Process for producing ethylene copolymer while mitigating reactor fouling

Abstract

The invention relates to process a process for preparing an ethylene copolymer and to a system for producing the ethylene copolymer.

Description

24POL YO 136-WO-ORD1PROCESS FOR PRODUCING ETHYLENE COPOLYMER WHILE MITIGATING REACTOR FOULINGFIELD OF INVENTION

[0001] The invention relates to a process of producing ethylene copolymers such as copolymers derived from ethylene and vinyl monomers such as 2-hydroxyethyl methacrylate (HEMA).The invention further relates to a system for preparing the ethylene based copolymers.BACKGROUND

[0002] One of the impediments facing the industrial scale production of ethylene copolymer is that of reactor fouling due to the self-polymerization of the comonomer. For example, it was observed that during the production of ethylene copolymers using vinyl monomers such as HEMA is the self-polymerization of comonomer which may occur in the preheater sections located upstream of the polymerization reactors. Such self-polymerization typically occurs when the comonomer is exposed to elevated temperature for example temperatures of about 75 °C - 163 °C. One of the reasons that cause self-polymerization and fouling is the temperature rise when the ethylene is mixed with the vinyl monomer such as acrylates in the reactor or in the upstream hardware such as compressor or the preheaters in a high pressure polymerization set up. Mitigating or temperature management of the mixing of the monomers is one suitable way of controlling fouling or thermal hotspots.

[0003] The self-polymerization results in a pre-polymer buildup on compressor parts and causes pre-polymer caking on the inner walls of tubing and piping leading to reduced production rates and reactor downtime. Self-initiation or self-polymerization of acrylate monomers have been investigated in the past. It is known that at temperatures as low as 80°C self-initiated polymerization may take place. For example, in the research publication titled “Self-Initiated Butyl Acrylate Polymerizations in Bulk and in Solution Monitored By In-Line Techniques’" (Polymers 2021, 13, 2021. https: / / doi.org / 10.3390 / polyml3122021), the publication describes that even at 80 °C, the butyl acrylate starts to self-polymerize (Pg 4 of 16 of the journal). Therefore, the temperature rise on mixing of vinyl-based monomers such as acrylates with ethylene needs to be kept at a suitable level to minimize the risk of self-polymerization and reactor fouling.24POL YO 136-WO-ORD2

[0004] Further the publication titled “ Theoretical Insights Into Thermal Self-Initiation Reactions of Acrylates’’’ (DOI: https: / / doi.org / 10.1016 / B978-0-12-815983-5.00004-0, Computational Quantum Chemistry.) describes under section 4.4.1 that self-initiation or selfpolymerization of methyl methacrylate have been reported at a temperature between 100-130 °C. However, in order to manage the possible temperature, rise on mixing of the monomers, cooling systems such as heat exchangers, extensive array of water jackets may have to be used. In some instances, inhibitor compounds may have to be used to manage any adverse reaction kinetics arising from temperature rise. Alternatively, injection of the comonomer may be carried out as a diluted stream with the use of diluents, which allows injection of high amounts of comonomers at very low temperatures at different locations of reactor. However, this leads to high operational cost as often ethylene is required to be compressed to the reactor pressure together with the comonomer. Further reducing the temperature of the comonomer stream below a certain limit increases the viscosity of the monomer stream, rendering it difficult to be injected into a reactor. Further too low a temperature may affect reaction kinetics and affect the overall polymerization process with ethylene.

[0005] In another approach, ethylene copolymer production systems have relied on adding foulant inhibitor into the oil used to lubricate the hyper-compressor plunger used in compressing the ethylene feed. This approach is problematic. When the inhibitor is incorporated into the lubricant oil, it is difficult to control and manage the amount of inhibitor that actually reaches the areas where self-polymerization occurs. Although the use of inhibitors is promising there is still room for improving process efficiencies in order to mitigate the risks of reactor fouling.

[0006] As a further consideration, producing ethylene copolymer with units derived from high monomer content (e.g. 1 wt.% or greater) can be a challenge as at high monomer concentration the residence time of the highly reactive monomer with the ethylene should be kept as small as possible along with minimizing any temperature rise on mixing the ethylene with the monomer.

[0007] EP4375304A1 describes a process for the manufacture of ethylene copolymers at high pressure using a specific tubular reactor specification and high-pressure liquid injection of comonomers and modifiers. Although the patent addresses reactor fouling, it does not describe temperature management when ethylene and comonomer streams are mixed prior to24POL YO 136-WO-ORD3polymerization. Neither does the patent teach how temperature rise can be managed when ethylene copolymer with high monomer content is to be produced.

[0008] As a further consideration, to improve reaction kinetics, the ethylene and the comonomer streams can be mixed in the preheater. The mixing of the ethylene and the comonomer in the preheater is beneficial for several reasons. The premixing of the ethylene and the vinyl comonomer feed in the preheater allows (a) initiation temperature control - and ensures that the entire feed entering the polymerization reactor to have uniform temperature, (b) mixing in the preheater ensures uniform distribution of ethylene and comonomer and any chain transfer agents, (c) increased conversion efficiency, (d) prevention of phase separation and reduced gel formation tendency. However as noted in the patent EP4375304A1 - The presence of high reactive comonomers increases fouling due to thermal polymerization at the tube inside wall, mainly of the comonomer, where the highest temperature is reached. The addition of inhibitor typically is not solving the problem as the efficiency of the inhibitor reduces significantly at the preheating temperatures. Further, the addition of comonomers directly in the polymerization reactor may also cause reactor fouling as the reactor is generally operating at high temperature.

