JP7037270B2 - Polyethylene resin composition for thin-walled containers - Google Patents

Description

The present invention relates to polyethylene resin compositions for thin-walled containers such as beverage containers and dairy containers.

Polyethylene resin has excellent low-temperature impact resistance, moldability, does not affect the flavor and taste of the contents, and can comply with the dairy ministry ordinance that is essential for raw milk containers. It has been used as a resin used in dairy products. In particular, we have provided products by injection molding using high-fluidity polyethylene resin for dairy products such as milk drinks and yogurt. However, from the viewpoint of productivity and cost reduction by thinning the product, the fluidity of the resin that can sufficiently flow to the end even with a thin product mold and the large number of products that can be obtained by one molding are available. It has been sought and it has been proposed to use a resin having a high melt flow (MFR) (see, for example, Patent Document 1). In addition, it has been proposed to use a polyethylene resin obtained by multi-stage polymerization (see, for example, Patent Documents 2 and 3) and to use polyethylene polymerized with a metallocene catalyst (see, for example, Patent Document 4).

Special Table 2009-538383 Gazette Japanese Unexamined Patent Publication No. 2006-160987 Japanese Unexamined Patent Publication No. 2011-153171 Japanese Unexamined Patent Publication No. 2006-124447

However, as in Patent Document 1, when the MFR is high, the molecular weight of the components constituting the resin is small, the drop impact strength is lowered and the product is easily cracked, and the low molecular weight component is increased, so that the flavor property is deteriorated. .. When the MFR exceeds 35, the amount of the low molecular weight component increases in the conventional catalyst system and the pelletizing method, and the odor component increases and the impact resistance decreases more than the decrease in the molecular weight.

When polymerization is carried out by multi-step polymerization as in Patent Documents 2 and 3, the higher the shear rate, the greater the decrease in viscosity and the improvement in moldability. However, in multi-step polymerization, polymerization of low molecular weight components is required. Therefore, a decrease in flavor is inevitable.
Further, the polyethylene resin obtained by the metallocene catalyst as in Patent Document 4 has a too narrow molecular weight distribution, so that the viscosity at the time of high-speed molding does not decrease and the fluidity is remarkably poor, and the odor derived from the catalyst is also generated. Inferior in flavor.

As described above, attempts have been made to optimize various properties such as MFR and molecular weight as a polyethylene resin for use in thin-walled containers such as beverage containers and dairy product containers, but thin-walled containers have been attempted. It has not been possible to provide a product that satisfies all of the above-mentioned various problems when used for use. Further, it is not disclosed in the publicly known literature that setting the MFR, density, and molecular weight distribution of the polyethylene resin composition for a thin-walled container to a specific range affects the rigidity and the drop impact resistance, and it is such. The specific method for obtaining the polyethylene resin composition is also not disclosed in the publicly known literature.

The present invention has been made in view of the above problems, and when a container is produced by thin-wall injection molding, it has high fluidity capable of high-speed molding, and the container drops while maintaining sufficient rigidity. It is an object of the present invention to provide a polyethylene resin composition for a thin-walled container which is excellent in drop impact resistance and can be used as a dairy beverage container for raw milk or the like.

As a result of diligent research, the present inventor has found that a polyethylene resin composition satisfying specific physical property requirements has high fluidity capable of high-speed molding, and a container obtained from such a polyethylene resin composition has sufficient rigidity. They have found that they have a drop impact property that can withstand a drop while holding them, and have found a production method for providing a polyethylene resin composition that satisfies the above specific physical property requirements, and have completed the present invention.
That is, the present invention relates to the following.

[1]
A polyethylene resin composition for a thin-walled container that satisfies the following requirements (a) to (c).
(A) Melting flow (MFR) of code D is 39 g / 10 minutes or more and less than 52 g / 10 minutes (b) Density is 955 to 975 kg / m ³
(C) The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 3.5 or more and 4.5 or less in the molecular weight distribution measurement by GPC [2].
The polyethylene resin composition for a thin-walled container according to [1], which further satisfies the requirements consisting of the following (d) to (h).
(D) Low molecular weight component by the ethanol extraction GC method is 50 ppm or less (e) The amount of terminal olefins measured by the IR method is 0.2 or less per 1000 carbon atoms (f) The amount of titanium residue in the resin is 0.5 ppm or more 1 .5 ppm or less (g) Crystallization start time at a temperature 11 ° C. lower than the melting point (Tm) is 1.5 minutes or less (h) Flexural modulus is 1000 MPa or more [3]
The 4% acetic acid solution extract by the evaporation residue measurement method was 15 ppm or less, the n-hexane extract was 2.6% or less, and the xylene soluble substance was 11.3% or less.
Conforms to ministry ordinances on milk and dairy ingredient standards, etc.
The polyethylene resin composition for a thin-walled container according to [1] or [2].
[4]
Contains more additives,
The additive is only 2500 ppm or less of calcium stearate specified in the Japanese Pharmacopoeia and / or titanium dioxide conforming to the standards such as food additives.
The polyethylene resin composition for a thin-walled container according to any one of [1] to [3].
[5]
A container formed by injection molding the polyethylene for a thin-walled molded container according to any one of [1] to [4].

The polyethylene resin composition for a thin-walled container of the present invention has excellent high fluidity, and can provide a thin-walled container having excellent rigidity without significantly reducing the drop impact resistance. Further, the thin-walled container obtained from the polyethylene resin composition of the present invention has excellent flavor and does not affect the taste, and is suitable for thin-walled containers for food applications such as milk drinks and yogurt containers.

Hereinafter, the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist thereof.

The polyethylene resin composition for a thin-walled container of the present invention (hereinafter, also referred to as a polyethylene resin composition) satisfies the following requirements (a) to (d) and ( h ) , and relates to component specifications of milk and dairy products. Conforms to the ministry ordinance .
(A) MFR of code D is 39 g / 10 minutes or more and less than 52 g / 10 minutes (b) Density is 955 to 975 kg / m ³
(C) The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) in the molecular weight distribution measurement by GPC is 3.5 or more and 4.2 or less.
(D) 50 ppm or less of low molecular weight components having 36 or less carbon atoms by the ethanol extraction GC method.
(H) Bending elastic modulus is 1050 MPa or more

The polyethylene resin composition satisfying the above requirements has high fluidity, and the thin-walled container obtained from the resin composition has the drop impact resistance required as a material. Conventionally, drop impact resistance and high fluidity are contradictory characteristics, and it is difficult to satisfy both. However, the polyethylene resin composition of the present invention has both drop impact resistance and high fluidity, and has a thin wall. A resin composition suitable for containers.
Further, the polyethylene resin composition of the present invention is a resin composition obtained by melt-kneading a mixture of polyethylene resin with additives added as needed, and pellets are preferably used as the form of the resin composition. Can be mentioned.

Further, the polyethylene resin composition for a thin-walled container of the present invention preferably satisfies the following requirements (d) to (h).
(D) Low molecular weight component by the ethanol extraction GC method is 50 ppm or less (e) The amount of terminal olefins measured by the IR method is 0.2 or less per 1000 carbon atoms (f) The amount of titanium residue in the resin is 0.5 ppm or more 1 .5 ppm or less (g) Crystallization start time at a temperature 11 ° C lower than the melting point (Tm) is 1.5 minutes or less (h) Flexural modulus is 1000 MPa or more

((A) MFR of code D)
The melt flow (MFR) of the polyethylene resin composition of the present invention is measured at a temperature of 190 ° C. and a load of 2.16 kg as defined in JIS K7210. The lower limit of MFR is that even thin-walled molded products can be molded without short shots (insufficient filling), and fluctuations such as resin temperature rise during molding do not increase and high-speed moldability is excellent. , 39 g / 10 minutes or more. The upper limit of MFR is less than 52 g / 10 minutes from the viewpoint of drop impact strength. Further, the MFR is preferably 40 g / 10 minutes or more and less than 45 g / 10 minutes.

((B) Density)
The density of the polyethylene resin composition of the present invention is measured by the density gradient tube method specified in the D method of JIS K7112. The lower limit of the density is 955 kg / m ³ or more from the viewpoint of the rigidity of the thin-walled container. The upper limit of the density is 975 kg / m ³ or less from the viewpoint of drop impact strength. The density is preferably 960 kg / m ³ or more and 970 kg / m ³ or less, and more preferably 962 kg / m ³ or more and 965 kg / m ³ or less.
The density of the polyethylene resin composition can be adjusted by changing the amount of comonomer added at the time of polymerization, and the density decreases as the amount of comonomer increases.

