JP2006111331A - Tubular container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tubular container showing a superior anti-stress crack characteristic, tearing strength and heat sealing characteristic. <P>SOLUTION: There is provided a tubular container made of polyethylene resin compound comprising an ethylene-α-olefin copolymer (A) having a density of 905 to 925 kg/m<SP>3</SP>, MFR of 1.0 to 10 g/10 min, Mw/Mn of 4 or less in which it is melted for 5 minutes at 200°C with a differential scanning calorimetry, after this operation, it is cooled down to 30°C at a cooling speed of 10°C/min, a temperature (Tm(°C)) at the maximum peak position in an endoergic curved line observed when its temperature is increased again at a temperature increasing speed of 10°C/min and a short chain branched (SCB) per 1,000 of the number of carbons satisfy a relation indicated by Tm<-1.8×SCB+138; and a high-pressure radical polymerization low-density polyethylene (B) with a density of 910 to 930 kg/m<SP>3</SP>and MFR of 0.1 to 10 g/10 min in which (A)/(B)(a weight ratio) is 5/95 to 45/55. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a tube container, and more particularly to a tube container excellent in stress crack resistance (hereinafter referred to as ESCR) and tear strength and excellent in heat sealability.

  Tubes for cosmetics such as hand creams, hair gels and cosmetic creams; tubes for daily use such as shampoos, rinses and detergents; tube containers for foods such as mayonnaise, soy sauce and wasabi are generally manufactured using an extrusion method. Yes. These tube containers are formed of, for example, a single layer of high-pressure low-density polyethylene or a multilayer provided with a gas barrier layer. These tube containers need flexibility and resilience when squeezed out, container strength (tear strength) due to expansion of the contents, ESCR due to penetration of the contents, and heat sealability to close the ends of the tubes. .

  Therefore, high-pressure low-density polyethylene has been used suitably since it has moderate flexibility and good heat-sealing properties. However, the high-pressure low-density polyethylene has a low ESCR, so depending on the contents, There are problems such as leakage of liquids, contents that are not suitable for use, and damage due to expansion of the contents due to low strength.

  As a method of overcoming this problem, it has been proposed to use a metallocene linear polyethylene (see, for example, Patent Document 1).

  In addition, it is known to use a composition comprising a high-pressure radical polymerization low-density polyethylene and an ethylene / α-olefin copolymer for a heel sheet material of an extrusion laminate material (see, for example, Patent Document 2). ), It is not known to be used as a tube container.

JP 11-49820 A JP-A-9-59440

  However, in the method proposed in Patent Document 1, since the metallocene linear polyethylene is too stiff, the problem remains that it is inferior in flexibility and resilience during squeezing. There is a demand for the appearance of a tube container that has the same flexibility and resiliency as conventional high-pressure low-density polyethylene, has excellent ESCR, high tear strength, and excellent heat sealability.

  Therefore, as a result of intensive studies on the above problems, the present inventors have found that a tube container made of a specific ethylene / α-olefin copolymer and a specific high-pressure radical polymerization low-density polyethylene (hereinafter referred to as LDPE) is flexible. The present invention has been completed by finding that it has excellent ESCR, high tear strength and excellent heat sealability.

That is, the present invention has (a) a density in the range of 905 to 925 kg / m ³ and (b) a melt flow rate (MFR) measured under a load of 190 ° C. and 21.18 N of 1.0 to 10 g / (C) The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 4 or less, and (d) 5 minutes at 200 ° C. by a differential scanning calorimeter. The temperature at the maximum peak position (Tm (° C.)) of the endothermic curve observed when melted, then cooled to 30 ° C. at a cooling rate of 10 ° C./min, and then heated again at a rate of temperature increase of 10 ° C./min. An ethylene / α-olefin copolymer (A) satisfying the relationship represented by the following formula (1) with the number of short chain branches (SCB) per 1000 carbon atoms determined from the measurement of the infrared absorption spectrum;
Tm <−1.8 × SCB + 138 (1)
(E) The density is in the range of 910 to 930 kg / m ³ , and (f) the melt flow rate (MFR) measured under a load of 190 ° C. and 21.18 N is in the range of 0.1 to 10 g / 10 min. The present invention relates to a tube container made of a polyethylene composition comprising LDPE (B) and having an ethylene / α-olefin copolymer (A) / LDPE (B) (weight ratio) of 5/95 to 45/55.

