, there is a need for new methods of carrying out continuous polymerization of monomers in carbon dioxide, especially liquid carbon dioxide and supercritical carbon dioxide.

SUMMARY OF THE INVENTION The present invention provides a continuous process for precipitation polymerization of various monomers in scCO ₂ . In this process, recycling of CO ₂ is achieved without significant recompression. Continuous processes require only smaller and therefore cheaper equipment due to the large volume, commodity-based polymers. Further, continuous removal of polymer from the system and recycling of monomer and supercritical flow can be facilitated in continuous systems. Most organic monomers are soluble in liquids and scCO ₂ (Journal of Org.
anic Chemistry, 1984, vol. 49 pgs. 5097-5101), while most polymers contain C
Being insoluble in O ₂ , this process can be utilized for the polymerization of various monomers without the use of any expensive surfactant. A continuous system in scCO ₂ can also be incorporated within the in situ step to purify the resulting polymer by supercritical flow extraction (SFE) (McHugh, MA, Krukoni.
s VJ Supercritical Fluids Extraction: Principles and Practice. Butterw
orth-Heineman, Stoneham, 1993).

Accordingly, a first aspect of the present invention is a method for carrying out continuous polymerization of monomers in a carbon dioxide reaction medium, which comprises (a) an apparatus comprising a continuous reaction vessel and a separator. And (b) performing a polymerization reaction in the reaction vessel by combining the monomer, the initiator and the carbon dioxide reaction medium in the reaction vessel, wherein the reaction medium is liquid or Consisting of supercritical carbon dioxide, the reaction comprising producing a solid polymer product in the reaction vessel, and then (c) withdrawing a continuous effluent stream from the reaction vessel during the polymerization reaction. Maintaining the continuous effluent as a liquid or supercritical fluid; and (d) passing the continuous effluent through the separator to separate the solid polymer from the continuous effluent. ,on the other hand A step of maintaining the effluent as a liquid or supercritical fluid, then, (e) returning a portion of the continuous effluent into the reaction vessel, while the effluent,
(Preferably at a pressure less than about 100 psi below the pressure in the reaction vessel)
Maintaining as a liquid or supercritical fluid, thereby minimizing the need to significantly recompress the continuous effluent stream before returning to the reaction vessel.

In one preferred embodiment, the combination of the monomer, the initiator and the carbon dioxide reaction medium, as described in step (b), is preferably carried out in the reaction vessel with the monomer, the initiator and the dioxide. It is carried out by continuously feeding with a carbon reaction medium. In another preferred embodiment, a purge is located downstream of the reaction vessel (described in detail herein) to remove an amount of effluent deemed appropriate by one of ordinary skill in the art. In these preferred embodiments, the at least a portion of the effluent returned to the reaction vessel is typically a fractional fraction less than one.

A second aspect of the present invention is an apparatus for continuously polymerizing monomers in carbon dioxide. The apparatus comprises a continuous reaction vessel, at least one inlet line connected to the reaction vessel, an outflow line connected to the reaction vessel, a separator connected to the outflow line, and the reaction. A return line for connecting the separator to a vessel whereby a liquid reaction medium or a supercritical reaction medium is returned from the separator to the reaction vessel, and (preferably a single unit in the reaction vessel). A control system that acts as a control means to maintain the reaction medium as a liquid or supercritical fluid in the separator and the return line (at a pressure that differs from the pressure in the reaction vessel by 50 psi or less and 100 psi or less during the polymerization of the monomers) It has and. In one embodiment, the solid polymer is kept in a separator.

The present invention can also be practiced by any suitable polymerization reaction including, but not limited to, precipitation polymerization reaction, microemulsion polymerization reaction, emulsion polymerization reaction, suspension polymerization reaction, and dispersion polymerization reaction. Although any suitable initiator can be used, it is preferably one that is soluble in the liquid or supercritical reaction medium. Initiators not consumed in the reaction vessel are also preferably returned to the reaction vessel in the reaction medium after the step of passing the effluent stream through the separator. Reuse of the initiator is especially desirable because the initiator is often toxic. Suitable separators include filters, cyclone separators, and, as described in detail herein.
It is a separator including a rotating device in the separator. If desired, a cooler is provided between the reaction vessel and the control valve and located on the outflow line. A recirculation pump is located between the one separator (or the separator most downstream from the reactor if multiple separators are used) and the reaction vessel and on the return line. May be located at or at any one other location. A condenser is provided between the first and second separators and the reaction vessel and on the return line.

[0010]   The present invention will now be described in detail with reference to the drawings.

Detailed Description of the Preferred Embodiments The present invention may be practiced in a reaction vessel by any reaction that produces a solid polymer product, usually a particulate material. Examples of polymerization reactions in which monomers are used to form polymers are those described in DeSimone et al., U.S. Pat.No. 5,679,737 and Clough et al., U.S. Pat.No. 5,780,565. (The disclosures of all patent citations cited herein are hereby incorporated by reference).

Preferably the monomer is a vinyl monomer. There are many examples of vinyl monomers,
These include aromatic vinyl monomers, conjugated diene monomers, unsaturated acid monomers, nitrogen-containing monomers, non-aromatic unsaturated monocarboxylic acid ester monomers, and fluorinated monomers. Not limited to. Mixtures of any of these monomers can be used to allow the formation of copolymers, terpolymers, and the like.

For the purposes of the present invention, the term “aromatic vinyl monomer” is to be interpreted broadly and includes, for example, allyl monomers and heterocyclic monomers. Exemplary aromatic vinyl monomers that can be used include, for example, styrene and styrene derivatives such as α-methylstyrene, p-methylstyrene, vinyltoluene, ethylstyrene, t-butylstyrene, monochlorostyrene, dichlorostyrene, vinylbenzyl chloride. , Vinylpyridine, fluorostyrene, alkoxystyrenes (eg paramethoxystyrene), and the like, and mixtures and mixtures thereof.

Suitable conjugated diene monomers that can be used are C ₄ and C ₉ dienes such as butadiene monomers such as 1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-. Butadiene and the like are not limited to these. Mixtures or copolymers of diene monomers can also be used.

A large number of unsaturated acid monomers can be used in the continuous polymerization. Exemplary monomers of this type include, but are not limited to, unsaturated monocarboxylic acid monomers or unsaturated dicarboxylic acid monomers such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, and the like. Not done. Derivatives, admixtures and mixtures of these can also be used.

Nitrogen-containing monomers that can be used are, for example, acrylamide-based monomers such as acrylamide, N-methiolacrylamide, N-methyolmethacrylamide, methacrylamide, N-isopropylacrylamide, Nt-butylacrylamide, NN-methylene-bis-acrylamide, acrylated N-methylol acrylamides such as N-methoxymethyl acrylamide and N-butoxymethyl acrylamide, and nitrides such as acrylonitrile and methacrylonitrile.

Non-aromatic unsaturated monocarboxylic acid ester monomers such as acrylates and methacrylates can be polymerized. Acrylates and methacrylates contain functional groups such as amino groups, hydroxy groups, epoxy groups and the like. Exemplary acrylates and methacrylates are methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, glycidyl acrylate, glycidyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxy. It includes propyl methacrylate, isobutyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2-hydroxybutyl methacrylate, n-propyl methacrylate and the like. An exemplary amino-functional methacrylate is
Includes t-butylaminoethylmethacrylate and dimethylaminoethylmethacrylate. Other monomers such as vinyl esters, vinyl halides, and vinylidene halides can also be used.

An exemplary fluoropolymer is a fluoroacrylate monomer such as 2- (N-
Ethyl perfluorooctane-sulfonamido) ethylhexyl acrylate (
"EtFOSEA"), 2- (N-ethylperfluorooctane-sulfonamido) ethyl methacrylate ("EtFOSEMA"), 2- (N-ethylperfluorooctane-sulfonamido) ethyl acrylate ("MtFOSEA")
, 1,1′-dihydroperfluorooctyl acrylate (“FOA”), 1,
1'-dihydroperfluorooctyl methacrylate ("FOMA"), 1,1
', 2,2'-Tetrahydroperfluoroalkyl acrylate, 1,1', 2
, 2'-Tetrahydroperfluoroalkyl-methacrylate and 2,4,6
Trifluoromethylstyrene, fluoroalkylene oxide monomers such as hexafluoropropylene oxide and perfluorocyclohexane oxide, and fluoroolefins such as tetrafluoroethylene, vinylidene fluoride,
Includes hexafluoropropylene, and chlorotrifluoroethylene, and fluoroalkyl vinyl ether monomers such as perfluoro (propyl vinyl ether) and perfluoro (methyl vinyl ether).