[0009] Accordingly, it is an objective of the present invention to provide for a process of producing ethylene copolymers with minimal reactor fouling and avoiding thermal runaway reactions. It is yet another objective of the present invention to manage the temperature rise when ethylene and comonomers streams are mixed prior to polymerization. It is yet another objective of the present invention to produce ethylene copolymers with low monomer content (e.g. 1 wt.% or higher) while limiting the temperature rise on mixing the ethylene stream with the comonomer stream prior to polymerization. It is yet another objective of the present invention is to provide for a system of producing ethylene copolymer.BRIEF DESCRIPTION OF THE DRAWINGS

[0001] For a more complete understanding, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0002] FIG. 1 is a schematic diagram illustrating an overview of the system for the production of ethylene copolymer in accordance with the present invention where the comonomer stream is injected in the second preheater (4b).24POL YO 136-WO-ORDDESCRIPTION

[0003] Accordingly, the one or more objectives of the present invention is achieved by a process for preparing an ethylene copolymer, the process comprising:(a) injecting an ethylene feed stream (1) into a compressor unit (2) to obtain an ethylene feed stream (3) comprising ethylene monomer, preferably wherein the ethylene feed stream (3) has a pressure of >180 MPa and < 320 MPa;(b) feeding at least a portion of the ethylene feed stream (3) into a first preheater (4a) positioned downstream to the compressor unit (2) to obtain an ethylene feed stream (6);(c) feeding at least a portion of the ethylene feed stream (6) into a second preheater (4b) positioned downstream to the first preheater (4a);(d) feeding a comonomer stream (5) comprising a vinyl monomer (D) into the second preheater (4b) such that the comonomer stream (5) is supplied to the second preheater (4b) by means of a dosing line (12) that is in fluid communication with the second preheater (4b);(e) contacting the ethylene feed stream (6) and the comonomer stream (5) in the second preheater (4b) and subsequently mixing the streams to obtain a product stream (8); and(f) feeding the product stream (8) into a reactor (20) positioned downstream to the second preheater (4b) and polymerizing the ethylene monomer and the vinyl monomer (D) to obtain the ethylene copolymer; and• wherein the comonomer stream (5) comprising a vinyl monomer (D) is injected into the second preheater (4b) at a flow rate of > 180 and < 3000 kg / hr; and • wherein the temperature (Th) of the comonomer stream (5) in the dosing line (12) prior to injecting into the second preheater (4b) ranges from > 30 °C and < 55 °C, preferably > 35 °C and < 55 °C; and• wherein the comonomer stream (5) on contacting with the ethylene feed stream (6) has a temperature of > 55 °C and < 90 °C, preferably > 60 °C and < 90 °C, preferably > 70 °C and < 87 °C.24POL YO 136-WO-ORD5

[0004] Preferably, the process comprises:(a) injecting an ethylene feed stream (1) into the compressor unit (2) to obtain an ethylene feed stream (3) comprising ethylene monomer, preferably wherein the ethylene feed stream (3) has a pressure of >180 MPa and < 320 MPa;(b) feeding at least a portion of the ethylene feed stream (3) into a first preheater (4a) positioned downstream to the compressor unit (2) to obtain an ethylene feed stream (6);(c) feeding at least a portion of the ethylene feed stream (6) into a second preheater (4b) positioned downstream to the first preheater (4a);(d) feeding a comonomer stream (5) comprising the vinyl monomer (D) into the second preheater (4b) such that the comonomer stream (5) is supplied to the second preheater (4b) by means of a dosing line (12) that is in fluid communication with the second preheater (4b);(e) contacting the ethylene feed stream (6) and the comonomer stream (5) in the second preheater (4b) and subsequently mixing the streams to obtain a product stream (8); and(f) feeding the product stream (8) into a reactor (20) positioned downstream to the second preheater (4b) and polymerizing the ethylene monomer and the vinyl monomer (D) to obtain the ethylene copolymer; and• wherein the comonomer stream (5) comprising a vinyl monomer (D) is injected into the second preheater (4b) at a flow rate of > 180 and < 3000 kg / hr; and • wherein the temperature (Th) of the comonomer stream (5) in the dosing line (12) prior to injecting into the second preheater (4b) ranges from > 30 °C and < 55 °C, preferably > 35 °C and < 55 °C; and• wherein the comonomer stream (5) on contacting with the ethylene feed stream (6) has a temperature of > 55 °C and < 90 °C, preferably > 60 °C and < 90 °C, preferably > 70 °C and < 87 °C; andwherein the vinyl-based monomer (D) is an acrylate based monomer (A) or an acrylate based ionomer (IA), preferably the vinyl based monomer (D) is an acrylate based monomer (A).

[0005] Preferably, the process comprises:24POL YO 136-WO-ORD6(a) injecting an ethylene feed stream (1) into the compressor unit (2) to obtain an ethylene feed stream (3) comprising ethylene monomer, preferably wherein the ethylene feed stream (3) has a pressure of >180 MPa and < 320 MPa;(b) feeding at least a portion of the ethylene feed stream (3) into a first preheater (4a) positioned downstream to the compressor unit (2) to obtain an ethylene feed stream (6);(c) feeding at least a portion of the ethylene feed stream (6) into a second preheater (4b) positioned downstream to the first preheater (4a);(d) feeding a comonomer stream (5) comprising the vinyl monomer (D) into the second preheater (4b) such that the comonomer stream (5) is supplied to the second preheater (4b) by means of a dosing line (12) that is in fluid communication with the second preheater (4b);(e) contacting the ethylene feed stream (6) and the comonomer stream (5) in the second preheater (4b) and subsequently mixing the streams to obtain a product stream (8); and(f) feeding the product stream (8) into a reactor (20) positioned downstream to the second preheater (4b) and polymerizing the ethylene monomer and the vinyl monomer (D) to obtain the ethylene copolymer; and• wherein the comonomer stream (5) comprising a vinyl monomer (D) is injected into the second preheater (4b) at a flow rate of > 180 and < 3000 kg / hr; and • wherein the temperature (Th) of the comonomer stream (5) in the dosing line (12) prior to injecting into the second preheater (4b) ranges from > 30 °C and < 55 °C, preferably > 35 °C and < 55 °C; and• wherein the comonomer stream (5) on contacting with the ethylene feed stream (6) has a temperature of > 55 °C and < 90 °C, preferably > 60 °C and < 90 °C, preferably > 70 °C and < 87 °C; andwherein the vinyl-based monomer (D) is an acrylate-based monomer (A).

