JP2011111579A - Polyethylene resin composition for bottle cap - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a defect of conventional technique, and in particular, to provide a polyethylene resin composition for a bottle cap, which is high in molding speed. <P>SOLUTION: The polyethylene resin composition for a bottle cap includes a polyethylene resin component and a cyclic aliphatic metal salt component, and the polyethylene resin component satisfies at least one of (a), (b), (c) and (d). (a) The polyethylene resin component is composed of a low molecular weight component (A) comprising an ethylene homopolymer having an MFR of code D within a range of 100-500 g/10 min and a high molecular weight component (B) comprising a copolymer of ethylene and a 3C-20C α-olefin, wherein the ratio of the low molecular weight component (A) is 70-30 wt.% and the ratio of the high molecular weight component (B) is 30-70 wt.%. (b) The MFR of code D of the resin component is 4.0-10.0 g/10 min. (c) The density of the resin component is 0.960 to 0.966 g/cm<SP>3</SP>. (d) The molecular weight distribution (Mw/Mn) is 8.0 to 12.0. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polyethylene resin composition for a cap containing a polyethylene resin component and a cyclic aliphatic metal component. More specifically, the polyethylene resin component is obtained using a specific polymerization catalyst, has high-speed moldability, and preferably has an environment resistance capable of withstanding the internal pressure of beverage bottles when the resin composition is used for a bottle cap. It is a polyethylene resin composition that also has excellent rigidity without reducing stress crack resistance (stress crack resistance, hereinafter referred to as ESCR). More preferably, the present invention relates to a polyethylene resin composition having no anisotropy, excellent dimensional stability, and excellent physical property balance such as opening torque.

  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. In particular, there is a great need for a resin composition with high fluidity in order to improve high-speed moldability. 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 cap is removed from the mold in a state of insufficient cooling, there is a problem that the screw part is crushed.

In order to mold at high speed, there are a method for increasing the crystallization speed of the resin used and a method for decreasing the molding temperature.
If the crystallization speed of the resin used can be increased, the resin can crystallize and solidify even if the cooling time is shortened. Therefore, the molding speed can be increased, and the problem of crushing of the screw part is also solved. The

As a method for increasing the crystallization speed of a polyethylene resin, a method of introducing long chain branching into the polyethylene resin by a catalyst technique or a crosslinking technique is known. When long-chain branching is introduced by catalytic technology, a method using a Philips catalyst is generally employed. However, since the polymer obtained by this catalyst has a very wide molecular weight distribution, the mechanical properties are remarkably inferior, and it is difficult to obtain polyethylene having good fluidity by adjusting the molecular weight, so that it can be used in the bottle cap field. It was extremely difficult. In addition, when long-chain branching is introduced using a crosslinking reaction, the mechanical properties are significantly reduced, and low molecular weight components by-produced by the crosslinking reaction cause odor. It was extremely difficult to use. In addition, a crystal nucleating agent is generally added to increase the crystallization speed of the crystalline resin. However, in the case of polyethylene, the reason is not clear. However, the addition of a crystal nucleating agent that is effective in improving the crystallization rate relative to other crystalline resins does not improve the crystallization rate, and the crystallization There has been no report of a crystal nucleating agent that has the effect of clearly increasing the speed. As described above, it has been difficult to increase the crystallization speed in the bottle cap field.
On the other hand, as a method for lowering the molding temperature, it is conceivable to make the resin to be used highly fluid. If the resin used is highly fluid, not only can the load on the extruder be low, the discharge rate can be increased, but the resin temperature can be lowered, and the time required to cool the resin is shortened. It is possible to mold at high speed without crushing the screw part when pulling out.
In general, the molecular weight is decreased to increase fluidity. Due to this low molecular weight, the stress crack resistance tends to decrease 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. However, lowering 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 pressure from the inside, and at the same time, the coefficient of friction increases and slipperiness increases. This causes a problem that the force (opening torque) when opening the cap becomes higher than necessary.

Although the cap disclosed in Patent Document 1 has good moldability and stress crack resistance, the density is low, the slippage with the bottle side at the screw portion is poor, and the force when opening the cap (opening torque) ) Was too expensive.
Patent Documents 2 and 3 disclose polyethylene compositions having a slightly increased density. Caps obtained from these polyethylene compositions are improved in terms of opening torque, but in order to maintain stress crack resistance, they have a high molecular weight and flowability is reduced. There was a problem that it could not be molded.

The polyethylene compositions disclosed in Patent Document 4 and Patent Document 5 have good stress crack resistance and good performance as a cap, but have low fluidity, an excessively high load on the extruder, and a molding speed. It was difficult to raise. Further, when the resin temperature is raised in order to reduce the load on the extruder, there has been a problem that the resin is not sufficiently cooled and the screw portion of the cap is crushed when the mold is removed.
In addition, since the ratio FRR (G / D) between the MFR of code G and the MFR of code D is high and the molecular weight distribution is wide, a flow mark is likely to appear on the top surface of the cap, and the molding shrinkage rate is also anisotropic. There was also a problem with the roundness of the cap dimensions.

Patent Document 6 discloses a polyethylene composition that retains ESCR, moderately increases density, and improves fluidity. However, when the fluidity is further increased, it is difficult to maintain sufficient stress crack resistance unless the density is lowered.
As described above, it has been difficult to increase the molding speed in the field of bottle caps.

JP 2000-159250 A JP 2002-348326 A Japanese Patent Laid-Open No. 2004-123955 JP 2000-248125 A JP 2002-60559 A JP 2004-244557 A

  Accordingly, an object of the present invention is to improve the drawbacks of the prior art, and in particular to provide a polyethylene resin composition for bottle caps having a high molding speed.

  As a result of intensive studies to improve the drawbacks of the prior art, the present inventors have used a cyclic aliphatic metal salt together with a polyethylene resin component as a component of the polyethylene resin composition, and the polyethylene resin component has specific physical properties. When satisfying the requirements, it was found that high fluidity during bottle cap production was achieved and high-speed molding was possible, and further research was conducted to complete the present invention.

That is, the present invention relates to the following:
(1) A polyethylene resin composition for bottle caps, comprising a polyethylene resin component and a cyclic aliphatic metal salt component, wherein the polyethylene resin component is selected from the following (a), (b), (c) and (d) A polyethylene resin composition for bottle caps satisfying at least one.
(A) The polyethylene resin component is a low molecular weight component (A) comprising an ethylene homopolymer having an MFR of code D in the range of 100 to 500 g / 10 min, and ethylene and an α-olefin having 3 to 20 carbon atoms. It consists of a high molecular weight component (B) made of a copolymer, the proportion of the low molecular weight component (A) is 70-30 wt%, and the proportion of the high molecular weight component (B) is 30-70 wt%.
(B) MFR of code D 4.0-10.0 g / 10 min
(C) Density of 0.960 to 0.966 g / cm ³
(D) A polyethylene resin composition for bottle caps having a molecular weight distribution (Mw / Mn) of 8.0 to 12.0.

(2) The polyethylene resin composition for bottle caps according to claim 1, wherein the polyethylene resin component satisfies the requirements consisting of (a), (b), (c) and (d).

(3) The polyethylene resin composition for bottle caps, wherein the polyethylene resin component further satisfies the following requirements (e) and (f).
(E) MFR of code G 180 to 500 g / 10 min
(F) Ratio FRR (G / D) 45 to 70 of MFR of code G and MFR of code D

(4) The polyethylene resin composition for bottle caps that satisfies the following requirements (g), (h), and (i).
(G) Environmental stress crack resistance (ESCR) of 10 hours or more (h) Resin measured with a 150 mm square, 2 mm thick film gate plate, injection molded at a cylinder temperature of 200 ° C. and a mold temperature of 50 ° C. The ratio (MD / TD) of the mold shrinkage (MD) in the flow direction and the mold shrinkage (TD) in the direction perpendicular to the resin flow is 1.0 to 2.5.
(I) 1/2 isothermal crystallization time at 126 ° C. measured with a differential scanning calorimeter (DSC) is 10 minutes or less

ここで、Ｍ^１および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、およ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、さらにＲ^１３、Ｒ^１４、Ｒ^１５、Ｒ^１６、Ｒ^１７、Ｒ^１８、Ｒ^１９、Ｒ^２０、Ｒ^２１、およびＲ^２２は、水素および炭素数１〜９の炭化水素基からなる群より互いに独立して選択され、さらに互いに隣接して位置したいずれか２つのＲ^１５〜Ｒ^２２の炭化水素基は任意に結合して環を形成していてもよい。 (5) The polyethylene resin composition for bottle caps, wherein the cyclic aliphatic metal salt component is represented by the following formula:

Here, M ¹ and M ² are independently selected from the group consisting of calcium, strontium, lithium, zinc, magnesium, and monobasic aluminum, and R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , and R ²² are any one selected independently from the group consisting of hydrogen and a hydrocarbon group having 1 to 9 carbon atoms, and further positioned adjacent to each other Two hydrocarbon groups of R ^{15 to} R ²² may be optionally combined to form a ring.

