JPH072812B2 - Ethylene copolymer and method for producing the same - Google Patents

Description

The present invention relates to an ethylene-based copolymer and a method for producing the same,
More specifically, it relates to a copolymer of ethylene and 1-butene excellent in mechanical strength and flexibility and a method for producing the same.

(Prior Art) A copolymer of ethylene and 1-butene is used alone or mixed with another polymer and formed into a film, a tape, a sheet, a hollow molded article, an injection molded article, or the like. It is also excellent as a resin modifier, and resins containing the copolymer are widely used in automobile parts, electric wires, and the like.

Heretofore, several ethylene / butene copolymers and resin compositions containing them have been proposed, but all of them are still unsatisfactory in terms of some required physical properties. For example, to improve mechanical strength such as tensile strength and to give flexibility,
This is not possible with conventionally known ethylene / butene copolymers. That is, if the ethylene content is increased or the molecular weight is increased as a method for improving the tensile strength, the flexibility is decreased, and as a modifier for polypropylene or other polyolefin resin, or as a single polymer. When this ethylene-butene copolymer is used as, the mechanical strength such as tensile strength is high,
The flexibility and impact resistance are insufficient. Since the ethylene / 1-butene copolymer is used after being molded into a film, a tape, a sheet, a hollow molded product, an injection molded product or the like, it is required to have high mechanical strength such as tensile strength.

(Problems to be Solved by the Invention) An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and provide an ethylene / butene copolymer excellent in mechanical strength and flexibility and a method for producing the same. .

(Means for Solving the Problems) As a result of intensive studies, the inventors of the present invention have found that a novel ethylene copolymer, which has not been known hitherto, achieves the above-mentioned object, and arrived at the present invention.

The ethylene-based copolymer of the present invention is an ethylene / 1-butene random copolymer having ethylene and 1-butene as main polymerization units and having a substantially linear structure, and (A) below.
It satisfies the requirements of (E).

(A) The bound ethylene content is 85 to 95 mol%, (B) the weight average molecular weight is 30,000 to 200,000, (C) the weight average molecular weight (Mw) and the number average molecular weight (Mn) The ratio Mw / Mn is 2 to 5, and (D) there are two melting points, high temperature side and low temperature side, which are determined by a differential scanning calorimeter, the high temperature side peak is 95 to 110 ° C, and the low temperature side peak. Is present at 40 to 85 ° C., (E) the ratio of heat absorption between the high temperature side and the low temperature side of the two melting points (heat amount ratio) determined by a differential scanning calorimeter is 4 to 30/96 to 70.
To be.

The ethylene-based copolymer of the present invention is a previously unknown copolymer having a specially controlled ethylene segment. That is, the copolymer of the present invention has a bound ethylene content of 85 to 95 mol% and a weight average molecular weight (Mw) to number average molecular weight (Mn) ratio Mw / Mn of 2 to 5. Moreover, the melting point determined by a differential scanning calorimeter (DSC) shows two peaks, a high temperature side peak exists at 95 to 110 ° C, and a low temperature side peak exists at 40 to 85 ° C. The ratio (weight ratio) of the heat absorption amount between the high temperature side and the low temperature side of the melting point determined by the mold calorimeter is 4 to 30/96 to 70.

The ethylene-based copolymer of the present invention satisfying the above requirements (A) to (E) has a mechanical strength sufficiently higher than that of a conventionally known ethylene copolymer, and has flexibility. Has excellent performance and excellent transparency without stickiness on the surface. In addition, 5% by weight of this new ethylene-based copolymer
The resin composition with the crystalline polypropylene or other polyolefin resin contained above is also an excellent one in which sufficiently high mechanical strength and flexibility are well balanced.

The Mw to Mn ratio (Mw / Mn) of the ethylene-based copolymer of the present invention is limited to a narrow range of 2 to 5 as described above from the viewpoint of reducing stickiness on the surface of the molded product.

