High-pressure low-density polyethylene production device and production method

Abstract

The present invention provides a high-pressure process low-density polyethylene production device and production method, which are excellent in the following characteristics: the obtained polyethylene has a small amount of smoke during processing and a small amount of fish eyes contained in a film made of the polyethylene. A high-pressure process polyethylene production device, wherein the production device has the following equipment: a first ethylene supply pipeline (11): a pipeline branched from an unreacted high-pressure ethylene pipeline (6) and connected to an unreacted ethylene holding cylindrical container (12), and used to reduce the pressure of unreacted high-pressure ethylene from the unreacted high-pressure ethylene pipeline (6) and supply the reduced-pressure unreacted ethylene to the unreacted ethylene holding cylindrical container (12); and an unreacted ethylene holding cylindrical container (12): a cylindrical container for holding the unreacted ethylene that has been reduced in pressure through the first ethylene supply pipeline (11).

Description

Technical Field

[0001] The present invention relates to a device and a method for producing low-density polyethylene by a high-pressure process. Background Art

[0002] It is known that ethylene is polymerized under high temperature and high pressure in the presence of a polymerization initiator to obtain an ethylene polymer by an apparatus and method (e.g., Patent Document 1 and Patent Document 2 and Non-Patent Document 1). The ethylene polymer produced by this high-pressure polymerization method has a wide range of uses, of which a large proportion is used or processed in the form of packaging films and other films. In these uses, the film is required to have excellent anti-blocking properties, etc.

[0003] Patent Document 1 describes an apparatus and method for producing polyethylene by a high-pressure process including a compressor, a reactor, a high-pressure separator, a low-pressure separator, and the like.

[0004] Patent Document 2 describes an apparatus and method for producing polyethylene by a high-pressure process, which includes a front-stage compressor, a middle-stage compressor, a rear-stage compressor, a reactor, a high-pressure separator, a low-pressure separator, and the like.

[0005] Non-patent document 1, pages 5-11 and 6-4, describes a high-pressure process low-density polyethylene production apparatus having a booster compressor, a primary compressor, an ultra-high pressure compressor, a tubular reactor or an autoclave reactor, a high-pressure separator, a low-pressure separator, and the like.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Publication No. 49-37434

[0009] Patent Document 2: Japanese Patent Publication No. 54-15317

[0010] Non-patent literature

[0011] Non-patent literature 1: SUSAN L. BELL, SRI Consulting Report No. 36D, LOW DENSITY POLYETHYLENE, September 2005 Summary of the invention

[0012] Problems to be solved by the invention

[0013] In this case, the problem to be solved by the present invention is to provide a high-pressure low-density polyethylene manufacturing device and manufacturing method having the following excellent characteristics, in which low molecular weight impurities including polymerization by-products, solvents and lubricating oils are economically and effectively separated and removed from ethylene high-pressure polymers during ethylene high-pressure polymerization (ethylene high-pressure polymerization in this specification includes not only ethylene homopolymerization but also copolymerization), and the obtained polyethylene polymer has less smoke generation during processing and less fish eyes contained in the film made from the polymer.

[0014] Means used to solve problems

[0015] The present inventors have conducted intensive studies in view of such background and have completed the present invention as a result.

[0016] That is, the present invention is as follows. [1]

[0018] A high-pressure polyethylene production device, wherein the production device has the following equipment:

[0019] a first ethylene supply pipeline (11): a pipeline branched from the unreacted high-pressure ethylene pipeline (6) and connected to the unreacted ethylene holding cylindrical container (12), and used to reduce the pressure of the unreacted high-pressure ethylene from the unreacted high-pressure ethylene pipeline (6) and supply the reduced-pressure unreacted ethylene to the unreacted ethylene holding cylindrical container (12); and

[0020] Unreacted ethylene holding cylindrical container (12): a cylindrical container for holding unreacted ethylene that has been depressurized after passing through the first ethylene supply pipe (11).

[0021] Hereinafter, [2] to

[10] are each a preferred aspect or embodiment of the present invention. [2]

[0023] The production apparatus according to [1], wherein the first ethylene supply pipeline (11) is the following pipeline:

[0024] A first ethylene supply pipeline (11) is a pipeline branched from the unreacted high-pressure ethylene pipeline (6) and connected to the unreacted ethylene holding cylindrical container (12), and is used to reduce the pressure of the unreacted high-pressure ethylene from the unreacted high-pressure ethylene pipeline (6) to a range of 0.8 MPa to 3 MPa, and to supply the unreacted high-pressure ethylene after the pressure reduction to the unreacted ethylene holding cylindrical container (12). [3]

[0026] The production apparatus according to [1] or [2], wherein the unreacted ethylene holding cylindrical container (12) is the following cylindrical container:

[0027] Unreacted ethylene holding cylindrical container (12): a cylindrical container for holding unreacted ethylene which has been depressurized to a pressure within a range of 0.8 MPa to 3 MPa at a temperature of -20°C to 0°C through the first ethylene supply pipe (11). [4]

[0029] The manufacturing device as described in any one of [1] to [3], wherein the manufacturing device further comprises the following equipment:

[0030] The rear section of the primary compressor (2) is a compressor that further compresses the ethylene supplied from the front section of the primary compressor (1);

[0031] Unreacted high-pressure ethylene pipeline (6): a pipeline for supplying the unreacted high-pressure ethylene separated in the high-pressure separator (5) to the secondary compressor (3); and

[0032] The second ethylene supply pipeline (13) is a pipeline used to connect the unreacted ethylene holding cylindrical container (12) to the primary compressor rear section (2), and to supply the decompressed unreacted ethylene from the unreacted ethylene holding cylindrical container (12) to the primary compressor rear section (2). [5]

