JPH06155676A - Stretch-wrap multilayered film - Google Patents

Abstract

PURPOSE:To obtain the title film having excellent elasticity recovery properties and a wide heat-sealing temp. range by forming an intermediate layer from a resin compsn. of a specific polypropylene resin, a hydrogenerated substance of a styrene/butadiene block copolymer and an ethylene/vinyl acetate copolymer and laminating layers of a specific ethylene/vinyl acetate copolymer to both surfaces of the intermediate layer. CONSTITUTION:An intermediate layer is formed from a resin compsn. consisting of 75-35wt.% of a polypropylene resin with an m.p. of 140 deg.C or higher and a melt index of 1-10g/10min (230 deg.C), 15-64wt.% of a styrene/butadiene block copolymer hydrogenated substance (SEBS) and 1-50wt.% of one of or both of an ethylene/vinyl acetate copolymer or an ethylene/alpha-olefin copolymer. A layer based on an ethylene/vinyl acetate copolymer with vinyl acetate content of 8-25wt.% and a melt index of 0.2-8g/10min (190 deg.C) is laminated to both surfaces of the intermediate layer. A heat sealing temp. range on a high temp. side is expanded by a polypropylene resin and proper elasticity recovery properties are imparted by SEBS.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer film, and more specifically, it has good transparency, moderate tackiness, good tear strength balance, excellent elastic recovery, and wrinkles during packaging.
The present invention relates to a stretch wrap film for food packaging, which can be packaged without causing slack and has a wide heat sealing temperature range.

[0002]

[Prior Art and Problems] As a pre-packaging film for stretch-packing fresh food such as vegetables, meat and fresh fish directly or in a state of being placed on a tray, polypropylene, instead of a conventional polyvinyl chloride film, Many stretch wrap films of polyolefin resin compositions such as low density polyethylene, linear low density polyethylene and ethylene-vinyl acetate copolymer have been developed.

A polyolefin-based stretch wrap multilayer film generally uses an ethylene-α-olefin copolymer as an intermediate layer in consideration of tackiness, cold resistance, puncture resistance, and the like. -Often laminated with vinyl acetate copolymer. However, although they are excellent in the finish at the time of packaging and the anti-fog property after packaging, the heat sealing temperature range is narrow, so the packaging conditions that can be completely sealed are also narrowed, which is a cause of difficult handling. There is.

The heat-sealing temperature range referred to here is a range from the temperature at which heat fusion starts at the time of heat-sealing to the temperature at which a pinhole is generated or less. That is, if the temperature at which the heat fusion is started is too low, handling becomes difficult, so that the temperature is preferably around 80 ° C., and the temperature at which pinholes are generated is preferably higher. Because if the heat fusion is not enough, the juice of the contents will come out from the unfused part and the overlapping parts of the packaging will peel off, and if the pinhole occurs, the contents will also be removed. This wide temperature range is very important for packaging suitability because it may cause juice leakage.

[0005] Further, when articles packed on a tray or the like are stacked at a store or the customer presses them with his / her fingers to confirm the packed contents, the elastic recovery property is small, so that the articles are partially pushed. There is a problem that the part that has been subjected to the repair does not recover and remains as it is, reducing the commercial value.

Therefore, in the case of a stretch wrap film of a polyolefin resin composition, compared to a polyvinyl chloride stretch film, there are problems in heat sealing so that the overlapped portions after packaging are not peeled off, and elastic recovery. There is an inferior problem. In other words, it is very important to improve elasticity recovery while maintaining good condition that transparency, adhesiveness and tear strength are good, and wrinkles and slack do not occur during packaging, and especially to amplify heat seal temperature range. Is. However, none of the conventionally developed stretch wrap packaging films can fully satisfy this point.

For example, in JP-A-61-44635, a propylene-α-olefin random copolymer of propylene and ethylene and at least one C _{4 to} C ₈ α-olefin is used as an intermediate layer, and ethylene-acetic acid is used. Stretch packaging films having a vinyl copolymer as an outer layer have been proposed. In Japanese Patent Publication No. 02-1668, a resin composition in which a polypropylene resin and a low crystalline ethylene-α-olefin copolymer are mixed is used as an intermediate layer, and ethylene-
A multilayer film having a vinyl acetate copolymer as an outer layer has been proposed. Further, JP-A-62-51440 proposes a stretch packaging film having a styrene-butadiene block copolymer as an intermediate layer and an ethylene-vinyl acetate copolymer as an outer layer as a hydrogenated derivative of a block copolymer. Has been done.

