Polyethylene for protective film and method for producing same

Abstract

The invention relates to polyethylene for a protective film and a manufacturing method thereof. Provided are: an ethylene-based polymer which further improves the balance between few fish eyes and good transparency; and a method for producing an ethylene-based polymer. An ethylene-based polymer in which the light scattering area value (RLS) of the ethylene-based polymer is from 350 to 540 (inclusive). RLS represents a light scattering area value of a solution obtained by dissolving 40 mg + / -0.2 mg of the ethylene-based polymer in 20 mL + / -0.1 mL of orthodichlorobenzene.

Description

Technical Field

[0001] The present invention relates to polyethylene for a protective film and a method for producing the same. Background Art

[0002] Polyethylene is processed and used as various films such as heavy packaging bags, shrink films, general packaging, thin films, protective films, extrusion laminated films, extrusion molded films, and foamed molded films. Among them, in particular, low-density polyethylene (LDPE) produced by a high-pressure free radical polymerization method has uses as an extrusion laminated film and a protective film (barrier film) after processing. The protective film is laminated (stuck) on an optical material or a metal plate to protect the optical material and the metal plate. For example, it is used as a protective film for protecting a film-shaped resist (dry film resist: DFR) used in circuit formation on a substrate. In terms of manufacturing such a film, a good balance between few fish eyes and good transparency of polyethylene is required. That is, the problem of the prior art is to obtain a film that is transparent and has few fish eyes (FE) under various film processing conditions.

[0003] Patent Document 1 describes a protective film for a dry film resist containing polyethylene obtained by a high-pressure method polyethylene production method.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2023-72420 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] Under such circumstances, the problem to be solved by the present invention is to provide a novel vinyl polymer (preferably low-density polyethylene (LDPE) by the high-pressure method) having a molecular weight distribution in which a high molecular weight component is moderately present (to the extent of showing transparency) and a ultra-high molecular weight component that causes gelation is small, and a method for producing the same.

[0009] Means for Solving the Problems

[0010] The present inventors conducted in-depth research in view of such a background, and as a result, completed the present invention.

[0011] That is, the present invention is as follows.

[0012] [1] A vinyl polymer, wherein the light scattering area value (RLS) of the vinyl polymer is 350 or more and 540 or less.

[0013] (The RLS represents the light scattering area value of a solution obtained by dissolving 40 mg ± 0.2 mg of the vinyl polymer in 20 mL ± 0.1 mL of ortho-dichlorobenzene.)

[0014] [2] The vinyl polymer according to [1], wherein the difference in the branch parameter (Δg’ Mab ) represented by the following (Formula 1) is 0.11 or more and 1 or less.

[0015]

[0016] Here, g’ Mab used in the calculation of the difference in the branch parameter (Δg’ Ma ), g’ Mb is obtained from the following (Formula 2) and (Formula 3).

[0017]

[0018]

[0019] (In the formula, M represents the absolute molecular weight of the vinyl polymer. W M represents the weight average fraction of the vinyl polymer having an absolute molecular weight of M. g’ M represents the reduced viscosity ratio of the absolute molecular weight M.)

[0020] [3] The vinyl polymer according to [1] or [2], wherein the characteristic relaxation time of the vinyl polymer is 0.90 seconds or more and 1.35 seconds or less, and the weight fraction of the component with Log 10 M of 5.85 or more is 2.2% by weight or more and 4.4% by weight or less.

[0021] (The characteristic relaxation time is a value obtained by fitting a curve obtained by plotting the complex viscosity against the angular frequency.)

[0022] (M represents the molecular weight of the vinyl polymer in terms of polyethylene.)

[0023] [4] The vinyl polymer according to any one of [1] to [3], wherein the oxidation induction time at 190 °C of the vinyl polymer measured using a thermogravimetric differential thermal analyzer (TG-DTA) is 11.5 minutes or more.

[0024] [5] The vinyl polymer according to any one of [1] to [4], wherein the vinyl polymer is low density polyethylene (LDPE) by the high pressure process.

[0025] [6] The vinyl polymer according to any one of [1] to [5], wherein the vinyl polymer is polyethylene for a protective film.

[0026] [7] A film, wherein the film comprises the vinyl polymer according to any one of [1] to [6].

[0027] [8] A protective film for a dry film resist, wherein the protective film for a dry film resist comprises the vinyl polymer according to any one of [1] to [6].

[0028] [9] A method for manufacturing a vinyl polymer, wherein the method for manufacturing a vinyl polymer has the following sequential steps:

[0029] A. Compressing ethylene monomer to a pressure of 100 MPa to 300 MPa using one or more compressors;

[0030] B. Introducing the compressed ethylene monomer into one or more reactors;

[0031] C. Introducing a mixture containing a polymerization initiator and a radical scavenger into the reactor, and polymerizing the ethylene monomer in the reactor to produce a mixture containing unreacted ethylene monomer and a vinyl polymer;

[0032] D. Separating the vinyl polymer from the reactor mixture.

[0033]

[10] The method for manufacturing a vinyl polymer according to [9], wherein in step C, the following mixture is introduced into the reactor, and in the mixture, the weight ratio of the polymerization initiator is 90 wt% to 99 wt% and the weight ratio of the radical scavenger is 1 wt% to 10 wt% based on the total weight of the polymerization initiator and the radical scavenger.

[0034]

[11] The method for manufacturing a vinyl polymer according to [9] or

[10] , wherein the vinyl polymer is the vinyl polymer according to any one of [1] to [6].

[0035] Advantages of the Invention

[0036] According to the present invention, a film that is transparent and has few fish eyes (FE) can be obtained. In addition, according to the present invention, the vinyl polymer for the film can be obtained by pre-mixing a polymerization initiator (e.g., peroxide) and a radical scavenger (e.g., BHT) and injecting the mixture into a polymerization tank and polymerizing the monomer. The present invention is characterized in that it is found that the light scattering area value (RLS) and the difference in branch parameters (Δg' Mab ) of the vinyl polymer are related to the balance between fish eyes and transparency, and by using this light scattering area value (RLS) and the difference in branch parameters (Δg'Mab )Set within a specific range to further improve the balance between few fish eyes and good transparency, and produce an ethylene polymer that further improves the applicability to a protective film and the handleability of the film. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A process schematic diagram showing an embodiment of a method for producing an ethylene polymer of the present invention and its production apparatus.

[0038] Figure 2 A curve showing the integral distribution of the molecular weights of the ethylene polymers produced in Example 1 and Comparative Example 1 obtained by gel permeation chromatography (GPC).

[0039] Figure 3 A schematic diagram showing an LS (light scattering detector) chromatogram for measuring the light scattering area of the ethylene polymers produced in Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0040] <Ethylene Polymer>

[0041] The ethylene polymer of the present invention is the following ethylene polymer:

[0042] An ethylene polymer, wherein the light scattering area value (RLS) of the ethylene polymer is 350 or more and 540 or less.

[0043] (RLS represents the light scattering area value of a solution obtained by dissolving 40 mg ± 0.2 mg of the ethylene polymer in 20 mL ± 0.1 mL of ortho-dichlorobenzene.)

[0044] The light scattering area value (RLS) is measured by the method described in the following examples.

[0045] From the viewpoint of the balance between few fish eyes and good transparency, the light scattering area value (RLS) is preferably 360 or more and 530 or less, more preferably 365 or more and 525 or less.

[0046] The ethylene polymer of the present invention preferably has a difference in branch parameters (Δg’ Mab 0>) of 0.11 or more and 1 or less.

