JPH0745227B2 - Film for heat shrink packaging - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a film for heat shrink packaging.

More specifically, the present invention relates to a heat-shrinkable film for packaging various articles which is heat-shrinkable at low temperature and has excellent transparency, adhesiveness, mechanical properties, low-temperature properties, and the like.

[Conventional technology]

The film obtained by stretching the thermoplastic resin film,
Since it has a property of shrinking by heating, it is used for heat shrink packaging in which various articles are roughly wrapped and the film is shrunk by hot air, a heat shrink tunnel or the like to adhere to a packaged item. Heat shrink wrapping has good wrapping effect and efficient packing work, so various products such as foods, toys, raw fabrics, textiles, fruits and vegetables, record jackets, audio tape cassettes, video tape cassettes, exercise equipment, household products. ,
It is used for packaging industrial parts, compact discs, IC products, daily necessities, sundries, etc.

Conventionally, as a film for heat shrink packaging, polyvinyl chloride, high pressure low density polyethylene, ethylene-vinyl acetate copolymer, linear ethylene-α- with a density of 0.910 g / ml or more.
A film made of an olefin copolymer, a linear ethylene-α-olefin copolymer having a density of 0.910 g / ml or less, a resin such as polypropylene, polyamide, or polybutadiene is used.

Polyvinyl chloride film has a relatively low heat shrinkage temperature of around 100 ° C, and has good gloss and transparency, but it generates hydrogen chloride gas when heated, corrodes incinerators and packaging machines, and is a plasticizer added. However, heat stabilizers and the like have problems of hygiene and bleeding, and are considered to be problems.

High-pressure low-density polyethylene film is used in large quantities because it has good impact resistance at low temperatures, heat seal strength, and is inexpensive, but its heat shrinkage temperature is as high as 120 to 130 ° C.
It has a drawback that it cannot be used for packaging articles that deteriorate or break when exposed to high temperatures. In addition, it is difficult to stretch highly in order to obtain high shrinkability.

The ethylene-vinyl acetate copolymer film is superior in transparency, heat sealability, low temperature heat shrinkability and the like to the high pressure low density polyethylene film, but is inferior in mechanical strength, heat resistance and film handling property.

A linear ethylene-α-olefin copolymer film having a density of 0.910 g / ml or more has excellent mechanical strength, but it is difficult to produce a highly stretched film, and the heat shrink temperature is also high.
It is relatively high at around 127 ° C, causing a problem.

An ethylene-α-olefin copolymer film having a density of 0.910 g / ml or less has a density of 0.910 g / ml or more ethylene-α.
-Compared to the olefin copolymer film, it has excellent transparency, low temperature heat sealability, low temperature heat shrinkability, etc., but has a problem in mechanical strength.

Polypropylene film is excellent in transparency and gloss, has a film flexibility, is easy to be applied to an automatic packaging machine, and is excellent in shrinkage force, but has problems in low-temperature heat sealability, low-temperature heat shrinkability, high shrinkability, and the like.

The polyamide-based film is excellent in transparency, film rigidity, impact resistance, etc., but is inferior in low-temperature shrinkability, low-temperature heat-sealing property, etc. Polybutadiene-based films have excellent low-temperature shrinkability, low-temperature heat-sealing properties, transparency, etc., but have good mechanical strength such as tear strength and tensile strength. is there.

[Problems to be Solved by the Invention]

The conventional heat-shrinkable packaging film has various problems as described above.

The present invention has no problem in food hygiene, and an object thereof is to provide a heat-shrinkable packaging film excellent in mechanical strength, transparency, gloss, low-temperature heat shrinkability, and high stretchability (high shrinkability). In particular, the conventional polyolefin heat shrinkable packaging film could not solve low temperature heat shrinkage, mechanical strength, transparency and high stretchability (high shrinkability) at the same time. The challenge is to expand the applications of packaging films.

[Means for Solving the Problems]

The present inventor focused on linear ethylene-butene-1-hexene-1 copolymer having a density of 0.910 g / ml or less, which has been recently developed, and started to exhibit excellent properties in the heat shrinkable packaging film field. Applied to complete the present invention.

That is, the heat-shrinkable packaging film of the present invention has a density of 0.910 g.
/ ml or less of linear ethylene-butene-1-hexene-1
A heat-shrinkable packaging film in which both outer layers selected from a middle layer made of a copolymer, an ethylene-vinyl acetate copolymer and / or a layer made of a high-pressure low-density polyethylene are laminated and stretched; 0.910 g / ml or less of linear ethylene-butene-1-
A film for heat-shrinkable packaging in which both outer layers made of an exene-1 copolymer, an intermediate layer selected from a layer made of an ethylene-vinyl acetate copolymer and / or a high-pressure low density polyethylene are laminated and stretched. ; Is included.

