Process for reducing ethylene volatiles during LDPE polymerization.

Abstract

An embodiment of a method for reducing unreacted ethylene monomer in a low density polyethylene (LDPE) polymerization process includes delivering a monomer feed comprising ethylene monomer to a compressor system to produce a pressurized feed having a pressure of at least 2000 bar; passing the pressurized feed to at least one free radical polymerization reactor to produce a reactor effluent comprising LDPE and unreacted ethylene monomer; and delivering the reactor effluent to a separation system comprising a first separation vessel, a second separation vessel, and a third separation vessel in series, wherein the third separation vessel has an operating pressure of 0.05 bar or less, and the third separation vessel produces a separated product comprising LDPE and 50 ppm or less unreacted ethylene monomer, wherein no stripping agent is added upstream of the third separation vessel.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 63 / 039,185, filed June 15, 2020, the entire disclosure of which is incorporated herein by reference.

[0002] FIELD OF THE INVENTION FIELD OF THE INVENTION Embodiments described herein relate generally to low density polyethylene (LDPE) polymerization processes, and specifically to LDPE polymerization processes that reduce unreacted ethylene monomer during LDPE polymerization. [Background technology]

[0003] Like many polymerization processes, LDPE polymerization processes can have some amount of unreacted monomer at the end of the process. As a result, current LDPE polymerization systems use separation systems to remove unreacted ethylene monomer. Despite these separation systems, obtaining an LDPE product from the final separator stage with an unreacted ethylene monomer content of less than 50 ppm remains a continuing challenge. Therefore, pellet purging, silo ventilation, and / or extrusion are required downstream of the separation system to reduce the amount of unreacted monomer ethylene in the LDPE product to less than 50 ppm.

[0004] Therefore, there continues to be a need for an improved separation process that provides an LDPE product from a separation system having less than 50 ppm of unreacted ethylene monomer in the LDPE product. Summary of the Invention

[0005]

[0006] Embodiments of the present disclosure fulfill this need for a separation system that results in an LDPE product having an unreacted ethylene monomer content of less than 50 ppm. Specifically, embodiments of the present disclosure accomplish this by using a separation system that has a third separation vessel under vacuum pressure and does not contain a stripping agent (e.g., water) upstream of the third separation vessel. Without being limited by theory, the present embodiments eliminate the need for purging, reducing process costs and improving system safety.

[0006] According to one embodiment, there is provided a method for reducing unreacted ethylene monomer in a low-density polyethylene (LDPE) polymerization process, the method comprising: delivering a monomer feed comprising ethylene monomer to a compressor system to produce a pressurized feed having a pressure of at least 2000 bar; passing the pressurized feed to at least one free-radical polymerization reactor to produce a reactor effluent comprising LDPE and unreacted ethylene monomer; and delivering the reactor effluent to a separation system comprising a first separation vessel, a second separation vessel, and a third separation vessel in series, the third separation vessel having an operating pressure of 0.05 bar or less, the third separation vessel producing a separated product comprising LDPE and 50 ppm or less of unreacted ethylene monomer, and no stripping agent added upstream of the third separation vessel.

[0007] These and other embodiments are described in more detail below in the detailed description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0008] The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the following drawings, in which like structure is indicated with like reference numerals and in which: [Figure 1] FIG. 1 is a schematic diagram of the present LDPE polymerization process, according to one or more embodiments of the present disclosure. [Figure 2]FIG. 2 is a schematic diagram of a three-stage separation system used in the present LDPE polymerization process of FIG. 1, in accordance with one or more embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] Certain embodiments of the present application will now be described. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the claimed subject matter to those skilled in the art.

[0010] The term "polymer" refers to a polymeric compound prepared by polymerizing monomers, whether of the same or different types. Thus, the general term polymer generally encompasses the term "homopolymer," which refers to a polymer prepared from only one type of monomer, as well as the term "copolymer," which refers to a polymer prepared from two or more different types of monomers. As used herein, the term "interpolymer" refers to a polymer prepared by polymerization of at least two different types of monomers. Thus, the general term interpolymer includes copolymers or polymers prepared from two or more different types of monomers, such as terpolymers.

