JP2006124447A - Polyethylene resin injection molded body - Google Patents

Abstract

An injection molded body made of a polyethylene resin having high rigidity and high impact characteristics and excellent fluidity in molding is obtained.
A polyethylene resin that satisfies the following requirements (A) to (D) is injection molded. (A) The density is 890 kg / m ³ or more and 980 kg / m ³ or less, (B) the number of long chain branches having 6 or more carbon atoms is 0.01 or more and 3 or less per 1,000 carbon atoms, the formula (C) Both (1) and formula (2) are satisfied, MS ₁₉₀ > 22 × MFR ^−0.88 (1) MS ₁₆₀ > 110−110 × log (MFR) (2) (D) Temperature rise by differential scanning calorimeter There is one endothermic curve peak obtained in the measurement.
[Selection figure] None

Description

  The present invention relates to a polyethylene resin injection-molded article molded using a specific polyethylene resin. More specifically, an injection molded article formed by using an ethylene homopolymer having a specific density, long chain branch number, MFR and melt tension, or a copolymer of ethylene and an α-olefin, such as a cup, a cap, It relates to containers, pallets, etc.

  At present, polyethylene-based resins are used as raw materials for various injection-molded products due to their excellent characteristics. However, in recent years, the plastics waste problem has attracted attention, and it is desired to reduce the thickness of the injection-molded products. In actual molding sites, reduction of molding time and the like has been studied for the purpose of cost reduction. In order to satisfy such requirements, it is important that the polyethylene resin injection-molded body has high rigidity and high impact strength. In the molding process of the molded body, even in a thin mold, The polyethylene resin needs to have sufficient fluidity.

  Conventionally, in the field of polyethylene resin injection molding, polyethylene resins mainly produced by Ziegler-Natta catalysts have been favorably used. Various problems occur when trying to solve the above-mentioned problems using this polyethylene resin. For example, if the polyethylene resin has sufficient fluidity, the impact strength of the obtained injection molded product becomes insufficient, and there is a problem that the molded product cannot be substantially thinned. Adhering to the mold makes long-term continuous production difficult. Therefore, there has recently been an attempt to apply a polyethylene resin produced with a metallocene catalyst to an injection molded article. However, although an injection-molded article using a metallocene catalyst is disclosed, the rigidity of the molded body is insufficient, and the fluidity at the time of molding is not satisfactory (for example, see Patent Document 1). Although a high-rigidity injection-molded article using a polyethylene resin composition based on a metallocene catalyst has been disclosed, the fluidity is not satisfactory, and the fluidity in a thin mold is not satisfactory. (For example, refer to Patent Document 2). Although a polyethylene resin injection molded product having a narrow molecular weight distribution is disclosed, the polyethylene resin used does not have sufficient fluidity that can be molded with a thin mold (for example, Patent Document 3). reference).

JP-A-10-193377 Japanese Patent Laid-Open No. 10-193379 JP 7-278229 A

  This invention solves said subject and provides the polyethylene-type resin injection molding using the ethylene homopolymer which meets specific requirements, or the copolymer of ethylene and the alpha olefin. . The polyethylene resin injection-molded article of the present invention has high rigidity and high impact characteristics, and has excellent fluidity in molding.

As a result of intensive studies, the inventor has found that a specific polyethylene-based resin has excellent fluidity and that the obtained molded article has excellent physical properties. That is, the present invention is an injection molding of a polyethylene-based resin that is an ethylene homopolymer or a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms and that satisfies the following requirements (A) to (D). It is related with the injection molding body made from a polyethylene-type resin characterized by the above-mentioned.
(A) The density is 890 kg / m ³ or more and 980 kg / m ³ or less,
(B) The number of long-chain branches having 6 or more carbon atoms is 0.01 to 3 per 1,000 carbon atoms,
(C) Melt tension (MS ₁₉₀ ) (mN) measured at 190 ° C. and MFR (g / 10 min, 190 ° C.) with a load of 2.16 kg are represented by the following formula (1)
MS ₁₉₀ > 22 × MFR ^−0.88 (1)
And the melt tension (MS ₁₆₀ ) (mN) measured at 160 ° C. and the MFR (g / 10 min, 190 ° C.) with a load of 2.16 kg satisfy the following formula (2):
MS ₁₆₀ > 110-110 × log (MFR) (2)
(D) There is one peak of the endothermic curve obtained in the temperature rise measurement by the differential scanning calorimeter. The present invention will be described in detail below.

