Ethylene-polar monomer copolymerization reactor system and copolymerization method

Abstract

The invention provides an ethylene-polar monomer copolymerization reaction system and a copolymerization method, and belongs to the field of high-pressure polymerization. According to the invention, the comonomer high-pressure injection pumps are additionally arranged at the side line feed ports of the reactor except the first reaction zone, and part of polar comonomers are injected into the reactor through the comonomer high-pressure injection pumps, so that the molar concentration of the polar comonomers in the materials in the reactor is flexibly adjusted; the polar comonomer is prevented from being consumed up too fast due to high reactivity rate of the polar comonomer, so that ethylene accumulation in the material and continuous dilution of the polar comonomer concentration are avoided, and the polar comonomer is basically and uniformly distributed on a polymer chain.

Description

Technical Field

[0001] The invention relates to the technical field of high-pressure production of ethylene-polar monomer copolymers, and in particular to a reactor system for ethylene-polar monomer copolymerization and an ethylene-polar monomer copolymerization method. Background Art

[0002] Polyethylene (PE) has become one of the most commonly used plastic materials due to its good chemical stability. However, its non-polar properties also limit its further application in areas requiring adhesion, compatibility, toughness, adhesion, surface properties and rheology. Copolymerization of ethylene with polar monomers is a direct choice and has attracted widespread attention. The high-pressure production technology of ethylene-polar monomer copolymers has now been industrialized, and the main commercial products are ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, etc. Among them, ethylene-acrylic acid copolymers generally include the following six types of copolymers: ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA) and ionomers. Ethylene-acrylic acid copolymers have good low-temperature performance and flexibility, excellent resistance to bending cracking and environmental stress cracking, and greater elasticity. They are often used in pipes, packaging materials, adhesives, inner and outer shielding layers of high-voltage cables, etc., and are high-value-added polyolefin products.

[0003] Commercial ethylene-acrylic acid copolymers are usually obtained by high-pressure free radical polymerization of ethylene and acrylic acid monomers. There are two main types of high-pressure free radical polymerization reactors for preparing ethylene and acrylic acid copolymers, namely autoclave reactors and tubular reactors. Since the reactivity ratios of ethylene and acrylic acid monomers differ greatly, at least 3 times, acrylic acid monomers are more easily inserted into the polymer chain, resulting in the inhomogeneity of the copolymer structure. Therefore, the high-pressure free radical copolymerization process of ethylene and acrylic acid monomers needs to focus on solving the problem of copolymer structural uniformity.

[0004] CN103237823B proposes to inject a comonomer such as acrylic acid or methacrylic acid directly into an autoclave reactor or a tubular reactor in one or more zones, wherein the chain transfer agent activity of the first zone is greater than that of the second zone, to prepare an ethylene-carboxylic acid copolymer with a narrow molecular weight distribution having a low gel level. CN110054715B proposes a method for preparing a polymer composition containing a polar comonomer (including vinyl acetate or n-butyl acrylate), wherein the concentration of the monomer and the unsaturated modifier is continuously increased by separating out the unreacted substances, thereby increasing the MI of the polymer. CN101454360A proposes a method for continuously preparing an ethylene copolymer by free radical copolymerization of ethylene with at least one comonomer in a cascade comprising at least two reactors, wherein one or more initiators are fed into the reaction mixture downstream of the first reactor to prepare an ethylene copolymer that is not prone to sticking or agglomeration and is still suitable as an impact modifier.

[0005] In the above-mentioned prior art, methods for regulating the molecular weight or terminal properties of copolymers by means of chain transfer agents, initiators, separation systems, etc. have been seen, but the problem of structural uniformity of ethylene-polar monomer copolymerization, especially ethylene-acrylic acid copolymers, is still rarely addressed. Summary of the invention

[0006] Based on this, it is necessary to provide a reactor system and copolymerization method for ethylene-polar monomer copolymerization in order to address the above problems. By additionally providing a high-pressure injection pump at each side feed port of the reactor, part of the polar comonomer is injected into the reactor system through the comonomer high-pressure injection pump, and the molar concentration of the polar comonomer in the material in the reactor is flexibly adjusted to avoid excessive consumption of the polar comonomer due to the high reactivity rate of the polar comonomer, thereby avoiding the accumulation of ethylene in the material and the continuous dilution of the polar comonomer concentration, and achieving a substantially uniform distribution of the polar comonomer on the polymer chain.