[0034] The manufacturing device as described in any one of [1] to [4], wherein the manufacturing device further comprises the following equipment:

[0035] Primary compressor front section (1): a compressor for compressing ethylene;

[0036] Secondary compressor (3): a compressor that further compresses the ethylene supplied from the rear section (2) of the primary compressor;

[0037] Reactor (4): a reactor for producing polyethylene by polymerizing ethylene supplied from the secondary compressor (3) and a polymerization initiator supplied to the reactor (4);

[0038] A high-pressure separator (5): a high-pressure separator to which the polyethylene obtained in the reactor (4) and the unreacted ethylene are supplied from the reactor (4) and the polyethylene and the unreacted high-pressure ethylene are separated;

[0039] A first polyethylene extraction pipeline (7): a pipeline for extracting the polyethylene separated in the high-pressure separator (5) from the high-pressure separator (5) and supplying it to the low-pressure separator (8);

[0040] Low-pressure separator (8): a separator for separating unreacted low-pressure ethylene contained in the polyethylene separated in the high-pressure separator (5) and supplied through the first polyethylene extraction pipeline (7) from the polyethylene;

[0041] Unreacted low-pressure ethylene supply pipeline (9): a pipeline for supplying the unreacted low-pressure ethylene separated in the low-pressure separator (8) to the front section of the primary compressor;

[0042] Second polyethylene extraction pipeline (10): a pipeline for extracting the polyethylene separated in the low-pressure separator (8); and

[0043] Fresh ethylene supply pipeline (14): a pipeline connected to the second ethylene supply pipeline (13) and used to supply fresh ethylene. [6]

[0045] A method for producing high-pressure polyethylene, wherein the method comprises the following steps:

[0046] Unreacted high-pressure ethylene recycling step: A step in which a portion of the unreacted ethylene separated in the high-pressure separator (5) is supplied to the secondary compressor (3) through the unreacted high-pressure ethylene pipeline (6), the remaining unreacted ethylene is decompressed through the first ethylene supply pipeline (11), the decompressed unreacted ethylene is supplied to the unreacted ethylene holding cylindrical container (12), and the unreacted ethylene is supplied to the rear section (2) of the primary compressor through the second ethylene supply pipeline (13). [7]

[0048] The production method according to [6], wherein the unreacted high-pressure ethylene recycling step is the following step:

[0049] An unreacted high-pressure ethylene recycling step: for the unreacted ethylene separated in the high-pressure separator (5), 50% by weight or more and less than 100% by weight of the unreacted ethylene in the unreacted ethylene is supplied to the secondary compressor (3) through the unreacted high-pressure ethylene pipeline (6), the remaining unreacted ethylene (greater than 0% by weight and less than 50% by weight) is depressurized to a range of 0.8 MPa to 3 MPa through the first ethylene supply pipeline (11), the unreacted ethylene depressurized to a range of 0.8 MPa to 3 MPa is supplied to an unreacted ethylene holding cylindrical container (12), and the unreacted ethylene is supplied to the rear section (2) of the primary compressor through the second ethylene supply pipeline (13). [8]

[0051] The manufacturing method as described in [6] or [7], wherein the manufacturing method further comprises the following steps:

[0052] Compression process: the process of compressing ethylene;

[0053] Reaction step: a step of supplying compressed ethylene and a polymerization initiator to a reactor (4) and polymerizing ethylene to produce polyethylene;

[0054] Separation step: a step of separating the polyethylene produced in the reactor (4) from unreacted ethylene in a high-pressure separator (5), extracting the produced polyethylene from the high-pressure separator (5), supplying the produced polyethylene to a low-pressure separator (8) through a first polyethylene extraction pipe (7), separating the unreacted ethylene contained in the polyethylene in the low-pressure separator (8), and extracting the polyethylene;

[0055] Unreacted low-pressure ethylene recycling step: a step of supplying the unreacted low-pressure ethylene separated in the low-pressure separator (8) to the primary compressor front section (1) through the unreacted low-pressure ethylene supply pipeline (9); and

[0056] Fresh ethylene supplying step: a step of supplying fresh ethylene from the fresh ethylene supplying pipe (14) to the second ethylene supplying pipe (13). [9]

[0058] The manufacturing method as described in [8], wherein the compression step is the following step:

[0059] Compression process: a process of compressing ethylene to a range of 0.04 MPa to 3 MPa using the front section (1) of the primary compressor, compressing the ethylene compressed in the front section (1) of the primary compressor to a range of 3 MPa to 20 MPa in the rear section (2) of the primary compressor, and compressing the ethylene compressed in the rear section (2) of the primary compressor to a range of 20 MPa to 200 MPa in the secondary compressor (3).

[10]

[0061] The production method according to any one of [6] to [9], wherein the production method uses a high-pressure polyethylene production apparatus.

[0062] Effects of the Invention

[0063] According to the present invention, it is possible to provide an apparatus and method for producing high-pressure low-density polyethylene having excellent characteristics that the obtained polyethylene polymer generates little smoke during processing and contains few fish eyes in a film made of the polyethylene. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 A schematic process diagram showing one embodiment of the production apparatus and method for high-pressure low-density polyethylene of the present invention. DETAILED DESCRIPTION

[0065] The following reference Figure 1 One embodiment of the production apparatus and production method of the present invention will be described in detail.

[0066] Ethylene gas is supplied to the polymerization reactor (4), a polymerization initiator is added, and ethylene is polymerized.

[0067] The polymerization mixture is discharged from the polymerization reactor (4) into a high-pressure separator (5) under reduced pressure, and separated into the produced polymer and unreacted ethylene gas.