The density of the polyethylene resin used in the present invention is 890 kg / m ³ or more and 980 kg / m ³ or less, preferably 920 kg / m ³ as a value measured by a density gradient tube method in accordance with JIS K6922-1 (1998). It is 965 kg / m ³ or less. When the density is less than 890 kg / m ³ , there is a problem that the obtained injection molded body has insufficient rigidity, and the molded body is easily deformed during use. In addition, since the impact strength of the injection molded product decreases as the density increases, the upper limit of the density is preferably 980 kg / m ³ .

The weight average molecular weight (M _w ) in terms of linear polyethylene of the polyethylene resin used in the present invention is 10,000 or more and 1,000,000 or less, preferably 20,000 or more and 700,000 or less, More preferably, it is 25,000 or more and 300,000 or less. When the _Mw is less than 10,000, the impact strength of the obtained injection-molded product is lowered, and a large amount of low molecular weight polyethylene adheres to the mold, making continuous molding difficult. On the other hand, if it exceeds 1,000,000, the fluidity in the thin mold is insufficient, and there is a possibility that a molded product cannot be obtained.

  The MFR of the polyethylene resin used in the present invention at 190 ° C. and a load of 2.16 kg is 0.1 g / 10 min to 200 g / 10 min, preferably 1 g / 10 min to 150 g / 10 min, more preferably 1 g. / 10 minutes or more and 50 g / 10 minutes or less. If it is less than 0.1 g / 10 minutes, it is difficult to perform injection molding, and if it exceeds 200 g / 10 minutes, the strength is not practical.

The number of long chain branches of the polyethylene resin used in the present invention is 0.01 or more and 1,000 or less per 1,000 carbon atoms. If it is less than 0.01, the fluidity is poor, and a good thin molded article may not be obtained. Moreover, when it exceeds three, there exists a possibility that it may become an injection molding body inferior to a mechanical property. The number of long-chain branches is the number of branches of a hexyl group or more (having 6 or more carbon atoms) detected by ¹³ C-NMR measurement.

The melt tension MS ₁₉₀ (mN) and MFR (g / 10 min, 190 ° C.) measured at 190 ° C. of the polyethylene resin used in the injection-molded product of the present invention are as follows:
MS ₁₉₀ > 22 × MFR ^−0.88 (1)
Preferably, the following formula (1) ′
MS ₁₉₀ > 30 × MFR− ^0.88 (1) ′
More preferably, the following formula (1) "
MS ₁₉₀ > 5 + 30 × MFR ^−0.88 (1) ”
It is in the relationship shown by. If the formula (1) is not satisfied, the fluidity is poor, and a good thin molded product may not be obtained.

The melt tension MS ₁₆₀ (mN) and MFR (g / 10 minutes, 190 ° C.) measured at 160 ° C. of the polyethylene resin used in the injection-molded article of the present invention are as follows:
MS ₁₆₀ > 110-110 × log (MFR) (2)
Preferably, the following formula (2) ′
MS ₁₆₀ > 130-110 × log (MFR) (2) ′
More preferably, the following formula (2) "
MS ₁₆₀ > 150-110 × log (MFR) (2) ”
It is in the relationship shown by. If the formula (2) is not satisfied, the fluidity is poor and a thin injection molded product may not be obtained.

  The polyethylene-based resin used in the injection-molded article of the present invention has one endothermic curve peak obtained in temperature rise measurement by a differential scanning calorimeter (DSC), and the injection-molded article obtained thereby Is excellent in dimensional stability and heat resistance. The endothermic curve is obtained by inserting 5 to 10 mg of sample into an aluminum pan and raising the temperature with DSC. Note that the temperature rise measurement is performed by previously leaving at 230 ° C. for 3 minutes, then lowering the temperature to −10 ° C. at 10 ° C./min, and then raising the temperature to 150 ° C. at a rate of 10 ° C./min .

