Ethylene-vinyl acetate copolymer and production method thereof

Abstract

The present invention relates to the field of ethylene-vinyl acetate copolymer production, and discloses an ethylene-vinyl acetate copolymer and a production method thereof, the method comprises: in the presence of an initiator solution, introducing a first material containing an ethylene monomer and a vinyl acetate monomer into a reactor to carry out a free radical polymerization reaction, a second material containing the ethylene-vinyl acetate copolymer is obtained; the content X of the initiator in the initiator solution meets the relational expression shown in the formula (I): 0.1 * ln (T + 273.15)-0.1 * ln (P)-0.2 * Y < X < 0.35 + 0.1 * ln (T + 273.15)-0.1 * ln (P)-0.3 * Y, and X < 1 is greater than 0; wherein the content of Y is 10-25 wt%. According to the technical scheme provided by the invention, the production load of the reactor is flexibly adjusted according to actual production requirements, the dispersity of the initiator in the reactor can be effectively improved, and the consumption of the initiator is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of ethylene-vinyl acetate copolymer production, and specifically relates to an ethylene-vinyl acetate copolymer and a production method thereof. Background Art

[0002] Ethylene-vinyl acetate copolymer resin (EVA) is a general-purpose resin with a very wide range of application fields. For example, EVA is widely used in fields such as foaming, films, wire and cable, hot melt adhesives, and toys. Since a large amount of vinyl acetate monomers are introduced into the molecular chain of EVA, the molecular chain is not easily crystallized, thus having good flexibility, compatibility, heat-sealing performance, and impact resistance.

[0003] As is well known, the high-pressure free radical polymerization reaction device is the main process for producing EVA products with a VA content of less than 40%, and the required reaction conditions are relatively harsh, with the reaction pressure reaching above 100 MPa. When producing EVA products, one or more initiators are usually required, and these initiators include oxygen and organic peroxides. During the actual operation of the device, there are often problems of mismatch between the initiator and the reaction conditions, resulting in too fast decomposition rate of the initiator and a large amount of residue, which in turn causes the initiator in the downstream equipment to continue to initiate other reactions, leading to frequent equipment maintenance, decline in product quality, and decline in the economic benefits of the device.

[0004] Generally, the decomposition reaction of the initiator satisfies the Arrhenius equation, that is, as the reaction temperature increases, the decomposition reaction rate of the initiator increases exponentially. The "cage effect" of the initiator leads to a decrease in the initiator efficiency and often causes a large consumption of the initiator. Although the initiator accounts for a small part of the production cost of EVA products, this will result in more unwanted decomposition by-products of the initiator in the products. In addition, as is well known to those skilled in the art, the dosage of the initiator is about one ten-thousandth to three-thousandths of the output of EVA products. If the pure initiator is directly introduced into the reactor, not only will the above-mentioned "cage effect" occur, resulting in a decrease in the initiator efficiency, but also due to the slow mixing rate of the initiator and the reaction materials in the reactor and the too fast local reaction rate, the safety risk of the reactor will be aggravated.

[0005] CN107108791A discloses a method for controlling the output and quality of ethylene-based polymers formed by high-pressure free radical polymerization. This prior art proposes to reduce the inlet pressure and control the total reaction consumption ratio of the initiator system at the highest temperature to control the output of the reactor and the molecular structure of polyethylene.

[0006] CN109679000A discloses a method for manufacturing ethylene polymers and using modifiers, and combines the initiator, the modifier, and one or more solvents and introduces them into the reactor at at least one position of the reactor.

[0007] CN110891986A discloses a method for preparing ethylene-vinyl acetate copolymer. In this method, a high-temperature initiator and a low-temperature initiator are used to prepare EVA products. In the compounded initiator, the weight ratio of the low-temperature initiator to the high-temperature initiator is 5:95 to 90:10.

[0008] CN107805289A discloses a method for preparing ethylene-vinyl acetate copolymer. The method includes: introducing a mixed material containing ethylene monomer, vinyl acetate monomer and molecular weight regulator into a tubular reactor for polymerization reaction. Among them, the initiator is added through multiple feeding points along the direction of material flow, and the weight of the vinyl acetate monomer accounts for 0.5-20% by weight of the total weight of the ethylene monomer and the vinyl acetate monomer.

[0009] Those skilled in the art have carried out a lot of research on the use method of initiators in ethylene-vinyl acetate copolymer products. However, in actual production, EVA manufacturers need to adjust the production scale in real time according to market demand, so that the polymerization reactor can complete production under different load conditions to prevent the situation of supply falling short of demand or supply exceeding demand. Due to the lack of understanding of the interaction laws among the material flow law, initiator decomposition law and polymerization reaction process in the reactor, only based on production experience, constantly trying, selecting the type and use method of initiators, which is very likely to cause waste of resources and decline in the production efficiency and economic benefits of the device. Summary of the Invention

[0010] The object of the present invention is to provide a production method capable of flexibly adjusting the output of ethylene-vinyl acetate copolymer within a specific range.