  The present invention is described in detail below.

The ethylene / α-olefin copolymer (A) used in the present invention has a density in the range of 905 to 925 kg / m ³ and a melt flow rate (hereinafter simply referred to as MFR) measured under a load of 190 ° C. and 21.18 N. ) In the range of 1.0 to 10 g / 10 min, and the ratio (hereinafter referred to as Mw / Mn) of the weight average molecular weight (hereinafter referred to as Mw) and the number average molecular weight (hereinafter referred to as Mn). Is 4 or less, melted at 200 ° C. for 5 minutes by a differential scanning calorimeter, then cooled to 30 ° C. at a cooling rate of 10 ° C./min, and then heated again at a temperature rising rate of 10 ° C./min. The temperature of the maximum peak position of the endothermic curve observed at this time (hereinafter simply referred to as Tm) and the number of short chain branches per 1000 carbon atoms (hereinafter referred to as SCB) determined from the measurement of infrared absorption spectra. Is the relationship represented by the above equation (1) An ethylene · alpha-olefin copolymer satisfying.

Here, when the density of the ethylene / α-olefin copolymer exceeds 925 kg / m ³ , the crystallinity of the ethylene / α-olefin copolymer increases, and the heat sealability of the resulting tube container decreases. On the other hand, when the density is less than 905 kg / m ³ , the obtained tube container becomes too soft and has poor restorability.

  In addition, when the MFR of the ethylene / α-olefin copolymer is less than 1.0 g / 10 minutes, the resulting polyethylene resin composition has a high melt shear viscosity, which increases the load on the extruder during processing. The drawdown property is also deteriorated and the molding processability is inferior. On the other hand, when the MFR is larger than 10 g / 10 minutes, the melt tension of the obtained polyethylene resin composition becomes small, so that the formability is deteriorated. In addition, since the molecular weight is small, the mechanical strength of the tube container is lowered.

  When the Mw / Mn of the ethylene / α-olefin copolymer exceeds 4, the low molecular weight component increases and the polyethylene resin composition becomes sticky. When the tube container is used, there is a high possibility of causing poor printing. It becomes.

  When the relationship between Tm and SCB of the ethylene / α-olefin copolymer deviates from the relationship of the above formula (1), the low molecular weight component increases and the polyethylene resin composition becomes sticky. This is likely to cause printing defects. In addition, the heat seal temperature that reaches the maximum strength at the time of heat sealing becomes high, and the production efficiency of the container is also inferior.

  The ethylene / α-olefin copolymer (A) used in the present invention may be any ethylene / α-olefin copolymer satisfying the above characteristics, and there is no particular limitation on the production method thereof. Among them, metallocene is used as a polymerization catalyst because it has excellent heat seal properties such as reaching the highest heat seal strength at a lower temperature than conventional LLDPE even at the same density as linear low density polyethylene (hereinafter referred to as LLDPE). An ethylene / α-olefin copolymer produced using a catalyst is preferred.

  The metallocene catalyst is a polymerization catalyst comprising a metallocene compound (hereinafter simply referred to as component (a)) as a main component, and the component (a) has, for example, a cyclopentadienyl group or a substituent. One group selected from a cyclopentadienyl group (substituted cyclopentadienyl group), an indenyl group, and a substituted indenyl group, and one group selected from a fluorenyl group and a substituted fluorenyl group were cross-linked by a cross-linking group. Examples thereof include transition metal compounds belonging to Group 4 of the periodic table having a ligand, and typical examples thereof include diphenylmethylene (1-cyclopentadienyl) (9-fluorenyl) zirconium dichloride, diphenylmethylene (3-methyl). -1-cyclopentadienyl) (9-fluorenyl) zirconium dichloride, diphenylmethylene Lopentadienyl) (2,7-dimethyl-9-fluorenyl) zirconium dichloride, diphenylmethylene (1-cyclopentadienyl) (2,7-di-t-butyl-9-fluorenyl) zirconium dichloride, diphenylmethylene (1-indenyl) ) (9-fluorenyl) zirconium dichloride, diphenylmethylene (4-phenyl-1-indenyl) (9-fluorenyl) zirconium dichloride, diphenylmethylene (4-phenyl-1-indenyl) (2,7-di-t-butyl- Examples thereof include dichloro compounds such as 9-fluorenyl) zirconium dichloride, and dimethyl compounds, diethyl compounds, dihydro compounds, diphenyl compounds, dibenzyl compounds and the like of the above metallocene compounds.

