JP3124346B2 - Stretch wrap multilayer film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to multilayer films, and more particularly to stretch wrap multilayer films having a wide heat seal temperature range.

[0002]

2. Description of the Related Art As a pre-packaging film for packaging a stretched food such as vegetables or fresh fish directly or in a state of being placed on a tray, a low-density polyethylene or the like is used instead of a conventional polyvinyl chloride film. Many stretch films of an ethylene-based resin composition such as an ethylene-vinyl acetate copolymer have been developed. For example,
JP-A-60-171148 discloses a multilayer film having a resin composition containing a polypropylene resin and a low-crystalline ethylene-α-olefin copolymer as an intermediate layer and an ethylene-vinyl acetate copolymer as an outer layer. Proposed.
JP-A-61-44635 discloses an ethylene-vinyl acetate copolymer comprising a propylene-α-olefin random copolymer of polypropylene and at least one of ethylene and a C _4-8 α-olefin as an intermediate layer. Has been proposed as a stretch wrapping film having as an outer layer.

[0003]

However, the former of the above proposals has been made with the aim of improving cold resistance and rigidity in particular, and is actually an intermediate made of a homopolypropylene resin and a low-crystalline ethylene-propylene copolymer. Only the layers are presented. In the latter, specifically, an ethylene-butene-1 copolymer, a propylene-ethylene-butene-1 copolymer, and a propylene-ethylene copolymer are used in the intermediate layer for the purpose of improving the extensibility and flexibility, particularly the tear strength. Using a kneaded product of a polymer or a propylene-hexene-1 copolymer, a good packaging state was confirmed only without breaking the corners in tray packaging. The present invention is similar to the conventional stretch packaging film described above, but has been made with the object of increasing the heat seal temperature range without impairing the adhesiveness and transparency of the conventional film. It is.

[0004]

According to the present invention According to an aspect of the propylene - ethylene random copolymer 50 to 90 wt%, and the copolymerization of α- olefins of ethylene and C ₄ -C ₈ body 1
Ethylene having a vinyl acetate content of 5 to 25% by weight and an MI of 0.2 to 5.0 g / 10 minutes as an outer layer on both surfaces of the resin composition containing 0 to 50% by weight as an intermediate layer. - the main component vinyl acetate copolymer, and ethylene containing amount
1 . There is provided a stretch wrap multilayer film comprising a resin composition containing 2 to 15% by weight of a propylene-ethylene random copolymer of 5 to 8% by weight.

[0005]

The stretch wrap multilayer film of the present invention comprises at least three layers of the intermediate layer and the outer layer laminated on both surfaces thereof as described above, and the intermediate layer and the outer layer laminated on both surfaces thereof (the outer layer or the inner layer when wrapped). By including a propylene-ethylene random copolymer in both of the resin compositions that constitute the resin composition, the suitability for packaging and impact resistance are good, and the temperature range for heat sealing is wide. In particular, it becomes wider toward the high temperature range, and lapping workability is improved.

Hereinafter, the present invention will be described in detail. The resin composition constituting the intermediate layer of the stretch-wrap multilayer film of the present invention has a propylene-ethylene random copolymer as a main component.
It contains about 50 to 90% by weight of an ethylene random copolymer. As the propylene-ethylene random copolymer to be used, for example, those having an ethylene content of about 1.5 to 8% by weight and a melt index (MI) of about 1 to 10 g / 10 minutes (230 ° C.) are preferably used. Can be In addition, these propylene-ethylene random copolymers can be appropriately selected from generally commercially available ones.
The copolymer of ethylene and a C _{4 to} C ₈ α-olefin, which is a component contained in addition to the above main components, in the resin composition constituting the intermediate layer of the present invention includes ethylene, C _{4 to} C ₈ Α
-Copolymers with one or more olefins can be used, and the copolymers can be used alone or as a mixture of two or more. For example, ethylene-butene-1,
Copolymers such as ethylene-4-methylpentene-1, ethylene-hexene-1, and ethylene-octene-1, or a mixture thereof can be used. In particular, MI
Is 0.3 to 5 g / 10 min (190 ° C.), density 0.890
Those having a thickness of 0.930 g / cm ³ are preferable.