((C) Mw / Mn)
The molecular weight distribution (Mw / Mn) of the polyethylene resin composition of the present invention can be obtained by preparing a calibration curve from a standard polystyrene sample using high temperature gel permeation chromatography (high temperature GPC). As the solvent for GPC, o-dichlorobenzene (ODCB) can be preferably used.
The upper limit of the Mw / Mn value of the polyethylene resin composition of the present invention is such that the amount of the component having a molecular weight of 1000 or less is sufficiently small, and the problem of odor caused by the amount of the component having a molecular weight of 1000 or less and the beverage in the bottle It is 4.5 or less from the viewpoint of suppressing problems of taste and flavor due to melting into. Further, since the number of components having a molecular weight of 1000 or less is sufficiently small, the drop impact resistance is sufficient. The lower limit of the Mw / Mn value of the polyethylene resin composition of the present invention is 3.5 or more from the viewpoint of preventing the resin pressure from increasing during high-speed injection of the thin-walled molded product into the mold, resulting in a short shot. be. The value of Mw / M of the polyethylene resin composition of the present invention is preferably 3.8 or more and 4.3 or less, and more preferably 4.0 or more and 4.2 or less.
The molecular weight distribution can be widened by multi-stage polymerization or mixing polyethylene having two or more kinds of molecular weights, but in the case of single-stage polymerization, it can be achieved by adjusting a catalyst having a relatively uniform active site and polymerization conditions. In addition, since a heat stabilizer cannot be used to comply with the category of the Ministry of Milk, etc., the heat stability of polyethylene resin autonomy is important, and the above molecular weight distribution is achieved by suppressing cross-linking and decomposition due to heating in the finish extrusion. Can be achieved.

((D) Low molecular weight component)
In the polyethylene resin composition of the present invention, the total of the low molecular weight components of C36 (36 carbon atoms) or less is ethanol from the polyethylene resin from the viewpoint of preventing deterioration of the flavor property of the content and deterioration of the taste of the content. The quantitative value of the extract extracted at 70 ° C. for 2 hours using the above as a solvent is preferably 50 ppm or less, more preferably 40 ppm or less, still more preferably 35 ppm or less.
Further, when the molded product has a large amount of low molecular weight components, it is preferable that the number of low molecular weight components is small because the printing may be bald if the ink is repelled or the printed surface is rubbed by hand when printing on the molded product.

((E) Amount of terminal olefin)
The low molecular weight component of the terminal olefin in polyethylene is the cause of the so-called poly odor, which is an irritating odor. In addition, a heat stabilizer cannot be added in order to comply with the first category of the ministerial ordinance concerning the component specifications of milk and dairy products. Therefore, in the polyethylene resin composition of the present invention, the amount of the terminal olefin measured by the IR method has a viewpoint of reducing the influence on the flavor property and taste of the content, a viewpoint of suppressing MFR change and oxidative deterioration at the time of pelletizing, and a viewpoint of suppressing oxidative deterioration. From the viewpoint of stability with respect to thermal history, the number is preferably 0.2 or less, more preferably 0.15 or less, and further preferably 0.1 or less per 1000 carbon atoms of polyethylene.
Since the amount of the terminal olefin differs depending on the reaction in which the polymerized polyethylene is desorbed from the catalyst metal, it depends on the type of catalyst and can be reduced by mild polymerization conditions.

((F) Amount of titanium residue)
As will be described later, the polyethylene resin composition of the present invention is preferably polymerized using a Ziegler-based catalyst. The amount of titanium residue in the polyethylene resin composition decreases as the catalytic activity of the polymerization increases. The lower limit of the content of titanium residue in the resin of the polyethylene resin composition of the present invention is preferably 0.5 ppm or more from the viewpoint of catalytic activity during the polymerization reaction. In addition, the upper limit of the content of titanium residue in the resin of the polyethylene resin composition of the present invention has sufficient catalytic activity, prevents odors, improves flavor properties, and is stable against heat history. From the viewpoint of the above, 1.5 ppm or less is preferable, 1.3 ppm or less is more preferable, and 1.0 ppm or less is further preferable.

((G) Crystallization start time at a temperature 11 ° C. lower than the melting point (Tm))
Crystallization time is one of the factors that determine the production cycle in injection molding. It is preferable that the crystallization time is as short as possible because the resin cannot be taken out as a product unless it is solidified after the resin is injected into the mold. On the other hand, if the crystallization time is too early, it may solidify before reaching the flow end of the mold, resulting in a short shot.
In the measurement of 1/2 isothermal crystallization temperature of the polyethylene resin composition of the present invention by the DSC method, the crystallization start time at a temperature 11 ° C. lower than the melting point (Tm) is 1.5 minutes or less.
The crystal start time at a temperature 11 ° C. lower than the melting point is preferably 0.5 minutes or more and 1.5 minutes or less, and more preferably 1.0 minutes or more and 1.2 minutes or less. The reason why the temperature is set 11 ° C. lower than the melting point is that the crystallization rate changes greatly depending on the temperature difference from the melting point, so that the temperature difference is constant.

((H) Bending elastic modulus is 1000 MPa or more)
The flexural modulus of the polyethylene resin composition of the present invention is preferably 1000 MPa or more, more preferably 1050 MPa or more, and even more preferably 1100 MPa, from the viewpoint of imparting sufficient hardness when a thin-walled molded product is molded. It is more preferably 1140 MPa or more, and even more preferably 1140 MPa or more.
The flexural modulus of the polyethylene resin can be adjusted by the proportion of the copolymerized comonomer, and as the proportion of the comonomer is increased, the flexural modulus becomes lower and the molded product becomes softer. The smaller the proportion of comonomer, the harder it becomes, and the proportion of comonomer becomes zero, that is, the bending elastic modulus of the polyethylene resin made of homopolymer becomes maximum.

It is preferable that the polyethylene resin composition of the present invention complies with the ministry ordinance regarding the component specifications of milk and dairy products. Specifically, the polyethylene resin composition contains 15 ppm or less of a 4% acetic acid solution extract by an evaporation residue measurement method, 2.6% or less of an n-hexane extract, and 11.3% of a xylene-soluble substance. The following is preferable. Further, in the polyethylene resin composition, the evaporation residue is 15 μg / ml or less, the potassium permanganate consumption is 5 μg / ml or less, arsenic is 0.1 μg / ml or less as arsenic trioxide, and heavy metal is 1 μg as lead. It is preferably / ml or less.
The acetic acid solution extract, n-hexane extract, xylene-soluble substance, potassium permanganate consumption, arsenic, and heavy metals may be measured according to the method described in the ministry ordinance on component specifications of milk and dairy products. can.

(Additive)
Additives, fillers and the like may be added to the polyethylene resin composition of the present invention as long as the effects of the present invention are not impaired. It is preferable not to add additives and fillers as much as possible from the viewpoint of suppressing elution into beverages and the like in the product. When the polyethylene resin composition of the present invention is used in a milk beverage container such as raw milk, the additive used is Appendix 4 (2) of the Ministerial Ordinance (Milk Ordinance) concerning the component specifications of milk and dairy products. It is limited by 1 milk, special milk, etc. (class 1) in the containers and packaging of milk, etc. or the standards of these raw materials and the standards of manufacturing methods. The additives used are, for example, phenol-based antioxidants and antioxidants such as phosphorus-based and sulfur-based, and the amount of the above-mentioned antioxidant added is 500 ppm or less in the polyethylene resin composition. It is preferably 300 ppm or less, and more preferably 100 ppm or less. Further, it is more preferable that the antioxidant is not added at all from the viewpoint of improving the flavor property. In addition, the polyethylene resin composition of the present invention can be suitably used for a container for milk beverages because it complies with the Ordinance of the Ministry of Milk, etc. when no antioxidant is added.

In addition, a small amount of lubricant may be added in order to improve the separability between the containers during the production of the containers. Examples of the lubricant to be added include calcium stearate, magnesium stearate and the like, and calcium stearate is preferable. The amount of the lubricant added is not particularly limited as long as it is within the range specified in the Pharmacopoeia compliance in the first class of the Ordinance of the Ministry of Milk, etc., and is 2500 ppm or less, preferably 800 ppm or less, more preferably 800 ppm or less in the polyethylene resin composition. It is 600 ppm or less, more preferably 300 ppm or less. Further, as the calcium stearate, for example, calcium stearate specified in the Japanese Pharmacopoeia can be preferably used.