[0007] The present invention provides a copolymerization method of ethylene-polar monomer, the method comprising the following steps:

[0008] 1) Ethylene and part of the polar comonomer are pressurized by a multi-stage compressor and then injected into the reaction zones of each stage of a high-pressure polymerization reactor; the high-pressure polymerization reactor is used for free radical copolymerization of ethylene and the polar comonomer, and is divided into at least two reaction zones with monomer feed ports according to the material flow direction, and each reaction zone except the first stage reaction zone is also provided with a comonomer high-pressure injection pump, and the comonomer high-pressure injection pump is used to adjustably inject the polar comonomer into the corresponding reaction zone;

[0009] 2) injecting comonomers adjustably into the reaction zones of each stage except the first stage reaction zone through a comonomer high pressure injection pump;

[0010] 3) The molar concentration of ethylene [E] and the molar concentration of the polar comonomer [A] in the reactor feed stream at the feed inlet of each reaction zone, including the first-stage reaction zone, satisfy the following relationship:

[0011]

[0012] where r E is the reactivity ratio of ethylene at the average reaction temperature and average operating pressure of the corresponding reaction zone, and r A is the reactivity ratio of the polar monomer at the average reaction temperature and average operating pressure of the corresponding reaction zone. F A is the mass fraction of the comonomer in the target ethylene-polar copolymer product, M A is the molecular weight of the polar comonomer, and M E is the molecular weight of ethylene.

[0013] Among them, at the monomer feed inlet of the first reaction zone, since there is no additional high-pressure injection pump for the comonomer to adjust the injection amount of the comonomer, it is necessary to control the contents of ethylene and the polar comonomer in the material before the multi-stage compressor so that the monomer feed inlet of the first reaction zone also satisfies the relationship in step 3). Preferably, the high-pressure polymerization reactor is a tubular reactor or a tank reactor, or a combination of both.

[0014] Preferably, the average operating pressure of the high-pressure polymerization reactor is 100 - 350 MPa, preferably in the range of 120 - 280 °C.

[0015] Preferably, the average operating temperature of the high-pressure tubular reactor is 120 °C - 330 °C, preferably in the range of 130 - 280 °C.

[0016] Preferably, the polar comonomer includes, but is not limited to, vinyl ethers, vinyl esters, halogenated olefins, acrylic esters, and other acrylic derivatives. Vinyl ethers such as vinyl methyl ether, vinyl n-butyl ether, vinyl phenyl ether, vinyl β-hydroxy-ethyl ether, and vinyl dimethylaminoethyl ether; olefins such as propylene, 1-butene, cis-2-butene, trans-2-butene, isobutene, 3,3-dimethyl-1-butene, 4-methyl-1-pentene, 1-octene, and styrene; vinyl esters such as vinyl acetate, vinyl butyrate, vinyl pivalate, and vinylene carbonate; halogenated olefins such as vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, vinyl chloride, vinylidene dichloride, tetrachloroethylene, and chlorotrifluoroethylene; acrylic esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, α-cyanoisopropyl acrylate, β-cyanoethyl acrylate, o-(3-phenylpropane-1,3-diketo)phenyl acrylate, methyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, methyl methacrylate, glycidyl methacrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl methacrylate, 3-hydroxy-4-carbomethoxyphenyl methacrylate, N,N-dimethylaminoethyl methacrylate, tert-butylaminoethyl methacrylate, 2-(1-aziridinyl)ethyl methacrylate, diethyl fumarate, diethyl maleate, and methyl crotonate; other acrylic derivatives such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, methyl hydroxymaleate, itaconic acid, acrylonitrile, fumaronitrile, N,N-dimethylacrylamide, N-isopropylacrylamide, N-tert-butylacrylamide, N-phenylacrylamide, diacetoneacrylamide, methacrylamide, N-phenylmethacrylamide, N-ethylmaleimide, and maleic anhydride; and other compounds such as allyl alcohol, vinyltrimethylsilane, vinyltriethoxysilane, N-vinylcarbazole, N-vinyl-N-methylacetamide, vinyldibutylphosphine oxide, vinyldiphenylphosphine oxide, bis-(2-chloroethyl)vinylphosphonate, and vinylmethyl sulfide. Preferred polar comonomers are methyl acrylate, ethyl acrylate, butyl acrylate, acrylic acid, and methacrylic acid.

[0017] Preferably, the ethylene-polar copolymer product refers to a binary copolymer formed from ethylene and a polar comonomer.

[0018] Preferably, 30-100 wt% of the material pressurized by a multi-stage compressor is fed into the monomer feed port of the first-stage reaction zone, preferably 50-80 wt%. Preferably, the amount of the material pressurized by the multi-stage compressor fed into each reaction zone other than the first reaction zone is 0-50 wt% of the pressurized material amount, preferably 10-30 wt%.

[0019] In the present invention, it is allowed that all the materials (100 wt%) after being pressurized by a multi-stage compressor are fed into the monomer feed port of the first-stage reaction zone. At this time, the amount of the materials after being pressurized by the multi-stage compressor fed into other reaction zones except the first reaction zone is 0. That is, except for several interfaces provided for supplementing comonomers and initiators, the high-pressure polymerization reactor has no additional side-line feed for injecting ethylene.

