JP2894120B2 - Stretch wrap multilayer film - Google Patents

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 particularly, to a film having good transparency, moderate tackiness, good balance of tear strength, excellent elastic recovery, wrinkles during packaging,
The present invention relates to a stretch wrap film for food packaging, which can be packaged without generation of slack, and particularly has a wide heat sealing temperature range.

[0002]

2. Description of the Related Art As a pre-packaging film for stretch packaging fresh foods such as vegetables, meat, and fresh fish directly or on a tray, polypropylene, instead of a conventional polyvinyl chloride film, is used. Many stretch wrap films of polyolefin-based resin compositions such as low-density polyethylene, linear low-density polyethylene, and ethylene-vinyl acetate copolymer have been developed.

[0003] Polyolefin-based stretch-wrap multilayer films generally use an ethylene-α-olefin copolymer for the intermediate layer in consideration of tackiness, cold resistance, piercing resistance and the like, and ethylene on both sides of this layer. -There are many laminates of vinyl acetate copolymer. However, these are excellent in finish at the time of packaging and anti-fogging property after packaging, but since the heat sealing temperature range is narrow, packaging conditions that can be completely sealed are also narrowed, causing difficulties in handling and causing problems. I have.

[0004] 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 pinholes are generated. In other words, the temperature at which the thermal fusion is started is too low, so that handling becomes difficult. Therefore, the temperature is preferably about 80 ° C., and the temperature at which pinholes are generated is preferably higher. This is because if the heat fusion is not sufficient, the juice of the contents will come out of the unfused parts, the overlapping parts of the packaging will peel off, and if the pinholes occur, the contents will not be removed. The wide temperature range is a very important factor in the suitability for packaging because it causes juice leakage.

[0005] In addition, when articles packed on a tray or the like are stacked in a store or when a customer presses them with a finger to check the packaged contents, the elastic recovery is small, so that the parts are partially pressed. There is a problem that the traced portion is left as it is without being recovered and the commercial value is reduced.

Accordingly, in the case of a stretch wrap film made of a polyolefin resin composition, the problem of heat sealing so as not to peel off the overlapped portion after packaging and the elastic recovery property are lower than that of a polyvinyl chloride stretch film. There is an inferior problem. In other words, it is very important to improve the elastic recovery property, and especially to amplify the heat seal temperature range, while maintaining a good state in which transparency, tackiness and tear strength are good, and wrinkles and looseness do not occur during packaging. It is. However, there is no stretch wrap packaging film that has been conventionally developed that can sufficiently satisfy this point.

For example, in Japanese Patent Application Laid-Open No. 61-44635, a propylene-α-olefin random copolymer of propylene and at least one of ethylene and a 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 blended is used as an intermediate layer.
A multilayer film having a vinyl acetate copolymer as an outer layer has been proposed. Further, JP-A-62-51440 proposes, as a hydrogenated derivative of a block copolymer, a stretch packaging film having a styrene-butadiene block copolymer as an intermediate layer and an ethylene-vinyl acetate copolymer as an outer layer. Have been.

[0008]

For example, Japanese Unexamined Patent Publication No.
No. 44635 discloses a propylene-ethylene-butene-1 random copolymer, a propylene-ethylene random copolymer, and a propylene-hexene-1 random copolymer for the purpose of improving elongation, flexibility, and tear strength. Used, but the α-olefin content is 4 to 19% by weight.
It has only been confirmed that good packaging can be achieved without breaking the corners in tray packaging, and it is not sufficient to expand the heat sealing temperature range and obtain excellent elastic recovery. It is enough.

Japanese Patent Publication No. 02-1668 is aimed at improving cold resistance and rigidity in particular. In practice, a homopolypropylene resin is formed by using a low-crystalline ethylene-α-olefin copolymer, that is, a rubber component. In order to maintain this, the concentration is as high as 78 to 90% by weight of the polypropylene resin.
However, in the case of stretch wrap multilayer films,
If the rigidity is high as in the present case, wrinkles and slack occur, so it is difficult to obtain a good package.