    Furthermore, examples of the metallocene catalyst used in the present invention include the following, but are not limited thereto.

Component (a) and the following general formula (2)
AlR ¹ ₃ (2)
(In the formula, each R ¹ is independently a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms.)
A catalyst comprising an organoaluminum compound represented by the following (hereinafter simply referred to as component (b)), a catalyst further comprising water,
Component (a) and the following general formula (3)

および／または下記一般式（４）

And / or the following general formula (4)

（式中、Ｒ^２は各々独立して水素原子または炭素数１〜２０の炭化水素基であり、ｐは２〜５０の整数である。）
で表されるアルミノキサン（以下、単に成分（ｃ）と記す。）からなる触媒、さらに成分（ｂ）を含んでなる触媒、
成分（ａ）と下記一般式（５）
［Ｒ^３Ｒ^４ _ｙ−１Ｍ^１Ｈ］［Ｍ^２Ａｒ_４］ （５）
（式中、［Ｒ^３Ｒ^４ _ｙ−１Ｍ^１Ｈ］はカチオンであり、Ｍ^１は周期表の第１５族または第１６族から選ばれる元素であり、Ｒ^３は炭素数１〜３０の炭化水素基であり、Ｒ^４は各々独立して水素原子または炭素数１〜３０の炭化水素基であり、ｙはＭ^１が第１５族元素の時ｙ＝３であり、Ｍ^１が第１６族元素の時ｙ＝２であり、［Ｍ^２Ａｒ_４］はアニオンであり、Ｍ^２はホウ素、アルミニウムまたはガリウムであり、Ａｒは各々独立して炭素数６〜２０のハロゲン置換アリール基である。）
で表されるプロトン酸塩（以下、単に成分（ｄ）と記す。）、下記一般式（６）
［Ｃ］［Ｍ^２Ａｒ_４］ （６）
（式中、Ｃはカルボニウムカチオンまたはトロピリウムカチオンであり、Ｍ^２はホウ素、アルミニウムまたはガリウムであり、Ａｒは各々独立して炭素数６〜２０のハロゲン置換アリール基である。）
で表されるルイス酸塩（以下に、単に成分（ｅ）と記す。）または下記一般式（７）
［Ｍ^３Ｌ^１ _ｚ］［Ｍ^２Ａｒ_４］ （７）
（式中、Ｍ^３は周期表の第１族、第８族、第９族、第１０族または第１１族の金属の陽イオンであり、Ｌ^１はルイス塩基またはシクロペンタジエニル基であり、ｚは０≦ｚ≦２であり、Ｍ^２はホウ素、アルミニウムまたはガリウムであり、Ａｒは各々独立して炭素数６〜２０のハロゲン置換アリール基である。）
で表される金属塩（以下、単に成分（ｆ）と記す。）から選ばれる少なくとも１種類の塩からなる触媒、さらに成分（ｂ）および／または成分（ｃ）を含んでなる触媒、
成分（ａ）と下記一般式（８）
Ｍ^２Ａｒ_３ （８）
（式中、Ｍ^２はホウ素、アルミニウムまたはガリウムであり、Ａｒは各々独立して炭素数６〜２０のハロゲン置換アリール基である。）
で表されるルイス酸（以下、単に成分（ｇ）と記す。）からなる触媒、さらに成分（ｂ）および／または成分（ｃ）を含んでなる触媒、
成分（ａ）と成分（ｇ）と成分（ｄ）、成分（ｅ）、成分（ｆ）から選ばれる少なくとも１種類の塩からなる触媒、さらに成分（ｂ）および／または成分（ｃ）を含んでなる触媒、
成分（ａ）と粘土鉱物（以下、単に成分（ｈ）と記す。）からなる触媒、さらに成分（ｂ）を含んでなる触媒、
特開平７−２２４１０６号公報、特開平９−５９３１０号公報、特開平１０−２３１３１２号公報、特開平１０−２３１３１３号公報等に例示される成分（ａ）と有機化合物で処理された粘土鉱物（以下、単に成分（ｉ）と記す。）からなる触媒、さらに成分（ｂ）を含んでなる触媒が挙げられる。