The polyethylene resin used in the injection-molded article of the present invention has a shrinkage factor (g ′ value) evaluated by gel permeation chromatography (GPC) / intrinsic viscometer of 0.1 or more and less than 0.9, and further 0.1 It is preferable that it is 0.7 or more, and this reduces shrinkage when the polyethylene resin is injection-molded, so that shrinkage of the obtained injection-molded body is reduced. The shrinkage factor (g ′ value) in the present invention is a parameter representing the degree of long-chain branching, and the intrinsic viscosity of the polyethylene-based resin at an absolute molecular weight three times the weight average molecular weight (M _w ) is completely different from the branching. It is the ratio of the intrinsic viscosity at the same molecular weight of no high density polyethylene (HDPE). Further, the relationship between the g ′ value and the contraction factor (g value) evaluated by the GPC / light scatterometer is preferably the formula (3), more preferably the formula (3) ′. Thus, the shrinkage rate of the molded product is further reduced. In addition, g value is a ratio of the root mean square of the inertial radius of this polyethylene-type resin in the absolute molecular weight 3 times _Mw , and the mean square of the inertial radius in the same molecular weight of HDPE without a branch.

0.2 <log (g ′) / log (g) <1.3 (3)
0.5 <log (g ′) / log (g) <1.0 (3) ′
Further, between the g value in an absolute molecular weight three times the _{M w (g 3M)} and g values of the absolute molecular weight of 1 × _{M w (g M),} formula (4), preferably of formula (4) ' More preferably, the relationship represented by the formula (4) "is desirable for reducing the shrinkage rate of the molded product.

0 <g _3M / g _M ≦ 1 (4)
0 <g _3M / g _M ≦ 0.9 (4) ′
0 <g _3M / g _M ≦ 0.8 (4) ”
The polyethylene resin constituting the injection molded article of the present invention is an ethylene polymer having a vinyl group at the terminal obtained by polymerizing ethylene, or a terminal obtained by copolymerizing ethylene and an olefin having 3 or more carbon atoms. Is an ethylene copolymer having a vinyl group,
(E) M _n is 2,000 or more,
(F) It is desirable to be obtained by polymerizing ethylene and optionally an olefin having 3 or more carbon atoms in the presence of a macromonomer having M _w / M _n of 2 or more and 5 or less. The macromonomer is an olefin polymer having a vinyl group at the terminal, preferably an ethylene polymer having a vinyl group at the terminal obtained by polymerizing ethylene, or copolymerizing ethylene and an olefin having 3 or more carbon atoms. The ethylene copolymer having a vinyl group at the terminal obtained by the above method, more preferably long chain branching (i.e., ¹³ C-NMR among branches other than the branch derived from olefin having 3 or more carbon atoms, which is optionally used). Linear ethylene polymer or linear ethylene copolymer having a vinyl group at the terminal, wherein the number of branches of hexyl groups detected by measurement is less than 0.01 per 1,000 main chain methylene carbons It is.

  Examples of the olefin having 3 or more carbon atoms include propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-butene, α-olefin such as vinylcycloalkane, norbornene, Examples include cyclic olefins such as norbornadiene, dienes such as butadiene or 1,4-hexadiene, and styrene. Two or more of these olefins can be mixed and used.

When an ethylene polymer having a vinyl group at the terminal or an ethylene copolymer having a vinyl group at the terminal is used as the macromonomer, the number average molecular weight (M _n ) in terms of linear polyethylene is 2,000 or more, Preferably it is 5,000 or more, More preferably, it is 10,000 or more. The weight average molecular weight (M _w ) in terms of linear polyethylene is 4,000 or more, preferably 10,000 or more, more preferably more than 15,000. The ratio of the weight average molecular weight (M _w ) to M _n (M _w / M _n ) is 2 or more and 5 or less, preferably 2 or more and 4 or less, more preferably 2 or more and 3.5 or less. . The following general formula (5)
Z = [X / (X + Y)] × 2 (5)
(Where X is the number of vinyl ends per 1,000 main chain methylene carbons of the macromonomer, and Y is the number of saturated ends per 1,000 main chain methylene carbons of the macromonomer.)
The ratio (Z) between the number of vinyl ends and the number of saturated ends represented by is from 0.25 to 1, preferably from 0.50 to 1. X and Y are determined by ¹ H-NMR, ¹³ C-NMR, FT-IR, or the like. For example, in ¹³ C-NMR, the presence and amount of vinyl end can be confirmed by peaks at 114 ppm and 139 ppm at the vinyl end and 32.3 ppm, 22.9 ppm and 14.1 ppm at the saturated end.