Further, a nucleating agent having an effect of increasing the crystallization rate can be added to the polyethylene resin composition of the present invention for the purpose of shortening the cooling time. The crystallization rate can be increased by adding a small amount of a pigment such as titanium dioxide. Further, as the titanium dioxide, for example, titanium dioxide conforming to the standards such as food additives can be preferably used. Titanium dioxide can be added within the range specified in the Pharmacopoeia compliance in Class 1 of the Ordinance of the Ministry of Milk, etc.

It is preferable not to add an antistatic agent, a light stabilizer, an ultraviolet absorber, an anti-fog agent, an organic peroxide, or the like to the polyethylene resin composition of the present invention.

Examples of the filler include talc, silica, carbon, mica, calcium carbonate, magnesium carbonate, wood flour and the like. Additives, fillers, titanium oxide, organic pigments and the like can be added in a masterbatch if necessary, but it is preferable not to add them from the viewpoint of preventing deterioration of flavor. When used in containers for raw milk, etc., the additives that can be used, such as calcium stearate conforming to the Pharmacopoeia and titanium oxide, which is a white pigment, are limited by the Ordinance of the Ministry of Milk, etc.

(Manufacturing method of polyethylene resin)
The polyethylene resin contained in the polyethylene resin composition of the present invention contains ethylene alone or one or more comonomer selected from ethylene and an α-olefin having 3 to 20 carbon atoms in the presence of a catalyst. , Manufactured by polymerizing at a ratio that gives the desired physical properties.

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, and the like. Examples thereof include 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, vinylcyclohexane and the like, and some of them can be combined and copolymerized. Among the above α-olefins, 1-butene is preferable.

The polyethylene resin in the present invention is preferably one or more comonomer selected from ethylene and an α-olefin having 3 to 20 carbon atoms. Further, in the polyethylene resin composition, the molar ratio of ethylene to the α-olefin having 3 to 20 carbon atoms is 90:10 to 99.9: 0.1 from the viewpoint of satisfying the density which is the requirement (b). However, it is preferably 98: 2 to 99.7: 0.3.
Further, in the production of polyethylene resin, the concentration of one or more comonomer selected from α-olefins having 3 to 20 carbon atoms is 100% with respect to all gas components in the reactor (total gas components are 100%). ), 0.1 to 10%, preferably 0.5 to 5.0%, more preferably 0.8 to 3.0%, still more preferably 1.0 to 2.5. %.

For the desired molecular weight and MFR, for example, a molecular weight modifier may be used when ethylene is polymerized alone or when ethylene and one or more comonomer selected from α-olefins having 3 to 20 carbon atoms are polymerized. As the molecular weight adjusting agent, hydrogen can be preferably mentioned. The hydrogen concentration when polymerizing the polyethylene resin is 40 to 70%, preferably 50 to 60%, based on the total gas components in the reactor.

The polyethylene resin in the present invention is preferably obtained by polymerizing using a Ziegler-type catalyst. A method for preparing a Ziegler-type catalyst will be described, but this does not limit the present invention. The Ziegler-type catalyst is a polymerization catalyst composed of a solid catalyst component [A] and an organoaluminum compound [B]. As a method for preparing the solid catalyst component [A], for example, a method in which the following steps (A-1) to (A-4) are sequentially performed can be mentioned.

1 mol of an organic magnesium component (hereinafter, also referred to as an organic magnesium compound represented by the general formula (i)) soluble in a hydrocarbon solvent represented by the following general formula (i) and the following general formula (ii). Step (A-1) of reacting 0.01 to 100 mol of the chlorosilane compound having the indicated Si—H bond (hereinafter, also referred to as a chlorosilane compound represented by the general formula (ii)) to obtain a solid.

(Al) α (Mg) β (R ¹ ) _p (R ² ) _q (OR ³ ) _r (i)

[In the formula, 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]

Ha _a SiCl _b R ⁴ _{4- (a + b)} (ii)

(In the formula, 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)

Step (A-2) to obtain a solid by reacting 1 mol of C-Mg bond contained in the solid obtained in the above step (A-1) with 0.05 to 20 mol of alcohol.

The solid obtained in the above step (A-2) is further reacted with an organometallic compound represented by the following general formula to obtain a solid (A-3);

AlR ⁵ _s Q _3-s

(In the formula, R ⁵ is a hydrocarbon group having 1 to 20 carbon atoms, Q represents a group selected from OR ⁶ , OSiR ⁷ R ⁸ R ⁹ , NR ¹⁰ R ¹¹ , SR ¹² and halogen, and R ⁶ ,, R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , and R ¹² are hydrogen atoms or hydrocarbon groups, and 0 <s).

The step (A-4) in which the titanium compound is reacted with the solid obtained in the above step (A-3) in the presence of the component (A-3);

The organic magnesium compound represented by the general formula (i) is shown in the form of a complex compound of organic magnesium soluble in a hydrocarbon solvent, and is a complex of R ₂ Mg and other metal compounds. It is all-encompassing. The relational expression 3α + 2β = p + q + r of the symbols α, β, p, q and r indicates the stoichiometry between the valence of the metal atom and the substituent. In the above general formula (i), the hydrocarbon group represented by R ¹ to R ² is, for example, an alkyl group, a cycloalkyl group and an aryl group. Examples of the alkyl group include methyl, ethyl, propyl, butyl, amyl, hexyl, decyl and the like, examples of the cycloalkyl group include cyclohexyl and the like, and examples of the aryl group include a phenyl group and the like. Be done. 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, and more preferably 0.5 to 10. Further, when an organic magnesium compound in which α in the general formula (i) is 0 is used, for example, when R ¹ is sec-butyl or the like, it is soluble in a hydrocarbon solvent, and such a compound is described in the present invention. Suitable. In the general formula (i), when α is 0, R ¹ and R ² are preferably any one of the following three groups (1), (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, and preferably both R ¹ and R ² have 4 to 6 carbon atoms. (2) R ¹ and R ² which are tertiary or tertiary alkyl groups are alkyl groups having different carbon atoms from each other, and preferably R ¹ is an alkyl group having 2 or 3 carbon atoms. R ² is an alkyl group having 4 or more carbon atoms (3) At least one of R ¹ and R ² is a hydrocarbon group having 6 or more carbon atoms, and preferably both R ¹ and R ² are carbon atoms. Alkyl group of number 6 or more

Examples of the secondary or tertiary alkyl group having 4 to 6 carbon atoms in the above (1) include sec-butyl, tert-butyl, 2-methylbutyl, 2-ethylpropyl, and 2,2-dimethylpropyl. Examples thereof include 2-methylpentyl, 2-ethylbutyl, 2,2-dimethylbutyl, 2-methyl-2-ethylpropyl and the like, with sec-butyl being preferred.

In the above (2), examples of the alkyl group having 2 or 3 carbon atoms include an ethyl group and a propyl group, and among them, an ethyl group is preferable. Examples of the alkyl group having 4 or more carbon atoms include a butyl group, an amyl group, a hexyl group, an octyl group and the like, and a butyl group and a hexyl group are particularly preferable. Examples of the hydrocarbon group having 6 or more carbon atoms in (3) include a hexyl group, an octyl group, a decyl group, a phenyl group and the like, of which a hexyl group, an octyl group and a decyl group are preferable, and a hexyl group is more preferable. preferable.

Generally, increasing the number of carbon atoms of an alkyl group makes it more soluble in a hydrocarbon solvent, but the viscosity of the solution tends to increase, and it is not preferable to use an alkyl group having a longer chain than necessary in terms of handling. The organic magnesium compound represented by the general formula (i) is used as a hydrocarbon solution, but the solution contains a small amount of a complexing agent such as ether, ester, or amine, or remains. It can be used without any problem even if it is used.

As the hydrocarbon group represented by R ³ in the general formula (i), an alkyl group or an aryl group having 3 to 10 carbon atoms is preferable. Examples of the alkyl group having 3 to 10 carbon atoms include 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 and the like can be mentioned, and examples of the aryl group include a phenyl group and the like. Of these, n-butyl, sec-butyl, 2-methylpentyl and 2-ethylhexyl are preferred.

