JP2012229355A - Polyethylene resin composition having excellent moldability and long term property and suitable for bottle cap, and bottle cap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new polyethylene resin composition for a bottle cap, which has excellent rigidity and excellent high speed moldability without deteriorating the environmental stress crack resistance (stress crack resistance) capable of withstanding the internal pressure of a beverage bottle, and further has excellent required performance in opening torque or the like.SOLUTION: The polyethylene resin composition satisfies the following requirements (a) to (d): (a) the MFR of a cord D measured under the conditions satisfying a temperature of 190°C and a load of 2.16 kg according to JIS K7210 is 3.5 to 10.0 g/10 min; (b) the density measured according to JIS K7112 is 963 to 967 Kg/m; (c) the isothermal crystallization time of the peak in 124°C obtained by crystallization time measurement according to DSC is ≤10 min; and (d) f50 rupture time obtained by an environmental stress crack resistance (ESCR) test is ≥20 hr.

Description

  The present invention relates to a polyethylene resin composition suitable for a cap and a bottle cap formed by molding them. More specifically, as a preferred embodiment thereof, a composition comprising a polyethylene resin obtained by using a specific polymerization catalyst, which is capable of withstanding an internal pressure of a beverage bottle or the like when used in a bottle cap. It is a polyethylene resin composition that combines excellent rigidity and excellent high-speed moldability without reducing the properties (stress crack resistance, hereinafter referred to as ESCR). Furthermore, it is related with the polyethylene resin composition which is excellent also in physical property balances, such as opening torque property.

  Conventionally, most bottle caps used in PET bottles such as carbonated drinks, soft drinks, and tea are made of aluminum or polypropylene as materials that can withstand the heat resistance during bottle filling and the internal pressure of the bottle. there were. However, recently, bottle caps for low temperature filling (aseptic) have been mainly made of polyethylene because of problems such as cost reduction, molding cycle shortening, and recycling.

  The performance required for the polyethylene resin composition that is the material of the bottle cap is rigidity, fluidity, and stress crack resistance. Recently, the shape of bottle caps has become more complex, and there is a strong demand to balance these performances to a high degree. And in order to improve high-speed moldability further, in addition to a resin composition with high fluidity, there is a high need for a resin composition having an increased crystallization speed. Molding methods for producing caps include injection molding and compression molding. Especially in compression molding, in order to increase productivity, the discharge rate of the extruder is increased and the rotation speed of the turntable is increased. It is necessary to raise. Increasing the rotational speed resulted in a shorter cooling time, resulting in insufficient cooling. If the resin used has high fluidity and a high crystallization speed, it can be molded at high speed. That is, when the resin used is highly fluid, not only the load on the extruder is low and the discharge rate can be increased, but also the resin temperature can be lowered. Further, if the crystallization speed can be further increased, the time required for cooling the resin is shortened, and the threaded portion can be molded without being crushed when the mold is removed.

In general, however, the molecular weight is lowered in order to increase fluidity, but this low molecular weight tends to lower the stress crack resistance when the cap is formed. In this case, in order to maintain the stress cracking property, it is necessary to reduce the density of the resin composition. Decreasing the density means lowering the rigidity of the bottle cap, and when it is used as a cap, deformation is likely to occur due to external force or internal pressure, and at the same time, the coefficient of friction becomes large and slipperiness is poor. Therefore, there arises a problem that the force (opening torque) when opening the cap becomes higher than necessary. For this reason, high-speed moldability has been maintained at the expense of some ESCR properties in order to maintain slipperiness, especially for applications that require high-speed moldability, such as tea applications.
On the other hand, high ESCR properties are required for hot applications and applications where internal pressure is applied. However, in order to maintain slipperiness, ESCR properties are secured by reducing fluidity, so productivity is sacrificed at the expense of high-speed moldability. Was down.

  Furthermore, caps are also required to be thinner from the viewpoint of reducing environmental burden and reducing costs by reducing the amount of resin, and rigidity is required to suppress deformation due to internal pressure etc. with thinner caps than before. Therefore, further densification is required.

  In this way, polyethylene bottle caps for PET bottles are divided into two types that emphasize high-speed molding and two types that emphasize ESCR. Therefore, two types of resin with different physical properties must be prepared, so efficient production can be achieved. The integration of both types was desired. Conventionally, however, a polyethylene resin that has a high MFR and a high crystallization speed to give sufficient high-speed moldability, and has a high ESCR property that can withstand heating and an increase in internal pressure, and satisfies all performances such as maintaining a high density. The composition never existed.

  There are resin compositions that have high fluidity and excellent moldability, and can shorten the cycle and increase production efficiency (see, for example, Patent Documents 1, 2, and 3). However, high fluidity and ESCR are in a contradictory relationship, and ESCR cannot reach the required level at all in systems higher than the required MFR.

  Similarly, there is a resin composition that has high fluidity and excellent moldability, can shorten the cycle, increase production efficiency, and is excellent in stress crack resistance, rigidity and impact resistance balance (for example, (See Patent Documents 4, 5, and 6). However, the required rigidity was insufficient because the density was kept low to maintain the balance. In addition, resin compositions with a balance of moldability, high fluidity, rigidity, impact resistance, ESCR property and slipperiness have been proposed (for example, Patent Documents 7 and 8), but the density is still insufficient and the ESCR is barely available. For some reason, a further increase in density leads to a decrease in ESCR.

  A polyethylene resin composition for containers, which is excellent in resistance to doming cracking as a test under environmental stress, and excellent in rigidity and moldability, has been proposed (for example, see Patent Document 9). However, in order to balance the above physical properties, the density and MFR are kept low, and not all the required characteristics are satisfied.

  Furthermore, it has excellent rigidity and excellent high-speed moldability without lowering ESCR, and when used for bottle caps, it has no anisotropy, excellent dimensional stability, and requirements for opening torque, etc. A novel polyethylene resin composition for bottle caps having excellent performance has been proposed (see, for example, Patent Documents 10 and 11). Although this composition satisfies the desired characteristics, it has been required to further speed up high speed molding by improving the crystallization speed.

  In order to improve productivity in the recent compression molding, the crystallization speed of the polyethylene resin is important. Particularly, the ESCR-oriented resin is insufficient in crystallization speed, which hinders the speeding up.

  Therefore, by selecting a polyolefin resin material that has a high crystallization speed, it is possible to achieve a high molding cycle, and it is excellent in plugging performance, plugging performance, moldability, high fluidity, and high-speed molding, and a balance between rigidity and impact resistance. In addition, a resin composition excellent in ESCR property and slip property has been proposed (see, for example, Patent Document 12). There was a problem that the crystallization speed was high, the fluidity was high, and the ESCR property achieved the required physical properties, but the rigidity was insufficient.

  There is also a proposal to improve the ESCR property by changing the polyethylene polymerization catalyst to a metallocene catalyst (see, for example, Patent Document 13). However, although the balance between the ESCR property and the impact property was improved, there was still a demand for improvement in the crystallization speed.

JP 2000-248125 A JP 2001-180704 A JP 2002-60559 A JP 2000-159250 A Japanese Patent Laid-Open No. 2008-19404 JP 2009-18868 A Japanese Patent Laying-Open No. 2005-320526 Japanese Patent Laid-Open No. 2004-123955 JP 2002-348326 A JP 2004-244557 A JP 2007-284667 A JP 2006-290944 A Japanese Patent Laid-Open No. 11-106432

  The present invention overcomes the limitations of the prior art, and when producing a bottle cap, high flowability and high crystallization speed enable high-speed molding, while maintaining sufficient rigidity as a cap, The present invention provides a polyethylene resin composition for a bottle cap that is excellent in environmental stress crack resistance (stress crack resistance) that can withstand the internal pressure of a beverage bottle. Furthermore, since the molecular weight distribution is narrow, the resin composition can be easily provided with features such as low anisotropy, excellent dimensional stability, and excellent opening torque.

