JPS60155210A - Stretch-packaging film - Google Patents

Abstract

PURPOSE:The titled film excellent in tear strength, etc., mainly consisting of an ethylene/octene-1 copolymer having a melt flow rate, a weight-average MW/ number-average MW ratio, and an octene-1 content, each in a specified range. CONSTITUTION:Ethylene is copolymerized with octene-1 to prepare an ethylene/ octene-1 copolymer having a melt flow rate of 0.5-2g/10min, a Q value represented by a weight-average MW/number-average MW ratio of 2-6, and an octene-1 content of 9-15wt%. The obtained copolymer is mixed with, if necessary, additives such as a lubricant (e.g., oleamide) and a tackifying agent (e.g., rosin) and inflation-molded to obtain the purpose stretch-packaging film. The obtained film has moderate lubricity and self-adhesiveness and excellent elongation, flexibility, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stretch packaging film for wrapping an object while stretching the film.

Place fresh foods, etc. on plastic trays, stack food in cans, bottles, paper cartons, etc. on cardboard trays, and stack items stored in corrugated pole boxes, etc. on pallets.
These are used as films for so-called stretch packaging, in which the film is stretched while being wrapped, using ethylene-based materials such as low-density polyethylene and ethylene-vinyl acetate copolymer instead of conventional polyvinyl chloride due to safety and health issues. The development of resin-based products is actively underway.

However, low-density polyethylene films such as low-density polyethylene and ethylene-butene-1 copolymer, which are already known for use in stretch packaging, are hard and difficult to stretch, so even if they are stretched forcibly, they either break or stretch unevenly. Furthermore, if the trays loaded with items to be packaged are deformed or destroyed, wrinkles may occur, making it impossible to obtain the necessary tightening force for packaging or to package products with commercial value. .

In addition, with ethylene-vinyl acetate copolymer films, if the vinyl acetate content, melt flow rate, etc. are appropriately selected, the above-mentioned problems with low-density polyethylene films can be solved; If the tray or pallet containing the items to be packaged has sharp corners, if the film is stretched while wrapping, the film may hit these sharp corners and be torn. There is a problem that
Furthermore, in the logistics process for stretch packaging,
When small tears occur in the film due to contact with various objects,
There is a problem in that the tear propagates and expands, resulting in a large tear, or this causes the package to come undone.

Furthermore, although the above-mentioned laminated film of low-density polyethylene film and ethylene-vinyl acetate copolymer film does not have the problem of being hard and difficult to stretch, it does not solve the above-mentioned problem of being easily torn during packaging and distribution processes. However, this is not a satisfactory solution, especially in highly stretched packaging such as cardboard tray packaging and pallet packaging.

The present invention was developed in view of the conventional problems with stretch packaging films, and aims to have appropriate slipperiness and self-adhesiveness, sufficient thermal adhesiveness, and transparency. It is an object of the present invention to provide a stretch packaging film which not only has excellent stretchability and flexibility, but also extremely excellent tear strength.

That is, the stretch packaging film of the present invention has a melt flow rate of 0.5 to 2 f/10 minutes, a Q value expressed as the ratio of weight average molecular weight to number average molecular weight of 2 to 6, and an octene-1 content. is composed of 9 to 15% by weight of ethylene-octene-1 copolymer.

In the present invention, it is essential that the ethylene resin is an ethylene-octene-1 copolymer, and that the octene-1 content thereof is 9 to 15% by weight. Comonomers other than octene-1, such as butene-1 and hexene-1,4-methylpentene-1, do not show sufficient improvement in tear strength during packaging. Furthermore, if the octene-1 content is less than 9% by weight, the extensibility and flexibility will be insufficient and the improvement in tear strength will be insufficient, and if it exceeds 15% by weight, it will be difficult to obtain sufficient tightening force. Furthermore, the production of the copolymer itself becomes difficult.

Furthermore, the ethylene-octene-1 copolymer in the present invention has a melt flow rate (MFR) of 0.5 to 2 f/
10 minutes, preferably 0.7 to 2f/10 minutes, and the Q value expressed as the ratio of weight average molecule It (Mw) to number average molecular weight (MN) (MW/MN) is 2 to 6, preferably It is 3-5.

If the MFR is less than o, sr/lo, the elongation is small, and 2y
If it exceeds /1o, the breaking strength will decrease, and extensibility will eventually become a problem. Further, when the Q value is less than 2, film forming itself is difficult, while when it exceeds 6, the breaking strength becomes low.