[0008]

[Problems to be Solved by the Invention]
In Japanese Patent No. 44635, a propylene-ethylene-butene-1 random copolymer, a propylene-ethylene random copolymer and a propylene-hexene-1 random copolymer are used as an intermediate layer for the purpose of improving extensibility, flexibility and tear strength. Used in, the α-olefin content is 4 to 19% by weight
It is a relatively high concentration and it has only been confirmed that good packaging can be done without breaking the corners in tray packaging, and there is no point in expanding the heat sealing temperature range and obtaining excellent elastic recovery. It is enough.

In Japanese Patent Publication No. 02-1668, the purpose is to improve especially cold resistance and rigidity. In practice, a low polypropylene ethylene-α-olefin copolymer, that is, a rubber component, is used in a homopolypropylene resin to improve rigidity. In order to maintain the above, the polypropylene resin has a high concentration of 78 to 90% by weight.
However, in the case of stretch wrap multilayer film,
When the rigidity is high as in the present case, it is difficult to obtain a good package because wrinkles and looseness occur.

In Japanese Patent Laid-Open No. 62-51440, the purpose is to improve the deformation recovery property, and the main component is a hydrogenated product of a styrene-butadiene block copolymer, and a non-aromatic mineral oil as a softening agent. , A composition containing a liquid or low molecular weight synthetic softener and paraffinic oil in an amount of 300 parts by weight or less relative to 100 parts by weight of the styrene-butadiene block copolymer is used as the intermediate layer.
It is insufficient to extend the heat seal temperature range, which is important for wrapping.

[0011]

OBJECTS OF THE INVENTION The object of the present invention is similar to the conventional stretch wrap multilayer film, but solves the above-mentioned problems, and in particular, the tackiness, transparency, and
The elastic recovery of the film is improved without impairing tear strength, etc., and various types of automatic push-up wrapping machines, pillow wrapping machines, and manual wrapping give good packages without wrinkles, sagging, etc. It is an object of the present invention to provide a film having excellent heat-sealing property at low temperature and widening the heat sealing temperature range so that the temperature at which pinholes are generated is on the high temperature side.

[0012]

[Means for Solving Problems] Therefore, as a means for solving this problem without deteriorating other properties, the heat sealing temperature range is widened to the high temperature side, and it is earnestly aimed at obtaining an excellent elastic recovery property. As a result of repeated research, (1) In order to secure heat sealability on the low temperature side, the inner and outer layers are mainly composed of an ethylene-vinyl acetate copolymer. (2) A polypropylene resin having a high melting point is selected as the resin for the intermediate layer to widen the heat seal temperature range on the high temperature side. (3) A styrene-butadiene block copolymer hydrogenated product (hereinafter abbreviated as SEBS), which has good molding stability and has no problem in food hygiene, is selected from the thermoplastic elastomers to impart appropriate elastic recovery. . As a result, they have reached the present invention.

That is, the present invention has a melting point of 140 ° C. or higher and a melt index of 1 to 10 g / 10 minutes (230
C.) 75 to 35% by weight of a resin composition containing a polypropylene resin as a main component, 15 to 64% by weight of a hydrogenated product of a styrene-butadiene-styrene block copolymer, and an ethylene-vinyl acetate copolymer or ethylene. A resin composition obtained by mixing one or both of the α-olefin copolymers in an amount of 1 to 50% by weight is used as an intermediate layer. The vinyl acetate content on both sides of the intermediate layer is 8 to 25% by weight, and the melt index is 0. 2-8g / 10 min (190 ° C) ethylene-
The average tangential elastic modulus in the TD direction (direction orthogonal to the molding direction) of a film formed by laminating layers containing a vinyl acetate copolymer as a main component in three layers is 14 kg / cm ² or more, and the tensile elastic modulus is It is to provide a stretch wrap multilayer film having a heat sealing temperature range of 400 to 2000 kg / cm ² and a heat sealing temperature range of 40 ° C. or higher.

