JPH07100741B2 - Stretch wrapping film - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a film for stretch packaging of foods.

[0002]

2. Description of the Related Art Conventionally, polyvinyl chloride resin (PV) is used as a film for so-called pre-packaging, in which foods such as fruits and vegetables, fresh fish, meat, side dishes, etc. are placed directly or on a lightweight tray such as plastic and stretch-wrapped with a film.
Many of C) type are used. This is because it is excellent in the suitability of the packaging machine and workability, and also in the recovery of elongation when stress is released, so-called elastic recovery, but in recent years it has become a problem in terms of environment and safety and hygiene. Tend to be. Therefore, various resin films replacing PVC-based resin have been studied. For example, in JP-A-61-89040, a film having butene-1 as an intermediate layer and ethylene-vinyl acetate copolymer resin (EVA) as an outer layer has been proposed. JP-A-2-206548 proposes a film having linear low-density polyethylene (L-LDPE) as an intermediate layer and EVA as an outer layer. All of these are attempts to bring the good points of individual resins together to bring them closer to PVC-based films by making multiple layers of different resins, but unfortunately they are still superior in performance to PVC-based films. Is not on the market.

[0003]

Since these non-PVC type stretch films are soft and easily stretchable, when the package is loaded, the film is loosened due to the weight of the package, or the tray edge part is partially formed. Stretch film easily tears. In addition, the adhesiveness between the films is low, and the heat seal
There are many drawbacks such as poor rubbing property, and there is a problem that it is significantly inferior to PVC-based films. MEANS TO SOLVE THE PROBLEM This invention solves the said conventional problem, and is not inferior to the property suitable for a stretch packaging film, ie, transparency, antifogging property, self-adhesiveness, and heat-sealing property compared with the conventional Kochi PVC stretch film. Another object of the present invention is to provide a non-PVC film having an appropriate tensile strength when stretched and an excellent elastic recovery force.

[0004]

Means for Solving the Problems As a result of various investigations for solving the above problems, the present inventors have inflation-molded a copolymer resin of ethylene and methacrylic acid having a methacrylic acid content of 8 to 12% by weight. The present inventors have found that the film-formed product is very effective as a stretch packaging film, and arrived at the present invention.

That is, the present invention provides an ethylene methacrylic acid copolymer resin (E having a methacrylic acid content of 8 to 12% by weight).
MMA) is a film formed by inflation molding, and the stress at 50% elongation is 1.1 to 1.5 times in the longitudinal and transverse directions at 100% elongation and 1.5 in the transverse direction at 200% elongation. The gist of the present invention is a stretch-wrapping film having a stretch stress of up to 2.0 times.

The EMMA used in the present invention has a transparency, an adhesive property, and a methacrylic acid content of less than 8% by weight.
The heat sealability deteriorates, and the properties as a stretch film cannot be satisfied. On the other hand, if the content of methacrylic acid exceeds 12% by weight, the blocking phenomenon between the films becomes large, making it difficult to rewind the film, which is unsuitable, and therefore the range of this content is necessary. When the content of methacrylic acid is within the above range, the transparency, antifogging property, and
It can exhibit self-adhesiveness and heat-sealing property.

In order to provide a suitable packaging property as a stretch wrapping film, that is, a stress when the film is stretched and an excellent elastic recovery force, a stretch stress characteristic, so-called S-S curve (Stress-Strain Curve) is used. ) It is necessary that the characteristics are within a certain range. The present inventors have found that the suitability for packaging PVC-based stretch films, that is, the suitability for packaging machines and the ease of hand work are due to this S-S curve characteristic. It has been found to be a requirement for obtaining films with very good wrapping suitability.

When the stress at 50% elongation of the film is set to 1, the stress at 100% elongation is 1.1 times both in the longitudinal and transverse directions, less than 9 l, and the stress in the transverse direction at 200% elongation is 1.5 times. In the case of a larger value, the film is apt to be stretched rapidly, and the edge portion or the like is likely to be broken at the time of wrapping in which the object to be packaged is put in the tray and wrapped. In addition, when a package is loaded, the film is stretched by the package above, and the package is loosened, so that the commercial value is easily reduced. On the contrary, when the stress at 50% stretching of the film is set to 1, the stress at 100% stretching is more than 1.3 times in the longitudinal and lateral directions, and the stress at 200% stretching is 2.0 times in the lateral direction. In the case of a large size, it requires a large amount of force to stretch the film, making it difficult to stretch it by hand.In the case of packaging with a machine, the tray containing the items to be packaged pushes the film up to wrap it. For example, the chucking portion at the end of the film at the time of pushing up is likely to come off. Further, since the stress is too strong, the tray itself is easily deformed.
The stretching in the present invention was performed by using a No. 1 dumbbell specified in JIS K 6301 and performing a tensile test at a speed of 200 mm / min in an atmosphere of 23 ° C. and a humidity of 50%.