[0047]

[0048] Here, g’ Mab used in the calculation of the difference in branch parameters (Δg’ Ma , g’ Mb is obtained from the following (Formula 2) and (Formula 3).

[0049]

[0050]

[0051] (In the formula, M represents the absolute molecular weight of the vinyl polymer. W M represents the weight average fraction of the vinyl polymer having an absolute molecular weight of M. g’ M represents the intrinsic viscosity ratio of the absolute molecular weight M.)

[0052] The difference in the branch parameter (Δg’ Mab ) is measured by the method described in the following examples.

[0053] From the viewpoint of the balance between few fish eyes and good transparency, the difference in the branch parameter (Δg’ Mab ) is preferably 0.115 or more and 0.95 or less, more preferably 0.12 or more and 0.9 or less.

[0054] The vinyl polymer of the present invention preferably has a characteristic relaxation time of 0.90 second or more and 1.35 seconds or less, and the weight fraction of the component having Log 10 M of 5.85 or more is 2.2% by weight or more and 4.4% by weight or less.

[0055] (The characteristic relaxation time is a value obtained by fitting a curve obtained by plotting the complex viscosity against the angular frequency.)

[0056] (A represents the molecular weight of the vinyl polymer in terms of polyethylene.)

[0057] The characteristic relaxation time is measured by the method described in the following examples.

[0058] From the viewpoint of the balance of the reaction of molecular motion to external force (when the relaxation time is short, the motion of molecules is fast, and when the relaxation time is long, the motion of molecules is slow), the characteristic relaxation time is preferably 0.92 second or more and 1.33 seconds or less, more preferably 0.94 second or more and 1.31 seconds or less.

[0059] Log 10 The weight fraction of the component having M of 5.85 or more is measured by the method described in the following examples.

[0060] From the viewpoint of the balance between few fish eyes and good transparency, the weight fraction of the component having Log 10 M of 5.85 or more is preferably 2.25% by weight or more and 4.35% by weight or less, more preferably 2.3% by weight or more and 4.3% by weight or less.

[0061] The ethylene-based polymer of the present invention preferably has an oxidation induction time at 190 °C measured using a thermogravimetric differential thermal analysis device (TG-DTA) of 11.5 minutes or more.

[0062] The oxidation induction time at 190 °C is measured by the method described in the following examples.

[0063] From the viewpoint that it is not easily oxidized when the oxidation induction time is long, the oxidation induction time at 190 °C is preferably 11.7 minutes or more, more preferably 11.9 minutes or more.

[0064] The ethylene-based polymer of the present invention is preferably low-density polyethylene (LDPE) by the high-pressure method.

[0065] The ethylene-based polymer of the present invention is preferably polyethylene for a protective film.

[0066] The film of the present invention preferably contains the above ethylene-based polymer.

[0067] The protective film for a dry film resist of the present invention preferably contains the above ethylene-based polymer.

[0068] The method for manufacturing the film and the protective film for a dry film resist from the ethylene-based polymer is not particularly limited, and can be manufactured by a method known to those skilled in the art.

[0069] From the viewpoint of film processability, the MFR of the ethylene-based polymer is preferably 1 (g / 10 minutes) or more and 6 (g / 10 minutes) or less, and more preferably 2.5 (g / 10 minutes) or more and 4.5 (g / 10 minutes) or less. When the MFR is less than 1 (g / 10 minutes), it becomes difficult to form a thin film, and when the MFR is greater than 6 (g / 10 minutes), the uniformity of the film thickness decreases.

[0070] From the viewpoint of film handleability, the density of the ethylene-based polymer is preferably 917 kg / m 3 or more and 930 kg / m 3 or less, and more preferably 921 kg / m 3 or more and 926 kg / m 3 or less. When the density is less than 917 kg / m 3 , the unwindability of the wound film decreases, and when the density is greater than 930 kg / m 3 , it is difficult to peel off from the resist after being attached to the resist.

[0071] <An Embodiment of the Manufacturing Method and Manufacturing Apparatus>

[0072] Hereinafter, with reference to Figure 1 One embodiment of the manufacturing method of the present invention and a manufacturing apparatus used as an example in the manufacturing method will be described in detail.

[0073] Ethylene gas is supplied from the latter stage of the primary compressor (2) to the secondary compressor (3) through the high-pressure ethylene pipeline (18), and is supplied into the polymerization reactor (4). A mixture containing a polymerization initiator and a radical scavenger is added, thereby polymerizing ethylene.

[0074] The polymerization mixture is discharged from the polymerization reactor (4) into the high-pressure separator (5), and separated into a produced polymer and unreacted ethylene gas.

[0075] The produced polymer separated in the high-pressure separator (5) is withdrawn through the polyethylene withdrawal pipeline (7) into the low-pressure separator (8), and further separated into ethylene polymer and unreacted ethylene gas. The ethylene polymer is withdrawn through the polyethylene withdrawal pipeline (10) and made into pellets in a pelletizer.

[0076] The unreacted ethylene gas separated in the low-pressure separator (8) is supplied through the unreacted low-pressure ethylene pipeline (9) to the unreacted ethylene holding cylinder (15). The unreacted ethylene gas held in the unreacted ethylene holding cylinder (15) is supplied through the ethylene pipeline (16) to the former stage of the primary compressor (1). A chain transfer agent (CTA) (17) is supplied into the ethylene pipeline (16) and supplied to the former stage of the primary compressor (1).

[0077] In the former stage of the primary compressor (1), the unreacted ethylene gas and the chain transfer agent (CTA) are compressed and supplied through the ethylene pipeline (13) to the latter stage of the primary compressor (2).

[0078] The unreacted ethylene gas separated in the high-pressure separator (5) is passed through the unreacted high-pressure ethylene pipeline (6), and the entire amount (100% by weight) of the unreacted ethylene gas is supplied to the inlet pipeline of the secondary compressor (3).

[0079] Fresh ethylene gas is supplied from the fresh ethylene supply pipeline (14) through the ethylene pipeline (13) to the latter stage of the primary compressor (2).

[0080] The mixed ethylene gas of the unreacted ethylene gas and the chain transfer agent (CTA) supplied from the former stage of the primary compressor (1) and the fresh ethylene gas is compressed in the latter stage of the primary compressor (2) and supplied to the secondary compressor (3).

[0081] The ethylene gas and the chain transfer agent (CTA) compressed in the secondary compressor (3) are supplied into the polymerization reactor (4), thereby continuously carrying out the polymerization reaction.

[0082] <Manufacturing Apparatus>

[0083] In the manufacturing method of the present invention, the manufacturing apparatus preferably used is, for example, a high-pressure polyethylene manufacturing apparatus having any one or more of the following devices.