[0020] The present invention also provides a reaction system for ethylene-polar monomer copolymerization for implementing the copolymerization method, which includes:

[0021] A high-pressure polymerization reactor for carrying out free radical copolymerization reaction of ethylene and polar comonomers, which is divided into at least two reaction zones with monomer feed ports according to the material flow direction;

[0022] A multi-stage compressor for pressurizing ethylene and part of the polar comonomers and feeding them into the monomer feed ports of each reaction zone;

[0023] A comonomer high-pressure injection pump connected to the monomer feed ports of other reaction zones except the first-stage reaction zone for adjustably injecting polar comonomers into other reaction zones except the first-stage reaction zone.

[0024] Preferably, the reaction system for ethylene-polar monomer copolymerization further includes:

[0025] A high-pressure separator for separating the product obtained from the high-pressure polymerization reactor to obtain a polymer-rich phase and high-pressure recycle materials containing ethylene monomer and comonomer;

[0026] A high-pressure recycle loop connected to the high-pressure separator for leading the high-pressure recycle materials separated by the high-pressure separator to the multi-stage compressor for recycle;

[0027] A low-pressure separator for receiving the polymer-rich phase separated by the high-pressure separator and separating it to obtain a polymer product and low-pressure recycle components;

[0028] A low-pressure recycle loop connected to the low-pressure separator for leading the low-pressure recycle components separated by the low-pressure separator to the multi-stage compressor for recycle.

[0029] Preferably, each reaction zone of the high-pressure polymerization reactor is also provided with a heat exchange jacket and an initiator injection port, and the outlet of the high-pressure polymerization reactor is connected with a cooler for cooling the materials.

[0030] The technical solution provided by the present invention has at least the following advantages:

[0031] (1) By additionally installing high-pressure injection pumps at the side-line feed ports of the reactor, part of the polar comonomer is injected into the reactor system through the high-pressure comonomer injection pump, flexibly adjusting the molar concentration of the polar comonomer in the reactor material, avoiding the rapid depletion of the polar comonomer due to its high reactivity ratio, thereby preventing the accumulation of ethylene and the continuous dilution of the polar comonomer concentration in the material, and achieving a substantially uniform distribution of the polar comonomer on the polymer chain.

[0032] (2) The reactor system and copolymerization method provided by the present invention can realize the production of ethylene-polar monomer copolymers with large differences in reactivity ratios in a high-pressure polymerization reactor, reducing the device cost and obtaining higher production capacity. Description of the Drawings

[0033] Figure 1 It is the reactor system for ethylene-polar monomer copolymerization used in the embodiments of the present invention.

[0034] The reference numerals in the figure are: 1 first compressor, 2 second compressor, 3 high-pressure free radical polymerization tubular reactor, 4 cooling water jacket, 5 / 6 comonomer high-pressure injection pump, 7 / 8 / 9 initiator injection pump, 10 reactor outlet valve, 11 cooler, 12 high-pressure separator, 13 high-pressure circulation loop, 14 low-pressure separator, 15 low-pressure circulation loop, 16 booster. Detailed Embodiments

[0035] The following is combined with Figure 1 to describe in detail the reactor system and copolymerization method for ethylene-polar monomer copolymerization of the present invention, but the present invention is not limited thereby.

[0036] As Figure 1As shown, taking the tubular reactor 3 with three reaction zones as an example, from left to right are the first reaction zone, the second reaction zone, and the third reaction zone. Fresh ethylene and part of the polar comonomer are compressed successively through the first compressor 1 and the second compressor 2, and the compressed monomers are respectively fed into each reaction zone. Among them, 30 - 100 wt% of the material pressurized by the multi-stage compressor is fed into the monomer inlet of the first-stage reaction zone, preferably 50 - 80 wt%. The amount of the material pressurized by the multi-stage compressor fed into each reaction zone except the first reaction zone is 0 - 50 wt% of the pressurized material amount, preferably 10 - 30 wt%. Another part of the polar comonomer is injected respectively through the polar comonomer injection pump 5 at the second reaction zone inlet and the polar comonomer injection pump 6 at the third reaction zone inlet, and the flow rates of the polar comonomer injection pumps 5 and 6 are adjustable. The initiator enters the first reaction zone to the third reaction zone from the starting point of each reaction zone respectively through the initiator injection pump 7, the initiator injection pump 8, and the initiator injection pump 9 to participate in the free radical copolymerization reaction. A cooling water jacket 4 is provided outside the reactors in each reaction zone to control the reaction temperature;

[0037] The reactor outlet valve 10 is opened, and the mixed material containing the ethylene-polar monomer copolymer enters the cooler 11 for cooling, and then enters the high-pressure separator 12 to separate a part of the high-pressure recycle material and the polymer-rich phase. The part of the high-pressure recycle material is recycled back through the high-pressure recycle loop 13 to participate in the free radical copolymerization reaction together with fresh ethylene and the polar comonomer; the polymer-rich phase is introduced into the low-pressure separator 14 for further separation to obtain a part of the low-pressure recycle material and the polymer phase. The part of the ethylene monomer and the polar comonomer are introduced into the booster 16 through the low-pressure recycle loop 15 for compression, and then participate in the free radical copolymerization reaction together with fresh ethylene and the polar comonomer. The polymer phase is led out of the low-pressure separator 14 for further post-treatment.