Japanese Unexamined Patent Publication (Kokai) No. 62-51440 discloses a non-aromatic mineral oil containing a hydrogenated styrene-butadiene block copolymer as a main component, and a softening agent. A liquid or low molecular weight synthetic softener, a composition in which paraffin-based oil is added in an amount of 300 parts by weight or less based on 100 parts by weight of the styrene-butadiene block copolymer is used as the intermediate layer.
It is insufficient to extend the heat sealing temperature range, which is important for packaging.

[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,
Improves the elastic recovery of the film without impairing the tear strength, etc., and obtains a good package without wrinkling, loosening, etc. in various automatic push-up packaging machines, pillow packaging machines, manual packaging, especially heat sealing An object of the present invention is to provide a film which has excellent heat-sealability at low temperatures and has a wide heat sealing temperature range so that the temperature at which pinholes are generated is on the high temperature side.

[0012]

[Means for Solving the Problems] Therefore, as a means for solving this problem, the heat sealing temperature range is extended to a high temperature side without deteriorating other characteristics, and the purpose is to obtain excellent elastic recovery. As a result of repeated studies, (1) In order to ensure the heat sealing property 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, and the heat sealing temperature range on the high temperature side is widened. (3) A hydrogenated styrene-butadiene block copolymer (hereinafter abbreviated as SEBS), which has good molding stability and has no problem in food hygiene, is selected from thermoplastic elastomers and imparts appropriate elastic recovery. . This has led to the present invention.

That is, according to the present invention, a melting point of 140 ° C. or more and a melt index of 1 to 10 g / 10 min (230
C), 75 to 35% by weight of a resin composition mainly containing a polypropylene resin, 15 to 64% by weight of a hydrogenated product of a styrene-butadiene-styrene block copolymer, and ethylene-vinyl acetate copolymer or ethylene. A resin composition prepared by mixing 1 to 50% by weight of one or both of an α-olefin copolymer is used as an intermediate layer. On both sides of the intermediate layer, a vinyl acetate content of 8 to 25% by weight and a melt index of 0. Ethylene of 2 to 8 g / 10 min (190 ° C.)
The tangential elastic modulus in the TD direction (the direction perpendicular to the molding direction) of the film composed of three layers formed by laminating layers mainly composed of vinyl acetate copolymer is 14 kg / cm ² or more, and the tensile elastic modulus is An object of the present invention 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 more.

By using a resin composition mainly composed of a 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, a film having a heat sealing temperature range extended to a high temperature side can be obtained. Can be provided. Melting point is 1
If the temperature is lower than 40 ° C., the amplification of the heat sealing temperature range is small, and it is difficult to stably obtain a sufficient heat sealing temperature range. Examples of such a polypropylene resin having a melting point of 140 ° C. or higher include a propylene-ethylene random copolymer having an ethylene content of less than 4% by weight and other propylene-α-olefin random copolymers.

The reason for limiting the melt index to 1 to 10 g / 10 minutes (230 ° C.) is that if it is less than 1 g / 10 minutes, poor kneading occurs at the time of extrusion, resulting in poor transparency and 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. When the content of the polypropylene resin is less than 35% by weight, the high temperature side of the heat sealing temperature range is lowered. When the content is more than 75% by weight, the film becomes hard, and wrinkles and looseness occur frequently during packaging, which is satisfactory. Packaging suitability cannot be obtained.

As the other resin composition of the intermediate layer, SEBS which is a thermoplastic elastomer is used. This resin is
At room temperature, the polystyrene part has a very small particle size because it has a special structure in which the polystyrene part is discontinuous in the same molecule and the polybutadiene part is continuous in the same molecule, and does not scatter visible light. , Transparency can be maintained. Further, in the temperature range in which molding is actually performed, a film can be formed by melting similarly to polypropylene and polyethylene, and the elastic recovery property of the stretch wrap multilayer film can be effectively imparted.

Further, SEB is used 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 heat stability during molding and food hygiene. Examples of such a resin include a melt index of 15 g / 10 min (200 ° C./5 k) such as Clayton G1652 and G1657 manufactured by Shell Japan Co., Ltd. and Tuftec H1041, H1052, and H1071 manufactured by Asahi Kasei Corporation.
g) Below, those having a styrene content of 8 to 35% by weight are preferred to ensure transparency, elastic recovery and molding stability.