[0084] ･ Front stage of primary compressor (1): A compressor for compressing ethylene;

[0085] ･ Rear stage of primary compressor (2): A compressor for further compressing the ethylene supplied from the front stage of the primary compressor (1);

[0086] ･ Secondary compressor (3): A compressor for further compressing the ethylene supplied from the rear stage of the primary compressor (2);

[0087] ･ Reactor (4): A reactor for polymerizing ethylene by using the ethylene supplied from the secondary compressor (3) and the polymerization initiator supplied to the reactor (4) to produce polyethylene;

[0088] ･ High-pressure separator (5): A high-pressure separator for supplying the polyethylene and unreacted ethylene obtained in the reactor (4) from the reactor (4) and separating the polyethylene from the unreacted high-pressure ethylene;

[0089] ･ 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);

[0090] ･ 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);

[0091] ･ Low-pressure separator (8): A separator for separating the unreacted low-pressure ethylene contained in the polyethylene separated in the high-pressure separator (5) and supplied through the polyethylene extraction pipeline (7) from the polyethylene;

[0092] ･ Unreacted low-pressure ethylene pipeline (9): A pipeline for supplying the unreacted low-pressure ethylene separated in the low-pressure separator (8) to the unreacted ethylene holding cylinder (15);

[0093] ･ Polyethylene extraction pipeline (10): A pipeline for extracting the polyethylene separated in the low-pressure separator (8);

[0094] ･ Ethylene supply pipeline (13): A pipeline for connecting the front stage of the primary compressor (1) and the rear stage of the primary compressor (2) and supplying the compressed unreacted ethylene from the front stage of the primary compressor (1) to the rear stage of the primary compressor (2), and converging with the fresh ethylene supply pipeline (14);

[0095] ･ Fresh ethylene supply pipeline (14): A pipeline for connecting with the ethylene supply pipeline (13) and supplying fresh ethylene;

[0096] ･ Unreacted ethylene holding cylinder (15): A cylinder that holds unreacted low-pressure ethylene supplied through the unreacted low-pressure ethylene pipeline (9);

[0097] ･ Unreacted low-pressure ethylene supply pipeline (16): A pipeline that connects the unreacted ethylene holding cylinder (15) to the front stage of the primary compressor (1) and supplies unreacted low-pressure ethylene from the unreacted ethylene holding cylinder (15) to the front stage of the primary compressor (1); and

[0098] Chain transfer agent (CTA) supply pipeline (17): A pipeline that is connected to the unreacted low-pressure ethylene supply pipeline (16) and supplies the chain transfer agent (CTA).

[0099] Front Stage of Primary Compressor (1)

[0100] The front stage of the primary compressor (1) is a compressor that compresses ethylene, for example, in the range of 0.04 MPa to 3 MPa.

[0101] Rear Stage of Primary Compressor (2)

[0102] The rear stage of the primary compressor (2) is a compressor that compresses the ethylene supplied from the front stage of the primary compressor (1), for example, in the range of 3 MPa to 20 MPa.

[0103] Secondary Compressor (3)

[0104] The secondary compressor (3) is a compressor that compresses the ethylene supplied from the rear stage of the primary compressor (2), for example, in the range of 20 MPa to 200 MPa.

[0105] Reactor (4)

[0106] The reactor (4) is a reactor that polymerizes ethylene using the ethylene supplied from the secondary compressor (3) and the polymerization initiator supplied to the reactor (4) to produce polyethylene.

[0107] The reactor (4) can be any one of a tubular reactor or a tank reactor, etc. High-pressure polymerization of ethylene can use a polymerization initiator such as oxygen or peroxide, etc., and can be carried out under conditions where the pressure is, for example, 20 MPa or more, preferably 100 MPa to 500 MPa, more preferably 100 MPa to 400 MPa, and the temperature is, for example, 100 °C or more, preferably 100 °C to 400 °C, more preferably 150 °C to 350 °C, and further more preferably 150 °C to 300 °C.

[0108] The ethylene feed stream entering the reactor (4) can contain, in addition to the polymerization initiator, a comonomer and a chain transfer agent.

[0109] High-Pressure Separator (5)

[0110] The high-pressure separator (5) is a high-pressure separator that supplies polyethylene and unreacted ethylene obtained in the reactor (4) by pressure reduction and separates the polyethylene from the unreacted high-pressure ethylene.

[0111] The reaction product mixture containing the polymer produced in the reactor (4), unreacted ethylene gas, polymerization by-products, solvent, lubricating oil, etc. enters the high-pressure separator (5) after passing through a pressure regulating valve as the case may be and is discharged under reduced pressure. A part of the polymer contained in the reaction product mixture is separated at a pressure of, for example, 10 MPa to 100 MPa, preferably 15 MPa to 100 MPa, more preferably 70 MPa or less, and at a temperature of, for example, 200 °C to 260 °C.

[0112] The separated polymer hardly contains low molecular weight substances with a weight average molecular weight of 5000 or less.

[0113] The polymer separated in the high-pressure separator (5) is transported to the low-pressure separator (8), the unreacted ethylene gas remaining in the polymer is separated and removed, and then it is taken out in the form of product polyethylene from the polyethylene extraction pipe (10).

[0114] Unreacted High-Pressure Ethylene Pipeline (6)

[0115] The unreacted high-pressure ethylene pipe (6) is a pipe for supplying the unreacted high-pressure ethylene separated in the high-pressure separator (5) to the secondary compressor (3).

[0116] Polyethylene Extraction Pipeline (7)

[0117] The 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).

[0118] Low-Pressure Separator (8)

[0119] The low-pressure separator (8) is a separator that separates the unreacted low-pressure ethylene contained in the polyethylene separated in the high-pressure separator (5) and supplied through the polyethylene extraction pipe (7) from the polyethylene.

[0120] The unreacted gas, for example, at about 200 °C to 250 °C, separated at the top in the low-pressure separator (8) is cooled to 20 °C to 50 °C in a cooler, and then, for example, transported to a separator to remove impurities such as solvent. The unreacted gas ethylene after removing the impurities is returned to the inlet of the front stage of the primary compressor (1) through the unreacted low-pressure ethylene supply pipe (16).

[0121] Unreacted Low-Pressure Ethylene Pipeline (9)

[0122] The unreacted low-pressure ethylene pipeline (9) is a pipeline for supplying the unreacted low-pressure ethylene separated in the low-pressure separator (8) to the front stage of the primary compressor. In the unreacted low-pressure ethylene pipeline (9), the pressure can be controlled, for example, at 0.01 MPa to 0.1 MPa and the temperature at 150 °C to 220 °C.

[0123] Polyethylene Extraction Pipeline (10)

[0124] The polyethylene extraction pipeline (10) is a pipeline for extracting the polyethylene separated in the low-pressure separator (8). The polyethylene extracted from the polyethylene extraction pipeline (10) can be processed into pellet products through an extruder, a cooler, a granulator, etc. The obtained polyethylene can be low-density polyethylene, for example, having a density of 910 kg / m 3 ~920 kg / m 3 of density.

[0125] Ethylene Supply Pipeline (13)

[0126] The ethylene supply pipeline (13) is a pipeline for connecting the front stage (1) and the rear stage (2) of the primary compressor and supplying the unreacted ethylene compressed to, for example, 0.04 MPa to 3 MPa from the front stage (1) of the primary compressor to the rear stage (2) of the primary compressor, and converges with the fresh ethylene supply pipeline (14).

[0127] Fresh Ethylene Supply Pipeline (14)

[0128] The fresh ethylene supply pipeline (14) is a pipeline for connecting with the ethylene supply pipeline (13) and supplying fresh ethylene. Fresh ethylene gas at 0.8 MPa to 3 MPa is supplied.

[0129] As an embodiment, the raw material ethylene gas is transported from the fresh ethylene supply pipeline (14) to the rear stage (2) of the primary compressor and 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 boosted to the polymerization pressure is transported to the reactor (4), and polymerization is carried out, for example, using oxygen or a peroxide initiator at a specified temperature of 150 °C to 300 °C.

