JP2007091783A - Film for retort packaging - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film for retort packaging excellent in the balance between thermal-fusion resistance and heat sealing properties and in impact resistance. <P>SOLUTION: The film for retort packaging has, as a surface layer, a layer comprising a polyethylene-based resin composition having a melt flow rate of 0.1-10 g/10 min and a density of 920-960 kg/m<SP>3</SP>. The polyethylene-based resin composition comprises 15-85 wt.% of an ethylene-α-olefin copolymer (I) and 85-15 wt.% of an ethylene-α-olefin copolymer (II). The ethylene-α-olefin copolymer (I) is obtained by copolymerizing ethylene and α-olefin using a metallocene catalyst and has a density of 920-970 kg/m<SP>3</SP>, a melt flow rate of 0.01-10 g/10 min, and an activation energy of flow (Ea) of less than 35 kJ/mol or a melt flow rate ratio (MFRR) of less than 30. The ethylene-α-olefin copolymer (II) is obtained by copolymerizing ethylene and α-olefin using a metallocene catalyst and has a density of 915-950 kg/m<SP>3</SP>, a melt flow rate of 0.01-50 g/10 min, an Ea of 35 kJ/mol or more and a MFRR of 30 or more. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a film for retort packaging.

In order to endure long-term storage of various cooked foods without deterioration, foods that have been stored in packaging bags, sealed, and heat-sterilized (so-called retort treatment) at a high temperature of 100 ° C or higher and high humidity are retort foods. As widely used. The film used for the packaging bag is required to have heat resistance and impact resistance in retort processing. For example, as a film made of a polyethylene resin, ethylene-α- having a density of 880 to 925 kg / m ^3. A film comprising a resin composition containing an olefin copolymer, an ethylene-α-olefin copolymer having a density of 930 to 950 Kg / m ³ , high-density polyethylene, and high-pressure low-density polyethylene has been proposed. (For example, refer to Patent Document 1).

JP 2004-189914 A

However, the above-mentioned film may be melted when the retort treatment is performed, or the sealing strength may be low, and is not sufficiently satisfactory in the balance between heat resistance and heat sealability. There was a thing. Also, the impact resistance was not fully satisfactory.
Under such circumstances, the problem to be solved by the present invention is to provide a film for retort packaging excellent in the balance between heat-fusible and heat-seal properties and impact resistance.

The first of the present invention is an ethylene-α-olefin copolymer (I) satisfying the following requirements (Ia), (Ib), (Ic) and (Id): 15 to 85 85% to 15% by weight of ethylene-α-olefin copolymer (II) satisfying the following requirements (II-a), (II-b), (II-c) and (II-d): (However, the total amount of the ethylene-α-olefin copolymer (I) and the ethylene-α-olefin copolymer (II) is 100% by weight), and the melt flow rate is 0.1 to 10 g. / 10 minutes, and relates to a film for retort packaging having a layer made of a polyethylene resin composition having a density of 920 to 960 kg / m ³ on the surface layer.
(Ia): An ethylene-α-olefin copolymer obtained by copolymerizing ethylene and an α-olefin having 4 to 12 carbon atoms using a metallocene catalyst.
(Ib): The density is 920 to 970 Kg / m ³ .
(Ic): Melt flow rate is 0.01 to 10 g / 10 min.
(Id): Flow activation energy (Ea) is less than 35 kJ / mol, or melt flow rate ratio (MFRR) is less than 30.
(II-a): An ethylene-α-olefin copolymer obtained by copolymerizing ethylene and an α-olefin having 3 to 12 carbon atoms.
(II-b): The density is 915 to 950 Kg / m ³ .
(II-c): The melt flow rate is 0.01 to 50 g / 10 min.
(II-d): Flow activation energy (Ea) is 35 kJ / mol or more, and melt flow rate ratio (MFRR) is 30 or more.

  The second aspect of the present invention relates to a retort food packaged with the above film and subjected to a retort treatment.

  According to the present invention, it is possible to provide a film for retort packaging that has an excellent balance between heat-resistant adhesion and heat sealability. Moreover, the film for retort packaging of this invention is excellent also in impact resistance, and its rigidity is also favorable.

  The ethylene-α-olefin copolymer (I) of the present invention is a copolymer obtained by copolymerizing ethylene and an α-olefin having 4 to 12 carbon atoms using a metallocene catalyst (requirements (I -a)). Examples of the α-olefin having 4 to 12 carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 4- Examples thereof include methyl-1-pentene and 4-methyl-1-hexene, and preferred are 1-hexene, 4-methyl-1-pentene and 1-octene. Moreover, said C4-C12 alpha olefin may be used independently and may use 2 or more types together.