The stretch packaging film of the present invention is made of the above-mentioned ethylene-octene-1 copolymer, and has a suitable slipperiness.
For example, fatty acid amides such as oleic acid amide, stearic acid amide, and erucic acid amide, stearic acid monoglyceride, stearic acid diglyceride, Fatty acid glycerin esters such as oleic acid monoglyceride, oleic acid diglyceride, ricinoleic acid triglyceride, acetyl ricinoleic acid glyceride, inorganic substances such as calcium carbonate, talc, silica, etc., as adhesives, castor oil derivatives, low molecular weight tone substances such as polybutene, sorbitan Other additives such as sorbitan fatty acid esters such as oleic acid esters and sorbitan lauric acid esters, rosin and rosin rust conductors, tackifiers such as petroleum resins and hydrogenated substances thereof, and rubbers are added as necessary.

In addition, the stretch packaging film of the present invention has extensibility,
From the viewpoint of flexibility, it is preferable to use a two- or three-layer laminated film in which an ethylene-vinyl acetate copolymer film is laminated on one or both surfaces of the ethylene-octene-1 copolymer film.

In that case, the ethylene-vinyl acetate copolymer has a vinyl acetate content of 3.5 to 25% by weight, preferably 10 to 25% by weight.
20 wt%, MFR 0.3-5 f/10 min,
Preferably it is 1-3 f/10 minutes. If the vinyl acetate content is less than 3.5% by weight, extensibility and flexibility will be insufficient, and if it exceeds 25% by weight, strength will be insufficient and still excessive tackiness will occur. On the other hand, if the MFR is less than 3 t/10 minutes, the elongation is small, and if it exceeds 5 t/10 minutes, the breaking strength is small, and extensibility becomes a problem in both cases.

Incidentally, the same additives used in the above-mentioned ethylene-octene-1 copolymer may be added to this ethylene-vinyl acetate copolymer as necessary.

The stretch packaging film of the present invention having the above structure is preferably formed by laminating ethylene-vinyl acetate copolymer films as described above and using a known T-die molding method, inflation molding method, or the like. In order to obtain a film with a sufficient balance of mechanical strength such as tear strength in the longitudinal and transverse directions, the inflation molding method is preferred, and the blow ratio at that time is preferably 3 to 6.

The thickness of the film of the present invention is usually 12 to 25 μm when used for packaging fresh foods placed on a plastic tray.
It is usually 25 to 100 μm for packaging of cans, bottles, food and beverages in paper cartons, etc. stacked on cardboard trays, and 2 μm for packaging of items stored in cardboard boxes, etc. stacked on pallets.
0 to 40μ, and when forming a laminated film with an ethylene-vinyl acetate copolymer film, the thickness composition ratio is 0.2μ for the ethylene-octene-1 copolymer film layer.
~0.8, and the ratio of the ethylene-vinyl acetate copolymer film layer is from 0.8 to 0.2.

The present invention will be explained in more detail with reference to Examples below.

Example I MFR1, 0 r710 min, Q value 3.8, octene-1
Including 1f11. 97% by weight of ethylene-octene-1 copolymer, 1.0% by weight of sorbitan oleate (manufactured by Daiichi Kogyo Seiyaku ■, Nurugen 40A), ricinoleic acid triglyceride (manufactured by Ito Seiyaku ■, refined castor oil)
A resin composition of 2.0% by weight was added to a resin composition with a diameter of 50 tan.
A stretch packaging film having a thickness of 18 μm was formed by inflation molding using an extruder of L/D 24 at a temperature of 180° C. and a blow ratio of 3.5.

Using this film, meat, fish, etc.
When vegetables were placed on each tray and wrapped using an automatic stretch wrapping machine, Fuji Pack System ■mA22, the film was found to be slightly hard, but the packaging was smooth and stable without tearing at the tray corners on any of the trays. The package was finished without wrinkles or looseness, and had a tight window and was of commercial value.