  The production method of the macromonomer in the present invention is not particularly limited, but when producing an ethylene polymer having a vinyl group at the terminal or an ethylene copolymer having a vinyl group at the terminal as the macromonomer, for example, the periodic table 3 A method of polymerizing ethylene using a catalyst containing a metallocene compound containing a transition metal selected from Group 4, Group 4, Group 5 and Group 6 as a main component can be used. Examples of the cocatalyst include organoaluminum compounds, proton acid salts, Lewis acid salts, metal salts, Lewis acids and clay minerals.

  The polyethylene resin used in the present invention is, for example, a catalyst containing a metallocene compound containing a transition metal selected from Group 3, Group 4, Group 5 and Group 6 of the periodic table as a main component. It is obtained by polymerizing ethylene and optionally an olefin having 3 or more carbon atoms in the presence of a monomer. Moreover, a cocatalyst can be used similarly to manufacture of a macromonomer. The polymerization temperature is in the range of -70 to 300 ° C, preferably 0 to 250 ° C, more preferably 20 to 150 ° C. The ethylene partial pressure is in the range of 0.001 to 300 MPa, preferably 0.005 to 50 MPa, and more preferably 0.01 to 10 MPa. Further, hydrogen may be present as a molecular weight regulator in the polymerization system.

  In the present invention, when ethylene and an olefin having 3 or more carbon atoms are polymerized in the presence of a macromonomer, the ethylene / olefin having 3 or more carbon atoms (molar ratio) is 1 to 200, preferably 3 to 100, and more preferably. 5 to 50 can be used.

  The polyethylene resin used in the injection molded product of the present invention is a heat resistance stabilizer, weather resistance stabilizer, antistatic agent, antifogging agent, antiblocking agent, slip agent, lubricant, nucleating agent, pigment, tackifier, carbon black, Known additives such as inorganic fillers or reinforcing agents such as talc, glass powder, and glass fiber, organic fillers or reinforcing agents, flame retardants, and neutron shielding agents can be blended. Moreover, it can also be used by mixing with other thermoplastic resins. Examples of these are tackifying resins, waxes, HDPE, L-LDPE, LDPE, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene / vinyl acetate copolymer, ethylene / vinyl alcohol copolymer. Examples thereof include polymers, polystyrene, and maleic anhydride graft products thereof. As a mixing method, each component can be mixed and kneaded using various kneaders such as a Banbury mixer, a roll mixer, a kneader, a high-speed rotary mixer, and an extruder, preferably a single screw or twin screw extruder. It can also be kneaded during injection molding. Furthermore, it can also mix by solution blend using a suitable good solvent.

  The injection molding machine may be a normal one, and there is no particular limitation on the mold to be used. A normal mold can be used, and the size and position of the cooling water flow path can be changed in advance. There is no need to select special water flow conditions. There are no particular limitations on the molding conditions such as cylinder temperature conditions, mold clamping pressure, injection pressure, injection time, and cooling time when molding the container, and normal conditions may be selected. The release of the molded product from the mold may be performed by a normal method of cooling to a temperature at which the molded product does not deform in the mold cavity and releasing the mold.

  As injection molding conditions, a cylinder temperature of 160 to 200 ° C., a mold temperature of 5 to 40 ° C., a screw rotation speed of 40 to 300 rpm, an injection pressure of 4 to 14 MPa, and the like can be used.

  The polyethylene resin used in the present invention has excellent fluidity as compared with the conventional polyethylene resin. For this reason, since injection molding can be performed even if a polyethylene resin having a large molecular weight is used, an injection molded product obtained therefrom has high rigidity and high impact characteristics.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

  Preparation of modified hectorite, preparation of a catalyst for producing a macromonomer, production of a macromonomer, production of polyethylene and solvent purification were all carried out under an inert gas atmosphere. As the preparation of modified hectorite, the preparation of a catalyst for producing a macromonomer, the production of a macromonomer, the solvent used for the production of polyethylene, all of the solvents previously purified, dried and deoxygenated in a known manner were used. Diphenylsilanediylbis (cyclopentadienyl) zirconium dichloride and diphenylmethylene (1-cyclopentadienyl) (2,7-di-t-butyl-9-fluorenyl) zirconium dichloride were synthesized and identified by known methods. Was used. A hexane solution (0.714M) of triisobutylaluminum was manufactured by Tosoh Finechem Corporation.