[0006] Preferably, the process comprises:(g) injecting an ethylene feed stream (1) into the compressor unit (2) to obtain an ethylene feed stream (3) comprising ethylene monomer, preferably wherein the ethylene feed stream (3) has a pressure of >180 MPa and < 320 MPa;24POL YO 136-WO-ORD7(h) feeding at least a portion of the ethylene feed stream (3) into a first preheater (4a) positioned downstream to the compressor unit (2) to obtain an ethylene feed stream (6);(i) feeding at least a portion of the ethylene feed stream (6) into a second preheater (4b) positioned downstream to the first preheater (4a);(j) feeding a comonomer stream (5) comprising the vinyl monomer (D) into the second preheater (4b) such that the comonomer stream (5) is supplied to the second preheater (4b) by means of a dosing line (12) that is in fluid communication with the second preheater (4b);(k) contacting the ethylene feed stream (6) and the comonomer stream (5) in the second preheater (4b) and subsequently mixing the streams to obtain a product stream (8); and(l) feeding the product stream (8) into a reactor (20) positioned downstream to the second preheater (4b) and polymerizing the ethylene monomer and the vinyl monomer (D) to obtain the ethylene copolymer; and• wherein the comonomer stream (5) comprising a vinyl monomer (D) is injected into the second preheater (4b) at a flow rate of > 180 and < 3000 kg / hr; and • wherein the temperature (Th) of the comonomer stream (5) in the dosing line (12) prior to injecting into the second preheater (4b) ranges from > 30 °C and < 55 °C, preferably > 35 °C and < 55 °C; and• wherein the comonomer stream (5) on contacting with the ethylene feed stream (6) has a temperature of > 60 °C and < 90 °C, preferably > 70 °C and < 87 °C; andwherein the vinyl-based monomer (D) is an acrylate-based monomer (A).

[0010] The invention now provides a process to prepare ethylene copolymer, while managing the temperature rise on mixing the ethylene with the vinyl monomer by injecting the vinyl monomer at a suitable location in a two-preheater set up each located upstream to the polymerization reactor. Further the temperature rise is managed by controlling the flow rate of the comonomer stream, temperature of the monomer stream and optionally the temperature of the ethylene stream when the monomer stream is introduced.24POL YO 136-WO-ORD8

[0011] Advantageously, the process of the present invention enables a skilled person to produce ethylene copolymers with minimal reactor fouling and avoiding thermal runaway reactions.

[0012] Further, the process of the present invention now allows a skilled person to manage the temperature rise when ethylene and comonomers streams are mixed prior to polymerization As a further advantage, the process of the present invention now allows a skilled person to produce ethylene copolymer with units derived from high monomer content (e.g. 1 wt.% and above) while limiting risks of reactor fouling. Managing the temperature rise when ethylene and vinyl monomer is mixed is an important factor in the entire production process, as not only reactor fouling and poor reaction kinetics is observed if the rise of temperature is not regulated but also the final ethylene copolymer has inconsistent properties.

[0013] Therefore, lower the spike in temperature in the preheater, lower are the risk of self-polymerization and poor reaction kinetics. For example, based on existing literature survey as described in the above section, when using acrylate based monomers, it is preferred that temperature on mixing does not exceed 90 °C, preferably does not exceed 85 °C, preferably does not exceed 80 °C to prevent any possibilities of self-polymerization.

[0014] As a further advantage the process of the present invention enables a skilled person to mix the ethylene and comonomer streams in the preheater itself ensuring the one or more benefits of improved reaction kinetics better monomer dispersion while managing any rise in temperature during the mixing of the streams.

[0015] The reactor (20) can be any suitable reactor such as an autoclave reactor, a tubular reactor, or a combination of an autoclave reactor in operative communication with a tubular reactor. The pre-heater heats the polymerization reactor (20) contents prior to injection of the free-radical initiator. The first preheater (4a) may be a water preheater. The injection of the comonomer stream (5) into the first preheater may be carried out using a suitable injection device such as a torpedo mixer as described in EP3565659A1 with the device comprising the annular part, a support structure, an injector part, and a supply channel. The temperature of the ethylene stream or the comonomer stream (5) may be measured using a sensor or a thermocouple.24POL YO 136-WO-ORD9

[0016] Advantageously, the process as described in the present invention enables a skilled person to produce ethylene copolymers without causing reactor fouling.

[0017] In some embodiments of the invention, the polymerization reaction may for example can take place in the tubular reactor using the high pressure CTR ™ technology as described in Chapter 7.9 of “Handbook of Petrochemicals Production Processes, 2nd Edition” (ISBN: 9781259643132).

[0018] Preferably, the first preheater (4a) is operated at a temperature of > 80 °C and < 120 °C, preferably > 80 °C and < 100 °C and the second preheater (4b) is operated at a temperature of > 110 °C and < 170 °C, preferably > 120 °C and < 140 °C, preferably > 125 °C and < 140 °C.

[0019] It is preferred that the second preheater is operated at temperature higher than the first preheater such that the temperature of the feed entering the reactor is closer to the temperature at which the polymerization takes place.

[0020] Preferably, the comonomer stream (5) comprising the vinyl monomer (D), is injected into the second preheater (4a) at a flow rate of > 180 and < 2500 kg / hr, preferably > 200 and < 1000 kg / hr, preferably > 220 and < 500 kg / hr.

[0021] Preferably, the comonomer stream (5) comprising the vinyl monomer (D), is injected into the second preheater (4b) at a concentration of > 0.1 wt.% and < 2.0 wt.%, preferably > 0.1 wt.% and < 1.8 wt.%, with regard to the total weight of the ethylene feed stream (6).

[0022] Preferably, the temperature of the comonomer stream (5) in the dosing line (12) prior to injecting into the second preheater (4b) ranges from > 35 °C and < 55 °C.

[0023] In an aspect of the invention, the comonomer stream (5) comprises > 95.0 wt.%, preferably > 98.0 wt.%, based on the total weight of comonomer stream (5) of the vinyl monomer (D).