[0011] To achieve the above object, the first aspect of the present invention provides a method for producing ethylene-vinyl acetate copolymer, the method includes:

[0012] In the presence of an initiator solution, introducing a first material containing ethylene monomer and vinyl acetate monomer into a reactor for free radical polymerization reaction to obtain a second material containing ethylene-vinyl acetate copolymer; the reactor includes at least 2 reaction zones;

[0013] The initiator solution contains an initiator and a solvent. The initiator is an organic peroxide with a half-life temperature of 90-210 °C at normal pressure; the solvent contains 0-70 wt% of C3-C 15 olefins and 30-100 wt% of C3-C 15 alkanes;

[0014] The average reaction temperature T of the reactor is 120 - 300 °C, and the average reaction pressure P is 100 - 300 MPa;

[0015] Define the content of ethylene - vinyl acetate copolymer in the second material as Y;

[0016] The content X of the initiator in the initiator solution satisfies the relational expression shown in formula (I):

[0017] Formula (I): 0.1×ln(T + 273.15) - 0.1×ln(P) - 0.2×Y < X < 0.35 + 0.1×ln(T + 273.15) - 0.1×ln(P) - 0.3×Y, and 0 < X < 1; where Y is 10 - 25 wt%;

[0018] The average reaction temperature of the reactor is the arithmetic mean of the reaction temperatures of each reaction zone of the reactor, and the average reaction pressure of the reactor is the arithmetic mean of the reaction pressures of each reaction zone of the reactor.

[0019] The second aspect of the present invention provides an ethylene - vinyl acetate copolymer prepared by the method described in the foregoing first aspect.

[0020] Compared with the prior art, the technical solution provided by the present invention has at least the following advantages:

[0021] (1) The present invention proposes a method for using an initiator in the production of ethylene - vinyl acetate copolymer. By using an initiator with a specific concentration at different temperatures and pressures, it can effectively improve the dispersibility of the initiator in the reactor, reduce the consumption of the initiator, and at the same time, flexibly adjust the production load of the reactor according to actual production needs.

[0022] (2) The technical solution provided by the present invention can enable the initiator to play a role efficiently, with a low initiator dosage and a low residual amount of the initiator in the reactor outlet material. As a result, the residual amount of the initiator in the reactor after - cooler and the polymer post - processing system is significantly reduced, and there are fewer gels in the product film - forming process.

[0023] (3) The present invention preferably uses a solvent containing olefins as the solvent for the initiator, and the present invention can control the olefin concentration in different reaction zones of the reactor, thereby easily adjusting the molecular weight distribution of the ethylene - vinyl acetate copolymer. During the free - radical polymerization process of the present invention, the olefin acts as a chain transfer agent. The micelles formed by the olefin and the initiator jointly experience the reaction zones from low temperature to high temperature, which can reduce the content of ethylene - vinyl acetate copolymer with a very high molecular weight, thereby reducing the probability of copolymer adhesion and fouling, and increasing the single - pass conversion rate of the reactants. Description of the Drawings

[0024] Figure 1 It is a schematic process diagram of a tubular reactor for producing ethylene-vinyl acetate copolymer;

[0025] Figure 2 It is a schematic process diagram of a stirred reactor for producing ethylene-vinyl acetate copolymer.

[0026] Description of the reference numerals in the drawings

[0027] 1 Compressor, 2 Reactor, 3, 4, 5 are all initiator feed pumps, 6 Pressure reducing valve, 7 High-pressure separator, 8 Low-pressure separator, 9 First material, 10 Compressed first material, 11 Initiator solution, 12 Second material, 13 High-pressure recycle material, 14 Low-pressure recycle material, 15 Ethylene-vinyl acetate copolymer. Specific embodiments

[0028] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0029] The atmospheric pressure referred to in the present invention is 0.1 MPa.

[0030] The "temperature at which the half-life is 10 s under atmospheric pressure" of the initiator described in the present invention refers to the temperature at which the half-life of the initiator is 10 s under atmospheric pressure.

[0031] As described above, the first aspect of the present invention provides a method for producing ethylene-vinyl acetate copolymer, the method comprising:

[0032] In the presence of an initiator solution, introducing a first material containing ethylene monomer and vinyl acetate monomer into a reactor for free radical polymerization reaction to obtain a second material containing ethylene-vinyl acetate copolymer; the reactor includes at least 2 reaction zones;

[0033] The initiator solution contains an initiator and a solvent, the initiator is an organic peroxide with a temperature at which the half-life is 10 s under atmospheric pressure of 90 - 210 °C; the solvent contains 0 - 70 wt% of C3 - C 15 olefins, 30 - 100 wt% of C3 - C 15 alkanes;

[0034] The average reaction temperature T of the reactor is 120 - 300 °C, and the average reaction pressure P is 100 - 300 MPa;

[0035] Define the content of ethylene-vinyl acetate copolymer in the second material as Y;

[0036] The content X of the initiator in the initiator solution satisfies the relational expression shown in formula (I):

[0037] Formula (I): 0.1×ln(T + 273.15) - 0.1×ln(P) - 0.2×Y < X < 0.35 + 0.1×ln(T + 273.15) - 0.1×ln(P) - 0.3×Y, and 0 < X < 1; where Y is 10 - 25 wt%;

[0038] The average reaction temperature of the reactor is the arithmetic mean of the reaction temperatures of each reaction zone of the reactor, and the average reaction pressure of the reactor is the arithmetic mean of the reaction pressures of each reaction zone of the reactor.