  Furthermore, various physical properties of the polyethylene resins in Examples and Comparative Examples were measured by the methods shown below.

-Molecular weight and molecular weight distribution-
The weight average molecular weight (M _w ) and number average molecular weight (M _n ) were measured by gel permeation chromatography (GPC). Tosoh Co., Ltd. HLC-8121GPC / HT is used as the GPC device, Tosoh Co., Ltd. TSKgel GMHhr-H (20) HT is used as the column, the column temperature is set to 140 ° C., and 1 is used as the eluent. The measurement was performed using 2,4-trichlorobenzene. A measurement sample was prepared at a concentration of 1.0 mg / mL, and 0.3 mL was injected and measured. The calibration curve of molecular weight is calibrated using a polystyrene sample having a known molecular weight. In addition, _Mw and _Mn were calculated | required as a value of linear polyethylene conversion.

-Contraction factor (g 'value)-
The shrinkage factor (g ′ value) is the [η] at 3 times the absolute molecular weight of _Mw determined by the method of measuring [η] of polyethylene resin fractionated by GPC, at the same molecular weight of HDPE without any branching. The value divided by [η]. Tosoh Co., Ltd. HLC-8121GPC / HT is used as the GPC device, Tosoh Co., Ltd. TSKgel GMHhr-H (20) HT is used as the column, the column temperature is set to 145 ° C., and 1 is used as the eluent. Measurement was performed using 2,4-trichlorobenzene. A measurement sample was prepared at a concentration of 2.0 mg / mL, and 0.3 mL was injected and measured. As a viscometer, a capillary differential pressure viscometer 210R + manufactured by Viscotek was used.

~ Shrink factor (g value) ~
The shrinkage factor (g value) was determined by a method of measuring the radius of inertia of a polyethylene resin fractionated by GPC by light scattering. This is a value obtained by dividing the root mean square of the radius of inertia at an absolute molecular weight of 3 times _Mw of the polyethylene resin used in the injection-molded product of the present invention by the root mean square of the same molecular weight of HDPE having no branches. As the light scattering detector, a multi-angle light scattering detector DAWV EOS manufactured by Wyatt Technology was used, and the wavelength of 690 nm was 29.5 °, 33.3 °, 39.0 °, 44.8 °, 50.7. °, 57.5 °, 64.4 °, 72.3 °, 81.1 °, 90.0 °, 98.9 °, 107.7 °, 116.6 °, 125.4 °, 133.2 Measurements were made at detection angles of °, 140.0 °, and 145.8 °.

~ Z value ~
The terminal structure of a macromonomer such as a vinyl terminal or a saturated terminal was measured by ¹³ C-NMR using a JNM-ECA400 type nuclear magnetic resonance apparatus manufactured by JEOL Ltd. The solvent is tetrachloroethane -d _2. The number of vinyl ends was determined from the average value of peaks at 114 ppm and 139 ppm as the number per 1,000 main chain methylene carbons (chemical shift: 30 ppm). Similarly, the number of saturated terminals was determined from the average value of peaks at 32.3 ppm, 22.9 ppm, and 14.1 ppm. From this vinyl terminal number (X) and saturated terminal number (Y), Z = [X / (X + Y)] × 2 was determined.

~density~
The density was measured by a density gradient tube method according to JIS K6922-1 (1998).

~ MFR ~
MFR was measured at 190 ° C. under a load of 2.16 kg in accordance with JIS K6922-1 (1998).

~ Number of long chain branches ~
The number of long chain branches of the polyethylene resin was measured by ¹³ C-NMR using a JNM-GSX270 type nuclear magnetic resonance apparatus manufactured by JEOL Ltd.