The organic magnesium compound represented by the general formula (i) or the organic magnesium complex is represented by the general formulas R ¹ MgX and R ¹ ₂ Mg (R ¹ has the above-mentioned meaning, and X is a halogen atom). An organic magnesium compound and an organic metal compound represented by the general formula, AlR ² ₃ or Al R ² _3-1 H (R ² has the above-mentioned meaning) are used as an inert carbon such as hexane, heptane, cyclohexane, benzene, or toluene. Reacted in a hydrocarbon medium between room temperature and 150 ° C., and subsequently, if necessary, the hydrocarbon represented by R ³ soluble in an alcohol having a hydrocarbon group represented by R ³ or a hydrocarbon solvent. It is obtained by a method of reacting with a hydrocarbyloxymagnesium compound having a hydrogen group and / or a hydrocarbyloxyaluminum compound.

In the above method, when an alcohol having a hydrocarbon group represented by R ³ is reacted with a reaction product of the organic magnesium compound and the organic metal compound (hereinafter, also referred to as an organic magnesium component), the order of the reactions is as follows. A method of adding an alcohol having a hydrocarbon group represented by R ³ to the organic magnesium component, a method of adding an organic magnesium component to an alcohol having a hydrocarbon group represented by R ³ , or both at the same time. Any method of addition can be used. In the present invention, the molar composition ratio of the organic magnesium component soluble in hydrocarbon and the alcohol having a hydrocarbon group represented by R ³ is not particularly limited, but the general formula (i) obtained as a result of the reaction is used. In the represented organic magnesium compound, the range of the molar composition ratio r / (α + β) of the alkoxy group to all metal atoms is 0 ≦ r / (α + β) ≦ 2, preferably 0 ≦ r / (α + β) <1. Is.

Examples of the hydrocarbon group represented by R ⁴ in the general formula (ii) include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group and the like. Specific examples of the aliphatic hydrocarbon group include methyl, ethyl, butyl, amyl, hexyl and decyl, and examples of the alicyclic hydrocarbon group include cyclohexyl and the like, and the aromatic hydrocarbons. Examples of the group include a phenyl group and the like. Among the hydrocarbon groups represented by R ⁴ , an alkyl group having 1 to 10 carbon atoms is preferable, and a lower alkyl group having 1 to 3 carbon atoms such as methyl, ethyl and propyl is more preferable.
Further, a and b are numbers larger than 0 that satisfy the relationship of a + b ≦ 4, and b is preferably 2 or 3.

Examples of the chlorosilane compound represented by the general formula (ii) include trichlorosilane (HSiCl ₃ ), monomethyldichlorosilane (HSiCl ₂ CH ₃ ), ethyldichlorosilane (HSiCl ₂ C ₂ H ₅ ), and 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 , dimethylchlorosilane (HSiCl (CH ₃ ) ₂ ), HSiCl Examples thereof include (C ₂ H ₅ ) ₂ , HSiClCH ₃ (iso-C ₃ H ₇ ), HSiClCH ₃ (C ₆ H ₅ ), and HSiCl (C ₆ H ₅ ) ₂ . One selected from these compounds, or a mixture of two or more selected from these compounds can be used as the chlorosilane compound. Among the above chlorosilane compounds, trichlorosilane, monomethyldichlorosilane, dimethylchlorosilane and ethyldichlorosilane are preferable, and trichlorosilane and monomethyldichlorosilane are more preferable.

In the reaction in the step (A-1), the chlorosilane compound represented by the general formula (ii) is previously subjected to an inert reaction solvent, for example, an aliphatic hydrocarbon such as n-hexane or n-heptane; benzene, toluene or xylene. Aromatic hydrocarbons such as; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; chlorinated hydrocarbons such as 1,2-dichloroethane, o-dichlorobenzene and dichloromethane; or ether solvents such as ether and tetrahydrofuran; or these. It is preferable to use the mixed solvent of the above after diluting. Among the above reaction solvents, an aliphatic hydrocarbon medium is preferable from the viewpoint of catalyst performance.
The temperature of the reaction is not particularly limited, but is preferably equal to or higher than the boiling point of chlorosilane or 40 ° C. or higher from the viewpoint of accelerating the reaction.
The molar ratio of the organic magnesium compound soluble in the hydrocarbon solvent represented by the general formula (i) and the chlorosilane compound having a Si—H bond represented by the general formula (ii) is not particularly limited, but is usually general formula. The amount is 0.01 to 100 mol of the chlorosilane compound represented by the general formula (ii) with respect to 1 mol of the organic magnesium compound soluble in the hydrocarbon solvent represented by (i), and the hydrocarbon represented by the general formula (i). The range is preferably 0.1 to 10 mol of the chlorosilane compound represented by the general formula (ii) with respect to 1 mol of the organic magnesium compound soluble in the solvent.

As a reaction method, for example, an organic magnesium compound soluble in the hydrocarbon solvent represented by the general formula (i) and a chlorosilane compound having a Si—H bond represented by the general formula (ii) are simultaneously introduced into the reaction system for reaction. The method of simultaneous addition, the method of injecting the chlorosilane compound into the reaction system in advance and then introducing the organic magnesium component into the reaction system to cause a reaction, and the method of injecting the organic magnesium component into the reaction system in advance. There is a method of adding the above chlorosilane compound and the like. Among the above reaction methods, a method in which the chlorosilane compound is previously charged into the reaction system and then the organic magnesium component is introduced into the reaction system to cause a reaction is preferable. The solid component obtained by the above reaction is separated by filtration or decantation method, and then thoroughly washed with an inert solvent such as n-hexane or n-heptane to remove unreacted substances and by-products. It is preferable to do so.

The solid obtained in step (A-1) is further treated with alcohol in step (A-2). Examples of the alcohol include saturated or unsaturated alcohols having 1 to 20 carbon atoms. Examples of the saturated or unsaturated alcohol having 1 to 20 carbon atoms include methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, amyl alcohol, hexyl alcohol, cyclohexanol, phenol, and cresol. Among the saturated or unsaturated alcohols having 1 to 20 carbon atoms, a linear alcohol having 3 to 8 carbon atoms is preferable.

The amount of the alcohol used is 0 to 20 mol, preferably 0.1 to 10 mol, preferably 0.1 to 10 mol, per 1 mol of the C-Mg bond contained in the solid obtained in step (A-1). More preferably, it is 2-8 mol. The reaction between the solid and alcohol obtained in step (A-1) can be carried out in the presence or absence of an inert solvent. As the inert solvent, any of the above-mentioned aliphatic, aromatic or alicyclic hydrocarbons in step (A-1) may be used. The temperature at the time of reaction is not particularly limited, but is preferably room temperature to 200 ° C.

As the titanium compound in the step (A-4), 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 R ¹³ is a hydrocarbon group. Examples of such hydrocarbon groups include aliphatic hydrocarbon groups such as methyl, ethyl, propyl, butyl, amyl, hexyl, 2-ethylhexyl, heptyl, octyl, decyl and allyl; cyclohexyl, 2-methylcyclohexyl, cyclopentyl and the like. Alicyclic hydrocarbon groups; aromatic hydrocarbon groups such as phenyl and naphthyl are mentioned, and an aliphatic hydrocarbon group is preferable. X is a halogen atom. Examples of such halogen atoms include chlorine, bromine and iodine, with chlorine being preferred. Two or more kinds of titanium compounds included in the above general formula can be mixed and used.

The reaction between the solid and the titanium compound obtained in step (A-3) can be carried out in an inert reaction solvent, and examples of the inert reaction medium include aliphatic hydrocarbons such as hexane and heptane; benzene, and the like. Aromatic hydrocarbons such as toluene; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane can be mentioned, with aliphatic hydrocarbons being preferred.
The amount of the titanium compound used is preferably 0.5 mol or less, more preferably 0.1 mol or less, per 1 mol of the C-Mg bond contained in the solid component. The reaction temperature is not particularly limited, but is preferably in the range of room temperature to 150 ° C.

In this case, it is also possible to make the organometallic compound component present. At that time, as the order of addition, any method of adding the titanium compound after the organic metal compound, adding the organic metal compound after the titanium compound, or adding both at the same time is possible, but the organic metal compound component can be added. Subsequently, it is preferable to add the titanium compound. In this case, the molar ratio of the organometallic compound to the titanium compound is preferably in the range of 0.5 to 2.

The catalyst thus obtained is used as a slurry solution with an inert solvent. Examples of the inert solvent 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. , Hydrocarbons such as chlorobenzene, and the like.