[0130] Unreacted Ethylene Holding Cylinder (15)

[0131] The unreacted ethylene holding cylinder (15) is a cylinder for holding the unreacted low-pressure ethylene supplied through the unreacted low-pressure ethylene pipeline (9) at a pressure of, for example, 0.01 MPa to 0.1 MPa and a temperature of 10 °C to 60 °C.

[0132] Unreacted Low-Pressure Ethylene Supply Pipeline (16)

[0133] The unreacted low-pressure ethylene supply pipe (16) is a pipe that connects the unreacted ethylene holding cylinder (15) to the front stage of the primary compressor (1) and supplies unreacted low-pressure ethylene from the unreacted ethylene holding cylinder (15) to the front stage of the primary compressor (1). In the unreacted low-pressure ethylene supply pipe (16), the pressure can be controlled, for example, at 0.01 MPa to 0.1 MPa and the temperature can be controlled, for example, at 10 °C to 60 °C.

[0134] Chain Transfer Agent (CTA) Supply Pipeline (17)

[0135] The chain transfer agent (CTA) supply pipe (17) is a pipe that is connected to the unreacted low-pressure ethylene supply pipe (16) and supplies the chain transfer agent (CTA). In the chain transfer agent (CTA) supply pipe (17), the pressure can be controlled, for example, at 0.01 MPa to 0.1 MPa and the temperature can be controlled, for example, at 10 °C to 60 °C.

[0136] High-Pressure Ethylene Pipeline (18)

[0137] The high-pressure ethylene pipe (18) is a pipe that connects the rear stage of the primary compressor (2) to the secondary compressor (3), and is used to supply unreacted high-pressure ethylene separated in the high-pressure separator (5) from the unreacted high-pressure ethylene pipe (6) to the secondary compressor (3) and to supply ethylene from the rear stage of the primary compressor (2) to the secondary compressor (3). In the high-pressure ethylene pipe (18), the pressure can be controlled, for example, at 10 MPa to 20 MPa and the temperature can be controlled, for example, at 10 °C to 60 °C.

[0138] <Manufacturing Method>

[0139] The method for producing an ethylene-based polymer of the present invention is the following method for producing an ethylene-based polymer.

[0140] A method for producing an ethylene-based polymer, wherein the method for producing the ethylene-based polymer has the following sequential steps:

[0141] A. Compressing ethylene monomer to a pressure of 100 MPa to 300 MPa using one or more compressors.

[0142] B. Introducing the compressed ethylene monomer into one or more reactors.

[0143] C. Introducing a mixture containing a polymerization initiator and a radical scavenger into the reactor, and polymerizing the ethylene monomer in the reactor to produce a mixture containing unreacted ethylene monomer and an ethylene-based polymer.

[0144] D. Separating the ethylene-based polymer from the reactor mixture.

[0145] The method for producing an ethylene-based polymer of the present invention preferably introduces the following mixture into a reactor in step C. In the mixture, the weight ratio of the polymerization initiator is 90% by weight to 99% by weight, and the weight ratio of the radical scavenger is 1% by weight to 10% by weight, based on the total weight of the polymerization initiator and the radical scavenger.

[0146] In the method for producing an ethylene-based polymer of the present invention, it is preferred that the ethylene-based polymer is the aforementioned ethylene-based polymer.

[0147] The method for producing an ethylene-based polymer of the present invention is preferably the above-described method for producing an ethylene-based polymer of the present invention.

[0148] As an embodiment, the method for producing an ethylene-based polymer of the present invention further includes the following steps:

[0149] ･ Compression step: A step of compressing ethylene;

[0150] ･ Reaction step: A step of supplying the compressed ethylene and a polymerization initiator to a reactor (4) and polymerizing ethylene under the conditions that the reactor pressure is 170 MPa to 220 MPa and the reaction temperature is 220 °C to 270 °C to produce polyethylene;

[0151] ･ Separation step: A step of separating the polyethylene produced in the reactor (4) and unreacted ethylene in a high-pressure separator (5), withdrawing the produced polyethylene from the high-pressure separator (5), supplying it to a low-pressure separator (8) through a withdrawal pipe (7), separating the unreacted ethylene contained in the polyethylene in the low-pressure separator (8), and withdrawing the polyethylene;

[0152] ･ Unreacted low-pressure ethylene recycle step: A step of supplying the unreacted low-pressure ethylene at a pressure of 0.01 MPa to 0.1 MPa and a temperature of 150 °C to 220 °C separated in the low-pressure separator (8) to an unreacted ethylene holding cylinder (15) through an unreacted low-pressure ethylene pipe (9); and

[0153] ･ Fresh ethylene supply step: A step of supplying fresh ethylene from a fresh ethylene pipe (14) to an ethylene pipe (13).

[0154] The production method of the present invention preferably further includes the following steps:

[0155] ･ Unreacted high-pressure ethylene recycle step: A step of decompressing the unreacted ethylene separated in the high-pressure separator (5) through an unreacted high-pressure ethylene pipe (6) and supplying the decompressed unreacted ethylene to a secondary compressor (3).

[0156] Compression Process

[0157] The compression process is not limited to compressing in one stage, and can include a process of compressing in two or more stages.

[0158] For example, the compression process is as follows:

[0159] Ethylene is compressed to a range of, for example, 0.04 MPa to 3 MPa by the front stage (1) of the primary compressor.

[0160] The ethylene compressed in the front stage (1) of the primary compressor is compressed to a range of, for example, 3 MPa to 20 MPa in the rear stage (2) of the primary compressor.

[0161] The ethylene compressed in the rear stage (2) of the primary compressor is compressed to a range of, for example, 20 MPa to 200 MPa in the secondary compressor (3).

[0162] Reaction Process

[0163] The reaction process is a process of supplying the ethylene compressed in the secondary compressor (3) and a polymerization initiator to the reactor (4) and polymerizing the ethylene to produce polyethylene.

[0164] The detailed operating conditions of the reaction process can be applied to the conditions described in the description of the above reactor (4).

[0165] Separation Process

[0166] The separation process is as follows:

[0167] In the high-pressure separator (5), the polyethylene produced in the reactor (4) and the unreacted ethylene are separated.

[0168] The produced polyethylene is withdrawn from the high-pressure separator (5) and supplied to the low-pressure separator (8) through the withdrawal pipe (7).

[0169] In the low-pressure separator (8), the unreacted ethylene contained in the polyethylene is separated, and the polyethylene is withdrawn.

[0170] The detailed operating conditions of the separation process in the high-pressure separator (5) and the low-pressure separator (8) can be applied to the conditions described in the description of the above high-pressure separator (5) and low-pressure separator (8).

[0171] Unreacted High-Pressure Ethylene Recycling Process

[0172] The unreacted high-pressure ethylene recycle process is a process of supplying the unreacted ethylene separated in the high-pressure separator (5) to the secondary compressor (3) through the unreacted high-pressure ethylene pipe (6).

[0173] 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).

[0174] Unreacted Low-Pressure Ethylene Recycling Process

[0175] The unreacted low-pressure ethylene recycling process is a process of supplying the unreacted low-pressure ethylene separated in the low-pressure separator (8) to the unreacted ethylene holding cylinder (15) through the unreacted low-pressure ethylene pipeline (9).

[0176] The detailed operating conditions of the unreacted low-pressure ethylene recycling process can be applied to the conditions described in the descriptions of the above-mentioned low-pressure separator (8), unreacted low-pressure ethylene pipeline (9), and unreacted ethylene holding cylinder (15).