[0068] The generated polymer separated in the high-pressure separator (5) is extracted into the low-pressure separator (8) through the first polyethylene extraction pipeline (7), and further separated into polyethylene and unreacted ethylene gas. The polyethylene is extracted through the second polyethylene extraction pipeline (10) and made into pellets in a pelletizer.

[0069] The unreacted ethylene gas separated in the low-pressure separator (8) is supplied to the front section (1) of the primary compressor through the unreacted low-pressure ethylene supply pipeline (9), the unreacted ethylene gas is compressed, and supplied to the rear section (2) of the primary compressor through the second ethylene supply pipeline (13).

[0070] A portion of the unreacted ethylene gas separated in the high-pressure separator (5) is supplied to the inlet pipe of the secondary compressor (3) through the unreacted high-pressure ethylene pipe (6), and the remaining unreacted ethylene gas is decompressed through the first ethylene supply pipe (11) and then supplied to the unreacted ethylene holding cylindrical container (12). The unreacted ethylene gas held in the unreacted ethylene holding cylindrical container (12) is supplied to the primary compressor rear section (2) through the second ethylene supply pipe (13).

[0071] Fresh ethylene is supplied from a fresh ethylene supply pipe (14) to the primary compressor rear section (2) through a second ethylene supply pipe (13).

[0072] Unreacted ethylene gas supplied from the primary compressor front section (1), unreacted ethylene gas supplied from the unreacted ethylene holding cylindrical container (12) and a mixed ethylene gas of fresh ethylene gas are compressed in the primary compressor rear section (2) and supplied to the secondary compressor (3).

[0073] The ethylene gas compressed in the secondary compressor (3) is supplied to the polymerization reactor (4), and the polymerization reaction is continuously carried out.

[0074] <Manufacturing Equipment>

[0075] The manufacturing device of the present invention is a manufacturing device for high-pressure polyethylene having the following equipment:

[0076] a first ethylene supply pipeline (11): a pipeline branched from the unreacted high-pressure ethylene pipeline (6) and connected to the unreacted ethylene holding cylindrical container (12), and used to reduce the pressure of the unreacted high-pressure ethylene from the unreacted high-pressure ethylene pipeline (6) and supply the reduced-pressure unreacted ethylene to the unreacted ethylene holding cylindrical container (12); and

[0077] Unreacted ethylene holding cylindrical container (12): a cylindrical container for holding unreacted ethylene that has been depressurized after passing through the first ethylene supply pipe (11).

[0078] Primary compressor front section (1)

[0079] The primary compressor front section (1) is a compressor that compresses ethylene within a range of, for example, 0.04 MPa to 3 MPa.

[0080] Primary compressor rear section (2)

[0081] The primary compressor rear section (2) is a compressor that compresses ethylene supplied from the primary compressor front section (1) within a range of, for example, 3 MPa to 20 MPa.

[0082] Secondary compressor (3)

[0083] The secondary compressor (3) is a compressor that compresses ethylene supplied from the rear stage (2) of the primary compressor within a range of, for example, 20 MPa to 200 MPa.

[0084] Reactor (4)

[0085] The reactor (4) is a reactor for producing polyethylene by polymerizing ethylene supplied from the secondary compressor (3) and a polymerization initiator supplied to the reactor (4).

[0086] Reactor (4) can be any one of a tubular reactor or a tank reactor, and ethylene high-pressure polymerization can be carried out, for example, using a polymerization initiator such as oxygen or peroxide under the following conditions: the pressure is, for example, above 20 MPa, preferably 100 MPa to 500 MPa, and more preferably 100 MPa to 400 MPa; the temperature is, for example, above 100°C, preferably 100°C to 400°C, more preferably 150°C to 350°C, and even more preferably 150°C to 300°C.

[0087] The ethylene stream entering the reactor (4) may contain comonomers and chain transfer agents in addition to the polymerization initiator.

[0088] High pressure separator (5)

[0089] The high-pressure separator (5) is a high-pressure separator that supplies the polyethylene obtained in the reactor (4) and the unreacted ethylene after decompression from the reactor (4) and separates the polyethylene from the unreacted high-pressure ethylene.

[0090] The reaction mixture containing the polymer generated in the reactor (4), unreacted ethylene gas, polymerization by-products, solvent and lubricating oil, etc., enters the high-pressure separator (5) after passing through a pressure regulating valve according to the situation and is discharged under reduced pressure. A part of the polymer contained in the reaction mixture is separated under the following conditions: the pressure is, for example, 10MPa to 100MPa, preferably 50MPa to 100MPa, and more preferably below 70MP, and the temperature is, for example, 200°C to 260°C.

[0091] The separated polymer contains almost no low molecular weight substances having a weight average molecular weight of 5,000 or less.

[0092] The polymer separated in the high-pressure separator (5) is sent to a low-pressure separator (8) to separate and remove the unreacted ethylene gas remaining in the polymer, and then taken out from the second polyethylene extraction pipeline (10) in the form of product polyethylene.

[0093] Unreacted high pressure ethylene pipeline (6)

[0094] The unreacted high-pressure ethylene pipeline (6) is a pipeline for supplying the unreacted high-pressure ethylene separated in the high-pressure separator (5) to the secondary compressor (3).

[0095] First polyethylene extraction pipe (7)

[0096] The first polyethylene extraction pipe (7) is a pipe for extracting the polyethylene separated in the high-pressure separator (5) from the high-pressure separator (5) and supplying it to the low-pressure separator (8).

[0097] Low pressure separator(8)

[0098] The low-pressure separator (8) is a separator for separating the unreacted low-pressure ethylene contained in the polyethylene separated in the high-pressure separator (5) and supplied through the first polyethylene extraction pipe (7) from the polyethylene.