[0024] Preferably, the ethylene feed stream (6) is fed to the second preheater (4b) at a flow rate of > 50 and < 120 tons / hour, preferably > 60 and < 100 tons / hour; and / or wherein the ethylene feed stream (6) in the second preheater (4b) is operated at a temperature (Te) of > 110 °C and < 150 °C, preferably > 120 °C and < 140 °C.24POL YO 136-WO-ORD10

[0025] Preferably, the reaction of the ethylene monomer with the vinyl monomer (D) is carried out in the reactor (20) at any pressure of >180 MPa and <350 MPa, preferably > 200 MPa and < 300 MPa and at any temperature of >100 °C and < 350 °C, preferably >125 °C and <310 °C, preferably >130 °C and < 300 °C; and / or wherein the reactor (20) is a tubular reactor.

[0026] Preferably wherein the ethylene copolymer comprises with regard to the total weight of the ethylene copolymer of:(i) > 80.0 and < 99.9 wt.%, preferably > 88.0 and < 96.0 wt.%, preferably > 90.0 and < 96.0 wt.%, of polymeric units derived from ethylene; and(ii) > 0.1 and < 20.0 wt.%, preferably > 4.0 and < 12.0 wt.%, preferably > 4.0 and < 10.0 wt.% of polymeric units derived from the vinyl based monomer (D), preferably wherein the content of ethylene and vinyl based monomer (D) is determined using13C NMR and / orJH NMR.

[0027] It is preferred that the ethylene copolymer comprises with regard to the total weight of the ethylene copolymer of (i) > 97.0 and < 99.0 wt.%, preferably > 98.0 and < 99.0 wt.%, of polymeric units derived from ethylene; and (ii) > 1.0 and < 3.0 wt.%, preferably > 1.0 and < 2.0 wt.%, of polymeric units derived from the vinyl-based monomer (D).

[0028] It is preferred that the ethylene copolymer comprises with regard to the total weight of the ethylene copolymer of (i) > 98.0 and < 99.0 wt.%, of polymeric units derived from ethylene; and (ii) > 1.0 and < 2.0 wt.%, of polymeric units derived from the vinyl-based monomer (D).

[0029] Preferably, (i) wherein the comonomer stream (5) comprising the vinyl monomer (D) is injected into the second preheater (4b) at a flow rate of > 200 and < 1000 kg / hr, preferably > 200 and < 500 kg / hr; and (ii) the comonomer stream (5) on contacting with the ethylene feed stream (6) has a temperature of > 60 °C and < 90 °C; and (iii) the temperature (Th) of the comonomer stream (5) in the dosing line (12) ranges from > 35 °C and < 55 °C; and (iv) wherein the comonomer stream (5) comprising the vinyl monomer (D), is injected into the second preheater (4b) at a concentration of > 0.1 wt.% and < 2.0 wt.%, preferably > 0.1 wt.% and < 1.8 wt.%, with regard to the total weight of the ethylene feed stream (6).

[0030] Preferably, the comonomer stream (5) is mixed with one or more inhibitor compound prior to injecting the comonomer stream (5) into the second preheater (4b).24POL YO 136-WO-ORD11Vinyl Monomer D

[0031] Preferably, the vinyl based monomer (D) is an acrylate based monomer (A) or an acrylate based ionomer (IA).

[0032] In an aspect of the invention, wherein the vinyl based monomer (D) is an acrylate based monomer (A) having a structure represented by the formula (II) or by formula (III):a) wherein the formula (II) is:• R14 is a moiety selected from the group consisting of: — CH2 — ; — [CH2]x — CH(CH3) — , wherein x >1 and <10; — CH2 — CHR4-[O — CH2 — CHRa]q — , wherein q >1 and < 10, and each Ra individually is selected from CH3 or H; and — CH2 — CH(OH)— CH2— ;• R10 is selected from — H or — CH3;• R11 is selected from — O — , — (CO) — (NH) — or — (CO) — O — ;• n=0 or 1; and• m >1 and <10; andb) wherein the formula (III) is:24POL YO 136-WO-ORD12• R16 is a moiety selected from the group consisting of: — CH2 — ; — [CH2]x — CH(CH3) — , wherein x >1 and <10; — CH2 — CHR4-[O — CH2 — CHRb]q— , wherein q >1 and <10, and each Rb individually is selected from CH3 or H; and — CH2 — CH(OH) — CH2 — ; • n >1 and <10; and• each R15 or R17 may individually be selected from — H or — CH3.

[0033] Preferably, the vinyl based monomer (D) is an acrylate based monomer (A) selected from the group consisting of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2,3 -dihydroxypropyl acrylate, 2,3 -dihydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, polypropylene glycol) monoacrylate, poly(propyleneglycol) monomethacrylate, poly(ethylene glycol) monoacrylate, poly(ethylene glycol) monomethacrylate, poly(ethylenepropyleneglycol) monomethacrylate and 2-hydroxyethyl vinyl ether, 1,4-butanediol dimethacrylate, hexanediol dimethacrylate, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, dodecanediol dimethacrylate, glycerol dimethacrylate, 1,4-butanediol diacrylate, hexanediol diacrylate, ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, dodecanediol diacrylate, glycerol diacrylate, glycerol 1,3 -di glycerolate diacrylate, glycerol 1,3-diglycerolate dimethacrylate, poly(ethylene glycol) dimethacrylate, polypropylene glycol) dimethacrylate, poly thylenepropyleneglycol) dimethacrylate, 1,4-butanediol divinyl ether, polypthylene glycol) divinyl ether, di(ethyleneglycol) divinyl ether, 1,5-hexadiene, 1,7-octadiene, 1,9-decadiene and 1,13 -tetradecadiene, preferably wherein the vinyl24POL YO 136-WO-ORD13based monomer (D) is an acrylate based monomer (A) selected from 2 -hydroxy ethyl methacrylate, 1,4-butanediol dimethacrylate and combinations thereof.