By using a resin composition containing polypropylene resin having a melting point of 140 ° C. or higher, which is one of the resin compositions of the intermediate layer of the present invention, as a main component, a film having a wide heat seal temperature range on the high temperature side can be obtained. Can be provided. Melting point is 1
When the temperature is lower than 40 ° C., amplification in the heat-sealing temperature range is small and it is difficult to stably obtain a sufficient heat-sealing temperature range. Examples of such polypropylene resins having a melting point of 140 ° C. or higher include propylene-ethylene random copolymers having an ethylene content of less than 4% by weight and other propylene-α-olefin random copolymers.

The reason why the melt index is limited to 1 to 10 g / 10 minutes (230 ° C.) is that if it is less than 1 g / 10 minutes, a kneading failure will occur at the time of extrusion and the transparency will deteriorate, resulting in 10 g / min.
If it exceeds 10 minutes, the stability of the film at the time of molding is poor, the quality is not stable, and the strength is reduced. Further, when the polypropylene resin is less than 35% by weight, the high temperature side of the heat sealing temperature range is lowered, and when it exceeds 75% by weight, the film becomes hard and wrinkles and slack frequently occur during packaging, which is satisfactory. Packaging suitability cannot be obtained.

SEBS which is a thermoplastic elastomer is used as the other resin composition of the intermediate layer. This resin is
At room temperature, the polystyrene part has a very small particle size in the same molecule and the polybutadiene part in a continuous state, so the polystyrene part has a very small particle size and does not scatter visible light. , Can maintain transparency. Further, in the temperature range where actual molding is performed, it can be made into a film by melting like polypropylene and polyethylene, and the elastic recovery of the stretch wrap multilayer film can be effectively imparted.

SEB as a thermoplastic elastomer
The use of S has good compatibility with polypropylene and polyethylene and can be handled in the same manner, and there is no problem in terms of thermal stability during molding and food hygiene. Examples of such a resin include Clayton G1652 and G1657 from Shell Japan and Tuftec H1041, H1052 and H1071 from Asahi Kasei Corporation, melt index 15 g / 10 min (200 ° C./5 k
g) or less, and those having a styrene content of 8 to 35% by weight are preferable in order to ensure transparency, elastic recovery and molding stability.

The amount of SEBS added is 15 to 64% by weight.
It is preferably 20 to 50% by weight. This is because if the SEBS addition amount in the intermediate layer resin composition is less than 15% by weight, a sufficient improvement effect in elastic recovery cannot be obtained, and if it exceeds 64% by weight, the content of polypropylene, which is the other resin, decreases. Therefore, the decrease in the heat-sealing temperature range on the high temperature side becomes large, and it becomes difficult to obtain a film having sufficient packaging suitability.

As another resin composition for the intermediate layer, in order to improve the tensile modulus and transparency, the melt index is preferably 0.5 to 5 g / 10 min (190 ° C.) and the density is 0.8.
A copolymer of ethylene of 95 to 0.935 g / cm ³ and at least one or more of C _{4 to} C ₈ α-olefins, a vinyl acetate content of 3 to 25% by weight, and a melt index of 0.2 to 8 g / One or both of ethylene-vinyl acetate copolymers for 10 minutes (190 ° C) are added in the range of 1 to 55% by weight. Here, the addition amount is limited, if it is less than 1% by weight, there is no effect of addition, and if it exceeds 50% by weight, there is almost no improvement effect even if the addition amount is increased. This is because it narrows the range.

The ethylene-vinyl acetate copolymer as the inner and outer layers of the present invention has a vinyl acetate content of 8 to 25% by weight,
Melt index 0.2 to 8 g / 10 minutes (190
C.), preferably 0.5 to 5 g / 10 minutes (190.degree. C.). This is because when the vinyl acetate content is less than 8% by weight, the tackiness does not appear, the elastic recovery property decreases, the temperature at which heat fusion starts is increased, and when it exceeds 25% by weight, the tackiness is too strong. Therefore, the suitability for packaging becomes poor. If the melt index is less than 0.2 g / 10 minutes, the extrudability will deteriorate, and
When it exceeds g / 10 minutes, the molding stability of the film is lowered and the physical properties of the film are not stable.