Examples of the organic aluminum 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, and tri-n-amylaluminum. Trialkylaluminum such as triiso-amylaluminum, trin-hexylaluminum, trin-octylaluminum, trin-decylaluminum, diethylaluminum chloride, ethylaluminum dichloride, diiso-butylaluminum chloride, ethylaluminum sesquichloride, diethyl Aluminum halides such as aluminum bromide, diethylaluminum ethoxide, alkoxyaluminum such as diiso-butylaluminum butoxide, syloxyalkylaluminum such as dimethylhydrosiloxyaluminumdimethyl, ethylmethylhydrosiloxyaluminumdiethyl, ethyldimethylsiloxyaluminumdiethyl and these. Mixtures are used, with trialkylaluminum being particularly preferred as it achieves the highest activity.

The solid catalyst component [A] and the organoaluminum compound [B] may be sequentially added into the polymerization system, or may be mixed in advance before the polymerization reaction. The ratio of both components to be combined is defined by the molar ratio of Ti in the solid catalyst component [A] and Al of the organoaluminum component [B], and Al / Ti = 0.3 to 1000.

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

(Manufacturing method of polyethylene resin composition)
The polyethylene resin obtained by polymerization is obtained as, for example, polyethylene powder, and if necessary, an additive is added and melt-kneaded using an extruder or the like to obtain a polyethylene resin composition. The characteristics of the polyethylene resin composition of the present invention change depending on the conditions of melt-kneading. In the present invention, it is important to simultaneously set the above three requirements (a) to (c) in a specific range, and in particular, it is important to set the MFR and the molecular weight distribution within the range of the present invention.

As a method for satisfying the requirements (a) to (c), for example, nitrogen is flowed through an extruder hopper from the viewpoint of suppressing the cross-linking decomposition reaction of the polyethylene resin obtained by polymerization during melt-kneading. Set the extruder temperature from under the hopper to the middle of the heater block to be below the melting point of the polyethylene resin and low; suppress the temperature rise in the compression zone; set the die temperature to a higher temperature than the extruder; etc. The means of the above can be preferably mentioned.

When the MFR in the polyethylene resin composition of the present invention exceeds 35, the amount of the low molecular weight component increases in the conventional pelletizing method, the odor component increases, and the impact resistance decreases.
Since the resin composition of the present invention cannot be added with a heat stabilizer in order to comply with the Ordinance No. 1 of the Ministry of Milk, etc., deterioration of the resin due to heat must be avoided as much as possible. Therefore, for melting during extrusion pelletization, thermal cross-linking and decomposition occur when heating is applied from the outside such as a heater, so melting by shear heat generation is sufficient.

When the container obtained from polyethylene resin is a thin container for beverages or the like, there are many laws and regulations as described above, so that there are restrictions on the use of additives such as heat stabilizers generally used for polyethylene. Therefore, it is necessary to suppress the use of heat stabilizers and to suppress the decomposition and denaturation of the polymer due to heating in melt kneading. From this point of view, it is preferable to introduce an inert gas such as nitrogen into the hopper portion that supplies the polyethylene powder to the extruder.

It is also important to control the temperature of the extruder. The temperature under the hopper is cooled with water, the set temperature of the heater of the extruder is gradually increased from the bottom of the hopper toward the tip, and the set temperature is also insulated or from under the hopper. It is preferable to set up to half of all cylinders at a temperature lower than that of polyethylene resin, for example, 120 ° C. On the other hand, the die portion at the tip of the extruder is conversely relatively high, and it is preferable to set the temperature to, for example, 150 ° C. When the cylinder has 10 stages, the temperature is water-cooled under the hopper and gradually set to 120, 120, 130, 130, 130, 140, 140, 140, 140 ° C. toward the tip. The temperature of the die is preferably 150 ° C. As a result, unnecessary shear heat generation when passing through the breaker plate where the flow path of the die outlet is narrow can be suppressed. Further, the extruder may be provided with a compression zone for the purpose of sufficiently kneading the additives and the like, and in that case, it is preferable to adjust the temperature and the extrusion speed so that heat generation is not generated there.
Examples of the extruder include a single-screw extruder and a twin-screw extruder, and the combined use of two or more extruders is not limited.
Further, when a polyethylene resin composition having a small amount of terminal olefins and titanium metal residues in the molecule is used, it is relatively stable with respect to thermal history, and by setting the resin temperature low and introducing an inert gas, it becomes thinner. A polyethylene resin composition suitable for a container can be obtained.

The polyethylene resin composition of the present invention can have a spiral flow length of 2 mm thickness of 70 cm or more when injection-molded at a cylinder temperature of 200 ° C., a mold temperature of 50 ° C., and a resin pressure of 70 MPa, and is a thin-walled molded product. It can reach the end sufficiently when injection molding into the mold of.
On the other hand, a flat plate formed by injection molding of a pin gate having a cylinder temperature of 200 ° C., a mold temperature of 50 ° C., a 150 mm square and a thickness of 1 mm preferably has a total energy strength of 8 J or more in the impact strength of a cone at 23 ° C.

Generally, the drop impact strength decreases as the thickness of the molded product is reduced. When the resin composition is introduced into the thin portion of the injection molding die, a large stress is applied to the resin, so that the gate portion of the die is particularly liable to be broken. If the fluidity of the resin is increased in order to prevent this, that is, if the MFR is increased, the molecular weight of polyethylene is lowered and the drop impact strength is lowered.
On the other hand, in the polyethylene resin composition of the present invention, the MFR is increased and the density is set to be high, and the molecular weight distribution is set to a relatively narrow range, so that the thin portion of the injection molding die can be obtained. It shows the effect of maintaining the fluidity of the product and maintaining the drop impact strength even if the molded product is thin.

The polyethylene resin composition of the present invention can be suitably used as a polyethylene resin composition for a thin-walled container, which is suitable as a material for a thin-walled container. Thin-walled containers are used for cup-shaped products such as milk drinks and soft drinks, liquid food containers such as yogurt and pudding cups, food trays and gums, containers for supplements and pharmaceuticals, film cases and various parts cases. The container of the present invention can obtain the polyethylene resin composition of the present invention by injection molding. The container of the present invention is preferably a thin-walled container. The thickness of the thin-walled container is 0.5 to 1.0 mm, preferably 0.6 to 0.8 mm.

The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples and the like. 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
The MFR of the code D represents a melt index and is a value measured by JIS K7210 under the conditions of a temperature of 190 ° C. and a load of 2.16 kg. The unit of MFR of the code D is g / 10 minutes.

(2) Density Density is a value measured according to ASTM D1505. The unit of density is kg / m ³ .

(3) Molecular weight distribution (Mw / Mn)
The molecular weight distribution was calculated by obtaining the weight average molecular weight (Mw) and the number average molecular weight (Mn) from the chart of the molecular weight distribution obtained from the high temperature gel permeation chromatographie (GPC). GPC-IR5 manufactured by PolymerChar is used as the GPC, and AT-807S (1) manufactured by Showa Denko Corporation and GMHHR-H (S) HT (2) manufactured by Tosoh Corporation are connected in series as the column. Connected and used. The mobile phase was treated under the conditions of o-dichlorobenzene (ODCB), column temperature 140 ° C., flow rate 1.0 ml / min, sample concentration 20 mg / solvent (ODCB) 10 ml, sample dissolution temperature 140 ° C., and sample dissolution time 1 hour. ..

(4) Amount of oligomer The amount of oligomer was measured by gas chromatography. 5 g of the sample and 5 ml of ethanol were placed in a 20 ml glass sample tube, and OV-17 (1.1 m) was used as a column. The column temperature was maintained at 140 ° C. for 2 minutes, the temperature was raised to 250 ° C. at a heating rate of 10 ° C./min, and the column temperature was maintained at 250 ° C. for 7 minutes. Nitrogen was used as the carrier gas, and the flow rate of the carrier gas was 50 ml / min. The detector used was FID.