[0039] Preferably, the content X of the initiator in the initiator solution satisfies the relational expression shown in formula (II):

[0040] Formula (II): 0.05 + 0.1×ln(T + 273.15) - 0.1×ln(P) - 0.2×Y < X < 0.25 + 0.1×ln(T + 273.15) - 0.1×ln(P) - 0.3×Y, and 0 < X < 1.

[0041] Preferably, the average reaction temperature T of the reactor is 140 - 260 °C, and the average reaction pressure P is 120 - 250 MPa.

[0042] Preferably, the initiator is an organic peroxide with a 10 s half-life temperature of 110 - 180 °C under normal pressure; the solvent contains 0 - 50 wt% of C3 - C8 olefins and 50 - 100 wt% of C 10 -C 15 alkanes.

[0043] More preferably, the initiator contains at least one initiator selected from 1,1,3,3 - tetramethylbutyl peroxynonanoate, bis(4 - tert - butylcyclohexyl) peroxydicarbonate, bis(2 - ethylhexyl) peroxydicarbonate, tert - butyl peroxynonanoate, tert - amyl peroxypivalate, tert - butyl peroxypivalate, tert - butyl peroxy - 2 - ethylhexanoate, tert - butyl peroxy - 3,5,5 - trimethylhexanoate, tert - butyl peroxybenzoate, tert - butyl peroxyacetate, di - tert - amyl peroxide, di - tert - butyl peroxide.

[0044] More preferably, the olefin is selected from at least one of propylene, 1 - butene, isobutene, 1 - pentene, 1 - hexene.

[0045] More preferably, the alkane is selected from at least one of n-decane, isodecane, n-undecane, isoundecane, n-dodecane, isododecane, n-tridecane, and isotridecane.

[0046] Preferably, each reaction zone in the reactor is independently provided with a first material feed port and an initiator solution feed port, and the reaction zones in the reactor are connected in series in sequence. Along the flow direction of the first material, the material after reaction in the upstream reaction zone enters the adjacent downstream reaction zone and participates in the radical polymerization reaction together with at least a part of the first material and at least a part of the initiator solution; the initiator solutions introduced into each reaction zone may be the same or different.

[0047] In the present invention, the type of initiator in the initiator solution introduced into each reaction zone can independently be a single initiator or a combination of 2 - 5 initiators; the type of solvent in the initiator solution introduced into each reaction zone can independently be a single solvent or a combination of multiple solvents, and the present invention has no special limitation in this regard. However, in order to more precisely obtain an ethylene-vinyl acetate copolymer within the desired yield range, the present invention provides a preferred specific embodiment.

[0048] Particularly preferably, the initiator solutions introduced into each reaction zone are the same, and the initiator in the initiator solution contains at least two initiators selected from bis(2-ethylhexyl) peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-amyl peroxy-tert-amyl, tert-butyl peroxy-tert-amyl, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy-3,5,5-trimethylhexanoate, tert-butyl peroxybenzoate, tert-butyl peroxyacetate, and di-tert-butyl peroxide, and the solvent is a combination of propylene and C 12 alkane.

[0049] Preferably, the reactor is a tank reactor or a tubular reactor, and the number of reaction zones of the tank reactor and the tubular reactor is independently 2 - 6.

[0050] Preferably, the reactor is a reactor with 2 reaction zones. Along the flow direction of the first material, they are the first reaction zone and the second reaction zone in sequence. The dosage ratio of the first material introduced into the first reaction zone and the second reaction zone of the reactor is 1:0.1 - 2; the dosage ratio of the initiator solution introduced into the first reaction zone and the second reaction zone is 1:0.1 - 10, preferably 1:0.1 - 2.

[0051] Preferably, the reactor is a reactor having three reaction zones. Along the direction of the flow of the first material, they are the first reaction zone, the second reaction zone, and the third reaction zone in sequence. The dosage ratio of the first material introduced into the first reaction zone, the second reaction zone, and the third reaction zone of the reactor is 1:0.1 - 2:0.1 - 2; the dosage ratio of the initiator solution introduced into the first reaction zone, the second reaction zone, and the third reaction zone is 1:0.1 - 10:0.1 - 10, preferably 1:0.1 - 2:0.1 - 2.

[0052] According to a particularly preferred specific embodiment 1, the reactor is a tubular reactor including two reaction zones. The ratio of the X values of the initiator solution introduced into the first reaction zone and the second reaction zone of the tubular reactor is 1:0.5 - 1; each reaction zone in the reactor is connected in series in sequence. Along the direction of the flow of the first material, the material after reaction in the upstream reaction zone enters the adjacent downstream reaction zone and participates in the free radical polymerization reaction together with at least a part of the first material and at least a part of the initiator solution.

[0053] According to a particularly preferred specific embodiment 2, the reactor is a tubular reactor including three reaction zones. The ratio of the X values of the initiator solution introduced into the first reaction zone, the second reaction zone, and the third reaction zone of the tubular reactor is 1:0.5 - 1:0.5 - 1; each reaction zone in the reactor is connected in series in sequence. Along the direction of the flow of the first material, the material after reaction in the upstream reaction zone enters the adjacent downstream reaction zone and participates in the free radical polymerization reaction together with at least a part of the first material and at least a part of the initiator solution.