  The inventors of the present invention have conducted extensive research to overcome the limitations of the prior art, and as a result, only when the polyethylene resin composition satisfies specific physical property requirements, it has high fluidity and crystallization during bottle cap production. Since the speed is high, high-speed molding is possible, and it has been found that it has excellent environmental stress crack resistance (stress crack resistance) that can withstand the internal pressure of a beverage bottle while maintaining sufficient rigidity as a cap. It came to. Further, in a preferred embodiment of the present invention, it has been found that since the molecular weight distribution is narrow, the anisotropy is small and the physical property balance such as dimensional stability and opening torque is excellent.

（式中、Ｍ_１及びＭ_２は、カルシウム、ストロンチウム、リチウム、亜鉛、マグネシウム及び一塩基性アルミニウムからなる群より互いに独立して選択され、更に、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_５、Ｒ_６、Ｒ_７、Ｒ_８、Ｒ_９、及びＲ_１０は、水素及びＣ_１〜Ｃ_９アルキルからなる群より互いに独立して選択され、更に、互いに隣接して位置した何れか２つのＲ_３〜Ｒ_１０アルキル基は任意に結合して炭素環を形成していてもよい。）
［５］上記［１］から［４］のいずれかに記載のポリエチレン樹脂組成物を成形してなるボトルキャップ
［６］前記ポリエチレン樹脂組成物を構成するポリエチレン樹脂の少なくとも一部を、担持型幾何拘束型シングルサイト触媒を用いるスラリー重合法により重合する工程を有することを特徴とする、上記［１］〜［４］のいずれかに記載のポリエチレン樹脂組成物の、製造方法。 That is, the present invention relates to the following [1] to [6].
[1] A polyethylene resin composition that satisfies the following requirements (a) to (d):
(A) According to JIS K7210, the MFR of Code D measured under conditions of a temperature of 190 ° C. and a load of 2.16 kg is 3.5 to 10.0 g / 10 min;
(B) the density measured according to JIS K7112 is 963 to 967 kg / m ³ ;
(C) Isothermal crystallization time of the peak at 124 ° C. obtained by crystallization time measurement by DSC is 10 minutes or less: and
(D) f50 fracture time obtained by an environmental stress crack test (ESCR) is 20 hours or more.
[2] The polyethylene resin composition according to the above [1], wherein the isothermal crystallization time of a peak at 124 ° C. obtained by crystallization time measurement by DSC is 5 minutes or less.
[3] The polyethylene resin composition comprises a low molecular weight component (A) and a high molecular weight component (B), and the proportion of the high molecular weight component (B) is 25 to 45% by mass. The polyethylene resin composition according to [1] or [2] above.
[4] The polyethylene according to any one of [1] to [3], further comprising 10 to 2000 ppm (by mass) of a crystal nucleating agent having a structure represented by the following general formula (1): Resin composition.

(Wherein M ₁ and M ₂ are independently selected from the group consisting of calcium, strontium, lithium, zinc, magnesium and monobasic aluminum, and further R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , and R ₁₀ are independently selected from the group consisting of hydrogen and C ₁ -C ₉ alkyl, and any one of the two located adjacent to each other Two R _{3 to} R ₁₀ alkyl groups may be optionally combined to form a carbocycle.)
[5] A bottle cap formed by molding the polyethylene resin composition according to any one of [1] to [4]. [6] At least a part of the polyethylene resin constituting the polyethylene resin composition is supported by a supported geometry. The method for producing a polyethylene resin composition according to any one of the above [1] to [4], comprising a step of polymerizing by a slurry polymerization method using a constrained single site catalyst.

  According to the present invention, it has excellent rigidity and excellent high-speed moldability without reducing environmental stress crack resistance (stress crack resistance) that can withstand the internal pressure of beverage bottles, and has a high crystallization speed and high cycle. In addition, when used as a cap, a novel polyethylene resin composition for bottle caps with excellent required performance such as opening torque could be provided. Therefore, the polyethylene resin composition of the present invention can be used for both ESCR-oriented type caps and high-speed molding-oriented type caps that have been divided into two types according to conventional applications. That is, the bottle cap of the present invention has sufficient environmental stress crack resistance (stress crack resistance) that can withstand the internal pressure of a beverage bottle, has excellent rigidity and excellent high-speed moldability, and has a high crystallization speed and high speed. Since it has features and effects excellent in cycleability, it can be integrated with two types of cap grades so far, making it ideal as a bottle cap application for beverage containers.

Hereinafter, the present invention will be described in more detail.
The polyethylene resin constituting the polyethylene resin composition according to the present invention can be produced by a vessel type slurry polymerization method using a Ziegler type catalyst, a Phillips type catalyst, a supported geometrically constrained single site catalyst, and particularly a supported type. It is preferable to use a geometrically constrained single site catalyst. The polyethylene resin is preferably produced by polymerizing ethylene and one or more comonomers selected from α-olefins having 3 to 20 carbon atoms in such a ratio that the desired density is obtained. .
At that time, in order to obtain a desired molecular weight and MFR, a molecular weight regulator such as hydrogen may be used.

  A low molecular weight component (A) composed of an ethylene homopolymer and a high molecular weight component (B) composed of a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, which is a preferred embodiment of the present invention. The polyethylene resin composition is composed of a low molecular weight component (A) and a high molecular weight component (B) which are separately polymerized and blended at a predetermined blending ratio, or powder blend or pellet blend, or connected in series. Either a multi-stage polymerization method obtained by successively polymerizing in two or more polymerization vessels or a method of blending each component obtained by simultaneous polymerization in two or more polymerization vessels connected in parallel in a slurry state or the like May be manufactured.

  The high molecular weight component (B) and the low molecular weight component (A) used in the preferred embodiment of the present invention are based on the relative molecular weight of each polyethylene resin constituting the polyethylene resin composition. ) Refers to a component having a higher molecular weight among the respective polyethylene resins.

Among them, the multi-stage polymerization method obtained by successively polymerizing in two or more polymerization vessels connected in series is most preferable from the viewpoint that the physical properties can be stably controlled and high-quality polyethylene is produced.
In particular, it is more preferable to polymerize the low molecular weight component (A) in the first stage polymerization tank and polymerize the high molecular weight component (B) in the second stage polymerization tank. In order to achieve both physical properties such as density and ESCR and moldability, in the first stage polymerization tank for polymerizing the low molecular weight component (A), an ethylene homopolymer is polymerized without feeding a comonomer, It is preferable to feed the comonomer to the second stage polymerization tank for polymerizing the high molecular weight component (B) to polymerize the copolymer.

  Although the high molecular weight component (B) can be polymerized in the first stage polymerization tank and the low molecular weight component (A) can be polymerized in the second stage polymerization tank, the unreacted comonomer remains when the comonomer is fed in the first stage. However, it is fed to the second stage polymerization tank as it is, and there is a possibility that a comonomer is also inserted into a low molecular weight component to form a copolymer, and it is impossible to increase the ESCR while keeping the density high. However, when trying to prevent such a phenomenon, the control becomes complicated.

  Further, the polyethylene resin composition according to a preferred embodiment of the present invention is preferably a low molecular weight component (A) composed of an ethylene homopolymer of 75 to 55% by mass, preferably ethylene and an α- having 3 to 20 carbon atoms. The high molecular weight component (B) made of a copolymer with olefin is preferably 25 to 45% by mass. More preferably, the low molecular weight component (A) is 60 to 70% by mass and the high molecular weight component (B) is 30 to 40% by mass. Preferably, when the amount of the low molecular weight component (A) made of an ethylene homopolymer is 60% by mass or more, the fluidity is sufficient, the extruder load is lowered, the crystallization speed is improved, and the high-speed moldability is excellent. In the case of 70% by mass or less, the high molecular weight component (B) is sufficient, and the ESCR is excellent.