Many copolymers can be formed from any of the above monomers, and it is known to those skilled in the art which monomer to choose. In one embodiment, a copolymer of maleic anhydride can be formed. Particularly preferred copolymers include, but are not limited to, styrene / maleic anhydride. Suitable copolymers include fluorinated ethylene propylene copolymer (tetrafluoroethylene and hexafluoropropylene copolymer), perfluoroalkoxy polymer (tetrafluoroethylene and perfluoropropyl vinyl ether or perfluoromethyl vinyl ether), sulfur dioxide alternating. Copolymers, for example, but not limited to, sulfur dioxide alternating copolymers with olefins, including butene or norbornene but also others, and ethylene alternating copolymers with tetrafluoroethylene. Other preferred copolymers include, but are not limited to: Ethylene / propylene / diene monomer ethylene / tetrafluoroethylene vinylidene fluoride / hexafluoropropylene styrene / acrylonitrile acrylonitrile / butadiene / styrene styrene / butadiene styrene / acrylonitrile acrylonitrile / butadiene / styrene styrene / polybutadiene (eg impact polystyrene) ethylene / Α-olefin ethylene / propylene / diene monomer ethylene / vinyl acetate ethylene / acrylate monomer / methyl acrylate monomer vinyl chloride / vinyl acetate butadiene / acrylonitrile ethylene / tetrafluoroethylene (TFE) tetrafluoroethylene / hexafluoro Propylene tetrafluoroethylene / vinyl ether monomer tetrafluoroethylene / Functional vinyl ether vinylidene fluoride / tetrafluoroethylene vinylidene fluoride / hexafluoropropylene

There are many initiators that can be used in the present invention and are known to those skilled in the art. Examples of initiators are described in DeSimone et al., US Patent Application No. 5,506,317, the entire disclosure of which is incorporated herein by reference. Organic free radical initiators are preferred, acetyl cyclohexane sulfonyl peroxide, diethyl peroxydicarbonate, diacetyl peroxy dicarbonate, dicyclohexyl peroxy dicarbonate, di-2-ethylhexyl peroxy dicarbonate and t-butyl perneodecanoate. 2,2′-azobis (methoxy-2,4-dimethylvaleronitrile), t-butylperpivalate, dioctanoyl peroxide, dilauroyl peroxide, and 2,2′-azobis (
2,4-dimethylvaleronitrile), t-butylazo-2-cyanobutane,
Dibenzoyl peroxide, t-butyl per-2-ethylhexanoate,
t-butyl permaleate, 2,2-azobis (isobutylnitrile), bis (t-butylperoxy) cyclohexane, t-butylperoxyiisopropylcarbonate, t-butylperacetate, 2,2-bis (T-butylperoxy) butane, dicumyl peroxide, di-t-butyl peroxide, py methane hydroperoxide, pinane hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, but not limited to these. Not done. Combinations of any of the above initiators can also be used.

In addition, the present invention can address catalytic reactions, such as catalytic reactions that use transition metal catalysts including, but not limited to, ions, nickel and palladium.
If desired, these catalysts can be used in combination with ligands such as monodentate ligands, bidentate ligands, tridentate ligands, etc. Which ligand is selected depends on the state of the art. Known in the field. Examples of such ligands are described in US patent application Ser. No. 09 / 185,891, filed Nov. 4, 1998, the entire disclosure of which is incorporated herein by reference. Shall be achieved.

Thus, in the present invention, exemplary polymers that can be used in the present invention and exemplary initiators that can be used for such polymers are Including but not limited to those formed from any. In one preferred embodiment, vinylidene fluoride (VF2) and acrylic acid (AA) are
Diethyl peroxydicarbonate (DE) as an organic free radical initiator for F2
2,2'-azobis (as PDC) as an organic free radical initiator for AA.
(Isobutyl nitrile) is used to polymerize alone or in combination. The initiator provides the end groups for the polymer chains and can provide the polymer with stable end groups if desired. In general, the invention is not limited to those described herein, alone, in combination to form a homopolymer, such as in combination to form a copolymer or terpolymer. Including polymerizing the body.

The reaction vessels used to carry out the present invention have various shapes or forms. For example, in one embodiment, the reaction vessel is a stirred or mechanically agitated reaction vessel, more preferably a stirred vessel that behaves as an "ideal" stirred tank reactor (CSTR). Type reaction vessel or continuous loop reactor,
More preferred are continuous loop reactors that behave as "ideal" stirred tank reactors. "Ideal stirred tank reactor" means that the reactor contents are thoroughly mixed and the system characteristics are uniform throughout; commercial conditions (eg, for reactor design and analysis purposes). Is a sufficiently close approximation in. It should be understood by one of ordinary skill in the art that an ideal stirred tank reactor may include physical configurations other than those described herein. For example, C. Hill, An Introduction
fo Chemical Engineering Kinetics and Reactor Design, page 270 (1977).
Another definition of an ideal reactor (eg CSTR) is a dimensionless exit age function E
(Θ) reaches a maximum within a dimensionless time period between Θ≈0, 0.05, or 0.10 and Θ = 0.20, 0.30, and 0.50, then , A reactor that decreases monotonically after reaching the maximum value. In one preferred embodiment of the ideal CSTR, the cumulative exit age distribution function F is Θ = 0.45 or 0.54 and 0.60.
Or having a value between 0.70. In one preferred embodiment, the ideal CS
The dimensionless exit age distribution of TR reaches its maximum at Θ = 0, and F at Θ = 1.
= 0.63. For the purposes of the present invention, Θ is defined as the actual time divided by the reactor space time, ie the time elapsed to process one feed volume of the reactor under certain conditions. It should be understood that other embodiments are certainly within the scope of the invention. For example, O. Levenspiel, Chemical
Reaction Engineering, 3rd Ed., Pp. 257-269, John Wiley & Sons, New York,
NY, (1999).

In one particular embodiment of the invention, a device for the continuous polymerization of monomers in carbon dioxide, said device comprising a continuous reaction vessel and an inlet line connected to said continuous reaction vessel. An outlet line connected to the reaction vessel, an inlet control valve connected to the outlet line, and a first separator and a second separator connected to the inlet control valve, The control valve includes: (i) a first position in which the first separator is in fluid communication with the outflow line, while the second separator is in liquid communication with the outflow line; and (ii) ) The second separator is in liquid communication with the outflow line, while the first separator is switchable between a second position not in liquid communication with the outflow line. A reactor and a second separator and the reaction vessel with the first A return line connecting each of the separator and the second separator, whereby a liquid or supercritical reaction medium is returned from the separator to the reaction vessel while solid The polymer is operated with a return line retained in the separator and with the return line to maintain the reaction medium as a liquid or supercritical fluid in the first separator and the second separator. Effluent from the continuous reaction vessel, wherein the effluent from the continuous reaction vessel continuously connects the first separator by switching the inlet control valve to the first position. While being able to pass, polymer can be removed from the second separator and (ii) by passing the second separator continuously by switching the inlet control valve to the second position. , The polymer is the first It can be removed from the vessel. The separator may be a filter separator or a cyclone separator, preferably a filter separator.
In certain embodiments, a single cyclone separator typically operates continuously, but when multiple cyclone separators operate in parallel, one cyclone separator is removed from the line for cleaning. be able to. Other features described herein may also be included.

As mentioned above, a continuous loop reactor can be used, and one embodiment of one example of such a system is shown as 400 in FIG. An inlet stream 410 comprising liquid or supercritical carbon dioxide, monomers, and an initiator passes through suitable openings (eg valves, fittings, etc.) and enters reaction vessel 440. The reaction vessel is
It comprises inner and outer walls 440a and 440b, respectively, and in this particular embodiment takes the form of a loop. The pump 430 facilitates circulation of the inlet stream throughout the reaction vessel 440 to ensure that the components are well mixed. In one preferred embodiment, as long as the flow rate of the inlet stream 410 is small compared to the flow rate of the fluid in the loop of the system, the system characteristics will be significantly different from one point to another within the reaction vessel 440. It does not change, that is, it is uniform throughout. In this way, the performance of the loop reactor as a stirred or mechanically disturbed reactor having system characteristics that vary significantly from one point to another throughout the reactor, It is almost the same. Preferably, reaction vessel 440 behaves like an ideal stirred tank reactor, as described in detail herein. As one of ordinary skill in the art will appreciate, the reaction vessel 440 may also include a mixer, heater, etc. to allow the components to be maintained at particular temperature and pressure conditions. Monomer is the reaction vessel 440
Reacts within to form solid polymer particles. Opening 460 (eg, back pressure valve) allows the contents of reaction vessel 440 to exit reaction vessel 440. The resulting effluent 460 may then be transported to other downstream processing mechanisms (eg, separators and recycling systems), as described herein. In addition, it should be appreciated that the continuous loop reactor 400 may include a device feature described herein, although it may be a feature not shown in FIG.

