JPH11286085A - Stretchable packaging film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stretchable packaging film which has good stretch properties, bottom surface sealing properties, and cutting properties and is well applicable to a high magnification stretch automatic packaging machine. SOLUTION: A stretchable packaging film having tree-layer structure comprising a backing layer and both surface layers of an ethylene-vinyl acetate copolymer and others is provided, in which the backing layer comprises a polypropylene resin in which the melt flow rate is 0.01-10 g/10 min, the ethylene unit content is 10-40 mole %, the molecular weight distribution (Mw/Mn) expressed by the ratio of weight-average molecular weight (Mw) to number- average molecular weight (Mn), which are obtained by a gel permeation chromatography is 6-16, and in an elution curve, in which the axis of abscissa indicates elution temperatures and the axis of ordinate indicates elution weight ratios, fractionated by a temperature programed elution fractionation method, the quantity of eluted components (A components) at below 20 deg.C is 20-53 wt.%, the quantity of eluted components (B components) at 20-100 deg.C is 20-75 wt.%, and the quantity of eluted components (C components) at 100 deg.C or above is 5-50 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film for stretch packaging. For more information,
The present invention relates to a stretch wrapping film suitable as a film used in a high-magnification stretch automatic wrapping machine that stretches and wraps the film about twice.

[0002]

2. Description of the Related Art Push-up and pillow-type packaging machines are mainly used as automatic packaging machines for wrapping and packaging foods such as fruits and vegetables, prepared foods, meat, and fresh fish directly or on a plastic tray. Recently, a high-magnification stretch packaging machine that stretches and packs a film in the width direction of the film has been put to practical use in order to save labor and improve work efficiency of the film and to cope with trays having various shapes and sizes.

[0003] As a film for high-magnification stretch packaging, a soft polyvinyl chloride (soft PVC) film is used, but since it does not have sufficient elongation characteristics and low-temperature characteristics, it is packaged in a place where the room temperature is low. If so, the film often breaks during stretching. Also,
The soft PVC film is regarded as an environmental problem because it generates toxic gas at the time of incineration and transfers a plasticizer to food.

On the other hand, as a polyolefin (PO) stretch packaging film, high-density polyethylene,
Films using low-density polyethylene, linear low-density polyethylene resin, and the like are known, but the film is hard and hard to stretch, and further causes deformation and breakage of the tray and the like during packaging, and is suitable for the above-described high-magnification stretch packaging. There was nothing. In addition, Japanese Patent Publication No. 2-1668 discloses a food packaging film in which an ethylene-vinyl acetate copolymer is laminated on both surfaces of an intermediate layer composed of a polypropylene resin and a low-crystalline ethylene-α-olefin copolymer. Proposed. However, this multilayer film also did not have sufficient flexibility and stretchability was not sufficient.

Further, Japanese Patent Application Laid-Open No. 6-256439 proposes a stretch packaging film in which a soft polypropylene is used as an intermediate layer and an ethylene-vinyl acetate copolymer is laminated on both sides. Although this laminated film has sufficient flexibility and stretchability, it has a strong rubber elasticity and a strong shrinkage force in the tensile direction of the film, and when stretched on a tray by automatic packaging, the film can be folded at the bottom of the tray (hereinafter, referred to as (Also referred to as bottom sealability). That is, the above film is in a state where the overlapping portion of the film at the tray bottom portion is stiffened at the time of packaging,
It was difficult to fold and seal the film pieces with sufficient overlap and adhesion. In this case, the tightness of the packaging is deteriorated, and the lower surface of the tray swells due to the poor adhesion of the overlapped portion, causing a problem that the tray is tilted at the time of display at a store. In addition, the film has a problem that the cutability of the film by the knurling blade at the time of automatic packaging is not sufficient, and the film cannot be cut with a smooth cut edge. Furthermore, when this film was produced by inflation molding, the stability of bubbles was poor and the film-forming properties were not sufficient.

[0006]

SUMMARY OF THE INVENTION As described above, the present invention solves the above-mentioned problems by providing excellent stretch characteristics, bottom sealability, and cutability, and is suitable for a high-magnification stretch automatic packaging machine. An object of the present invention is to provide a stretch packaging film having suitability for a packaging machine.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, the base material layer is made of a specific propylene-based resin, and both surface layers have heat sealing properties. The present inventors have found that the above problems can be solved by a stretch packaging film made of a resin having the same, and have completed the present invention.