The metallocene catalyst is preferably a catalyst containing a transition metal compound having a group having a cyclopentadiene-type anion skeleton (hereinafter referred to as a metallocene compound) as a catalyst component. Examples of the transition metal compound having a group having a cyclopentadiene-type anion skeleton include, for example, a general formula ML _a X _na (wherein M is a group 4 or lanthanide series transition metal atom of the periodic table of elements). Is a group having a cyclopentadiene-type anion skeleton or a group containing a heteroatom, at least one of which is a group having a cyclopentadiene-type anion skeleton, wherein a plurality of L may be cross-linked to each other, X is a halogen atom , Hydrogen or a hydrocarbon group having 1 to 20 carbon atoms, n represents the valence of the transition metal atom, and a is an integer satisfying 0 <a ≦ n. , At least two types may be used in combination.

  In addition to the above metallocene compounds, the metallocene catalyst usually has (1) an organoaluminum compound such as triethylaluminum and triisobutylaluminum, (2) an alumoxane compound such as methylalumoxane, (3) trityltetrakispenta Ionic compounds such as fluorophenylborate and N, N-dimethylanilinium tetrakispentafluorophenylborate are included.

The metallocene catalyst may be a metallocene compound and the above-mentioned promoter supported on a particulate carrier. The particulate carrier is preferably a porous material, and is an inorganic oxide such as SiO ₂ , Al ₂ O ₃ , MgO, ZrO ₂ , TiO ₂ , B ₂ O ₃ , CaO, ZnO, BaO, ThO ₂ ; Clay and clay minerals such as montmorillonite, hectorite, laponite and saponite; organic polymers such as polyethylene, polypropylene and styrene-divinylbenzene copolymer are used.

  Examples of the metallocene catalyst include, for example, JP-A-58-19309, JP-A-60-35006, JP-A-60-35007, JP-A-60-35008, JP-A-61-108610. JP, 61-130314, 61-276805, 61-296008, 63-89505, 3-163088, 3- No. 234709, JP-A-4-268307, JP-A-6-336502, JP-A-7-224106, JP-A-9-183816, JP-A-9-87313, etc. can give.

  Examples of the ethylene-α-olefin copolymer (I) include ethylene-1-butene copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-1-hexene copolymer, and ethylene-1. -Octene copolymer, ethylene-1-butene-1-hexene copolymer and the like, preferably ethylene-1-hexene copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-1 -An octene copolymer and an ethylene-1-butene-1-hexene copolymer, more preferably an ethylene-1-hexene copolymer.

The density of the ethylene-α-olefin copolymer (I) is 920 to 970 Kg / m ³ (requirement (Ib)). Said seal degree of heat fusible, in view of enhancing the rigidity, is preferably 923 kg / m ³ or more, more preferably 925 kg / m ³ or more. Moreover, from a viewpoint of improving heat-sealing property and impact resistance, Preferably it is 950 kg / m < ³ > or less, More preferably, it is 940 kg / m < ³ > or less. In addition, this density is measured in accordance with the underwater substitution method prescribed | regulated to JISK7112-1980 using the sample which annealed as described in JISK6760-1995.

  The melt flow rate (MFR) of the ethylene-α-olefin copolymer (I) is 0.01 to 10 g / 10 min (requirement (Ic)). The MFR is preferably 0.25 g / 10 min or more, more preferably 0.4 g / 10 min or more, from the viewpoint of improving the extrusion processability. Moreover, from a viewpoint of improving impact resistance, Preferably it is 8 g / 10min or less, More preferably, it is 5 g / 10min or less. The MFR is measured by the A method according to the method specified in JIS K7210-1995 under the conditions of a load of 21.18 N and a temperature of 190 ° C.

  The ethylene-α-olefin copolymer (I) is a linear or substantially linear copolymer having a flow activation energy (Ea) of less than 35 kJ / mol, or a melt flow rate. It is a copolymer having a ratio (MFRR) of less than 30 (requirement (Id)). As the ethylene-α-olefin copolymer (I), a copolymer having an Ea of less than 35 kJ / mol and an MFRR of less than 30 is preferable. Further, the Ea is preferably 30 kJ / mol or less from the viewpoint of enhancing heat-resistant fusion resistance and impact resistance. The MFRR is preferably 28 or less from the viewpoint of improving impact resistance.