FIG. 13 shows one embodiment in which the separator is present in the form of multiple parallel filters, shown in this example as 100a and 100b. The additional filter
It may be adopted by those skilled in the art when deemed necessary. In this embodiment, the effluent stream 120 from the continuous reaction vessel enters one of the filters 100a or 100b by diverting the effluent stream 120 to the desired filter.
The polymer is collected in any of the filters and the resulting effluent stream 130 is
Liquid or supercritical fluid, unreacted initiator (if present), and (
Comprising unreacted monomer (if present). Stream 130 is then repressurized by compressor 110 and the resulting stream 135 is returned to the reaction vessel for reuse. Although not shown, a purge is preferably present between the filters 100a and 100b and the compressor to discharge a portion of the effluent. When sufficient polymer is collected on the filter and the pressure drop across the filter becomes undesired, the flow is diverted and stream 120 passes through the fresh filter. The polymer is then collected from the off-line filter. The above procedure can be repeated as many times as one of ordinary skill in the art deems appropriate.

FIG. 14 is another embodiment of a separator 200 that can be used in accordance with the present invention. An effluent stream 210 containing polymer, liquid or supercritical fluid, unreacted monomer (if present), and unreacted initiator (if present) enters the separator. During operation of the separator 200, the liquid or supercritical fluid, unreacted monomer (if present), and unreacted initiator (if present) are trapped in the holes 240 in the inner wall 260 of the separator. Pass through. The wall 260 can be formed from a variety of porous materials including but not limited to sintered metals, ceramics, and the like. After passing through wall 260, the fluid stream enters chamber 270 and exits this chamber through outlet line 280. The flow exiting through outlet line 280 is discarded if deemed appropriate. As an example, the stream is returned to the reaction vessel for reuse. Preferably, the pore size is defined so that the polymer does not pass through and collects on the inner surface of wall 260.

The rotating device 220 with the driving device 225 exists in various forms, is provided in the separator, and is used to continuously remove the polymer collected on the inner surface of the wall 260. In this embodiment, the rotating device 220 is in the form of a screw, but other types of devices can be employed within the scope of the invention. The screw 220 removes the polymer from the wall 260 and conveys the polymer through the bottom 250 of the separator. The solid wall 290 surrounds the bottom of the screw, as shown in FIG. Bottom 25
In order to minimize the loss of reaction medium and unreacted monomer and initiator due to
The screw 220 melts the polymer and forms a seal within the screw 220. The molten polymer is conveyed through outlet 250 from the high pressure region of the apparatus to a region of near atmospheric pressure where it is cooled and processed by techniques known to those skilled in the art. In this way, the separator 200 can operate continuously.

One preferred embodiment for a cyclone type separator is shown in FIG. In this embodiment, cyclone 310 is in fluid communication with parallel filters 320a and 320b located downstream of cyclone 310. Liquid or supercritical fluid, unreacted monomer (if present), and (if present)
An incoming effluent stream 330 containing unreacted initiator enters cyclone 310, which causes
The bottoms stream 340 containing a relatively high percentage of polymer, mainly liquid or supercritical fluid, unreacted monomer (if present), and unreacted initiator (if present), and heavy A top stream 350 including coalescence is formed. The top stream 350 is
It is diverted to either filter 320a or 320b in the manner described above (see FIG. 13). With this arrangement, polymer is removed from stream 350 and the resulting outlet stream 360 contains only sufficiently low levels of polymer, which results in outlet stream 3
60 is suitable for being returned to the reaction vessel for reuse if desired. The polymer can then be collected from both filters 320a and 320b using suitable techniques.

In one embodiment of the invention is a method for carrying out a continuous polymerization of monomers in a carbon dioxide reaction medium, said method comprising: (a) a continuous reaction vessel and a first separator. Second
And (b) performing a polymerization reaction in the reaction vessel by combining a monomer, an initiator and a carbon dioxide reaction medium in the reaction vessel. Wherein said reaction medium comprises liquid carbon dioxide or supercritical carbon dioxide, said reaction comprising the step of producing a solid polymer product in said reaction vessel, and then (c) said step during said polymerization reaction. Removing a continuous effluent stream from a reaction vessel, wherein the effluent stream is passed through the first separator while maintaining the effluent stream as a liquid or supercritical fluid, wherein the solids weight from the effluent stream is maintained. Separating the coalescence, then returning the effluent stream to the reaction vessel, and then (
d) withdrawing a continuous effluent from the reaction vessel during the polymerization reaction and passing the effluent through the second separator, while maintaining the effluent as a liquid or supercritical fluid; From the solid polymer, and then returning at least a portion of the effluent stream to the reaction vessel, while at the same time separating the separated in the first separator during the withdrawal step (c). Removing the solid polymer. Preferably, following step (d), (e) repeating said withdrawing step (c), while at the same time during said withdrawing step (d) in said second separator. A step of removing the separated solid polymer is performed. Preferably an initiator is used in step (b). Preferably, a purge is located between the separator and the reaction vessel and placed in the polymerization return line to remove any amount of effluent stream deemed suitable by one of ordinary skill in the art. In these preferred embodiments, the at least a portion of the effluent returned to the reaction vessel is typically a fractional fraction less than one.

Any suitable system or apparatus (preferably at a pressure that differs from the pressure in the reaction vessel by 100 psi or less during the polymerization of the monomers in the reaction vessel) may be the separator and the It can be used as a control means for maintaining the reaction medium as a liquid or supercritical fluid in the return line. An example is filling a fluid into the system, said filling being controlled by using a computer, which may be analog or digital, and removing the reaction medium from the system, said removing Is controlled by using a computer, which may be analog or digital, and heating the system, said heating being controlled by using a computer, which may be analog or digital; Removing heat from the device, the removal of heat being controlled by using a computer, which may be analog or digital, and pumping the reaction medium, the pumping being analog or digital Including being controlled by using a computer, These are not limited.

[0032]   The present invention is explained in detail by the following non-limiting examples.

Example 1 (Chain Growth Reaction Precipitation Polymerization) The experimental system was a strongly mixed and continuously stirred tank reactor (CSTR).
) Followed by two high pressure filters in parallel, where the polymer is collected. This method is broadly applicable to various monomers with heterogeneous polymerization, both with and without surfactants. Here we report our experiments with vinylidene fluoride (VF2) carried out at a temperature of 75 ° C., a pressure of 275 bar, and a residence time of 15-50 minutes. Poly (vinylidene fluoride) polymer (PVDF) is collected as a dry "free flowing" powder and is characterized by gel permeation chromatography (GPC).

(Materials) VF2 monomer was donated by Solvary Research, Belgium, SFF / SF
C grade CO ₂ was donated by Air Products & Chemicals, Inc. All other chemicals were obtained from Aldrich Chemical Company.

(Initiator Combination) The DEPDC (diethyl peroxydicarbonate) initiator was synthesized by extracting the initiator into Feron 113 using water as the reaction medium (Mageli, O.
.L .; Sheppard, CS; In Organic Peroxides, Vol. I, Swern d, Eds .; Wiley-
Interscience, New York, 1970 pp. 1-104; Hiatt, R. In Organic Peroxides,
Vol. II, Swern D, Eds .; Wiley-Intrerscience, New York, 1970 pp. 799-929;
Strain, F .; Bissinger, WE; Dial, WR; Rudolf, H .; DeWitt, BJ; Stev
ens, HC; Langston, JHJ Am. Chem. Soc. 1950, 72, 1254-1263). All manipulations of the initiator were done in an ice bath and the final product was stored in a cold room at -20 ° C. The iodometric technique ASTM Method E298-91 was utilized to determine the concentration of active peroxide in solution.

Polymerization Device A schematic diagram of the device used for polymerization is shown in FIG. Carbon dioxide 14 and monomer 15 are continuously pumped by the Isco syringe pump in constant flow mode, mixed by the element static mixer 8 and then enter the reactor 18. The initiator solution is also continuously pumped by the Isco syringe pump 19 in constant flow mode and enters the reactor 18 as a separate stream. All supply lines have check valves to prevent backflow, thermocouples and rupture discs for safety in case of overpressurization. CSTR is AE dis
80 with magnetic drive (magnedrive) to mix components by persimax impeller
It is a 0mL Autoclave Engineers (AE) pressure cooker. The reactor is heated by a furnace and installed with a pressure transducer (Druck) and a thermowell (Omeg) containing a thermocouple.
a Engineering). FIG. 1 shows a continuously stirred tank reactor 18. Other reactors, such as the continuous loop reactors described herein and others, may also be employed in the system shown in FIG.