That is, the present invention has a three-layer structure consisting of a base layer and a heat-sealing surface layer, wherein the base layer has a melt flow rate of 0.01 to 10 g / 10 minutes and an ethylene unit. And the molecular weight distribution (Mw / Mn) represented by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) determined by gel permeation chromatography is 6 to 16. In the elution curve represented by the elution temperature (° C.) on the horizontal axis and the elution weight ratio on the vertical axis, the amount of the eluting component (A component) at less than 20 ° C. was 20 to 53% by weight, the amount of the eluted component (component B) at 20 ° C or higher and lower than 100 ° C is 20 to 75%
5% to 5% by weight of eluted component (C component) at 100 ° C. or more
This is a stretch packaging film made of 0% by weight of a propylene-based resin.

The melt flow rate (hereinafter referred to as MFR) of the propylene resin used for the base layer of the stretch packaging film of the present invention is 0.01 to 10 g / 10.
Min, preferably 0.05 to 7 g / 10 min. The MF
When R is less than 0.01, the molding processability of the film deteriorates, and the transparency further decreases, which is not preferable. The MF
When R exceeds 10, the film-forming properties and stretchability of the film are undesirably reduced.

[0010] The propylene resin used in the present invention comprises:
The content of the ethylene unit is 10 to 40 mol%, preferably 15 to 35 mol%. The content of the ethylene unit is
If it is less than 10 mol%, the stretchability is undesirably reduced. On the other hand, when the content of the ethylene unit exceeds 40 mol%, the transparency of the film is reduced, and the sealing property at the bottom and the cut property are unfavorably reduced.

The propylene resin used in the present invention comprises:
Gel permeation chromatography (GPC
The molecular weight distribution (Mw / Mn) represented by the ratio between the weight average molecular weight (Mw) and the number average molecular weight (Mn) measured by the above method is 6 to 16, preferably 8 to 15. When the molecular weight distribution is less than 6, the film forming property and the bottom sealing property and the cut property at the time of high-speed molding are reduced, and when the molecular weight distribution is more than 16, the orientation of the film at the time of the molding is increased and the stretchability is reduced. Is not preferred.

In the present invention, the elevated temperature elution fractionation method refers to, for example, Journal of Applied Pol
ymer Science; Applied Poly
mer Symposium 45, 1-24 (199
0). First, a high-temperature polymer solution is introduced into a column filled with a diatomaceous earth filler, and the column temperature is gradually decreased to crystallize the filler surface in order from the component with the highest melting point. This is a method in which the eluted polymer component is fractionated by gradually elevating it to elute it in order from the component having the lower melting point. In the present invention, as shown in Examples, SSC-7300 manufactured by Senshu Kagaku Co., Ltd. was used as a measuring device, the solvent was O-dichlorobenzene, the flow rate was 2.5 ml / min, the temperature was raised at 4 ° C./hr, and the column was Φ30 mm × This is a value measured under the condition of 300 mm.

The propylene-based resin 2 used in the present invention
The elution component (component A) at a temperature lower than 0 ° C. is 20 to 53% by weight.
And preferably 25 to 45% by weight. If the elution amount of the component A is less than 20% by weight, sufficient flexibility cannot be obtained, and as a result, the stretchability decreases, which is not preferable.
When the elution amount of the component A is more than 53% by weight, the bottom sealing property and the cut property are undesirably reduced. In order to obtain good stretchability, bottom sealability and cutability, the content of the ethylene unit in the component A must be 2%.
Suitably, it is between 0 and 50 mol%, more preferably between 25 and 50 mol%.

The propylene resin 2 used in the present invention
The eluted component (component B) at a temperature of 0 ° C or higher and lower than 100 ° C is 20 to 20 ° C.
It is 75% by weight, preferably 30 to 60% by weight. If the elution amount of the component B is less than 20% by weight, the transparency of the film decreases, and if it exceeds 75% by weight, the bottom sealing property and the cut property deteriorate, which is not preferable. Also,
In order to obtain better transparency, the content of the ethylene unit in the component B is preferably less than 20 mol%.

[0015] One of the propylene-based resins used in the present invention
The eluted component (component C) at 00 ° C or more is 5 to 50% by weight.
And preferably 5 to 40% by weight. When the elution amount of the component C is less than 5% by weight, the sealing property at the bottom and the cut property are reduced, and when it exceeds 50% by weight, the stretch property is undesirably reduced. The propylene-based resin used in the present invention preferably has a peak top temperature of 120 ° C. or higher in the component C from the viewpoint of heat resistance and cutability of the film during heat sealing. Further, it is preferable that the component C is a highly crystalline polypropylene component that elutes components eluted at 120 ° C. or higher by 50% or more from the viewpoint of heat resistance of the film at the time of heat sealing.