The flow activation energy (Ea) is a master curve showing the dependence of the melt complex viscosity (unit: Pa · sec) at 190 ° C. on the angular frequency (unit: rad / sec) based on the temperature-time superposition principle. Is a numerical value calculated by the Arrhenius equation from the shift factor (a _T ) at the time of creating the value, and is a value obtained by the following method. That is, the melt complex viscosity-angular frequency curve of the ethylene-α-olefin copolymer at temperatures of 130 ° C., 150 ° C., 170 ° C. and 190 ° C. (T, unit: ° C.) (the unit of melt complex viscosity is Pa · sec. The unit of the angular frequency is rad / sec.), Based on the temperature-time superposition principle, for each melt complex viscosity-angular frequency curve at each temperature (T), The shift factor (a _T ) at each temperature (T) obtained when superposed on the melt complex viscosity-angular frequency curve of the coalescence is obtained, and each temperature (T) and the shift factor at each temperature ( _T ) are obtained. From (a _T ), a first-order approximate expression (formula (I) below) of [ln (a _T )] and [1 / (T + 273.16)] is calculated by the method of least squares. Next, Ea is obtained from the slope m of the linear expression and the following expression (II).
ln (a _T ) = m (1 / (T + 273.16)) + n (I)
Ea = | 0.008314 × m | (II)
a _T : Shift factor Ea: Activation energy of flow (unit: kJ / mol)
T: Temperature (unit: ° C)
For the calculation, commercially available calculation software may be used. As the calculation software, Rheos V. manufactured by Rheometrics is used. 4.4.4.
The shift factor (a _T ) is obtained by moving the logarithmic curve of the melt complex viscosity-angular frequency at each temperature (T) in the log (Y) = − log (X) axis direction (however, the Y axis Is the complex viscosity of the melt, and the X axis is the angular frequency.), And the amount of movement when superposed on the melt complex viscosity-angular frequency curve at 190 ° C., in the superposition, melting at each temperature (T) The logarithmic curve of complex viscosity-angular frequency is shifted for each curve by the angular frequency a _T times and the melt complex viscosity 1 / a _T times. Moreover, the correlation coefficient when calculating | requiring (I) Formula by the least squares method from the value of four points | pieces, 130 degreeC, 150 degreeC, 170 degreeC, and 190 degreeC is usually 0.99 or more.

  The melt complex viscosity-angular frequency curve is measured using a viscoelasticity measuring apparatus (for example, Rheometrics Mechanical Spectrometer RMS-800 manufactured by Rheometrics), and usually geometry: parallel plate, plate diameter: 25 mm, plate interval: 1. It is performed under the conditions of 5 to 2 mm, strain: 5%, angular frequency: 0.1 to 100 rad / sec. The measurement is performed in a nitrogen atmosphere, and it is preferable that an appropriate amount (for example, 1000 ppm) of an antioxidant is added to the measurement sample in advance.

  The melt flow rate ratio (MFRR) is a temperature measured according to JIS K7210-1995, measured at a temperature of 190 ° C. under a load of 211.8 N, and a temperature of 190 ° C. specified in JIS K7210-1995. It is the value divided by the melt flow rate measured under the condition of a load of 21.18N.

  As a manufacturing method of ethylene-alpha-olefin copolymer (I), the well-known olefin polymerization method using a metallocene catalyst is mention | raise | lifted. Known olefin polymerization methods include, for example, solution polymerization method, slurry polymerization method, high pressure ion polymerization method, gas phase polymerization method, etc., preferably gas phase polymerization method, solution polymerization method, high pressure ion polymerization method, More preferred is a gas phase polymerization method.

  The ethylene-α-olefin copolymer (II) is a copolymer obtained by copolymerizing ethylene and an α-olefin having 3 to 12 carbon atoms (requirement (II-a)). Examples of the α-olefin having 3 to 12 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, Examples include 4-methyl-1-pentene and 4-methyl-1-hexene, and preferred are 1-butene, 1-hexene and 1-octene. Moreover, said C3-C12 alpha olefin may be used independently and may use 2 or more types together.

  Examples of the ethylene-α-olefin copolymer (II) include an ethylene-1-butene copolymer, an ethylene-4-methyl-1-pentene copolymer, an ethylene-1-hexene copolymer, and ethylene-1. -Octene copolymer, ethylene-1-butene-1-hexene copolymer and the like, preferably ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer And ethylene-1-butene-1-hexene copolymer, more preferably ethylene-1-hexene copolymer and ethylene-1-butene-1-hexene copolymer.

The density of the ethylene-α-olefin copolymer (II) is 915 to 950 Kg / m ³ (requirement (II-b)). The density is preferably 920 kg / m ³ or more, and more preferably 925 kg / m ³ or more, from the viewpoint of improving heat-resistant adhesion and rigidity. Moreover, heat-sealing property, in view of enhancing the impact resistance, preferably at 945 kg / m ³ or less, more preferably 940 kg / m ³ or less. In addition, this density is measured in accordance with the underwater substitution method prescribed | regulated to JISK7112-1980 using the sample which annealed as described in JISK6760-1995.

  The melt flow rate (MFR) of the ethylene-α-olefin copolymer (II) is 0.01 to 10 g / 10 min (requirement (II-c)). The MFR is preferably 0.05 g / 10 min or more, more preferably 0.07 g / 10 min or more, from the viewpoint of improving the extrusion processability. Moreover, from a viewpoint of improving impact resistance, Preferably it is 10 g / 10min or less, More preferably, it is 2 g / 10min or less, More preferably, it is 1 g / 10min or less. The MFR is measured by the A method according to the method specified in JIS K7210-1995 under the conditions of a load of 21.18 N and a temperature of 190 ° C.

  The ethylene-α-olefin copolymer (II) is an ethylene-α-olefin copolymer having many long-chain branches, and such an ethylene-α-olefin copolymer is a conventionally known ordinary ethylene- Compared with the α-olefin copolymer, the flow activation energy (Ea) is high, 35 kJ / mol or more, the melt flow rate ratio (MFRR) is high, 30 or more (requirement (II-d) ). The Ea is preferably 40 kJ / mol or more, more preferably 50 kJ / mol or more, and further preferably 60 kJ / mol or more, from the viewpoint of improving the heat sealability. Moreover, from a viewpoint of raising impact resistance more, Preferably it is 100 kJ / mol or less, More preferably, it is 90 kJ / mol or less. Further, the MFRR is preferably 35 or more from the viewpoint of enhancing the heat sealability. Moreover, from a viewpoint of improving impact resistance more, Preferably it is 500 or less, More preferably, it is 400 or less. Ea and MFRR are measured by the method described above.

  The molecular weight distribution (Mw / Mn) of the ethylene-α-olefin copolymer (II) is preferably 5 or more, more preferably 6 or more, and still more preferably 8 or more, from the viewpoint of improving heat sealability. is there. Moreover, from a viewpoint of improving impact resistance, Preferably it is 25 or less, More preferably, it is 20 or less, More preferably, it is 17 or less. The molecular weight distribution (Mw / Mn) is a value obtained by calculating a polystyrene-reduced weight average molecular weight (Mw) and number average molecular weight (Mn) by gel permeation chromatography, and dividing Mw by Mn (Mw / Mn). Mn).

  As a method for producing the ethylene-α-olefin copolymer (II), a catalyst obtained by contacting the following promoter support (A), the crosslinked bisindenyl zirconium complex (B) and the organoaluminum compound (C) is used. Examples thereof include a method of copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms in the presence.

The promoter support (A) comprises (a) diethylzinc, (b) fluorinated phenol, (c) water, (d) silica and (e) trimethyldisilazane (((CH ₃ ) ₃ Si) ₂ NH). It is a carrier obtained by contact.

The amount of each component (a), (b), (c) used is not particularly limited, but the molar ratio of the amount of each component used is the component (a): component (b): component (c) = 1: When y: z, y and z preferably satisfy the following formula.
| 2-y-2z | ≦ 1
Y in the above formula is preferably a number of 0.01 to 1.99, more preferably a number of 0.10 to 1.80, and still more preferably a number of 0.20 to 1.50. Most preferably, the number is 0.30 to 1.00.

  The amount of the component (d) used relative to the component (a) is such that the number of moles of zinc atoms contained in the particles obtained by contacting the component (a) and the component (d) is 1 g of the particles. The amount is preferably 0.1 mmol or more, and more preferably 0.5 to 20 mmol. The amount of the component (e) to be used with respect to the component (d) is preferably an amount that makes the component (e) 0.1 mmol or more per 1 g of the component (d), and an amount that becomes 0.5 to 20 mmol. More preferably.

  The cross-linked bisindenyl zirconium complex (B) is preferably racemic-ethylenebis (1-indenyl) zirconium dichloride or racemic-ethylenebis (1-indenyl) zirconium diphenoxide.

  The organoaluminum compound (C) is preferably triisobutylaluminum or trinormaloctylaluminum.

The amount of the bridged bisindenyl zirconium complex (B) used is preferably 5 × 10 ^{−6 to} 5 × 10 ⁻⁴ mol per 1 g of the promoter support (A). The amount of the organoaluminum compound (C) used is preferably such that the aluminum atom of the organoaluminum compound (C) is 1 to 2000 moles per mole of zirconium atoms in the cross-linked bisindenyl zirconium complex (B). is there.

  The polymerization method is preferably a continuous polymerization method involving the formation of ethylene-α-olefin copolymer particles, for example, continuous gas phase polymerization, continuous slurry polymerization, continuous bulk polymerization, preferably continuous gas phase Polymerization. The gas phase polymerization reaction apparatus is usually an apparatus having a fluidized bed type reaction tank, and preferably an apparatus having a fluidized bed type reaction tank having an enlarged portion. A stirring blade may be installed in the reaction vessel.

As a method for supplying each component used in the production of the ethylene-α-olefin copolymer (II) to the reaction vessel, an inert gas such as nitrogen or argon, hydrogen, ethylene or the like is usually used. And a method of supplying each component in a solution or slurry after dissolving or diluting each component in a solvent. Each component of the catalyst may be supplied individually, or arbitrary components may be supplied in contact in advance in an arbitrary order.
Moreover, it is preferable to carry out prepolymerization before carrying out the main polymerization and to use the prepolymerized prepolymerized catalyst component as a catalyst component or catalyst for the main polymerization.

The polymerization temperature is usually lower than the temperature at which the ethylene-α-olefin copolymer melts, preferably 0 to 150 ° C, more preferably 30 to 100 ° C.
Further, hydrogen may be added as a molecular weight regulator for the purpose of regulating the melt fluidity of the copolymer. An inert gas may coexist in the mixed gas.

  As content of ethylene-alpha-olefin copolymer (I) and ethylene-alpha-olefin copolymer (II) in the polyethylene-type resin composition of this invention, ethylene-alpha-olefin copolymer (I) The content of the ethylene-α-olefin copolymer (II) is 85 to 15% by weight (provided that the ethylene-α-olefin copolymer (I) and (The total amount of the ethylene-α-olefin copolymer (II) is 100% by weight.) If the content of the ethylene-α-olefin copolymer (I) is too small (the content of the ethylene-α-olefin copolymer (II) is too large), the heat-resistant fusing property may decrease, and ethylene When the content of the -α-olefin copolymer (I) is too large (the content of the ethylene-α-olefin copolymer (II) is too small), the heat sealability and impact resistance may be lowered. . Preferably, the content of the ethylene-α-olefin copolymer (I) is 50 to 80% by weight, and the content of the ethylene-α-olefin copolymer (II) is 50 to 20% by weight.

  The melt flow rate (MFR) of the polyethylene-based resin composition of the present invention measured under the conditions of a temperature of 190 ° C. and a load of 21.18 N specified in JIS K7210-1995 is 0.1 to 10 g / 10 min. . If the MFR is too low, the heat sealability and the extrudability may be lowered, preferably 0.2 g / 10 min or more, more preferably 0.4 g / 10 min or more. Moreover, when this MFR is too high, impact resistance may fall, Preferably it is 5 g / 10min or less, More preferably, it is 3 g / 10min or less.

The density of the polyethylene resin composition of the present invention is 920 to 960 Kg / m ³ . When the density is too low, heat resistance and rigidity may be lowered, and it is preferably 923 Kg / m ³ or more, more preferably 925 Kg / m ³ or more. On the other hand, if the density is too high, heat sealability and impact resistance may be lowered, preferably 950 Kg / m ³ or less, more preferably 940 Kg / m ³ or less.

  The polyethylene resin composition of the present invention can be produced, for example, by dry blending or melt blending the ethylene-α-olefin copolymer (I) and the ethylene-α-olefin copolymer (II). Various blenders such as a Henschel mixer and a tumbler mixer can be used for dry blending, and various mixers such as a single screw extruder, twin screw extruder, Banbury mixer, and hot roll can be used for melt blending. it can.

  The polyethylene-based resin composition of the present invention may contain additives such as an antioxidant, a lubricant, an antistatic agent, a processability improver, and an antiblocking agent as necessary. These additives may be used alone or in combination of at least two kinds.

  Examples of the antioxidant include 2,6-di-t-butyl-p-cresol (BHT), tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane. (Product name: IRGANOX 1010, manufactured by Ciba Specialty Chemicals), n-octadecyl-3- (4′-hydroxy-3,5′-di-t-butylphenyl) propionate (trade names: IRGANOX 1076, Ciba Specialty) Phenolic antioxidants such as Chemicals); bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite, tris (2,4-di-t-butylphenyl) phosphite, 2,4 , 8,10-Tetra-t-butyl-6- [3- (3-methyl-4-hydroxy-5-t-butylphenyl) And phosphite antioxidants such as propoxy] dibenzo [d, f] [1,3,2] dioxaphosphine (trade name: Sumilizer GP, manufactured by Sumitomo Chemical Co., Ltd.).

  Examples of the lubricant include higher fatty acid amides and higher fatty acid esters, and examples of the antistatic agent include glycerin esters, sorbitan acid esters, and polyethylene glycol esters of fatty acids having 8 to 22 carbon atoms. Examples of the processability improver include fatty acid metal salts such as calcium stearate, fluorine resins, and the like, and examples of the antiblocking agent include inorganic antiblocking agents and organic antiblocking agents, and inorganic blocking prevention. Examples of the agent include silica, calcium carbonate, and talc. Examples of the organic anti-blocking agent include crosslinked polymethyl methacrylate, crosslinked poly (methyl methacrylate-styrene) copolymer, crosslinked silicone, and crosslinked. Examples thereof include polystyrene powder.

  The film for retort packaging of this invention is a film which has a layer which consists of the above-mentioned polyethylene-type resin composition in a surface layer. The film may be a single-layer film or a multilayer film. In the case of a multilayer film, it is sufficient that a layer made of the above-described polyethylene-based resin composition is included in at least one of the surface layers.

  As a method for producing the film for retort packaging of the present invention, a known method is used, and examples thereof include an inflation film molding method, a T-die cast film molding method, a calendar molding method, and a press molding method.

  In the case of a multilayer film, a co-extrusion method may be used in an extrusion method such as an inflation film molding method or a T-die cast film molding method, or an extrusion coating method (extrusion laminating method) may be used. Further, the formed film may be laminated with another film by a known laminating method, for example, a dry laminating method, a wet laminating method, a sand laminating method, a hot melt laminating method or the like. Examples of the other film include cellophane, paper, paperboard, woven fabric, aluminum foil, polyamide resin such as nylon 6 and nylon 66, polyester resin such as polyethylene terephthalate and polybutylene terephthalate, and stretched polypropylene.

  The thickness of the film for retort packaging of this invention is 20-200 micrometers normally, Preferably it is 25-100 micrometers, More preferably, it is 30-80 micrometers.

  Next, this invention is demonstrated based on an Example and a comparative example.

  The physical properties used in Examples and Comparative Examples were measured according to the following method.

(1) Density (Unit: Kg / m ³ )
It measured according to the method prescribed | regulated to the underwater substitution method among JISK7112-1980. The sample was annealed according to JIS K6760-1995.

(2) Melt flow rate (MFR, unit: g / 10 minutes)
According to the method defined in JIS K7210-1995, the measurement was performed by the A method under the conditions of a load of 21.18 N and a temperature of 190 ° C.

(3) Melt flow rate ratio (MFRR)
In accordance with the method defined in JIS K7210-1995, the melt flow rate value measured by the A method under the conditions of a load of 211.8 N and a temperature of 190 ° C. was measured by the A method under the conditions of a load of 21.18 N and a temperature of 190 ° C. The value divided by the flow rate value was defined as MFRR.

(4) Flow activation energy (Ea, unit: kJ / mol)
Using a viscoelasticity measuring device (Rheometrics Mechanical Spectrometer RMS-800 manufactured by Rheometrics), a melt complex viscosity-angular frequency curve at 130 ° C., 150 ° C., 170 ° C. and 190 ° C. was measured under the following measurement conditions. From the obtained melt complex viscosity-angular frequency curve, calculation software Rhios V. The activation energy (Ea) was determined using 4.4.4.
<Measurement conditions>
Geometry: Parallel plate Plate diameter: 25mm
Plate spacing: 1.5-2mm
Strain: 5%
Angular frequency: 0.1 to 100 rad / sec Measurement atmosphere: Nitrogen

(5) Molecular weight distribution (Mw / Mn)
Using a gel permeation chromatograph (GPC) method, a weight average molecular weight (Mw) and a number average molecular weight (Mn) were measured under the following conditions to obtain a molecular weight distribution (Mw / Mn).
<Measurement conditions>
Device: Waters 150C manufactured by Water
Separation column: TOSOH TSKgelGMH-HT
Measurement temperature: 145 ° C
Carrier: Orthodichlorobenzene Flow rate: 1.0 mL / min Injection volume: 500 μL
Detector: Differential refraction

(6) Heat-resistant fusing property (unit: N / 15mm width)
After two films are stacked, the two stacked films are sandwiched between two glass plates of 10cm x 10cm, and the two opposite faces of the glass plate are fixed with clips (size 63mm) and retort Using a kettle, heat treatment was performed in hot water at a predetermined temperature (105 ° C., 110 ° C. or 115 ° C.) for 30 minutes. Then, after cooling and drying for 10 minutes in a hot water shower at 40 ° C., the film is made into a strip of 15 mm × 10 cm, and the force required for peeling between the films is determined by a tensile tester (180 ° peeling, pulling speed: 200 mm / min, chuck distance: 50 mm). It shows that it is excellent in heat-resistant fusion property, so that this value is small. In addition, the thing which cannot be peeled was made into "fusion | fusion".