[0054] According to a preferred specific embodiment 3, the reactor is a tubular reactor including three reaction zones, and the first material is respectively introduced into the first reaction zone and the second reaction zone of the tubular reactor; and the dosage ratio of the first material introduced into the first reaction zone and the second reaction zone of the tubular reactor is 1:0.5 - 1; the ratio of the X values of the initiator solution introduced into the first reaction zone, the second reaction zone, and the third reaction zone of the tubular reactor is 1:0.5 - 1:0.5 - 1; each reaction zone is connected in series in sequence. Along the direction of the flow of the first material, the material after reaction in the first reaction zone enters the adjacent second reaction zone and participates in the free radical polymerization reaction together with at least a part of the first material and at least a part of the initiator solution introduced into the second reaction zone. The material after reaction in the second reaction zone enters the adjacent third reaction zone and participates in the free radical polymerization reaction together with at least a part of the initiator solution introduced into the third reaction zone.

[0055] According to a preferred specific embodiment 4, the reactor is a tubular reactor comprising 3 reaction zones, and all of the first material is introduced into the first reaction zone of the tubular reactor; the ratio of the X values of the initiator solution introduced into the first reaction zone, the second reaction zone, and the third reaction zone of the tubular reactor is 1:0.5 - 1:0.5 - 1; the reaction zones in the tubular reactor are connected in series in sequence, and along the flow direction of the first material, the material after reaction in the upstream reaction zone enters the adjacent downstream reaction zone and participates in the free radical polymerization reaction together with at least a part of the initiator solution.

[0056] According to a particularly preferred specific embodiment 5, the reactor is a tank reactor comprising 2 reaction zones, and the ratio of the X values of the initiator solution introduced into the first reaction zone and the second reaction zone of the tank reactor is 1:0.3 - 1; the reaction zones in the reactor are connected in series in sequence, and along the flow direction of the first material, the material after reaction in the upstream reaction zone enters the adjacent downstream reaction zone and participates in the free radical polymerization reaction together with at least a part of the first material and at least a part of the initiator solution.

[0057] According to a particularly preferred specific embodiment 6, the reactor is a tank reactor comprising 3 reaction zones, and the ratio of the X values of the initiator solution introduced into the first reaction zone, the second reaction zone, and the third reaction zone of the tank reactor is 1:0.3 - 1:0.3 - 1; the reaction zones in the reactor are connected in series in sequence, and along the flow direction of the first material, the material after reaction in the upstream reaction zone enters the adjacent downstream reaction zone and participates in the free radical polymerization reaction together with at least a part of the first material and at least a part of the initiator solution.

[0058] Preferably, the first material introduced into the first reaction zone of the tank reactor is divided into two streams, one of which is cooled and introduced into the first reaction zone from the top of the tank reactor, and the other is introduced into the first reaction zone from the first material feed port of the first reaction zone.

[0059] Preferably, the content of vinyl acetate monomer in the first material is 1 - 50 wt%.

[0060] More preferably, the reactor is a tank reactor, and the content of vinyl acetate monomer in the first material is 1 - 50 wt%.

[0061] More preferably, the reactor is a tubular reactor, and the content of vinyl acetate monomer in the first material is 1 - 35 wt%.

[0062] Preferably, the flow rate of the first material is 10 - 200 t / h, more preferably 40 - 180 t / h; the maximum flow velocity is 5 - 30 m / s, more preferably 7 - 20 m / s.

[0063] Preferably, the reaction time for the free radical polymerization reaction in each reaction zone of the reactor is independently 5 - 100 s, preferably 6 - 50 s.

[0064] Preferably, in the present invention, along the flow direction of the first material, the reaction temperature for the free radical polymerization reaction in each reaction zone of the reactor shows a gradually increasing trend, and the temperature difference between adjacent reaction zones is 10 - 20 °C. The inventors of the present invention found in the research that the reaction system participating in the free radical polymerization reaction experiences reaction zones from low temperature to high temperature, which can reduce the content of ethylene-vinyl acetate copolymer with very high molecular weight, thereby reducing the probability of copolymer sticking and fouling on the wall, and improving the single-pass conversion rate of the reactants.

[0065] Preferably, the volume ratio of the first reaction zone to the second reaction zone of the reactor is 0.3 - 5:1, more preferably 0.5 - 2:1. The inventors of the present invention found in the research that controlling the volume ratio of the first reaction zone to the second reaction zone of the reactor within this more preferred range can more easily regulate the proportion of the copolymer in different reaction zones and more effectively regulate the molecular chain structure of the copolymer.

[0066] According to a preferred specific method, the method of the present invention further includes: compressing the ethylene monomer and the vinyl acetate monomer by using a compressor to obtain the compressed first material, and then introducing the compressed first material into the reactor for the free radical polymerization reaction.

[0067] The present invention controls the compression conditions so that the ethylene monomer is transported in a supercritical state.

[0068] According to another preferred specific embodiment, the method further includes: subjecting the second material to high-pressure separation at 10 - 40 MPa and low-pressure separation at 0.1 - 0.5 MPa in sequence, and granulating the obtained ethylene-vinyl acetate copolymer to obtain the ethylene-vinyl acetate copolymer product.