The amount of SEBS added is 15 to 64% by weight.
Preferably, it is 20 to 50% by weight. This is because if the amount of SEBS added to 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 the other resin, polypropylene, decreases. For this reason, 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 95 to 0.935 g / cm ³ of ethylene and at least one kind of C _{4 to} C ₈ α-olefin, having a vinyl acetate content of 3 to 25% by weight and a melt index of 0.2 to ₈ g / cm ^3. One or both of the ethylene-vinyl acetate copolymer for 10 minutes (190 ° C.) is added in the range of 1 to 55% by weight. Here, the amount of addition is limited when the amount is less than 1% by weight, there is no effect of addition, and when it exceeds 50% by weight, even if the amount of addition is increased, there is almost no improvement effect. This is to narrow the range.

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

Further, in order to improve the heat resistance, the melting point is 140 ° C. or more, and the melt index is 1.0 to 10 g / 1.
At 0 minutes (230 ° C.) propylene-ethylene random copolymer or at a density of 0.895 to 0.935 g / cm ³ ,
Melt index 0.5-5g / 10min (190 ° C)
Ethylene-α-olefin (C ₄ -C ₈ ) copolymer may be added.

The resin composition constituting the inner and outer layers of the stretch wrap film of the present invention contains a fatty acid ester containing an ethylene-vinyl acetate copolymer as a main component and having no problem in food hygiene, especially sorbitan, glycerin, polyglycerin and the like. Fatty acid esters and ethylene oxide adducts, 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, or 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,
It is preferable to improve the 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, an outer layer and an inner layer 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
If it is less than m, the film is easily broken, and the problem of perforation at the time of packaging increases. On the other hand, if it exceeds 25 μm, the stress with respect to the elongation of the film increases, and the stretch wrapping property deteriorates. The thickness ratio of the outer layer: intermediate layer: inner layer is not particularly limited, but is preferably 1: 0.2-2: 0.5-
3 is good.

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

In the inflation multilayer molding, two or three extruders are used to simultaneously extrude a resin from an annular three-layer die into a three-layer structure, and are molded at a blow ratio of 3 to 15. Here, when the blow ratio is less than 3, the balance of the tear strength, which is important in the physical properties of the film, is deteriorated, and the film is easily torn during packaging or during handling of the packaged product. Further, when it exceeds 15, there are many remodeling points on the apparatus, and it is difficult to make it an actual production machine.

It is preferable that the average tangential elastic modulus of the three-layer film formed according to the present invention when stretched from 30% to 60% in the TD direction is 14 kg / cm ² or more. The average tangential elastic modulus referred to here is a value obtained by a method described below, and the reason for limiting the TD direction in particular is that the film is obtained by an inflation method or a T-die method. This is because the average tangential elastic modulus in the TD direction is clearly smaller than that in the MD direction, is strongly related to elastic recovery, 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 the 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 distance between the grips of the test piece of the Instron type universal tensile tester was set to 40 mm, and the test piece was attached so that there was no looseness or one-sided tension.
Record the stress-strain curve with a recorder at 00 mm / min until the distance between the grips of the test specimens is 80 mm. From the stress-strain curve, the distance between the grips of the test piece was 52 mm (30% elongation).
And 64 mm (60% elongation) stress M30 (kg) and M6
0 (kg) is read, and the average tangential elastic modulus is determined by the following equation.

The reason why the average tangential elastic modulus is obtained from the stress at the time of stretching 30% and 60% of the stress-strain curve is as follows.
% 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 stretched at 100%, even a polyvinyl chloride stretch wrap film excellent in finger press recovery property will have a permanent set exceeding 10%, which is suitable for actual evaluation. Because there is no. In the stress-strain curve, between 30% and 60% elongation,
This curve can be regarded as almost a straight line, and the average tangential elastic modulus can be easily obtained from the above equation.

In the case of a stretch wrap multilayer film having an average tangential elastic modulus of less than 14 kg / cm ² , there are some which show sufficient wrapping suitability in stretch wrapping, but the wrapped product placed on a tray is pressed slightly from above the film. When
The phenomenon of partial elongation is likely to occur, and the portion will not return to its original state, leaving a mark, which impairs the value of the package as a product. Therefore, this value must be increased in order to eliminate traces of stacking packages or pressing with a finger.