(7) Heat seal strength (unit: N / 15mm width)
After the two films were superposed, the two superposed films were heat sealed using a heat sealer (manufactured by Tester Sangyo Co., Ltd.) under the following sealing conditions.
Sealing temperature: 140 ° C, 160 ° C
Sealing time: 1 second Sealing pressure: 0.98 MPa
Seal width: 10mm
After conditioning the obtained sample at 23 ° C. for 24 hours or more, a test piece having a width of 15 mm was cut from the seal width direction in a direction perpendicular to the seal width direction, and then the seal portion of the test piece was 200 mm / min by a tensile tester. The seal peeled at a speed of 180 °, and the seal strength at each seal temperature was measured. The higher the seal strength, the better the heat sealability.

(8) Dirt impact strength (unit: kJ / m)
The dart impact strength was measured according to the method (Method A) defined in ASTM D1709-75. The higher this value, the better the impact resistance of the film.

The following PE-1 to PE-3 were used as the ethylene-based polymers as raw materials in the examples and comparative examples. The physical properties are shown in Table 1.
PE-1: Sumikasen E FV407 (manufactured by Nippon Evolution, sold by Sumitomo Chemical,
(Ethylene-1-hexene copolymer produced using a metallocene catalyst)
PE-2: Ethylene-1-hexene copolymer PE-3 obtained by the preparation method described later: Sumikacene F200-0 (manufactured by Sumitomo Chemical Co., Ltd., high-pressure low-density polyethylene)

(9) Rigidity (1% SM, unit: MPa)
A strip-shaped test piece having a width of 20 mm and a length of 120 mm was sampled so that the longitudinal direction was a take-up direction (MD) and a direction (TD) perpendicular to the MD direction, and the test piece was used to make a chuck. A tensile test was performed under the conditions of a distance of 60 mm and a tensile speed of 5 mm / min, and a stress-strain curve was measured. From the stress-strain curve, the load at 1% elongation (unit: N) was determined, and 1% SM was calculated from the following formula to obtain the rigidity of the multilayer film.
1% SM = [F / (t × l)] / [s / L ₀ ] / 10 ⁶
F: Load at 1% elongation (unit: N)
t: Test piece thickness (unit: m)
l: Specimen width (Unit: m, 0.02)
L ₀ : Distance between chucks (Unit: m, 0.06)
s: 1% distortion (Unit: m, 0.0006)

<Preparation method of PE-2>
(1) Preparation of promoter support In the same manner as the preparation of component (A) in Example 10 (1) and (2) of JP-A No. 2003-171415, a solid product (hereinafter referred to as solid product (a) )).

(2) Prepolymerization Into an autoclave with a stirrer having an internal volume of 210 liters, which was previously purged with nitrogen, 0.71 kg of the solid product (a), 80 liters of butane, 0.02 kg of 1-butene, 12 hydrogen as normal temperature and normal pressure After charging the liter, the autoclave was raised to 40 ° C. Further, 0.03 MPa of ethylene was charged at a gas phase pressure in the autoclave, and after the system was stabilized, 208 mmol of triisobutylaluminum and 73 mmol of racemic-ethylenebis (1-indenyl) zirconium diphenoxide were added to initiate polymerization. While raising the temperature to 49 ° C. and continuously supplying ethylene and hydrogen, prepolymerization was carried out at 49 ° C. for a total of 6 hours. After the polymerization was completed, ethylene, butane, hydrogen gas and the like were purged, and the remaining solid was vacuum dried at room temperature, so that 13 g of ethylene-1-butene copolymer per 1 g of the solid product (a) was prepolymerized. A catalyst component (hereinafter referred to as pre-polymerization catalyst component (a)) was obtained.

(3) Continuous gas phase polymerization Using the above prepolymerization catalyst component (a), ethylene and 1-hexene were copolymerized in a continuous fluidized bed gas phase polymerization apparatus. Polymerization conditions were as follows: temperature 75 ° C., total pressure 2 MPa, gas linear velocity 0.24 m / s, hydrogen molar ratio to ethylene 0.23%, 1-hexene molar ratio to ethylene 0.55%, and gas composition during polymerization In order to maintain a constant, ethylene, 1-hexene and hydrogen were continuously supplied. Further, the pre-polymerization catalyst component (a) and triisobutylaluminum were continuously supplied at a constant ratio so that the total powder weight of the fluidized bed was maintained at 100 kg and the average polymerization time was 5.6 hr. By the polymerization, an ethylene-1-hexene copolymer powder was obtained with a production efficiency of 17.8 kg / hr.

