CA2204677A1 - Process for preparing ethylene/vinyl acetate copolymers - Google Patents
Process for preparing ethylene/vinyl acetate copolymersInfo
- Publication number
- CA2204677A1 CA2204677A1 CA002204677A CA2204677A CA2204677A1 CA 2204677 A1 CA2204677 A1 CA 2204677A1 CA 002204677 A CA002204677 A CA 002204677A CA 2204677 A CA2204677 A CA 2204677A CA 2204677 A1 CA2204677 A1 CA 2204677A1
- Authority
- CA
- Canada
- Prior art keywords
- ethylene
- vinyl acetate
- process according
- polymerisation
- pressure
- 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.)
- Abandoned
Links
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 title claims abstract description 24
- 239000005977 Ethylene Substances 0.000 title claims abstract description 24
- 229920001577 copolymer Polymers 0.000 title claims abstract description 10
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 6
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 48
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 24
- 239000000178 monomer Substances 0.000 claims abstract description 23
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 14
- 238000000034 method Methods 0.000 claims description 30
- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical compound CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 claims description 23
- 238000006243 chemical reaction Methods 0.000 claims description 13
- 239000011541 reaction mixture Substances 0.000 claims description 12
- 239000000203 mixture Substances 0.000 claims description 11
- BAPJBEWLBFYGME-UHFFFAOYSA-N Methyl acrylate Chemical compound COC(=O)C=C BAPJBEWLBFYGME-UHFFFAOYSA-N 0.000 claims description 10
- 230000035484 reaction time Effects 0.000 claims description 3
- 239000003701 inert diluent Substances 0.000 claims description 2
- 230000006835 compression Effects 0.000 claims 1
- 238000007906 compression Methods 0.000 claims 1
- 229940117958 vinyl acetate Drugs 0.000 description 23
- 229920000642 polymer Polymers 0.000 description 11
- 239000002904 solvent Substances 0.000 description 7
- 239000003999 initiator Substances 0.000 description 6
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 239000000839 emulsion Substances 0.000 description 3
- 230000017525 heat dissipation Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000000155 melt Substances 0.000 description 3
- DKGAVHZHDRPRBM-UHFFFAOYSA-N Tert-Butanol Chemical compound CC(C)(C)O DKGAVHZHDRPRBM-UHFFFAOYSA-N 0.000 description 2
- LSXWFXONGKSEMY-UHFFFAOYSA-N di-tert-butyl peroxide Chemical compound CC(C)(C)OOC(C)(C)C LSXWFXONGKSEMY-UHFFFAOYSA-N 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 229920001971 elastomer Polymers 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 238000006116 polymerization reaction Methods 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- GJBRNHKUVLOCEB-UHFFFAOYSA-N tert-butyl benzenecarboperoxoate Chemical compound CC(C)(C)OOC(=O)C1=CC=CC=C1 GJBRNHKUVLOCEB-UHFFFAOYSA-N 0.000 description 2
- MTLWTRLYHAQCAM-UHFFFAOYSA-N 2-[(1-cyano-2-methylpropyl)diazenyl]-3-methylbutanenitrile Chemical compound CC(C)C(C#N)N=NC(C#N)C(C)C MTLWTRLYHAQCAM-UHFFFAOYSA-N 0.000 description 1
- OMPJBNCRMGITSC-UHFFFAOYSA-N Benzoylperoxide Chemical compound C=1C=CC=CC=1C(=O)OOC(=O)C1=CC=CC=C1 OMPJBNCRMGITSC-UHFFFAOYSA-N 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 1
- 229920003346 Levapren® Polymers 0.000 description 1
- 241000221013 Viscum album Species 0.000 description 1
- 150000001252 acrylic acid derivatives Chemical class 0.000 description 1
- -1 alkenyl acetates Chemical class 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 235000019400 benzoyl peroxide Nutrition 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000003085 diluting agent Substances 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 239000000806 elastomer Substances 0.000 description 1
- 238000004945 emulsification Methods 0.000 description 1
- 229920006228 ethylene acrylate copolymer Polymers 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 150000002734 metacrylic acid derivatives Chemical class 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 150000002978 peroxides Chemical class 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 239000005060 rubber Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000006276 transfer reaction Methods 0.000 description 1
- 230000035899 viability Effects 0.000 description 1
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
Classifications
-
- 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
- C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F210/02—Ethene
-
- 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
- C08F218/00—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 an acyloxy radical of a saturated carboxylic acid, of carbonic acid or of a haloformic acid
- C08F218/02—Esters of monocarboxylic acids
- C08F218/04—Vinyl esters
- C08F218/08—Vinyl acetate
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
- Polymerisation Methods In General (AREA)
Abstract
The invention relates to a process for preparing copolymers of ethylene and polar monomers in the presence of supercritical carbon dioxide.