Furthermore, in order to improve heat resistance, the melting point is 140 ° C. or higher and the melt index is 1.0 to 10 g / 1.
0 minutes (230 ° C.) propylene-ethylene random copolymer or density 0.895-0.935 g / cm ³ ,
Melt index 0.5-5g / 10 minutes (190 ° C)
The ethylene-α-olefin (C _{4 to} C ₈ ) copolymer and the like may be added.

The resin composition constituting the inner and outer layers of the stretch wrap film of the present invention contains an ethylene-vinyl acetate copolymer as a main component and is a fatty acid ester having no particular problem in food hygiene, particularly sorbitan, glycerin, polyglycerin and the like. Fatty acid ester and ethylene oxide adduct of, for example, glycerin monooleate, sorbitan laurate,
It is preferable to add about 0.5 to 5% by weight of a surfactant such as sorbitan oleate, diglycerin laurate, diglycerin oleate, and polyoxyethylene alkyl ether. The addition of a surfactant does not impair the gloss and transparency of the stretch wrap multilayer film, and is self-adhesive, slippery, and
Preferred for improving antifogging property.

Further, it is preferable to add a neutralizing agent, an antioxidant and the like to the resin composition constituting the intermediate layer in order to prevent adverse effects such as catalyst residues. Further, the same surfactant as that added to the inner and outer layers may be added in an amount of 0.5 to 5% by weight.

The stretch wrap multilayer film of the present invention is composed of an intermediate layer and an outer layer and an inner layer which are laminated on both sides thereof, and the total thickness thereof is preferably 5 to 25 μm.
m. The reason for limiting the thickness to 5 to 25 μm is 5 μm
If it is less than m, the film is likely to be broken, and the problem of perforation during packaging becomes large. On the other hand, when it exceeds 25 μm, the stress against the elongation of the film becomes large and the stretch wrapping property deteriorates. The layer thickness ratio of outer layer: intermediate layer: inner layer is not particularly limited, but is preferably 1: 0.2 to 2: 0.5.
3 is good.

In the stretch wrap multilayer film of the present invention, the above intermediate layer resin composition and inner and outer layer resin composition are subjected to inflation molding or T molding using a plurality of extruders.
Lamination molding can be carried out by a known method such as coextrusion molding by die molding. In order to obtain a film having a well-balanced tear strength in the MD direction (molding direction) and the TD direction (direction orthogonal to the molding direction), it is preferable to apply the coextrusion molding method of the inflation method.

In the inflation multi-layer molding, two or three extruders are used, and the resin is extruded from the annular three-layer die at the same time in a layer structure of three layers, and is molded at a blow ratio of 3 to 15. Here, when the blow ratio is less than 3, the balance of tear strength, which is important in the physical properties of the film, becomes poor, and the film is likely to tear during packaging or during handling of the packaged product. Further, when the number exceeds 15, many modifications are made on the apparatus, and it is difficult to make it an actual production machine.

The average tangential elastic modulus at 30% to 60% elongation in the TD direction of the three-layer film constituted by the present invention is preferably 14 kg / cm ² or more. The average tangential elastic modulus referred to here is a value obtained by the method described below, and the reason why the film is limited to the TD direction in particular includes an inflation method and a T-die method for obtaining the film. This is because the average tangential elastic modulus in the TD direction is obviously smaller than that in the MD direction, is strongly related to the elastic recoverability, and is in good agreement with the experimental results.

The average tangential elastic modulus in the TD direction is obtained by cutting a test piece having a width of 10 mm and a length of 100 mm from a stretch wrap three-layer film. After adjusting this test piece according to JIS K7127, the measurement atmosphere temperature was 23 ° C. and the relative humidity was 5
In the measurement room adjusted to 0%, the interval between the grips of the test pieces of the Instron universal tensile tester was set to 40 mm, and the test pieces were attached so that there was no slack or tension, and the pulling speed was 2
Record the stress-strain curve with a recorder until the distance between the grips of the test piece is 80 mm at 00 mm / min. From this stress-strain curve, stress M30 (kg) and M60 at which the distance between the grips of the test piece was 52 m (30% stretch) and 64 mm (60% stretch), respectively.
(Kg) is read and the average tangential elastic modulus is calculated by the following formula.