[0011] "Polyethylene" or "ethylene-based polymer" means a polymer containing greater than 50 mole percent units derived from ethylene monomers. This includes ethylene-based homopolymers or copolymers (meaning the units are derived from two or more comonomers). Common forms of ethylene-based polymers known in the art include, but are not limited to, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ultra-low-density polyethylene (ULDPE), very low-density polyethylene (VLDPE), single-site catalyzed linear low-density polyethylene (m-LLDPE), including both linear and substantially linear low-density resins, medium-density polyethylene (MDPE), and high-density polyethylene (HDPE).

[0012] As used herein, the term "composition" refers to a mixture of materials that comprise the composition, as well as reaction products and decomposition products formed from the materials of the composition.

[0013] The terms "blend," "polymer blend," and the like refer to a composition of two or more polymers. Such blends may or may not be miscible. Such blends may or may not be phase separated. Such blends may or may not contain one or more domain configurations as determined from transmission electron spectroscopy, light scattering, X-ray scattering, and any other method known in the art. A blend is not a laminate, although one or more layers of a laminate may contain the blend. Such blends may be prepared as dry blends or may be formed in situ (e.g., in a reactor), as melt blends, or using other techniques known to those skilled in the art.

[0014] The terms "comprising," "including," "having," and their derivatives are not intended to exclude the presence of any additional component, step, or procedure, whether specifically disclosed or not. For the avoidance of doubt, all compositions claimed through the use of the term "comprising" may include any additional additive, adjuvant, or compound, whether polymeric or otherwise, unless otherwise stated to the contrary. In contrast, the term "consisting essentially of" excludes from the scope of any subsequent description any other component, step, or procedure, except those that are not essential to operability. The term "consisting of" excludes any component, step, or procedure not specifically delineated or listed.

[0015] An embodiment of the present process for reducing unreacted ethylene monomer in low-density polyethylene (LDPE) polymerization is now described. Referring to system 10 of FIG. 1, a monomer feed 5 comprising ethylene monomer is fed to compressor system 20 to produce a pressurized feed 26 having a pressure of at least 2000 bar. Although not shown, it is contemplated that in some embodiments, the monomer feed 5 may be pressurized prior to delivery to compressor system 20. For example, the monomer feed may be delivered at a pressure of less than 100 bar, or less than 50 bar, or less than 20 bar. All bar measurements in this disclosure are absolute pressure values.

[0016] Referring again to FIG. 1 , compressor system 20 may include one or more compressors in parallel or series. As shown in FIG. 1 , compressor system 20 may include a primary compressor 22 and a secondary compressor 24 downstream from primary compressor 22. Primary compressor 22 may compress monomer feed 5 so that feed 23 to secondary compressor 24 has a pressure of at least 200 bar. In one or more embodiments, primary compressor 22 may compress the monomer feed to a pressure of 200 to 1000 bar, or 300 to 900 bar. To achieve this compression, primary compressor 22 may include one or more compression stages.

[0017] The secondary compressor 24, which may also be referred to as a hyper compressor, compresses the feedstock 23 to a pressure of at least 2000 bar, or at least 2500 bar, or at least 3000 bar. Like the primary compressor 22, the secondary compressor 24 may include one or more compression stages. In one or more embodiments, the secondary compressor 24 may comprise a plunger reciprocating compressor and may consist of single or multiple compression stages.

[0018] 1, the pressurized feedstock 26 exiting the compressor system 20 is sent to at least one free radical polymerization reactor 30 to produce a reactor effluent 32 comprising LDPE and unreacted ethylene monomer. As shown, a polymerization initiator 40 may be added to the free radical polymerization reactor 30.

[0019] The free radical polymerization reactor 30 may include one or more autoclave reactors or tubular reactors. The pressure in each autoclave or tubular reactor zone may be 1000 to 4000 bar, or 1500 to 3600 bar, or 2000 to 3200 bar. The polymerization temperature in each tubular reactor zone may be 100°C to 400°C, or 150°C to 360°C, or 180°C to 340°C. The polymerization temperature in each autoclave reactor zone may be 150 to 300°C, more typically 165 to 290°C, and even more typically 180 to 280°C.

[0020] 1 and 2, reactor effluent 32 from free radical polymerization reactor 30 may be fed to a separation system comprising a first separation vessel 70, a second separation vessel 90, and a third separation vessel 110 in series. However, in some embodiments, reactor effluent 32 may be fed to a pressure reducing valve 50 which reduces the pressure to produce stream 52 having a pressure of 175 to 800 bar. Stream 52 may then be fed to a downstream cooler 60, where the temperature of stream 62 exiting the cooler is reduced to 180 to 280° C. before being fed to the separation system.