~ Melting tension (MS) ~
The polyethylene used for the measurement of melt tension (MS) is pre-added with 1,500 ppm Irganox 1010 ^TM (manufactured by Ciba Specialty Chemicals) and 1,500 ppm Irgafos 168 ^TM (manufactured by Ciba Specialty Chemicals) as a heat stabilizer. An internal mixer (trade name: Labo Plast Mill, manufactured by Toyo Seiki Seisakusho Co., Ltd.) was used, which was kneaded for 3 minutes at 190 ° C. and a rotation speed of 30 rpm under a nitrogen stream. The melt tension (MS) is a capillary viscometer (Toyo Seiki Seisakusho, trade name: Capillograph) with a barrel diameter of 9.55 mm, a length (L) of 8 mm, a diameter (D) of 2.095 mm, and an inflow angle of 90 °. A die was mounted and measured. For MS, the temperature was set to 160 ° C. or 190 ° C., the piston lowering speed was set to 10 mm / min, the stretch ratio was set to 47, and the load (mN) required for take-up was MS.

~ Number of endothermic peaks ~
Measurement was performed using DSC (trade name: DSC-7, manufactured by Perkin Elmer). 5-10 mg of polyethylene-based resin is inserted into an aluminum pan, placed on the DSC, then heated to 230 ° C. at a temperature increase rate of 80 ° C./min, and left at 230 ° C. for 3 minutes. Thereafter, the temperature is cooled to −10 ° C. at a rate of temperature decrease of 10 ° C./min, and the temperature is increased / decreased from −10 ° C. to 150 ° C. at a rate of temperature increase of 10 ° C./min. The number of endothermic curves observed at the time of temperature increase was evaluated.

~ Evaluation of fluidity ~
Using a Toshiba injection molding machine IS-100E, a 0.6mm thick spiral groove mold, a molten polyethylene resin composition is injected by injection from the center gate to make a molded product, and its flow distance (spiral flow distance) ) To evaluate the fluidity. Spiral flow distance (SFD) was measured under conditions of an injection pressure of 75 MPa, an injection time of 10 seconds, a mold temperature of 40 ° C., a resin temperature of 160 ° C., and 190 ° C.

~ Physical properties of compacts ~
Using a Toshiba injection molding machine IS-100E, a flat plate having a thickness of 1 mm, a length of 10 cm, and a width of 10 cm was formed. The obtained flat plate was evaluated for Izod impact strength (JIS K7106) and Olsen bending stiffness (JIS K7110).

Example 1
[Preparation of modified hectorite]
After adding 60 mL of ethanol and 2.0 mL of 37% concentrated hydrochloric acid to 60 mL of water, 6.55 g (0.022 mol) of N, N-dimethyloctadecylamine was added to the resulting solution and heated to 60 ° C. An N, N-dimethyloctadecylamine hydrochloride solution was prepared. To this solution was added 20 g of hectorite. The suspension was stirred at 60 ° C. for 3 hours, the supernatant was removed, and then washed with 1 L of 60 ° C. water. Then, it dried at 60 degreeC and 10 < ^-3 > torr for 24 hours, and the modified | denatured hectorite with an average particle diameter of 5.2 micrometers was obtained by grind | pulverizing with a jet mill. As a result of elemental analysis, the amount of ions per gram of modified hectorite was 0.85 mmol.

[Preparation of catalyst for macromonomer production]
8.0 g of the above modified hectorite is suspended in 29 mL of hexane, 46 mL of hexane solution of triisobutylaluminum (0.714M) is added, and the mixture is stirred for 1 hour at room temperature, whereby contact formation of the modified hectorite and triisobutylaluminum occurs. I got a thing. On the other hand, 151 mg (320 μmol) of diphenylsilanediylbis (cyclopentadienyl) zirconium dichloride dissolved in toluene was added and stirred overnight at room temperature to obtain a catalyst slurry (100 g / L).

[Manufacture of macromonomer]
To a 10 L autoclave, 6,000 mL of hexane and 5.0 mL of a hexane solution of triisobutylaluminum (0.714 mol / L) were introduced, and the internal temperature of the autoclave was raised to 85 ° C. To this autoclave, 0.88 mL of the catalyst slurry was added, and ethylene was introduced until the partial pressure reached 1.2 MPa to initiate polymerization. During the polymerization, ethylene was continuously introduced so that the partial pressure was kept at 1.2 MPa. The polymerization temperature was controlled at 85 ° C. 90 minutes after the start of the polymerization, the internal temperature was lowered to 50 ° C. and the internal pressure of the autoclave was depressurized to 0.1 MPa, and then nitrogen was introduced into the autoclave until the pressure became 0.6 MPa and depressurized. This operation was repeated 5 times. The _Mn of the macromonomer extracted from the autoclave was 14,400, and _Mw / _Mn was 3.02. When the terminal structure of the macromonomer was analyzed by ¹³ C-NMR, the number of vinyl terminals and the number of saturated terminals were determined. The ratio (Z) was Z = 0.65. In ¹³ C-NMR, 0.41 methyl branches per 1,000 carbon atoms and 0.96 ethyl branches per 1,000 carbon atoms were detected. Furthermore, long chain branching was not detected in ¹³ C-NMR.