(In the formula, each R ² is independently a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and p is an integer of 2 to 50.)
A catalyst comprising an aluminoxane represented by the following (hereinafter simply referred to as component (c)), a catalyst further comprising component (b),
Component (a) and the following general formula (5)
_{^{[R 3 R 4 y-1}} M 1 H] [M 2 Ar 4] (5)
(Wherein [R ³ R ⁴ _y-1 M ¹ H] is a cation, M ¹ is an element selected from Group 15 or Group 16 of the periodic table, and R ³ has 1 to 30 carbon atoms. a hydrocarbon group, ^{R 4} are each independently hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, y is when y = 3 for ^{M 1} is a group 15 element, ^{M 1} is 16 In the case of a group element, y = 2, [M ² Ar ₄ ] is an anion, M ² is boron, aluminum or gallium, and Ar is each independently a halogen-substituted aryl group having 6 to 20 carbon atoms. .)
(Hereinafter simply referred to as component (d)), represented by the following general formula (6)
[C] [M ² Ar ₄ ] (6)
(Wherein, C is a carbonium cation or a tropylium cation, M ² is boron, aluminum or gallium, and Ar is each independently a halogen-substituted aryl group having 6 to 20 carbon atoms.)
Or a Lewis acid salt represented by the following formula (7) or the following general formula (7)
[M ³ L ¹ _z ] [M ² Ar ₄ ] (7)
(Wherein M ³ is a metal cation of Group 1, Group 8, Group 9, Group 10 or Group 11 of the Periodic Table, and L ¹ is a Lewis base or a cyclopentadienyl group. Z is 0 ≦ z ≦ 2, M ² is boron, aluminum or gallium, and Ar is each independently a halogen-substituted aryl group having 6 to 20 carbon atoms.)
A catalyst comprising at least one salt selected from metal salts represented by the following (hereinafter simply referred to as component (f)), a catalyst comprising component (b) and / or component (c),
Component (a) and the following general formula (8)
M ² Ar ₃ (8)
(Wherein M ² is boron, aluminum or gallium, and Ar is each independently a halogen-substituted aryl group having 6 to 20 carbon atoms.)
A catalyst comprising a Lewis acid represented by (hereinafter, simply referred to as component (g)), a catalyst further comprising component (b) and / or component (c),
A catalyst comprising at least one salt selected from component (a), component (g), component (d), component (e) and component (f), and further comprising component (b) and / or component (c) A catalyst consisting of,
A catalyst comprising component (a) and a clay mineral (hereinafter simply referred to as component (h)), a catalyst further comprising component (b),
Clay minerals treated with component (a) and an organic compound exemplified in JP-A-7-224106, JP-A-9-59310, JP-A-10-223112, JP-A-10-231313, etc. Hereinafter, a catalyst comprising simply component (i)) and a catalyst comprising further component (b) may be mentioned.

Further, the α-olefin used in the ethylene / α-olefin copolymer may be represented by the general formula R—CH═CH _2.
(In the formula, R is an alkyl group having 1 or more carbon atoms.)
It is represented by Examples include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 4-methyl-1-pentene, 4-methyl-1-hexene, Examples include 4,4-dimethyl-1-pentene and octadecene. Among them, since the obtained polyethylene resin composition is excellent in tensile strength, tear strength, impact strength, heat seal strength and the like when used as a container, particularly a tubular cylindrical container, an α-olefin having 5 to 10 carbon atoms is preferable. In particular, 1-hexene, 1-heptene, 1-octene and 4-methyl-1-pentene are preferable.

  The ethylene / α-olefin copolymer is obtained by copolymerizing at least one of these α-olefins with ethylene. Specifically, the ethylene-1-hexene copolymer and the ethylene-1-heptene copolymer are used. Examples thereof include a polymer, an ethylene-1-octene copolymer, an ethylene-4-methyl-1-pentene copolymer, and an ethylene-propylene-1-hexene terpolymer.

The LDPE (B) used in the present invention is an LDPE having a density in the range of 910 to 930 kg / m ³ and an MFR in the range of 0.1 to 10 g / 10 minutes.

Here, in the case of LDPE having a density of less than 910 kg / m ³ , the tube container becomes soft and inferior in restorability. On the other hand, it is difficult to obtain LDPE having a density greater than 930 kg / m ³ .