The effluent exits the CSTR 18 through the bottom and into a two 280 mL filter housing (Headline) containing a 1 μm filter where the solid polymer is collected by a three-way ball valve 10 (HIP). Be guided. Unreacted monomer, initiator and CO ₂
Passes through the filter and flows through the heated control valve 12. This control valve functions as a back pressure regulator, which controls the reactor pressure to the desired set point. The effluent stream is passed through a water bath to remove unreacted peroxide, while gaseous CO ₂
And the monomer flows into the fume hood and is safely ventilated. Very low levels of polymer were found in the water bath, therefore almost all precipitated polymer was 1 μm.
collected on m filters.

The entire polymerizer 20 was computer controlled and monitored. Supervisory Control and Data Acquisition (SCADA) System is National Instruments Bridge VIEW
It consists of software and a Fieldpoint input / output module. An input module was used to read the pressure transducer and thermocouple. An output module was used to control the reactor furnace and control valves. All control functions were performed using the PID algorithm.

Polymerization Procedure The reactor was first heated to the desired temperature and the stirrer was operated at 1800 rpm.
PRM). The system was then purged with N ₂ . After about 2 hours the control valve was closed and the system was pressurized with CO ₂ to the desired reactor pressure. Desired CO ₂ flow rate is set, the temperature and pressure of the system was stabilized. The temperature control was ± 0.2 ° C and the pressure control was ± 1 bar. Once the system stabilizes, the initiator flow rate is set and the initiator will remove impurities to remove impurities.
Flowed through the system for at least 3 residence times. Monomer flow was then started. After at least 5 residence times have elapsed after the introduction of the monomer, with the CSTR in a steady state, the three-way valve is switched and the stream exiting CSTR is fed to an empty filter / collector where the steady state polymer is Were collected over 30-60 minutes.
After this time the ball valve was switched, the effluent flowed back to the original collector, the monomer and initiator feed streams were stopped and only pure CO ₂ passed through the system for purification. Supplied. The system was finally ventilated and the polymer collected and weighed.

[0040] (Results and explanations)   We used scCO as shown in Figure 1.₂For precipitation polymerization in
Developed and demonstrated a one-time transit system. Table 1 shows VF initiated by DEPDC
2 shows reactor conditions for some experiments with 2 polymerizations. Table 2 shows the results of the polymerization,
Of the poly (vinylidene fluoride) (PVDF) polymer produced in these experiments
And GPC data for. Conversion of VF2 in these polymerizations (conversion
The ratio = the number of moles of the reaction monomer / the number of moles of the supplied monomer) was 7 to 24%. Bag
Unlike the Thi polymerization, high conversion was not required in the continuous system, because
This is because the lava monomer is reused. CSTR Polymerization rate for soot TE (R _p ) Is a maximum of 19 × 10 at a feed monomer concentration of 1.7 liters.^-Fivemol / L
・ S reached. This rate increases with increasing monomer concentration. scCO₂During ~
In a batch polymerization of VF2 at 65 ° C. using an acyl peroxide at 65 ° C.
． Average R at 0M monomer concentration_pIs 0.2 × 10^-FiveIt was mol / (Ls)
(Kipp, B. PhD Thesis, University of North Carolina-Chapel Hill. 1998).

[0041]

[Table 1]

[0042]

[Table 2]

[0043]   GPC results show that the molecular weight distribution (MWD) is monomodal.

Conclusion This example illustrates a system for continuous polymerization of various monomers with scCO ₂ . The feasibility of continuous precipitation polymerization of VF2 and AA was demonstrated using a strongly agitated, continuously stirred tank reactor (CSTR). VF in CSTR
The polymerization rate of 2 is significantly higher than the average batch polymerization rate under similar conditions.

Example 2 Continuous Precipitation Polymerization of Vinylidene Fluoride in Supercritical Carbon Dioxide: Comparison of Experimental R _p with Model R _p This example illustrates heterogeneous polymerization of vinylidene fluoride. . Poly (vinylidene fluoride) (PVDF) is a semi-crystalline polymer, produced commercially by emulsion batch technology or suspension batch technology at polymerization conditions of 10-200 bar at temperatures of 10-130 ° C. (Dohany, JE and JS Humphrey, Vinylide
ne Fluoride Polymers, in Encyclopedia of Polymer Science and Engineering
, HF Mark et al., Editors. 1989, Wiley: New York.p. 532-548; Russo, S., M.
Pianca, and G. Moggi, Poly (vinylidene fluoride), in Polymeric Materials
Encyclopedia, JC Salamone, Editor. 1996, CRC; Boca Raton.p. 7123-712
7). Emulsion technology requires that the final polymer latex be first agglomerated, thoroughly washed, then spray dried and then a free flowing powder is obtained. Suspension technology requires separating the polymer from the aqueous phase by cleaning and then drying. Vinylidene fluoride monomers usually do not contain initiators, PVDF polymers do not require additives for stabilization during melt processing,
This makes this polymer suitable for applications such as ultrapure water where high purity substances are required. Due to the inherent shortcomings of traditional techniques for preparing PVDF, such as additives required for polymerization and difficult to treat waste streams, continuous and environmentally friendly processes are attractive Target.

This example also demonstrates the kinetics and kinetic kinetics of VF2 polymerization initiated by the organic peroxide diethylperoxydicarbonate (DEPDC) using the novel highly disturbed continuous system of the present invention. The mechanism will be explained. Without intending to be bound by theory, the information gained from this study develops a predictive kinetic model that can account for polymerization rate (R _p ) and molecular weight distribution (MWD) for experimental conditions of interest. Useful for. To date, no systematic investigation of the kinetics of free radical polymerizations carried out in CO ₂ in batch or using CSTR has been performed. Similarly, very little polymerization data, especially PVD
No F system, generally in the literature in the field of fluorinated monomers. We have herein performed at a speed of 1300 to 2700 rpm and an initiator inlet concentration of 8-50 (x
10 ^-4 ) M, the monomer inlet concentration is 0.4 to 3.5 M, and the temperature is (CO ₂
Is at a constant concentration of 0.74 g / ml) and a residence time of 10 to 50 minutes. The polymer was in all cases collected as a dry "free-flowing" powder and characterized by gel permeation chromatography (GPC).

1. Materials and Methods (Materials) VF2 monomer is provided by Solvay Research, Belgium, SFE / SFC
Grade CO ₂ was provided by Air Product & Chemicals, Inc. All other chemicals were obtained from Aldrich Chemical Company.

(Synthesis of Initiator) The DEPDC initiator uses water as a reaction medium, and the initiator is extracted to Freon 11
3 (HPLC grade) and synthesized as previously described (Mageli, O.
L. and CS Sheppard, Organic Peroxides, ed. D. Swern. Vol. I. 1970, Ne
w York; Wiley-Interscience. 1-104 .: Hiatt, R., Organic Peroxides, ed. Sw
ern d. Vol. II. 1970, New York: Wiley-Interscience. 799-929). All manipulations of the initiator were done in an ice bath and the final product was stored in a cold room at -20 ° C.
The iodometric technique ASTM Method E 298-91 was utilized to determine the concentration of active peroxide in solution.

Polymerization Apparatus The apparatus and polymerization procedure are described in Example 1 above. Modifications to the system for this example include: a) Reactor furnace with temperature jacket (Autoclave Engin
eering) and heating / cooling fluid is circulated through the temperature jacket for excellent temperature control of the reactor, and b) outlet directly through the HPLC valve (Valco) (after filtration). Gas chromatography for sampling flow (SRI 8610C)
(The GC column is a silica column, while the oven temperature is
Was isothermal at 55 ° C.), c) to cool the effluent polymer stream to ambient temperature,
Adding a countercurrent heat exchanger on the outflow line of the CSTR.

(GPC) All gel permeation chromatography (GPC) measurements of PVDF polymer specimens were performed with 2 × HR5E and 1 using N, N-dimethylformamide (DMF) modified with LiBr 0.1M. × Waters-Alliance HPLC with HR2E column
Made on the system. 1) The condition that the column compartment temperature is 40 ° C., 2) The condition that the flow rate of the mobile phase is 1 ml / min, and 3) The sample injection volume is 100 μl
And 4) the sample is not filtered and 5) the concentration of the sample in the mobile phase is 0.1% by weight (the sample is in the mobile phase at 60 ° C. for 1 hour). Adjusted but can be injected at room temperature). GPC calibration was performed at 40 ° C. directly with a calibration curve obtained using narrow MWD PMMA standards purchased from Polymer Laboratories Ltd. Mark-Hou for universal calibration curves
The wink constant is K = 1.3210 ^-4 , a = 0.674 in PMMA, and K
= 1.14 × 10 ⁻⁵ , and PVDF had a = 0.97.