In the present invention, as the resin composition constituting the intermediate layer, a resin composition obtained by further adding the above ethylene-α-olefin copolymer to a propylene-ethylene random copolymer as a main component is used. In addition, the transparency of the stretch wrap film can be improved. As described above, the resin composition constituting the intermediate layer of the present invention comprises a propylene-ethylene random copolymer, ethylene and C ₄
Made of a copolymer of α- olefins -C _8, the formulation, propylene is a main component - 10 of the ethylene random copolymer 50 to 90 wt%, ethylene -α- olefin copolymer It is carried out at a ratio of 50% by weight, and a surfactant or the like may be further added. When the blending ratio of the propylene-ethylene random copolymer is less than 50% by weight, the high temperature side of the heat sealing temperature range becomes narrow, and
If it exceeds 90% by weight, transparency is undesirably reduced.

In the present invention, the resin composition constituting the outer layer laminated on both surfaces of the intermediate layer made of the above resin composition is a resin composition whose main component is an ethylene-vinyl acetate copolymer. . As an ethylene-vinyl acetate copolymer which is a main component of the resin composition constituting the outer layer, the content of vinyl acetate is 5 to 25% by weight, and the MI is 0.2 to 0.2%.
5.0 g / 10 minutes (190 ° C.), preferably 0.5 to
Those having a weight of 3.0 g / 10 minutes (190 ° C.) are suitably used. The resin composition constituting the outer layer of the present invention contains a propylene-ethylene random copolymer in addition to the above main components. As the propylene-ethylene random copolymer as the contained component, the same copolymer as the propylene-ethylene random copolymer constituting the main component of the resin composition for the intermediate layer can be used.

The resin composition constituting the outer layer of the present invention preferably contains about 2 to 15% by weight of a propylene-ethylene random copolymer. If the propylene-ethylene random copolymer exceeds about 15% by weight, transparency is lost, and if it is less than about 2% by weight, the heat sealing temperature range is undesirably narrow. Further, the propylene-ethylene random copolymer contained in each outer layer may be completely the same or different. Furthermore, in the resin composition of the outer layer in the present invention, particularly, a fatty acid ester having no problem in food hygiene, for example, a surfactant such as sorbitan oleate, polyglycerin oleate, or diglycerin steate is added in an amount of about 1 to 5% by weight. It is preferred to add. The addition of a surfactant is preferable because self-adhesiveness, slipperiness, antifogging property, and the like can be improved without impairing the gloss and transparency of the stretch-wrap multilayer film.

The stretch wrap multilayer film of the present invention comprises at least three layers of the above-mentioned intermediate layer and each outer layer laminated on both surfaces thereof, and the thickness thereof is preferably from 8 to
The layer thickness ratio of the outer layer: the intermediate layer: the outer layer is not particularly limited, but is preferably 1: 0.3 to 2:
A range of 1 is preferred. The stretch wrap multilayer film of the present invention uses the above-described intermediate layer resin composition and outer layer resin composition, and uses a plurality of extruders to form a known film such as a co-extrusion method or an extrusion lamination method by inflation molding or T-die molding. It can be formed by lamination. In particular, in order to obtain a film having a well-balanced mechanical strength such as a tear strength in a longitudinal direction and a transverse direction, it is preferable to apply a co-extrusion method of inflation molding.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. However, the present invention is not limited by the following examples. In addition, each test in this example was performed by the following method. (1) Packaging test Teraoka Seiki AW2600Jr. Using a PE-type machine, the three-layer film obtained in each Example was used to package the foamed styrene tray, and the state of each package was observed. As a result of visual observation,
The case where the packaging state was good was evaluated as ○, the case where wrinkles occurred was evaluated as Δ, and the case where it was defective was evaluated as ×. (2) Measurement of seal temperature range (Presentation) Using a wrapper ARC450 type prepack E made by Sunpack, it was packed in an expanded styrene tray, and the heat seal temperature range was measured by changing the hot plate temperature and the heating time.