  Ratio of low molecular weight component (A) preferably consisting of ethylene homopolymer and high molecular weight component (B) preferably consisting of a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms in two-stage continuous polymerization Can be ascertained from the amount of resin produced. For example, a value obtained by subtracting the amount of polymer obtained in the first stage polymerization tank from the finally obtained polymer production amount corresponds to the amount of polymer obtained in the second stage polymerization tank.

The density of the low molecular weight component (A) preferably made of an ethylene homopolymer is preferably 971 kg / m ³ or more. More preferably, the density is 973 kg / m ³ or more. Thereby, the density of the high molecular weight component (B) preferably made of a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms can be reduced, and many comonomer can be added to the high molecular weight component (B). Therefore, it is possible to maintain high physical properties such as ESCR. Preferably, when the density of the low molecular weight component (A) comprising an ethylene homopolymer is less than 971 kg / m ^{3, the} high molecular weight component preferably comprising a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms Since the density of (B) cannot be lowered sufficiently, the ESCR may be lowered.

  The MFR of the low molecular weight component (A) code D used in the preferred embodiment of the present invention, preferably made of an ethylene homopolymer, is usually 100 to 500 g / 10 min, preferably 200 to 400 g / 10 min. . Since fluidity is ensured by this low molecular weight component (A), when it is 100 g / 10 min or more, the resin pressure of the extruder does not increase so much during cap molding, which is advantageous for high-speed molding. On the other hand, when it is 500 g / 10 min or less, low molecular weight components such as wax are reduced, and there is no fear of dissolving into the beverage in the bottle, which is preferable.

  The resin composition of the present invention has a code D MFR (JIS K7210: 1999, 190 ° C., 2.16 kg load) in the range of 3.5 to 10.0 g / 10 min, preferably 5.0 to 10. The range is 0 g / 10 min, and more preferably 5.0 to 7.0 g / 10 min. When the MFR value of Code D is 3.5 g / 10 min or more, not only sufficient fluidity can be obtained during molding, but also fluctuations such as an increase in resin temperature during molding are small, and high-speed moldability is excellent. Moreover, when it is 10.0 g / 10min or less, the stress crack resistance which prevents the stress crack which may lead to a cap crack is enough, and it is practically used.

  Moreover, it is preferable that the value of MFR (JIS K7210: 1999, 190 degreeC, 21.6 kg load) of the code | cord | chord G is 120-500 g / 10min. More preferably, it is 160-400 g / 10min. If this value is 120 g / 10 min or more, high-speed moldability is excellent, and if it is 500 g / 10 min or less, good stress crack resistance (ESCR) is obtained.

  High-speed formability here means that the load on the extruder is reduced under the same conditions (especially at the same temperature), the discharge speed can be increased, and the temperature can be lowered so that the load on the extruder is the same. I can judge.

  The ratio of the MFR of code G to the MFR of code D, (the MFR of code G / the MFR of code D), which is the physical property described below, is generally a numerical value correlated with the molecular weight distribution. As the distribution becomes wider, the value of (MFR of code G / MFR of code D) tends to increase, but the polyethylene resin composition of the present invention (MFR of code G / MFR of code D) is 50 or more. It is preferably 100 or less, more preferably 80 or more and 100 or less. When this value is 50 or more, the load on the extruder at the time of molding becomes low, which is preferable in terms of high-speed moldability, and the ESCR property is sufficient. On the other hand, when it is 100 or less, the impact strength is sufficient, the flow mark does not appear on the top surface of the cap molded product, the cap shrinkage rate of the cap has no anisotropy, and the roundness of the cap increases.

The density of the resin composition of the present invention measured according to JIS K7211 is in the range of 963 to 967 kg / m ³ . In order to improve the stress crack resistance, it is effective to reduce the density of the resin. However, in the resin composition for bottle caps, when the density is 963 kg / m ³ or more, the rigidity of the cap is sufficient. Thus, it is possible to effectively suppress problems such as deformation when being loaded into the bottle and deformation of the cap when the bottle filled with the beverage is stored at a high temperature. In addition, there is a problem that the screw part is easy to slide with the bottle body side, and the force (opening torque) when opening the cap is too high to allow the child or woman to open the cap effectively. Can be suppressed. On the other hand, when it is 967 kg / m ³ or less, sufficient ESCR can be maintained.

  Further, the polyethylene resin composition of the present invention has an environmental stress crack resistance (hereinafter referred to as ESCR) measured by a constant strain environmental stress crack test method described in JIS K6760 for 20 hours or more. As a specific measurement method, a 10% by weight aqueous solution of Igepal CO-630 manufactured by Rhodia Nikka Co., Ltd. is used as a test solution, and the probability of cracking due to environmental stress is 50% (hereinafter referred to as f50). Was measured as an ESCR value. The unit is time. If this value is 20 hours or longer, the possibility of the cap bursting due to the internal pressure of the bottle is low. Moreover, even when the bottle is excessively tightened when loaded into the bottle, cracks are rarely generated when stored for a long time.

  Since the polyethylene resin composition of the present invention has a high density, it has rigidity when molded into a cap, and deformation due to the internal pressure of the bottle is effectively suppressed. One index for evaluating rigidity is measurement of tensile yield stress. This can be measured using an injection molded piece molded at 210 ° C. as a sample in accordance with the method described in JIS K7161. A preferred range is 25-30 MPa. If it is 25 MPa or more, there is little risk of deformation and leakage of the beverage even when the internal pressure of the bottle rises. When the pressure is 30 MPa or less, sufficient ESCR is obtained.

A preferred embodiment of the polyethylene resin composition of the present invention is preferably a low molecular weight component (A) which is an ethylene homopolymer having a narrow molecular weight distribution and a high molecular weight component (B) which is preferably an ethylene copolymer having a narrow molecular weight distribution. Because it consists of, it has excellent impact resistance. The impact resistance can be evaluated, for example, by determining the Charpy impact strength described in JIS K7111. The Charpy impact strength is preferably in the range of 4~7kJ / m ^2, shows a sufficient drop impact strength at 4 kJ / m ² or more, when dropped bottles, it may no leak beverage cracked cap . On the other hand, when the density is 7 kJ / m ² or less, the density is appropriate and the ESCR is sufficiently long.

  The index (Mw / Mn) indicating the molecular weight distribution of the polyethylene resin composition of the present invention can be determined by preparing a calibration curve from a standard polystyrene sample using high temperature gel permeation chromatography (high temperature GPC). . The value of Mw / Mn is preferably 8.0 to 12.0. More preferably, it is the range of 10.0-12.0. When Mw / Mn is 8.0 or more, the high molecular weight component is sufficiently present, so that the decrease in ESCR can be suppressed. When Mw / Mn is 12.0 or less, since there are few low molecular weight components like a wax, it can prevent melt | dissolution to the drink in a bottle. Further, since the molecular weight distribution is not excessively widened, the impact strength is maintained, and the cap is not easily broken by a drop impact. Furthermore, since the molecular weight distribution is not excessively wide, anisotropy occurs during molding, the roundness of the cap decreases, and the phenomenon such as non-uniform adhesion to the bottle can be suppressed.

  The isothermal crystallization time of the peak at 124 ° C. obtained by measuring the isothermal crystallization time by DSC of the polyethylene resin composition of the present invention is 10 minutes or less, and preferably 5 minutes or less. The crystallization speed affects the time from injection to solidification in injection molding and solidification, and in compression molding, the length of time from compression to solidification after placing resin in the mold. Solidify quickly. In recent injection molding and compression molding, the cooling time until the molded product is taken out from the injection or compression is limited by the high cycle, and it is necessary to advance the solidification time in order to accelerate the molding cycle. If the product is taken out without being sufficiently solidified, the mold structure of the cap is a so-called unreasonable structure, so that deformation called screw dripping occurs and the commercial value is impaired. Therefore, the long crystallization time hinders the high cycle when such a resin is used. If the crystallization time is 10 minutes or less, a sufficiently short high cycle property can be achieved.