  In addition, when the LDPE is less than 0.1 g / 10 min, the melt shear viscosity is increased, the load on the extruder when the polyethylene resin composition is molded is increased, and the drawdown property is also deteriorated. It becomes inferior. On the other hand, when the LDPE is larger than 10 g / 10 minutes, the melt tension becomes small, so that the formability in forming the tube container is deteriorated, and the molecular weight is reduced, so that the mechanical strength of the tube container is lowered.

  Such LDPE can be obtained by an ordinary polymerization method generally known as a high-pressure radical polymerization method, and is obtained as a commercial product, for example, as (trade name) Petrocene series (manufactured by Tosoh Corporation). It is also possible.

  The polyethylene resin composition used in the present invention comprises an ethylene / α-olefin copolymer (A) / LDPE (B) (weight ratio) = 5/95 to 45/55. More preferably, it consists of ethylene / α-olefin copolymer (A) / LDPE (B) (weight ratio) = 10/90 to 40/60. Here, when the ethylene / α-olefin copolymer (A) / LDPE (B) is less than 5/95, the resulting tube container is inferior in ESCR and tear strength. On the other hand, when it exceeds ethylene / α-olefin copolymer (A) / LDPE (B) = 45/55, the load on the extruder when adjusting the polyethylene resin composition is increased and the moldability is also improved. It will be inferior.

  In the polyethylene resin composition used in the present invention, one or a mixture of two or more of the ethylene / α-olefin copolymer (A) and LDPE (B) can be used.

  The polyethylene resin composition used in the present invention is a method in which ethylene / α-olefin copolymer (A) and LDPE (B) are mixed by a conventionally known method such as a Henschel mixer, a V-blender, a ribbon blender, a tumbler blender or the like. Alternatively, the mixture obtained by such a method can be obtained by further kneading and granulating with a single screw extruder, a twin screw extruder, a kneader, a Banbury mixer or the like.

  In addition, the polyethylene resin composition used in the present invention may contain, as necessary, conventionally known antioxidants, weathering stabilizers, antistatic agents, lubricants, fillers, pigments, and the like as long as the object of the present invention is not impaired. Can be blended.

  The molded product molded with the polyethylene resin composition used in the present invention is excellent in ESCR and tear strength, and thus can be used as various containers, particularly tube containers. Further, tube containers include hand creams, hair gels, cosmetic creams, etc. Tubes for daily use such as shampoos, rinses, detergents and the like; containers for foods such as mayonnaise, soy sauce and wasabi can also be used. And as a method of shaping to a tube container, shaping can be performed by an extrusion method.

  The thickness of the tube container of the present invention is not particularly limited, and is generally a tube container in the range of 0.3 to 0.8 mm from the viewpoint of balance between flexibility and resilience, container strength, economy, and the like. It is preferable that

  The tube container of the present invention is excellent in ESCR and tear strength, and also excellent in heat sealability. This tube container has excellent ESCR, so that it can prevent accidents such as leakage and exudation of contents during manufacture, storage, transportation, and use, and it also has high tear strength, so it can be expanded. Damage can be prevented and the thickness and weight can be reduced, which is economically useful. Further, since the heat sealability is good, the conventional heat seal equipment can be used as it is, which is economical.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

  Various physical properties of the ethylene / α-olefin copolymer, LDPE and the obtained tube container used in Examples and Comparative Examples were measured by the following methods.

<Density>
In accordance with JIS K 7112 (1980), a sample which had been immersed in boiling water at 100 ° C. for 1 hour and then allowed to cool at room temperature was measured with a density gradient tube maintained at 23 ° C.

<Melt flow rate (MFR)>
According to JIS K 7210 (1995), it was measured under a load of 190 ° C. and 21.18 N.

<Melting point>
It measured using the differential scanning calorimeter (Perkin Elmer Co., Ltd. make, brand name DSC-7). The temperature at the maximum peak position of the endothermic curve obtained when the sample was melted at 200 ° C. for 5 minutes in the apparatus and then cooled to 30 ° C. at 10 ° C./min was again raised at 10 ° C./min. The melting point.

<Mw / Mn ratio>
Mn and Mw in terms of standard polystyrene were determined from an elution curve obtained by gel permeation chromatography (hereinafter GPC), and Mw / Mn was determined therefrom.