[0021] 1 , third separation vessel 110 operates at vacuum pressure and, therefore, has an operating pressure of 0.05 bar or less. Because of this very low pressure, third separation vessel 110 is able to produce a separation product 112 comprising LDPE and 50 ppm or less of unreacted ethylene monomer without the addition of a stripping agent upstream of third separation vessel 110. In a further embodiment, separation product 112 comprises 30 ppm or less of unreacted ethylene monomer.

[0022] First separation vessel 70 may operate at a pressure of 150-350 bar and a temperature of 180-280° C. First separation vessel 70, sometimes referred to as a high pressure separator, separates unreacted ethylene monomer volatiles 74, which typically exit through the top of first separation vessel 70, while first separator polymer effluent 72 exits from the bottom of first separation vessel 70.

[0023] As shown in the embodiment of Figures 1 and 2, the separation system can include a pressure reducing valve 80 disposed between first separation vessel 70 and second separation vessel 90. Pressure reducing valve 80 reduces the pressure of first separator polymer effluent 72 to result in stream 82 having a pressure of 1 to 5 bar. Second separation vessel 90, sometimes referred to as the low-pressure separator, operates at a pressure of 1 to 5 bar and a temperature of 180 to 260°C. Second separation vessel 90 receives stream 82 and further separates unreacted ethylene monomer volatiles 94, which are typically discharged through the top of second separation vessel 90. Meanwhile, second separator polymer effluent 92 is discharged from the bottom of second separation vessel 90.

[0024] 1 and 2, an additive stream 86, for example, an antioxidant additive, may be introduced into a second separation vessel 90. The second separation vessel 90 may include a gear pump 91 adjacent its bottom for discharging a second separator polymer effluent 92 from the second separation vessel 90. Suitable gear pumps or positive displacement pumps are well known to those skilled in the art.

[0025] Additionally, as shown in FIGS. 1 and 2, an additive stream 96 may be present between second separation vessel 90 and third separation vessel 110. Additives in additive stream 86 or 96 may include UV stabilizers, lubricants, antioxidants, colorants, antistatic agents, flame retardants, etc. In one or more embodiments, these additives may include antioxidants or talc. As shown in FIGS. 1 and 2, additive stream 96 may be mixed in-line with second separator polymer effluent 92 or may be mixed in a static mixer 100 disposed upstream of third separation vessel 110. Suitable commercially available embodiments of antioxidants may include Irganox® 1010 or Irganox® 1076 from BASF. In one or more embodiments, less than 4000 ppm of additive may be included in additive feed 96, or less than 2000 ppm, or less than 1000 ppm, or less than 200 ppm, or less than 100 ppm may be included in additive stream 86 or 96. Without being bound by theory, these additives added upstream of second separation vessel 90 or third separation vessel 110 may mitigate potential gel formation that may occur under vacuum pressure.

[0026] Referring again to FIG. 1 , there is no stripping agent added upstream of third separation vessel 110. As used herein, “stripping agent” means feedwater. By operating third separation vessel 110 at a very low vacuum, this embodiment obtains a product with very low ethylene monomer volatiles without including a stripping agent between second separation vessel 90 and third separation vessel 110. As an added benefit, eliminating the stripping agent may also eliminate or reduce the need for a water separation unit downstream of third separation vessel 110. Thus, eliminating a stripping agent (e.g., feedwater) may improve process efficiency and reduce costs.

[0027] In addition to operating at vacuum pressure, the third separation vessel 110, sometimes referred to as a devolatilization reactor, may operate at a temperature of 180-260°C to separate unreacted ethylene monomer volatiles 114 and obtain a separated product 112 containing LDPE and 50 ppm or less of unreacted ethylene monomer. In further embodiments, the third separation vessel 110 may have an operating temperature of 200-240°C, or 220-235°C. Without being limited by theory, maintaining the temperature of the third vessel below 235°C may be beneficial to prevent gel formation at these low vacuum pressures. While vacuum pressure is defined herein as less than 0.05 bar, the third separation vessel 110 may operate at a pressure of 0.01-0.05 bar, or 0.01-0.03 bar, or 0.03-0.05 bar.

[0028] Similar to second separation vessel 90, third separation vessel 110 may include a gear pump 111 disposed adjacent its bottom for discharging a separation product 112 comprising LDPE and 50 ppm or less of unreacted ethylene monomer.