Next, the specific catalyst used in the manufacturing method which is preferable embodiment of this invention is demonstrated.
The supported geometrically constrained single site catalyst (hereinafter also referred to as “metallocene supported catalyst”) used in the above polymerization method is (a) a carrier material, (b) an organoaluminum, and (c) a cyclic η-binding anion. It is prepared from a transition metal compound having a ligand and (d) an activator capable of reacting with the transition metal compound having the cyclic η-bonding anion ligand to form a complex that exhibits catalytic activity. Japanese Patent Laid-Open No. 11-166209 discloses that titanium is used as a transition metal atom in the transition metal compound having a cyclic η-bonding anion ligand (c).

The carrier substance (a) may be either an organic carrier or an inorganic carrier. As the organic carrier, preferably (1) an α-olefin polymer having 2 to 20 carbon atoms, such as polyethylene, polypropylene, polybutene-1, ethylene / propylene copolymer, ethylene / hexene-1 copolymer, Propylene / butene-1 copolymer, ethylene / hexene-1 copolymer, etc., (2) aromatic unsaturated hydrocarbon copolymer, such as polystyrene, styrene / divinylbenzene copolymer, and (3) polar Group-containing polymer polymers such as polyacrylic acid esters, polymethacrylic acid esters, polyacrylonitrile, polyvinyl chloride, polyamide, polycarbonate and the like can be mentioned. Examples of the inorganic carrier include (4) inorganic oxides such as SiO ₂ , Al ₂ O ₃ , MgO, TiO ₂ , B ₂ O ₃ , CaO, ZnO, BaO, ThO, SiO ₂ —MgO, SiO ₂ —Al ₂ O. ₃ , SiO ₂ —MgO, SiO ₂ —V ₂ O _5, etc. (5) Inorganic halogen compounds such as MgCl ₂ , AlCl ₃ , MnCl _2, etc., (6) Inorganic carbonates, sulfates, nitrates such as Na ₂ CO ₃ , K ₂ CO ₃ , CaCO ₃ , MgCO ₃ , Al ₂ (SO ₄ ) ₃ , BaSO ₄ , KNO ₃ , Mg (NO ₃ ) _2, etc. (7) Hydroxides such as Mg (OH ) ₂ , Al (OH) ₃ , Ca (OH) _{3 and the} like. The most preferred carrier is SiO _2.

  The particle size of the carrier is arbitrary, but generally 1 μm to 3000 μm. From the viewpoint of particle dispersibility, the particle size distribution is preferably in the range of 10 to 1000 μm. The particle size was measured with a laser diffraction particle size distribution measuring apparatus using a flow cell.

The carrier material is treated with (a) an organoaluminum compound as necessary. As a preferred organoaluminum compound, a linear or cyclic polymer represented by the general formula (—Al (R) O—) _n (wherein R is a hydrocarbon group having 1 to 10 carbon atoms, Including those substituted with a partial halogen atom and / or RO group, where n is the degree of polymerization and is 5 or more, preferably 10 or more.) Specific examples include R as a methyl group, an ethyl group, Examples thereof include methylalumoxane, ethylalumoxane, and isobutylethylalumoxane, which are isobutylethyl groups.

  Still other organoaluminum compounds include trialkyl aluminum, dialkyl halogeno aluminum, sesquialkyl halogeno aluminum, armenyl aluminum, dialkyl hydroaluminum, sesquialkyl hydroaluminum and the like.

  Specific examples of other organoaluminum compounds include trialkylaluminum such as trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, and trioctylaluminum, dialkylhalogenoaluminum such as dimethylaluminum chloride and diethylaluminum chloride, and sesquimethylaluminum. Examples thereof include sesquialkyl halogenoaluminums such as chloride and sesquiethylaluminum chloride, ethylaluminum dichloride, diethylaluminum hydride, diisobutylaluminum hydride, and sesquiethylaluminum hydride. Of these, trimethylaluminum, triethylaluminum, triisobutylaluminum, diethylaluminum hydride and diisobutylaluminum hydride are most preferred.

The supported catalyst includes, for example, a transition metal compound having (c) a cyclic η-bonding anion ligand represented by the following general formula (2).
L ₁ MX _p X ′ _q − (2)

In the general formula (2), M is the number of oxide is one or more ligands L and eta ⁵ binding + 2, + 3, a + 4 long period periodic table group 4 transition metals, particularly transition metals As titanium, titanium is preferable.

  L is a cyclic η-bonding anion ligand, each independently a cyclopentadienyl group, an indenyl group, a tetrahydroindenyl group, a fluorenyl group, a tetrahydrofluorenyl group, or an octahydrofluorenyl group. These groups are hydrocarbon groups containing up to 20 non-hydrogen atoms, halogens, halogen-substituted hydrocarbon groups, aminohydrocarbyl groups, hydrocarbyloxy groups, dihydrocarbylamino groups, dihydrocarbylphosphino groups, silyl groups Optionally having 1 to 8 substituents each independently selected from an aminosilyl group, a hydrocarbyloxysilyl group, and a halosilyl group, and further two hydrocarbyls containing up to 20 non-hydrogen atoms. Diyl, halohydrocarbadiyl, hydrocarbyleneoxy, hydrocarbyleneamino, di Diyl, Haroshirajiiru, may be linked by a divalent substituent such as an aminosilane.

  Each X is independently a monovalent anionic σ-bonded ligand having up to 60 non-hydrogen atoms, a divalent anionic σ-bonded ligand that binds to M divalently, or M and L Are each a divalent anion σ-bonded ligand that binds with one valence.

  X 'is a neutral Lewis base coordination compound independently selected from phosphine, ether, amine, olefin and / or conjugated diene having 4 to 40 carbon atoms.

  L is an integer of 1 or 2. p is an integer of 0, 1 or 2, and X is a monovalent anionic σ-bonded ligand or a divalent anionic σ-bonded coordination which binds to M and L each with a single valence. P is less than the formal oxidation number of M when it is a child, or p is smaller than the formal oxidation number of M when X is a divalent anionic σ-bonded ligand that binds to M in a divalent manner. Less than l + 1. Q is 0, 1 or 2. The transition metal compound (c) is preferably 1 = 1 in the general formula (2).

一般式（３）中、Ｍは形式酸化数＋２、＋３又は＋４のチタニウム、ジルコニウム、ハフニウムであり、特にチタニウムが好ましい。 For example, a suitable example of the transition metal compound (c) is represented by the following general formula (3).

In the general formula (3), M is titanium, zirconium or hafnium having a formal oxidation number of +2, +3 or +4, and titanium is particularly preferable.

Each R ³ is independently hydrogen, a hydrocarbon group, a silyl group, a germyl group, a cyano group, a halogen, or a composite group thereof, and each can have up to 20 non-hydrogen atoms. Further, adjacent R ³ may be cyclic by forming a divalent derivative such as hydrocarbadiyl, diradii, or germanadyl.

X ″ each independently represents a halogen, a hydrocarbon group, a hydrocarbyloxy group, a hydrocarbylamino group, or a silyl group, each having up to 20 non-hydrogen atoms, and two X ″ having 5 to 5 carbon atoms Thirty neutral conjugated dienes or divalent derivatives may be formed.
Y is -O-, -S-, -NR ^* -, -PR ^* -, and Z is SiR ^* ₂ , CR ^* ₂ , SiR ^* ₂ SiR ^* ₂ , CR ^* ₂ CR ^* ₂ , CR ^* = CR ^* , CR ^* ₂ SiR ^* ₂ or GeR ^* ₂ , where R ^* is each independently an alkyl or aryl group having 1 to 12 carbon atoms. N is an integer of 1 to 3.
Furthermore, as a transition metal compound (c), a more suitable example is represented by the following general formula (4) and the following general formula (5).