In order to obtain the film having the tensile stress of the present invention, it is necessary to use the EMMA and also the inflation method as a processing method. This inflation method is a known air-cooling method or water-cooling method, and is suitable for stretch wrapping and is 3 to 50 μm, preferably 8 to
In producing a film with a thickness of 30 μm, if the blow ratio is molded in the range of 1.5 to 4.0, the desired SS
Curve characteristics can be obtained. In addition to this inflation method, the T-die method is generally used as a film processing method. In the case of the T-die method, the melt discharged from the die is spread only in the flow direction (longitudinal direction) to form the film. Since the S-S curve characteristic in the lateral direction is not satisfied because of the expansion, the inflation method can extend not only in the flow direction (vertical direction) but also in the lateral direction by controlling the blow ratio.

Further, in molding the EMMA used in the present invention, the obtained film has antifogging property, antistatic property,
0.5 to 5.0% by weight of at least one of glycerin fatty acid ester-based, sorbitan fatty acid ester-based, polyglycerin fatty acid ester-based, and ethylene oxide adduct-based surfactants for the purpose of imparting appropriate slipperiness. , Preferably 1.0 to 3.0% by weight may be added.
In addition, at least one kind selected from rosin-based resins, polybutene resins, and polyterpene resins can be added for the purpose of increasing the adhesive strength.

[0011]

The present invention is based on EMAA and has a methacrylic acid content of 8
It is excellent in transparency, anti-fogging property, self-adhesiveness, heat sealability, and moderate tensile strength when stretched by inflation molding of 12 to 12 wt% blow ratio in the range of 1.5 to 4.0. A stretch packaging film having strength and excellent elastic recovery can be obtained.

[0012]

(Example) EMAA ("Nucrel AN-4216" manufactured by Mitsui-DuPont Polychemical Co., Ltd.) MFR (melt blow lacciole) 10.0 g / min, density 0.93 g / cm ³ , methacrylic acid content Is 9.0%)
98.5% by weight, diglycerin laurate 1.5% by weight
By kneading the composition containing the composition at 140 ° C. using an extruder having a diameter of 90 mm and L / D = 28, and performing inflation molding at a die temperature of 150 ° C. and a blow ratio of 2.3,
A stretch packaging film having a thickness of 14 μm was produced. (Example 2) Kneading temperature of 165 ° C, die temperature of 170 ° C
A stretch packaging film was produced in the same manner as in Example 1 except that. (Example 3) Kneading temperature is 185 ° C, die temperature is 195 ° C
A stretch packaging film was produced in the same manner as in Example 1 except that. (Example 4) Example 3 except that the blow ratio was 3.2.
A film for stretch packaging was manufactured in the same manner as in.

Physical properties of the stretch wrapping films produced in Examples 1 to 4, and using these, meat, fish, and vegetables were placed on a tray, and the stretch automatic wrapping machine (A-18XY manufactured by Fuji Pack) was used. Table 1 shows the suitability for a packaging machine and the suitability for a low temperature when the packaging is performed. Comparative Examples 1 and 2 are PVC stretch films, E, which are conventionally used, respectively.
It is an example of a VA stretch film. Polypropylene, polypropylene containing an inorganic material, expanded polystyrene, expanded polystyrene, impact-resistant polystyrene, etc. are used for the tray, but the results in Table 1 were not affected by the tray material.

[0014]

[Table 1]

[0015]

The stretch packaging film of the present invention comprises:
At present, it is a film suitable as a substitute for the PVC stretch film, which is the most proven film for pre-packaging.

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Claims (1)

[Claims] 1. A film formed by inflation molding of an ethylene methacrylic acid copolymer resin having a methacrylic acid content of 8 to 12% by weight. The film is stretched at 100% elongation against the stress at 50% elongation. And 1.1 to 1.5
A film for stretch packaging, which has a tensile stress of 1.5 to 2.0 times in the transverse direction when stretched by 200%.