[0099] The unreacted gas separated to the top in the low-pressure separator (8) at, for example, about 200° C. to about 250° C. is cooled to, for example, 20° C. to 50° C. in a cooler, and then, for example, sent to the separator to remove impurities such as solvent. The unreacted gaseous ethylene after the impurities are removed is returned to the inlet of the primary compressor front section (1) through the unreacted low-pressure ethylene supply pipeline (9).

[0100] Unreacted low pressure ethylene supply pipeline (9)

[0101] The unreacted low-pressure ethylene supply pipeline (9) is a pipeline for supplying the unreacted low-pressure ethylene separated in the low-pressure separator (8) to the front section of the primary compressor. The unreacted low-pressure ethylene supply pipeline (9) can be controlled at a pressure of, for example, 0.01 MPa to 0.1 MPa and a temperature of, for example, 150° C. to 220° C.

[0102] Second polyethylene extraction pipe (10)

[0103] The second polyethylene extraction pipeline (10) is a pipeline for extracting the polyethylene separated in the low-pressure separator (8). The polyethylene extracted from the second polyethylene extraction pipeline (10) can be processed into a pellet product by an extruder, a cooler, a pelletizer, etc. The obtained polyethylene can be a low-density polyethylene, for example, having a density of 910 kg / m 3 ~920kg / m 3 density.

[0104] First ethylene supply pipeline (11)

[0105] The first ethylene supply pipeline (11) is a pipeline that branches from the unreacted high-pressure ethylene pipeline (6) and is connected to the unreacted ethylene holding cylindrical container (12), and is used to reduce the pressure of a portion of the unreacted high-pressure ethylene from the unreacted high-pressure ethylene pipeline (6) (for example, greater than 0% by weight and less than or equal to 50% by weight, preferably less than 40% by weight, and more preferably less than 30% by weight) to a range of, for example, 0.8 MPa to 3 MPa, and to supply the reduced-pressure unreacted ethylene to the unreacted ethylene holding cylindrical container (12).

[0106] Unreacted ethylene holding cylindrical container (12)

[0107] The unreacted ethylene holding cylindrical container (12) is a cylindrical container that holds unreacted ethylene that has passed through the first ethylene supply pipe (11) and has been depressurized to a pressure within a range of 0.8 MPa to 3 MPa at a temperature of, for example, -20°C to 0°C.

[0108] Second ethylene supply pipeline (13)

[0109] The second ethylene supply pipe (13) is a pipe for connecting the unreacted ethylene holding cylindrical container (12) to the primary compressor rear section (2), and for supplying unreacted ethylene from the unreacted ethylene holding cylindrical container (12) to the primary compressor rear section (2).

[0110] Fresh Ethylene Supply Pipeline (14)

[0111] The fresh ethylene supply pipe (14) is connected to the second ethylene supply pipe (13) and is used to supply fresh ethylene. For example, fresh ethylene gas at 0.8 MPa to 3 MPa is supplied.

[0112] As an embodiment, the raw material ethylene gas is fed from the fresh ethylene supply pipeline (14) to the primary compressor rear section (2), compressed to a range of, for example, 3 MPa to 20 MPa, and then further compressed to a range of, for example, 20 MPa to 200 MPa in the secondary compressor (3). The gas pressurized to the polymerization pressure is fed to the reactor (4), and polymerization is carried out at a predetermined temperature of, for example, 150° C. to 300° C. using oxygen or a peroxide initiator.

[0113] <Manufacturing method>

[0114] The production method of the present invention is a production method of high-pressure polyethylene comprising the following steps:

[0115] Unreacted high-pressure ethylene recycling step: A step in which a portion of the unreacted ethylene separated in the high-pressure separator (5) is supplied to the secondary compressor (3) through the unreacted high-pressure ethylene pipeline (6), the remaining unreacted ethylene is decompressed through the first ethylene supply pipeline (11), the decompressed unreacted ethylene is supplied to the unreacted ethylene holding cylindrical container (12), and the unreacted ethylene is supplied to the rear section (2) of the primary compressor through the second ethylene supply pipeline (13).

[0116] Compression process

[0117] The compression process is not limited to compression in one step, and may include a process of compression in two or more steps.

[0118] For example, the compression process is as follows:

[0119] The ethylene is compressed by the primary compressor front section (1) to a pressure within the range of, for example, 0.04 MPa to 3 MPa.

[0120] In the primary compressor rear section (2), the ethylene compressed in the primary compressor front section (1) is compressed to a pressure within a range of, for example, 3 MPa to 20 MPa.

[0121] In the secondary compressor (3), ethylene compressed in the rear stage (2) of the primary compressor is compressed to a pressure within a range of, for example, 20 MPa to 200 MPa.

[0122] Reaction process

[0123] The reaction step is a step of supplying ethylene compressed in the secondary compressor (3) and a polymerization initiator to a reactor (4) to polymerize ethylene to produce polyethylene.

[0124] The detailed operating conditions of the reaction step can be the same as those described in the description of the above reactor (4).

[0125] Separation process

[0126] The separation process is as follows:

[0127] The polyethylene produced in the reactor (4) and the unreacted ethylene are separated in the high-pressure separator (5).

[0128] The generated polyethylene is extracted from the high-pressure separator (5) and supplied to the low-pressure separator (8) through the first polyethylene extraction pipeline (7).

[0129] Unreacted ethylene contained in the polyethylene is separated in the low-pressure separator (8), and the polyethylene is extracted.

[0130] The detailed operating conditions of the separation steps in the high-pressure separator (5) and the low-pressure separator (8) can be applied to the conditions described in the description of the high-pressure separator (5) and the low-pressure separator (8) described above.