(5) Amount of terminal olefin The amount of terminal olefin was measured using JASCO FTIR4200 manufactured by JASCO Corporation. The measurement sheet was preheated for 3 minutes while pressurizing at 200 ° C. and 1 MPa by placing a required amount of pellets on a press die plate containing a 0.5 mm thick mold in accordance with JIS K6922-2. Subsequently, pressurization and depressurization at 1 MPa were repeated 7 times over 2 minutes, and then pressurization and depressurization at 10 MPa were repeated 4 times. Finally, the mixture was pressurized at 10 MPa for 2 minutes and then cooled at an average cooling rate of 15 ° C./min for 12 minutes to prepare a measuring sheet having a thickness of 0.5 mm.
The amount of terminal olefins was measured according to the method for quantifying heterologous bonds of polyethylene in the Polymer Handbook of the Japan Society for Analytical Chemistry. The amount of double bond (pieces / 1000C) was determined by measuring the absorbance A of the terminal vinyl (pieces / 1000C) of 910 cm ^-1 . The calculation formula is shown below.

Amount of terminal olefin = 0.114A ₉₁₀ / (ρ × t)

A is the absorbance, ρ is the density (g / cm ³ ), and t is the thickness (mm).

(6) Titanium residue The sample was weighed in a Teflon (registered trademark) decomposition container, high-purity nitric acid (Ultrapure manufactured by Kanto Chemical Co., Inc.) was added, and the sample was pressure-decomposed by a microwave decomposition apparatus. Ultrapure water was added to this to make the volume constant. Quantification was performed by the internal standard method using IPC-MS (Thermo Fisher Scientific Co., Ltd. X7 ICP-MS), and the titanium content in the sample was determined by subtracting the operation blank value performed at the same time.

(7) Crystallization start time at Tm-11 ° C. The crystallization start time at Tm-11 ° C was measured using DSC8000 manufactured by Perkinermer. First, after holding at 50 ° C. for 1 minute, the temperature is raised to 180 ° C. at a heating rate of 200 ° C./min, held at 180 ° C. for 5 minutes, the temperature is lowered to 50 ° C. at a temperature lowering rate of 10 ° C./min, and the temperature is lowered to 50 ° C. for 5 minutes. Then, the temperature was raised again to 180 ° C. at a heating rate of 10 ° C./min, and the melting point was measured from the peak temperature of the melting curve. Next, the crystallization behavior when the sample was melted at 180 ° C., cooled to a temperature 11 ° C. lower than the melting point at 200 ° C./min, and kept at a temperature 11 ° C. lower than the melting point was recorded. The time at which the exothermic peak due to crystallization became maximum after the target measurement temperature was reached was defined as the crystallization start time.

(8) Bending elastic modulus A dumbbell type test piece was formed by injection molding based on JIS K7171, and a bending measurement test piece was cut out from the dumbbell type test piece to measure the bending elastic modulus. A high flexural modulus indicates a high rigidity.

(9) SFD
Using the Sumitomo Heavy Industries injection molding machine SE130DUZ, a molten polyethylene resin composition is press-fitted by injection from the central gate using a swirl groove mold with a wall thickness of 0.6 mm to make a molded product, and its flow distance (spiral flow distance). (SFD)) was used to evaluate the fluidity. The spiral flow distance (SFD) was measured under the conditions of a resin temperature of 200 ° C., a mold temperature of 50 ° C., and an injection pressure of 70 MPa.

(10) Odor The odor of the cup obtained by injection molding was evaluated by 10 panelists by a sensory test. For the sensory test, a cup obtained by injection molding prepared by cutting so that the surface area of one side was 500 cm ² was placed in a sealable 500 cc odor bottle. The odor bottle is heated at 50 ° C. for 30 minutes in a sealed state and then cooled at 23 ° C. for 30 minutes to evaluate the odor of the odor bottle. When it was judged that five or more panelists felt unpleasant odors such as pungent odor, poly odor, and waxy odor, it was evaluated as defective (x).

(11) Taste 10 panelists evaluate the taste of water in a cup obtained by injection molding by sensory evaluation. For sensory evaluation, put tasteless and odorless water in a cup obtained by injection molding, seal it, heat it at 50 ° C for 30 minutes, cool it at 23 ° C for 30 minutes, open the lid and put water in the mouth to evaluate the taste. did. When it was judged that five or more panelists felt an unpleasant taste or an unpleasant taste, it was evaluated as defective.

(12) Conformity test of ministry ordinance (Ministry of Milk, etc.) regarding component standards of milk and dairy products Compliance with ministry ordinance (Ministry of Milk, etc.) regarding component standards of milk and dairy products is based on the standards described in the raw material standards for containers such as milk. It was measured by the specified method. Heavy metals, evaporation residues, and potassium permanganate consumption were measured as elution tests, and n-hexane extract, xylene soluble matter, arsenic, and heavy metals were measured as material tests. If the measured value is below the standard value, it is suitable, and if it exceeds the standard value, it is unsuitable. The standard values are 1 ppm or less for heavy metals in the elution test, 15 ppm or less for evaporation residue (4% acetic acid), 5 ppm or less for potassium permanganate consumption, 2.6% or less for n-hexane extraction in the material test, and xylene. The solubilizer is 11.3% or less, arsenic is 2 ppm or less, and heavy metal is 20 ppm or less.

(13) Printability The test sample is treated with a corona discharge surface treatment condition: 20 w / m ² / min, then water-based ink manufactured by Toyo Ink Co., Ltd. is applied, dried, and then rubbed with a finger to print. I checked if it could be peeled off. Those that had the ink peeled off were marked with x, and those that did not peel off were marked with ○.

(Preparation of solid catalyst component [A])
(1) Synthesis of magnesium-containing solid by reaction with chlorosilane compound 2740 mL of trichlorosilane (HSICl ₃ ) as a 2 mol / L n-heptane solution was charged into a sufficiently nitrogen-substituted 15 L reactor at 65 ° C. with stirring. AlMg ₆ (C ₂ H ₅ ) ₃ (n-C ₄ H ₉ ) _10.8 (On-C ₄ H ₉ ) _1.2 N-heptane solution of organic magnesium component shown in 1.2 (5 mol in magnesium equivalent) ) Was added over 1 hour, and the reaction was further carried out at 65 ° C. for 1 hour with stirring. After completion of the reaction, the supernatant was removed and washed with 7 L of n-hexane four times to obtain a solid substance slurry. As a result of analyzing the solid obtained by separating and drying this solid substance slurry, Mg 8.62 mmol, Cl 17.1 mmol, and n-butoxy group (On-C ₄ H ₉ ) 0.84 mmol were contained per 1 g of the solid. ..

(2) Preparation of solid catalyst The slurry containing 500 g of the solid was reacted with 2160 mL of an n-hexane solution of 1 mol / L of n-butyl alcohol at 50 ° C. for 1 hour with stirring. After completion of the reaction, the supernatant was removed and washed once with 7 L of n-hexane. The slurry was kept at 50 ° C., and 970 mL of an n-hexane solution of 1 mol / L diethylaluminum chloride was added under stirring and reacted for 1 hour. After completion of the reaction, the supernatant was removed and washed twice with 7 L of n-hexane. The slurry was kept at 50 ° C., 270 mL of a 1 mol / L n-hexane solution of diethylaluminum chloride and 270 mL of an n-hexane solution of 1 mol / L titanium tetrachloride were added, and the mixture was reacted for 2 hours. After completion of the reaction, the supernatant was removed, and the mixture was washed 4 times with 7 L of n-hexane while keeping the internal temperature at 50 ° C. to obtain a solid catalyst component as a hexane slurry solution. The chloride ion concentration in the supernatant of this solid catalyst slurry solution was 2.5 mmol / L, and the aluminum ion concentration was 4.5 mmol / L.

[Comparative Example 1]
Using the solid catalyst obtained above, a single slurry polymerization was carried out using 1-butene as a comonomer. Ethylene and 1-butene were supplied to the polymerization tank and polymerized at 85 ° C., 0.98 MPa, hydrogen concentration 54%, and 1-butene concentration 2.0%.
To the obtained powdered resin, 350 ppm of calcium stearate as an additive was added and blended with a Henschel mixer. A twin-screw extruder (manufactured by Japan Steel Works; TEX44HCT-49PW-7V) is used, and the hopper that supplies powder is open to the atmosphere, the temperature of the 10-stage cylinder and die is set to 200 ° C, and the extrusion rate is 35 kg / hour. Extrusion while kneading under the conditions to obtain composition pellets. The results are shown in Table 1.

[Comparative Example 2]
Polymerization was carried out in the same manner as in Example 1 except that the hydrogen concentration was 54% and the 1-butene concentration was 3.8%. Introduce nitrogen into the ^hopper that supplies The temperature of the die was set to 150 ° C. in a stepwise manner at 140 ° C., and the mixture was extruded while kneading under the conditions of an extrusion rate of 35 kg / hour and a screw rotation speed of 50 rpm to obtain composition pellets.
Each physical property value and evaluation data were obtained based on the above-mentioned measurement method. The results are shown in Table 1. The resin composition obtained in Comparative Example 2 had high rigidity and good impact strength of falling cones, but the fluidity was slightly insufficient. Good results were also shown in the odor test and taste test by the panelists. It was conforming in the milk ministry ordinance conformity test.

[Comparative Example 3]
The composition pellets were obtained by polymerization and extrusion in the same manner as in Comparative Example 1 except that the hydrogen concentration was 54% and the 1-butene concentration was 4.8%.
Each physical property value and evaluation data were obtained based on the above-mentioned measurement method. The results are shown in Table 1. The resin composition obtained in Comparative Example 3 had good fluidity, but the result was that the rigidity and the impact strength of the cone drop were insufficient. Good results were shown in the odor test and taste test by the panelists. It was conforming in the milk ministry ordinance conformity test.

[Comparative Example 4]
The composition pellets were obtained by polymerization and extrusion in the same manner as in Comparative Example 1 except that the hydrogen concentration was 58% and the 1-butene concentration was 4.5%.
Each physical property value and evaluation data were obtained based on the above-mentioned measurement method. The results are shown in Table 1. The resin composition obtained in Comparative Example 4 had high rigidity and particularly good fluidity, but had low impact strength of falling cones. Furthermore, in the odor test and taste test by panelists, the waxy odor was strong, and half of the panelists felt a strange taste in the taste test. It was conforming in the milk ministry ordinance conformity test.

[Comparative Example 5]
The composition pellets were obtained by polymerization and extrusion in the same manner as in Comparative Example 1 except that the hydrogen concentration was 50% and the 1-butene concentration was 8.1%.
Each physical property value and evaluation data were obtained based on the above-mentioned measurement method. The results are shown in Table 1. The resin composition obtained in Comparative Example 5 had good fluidity and impact strength of falling cones, but the result was that the rigidity was insufficient. Good results were shown in the odor test and taste test by the panelists. It was conforming in the milk ministry ordinance conformity test.

[Example 1]
Polyethylene powder was obtained under the same conditions as in Comparative Example 1. To the obtained powdered resin, 350 ppm of calcium stearate as an additive was added and blended with a Henschel mixer. Using a twin-screw extruder (manufactured by Japan Steel Works; TEX44HCT-49PW-7V), nitrogen is introduced into the hopper that supplies powder at a rate of 1 m ³ / hour, and the temperature of the 10-stage cylinder is set under the hopper. Water-cooled, set to 120, 120, 130, 130, 130, 140, 140, 140, 140 ° C in stages toward the tip, set the die temperature to 150 ° C, extrusion rate 35 kg / hour, screw rotation speed 50 rotations. The composition pellets were obtained by extruding while kneading under the condition of / min.
Each physical property value and evaluation data were obtained based on the above-mentioned measurement method. The results are shown in Table 1. The resin composition obtained in Example 1 had high rigidity, good fluidity, and good impact strength of falling cones. Furthermore, good results were shown in the odor test and taste test by the panelists. It was conforming in the milk ministry ordinance conformity test.

[Example 2]
The composition pellets were obtained by polymerization and extrusion in the same manner as in Example 1 except that the pressure was 0.97 MPa, the hydrogen concentration was 55%, and the 1-butene concentration was 4.5%.
Each physical property value and evaluation data were obtained based on the above-mentioned measurement method. The results are shown in Table 1. The resin composition obtained in Example 2 had high rigidity, good fluidity, and good impact strength of falling cones. Furthermore, good results were shown in the odor test and taste test by the panelists. It was conforming in the milk ministry ordinance conformity test.

[Example 3]
The composition pellets were obtained by polymerization and extrusion in the same manner as in Example 1 except that the pressure was 0.97 MPa, the hydrogen concentration was 55%, and the 1-butene concentration was 2.0%.
Each physical property value and evaluation data were obtained based on the above-mentioned measurement method. The results are shown in Table 1. The resin composition obtained in Example 3 had higher rigidity, and had good fluidity and impact strength of falling cones. Furthermore, good results were shown in the odor test and taste test by the panelists. It was conforming in the milk ministry ordinance conformity test.

[Comparative Example 6]
A 1 mol / L hydroxytrichlorosilane hexane solution (4 L) was placed in a stainless steel autoclave having an internal volume of 20 L sufficiently substituted with nitrogen, and the composition formula AlMg ₅ (C ₄ H ₉ ) ₁₁ (OC ₂ H ₅ ) was stirred at 50 ° C. ) 9 L of a hexane solution of the organic magnesium compound represented by ₂ (corresponding to 6.5 mol of magnesium) was added dropwise over 4 hours, and the reaction was further carried out at 50 ° C. for 1 hour with stirring. After completion of the reaction, the supernatant was removed and washed with 7 L of hexane four times. As a result of analyzing this carrier, the amount of magnesium contained in 1 g of the carrier was 8.44 mmol.
450 mL of 1 mol / L 1-propanol hexane solution was added to 13 L of the hexane slurry containing 500 g of the carrier over 30 minutes with stirring at 50 ° C. After the addition, the reaction was continued at 50 ° C. for 1 hour. After completion of the reaction, 7 L of the supernatant was removed, 6.4 L of hexane was added, and 600 mL of a 1 mol / L diethylaluminum chloride hexane solution was added at a temperature of 65 ° C. over 1 hour and 30 minutes. After the addition, the reaction was continued at 65 ° C. for 1 hour. After completion of the reaction, 7 L of the supernatant was removed, and the mixture was washed 4 times with 7 L of hexane. Remove 600 mL of the supernatant of the slurry after washing, add 265 mL of 1 mol / L diethylaluminum chloride hexane solution over 5 minutes while stirring at 50 ° C., and then add 265 mL of 1 mol / L titanium tetrachloride hexane solution over 5 minutes. Was added. After the addition, the reaction was continued at 50 ° C. for 2 hours. After completion of the reaction, 7 L of the supernatant was removed, and the solid catalyst component was prepared by washing with 7 L of hexane four times. The amount of titanium contained in 1 g of this solid catalyst component was 0.52 mmol.
Using the solid catalyst obtained above, a single slurry polymerization was carried out using 1-butene as a comonomer. Ethylene and 1-butene were supplied to the polymerization tank and polymerized at 85 ° C., 0.98 MPa, hydrogen concentration 56%, and 1-butene concentration 1.5%. To the obtained powdered resin, 350 ppm of calcium stearate as an additive was added and blended with a Henschel mixer. This was extruded using a twin-screw extruder (manufactured by Japan Steel Works, Ltd .; TEX44HCT-49PW-7V) while kneading under the same nitrogen introduction, temperature profile, and conditions as in Example 1 to obtain composition pellets.
Each physical property value and evaluation data were obtained based on the above-mentioned measurement method. The results are shown in Table 1. The resin composition obtained in Comparative Example 6 had high rigidity and good fluidity, but had a slightly wide molecular weight distribution and insufficient impact strength for falling cones. Good results were shown in the odor test and taste test by the panelists. It was conforming in the milk ministry ordinance conformity test.

[Comparative Example 7]
In a fully nitrogen-substituted 15 L reactor, 2740 mL of tetrachlorotitanium (TiCl ₄ ) was charged as a 2 mol / L n-heptane solution, kept at 65 ° C. with stirring, and the composition formula AlMg ₆ (C ₂ H ₅ ). ₃ (i _- C 4H ₉ ) 7 L of an n-heptane solution of the organic magnesium component shown in ₃ was added over 1 hour, and the reaction was further carried out at 65 ° C. for 1 hour with stirring. After completion of the reaction, the supernatant was removed and washed with 7 L of n-hexane four times to obtain a solid slurry. This solid slurry was separated and dried to obtain a solid catalyst.
Using the solid catalyst obtained above, a single slurry polymerization was carried out using 1-butene as a comonomer. Ethylene and 1-butene were supplied to the polymerization tank and polymerized at 85 ° C., 0.96 MPa, hydrogen concentration 55%, and 1-butene concentration 1.7%. To the obtained powdered resin, 350 ppm of calcium stearate as an additive was added and blended with a Henschel mixer. This was extruded using a twin-screw extruder (manufactured by Japan Steel Works, Ltd .; TEX44HCT-49PW-7V) while kneading under the same nitrogen introduction, temperature profile, and conditions as in Example 1 to obtain composition pellets.
Each physical property value and evaluation data were obtained based on the above-mentioned measurement method. The results are shown in Table 1. The resin composition obtained in Comparative Example 7 had high rigidity and good fluidity, but had a slightly wide molecular weight distribution and insufficient impact strength for falling cones. Good results were shown in the odor test and taste test by the panelists. It was conforming in the milk ministry ordinance conformity test.