The linear ethylene-butene-1-hexene-1 copolymer used in the present invention is formed by a combination of a Group IV-VIII transition metal compound and a Group I-III organometal in the periodic table. It is produced by a gas phase low pressure method using a catalyst, a so-called Ziegler catalyst.

More specifically, the linear ethylene-butene-1-hexene-1 copolymer is (a) 0.35: to 8.0 at a temperature of 10 ° to 80 ° C. and a pressure of 7,000 KPa or less in the fluidized bed reaction zone. 1 (the total moles of butene-1 and hexene-1, but the molar ratio of butene-1 and hexene-1 is 0.5: 1 to 2: 1) to ethylene, ethylene, butene-1 and hexene-1. And (b) a gas mixture containing at least 25 mol% of at least one diluent gas having the formula: Mg _m Ti (OR) _n X _p [ED) _q [wherein R is 1 to 14 carbon atoms. Is an aliphatic or aromatic hydrocarbon group or COR ', wherein R'is an aliphatic or aromatic hydrocarbon group having 1 to 14 carbon atoms, and X is Cl, Br, I. And a mixture thereof, ED is an alkyl ester of an aliphatic or aromatic acid, an aliphatic ether, a cyclic ether. An organic electron-donating compound selected from the group consisting of a ter and an aliphatic ketone, m is 0.5 to 56, n is 0.1 or 2, p is 2 to 116, and q is 2 to 85. ] The precursor composition is diluted with an inert carrier material and continuously contacted with particles of a catalyst system comprising a precursor composition having the formula: Al (R ') _{d X'e} H _f [wherein , X ′ is Cl or OR ″, and R ′ and R ″ are 1
A saturated hydrocarbon group having 14 to 14 carbon atoms, e is 0 to 1.5, f is 0 or 1, and d + e + f = 3].
A method for continuous production of ethylene copolymers, characterized in that the activating compound is used in an amount such that the molar ratio of total aluminum to titanium in the reaction zone is 10: 1 to 400: 1. It is a thing.

Ethylene-butene-1-hexene-used in the present invention
1 copolymer is a linear polymer having a density of 0.910 g / ml or less, wherein the ethylene portion is about 50 to 75% by weight in the copolymer, and the remaining amount is 50 to 25% by weight. 1 and the total amount of hexene-1, and the ratio of butene-1 and bexene-1 is
It is in the range of 0.5: 1 to 2: 1. The ethylene-butene of the present invention
The method for producing the 1-hexene-1 copolymer is described in detail in JP-A-59-230011.

The ethylene-vinyl acetate copolymer used in the present invention is
It is preferable that Ml is in the range of 0.3 to 3 g / 10 min. Ml
If it is less than 0.3, there is a drawback that the extruder is overloaded during the film forming and the productivity cannot be increased. Also Ml
When it is more than 3.0, problems occur in the tensile strength of the film, tear resistance due to sharp corners, etc., which is not desirable.

The content of vinyl acetate is 5 to 25% by weight, preferably 10
~ 20% by weight. When it is 5% by weight or less, low-temperature heat shrinkage is not exhibited, and stretchability, flexibility and transparency are insufficient, which is not desirable. If it exceeds 25% by weight, heat resistance, tensile strength, tear resistance due to sharp corners and the like are insufficient, which is not desirable.

The high-pressure density polyethylene used in the present invention has a density
0.915-0.918g / ml, Ml is 100-500.

When Ml is 100 or less, low temperature heat sealability is lost,
It is not desirable, and when it is 500 or more, mechanical strength and stretchability are deteriorated, which is not desirable.

An antifogging agent, an antistatic agent, an antiblocking agent and the like can be added to the heat shrinkable packaging film of the present invention.

The heat-shrinkable packaging film of the present invention includes fruits and vegetables, fresh foods, seafood, raw meat, processed meats, vegetables, cans, bottles, food and drink in paper containers, newspapers, magazines, books, industrial parts, electronic parts, Machinery / electrical products, wood products, industrial chemicals, plastic packaging bags, grass, marine products, wool, cotton, toys, transition fabrics, textile products, records, cassette tapes, audio tapes,
The tape is wrapped around a video tape or the like as it is, or a tape, a pallet, or a cardboard that has been loaded, placed, or pinched, and the film is heat-shrinked by hot air, a heat-shrinking tunnel, or the like to be wrapped.

The thickness of the heat-shrinkable packaging film of the present invention varies depending on the weight and volume of the object to be packaged, but if the weight is small and the volume is 15 μ to 50 μ, it is sufficient for heavy and large volumes. , 50 to 100 μ.

The heat-shrinkable packaging film of the present invention is used by making a monolayer or multilayer film by a T-die method, an inflation method or the like. The multilayer film is produced by a co-extrusion method, and may be produced by any of in-die bonding and out-die bonding.