[0051] (Polymerization control)   Polymerization is carried out in our continuous system in a highly disturbed CSTR, CO ₂ , VF2 and DEPDC are continuously fed to the reactor and mixed under isothermal conditions
While the heterogeneous polymer produced, namely PVDF and CO₂And not yet
Reactions VF2 and DEPDC leave the reactor continuously. Reuse the current
However, it is not implemented (for simplicity and to prevent the accumulation of impurities). reaction
Control of vessel temperature (T) and pressure (P) was very good during the polymerization,
It varied within very narrow tolerances (T = ± 0.2 ° C. and P = ± 1 bar). Syringe
The feed rate of initiator and monomer from the pump is ± 0.1%.

(Achievement of steady state) To determine the arrival of steady state (SS), gas chromatography (GC)
Both analysis and varying polymer collection time were used. The CO ₂ and VF2 peaks could be separated by GC. Calibration of the GC was performed using CO ₂ and VF 2 flow rates determined by syringe pump. (By cooling the syringe pump by chiller circulator, condensation is facilitated liquefied gas) cooled syringe pump concentration of VF2 and CO ₂ and heated reaction vessel is provided by Solvay for VF2 Determined from data (Peng-Robin
son state equation), while the CO ₂ concentration is calculated according to the US National Institute of Standards and T
Determined from echnology (NIST) data.

2. Results and Description (Steady State Attainment) FIG. 2 shows the GC analysis used to determine steady state attainment for a typical polymerization run. In this figure, the effluent VF2 concentration is measured as a function of time, in the unit τ of reactor residence time. In a typical polymerization run, the steady state is
It arrives after about 5τ has passed. Polymer collection is usually initiated after 5τ by switching to the SS collector. When the SS polymer collection is complete, the outlet flow is non-S
Upon returning to the S filter, the SS polymer became immiscible with the non-SS polymer. After the reactor was on stream for at least 5τ, it was found that the polymer collection at various lengths of time had the same gravity / collection time ratio, confirming that the GC analysis results were correct. .

Phase Behavior Under the experimental conditions studied, monomer, VF2 (HFC-1131a), and free radical initiators were used in all experimental ranges studied (by off-line studies in high pressure view cells). DEPDC is possible to understand are compatible with CO _2, whereas the polymer powder PVDF thus formed was found to be incompatible in CO ₂ or VF2 (Lora, M., JS Lim , and MA McHugh, Comparison of the solubility of
PVF and PVDF in Supercritical CH2F2 and CO2 and in CO2 with Acetone, Dim
ethy Ether, and Ethanol. J. Phys. Chem. B., 1999. 103 (14); p. 2818-2822)
. This phase behavior defines precipitation polymerization. As described in Example 1, all polymer powders formed were collected by a 1 μm filter and only very low levels of polymer were found in the outlet water bath. The inside of the reactor after each reaction was usually very lightly coated with powder. The thin powder layer was always dry, non-sticky and could be easily wiped from the reactor wall. The adhesive film-formed product is
It was not observed and the reactor wall temperature did not exceed the melting point of the polymer. Under these experimental conditions, there was no evidence of powder deposits on or in the reactor walls,
This is because the powder bed is always very thin and experiments varying the collection time of steady state flow resulted in the same polymer weight / collection time ratio.

RTD and Initiator Degradation Studies The residence time distribution (RTD) of the experimental reactor and the degradation kinetics of the DEPDC free radical initiator were determined. R of the reactor under all conditions studied
It was found that TD models the ideal CSTR RTD. These experiments were carried out in pure CO ₂ under the typical experimental conditions of T and P in the absence of any polymer powder.

Table 3 provides the initiator decomposition rate constants for DEPDC in scCO ₂ .
Significant solvent dependency, compared to literature values using radical scavengers 2,2'-oxydiethylene bis (allyl carbonate) as a solvent, were not observed in the degradation of DEPDC in scCO _2. (Strain, F., et al, Esters of Pero
xycarbonic Acid. J. Amer. Chem. Soc., 1950. 72; p. 1254-1263). The confirmed initiator efficiency f = 0.6 is also very typical for organic peroxides (Ham
ielec, AE and H. Tobita, Polymerization Processes. Ullman's Encyclope
dia of Industrial Chemistry. 1992.331). In the kinetic analysis of PVDF polymerization described in this article, the k _{D of} Table 3 was used, while f = 0.6 was used for the initiator efficiency at all temperatures studied.

[0057]

[Table 3]

Effect of Disturbance on VF2 Polymerization Our first polymerization experiment addressed the effect of perturbation on polymerization. FIG. 3 provides the effect of agitation speed and agitation type on monomer conversion (X). 6-bladed Ru
1.25 "diameter dispersimax which is shton type turbine (d / D = 0.42)
The ® Disturber was studied from 1300 to 2700 rpm. This type of disturber mainly provides radial flow (Greakoplis, CJ, Transport Processes
and Unit Operations. Third ed. 1993, Englewood Cliffs, New Jersey; Prent
ice Hall). It is clear that this conversion is not affected by the stirring speed in the investigated area. An in-house designed gradient vane turbine agitator (Agitator) was also investigated at the lowest agitation speed investigated of 1300 rpm. This agitator is a 4-blade, 45 ° gradient, upward pumping agitator designed to provide a combination of axial and radial flow to suspend the precipitated particles. There is. This agitator was studied at the lowest rpm value to minimize wear in the event of any offset during manufacturing. The conversion obtained with this agitator is the same as that obtained with the Dispersimax® impeller, which is
It is shown that there was no effect of the disturber geometry on conversion in the conditions studied. In addition to the conversion being the same in the mixed studies, the PVDF molecular weight (MW) determined by gel permeation chromatography (GPC) was the polymer collected at both RPM minimums studied in both agitators. It was found to be identical in the specimen and the RPM maximum studied in the Dispersimax® impeller. The results obtained from the X and MW data led us to believe that the kinetics were unaffected by admixture in this study. In all subsequent experiments reported, the Dispersimax® impeller was used at a stirring speed of 1800 rpm.

(Determination of Polymerization Rate (R _p ) Model Equation) (i) Determination of Order of Monomer In order to derive a model equation for the polymerization rate (R _p ), firstly, a monomer amount is used. The order of reaction for both the body and the initiator has to be determined. The mass balance for the monomers around the reactor, modeled as an ideal CSTR, was simplified to provide a polymerization rate of:

[Equation 1]

[0060]   In an ideal CSTR, the reactor concentration is the same as the outlet concentration (Levenspiel,
O., Chemical Reaction Engineering. Second ed. 1972, New York; Joh Wiley
& Sons). In the studies reported herein, the exit monomer concentration was
Mass balance by weighing gravimetrically the polymer collected under normal conditions)
And confirmed by online GC analysis. This allows us to _p Could be determined because the inlet monomer brain and and reactor residence time
This is because both the average values τ are known. Figure 4 shows R_pPair [VF2]^1.0The plot
And the plot shows that this polymerization is linear to the monomer.
. Primary dependence is generally obtained with free radical kinetics for monomer consumption
(Odian, G., Principles of Polymerization. 3rd ed. 1991, New York: John W
iley & sons, Inc).

In subsequent experiments, a monomer inlet concentration of 0.82M was used. Equation 2 was used for R _p determined empirically and reported herein.

Ii) Determining the order of the initiator The inlet concentration in the reactor, which is the same as the outlet concentration for an ideal CSTR, is given by:

[Equation 2] Accordingly, the concentration of the initiator in the reactor is given by outlet concentration [I] _OUT, the outlet concentration [I] _OUT has an inlet concentration [I] _IN, and the average residence time tau, is provided (Table 3 The decomposition rate k _D. FIG. 5 provides a plot of monomer conversion (X) versus inlet initiator concentration [I] _IN . It is clear that the conversion increases with increasing initiator concentration, since more free radicals are generated to initiate the polymer chains.

[0063]   Figure 6 shows R_pPair [I]_OUT ^0.5Provides a plot of the
It shows that the order of the reaction with respect to it is 0.5. However, a slight offset error [
II^*]^0.5Please note that occurred. In further calculations, [I-I ^* ]^0.5Is used to address this error. 3 mM in subsequent experiments
An initiator inlet concentration of 3 was used.