Further, in the melting point obtained by the differential scanning calorimeter (DSC), two peaks, a high temperature side peak and a low temperature side peak, are shown to indicate that ethylene and 1-butene are specially controlled and copolymerized. In particular, the copolymer part having a peak on the high temperature side has the function of increasing the mechanical strength, and the peak on the low temperature side shows the function of having flexibility while maintaining some mechanical strength. Conceivable. In particular, the high temperature side peak is a characteristic of the copolymer of the present invention in that it is crystallized to the extent that flexibility is not significantly impaired, and it is considered that the physical properties of the copolymer of the present invention are greatly affected.

Further, in the copolymer of the present invention, the ratio of the endothermic amounts on the high temperature side and the low temperature side of the melting point determined by a differential scanning calorimeter is 4
It is necessary to be -30 / 96-70 (weight ratio). That is, the proportion of the copolymer showing the peak on the high temperature side is required to be 4 to 30% of the total endothermic amount of the copolymer at 95 to 110 ° C. determined by the differential scanning calorimeter (DSC). . When it is less than 4%, mechanical strength such as tensile strength is almost equal to that of conventional ethylene / butene copolymers, and no superiority is found. On the other hand, when it is more than 30%, mechanical strength is increased. It is not preferable in terms of flexibility.

The ethylene-based copolymer of the present invention is, for example, under selected conditions, that is, as a polymerization catalyst, vanadium oxytrichloride (VOCl ₃ ), vanadium tetrachloride (VCl ₄ ), alkyl vanadate [VO (OR ₁ ) ₃ However, R ₁ in the formula has 2 to 2 carbon atoms.
8 alkyl group] and VOCl ₃ and an alcohol (R ₂ OH, where R ₂ is an alkyl group having 2 to 8 carbon atoms) a reaction mixture [where VOCl ₃ and R ₂ OH are mixed in moles]. R ₂ O in ratio
H / VOCl ₃ = 1/1 to 3/1] and a soluble vanadium compound selected from the general formula RAlX ₂ (wherein R represents an alkyl group having 2 to 6 carbon atoms, and X represents a chlorine atom or a bromine atom). Using a catalyst having a composition ratio (molar ratio) of Al / V = 10/1 to 200/1 of the represented dihalogenated organoaluminum compound, ethylene and 1-butene were added at a polymerization temperature of -50 to 119.
It is produced by copolymerizing at ℃.

In the present invention, ethylene and 1-butene are the above-mentioned specific soluble vanadium compound and the general formula RAlX ₂ (wherein R is
And X have the above meaning) and are polymerized using a catalyst composed of a dihalogenated organoaluminum compound.

Examples of the dihalogenated organoaluminum compound include ethyl aluminum dichloride, n-butyl aluminum dichloride, isopropyl aluminum dichloride, isobutyl aluminum dichloride, hexyl aluminum dichloride, ethyl aluminum dibromide,
Ethyl aluminum dichloride and isobutyl aluminum dichloride are preferably used in terms of economy, such as isobutyl aluminum dibromide. Further, in place of the dihalogenated organoaluminum compound, it is also possible to use a combination of two or more other aluminum compounds which substantially become the dihalogenated organoaluminum compound. For example, a mixture of R ₂ AlX and AlX ₃ in 1/1 (molar ratio), R ₃ Al
A 2/1 (molar ratio) mixture of AlX ₃ or the like is used.

As the soluble vanadium compound, a vanadium compound soluble in a polymerization solvent, specifically, vanadium oxytrichloride (VOCl ₃ ), vanadium tetrachloride (VCl ₄ ), alkyl vanadate [VO (OR ₁ ) ₃ , R ₁ has 2 to 2 carbon atoms
8 alkyl group] and VOCl ₃ and an alcohol (R ₂ OH, where R ₂ is an alkyl group having 2 to 8 carbon atoms) a reaction mixture [where VOCl ₃ and R ₂ OH are mixed in moles]. R ₂ O in ratio
H / VOCl ₃ = 1/1 to 3/1] is used as the soluble vanadium compound. Examples of the alkyl vanadate include ethyl vanadate, n-propyl vanadate, isopropyl vanadate, n-butyl vanadate, sec-butyl vanadate, 2-ethylhexyl vanadate, and the like.
Examples of the alcohol to be reacted with VOCl ₃ include ethyl alcohol, n-propyl alcohol, n-butyl alcohol, 2-ethylhexyl alcohol and the like.