The average tangential elastic modulus is calculated from the stress at the time of stretching 30% and 60% of the stress-strain curve.
If less than%, it is affected by the inflection point of the stress-strain curve,
If it exceeds 60%, the permanent set is large. For example, if it is 100% stretched, even a polyvinyl chloride stretch wrap film having excellent finger-push recovery has a permanent set of more than 10%, which is suitable for actual evaluation. Because there is no. Also, in the stress-strain curve between 30% and 60% stretching,
This curve can be regarded as almost a straight line, and the average tangential elastic modulus can be easily obtained by the above formula.

In the case of a stretch wrap multilayer film having an average tangential elastic modulus of less than 14 kg / cm ^{2, some} of the stretch wrap multilayer films have sufficient wrapping suitability, but the one wrapped in a tray and pressed a little strongly from the top of the film. When
The phenomenon of partial expansion is likely to occur, and that part does not return to its original state, leaving traces, which impairs the value of the package as a product. Therefore, this value must be increased in order to eliminate the marks when the packages are stacked or pushed with a finger.

The tensile modulus of elasticity of the three-layer film constituted by the present invention is 400 to
Those in the range of 2000 kg / cm ² are suitable as a film for stretch wrap packaging. Tensile modulus of 4
The reason why it is limited to 00 to 2000 kg / cm ² is 2
This is because if it exceeds 000 kg / cm ³ , wrinkles and slack occur during packaging in both the MD and TD directions of the film, and a good package cannot be obtained. In addition, the tensile elastic modulus is 400 kg / cm
^When it is less than ² , the film becomes too soft and the handleability of the film deteriorates, which is not preferable.

The tensile modulus referred to here is a tensile speed of 5 m.
JIS K except m / min and distance between grips 40mm
It is a tensile split gland elastic modulus (2% strain) obtained according to 7127.

Furthermore, the three-layer film constituted according to the present invention preferably has a heat sealing temperature range of 40 ° C. or higher. This is because, in the case of an automatic packaging machine or a device for manual packaging, the sealing temperature varies by about 30 ° C. depending on the fluctuation range of the temperature control of the heat seal part and the packaging frequency.
Therefore, in order to achieve stable sealing, the heat sealing temperature range of the film needs to be 40 ° C. or higher.

In the present invention, the ears and hollow portions removed from the product film may be pelletized and mixed with the inner and outer layers for the purpose of improving the yield on an actual commercial basis. Further, when returning to the intermediate layer, it is possible to mix the intermediate layer within a range where the composition of the intermediate layer does not deviate from the scope of the claims of this patent. Mixing beyond this range causes adverse effects due to variations in the heat seal temperature range and elastic recovery.

[0035]

INDUSTRIAL APPLICABILITY The present invention has good transparency, tackiness, and tear strength, does not cause wrinkles and slack during packaging, and has an elastic recovery property which has been insufficient particularly in conventional polyolefin stretch wrap films. It is possible to provide a film having a good balance between improvement and amplification of the heat seal temperature range. Therefore, it is possible to substitute the polyvinyl chloride film. Further, it is more excellent in maintaining the freshness of meat, fish, vegetables, fruits, prepared foods, etc. due to its moderate oxygen permeability and lower water permeability than polyvinyl chloride.

[0036]

【Example】

Example 1 Ethylene content 2.2% by weight, melt index 2.
5 g / 10 minutes (230 ° C.), melting point 150 ° C. propylene-ethylene random copolymer 40% by weight, SEBS (Shell Japan Krayton G-1657) 45% by weight, vinyl acetate content 15% by weight and melt index 0. 8 g / 10 minutes (190 ° C.) ethylene-vinyl acetate copolymer 14% by weight resin composition, surfactant diglycerin oleate (manufactured by Riken Vitamin: trade name O-71D
E) 1.0% by weight was mixed to obtain an intermediate layer resin composition.