Example 2 A resin composition consisting of the same ethylene-octene-1 copolymer, sorbitan oleate, and ricinoleic acid triglyceride as used in Example 1 was prepared using a resin composition with a diameter of 65 tan.
, kneaded at 180°C using an extruder of L/D 25,
On the other hand, vinyl acetate content 15% by weight, MFR2, of/1
A resin composition having the same formulation as in Example I+111 except that the base resin was an ethylene-vinyl acetate copolymer of 0 was kneaded at 160°C using an extruder with a diameter of 50 mm and L/I) of 24. Both were fed into one annular three-layer die, and a resin composition made of ethylene-octene-1 copolymer was used as an intermediate layer with a thickness of 6 μm, and a resin composition made of ethylene-vinyl acetate copolymer was fed into each die. A stretch packaging film having a three-layer structure with a total thickness of 18 μm was formed by inflation molding with a die of 1 m at 180° C. and a blow ratio of 4.0 so that both surface layers had a thickness of 6 μm.

When stretch wrapping was carried out in the same manner as in Example 1 using this film, the wrapping could be done extremely smoothly without tearing at the tray corners, etc., and the finished wrapping was very smooth with a tightening window without wrinkles or looseness. It was a high quality product.

Example 3 100 parts by weight of the same ethylene-octene-1 copolymer used in Example 1, 0.1 part by weight of silica powder with an average particle size of 5 μm, and 0.3 part by weight of stearic acid amide were mixed into
The fins were kneaded at 180°C using an extruder with L/D 24, and on the other hand, 100 parts by weight of the same ethylene-vinyl acetate copolymer used in Example 2, 0.1 part by weight of silica powder, and 0 parts by weight of stearamide were mixed. .1 part by weight, diameter 65++m.

They were kneaded at 160°C using an extruder with a L/D of 25, and both were fed to one annular two-layer die to form ethylene-octene-
1. The resin composition made of copolymer wood was made to have a thickness of 25μ, and the resin composition made of ethylene-vinyl acetate copolymer was made to have a thickness of 25 μm.
A two-layer stretch packaging film having a total thickness of 50 μm was formed by inflation molding at a die temperature of 180° C. and a blow ratio of 4.0.

Using this film, an ethylene-vinegar vinyl copolymer was used to stretch and package 12 1,000 ton/brick containers containing beverages stacked on cardboard trays by stretching them in biaxial directions, Fuji Pack System mA110. Packaging was carried out with the combined layer facing the packaged object.

The results are shown in Table 1 along with the physical properties of the film.

Examples 4 to 6 Stretch packaging films were formed in the same manner as in Example 3, except that the ethylene-octene-1 copolymer shown in Table 1 was used, and packaging was performed using the films. The results are shown in Table 1 along with the physical properties of the film.

Comparative Examples 1 to 3 Ethylene-butene-1 copolymer shown in Table 1, ethylene-
Same as Example 3 except that hexene-1 copolymer and ethylene-octene-1 copolymer were used, respectively.
A stretch packaging film was formed and packaging was performed using the film. The results are shown in Table 1 along with the physical properties of the film.

(Leaving space below) Implementation N7 The same ethylene-octene-1 copolymer used in Example 1 was kneaded at 180°C using an extruder with a diameter of 501111X L/D24, while the same ethylene-octene-1 copolymer used in Example 2 was kneaded at 180°C. Same as vinyl acetate copolymer 98% needles (Example 2)
The resin composition with 2% by weight of sorbitan oleate used in was kneaded at 160°C using an extruder with a diameter of 65 mm and L/D of 25, and both were fed into one annular two-layer die and ethylene- The octene-1 copolymer was made to have a thickness of 15μ, the resin composition made of ethylene-vinyl acetate copolymer was made to have a thickness of 10μ, and the die temperature was 1.
A two-layer stretch packaging film having a total thickness of 25 μm was formed by inflation molding at 80° C. and a blow ratio of 4.0.

This automatic stretch wrapping machine uses this film to stretch and wrap six cardboard boxes (+g 57crRX, % line 47cm x height 55m) stacked on a wooden pallet in the -axis direction, manufactured by Konan Machinery Co., Ltd. When packaging was carried out using Ecotsu Master at a stretching rate of 25% with the layer made of ethylene-vinyl acetate copolymer placed on the packaged object side, good packaging workability was demonstrated without tearing at the corners of the pallet or cardboard box. . Furthermore, although a notch of approximately 2 ctn was made with a knife in the film after packaging, the notch did not propagate or expand.

Patent applicant Mitsubishi Yuka Co., Ltd. Agent: Patent Attorney Hidetoshi Furukawa (1 other person)

Claims (1)

[Claims] Melt flow rate is 0.5 to 2 f/10 min, Q value expressed as the ratio of weight average molecular weight to number average molecular weight is 2 to 2
6 and an ethylene-octene-1 copolymer having an octene-1 content of 9 to 15% by weight.