The propylene resin used in the present invention has a transparency (B / A) ratio between the amount of the component B and the amount of the component A (B / A).
In consideration of the balance of flexibility, 0.8 or more is preferable, and 0.9 or more is more preferable.

The propylene resin used in the present invention is:
It is generally constituted by a polypropylene component and a propylene-ethylene random copolymer component. The polypropylene component may be a propylene homopolymer or a random copolymer of propylene and a small amount of another α-olefin. Other α-olefins include ethylene, 1-
Examples thereof include butene, 3-methyl-1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, and 1-decene, and the content is preferably 8 mol% or less.

The propylene-based resin may be a so-called block copolymer in which the above-mentioned polypropylene component and propylene-ethylene random copolymer component are arranged in one molecular chain, or may be a polypropylene component and propylene-ethylene random copolymer. It is preferable that the polymer component is mixed microscopically with a molecular chain composed of a single component to such an extent that it cannot be achieved by mechanical mixing, in order to obtain better transparency.

The propylene resin used in the present invention is:
In addition to the above-mentioned polypropylene component and propylene-ethylene random copolymer component, other α-olefin polymers may be used in a range that does not impair the effect of the stretch packaging film of the present invention, for example, in a range of 5% by weight or less. It may be contained as a block copolymer component.

The method for producing the propylene resin used in the present invention is not particularly limited as long as it satisfies the requirements of the present invention. For example, it can be obtained by the following method.

The following catalyst components [A], [B], [C] and [D] [A] Titanium compound [B] Organoaluminum compound [C] Organosilicon compound [D] Carboxyester or ethers In this method, propylene is polymerized in the presence of at least one kind of electron donating compound, and then random copolymerization of propylene and ethylene is performed under the following conditions.

As the titanium compound [A], a titanium compound known to be used for polymerization of olefins can be used without any limitation. Among them, a titanium compound capable of obtaining a polymer having high stereoregularity at a high yield when used for the polymerization of propylene is preferable. These titanium compounds are roughly classified into a supported titanium compound and a titanium trichloride compound. As a method for producing the supported titanium compound, a known method is employed without any limitation. For example, JP-A-56-155206
JP, 56-136806, 57-34103,
58-8706, 58-83006, 58-18
3709, 59-206408, 59-21931
1, 60-81208, 60-81209, 60
-186508, 60-192708, 61-21
1309, 61-271304, 62-1520
9, 62-11706, 62-72702, 62
For example, the method described in US Pat.

Examples of the titanium trichloride compound include known α, β, γ and δ-titanium trichloride. The method for preparing these titanium trichloride compounds is described in, for example, JP-A-47-34478, JP-A-50-126590, JP-A-50-114394, JP-A-50-93888, and JP-A-50-93888.
23091, 50-74594, 50-9848
9, 51-136625, and 52-35283.

Next, as the organoaluminum compound [B], a compound known to be used for the polymerization of olefin is employed without any limitation. For example, trimethyl aluminum,
Trialkylaluminums such as triethylaluminum, tri-npropylaluminum, and tri-n-hexylaluminum; diethylaluminum monohydrides such as diethylaluminum monochloride; alkylaluminum chlorides such as methylaluminum sesquichloride.

Further, as the organosilicon compound [C], a compound known to be used for improving the stereoregularity of an olefin is employed without any limitation, and the atom directly connected to the silicon atom is tertiary carbon. A chain hydrocarbon, or
An organosilicon compound having a bulky substituent such as a cyclic hydrocarbon that is a secondary carbon is preferable because the stereoregularity of the obtained polypropylene component can be increased. Specific examples include organosilicon compounds such as di-t-butyldimethoxysilane, t-butylethyldimethoxysilane, dicyclopentyldimethoxysilane, t-butylmethyldimethoxysilane, cyclopentylmethyldimethoxysilane, and cyclopentylisobutyldimethoxysilane. . In addition, a plurality of these organosilicon compounds can be used simultaneously.