[0131] Unreacted high-pressure ethylene recycling process

[0132] The unreacted high-pressure ethylene recycling process is as follows:

[0133] A portion (e.g., 50% by weight or more and less than 100% by weight, preferably 60% by weight or more, more preferably 70% by weight or more) of the unreacted ethylene separated in the high-pressure separator (5) is supplied to the secondary compressor (3) through the unreacted high-pressure ethylene pipeline (6), and the remaining (e.g., 0% by weight or less and 50% by weight, preferably 40% by weight or less, more preferably 30% by weight or less) of the unreacted ethylene is depressurized to, for example, a range of 0.8 MPa to 3 MPa through the first ethylene supply pipeline (11).

[0134] The unreacted ethylene which has been depressurized to a range of, for example, 0.8 MPa to 3 MPa is supplied to an unreacted ethylene holding cylindrical container (12).

[0135] Unreacted ethylene is supplied to the primary compressor rear section (2) through a second ethylene supply pipe (13).

[0136] The detailed operating conditions of the unreacted high-pressure ethylene recycling process can be applied to the conditions described in the description of the above-mentioned unreacted high-pressure ethylene pipeline (6), the first ethylene supply pipeline (11), the unreacted ethylene holding cylindrical container (12) and the second ethylene supply pipeline (13).

[0137] Unreacted low-pressure ethylene recycling process

[0138] The unreacted low-pressure ethylene recycling step is a step of supplying the unreacted low-pressure ethylene separated in the low-pressure separator (8) to the primary compressor front section (1) through the unreacted low-pressure ethylene supply pipeline (9).

[0139] The detailed operating conditions of the unreacted low-pressure ethylene recycling step can be applied to the conditions described in the above description of the low-pressure separator (8) and the unreacted low-pressure ethylene supply pipeline (9).

[0140] Fresh ethylene supply process

[0141] The fresh ethylene supply process is as follows:

[0142] Fresh ethylene is supplied from a fresh ethylene supply pipe (14) to a second ethylene supply pipe (13), and fresh ethylene is supplied to a primary compressor rear section (2) through the second ethylene supply pipe (13).

[0143] The detailed operating conditions of the fresh ethylene supply step can be applied to the conditions described in the description of the fresh ethylene supply pipeline (14) and the second ethylene supply pipeline (13).

[0144] The present invention can be practiced using a high pressure ethylene polymerization unit having a high pressure circulating gas system.

[0145] In the present invention, all polymerization initiators and chain transfer agents known for use in the polymerization or copolymerization of ethylene can be used.

[0146] <Polymerization Initiator>

[0147] In the present invention, all polymerization initiators known for polymerization or copolymerization of ethylene can be used.

[0148] As the polymerization initiator, for example, the following substances can be listed as suitable examples: hydrogen peroxide; organic peroxides such as lauroyl peroxide, dipropionyl peroxide, benzoyl peroxide, di-tert-butyl peroxide, tert-butyl hydroperoxide, trimethylhexanoyl peroxide, diisopropyl peroxydicarbonate, tert-butyl peroxyacetate, and tert-butyl peroxyisobutyrate; hydrogen peroxide: molecular oxygen; azo compounds such as azobisisobutyronitrile and azobisisovaleronitrile; tert-butyl perbenzoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxyisopropyl carbonate, oxygen, etc.

[0149] <Chain transfer agent>

[0150] In the present invention, all chain transfer agents known for use in the polymerization or copolymerization of ethylene can be used.

[0151] As chain transfer agents, the following substances can be listed as suitable examples: chain alkanes such as ethane, propane, butane, heptane, hexane, and pentane; α-olefins such as propylene, 1-butene, 1-hexene, and 3-methyl-1-butene; aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, and n-butyraldehyde; ketones such as acetone, methyl ethyl ketone, diethyl ketone, diisopropyl ketone, cyclohexanone, and methyl isopropyl ketone; aromatic hydrocarbons; chlorinated hydrocarbons, etc.

[0152] <Comonomer>

[0153] The apparatus and method of the present invention can also be applied to the copolymerization of ethylene and other comonomers copolymerizable with ethylene.

[0154] In the present invention, for example, all comonomers known to copolymerize with ethylene such as compounds having ethylenically unsaturated groups can be used. The compounds having ethylenically unsaturated groups include acrylic acid and its alkyl esters, methacrylic acid and its alkyl esters, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, vinyl chloride, vinylidene chloride, vinyl fluoride, vinyl acetate, vinyl propionate, N-vinyl imide compounds, vinyl aromatic compounds, vinyl ether compounds, vinyl ketone compounds, and the like.

[0155] The comonomer can be used in an amount greater than 0 wt% and about 50 wt% or less, preferably about 40 wt% or less, more preferably about 30 wt% or less, and even more preferably about 20 wt% or less in the obtained copolymer.

[0156] The comonomer can be added to any equipment and process. For example, the comonomer can be added to equipment and processes from the compressor to the reactor.

[0157] Example 1

[0158] Ethylene gas was supplied to the polymerization reactor 4 at 34,000 kg / hour, and polymerization was carried out by adding t-butyl peroxybenzoate as an initiator under the conditions of a pressure of 141 to 163 MPa and a temperature of 245 to 265° C. The amount of polymer produced was 8,000 kg / hour.

[0159] The polymerization mixture was discharged from the polymerization reactor 4 to a 20 MPa high-pressure separator 5, and separated at 230°C into a produced polymer and unreacted ethylene gas.

[0160] The produced polymer separated in the high-pressure separator 5 is extracted into a 0.03 MPa low-pressure separator 8 through a first polyethylene extraction pipe 7, and further separated into polyethylene and unreacted ethylene gas at 200° C. The polyethylene is extracted through a second polyethylene extraction pipe 10 and made into pellets in a pelletizer.