[0038] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the raw materials are all commercially available products.

[0039] The reactivity ratio data for the free radical copolymerization of ethylene and each polar monomer in the following examples are referenced from the literature: (1) Buback, M.; Busch, M.; Lovis, K.; Mahling, F. O., High-pressure free-radical copolymerization of ethene and butyl acrylate. Macromolecular Chemistry and Physics 1996, 197, (1), 303 - 313; (2) Buback, M.; Wittkowski, L.; Lehmann, S. A.; Mahling, F. O., High-pressure free-radical copolymerization of ethene-methacrylic acid and of ethene-acrylic acid, 1 (Meth)acrylic acid reactivity ratios. Macromolecular Chemistry and Physics 1999, 200 (8), 1935 - 1941; (3) Kiparissides, C.; Baltsas, A.; Papadopoulos, S.; Congalidis, J. P.; Richards, J. R.; Kelly, M. B.; Ye, Y., Mathematical modeling of free-radical ethylene copolymerization in high-pressure tubular reactors. Industrial & Engineering Chemistry Research 2005, 44 (8), 2592 - 2605.

[0040] In the following examples, Figure 1The radical copolymerization reaction of ethylene and polar monomers is carried out in the high-pressure tubular reactor shown. The reactor consists of three reaction zones. From left to right, they are the first reaction zone, the second reaction zone, and the third reaction zone. The tube lengths of the first, second, and third reaction zones are 600 m, 400 m, and 400 m respectively. The inner diameter of the reaction tube is 0.05 m. Fresh ethylene and a part of the polar comonomer are compressed successively through the first compressor and the second compressor, and the compressed monomers are fed into each reaction zone respectively. The feeding amount of the first reaction zone is 67 wt% of the total amount, the second reaction zone is 20 wt% of the total amount, and the third reaction zone is 13 wt% of the total amount. Another part of the polar comonomer is injected through the polar comonomer injection pump at the feed port of the second reaction zone and the polar comonomer injection pump at the feed port of the third reaction zone, and the flow rates of the two polar comonomer injection pumps can be adjusted. There are initiator injection ports in all three reaction zones, and the corresponding initiators are injected from the starting points of each reaction zone.

[0041] Example 1

[0042] The radical copolymerization reaction of ethylene monomer and butyl acrylate monomer is carried out in Figure 1 the high-pressure tubular reactor shown to obtain an ethylene-butyl acrylate copolymer. The average polymerization pressure of the reactor is 200 MPa, and the average polymerization temperature is 200 °C. At this temperature and pressure, the reactivity ratio r E of ethylene is 0.045, and the reactivity ratio r A of butyl acrylate is 4.4. The mass fraction F A of the comonomer in the target ethylene-polar copolymer product is 30 wt%.

[0043] The flow rates of ethylene and butyl acrylate entering the first reaction zone from the main feed port are 18566 kg·h -1 and 386.6 kg·h -1 respectively.

[0044] The flow rates of ethylene and butyl acrylate entering the second reaction zone from the side feed port of the second reaction zone are 5570 kg·h -1 and 116.0 kg·h -1 respectively.

[0045] The flow rates of ethylene and butyl acrylate entering the third reaction zone from the side feed port of the third reaction zone are 3713 kg·h -1 and 77.31 kg·h -1 respectively.

[0046] The flow rate of butyl acrylate injected into the reactor by the polar comonomer injection pump at the feed port of the second reaction zone is 367.3 kg·h -1 respectively.

[0047] The flow rate of butyl acrylate injected into the reactor by the polar comonomer injection pump at the feed inlet of the third reaction zone is 460.9 kg·h -1 .

[0048] Since the reactivity ratio of butyl acrylate is significantly higher than that of ethylene, the butyl acrylate in each reaction zone is basically consumed, and the conversion rate of butyl acrylate reaches 100%.

[0049] The conversion rates of ethylene in the first, second, and third reaction zones are 8%, 7%, and 5% respectively.

[0050] The linear velocities of the monomer and polymer mixed materials in the first, second, and third reaction zones are 14.91 m / s, 15.40 m / s, and 15.79 m / s respectively.

[0051] According to the above operating parameters, the molar concentrations of ethylene [E] and butyl acrylate [A] in the reactor feed stream at the feed inlets of the first, second, and third reaction zones are shown in Table 1.