[0034] Preferably wherein the acrylate monomer is 2-hydroxyethyl methacrylate. In other words, the vinyl monomer (D) is 2-hydroxyethyl methacrylate. Preferably, the ethylene copolymer comprises polymeric units derived from ethylene and 2-hydroxyethyl methacrylate.

[0035] Preferably, the comonomer stream (5) comprising the vinyl monomer (D) is injected into the second preheater (4b) at a flow rate of > 200 and < 1000 kg / hr, preferably > 200 and < 500 kg / hr; and (ii) the comonomer stream (5) on contacting with the ethylene feed stream (6) has a temperature of > 60 °C and < 90 °C; and (iii) the temperature (Th) of the comonomer stream (5) in the dosing line (12) and prior to injecting into the second preheater (4b) ranges from > 35 °C and < 55 °C; and (iii) wherein the vinyl based monomer (D) is 2- hydroxyethyl methacrylate; and (iv) wherein the ethylene copolymer comprises with regard to the total weight of the ethylene copolymer of > 90.0 and < 99.9 wt.%, of polymeric units derived from ethylene; and > 0.1 and < 10.0 wt.% of polymeric units derived from 2-hydroxyethyl methacrylate.

[0036] Preferably, the comonomer stream (5) comprising the vinyl monomer (D) is injected into the second preheater (4b) at a flow rate of > 200 and < 500 kg / hr; and (ii) the comonomer stream (5) on contacting with the ethylene feed stream (6) has a temperature of > 60 °C and < 90 °C; and (iii) the temperature (Th) of the comonomer stream (5) in the dosing line (12) and prior to injecting into the second preheater (4b) ranges from > 35 °C and < 55 °C; and (iii) wherein the vinyl based monomer (D) is 2-hydroxyethyl methacrylate; and (iv) wherein the ethylene copolymer comprises with regard to the total weight of the ethylene copolymer of > 97.0 and < 99.0 wt.%, preferably > 98.0 and < 99.0 wt.%, of polymeric units derived from ethylene; and > 1.0 and <3.0 wt.%, preferably > 1.0 and <2.0 wt.%, of polymeric units derived from 2-hydroxyethyl methacrylate.24POL Y0136-WO-ORD14

[0037] Preferably, the comonomer stream (5) comprising the vinyl monomer (D) is injected into the second preheater (4b) at a flow rate of > 200 and < 500 kg / hr; and (ii) the comonomer stream (5) on contacting with the ethylene feed stream (6) has a temperature of > 60 °C and < 90 °C; and (iii) the temperature (Th) of the comonomer stream (5) in the dosing line (12) and prior to injecting into the second preheater (4b) ranges from > 35 °C and < 55 °C; and (iii) wherein the vinyl based monomer (D) is 2-hydroxyethyl methacrylate; and (iv) wherein the ethylene copolymer comprises with regard to the total weight of the ethylene copolymer of > 98.0 and < 99.0 wt.%, of polymeric units derived from ethylene; and > 1.0 and < 2.0 wt.%, of polymeric units derived from 2-hydroxyethyl methacrylate.

[0038] Preferably, the vinyl based monomer (D) is an acrylate based ionomer (IA) having any one of structure selected from:tBuAEM-AAMPSApreferably wherein the vinyl based monomer (D) is an acrylate based ionomer (IA) represented by the structure below and defined as MAMADAME:24POL YO 136-WO-ORD15MAMAEMME , where the ionomer MAMADAME is derived from methacrylic acid (MA) and dimethylaminoethyl methacrylic acid (MADAME).

[0039] Preferably wherein, wherein the reaction of the ethylene monomer with the vinyl based monomer (D) is carried out in presence of initiators wherein the initiator is introduced in the reactor (20) in an amount of > 0 ppm and < 300 ppm, preferably > 0 ppm and < 200 ppm, with regard to the total weight of the product stream (8); and wherein the initiator is selected from organic peroxides, azo based compounds and combinations thereof.

[0040] In some embodiments of the invention, chain transfer agents such as propylene may be added to the ethylene stream prior to injecting the stream into the compressor. In another embodiment of the invention initiator compounds may for example be added in in the reactor.

[0041] The polymerisation temperature in the polymerization reactor can be optimally controlled by metering an initiator for example an organic peroxide or a mixture of initiators at one injection point or at different injection points. The man skilled in the art has to determine the suitable initiators or mixture of initiators, the concentration of the initiator and the the injection point(s) being most suitable to be used.

[0042] The polymerisation process may for example be performed in the presence of an initiator. Such initiator may for example be an initiator composition comprising one or more selected from organic peroxides or azo compounds. Suitable organic peroxides may for example include diacyl peroxides, dialkyl peroxides, peroxymonocarbonates, peroxydicarbonates, peroxyketals, peroxyesters, cyclic peroxides, hydroperoxides. Suitable azo compounds may for example include 2,2'-azodi(isobutyronitrile), 2,2'-azodi(2-methylbutyronitrile), 1,1'- azodi(hexahydrobenzonitrile).

[0043] In an embodiment, the free radical initiator composition may for example comprise 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl peroxypivalate and / or t-butyl peroxy24POL YO 136-WO-ORD16benzoate. Such initiators may for example be fed to the tubular reactor in a pure form or as a solution in a solvent. As solvent, for example a C2-C20 normal paraffin or C2-C20 isoparaffin may be used. For example, such solution may comprise >2.0% and <65.0% by weight of initiator, alternatively >5.0% and <40.0% by weight, alternatively >10.0% and <30.0% by weight, compared to the total weight of the solution.

[0044] After finishing off the polymerization, and having applied multiple cooling steps, the reaction mixture is depressurized and / or cooled and separated in a high pressure separator (HPS). The high pressure separator separates the reaction mixture into an ethylene rich stream, containing minor amounts of waxes and / or entrained polymer, and a polymer rich stream, which is sent for further separation to the low pressure separator (LPS).

[0045] Ethylene stream is cooled down and cleaned in stream. Stream is a purge stream to remove impurities and / or inerts. The ethylene-based polymer separated in the LPS is further processed. The ethylene removed in the LPS is fed to the booster compressor, where during the compression condensable, like solvent, lubrication oil and other liquids, are collected and removed.System

[0046] In an aspect of the invention, the invention relates to a system for producing ethylene copolymer according to the process of the present invention, wherein the system comprises:(a) the compressor unit (2) configured to receive the ethylene feedstream (1);(b) the first preheater (4a) positioned downstream to the compressor unit (2) and in fluid communication with the compressor unit (2) and adapted to receive the ethylene stream (3);(c) the second preheater (4b) positioned downstream to the first preheater (4a) and in fluid communication with the first preheater (4a) and adapted to receive the ethylene stream (6);(d) the dosing line (12) configured to feed the comonomer stream (5) to the second preheater (4b), wherein the dosing line (12) is in fluid communication with the24POL Y0136-W0-0RD17second preheater (4b) and with a pump (15) that is configured to supply the comonomer stream (5); and(e) the reactor (20) positioned downstream to the second preheater (4b) and in fluid communication with the second preheater (4b) and adapted to receive the product stream (8); wherein the reactor (20) is configured to polymerize the ethylene monomer with the vinyl based monomer (D) to obtain the ethylene copolymer.

[0047] The invention will now be demonstrated with the following non-limiting examples.EXAMPLES

[0048] Purpose: To evaluate the process for the production of ethylene-HEMA based copolymer and whether the process of the present invention can be carried out by mixing the ethylene and the monomer 2-hydroxyethyl methacrylate (HEMA) while maintain any rise in temperature on mixing. To evaluate the success of the process parameters in accordance with the invention, experiments were conducted to observe whether the HEMA comonomer stream at the point of contact with the ethylene stream would have a temperature below 90 °C, a temperature indicative of high risks of acrylate self-polymerization.

[0049] Material and process conditions: The details of the materials are provided below:Table 124POL YO 136-WO-ORD

[0050] Process Operation - The direct injection of the comonomer at the proper conditions allows the use of the comonomer without further dilution saving the compression installation and energy costs associated with extra volume of ethylene used, for cooling down the HEMA stream to be injected. The HEMA comonomer stream was injected into the second preheater slightly above ambient pressures. The HEMA monomer stream was injected at the center of the preheater at temperatures below ethylene stream. The injection of the HEMA was done using an injection device as described in the patent EP3565659B1, with the device comprising the annular part, a support structure, an injector part, and a supply channel. The monomer streams were mixed within the first meters after the injection.

[0051] In a high-pressure tubular reactor, ethylene copolymers were prepared by reacting a feed mixture comprising ethylene and the HEMA monomer. In addition, a quantity of 1.40 mol % of isopropanol with regard to the molar quantity of ethylene was fed.

[0052] The reaction was performed at a pressure of 200 MPa and at a temperature of 200-210 °C. The reaction was initiated by addition of a 4.0 g / 1 solution of t-butyl peroxy pivalate (t-BPP) in heptane. The average residence time in the tubular reactor in all examples was 45 s. The obtained ethylene polymer was collected.

[0053] Table 2, shows the operating parameters when HEMA comonomer was injected in the second preheater (4b) where the ethylene stream has a temperature of 135 °C and the temperature of the comonomer (5) in the dosing line (12) being 40 °C. The references IE1 and IE2 being inventive examples while CE1-C4 are comparative examples.24POL Y0136-W0-0RD19Table 2

[0054] Table 3, shows the operating parameters when HEMA comonomer was injected in the second preheater (4b) where the ethylene stream has a temperature of 135 °C and the temperature of the comonomer stream (5) in the dosing line (12) was maintained at 60 °C.Table 3

[0055] From Table 2, it is evident that for references IE1-IE2, the HEMA comonomer stream on contact with the ethylene stream (6), reaches a temperature, which is desirably below the temperature of 90 °C. The introduction of the HEMA monomer stream (5) in the second preheater 4(b), which is positioned closer to the polymerization reactor, reduces residence time of the stream comprising ethylene and the highly reactive HEMA monomer.

[0056] This is particularly advantageous, as with relatively higher concentration of the HEMA monomer, a longer residence time allows the chance of the ethylene and HEMA monomer to react and form oligomers leading to fouling in the preheater. On the other hand, from table 2 it is evident that by managing the flow rate of the monomer stream (5) and the temperature of the24POL YO 136-WO-ORD20monomer stream prior to injection (below 60 °C), the temperature rise on mixing the ethylene and the HEMA monomer prior to polymerization is addressed.

[0057] For example, IE1 and IE2 it is evident that for producing ethylene copolymer containing units derived from relatively high HEMA content, it is suitable to inject the HEMA comonomer stream (5) in the second preheater at relatively high flow rate while ensuring the temperature of the HEMA stream (5) is within a certain threshold.

[0058] Further, based on CE1, it is observed at low flow rate of 65 kg / hr and even when supplied at a relatively low dosing temperature of 40 °C, the temperature of the HEMA stream reached almost 108 °C on contact with the ethylene stream (3). which may induce selfpolymerization of HEMA, cause thermal runway and cause reactor fouling. To manage such temperature rise use of cooling mechanism such as diluent, heat exchangers or inhibitor compounds are required to manage the rise in temperature and prevent fouling or any adverse effect of polymerization kinetics.

[0059] Further from CE2-CE4, when the dosing temperature of the HEMA stream (5) was 60 °C, the temperature of the HEMA stream (5) reached above 90°C on contact with the ethylene stream which is undesirable.

[0060] It was further observed that the obtained ethylene copolymer for CE1, CE2, CE3 and CE4 had inconsistent properties with poor monomer incorporation when determined using13C NMR and / or 1H NMR and also had large amounts of oligomer formation. This was on expected lines as shown in previous literature that at temperature from 80 °C and above, acrylates tend to start self-polymerization.