(4) Granulation of ethylene-1-hexene copolymer powder Blended with the ethylene-1-hexene copolymer powder obtained above with 1000 ppm of calcium stearate and 1500 ppm of Sumilizer GP (Sumitomo Chemical Co., Ltd.) By using an extruder (LCM50 manufactured by Kobe Steel, Ltd.), granulation is performed under conditions of a feed rate of 50 kg / hr, a screw rotation speed of 450 rpm, a gate opening of 50%, a suction pressure of 0.2 MPa, and a resin temperature of 200 to 230 ° C. The pellet of the ethylene-1-hexene copolymer was obtained.

Example 1
A mixture of 70 parts by weight of PE-1 and 30 parts by weight of PE-2 and 100 parts by weight of a dry blend of 3 parts by weight of an antiblocking agent and a lubricant masterbatch was subjected to inflation molding under the following molding conditions, and the thickness was 50 μm. Inflation film was obtained. Table 2 shows the physical properties of a mixture of 70% by weight of PE-1 and 30% by weight of PE-2 and the properties of the resulting blown film.
<Molding conditions>
Molding machine: Modern machinery 50mmφ inflation molding machine Screw: Barrier type screw Dies: 125mmφ (diameter), 2.0mm (lip width)
Air ring: 2-gap type Molding temperature: 170 ° C
Take-off speed: 12m / min

Example 2
Example 1 except that 100 parts by weight of a mixture of 30% PE-1 and 70% PE-2 by dry blending 3 parts by weight of an anti-blocking agent and a lubricant masterbatch was blown. It was done by the method. The results are shown in Table 2.

Comparative Example 1
A dry blend of 100 parts by weight of PE-1 with 3 parts by weight of an antiblocking agent and a lubricant masterbatch was carried out in the same manner as in Example 1 except that it was subjected to inflation molding. The results are shown in Table 2.

Comparative Example 2
A dry blend of 100 parts by weight of PE-2 with 3 parts by weight of an antiblocking agent and a lubricant masterbatch was carried out in the same manner as in Example 1 except that it was subjected to inflation molding. The results are shown in Table 2.

Comparative Example 3
Example 1 except that 100 parts by weight of a mixture of 70% PE-1 and 30% PE-3 by dry blending 3 parts by weight of an antiblocking agent and a lubricant masterbatch was blown. It was done by the method. The results are shown in Table 2.

Comparative Example 4
Example 1 except that 100 parts by weight of a mixture of 30% by weight of PE-1 and 70% by weight of PE-3 was dry blended with 3 parts by weight of an antiblocking agent and a lubricant masterbatch, and subjected to inflation molding. It was done by the method. The results are shown in Table 2.

Claims (3)

The ethylene-α-olefin copolymer (I) satisfying the following requirements (Ia), (Ib), (Ic) and (Id) is 15 to 85% by weight, II-a), (II-b), (II-c) and (II-d) containing ethylene-α-olefin copolymer (II) satisfying 85 to 15% by weight (provided that ethylene The total amount of the α-olefin copolymer (I) and the ethylene-α-olefin copolymer (II) is 100% by weight.), The melt flow rate is 0.1 to 10 g / 10 min, and the density A film for retort packaging having a layer made of a polyethylene resin composition having a surface area of 920 to 960 kg / m ³ .
(Ia): An ethylene-α-olefin copolymer obtained by copolymerizing ethylene and an α-olefin having 4 to 12 carbon atoms using a metallocene catalyst.
(Ib): The density is 920 to 970 Kg / m ³ .
(Ic): Melt flow rate is 0.01 to 10 g / 10 min.
(Id): Flow activation energy (Ea) is less than 35 kJ / mol, or melt flow rate ratio (MFRR) is less than 30.
(II-a): An ethylene-α-olefin copolymer obtained by copolymerizing ethylene and an α-olefin having 3 to 12 carbon atoms.
(II-b): The density is 915 to 950 Kg / m ³ .
(II-c): The melt flow rate is 0.01 to 50 g / 10 min.
(II-d): Flow activation energy (Ea) is 35 kJ / mol or more, and melt flow rate ratio (MFRR) is 30 or more.   The retort packaging film comprising the resin composition according to claim 1, wherein the ethylene-α-olefin copolymer (II) has a molecular weight distribution (Mw / Mn) of 5 to 25. A retort food packaged by the film according to claim 1 or 2 and subjected to a retort treatment.