[0052] Table 1

[0053]

[0054] The molar concentration of ethylene [E] and the molar concentration of polar comonomer [A] in the reactor feed stream at the feed inlet of the first reaction zone satisfy the quantitative relationship proposed by the present invention:

[0055]

[0056] The molar concentration of ethylene [E] and the molar concentration of polar comonomer [A] in the reactor feed stream at the feed inlet of the second reaction zone satisfy the quantitative relationship proposed by the present invention:

[0057]

[0058] The molar concentration of ethylene [E] and the molar concentration of polar comonomer [A] in the reactor feed stream at the feed inlet of the third reaction zone satisfy the quantitative relationship proposed by the present invention:

[0059]

[0060] The obtained copolymer product was measured by the combination of gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FTIR). The mass content of butyl acrylate in the ethylene-butyl acrylate copolymer was about 30 wt%. The GPC-FTIR curve showed that the ester groups of butyl acrylate were evenly distributed on the polymers in each molecular weight range. According to the total consumption of ethylene and butyl acrylate in the reactor respectively, the mass content of butyl acrylate in the polymer product was also calculated to be 29.94 wt%, which was basically consistent with the GPC-FTIR detection result. The obtained ethylene-butyl acrylate copolymer met the requirements of the target product.

[0061] In this example, since butyl acrylate comonomer was additionally supplemented at the feed inlets of both the second reaction zone and the third reaction zone, the molar concentration of ethylene and the molar concentration of butyl acrylate in the feed stream in the reactor met the requirements of the present invention, avoiding the accumulation of ethylene in the material and the continuous dilution of the concentration of the polar comonomer due to the high reactivity ratio of butyl acrylate, and realizing the basic uniform distribution of butyl acrylate on the polymer chain.

[0062] Example 2

[0063] Ethylene monomer and butyl acrylate monomer were subjected to free radical copolymerization reaction in the high-pressure tubular reactor shown in Figure 1 to obtain an ethylene-butyl acrylate copolymer. The average polymerization pressure of the reactor was 200 MPa, and the average polymerization temperature was 220 °C. At this temperature and pressure, the reactivity ratio r E of ethylene was 0.052, and the reactivity ratio r A of butyl acrylate was 3.4. The mass fraction F A of the comonomer in the target ethylene-polar copolymer product was 35 wt%.

[0064] The flow rates of ethylene and butyl acrylate entering the first reaction zone from the main feed inlet were 18566 kg·h -1 and 574.3 kg·h -1 respectively.

[0065] The flow rates of ethylene and butyl acrylate entering the second reaction zone from the side feed inlet of the second reaction zone were 5570 kg·h -1 and 172.3 kg·h -1 respectively.

[0066] The flow rates of ethylene and butyl acrylate entering the third reaction zone from the side feed inlet of the third reaction zone were 3713 kg·h -1 and 114.9 kg·h -1 respectively.

[0067] The flow rate of butyl acrylate injected into the reactor by the polar comonomer injection pump at the feed inlet of the second reaction zone was 539.5 kg·h -1 respectively.

[0068] The flow rate of butyl acrylate injected into the reactor by the polar comonomer injection pump at the feed inlet of the third reaction zone is 671.4 kg / h -1 .

[0069] Since the reactivity ratio of butyl acrylate is significantly higher than that of ethylene, the butyl acrylate in each reaction zone is basically consumed, and the conversion rate of butyl acrylate reaches 100%.

[0070] The conversion rates of ethylene in the first, second, and third reaction zones are 9%, 8%, and 5.6% respectively.

[0071] The linear velocities of the monomer and polymer mixed materials in the first, second, and third reaction zones are 14.89 m / s, 15.37 m / s, and 15.76 m / s respectively.

[0072] According to the above operating parameters, the ethylene molar concentration [E] and butyl acrylate molar concentration [A] in the reactor feed stream at the feed inlets of the first, second, and third reaction zones are shown in Table 2.

[0073] Table 2

[0074]

[0075] The ethylene molar concentration [E] and polar comonomer molar concentration [A] in the reactor feed stream at the feed inlet of the first reaction zone satisfy the quantitative relationship proposed by the present invention:

[0076]

[0077] The ethylene molar concentration [E] and polar comonomer molar concentration [A] in the reactor feed stream at the feed inlet of the second reaction zone satisfy the quantitative relationship proposed by the present invention:

[0078]

[0079] The ethylene molar concentration [E] and polar comonomer molar concentration [A] in the reactor feed stream at the feed inlet of the third reaction zone satisfy the quantitative relationship proposed by the present invention:

[0080]

[0081] The obtained copolymer product was measured by GPC-FTIR, and the mass content of butyl acrylate in the ethylene-butyl acrylate copolymer was about 35 wt%. The GPC-FTIR curve showed that the ester groups of butyl acrylate were evenly distributed on the polymers in each molecular weight range. According to the total consumption of ethylene and butyl acrylate in the reactor respectively, the mass content of butyl acrylate in the polymer product was also calculated to be 34.97 wt%, which was basically consistent with the GPC-FTIR detection result. The obtained ethylene-butyl acrylate copolymer met the requirements of the target product.