In general formulas (4) and (5), each R ³ is independently hydrogen, a hydrocarbon group, a silyl group, a germyl group, a cyano group, a halogen, or a composite group thereof, and each has up to 20 non-hydrogen atoms. Can have. The transition metal M is titanium, zirconium or hafnium, with titanium being preferred.

  The definitions of Z, Y, X and X 'are as described above. p is 0, 1 or 2, and q is 0 or 1. However, when p is 2 and q is 0, the oxidation number of M is +4, and X is halogen, hydrocarbon group, hydrocarbyloxy group, dihydrocarbylamino group, dihydrocarbyl phosphide group, hydrocarbyl sulfide group, silyl group Group or a composite group thereof, having up to 20 non-hydrogen atoms.

  When p is 1 and q is 0, the oxidation number of M is +3, and X is an allyl group, 2- (N, N-dimethylaminomethyl) phenyl group or 2- (N, N-dimethyl). -A stabilized anionic ligand selected from aminobenzyl groups, or the oxidation number of M is +4 and X is a derivative of a divalent conjugated diene, or both M and X are metallocyclopentene groups Is forming.

In addition, when p is 0 and q is 1, the oxidation number of M is +2, and X ′ is a neutral conjugated or non-conjugated diene, optionally substituted with one or more hydrocarbons. Also, the X ′ may contain up to 40 carbon atoms and forms a π-type complex with M. Furthermore, in the present invention, the most preferable examples of the transition metal compound (c) are represented by the following general formula (6) and the following general formula (7).

In general formulas (6) and (7), each R ³ is independently hydrogen or an alkyl group having 1 to 6 carbon atoms. The M is titanium, Y is ^{-O -, - S -, -} NR * -, - PR * - a and, ^{Z *} is _{^{SiR * 2, CR * 2,}} SiR * 2 SiR * 2, CR * 2 _{^{CR * 2, CR * = CR}} *, a _CR * 2 SiR _2, or ^GeR _{* 2,} wherein ^{R *} are each independently hydrogen or a hydrocarbon group, hydrocarbyloxy group, a silyl group, a halogenated alkyl group, halogen Aryl group or a composite group thereof. The R ^* may have up to 20 non-hydrogen atoms, and optionally is Z ^* 2 two medium R ^* s or Z ^* in R ^* and in Y medium R ^* have a circular Also good.

p is 0, 1 or 2, and q is 0 or 1. However, when p is 2 and q is 0, the oxidation number of M is +4, and X is each independently a methyl group or a hydrobenzyl group.
When p is 1 and q is 0, the oxidation number of M is +3 and X is a 2- (N, N-dimethyl) -aminobenzyl group, or the oxidation number of M is +4. X is 2-butene-1,4-diyl.
When p is 0 and q is 1, the oxidation number of M is +2, and X ′ is 1,4-diphenyl-1,3-butadiene or 1,3-pentadiene.
The dienes are examples of asymmetric dienes that form metal complexes, and are actually mixtures of geometric isomers.
Further, the metallocene-supported catalyst includes (d) an activator capable of forming a complex that reacts with a transition metal compound and exhibits catalytic activity. Usually, in a metallocene supported catalyst, the complex formed by the transition metal compound (c) and the activator (d) exhibits a high olefin polymerization activity as a catalytically active species.

Examples of the activator (d) include compounds represented by the following general formula (8).
[L−H] ^{d +} [M _m Q _t ] ^d− (8)
However, in the general formula (8), [L-H] ^{d +} is a proton-provided Bronsted acid, and L is a neutral Lewis base. [M _m Q _t ] ^d- is a compatible non-coordinating anion, M is a metal or metalloid selected from Groups 5 to 15 of the periodic table, and Q is independently a hydride or dialkylamide. Group, halide, alkoxide group, allyloxide group, hydrocarbon group, substituted hydrocarbon group having up to 20 carbon atoms, and Q which is a halide is 1 or less. M is an integer from 1 to 7, t is an integer from 2 to 14, d is an integer from 1 to 7, and t−m = d.

A more preferred example of the activator (d) is a compound represented by the following general formula (9).
^{_{[L-H] d + [}} M m Q w (G u (T-H) r) z] d- - (9)
However, in the general formula (9), [L—H] ^{d +} is a proton-provided Bronsted acid, and L is a neutral Lewis base. Also a _{[M m Q w (G u} (T-H) r) z] d- is a non-coordinating anion compatible, M is a metal or metalloid selected from Group 5 to Group 15 of the periodic table Each Q is independently a hydride, a dialkylamide group, a halide, an alkoxide group, an allyloxide group, a hydrocarbon group or a substituted hydrocarbon group having up to 20 carbon atoms, and the Q as a halide is 1 or less. G is a polyvalent hydrocarbon group having a valence of r + 1 which binds to M and T, and T is O, S, NR or PR, where R is a hydrocarbyl group, a trihydrocarbylsilyl group, a trihydrocarbylgermanium. A group or hydrogen.
M is an integer of 1 to 7, w is an integer of 0 to 7, u is an integer of 0 or 1, r is an integer of 1 to 3, z is an integer of 1 to 8, w + z-m = d.
A more preferred example of the activator (d) is a compound represented by the following general formula (10).
[LH] ⁺ [BQ ₃ Q ^* ] ⁻ − (10)
However, in the general formula (10), [L-H] ^{d +} is a proton-provided Bronsted acid, and L is a neutral Lewis base. [BQ ₃ Q ^* ] ⁻ is a compatible non-coordinating anion, B is a boron atom, Q is a pentafluorophenyl group, and Q ^* has 6 to 6 carbon atoms having one OH group as a substituent. 20 substituted aryl groups.

  Specific examples of non-coordinating anions include triphenyl (hydroxyphenyl) borate, diphenyl-di (hydroxyphenyl) borate, triphenyl (2,4-dihydroxyphenyl) borate, tri (p-tolyl) phenyl (hydroxyphenyl). ) Borate, tris (pentafluorophenyl) (hydroxyphenyl) borate, tris (2,4-dimethylphenyl) (hydroxyphenyl) borate, tris (3,5-dimethylphenyl) (hydroxyphenyl) borate, tris (3,5 -Di-trifluoromethylphenyl) (hydroxyphenyl) borate, tris (pentafluorophenyl) (2-hydroxyethyl) borate, tris (pentafluorophenyl) (4-hydroxybutyl) borate, tris (pentafluoro) Enyl) (4-hydroxy-cyclohexyl) borate, tris (pentafluorophenyl) (4- (4′-hydroxyphenyl) phenyl) borate, tris (pentafluorophenyl) (6-hydroxy-2-naphthyl) borate and the like. Most preferred is tris (pentafluorophenyl) (hydroxyphenyl) borate.

  Specific examples of other preferable compatible non-coordinating anions include borates in which the hydroxy group of the borate exemplified above is replaced with NHR. Here, R is preferably a methyl group, an ethyl group or a tert-butyl group.

  Specific examples of the proton-providing Bronsted acid include, for example, triethylammonium, tripropylammonium, tri (n-butyl) ammonium, trimethylammonium, tributylammonium, and tri (n-octyl) ammonium, diethylmethylammonium. , Dibutylmethylammonium, dibutylethylammonium, dihexylmethylammonium, dioctylmethylammonium, didecylmethylammonium, didodecylmethylammonium, ditetradecylmethylammonium, dihexadecylmethylammonium, dioctadecylmethylammonium, diicosylmethylammonium, Trialkyl group-substituted ammonium cations such as bis (hydrogenated tallow alkyl) methylammonium N, N-dimethylanilinium, N, N-diethylanilinium, N, N-2,4,6-pentamethylanilinium, N, N-dimethylbenzylanilinium, etc. Also suitable are dialkylanilinium cations.