In the present invention, it is important to use the dihalogenated organoaluminum compound as one component of the catalyst, and when another organoaluminum compound is used, it is not possible to produce the improved ethylene copolymer of the present invention. Can not.

The composition ratio (molar ratio) of the organohalogenated aluminum compound and the soluble vanadium compound is Al / V = 10/1 to 200/1,
It is preferably 10/1 to 150/1. The smaller Al / V gives an ethylene-based copolymer containing a larger amount of a component having a melting point on the high temperature side (hereinafter, abbreviated as High Tm-EBM). However, when Al / V is less than 10/1, the molecular weight distribution (indicated by Mw / Mn) becomes broad and the surface stickiness of the molded product deteriorates, while Al / V is greater than 200/1. In this case, the production ratio of High Tm-EBM is lowered, and the copolymer of the present invention, which is excellent in tensile strength and flexibility, cannot be obtained.

If necessary, an activity improver can be added to the catalyst system used in the present invention. As an activity enhancer,
For example, polyhalogen compounds such as trichloroacetic acid ester and 2,3,4,4-tetrachlorobutenoic acid ester are used. If necessary, an electron donor such as alcohols, ketones, amines, carboxylic acids or salts thereof may be mixed with the vanadium compound or the aluminum compound in advance or added at the same time.

As the polymerization solvent used in the polymerization in the present invention, an aliphatic hydrocarbon compound having 3 to 10 carbon atoms, 1 to 1 carbon atom
5 halogenated aliphatic hydrocarbon compounds such as propane, butane, pentane, hexane, heptane, octane, decane, 1-butene, methyl chloride, ethyl chloride, methylene chloride, ethylene chloride and the like are used, preferably n
-Hexane, n-heptane are used. Polymerization temperature is-
The temperature is 50 to 119 ° C, preferably -20 to 40 ° C. If the temperature is lower than -50 ° C, a large amount of energy is required for cooling, which is economically disadvantageous. If it exceeds 119 ° C, the polymerization activity will be extremely low. Further, the molecular weight of the copolymer is unlikely to increase, or a product having a large amount of low molecular weight products is obtained. During the polymerization, the pressure is maintained under reduced pressure (100 mmHg) or under pressure (50 atm). The molecular weight can be controlled to some extent depending on the catalyst composition ratio, the catalyst amount, the catalyst species, the polymerization temperature, etc. described above, but a molecular weight controlling agent such as hydrogen can also be used. Separation of the produced copolymer from the reaction catalyst and unreacted monomers, termination of the activity of the catalyst used, removal of the catalyst residue, drying of the copolymer, molding such as granulation and the like are carried out by known methods.

The novel ethylene copolymer thus obtained is a crystalline polypropylene resin obtained by copolymerizing 20% by weight or less of crystalline homopolypropylene and / or α-olefin other than propylene alone or other olefins (co). It is used as an ethylene-based copolymer resin composition by mixing 5% by weight, preferably 10% by weight or more with a polymer resin. Further, depending on the purpose, other olefin (co) polymer rubbers, olefin (co) polymers modified by grafting of carboxylic acids and the like, and optionally organic system,
Inorganic filler, mixed with a reinforcing agent such as fiber, subjected to means such as lamination, film, tape, sheet, hollow molded article,
Used as injection molded products.

(Effects of the Invention) The ethylene-based copolymer of the present invention can be produced for the first time under selected production conditions.
Different from butene copolymer, it is excellent in mechanical strength such as tensile strength, and is also excellent in transparency, flexibility and surface stickiness. Also, with this ethylene-based copolymer,
The ethylene-based copolymer composition of the present invention comprising polypropylene or other polyolefin resin is an excellent one having well-balanced mechanical strength and flexibility.