(3) Measurement of physical properties Strength at break (Kg / cm ² ): ASTM D 882 Elongation (%): ASTM D 882 Tear strength (Kg / cm): JIS P8116 Puncture strength: For universal tensile tester The test piece was uniformly attached to a clamp having an inner diameter of 100 mm so as not to cause wrinkling and sagging. Then, a push rod having a radius of curvature of 2 mm at the tip and a diameter of 4 mm was attached to the crosshead, and the pressure was applied at a pressing speed of 500 mm / min. The strength (g) and elongation (%) of the pressure bar breaking through the test piece were measured. Adhesive force (g / 8cm): Two pieces of 80 mm x 150 mm test pieces were stuck together and peeled off at a crosshead speed of 500 mm / min in a direction perpendicular to the short side end. Lateral stress was determined. Transparency (haze): ASTM D 1003

Example 1 Ethylene content 4% by weight, MI 2.7 g / 10 min (23
0 ° C.), 60% by weight of a propylene-ethylene random copolymer, a density of 0.905 g / cm ³ , and an MI of 0.8 g / 1.
0 minute (190 ° C.) ethylene-octene-1 copolymer 4
0% by weight was kneaded at 190 ° C. using an extruder having a screw diameter of 55 mmφ and L / D = 28 to obtain an intermediate layer resin composition. On the other hand, an ethylene content of 3% by weight and MI of 9.0 g /
10 minutes (230 ° C.) propylene-ethylene random copolymer 6% by weight, vinyl acetate content 15% by weight, MI
0.8 g / 10 minutes (190 ° C.) of ethylene-vinyl acetate copolymer and 2.0% by weight of a surfactant, diglycerin stearate (manufactured by Riken Vitamin Co., Ltd.) were prepared in a twin-screw kneading apparatus, and the screw diameter was adjusted. The mixture was kneaded at 190 ° C. using an extruder having a diameter of 55 mm and L / D = 28 to obtain an outer layer resin composition. Next, the two compositions obtained as described above are supplied to one annular die so that the intermediate layer and the outer layers on both sides thereof are laminated at a thickness of 5 μm, and blown at 190 ° C. at a blow ratio of 3.5. It was molded to obtain a stretch wrap multilayer film. Each physical property measurement, packaging test, and sealing temperature range of the obtained three-layer film were measured. The results are shown in Table 1.

[0014]

[Table 1]

Example 2 As a resin composition for the intermediate layer, instead of the ethylene-octene-1 copolymer, a density of 0.905 g / cm ³ and a MI 1.5
g / 10 minutes (190 ° C.) of ethylene-butene-1 copolymer (40% by weight), and sorbitan monooleate (Daiichi Kogyo Seiyaku Co., Ltd.) instead of diglycerin stearate as a surfactant in the outer layer resin composition Product name: Sorgen 40
A) A stretch-wrap multilayer film was obtained in the same manner as in Example 1 except that 2.0% by weight was used. 3 obtained
The physical properties, the packaging test, and the heat sealing range of the layer film were measured in the same manner as in Example 1. The results are shown in Table 1.

Example 3 Instead of the ethylene-octene-1 copolymer as the intermediate layer resin composition, the density was 0.895 g / cm ³ and the MI was 3.0.
A stretch-wrap multilayer film was obtained in the same manner as in Example 1 except that the ethylene-butene-1 copolymer of g / 10 minutes (190 ° C) was 40% by weight. The physical properties, the packaging test, and the heat sealing range of the obtained three-layer film were measured in the same manner as in Example 1. The results are shown in Table 1.

Example 4 As an intermediate layer resin composition, an ethylene content of 4% by weight and MI
2.7 g / 10 minutes (230 ° C.) 50% by weight of a propylene-ethylene random copolymer and a density of 0.905 g /
A stretch-wrap multilayer film was obtained in the same manner as in Example 1, except that the ethylene-octene-1 copolymer having a cm ³ of 0.8 g / 10 minutes (190 ° C.) and MI of 0.8 g / 10 minutes was used. The physical properties, the packaging test, and the heat sealing range of the obtained three-layer film were measured in the same manner as in Example 1. The results are shown in Table 1.