Although a 1/2 order dependence is usually obtained in free radical kinetics for initiator consumption, conventional heterogeneous polymerizations such as vinyl chloride or acrylonitrile polymerizations often exceed this classical value. Indicates the initiator width index (Eastmond, GC,
Radical Polymerization, in Encyclopedia of Polymer Science and Engineer
ing, H. Mark, Editor, p. 708-855). This behavior is often attributed to polymer radicals that precipitate during the reaction in an insoluble environment, "scavenging" or "radical" the radicals.
It forms a tightly coiled chain that occludes. These trapped radicals can react with the monomer but are difficult to stop, thus causing self-acceleration and a breadth index greater than 0.5. Radical scavenging usually decreases with increasing polymerization temperature. We used a relatively high temperature in this study, namely 75 ° C.
Radical scavenging was minimized as a result of increasing the free volume of the polymer and the mobility of the chain ends, using CO ₂ density which causes the polymer chains to be plasticized. .

Iii) Determining the κ _p / κ _t ^0.5 ratio To continue our aim to determine the appropriate model equation for R _p of VF2 in our experimental system in scCO ₂ , and , Assuming simple chain growth kinetics within the CSTR, we can develop our model using the following main assumptions: Assumption (1) Polymerization in the fluid phase only. Assumption (2) QSSA, LCA. The quasi-steady state assumption (QSSA) is considered for radical species. Moreover, since large molecular weights are usually obtained, the long chain hypothesis (LCA) is introduced, thus ignoring any dependence of the reaction on length. That is,

[Equation 3] and,

[Equation 4] Is established. Combining (8) and (9) yields:

[Equation 5] However,

[Equation 6] Is. We can derive the following formula for the theoretical R _p for our experimental reactor.

[Equation 7]   Equation 12 is expressed as R_pIt is called a model formula for determining. Our model formula
To take advantage of 12, we first_p/ Κ_l ^0.5Determine the experimental value for the ratio
This experimental value must be₂Only the reactor temperature for density
(The polarity of the solvent generated by the monomer concentration also affects this ratio.)
Sound). Studying the effect of reaction temperature on our polymerization, κ as a function of temperature _p / Κ_l ^0.5In order to be able to determine that the reactor pressure was changed to 0.74 g / ml
CO₂A constant density of was obtained. Combining equations (12) and (2) gives κ_p/ Κ_l ^0.5 The following equation is obtained which allows to determine empirically.

[Equation 8] The above equation allows us to use the Arrhenius equation for the κ _p / κ _l ^0.5 ratio.

[Equation 9]

[0066]   FIG. 7 provides a plot of Equation 14, which is linear and the system
, It follows that the Arrhenius equation is followed in the region to be investigated. 69 kj / mol E _p -(E_tThe / 2) value was determined from this plot. Table 4 shows the four studied
Κ determined at temperature_p/ Κ_l ^0.5Provide the value.

FIG. 8 shows the effect of reactor temperature on the experimentally determined R _p (determined from equation 2) and compares these values with those predicted from model equation 12. The agreement with the model formula is very good. As expected, R _p increases rapidly with temperature.

[0068]

[Table 4]

Effect of Reactor Residence Time (τ) on R _p To test our developed model under various experimental conditions, the effect of the average residence time τ controlled by the reactant flow was 10 Investigated within the -50 minute area. CO ₂
The monomer and initiator flow rates were adjusted for each of the τ values studied to equalize the monomer and initiator inlet concentrations. FIG. 9 provides the experimentally determined R _p values from Equation 2 and compares these values with the values calculated from our model Equation 12. The R _p value decreases as τ increases, as expected, because the lower τ value has the highest [VF2] _OUT and [I] _OUT values.
Once again, the experimental data follow the model equation very closely.

FIG. 10 provides a parity plot of all the experimental data reported in this study, which compares the experimental R _p data determined from Equation 2 with the data predicted from model Equation 12. Compare. This plot provides strong evidence that R _p is very well represented by our simple model equation 12.
This behavior indicates that we can represent our precipitation polymerization as a pseudo-bulk system.

(Determination of Model Equation Representing PVDF MWD) Our model equation for M _n is a) that heterogeneous polymerization occurs in a single phase,
b) no chain transfer is present, c) all termination reactions occur due to compounding, and d) the cumulative polymer distribution is identical to the instantaneous distribution (this is
, Which is true in an ideal CSTR), and is obtained from the kinetic chain length ν. In other words, the instantaneous MWD defines the maximum probability distribution with a polydispersity index of 1.5, in which case all termination reactions occur due to compounding (Flory
, PJ, Principles of Polymer Chemistry. 1953, Ithaca, New York; Cornell
University Press. 161).

[Equation 10]

[Equation 11]

FIG. 11 shows how the number average and weight average molecular weights (M _n and M _w ) increase with increasing monomer concentration and provides a comparison with the model equation. Our experimental data fit reasonably well to the simple model equation at low monomer concentrations for M _n and very well to M _w over all monomer concentrations studied. I understand.

Conclusion In the precipitation polymerization of VF2 and scCO ₂ , a simple chain growth kinetics was approximated due to this heterogeneous polymerization and the order of reaction to the initiator was 0.5.
Was found, and it was found to be 1.0 for the monomer. It was found that the stirring speed and the stirrer design had no effect on the polymerization rate. The conversion of VF2 in these polymerizations is 7 to 26%, and the polymerization rate (R _p ) is 75.
A maximum value of 34 × 10 ⁻⁵ was reached at a VF2 feed monomer concentration of 3.5 mol / L at 0 ° C. The poly (vinylidene fluoride) (PVDF) polymer was collected as a dry “free-flow” powder and characterized by gel permeation chromatography (GPC), M _w was 104 kg / mol and PDI was 1. Reached as low as 3. Polymer chain termination appears to occur due to compounding.

Example 3 Large Device One embodiment of a large device embodying the present invention is shown in FIG. The initiator is continuously fed to the reactor at the point where it is separated from the carbon dioxide and the monomer together with the carbon dioxide and the monomer, and the carbon dioxide and the monomer are fed to the recirculation line by the recirculation pump. Be introduced through. Make-up CO ₂ and monomer can be introduced through the top of the reactor if desired, as described above. Upon exiting the reactor, the effluent is cooled and transported to a separator (eg filter or cyclone form). The polymer product exits through the bottom of the reactor and is collected in the separator. Carbon dioxide can be used to help transport polymer through the top or bottom of the reactor to a low pressure bag filter or extractor hopper.

An effluent stream consisting of carbon dioxide, unreacted monomer (if present), and unreacted initiator (if present) was fed to the reactor as shown in FIG. It is returned and reused. The purge is discharged as part of the effluent stream. A liquid stream can optionally be collected if desired through the bottom of the condenser.

Example 4 Residence Time Distribution of Experimental Reactor The residence time distribution of the experimental reactor of the present invention was evaluated using pulse injection of tracer. At temperatures between 50 ° C. and 90 ° C., pressures between 207 and 320 bar, and average residence times as low as 13 minutes, the experimental reactor behaved as an ideal CSTR. The results are shown in Figure 16.

In the drawings and specification, there have been disclosed exemplary preferred embodiments of the invention,
Although specific terms have been used, they are used in their generic and descriptive sense only and not for purposes of limitation, and the scope of the invention is defined in the claims. There is.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a small continuous polymerization apparatus using a filter separator without reusing the reaction medium.

FIG. 2 is a GC analysis to reach a steady state for the polymerization of VF2. Polymerization conditions are P = 276 bar, T = 75 ° C., v _co2 = 26 g / min, [VF2] _INLET =
0.77 M, [DEPDC] _INLET = 3 mM, and τ = 21 min.

[Figure 3]   It is the effect of stirring on the monomer conversion (X). Points are experimental data, lines are
, Linear least squares regression suitable for points. Polymerization conditions are P = 276 bar, T = 75
° C, vco2 = 26 g / min, [VF2]_INLET= 0.77M, [EPDC]_{I NLET} = 3 mM, and τ = 21 minutes. ◆ = Dispersimax (registered trademark) Impelle
r, black square = impeller pumping upwards.

FIG. 4 is a plot of R _P vs. [VF2] _OUT ^1.0 showing the first-order dependence of polymerization rate on monomer concentration. The points are the experimental data and the lines are the linear least-squares regression fitted to the points. The polymerization conditions are P = 276 bar, T = 75 ° C., v _co2 = 26 g / min,
[EPDC] _INLET = 0.77M, and τ = 21 minutes.

FIG. 5: Effect of inlet initiator concentration [I] _{IN on} monomer conversion (X). Polymerization conditions were P = 276 bar, T = 75 ° C., v _co2 = 26 g / min, [VF2] _INLET = 0.77 M, and τ = 21 minutes.

FIG. 6 is a plot of R _P / [VF2] _OUT vs. [I] _OUT ^0.5 showing the square root dependence of polymerization rate on initiator concentration. The points are the experimental data and the lines are the linear least-squares regression fitted to the points. The polymerization conditions are the same as in FIG.

[Figure 7]   Κ, showing suitability for dynamic analysis_p/ Κ_l ^0.5It is a plot of 1 / T
. The line is a linear least squares regression fitted to the points. Polymerization condition is ρ_CO2= 0.74 g / m
l, v_co2= 26 g / min, [VF2] I_NLET= 0.77M, [DEPDC]_{I NLET} = 3.0 mM, and τ = 21 minutes.

FIG. 8 shows the effect of polymerization temperature on the polymerization rate (R _p ). Points are experimental data. The line is the model equation 12 for R _p . Experimental conditions are described in FIG.

FIG. 9: Effect of average reactor residence time τ on polymerization rate (R _p ). Points are experimental data. The line is the model equation 12 for R _p . The polymerization conditions are P = 276
Bar, T = 75 ° C., v _co2 = 26 g / min, [VF2] INLET = 0.7
7M, and [DEPDC] _INLET = 3.0 mM.

FIG. 10 is a parity plot showing that all experimental data are suitable for the data predicted from model equation 12.

FIG. 11: Effect of outlet monomer concentration [VF2] _{OUT on} number average molecular weight and weight average molecular weight M _N and M _W experimentally determined by GPC. Points are experimental data. The polymerization conditions are the same as in FIG.

FIG. 12 is a schematic diagram of a large continuous polymerization apparatus using a cyclone separator in which the reaction medium is reused.

FIG. 13 is a schematic diagram of a separator in the form of a plurality of parallel filters enabling collection of polymer and recycling of the reaction medium according to one method of the present invention.

FIG. 14 is a schematic representation of a separator in the form of a continuously agitated device that allows the collection of polymer and the recycling of the reaction medium according to one method of the present invention.

FIG. 15 is a schematic representation of a cyclone-shaped separator in combination with a filter used to separate polymer from the reaction medium, which allows the reuse of the reaction medium.

FIG. 16: Dimensionless exit age distribution function E (Θ) in an ideal CSTR and experimental reactor.
) Is a comparison graph of Θ.

FIG. 17   1 is a schematic diagram of a continuous loop reactor that may be used in accordance with the present invention.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B01J 3/02 B01J 3/02 CE 3/04 3/04 G Z C08F 2/01 C08F 2/01 4 / 32 4/32 (71) Applicant University of North Carolina at Chapel Hill North Carolina, USA 27599-4105, Chapel Hill, Campus Box 4105, Bynum Hall 308 (72) Inventor Carpentier, Paul A. N 5 Ontario, Canada Canada 4 G2, Windermere Road, London 1201–675 (72) Inventor Decimone, Joseph M. 27516, North Carolina, USA Crescent Ridge, Chapel Hill・ Drive 7315 (72) Inventor Roberts, George W. St. Mary's Street 1610 F Term, Raleigh, 27608, North Carolina, USA (Reference) 4J011 AA09 AA10 HA01 HB12 HB19 HB22 4J015 AA03 BA03 BA05 BA08

Claims (68)