(6) A method for producing a polyethylene resin composition for bottle caps, including the following steps:
-Preparing a polyethylene resin component satisfying at least one of (a), (b), (c) and (d):
(A) The polyethylene resin component is a low molecular weight component (A) comprising an ethylene homopolymer having an MFR of code D in the range of 100 to 500 g / 10 min, and ethylene and an α-olefin having 3 to 20 carbon atoms. It consists of a high molecular weight component (B) made of a copolymer, the proportion of the low molecular weight component (A) is 70-30 wt%, and the proportion of the high molecular weight component (B) is 30-70 wt%.
(B) MFR of code D 4.0-10.0 g / 10 min
(C) Density of 0.960 to 0.966 g / cm ³
(D) Molecular weight distribution (Mw / Mn) is 8.0 to 12.0
A step of mixing a cycloaliphatic metal salt component with the polyethylene resin component, and a step of obtaining a polyethylene resin composition for a bottle cap comprising a polyethylene resin component and a cycloaliphatic metal salt component.
(7) A bottle cap comprising the polyethylene resin composition for a bottle cap according to any one of (1) to (5).

According to the present invention, when producing a bottle cap, the crystallization speed is fast and the high fluidity reduces the load on the extruder, and the high-speed molding is possible without crushing the screw part when the mold is pulled out. A polyethylene resin composition for bottle caps is provided.
In a preferred embodiment of the present invention, the resin composition according to the present invention is excellent in environmental stress crack resistance (stress crack resistance) capable of withstanding the internal pressure of a beverage bottle while maintaining sufficient rigidity as a cap. Has a narrow molecular weight distribution, has little anisotropy, is excellent in dimensional stability, and has excellent characteristics of opening torque and slipperiness.
That is, according to the present invention, a polyethylene resin composition for bottle caps having excellent high-speed moldability is provided, and in a preferred embodiment, environmental stress crack resistance (stress crack resistance) capable of withstanding the internal pressure of a beverage bottle is provided. A novel polyethylene resin composition for bottle caps that has excellent rigidity without degradation, no anisotropy, excellent dimensional stability, and required performance such as opening torque when used for bottle caps. Things are provided. Therefore, the polyethylene resin composition of the present invention has an exceptional effect that it is extremely suitable for use as a bottle cap for beverage containers.

Hereinafter, the present invention will be specifically described.
As described above, the polyethylene resin composition for bottle caps of the present invention contains a polyethylene resin component and a cyclic aliphatic metal salt component.
The method for preparing the polyethylene resin component according to the present invention is not particularly limited. For example, one or more comonomer selected from ethylene and an α-olefin having 3 to 20 carbon atoms using a specific Ziegler type catalyst. Is polymerized in such a ratio that the desired physical properties are obtained.
At that time, in order to obtain a desired molecular weight and MFR, a molecular weight regulator such as hydrogen may be used.

Next, the preparation method of the specific Ziegler type catalyst used for this invention is demonstrated.
The specific Ziegler-type catalyst for obtaining the polyethylene resin component according to the present invention is a polymerization catalyst comprising a solid catalyst component [A] and an organoaluminum compound [B]. The preparation method of the solid catalyst component [A] includes (A-1) (i) general formula (Al) _α (Mg) _β (R ¹ ) _p (R ² ) _q (OR ³ ) _r [wherein R ¹ , R ² and R ³ are hydrocarbon groups having 2 to 20 carbon atoms, and α, β, p, q and r are numbers satisfying the following relationship.
0 ≦ α, 0 <β, 0 ≦ p, 0 ≦ q, 0 ≦ r, p + q> 0, 0 ≦ r / (α + β) ≦ 2, 3α + 2β = p + q + r]
1 mol of an organic magnesium component soluble in a hydrocarbon solvent represented by
(Ii) the general formula ^{_{H a SiCl b R 4 4- (}} a + b) ( wherein, R ⁴ is a hydrocarbon group having 1 to 20 carbon atoms, is a number that satisfies the following relationship with a and b 0 <a, 0 <b, a + b ≦ 4) with respect to 1 mol of C—Mg bonds contained in a solid obtained by reacting 0.01 to 100 mol of a chlorosilane compound having a Si—H bond represented by ,
(A-2) A solid obtained by reacting 0.05 to 20 moles of alcohol is further subjected to (A-3) general formula AlR ⁵ _s Q _3-s
(Wherein R ⁵ is a hydrocarbon group having 1 to 20 carbon atoms, Q represents an ^{OR 6, OSiR 7 R 8 R} 9, NR 10 R 11, SR 12 and group selected from halogen, R ^6, R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ and R ¹² are hydrogen atoms or hydrocarbon groups, and 0 <s) is converted into a solid obtained by reacting an organometallic compound represented by (A− 4) Obtained by reacting a titanium compound in the presence of the component (A-3).

The organomagnesium compound used here has the general formula (Al) _α (Mg) _β (R ¹ ) _p (R ² ) _q (OR ³ ) _r [wherein R ¹ , R ² and R ³ have 2 carbon atoms. ˜20 hydrocarbon groups, and α, β, p, q and r are numbers satisfying the following relationship. 0 ≦ α, 0 <β, 0 ≦ p, 0 ≦ q, 0 ≦ r, 0 ≦ r / (α + β) ≦ 2, 3α + 2β = p + q + r]. This compound is shown as a complex form of organomagnesium soluble in a hydrocarbon solvent, but encompasses all of R ₂ Mg and complexes of these with other metal compounds. The relational expression 3α + 2β = p + q + r of the symbols α, β, p, q, r indicates the stoichiometry between the valence of the metal atom and the substituent.

The hydrocarbon group represented by R ¹ to R ² in the above formula is an alkyl group, a cycloalkyl group or an aryl group, such as methyl, ethyl, propyl, butyl, amyl, hexyl, decyl, cyclohexyl, phenyl group, etc. R ¹ is preferably an alkyl group. The ratio β / α of magnesium to aluminum can be arbitrarily set, but is preferably 0.1 to 30, particularly preferably 0.5 to 10. In addition, when a certain organomagnesium compound in which α = 0 is used, for example, if R ¹ is sec-butyl or the like, it is soluble in a hydrocarbon solvent, and such a compound also has preferable results in the present invention. give.

In the general formula (Al) _α (Mg) _β (R ¹ ) _p (R ² ) _q (OR ³ ) _r , R ¹ and R ^{2 in} the case of α = 0 are the following three groups (1), ( It is recommended that it is one of 2) and (3).
(1) At least one of R ¹ and R ² is a secondary or tertiary alkyl group having 4 to 6 carbon atoms, preferably R ¹ and R ² both have 4 to 6 carbon atoms, At least one is a secondary or tertiary alkyl group.
(2) R ¹ and R ² are alkyl groups having different carbon atoms, preferably R ¹ is an alkyl group having 2 or 3 carbon atoms, and R ² is an alkyl group having 4 or more carbon atoms. Be.
(3) At least one of R ¹ and R ² is a hydrocarbon group having 6 or more carbon atoms, preferably, R ¹ and R ² are both alkyl groups having 6 or more carbon atoms.
These groups are specifically shown below.

As the secondary or tertiary alkyl group having 4 to 6 carbon atoms in (1), sec-butyl, tert-butyl, 2-methylbutyl, 2-ethylpropyl, 2,2-dimethylpropyl, 2-methyl Pentyl, 2-ethylbutyl, 2,2-dimethylbutyl, 2-methyl-2-ethylpropyl and the like are used, and sec-butyl is particularly preferable.
Next, in (2), examples of the alkyl group having 2 or 3 carbon atoms include an ethyl group and a propyl group, and the ethyl group is particularly preferable. Examples of the alkyl group having 4 or more carbon atoms include a butyl group, an amyl group, a hexyl group, and an octyl group, and a butyl group and a hexyl group are particularly preferable.
In (3), examples of the alkyl group having 6 or more carbon atoms include a hexyl group, an octyl group, a decyl group, and a phenyl group. An alkyl group is preferred, and a hexyl group is particularly preferred.

  In general, increasing the number of carbon atoms in an alkyl group facilitates dissolution in a hydrocarbon solvent, but the solution tends to increase in viscosity, and use of an unnecessarily long alkyl group is not preferred in handling. In addition, although the said organomagnesium compound is used as a hydrocarbon solution, even if trace amount of complexing agents, such as ether, ester, an amine, are contained in this solution slightly or it can remain, it can be used.

Next, the alkoxy group (OR ³ ) will be described. The hydrocarbon group represented by R ³ is preferably an alkyl group having 3 to 10 carbon atoms or an aryl group. Specifically, for example, n-propyl, n-butyl, sec-butyl, tert-butyl, amyl, hexyl, 2-methylpentyl, 2-ethylbutyl, 2-ethylpentyl, 2-ethylhexyl, 2-ethyl-4 -Methylpentyl, 2-propylheptyl, 2-ethyl-5-methyloctyl, n-octyl, n-decyl, phenyl group and the like, preferably n-butyl, sec-butyl, 2-methylpentyl and 2- Ethyl hexyl.