[0029] A variety of separation vessel configurations and equipment are contemplated as suitable for the first separation vessel 70, second separation vessel 90, and third separation vessel 110. While a variety of shapes are contemplated, one or more of the first separation vessel 70, second separation vessel 90, and third separation vessel 110 may have an upper generally cylindrical portion and a lower inverted conical portion. In each case, the inlet to the first separation vessel 70, second separation vessel 90, and third separation vessel 110 may be through the upper cylindrical wall of the vessel 70, 90, 110, with unreacted ethylene monomer volatiles vaporizing and exiting through the upper cylindrical portion while the polymer product exits through the bottom conical portion.

[0030] As is well known to those skilled in the art, third separation vessel 110 may require a heat source to flash and thereby separate ethylene monomer volatiles from the polymer feed.

[0031] In one embodiment of the third separation vessel 110, the third separation vessel 110 may include a distributor to improve devolatilization. During devolatilization, unreacted ethylene monomer volatiles are flashed by vacuum, thereby allowing the LDPE polymer to separate from the unreacted ethylene monomer volatiles. This process of separating the LDPE polymer from the volatiles involves generating foam bubbles. These bubbles generally include a polymer skin in which the volatiles are trapped. Once the bubbles grow to a sufficient size, they coalesce and rupture, allowing the volatile compounds to be released from the polymer skin. As a result, it may be desirable for this release of volatiles (from the bubbles) to occur in a separate device, such as a distributor, as opposed to a heating device.

[0032] Various compositions are contemplated for the separation vessels 70, 90, and 110. Specifically, the third separation vessel 110 and the distributors may be optimized with materials aimed at minimizing gel formation. For example, and without limitation, these materials may include, but are not limited to, polytetrafluoroethylene or stainless steel. Various distributor designs are contemplated, with some distributors providing efficiencies at least three times better than perfect balance.

[0033] Referring again to FIG. 1 , the separated product 112 from the third separation vessel 110, containing LDPE and 50 ppm or less of unreacted ethylene monomer, can be directly fed to downstream processing and / or transportation 120. As used herein, “downstream processing and / or transportation” can include directly delivering the separated product 112 to a storage vessel, such as a pelletizing unit, hydraulic conveying system, receiving tower, granule / water separation unit, dense phase conveying system, railcar, or the like. However, the present process eliminates a purging step, e.g., venting in a post-palletization purge silo. This extra step is costly, and the venting is environmentally undesirable. In further embodiments, the present process can eliminate expensive extruders and monomer breakers, thereby reducing costs and improving process efficiency. Note that some storage systems, such as vented railcars, can further reduce the unreacted ethylene monomer content. However, this is not necessary because the separated product 112 from the third separation vessel 110 has a sufficiently reduced unreacted ethylene monomer content.

[0034] 2, additive stream 116 may be added downstream of third separation vessel 110. In certain embodiments, an antioxidant along with slip agent and talc may be added downstream of third separation vessel 110, for example, via a side arm extruder downstream of gear pump 111.

[0035] initiator A variety of initiator 40 compositions are contemplated as suitable for addition to reactor 30. However, the initiator must be minimally effective within the temperature ranges described above for reactor 30. Free-radical initiators may include organic peroxides, such as peresters, perketals, peroxyketones, percarbonates, and cyclic polyfunctional peroxides. These organic peroxide initiators are used in conventional amounts, typically in amounts of 0.005 to 0.2 wt.% based on the weight of the polymerizable monomers. The peroxide may be injected as a dilute solution in a suitable solvent, such as a hydrocarbon solvent. Other suitable initiators include azodicarboxylic acid esters, azodicarboxylic acid dinitriles, and 1,1,2,2-tetramethylethane derivatives, as well as other components capable of forming free radicals within the desired operating temperature range.

[0036] Chain Transfer Agents (CTAs) Chain transfer agents (CTAs) or telogens are used in polymerization processes to control the melt index. Chain transfer is associated with the termination of growing polymer chains, thus limiting the final molecular weight of the polymer material. Chain transfer agents are typically hydrogen atom donors that react with growing polymer chains and terminate the chain polymerization reaction. These agents can be of many different types, ranging from saturated or unsaturated hydrocarbons to aldehydes, ketones, or alcohols. By controlling the concentration of the selected chain transfer agent, the length of the polymer chains and therefore the molecular weight, e.g., the number average molecular weight Mn, can be controlled. The melt flow index (MFI or I2) of the polymer, which is related to Mn, is also controlled.