[0161] The unreacted ethylene gas separated in the low-pressure separator 8 is supplied to the primary compressor front section 1 at 0.03 MPa through the unreacted low-pressure ethylene supply pipeline 9, the unreacted ethylene gas is compressed to 2.6 MPa, and supplied to the primary compressor rear section 2 through the second ethylene supply pipeline 13.

[0162] The unreacted ethylene gas separated in the high-pressure separator 5 is depressurized to 19 MPa through the unreacted high-pressure ethylene pipeline 6, and 82 wt% of the unreacted ethylene gas is supplied to the inlet pipeline of the secondary compressor 3. The remaining 18 wt% of the unreacted ethylene gas is depressurized to 2.6 MPa through the first ethylene supply pipeline 11 and supplied to the unreacted ethylene holding cylindrical container 12 at a temperature of -12°C. The unreacted ethylene gas of 2.6 MPa held in the unreacted ethylene holding cylindrical container 12 is supplied to the primary compressor rear section 2 through the second ethylene supply pipeline 13.

[0163] Fresh ethylene gas at 2.6 MPa is supplied from the fresh ethylene supply pipe 14 to the primary compressor rear section 2 through the second ethylene supply pipe 13 .

[0164] In the primary compressor rear section 2 , the unreacted ethylene gas supplied from the primary compressor front section 1 and the mixed ethylene gas of the unreacted ethylene gas supplied from the unreacted ethylene holding cylindrical container 12 and fresh ethylene gas are compressed to 19 MPa and supplied to the secondary compressor 3 .

[0165] The ethylene gas compressed to 178 MPa in the secondary compressor 3 was supplied to the polymerization reactor 4, and the polymerization reaction was continuously performed.

[0166] Comparative Example 1

[0167] Ethylene gas was supplied to the polymerization reactor 4 at 33,000 kg / hour, and polymerization was carried out by adding t-butyl peroxybenzoate as an initiator under the conditions of a pressure of 141 to 163 MPa and a temperature of 245 to 265° C. The amount of polymer produced was 8,000 kg / hour.

[0168] The polymerization mixture was discharged from the polymerization reactor 4 to the 19 MPa high-pressure separator 5, and separated into the produced polymer and unreacted ethylene gas at 230°C.

[0169] The produced polymer separated in the high-pressure separator 5 is extracted into a 0.03 MPa low-pressure separator 8 through a first polyethylene extraction pipe 7, and further separated into polyethylene and unreacted ethylene gas at 200° C. The polyethylene is extracted through a second polyethylene extraction pipe 10 and made into pellets in a pelletizer.

[0170] The unreacted ethylene gas separated in the low-pressure separator 8 is supplied to the primary compressor front section 1 at 0.03 MPa through the unreacted low-pressure ethylene supply pipeline 9, the unreacted ethylene gas is compressed to 2.6 MPa, and supplied to the primary compressor rear section 2 through the second ethylene supply pipeline 13.

[0171] The unreacted ethylene gas separated in the high-pressure separator 5 was depressurized to 18 MPa through the unreacted high-pressure ethylene pipeline 6 , and the entire amount (100 wt %) of the unreacted ethylene gas was supplied to the inlet pipeline of the secondary compressor 3 .

[0172] Fresh ethylene gas at 2.6 MPa is supplied from the fresh ethylene supply pipe 14 to the primary compressor rear section 2 through the second ethylene supply pipe 13 .

[0173] The mixed ethylene gas of the unreacted ethylene gas and the fresh ethylene gas supplied from the primary compressor front section 1 is compressed to 18 MPa in the primary compressor rear section 2 and supplied to the secondary compressor 3 .

[0174] The ethylene gas compressed to 178 MPa in the secondary compressor 3 was supplied to the polymerization reactor 4, and the polymerization reaction was continuously performed.

[0175] Example 2

[0176] Ethylene gas was supplied to the polymerization reactor 4 at 34,000 kg / hour, and polymerization was carried out by adding t-butyl peroxybenzoate as an initiator under the conditions of a pressure of 130 MPa to 147 MPa and a temperature of 240° C. to 265° C. The amount of polymer produced was 8,000 kg / hour.

[0177] The polymerization mixture was discharged from the polymerization reactor 4 to the high-pressure separator 5 at 19 MPa, and separated at 200°C into a produced polymer and unreacted ethylene gas.

[0178] The produced polymer separated in the high-pressure separator 5 is extracted into a 0.03 MPa low-pressure separator 8 through a first polyethylene extraction pipe 7, and further separated into polyethylene and unreacted ethylene gas at 180° C. The polyethylene is extracted through a second polyethylene extraction pipe 10 and made into pellets in a pelletizer.

[0179] The unreacted ethylene gas separated in the low-pressure separator 8 is supplied to the primary compressor front section 1 at 0.03 MPa through the unreacted low-pressure ethylene supply pipeline 9, the unreacted ethylene gas is compressed to 2.7 MPa, and supplied to the primary compressor rear section 2 through the second ethylene supply pipeline 13.

[0180] The unreacted ethylene gas separated in the high-pressure separator 5 is depressurized to 19 MPa through the unreacted high-pressure ethylene pipeline 6, and 84 wt% of the unreacted ethylene gas is supplied to the inlet pipeline of the secondary compressor 3. The remaining 16 wt% of the unreacted ethylene gas is depressurized to 2.7 MPa through the first ethylene supply pipeline 11 and supplied to the unreacted ethylene holding cylindrical container 12 at a temperature of -7°C. The unreacted ethylene gas of 2.7 MPa held in the unreacted ethylene holding cylindrical container 12 is supplied to the primary compressor rear section 2 through the second ethylene supply pipeline 13.

[0181] Fresh ethylene gas at 2.7 MPa is supplied from the fresh ethylene supply pipe 14 to the primary compressor rear section 2 through the second ethylene supply pipe 13 .