Further, at least one kind of electron donating compound [D] selected from carboxylic acid esters or ethers
A compound known to be used for improving the stereoregularity of an olefin is employed without any limitation. Specifically, carboxylic acid esters such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, ethyl valerate, ethyl stearate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, ethyl benzoate; methyl ether, Examples include ethers such as ethyl ether, isopropyl ether, isoamyl ether, anisole, and diethylene glycol methyl ether. Among them, carboxylic acid esters such as butyl acetate and methyl methacrylate are preferred. It is preferable to use two or more of the carboxylic acid esters or ethers at the same time to obtain a propylene-based resin having a specific crystallinity distribution.

Combination of the titanium compound [A], organoaluminum compound [B], organosilicon compound [C] and at least one electron donor [D] selected from carboxylic esters or ethers used in the present invention. Is a supported titanium compound-trialkylaluminum-organosilicon compound-electron donor titanium trichloride compound-diethylaluminum monohalide-organosilicon compound-electron donor titanium trichloride compound-trialkylaluminum-organosilicon compound-electron donor And a combination of supported titanium compound-titanium trichloride compound-trialkylaluminum-organosilicon compound-electron donor is preferable in producing the propylene-based resin by adopting other production conditions in the present invention. .

In the present invention, before the main polymerization in the presence of each of the above components, the titanium compound [A] is converted to the above titanium compound [A].
[B] and [C], or [B] and [D], or [B],
Preliminary polymerization of the α-olefin in the presence of [C] and [D] is preferred because the amount of low molecular weight components produced in the resulting propylene resin can be reduced. Further, if necessary, in addition to the respective combinations using the above [B], [C], and [D], an iodine compound [E] represented by the general formula (i) [E] an iodine compound RI general formula (I) (where R is an iodine atom or an alkyl group having 1 to 7 carbon atoms or a phenyl group), the prepolymerization of an α-olefin is carried out in the presence of a low molecular weight component of a propylene resin obtained. This is a preferred embodiment because the generation amount of can be further reduced.

The proportion of the organoaluminum compound [B] used in the prepolymerization is such that the titanium compound [A] is mixed with Al
/ Ti (molar ratio) of 0.1 to 100, preferably 0.1
And at least one electron donor [D] selected from the group consisting of an organosilicon compound [C] and a carboxylic acid ester or ether, if necessary.
Is the ratio of [C] / Ti to the titanium compound [A].
(Molar ratio), [D] / Ti (molar ratio) 0.01 to 100,
Preferably, the range of 0.01 to 10 is respectively suitable. Further, an iodine compound [E] optionally used
Is preferably in the range of 0.1 to 100, preferably 0.5 to 50, in terms of I / Ti (molar ratio) with respect to the titanium compound [A].

Specific examples of the iodine compound that can be suitably used in the prepolymerization are as follows. For example, iodine,
Examples include methyl iodide, ethyl iodide, propyl iodide, butyl iodide, iodobenzene, p-iodine toluene and the like. Particularly, methyl iodide and ethyl iodide are preferred.

The amount of pre-polymerization of the α-olefin in the presence of the catalyst component varies depending on the pre-polymerization conditions, but is generally from 0.1 to 500 g / g · Ti compound, preferably from 1 to 100 g / g · Ti. A range of compounds is sufficient. The α-olefin used in the prepolymerization may be propylene alone, for example, 5 mol% or less of another α-olefin such as ethylene or 1-butene as long as it does not adversely affect the physical properties of the propylene resin. , 3
-Methyl-1-butene, 4-methyl-1-pentene, 1
-Hexene, 1-octene, 1-decene and the like may be mixed with propylene. Further, the prepolymerization may be performed in multiple stages, and a different α-olefin monomer may be prepolymerized in each stage. It is also possible to make hydrogen coexist at each prepolymerization stage.

In the prepolymerization, it is usually preferable to apply slurry polymerization, and hexane, heptane,
Cyclohexane, benzene and the like can be used alone or as a mixture. The pre-polymerization temperature is preferably in the range of −20 to 100 ° C., particularly preferably in the range of 0 to 60 ° C. The pre-polymerization time may be appropriately determined according to the pre-polymerization temperature and the amount of polymerization in the pre-polymerization. The pressure in the prepolymerization is not limited, but in the case of slurry polymerization, it is generally from atmospheric pressure to 500.
It is about 000 Pascal. The preliminary polymerization may be performed in any of batch, semi-batch, and continuous methods.

The main polymerization is carried out after the preliminary polymerization. In the main polymerization, propylene is firstly polymerized, and then propylene-ethylene random copolymerization is performed in the presence of the catalyst-containing prepolymer obtained by the above prepolymerization. The catalyst components added during the prepolymerization can be used as they are, but it is preferable that the components other than the titanium compound are newly added and adjusted during the main polymerization.

The above [A], [B] and [C] used in the main polymerization
Since the amount of each catalyst component and the polymerization conditions of [D] differ depending on the type of the catalyst component, the optimum use amount and polymerization conditions may be determined in advance according to the type of these catalyst components. Examples of the amount of the catalyst component and the polymerization conditions suitably used are as follows.

As the organoaluminum compound [B] used in the main polymerization, those described above can be used without any limitation. The amount of the organoaluminum compound used is 1 to 10 in terms of Al / Ti (molar ratio) based on titanium atoms in the catalyst-containing prepolymer.
00, preferably 2 to 500.

The organosilicon compound [C] used in the main polymerization
Is used without any limitation for the compounds described above. The amount of the organosilicon compound used in the main polymerization is 0.001-1000, preferably 0.1-500, in terms of Si / Ti (molar ratio), based on the titanium atoms in the catalyst-containing prepolymer. .

As the at least one electron donor [D] selected from carboxylic acid esters or ethers used in the main polymerization, those described above are employed without any limitation.
The amount of the at least one electron donor selected from the carboxylic acid esters or ethers used in the main polymerization is 0.001 to 1000, preferably in a molar ratio to titanium atoms in the catalyst-containing prepolymer. , 0.1-50
0.

In the main polymerization, propylene is firstly polymerized. The polymerization of propylene is carried out by propylene alone or propylene and other α within a range satisfying the requirements of the present invention.
It may be carried out by supplying a mixture of olefins. To illustrate typical conditions of propylene polymerization, the polymerization temperature is:
It is preferable to adopt the temperature in the range of 80 ° C. or less, particularly 20 to 70 ° C. Further, if necessary, hydrogen can be allowed to coexist as a molecular weight regulator. Further, the polymerization may be any method such as slurry polymerization using propylene itself as a solvent, gas phase polymerization, solution polymerization and the like. The polymerization system may be a batch system, a semi-batch system, or a continuous system. Further, the polymerization can be carried out in two or more stages having different conditions such as hydrogen concentration and polymerization temperature.

Next, random copolymerization of propylene and ethylene is performed. In the random copolymerization of propylene and ethylene, in the case of slurry polymerization using propylene itself as a solvent, ethylene gas is supplied following the propylene polymerization, and in the case of gas phase polymerization, mixing of propylene and ethylene gas is performed. It is implemented by supplying gas.

The random copolymerization temperature of propylene and ethylene is preferably from 80 ° C. or less, particularly from 20 to 70 ° C. If necessary, hydrogen can also be used as a molecular weight regulator, and the polymerization can be carried out by changing the hydrogen concentration at that time in multiple stages.

By selecting a specific catalyst in the random copolymerization of ethylene and propylene following the propylene polymerization, a propylene-based resin having the target molecular weight distribution, crystallinity distribution, etc. can be produced in one step.
In order to obtain a wide molecular weight distribution and crystallinity distribution of the propylene-based resin used in the present invention, random copolymerization is performed in multiple stages, and production is performed by a method in which polymerization conditions such as hydrogen concentration and ethylene concentration are changed at each stage. Can be. In such a multi-stage copolymerization, the polymerization conditions may be appropriately selected so that the ratio of the component A and the component B described above, and further, the ratio of the component C and the component C are obtained.

The random copolymerization of propylene and ethylene may be any of a batch system, a semi-batch system, and a continuous system, and the polymerization may be carried out in multiple stages. Further, the polymerization in this step may employ any method of slurry polymerization, gas phase polymerization, and solution polymerization.

Next, in the stretch packaging film of the present invention, a heat-sealing surface layer is laminated on both surfaces of the above-described base material layer made of a propylene-based resin. That is, the base material layer made of the propylene-based resin, since the single-layer film does not have sufficient heat sealability required for a stretch packaging film, is made of a resin having the heat sealability as described above on its surface. The surface layers are laminated to form a laminated film.

Here, as the resin constituting both surface layers of the heat sealing property, a resin having a heat sealing property used as a surface layer resin of a conventional laminated film for stretch packaging can be used without limitation. Preferably, the melting point is 1
A resin having a temperature of 30 ° C. or lower can be used. For example, ethylene-α
-Olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer and the like can be used. Here, the α-olefin used for the ethylene-α-olefin copolymer includes propylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene. , 1-decene and the like having 3 to 12 carbon atoms. These α-olefins may be used alone or in combination of two or more. The ethylene-α-olefin copolymer has an ethylene unit content of 50 mol%.
As described above, it is preferably 70 to 99 mol%, and the content of the α-olefin unit is preferably 50 mol% or less, more preferably 30 to 1 mol%.

In the present invention, the resin having heat sealability has an ethylene unit content of 95 to 80% by weight.
And an ethylene-vinyl acetate copolymer having a vinyl acetate unit content of 5 to 20% by weight is particularly preferred from the viewpoint of having excellent heat sealing properties and also capable of imparting good adhesiveness to the film.

In the present invention, the resin constituting the base layer and the both surface layers may contain, if necessary, additional components such as low-molecular viscous substances such as polybutene and paraffin, antifogging agents, pressure-sensitive adhesives, Stabilizers, gas adsorbents, coloring agents, fragrances, antibacterial agents and the like can be added.

Next, the method for producing the stretch packaging film of the present invention is not particularly limited.
Each layer resin granulated as required is extruded at a melting point or higher by an individual extruder, laminated in a multilayer die, and extruded into a film. Film formation by multilayer extrusion includes T-die casting, upward air-cooled inflation, downward water-cooled inflation, and the like. In particular, among the above-mentioned molding methods, the upward air-cooled inflation method is preferable from the viewpoint of the balance between the vertical and horizontal properties of the film and the productivity.

The stretch packaging film of the present invention generally has a thickness of 5 to 50 μm, preferably 7 to 30 μm as a whole. If it is thinner than the above thickness,
Not only is it difficult to form an accurate film, but the film strength tends to decrease. When the thickness is larger than the above-mentioned thickness, not only is it disadvantageous in terms of cost, but also it tends to be difficult to perform tight packaging. Further, the thickness of each surface layer is preferably 10 to 100% of the thickness of the base material layer from the viewpoint of heat sealability.

[0049]

The film for stretch packaging of the present invention comprises:
Excellent transparency, 1.5 to 3 in the film width direction
It has good stretchability suitable for high-magnification stretch packaging in which it is stretched 1.5 times, more preferably 1.5 to 2.5 times. In addition, it is excellent in cutting property and bottom sealing property, and has good suitability for packaging machines. In addition, during production by the inflation method or the like, the film-forming property is good.

[0050]

EXAMPLES Examples and comparative examples will be shown below to specifically explain the present invention, but the present invention is not limited to these examples. In the following Examples and Comparative Examples, various measured values were measured by the following methods.

1) Measurement method (1) Measurement of MFR According to JIS K7210, propylene resin is 23
The ethylene-vinyl acetate copolymer was measured at 0 ° C. under a load of 2.16 Kg and at 190 ° C. under a load of 2.16 kg. (2) Measurement of ethylene unit content by ¹³ C-NMR Peaks were assigned by the method described in Polymer 29, 1848 (1988), and Macr was assigned.
The ethylene content was measured by the method described in Omolecus 10, 773 (1977).

(3) Measurement of molecular weight distribution The molecular weight distribution was measured by GPC (gel permeation chromatography). It was measured at 135 ° C. using O-dichlorobenzene as a solvent by SSC-7100 manufactured by Senshu Kagaku. The column used was Shodex UT807,
At 806M, the calibration curve was used as standard data and the weight average molecular weight was 950, 2900, 10,000, 49,980,270.
And 4.9 million polystyrene.

(4) Heated Elution Fractionation Method SSC-7300 manufactured by Senshu Scientific Co., Ltd. was used under the following measurement conditions.

Solvent: O-dichlorobenzene Flow rate: 2.5 ml / min Heating rate: 4 ° C./hr Sample concentration: 0.7 wt% Sample injection amount: 100 ml Detector: infrared detector, wavelength 3.41 μm column; Φ30mm × 300mm Filler; Chromosorb P 30-60me
sh Column cooling rate: 2.0 ° C./hr (5) Measurement of haze Measurement was performed according to JIS K7105.

(6) Film forming property In film forming by multilayer upward air-cooled inflation, the film forming stability at a film forming speed of 85 m / min was determined as follows.
It was evaluated on a scale.

；: The film can be formed without any problem and the bubble stability is good.

Δ: Film formation is possible, but bubble stability is poor.

×: Film formation is not possible.

(7) Stretchability Using a stretch automatic wrapping machine AW-3600 manufactured by Teraoka Seiko Co., Ltd., a film having a width of 300 mm was stretched 100% in the width direction, and the stretchability of the film was evaluated in two steps.

；: No film breakage occurs during stretching.

×: Film break occurs during stretching.

(8) Suitability of packaging machine Using a stretch automatic packaging machine AW-3600 manufactured by Teraoka Seiko Co., Ltd., 200 g of clay was placed on a foamed polystyrene tray of 12 cm × 12 cm × 1.5 cm, and the width was 300
mm film was stretched 85% in the width direction and wrapped. In the above stretching operation, the following items were evaluated.

Cutability In an automatic packaging machine, whether the film could be cut with a knives blade was evaluated in three steps.

；: Cut is possible without any problem.

Δ: Cutting is possible, but the cut is not smooth.

X: Cut property is insufficient.

Bottom Sealing Property The sealing property of the film at the bottom of the tray after packaging was evaluated by the length of the overlapping width of the film pieces stretched from both ends of the film and overlapped and sealed at the bottom of the tray.

2) Resin used: Propylene resin Propylene resin (Preliminary polymerization) After sufficiently replacing a 1-liter glass autoclave reactor equipped with a stirrer with nitrogen gas, 400 ml of heptane was charged. Reactor temperature 2
After maintaining at 0 ° C. and adding 0.18 mmol of butyl acetate, 22.7 mmol of ethyl iodide, 18.5 mmol of diethylaluminum chloride and 22.7 mmol of titanium trichloride (manufactured by Marubeni Solvay Chemical), propylene was added per 1 g of titanium trichloride. It was introduced into the reactor continuously for 3 minutes to a volume of 3 g. The temperature during this period was kept at 20 ° C. After stopping the supply of propylene, the inside of the reactor was sufficiently replaced with nitrogen gas, and the obtained titanium-containing polypropylene was washed four times with purified heptane. As a result of the analysis, 2.9 g of propylene was polymerized per 1 g of titanium trichloride.

(Main polymerization) 10 liters of liquid propylene was placed in a 20 liter autoclave purged with nitrogen.
0.70 mmol of diethylaluminum chloride, 0.07 mmol of butyl acetate, 0.07 mmol of dicyclopentyldimethoxysilane, and hydrogen having a concentration of 3 m in the gas phase
ol%, and the internal temperature of the autoclave is adjusted to 45.
The temperature was raised to ° C. 0.087 mmol of titanium-containing polypropylene obtained by pre-polymerization was added as titanium trichloride,
Polymerization of propylene was performed at 45 ° C. for 30 minutes (step 1). Next, ethylene was supplied at a concentration of 3 mol% while confirming the ethylene gas concentration in the gas phase by gas chromatography, and polymerization was performed for 60 minutes (step 2). Next, the ethylene gas concentration in the gas phase was supplied so as to be maintained at 9 mol%, and polymerization was performed for 60 minutes (step 3) to obtain a polymer.

Propylene resin In step 1 of the main polymerization of the propylene resin, the polymerization time of propylene was set to 60 minutes. In step 3, ethylene was supplied so that the ethylene gas concentration in the gas phase was maintained at 13 mol%. The same operation as for the propylene-based resin was performed, except that random copolymerization was performed for 5 minutes.

Propylene Resin The same operation as for the propylene resin was carried out except that the polymerization time of propylene was changed to 90 minutes in Step 1 of the main polymerization of the propylene resin.

Propylene resin Except that hydrogen was added in step 1 of the main polymerization of the propylene resin so that the concentration of hydrogen in the gas phase became 10 mol%,
The same operation as for the propylene-based resin was performed.

Propylene resin Except that hydrogen was added in step 1 of the main polymerization of the propylene resin so that the concentration of hydrogen in the gas phase became 16 mol%,
The same operation as for the propylene-based resin was performed.

Propylene Resin A propylene resin was used except that the polymerization time of propylene was 60 minutes in the main polymerization step 1 of the propylene resin, the polymerization in the step 2 was not performed, and the polymerization time in the step 3 was 120 minutes. The same operation as described above was performed.

Propylene resin The same operation as for the propylene resin was carried out except that the polymerization time of propylene was changed to 120 minutes in Step 1 of the main polymerization of the propylene resin.