[Production of polyethylene]
To a 10 L autoclave containing the macromonomer produced above, 1.4 mL of a hexane solution (0.714 mol / L) of triisobutylaluminum and diphenylmethylene (1-cyclopentadienyl) (2,7-di-t-butyl) -9-Fluorenyl) zirconium dichloride 7 μmol was introduced, and the internal temperature of the autoclave was raised to 60 ° C., followed by stirring for 30 minutes. Subsequently, after raising the internal temperature of the autoclave to 90 ° C., an ethylene / hydrogen mixed gas (2,000 ppm of hydrogen) was introduced until the partial pressure became 0.3 MPa to initiate polymerization. During the polymerization, an ethylene / hydrogen mixed gas was continuously introduced so that the partial pressure was maintained at 0.3 MPa. The polymerization temperature was controlled at 90 ° C. After 173 minutes from the start of polymerization, the internal pressure of the autoclave was released, and the contents were suction filtered. After drying, 865 g of polymer was obtained. The obtained polyethylene had an MFR of 4.3 g / 10 min, a density of 960 kg / m ³ , an M _w of 9.6 × 10 ⁴ , an M _w / M _n of 6.6, and a long chain branching number of 0.03. / 1,000 carbon, the peak of the endothermic curve obtained in the temperature rise measurement with a differential scanning calorimeter was one. The SFD, Olzen bending stiffness, and Izod impact strength of the obtained polyethylene were measured according to the evaluation methods described above. As a result, the obtained polyethylene showed good fluidity, and the injection-molded product also had excellent physical properties. The physical properties are shown in Tables 1-4.

Example 2
[Production of polyethylene]
In a 10 L autoclave containing the macromonomer produced in Example 1, 1.4 mL of a hexane solution (0.714 mol / L) of triisobutylaluminum and diphenylmethylene (1-cyclopentadienyl) (2,7-di-t -Butyl-9-fluorenyl) zirconium dichloride 7 μmol was introduced, and the internal temperature of the autoclave was raised to 90 ° C. Polymerization was initiated by introducing an ethylene / hydrogen mixed gas (hydrogen 3,000 ppm) until the partial pressure reached 0.3 MPa. During the polymerization, an ethylene / hydrogen mixed gas was continuously introduced so that the partial pressure was maintained at 0.3 MPa. The polymerization temperature was controlled at 90 ° C. 194 minutes after the start of polymerization, the internal pressure of the autoclave was released, and the contents were suction filtered. After drying, 870 g of polymer was obtained. The obtained polyethylene has an MFR of 6.1 g / 10 min, a density of 958 kg / m ³ , an M _w of 9.7 × 10 ⁴ , an M _w / M _n of 7.2, and a long chain branching number of 0.03. / 1,000 carbon, the peak of the endothermic curve obtained in the temperature rise measurement with a differential scanning calorimeter was one. The obtained polyethylene had good fluidity, and the injection molded article also had excellent physical properties. The physical properties are shown in Tables 1-4.

Example 3
[Production of polyethylene]
To the 10 L autoclave containing the macromonomer produced in Example 1, 5 mL of a hexane solution (0.714 mol / L) of triisobutylaluminum and 50 μmol of diphenylmethylene (1-indenyl) (9-fluorenyl) zirconium dichloride were introduced. Was raised to 85 ° C. Ethylene was introduced until the partial pressure reached 0.3 MPa to initiate polymerization. During the polymerization, ethylene was continuously introduced so that the partial pressure was maintained at 0.3 MPa. The polymerization temperature was controlled at 85 ° C. 126 minutes after the start of polymerization, the internal pressure of the autoclave was released, and the contents were suction filtered. After drying, 805 g of polymer was obtained. The obtained polyethylene had an MFR of 8.0 g / 10 min, a density of 972 kg / m ³ , an M _w of 8.6 × 10 ⁴ , an M _w / M _n of 6.4, and a long chain branching number of 0.03. / 1,000 carbon, the peak of the endothermic curve obtained in the temperature rise measurement with a differential scanning calorimeter was one. The obtained polyethylene had good fluidity, and the injection molded article also had excellent physical properties. The physical properties are shown in Tables 1-4.