[0182] In the primary compressor rear section 2 , the unreacted ethylene gas supplied from the primary compressor front section 1 and the mixed ethylene gas of the unreacted ethylene gas supplied from the unreacted ethylene holding cylindrical container 12 and fresh ethylene gas are compressed to 19 MPa and supplied to the secondary compressor 3 .

[0183] The ethylene gas compressed to 165 MPa in the secondary compressor 3 was supplied to the polymerization reactor 4, and the polymerization reaction was continuously performed.

[0184] Comparative Example 2

[0185] Ethylene gas was supplied to the polymerization reactor 4 at 33,000 kg / hour, and polymerization was carried out by adding tert-butyl peroxybenzoate as an initiator under the conditions of a pressure of 131 MPa to 147 MPa and a temperature of 240° C. to 265° C. The amount of polymer produced was 9,000 kg / hour.

[0186] The polymerization mixture was discharged from the polymerization reactor 4 to the 19 MPa high-pressure separator 5, and separated into the produced polymer and unreacted ethylene gas at 210°C.

[0187] The produced polymer separated in the high-pressure separator 5 is extracted into a 0.03 MPa low-pressure separator 8 through a first polyethylene extraction pipe 7, and further separated into polyethylene and unreacted ethylene gas at 190° C. The polyethylene is extracted through a second polyethylene extraction pipe 10 and made into pellets in a pelletizer.

[0188] The unreacted ethylene gas separated in the low-pressure separator 8 is supplied to the primary compressor front section 1 at 0.03 MPa through the unreacted low-pressure ethylene supply pipeline 9, the unreacted ethylene gas is compressed to 2.7 MPa, and supplied to the primary compressor rear section 2 through the second ethylene supply pipeline 13.

[0189] The unreacted ethylene gas separated in the high-pressure separator 5 was depressurized to 17 MPa through the unreacted high-pressure ethylene pipeline 6 , and the entire amount (100 wt %) of the unreacted ethylene gas was supplied to the inlet pipeline of the secondary compressor 3 .

[0190] Fresh ethylene gas at 2.7 MPa is supplied from the fresh ethylene supply pipe 14 to the primary compressor rear section 2 through the second ethylene supply pipe 13 .

[0191] The mixed ethylene gas of the unreacted ethylene gas and the fresh ethylene gas supplied from the primary compressor front section 1 is compressed to 17 MPa in the primary compressor rear section 2 and supplied to the secondary compressor 3 .

[0192] The ethylene gas compressed to 163 MPa in the secondary compressor 3 was supplied to the polymerization reactor 4, and the polymerization reaction was continuously performed.

[0193] <Analysis and measurement methods for polyethylene>

[0194] The polyethylene extracted through the second polyethylene extraction pipe 10 and pelletized in the pelletizer was analyzed by the following method.

[0195] (1) Density determination method (unit: kg / m 3 )

[0196] Annealing described in JIS K6922-2 was performed, and then measurement was performed by the A method according to the method specified in JIS K7112.

[0197] (2) Melt flow rate (MFR) measurement method (unit: g / 10 minutes)

[0198] The measurement was performed by the A method according to the method specified in JIS K7210-1 under the conditions of a temperature of 190° C. and a load of 2.16 kg.

[0199] (3) Determination of heptane extraction amount

[0200] 100 g of each pellet and 250 mL of n-heptane (manufactured by Kanto Chemical Co., Ltd.) were added to a 500 mL conical flask and allowed to stand in a thermostatic bath at 30°C for 90 hours. The recovered extract was concentrated to 50 mL using a rotary evaporator, poured into a pre-dried aluminum cup, and dried to a solid on a 70°C water bath. Then, it was dried at 105°C for 30 minutes, cooled in a dryer for 30 minutes, and the measured mass was divided by the original 100 g, and the value expressed as a percentage was used as the heptane extraction amount.

[0201] (4) Smoke test during film forming

[0202] A coat hanger type horizontal die (die width 200 mm, die lip 1.5 mm) was installed in a φ30 mm extruder manufactured by Union Plastics Co., Ltd., and the processing temperature was set to 260° C. Each pellet was extruded from the extruder at 7 kg / hour, and the smoke generated within 1 minute was collected and measured using a digital dust meter LD-5D manufactured by Shibata Science Co., Ltd. The smoke amount used was the average value of 5 measured values.

[0203] (5) Determination method of fisheye (FE) of blown film

[0204] Using a blown film molding machine manufactured by PLACO Co., Ltd. (extruder: EX-30 type screw: 30mmφ, L / D=28, die lip: 0.8mm), the processing temperature was set to 150°C, and each pellet was extruded at a discharge rate of 5kg / hour to form a film with a thickness of 50μm. The film production line was irradiated with light from the light source unit, and its image was input through the Line Sensor Camera XCM6060SAT2-V3-FN manufactured by Japan Electro-Sensory Device Co., Ltd. installed in the production line, and the image processing device SCANTEC-Elements2 manufactured by Nagase Industry Co., Ltd. was used to detect defects. As the recognition conditions of the threshold value, it was set to (clear): 0, (white): 0, (black): -20, (deep black): 0, and as for the size, the size with a diameter of 200μm or more was counted as FE.