Measuring instrument: GPC (model) 150C manufactured by Waters
Column: (trade name) TSK gelGMHHR-H (S) (Tosoh Corporation)
Measuring solvent: o-dichlorobenzene Sample concentration: 0.1 wt%
Measurement temperature: 140 ° C
Flow rate: 1.0 ml / min <Number of short chain branches (SCB)>
The number of short chain branches (SCB) in the molecular chain is a methyl group located at 1378 cm ⁻¹ using a Fourier transform infrared absorption spectrometer (trade name: FT-IR spectrometer 1760X, manufactured by PerkinElmer Co., Ltd.). It was obtained from the intensity of the absorption band corresponding to the bending vibration.

<ESCR>
In accordance with ASTM D1693, a 38 × 13 × 3 mm test piece was punched from a 3 mm thick press-molded plate, immersed in boiling water at 100 ° C. for 1 hour, and then conditioned at 23 ° C. for 24 hours. A predetermined notch was put in the test piece, and the test piece was placed in a holder, and then immersed in a 10% solution of (trade name) Nonion NS210 (manufactured by NOF Corporation), and the time until cracks were generated was measured.

<Elmendorf tear strength (MD, TD)>
Measured based on JIS K 7128-3 (right angle tear method) (1998). As a sample, a tube (thickness 0.5 mm) obtained by extrusion molding was developed, and a test piece was punched in the flow direction (MD) and the orthogonal direction (TD) and measured.

<Heat seal strength>
As a sample, a tube (thickness 0.5 mm) obtained by extrusion molding was cut to a length of 100 mm, one end was closed, and the sample was subjected to a heat seal test. The method of heat sealing is to use a heat seal tester (trade name TP-701, manufactured by Tester Sangyo Co., Ltd.), seal the area 5 mm wide from the end with a seal pressure of 0.2 MPa, a seal temperature of 140 ° C., and a seal time of 2 seconds It is performed by heat sealing, and the peel strength of the seal part is determined by pulling the seal part cut into a strip shape with a width of 15 mm using a push-pull scale (manufactured by Imada Seisakusho, product name FB-30). The load was measured.

(Ethylene / α-olefin copolymer)
The ethylene / α-olefin copolymers used in Examples and Comparative Examples were produced by the following methods or used commercially. The polymerization operation, reaction, and solvent purification during the production were all performed in an inert gas atmosphere. Moreover, the solvent etc. which were used for the reaction were all purified, dried and deoxygenated by a known method in advance. Furthermore, the compound used for the reaction was synthesized and identified by a known method.

Synthesis Example 1 (Preparation of ethylene / α-olefin copolymer (A1))
<Preparation of polymerization catalyst>
In a 20 liter stainless steel container under a nitrogen atmosphere, 3.3 liters of heptane, 2.5 mol (3.6 liters) of heptane solution of triisopropylaluminum per aluminum atom and diphenylmethylene (cyclopentadienyl) (9-fluorenyl) zirconium 10 mmol of dichloride was added per zirconium atom and stirred for 1 hour. Thereto, 11 mmol of N, N-dimethylanilinium tetrakis (pentafluorophenyl) borate was added per boron atom and stirred for 12 hours. A catalyst was prepared by adding 8.7 liters of an aliphatic saturated hydrocarbon solvent (IP solvent 2835 (manufactured by Idemitsu Petrochemical Co., Ltd.)) to the obtained suspension system (zirconium concentration 0.64 mmol / L).

<Polymerization>
Polymerization was carried out using a tank reactor. Ethylene, 1-hexene and ethane were continuously injected into the reactor, the total pressure was set to 90 MPa, the 1-hexene concentration was 27.0 mol%, and the reactor was stirred at 1500 rpm. Then, the catalyst was continuously supplied from the supply port of the reactor, and polymerization was performed so that the average temperature was maintained at 160 ° C. As a result, an ethylene-1-hexene copolymer having a density of 920 kg / m ³ , MFR 2.0 g / 10 min, Tm 112 ° C., Mw / Mn = 2.5, SCB = 9.4 / 1000 C (hereinafter referred to as ethylene · α -Olefin copolymer (A1)) was obtained.

  0.05 parts by weight of a phenolic antioxidant (trade name: IRGANOX 1010, manufactured by Ciba Specialty Chemicals), 100 parts by weight of the ethylene / α-olefin copolymer (A1) obtained by the above method, phosphorous antioxidant 0.05 parts by weight of the agent (trade name IRGANOX 168, manufactured by Ciba Specialty Chemicals) and 0.05 part by weight of calcium stearate (trade name: calcium stearate, manufactured by Tannan Chemical Co., Ltd.) ), Manufactured by Model PDA-50), and melt extruded at 180 ° C. and 60 rpm to be pelletized.

Synthesis Example 2 (Preparation of ethylene / α-olefin copolymer (A2))
Polymerization was carried out in the same manner as in Synthesis Example 1 except that the 1-hexene concentration during polymerization was changed to 40.0 mol%. As a result, an ethylene-1-hexene copolymer having a density of 910 kg / m ³ , MFR 4.0 g / 10 min, Tm 104 ° C., Mw / Mn = 2.5, SCB = 15.8 pieces / 1000 C (hereinafter referred to as ethylene α- Olefin copolymer (A2)) was obtained. The ethylene / α-olefin copolymer (A2) was pelletized by the same method as in Synthesis Example 1.

実施例１
合成例１により得られたエチレン・α−オレフィン共重合体（Ａ１）／ＬＤＰＥ（東ソー（株）製、商品名ペトロセン１８０Ｒ；密度９２２ｋｇ／ｍ^３、ＭＦＲ２．０ｇ／１０分、Ｔｍ１１０℃、Ｍｗ／Ｍｎ＝４．８）（以下、ＬＤＰＥ（Ｂ１）と記す。）（重量比）＝２５／７５でタンブラーブレンダーで混合し、さらに一軸押出機で溶融混練した後、造粒することによりポリエチレン樹脂組成物ペレットを得た。このポリエチレン樹脂組成物のＥＳＣＲは３３ｈｒ（Ｆ５０）であった。
得られたポリエチレン樹脂組成物をチューブ押出機（ＧＭエンジニアリング社製、押出機シリンダー径６０ｍｍφ、ダイス径５０ｍｍ、リップクリアランス１．２ｍｍ）を用い、押出機、ダイの設定温度を１６０℃とし、引取速度を３ｍ／ｍｉｎ、容器厚みを０．５ｍｍとした成形条件でチューブ容器とした。

Example 1
Ethylene / α-olefin copolymer (A1) / LDPE obtained by Synthesis Example 1 (trade name Petrocene 180R manufactured by Tosoh Corp .; density 922 kg / m ³ , MFR 2.0 g / 10 min, Tm 110 ° C., Mw / Mn = 4.8) (hereinafter referred to as LDPE (B1)) (weight ratio) = 25/75. Mixing with a tumbler blender, melt-kneading with a single screw extruder, and granulating, then polyethylene resin composition Product pellets were obtained. The ESCR of this polyethylene resin composition was 33 hr (F50).
Using the obtained polyethylene resin composition, a tube extruder (manufactured by GM Engineering Co., Ltd., extruder cylinder diameter 60 mmφ, die diameter 50 mm, lip clearance 1.2 mm) was set at an extruder and die set temperature of 160 ° C., and the take-off speed Was formed into a tube container under molding conditions of 3 m / min and a container thickness of 0.5 mm.

  The obtained tube container had an Elmendorf tear strength (MD) of 128 N / mm and a heat seal strength of 57 N / 15 mm. A tube container having good ESCR and excellent tear strength and heat seal strength was obtained.

Example 2
Ethylene / α-olefin copolymer (A1) / LDPE (B1) (weight ratio) = 25/75 was changed to ethylene / α-olefin copolymer (A1) / LDPE (trade name Petrocene 360, manufactured by Tosoh Corporation); Density 919 kg / m ³ , MFR 1.6 g / 10 min, Tm 108 ° C., Mw / Mn = 8.4) (hereinafter referred to as LDPE (B2)) (weight ratio) = 10/90 A tube container was obtained in the same manner as in 1.

  The obtained tube container had an ESCR of 15 hr (F50), an Elmendorf tear strength (MD) of 109 N / mm, and a heat seal strength of 56 N / 15 mm. A tube container having good ESCR and excellent tear strength and heat seal strength was obtained.

Example 3
Ethylene / α-olefin copolymer (A1) / LDPE (B1) (weight ratio) = 25/75 and ethylene / α-olefin copolymer (A2) / LDPE (B1) (weight ratio) = 40/60 A tube container was obtained in the same manner as in Example 1 except that.

  The obtained tube container had an ESCR of 100 hr or more (F50), an Elmendorf tear strength (MD) of 143 N / mm, and a heat seal strength of 65 N / 15 mm. A tube container having good ESCR and excellent tear strength and heat seal strength was obtained.

Comparative Example 1
A tube container was obtained in the same manner as in Example 1 except that ethylene / α-olefin copolymer (A1) / LDPE (B1) (weight ratio) = 25/75 was used as LDPE (B1) alone.

  The obtained tube container had an ESCR of 1 hr (F50), an Elmendorf tear strength (MD) of 100 N / mm, and a heat seal strength of 56 N / 15 mm. However, the ESCR is extremely low and some contents cannot be used as containers.

Comparative Example 2
A tube container was obtained in the same manner as in Example 1 except that ethylene / α-olefin copolymer (A1) / LDPE (B1) (weight ratio) = 25/75 was used as LDPE (B2) alone.

  The obtained tube container had an ESCR of 8 hr (F50), an Elmendorf tear strength (MD) of 94 N / mm, and a heat seal strength of 52 N / 15 mm. However, the tear strength was low.

Comparative Example 3
Ethylene / α-olefin copolymer (A1) / LDPE (B1) (weight ratio) = 25/75 was changed to ethylene / α-olefin copolymer (produced by Tosoh Corporation, ethylene-1-hexene copolymer (product) Name: Nipolon Z ZF230); density 920 kg / m ³ , MFR 2.0 g / 10 min, Tm 123 ° C., Mw / Mn = 4.1, SCB = 12.7 / 1000C) / LDPE (B1) (weight ratio) = A tube container was obtained in the same manner as in Example 1 except that the ratio was 25/75.

  The obtained tube container has an ESCR of 25 hr (F50), an Elmendorf tear strength (MD) of 120 N / mm, a heat seal strength of 0 N / 15 mm (partially unfused), and the tube container cannot be fused. Therefore, it was not usable.

Comparative Example 4
Ethylene / α-olefin copolymer (A1) / LDPE (B1) (weight ratio) = 25/75 was changed to ethylene / α-olefin copolymer (Ube Industries, Ltd., ethylene-1-hexene copolymer ( Product name: UMERIT 2040FC); density 919 kg / m ³ , MFR 3.7 g / 10 min, Tm 121 ° C., Mw / Mn = 3.3, SCB = 11/1000 C) / LDPE (B1) (weight ratio) = 25 / A tube container was obtained in the same manner as in Example 1 except that it was 75.

  The obtained tube container has an ESCR of 30 hr (F50), an Elmendorf tear strength (MD) of 125 N / mm, a heat seal strength of 0 N / 15 mm (partially unfused), and the tube container cannot be fused. Therefore, it was not usable.

Claims (1)

(A) The density is in the range of 905 to 925 kg / m ³ , (b) The melt flow rate (MFR) measured under a load of 190 ° C. and 21.18 N is in the range of 1.0 to 10 g / 10 min. (C) The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 4 or less, (d) melting at 200 ° C. for 5 minutes by a differential scanning calorimeter, and then cooling rate From the measurement of the temperature at the maximum peak position (Tm (° C.)) of the endothermic curve observed when cooling to 10 ° C./min to 30 ° C. and raising the temperature again at the rate of temperature increase of 10 ° C./min and the infrared absorption spectrum An ethylene / α-olefin copolymer (A) satisfying the relationship represented by the following formula (1) with the number of short chain branches (SCB) per 1000 carbon atoms required;
Tm <−1.8 × SCB + 138 (1)
(E) The density is in the range of 910 to 930 kg / m ³ , and (f) the melt flow rate (MFR) measured under a load of 190 ° C. and 21.18 N is in the range of 0.1 to 10 g / 10 min. High-pressure radical polymerization method low-density polyethylene (B), ethylene / α-olefin copolymer (A) / high-pressure radical polymerization method low-density polyethylene (B) (weight ratio) is 5/95 to 45/55. A tube container made of a polyethylene resin composition.