  Examples of the olefin polymerized in the catalyst system used in the preferred embodiment of the present invention include ethylene and α-olefins having 3 to 20 carbon atoms. Typical examples of α-olefins having 3 to 20 carbon atoms include Propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, Vinylcyclohexane and the like can be mentioned, and some of them can be combined and copolymerized.

  As the polymerization solvent, a hydrocarbon solvent usually used for slurry polymerization is used. Specifically, aliphatic hydrocarbons such as hexane and heptane, aromatic hydrocarbons such as benzene, toluene and xylene, and alicyclic hydrocarbons such as cyclohexane and methylcyclohexane alone or a mixture thereof are used. The polymerization temperature is in the range of room temperature to 100 ° C, preferably 50 ° C to 90 ° C. The polymerization pressure is carried out in the range of normal pressure to 100 atm. The molecular weight of the resulting polymer can be adjusted by allowing hydrogen to be present in the polymerization system or changing the polymerization temperature.

  The polyethylene resin composition of the present invention is a resin composition that is excellent in ESCR and has a well-balanced crystallization rate, but it is preferable to add a crystal nucleating agent for higher functionality while maintaining the balance. .

The resin composition of the present invention and the blow bottle formed by blow-molding the composition preferably contain 10 to 2000 ppm (by mass) of a crystal nucleating agent having a structure represented by the following general formula (1).

In the general formula (1), M ₁ and M ₂ are independently selected from the group consisting of calcium, strontium, lithium, zinc, magnesium, and monobasic aluminum, and R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , and R ₁₀ are independently selected from the group consisting of hydrogen and C ₁ -C ₉ alkyl and are located adjacent to each other Any two R _{3 to} R ₁₀ alkyl groups may be optionally combined to form a carbocycle.

As an example, a compound having a structure represented by the following general formula (11) in which R _{1 to} R ₂ are hydrogen can be mentioned, and can be obtained as a product name EXP-20 from Milliken Japan.

  The addition amount of the crystal nucleating agent is preferably 10 ppm or more and 1000 ppm or less, more preferably 30 ppm or more and 500 ppm or less, and further preferably 50 ppm or more and 100 ppm or less with respect to the total mass of the composition. Especially preferably, it is 50 ppm or more and 80 ppm or less. The crystallization rate is sufficiently high at 10 ppm or more, but the ESCR decreases as the amount increases, so it is preferable to adjust the addition amount so that the decrease in ESCR does not become a problem. On the other hand, at 1000 ppm or less, an effect of improving the crystallization speed commensurate with the amount added is observed.

  A bottle cap which is a preferred embodiment of the present invention is suitably molded mainly by injection molding or compression molding (compression molding) using the polyethylene resin composition described above. By using the polyethylene resin composition of the present invention, high-speed molding can be achieved and high cycles can be achieved. Since MFR is high and the crystallization speed is high, it is particularly suitable for high cycle compression molding. Moreover, since it is excellent in ESCR property, it can be used also for the cap used for a hot drink. Conventional polyethylene resins for hot beverage caps have a low MFR and a low crystallization rate in order to enhance the ESCR properties, and especially in compression molding, the resin pressure rise and solidification of the extruder slows down during release. However, by using the resin composition of the present invention, for example, a high cycle can be achieved up to the molding speed of compression molding of caps for tea plastic bottles. This makes it possible to integrate the cap material for tea and hot beverage, which has conventionally been two stands.

  A small amount of a lubricant may be added to improve the cap opening performance. Examples of the lubricant to be added include calcium stearate and magnesium stearate, and the amount added is usually 800 ppm or less, preferably 600 ppm or less, more preferably 300 ppm or less, based on mass.

  In addition to the crystal nucleating agent, a small amount of various additives and fillers may be added to the polyethylene resin composition of the present invention as long as the effects of the present invention are not impaired. In view of suppressing the elution of, it is preferable not to add as much as possible. As the additive used, a phenolic antioxidant is good, and using an antioxidant such as phosphorus or sulfur is not preferable because the taste of the beverage in the bottle may change.

  The amount of the phenolic antioxidant to be added is usually 500 ppm or less, preferably 300 ppm or less, more preferably 100 ppm or less on the mass basis, and from the point of flavor properties, it may not be added at all. Most preferred. Further, when not added at all, it can be used for a cap of a milk drink because it complies with the ordinance of milk and the like.

  “ppm (mass basis)” indicates a proportion of mass, and “1 ppm (mass basis)” indicates 1 g per million of mass per 1 g of mass.

  Antistatic agents, light stabilizers, ultraviolet absorbers, antifogging agents, organic peroxides and the like are preferably not added as much as possible. Examples of the filler include talc, silica, carbon, mica, calcium carbonate, magnesium carbonate, and wood powder. If necessary, it can be added in a masterbatch to use titanium oxide or organic pigment, but it can also reduce flavor, so these additives and fillers, titanium oxide, organic Addition of pigments should be avoided as much as possible.

  The present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

In the present invention and the following examples and comparative examples, the symbols and measurement methods shown are as follows.
(1) MFR (Code D):
It represents a melt index, and was measured according to JIS K7210 under conditions of a temperature of 190 ° C. and a load of 2.16 kg. The unit is g / 10 min.
(2) MFR (Code G):
It represents a melt index, and was measured according to JIS K7210 at a temperature of 190 ° C. and a load of 21.6 kg. The unit is g / 10 min.
(3) MFR (Code G) / (MFR (Code D):
The ratio between the above MFR (code G) and MFR (code D) is represented.
(4) Density:
It measured by D method density gradient tube method according to JISK7112. The unit is kg / m ³ .
(5) Molecular weight distribution (Mw / Mn):
High temperature gel permeation chromatography (GPC) is measured, and can be obtained from the ratio of weight average molecular weight (Mw) and number average molecular weight (Mn) in the obtained molecular weight distribution chart. High-temperature GPC measurement uses Waters Alliance GPCV2000, and the column consists of Showa Denko Co., Ltd. AT-807S (one) and Tosoh Co., Ltd. GMHHR-H (S) HT (two) in series. To the mobile phase under the conditions of trichlorobenzene (TCB), column temperature 140 ° C., flow rate 1.0 ml / min, sample concentration 20 mg / solvent (TCB) 10 ml, sample dissolution temperature 140 ° C., sample dissolution time 1 hour. went.
(6) Environmental stress crack resistance (ESCR):
This was a constant strain environmental stress cracking test, and was performed by the method described in JIS K6760. As a test solution, a 10% by weight aqueous solution of Igepal CO-630 manufactured by Rhodia Nikka Co., Ltd. is used, and the time at which the probability of cracking due to environmental stress is 50% (hereinafter referred to as f50) is measured. The value of ESCR was used. The unit is time.
(7) Charpy impact strength:
An injection-molded piece molded at 210 ° C. was used as a sample, and was obtained by the method described in JIS K7111. The temperature is 23 ° C. The unit is kJ / m ² .
(8) Flexural modulus:
Using the test piece of (7) above, it was determined by the method described in JIS K7171. The temperature is 23 ° C. The unit is MPa.
(9) Melting point (Tm) and crystallization temperature (Tc) by differential scanning calorimetry (DSC) method:
Using a Pyris 1 DSC manufactured by Perkin Elmer, the sample weight was 5 mg, and the temperature range from 25 ° C. to 180 ° C. in a nitrogen atmosphere was first raised to 180 ° C. at 100 ° C./min, and then held at 180 ° C. for 5 minutes. The sample was cooled to 25 ° C. at a temperature lowering rate of 10 ° C./min. Further, after holding at 25 ° C. for 5 minutes, the temperature was raised at a rate of temperature rise of 10 ° C./min, and the resulting peak top was taken as the melting point (Tm).
(10) Isothermal crystallization time (min) by differential scanning calorimeter (DSC) method:
Using a Perkin Elmer Pyris1 DSC, the sample weight was 5 mg under a nitrogen atmosphere. After holding at 50 ° C. for 1 minute, when heated up to 180 ° C. at a heating rate of 200 ° C./min, kept at 180 ° C. for 5 minutes, cooled to 124 ° C. at a cooling rate of 80 ° C./min, and held at that temperature The crystallization time (peak) from the time when the temperature was reached was measured.