On the other hand, a vinyl acetate content of 15% by weight, an ethylene-vinyl acetate copolymer having a melt index of 0.8 g / 10 minutes (190 ° C.) of 98% by weight, and a surfactant diglycerin oleate (manufactured by Riken Vitamin: trade name) O-7
1 DE) 2 wt% was mixed to obtain an outer layer / inner layer resin composition. Then, the resin composition obtained as described above was extruded using three extruders having a screw diameter of 55 mmφ at an extrusion temperature of 200 ° C. for the intermediate layer and 190 ° C. for the outer layer / inner layer, and the intermediate layer was 3 μm, and the outer layer / inner layer was Was supplied to one annular die so as to be laminated at 5 μm, and inflation-molded at a blow ratio of 5.0 to obtain a stretch-wrap multilayer film.

Measurement of physical properties of the obtained three-layer film, evaluation using various polystyrene trays suitable for automatic packing machine using WINIMARKII manufactured by Ishida Koki, using hand pack ARC450 type prick E manufactured by Sunpack Each of these was packaged in various polystyrene trays, the suitability of the handler was evaluated, and the hot plate temperature was changed to measure the heat seal temperature range. The results are shown in Table 1.
In addition, each physical property was measured by the following method. Melt index It carried out according to JIS K7210. Density Measured according to JIS K7112. Melting point According to ASTM D3418, the temperature decrease rate was changed to 2 ° C./min and measurement was performed. Tensile elongation at break Measured according to JIS K7127. Impact strength In accordance with JIS P8134, the triangular pyramid at the penetrating part of the pendulum was changed to a 1-inch sphere for measurement. Transparency (haze) Measured according to JIS K7105. In terms of impact strength, there is no practical problem if it is 5 kcm or more. As for transparency, if it is 3% or less, there is no practical problem.

Example 2 Ethylene content 2.2% by weight, melt index 2.
5 g / 10 minutes (230 ° C.), melting point 150 ° C. propylene-ethylene random copolymer 40% by weight, SEBS (Clayton G-1657, Shell Japan Co.) 30% by weight, vinyl acetate content 15% by weight, melt index 0. Stitch wrap multilayer molded in the same manner as in Example 1 except that the resin composition was 8 g / 10 min (190 ° C.) 29% by weight of ethylene-vinyl acetate copolymer, and the surfactant was diglycerin oleate 1% by weight. I got a film. The physical properties, packaging characteristics, and heat sealing temperature range of the obtained multilayer film were measured in the same manner as in Example 1, and the results are shown in Table 1.

Example 3 As an intermediate layer resin composition, ethylene content 3.3% by weight,
Propylene-ethylene random copolymer 6 having a melt index of 2.3 g / 10 minutes (230 ° C.) and a melting point of 143 ° C.
5% by weight, SEBS (Clayton G-1657) 30% by weight, density 0.905 g / cm ³ , melt index 1.5 g / 10 min (190 ° C.) ethylene-butene-1.
Copolymer 4% by weight, surfactant diglycerin oleate 1
A stretch wrap multilayer film was obtained by molding in the same manner as in Example 1 except that the weight percentage was changed. The physical properties, packaging characteristics, and heat sealing temperature range of the obtained multilayer film were measured in the same manner as in Example 1, and the results are shown in Table 1.

Example 4 Melt index 2.3 g / as the resin composition for the intermediate layer
10 minutes (230 ° C.), melting point 143 ° C., propylene-ethylene random copolymer 50% by weight, SEBS (Clayton G-1657) 30% by weight, density 0.905 g / cm 3.
³ , ethylene with a melt index of 1.5 g / 10 min
A stretch wrap multilayer film was obtained in the same manner as in Example 1, except that the butene-1 copolymer was 19% by weight and the surfactant diglycerin oleate was 1% by weight. The physical properties, packaging characteristics, and heat sealing temperature range of the obtained multilayer film were measured in the same manner as in Example 1, and the results are shown in Table 1.

Example 5 Melt index 2.3 g / as a resin composition for the intermediate layer
10 minutes (230 ° C.), melting point 143 ° C., propylene-ethylene random copolymer 50% by weight, SEBS (Klaton G-1657) 20% by weight, density 0.905 g / cm 3.
³ , ethylene with a melt index of 1.5 g / 10 min
A stretch wrap multilayer film was obtained in the same manner as in Example 1 except that the butene-1 copolymer was 29% by weight and the surfactant diglycerin oleate was 1% by weight. The physical properties, packaging characteristics, and heat sealing temperature range of the obtained multilayer film were measured in the same manner as in Example 1, and the results are shown in Table 1.