[0061] It is now demonstrated that the invention now provides a process to prepare ethylene copolymer such as ethylene-HEMA copolymers with units derived from a high monomer content, while managing the temperature rise on mixing the ethylene with the HEMA monomer. The temperature management was achieved by injecting the vinyl monomer at a suitable location (second preheater 4(b)) in a two-preheater set up each located upstream to the tubular reactor. As a further measure, the invention now shows that by controlling the flow rate, temperature of the monomer stream and the temperature of the ethylene stream the overall temperature rise can be effectively managed.24POL Y0136-W0-0RD21

[0062] By injecting the monomer in the second preheater, residence time of the stream containing ethylene and HEMA monomer was reduced thereby further mitigating the risks reactor fouling, thermal runaways and adverse reaction kinetics.

[0063] The content of recurring units derived from HEMA was determined via NMR, wherein the sample is dissolved in deuterated tetrachloroethane at 120° C. The NMR spectra is recorded with a Bruker Avance 500 NMR spectrometer equipped with a 10 mm diameter cryocooled probe head, operating at 125° C., to obtain both 'H-NMR and13C-NMR spectra, measuring time13C-NMR 3 hrs, *H-NMR 30 min.

Claims

24POL YO 136-WO-ORD22CLAIMS1. A process for preparing an ethylene copolymer, wherein the process comprises:(a) injecting an ethylene feed stream (1) into a compressor unit (2) to obtain an ethylene feed stream (3) comprising ethylene monomer, preferably wherein the ethylene feed stream (3) has a pressure of >180 MPa and < 320 MPa;(b) feeding at least a portion of the ethylene feed stream (3) into a first preheater (4a) positioned downstream to the compressor unit (2) to obtain an ethylene feed stream (6);(c) feeding at least a portion of the ethylene feed stream (6) into a second preheater (4b) positioned downstream to the first preheater (4a);(d) feeding a comonomer stream (5) comprising a vinyl monomer (D) into the second preheater (4b) such that the comonomer stream (5) is supplied to the second preheater (4b) by means of a dosing line (12) that is in fluid communication with the second preheater (4b);(e) contacting the ethylene feed stream (6) and the comonomer stream (5) in the second preheater (4b) and subsequently mixing the streams to obtain a product stream (8); and(f) feeding the product stream (8) into a reactor (20) positioned downstream to the second preheater (4b) and polymerizing the ethylene monomer and the vinyl monomer (D) to obtain the ethylene copolymer; and• wherein the comonomer stream (5) comprising a vinyl monomer (D) is injected into the second preheater (4b) at a flow rate of > 180 and < 3000 kg / hr; and • wherein the temperature (Th) of the comonomer stream (5) in the dosing line (12) prior to injecting into the second preheater (4b) ranges from > 30 °C and < 55 °C, preferably > 35 °C and < 55 °C; and• wherein the comonomer stream (5) on contacting with the ethylene feed stream (6) has a temperature of > 55 °C and < 90 °C, preferably > 60 °C and < 90 °C, preferably > 70 °C and < 87 °C.POL YO 136-WO-ORD232. The process of claim 1, wherein the comonomer stream (5) comprising a vinyl monomer (D), is injected into the second preheater (4a) at a flow rate of > 180 and < 2500 kg / hr, preferably > 200 and < 1000 kg / hr, preferably > 220 and < 500 kg / hr.

3. The process according to any one of claims 1-2, wherein the comonomer stream (5) comprising the vinyl monomer (D), is injected into the second preheater (4b) at a concentration of > 0.1 wt.% and < 2.0 wt.%, preferably > 0.1 wt.% and < 1.8 wt.%, with regard to the total weight of the ethylene feed stream (6).

4. The process according to any one of claims 1-3, wherein the first preheater (4a) is operated at a temperature of > 80 °C and < 120 °C, preferably > 80 °C and < 100 °C and the second preheater (4b) is operated at a temperature of > 110 °C and < 170 °C, preferably > 120 °C and < 140 °C, preferably > 125 °C and < 140 °C.

5. The process according to any one of claims 1-4, temperature of the comonomer stream (5) in the dosing line (12) prior to injecting into the second preheater (4b) ranges from > 35 °C and < 55 °C.

6. The process according to any one of claims 1-5, wherein the ethylene copolymer comprises with regard to the total weight of the ethylene copolymer of:(i) > 80.0 and < 99.9 wt.%, preferably > 88.0 and < 96.0 wt.%, preferably > 90.0 and < 96.0 wt.%, preferably of polymeric units derived from ethylene; and(ii) > 0.1 and < 20.0 wt.%, preferably > 4.0 and < 12.0 wt.%, preferably > 4.0 and < 10.0 wt.% of polymeric units derived from the vinyl-based monomer (D), preferably wherein the content of ethylene and vinyl based monomer (D) is determined using13C NMR and / orJH NMR; andpreferably wherein the ethylene copolymer comprises with regard to the total weight of the ethylene copolymer of (i) > 97.0 and < 99.0 wt.%, preferably > 98.0 and < 99.0 wt.%, of polymeric units derived from ethylene; and (ii) > 1.0 and < 3.0 wt.%, preferably > 1.0 and < 2.0 wt.%, of polymeric units derived from the vinyl-based monomer (D).POL YO 136-WO-ORD247. The process according to any one of claims 1-6, wherein the ethylene feed stream (6) is fed to the second preheater (4b) at a flow rate of > 50 and < 120 tons / hour, preferably > 60 and < 100 tons / hour; and / or wherein the ethylene feed stream (6) in the second preheater (4b) is operated a temperature (Te) of > 110 °C and < 150 °C, preferably > 120 °C and < 140 °C.

8. The process according to any one of claims 1-7, wherein the reaction of the ethylene monomer with the vinyl monomer (D) is carried out in the reactor (20) at any pressure of >180 MPa and <350 MPa, preferably > 200 MPa and < 300 MPa and at any temperature of >100 °C and < 350 °C, preferably >125 °C and <310 °C, preferably >130 °C and < 300 °C; and / or wherein the reactor (20) is a tubular reactor.