[Preparation of metallocene catalyst]
<Preparation of metallocene supported catalyst [A]>
Silica P-10 [manufactured by Fuji Silysia Ltd. (Japan)] (trademark) was calcined at 400 ° C. for 5 hours in a nitrogen atmosphere and dehydrated. Ethoxydiethylaluminum was reacted with surface hydroxyl groups to generate ethane gas, and the amount of ethane gas generated was measured using a gas burette. The initial amount of the surface hydroxyl group of dehydrated silica was determined based on the amount of ethane gas generated, and found to be 1.3 mmol / g-SiO ₂ . In a 1.8 liter autoclave, 40 g of this dehydrated silica was dispersed in 800 cc of hexane to obtain a slurry. While maintaining the resulting slurry at 50 ° C. with stirring, 60 cc of a hexane solution of triethylaluminum (concentration 1 mol / liter) was added, and then stirred for 2 hours to react triethylaluminum with the surface hydroxyl group of silica to be treated with triethylaluminum. In addition, a component [D] containing silica and a supernatant liquid and having all surface hydroxyl groups of the silica treated with triethylaluminum capped with triethylaluminum was obtained. Thereafter, the supernatant liquid in the obtained reaction mixture was removed by decantation to remove unreacted triethylaluminum in the supernatant liquid. Thereafter, an appropriate amount of hexane was added to obtain 800 cc of a hexane slurry of silica treated with triethylaluminum. On the other hand, 200 mmol of [(Nt-butylamide) (tetramethyl-η5-cyclopentadienyl) dimethylsilane] titanium-1,3-pentadiene (hereinafter referred to as “titanium complex”) was added to Isopar E [Exxon Chemical Company (USA) 1) 1 mol / liter hexane solution of composition formula AlMg ₆ (C ₂ H ₅ ) ₃ (n-C ₄ H ₉ ) ₁₂ dissolved in 1000 cc and previously synthesized from triethylaluminum and dibutylmagnesium 20 cc, and further hexane was added to adjust the titanium complex concentration to 0.1 mol / liter to obtain component [E].

  Also, 5.7 g of bis (hydrogenated tallow alkyl) methylammonium-tris (pentafluorophenyl) (4-hydroxyphenyl) borate (hereinafter abbreviated as “borate”) was added to 50 cc of toluene and dissolved, A 100 mmol / liter toluene solution was obtained. To this toluene solution of borate, 5 cc of a 1 mol / liter hexane solution of ethoxydiethylaluminum was added at room temperature, and further hexane was added so that the borate concentration in the toluene solution was 70 mmol / liter. Then, it stirred at room temperature for 1 hour and obtained the reaction mixture containing a borate.

  46 cc of this reaction mixture containing borate was added to 800 cc of the slurry of component [D] obtained above with stirring at 15 to 20 ° C., and the borate was supported on silica by physical adsorption. Thus, a slurry of silica carrying borate was obtained. Further, 32 cc of the component [E] obtained above was added and stirred for 3 hours to react the titanium complex with borate. Thus, a metallocene-supported catalyst [A] containing silica and a supernatant liquid and having catalytically active species formed on the silica was obtained.

<Preparation of liquid promoter component [B]>
As organomagnesium _compound, using an organic magnesium compound represented by the _{AlMg 6 (C 2 H 5)} 3 (n-C 4 H 9) 12. Methylhydropolysiloxane (viscosity 20 centistokes at 25 ° C.) was used as the siloxane compound to be reacted with this. To a 200 cc flask, 40 cc of hexane and AlMg ₆ (C ₂ H ₅ ) ₃ (n-C ₄ H ₉ ) ₁₂ were added with stirring while adding 37.8 mmol as the total amount of Mg and Al. Liquid promoter component [B] was prepared by adding 40 cc of hexane containing 2.27 g (37.8 mmol) of siloxane with stirring, and then raising the temperature to 80 ° C. and reacting with stirring for 3 hours. .

  A combination of the metallocene supported catalyst [A] and the liquid promoter component [B] was used as a metallocene catalyst to prepare a metallocene catalyst-based high-density polyethylene.

[Example 1]
Using the metallocene catalyst obtained above, two-stage polymerization using two polymerization tanks connected in series was performed by a continuous slurry polymerization method. The comonomer used is 1-butene. In the first stage polymerization tank, only ethylene is supplied as a monomer, temperature is 70 ° C., hydrogen as a molecular weight regulator is supplied at a ratio of 1.01 mol%, and the total pressure is kept at 3.0 Kg / cm ² G. In the second stage, polymerization was carried out at a temperature of 75 ° C. by supplying 0.23 mol% of 1-butene and 550 mol ppm of hydrogen and maintaining the total pressure at 6.2 Kg / cm ² G. The production ratio of the low molecular weight component (A) composed of an ethylene homopolymer obtained in the first stage polymerization tank is 70% by mass, and the high molecular weight component (B) composed of a copolymer obtained in the second stage polymerization tank. The production rate was set to 30% by mass. To the obtained powder, 800 mol ppm of calcium stearate was added as an additive and blended with a Henschel mixer. This was extruded using a twin-screw extruder (manufactured by Nippon Steel Co., Ltd .; TEX44HCT-49PW-7V) under conditions of a cylinder temperature of 200 ° C. and an extrusion rate of 35 kg / hour to obtain composition pellets.

  Each physical property value and evaluation data were obtained based on the measurement method described above. The results are shown in the table. The resin composition obtained in Example 1 was excellent in rigidity, fluidity and stress crack resistance (ESCR), and had a short isothermal crystallization time.

[Example 2]
Extrusion was carried out in the same manner as in Example 1 except that 800 ppm of calcium stearate as an additive and 60 ppm of Milpeken Japan Co., Ltd. EXP-20 as a crystal nucleating agent were added to the powder obtained in Example 1. Pellets were obtained.

  Each physical property value and evaluation data were obtained based on the measurement method described above. The results are shown in Table 1. The resin composition obtained in Example 1 had high rigidity and fluidity, the isothermal crystallization time was sufficiently short, and the stress crack resistance (ESCR) was also good.

[Comparative Example 1]
Extruded in the same manner as in Example 1 except that 800 ppm of calcium stearate as an additive and 100 ppm of EXP-20 manufactured by Milliken Japan Co., Ltd. as a crystal nucleating agent were added to the powder obtained in Example 1 (both based on mass). Pellets were obtained.

  Each physical property value and evaluation data were obtained based on the measurement method described above. The results are shown in Table 1. The resin composition obtained in Example 1 had high rigidity and fluidity, and the isothermal crystallization time was sufficiently short, but the stress crack resistance (ESCR) was lowered.

[Comparative Example 2]
The second stage of the two-stage polymerization was carried out except that the polymerization was carried out at a temperature of 75 ° C. by supplying 1-butene at a rate of 0.27 mol% and hydrogen at a ratio of 730 mol ppm and maintaining the total pressure at 5.9 Kg / cm ² G. Pellets were obtained in the same manner as in Example 1.

  Each physical property value and evaluation data were obtained based on the measurement method described above. The results are shown in the table. The resin composition obtained in Comparative Example 2 was excellent in rigidity and fluidity, but was slightly inferior in stress crack resistance (ESCR), and the isothermal crystallization time was long.