(Examples) Hereinafter, the present invention will be described in detail with reference to Examples.

The following analytical means and physical property evaluation methods were used to identify the ethylene-based copolymer of the present invention.

(Ethylene content) ¹ H-NMR and ¹³ C of ethylene / α / olefin copolymer
The ethylene / α-olefin composition ratio was determined using -NMR, and a calibration curve was prepared by infrared analysis. The composition of the copolymer obtained in each example was determined based on this calibration curve.

(Mw / Mn) According to Takeuchi's "Gel Permeation Chromatograph" (published by Maruzen Co., Ltd.), the measurement was performed as follows.

(1) Using standard polystyrene of known molecular weight (manufactured by Toyo Soda Co., Ltd., monodisperse polystyrene), the molecular weight M and its GPC (Gel Permeation Chromatograph) count were measured, and the correlation between the molecular weight M and EV (Elution Volume) Plot a calibration curve. The concentration at this time is 0.02% by weight. The standard polystyrene calibration curve is corrected to the EBM calibration curve by the universal method.

(2) The GPC pattern of the sample is taken by the GPC measurement method, and M is obtained by the above (1). The sample preparation conditions and GPC measurement conditions in that case are as follows.

(Sample preparation conditions) (a) o-dichlorobenzene solvent as an anti-aging agent 2,
Add 0.08% of 6-di-t-butyl-cresol and dissolve.

(B) The sample is dispensed into an Erlenmeyer flask together with o-dichlorobenzene so as to be 0.1%.

(C) The Erlenmeyer flask is heated to 120 ° C. and dissolved by stirring for about 60 minutes.

(D) The solvent obtained in (c) is applied to GPC. In addition, it is automatically filtered by a 0.5 micron sintered filter in the GPC device.

(GPC measurement conditions) (a) Device: Waters 150C type (b) Column: Toyo Soda Co., Ltd. H type (c) Sample amount: 500 micro (d) Temperature: 120 ° C (e) Flow rate: 1 ml / Min (f) Total theoretical plate number of column: 1 * 10 2 * 10 (measured value with acetone) (Measurement method of melting point and endothermic amount with differential scanning calorimeter) Differential scanning calorimeter is 910 Deferential Scan manufactured by Dupont
A ning Calolimeter (hereinafter abbreviated as DSC) was used, and a recorder used was a 990-type Thermal Analyzer manufactured by Dupont. The sample amount was 0.1 mg, and as the reference, alumina (Shimadzu Corporation DSC standard sample) 10.1 mg was used. For the measurement, the sample and Reference are loaded into the DSC, heated to 180 ° C, and then cooled to -100 ° C at a constant rate of 10 ° C for 1 minute. Then, the sample is analyzed up to 170 ° C. at a constant heating rate of 20 ° C. in 1 minute. The typical DSC pattern obtained is shown in FIG.

In FIG. 1, P ₁ and P ₂ are referred to as Tm peaks, the high temperature side Tm peak in the ethylene-based copolymer of the present invention refers to P ₂ , and the low temperature side Tm peak refers to P _1. The Tm temperature value is read from the temperature coordinate axis at each point.

(Calculation of Crystal Endotherm) Tangent line (a) of low temperature side baselines A to B in FIG.
Ask for. Next, endothermic peaks B to C that are considered to be the Tg part
Find the tangent (b) of the part. The intersection of the tangents (a) and (b) is defined as (A), and the perpendicular (c) is drawn from (A). Then, h is calculated according to the following equation (1).

h (mm) = 2.25 x S (mg) (1) (however, h is the distance (mm) from (a) in the DSC chart original, S is the sample amount (mg)) (a) to the vertical line (c) A horizontal line (d) is drawn along the distance h. The intersection (a) between the horizontal line (d) and the endothermic curve is obtained.