[0177] Chain Transfer Agent (CTA) Supply Process

[0178] The chain transfer agent (CTA) supply process is, for example, a process of supplying the chain transfer agent (CTA) from the chain transfer agent (CTA) supply pipeline (17) to the unreacted low-pressure ethylene supply pipeline (16).

[0179] The detailed operating conditions of the chain transfer agent (CTA) supply process can, for example, be applied to the conditions described in the descriptions of the above-mentioned chain transfer agent (CTA) supply pipeline (17) and unreacted low-pressure ethylene supply pipeline (16). However, in the present invention, it is not necessarily required to supply the chain transfer agent (CTA) to the unreacted low-pressure ethylene supply pipeline (16).

[0180] Fresh Ethylene Supply Process

[0181] The fresh ethylene supply process is as follows:

[0182] Supply fresh ethylene from the fresh ethylene supply pipeline (14) to the ethylene supply pipeline (13),

[0183] and supply it to the latter stage of the primary compressor (2) through the ethylene supply pipeline (13).

[0184] The detailed operating conditions of the fresh ethylene supply process can be applied to the conditions described in the descriptions of the above-mentioned fresh ethylene supply pipeline (14) and ethylene supply pipeline (13).

[0185] The present invention can be implemented using a high-pressure ethylene polymerization apparatus having a high-pressure recycle gas system.

[0186] In the present invention, all polymerization initiators and chain transfer agents known for the polymerization or copolymerization of ethylene can be used.

[0187] <Polymerization initiator>

[0188] In the present invention, all polymerization initiators known to be used for the polymerization or copolymerization of ethylene can be used.

[0189] As the polymerization initiator, for example, the following can be cited: organic peroxides such as hydrogen peroxide, lauroyl peroxide, dipropionyl peroxide, benzoyl peroxide, di-tert-butyl peroxide, tert-butyl hydroperoxide, trimethylhexanoyl peroxide, diisopropyl peroxydicarbonate, tert-butyl peracetate, tert-butyl perisobutyrate; hydrogen peroxide: molecular oxygen; azo compounds such as azobisisobutyronitrile, azoisobutylvaleronitrile; tert-butyl peroxybenzoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxyisopropyl carbonate, oxygen, etc. are preferred examples.

[0190] <Chain transfer agent>

[0191] In the present invention, all chain transfer agents known to be used for the polymerization or copolymerization of ethylene can be used.

[0192] As the chain transfer agent, for example, the following can be cited: alkanes such as ethane, propane, butane, heptane, hexane, pentane; α-olefins such as propylene, 1-butene, 1-hexene, 3-methyl-1-butene; aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde; ketones such as acetone, methyl ethyl ketone, diethyl methyl ketone, diisopropyl methyl ketone, cyclohexanone, methyl isopropyl ketone; aromatic hydrocarbons; chlorinated hydrocarbons, etc. are preferred examples. It is preferable to supply ethane, propane, and propylene as the chain transfer agent (CTA), and the ratio of the propane concentration to the total CTA concentration is preferably adjusted to 0.30 to 0.45 and the chain transfer agent (CTA) is supplied (wherein the concentration is the concentration based on volume, and the total volume of ethylene, ethane, propane, and propylene is set to 100 volumes).

[0193] <Comonomer>

[0194] The method of the present invention and the apparatus used in this method can also be applied to the copolymerization of ethylene with other comonomers capable of copolymerizing with ethylene.

[0195] In the present invention, for example, all comonomers known to copolymerize with ethylene, including compounds having an ethylenically unsaturated group such as acrylic acid, methacrylic acid and their alkyl esters, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, vinyl chloride, vinylidene chloride, vinyl fluoride, vinyl acetate, vinyl propionate, N-vinylimide compounds, vinyl aryl compounds, vinyl ether compounds, and vinyl ketone compounds, etc., can be used.

[0196] The comonomer can be used in such an amount that the comonomer is contained in the resulting copolymer in an amount greater than 0% by weight and less than or equal to about 50% by weight, preferably about 40% by weight or less, more preferably about 30% by weight or less, and still more preferably about 20% by weight or less.

[0197] The comonomer can be added to any device and process. For example, the comonomer can be added to devices and processes from around the compressor to around the reactor, etc.

[0198] <Free radical scavenger>

[0199] In the present invention, all free radical scavengers known to be used for the polymerization or copolymerization of ethylene can be used.

[0200] Examples of the free radical scavenger include 2,6-di-tert-butyl-4-methylphenol, dibutylhydroxytoluene (BHT), etc. as preferred examples.

[0201] The supply amount of the free radical scavenger to the reactor is preferably 0.2 kg / hour to 0.5 kg / hour, more preferably 0.3 kg / hour to 0.4 kg / hour.

[0202] Examples

[0203] <Method for measuring physical properties of polyethylene>

[0204] The physical properties of the vinyl polymers (hereinafter also referred to as polyethylene) produced in the following examples and comparative examples were measured according to the following method.

[0205] (1) Melt flow rate (MFR, unit: g / 10 minutes)

[0206] The melt flow rate was measured by method A in the method specified in JIS K7210-1995 under the conditions of a load of 21.18 N and a temperature of 190 °C.

[0207] (2) Density (unit: kg / m 3 )

[0208] Annealing was carried out as described in JIS K6922-2, and then the measurement was carried out by method A according to the method specified in JIS K7112.

[0209] (3) Weight fraction (W 10 of components with Log Log10M≥5.85 M of 5.85 or more (unit: weight%) (M represents the molecular weight in terms of polyethylene)

[0210] The molecular weight distribution of polyethylene was determined by gel permeation chromatography (GPC). The GPC measurement was carried out under the following conditions. The baseline on the chromatogram was specified and the peaks were designated according to the description in ISO16014-1. The weight fraction (W 10 of components with Log Log10M≥5.85 [weight%])(M represents the molecular weight in terms of polyethylene) was calculated from the integral distribution (seeFigure 2 )。W Log10M≥5.85 [% by weight] = (Integral value of the integral distribution curve of the part where M ≥ 5.85) / (Integral value of the entire integral distribution curve). 10 M≥5.85 part of the integral distribution curve integral value) / (integral distribution curve overall integral value).

[0211] (GPC apparatus and software)

[0212] Apparatus: HLC - 8321GPC / HT (manufactured by Tosoh Corporation)

[0213] (Measurement conditions)

[0214] GPC column: TSKgel GMHHR - H(S)HT 7.8mm I.D.×300mm (manufactured by Tosoh Corporation), 3 columns

[0215] Mobile phase: Prepared by adding dibutylhydroxytoluene (BHT) at a concentration of 0.1 w / V, i.e., 0.1 g / 100 mL, to o - dichlorobenzene (manufactured by Wako Pure Chemical Industries, Ltd., special grade) and then used.

[0216] Flow rate: 1 mL / min

[0217] Column oven temperature: 145 °C

[0218] Autosampler temperature: 145 °C

[0219] System oven temperature: 45 °C

[0220] Detection: Differential refractive index detector (RID)

[0221] RID sample cell temperature: 145 °C

[0222] Sample solution injection volume: 300 μL

[0223] Standard substances for GPC column calibration: Standard polystyrene manufactured by Tosoh Corporation was weighed in the combinations shown in the following table, 5 mL of o - dichlorobenzene (having the same composition as the mobile phase) was added, and it was oscillated at 145 °C for 120 minutes to dissolve and prepare.