[Comparative Example 3]
In the first stage polymerization tank, only ethylene is supplied as a monomer, temperature is 70 ° C., hydrogen as a molecular weight regulator is supplied at a ratio of 0.69%, and the total pressure is kept at 2.8 Kg / cm ² G. The second stage is the same as Example 1 except that polymerization was carried out at a temperature of 75 ° C. by supplying 1-butene at a ratio of 0.26 mol% and hydrogen at a ratio of 820 mol ppm and keeping the total pressure at 8.6 Kg / cm ² G. Pellets were obtained in the same manner.

  Each physical property value and evaluation data were obtained based on the measurement method described above. The results are shown in the table. The resin composition obtained in Comparative Example 3 was excellent in rigidity and fluidity, but was inferior in stress crack resistance (ESCR) and had a long isothermal crystallization time.

(Preparation of solid catalyst component [F])
(1) Synthesis of magnesium-containing solid by reaction with chlorosilane compound 2740 ml of trichlorosilane (HSiCl ₃ ) as a 2 mol / liter n-heptane solution was charged into a 15 liter reactor sufficiently purged with nitrogen and stirred. While maintaining at 65 ° C., an n-heptane solution of an organomagnesium component represented by the composition formula AlMg ₆ (C ₂ H ₅ ) ₃ (n—C ₄ H ₉ ) _10.8 (On—C ₄ H ₉ ) _1.2 7 liters (5 mol in terms of magnesium) was added over 1 hour, and the mixture was further reacted with stirring at 65 ° C. for 1 hour. After completion of the reaction, the supernatant was removed and washed 4 times with 7 liters of n-hexane to obtain a solid material slurry. As a result of separation and drying analysis of this solid, it contained 8.62 mmol of Mg, 17.1 mmol of Cl, and 0.84 mmol of n-butoxy group (On-C ₄ H ₉ ) per gram of the solid.
(2) Preparation of Solid Catalyst A slurry containing 500 g of the solid was reacted with 2160 ml of n-butyl alcohol 1 mol / liter n-hexane solution at 50 ° C. for 1 hour with stirring. After completion of the reaction, the supernatant was removed and washed once with 7 liters of n-hexane. The slurry was kept at 50 ° C., and 970 ml of n-hexane solution of 1 mol / liter of diethylaluminum chloride was added with stirring and reacted for 1 hour. After completion of the reaction, the supernatant was removed and washed twice with 7 liters of n-hexane. This slurry was kept at 50 ° C., 270 ml of n-hexane solution of 1 mol / liter of diethylaluminum chloride and 270 ml of n-hexane solution of 1 mol / liter of titanium tetrachloride were added and reacted for 2 hours. After completion of the reaction, the supernatant was removed and washed with 7 liters of n-hexane four times while maintaining the internal temperature at 50 ° C. to obtain a solid catalyst component as a hexane slurry solution. The chlorine ion concentration in the supernatant of the solid catalyst slurry solution was 2.5 mmol / liter, and the aluminum ion concentration was 4.5 mmol / liter.

[Comparative Example 4]
Using the solid catalyst obtained above, two-stage polymerization was carried out by two polymerization tanks connected in series by a continuous slurry polymerization method. The comonomer used is 1-butene. Polymerization was carried out by supplying only ethylene as a monomer to the first stage polymerization tank and ethylene and 1-butene in the second stage. 60% by mass of the production amount of the low molecular weight component (A) composed of the ethylene homopolymer obtained in the first stage polymerization tank, and the high molecular weight component (B) composed of the copolymer obtained in the second stage polymerization tank The production rate was set to 40% by mass. To the obtained powder, 800 ppm (mass basis) of calcium stearate was added as an additive, and blended with a Henschel mixer. This was extruded using a twin-screw extruder (manufactured by Nippon Steel Co., Ltd .; TEX44HCT-49PW-7V) under conditions of a cylinder temperature of 200 ° C. and an extrusion rate of 35 kg / hour to obtain composition pellets.
Each physical property value and evaluation data were obtained based on the measurement method described above. The results are shown in the table. The resin composition obtained in Comparative Example 4 had high rigidity and fluidity and good stress crack resistance (ESCR), but the isothermal crystallization time was long.

[Comparative Example 5]
Extruded in the same manner as in Comparative Example 4 except that 800 ppm of calcium stearate as an additive and 50 ppm (all based on mass) of EXP-20 manufactured by Milliken Japan were added as a crystal nucleating agent to the powder obtained in Comparative Example 4. Pellets were obtained.
Each physical property value and evaluation data were obtained based on the measurement method described above. The results are shown in the table. The resin composition obtained in Comparative Example 5 had high rigidity and fluidity, and the isothermal crystallization time was sufficiently short, but the stress crack resistance (ESCR) was greatly reduced.

[Comparative Example 6]
When an ethylene homopolymer was polymerized under the condition that the MFR of Code D was 800 g / 10 min, the polymerization was carried out by a continuous two-stage polymerization method using a Ziegler catalyst having an Mw / Mn of 8.9. The ratio of the production amount of the low molecular weight component (A) consisting of the ethylene homopolymer obtained in the first stage polymerization tank is increased to 75% by mass, and the high molecular weight component consisting of the copolymer obtained in the second stage polymerization tank ( The ratio of the production amount of B) was set to 25% by mass. The physical properties of the finally obtained polyethylene resin composition are shown in the table. Although the ESCR was maintained and the isothermal crystallization time was sufficiently short, the MFR of the code D of the resin composition was low and the high-speed moldability was insufficient.

  When producing a bottle cap, the polyethylene resin composition of the present invention can be molded at high speed because of its high fluidity and high crystallization speed, and it can withstand the internal pressure of the bottle while maintaining sufficient rigidity as a cap. It is a polyethylene resin composition excellent in environmental stress crack resistance (stress crack resistance), and has high industrial applicability, such as being suitably usable for bottle cap applications.

Claims (6)

A polyethylene resin composition that satisfies the following requirements (a) to (d):
(A) According to JIS K7210, the MFR of Code D measured under conditions of a temperature of 190 ° C. and a load of 2.16 kg is 3.5 to 10.0 g / 10 min;
(B) the density measured according to JIS K7112 is 963 to 967 kg / m ³ ;
(C) the isothermal crystallization time of the peak at 124 ° C. obtained by measuring the crystallization time by DSC is 10 minutes or less; and
(D) f50 fracture time obtained by an environmental stress crack test (ESCR) is 20 hours or more.   The polyethylene resin composition according to claim 1, wherein the isothermal crystallization time of a peak at 124 ° C obtained by measuring the crystallization time by DSC is 5 minutes or less.   The polyethylene resin composition comprises a low molecular weight component (A) and a high molecular weight component (B), and the ratio of the high molecular weight component (B) is 25 to 45% by mass. 3. The polyethylene resin composition according to 1 or 2. The polyethylene resin composition according to any one of claims 1 to 3, further comprising 10 to 2000 ppm (by mass) of a crystal nucleating agent having a structure represented by the following general formula (1).

(Wherein M ₁ and M ₂ are independently selected from the group consisting of calcium, strontium, lithium, zinc, magnesium and monobasic aluminum, and further R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , and R ₁₀ are independently selected from the group consisting of hydrogen and C ₁ -C ₉ alkyl, and any one of the two located adjacent to each other Two R _{3 to} R ₁₀ alkyl groups may be optionally combined to form a carbocycle.)   A bottle cap formed by molding the polyethylene resin composition according to claim 1.   5. The method according to claim 1, further comprising a step of polymerizing at least a part of the polyethylene resin constituting the polyethylene resin composition by a slurry polymerization method using a supported geometrically constrained single site catalyst. The manufacturing method of the polyethylene resin composition of description.