A tangent line (e) between the intersection point (a) and the high temperature side base lines D to E is drawn. The shaded area surrounded by the tangent line (e) and the endothermic curve was taken as the total crystal component.

Subsequently, the crystal part was divided at the position of 90 ° C., and the crystal part of 90 ° C. or higher was treated as the high temperature endotherm and the crystal part of 90 ° C. or lower was treated as the low temperature endotherm. The total crystal components and the endothermic amounts of each of the high temperature side and the low temperature side were calculated based on indium (standard sample for DSC manufactured by Dupont) by obtaining each area (hatched portion).

(Other evaluation methods) (1) Tensile strength and tensile elongation JIS K 6301 was followed.

(2) Surface Stickiness of Molded Product The following standard was used based on the feel of the surface skin of the molded sheet used in (1) above.

Samples with no stickiness: ◎ Samples with almost no stickiness: ○ Samples with a slight stickiness: △ Samples with a clear stickiness: × (3) Transparency polypropylene (Mitsubishi Yuka ( Co., Ltd., Noblen FW-
80/20 of 3) and ethylene / 1-butene copolymer (EBM)
(Weight ratio) 100 parts by weight of mixture and antioxidant (Irganox
1010, manufactured by Ciba Geigy) 0.1 part by weight is mixed at 210 ° C. using a 55 mmφ ruder, and then 0.5 according to JIS K 6758.
mm sheets were made. Then, the haze was measured according to JIS K 7105.

(4) Flexibility The molded sheet used in the above (1) was bent with both hands and shown according to the following criteria.

Sample with excellent flexibility: ◎ Sample with relatively excellent flexibility: ○ Sample with slightly poor flexibility: △ Sample with poor flexibility: × Example 1 (Polymerization of ethylene / 1-butene copolymer) Stirring blade and jacket After fully replacing the 3 stainless steel polymerization vessel equipped with a cooling device with N ₂ gas, n-hexane 1.5 was charged as a polymerization solvent, and 1-butene 400 g was further added.
Was injected. Next, use ethylene gas at a gauge pressure of 8 kg / cm ²
Until it reaches 13 kg / cm ² by further injecting hydrogen gas.
I chose The temperature inside the polymerization vessel was adjusted to 20 ° C by passing temperature-controlled water through the jacket.

Then, in a catalyst charging container attached to the polymerization vessel, n of ethyl aluminum dichloride (hereinafter, abbreviated as EADC) was placed.
-The hexane solution was pressured with 24 mmol of Al atoms and stirring was started. Further, using the same catalyst charging device as described above, vanadium oxytrichloride (hereinafter abbreviated as VOCl ₃ ) and n
A n-hexane solution of a mixed reaction product of n-BuOH / V = 3/1 (molar ratio) with -butyl alcohol (hereinafter, abbreviated as n-BuOH) was injected at 0.4 mmol with V atom to perform polymerization reaction (batch). Reaction) was started. After 5 minutes, the valve attached to the upper part of the polymerization reactor was opened, the pressurized monomer gas was released, and a small amount of methyl alcohol in which the antioxidant was dissolved was removed.
The reaction was stopped by adding 10 ml.

Steam was blown into the reaction product in which the reaction was stopped to remove the solvent and unreacted monomers, and the resulting ethylene copolymer (hereinafter abbreviated as EBM) solid matter was heated at 110 ° C. using a hot roll. Dried.

(Analysis of ethylene copolymer and evaluation of physical properties) The yield of EBM thus obtained and the results obtained by the above-mentioned analytical means and physical property evaluation method are shown in Table 1.

The obtained EBM has a high temperature side Tm peak (P ₂ ) of 102 ° C by DSC.
The proportion of the crystal components at 90 to 103 ℃ was 14.8% of the total crystal part.

It can be seen that this copolymer is excellent in both tensile strength and flexibility.

Comparative Example 1 Instead of the EBM obtained in Example 1, a commercially available EBM having the same ethylene content as in Example 1 (Mitsui Petrochemical Co., Ltd.) was used.
Table 1 shows the results of the analysis and evaluation of physical properties when using Tuffmer A4090 manufactured by Tsubama Corporation.