Example 6 Ethylene content 3.3% by weight as an intermediate layer resin composition,
Propylene-ethylene random copolymer 4 having a melt index of 2.3 g / 10 minutes (230 ° C.) and a melting point of 143 ° C.
0% by weight, 35% by weight of SEBS (Clayton G-1657), 24% by weight of ethylene-vinyl acetate copolymer having a vinyl acetate content of 15% by weight and a melt index of 0.8 g / 10 min (190 ° C.), a surfactant. A stretch wrap multilayer film was obtained by molding in the same manner as in Example 1 except that 1% by weight of diglycerin oleate was used. The physical properties, packaging characteristics, and heat-sealing temperature range of the obtained multilayer film are shown in Example 1.
The measurement was performed in the same manner as above and the results are shown in Table 1.

Comparative Example 1 Ethylene content 3.3% by weight as an intermediate layer resin composition,
Propylene-ethylene random copolymer 8 having a melt index of 2.3 g / 10 minutes (230 ° C.) and a melting point of 143 ° C.
Ethylene-butene-1 with 0% by weight, SEBS (Kraton G-1657) 8% by weight, density 0.905 g / cm ³ , melt index 1.5 g / 10 min (190 ° C.).
A stretch-wrap multilayer film was obtained by molding in the same manner as in Example 1 except that the copolymer was 11% by weight and the surfactant diglycerin oleate was used. The physical properties, packaging characteristics, and heat sealing temperature range of the obtained multilayer film were measured in the same manner as in Example 1, and the results are shown in Table 1. Since this film has a high tensile elastic modulus, wrinkles and slack were generated during the packaging in both the automatic packaging machine and the manual packaging machine, and the elastic recovery property was poor and a satisfactory product could not be obtained.

Comparative Example 2 99% by weight of ethylene-butene-1 copolymer having a density of 0.905 g / cm ³ , a melt index of 1.5 g / 10 minutes (190 ° C.) as a resin composition for the intermediate layer, and a diglycerin surfactant. A stretch-wrap multilayer film was obtained by molding in the same manner as in Example 1 except that 1% by weight of oleate was used. The physical properties, packaging characteristics, and heat sealing temperature range of the obtained multilayer film were measured in the same manner as in Example 1, and the results are shown in Table 1. This film has a melting point of 140 ° C in the resin composition of the intermediate layer.
Since the above polypropylene resin was not used, the heat sealing temperature range was narrow, pinholes were easily generated during heat sealing in an automatic packaging machine, and the film was difficult to handle.

Comparative Example 3 SEBS (Clayton G-16) was used as the intermediate layer resin composition.
57) A stretch wrap multilayer film was obtained by molding in the same manner as in Example 1 except that a single body was used. The physical properties, packaging characteristics, and heat sealing temperature range of the obtained multilayer film were measured in the same manner as in Example 1, and the results are shown in Table 1. Since the polypropylene resin having a melting point of 140 ° C. or higher is not used in the resin composition for the intermediate layer, this film has a narrow heat sealing temperature range and is difficult to handle. Also,
Since high-speed moldability during film molding is poor, it is necessary to study molding conditions and molding equipment in order to increase productivity.

[0047]

[Table 1]

Claims (1)

[Claims] 1. A polypropylene resin having a melting point of 140 ° C. or higher and a melt index of 1 to 10 g / 10 min (230 ° C.), 75 to 35% by weight, and a hydrogenated product of a styrene-butadiene block copolymer, 15 to 64% by weight. % And 1 to 50% by weight of one or both of the ethylene-vinyl acetate copolymer and the ethylene-α-olefin copolymer as an intermediate layer, and vinyl acetate is provided on both sides of the intermediate layer. A trench containing a content of 8 to 25% by weight and a melt index of 0.2 to 8 g / 10 min (190 ° C.), which is a main component of an ethylene-vinyl acetate copolymer, and has three layers. Wrap multilayer film.