[0082] In this example, since butyl acrylate comonomer was additionally supplemented at the feed inlets of the second reaction zone and the third reaction zone, the molar concentration of ethylene and the molar concentration of butyl acrylate in the feed stream in the reactor met the requirements of the present invention, avoiding the accumulation of ethylene in the material and the continuous dilution of the concentration of the polar comonomer due to the high reactivity ratio of butyl acrylate, and realizing the basic uniform distribution of butyl acrylate on the polymer chain.

[0083] Example 3

[0084] Table The radical copolymerization reaction of ethylene monomer and acrylic acid monomer was carried out in the Figure 1 shown high-pressure tubular reactor to obtain an ethylene-acrylic acid copolymer. The average polymerization pressure of the reactor was 200 MPa, and the average polymerization temperature was 240 °C. At this temperature and pressure, the reactivity ratio r E of ethylene was 0.049, and the reactivity ratio r A of acrylic acid was 8.0. The mass fraction F A of the comonomer in the target ethylene-polar copolymer product was 30 wt%.

[0085] The flow rates of ethylene and acrylic acid entering the first reaction zone from the main feed inlet were 18566 kg·h -1 , 430.6 kg·h -1 .

[0086] The flow rates of ethylene and acrylic acid entering the second reaction zone from the side feed inlet of the second reaction zone were 5570 kg·h -1 , 129.2 kg·h -1 .

[0087] The flow rates of ethylene and acrylic acid entering the third reaction zone from the side feed inlet of the third reaction zone were 3713 kg·h -1 , 86.13 kg·h -1 .

[0088] The flow rate of acrylic acid injected into the reactor by the polar comonomer injection pump at the feed inlet of the second reaction zone was 397.1 kg·h -1 .

[0089] The flow rate of acrylic acid injected into the reactor by the polar comonomer injection pump at the feed inlet of the third reaction zone is 511.2 kg·h -1 .

[0090] Since the reactivity ratio of acrylic acid is significantly higher than that of ethylene, the acrylic acid in each reaction zone is basically consumed, and the conversion rate of acrylic acid reaches 100%.

[0091] The conversion rates of ethylene in the first, second, and third reaction zones are 9%, 8%, and 6% respectively.

[0092] The linear velocities of the monomer and polymer mixed materials in the first, second, and third reaction zones are 13.82 m / s, 14.16 m / s, and 14.95 m / s respectively.

[0093] According to the above operating parameters, the molar concentrations of ethylene [E] and acrylic acid [A] in the reactor feed stream at the feed inlets of the first, second, and third reaction zones are shown in Table 3.

[0094] Table 3

[0095]

[0096] The molar concentration of ethylene [E] and the molar concentration of polar comonomer [A] in the reactor feed stream at the feed inlet of the first reaction zone satisfy the quantitative relationship proposed by the present invention:

[0097]

[0098] The molar concentration of ethylene [E] and the molar concentration of polar comonomer [A] in the reactor feed stream at the feed inlet of the second reaction zone satisfy the quantitative relationship proposed by the present invention:

[0099]

[0100] The molar concentration of ethylene [E] and the molar concentration of polar comonomer [A] in the reactor feed stream at the feed inlet of the third reaction zone satisfy the quantitative relationship proposed by the present invention:

[0101]

[0102] The mass content of acrylic acid in the ethylene-acrylic acid copolymer obtained by GPC-FTIR is about 30 wt%. The GPC-FTIR curve shows that the carboxyl groups of acrylic acid are evenly distributed on the polymers in each molecular weight range. According to the total consumption of ethylene and acrylic acid in the reactor, the mass content of acrylic acid in the polymer product can also be calculated to be 29.91 wt%, which is basically consistent with the GPC-FTIR test results. The obtained ethylene-acrylic acid copolymer meets the requirements of the target product.

[0103] In this embodiment, since acrylic acid comonomers are additionally supplemented at the feed inlets of both the second reaction zone and the third reaction zone, the molar concentration of ethylene and the molar concentration of acrylic acid in the feed stream in the reactor meet the requirements of the present invention, avoiding the accumulation of ethylene in the material and the continuous dilution of the concentration of the polar comonomer due to the high reactivity ratio of acrylic acid, and achieving the basic uniform distribution of acrylic acid on the polymer chain.