It can be seen that both the tensile strength and the flexibility are inferior to those in the case of Example 1.

Comparative Example 2 Instead of ethyl aluminum dichloride, organoaluminum sesquichloride (hereinafter abbreviated as ESC) was used,
Blow pressure of ethylene to 10kg / cm ² and hydrogen gas to 15kg / c
The same treatment as in Example 1 was carried out except for m ² to obtain EBM.

The results of yield, analysis and evaluation of physical properties of the obtained EBM are
Shown in the table.

It can be seen that although the tensile strength is almost the same as in the case of Example 1, the flexibility is inferior.

Comparative Example 3 Commercially available EBM (Tufmer A40 manufactured by Mitsui Petrochemical Co., Ltd.) having a Tm peak almost equal to P ₁ in the copolymer of Example 1.
85) 92 parts by weight of low-density polyethylene (Mitsubishi Petrochemical Co., Ltd.)
(Yukaron 9150-M) 8 parts by weight using a 55 mφ extruder 2
Melt mixed at 30 ° C.

The results of analysis and evaluation of physical properties of this mixture are shown in Table 1.

Compared with the case of Example 1, this mixture had a high Tm peak (P ₂ ) at the high temperature side of 120 ° C. even if the ratio of the endotherm (Q ₂ ) at 90 ° C. or higher was the same. It turns out that is damaged.

Example 2 The amount of a mixed reaction product of vanadium oxychloride and n-butyl alcohol was 0.5 mmol by V atom, and the amount of EADC was 1 atom by Al atom.
The EBM was obtained by treating the same as Example 1 except that the amount was 0 mmol.

The results of yield, analysis and evaluation of physical properties of the obtained EBM are
Shown in the table.

It can be seen that this copolymer is excellent in both tensile strength and flexibility.

Comparative Example 4 An EBM was obtained by treating the amount of EADC with Al atom at 2.5 mmol and otherwise treating in the same manner as in Example 2.

The results of yield, analysis and evaluation of physical properties of the obtained EBM are
Shown in the table.

It can be seen that the Mw / Mn of this copolymer is very broad, and the surface stickiness of the molded product is inferior.

Example 3 An EBM was obtained by treating the vanadium compound with VOCl ₃ and otherwise treating it in the same manner as in Example 1.

The results of yield, analysis and evaluation of physical properties of the obtained EBM are
Shown in the table.

It can be seen that this copolymer is excellent in both tensile strength and flexibility.

Comparative Example 5 The EBM obtained in Example 2 was made into a 5 wt% solution with warm cyclohexane and then cooled to room temperature.

Methanol was added dropwise to the cloudy solution to precipitate most of the polymer, and the polymer after precipitation was dried with a 110 ° C. roll, and 85% of the polymer used for dissolution was recovered. The results of analysis and evaluation of physical properties of this polymer are shown in Table 1.

Although both P ₁ and P _{2 of} this copolymer are almost the same as those of Example 2, it is found that the molded product is inferior in flexibility because the endothermic amount (Q ₂ ) of 90 ° C. or higher is large.

Example 4 An EBM was obtained by the same procedure as in Example 1 except that vanadium tetrachloride (VCl ₄ ) was used as the vanadium compound. The results of yield, analysis and evaluation of physical properties of the obtained EBM are shown in Table 2. From Table 2, it can be seen that this copolymer is excellent in both tensile strength and flexibility.

Example 5 Example 2 to give the EBM except for using as the vanadium compound n- butyl vanadate [VO (OBu _3)] is treated in the same manner as in Example 2. The results of yield, analysis and evaluation of physical properties of the obtained EBM are shown in Table 2. From Table 2, it can be seen that this copolymer is excellent in both tensile strength and flexibility.

Comparative Example 6 In Example 3, ethyl aluminum dichloride (EA
Instead of DC), organoaluminum squichloride (hereinafter abbreviated as ESC) is used, and the blowing pressure of ethylene is 10 kg.
EBM was obtained by treating in the same manner as in Example 3 except that the pressure was changed to / cm ² and the hydrogen gas was changed to 15 kg / cm ² . The results of yield, analysis and evaluation of physical properties of the obtained EBM are shown in Table 2. This copolymer has a melting point of 86 ° C (P ₁ ) of 1 with a differential scanning calorimeter.
Since there are only one piece, good mechanical strength and flexibility cannot be obtained at the same time.

[Brief description of drawings]

FIG. 1 shows a typical DSC of the ethylene copolymer of the present invention.
The figure which shows a pattern, FIG. 2 is a flowchart figure of the manufacturing method of the ethylene-type copolymer of this invention. P ₁ ...... Low temperature side Tm peak, P ₂ ...... High temperature side Tm peak.

Front page continuation (72) Inventor Sadahide Yamazaki 2-11-24 Tsukiji, Chuo-ku, Tokyo Within Nippon Synthetic Rubber Co., Ltd. (56) Reference JP-A-51-41784 (JP, A) JP-A-57 -105411 (JP, A) JP-A-63-17912 (JP, A) JP-A-62-53313 (JP, A)

Claims (2)

[Claims] 1. An ethylene / 1-butene random copolymer having ethylene and 1-butene as main polymerization units and having a substantially linear structure, and satisfying the following requirements (A) to (E). An ethylene-based copolymer characterized by: (A) Ethylene unit content is 85 to 95 mol%, (B) Weight average molecular weight is 30,000 to 200,000, (C) Weight average molecular weight (Mw) and number average molecular weight (Mn) The ratio Mw / Mn is 2 to 5, and (D) there are two melting points, high temperature side and low temperature side, which are determined by a differential scanning calorimeter, the high temperature side peak is 95 to 110 ° C, and the low temperature side peak. Is present at 40 to 85 ° C., (E) the ratio of heat absorption between the high temperature side and the low temperature side of the two melting points (heat amount ratio) determined by a differential scanning calorimeter is 4 to 30/96 to 70.
To be. 2. A polymerization catalyst comprising vanadium oxytrichloride (VOCl ₃ ), vanadium tetrachloride (VCl ₄ ), alkylvanadate [VO (OR ₁ ) _{3 wherein} R ₁ has 2 to 2 carbon atoms.
8 alkyl group] and a reaction mixture of VOCl ₃ and alcohol (R ₂ OH, where R ₂ is an alkyl group having 2 to 8 carbon atoms) (provided that the mixing ratio of VOCl ₃ and R ₂ OH is mol). R ₂ O in ratio
H / VOCl ₃ = 1/1 to 3/1) and a soluble vanadium compound selected from the general formula RAlX ₂ (wherein R represents an alkyl group having 2 to 6 carbon atoms, and X represents a chlorine atom or a bromine atom) Using a catalyst having a composition ratio (molar ratio) of Al / V = 10/1 to 200/1 of the dihalogenated organoaluminum compound, ethylene is copolymerized with 1-butene to give ethylene. Ethylene. 1-butene as a main polymerized unit having a substantially linear structure satisfying the following requirements (A) to (E):
A process for producing an ethylene-based copolymer, which comprises obtaining a butene random copolymer. (A) Ethylene unit content is 85 to 95 mol%, (B) Weight average molecular weight is 30,000 to 200,000, (C) Weight average molecular weight (Mw) and number average molecular weight (Mn) The ratio Mw / Mn is 2 to 5, and (D) there are two melting points, high temperature side and low temperature side, which are determined by a differential scanning calorimeter, the high temperature side peak is 95 to 110 ° C, and the low temperature side peak. Is present at 40 to 85 ° C., (E) the ratio of heat absorption between the high temperature side and the low temperature side of the two melting points (heat amount ratio) determined by a differential scanning calorimeter is 4 to 30/96 to 70.
To be.