Further, the tensile elastic modulus of the three-layer film constituted by the present invention obtained by the method described below is 400 to 400.
A material in the range of 2,000 kg / cm ² is suitable as a stretch wrap packaging film. Tensile modulus 4
The reason for limiting to 00-2000 kg / cm ² is 2
If it exceeds 000 kg / cm ² , wrinkles and slackness occur during packaging in both the film MD and TD directions, and a good package cannot be obtained. Also, the tensile modulus is 400 kg / cm
^If it is less than ² , the film becomes too soft, and the handleability of the film becomes poor.

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

Further, the three-layer film constituted according to the present invention preferably has a heat sealing temperature range of 40 ° C. or higher. Because, in the case of an automatic wrapping machine or a manual wrapping machine, the sealing temperature varies by about 30 ° C. depending on the fluctuation width of the temperature control of the heat sealing part and the packaging frequency,
Therefore, in order to enable stable sealing, the heat sealing temperature range of the film must be 40 ° C. or higher.

In the present invention, for the purpose of improving the yield on an actual commercial basis, the ears and hollow portions removed from the product film may be pelletized and mixed with the inner layer and the outer layer. If the composition is to be returned to the intermediate layer, the composition can be mixed as long as the composition of the intermediate layer does not deviate from the scope of the present invention. If the mixing exceeds this range, adverse effects occur because the heat sealing temperature range and the elastic recovery vary.

[0035]

Industrial Applicability The present invention has good transparency, tackiness and tear strength, and does not cause wrinkles or looseness during packaging. In particular, the elastic recovery property of conventional polyolefin-based stretch wrap films was insufficient. It is possible to provide a film in which the improvement and the amplification of the heat sealing temperature range are well-balanced. Therefore, it is possible to substitute a polyvinyl chloride film. Furthermore, because of appropriate oxygen permeability and lower moisture permeability than polyvinyl chloride, it is more excellent in maintaining freshness of meat, fish, vegetables, fruits, prepared foods and the like.

[0036]

【Example】

Example 1 Ethylene content 2.2% by weight, melt index 2.
5 g / 10 min (230 ° C.), 40% by weight of a propylene-ethylene random copolymer having a melting point of 150 ° C., 45% by weight of SEBS (Clayton G-1657, Shell Japan Co.), 15% by weight of vinyl acetate, and a melt index of 0.1%. 8 g / 10 min (190 ° C) ethylene-vinyl acetate copolymer 14% by weight resin composition, surfactant diglycerol oleate (manufactured by Riken Vitamin: trade name O-71D)
E) 1.0 wt% was mixed to obtain an intermediate layer resin composition.

On the other hand, 98% by weight of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 15% by weight, a melt index of 0.8 g / 10 minutes (190 ° C.) and a surfactant diglycerin oleate (manufactured by Riken Vitamin, trade name) O-7
1DE) 2% by weight were mixed to obtain an outer layer / inner layer resin composition. Next, 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 and inner layers. Were supplied to one annular die so as to be laminated at a thickness of 5 μm, and were blown at a blow ratio of 5.0 to obtain a stretch-wrap multilayer film.

The physical properties of the obtained three-layer film were measured and evaluated using various polystyrene trays suitable for an automatic packaging machine using WminiMARK II manufactured by Ishida Koki Co., Ltd. Then, it was packed in various polystyrene trays, and the suitability for the handler wrapper was evaluated, and the heat 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 This was performed according to JIS K7210. Density Measured according to JIS K7112. Melting point: Measured at a temperature lowering rate of 2 ° C./min according to ASTM D3418. Tensile elongation at break was measured according to JIS K7127. Impact strength According to JIS P8134, measurement was performed by changing the triangular weight of the pendulum penetrating portion to a 1-inch ball. Transparency (haze) Measured according to JIS K7105. In terms of impact strength, there is no practical problem if the impact strength is 5 k · cm or more. There is no practical problem if the transparency is 3% or less.