Propylene resin Propylene-ethylene block copolymer; T310E
Table 1 shows the physical properties of the above propylene-based resins (from Tokuyama).

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[Table 1]

Surface layer resin ethylene-vinyl acetate copolymer Evaflex V5714 (manufactured by DuPont-Mitsui Polychemicals), vinyl acetate content 16% by weight, MFR 2.7 ethylene-vinyl acetate copolymer Evaflex P1207 ( Mitsui DuPont Polychemical Co., Ltd.), vinyl acetate content 12% by weight, MFR2.5 Example 1 98% by weight of a propylene-based resin as a resin of the base material layer,
Using a composition consisting of 2% by weight of diglycerin sesquiolate, 99% by weight of ethylene-vinyl acetate copolymer and 1% by weight of diglycerin monooleate were used as the resin for the surface layer.
Was used. Using a multilayer upward blown film molding machine, these resins were prepared by mixing a propylene-based resin from a second layer extruder and an ethylene-vinyl acetate copolymer from a first layer and a third layer extruder into a first layer: a second layer. layer:
The third layer is extruded into an annular die with a discharge amount of 1: 4: 1,
They were laminated in an annular die at 200 ° C. and extruded into a film. Then, air is blown into the inside of the molten cylindrical film, and air at 10 ° C. is blown annularly from outside to solidify by air-cooling, a blow ratio of 7.0, and a film forming speed of 85 m /.
And a film having a thickness of 13 μm was obtained. Table 2 shows the evaluation results of the obtained films.

Example 2 The procedure of Example 1 was repeated, except that a propylene resin was used instead of the propylene resin. Table 2 shows the evaluation results of the obtained films.

Example 3 The procedure of Example 1 was repeated, except that a propylene-based resin was used instead of the propylene-based resin. Table 2 shows the evaluation results of the obtained films.

Example 4 The procedure of Example 1 was repeated, except that a propylene resin was used instead of the propylene resin. Table 2 shows the evaluation results of the obtained films.

Example 5 The procedure of Example 1 was repeated, except that the ethylene-vinyl acetate copolymer was used instead of the ethylene-vinyl acetate copolymer. Table 2 shows the evaluation results of the obtained films.

Comparative Example 1 The procedure of Example 1 was repeated, except that a propylene resin was used instead of the propylene resin. Since it was impossible to form a film at a film forming speed of 85 m / min,
The film was formed at 40 m / min. Table 2 shows the evaluation results of the obtained films.

Comparative Example 2 Example 1 was repeated, except that a propylene-based resin was used instead of the propylene-based resin. Table 2 shows the evaluation results of the obtained films.

Comparative Example 3 The procedure of Example 1 was repeated, except that the propylene resin was used instead of the propylene resin. Table 2 shows the evaluation results of the obtained films.

Comparative Example 4 The procedure of Example 1 was repeated, except that a propylene resin was used instead of the propylene resin. Table 2 shows the evaluation results of the obtained films.

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[Table 2]

Claims (3)

[Claims] The present invention has a three-layer structure comprising a base material layer and a heat-sealing surface layer, wherein the base material layer has a melt flow rate of 0.01 to 10 g / 10 min and a content of ethylene units of 0.01 to 10 g / 10 min. The molecular weight distribution (Mw / M) is from 10 to 40 mol% and can be represented by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) determined by gel permeation chromatography.
n) is 6 to 16, and the elution component (A) at a temperature lower than 20 ° C. in the elution curve represented by the elution temperature (° C.) on the horizontal axis and the elution weight ratio on the vertical axis, which was fractionated by the elevated temperature elution fractionation method. Component) in an amount of 20 to 53% by weight, and the amount of the eluted component (component B) at 20 ° C. or more and less than 100 ° C. is 20 to 75% by weight.
A stretch packaging film comprising a propylene-based resin having an elution component (component C) at 0 ° C or higher of 5 to 50% by weight. 2. The content of the ethylene unit of the component A, which has been separated by the temperature-rise elution fractionation method according to claim 1, is 20 to 50.
2. The stretch packaging film according to claim 1, wherein the content of the ethylene unit of the component B is less than 20 mol%. 3. The surface layer according to claim 1, wherein the content of the ethylene unit is 95 to 95.
80% by weight, and the content of vinyl acetate units is 5 to 20.
The stretch packaging film according to claim 1, comprising a weight percent of an ethylene-vinyl acetate copolymer.