Description
CA 02204677 1997-0=,-07 Le A 31 682-Forei~n Countries / NP/ngb/S-P
Process for preparing ethylene/vinyl acetate copolymers The invention relates to a process for preparing copolymers of ethylene and polar S monomers in the presence of supercritical carbon dioxide.
Ethylene/vinyl acetate copolymers (Levapren) may generally be prepared by continuous solution, emulsion or bulk polymerisation. Polymerisation is radically initiated and produces copolymers with a statistical distribution of the monomeric units.
The copolymerisation parameters for ethylene and vinyl acetate are close to 1.
"Azeotropic" behaviour is produced, e.g. for a mixture with 50 wt.% each of ethylene and vinyl acetate at 90~C and a pressure of lO00 bar (US-A 3 168 456, R.D. Burkhart, J. Poly. Sci. part A 1 (1963) 1137). With this type of monomer mixture, the composition of the polymer remains constant over a wide conversion range. The copolymerisation parameters depend on the temperature, the pressure and on an optionally present solvent.
Industrially, EVM polymers are prepared either by continuous bulk polymerisationat pressures of 1000 to 3000 bar (G.W. Gilby, Dev. Rubber Technol. 3 (1981) 101) or in solution (US-A 3 325 460, DE-A 14 95 767, DE-A 14 95 660, DE-A
11 26 613, DE-A 11 26 614) at pressures of 200 to 1000 bar. The products obtained in the bulk process have a maximum vinyl acetate content of 45 %
because only low average molecular weights can be achieved due to the high transfer constant of vinyl acetate at high concentrations (H. Bartl, Kautsch., Gummi, Kunst. 25 (1972) 425).
Solution polymerisation allows the use of a wide range of comonomer ratios. The lower limit for the amount of vinyl acetate in this process is determined by thecritical demixing pressure. In order to reduce the formation of partly gelled material, polymerisation has to be performed above the critical demixing pressure.
The compressive strength of the reactors which can be technically achieved sets limits here.
In a solution polymerisation process, a mixture of ethylene/vinyl acetate (optionally in the "azeotropic" ratio) is used with the addition of as little aspossible transferring solvent, e.g. tert.-butanol, benzene, toluene (EP-A 374 666, CA 02204677 1997-0~-07 Le A 31 682-Forei~n Countries EP-A 374 664, EP-A 374 660). For the polymerisation of ethylene and vinyl acetate in tert.-butanol, the documents mentioned cite measures for obtaining asgel-free a product as possible and for avoiding phase demixing during reaction. In a high-pressure polymerisation unit, depending on the pressure limitation, 5 copolymers with a specific minimum vinyl acetate content can be prepared. In a380 bar unit, these are products containing approximately 40 wt.% of vinyl acetate. Polymerisation is generally performed in a multi-stage stirred reactor cascade.
Emulsion processes performed at pressures of 1 to 200 bar and in the temperature10 range 30 to 70~C are also known for the preparation of ethylene/vinyl acetatecopolymers. The polymers have a high gel content and cannot be vulcanised (B.V.
Mitra and M.R. Katti, Pop. Plast. 18 (1973) 15). The vinyl acetate content is 60 to 100 %.
The use of a solvent and polymerisation in an emulsion, as compared with pure 15 bulk polymerisation, leads to the reaction mixture being much less viscous and to greatly improved heat dissipation in the reactor.
A substantial disadvantage of solution polymerisation is the technically complicated procedure for removing and recovering the solvent. In the case of emulsion polymerisation, the effluent which is produced has to be processed.
20 Bulk polymerisation leads, at high conversions, to very viscous reaction melts so that the transport of heat and material within the system is inhibited and technical problems occur during the reaction procedure. In the currently conventional process for bulk polymerisation, the potential conversions are therefore less than 20 %, while in a solution process, conversions of up to 70 % can be achieved.