Example 2 Ethylene content 2.2% by weight, melt index 2.
5 g / 10 min (230 ° C.), 40% by weight of propylene-ethylene random copolymer having a melting point of 150 ° C., 30% by weight of SEBS (Clayton G-1657, Shell Japan), 15% by weight of vinyl acetate and a melt index of 0.1%. 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 1% by weight of surfactant diglycerin oleate. A film was obtained. 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, an ethylene content of 3.3% by weight was used.
Propylene-ethylene random copolymer 6 having a melt index of 2.3 g / 10 minutes (230 ° C.) and a melting point of 143 ° C.
Ethylene-butene-1 having 5% by weight, 30% by weight of SEBS (Clayton G-1657), a density of 0.905 g / cm ³ and a melt index of 1.5 g / 10 minutes (190 ° C.).
4% by weight of copolymer, surfactant diglycerol oleate 1
A stretch wrap multilayer film was obtained by molding in the same manner as in Example 1 except that the amount was changed to% 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 4 The intermediate layer resin composition had a melt index of 2.3 g /
10 minutes (230 ° C), 50% by weight of a propylene-ethylene random copolymer having a melting point of 143 ° C, 30% by weight of SEBS (Clayton G-1657), density of 0.905 g / cm
³ , ethylene melt index 1.5g / 10min
A stretch wrap multilayer film was obtained by molding 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 The intermediate layer resin composition had a melt index of 2.3 g /
10 minutes (230 ° C.), 50% by weight of a propylene-ethylene random copolymer having a melting point of 143 ° C., 20% by weight of SEBS (Clayton G-1657), density of 0.905 g / cm
³ , ethylene melt index 1.5g / 10min
A stretch-wrap multilayer film was obtained by molding 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 The intermediate layer resin composition had an ethylene content of 3.3% by weight.
Propylene-ethylene random copolymer 4 having a melt index of 2.3 g / 10 min (230 ° C.) and a melting point of 143 ° C.
0 wt%, SEBS (Clayton G-1657) 35 wt%, vinyl acetate content 15 wt%, melt index 0.8 g / 10 min (190 ° C.) 24 wt% of ethylene-vinyl acetate copolymer, surfactant A stretch wrap multilayer film was obtained by molding in the same manner as in Example 1 except that diglycerin oleate was 1% by weight. Example 1 shows the physical properties, packaging characteristics, and heat seal temperature range of the obtained multilayer film in Example 1.
The results are shown in Table 1.

Comparative Example 1 As an intermediate layer resin composition, an ethylene content of 3.3% by weight was used.
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 having 0% by weight, 8% by weight of SEBS (Clayton G-1657), a density of 0.905 g / cm ³ , and a melt index of 1.5 g / 10 minutes (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. 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 had a high tensile modulus, wrinkles and slackness were generated at the time of packaging in both automatic packaging machines and manual packaging machines.

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

Comparative Example 3 SEBS (Clayton G-16) was used as the intermediate layer resin composition.
57) Except for using a single body, molding was performed in the same manner as in Example 1 to obtain a stretch-wrap multilayer 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. Since this film did not use a polypropylene resin having a melting point of 140 ° C. or higher in the intermediate layer resin composition, the heat sealing temperature range was narrow and the film was difficult to handle. Also,
Since high-speed moldability during film formation is inferior, it is necessary to consider molding conditions and molding equipment in order to increase productivity.

[0047]

[Table 1]

Claims (4)

(57) [Claims] 1. A polypropylene resin having 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, and a hydrogenated product of a styrene-butadiene block copolymer 15 to 64% by weight. % And a resin composition obtained by mixing 1 to 50% by weight of one or both of an ethylene-vinyl acetate copolymer or an ethylene-α-olefin copolymer as an intermediate layer, and vinyl acetate on both sides of the intermediate layer. Tensile elasticity consisting of three layers consisting of laminated layers mainly composed of an ethylene-vinyl acetate copolymer having a content of 8 to 25% by weight and a melt index of 0.2 to 8 g / 10 minutes (190 ° C.). <br/> rate of 400~2000kg / cm ² stress Tsu Chirappu multilayer film. 2. The stretch wrap multilayer film according to claim 1, wherein
The film is in the TD direction (the direction perpendicular to the molding direction)
Average tangential elastic modulus of 14 kg / cm ^Two That's all
A stretch wrap multilayer film characterized by the following. 3. The stretch wrap multilayer according to claim 1, wherein:
The film has a heat seal temperature range of 40 ° C or higher.
A stretch wrap multilayer film characterized by the above-mentioned. 4. The stretch wrap multilayer according to claim 1, wherein
The film has a haze of 3% or less.
Tretch wrap multilayer film.