[0224] [Table 0]

[0225]

[0226] (Sample solution preparation conditions)

[0227] Solvent: Prepared by adding BHT at a concentration of 0.1 w / V (0.1 g / 100 mL) to o - dichlorobenzene (manufactured by Wako Pure Chemical Industries, Ltd., special grade) and then used.

[0228] Sample solution concentration: 1 mg / mL

[0229] Automatic oscillator for dissolution: DF-8020 (manufactured by Tosoh Corporation)

[0230] Dissolution conditions: Seal 5 mg of the sample in a 1000-mesh SUS wire mesh bag, place the wire mesh bag containing the sample in a test tube, add 5 mL of solvent to the test tube, cover the test tube with aluminum foil, place the test tube in the oscillator, and stir at 145 °C for 120 minutes at a stirring speed of 60 reciprocations per minute.

[0231] (4) Calculation of the light scattering area value (R LS )(unit: mV×mL)

[0232] The light scattering area value uses the value of the light scattering area LS obtained when injecting 300 μL of a solution obtained by dissolving polyethylene of each example and each comparative example in o-dichlorobenzene at a concentration of 40 mg ± 0.2 mg / 20 mL ± 0.1 mL using a liquid chromatography (LC) apparatus equipped with a light scattering detector.

[0233] The larger the light scattering area value (R LS ), that is, the larger the light scattering area LS of the solution obtained by dissolving polyethylene in o-dichlorobenzene, the more the amount of ultra-high molecular weight component in the polyethylene.

[0234] The measurement conditions are as follows.

[0235] ･ LC apparatus: HLC-8121GPC / HT (manufactured by Tosoh Corporation)

[0236] ･ Light scattering detector: PD2040 (manufactured by Precision Detectors)

[0237] ･ Laser light source: wavelength 685 nm

[0238] ･ GPC column: PLgel MIXED-A LS 300×7.5 mm

[0239] (manufactured by Agilent Technologies) × 3 columns

[0240] ･ Concentration of the sample solution: 40 mg ± 0.2 mg / 20 mL ± 0.1 mL

[0241] ･ Injection volume: 300 μL

[0242] ･ Measurement temperature: 140 °C

[0243] ･ Dissolution conditions: Stir at 145 °C for 2 hours

[0244] ･ Automatic oscillator for dissolution: DF-8020 (manufactured by Tosoh Corporation)

[0245] ･ Solvent and mobile phase: o-dichlorobenzene containing 0.1 w / V of BHT (manufactured by Wako Pure Chemical Industries, Ltd., special grade)

[0246] ･ Flow rate of mobile phase: 1.0 mL / min

[0247] Specifically, a light scattering detector (LS) was connected to the LC device. It should be noted that the scattering angle for light scattering detection was 90°. The LS was set inside the column oven of the LC device.

[0248] Specifically, the dissolution of the sample was carried out as follows. First, 40.0 mg of the sample and 20.0 mL of the solvent were added to a 30 mL screw vial, the vial was sealed tightly, and the screw vial was placed in a DF-8020 (manufactured by Tosoh Corporation) and stirred at 140 °C for 2 hours to dissolve the sample.

[0249] Baseline processing was performed on the obtained LS chromatogram, and the light scattering area was calculated (refer to Figure 3 ).

[0250] When calculating the light scattering area, the data processing software OmniSEC (version 4.7) of Malvern was used.

[0251] (5) Calculation of shrinkage factor g’ (g’ Ma , g’ Mb ) and difference in branching parameter Δg’ Mab

[0252] The shrinkage factor g’ of the sample was measured using a gel permeation chromatograph (3D-GPC) equipped with a differential refractive index detector, a viscosity detector, and a light scattering detector.

[0253] ​Use Tosoh Corporation's HLC-8121GPC / HT as the GPC equipped with a refractive index detector (RI). Additionally, connect PD2040 from Precision Detectors, which is a light scattering detector (LS), to the GPC device. The scattering angle for light scattering detection is 90°. Also, connect H502 from Viscotek Corporation, which is a viscosity detector (VISC), to the GPC device. The LS and VISC are set inside the column oven of the GPC device and are connected in the order of LS, RI, VISC. In the calibration of LS and VISC and the correction of the delay volume between detectors, use F10 from NIST, which is a polystyrene reference material, at a solution concentration of 2 mg / ml (the weight-average molecular weight Mw is 96,400 and the polydispersity is 1.01). Use o-dichlorobenzene added with dibutylhydroxytoluene as a stabilizer at a concentration of 0.5 mg / mL as the mobile phase and solvent. The dissolution conditions of the sample are stirring for 2 hours at 145 °C. Set the flow rate to 1 ml / min. Regarding the column, connect 3 Agilent PLgel MIXED-A LS columns and use them. Set the temperatures of the column, injection part, and each detector to 140 °C. Set the sample solution concentration to 2 mg / mL. Set the injection volume of the sample solution (sample quantitative loop volume) to 0.3 ml. Set the refractive index increment (dn / dc) of NIST1475a and the sample in o-dichlorobenzene to -0.079 mL / g. Set the dn / dc of the polystyrene reference material to 0.079 mL / g. When calculating the absolute molecular weight and intrinsic viscosity ([η]) based on the data of each detector, use the data processing software OmniSEC (version 4.7) from Malvern and refer to the literature "Size Exclusion Chromatography", Springer (1999) for calculation. Note that the refractive index increment refers to the rate of change of the refractive index with respect to the change in concentration.

[0254] (Calculation of shrinkage factor g' Ma 、g' Mb )

[0255] The shrinkage factor g' is calculated from the ratio of the intrinsic viscosity ([η]sample) obtained by measuring the sample using the above device to the intrinsic viscosity ([η]PE) of linear polyethylene ([η]sample / [η]PE). The weight average of the ratio of the above intrinsic viscosities within the range of the common logarithm logM of the absolute molecular weight M from 4.2 to 4.4 is set as g' of the sample Ma , and the weight average of the ratio of the intrinsic viscosities within the range of logM from 4.4 to 5.4 is set as g' Mb . g' Ma and g'Mb They are calculated respectively by the following (Equation 2) and (Equation 3).

[0256]

[0257]

[0258] (Calculation of the difference in the side-chain parameter (Δg’ Mab ))

[0259] The difference in the side-chain parameter (Δg’ Mab ) uses g’ obtained from (Equation 2) and (Equation 3) Ma and g’ Mb and is obtained by the following (Equation 1).

[0260]

[0261] Here, M represents the absolute molecular weight, and W M represents the weight-average fraction of the absolute molecular weight M. The [η]PE of linear polyethylene is calculated by the following formula described in "Size Exclusion Chromatography, Springer (1999)" and used.

[0262]

[0263] Here, M is the absolute molecular weight.

[0264] α0 and K0 of Equation (IV) are obtained by the following method.

[0265] α0 is the value obtained by the following method, which includes: taking the logarithm of the absolute molecular weight of the polyethylene standard substance 1475a as the horizontal axis, taking the logarithm of the intrinsic viscosity of the polyethylene standard substance 1475a as the vertical axis, plotting the measured data, and in the range where the horizontal axis is above the logarithm of the weight-average molecular weight of the polyethylene standard substance 1475a and below the logarithm of the z-average molecular weight, performing the least-squares approximation on the logarithm of the absolute molecular weight and the logarithm of the intrinsic viscosity using Equation (I-I), and taking the value of the slope of the straight line representing Equation (I-I) as α0.

[0266] log[η0]=α0logM0+logK0 (I-I)

[0267] (In Equation (I-I), [η0] represents the intrinsic viscosity of the polyethylene standard substance 1475a (unit: dl / g), M0 represents the absolute molecular weight of the polyethylene standard substance 1475a, and K0 is a constant.)

[0268] <Measurement conditions>

[0269] GPC apparatus: HLC-8121GPC / HT (manufactured by Tosoh Corporation)

[0270] Light scattering detector: Precision Detectors PD2040

[0271] Differential pressure viscometer: Viscotek H502

[0272] GPC column: PLgel MIXED-A LS 300×7.5 mm

[0273] (manufactured by Agilent Technologies) × 3 columns

[0274] Sample solution concentration: 2 mg / ml

[0275] Injection volume: 0.3 ml

[0276] Measurement temperature: 140 °C

[0277] Dissolution conditions: Stir at 145 °C for 2 hours

[0278] Solvent and mobile phase: o-dichlorobenzene (Wako special grade) containing 0.05 wt% of dibutylhydroxytoluene

[0279] Mobile phase flow rate: 1 mL / min

[0280] Measurement time: Approximately 1 hour

[0281] (6) Characteristic relaxation time (unit: second)

[0282] The test pieces for measurement were prepared using a hot press. They were preheated at 150 °C for 5 minutes, pressed at 5 MPa and 150 °C for 5 minutes, and cooled at 25 °C for 5 minutes, thereby preparing test pieces for measurement with a thickness of approximately 2 mm and a diameter of approximately 25 mm. Frequency dispersion measurement was carried out using ARES-G2 (manufactured by TA Instruments), a strain-controlled rotational viscometer, and the characteristic relaxation time was calculated. Parallel plates were installed in the apparatus, and only the fixtures were preheated at 130 °C for approximately 30 minutes. The test piece was installed on the preheated fixtures and allowed to stand for approximately 5 minutes. The distance between the parallel plates was adjusted to approximately 2 mm and allowed to stand for approximately 5 minutes. Frequency dispersion measurement was carried out at a strain of 5%, angular frequencies from 100 rad / s to 0.1 rad / s (5 logarithmically equally spaced points were measured for each order of magnitude), and temperatures of 130 °C, 150 °C, 170 °C, and 190 °C. The master curve of the complex viscosity - angular frequency curve at 190 °C was prepared using TRIOS (manufactured by TA Instruments) from the obtained complex viscosity - angular frequency curves. Using TA Orchestrator (manufactured by TA Instruments), the obtained master curve was fitted with the following formula (1) to calculate the characteristic relaxation time τ.

[0283]

[0284] Here, η* is the complex viscosity, η0 is the zero-shear viscosity, ω is the angular frequency, τ is the characteristic relaxation time, and n is the non-Newtonian index.

[0285] (7) Oxidation induction time (unit: minute)

[0286] The sample placed in an open aluminum container is set in a thermogravimetric differential thermal analyzer. It is heated from room temperature to 190 °C at a rate of 20 °C / minute in a nitrogen atmosphere and held for 5 minutes for temperature stabilization. Then, the atmosphere is switched to air, and differential thermal measurement is started. The oxidation induction time is obtained by reading the time from the switch to the air atmosphere until heat release starts due to the oxidation reaction at the intersection of the baseline of the differential heat and the tangent of the maximum gradient.

[0287] <Measurement conditions>

[0288] Thermogravimetric differential thermal analyzer: Hitachi High-Technologies Corporation, TG / DTA6200

[0289] Sample shape: pressed film (thickness 0.3 mm)

[0290] Sample amount: 3 mg ± 0.3 mg

[0291] Sample pan: open aluminum container

[0292] Measurement atmosphere: nitrogen atmosphere (200 ml / minute), air atmosphere (200 ml / minute)

[0293] Heating rate: 20 °C / minute

[0294] Measurement temperature: 190 °C

[0295] (8) Molding of the polyethylene film for fish-eye measurement

[0296] A blown film was produced under the following processing conditions.

[0297] Processing equipment: manufactured by PLACO Company, L-40A

[0298] Screw diameter: 40 mm φ

[0299] L / D: 26

[0300] Die diameter: 75 mm φ

[0301] Die lip gap: 1.0 mm

[0302] Set temperature: 150 °C

[0303] BUR: 1.78

[0304] Film thickness: 60 μm

[0305] Screw rotation speed: 60 rpm

[0306] Tractor: Manufactured by Tajima Kogyo Co., Ltd., TW2B

[0307] (9) Measurement of fish eyes (FE) (unit: pieces / m 2 )

[0308] The fish eyes were measured during film formation using a defect detector installed in the blown film forming machine.

[0309] Inspection device: Manufactured by Futec Co., Ltd., MaxEye.C

[0310] Detection ability in width direction: 0.045 mm / bit

[0311] Detection ability in flow direction: 0.040 mm / scan

[0312] Light projection distance: 200 mm

[0313] Light reception distance: 473 mm

[0314] Inspection width: 180 mm

[0315] Inspection area: 18 m 2

[0316] Detection sensitivity: 90

[0317] FE size division (50 μm - 100 μm):

[0318] Width 0.045 mm × length 0.05 mm ≤ FE < width 0.09 mm × length 0.10 mm

[0319] FE size division (100 μm - 200 μm):

[0320] Width 0.09 mm × length 0.10 mm ≤ FE < width 0.18 mm × length 0.20 mm

[0321] Based on the measurement results, the number of FEs (pieces / m 2 for a film with a thickness of 120 μm (two 60-μm films overlapped) per 1 m 2 ) was calculated.

[0322] (10) Molding of haze-containing polyethylene film

[0323] The blown film was produced under the following processing conditions.

[0324] Processing equipment: Manufactured by PLACO Co., Ltd., L-40A

[0325] Screw diameter: 40 mm φ

[0326] L / D: 28

[0327] Die diameter: 60 mm φ

[0328] Lip gap: 0.5 mm

[0329] Set temperature: 150 °C

[0330] FLD: 210 mm

[0331] BUR: 1.5 and 3.0

[0332] Film thickness: 50 μm

[0333] Discharge rate: 5.5 kg / hour

[0334] Winder: Manufactured by Showa Kogyo Co., Ltd., Twin-shaft fixed winder TWK-400

[0335] Set the discharge rate to be constant, adjust the draw speed when BUR changes, and adjust the film thickness to 50 μm.

[0336] (11) Measurement of haze (unit: %)

[0337] For the blown film formed, use an integrating sphere type light transmittance measuring device (ToYO SEIKI SEISAKUSHO CO., LTD., DIRECT READING HAZE METER) based on ASTM D 1003 to obtain the haze. The smaller this value, the higher the transparency. The value obtained by subtracting the haze at BUR = 3.0 from the haze at BUR = 1.5 is defined as Δ haze. The larger this value, the easier it is to adjust to the desired haze.

[0338] It should be noted that the relationship between the blowing processing conditions of LDPE and haze is as follows:

[0339] For LDPE, by increasing BUR (lowering the draw speed), the deformation speed during film forming decreases, so the molten resin becomes easier to relax and the haze decreases.

[0340] In addition, the meaning of the maximum value - minimum value of haze (Δ haze) when adjusting BUR is as follows:

[0341] When BUR = 1.5, the haze is the maximum, and when BUR = 3.0, the haze is the minimum. With a large haze difference (Δ haze), it is possible to adjust to a wide range of desired haze.

[0342] [Examples and Comparative Examples]

[0343] Hereinafter, the present invention will be described by way of examples and comparative examples.