[0037] Chain transfer agents include, but are not limited to, naphthenic hydrocarbons, aliphatic hydrocarbons such as propane, pentane, hexane, cyclohexane, n-butane, and isobutane; ketones such as acetone, diethyl ketone, or diamyl ketone; aldehydes such as formaldehyde, acetaldehyde, and propionaldehyde; olefins such as propylene and butene; and saturated aliphatic aldehyde alcohols such as methanol, ethanol, propanol, or butanol.

[0038] polymer In one embodiment, the ethylene-based polymers of this invention have a density, i.e., grams per cubic centimeter (g / cc or g / cm3), from 0.914 to 0.930, more typically from 0.916 to 0.930, and even more typically from 0.918 to 0.926. In one embodiment, the ethylene-based polymers of this invention have a melt index (I2) at 190°C / 2.16 kg from 0.1 to 40 g / 10 min, or from 0.2 to 25 g / 10 min. In some embodiments, the LDPE can have a lower I2 of from 0.1 to 10 g / 10 min, or from 0.1 to 1 g / 10 min. Alternatively, the LDPE can have a higher melt index (I2) of from 5 to 40 g / 10 min, or from 10 to 25 g / 10 min, or from 15 to 25 g / 10 min.

[0039] Monomers and Comonomers The term ethylene-based polymer may refer to a homopolymer of ethylene, such as an LDPE homopolymer, or a copolymer of ethylene with one or more comonomers. Suitable comonomers include ethylenically unsaturated monomers, particularly C 3~20 These may include, but are not limited to, α-olefins, diolefins, polyenes, and polar comonomers, including those with carboxylic acid, acrylate, or acetate functionality, such as, but not limited to, methacrylic acid, acrylic acid, vinyl acetate, methyl acrylate, isobutyl acrylate, n-butyl acrylate, glycidyl methacrylate, and the monoethyl ester of maleic acid.

[0040] blend The ethylene-based polymer can be blended with one or more other polymers, such as, but not limited to, linear low-density polyethylene (LLDPE); copolymers of ethylene with one or more α-olefins, such as, but not limited to, propylene, butene-1, pentene-1,4-methylpentene-1, pentene-1, hexene-1, and octene-1; and high-density polyethylene (HDPE) having a density of 0.940 to 0.970 g / cc. The amount of the ethylene-based polymer in the blend can vary, but is typically 10 to 90 weight percent (wt%), or 15 to 85 wt%, or 20 to 80 wt%, based on the weight of the polymers in the blend.

[0041] Purpose LDPE can be used in a variety of conventional thermoplastic manufacturing processes to produce useful articles such as films; molded articles, e.g., blow-molded, injection-molded, or rotationally molded articles; foams; wire and cable, fibers, extrusion coatings, and woven or nonwoven fabrics. [Example]

[0042] Test Method Test methods include:

[0043] Melt Index The melt index I2 (or I2) of the polymer samples was measured according to ASTM D-1238 (Method B) at 190°C and a load of 2.16 kg, respectively.

[0044] density Samples for density measurements were prepared according to ASTM D4703. Measurements were performed according to ASTM D792, Method B, within 1 hour of sample pressing.

[0045] Examples 1 and 2 Two commercially available Dow grades were used for the experimental pilot plant setup: LDPE 780E (Example 1) with a melt index of 20 g / 10 min and LDPE 150E (Example 2) with a melt index of 0.25 g / 10 min. Nitrogen-purged pellets were fed into a single-screw extruder, which was used to melt the pellets and send the molten material to a separator. The line between the extruder and the separator was equipped with heated oil and a static mixer element. This line was used to control the temperature throughout the separator. Ethylene was introduced upstream of the static mixing element to ensure good mixing before the separator. Ethylene was supplied and metered using bottled ethylene and a flow meter and control valve. The combined stream of molten polymer and ethylene was fed into a separator with vacuum capability. The separator was equipped with temperature and pressure instruments. A gear pump was attached to the bottom of the separator, and a single molten strand was fed into a water bath. The strand emerging from the water bath was air-dried and fed into a strand chopper. The pellets were collected at the exit of the strand chopper and measured for ethylene volatiles. Additional process conditions are shown in Tables 1 and 2 below.