These organomagnesium compounds or organomagnesium complexes are composed of an organomagnesium compound represented by the general formulas R ¹ MgX, R ¹ ₂ Mg (R ¹ is as defined above, and X is a halogen), a general formula, Al An organometallic compound represented by R ² ₃ or AlR ² _3-1 H (R ² has the above-mentioned meaning) is heated at room temperature to 150 in an inert hydrocarbon medium such as hexane, heptane, cyclohexane, benzene and toluene. The hydrocarbyloxymagnesium compound having a hydrocarbon group represented by R ³ that is soluble in an alcohol or hydrocarbon solvent having a hydrocarbon group represented by R ³ , if necessary, followed by reaction between And / or by a method of reacting with a hydrocarbyloxyaluminum compound.

  Among these, when the organic magnesium component soluble in hydrocarbon and the alcohol are reacted, the order of the reaction is such that the alcohol is added to the organic magnesium component, the organic magnesium component is added to the alcohol, or Any method of adding both at the same time can be used. In the present invention, the reaction ratio between the organic magnesium component soluble in hydrocarbon and the alcohol is not particularly limited, but as a result of the reaction, the molar composition ratio of alkoxy groups to all metal atoms in the resulting alkoxy group-containing organomagnesium component. The range of r / (α + β) is 0 ≦ r / (α + β) ≦ 2, and 0 ≦ r / (α + β) <1 is particularly preferable.

Next, the chlorosilane compound having an Si—H bond used in the preparation of the solid catalyst component [A] used for obtaining the polyethylene resin component according to the present invention will be described.
As the chlorosilane compound, a general formula, H _a SiCl _b R ⁴ 4− _{(a + b)} (wherein R ⁴ is a hydrocarbon group having 1 to 20 carbon atoms, and a and b are numbers satisfying the following relationship: 0 <a, 0 <b, a + b ≦ 4). The hydrocarbon group represented by R ⁴ in the above formula is an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group. For example, methyl, ethyl, butyl, amyl, hexyl, decyl, cyclohexyl A phenyl group and the like, preferably an alkyl group having 1 to 10 carbon atoms, and particularly preferably a lower alkyl group such as methyl, ethyl and propyl. Further, a and b are numbers larger than 0 satisfying the relationship of a + b ≦ 4, and it is particularly preferable that b is 2 or 3.

These compounds include HSiCl ₃ , HSiCl ₂ CH ₃ , HSiCl ₂ C ₂ H ₅ , HSiCl ₂ n-C ₃ H ₇ , HSiCl ₂ iso-C ₃ H ₇ , HSiCl ₂ n-C ₄ H ₉ , HSiCl _{2 C 6 H 5, HSiCl 2 (} 4-Cl-C 6 H 4), HSiCl 2 CH = CH 2, HSiCl 2 CH 2 C 6 H 5, HSiCl 2 (1-C 10 H 7), HSiCl 2 CH 2 CH = CH ₂ , H ₂ SiClCH ₃ , H ₂ SiClC ₂ H ₅ , HSiCl (CH ₃ ) ₂ , HSiCl (C ₂ H ₅ ) ₂ , HSiClCH ₃ (iso-C ₃ H ₇ ), HSiClCH ₃ (C ₆ H ₅ ), HSiCl (C ₆ H ₅ ) _{2 and the} like, and a chlorosilane compound composed of these compounds or a mixture of two or more selected from these compounds is used. As the chlorosilane compound, trichlorosilane, monomethyldichlorosilane, dimethylchlorosilane, and ethyldichlorosilane are preferable, and trichlorosilane and monomethyldichlorosilane are particularly preferable.

  Next, the reaction between the organomagnesium component and the chlorosilane compound will be described. In the reaction, the chlorosilane compound is previously an inert reaction solvent, for example, an aliphatic hydrocarbon such as n-hexane or n-heptane, an aromatic hydrocarbon such as benzene, toluene or xylene, or an alicyclic such as cyclohexane or methylcyclohexane. It is preferable to use after diluting with hydrocarbons, chlorinated hydrocarbons such as 1,2-dichloroethane, o-dichlorobenzene and dichloromethane, ether-based media such as ether and tetrahydrofuran, or mixed media thereof. In view of the performance of the catalyst, an aliphatic hydrocarbon medium is preferred. Although the reaction temperature is not particularly limited, it is preferably carried out at a temperature not lower than the boiling point of chlorosilane or not lower than 40 ° C. for the progress of the reaction. Although there is no restriction | limiting in particular also in the reaction ratio of 2 types of components, Usually, it is 0.01-100 mol of chlorosilane compounds with respect to 1 mol of organomagnesium components, Preferably it is 0.1-0.1 mol of chlorosilane compounds with respect to 1 mol of organic magnesium components. The range is 10 moles.

  Regarding the reaction method, a method of simultaneous addition in which two kinds of components are simultaneously introduced into the reaction zone, a method of reacting while introducing a chlorosilane compound into the reaction zone in advance, and a reaction in which an organomagnesium component is introduced into the reaction zone, or There is a method in which an organic magnesium component is charged in advance and a chlorosilane compound is added. A method in which a chlorosilane compound is charged in a reaction zone in advance and then reacted while introducing the organic magnesium component into the reaction zone gives a preferable result. The solid component obtained by the above reaction is separated by filtration or decantation, and then thoroughly washed with an inert solvent such as n-hexane or n-heptane to remove unreacted products or by-products. Is preferred.

The solid (A-1) obtained as described above is further treated with alcohol. Examples of the alcohol used at this time include saturated or unsaturated alcohols having 1 to 20 carbon atoms. Examples of such alcohols include methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, amyl alcohol, hexyl alcohol, cyclohexanol, phenol, cresol, and the like, and C ₃ to C ₈ linear alcohols are particularly preferable. .

  Next, the amount of alcohol used is 0 to 20 mol, preferably 0.1 to 10 mol, particularly preferably 0.2 to 8 mol per mol of C—Mg bond contained in the solid (A-1). The range of moles. The reaction between the solid (A-1) and the alcohol is carried out in the presence or absence of an inert medium. As the inert medium, any of the aforementioned aliphatic, aromatic or alicyclic hydrocarbons may be used. The temperature during the reaction is not particularly limited, but it is preferably carried out at room temperature to 200 ° C.

Next, the titanium compound will be described. As the titanium compound, a titanium compound represented by the general formula Ti (OR ¹³ ) _u X _4-u is used. In the formula, u is a number of 0 ≦ u ≦ 4, and examples of the hydrocarbon group represented by R ¹³ include methyl, ethyl, propyl, butyl, amyl, hexyl, 2-ethylhexyl, heptyl, octyl, decyl, allyl and the like. An aliphatic hydrocarbon group, an alicyclic hydrocarbon group such as cyclohexyl, 2-methylcyclohexyl and cyclopentyl, an aromatic hydrocarbon group such as phenyl and naphthyl, and the like, and an aliphatic hydrocarbon group is preferred. Examples of the halogen represented by X include chlorine, bromine and iodine, with chlorine being preferred. It is possible to use a mixture of two or more of the titanium compounds selected from the above.
An inert reaction medium is used for the reaction between the solid substance and the titanium compound. Examples of the inert reaction medium include aliphatic hydrocarbons such as hexane and heptane, aromatic hydrocarbons such as benzene and toluene, cyclohexane, and methylcyclohexane. Alicyclic hydrocarbons, and the like, but aliphatic hydrocarbons are preferred. The amount of the titanium compound used is preferably 0.5 mol or less, particularly preferably 0.1 mol or less, per mol of C—Mg bonds contained in the solid component. Although there is no restriction | limiting in particular about reaction temperature, It is preferable to carry out in the range of room temperature to 150 degreeC. In this case, the organometallic compound component can be present. In this case, the addition order may be any method of adding the titanium compound after the organometallic compound, adding the organometallic compound after the titanium compound, or adding both at the same time. Subsequently, it is preferable to add a titanium compound. In this case, the molar ratio between the organometallic compound and the titanium compound is preferably in the range of 0.5-2.

  The catalyst thus obtained is used as a slurry solution with an inert solvent. Examples of inert solvents include aliphatic hydrocarbons such as hexane and heptane, aromatic hydrocarbons such as benzene, toluene and xylene, alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, 1,2-dichloroethane, and carbon tetrachloride. And halogenated hydrocarbons such as chlorobenzene.