Example 5 As an intermediate layer resin composition, an ethylene content of 4% by weight and MI
2.7 g / 10 minutes (230 ° C.) 80% by weight of a propylene-ethylene random copolymer and a density of 0.905 g /
A stretch-wrap multilayer film was obtained in the same manner as in Example 1 except that the ethylene-octene-1 copolymer having a cm ³ of 0.8 g / 10 minutes (190 ° C.) and MI of 20% by weight was used. The physical properties, the packaging test, and the heat sealing range of the obtained three-layer film were measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 As an intermediate layer resin composition, an ethylene content of 4% by weight and MI
2.7 g / 10 minutes (230 ° C.) 50% by weight of a propylene-ethylene random copolymer and a density of 0.905 g /
cm ³ , MI 0.8 g / 10 min (190 ° C.) 50% by weight of ethylene-octene-1 copolymer, vinyl acetate content 15% by weight as outer layer resin composition, MI 0.8 g /
Ethylene-vinyl acetate copolymer 9 for 10 minutes (190 ° C.)
A stretch wrap multilayer film was obtained in the same manner as in Example 1, except that 8% by weight and 2% by weight of diglycerin oleate were used. The physical properties, the packaging test, and the heat sealing range of the obtained three-layer film were measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2 The intermediate layer resin composition had a density of 0.905 g / cm ³ ,
MI 1.5 g / 10 min (190 ° C.) ethylene-butene
-A stretch wrap multilayer film was obtained in the same manner as in Example 1 except that the amount of 1 copolymer was changed to 100% by weight. The physical properties, the packaging test, and the heat sealing range of the obtained three-layer film were measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 3 As an intermediate layer resin composition, an ethylene content of 4% by weight, MI
2.7 g / 10 minutes (230 ° C.) 20% by weight of a propylene-ethylene random copolymer and a density of 0.905 g /
A stretch-wrap multilayer film was obtained in the same manner as in Example 1 except that the ethylene-octene-1 copolymer having a cm ³ of 0.8 g / 10 min (190 ° C.) and an MI of 80% by weight was used. The physical properties, the packaging test, and the heat sealing range of the obtained three-layer film were measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 4 The intermediate layer resin composition had an ethylene content of 4% by weight and an MI of 4% by weight.
Example 1 except that 2.7 g / 10 minutes (230 ° C.) of 100% by weight of a propylene-ethylene random copolymer was used.
A stretch wrap multilayer film was obtained in the same manner as described above. The physical properties, the packaging test, and the heat sealing range of the obtained three-layer film were measured in the same manner as in Example 1. The results are shown in Table 1.

[0023]

According to the stretch wrap multilayer film of the present invention, the propylene-ethylene random copolymer is used for both the intermediate layer and the outer layer, so that the properties of the conventional wrap film, such as transparency, are not impaired. The temperature range widens, and it is useful as a stretch wrap film for various types, particularly fresh foods.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yutaka Harada 1029 Onoda, Onoda-shi, Yamaguchi Prefecture Examiner, Chief Resin Co., Ltd. Hiroaki Hirai (56) References JP-A-60-171148 (JP, A) JP-A Sho 55-118859 (JP, A) JP-A-55-84660 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (2)

(57) [Claims] An intermediate layer comprising a resin composition containing 50 to 90% by weight of a propylene-ethylene random copolymer and 10 to 50% by weight of a copolymer of ethylene and a C _{4 to} C ₈ α-olefin, As an outer layer on both surfaces of the intermediate layer, a vinyl acetate content of 5 to 25% by weight and an MI of 0.2 to 5.0 g /
Propylene having an ethylene-vinyl acetate copolymer for 10 minutes as a main component and an ethylene content of 1.5 to 8% by weight.
A stretch wrap multilayer film comprising a resin composition containing 2 to 15% by weight of an ethylene random copolymer laminated. To [claim 2] outer layer, further, I of food hygiene problems
2. A method according to claim 1, wherein a surfactant such as sorbitan oleate, polyglycerin oleate or diglycerin steate, which is a fatty acid ester, is added in an amount of 1 to 5% by weight.
5. The stretch wrap multilayer film according to 4.