[0344] The physical property values of the polyethylene produced in Examples 1 to 2 and Comparative Examples 1 to 2 described below are shown in Table 1.

[0345] [Table 1]

[0346]

[0347] Examples 1, 2 and Comparative Examples 1, 2

[0348] Ethylene gas is supplied from the secondary compressor 3 to the reactor 4 at a rate of 14.4 tons / hour to 16.8 tons / hour (recorded in Table 2), and tert-butyl peroxy-2-ethylhexanoate as a polymerization initiator is supplied to the reactor 4 (recorded in Table 2). Ethylene is polymerized under the conditions of a pressure of 142 MPa to 195 MPa (recorded in Table 2) and a temperature of 232 °C to 235 °C (recorded in Table 2). The amount of polymer produced is 2.3 tons / hour to 2.5 tons / hour (recorded in Table 2). In Examples 1 and 2, a mixture obtained by adding 2,6-di-tert-butyl-4-methylphenol as a radical scavenger to the polymerization initiator is supplied to the reactor 4, and then ethylene is polymerized. The supply amount of the radical scavenger to the reactor 4 is 0.33 kg / hour to 0.39 kg / hour (recorded in Table 2).

[0349] After depressurization, the polymerization mixture is discharged from the reactor 4 to the high-pressure separator 5 and separated into the produced polymer and unreacted ethylene gas.

[0350] The produced polymer separated in the high-pressure separator 5 is depressurized through the polyethylene extraction pipe 7 and then extracted into the low-pressure separator 8, and further separated into the produced polymer and unreacted ethylene gas.

[0351] The produced polymer is extracted through the polyethylene extraction pipe 10 and pelletized using a pelletizer.

[0352] The unreacted ethylene gas separated in the high-pressure separator 5 and the low-pressure separator 8 is compressed by the front stage of the primary compressor 1, the rear stage of the primary compressor 2, and the secondary compressor 3 and supplied to the reactor 4, thereby continuously performing the polymerization reaction.

[0353] Ethane, propane, and propylene, which serve as a chain transfer agent (CTA) 17, are supplied to an ethylene pipeline 16 and are fed from the front stage of a primary compressor 1, through the rear stage of the primary compressor 2 and a secondary compressor 3, into a reactor 4. The concentrations of ethane, propane, and propylene, which serve as the chain transfer agent (CTA), are respectively measured using a gas chromatograph provided on a high-pressure ethylene pipeline 18, and the propylene concentration in the total gas volume (ethylene, ethane, propane, propylene) is adjusted to 0.01 vol% to 1.22 vol% (recorded in Table 2), and the total CTA (ethane, propane, propylene) concentration is adjusted to 1.93 vol% to 3.21 vol% (recorded in Table 2).

[0354] It should be noted that in Comparative Examples 1 and 2, the produced polymer was withdrawn through a polyethylene withdrawal pipeline 10, and then a radical scavenger was added to the produced polymer and made into pellets. Therefore, the amount of the radical scavenger contained in the pellet product is substantially equal to that in Example 2.

[0355] [Table 2]

[0356]

[0357] From the results of Tables 1 and 2, it can be confirmed that, compared with Comparative Examples 1 and 2 in which no radical scavenger was supplied in the polymerization initiator supply step, in Examples 1 and 2 in which a mixture of a polymerization initiator and a radical scavenger was supplied in the polymerization initiator supply step, the polyethylene film obtained has extremely few fish eyes while maintaining the easy adjustability of the haze of the obtained film.

[0358] Industrial Applicability

[0359] According to the present invention, by introducing a mixture containing a polymerization initiator and a radical scavenger into a reactor and polymerizing an ethylene monomer in a method for producing an ethylene-based polymer, an ethylene-based polymer capable of obtaining a film with a further improved balance between few fish eyes and good transparency can be provided.

[0360] The use of the ethylene-based polymer of the present invention is for various films such as protective films for forming circuit boards including narrower wiring widths, heavy packaging bags, shrink films, general packaging, thin films, protective films (barrier films), extrusion laminating films, extrusion molding films, foaming molding films, etc., and is suitable for various components of home appliances, various components of housing equipment, various industrial components, various building materials components, various automotive interior and exterior components, etc., and has high practicality in various fields of industries such as the electrical and electronic industry, household goods, transportation machinery industry, and building construction industry.

Claims

1. An ethylene-based polymer, wherein, The light scattering area value (RLS) of the vinyl polymer is 350 or more and 540 or less. RLS represents the light scattering area value of a solution obtained by dissolving 40 mg ± 0.2 mg of the vinyl polymer in 20 mL ± 0.1 mL of orthodichlorobenzene.

2. The vinyl polymer according to claim 1, wherein The difference (Δg') of the branch parameter of the vinyl polymer represented by the following (Formula 1) Mab is 0.11 or more and 1 or less. Here, in the calculation of the difference in the branched-chain parameters (Δg’ Mab ), g’ Ma , g’ Mb is obtained from the following (Equation 2) and (Equation 3). In the formula, M represents the absolute molecular weight of the vinyl polymer; W M represents the weight average fraction of the vinyl polymer having an absolute molecular weight M; g’ M represents the intrinsic viscosity ratio of the absolute molecular weight M.

3. The vinyl polymer according to claim 1 or claim 2, wherein The characteristic relaxation time of the vinyl polymer is 0.90 seconds or more and 1.35 seconds or less, and the weight fraction of the component with Log 10 M of 5.85 or more is 2.2% by weight or more and 4.4% by weight or less, The characteristic relaxation time is a value obtained by fitting a curve obtained by plotting the complex viscosity against the angular frequency. M represents the molecular weight of the vinyl polymer in terms of polyethylene conversion.

4. The vinyl polymer according to claim 1 or claim 2, wherein, The oxidation induction time at 190 °C of the vinyl polymer measured using a thermogravimetric differential thermal analyzer (TG-DTA) is 11.5 minutes or more.

5. The vinyl polymer according to claim 1 or claim 2, wherein, The vinyl polymer is low-density polyethylene (LDPE) by the high-pressure process.

6. The vinyl polymer according to claim 1 or claim 2, wherein, The vinyl polymer is polyethylene for a protective film.

7. A membrane, wherein, The film contains the vinyl polymer according to claim 1 or claim 2.

8. A protective film for a dry film resist, wherein, The protective film for a dry film resist contains the vinyl polymer according to claim 1 or claim 2.

9. A method for manufacturing an ethylene-based polymer, wherein, The method for producing the vinyl polymer has the following sequential steps: A. Compressing ethylene monomer to a pressure of 100 MPa to 300 MPa using one or more compressors; B. Introducing the compressed ethylene monomer into one or more reactors; C. Introducing a mixture containing a polymerization initiator and a radical scavenger into the reactor, and polymerizing the ethylene monomer in the reactor to generate a mixture containing unreacted ethylene monomer and vinyl polymer; D. Separating the vinyl polymer from the reactor mixture.

10. The method for producing an ethylene-based polymer according to claim 9, wherein, In step C, a mixture is introduced into the reactor in which the weight ratio of the polymerization initiator is 90% by weight to 99% by weight and the weight ratio of the radical scavenger is 1% by weight to 10% by weight based on the total weight of the polymerization initiator and the radical scavenger.

11. The method for manufacturing an ethylene-based polymer according to claim 9 or claim 10, wherein, The vinyl polymer is the vinyl polymer according to claim 1 or claim 2.

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