25 The removal of residual monomers is performed by distillation, e.g. in technically complicated screw, thin layer or extrusion evaporators (DE-A 21 38 176).
An alternative to this procedure is extraction of the residual monomers from thepolymer. Extraction may be performed, for instance, with supercritical CO2 (DE-A33 23 940, US-A 4 695 621 A, US-A 4 703 105, DE-A 39 38 877). Depending on 30 the conditions, residual monomer concentrations of 50 to 15 ppm are produced by this procedure.
CA 02204677 1997-0~-07 Le A 31 682-Forei~n Countries The present invention is therefore based on the object of providing a process bymeans of which copolymers of ethylene and polar monomers like vinylacetate or methylacrylate are obtained in a diluent which enables efficient heat dissipation, keeps the viscosity of the reaction mixture low, has effective material transport 5 properties, has small transfer constants, is physiologically harmless, can be readily removed from the polymer and facilitates removal of residual monomers.
The object is achieved according to the invention by a process for preparing copolymers of ethylene and polar monomers in the presence of supercritical carbon dioxide as an inert diluent.
10 In the radical solution polymerisations which may be performed using this process, vinyl acetate, acrylates, methacrylates, alkenyl acetates and CO (carbon monoxide) can be used as monomers in addition to ethylene. Preferred monomers are vinylacetate and methylacrylate.
The properties of carbon dioxide in the supercritical state have been described by J.A. Hatt, J. Org. Chem. _ (1984) 5097. According to that, the critical point for carbon dioxide is at about 31~C and 73 bar.
Polymerisation may be performed in a pressure range from 73 to 3000 bar and at temperatures above 31~C. Pressures of 100 to 500 bar are preferred. The preferred polymerisation temperature is 60 to 150~C.
20 Ethylene and vinyl acetate or methylacrylate are present in the monomer mixture in a ratio by weight of 20/80 to 80/20.
The polymerisation reaction is started with the assistance of initiators which decompose into radicals. All initiators which are known for the polymerisation of monomers may be used. In the temperature range 80 to 130~C, for example, 25 dibenzoyl peroxide, 2,2-azobis-(isobutyronitrile), tert.-butyl perpivalate, azobis-isovaleronitrile, are suitable. At temperatures above 120~C, tert.-butyl perbenzoate (tBPB) can be used, above 145~C, peroxides such as di-tert.-butyl peroxide (DTBP) can be used. The selection of a suitable radical producer is governed, asusual, by the polymerisation temperature striven for and by the kinetics of 30 polymerisation.
CA 02204677 1997-0~-07 Le A 31 682-Forei~n Countries The initiators are used in conventional amounts for polymerisation; 0.005 to 10,preferably 0.01 to 5 parts by weight of initiator per 100 parts by weight of monomers. 5 to 1500, preferably 50 to 900 parts by weight of CO2 are generally used, with reference to 100 parts by weight of monomer mixture. In some cases itmay be advantageous to use only 5 to 200 parts by weight, or even only 20 to 70 parts by weight of CO2 to 100 parts by weight of monomer mixture The polymerisation reaction may be performed batch-wise or continuously in appropriately designed pressurised equipment.
In order to remove heat produced during polymerisation, it is desirable that thepressurised equipment be provided with a cooling system. Furthermore, the equipment should be heatable and be provided with mixing devices, e.g. stirrers (paddle, anchor or gas dispersion stirrers).
Polymerisation may be performed, for instance, in such a way that vinyl acetate is initially introduced into a pressurised container and the initiator dissolved therein, the autoclave is sealed and gaseous ethylene and liquid carbon dioxide are then introduced. The reaction mixture is then heated to the desired polymerisation temperature. After termination of polymerisation, the reaction mixture is cooledand the carbon dioxide is separated by reducing the pressure. The polymers are then obtained as solid residue.
A particularly advantageous method of performing the process according to the invention consists of performing the reaction in a continuously fed tubular reactor.
Basically any pressure-resistant equipment in which the ratio of length to diameter is greater than 10 is suitable as a tubular reactor. The length of the reaction tube is governed by the reaction time which can vary between wide limits depending on the temperature, pressure, CO2 content and initiator concentration. A continuousreaction performed in a multi-stage stirred reactor cascade is also advantageous.
The reaction time for the process according to the invention is 1 to 10 hours.