  Examples of the organoaluminum compound [B] used together with the solid catalyst component [A] of the present invention include trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, triiso-butylaluminum, tri-n-amylaluminum, Trialkylaluminum such as triiso-amylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, tri-n-decylaluminum, diethylaluminum chloride, ethylaluminum dichloride, diiso-butylaluminum chloride, ethylaluminum sesquichloride, diethyl Alkoxyaluminum such as aluminum halide such as aluminum bromide, diethylaluminum ethoxide, diiso-butylaluminum butoxide Siloxyalkylaluminums such as dimethyl, dimethylhydrosiloxyaluminum dimethyl, ethylmethylhydrosiloxyaluminum diethyl, ethyldimethylsiloxyaluminum diethyl and mixtures thereof are used, and trialkylaluminum is particularly preferred because the highest activity is achieved.

  Examples of the olefin polymerized in the catalyst system of the present invention include ethylene and an α-olefin having 3 to 20 carbon atoms. Typical examples of the α-olefin 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, etc. Some of these can be combined and copolymerized. The solid catalyst component and the organoaluminum compound may be added to the polymerization system under the polymerization conditions, or may be mixed in advance prior to the polymerization. The ratio of the two components to be combined is defined by the molar ratio of Ti in the solid catalyst component and Al in the organoaluminum component, and Al / Ti = 0.3 to 1000.

  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.

For the preparation of a polyethylene resin component comprising a low molecular weight component (A) comprising an ethylene homopolymer of the present invention and a high molecular weight component (B) comprising a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms. Is a method of polymerizing a low molecular weight component A and a high molecular weight component B separately, and blending them at a predetermined blending ratio, or a powder blend or a pellet blend, or successively in two or more polymerizers connected in series. Alternatively, a multi-stage polymerization method obtained by polymerizing in the same manner, or a method of blending each component obtained by polymerizing simultaneously in two or more polymerization vessels connected in parallel in a slurry state or the like may be used.
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.

  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 co-monomer is not left, the unreacted comonomer is not fed into the second stage polymerization tank as it is, and there is no risk of the comonomer being inserted into the low molecular weight component to form a copolymer. It becomes easy to increase the ESCR while maintaining it.

Moreover, the polyethylene resin composition for bottle caps of the present invention is a polyethylene resin composition for bottle caps in which the polyethylene resin component satisfies at least one of the following (a), (b), (c) and (d). is there:
(A) The polyethylene resin component is a low molecular weight component (A) comprising an ethylene homopolymer having an MFR of code D in the range of 100 to 500 g / 10 min, and ethylene and an α-olefin having 3 to 20 carbon atoms. It consists of a high molecular weight component (B) made of a copolymer, the proportion of the low molecular weight component (A) is 70-30 wt%, and the proportion of the high molecular weight component (B) is 30-70 wt%.
(B) MFR of code D 4.0-10.0 g / 10 min
(C) Density of 0.960 to 0.966 g / cm ³
(D) Molecular weight distribution (Mw / Mn) is 8.0 to 12.0.

  To explain the above (a), the polyethylene resin component for bottle caps of the present invention is a low molecular weight component (A) made of an ethylene homopolymer of 70 to 30 wt%, ethylene and an α-olefin having 3 to 20 carbon atoms. The high molecular weight component (B) consisting of a copolymer with is 30 to 70 wt%. The polyethylene resin component preferably has a low molecular weight component (A) of 65 to 50 wt% and a high molecular weight component (B) of 35 to 50 wt%. By setting the amount of the low molecular weight component (A) made of an ethylene homopolymer to 30 wt% or more, it is possible to obtain a composition having high fluidity, low extruder load, and excellent high-speed moldability. Further, by setting the amount of the low molecular weight component (A) to 70 wt% or less, the high molecular weight component is increased, and excellent ESCR can be achieved.

  The ratio of the low molecular weight component (A) composed of an ethylene homopolymer and the high molecular weight component (B) composed of a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms in the two-stage continuous polymerization is It is possible to grasp from the production volume. 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) made of an ethylene homopolymer is preferably 0.971 g / cm ³ or more, more preferably 0.973 g / cm ³ or more. As a result, the density of the high molecular weight component (B) made of a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms can be reduced, and many comonomers are introduced into the high molecular weight component (B). Therefore, it is possible to maintain high physical properties such as ESCR. By setting the density of the low molecular weight component (A) made of an ethylene homopolymer to 0.971 g / cm ³ or more, a high molecular weight component made of a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms ( Since the density of B) can be sufficiently reduced, the ESCR is not insufficient.

  As for the above (b), the resin component of the present invention has an MFRD in the range of 4.0 to 10.0 g / 10 min, preferably in the range of 4.0 to 8.0 g / 10 min, more preferably 4 0.0 to 7.0 g / 10 min. By setting the MFRD value to 4.0 g / 10 min or more, sufficient fluidity can be obtained during molding, and fluctuations such as an increase in resin temperature during molding can be reduced, thereby achieving high-speed moldability. Moreover, by making the value of MFRD 10.0 g / 10 min or less, the stress crack resistance that may lead to cap cracking does not deteriorate, and the practicality is excellent.

Moreover, about said (c), it is preferable that it is the range of 0.960-0.966 g / cm < ³ > as a density of a polyethylene resin component. In order to improve stress crack resistance, it is effective to reduce the density of the resin. However, in the resin component for the bottle cap, the rigidity of the cap can be increased by setting the density to 0.960 g / cm ³ or more. There is no fear that the bottle will be deformed when it is loaded into the bottle, or that the cap will be deformed when the bottle filled with the beverage is stored at a high temperature. In addition, the sliding property of the screw portion with the bottle body side is poor, the force (opening torque) when opening the cap is too high, and the problem that the cap cannot be opened with the force of a child or woman does not occur. Moreover, sufficient ESCR can be maintained by setting it as 0.966 g / cm < ³ > or less.

  Furthermore, for (d) above, the molecular weight distribution (Mw / Mn) of the polyethylene resin composition of the present invention is prepared from a standard polystyrene sample using high temperature gel permeation chromatography (high temperature GPC). Can be obtained. In the present invention, the value of Mw / Mn is preferably from 8.0 to 12.0, and more preferably from 9.0 to 12.0. By setting Mw / Mn to 8.0 or more, the high molecular weight component is not reduced, and there is no fear that ESCR is insufficient. Moreover, by setting Mw / Mn to 12.0 or less, low molecular weight components such as wax are reduced, and there is no fear of dissolving into the beverage in the bottle. In this case, furthermore, since the molecular weight distribution does not spread, the impact strength is not lowered, so that there is no concern that the cap is easily broken by a drop impact. Further, by avoiding the spread of the molecular weight distribution, anisotropy does not occur at the time of molding, and the roundness of the cap does not decrease, so that there is no concern that the adhesiveness with the bottle becomes uneven.

Another preferred embodiment of the polyethylene resin composition for bottle caps of the present invention will be described below.
MFR (JIS K7210: 1999, 190 ° C., 2.16 kg load; hereinafter referred to as “MFRD”) of the low molecular weight component (A) code D consisting of the ethylene homopolymer of the present invention is 100 to 500 g / 10 min. Preferably, it is 200-400 g / 10min. Since fluidity is ensured by this low molecular weight component, by setting the MFRD to 100 g / 10 min or more, the resin pressure of the extruder does not increase excessively at the time of cap molding, and high speed molding becomes possible. Moreover, by setting it as 500 g / 10min or less, there are few low molecular weight components like a wax, and there is no possibility of melt | dissolving in the drink in a bottle, and it is preferable.

  For the molecular weight distribution (Mw / Mn) of the low molecular weight component (A) comprising the ethylene homopolymer of the present invention, a calibration curve was created from a standard polystyrene sample using high temperature gel permeation chromatography (high temperature GPC). Can be obtained. The value of Mw / Mn of the present invention is 4.0 to 5.0, more preferably 4.5 to 5.0. By setting the value of Mw / Mn to 5.0 or less, the amount of components having a molecular weight of 1000 or less is reduced, and there is no possibility of causing problems such as odor problems and dissolution into beverages in bottles. . In addition, the impact strength can be increased by narrowing the molecular weight distribution. By narrowing the Mw / Mn of the low molecular weight component (A), the high molecular weight component contained in the low molecular weight component (A) can be reduced as much as possible, and the ethylene and carbon number contributing to the physical properties such as ESCR are 3 The high molecular weight component (B) consisting of a copolymer with -20 α-olefin can be effectively increased. This effect is extremely important in maintaining the ESCR of the polyethylene resin component of the present invention. By using the above-described catalyst, this Mw / Mn value can be satisfied.

Further, the value of MFR (JIS K7210: 1999, 190 ° C., 21.6 kg load; hereinafter referred to as “MFRG”) of the code G is preferably 180 to 500 g / 10 min, more preferably 200 to 400 g / 10 min. When this value is 180 g / 10 min or more, high-speed moldability is excellent, and when 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, the discharge speed can be increased, the temperature can be lowered so that the load on the extruder is the same, and how much the crystallization speed can be increased. Judgment can be made depending on whether it can be done quickly.

  Next, the value of the ratio FRR (G / D) between MFRG and MFRD is generally a numerical value correlated with the molecular weight distribution. When the molecular weight distribution becomes wider, the value of this FRR (G / D) becomes larger. The FRR (G / D) of the polyethylene resin component of the present invention is preferably 45 or more and 70 or less, more preferably 45 or more and 60 or less, and further preferably 45 or more and 55 or less. By setting this value to 45 or more, the load on the extruder during molding is reduced, which is preferable in terms of high-speed moldability. In this case, there is no concern that the stress crack resistance is not sufficient. Furthermore, by setting the value of FRR (G / D) to 70 or less, the impact strength does not decrease, the flow mark does not easily occur on the top surface of the cap molded product, and the cap molding shrinkage rate has no anisotropy. This eliminates the concern that the roundness of the cap will decrease.

  In addition, the polyethylene resin composition of the present invention is formed by injection molding at a cylinder temperature of 200 ° C. and a mold temperature of 50 ° C., and a molding shrinkage in the flow direction of the resin measured by a 150 mm square and 2 mm thick film gate plate ( MD) and the ratio (MD / TD) of the mold shrinkage (TD) in the direction perpendicular to the resin flow are in the range of 1.0 to 2.5, more preferably 1.0 to 2.4. It is important to be in range. By setting MD / TD to 2.5 or less, the roundness of the cap molded product is increased, and there is no concern that problems such as the cap dimensions not matching the bottle occur.

  In addition, 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 of 10 hours or more. Is preferred. 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. By setting this value to 10 hours or more, there is no concern that the cap bursts due to the internal pressure of the bottle. Further, in this case, there is no concern that cracks will occur even if the bottle is stored for a long time while being over-tightened when loaded into the bottle.

  Furthermore, the polyethylene resin composition of the present invention uses an injection-molded piece molded at a cylinder temperature of 210 ° C. and a mold temperature of 40 ° C. as a sample, and has a nominal strain at tensile fracture of 200 to 600 measured by the method described in JIS K7161. %, And more preferably 300 to 500%. When the nominal strain at the time of tensile fracture is 200% or more, the cap becomes strong and there is no concern that cracks are likely to occur. By setting the nominal strain at the time of tensile fracture to 600% or less, the bridge portion is easily cut when the cap is opened, and the bridge portion does not remain. That is, in this case, when a person leaves the bridge portion when the bridge portion is left, the lip portion comes into contact and feels pain, and in some cases, there is no fear of cutting the lips.

  By increasing the density, the polyethylene resin composition of the present invention has high rigidity when molded into a cap, and can be prevented from being deformed by the internal pressure of the bottle. 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 preferable range of the tensile yield stress is 25 to 30 MPa. By setting the tensile yield stress to 25 MPa or more, there is no concern that the beverage will leak due to deformation when the internal pressure of the bottle rises. Moreover, sufficient ESCR with high rigidity can be obtained by making a tensile yield stress into 30 Mpa or less.

The polyethylene resin composition of the present invention is excellent in impact resistance because it comprises a low molecular weight component (A) of an ethylene homopolymer having a narrow molecular weight distribution and a high molecular weight component (B) of an ethylene copolymer having a narrow molecular weight distribution. 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. By setting the Charpy impact strength to 4 kJ / m ² or more, when the bottle is dropped, it is possible to eliminate the risk that the cap breaks and the beverage leaks. On the other hand, when the Charpy impact strength is 7 kJ / m ² or less, the density does not increase and a sufficient ESCR can be obtained.

  The polyethylene resin composition of the present invention has a low capillographic melt viscosity, good fluidity, and excellent high-speed moldability. Capillograph melt viscosity at 180 ° C. and a shear rate of 1065 / sec (Capillograph 1D type, manufactured by Toyo Seiki Seisakusho, orifice size: D = 0.770 mm, L = 50.8 mm) is 200 Pa · sec or less and high-speed moldability is obtained. It becomes good.

  Since the polyethylene resin composition of the present invention has a high crystallization speed during molding, it is excellent in high-speed moldability. As for the crystallization rate, if the ½ isothermal crystallization time at 126 ° C. measured by a differential scanning calorimeter (DSC) is 10 minutes or less, the high-speed moldability is good.

The cycloaliphatic metal salt in the present invention is, for example, a compound represented by the following formula.

Here, M ¹ and M ² are independently selected from the group consisting of calcium, strontium, lithium, zinc, magnesium, and monobasic aluminum, or M ¹ and M ² collectively represent one divalent group. A metal ion, and R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , and R ²² are each composed of hydrogen and a hydrocarbon group having 1 to 9 carbon atoms. Any two of the R ^{15 to} R ²² hydrocarbon groups selected independently from each other and located adjacent to each other may be optionally combined to form a ring.
M ¹ and M ² are preferably one divalent metal ion as a whole. Among these, it is more preferable that M ¹ and M ² are divalent calcium ions.

  The weight fraction of the cycloaliphatic metal salt with respect to the polyethylene resin component is not particularly limited, and is, for example, in the range of 10 ppm to 5000 ppm by weight. The said weight fraction becomes like this. Preferably they are 10 weight ppm or more and 1000 weight ppm or less, More preferably, they are 50 weight ppm or more and 700 weight ppm or less. By setting the weight fraction of the cycloaliphatic metal salt to the polyethylene resin component to 5000 ppm by weight or less, there is no concern that the ESCR will decrease. Further, by setting the weight fraction of the cycloaliphatic metal salt to 10 ppm by weight or more, an effect of increasing the crystallization speed can be obtained, and the crystallization time can be shortened, so that high-speed productivity is achieved.

  In the present invention, the cycloaliphatic metal salt is added to the polyethylene resin by directly adding the cycloaliphatic metal salt to the polyethylene resin, a masterbatch containing the cycloaliphatic metal salt is prepared in advance, and this masterbatch is added. Although there is a method, a method of adding a masterbatch is preferable for improving the dispersibility of the cycloaliphatic metal salt. By improving the dispersibility of the cycloaliphatic metal salt, the effect of shortening the crystallization time is enhanced.

The polyethylene resin composition for bottle caps of the present invention can be produced by a production method including a step of adding a cycloaliphatic metal salt to an ethylene resin component. In addition, when adding the cycloaliphatic metal salt, a fatty acid salt is preferably used in combination.
The fatty acid salt in the present invention includes an anion having 12 to 22 carbon atoms and a cation, and the cation is preferably selected from the group consisting of zinc, calcium, lithium, magnesium, and sodium. In addition, as the fatty acid salt in the present invention, a stearic acid compound is preferable, and among them, zinc stearate is particularly preferable.
In the present invention, the weight fraction of the fatty acid salt relative to the cyclic aliphatic metal salt is preferably 0.05 to 20, and more preferably 0.1 to 10.

  The method for adding a fatty acid salt to a polyethylene resin in the present invention includes a method in which a cycloaliphatic metal salt and a fatty acid salt are directly added separately to the polyethylene resin, and the polyethylene resin is previously mixed with the fatty acid salt and the cycloaliphatic metal salt. A method for directly adding a cycloaliphatic metal salt and a fatty acid salt to a polyethylene resin, a method for adding a cycloaliphatic metal salt directly to a polyethylene resin as a master batch, a method for directly adding a fatty acid salt, and a cycloaliphatic metal salt and a fatty acid salt in advance. There is a method of preparing a master batch and adding the master batch to a polyethylene resin. However, a method of preparing a master batch including a cyclic aliphatic metal salt and a fatty acid salt in advance and adding the master batch to the polyethylene resin is available. preferable.

  The polyethylene resin composition of the present invention may contain a small amount of additives, fillers and the like within a range not impairing the effects of the present invention, but can be considered in consideration of suppressing elution into the beverage in the bottle. It is preferable not to add as much as possible. As additives used, phenolic antioxidants are good, and by preventing the use of antioxidants such as phosphorus and sulfur, it is possible to prevent the taste of the beverage in the bottle from changing. It is possible and preferable.

  The amount of the phenolic antioxidant to be added is 500 ppm or less, preferably 300 ppm or less, more preferably 100 ppm or less, and most preferably no addition from the viewpoint of flavor. Further, when not added at all, it can be used for a cap of a milk drink because it complies with a ministerial ordinance such as milk.

  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, magnesium stearate and the like, and the addition amount is 800 ppm by weight or less, preferably 600 ppm by weight or less, more preferably 300 ppm by weight or less.

  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 is possible to add titanium oxide or an organic pigment in a masterbatch, but by not adding these, the cause of reducing the flavor property can be eliminated. Therefore, it is preferable not to add these additives, fillers, titanium oxide, organic pigments and the like.

In another aspect, the present invention provides a method for producing a polyethylene resin composition for bottle caps, comprising the following steps:
-Preparing a polyethylene resin component satisfying at least one of (a), (b), (c) and (d):
(A) The polyethylene resin component is a low molecular weight component (A) comprising an ethylene homopolymer having an MFR of code D in the range of 100 to 500 g / 10 min, and ethylene and an α-olefin having 3 to 20 carbon atoms. It consists of a high molecular weight component (B) made of a copolymer, the proportion of the low molecular weight component (A) is 70-30 wt%, and the proportion of the high molecular weight component (B) is 30-70 wt%.
(B) MFR of code D 4.0-10.0 g / 10 min
(C) Density of 0.960 to 0.966 g / cm ³
(D) Molecular weight distribution (Mw / Mn) is 8.0 to 12.0
A step of mixing a cycloaliphatic metal salt component with the polyethylene resin component, and a step of obtaining the polyethylene resin composition for a bottle cap comprising a polyethylene resin component and a cycloaliphatic metal salt component.

Each said step can be performed by the method already described in the method for producing the polyethylene resin composition for bottle caps of the present invention.
Moreover, manufacture of the bottle cap of this invention can be performed by a well-known manufacturing method using the polyethylene resin composition for bottle caps of this invention.

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 (MFRD) of code D:
It represents a melt index and is a value measured according to JIS K7210 under conditions of a temperature of 190 ° C. and a load of 2.16 kg, and its unit is g / 10 min.
(2) MFR of code G (MFRG):
It represents a melt index and is a value measured according to JIS K7210 under conditions of a temperature of 190 ° C. and a load of 21.6 kg, and its unit is g / 10 min.
(3) FRR (G / D):
The ratio of the MFR of the code G and the MFR of the code D is represented.
(4) Density:
It is a value measured according to ASTM D1505, and the unit is g / cm 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. For high temperature GPC measurement, Alliance GPCV 2000 manufactured by Waters was used, and AT-807S (1) manufactured by Showa Denko KK and GMHHR-H (S) HT manufactured by Tosoh Co., Ltd. (2) were used for the column. Connected in series, the mobile phase was trichlorobenzene (TCB), column temperature 140 ° C., flow rate 1.0 ml / min, sample concentration 20 mg / solvent 10 ml, sample dissolution temperature 140 ° C., sample dissolution time 1 hour. . The unit is% by weight.

(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 when 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) Nominal strain at tensile fracture:
An injection-molded piece molded at 210 ° C. was used as a sample, and measurement was performed by the method described in JIS K7161. The unit is%.
(8) Tensile yield stress:
Measurement was performed in the same manner as in (7) above. The unit is MPa.
(9) Charpy impact strength:
The injection-molded piece prepared in (7) above was determined by the method described in JIS K7111. The measurement temperature is 23 ° C. The unit is kJ / m ² .
(10) Anisotropy:
A film gate flat plate of 150 mm × 150 mm × 2 mm at a cylinder temperature of 200 ° C. is injection-molded under conditions of a mold temperature of 50 ° C. (Injection molding machine: Injection molding machine IS-150EN manufactured by Toshiba Machine, injection pressure of about 600 to 700 kgf / cm ² , Injection speed 50%). After molding, the film gate flat plate was left in a constant temperature room for 2 days. Two days later, the difference in the size of the molded product with respect to the size of the mold was measured, and the molding shrinkage was determined by the following equation. The unit is%.
{(Dimension of mold)-(dimension of molded product)} × 100 / (dimension of mold)
The molding shrinkage (MD) in the flow direction of the resin and the molding shrinkage (TD) in the direction perpendicular to the flow of the resin are obtained from each central portion of the flat plate, and the ratio (MD / TD) of the molding shrinkage is obtained. In the case of .5 or more, it was judged that there was anisotropy, the roundness of the product when the cap was molded was insufficient, and the dimensional stability was insufficient.

(11) High-speed moldability-1:
Capillograph melt viscosity at 180 ° C. and shear rate of 1065 / sec (Capillograph 1D type, manufactured by Toyo Seiki Seisakusho, orifice size: D = 0.770 mm, L = 50.8 mm) is 200 Pa · sec or less and high-speed moldability It was judged that the resin temperature was good and the resin temperature during cap production could be lowered.
(12) High-speed moldability-2:
If the ½ isothermal crystallization time at 126 ° C. measured with a differential scanning calorimeter (DSC Pyris 1, manufactured by PerkinElmer, sample amount: 8 mg) is 10 minutes or less, high-speed moldability is good, and cap production It was judged that the inadequate cooling could be resolved.

(Preparation of solid catalyst component [A])
A chlorosilane compound and 15 liter reactor was synthesized thoroughly purged with nitrogen magnesium-containing solid by reaction, 2740 ml was charged trichlorosilane and (HSiCl ₃₎ as n- heptane solution of 2 mol / l, with stirring 65 ° C. And 7 liters of an n-heptane solution of an organic magnesium 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 (5 in terms of magnesium) Mol) 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 separating and drying this solid, analysis revealed that 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.

Preparation of Solid Catalyst A slurry containing 500 g of the above 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. The 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.

[Example 1]
Two-stage polymerization using two polymerization tanks connected in series was performed by the continuous slurry polymerization method using the solid catalyst obtained above. 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. The production rate of the low molecular weight component (A) composed of the ethylene homopolymer obtained in the first stage polymerization tank is 60 wt%, 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 wt%. The resin component described in Table 1 was obtained. To the obtained powder resin, 800 ppm by weight of calcium stearate and 200 wt. PPM of a cyclic aliphatic metal salt component were added as additives, 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. The structural formula of the cycloaliphatic metal salt component used in the examples is shown in the following formula.

  The blending ratio of the low molecular weight component (A) and the high molecular weight component (B) was determined from the production amount of each component. The physical properties of the composition are shown in Table 1. The resin composition obtained in Example 1 has a low crack crack viscosity at 180 ° C., a shear rate of 1065 / sec, which is an index of stress crack resistance (ESCR), high-speed moldability-1 during cap production, and high speed. The ½ isothermal crystallization time at 126 ° C., which is an index of moldability-2, was also fast, and good results were obtained for the molding shrinkage ratio, which is an anisotropy index, and all physical properties.

[Example 2]
The same two-stage polymerization as in Example 1 was carried out, and the resulting powdery resin was added with 800 ppm by weight of calcium stearate as an additive and 5% by weight of a combined system of cyclic aliphatic metal salt and fatty acid salt. Batch (master batch obtained by carrying out the same two-stage polymerization as in Example 1 and adding 5% by weight of MILLIKEN Hyperform HPN-20E, kneading, extruding, and pelletizing) to the obtained resin in powder state. .4 wt% was added, and the final cycloaliphatic metal salt addition ratio was added in the same 200 wt ppm as in Example 1, and the same kneading and extrusion as in Example 1 were performed to obtain composition pellets. . The physical properties of the composition are shown in Table 1. The resin composition obtained in Example 2 has better stress crack resistance (ESCR) than that in Example 1, and high-speed moldability-1, high-speed productivity-2, and anisotropy, which are indices during cap production. Good results were obtained with respect to the molding shrinkage ratio, which is an index of the measurement, and all physical properties.

[Example 3]
Using the two-stage polymerization apparatus described in Example 1, the same two-stage polymerization as in Example 1 was performed, and calcium stearate as an additive described in Example 2 was added to the obtained powdery resin as 800 ppm by weight. And 1% by weight of a master batch to which 5% by weight of a combined system of cycloaliphatic metal salt and fatty acid salt was added, and the final addition ratio of cycloaliphatic metal salt was 500ppm by weight. Resin pellets were obtained in the same manner as in Example 2. The physical properties of the composition are shown in Table 1. All of ESCR, high-speed moldability-1, high-speed moldability-2, anisotropy, and basic physical properties were good results.

[Example 4]
Polymerization was carried out using the two-stage polymerization apparatus described in Example 1, the first polymerization tank was polymerized in the same manner as in Example 1, and the hydrogen supply amount was reduced in the second polymerization tank. Polymerization was carried out by setting the molecular weight of the high molecular weight component (B) made of the copolymer to be high and setting the MFRD of the finally obtained polyethylene resin component to be as low as 4.5 g / 10 min. The same amount of the cyclic aliphatic metal salt and fatty acid salt master batch described in Example 2 is added to the obtained powdered resin, and the final amount of the cyclic aliphatic metal salt is the same as in Example 2. The resin pellets were obtained at 200 ppm by weight. The physical properties of the composition are shown in Table 1. All of ESCR, high-speed moldability-1, high-speed moldability-2, anisotropy, and basic physical properties were good results.

[Example 5]
The same two-stage polymerization as in Example 4 was performed, and the same amount of a cyclic aliphatic metal salt and fatty acid salt master batch was added to the resulting powdery resin as in Example 3, and finally The cycloaliphatic metal salt was also made the same amount of 500 ppm by weight as in Example 3 to obtain resin pellets. The physical properties of the composition are shown in Table 1. All of ESCR, high-speed moldability-1, high-speed moldability-2, anisotropy, and basic physical properties were good results.

[Example 6]
As in Example 3, except that the proportion of the low molecular weight component (A) was changed to 55 wt% and the proportion of the high molecular weight component (B) was changed to 45 wt% by changing the proportion of ethylene supplied to the polymerization tank. Polymerization was performed to obtain a powder composition (resin component) shown in Table 1. The final cyclic fat was added to this powder composition by adding 1 wt% of a master batch obtained by adding 800 wt ppm of the same calcium stearate as in Example 3 and 5 wt% of the combined system of cyclic aliphatic metal salt and fatty acid salt. The resin pellet was obtained by setting the addition ratio of the group metal salt to 500 ppm by weight. The physical properties of the composition are shown in Table 1. All of ESCR, high-speed moldability-1, high-speed moldability-2, anisotropy, and basic physical properties were good results.

[Example 7]
By changing the ratio of the ethylene supply amount to the polymerization tank, the ratio of the low molecular weight component (A) was changed to 50 wt%, and the ratio of the high molecular weight component (B) was changed to 50 wt%. Resin pellets were obtained. The physical properties of the composition are shown in Table 1. All of ESCR, high-speed moldability-1, high-speed moldability-2, anisotropy, and basic physical properties were good results.

[Example 8]
The same procedure as in Example 6 was performed except that the MFRD of the low molecular weight component (A) was changed to 150 g / min by decreasing the hydrogen supply amount to the first stage polymerization tank and lowering the hydrogen concentration in the polymerization tank. . The physical properties of the composition are shown in Table 1. ESCR, high-speed moldability-1, high-speed moldability-2, anisotropy, and basic physical properties were all good results.

[Example 9]
The same procedure as in Example 6 was performed except that the MFRD of the low molecular weight component (A) was changed to 480 g / min by increasing the hydrogen supply amount to the first stage polymerization tank and increasing the hydrogen concentration in the polymerization tank. . The physical properties of the composition are shown in Table 1. ESCR, high-speed moldability-1, high-speed moldability-2, anisotropy, and basic physical properties were all good results.

[Example 10]
The first stage polymerization tank performs the same polymerization as in Example 2, and the density of the polyethylene resin composition finally obtained is reduced by reducing the supply amount of 1-butene as a comonomer in the second stage polymerization tank. Polymerization was carried out at a setting as high as 0.966 g / cm ³ . Otherwise in the same manner as in Example 2, resin pellets were obtained. The physical properties of the obtained polyethylene resin composition are shown in Table 1. ESCR, high-speed moldability-1, high-speed moldability-2, anisotropy, and basic physical properties were all good results.

[Example 11]
Polymerization was carried out using the two-stage polymerization apparatus described in Example 1, and 800 wt ppm of calcium stearate as an additive described in Example 2 and 5% by weight of a combined system of cyclic aliphatic metal salt and fatty acid salt were added. 1% by weight of the master batch was added, and the final cycloaliphatic metal salt addition ratio was 500 ppm by weight. After extrusion, resin pellets were obtained. However, in Example 11, the molecular weight of the high molecular weight component (B) made of the resulting copolymer is set high by reducing the amount of hydrogen supplied in the second stage polymerization tank, and finally obtained. Polymerization was carried out by setting the MFRD of the polyethylene resin composition to be as low as 3.7 g / 10 min. The physical properties of the obtained polyethylene resin composition are shown in Table 1. The rigidity was high, the ESCR was also high, and the ½ isothermal crystallization time at 126 ° C., which is an index of high-speed moldability-2, was also good.

[Example 12]
Polymerization was carried out using the two-stage polymerization apparatus described in Example 1, and 800 wt ppm of calcium stearate as an additive described in Example 2 and 5% by weight of a combined system of cyclic aliphatic metal salt and fatty acid salt were added. 1% by weight of the master batch was added, and the final cycloaliphatic metal salt addition ratio was 500 ppm by weight. After extrusion, resin pellets were obtained. However, in Example 12, the molecular weight of the high molecular weight component (B) made of the resulting copolymer is set low by increasing the amount of hydrogen supplied in the second stage polymerization tank, and finally obtained. Polymerization was carried out by setting the MFRD of the polyethylene resin composition to be as high as 10.8 g / 10 min. The physical properties of the obtained polyethylene resin composition are shown in Table 1. Rigidity, anisotropy, high-speed moldability-1 and high-speed moldability-2 were judged to be good.

[Example 13]
By reducing the amount of hydrogen supplied to the first stage polymerization tank, the molecular weight of the resulting low molecular weight component (A) composed of an ethylene homopolymer was set to be high, and the MFRD was set to 20 g / 10 min. Furthermore, in order to adjust the MFRD of the final polyethylene resin composition, the amount of hydrogen supplied in the second stage polymerization tank is increased, and the molecular weight of the high molecular weight component (B) made of the resulting copolymer is lowered. Except for the above, the same procedure as in Example 6 was performed. The physical properties of the obtained polyethylene resin composition are shown in Table 1. The molecular weight distribution (Mw / Mn) is 7 because the molecular weight of the low molecular weight component (A) made of ethylene homopolymer is set higher and the molecular weight of the high molecular weight component (B) made of copolymer is set lower. .6 and the FRR (G / D) value was reduced to 40. It was judged that rigidity, high-speed moldability-1 and high-speed moldability-2 were all good.

[Example 14]
By increasing the amount of hydrogen supplied to the first stage polymerization tank, the molecular weight of the resulting low molecular weight component (A) composed of an ethylene homopolymer was set to be low, and the MFRD was set to 1200 g / 10 min. Furthermore, in order to adjust the MFRD of the final polyethylene resin composition, the amount of hydrogen supplied in the second stage polymerization tank was reduced, and the molecular weight of the high molecular weight component (B) made of the resulting copolymer was increased. Were carried out in the same manner as in Example 6. The physical properties of the obtained polyethylene resin composition are shown in Table 1. The molecular weight distribution (Mw / Mn) is 14 because the molecular weight of the low molecular weight component (A) made of ethylene homopolymer is set low and the molecular weight of the high molecular weight component (B) made of copolymer is set high. .2 and the FRR (G / D) value increased to 74. The physical properties of the obtained polyethylene resin composition are shown in Table 1. Rigidity, ESCR, high-speed moldability-1 and high-speed moldability-2 were judged to be good.

[Example 15]
Example 6 except that the density of the polyethylene resin composition obtained was set to 0.958 g / cm ³ by increasing the supply amount of 1-butene as a comonomer in the second stage polymerization tank. It carried out similarly. As a result, the density of the high molecular weight component (B) of the copolymer obtained in the second stage polymerization tank was calculated to be 0.937 g / cm ³ . The physical properties of the obtained polyethylene resin composition are shown in Table 1. It was judged that ESCR, high-speed moldability-1 and high-speed moldability-2 were all good.

[Example 16]
By changing the ratio of the ethylene supply amount to each polymerization tank, the ratio of the production amount of the low molecular weight component (A) made of the ethylene homopolymer obtained in the first stage polymerization tank is reduced to 25 wt%, and the second stage polymerization is performed. The production rate of the high molecular weight component (B) made of the copolymer obtained in the tank was set to 75 wt%. Furthermore, since the ratio of the low molecular weight component (A) made of an ethylene homopolymer was reduced, the amount of hydrogen supplied to the second stage polymerization tank was increased, and the high molecular weight component (B) made of a copolymer was increased. The MFRD of the obtained polyethylene resin component was controlled by lowering the molecular weight. As a additive, calcium stearate is added in an amount of 800 ppm by weight, a masterbatch containing 5% by weight of a combined system of a cyclic aliphatic metal salt and a fatty acid salt is added by 1% by weight, and the final cyclic aliphatic metal salt addition ratio is 500%. Weight ppm was added to obtain pellets. The physical properties of the obtained polyethylene resin composition are shown in Table 1. Rigidity, high-speed moldability-1 and high-speed moldability-2 were judged to be good.

[Example 17]
The ratio of the production amount of the low molecular weight component (A) composed of the ethylene homopolymer obtained in the first stage polymerization tank is increased to 75 wt%, and the high molecular weight component (B) composed of the copolymer obtained in the second stage polymerization tank. ) Production rate was set to 25 wt%. Furthermore, since the proportion of the low molecular weight component (A) made of an ethylene homopolymer was increased, the amount of hydrogen supplied to the second stage polymerization tank was reduced, and the high molecular weight component (B) made of a copolymer was reduced. The same procedure as in Example 6 was performed except that the MFRD of the obtained polyethylene resin component was controlled by increasing the molecular weight. The physical properties of the obtained polyethylene resin composition are shown in Table 1. It was judged that rigidity, high-speed moldability-1 and high-speed moldability-2 were all good.

[Example 18]
When an ethylene homopolymer was polymerized under a condition that the MFRD was 800 g / 10 min, a Ziegler catalyst having an Mw / Mn of 8.9 was used in a continuous two-stage polymerization method. Further, similarly to Example 17, the ratio of the production amount of the low molecular weight component (A) composed of the ethylene homopolymer obtained in the first stage polymerization tank was set to 75 wt%, and the co-polymer obtained in the second stage polymerization tank was obtained. The production rate of the high molecular weight component (B) made of a polymer was set to 25 wt%. Table 1 shows the physical properties of the obtained polyethylene resin component. The ESCR was maintained and the high-speed moldability-1 was judged to be good.

[Example 19]
When the ethylene homopolymer was polymerized under a condition that the MFRD was 100 g / 10 min, a Ziegler catalyst having an Mw / Mn of 5.1 was used in a continuous two-stage polymerization method. Further, as in Example 3, the ratio of the production amount of the low molecular weight component (A) made of an ethylene homopolymer obtained in the first stage polymerization tank was set to 60 wt%, and the co-polymer obtained in the second stage polymerization tank was used. The production rate of the high molecular weight component (B) made of a polymer was set to 40 wt%. As a additive, calcium stearate is added in an amount of 800 ppm by weight, a masterbatch containing 5% by weight of a combined system of a cyclic aliphatic metal salt and a fatty acid salt is added by 1% by weight, and the final cyclic aliphatic metal salt addition ratio is 500%. Weight ppm was added to obtain pellets. Table 1 shows the physical properties of the finally obtained polyethylene resin composition. Good high-speed moldability-1 and high-speed moldability-2 were recognized.

[Comparative Example 1]
In Comparative Example 1, the same polymerization as in Example 1, Example 2, and Example 3 was performed using the two-stage polymerization apparatus described in Example 1, the cyclic aliphatic metal salt was extruded without addition, and the resin Pellets were obtained. Table 2 shows the physical properties of the obtained polyethylene resin composition. ESCR, high-speed moldability-1, anisotropy, and basic physical properties were good, but the 1/2 isothermal crystallization time at 126 ° C., which is an index of high-speed moldability-2, was slow, and high-speed moldability was difficult. It was judged.

[Comparative Example 2]
In the same manner as in Comparative Example 1, the same polymerization as in Examples 4 and 5 was performed, and the cyclic aliphatic metal salt was extruded without addition to obtain resin pellets. Table 2 shows the physical properties of the obtained polyethylene resin composition. Results similar to Comparative Example 1 were good in ESCR, high-speed moldability-1, anisotropy and basic physical properties, but 1/2 isothermal crystallization time at 126 ° C., which is an index of high-speed moldability-2. However, it was judged that high-speed moldability was difficult.

[Comparative Examples 3 to 6]
Polymerization similar to that in Examples 6 to 9 was performed, and the cyclic aliphatic metal salt was extruded without addition to obtain resin pellets. Table 2 shows the physical properties of the obtained polyethylene resin composition. The results were the same as in Comparative Example 1 and Comparative Example 2, and the ESCR, high-speed moldability-1, anisotropy and basic physical properties were good, but 1/2 at 126 ° C., which is an index of high-speed moldability-2. It was judged that isothermal crystallization time was slow and high-speed moldability was difficult.

[Comparative Example 7]
By reducing the supply amount of 1-butene as a comonomer in the second stage polymerization tank, the density of the obtained polyethylene resin composition was set to be 0.968 g / cm ^3, and the cyclic aliphatic metal salt The same procedure as in Example 6 was performed except that was not added. As a result, the density of the high molecular weight component (B) made of the copolymer obtained in the second stage polymerization tank was calculated to be 0.959 g / cm ³ . Cyclic aliphatic metal salts were extruded without addition to obtain resin pellets. Table 2 shows the physical properties of the obtained polyethylene resin composition. Rigidity and high-speed moldability-1 were judged to be good, but the density of the high molecular weight component (B) consisting of the copolymer obtained in the second stage polymerization tank that strongly affects ESCR was too high. Therefore, the most important ESCR among the cap characteristics was insufficient. Although the density of the polyethylene resin composition was high, since no cycloaliphatic metal salt was added, the ½ isothermal crystallization time was slow and the high-speed moldability-2 was inferior.

[Comparative Example 8]
When an ethylene homopolymer was polymerized under a condition that the MFRD was 800 g / 10 min, a Ziegler catalyst having an Mw / Mn of 12.2 was used in a continuous two-stage polymerization method. However, butene-1 was also introduced into the first stage polymerization tank, and the polymer obtained in the first stage polymerization tank was a copolymer having a density of 0.955 g / cm ³ . Further, similarly to Example 17, the ratio of the production amount of the low molecular weight component (A) composed of the ethylene homopolymer obtained in the first stage polymerization tank was set to 75 wt%, and the co-polymer obtained in the second stage polymerization tank was obtained. The production rate of the high molecular weight component (B) made of a polymer was set to 25 wt%. Table 2 shows the physical properties of the obtained polyethylene resin component. Although the ESCR is extremely high, the molding shrinkage ratio, which is an anisotropy index, is high, the rigidity required for the cap is insufficient, the MFRD of the resin composition is low, high-speed moldability-1, high-speed molding Sex-2 was also lacking.

  The polyethylene resin composition for bottle caps provided by the present invention 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. However, when used for a bottle cap, it is optimally used as a bottle cap for a beverage container having no anisotropy, excellent dimensional stability, and excellent performance such as opening torque.

Claims (7)

A polyethylene resin composition for a bottle cap, comprising a polyethylene resin component and a cyclic aliphatic metal salt component, wherein the polyethylene resin component is at least one of the following (a), (b), (c) and (d): A polyethylene cap composition for bottle caps that meets the requirements.
(A) The polyethylene resin component is a low molecular weight component (A) comprising an ethylene homopolymer having an MFR of code D in the range of 100 to 500 g / 10 min, and ethylene and an α-olefin having 3 to 20 carbon atoms. It consists of a high molecular weight component (B) made of a copolymer, the proportion of the low molecular weight component (A) is 70-30 wt%, and the proportion of the high molecular weight component (B) is 30-70 wt%.
(B) MFR of code D 4.0-10.0 g / 10 min
(C) Density of 0.960 to 0.966 g / cm ³
(D) A polyethylene resin composition for bottle caps having a molecular weight distribution (Mw / Mn) of 8.0 to 12.0.   The polyethylene resin composition for bottle caps according to claim 1, wherein the polyethylene resin component satisfies the requirement consisting of (a), (b), (c) and (d). The polyethylene resin composition for bottle caps according to claim 1 or 2, wherein the polyethylene resin component further satisfies the following requirements (e) and (f).
(E) MFR of code G 180 to 500 g / 10 min
(F) Ratio FRR (G / D) 45 to 70 of MFR of code G and MFR of code D The polyethylene resin composition for bottle caps according to any one of claims 1 to 3, which satisfies the following requirements (g), (h) and (i).
(G) Environmental stress crack resistance (ESCR) of 10 hours or more (h) Resin measured with a 150 mm square, 2 mm thick film gate plate, injection molded at a cylinder temperature of 200 ° C. and a mold temperature of 50 ° C. The ratio (MD / TD) of the mold shrinkage (MD) in the flow direction and the mold shrinkage (TD) in the direction perpendicular to the resin flow is 1.0 to 2.5.
(I) 1/2 isothermal crystallization time at 126 ° C. measured with a differential scanning calorimeter (DSC) is 10 minutes or less The polyethylene resin composition for bottle caps according to any one of claims 1 to 4, wherein the cycloaliphatic metal salt component is represented by the following formula:

Here, M ¹ and M ² are independently selected from the group consisting of calcium, strontium, lithium, zinc, magnesium, and monobasic aluminum, or M ¹ and M ² collectively represent one divalent group. A metal ion, and R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , and R ²² are each composed of hydrogen and a hydrocarbon group having 1 to 9 carbon atoms. Any two R ^{15 to} R ²² hydrocarbon groups selected independently from each other and located adjacent to each other may be optionally combined to form a ring. The manufacturing method of the polyethylene resin composition for bottle caps including the following steps:
-Preparing a polyethylene resin component satisfying at least one of (a), (b), (c) and (d):
(A) The ratio of the low molecular weight component (A) made of an ethylene homopolymer having an MFR of code D in the range of 100 to 500 g / 10 min is 70 to 30 wt%, and ethylene and an α-olefin having 3 to 20 carbon atoms The proportion of the high molecular weight component (B) consisting of a copolymer with 30 to 70 wt%
(B) MFR of code D 4.0-10.0 g / 10 min
(C) Density of 0.960 to 0.966 g / cm ³
(D) Molecular weight distribution (Mw / Mn) is 8.0 to 12.0
A step of mixing a cycloaliphatic metal salt component with the polyethylene resin component, and a step of obtaining a polyethylene resin composition for a bottle cap comprising a polyethylene resin component and a cycloaliphatic metal salt component. The bottle cap which consists of a polyethylene resin composition for bottle caps in any one of Claims 1-5.