9. The process according to any one of claims 1-8, (i) wherein the comonomer stream (5) comprising the vinyl monomer (D) is injected into the second preheater (4b) at a flow rate of > 200 and < 1000 kg / hr, preferably > 200 and < 500 kg / hr; and (ii) the comonomer stream (5) on contacting with the ethylene feed stream (6) has a temperature of > 60 °C and < 90 °C; and (iii) the temperature (Th) of the comonomer stream (5) in the dosing line (12) ranges from > 35 °C and < 55 °C; and (iv) wherein the comonomer stream (5) comprising the vinyl monomer (D), is injected into the second preheater (4b) at a concentration of > 0.1 wt.% and < 2.0 wt.%, preferably > 0.1 wt.% and < 1.8 wt.%, with regard to the total weight of the ethylene feed stream (6).

10. The process according to any one of claims 1-9, wherein the comonomer stream (5) is mixed with one or more inhibitor compound prior to injecting the comonomer stream (5) into the second preheater (4b).

11. The process according to any one of claims 1-10, wherein the vinyl based monomer (D) is an acrylate based monomer (A) or an acrylate based ionomer (IA), preferably the vinyl based monomer (D) is an acrylate based monomer (A).POL YO 136-WO-ORD2512. The process according to any one claims 1-11, wherein the vinyl based monomer (D) is an acrylate based monomer (A) selected from the group consisting of 2-hydroxy ethyl acrylate, 2-hydroxy ethyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 2- hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2,3 -dihydroxypropyl acrylate, 2,3- dihydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, polypropylene glycol) monoacrylate, poly(propyleneglycol) monomethacrylate, poly(ethylene glycol) monoacrylate, poly(ethylene glycol) monomethacrylate, poly(ethylenepropyleneglycol) monomethacrylate and 2-hydroxy ethyl vinyl ether, 1,4- butanediol dimethacrylate, hexanediol dimethacrylate, ethylene glycol dimethacrylate, 1,3- butylene glycol dimethacrylate, dodecanediol dimethacrylate, glycerol dimethacrylate, 1,4-butanediol diacrylate, hexanediol diacrylate, ethylene glycol diacrylate, 1,3 -butylene glycol diacrylate, dodecanediol diacrylate, glycerol diacrylate, glycerol 1,3-diglycerolate diacrylate, glycerol 1,3-diglycerolate dimethacrylate, poly(ethylene glycol) dimethacrylate, polypropylene glycol) dimethacrylate, poly(ethylenepropyleneglycol) dimethacrylate, 1,4-butanediol divinyl ether, poly thylene glycol) divinyl ether, di(ethyleneglycol) divinyl ether, 1,5-hexadiene, 1,7-octadiene, 1,9-decadiene and 1,13- tetradecadiene, preferably wherein the vinyl based monomer (D) is an acrylate based monomer (A) selected from 2-hydroxy ethyl methacrylate, 1,4-butanediol dimethacrylate and combinations thereof, preferably wherein the acrylate monomer is 2-hydroxyethyl methacrylate.

13. The process according to any one of claims 1-12, (i) wherein the comonomer stream (5) comprising the vinyl monomer (D) is injected into the second preheater (4b) at a flow rate of > 200 and < 1000 kg / hr, preferably > 200 and < 500 kg / hr; and (ii) the comonomer stream (5) on contacting with the ethylene feed stream (6) has a temperature of > 60 °C and < 90 °C; and (iii) the temperature (Th) of the comonomer stream (5) in the dosing line (12) and prior to injecting into the second preheater (4b) ranges from > 35 °C and < 55 °C; and (iii) wherein the vinyl based monomer (D) is 2-hydroxyethyl methacrylate; and (iv) wherein the ethylene copolymer comprises with regard to the total weight of the ethylenePOL YO 136-WO-ORD26copolymer of > 90.0 and < 99.9 wt.%, of polymeric units derived from ethylene; and > 0.1 and < 10.0 wt.% of polymeric units derived from 2 -hydroxy ethyl methacrylate.

14. The process according to anyone claims 1-13, (i) wherein the comonomer stream (5) comprising the vinyl monomer (D) is injected into the second preheater (4b) at a flow rate of > 200 and < 500 kg / hr; and (ii) the comonomer stream (5) on contacting with the ethylene feed stream (6) has a temperature of > 60 °C and < 90 °C; and (iii) the temperature (Th) of the comonomer stream (5) in the dosing line (12) and prior to injecting into the second preheater (4b) ranges from > 35 °C and < 55 °C; and (iii) wherein the vinyl based monomer (D) is 2-hydroxyethyl methacrylate; and (iv) wherein the ethylene copolymer comprises with regard to the total weight of the ethylene copolymer of > 97.0 and < 99.0 wt.%, preferably > 98.0 and < 99.0 wt.%, of polymeric units derived from ethylene; and > 1.0 and < 3.0 wt.%, preferably > 1.0 and < 2.0 wt.%, of polymeric units derived from 2- hydroxy ethyl methacrylate.

15. A system for producing ethylene copolymer according to the process as claimed in any one of claims 1-14, wherein the system comprises:(a) the compressor unit (2) configured to receive the ethylene feedstream (1);(b) the first preheater (4a) positioned downstream to the compressor unit (2) and in fluid communication with the compressor unit (2) and adapted to receive the ethylene stream (3);(c) the second preheater (4b) positioned downstream to the first preheater (4a) and in fluid communication with the first preheater (4a) and adapted to receive the ethylene stream (6);(d) the dosing line (12) configured to feed the comonomer stream (5) to the second preheater (4b), wherein the dosing line (12) is in fluid communication with the second preheater (4b) and with a pump (15) that is configured to supply the comonomer stream (5); and(e) the reactor (20) positioned downstream to the second preheater (4b) and in fluid communication with the second preheater (4b) and adapted to receive the productPOL Y0136-WO-ORD27stream (8); wherein the reactor (20) is configured to polymerize the ethylene monomer with the vinyl based monomer (D) to obtain the ethylene copolymer.

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