The continuous or batchwise reduction in pressure in the reaction mixture may basically be performed using any conventional technical devices, for instance, valves, nozzles or pressure reduction tubes. All or some of the gases obtained during this procedure are preferably returned to the process.
CA 02204677 1997-0=,-07 Le A 31 682-Forei~n Countries In order to reduce the concentration of residual monomers in the polymer, it is advantageous to perform the pressure reduction procedure in such a way that the polymer is present as a melt at the end of the reaction period. This means that residual monomers are extracted from the polymer phase into the CO2-rich phase 5 during a controlled pressure reduction step. To achieve conventional requirements relating to the residual monomer content, it may be advantageous to add additional supercritical CO2 to the reactor prior to reducing the pressure. After returning the pressure to atmospheric, the polymer is obtained as a melt with a uniform tem-perature and can be granulated.
10 During radical solution polymerisation, the use of supercritical CO2 has proved to be particularly advantageous because, in contrast to most other solvents, virtually no transfer reactions are observed and thus higher molecular weights are achieved.
Furthermore, polymerisation in supercritical CO2, as compared with poly-merisations in conventional solvents, results in a lower viscosity.
15 The two processes mentioned may be used with particular advantage to prepare polymers with high molecular weights, in particular elastomers. Products with very little tackiness and better vulcanising properties are produced, these having reatly improved properties as compared with the background prior art relating to EVM
and AEM rubbers.
20 The low viscosities of polymerisation mixtures using supercritical CO2 enablepolymerisation to be continued to higher conversions because the heat dissipation is greatly improved and the mixtures are easier to stir. These process advantages improve the economic viability of the process as performed hitherto.
Due to the lack of hitherto conventional solvents, recovery and purification steps 25 are also unnecessary. Working up the polymerisation mixtures is preferably performed in such a way that any remaining monomers are also largely removed when the CO2 is separated. Further purification of the polymer may than take place in a conventional manner.
CA 02204677 1997-OF,-07 Le A 31 682-Forei~n Countries Examples Average molecular weights and molecular weight distributions were determined using GPC analysis and the products were chemically characterised by means of FTIR.
5 Example 1 22.5 g of vinyl acetate, 42.5 bar of ethylene and 0.502 g of azobis-isobutyrodinitrile were initially introduced into a 400 ml autoclave. 87 g of carbon dioxide were then metered into the autoclave, this being provided with a stirrerand a heating device. The reaction mixture was stirred (800 rpm) and heated to 70~C. The pressure was then 100 bar. When the reaction mixture had been at 70~C and 100 bar for 6 hours, the contents of the autoclave were cooled and returned to atmospheric pressure. A colourless product was obtained with a yieldof 24 % . The average molecular weight of the product was 15.3 x 10' g/mol. The product contained 72 % vinyl acetate.
Example 2 43 g of vinyl acetate, 58 bar of ethylene and 0.5024 g of azobis-isobutyrodinitrile were initially introduced into a 400 ml autoclave. 80 g of carbon dioxide were then metered into the autoclave which was provided with a stirrer and a heater.
The reaction mixture was stirred (800 rpm) and heated to 80~C. The pressure was then 118 bar. When the reaction mixture had been at 80~C and 118 bar for 6 hours, the contents of the autoclave were cooled and returned to atmospheric pressure. A colourless product was obtained with a yield of 40 %. The average molecular weight of the product was 148 x 103 g/mol (with a non-uniformity of 6). The product contained 56 % vinyl acetate.
Example 3 22.5 g of vinyl acetate, 42.5 bar of ethylene and 0.5024 g of azobis-isobutyrodinitrile were initially introduced into a 400 ml autoclave. 180 g of carbon dioxide were then metered into the autoclave which was provided with a stirrer and a heater. The reaction mixture was stirred (800 rpm) and heated to 80~C. The pressure was then 170 bar. When the reaction mixture had been at . CA 02204677 1997-0~-07 Le A 31 682-Forei~n Countries 80~C and 170 bar for 6 hours, the contents of the autoclave were cooled and returned to atmospheric pressure. A colourless product was obtained with a yieldof 12 %. The average molecular weight of the product was 5 x 103 g/mol (with a non-uniformity of 0.92). The product contained 54 % vinyl acetate.
Process for preparing ethylene/vinyl acetate copolymers The invention relates to a process for preparing copolymers of ethylene and polar S monomers in the presence of supercritical carbon dioxide.