[Comparative Example 8]
Using the same catalyst as in Example 1, two-stage polymerization was carried out using two polymerization tanks connected in series by a continuous slurry polymerization method. The comonomer used is 1-butene. Only ethylene is supplied as a monomer to the first-stage polymerization tank, and polymerization is performed at a temperature of 85 ° C., a pressure of 5.8 MPa, and a hydrogen concentration of 57%, and ethylene and 1-butene are supplied to the second stage at 85 ° C. Polymerization was carried out at 2.7 kg / cm ³ G, hydrogen concentration 25%, and 1-butene concentration 1.7%. The ratio of the production amount of the low molecular weight component made of the ethylene homopolymer obtained in the first stage polymerization tank is 60 wt%, and the ratio of the production amount of the high molecular weight component made of the copolymer obtained in the second stage polymerization tank is 40 wt%. Set to%. To the obtained powdered resin, 350 ppm of calcium stearate as an additive was added and blended with a Henschel mixer. This was extruded using a twin-screw extruder (manufactured by Japan Steel Works, Ltd .; TEX44HCT-49PW-7V) while kneading under the same nitrogen introduction, temperature profile, and conditions as in Example 1 to obtain composition pellets.
Each physical property value and evaluation data were obtained based on the above-mentioned measurement method. The results are shown in Table 1. The resin composition obtained in Comparative Example 8 had good fluidity and rigidity, but the result was that the impact strength of the falling cone was insufficient. In the odor test and taste test by the panelists, there were some panelists who felt a strange taste. It was conforming in the milk ministry ordinance conformity test.

[Comparative Example 9]
6.2 g (8.8 mmol) of triethylammonium tris (pentafluorophenyl) (4-hydroxyphenyl) borate was added to 4 L of toluene and stirred at 90 ° C. for 30 minutes. Next, 40 mL of a toluene solution of 1 mol / L trihexylaluminum was added to this stirred solution, and the mixture was further stirred at 90 ° C. for 1 minute to obtain triethylammoniumtris (pentafluorophenyl) (4-hydroxyphenyl) borate and toluene of trihexylaluminum. A solution was obtained. On the other hand, silica was treated with a nitrogen stream at 500 ° C. for 3 hours, and the treated silica was placed in 1.7 L of toluene and stirred to obtain a silica slurry solution. A toluene solution of the above triethylammonium tris (pentafluorophenyl) (4-hydroxyphenyl) borate and trihexylaluminum was added to this silica slurry solution, and the mixture was stirred at 90 ° C. for 3 hours. Next, 206 mL of a toluene solution of 1 mol / L trihexyl aluminum was added, and the mixture was further stirred at 90 ° C. for 1 hour. The supernatant was then decanted 5 times with toluene at 90 ° C. to remove excess trihexylaluminum to give a mixture. 0.218 mol / L dark purple titanium (N-1,1-dimethylethyl) dimethyl (1- (1,2,3,4,5, -eta) -2,3,4,5-tetramethyl- Add 20 mL of ISOPARTME (manufactured by ExxonMobile Chemical, USA) solution of 2,4-cyclopentadiene-1-yl) silanaminate) ((2-) N)-(η ^4-1,3 -pentadiene) to the above mixture for 3 hours. Stirring gave a green bearing catalyst.
Using the solid catalyst obtained above, a single slurry polymerization was carried out using 1-butene as a comonomer. Ethylene and 1-butene were supplied to the polymerization tank and polymerized at 70 ° C., 0.98 MPa, hydrogen concentration 56%, and 1-butene concentration 1.6%. To the obtained powdered resin, 350 ppm of calcium stearate as an additive was added and blended with a Henschel mixer. This was extruded using a twin-screw extruder (manufactured by Japan Steel Works, Ltd .; TEX44HCT-49PW-7V) while kneading under the same nitrogen introduction, temperature profile, and conditions as in Example 1 to obtain composition pellets.
Each physical property value and evaluation data were obtained based on the above-mentioned measurement method. The results are shown in Table 1. The resin composition obtained in Comparative Example 9 had high rigidity and good impact strength of falling cones, but the molecular weight distribution was too narrow, resulting in inferior fluidity. In addition, good results were obtained in the odor test and taste test by the panelists. It was conforming in the milk ministry ordinance conformity test.

[Comparative Example 10]
4 mol of chromium trioxide is dissolved in 80 L of distilled water, 20 kg of silica (grade 952 manufactured by WR Grace and Company) is immersed in this solution, stirred at room temperature for 1 hour, and then the slurry is heated to retain water. Then, after drying under reduced pressure at 120 ° C. for 10 hours, dry air was circulated and calcined at 600 ° C. for 5 hours to obtain a chromium oxide catalyst containing 1.0% by weight of chromium.
Using the solid catalyst obtained above, a single slurry polymerization was carried out using 1-butene as a comonomer. Ethylene and 1-butene were supplied to the polymerization tank and polymerized at 86 ° C., 0.98 MPa, hydrogen concentration 50%, and 1-butene concentration 4.9%.
To the obtained powdered resin, 350 ppm of calcium stearate as an additive was added and blended with a Henschel mixer. This was extruded using a twin-screw extruder (manufactured by Japan Steel Works, Ltd .; TEX44HCT-49PW-7V) while kneading under the same nitrogen introduction, temperature profile, and conditions as in Example 1 to obtain composition pellets.
Each physical property value and evaluation data were obtained based on the above-mentioned measurement method. The results are shown in Table 1. The resin composition obtained in Comparative Example 10 had good rigidity and fluidity, but the impact strength of the cone was insufficient due to the widening of the molecular weight distribution. In addition, in the odor test and taste test by the panelists, the poly odor due to the olefin and the taste difference were felt. In addition, in the milk ministry ordinance conformity test, the amount of n-hexane extracted was large and unsuitable.

The polyethylene composition of the present invention is useful for injection molding of thin-walled containers, and can be particularly suitably used in the field of milk-based beverage containers and the like.

Claims (6)

A polyethylene resin composition for a thin-walled container that meets the following requirements (a) to (d) and (h) and conforms to the ministry's ordinance on the component standards of milk and dairy products.
(A) Melting flow (MFR) of code D is 39 g / 10 minutes or more and less than 52 g / 10 minutes (b) Density is 955 to 975 kg / m ³
(C) The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 3.5 or more and 4.2 or less in the molecular weight distribution measurement by GPC. Less than 50 low molecular weight components are 50 ppm or less (h) Flexural modulus is 1050 MPa or more The polyethylene resin composition for a thin-walled container according to claim 1, further satisfying the following requirements (e) to (g).
(E) The amount of terminal olefins measured by the IR method is 0.2 or less per 1000 carbon atoms. (F) The amount of titanium residue in the resin is 0.5 ppm or more and 1.5 ppm or less (g) 11 ° C. lower than the melting point (Tm). Crystallization start time at temperature is 1.5 minutes or less The 4% acetic acid solution extract by the evaporation residue measurement method is 15 ppm or less, the n-hexane extract is 2.6% or less, and the xylene soluble substance is 11.3% or less.
The polyethylene resin composition for a thin-walled container according to claim 1 or 2. Contains more additives,
The additive is only 2500 ppm or less of calcium stearate specified in the Japanese Pharmacopoeia and / or titanium dioxide conforming to the standards such as food additives.
The polyethylene resin composition for a thin-walled container according to any one of claims 1 to 3. One of claims 1 to 4, wherein the spiral flow length of 2 mm thickness when injection molded with an injection molding machine at a cylinder temperature of 200 ° C., a mold temperature of 50 ° C., and a resin pressure of 70 MPa is 70 cm or more. The polyethylene resin composition for a thin-walled container according to the above item. A container obtained by injection molding the polyethylene resin composition for a thin-walled container according to any one of claims 1 to 5.