[0104] Comparative Example 1

[0105] The difference between Comparative Example 1 and Example 1 is that the flow rate of butyl acrylate injected into the reactor by the polar comonomer injection pump at the feed inlets of the second and third reaction zones is only half of that in Example 1. The flow rate of butyl acrylate injected into the reactor by the polar comonomer injection pump at the feed inlet of the second reaction zone in Comparative Example 1 is 183.7 kg·h -1 , and the flow rate of butyl acrylate injected into the reactor by the polar comonomer injection pump at the feed inlet of the third reaction zone is 230.4 kg·h -1 .

[0106] Affected by the addition amount of acrylic acid, the linear velocities of the monomer and polymer mixed materials in the second and third reaction zones are reduced to 15.26 m / s and 15.57 m / s.

[0107] According to the above operating parameters, the molar concentration of ethylene [E] and the molar concentration of butyl acrylate [A] in the feed stream in the reactor at the feed inlets of the first, second, and third reaction zones are shown in Table 4.

[0108] Table 4

[0109]

[0110] The molar concentration of ethylene [E] and the molar concentration of the polar comonomer [A] in the feed stream in the reactor at the feed inlet of the first reaction zone still satisfy the quantitative relationship proposed by the present invention:

[0111]

[0112] The molar concentration of ethylene [E] and the molar concentration of the polar comonomer [A] in the feed stream in the reactor at the feed inlet of the second reaction zone no longer satisfy the quantitative relationship proposed by the present invention:

[0113]

[0114] The molar concentration of ethylene [E] and the molar concentration of the polar comonomer [A] in the feed stream in the reactor at the feed inlet of the third reaction zone no longer satisfy the quantitative relationship proposed by the present invention:

[0115]

[0116] The mass content of butyl acrylate in the obtained copolymer product was measured by GPC-FTIR to be approximately 22 wt% in the ethylene-butyl acrylate copolymer. The GPC-FTIR curve showed that except for the lower molecular weight part where the ester group content of butyl acrylate in the polymer was less, the ester groups were evenly distributed on the polymers in the remaining molecular weight ranges. Based on the total consumption of ethylene and butyl acrylate in the reactor respectively, the mass content of butyl acrylate in the polymer product was also calculated to be 21.91 wt%, which was basically consistent with the GPC-FTIR test result. The obtained ethylene-butyl acrylate copolymer did not meet the requirements of the target product.

[0117] Compared with Example 1, in Comparative Example 1, since the additional butyl acrylate comonomer supplemented at the feed inlets of the second and third reaction zones was only half of that in Example 1, the ethylene molar concentration and butyl acrylate molar concentration in the feed streams in the second and third reaction zones did not meet the requirements of the present invention. Therefore, the butyl acrylate in the lower molecular weight part of the copolymer was not evenly distributed on the polymer chains, resulting in the inhomogeneity of the copolymer structure.

[0118] Comparative Example 2

[0119] The difference between Comparative Example 2 and Example 1 was that the polar comonomer injection pumps at the feed inlets of the second and third reaction zones did not supplement butyl acrylate to the reactor, that is, the flow rates of butyl acrylate injected by the polar comonomer injection pumps at the feed inlets of the second and third reaction zones into the reactor were both 0.

[0120] Affected by the addition amount of acrylic acid, the linear velocities of the monomer and polymer mixed materials in the second and third reaction zones were reduced to 15.02 m / s and 15.23 m / s.

[0121] According to the above operating parameters, the ethylene molar concentration [E] and butyl acrylate molar concentration [A] in the feed streams in the reactors at the feed inlets of the first, second, and third reaction zones were as shown in Table 5.

[0122] Table 5

[0123]

[0124] The ethylene molar concentration [E] and polar comonomer molar concentration [A] in the feed stream in the reactor at the feed inlet of the first reaction zone still satisfied the quantitative relationship proposed by the present invention:

[0125]

[0126] The ethylene molar concentration [E] and polar comonomer molar concentration [A] in the feed stream in the reactor at the feed inlet of the second reaction zone no longer satisfied the quantitative relationship proposed by the present invention:

[0127]

[0128] The molar concentration of ethylene [E] and the molar concentration of polar comonomer [A] in the material flow in the reactor at the feed inlet of the third reaction zone no longer satisfy the quantitative relationship proposed by the present invention:

[0129]

[0130] The mass content of butyl acrylate in the ethylene-butyl acrylate copolymer obtained by GPC-FTIR is about 13 wt%. The GPC-FTIR curve shows that only a small amount of ester groups of butyl acrylate are contained in the polymer with high molecular weight, and no ester groups are seen on the polymers in the remaining molecular weight ranges. According to the total consumption of ethylene and butyl acrylate in the reactor respectively, the mass content of butyl acrylate in the polymer product can also be calculated to be 12.89 wt%, which is basically consistent with the GPC-FTIR detection result. The obtained ethylene-butyl acrylate copolymer fails to meet the requirements of the target product.