Ethylene/vinyl acetate copolymers (Levapren) may generally be prepared by continuous solution, emulsion or bulk polymerisation. Polymerisation is radically initiated and produces copolymers with a statistical distribution of the monomeric units.
The copolymerisation parameters for ethylene and vinyl acetate are close to 1.
"Azeotropic" behaviour is produced, e.g. for a mixture with 50 wt.% each of ethylene and vinyl acetate at 90~C and a pressure of lO00 bar (US-A 3 168 456, R.D. Burkhart, J. Poly. Sci. part A 1 (1963) 1137). With this type of monomer mixture, the composition of the polymer remains constant over a wide conversion range. The copolymerisation parameters depend on the temperature, the pressure and on an optionally present solvent.
Industrially, EVM polymers are prepared either by continuous bulk polymerisationat pressures of 1000 to 3000 bar (G.W. Gilby, Dev. Rubber Technol. 3 (1981) 101) or in solution (US-A 3 325 460, DE-A 14 95 767, DE-A 14 95 660, DE-A
11 26 613, DE-A 11 26 614) at pressures of 200 to 1000 bar. The products obtained in the bulk process have a maximum vinyl acetate content of 45 %
because only low average molecular weights can be achieved due to the high transfer constant of vinyl acetate at high concentrations (H. Bartl, Kautsch., Gummi, Kunst. 25 (1972) 425).
Solution polymerisation allows the use of a wide range of comonomer ratios. The lower limit for the amount of vinyl acetate in this process is determined by thecritical demixing pressure. In order to reduce the formation of partly gelled material, polymerisation has to be performed above the critical demixing pressure.
The compressive strength of the reactors which can be technically achieved sets limits here.
In a solution polymerisation process, a mixture of ethylene/vinyl acetate (optionally in the "azeotropic" ratio) is used with the addition of as little aspossible transferring solvent, e.g. tert.-butanol, benzene, toluene (EP-A 374 666, CA 02204677 1997-0~-07 Le A 31 682-Forei~n Countries EP-A 374 664, EP-A 374 660). For the polymerisation of ethylene and vinyl acetate in tert.-butanol, the documents mentioned cite measures for obtaining asgel-free a product as possible and for avoiding phase demixing during reaction. In a high-pressure polymerisation unit, depending on the pressure limitation, 5 copolymers with a specific minimum vinyl acetate content can be prepared. In a380 bar unit, these are products containing approximately 40 wt.% of vinyl acetate. Polymerisation is generally performed in a multi-stage stirred reactor cascade.
Emulsion processes performed at pressures of 1 to 200 bar and in the temperature10 range 30 to 70~C are also known for the preparation of ethylene/vinyl acetatecopolymers. The polymers have a high gel content and cannot be vulcanised (B.V.
Mitra and M.R. Katti, Pop. Plast. 18 (1973) 15). The vinyl acetate content is 60 to 100 %.
The use of a solvent and polymerisation in an emulsion, as compared with pure 15 bulk polymerisation, leads to the reaction mixture being much less viscous and to greatly improved heat dissipation in the reactor.
A substantial disadvantage of solution polymerisation is the technically complicated procedure for removing and recovering the solvent. In the case of emulsion polymerisation, the effluent which is produced has to be processed.
20 Bulk polymerisation leads, at high conversions, to very viscous reaction melts so that the transport of heat and material within the system is inhibited and technical problems occur during the reaction procedure. In the currently conventional process for bulk polymerisation, the potential conversions are therefore less than 20 %, while in a solution process, conversions of up to 70 % can be achieved.
25 The removal of residual monomers is performed by distillation, e.g. in technically complicated screw, thin layer or extrusion evaporators (DE-A 21 38 176).
An alternative to this procedure is extraction of the residual monomers from thepolymer. Extraction may be performed, for instance, with supercritical CO2 (DE-A33 23 940, US-A 4 695 621 A, US-A 4 703 105, DE-A 39 38 877). Depending on 30 the conditions, residual monomer concentrations of 50 to 15 ppm are produced by this procedure.
CA 02204677 1997-0~-07 Le A 31 682-Forei~n Countries The present invention is therefore based on the object of providing a process bymeans of which copolymers of ethylene and polar monomers like vinylacetate or methylacrylate are obtained in a diluent which enables efficient heat dissipation, keeps the viscosity of the reaction mixture low, has effective material transport 5 properties, has small transfer constants, is physiologically harmless, can be readily removed from the polymer and facilitates removal of residual monomers.
The object is achieved according to the invention by a process for preparing copolymers of ethylene and polar monomers in the presence of supercritical carbon dioxide as an inert diluent.
10 In the radical solution polymerisations which may be performed using this process, vinyl acetate, acrylates, methacrylates, alkenyl acetates and CO (carbon monoxide) can be used as monomers in addition to ethylene. Preferred monomers are vinylacetate and methylacrylate.
The properties of carbon dioxide in the supercritical state have been described by J.A. Hatt, J. Org. Chem. _ (1984) 5097. According to that, the critical point for carbon dioxide is at about 31~C and 73 bar.
Polymerisation may be performed in a pressure range from 73 to 3000 bar and at temperatures above 31~C. Pressures of 100 to 500 bar are preferred. The preferred polymerisation temperature is 60 to 150~C.
20 Ethylene and vinyl acetate or methylacrylate are present in the monomer mixture in a ratio by weight of 20/80 to 80/20.
The polymerisation reaction is started with the assistance of initiators which decompose into radicals. All initiators which are known for the polymerisation of monomers may be used. In the temperature range 80 to 130~C, for example, 25 dibenzoyl peroxide, 2,2-azobis-(isobutyronitrile), tert.-butyl perpivalate, azobis-isovaleronitrile, are suitable. At temperatures above 120~C, tert.-butyl perbenzoate (tBPB) can be used, above 145~C, peroxides such as di-tert.-butyl peroxide (DTBP) can be used. The selection of a suitable radical producer is governed, asusual, by the polymerisation temperature striven for and by the kinetics of 30 polymerisation.
CA 02204677 1997-0~-07 Le A 31 682-Forei~n Countries The initiators are used in conventional amounts for polymerisation; 0.005 to 10,preferably 0.01 to 5 parts by weight of initiator per 100 parts by weight of monomers. 5 to 1500, preferably 50 to 900 parts by weight of CO2 are generally used, with reference to 100 parts by weight of monomer mixture. In some cases itmay be advantageous to use only 5 to 200 parts by weight, or even only 20 to 70 parts by weight of CO2 to 100 parts by weight of monomer mixture The polymerisation reaction may be performed batch-wise or continuously in appropriately designed pressurised equipment.
In order to remove heat produced during polymerisation, it is desirable that thepressurised equipment be provided with a cooling system. Furthermore, the equipment should be heatable and be provided with mixing devices, e.g. stirrers (paddle, anchor or gas dispersion stirrers).
Polymerisation may be performed, for instance, in such a way that vinyl acetate is initially introduced into a pressurised container and the initiator dissolved therein, the autoclave is sealed and gaseous ethylene and liquid carbon dioxide are then introduced. The reaction mixture is then heated to the desired polymerisation temperature. After termination of polymerisation, the reaction mixture is cooledand the carbon dioxide is separated by reducing the pressure. The polymers are then obtained as solid residue.
A particularly advantageous method of performing the process according to the invention consists of performing the reaction in a continuously fed tubular reactor.
Basically any pressure-resistant equipment in which the ratio of length to diameter is greater than 10 is suitable as a tubular reactor. The length of the reaction tube is governed by the reaction time which can vary between wide limits depending on the temperature, pressure, CO2 content and initiator concentration. A continuousreaction performed in a multi-stage stirred reactor cascade is also advantageous.
The reaction time for the process according to the invention is 1 to 10 hours.
The continuous or batchwise reduction in pressure in the reaction mixture may basically be performed using any conventional technical devices, for instance, valves, nozzles or pressure reduction tubes. All or some of the gases obtained during this procedure are preferably returned to the process.
CA 02204677 1997-0=,-07 Le A 31 682-Forei~n Countries In order to reduce the concentration of residual monomers in the polymer, it is advantageous to perform the pressure reduction procedure in such a way that the polymer is present as a melt at the end of the reaction period. This means that residual monomers are extracted from the polymer phase into the CO2-rich phase 5 during a controlled pressure reduction step. To achieve conventional requirements relating to the residual monomer content, it may be advantageous to add additional supercritical CO2 to the reactor prior to reducing the pressure. After returning the pressure to atmospheric, the polymer is obtained as a melt with a uniform tem-perature and can be granulated.
10 During radical solution polymerisation, the use of supercritical CO2 has proved to be particularly advantageous because, in contrast to most other solvents, virtually no transfer reactions are observed and thus higher molecular weights are achieved.
Furthermore, polymerisation in supercritical CO2, as compared with poly-merisations in conventional solvents, results in a lower viscosity.
15 The two processes mentioned may be used with particular advantage to prepare polymers with high molecular weights, in particular elastomers. Products with very little tackiness and better vulcanising properties are produced, these having reatly improved properties as compared with the background prior art relating to EVM
and AEM rubbers.
20 The low viscosities of polymerisation mixtures using supercritical CO2 enablepolymerisation to be continued to higher conversions because the heat dissipation is greatly improved and the mixtures are easier to stir. These process advantages improve the economic viability of the process as performed hitherto.
Due to the lack of hitherto conventional solvents, recovery and purification steps 25 are also unnecessary. Working up the polymerisation mixtures is preferably performed in such a way that any remaining monomers are also largely removed when the CO2 is separated. Further purification of the polymer may than take place in a conventional manner.
CA 02204677 1997-OF,-07 Le A 31 682-Forei~n Countries Examples Average molecular weights and molecular weight distributions were determined using GPC analysis and the products were chemically characterised by means of FTIR.
5 Example 1 22.5 g of vinyl acetate, 42.5 bar of ethylene and 0.502 g of azobis-isobutyrodinitrile were initially introduced into a 400 ml autoclave. 87 g of carbon dioxide were then metered into the autoclave, this being provided with a stirrerand a heating device. The reaction mixture was stirred (800 rpm) and heated to 70~C. The pressure was then 100 bar. When the reaction mixture had been at 70~C and 100 bar for 6 hours, the contents of the autoclave were cooled and returned to atmospheric pressure. A colourless product was obtained with a yieldof 24 % . The average molecular weight of the product was 15.3 x 10' g/mol. The product contained 72 % vinyl acetate.
Example 2 43 g of vinyl acetate, 58 bar of ethylene and 0.5024 g of azobis-isobutyrodinitrile were initially introduced into a 400 ml autoclave. 80 g of carbon dioxide were then metered into the autoclave which was provided with a stirrer and a heater.
The reaction mixture was stirred (800 rpm) and heated to 80~C. The pressure was then 118 bar. When the reaction mixture had been at 80~C and 118 bar for 6 hours, the contents of the autoclave were cooled and returned to atmospheric pressure. A colourless product was obtained with a yield of 40 %. The average molecular weight of the product was 148 x 103 g/mol (with a non-uniformity of 6). The product contained 56 % vinyl acetate.
Example 3 22.5 g of vinyl acetate, 42.5 bar of ethylene and 0.5024 g of azobis-isobutyrodinitrile were initially introduced into a 400 ml autoclave. 180 g of carbon dioxide were then metered into the autoclave which was provided with a stirrer and a heater. The reaction mixture was stirred (800 rpm) and heated to 80~C. The pressure was then 170 bar. When the reaction mixture had been at . CA 02204677 1997-0~-07 Le A 31 682-Forei~n Countries 80~C and 170 bar for 6 hours, the contents of the autoclave were cooled and returned to atmospheric pressure. A colourless product was obtained with a yieldof 12 %. The average molecular weight of the product was 5 x 103 g/mol (with a non-uniformity of 0.92). The product contained 54 % vinyl acetate.
Claims (10)
1. A process for preparing a copolymer of ethylene and a polar monomer, wherein the ethylene and the polar monomer are reacted under pressure in the presence of supercritical carbon dioxide as an inert diluent.
2. A process according to claim 1, wherein ethylene and vinyl acetate are polymerised in the presence of supercritical carbon dioxide at a temperature of 31°C to 200°C and a pressure of 73 to 3000 bar.
3. A process according to claim 1, wherein ethylene and methylacrylate are polymerised in the presence of supercritical carbon dioxide at a temperature of 31°C to 200°C
and a pressure of 73 to 3000 bar.
and a pressure of 73 to 3000 bar.
4. A process according to any one of claims 1 to 3, wherein 5 to 1500 wt.% of carbon dioxide, with reference to the monomer mixture, is used.