Comparative Example 1
A commercially available high-density polyethylene (Nipolon Hard # 2000, manufactured by Tosoh Corp., MFR = 15 g / 10 min, density 960 kg / m ³ ) having one endothermic curve peak obtained in temperature rise measurement with a differential scanning calorimeter. ), Injection molding was attempted in the same manner as in Example 1, but the fluidity was insufficient and the impact strength of the molded article was insufficient. The physical properties are shown in Tables 1-4.

Comparative Example 2
A commercially available high-density polyethylene (Nipolon Hard # 2500, manufactured by Tosoh Corp., MFR = 8 g / 10 min, density 961 kg / m ³ ) having one peak of the endothermic curve obtained in the temperature rise measurement with a differential scanning calorimeter. ), Injection molding was attempted in the same manner as in Example 1, but the fluidity was insufficient and the impact strength of the molded article was insufficient. The physical properties are shown in Tables 1-4.

Comparative Example 3
A commercially available low density polyethylene (Petrocene 203, manufactured by Tosoh Corporation, MFR = 8 g / 10 min, density 919 kg / m ³ ) having one peak of the endothermic curve obtained in the temperature rise measurement with a differential scanning calorimeter. Was used, and injection molding was attempted in the same manner as in Example 1, but the flowability was sufficient, but the rigidity of the molded body was insufficient. The physical properties are shown in Tables 1-4.

Comparative Example 4
A commercially available metallocene linear low density polyethylene (affinity PT1450, manufactured by Dow Chemical Co., MFR = 7.5 g / 10 min), which has one peak of the endothermic curve obtained in the temperature rise measurement with a differential scanning calorimeter. Although injection molding was attempted by the same method as in Example 1 using a density of 902 kg / m ³ ), in addition to insufficient fluidity, the molded article had insufficient rigidity. The physical properties are shown in Tables 1-4.

Claims (4)

A polyethylene resin injection-molded article obtained by injection molding a polyethylene resin that satisfies the following requirements (A) to (D).
(A) The density is 890 kg / m ³ or more and 980 kg / m ³ or less,
(B) The number of long-chain branches having 6 or more carbon atoms is 0.01 to 3 per 1,000 carbon atoms,
(C) Melt tension (MS ₁₉₀ ) (mN) measured at 190 ° C. and MFR (g / 10 min, 190 ° C.) with a load of 2.16 kg are represented by the following formula (1)
MS ₁₉₀ > 22 × MFR ^−0.88 (1)
And the melt tension (MS ₁₆₀ ) (mN) measured at 160 ° C. and the MFR (g / 10 min, 190 ° C.) with a load of 2.16 kg satisfy the following formula (2):
MS ₁₆₀ > 110-110 × log (MFR) (2)
(D) There is one peak of the endothermic curve obtained in temperature rise measurement with a differential scanning calorimeter. An ethylene polymer having a vinyl group at a terminal obtained by polymerizing ethylene, or an ethylene copolymer having a vinyl group at a terminal obtained by copolymerizing ethylene and an olefin having 3 or more carbon atoms;
(E) M _n is 2,000 or more,
(F) A polyethylene resin obtained by polymerizing ethylene and optionally an olefin having 3 or more carbon atoms is used in the presence of a macromonomer having M _w / M _n of 2 or more and 5 or less. Item 2. An injection molded article made of polyethylene resin according to Item 1. (A) 'a polyethylene based resin injection molded article according to claim 1 or 2 in which density is characterized by using a polyethylene-based resin is 920 kg / ^{m 3} or more 965 kg / ^{m 3} or less. (G) Polyethylene resin injection molding according to claims 1 to 3, wherein a polyethylene resin having an MFR at 190 ° C and a load of 2.16 kg is 1 g / 10 min to 50 g / 10 min. body.