[0046] Example 1 - LDPE 780E with I2 of 20 g / 10 min In Example 1, multiple pilot plant separation experiments were conducted in the synthesis process of DOW™ LDPE 780E, a commercially available LDPE from The Dow Chemical Company (Midland, MI) with a density of 0.923 g / cc and an I2 of 20 g / 10 min. As shown in Table 1, Inventive Examples 1 and 2, which were devolatilized in a third separation vessel operating at a vacuum pressure of 0.05 bar or less, yielded final LDPE products with unreacted ethylene monomer contents of 11 ppm or 20 ppm, respectively, without the use of any stripping agent, while Comparative Examples A and B contained 1 wt % and 2 wt %, respectively, of a water stripping agent to reduce the unreacted ethylene monomer content.

[0047] [Table 1]

[0048] Example 2 - LDPE 150E with I2 of 0.25 g / 10 min In Example 2, several pilot plant separation experiments were also conducted in the synthesis process of DOW™ LDPE 150E, a commercially available LDPE from The Dow Chemical Company (Midland, MI) with a density of 0.921 g / cc and an I2 of 0.25 g / 10 min. As shown in Table 2, Inventive Examples 3 and 4, which were devolatilized in a third separation vessel operating at a vacuum pressure of 0.03 bar, yielded final LDPE products with unreacted ethylene monomer contents of 32 ppm and 21 ppm, respectively, while Comparative Examples D and E contained 1 wt. % water stripping agent to reduce the unreacted ethylene monomer content. Inventive Example 3 achieved unreacted ethylene monomer removal at a lower temperature of 230°C. In contrast, Comparative Example C, which used a third separation vessel operating at a pressure greater than 0.05 bar, unsatisfactorily yielded a final LDPE product with an unreacted ethylene monomer content of 104 ppm. Furthermore, Comparative Example E, which employed a third separation vessel operating at a pressure greater than 0.05 bar (0.15 bar) and 1 wt. % stripping agent, was unable to reduce the unreacted ethylene monomer content below 50 ppm.

[0049] [Table 2]

[0050] It will be apparent that modifications and variations are possible without departing from the scope of the present disclosure, as defined in the appended claims. More specifically, while certain aspects of the present disclosure have been identified herein as preferred or particularly advantageous, it is not intended that the present disclosure be necessarily limited to these aspects.

Claims

1. 1. A method for reducing unreacted ethylene monomer in a low density polyethylene (LDPE) polymerization process, comprising: delivering a monomer feed comprising ethylene monomer to a compressor system to produce a pressurized feed having a pressure of at least 2000 bar; passing the pressurized feedstock to at least one free radical polymerization reactor to produce a reactor effluent comprising the LDPE and the unreacted ethylene monomer; delivering the reactor effluent to a separation system comprising a first separation vessel, a second separation vessel, and a third separation vessel in series, the third separation vessel having an operating pressure of 0.05 bar or less, the third separation vessel producing a separated product comprising LDPE and 50 ppm or less of the unreacted ethylene monomer, and no stripping agent added upstream of the third separation vessel; adding an additive to the separation system upstream of the third separation vessel, the additive being added between the second separation vessel and the third separation vessel.

2. 10. The method of claim 1, further comprising pelletizing the separated product without a subsequent purging step.

3. 10. The method of claim 1, wherein less than 200 ppm of additive is added.

4. The method of any one of claims 1 to 3, wherein the separated product contains 30 ppm or less of unreacted ethylene monomer.

5. The method of any one of claims 1 to 4, wherein the third separation vessel operates at a temperature of 180 to 260°C.

6. The method of any one of claims 1 to 5, wherein the first separation vessel operates at a pressure of 150 to 350 bar.

7. The method of any one of claims 1 to 6, wherein the second separation vessel operates at a pressure of 1 to 5 bar.

8. The method of any one of claims 1 to 7, wherein the separation system includes a pressure reducing valve disposed between the first separation vessel and the second separation vessel.

9. The method of any one of claims 1 to 8, wherein the compressor system comprises a primary compressor and a secondary compressor downstream of the primary compressor.

10. 10. The method of claim 9, wherein the primary compressor increases the pressure of the monomer feed to a pressure of at least 200 bar before feeding to the secondary compressor.

11. The method of any one of claims 1 to 10, wherein the free radical polymerization reactor comprises at least one tubular reactor or at least one autoclave reactor.

12. The method of any one of claims 1 to 11, wherein the reactor effluent is sent to a pressure reducing valve upstream of the separation system.

13. The monomer feedstock is C ３ ~C １２ The process of any one of claims 1 to 12, comprising an olefinic comonomer or a polar comonomer.

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