[0131] Compared with Example 1, in Comparative Example 2, since no additional butyl acrylate is supplemented at the feed inlets of the second reaction zone and the third reaction zone, the molar concentration of ethylene and the molar concentration of butyl acrylate in the material flow in the second reaction zone and the third reaction zone cannot meet the requirements of the present invention. Due to the high reactivity ratio of butyl acrylate, it is consumed too quickly, resulting in the continuous accumulation of ethylene in the material and causing obvious inhomogeneity in the copolymer structure.

[0132] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention patent. For those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A copolymerization method of ethylene and polar monomers, characterized in that, The method comprises the following steps: 1) Ethylene and a partial polar comonomer are respectively injected into reaction zones at all levels of a high-pressure polymerization reactor after being pressurized by a multi-stage compressor; the high-pressure polymerization reactor is used for the free-radical copolymerization reaction of ethylene and the polar comonomer, and is divided into at least two reaction zones with monomer inlets according to the material flow direction. In addition to the first-stage reaction zone, each of the other reaction zones is also provided with a high-pressure injection pump for the comonomer, and the high-pressure injection pump for the comonomer is used to adjustably inject the polar comonomer into the corresponding reaction zone; 2) The high-pressure injection pump for the comonomer is used to adjustably inject the comonomer into each of the other reaction zones except the first-stage reaction zone; 3) The molar concentration [E] of ethylene and the molar concentration [A] of the polar comonomer in the material flow in the reactor at the inlet of each reaction zone including the first-stage reaction zone satisfy the following relationship: where r E is the reactivity ratio of ethylene under the average reaction temperature and average operating pressure in the corresponding reaction zone, and r A is the reactivity ratio of the polar monomer under the average reaction temperature and average operating pressure in the corresponding reaction zone. F A is the mass fraction of the comonomer in the target ethylene-polar copolymer product. M A is the molecular weight of the polar comonomer, and M E is the molecular weight of ethylene.

2. The method according to claim 1, wherein The high-pressure polymerization reactor is a tubular reactor or a kettle reactor, or a combination of both.

3. The method according to claim 1, wherein The average operating pressure of the high-pressure polymerization reactor is 100-350 MPa, preferably in the range of 120-280 MPa.

4. The method according to claim 1, characterized in that The average operating temperature of the high-pressure polymerization reactor is 120°C-330°C, preferably in the range of 130-280°C.

5. The method according to claim 1, wherein The polar comonomer includes but is not limited to vinyl ether, vinyl ester, halogenated olefin, acrylic ester, and other acrylic derivatives; preferred polar comonomers are methyl acrylate, ethyl acrylate, butyl acrylate, acrylic acid, methacrylic acid, and vinyl acetate.

6. The method according to claim 1, characterized in that, 30-100 wt% of the material pressurized by the multi-stage compressor is fed into the monomer inlet of the first-stage reaction zone, preferably 50-80 wt%.

7. The method according to claim 1, characterized in that The amount of the material pressurized by the multi-stage compressor fed into each reaction zone except the first reaction zone is 0-50 wt% of the pressurized material amount, preferably 10-30 wt%.

8. A reaction system for ethylene-polar monomer copolymerization implementing the copolymerization method according to claim 1, characterized in that, Including: A high-pressure polymerization reactor for the free-radical copolymerization reaction of ethylene and the polar comonomer, which is divided into at least two reaction zones with monomer inlets according to the material flow direction; A multi-stage compressor for pressurizing ethylene and a partial polar comonomer and feeding them into the monomer inlets of each reaction zone; A high-pressure injection pump for the comonomer, which is connected to the monomer inlet of each of the other reaction zones except the first-stage reaction zone and is used to adjustably inject the polar comonomer into each of the other reaction zones except the first-stage reaction zone.

9. The reaction system for copolymerization of ethylene and polar monomers according to claim 8, characterized in that, It further includes: A high-pressure separator for separating the product obtained from the high-pressure polymerization reactor to obtain a polymer-rich phase and a high-pressure recycle material containing ethylene monomer and comonomer; A high-pressure recycle loop, which is connected to the high-pressure separator and leads the high-pressure recycle material separated by the high-pressure separator to the multi-stage compressor for recycle; A low-pressure separator, which receives the polymer-rich phase separated by the high-pressure separator and separates it to obtain a polymer product and a low-pressure recycle component; A low-pressure recycle loop, which is connected to the low-pressure separator and leads the low-pressure recycle component separated by the low-pressure separator to the multi-stage compressor for recycle.

10. The reaction system for copolymerization of ethylene and polar monomers according to claim 8, characterized in that, Each reaction zone of the high-pressure polymerization reactor is also provided with a heat exchange jacket and an initiator injection port, and the outlet of the high-pressure polymerization reactor is connected to a cooler to cool the material.

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