[0205] result

[0206] Table 1

[0207] Example 1 Comparative Example 1 Example 2 Comparative Example 2 <![CDATA[Density (kg / m 3 )]]> 918.8 918.7 919.4 919.7 Melt flow rate (g / 10 minutes) 1.4 1.5 19.6 19.4 Whether or not unreacted ethylene is supplied to the cylindrical container (12) have none have none Heptane extraction amount (weight %) 0.29 0.31 0.46 0.47 Smoke test (pieces / minute) 35 52 571 722 <![CDATA[FE count during the formation of 30mm blown film (pcs / m 2 )]]> 10.8 14.7 5.7 11.8

[0208] Industrial Applicability

[0209] The manufacturing device and manufacturing method of high-pressure low-density polyethylene of the present invention have the following excellent characteristics: in the high-pressure polymerization of ethylene, low molecular weight impurities including polymerization by-products, solvents and lubricating oils are economically and effectively separated and removed from the high-pressure ethylene polymer, the obtained polyethylene polymer has a small amount of smoke during processing, and the film made from the polymer contains few fish eyes, so it is particularly preferably used as a film material, suitable for use in various films, various automobile interior and exterior parts, various parts of household appliances, various residential equipment machine parts, various industrial parts, various building material parts, etc., and has high practicality in various fields of industries such as household goods, transportation machinery industry, electrical and electronic industry, and building construction industry.

Claims

1. A device for producing high-pressure polyethylene, wherein: The manufacturing device has the following equipment: A first ethylene supply pipeline (11) is a pipeline branched from the unreacted high-pressure ethylene pipeline (6) and connected to the unreacted ethylene holding cylindrical container (12), and is used to reduce the pressure of the unreacted high-pressure ethylene from the unreacted high-pressure ethylene pipeline (6) to a range of 0.8 MPa to 3 MPa, and to supply the unreacted high-pressure ethylene after the pressure reduction to the unreacted ethylene holding cylindrical container (12); Unreacted ethylene holding cylindrical container (12): a cylindrical container for holding unreacted ethylene which has been depressurized to a range of 0.8 MPa to 3 MPa at a temperature of -20°C to 0°C through the first ethylene supply pipe (11); The rear section of the primary compressor (2) is a compressor that further compresses the ethylene supplied from the front section of the primary compressor (1); Unreacted high-pressure ethylene pipeline (6): a pipeline for supplying the unreacted high-pressure ethylene separated in the high-pressure separator (5) to the secondary compressor (3); A second ethylene supply pipeline (13): a pipeline for connecting the unreacted ethylene holding cylindrical container (12) to the primary compressor rear section (2), and for supplying the depressurized unreacted ethylene from the unreacted ethylene holding cylindrical container (12) to the primary compressor rear section (2); Primary compressor front section (1): a compressor for compressing ethylene; Secondary compressor (3): a compressor that further compresses the ethylene supplied from the rear section (2) of the primary compressor; Reactor (4): a reactor for producing polyethylene by polymerizing ethylene supplied from the secondary compressor (3) and a polymerization initiator supplied to the reactor (4); A high-pressure separator (5): a high-pressure separator to which the polyethylene obtained in the reactor (4) and unreacted ethylene are supplied from the reactor (4) and the polyethylene and unreacted high-pressure ethylene are separated; A first polyethylene extraction pipeline (7): a pipeline for extracting the polyethylene separated in the high-pressure separator (5) from the high-pressure separator (5) and supplying it to the low-pressure separator (8); Low-pressure separator (8): a separator for separating unreacted low-pressure ethylene contained in the polyethylene separated in the high-pressure separator (5) and supplied through the first polyethylene extraction pipeline (7) from the polyethylene; Unreacted low-pressure ethylene supply pipeline (9): a pipeline for supplying the unreacted low-pressure ethylene separated in the low-pressure separator (8) to the front section of the primary compressor; Second polyethylene extraction pipeline (10): a pipeline for extracting the polyethylene separated in the low-pressure separator (8); and Fresh ethylene supply pipeline (14): a pipeline connected to the second ethylene supply pipeline (13) and used to supply fresh ethylene.

2. A method for producing high-pressure polyethylene, wherein: The manufacturing method comprises the following steps: An unreacted high-pressure ethylene recycling step: for the unreacted ethylene separated in the high-pressure separator (5), 50% by weight or more and less than 100% by weight of the unreacted ethylene in the unreacted ethylene is supplied to the secondary compressor (3) through the unreacted high-pressure ethylene pipeline (6), the remaining unreacted ethylene, i.e., greater than 0% by weight and less than 50% by weight, is depressurized to a range of 0.8 MPa to 3 MPa through the first ethylene supply pipeline (11), the unreacted ethylene depressurized to a range of 0.8 MPa to 3 MPa is supplied to an unreacted ethylene holding cylindrical container (12), and the unreacted ethylene is supplied to the rear section (2) of the primary compressor through the second ethylene supply pipeline (13); Compression step: a step of compressing ethylene to a range of 0.04 MPa to 3 MPa using a primary compressor front section (1), compressing the ethylene compressed in the primary compressor front section (1) to a range of 3 MPa to 20 MPa in a primary compressor rear section (2), and compressing the ethylene compressed in the primary compressor rear section (2) to a range of 20 MPa to 200 MPa in a secondary compressor (3); Reaction step: a step of supplying compressed ethylene and a polymerization initiator to a reactor (4) and polymerizing ethylene to produce polyethylene; Separation step: a step of separating the polyethylene produced in the reactor (4) from unreacted ethylene in a high-pressure separator (5), extracting the produced polyethylene from the high-pressure separator (5), supplying the produced polyethylene to a low-pressure separator (8) through a first polyethylene extraction pipe (7), separating the unreacted ethylene contained in the polyethylene in the low-pressure separator (8), and extracting the polyethylene; Unreacted low-pressure ethylene recycling step: a step of supplying the unreacted low-pressure ethylene separated in the low-pressure separator (8) to the primary compressor front section (1) through the unreacted low-pressure ethylene supply pipeline (9); and Fresh ethylene supplying step: a step of supplying fresh ethylene from the fresh ethylene supplying pipe (14) to the second ethylene supplying pipe (13).

3. The manufacturing method according to claim 2, wherein: The production method uses a high-pressure polyethylene production device.

Images