5. A process according to claim 2, wherein ethylene and vinyl acetate are used in a molar ratio of 20/80 to 80/20.
6. A process according to claim 3, wherein ethylene and methylacrylate are used in a molar ratio of 20/80 to 80/20.
7. A process according to any one of claims 1 to 6, wherein the reaction time is 1 to 10 hours.
8. A process according to any one of claims 1 to 7, wherein the reaction is performed in a tubular-flow reactor.
9. A process according to any one of claims 1 to 8, wherein the reaction is performed in a multi-stage stirred reactor cascade.
10. A process according to any one of claims 1 to 9, wherein the reaction mixture is returned to atmospheric pressure after leaving the reactor and all or some of the gas obtained is returned to the process after compression.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19618833.4 | 1996-05-10 | ||
| DE19618833A DE19618833A1 (en) | 1996-05-10 | 1996-05-10 | Process for the production of ethylene-vinyl acetate copolymers |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2204677A1 true CA2204677A1 (en) | 1997-11-10 |
Family
ID=7793934
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002204677A Abandoned CA2204677A1 (en) | 1996-05-10 | 1997-05-07 | Process for preparing ethylene/vinyl acetate copolymers |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0806438A3 (en) |
| JP (1) | JPH1045838A (en) |
| CA (1) | CA2204677A1 (en) |
| DE (1) | DE19618833A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6762254B1 (en) | 1999-05-17 | 2004-07-13 | Basf Aktiengesellschaft | Ethylene(meth)acrylate copolymers with low residual content in comonomers |
| US20120222422A1 (en) * | 2011-03-02 | 2012-09-06 | Aither Chemicals, LLC. | Methods for integrated natural gas purification and products produced therefrom |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3862489B2 (en) * | 1999-12-14 | 2006-12-27 | 日東電工株式会社 | Re-peeling adhesive sheet |
| DE10031005A1 (en) | 2000-06-30 | 2002-01-17 | Schleifring Und Appbau Gmbh | Self-diagnosing transmission system - Intelligent slip ring |
| DE10054114A1 (en) * | 2000-10-31 | 2002-05-16 | Dupont Performance Coatings | Process for the preparation of powder coating compositions |
| JP5474331B2 (en) * | 2008-10-30 | 2014-04-16 | 東海ゴム工業株式会社 | Dielectric film, and actuator, sensor, and transducer using the same |
| CN107868158A (en) * | 2016-09-22 | 2018-04-03 | 中国石油天然气股份有限公司 | Method for copolymerizing ethylene and ester |
| WO2019124675A1 (en) | 2017-12-18 | 2019-06-27 | 주식회사 엘지화학 | Ethylene vinyl acetate copolymer and preparation method therefor |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3522228A (en) * | 1966-05-19 | 1970-07-28 | Sumitomo Chemical Co | Novel method for polymerizing a vinyl compound in the presence of a carbon dioxide medium |
| DE3665594D1 (en) * | 1985-10-22 | 1989-10-19 | Basf Ag | Process for preparing powdery polymers |
| DE3609829A1 (en) * | 1986-03-22 | 1987-09-24 | Basf Ag | METHOD FOR PRODUCING POWDERED CROSSLINKED COPOLYMERISATS |
| US5527865A (en) * | 1995-03-24 | 1996-06-18 | The University Of North Carolina At Chapel Hill | Multi-phase polymerization process |
-
1996
- 1996-05-10 DE DE19618833A patent/DE19618833A1/en not_active Withdrawn
-
1997
- 1997-04-29 EP EP97107047A patent/EP0806438A3/en not_active Withdrawn
- 1997-05-06 JP JP9130536A patent/JPH1045838A/en active Pending
- 1997-05-07 CA CA002204677A patent/CA2204677A1/en not_active Abandoned
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6762254B1 (en) | 1999-05-17 | 2004-07-13 | Basf Aktiengesellschaft | Ethylene(meth)acrylate copolymers with low residual content in comonomers |
| US20120222422A1 (en) * | 2011-03-02 | 2012-09-06 | Aither Chemicals, LLC. | Methods for integrated natural gas purification and products produced therefrom |
| US9676695B2 (en) * | 2011-03-02 | 2017-06-13 | Aither Chemical LLC | Methods for integrated natural gas purification and products produced therefrom |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH1045838A (en) | 1998-02-17 |
| EP0806438A3 (en) | 1998-05-13 |
| DE19618833A1 (en) | 1997-11-13 |
| EP0806438A2 (en) | 1997-11-12 |
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