[0069] As described above, the second aspect of the present invention provides an ethylene-vinyl acetate copolymer prepared by the method described in the first aspect above.

[0070] For a better understanding of the purpose, process technology and functions of the present invention, the following combines Figure 1 to describe in detail the preferred specific embodiments of the present invention, but does not limit the present invention thereby. Figure 1The tubular reactor 2-1 shown is composed of three reaction zones, which are the first reaction zone, the second reaction zone, and the third reaction zone in sequence from left to right. The method of the present invention includes:

[0071] The first material 9 is compressed by the compressor 1 to obtain the compressed first material 10. The compressed first material 10 enters the first reaction zone and the second reaction zone through the first material inlet of each reaction zone. The initiator solution 11 enters the first reaction zone, the second reaction zone, and the third reaction zone respectively from the starting point of each reaction zone through the initiator feed pump 3, the initiator feed pump 4, and the initiator feed pump 5 to participate in the free radical polymerization reaction. Each reaction zone is connected in series in sequence. Along the flow direction of the first material, the reacted material in the upstream reaction zone enters the adjacent downstream reaction zone and participates in the free radical polymerization reaction together with at least a part of the first material and / or at least a part of the initiator solution to obtain the second material 12;

[0072] The second material 12 enters the high-pressure separator 7 through the pressure reducing valve 6, removes the high-pressure circulating material 13, introduces the remaining material into the low-pressure separator 8, removes the low-pressure circulating material 14, and obtains the ethylene-vinyl acetate copolymer 15.

[0073] For a better understanding of the purpose, process technology, and functions of the present invention, the following Figure 2 describes in detail the preferred specific embodiments of the present invention, but does not limit the present invention thereto. Figure 2 The shown tank reactor 2-2 is composed of two reaction zones, which are the first reaction zone and the second reaction zone in sequence from top to bottom. The method of the present invention includes:

[0074] The first material 9 is compressed by the compressor 1 to obtain the compressed first material 10. A part of the compressed first material 10 is introduced into the first reaction zone from the top of the reactor 2-2 after being cooled, a part of the compressed first material 10 is introduced into the first reaction zone through the first material inlet of the first reaction zone, and the remaining part of the compressed first material 10 is introduced into the second reaction zone through the first material inlet of the second reaction zone. The initiator solution 11 enters the first reaction zone and the second reaction zone respectively from the starting point of each reaction zone through the initiator feed pump 3 and the initiator feed pump 4 to participate in the free radical polymerization reaction. Each reaction zone is connected in series in sequence. Along the flow direction of the first material, the reacted material in the upstream reaction zone enters the adjacent downstream reaction zone and participates in the free radical polymerization reaction together with at least a part of the first material and at least a part of the initiator solution to obtain the second material 12;

[0075] The second material 12 enters the high-pressure separator 7 through the pressure reducing valve 6, removes the high-pressure circulating material 13, introduces the remaining material into the low-pressure separator 8, removes the low-pressure circulating material 14, and obtains the ethylene-vinyl acetate copolymer 15.

[0076] The present invention will be described in detail below with examples. In the following examples, unless otherwise specified, the raw materials are all commercially available products.

[0077] Solvent I: 20 wt% propylene and 80 wt% C 12 isoparaffin (CAS No. 31807-55-3);

[0078] Solvent II: 100 wt% C 12 isoparaffin (CAS No. 31807-55-3);

[0079] Initiator I: A mixture of bis(2-ethylhexyl) peroxydicarbonate (CAS No. 16111-62-9), tert-amyl peroxy pivalate, tert-butyl peroxy 2-ethylhexanoate, and tert-butyl peroxybenzoate, with a mass ratio of 1:1:1:0.5. The 10 s half-life temperatures at atmospheric pressure are 116.4 °C, 124.7 °C, 151.98 °C, and 179.1 °C respectively;

[0080] Initiator II: A mixture of bis(2-ethylhexyl) peroxydicarbonate and tert-amyl peroxy pivalate, with a mass ratio of 1:0.5. The 10 s half-life temperatures at atmospheric pressure are 116.4 °C and 124.7 °C.

[0081] Initiator III: Diisobutyryl peroxide, with a 10 s half-life temperature of 89.0 °C at atmospheric pressure;

[0082] In the following examples, the content of ethylene-vinyl acetate copolymer in the actually obtained second material = (output of ethylene-vinyl acetate copolymer (t / h) ÷ flow rate of the first material (t / h)) × 100%.

[0083] Example 1

[0084] According to Figure 1 the shown process to produce ethylene-vinyl acetate copolymer, the reactor used is a tubular reactor with 3 reaction zones. Along the flow direction of the first material, from left to right are the first reaction zone, the second reaction zone, and the third reaction zone. The volume ratio of the first reaction zone to the second reaction zone is 0.8:1. The content Y of ethylene-vinyl acetate copolymer in the obtained second material is set to 17 wt%.

[0085] The first material containing ethylene monomer and vinyl acetate monomer is compressed by a compressor to obtain the compressed first material. The compressed first material enters the first reaction zone and the second reaction zone through the first material feed inlet of the first reaction zone and the second reaction zone. The initiator solution enters the first reaction zone, the second reaction zone, and the third reaction zone respectively from the starting point of each reaction zone through the initiator feed pump to participate in the free radical polymerization reaction. Each reaction zone is connected in series in turn. Along the flow direction of the first material, the material after reaction in the first reaction zone enters the adjacent second reaction zone and participates in the free radical polymerization reaction together with a part of the first material and a part of the initiator solution introduced into the second reaction zone. The material after reaction in the second reaction zone enters the adjacent third reaction zone and participates in the free radical polymerization reaction together with a part of the initiator solution introduced into the third reaction zone to obtain the second material. After the second material passes through the pressure reducing valve, it is subjected to high-pressure separation at 28 MPa and low-pressure separation at 0.13 MPa in turn, and the obtained ethylene-vinyl acetate copolymer is granulated to obtain an ethylene-vinyl acetate copolymer product;

[0086] The content of vinyl acetate monomer in the first material is 14 wt%, the flow rate of the first material is 96.5 t / h, and the maximum flow velocity is 17 m / s; the dosage ratio of the first material introduced into the first reaction zone and the second reaction zone of the tubular reactor is 1:1.5; the dosage ratio of the initiator solution introduced into the first reaction zone, the second reaction zone, and the third reaction zone is 1:1:0.8;

[0087] In the initiator solution in the first reaction zone of the tubular reactor, the initiator is initiator I, the solvent is solvent I, and the initiator content X is 21 wt%; the average reaction temperature T1 is 195 °C, the average reaction pressure P1 is 250 MPa, and the reaction time is 9.0 s;

[0088] In the initiator solution in the second reaction zone of the tubular reactor, the initiator is initiator I, the solvent is solvent I, and the initiator content X is 18 wt%; the average reaction temperature T2 is 210 °C, the average reaction pressure P2 is 235 MPa, and the reaction time is 7.5 s;

[0089] In the initiator solution in the third reaction zone of the tubular reactor, the initiator is initiator I, the solvent is solvent I, and the initiator content X is 18 wt%; the average reaction temperature T3 is 220 °C, the average reaction pressure P3 is 211 MPa, and the reaction time is 30 s;

[0090] The average reaction temperature T of the tubular reactor is 208 °C, the average reaction pressure P of the tubular reactor is 232 MPa, and the initiator content X in the initiator solution used in the three reaction zones of the tubular reactor all satisfies the relational expression shown in formula (II), and 0 < X < 1;

[0091] The initiator consumption is 26.83 kg / h, the solvent consumption is 113.9 kg / h, the output of ethylene-vinyl acetate copolymer is 16.3 t / h, and the content of ethylene-vinyl acetate copolymer in the actually obtained second material is 16.89 wt%.

[0092] Example 2

[0093] According to Figure 1 the process shown to produce ethylene-vinyl acetate copolymer, which is carried out using a process similar to that of Example 1, and the differences are as follows:

[0094] Adjust the initiator content in the initiator solution used in the first zone to 35 wt%;

[0095] Adjust the initiator content in the initiator solution used in the second zone to 32 wt%;

[0096] Adjust the initiator content in the initiator solution used in the third zone to 32 wt%;

[0097] The types of initiator and solvent in the initiator solution remain unchanged;

[0098] For the initiator solutions used in the three reaction zones of the tubular reactor, the initiator content X all satisfies the relational expression shown in formula (I), and 0 < X < 1;

[0099] The initiator consumption is 29.67 kg / h, the solvent consumption is 59.9 kg / h, the output of ethylene-vinyl acetate copolymer is 15.9 t / h, and the content of ethylene-vinyl acetate copolymer in the actually obtained second material is 16.48 wt%.

[0100] Example 3

[0101] According to Figure 1 the process shown to produce ethylene-vinyl acetate copolymer, which is carried out using a process similar to that of Example 1, and the differences are as follows:

[0102] Adjust the initiator content in the initiator solution used in the first zone to 5 wt%;

[0103] Adjust the initiator content in the initiator solution used in the second zone to 5 wt%;

[0104] Adjust the initiator content in the initiator solution used in the third zone to 5 wt%;

[0105] The types of initiator and solvent in the initiator solution remain unchanged;

[0106] For the initiator solutions used in the three reaction zones of the tubular reactor, the initiator content X all satisfies the relational expression shown in formula (I), and 0 < X < 1;

[0107] The initiator consumption is 25.33 kg / h, the solvent consumption is 481.2 kg / h, the output of ethylene-vinyl acetate copolymer is 16.5 t / h, and the content of ethylene-vinyl acetate copolymer in the actually obtained second material is 17.10 wt%.

[0108] Example 4

[0109] According to Figure 2 The process shown is used to produce ethylene-vinyl acetate copolymer. The reactor used is a tank reactor with 2 reaction zones. Along the flow direction of the first material, from top to bottom, there are a first reaction zone and a second reaction zone in sequence. The volume ratio of the first reaction zone to the second reaction zone is 1:1. The content Y of ethylene-vinyl acetate copolymer in the obtained second material is set to 10 wt%.

[0110] The first material is compressed by a compressor to obtain the compressed first material. A part of the compressed first material is cooled and then introduced into the first reaction zone from the top of the reactor. A part of the compressed first material is introduced into the first reaction zone through the first material feed port of the first reaction zone. The remaining part of the compressed first material is introduced into the second reaction zone through the first material feed port of the second reaction zone. The initiator solution enters the first reaction zone and the second reaction zone respectively from the starting points of each reaction zone through the initiator feed pump to participate in the free radical polymerization reaction. The first reaction zone and the second reaction zone are in series. Along the flow direction of the first material, the reacted material in the first reaction zone enters the second reaction zone and participates in the free radical polymerization reaction together with a part of the first material and a part of the initiator solution introduced into the second reaction zone to obtain the second material; after the second material passes through a pressure reducing valve, it is subjected to high-pressure separation at 24 MPa and low-pressure separation at 0.15 MPa in sequence. The obtained ethylene-vinyl acetate copolymer is granulated to obtain an ethylene-vinyl acetate copolymer product;

[0111] The content of vinyl acetate monomer in the first material is 18 wt%, the flow rate of the first material is 75.1 t / h, and the maximum flow velocity is 25 m / s; the dosage ratio of the first material introduced into the first reaction zone and the second reaction zone of the tank reactor is 1:0.5; the dosage ratio of the initiator solution introduced into the first reaction zone and the second reaction zone is 1:1;

[0112] The initiator in the initiator solution in the first reaction zone of the tank reactor is Initiator II, the solvent is Solvent II, and the initiator content X is 25 wt%; the average reaction temperature T1 is 170 °C, the average reaction pressure P1 is 180 MPa, and the reaction time is 15 s;

[0113] In the initiator solution in the second reaction zone of the autoclave reactor, the initiator is Initiator II, the solvent is Solvent II, and the initiator content X is 25 wt%; the average reaction temperature T2 is 170 °C, the average reaction pressure P2 is 180 MPa, and the reaction time is 10 s;

[0114] The average reaction temperature T of the autoclave reactor is 170 °C, and the average reaction pressure P is 180 MPa; the initiator content X in the initiator solutions used in the two reaction zones of the autoclave reactor all satisfies the relational expression shown in formula (II), and 0 < X < 1;

[0115] The initiator consumption is 15.8 kg / h, the solvent consumption is 47.3 kg / h, the output of ethylene-vinyl acetate copolymer is 7.89 t / h, and the content of ethylene-vinyl acetate copolymer in the actually obtained second material is 10.2 wt%.

[0116] Comparative Example 1

[0117] According to Figure 1 The process shown is used to produce ethylene-vinyl acetate copolymer, and a process similar to that of Example 1 is adopted. The differences are as follows:

[0118] The content of the initiator in the initiator solution used in the first partition is adjusted to 40 wt%;

[0119] The content of the initiator in the initiator solution used in the second partition is adjusted to 40 wt%;

[0120] The content of the initiator in the initiator solution used in the third partition is adjusted to 40 wt%;

[0121] The types of the initiator and the solvent in the initiator solution remain unchanged; an ethylene-vinyl acetate copolymer product is prepared;

[0122] The initiator content X in the initiator solutions used in the three reaction zones of the tubular reactor does not satisfy the relational expressions shown in formula (I) or formula (II);

[0123] The initiator consumption is 31.02 kg / h, the solvent consumption is 46.5 kg / h, the output of ethylene-vinyl acetate copolymer is 15.0 t / h, and the content of ethylene-vinyl acetate copolymer in the actually obtained second material is 15.54 wt%.

[0124] Compared with Example 1, the output of the ethylene-vinyl acetate copolymer in Comparative Example 1 is lower, and the degree of deviation from the set value Y is greater, and the consumption of the initiator is higher.

[0125] Comparative Example 2

[0126] According to Figure 2The ethylene-vinyl acetate copolymer is produced by the process shown below, which is carried out in a similar process to Example 4, except that:

[0127] The content of the initiator in the initiator solution used in the first partition is adjusted to 43 wt%.

[0128] The content of the initiator in the initiator solution used in the second partition is adjusted to 43 wt%.

[0129] Both the type of the initiator and the solvent in the initiator solution remain unchanged; an ethylene-vinyl acetate copolymer product is prepared.

[0130] The content X of the initiator in the initiator solution used in the two reaction zones of the autoclave reactor does not satisfy the relational expressions shown in Formula (I) or Formula (II).

[0131] The initiator consumption is 18.9 kg / h, the solvent consumption is 25.0 kg / h, the output of the ethylene-vinyl acetate copolymer is 7.3 t / h, and the content of the ethylene-vinyl acetate copolymer in the actually obtained second material is 9.72 wt%.

[0132] Compared with Example 4, the output of the ethylene-vinyl acetate copolymer in Comparative Example 2 is lower, and the degree of deviation from the set value Y is greater, and the initiator consumption is higher.

[0133] Comparative Example 3

[0134] According to Figure 2 The ethylene-vinyl acetate copolymer is produced by the process shown below, which is carried out in a similar process to Example 4, except that:

[0135] The type of the initiator in the initiator solution is replaced from Initiator II with an equal weight of Initiator III, and the introduction ratio of the initiator solution in each reaction zone and the content of the initiator in the initiator solution remain unchanged; an ethylene-vinyl acetate copolymer product is prepared.

[0136] The initiator consumption is 15.8 kg / h, the solvent consumption is 47.3 kg / h, the output of the ethylene-vinyl acetate copolymer is 3.4 t / h, and the content of the ethylene-vinyl acetate copolymer in the actually obtained second material is 4.53 wt%.

[0137] Compared with Example 4, the output of the ethylene-vinyl acetate copolymer in Comparative Example 3 is lower.

[0138] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for producing ethylene-vinyl acetate copolymer, characterized in that, The method comprises: In the presence of an initiator solution, introducing a first material containing ethylene monomer and vinyl acetate monomer into a reactor for free radical polymerization reaction to obtain a second material containing ethylene-vinyl acetate copolymer; the reactor comprises at least 2 reaction zones; The initiator solution contains an initiator and a solvent. The initiator is an organic peroxide with a half-life temperature of 90-210 °C at normal pressure for 10 s. The solvent contains 0-70 wt% of C3-C 15 olefins and 30-100 wt% of C3-C 15 alkanes; The average reaction temperature T of the reactor is 120 - 300 °C, and the average reaction pressure P is 100 - 300 MPa; Define the content of ethylene-vinyl acetate copolymer in the second material as Y; The content X of the initiator in the initiator solution satisfies the relational expression shown in formula (I): Formula (I): 0.1×ln(T + 273.15) - 0.1×ln(P) - 0.2×Y < X < 0.35 + 0.1×ln(T + 273.15) - 0.1×ln(P) - 0.3×Y, and 0 < X < 1; wherein, Y is 10 - 25 wt%; The average reaction temperature of the reactor is the arithmetic mean of the reaction temperatures of each reaction zone of the reactor, and the average reaction pressure of the reactor is the arithmetic mean of the reaction pressures of each reaction zone of the reactor.

2. The method according to claim 1, characterized in that, The content X of the initiator in the initiator solution satisfies the relational expression shown in formula (II): Formula (II): 0.05 + 0.1×ln(T + 273.15) - 0.1×ln(P) - 0.2×Y < X < 0.25 + 0.1×ln(T + 273.15) - 0.1×ln(P) - 0.3×Y, and 0 < X < 1.

3. The method according to claim 1 or 2, characterized in that, The initiator is an organic peroxide with a 10s half-life temperature of 110 - 180 °C under normal pressure; the solvent contains 0 - 50 wt% of C3 - C8 olefins and 50 - 100 wt% of C 10 -C 15 alkanes; Preferably, the initiator contains at least one initiator selected from 1,1,3,3-tetramethylbutyl peroxynoate, bis(4-tert-butylcyclohexyl) peroxydicarbonate, bis(2-ethylhexyl) peroxydicarbonate, tert-butyl peroxynoate, tert-amyl peroxypivalate, tert-butyl peroxypivalate, tert-butyl 2-ethylhexanoate, tert-butyl 3,5,5-trimethylhexanoate, tert-butyl perbenzoate, tert-butyl peracetate, di-tert-amyl peroxide, di-tert-butyl peroxide; Preferably, the olefin is at least one selected from propylene, 1-butene, isobutene, 1-pentene, 1-hexene; Preferably, the alkane is at least one selected from n-decane, isodecane, n-undecane, isoundecane, n-dodecane, isododecane, n-tridecane, isotridecane; 4. The method according to any one of claims 1 to 3, characterized in that Each reaction zone in the reactor is independently provided with a first material inlet and an initiator solution inlet, and the reaction zones in the reactor are connected in series in sequence. Along the flowing direction of the first material, the material after reaction in the upstream reaction zone enters the adjacent downstream reaction zone and participates in the free radical polymerization reaction together with at least a part of the first material and at least a part of the initiator solution; the initiator solutions introduced into each reaction zone are the same or different.

5. The method according to claim 4, characterized in that, The reactor is a tubular reactor comprising 3 reaction zones, and the dosage ratios of the first material introduced into the first reaction zone, the second reaction zone, and the third reaction zone of the tubular reactor are 1:0.1 - 2:0.1 - 2; The dosage ratios of the initiator solution introduced into the first reaction zone, the second reaction zone, and the third reaction zone of the tubular reactor are 1:0.1-10:0.1-10.

6. The method according to claim 4, wherein The reactor is a tank reactor including two reaction zones, and the dosage ratio of the first material introduced into the first reaction zone and the second reaction zone of the tank reactor is 1:0.1-2; The dosage ratios of the initiator solution introduced into the first reaction zone and the second reaction zone of the tank reactor are 1:0.1-10.

7. The method according to any one of claims 1-4, characterized in that, The content of vinyl acetate monomer in the first material is 1-50 wt%. Preferably, the reactor is a tank reactor, and the content of vinyl acetate monomer in the first material is 1-50 wt%. Preferably, the reactor is a tubular reactor, and the content of vinyl acetate monomer in the first material is 1-35 wt%.

8. The method according to any one of claims 1-7, characterized in that, The flow rate of the first material is 10-200 t / h, and the maximum flow velocity is 5-30 m / s; and / or, The reaction time for carrying out the radical polymerization reaction in each reaction zone of the reactor is independently 5-100 s.

9. The method according to any one of claims 1-8, characterized in that The volume ratio of the first reaction zone to the second reaction zone of the reactor is 0.3-5:1, preferably 0.5-2:

1.

10. An ethylene-vinyl acetate copolymer prepared by the method according to any one of claims 1-9.

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