[Claims] 1. A method for carrying out continuous polymerization of monomers in a carbon dioxide reaction medium, the method comprising: (a) providing an apparatus comprising a continuous reaction vessel and a separator; (b) the reaction. A step of carrying out a polymerization reaction in the reaction vessel by combining a monomer, an initiator and a carbon dioxide reaction medium in the vessel, wherein the reaction medium consists of liquid or supercritical carbon dioxide, and the reaction is Producing a solid polymer product in the reaction vessel, and (c) withdrawing a continuous effluent stream from the reaction vessel during the polymerization reaction, wherein the continuous effluent stream Is maintained as a liquid or supercritical fluid, and (d) passing the continuous effluent stream through the separator to separate the solid polymer from the continuous effluent stream, while the effluent stream is a liquid. Or super Maintaining as a boundary fluid, and then (e) returning a portion of the continuous effluent to the reaction vessel while the effluent is liquid at a pressure less than about 100 psi below the pressure in the reaction vessel. Maintaining as a stream or a supercritical stream, whereby the need to significantly recompress the continuous effluent stream before returning to the reaction vessel is minimized. 2. The method according to claim 1, wherein the polymerization reaction is selected from the group consisting of precipitation polymerization reaction, microemulsion polymerization reaction, emulsion polymerization reaction, suspension polymerization reaction, and dispersion polymerization reaction. 3. The method of claim 1, wherein the initiator is soluble in a liquid reaction medium or a supercritical reaction medium. 4. The method of claim 3, wherein the initiator is toxic. 5. The method according to claim 1, wherein the reaction vessel is a stirred tank reactor. 6. The method of claim 1, wherein the reaction vessel is an ideal stirred reactor. 7. The method of claim 1, wherein the reaction vessel is a continuous loop reactor. 8. A dimensionless exit age distribution function ((0) that the reaction vessel reaches a maximum between Θ≈0 and Θ≈0.3 and then monotonically decreases after reaching the maximum.
The method of claim 1, configured to provide E (Θ)). 9. The reaction vessel comprises about 0.45 to about 0.70 when Θ = 1.
The method of claim 1, configured to provide a cumulative exit age distribution (F) of the. 10. The method of claim 1, wherein the monomer is a vinyl monomer. 11. The vinyl monomer is an aromatic vinyl monomer, a conjugated diene monomer, an unsaturated acid monomer, a nitrogen-containing monomer, or a non-aromatic unsaturated monocarboxylic acid ester monomer. 11. The method of claim 10 selected from the group consisting of :, and mixtures thereof. 12. The method of claim 1, wherein the monomer is a fluorinated monomer. 13. The fluorinated monomer is selected from the group consisting of fluoroacrylate monomers, fluorostyrene monomers, fluoroalkylene oxide monomers, fluoroolefin monomers, and mixtures thereof. Item 12. The method according to Item 12. 14. The method of claim 1, wherein the monomer is vinylidene fluoride. 15. The method of claim 1, wherein the monomer is acrylic acid. 16. The method of claim 1, wherein the polymer is a copolymer. 17. The method of claim 1, wherein the initiator is a free radical initiator. 18. The initiator is acetylcyclohexanesulfonyl peroxide, diacetylperoxydicarbonate, diethylperoxydicarbonate, dicyclohexylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, and t-butylperneodeca. Noate and 2
, 2'-azobis (methoxy-2,4-dimethylvaleronitrile), t-butylperpivalate, dioctanoyl peroxide, dilauroyl peroxide, and 2,2'-azobis (2,4-dimethylvaleronitrile) Nitrile), t-butylazo-2-cyanobutane, dibenzoyl peroxide, t-butylper-2-
Ethyl hexanoate, t-butyl permaleate, 2,2-azobis (isobutylnitrile), bis (t-butylperoxy) cyclohexane, t-butylperoxyiisopropylcarbonate, t-butylperacetate ,
2,2-bis (t-butylperoxy) butane, dicumyl peroxide, di-
t-amyl peroxide, di-t-butyl peroxide, p-methane hydroperoxide, pinane hydroperoxide, cumene hydroperoxide,
18. The method of claim 17, selected from the group consisting of t-butyl hydroperoxide and mixtures thereof. 19. An apparatus for continuously polymerizing monomers in carbon dioxide, comprising:
A continuous reaction vessel, an outflow line connected to the reaction vessel, a separator connected to the outflow line, and a return line connecting the separator to the reaction vessel, which is a liquid reaction medium or super A critical reaction medium is returned from the separator to the reaction vessel, while a return line for holding the solid polymer in the separator and the reaction vessel during polymerization of the monomers in the reaction vessel. Control means for maintaining the reaction medium as a liquid or supercritical fluid in the separator and the return line at a pressure that differs by no more than 100 psi from the internal pressure. 20. The device of claim 19, wherein the separator is a filter. 21. The apparatus of claim 19, wherein the separator comprises a plurality of filters connected in parallel with each other. 22. The apparatus of claim 19, wherein the separator comprises a rotating device located within the separator. 23. The apparatus of claim 19, wherein the separator is a cyclone separator. 24. The apparatus of claim 19, further comprising a filter located downstream of the cyclone separator and in fluid communication with the cyclone separator. 25. The apparatus according to claim 19, further comprising a cooler located between the reaction vessel and the control valve and located on the outflow line. 26. The recirculation pump according to claim 19, further comprising a recirculation pump located between the first separator and the second separator and the reaction vessel and located on the return line. apparatus. 27. The apparatus of claim 19 further comprising a condenser located between the first and second separators and the reaction vessel and on the return line. . 28. The apparatus according to claim 19, wherein the reaction vessel is a stirred tank reactor. 29. The apparatus of claim 19 wherein the reaction vessel is an ideal stirred tank reactor. 30. The apparatus according to claim 19, wherein the reaction vessel is a continuous loop reactor. 31. The dimensionless exit age distribution function (E (E (1)) where the reaction vessel reaches a maximum between Θ≈0 and Θ≈0.3, and then monotonically decreases after reaching the maximum. 20. The device of claim 19, configured to provide Θ)). 32. The reaction vessel comprises about 0.45 to about 0.7 when Θ = 1.
20. The device of claim 19, configured to provide a cumulative exit age distribution (F) of zero. 33. A method for carrying out continuous polymerization of monomers in a carbon dioxide reaction medium, comprising: (a) preparing an apparatus comprising a continuous reaction vessel, a first separator and a second separator. And (b) performing a polymerization reaction in the reaction vessel by combining a monomer, an initiator and a carbon dioxide reaction medium in the reaction vessel, wherein the reaction medium is liquid carbon dioxide. Or consisting of supercritical carbon dioxide, the reaction comprising the steps of producing a solid polymer product in the reaction vessel, and then (c) withdrawing a continuous effluent stream from the reaction vessel during the polymerization reaction. Wherein the effluent stream is passed through the first separator while maintaining the effluent stream as a liquid or supercritical fluid to separate the solid polymer from the effluent stream, then:
Returning the effluent stream to the reaction vessel, and (d) withdrawing a continuous effluent stream from the reaction vessel during the polymerization reaction and passing the effluent stream through the second separator, while Maintaining the effluent as a liquid or supercritical fluid to separate the solid polymer from the effluent, and then returning at least a portion of the effluent to the reaction vessel while simultaneously performing the withdrawal step (c). In between, removing the solid polymer separated in the first separator. 34. Subsequent to step (d): (e) repeating said withdrawal step (c), while simultaneously said said second separator during said withdrawal step (d). 34. The method of claim 33, wherein the step of removing the solid polymer separated within is performed. 35. The method of claim 33, wherein the polymerization reaction is selected from the group consisting of precipitation polymerization reaction, microemulsion polymerization reaction, emulsion polymerization reaction, suspension polymerization reaction, and dispersion polymerization reaction. 36. The method of claim 33, wherein the initiator is soluble in a liquid reaction medium or a supercritical reaction medium. 37. The method of claim 33, wherein the initiator is returned to the reaction vessel in the reaction medium after the step of passing the effluent stream through the separator. 38. The method of claim 33, wherein the initiator is toxic. 39. The method according to claim 33, wherein the reaction vessel is a stirred tank reactor. 40. The method of claim 33, wherein the reaction vessel is an ideal stirred tank reactor. 41. The method of claim 33, wherein the reaction vessel is a continuous loop reactor. 42. A dimensionless exit age distribution function (E) in which the reaction vessel reaches a maximum between Θ≈0 and Θ≈0.3, and then monotonically decreases after reaching the maximum. 34. The method of claim 33 configured to provide (Θ)). 43. The reaction vessel comprises about 0.45 to about 0.7 when Θ = 1.
34. The method of claim 33 configured to provide a cumulative exit age distribution (F) of 5. 44. The method of claim 33, wherein the monomer is a vinyl monomer. 45. The vinyl monomer is an aromatic vinyl monomer, a conjugated diene monomer, an unsaturated acid monomer, a nitrogen-containing monomer, or a non-aromatic unsaturated monocarboxylic acid ester monomer. 45. The method of claim 44, selected from the group consisting of :, and mixtures thereof. 46. The method of claim 33, wherein the monomer is a fluorinated monomer. 47. The fluorinated monomer is selected from the group consisting of fluoroacrylate monomers, fluorostyrene monomers, fluoroalkylene oxide monomers, fluoroolefin monomers, and mixtures thereof. Item 46. The method according to Item 46. 48. The method of claim 33, wherein the monomer is vinylidene fluoride. 49. The method of claim 33, wherein the monomer is acrylic acid. 50. The method of claim 33, wherein the polymer is a copolymer. 51. The method of claim 33, wherein the initiator is a free radical initiator. 52. The initiator is acetylcyclohexanesulfonyl peroxide, diacetylperoxydicarbonate, diethylperoxydicarbonate, dicyclohexylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, and t-butylperneodeca. Noate and 2
, 2'-azobis (methoxy-2,4-dimethylvaleronitrile), t-butylperpivalate, dioctanoyl peroxide, dilauroyl peroxide, and 2,2'-azobis (2,4-dimethylvaleronitrile) Nitrile), t-butylazo-2-cyanobutane, dibenzoyl peroxide, t-butylper-2-ethylhexanoate, t-butylpermaleate, 2,2-azobis (isobutylnitrile), t -Butyl peracetate, 2,2-bis (t-butylperoxy) butane, dicumyl peroxide, di-t-amyl peroxide, di-t-butyl peroxide, p-methane hydroperoxide, and pinanhydro Peroxides, cumene hydroperoxides, t-butyl hydroperoxides and mixtures thereof 52. The method of claim 51 selected from the group consisting of 53. An apparatus for continuously polymerizing monomers in carbon dioxide, comprising a continuous reaction vessel, an inlet line connected to the continuous reaction vessel, and an outflow line connected to the reaction vessel. An inlet control valve connected to the outflow line, a first separator and a second separator connected to the inlet control valve, the control valve comprising: (i) the first separator; A separator is in liquid communication with the outflow line, while the second separator is in a first position not in liquid communication with the outflow line; and (ii)
The second separator is in fluid communication with the outflow line, while the first separator is switchable between a second position not in liquid communication with the outflow line. And a second separator, and a return line connecting each of the first separator and the second separator to the reaction vessel, in this way a liquid reaction medium or a supercritical reaction medium Is returned from the separator to the reaction vessel, while the solid polymer is retained in the separator in a return line and in the first and second separators liquid or supercritical. Control means operatively coupled to the return line for maintaining the reaction medium as a fluid, wherein effluent from the continuous reaction vessel comprises (i) the inlet control valve to the first By switching to the position, the first Polymer can be removed from the second separator while it can be continuously passed through the separator, and (ii) the second separator can be connected continuously by switching the inlet control valve to the second position. A device in which the polymer can be removed from the first separator while the polymer can be passed through. 54. The apparatus of claim 53, wherein the first separator and the second separator are filters. 55. The apparatus of claim 53, wherein the first separator and the second separator are cyclone separators. 56. The apparatus of claim 53, each further comprising a filter located upstream of each of the cyclone separators and in fluid communication with each of the cyclone separators. 57. The apparatus of claim 53, wherein the separator comprises a plurality of filters in parallel with each other. 58. The apparatus of claim 53, wherein the separator comprises a rotating device located within the separator. 59. The apparatus according to claim 53, further comprising a cooler located between the reaction vessel and the control valve and located on the outflow line. 60. The recycle pump according to claim 53, further comprising a recirculation pump located between the first separator and the second separator and the reaction vessel and located on the return line. Equipment. 61. The method according to claim 53, further comprising a condenser located between the first separator and the second separator and the reaction vessel and located on the return line. apparatus. 62. An outlet control valve connected to the return line, and an outlet line connecting each of the separators to the outlet control valve, wherein the outlet control valve comprises: One separator is in liquid communication with the return line, while the second separator is in a first position not in liquid communication with the return line, and the second separator is in liquid communication with the return line. 54. The apparatus of claim 53, wherein the first separator is switchable between the return line and a second position that is not in liquid communication. 63. Further, the inlet control valve and the outlet control valve are simultaneously switched to the first position, the second control valve
63. The apparatus according to claim 62, comprising control means for simultaneously switching the inlet control valve and the outlet control valve at the position. 64. The apparatus according to claim 53, wherein the reaction vessel is a stirred tank reactor. 65. The apparatus of claim 53, wherein the reaction vessel is an ideal stirred tank reactor. 66. The apparatus according to claim 53, wherein the reaction vessel is a continuous loop reactor. 67. A dimensionless exit age distribution function (E (E (a
54. Apparatus according to claim 53 having Θ)). 68. The reaction vessel comprises from about 0.45 to about 0.7 when Θ = 1.
54. The device of claim 53 configured to provide a cumulative exit age distribution (F) of zero.