As the stretching method, there are a uniaxial stretching method such as roll stretching and roll rolling, a biaxial stretching method such as a tenter method and a tubular method, and a linear ethylene-containing resin having a density of 0.910 g / ml or less used in the present invention. Butene-1-hexene-1 copolymer has a high melting viscosity and is difficult to form by a normal film forming method.
Although the heat shrinkable packaging film having better properties is formed by the method of 63-2828567, the present invention is not limited to the film produced by this method.

〔Example〕

(Example 1) 100 parts by weight of an ethylene-butene-1-exene-1 copolymer (ethylene 70% by weight, butene-1 10% by weight, hexene-1 120% by weight, density 0.910, Ml = 1) as an intermediate layer Prepared by adding 0.1 parts by weight of silica powder to an ethylene-vinyl acetate copolymer (ethylene 82%,
18% vinyl acetate and Ml = 2.5 density 0.94) were prepared. Using these resins, an inflation film was produced by air cooling under the following apparatus and processing conditions, and this was stretched 3 times in each of the length and width with a biaxial stretching device.

(1) Extruder: Inflation processing equipment manufactured by Placo Co., Ltd. Diameter 40 mm x 2 units L / D = 28 (2) Annular three-layer die: θ: 150 mm Die gap: 1.0 mm (3) Cooling device: Single lip straight and With conical color (4) Discharge rate: 45Kg / hr (5) Die temperature: 180 ° C (6) Blow ratio: 4.0 Manufactured laminated film Intermediate layer thickness 10μ Both outer layers thickness 5μ Laminated film evaluation ・ Tear strength of film: Longitudinal tear strength is 47 Kg / c
m, lateral direction is 112 Kg / cm, and it has sufficient practicality.

-Haze: Measured according to JIS K-6714, the numerical value is 2.5, and there is sufficient practicality.

-Tensile strength of film: Tensile strength in the machine direction is 308 Kg / c
m ^2, transverse is 304Kg / cm ^2, practicality is enough.

-Impact strength: 215g, practically sufficient.

-Heat shrinkage: Film size 10 x 10 cm, using glycerin bath. The heat shrinkage in the machine direction and the transverse direction of the film was measured at a soaking time of 5 seconds and a temperature of 100 ° C and 130 ° C.

 100 ℃ 130 ℃ Vertical direction -12% -71% Horizontal direction -12% -42% ・ Penetration strength: 3.2Kg, which is practical.

(When the film is stretched 30%, the pencil-shaped tip (radius
Strength when breaking through at 0.5mm tip R0.5mm)) The following data is shown in Table 1.

(Examples 2 to 4 and Comparative Examples 1 to 8) In the same manner as in Example 1, heat shrinkable packaging films having the configurations shown in Examples 2 to 4 and Comparative Examples 1 to 8 in Table 1 below are prepared and their physical properties are shown. Was evaluated. The results are shown in Table 1.

As is clear from the data in Table 1, the films of Examples 1 to 4 were in proportion to the films of Comparative Examples 1 to 8 in tear strength, haze, tensile strength, impact strength, breakthrough strength and low temperature heat shrinkability. It can be seen that the film is excellent as a heat-shrinkable packaging film due to its excellent overall properties.

[Effect of the Invention] Linear ethylene-butene-1-having a density of 0.910 g / ml or less
The heat-shrinkable packaging film of the present invention, which is composed of a hexene-1 copolymer and has a stretched film layer as a main constituent layer, has a tear strength and a tensile strength as compared with conventional polyolefin heat-shrinkable packaging films. It has excellent mechanical strength such as impact strength and breakthrough strength, good transparency, and excellent low-temperature heat shrinkability, so it is an extremely excellent film for heat shrink packaging, and has high mechanical strength even when it is thinned. Therefore, it is possible to reduce the material constituting the film, it is possible to heat-shrink at low temperature to save energy, and it is possible to wrap in a short time, so that there is no risk of degrading the contents during packaging, It is extremely suitable for packaging raw meat, raw vegetables, electronic parts and other articles that dislike heat.

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Claims (2)

[Claims] 1. A straight-chain ethylene having a density of 0.910 g / ml or less.
Both outer layers selected from a middle layer made of butene-1-hexene-1 copolymer, a layer made of ethylene-vinyl acetate copolymer and / or a high-pressure low density polyethylene are laminated and stretched. A film for heat-shrink packaging characterized by: 2. Linear ethylene having a density of 0.910 g / ml or less
Both outer layers made of butene-1-hexene-1 copolymer, an intermediate layer selected from layers made of ethylene-vinyl acetate copolymer and / or high-pressure low-density polyethylene are laminated and stretched. A film for heat-shrink packaging characterized by: