JP2001212913A - Stretch packaging film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stretch packaging film having flexibility, strength and transparency necessary as stretch packaging, excellent in rustproof effect and self-adhesiveness and suitable for packaging a steel coil. SOLUTION: The stretch packaging film has at least a three-layered structure of outer, intermediate and inner layers. The outer layer comprises a polyamide resin and the intermediate layer comprises a composition prepared by compounding a volatile rustproof agent with low density polyethylene and/or straight chain low density polyethylene with a density of 0.920-0.935 g/cm3 and the inner layer comprises an ethylene/vinyl acetate copolymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretch wrapping film which is excellent in flexibility, transparency, tackiness and rust prevention and can be suitably used for stretch wrapping of steel coils and the like.

[0002]

2. Description of the Related Art Conventionally, as a method of packaging a rust-resistant steel coil or the like, a method of packaging with a moisture-proof polyethylene resin film, a method of packaging an article to be packaged with rust-proof paper covered, and the like have been used. Have been done. However, the former polyethylene-based resin film is not sufficiently rustproof, and there is a problem that even when a thick film having a thickness of about 100 μm is used, the end face of the coil is particularly likely to rust during storage.

In the latter case, since the rust-proof paper is opaque, it is not possible to inspect the appearance of the article to be packaged, such as a steel coil, after packaging, and to use an adhesive applied to the rust-proof paper after use. There is a problem that the rust-proof paper cannot be recycled because it is difficult to separate the rust-proof paper.

[0004] On the other hand, in recent years, from the viewpoint of environmental protection, paperless packaging of steel coils and the like has been demanded, and attention has been paid to stretch packaging, and practical use thereof has been studied. As a film for stretch packaging used in such applications, in addition to excellent flexibility and strength, which are stretch suitability for automatic packaging, excellent transparency, rust prevention effect, adhesiveness, etc. are important qualities. is there.

[0005] However, in the case of stretch packaging, a thin film is used in order to enhance the adhesion to the article to be packaged.
If the rust preventive is added more than necessary, the bleed out of the rust preventive on the film surface increases in proportion to the increase of the rust preventive, so that even if the adhesive is applied or compounded, the adhesiveness is impaired. It is a fact. If the adhesiveness is insufficient, a gap occurs between the packaged object and the film after stretch packaging,
Moisture enters from here, and rust easily occurs in the steel coil. Further, in consideration of the rust-preventing effect, the vaporizable rust preventive is preferably released only to the steel coil side, which is the article to be packaged.

As a film using a rust preventive, for example, Japanese Patent Publication No. 64-8019 discloses a free carboxylic acid in a random copolymer of an α-olefin and an α, β-ethylenically unsaturated monocarboxylic acid. A polyolefin-based resin obtained by partially neutralizing a polyolefin-based resin obtained by partially neutralizing with an alkali metal ion or the like, a polyolefin-based resin composition for packaging metal products is shown, comprising the resin composition Films are known.

The resin composition described in the above publication has good compatibility between the polyolefin resin and the vaporizable rust inhibitor, and can uniformly disperse the vaporizable rust inhibitor at a high content. In this case, there is little bleeding of the vaporizable rust inhibitor on the film surface, and the film has excellent heat sealability. However, in the case of a single-layer film using the above-mentioned polyolefin-based resin composition, there is no layer that shields the volatilization of the vaporizable rust inhibitor, so that the vaporizable rust inhibitor volatilizes gradually, and the rust-proofing property decreases with time. Was large. or,
When this is used for packaging, heat sealing work is necessary, and further, adhesiveness for stretch packaging,
Since flexibility was not ensured, it was unsuitable for stretch packaging.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and has the flexibility, strength, etc., and is excellent in transparency, rust prevention, adhesiveness, etc., and is used for stretching steel coils and the like. An object is to provide a film suitable for packaging.

[0009]

The stretch packaging film according to the first aspect of the present invention (hereinafter referred to as "the present invention 1") has at least a three-layer structure of an outer layer, an intermediate layer and an inner layer. A low-density polyethylene and / or linear low-density polyethylene having a density of 0.920 to 0.935 g / cm ³ , which is made of a polyamide resin, is mixed with a vaporizable rust inhibitor, and the inner layer is made of ethylene. -It is characterized by comprising a vinyl acetate copolymer.

The invention according to claim 2 (hereinafter referred to as “the present invention 2”)
Stretch packaging film) has an at least three-layer structure of an outer layer, an intermediate layer and an inner layer, the outer layer is made of an ethylene-vinyl alcohol copolymer, and the intermediate layer has a density of 0.920 to 0.935 g / cm. ³ , characterized in that a low-density polyethylene and / or a linear low-density polyethylene is blended with a vaporizable rust inhibitor, and the inner layer is made of an ethylene-vinyl acetate copolymer.

The invention according to claim 3 (hereinafter referred to as “the present invention 3”)
The stretch packaging film of the present invention has at least a three-layer structure of an outer layer, an intermediate layer, and an inner layer, the outer layer is made of a polyolefin resin, and the intermediate layer has a density of 0.920-0.
935 g / cm ³ of low-density polyethylene and / or linear low-density polyethylene containing a volatilizable rust inhibitor, and the inner layer is polymerized using a metallocene catalyst having a single polymerization active site, and has a molecular weight of It is made of a linear low-density polyethylene having a distribution Mw / Mn (Mw; weight average molecular weight, Mn; number average molecular weight) of 1.5 to 3.0.

The invention according to claim 4 (hereinafter referred to as “the present invention 4”)
The film for stretch wrapping has a three-layer structure of an outer layer, an intermediate layer, and an inner layer, and the outer layer has a density of 0.
895 to 0.925 g / cm ³ of low-density polyethylene and / or linear low-density polyethylene, the intermediate layer having a weight-average molecular weight of 80,000 to 500,000 and an elution amount measured by a cross fractionation chromatography method But below 0 ° C
0 to 60% by weight, 30 to 55% by weight above 0 to 90 ° C, and 15% in any 5 ° C range in this temperature range.
% By weight or less, a vaporizable rust inhibitor is blended with a polypropylene resin having a weight of more than 90 to 130 ° C. and 5 to 20 weight%, and the inner layer is made of an ethylene-vinyl acetate copolymer. .

First, the stretch packaging film of the present invention 1 will be described. Examples of the polyamide resin constituting the outer layer used in the present invention 1 include 6-nylon, 6,6-nylon, 12-nylon, and the like.
These may be used alone or in combination of two or more. Among them, 6-nylon is preferred because it is excellent in flexibility, strength, transparency and the like. When the melting point of the polyamide resin is low, extrusion becomes difficult, and the appearance of the obtained stretch packaging film is deteriorated.

An adhesive resin may be added to the polyamide-based resin in order to improve the interlayer adhesion strength with an intermediate layer described later. As the adhesive resin, for example,
Rubber resins such as polybutene, polyisobutylene, butyl rubber, polybutadiene, and polyisoprene; acid-modified polyolefin resins such as acid-modified polyethylene resins and acid-modified polypropylene resins; Since blocking of the packaging film is likely to occur, the amount is preferably 20 parts by weight or less based on 100 parts by weight of the polyamide resin.

The intermediate layer used in the present invention 1 is composed of low-density polyethylene and / or linear low-density polyethylene (both are referred to as “polyethylene resin (1)”). If the density of the polyethylene resin (1) is too small, the stretch packaging film obtained is too stretched, so that it is difficult to beautifully perform stretch packaging,
When the size is large, the compatibility with the volatile rust preventive described below is reduced, so that the bleed out amount of the volatile rust preventive of the obtained stretch packaging film becomes excessive, the surface is easily whitened, and the tackiness is increased. Is reduced, making it difficult to stretch-wrap beautifully.
g / cm ³ , preferably 0.922 to 0.9
It is 28 g / cm ³ .

If the melt flow rate (hereinafter referred to as "MFR") of the polyethylene resin (1) is small, extrusion becomes difficult, the appearance of the obtained stretch packaging film becomes poor, and if it is large, the obtained stretch film becomes poor. Since the heat resistance, strength and the like of the packaging film are reduced, the content of the film is reduced to 0.
5-8 g / 10 min is preferred. The above MFR is JIS
It is a value measured according to K7210. When the intermediate layer is composed of the polyethylene resin (1), a stretch packaging film having excellent flexibility and elasticity can be obtained, and the bleed-out amount and speed of the rust preventive can be easily adjusted.

An adhesive resin may be added to the polyethylene resin (1) in order to improve the interlayer adhesive strength between the outer layer and an inner layer described later. As the adhesive resin, those similar to those used for the outer layer may be mentioned, and when the amount of addition is increased, the rust-proofing property, strength and the like of the obtained stretch packaging film are reduced. (1) It is preferably 20 parts by weight or less based on 100 parts by weight.

The polyethylene resin (1) is mixed with a vaporizable rust inhibitor. As the vaporizable rust preventive, any conventionally known volatilizable rust preventive may be used, but it is preferable that the volatilizable rust preventive comprises at least one selected from the group consisting of a nitrite, an ammonium compound and a urea compound.

Examples of the nitrite include potassium nitrite, sodium nitrite, calcium nitrite, and magnesium nitrite. Examples of the ammonium compound include ammonium benzoate, ammonium phthalate, ammonium stearate, and the like. Examples thereof include dicyclohexylammonium nitrite and diisopropylammonium nitrite. Examples of the urea-based compound include urea, phenyl carbamate, and urothrombin.

When the amount of the above-mentioned vaporizable rust preventive is too small, the obtained rust-proofing property of the stretch wrapping film is low, and when it is too large, the bleed-out amount of the vaporizable rust preventive of the stretch wrapping film is too large. And the surface is easily whitened, and the adhesiveness is reduced, so that it is difficult to stretch-pack beautifully. Therefore, 0.5 to 30 parts by weight of the polyethylene-based resin (1) is used in an amount of 0.5 to 30 parts by weight. Preferably, it is more preferably 1 to 10 parts by weight.

The ethylene-vinyl acetate copolymer constituting the inner layer used in the present invention 1 is not particularly limited, but if the vinyl acetate content is reduced, the flexibility of the obtained film for stretch packaging decreases. Since the heat resistance, strength and the like of the obtained stretch packaging film decrease as the content increases, the content is preferably 5 to 30% by weight. As the MFR of the ethylene-vinyl acetate copolymer becomes smaller, extrusion becomes difficult, the appearance of the obtained stretch packaging film becomes poor, and as it becomes larger, the heat resistance, strength, etc. of the obtained stretch packaging film decrease. , 1
10 g / 10 min is preferred.

The ethylene-vinyl acetate copolymer includes:
An adhesive resin may be added in order to improve the interlayer adhesion strength with the intermediate layer and to improve the adhesion with the article to be packaged. As the adhesive resin, those similar to those used for the outer layer may be mentioned, and the more the amount thereof is added, the more the blocking of the obtained stretch packaging film is likely to occur, so that the ethylene-vinyl acetate copolymer is used. 20 parts by weight or less is preferable for 100 parts by weight.

As the thickness of the stretch packaging film of the present invention 1 becomes thinner, the strength decreases, and if it becomes thicker, the flexibility decreases and it becomes difficult to perform beautifully stretch-packaged.
It is preferably from 30 to 100 μm, more preferably from 50 to 7 μm.
0 μm. The thickness ratio of each layer is preferably 1: 6: 1 to 3: 1: 3 for the outer layer: intermediate layer: inner layer, and more preferably 1: 4: 1 to 2: 1: 2. When the intermediate layer is thick, the bleed-out amount of the vaporizable rust preventive of the stretch packaging film becomes excessive, the surface is easily whitened, and the adhesiveness is reduced, so that it is difficult to beautifully perform stretch packaging. Further, since the outer layer becomes thinner, the vaporizable rust inhibitor easily bleeds out to the outer layer side, and the rust prevention effect is reduced. When the thickness of the intermediate layer is reduced, the amount of the vaporizable rust inhibitor is reduced, so that the bleed-out amount of the vaporizable rust inhibitor in the stretch packaging film is insufficient, the rust resistance is reduced, and the inner layer is further thickened. As a result, the initial rust resistance is reduced. Also, the thickness ratio of the inner layer and the outer layer is not particularly limited,
Although it may be determined as appropriate, if the inner layer is too thicker than the outer layer, the vaporizable rust inhibitor tends to bleed out to the outer layer side and the rust prevention effect is reduced, so the thickness of the inner layer is twice the thickness of the outer layer. Or less, more preferably 1.2
Less than twice.

Next, the stretch packaging film of the present invention 2 will be described. The ethylene-vinyl alcohol copolymer constituting the outer layer used in the present invention 2 is not particularly limited. However, when the ethylene content is low, the permeability of water vapor is high, and when the ethylene content is high, the permeability of oxygen is high. Therefore, the content is preferably 20 to 70 mol% because the rust resistance of the obtained stretch packaging film decreases.

When the MFR of the ethylene-vinyl alcohol copolymer is small, extrusion becomes difficult, and the appearance of the obtained stretch packaging film deteriorates. When the MFR of the ethylene-vinyl alcohol copolymer increases, the heat resistance and strength of the obtained stretch packaging film become poor. Since it decreases, 1 to 10 g / 10 minutes is preferable.

An adhesive resin may be added to the ethylene-vinyl alcohol copolymer in order to improve the interlayer adhesion strength with an intermediate layer described later. As the adhesive resin, those similar to those used in the present invention 1 can be mentioned. When the amount of addition is large, blocking of the obtained stretch packaging film is likely to occur. It is preferably 20 parts by weight or less based on 100 parts by weight of the polymer.

The intermediate layer and the inner layer used in the present invention 2 are:
These are the same as the intermediate layer and the inner layer used in the present invention 1, respectively.

The thickness of the stretch packaging film of the present invention 2 and the thickness ratio of each layer are the same as those of the stretch packaging film of the present invention 1 described above. That is, the thickness of the stretch packaging film is preferably from 30 to 100 μm, more preferably from 50 to 70 μm, and the thickness ratio of the outer layer: intermediate layer: inner layer is 1: 6: 1 to 3: 1: 3. And more preferably 1: 4: 1 to 2: 1: 2. The thickness of the inner layer is preferably not more than twice the thickness of the outer layer, and more preferably not more than 1.2 times.

Next, the stretch wrapping film of the present invention 3 will be described. The polyolefin resin constituting the outer layer used in the present invention 3 is not particularly limited as long as it has required flexibility, strength, transparency and the like. For example, low density polyethylene, medium density polyethylene , High density polyethylene, linear low density polyethylene,
Polyethylene resins such as ethylene-propylene copolymer containing ethylene as a main component; polypropylene resins such as polypropylene and ethylene-propylene copolymer containing propylene as a main component; and polybutene. Or two or more of them may be used in combination. Among them, polyethylene resins are preferable because of their excellent flexibility, and those which are polymerized without using a metallocene catalyst in order to prevent the vaporizable rust preventive compounded in the intermediate layer described later from bleeding out from the outer layer side. Is preferred. Further, those having a larger molecular weight than the polyethylene resin (1) used for the intermediate layer described later and the linear low-density polyethylene constituting the inner layer are preferable.

If the MFR of the polyolefin resin is small, extrusion becomes difficult, and the appearance of the obtained stretch packaging film becomes poor. If the MFR of the polyolefin resin becomes large, the heat resistance, strength and the like of the obtained stretch packaging film decrease. 0.1 to 10 g / 10 min is preferable.

An adhesive resin may be added to the above-mentioned polyolefin resin in order to improve the interlayer adhesion strength with an intermediate layer described later. Examples of the adhesive resin include those similar to those used in the present invention 1 described above. When the amount of the adhesive resin increases, blocking of the obtained stretch wrapping film easily occurs. 20 parts by weight or less based on parts by weight.

Further, a resin layer excellent in shielding property of the vaporizable rust inhibitor may be further formed outside the outer layer. Examples of the resin constituting the resin layer include a polyamide resin and an ethylene-vinyl alcohol copolymer, and the polyamide resin and the ethylene-vinyl alcohol copolymer used in the present invention 1 are used. The same thing as the thing is mentioned.

The intermediate layer used in the third invention is the same as the intermediate layer used in the first invention.

The linear low-density polyethylene constituting the inner layer used in the present invention 3 is limited to a linear low-density polyethylene polymerized using a metallocene catalyst having a single active site. Α that constitutes linear low-density polyethylene
Examples of the olefin include 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and the like.

The molecular weight distribution Mw / Mn of the linear low-density polyethylene polymerized using the above metallocene catalyst (M
w; weight average molecular weight, Mn; number average molecular weight), the smaller the stretchability of the obtained stretch packaging film is, the more difficult it is to beautifully stretch-pack it; It is difficult for the rust preventive agent to bleed out from the inner layer side, the rust prevention of the obtained stretch packaging film is reduced, and the transparency of the obtained stretch packaging film is reduced.
Limited to 3. The molecular weight distribution Mw / Mn is, for example, a high-temperature GPC (trade name “150” manufactured by WATERS).
Weight average molecular weight (Mw) measured using CV ")
And a number average molecular weight (Mn).

When the MFR of the linear low-density polyethylene polymerized using the above metallocene catalyst is small, extrusion becomes difficult, and the appearance of the obtained stretch packaging film becomes poor. 0.1 to 1
0 g / 10 min is preferred. By forming the inner layer with such a linear low-density polyethylene polymerized using a metallocene catalyst, the obtained stretch packaging film has excellent flexibility, transparency, impact resistance, and tear resistance. It will be.

The linear low-density polyethylene polymerized by using the metallocene catalyst has an adhesive property to improve the interlayer adhesion strength with the intermediate layer and the adhesiveness with the packaged object. A resin may be added. Examples of the adhesive resin include those similar to those used in the present invention 1 described above. The larger the amount of the resin, the more likely the resulting stretch packaging film is to be blocked. It is preferably 20 parts by weight or less based on 100 parts by weight of polyethylene.

The thickness of the stretch packaging film of the present invention 3 and the thickness of each layer are the same as those of the stretch packaging film of the present invention 1 described above. That is, the thickness of the stretch packaging film is preferably 30 to 100 μm, more preferably 50 to 70 μm, and the thickness ratio of each layer is as follows:
The ratio of the intermediate layer to the inner layer is preferably 1: 6: 1 to 3: 1: 3, and more preferably 1: 4: 1 to 2: 1: 2.
The thickness of the inner layer is preferably not more than twice the thickness of the outer layer, and more preferably not more than 1.2 times.

Next, the stretch packaging film of the present invention 4 will be described. The outer layer used in the present invention 4 is a low-density polyethylene and / or a linear low-density polyethylene (hereinafter, both are referred to as “polyethylene resin (2)”).
Consists of When the density of the polyethylene resin (2) decreases, the strength of the obtained stretch packaging film decreases, and when the density increases, the flexibility, transparency, elongation recovery, and the like of the obtained stretch packaging film decrease. , 0.895 to 0.925 g / cm ³ .

MFR of the polyethylene resin (2)
The smaller the size, the more difficult it is to extrude, the worse the appearance of the obtained stretch packaging film, and the larger the size, the lower the heat resistance and strength of the obtained stretch packaging film. preferable.

An adhesive resin may be added to the polyethylene resin (2) in order to improve the interlayer adhesion strength with an intermediate layer described later. As an adhesive resin,
The same ones as those used in the present invention 1 can be used, and when the added amount is large, blocking of the obtained stretch packaging film is easily caused. Therefore, the added amount is based on 100 parts by weight of the polyethylene resin (2). , 20 parts by weight or less.

Further, a resin layer excellent in shielding property of the vaporizable rust inhibitor may be further formed outside the outer layer. Examples of the resin constituting the resin layer include a polyamide resin and an ethylene-vinyl alcohol copolymer, and the polyamide resin and the ethylene-vinyl alcohol copolymer used in the present invention 1 are used. The same thing as the thing is mentioned.

The intermediate layer used in the present invention 4 is composed of a polypropylene resin. The weight average molecular weight of the polypropylene resin is reduced, the heat resistance, strength, extensibility, etc. of the obtained stretch packaging film are reduced,
The larger the size, the lower the flexibility of the obtained film for stretch wrapping. The weight average molecular weight is a value measured together with the resin elution amount by the cross fractionation chromatography described below. The resin elution amount of the polypropylene-based resin measured by the cross fractionation chromatographic method is lower at 0 ° C. or lower, the flexibility of the obtained stretch packaging film is reduced, and when the amount is increased, the strength of the obtained stretch packaging film is reduced. 30 to 60% by weight, and when the temperature is lower than 0 to 90 ° C., the flexibility of the obtained stretch packaging film decreases, and when the amount increases, the stretch recovery of the obtained stretch packaging film decreases. 5% to 20% by weight because the flexibility of the obtained stretch packaging film decreases when the temperature is lower than 90 to 130 ° C., and the stretch recovery property of the obtained stretch packaging film decreases when the temperature decreases. . Further, the resin elution amount in an arbitrary 5 ° C. range in a temperature range of more than 0 to 90 ° C. is not more than 15% by weight since the flexibility and elongation recovery properties of the obtained stretch packaging film are reduced as the amount increases. is there.

The resin elution amount by the above-mentioned cross fractionation chromatography is a value measured by the following method. First, after dissolving the polypropylene-based resin in o-dichlorobenzene at 140 ° C. or at a temperature at which the polypropylene-based resin is completely dissolved, the polypropylene-based resin is cooled at a constant rate, and the surface of the inert carrier prepared in advance has a crystalline property. Generated as a thin polymer layer in order of decreasing height. Next, the temperature is increased continuously or stepwise,
The concentration of the eluted components is sequentially detected, and the composition distribution (crystallinity distribution) is measured (temperature-elution elution fractionation). At the same time, the eluted components are analyzed by high-temperature GPC to measure the molecular weight and the molecular weight distribution. In the present invention, as a measuring device, a cross separation chromatograph device (manufactured by Mitsubishi Chemical Corporation, trade name “CFC-
T150A type ").

When the MFR of the polypropylene-based resin is small, extrusion becomes difficult, and the appearance of the obtained stretch packaging film becomes poor. When the MFR of the polypropylene resin becomes large, the heat resistance, strength and the like of the obtained stretch packaging film decrease. 0.5 to 10 g / 10 min is preferred.

Examples of such a polypropylene-based resin include those obtained by blending a rubbery resin with polypropylene, propylene-α-olefin copolymer, and the like. And PER (trade name) (manufactured by Tokuyama Corporation).

A volatile rust inhibitor is blended with the polypropylene resin. As the vaporizable rust inhibitor, the present invention 1
The same ones used in the above are used. The blending amount of the above-mentioned vaporizable rust preventive decreases the rust-preventive property of the obtained stretch wrapping film as the amount decreases, and the bleed-out amount of the vaporizable rust preventive in the obtained stretch wrapping film increases as the amount increases, and Is easy to whiten, and it becomes difficult to stretch pack beautifully due to reduced adhesiveness. Therefore, the amount is preferably 0.5 to 30 parts by weight, more preferably 1 to 30 parts by weight, based on 100 parts by weight of the polypropylene resin. To 10 parts by weight.

An adhesive resin may be added to the polypropylene resin in order to improve the interlayer adhesive strength between the outer layer and an inner layer described later. As the adhesive resin, those similar to those used in the above-mentioned present invention 1 can be mentioned, and when the added amount is large, the rust-proofing property, strength and the like of the obtained stretch packaging film are reduced. It is preferably 20 parts by weight or less based on 100 parts by weight of the resin.

The inner layer used in the fourth invention is the same as the inner layer used in the first invention.

The thickness of the stretch packaging film of the present invention 4 and the thickness ratio of each layer are the same as those of the above stretch packaging film of the present invention 1. That is, the thickness of the stretch packaging film is preferably from 30 to 100 μm, more preferably from 50 to 70 μm, and the thickness ratio of the outer layer: intermediate layer: inner layer is 1: 6: 1 to 3: 1: 3. And more preferably 1: 4: 1 to 2: 1: 2. The thickness of the inner layer is preferably not more than twice the thickness of the outer layer, and more preferably not more than 1.2 times.

The method for producing the stretch packaging films of the present inventions 1 to 4 is not particularly limited, and any conventionally known method may be employed. Examples of a method for laminating each layer include coextrusion and extrusion lamination. Among them, lamination by a co-extrusion method is preferable because quenching can be performed and the obtained stretch packaging film has excellent transparency. Further, by keeping the cooling roll flat, the obtained stretch packaging film has excellent gloss. Further, as a film forming method, for example, an inflation method,
T-die method and the like can be mentioned.

The stretch packaging film of the present invention 1-4 has an inner layer on the side of the package when the stretch packaging is performed. With this configuration, the vaporizable rust preventive bleeds out mainly to the inner layer side, that is, to the side of the packaged object such as a steel coil, thereby having an excellent rust preventive effect.

The stretch packaging film of the present invention may further contain a filler, a softener, a plasticizer, a surfactant, if necessary, as long as the physical properties are not impaired.
Various additives such as a coupling agent, an antioxidant, a heat stabilizer, an ultraviolet absorber, a colorant, a flame retardant, and an antistatic agent may be added, and an adhesive resin layer or the like is further provided between the layers. May be formed.

[0054]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. (Examples 1 and 2) Outer layer resin: 6-nylon (melting point 230 ° C. or less, MFR =
4 g / 10 min) Intermediate layer resin: low density polyethylene (density 0.927 g /
(cm ³ , MFR = 4 g / min) 100 parts by weight of sodium nitrite, urea, dicyclohexylammonium nitrite and diisopropylammonium nitrite, 3 parts by weight of a volatilizable rust inhibitor added to the inner layer resin:
Ethylene-vinyl acetate copolymer (vinyl acetate content 19
% By weight, density 0.940 g / cm ³ , MFR = 2.5 g
/ 10 min) The outer layer resin, the intermediate layer resin and the inner layer resin were co-extruded and extruded by an inflation method to obtain a stretch packaging film. The thickness of the obtained film for stretch packaging was 60 μm, and the thickness ratio of each layer was as shown in Table 1.

Examples 3 and 4 Outer layer resin: ethylene-vinyl alcohol copolymer (ethylene content: 40 mol%, MFR = 4 g / 10 min) Intermediate layer resin: low density polyethylene (density: 0.927 g /
(cm ³ , MFR = 4 g / 10 min) 100 parts by weight added with 3 parts by weight of a vaporizable rust inhibitor consisting of sodium nitrite, urea, dicyclohexyl ammonium nitrite and diisopropyl ammonium nitrite Inner layer resin: ethylene-acetic acid Vinyl copolymer (vinyl acetate content 19% by weight, density 0.940 g / cm ³ , MFR
= 2.5 g / 10 min) The outer layer resin, the intermediate layer resin and the inner layer resin were co-extruded and extruded by an inflation method to obtain a stretch packaging film. The thickness of the obtained film for stretch packaging was 60 μm, and the thickness ratio of each layer was as shown in Table 1.

(Comparative Example 1) A film for stretch packaging was obtained in the same manner as in Example 1 except that no volatile rust preventive agent was added to the intermediate layer. The thickness of the obtained film for stretch packaging was 60 μm, and the thickness ratio of each layer was as shown in Table 1.

(Comparative Example 2) A film for stretch packaging was obtained in the same manner as in Example 3 except that no volatile rust preventive agent was added to the intermediate layer. The thickness of the obtained film for stretch packaging was 60 μm, and the thickness ratio of each layer was as shown in Table 1.

(Comparative Example 3) Only the intermediate layer resin of Example 1 was extruded by an inflation method to obtain a single-layer stretch packaging film. The thickness of the obtained stretch packaging film was 60 μm.

(Examples 5 and 6) Outer layer resin: linear low-density polyethylene polymerized without using a metallocene catalyst (density 0.920 g / cm ³ , MF
R = 2.1 g / 10 min) Intermediate layer resin: low density polyethylene (density 0.927 g /
(cm ³ , MFR = 4 g / 10 min) 100 parts by weight of 3 parts by weight of a vaporizable rust inhibitor consisting of sodium nitrite, urea, dicyclohexylammonium nitrite and diisopropylammonium nitrite Inner layer resin: metallocene catalyst Linear low-density polyethylene (density 0.927 g / cm ³ , MFR
= 2 g / 10 min, Mw / Mn = 2.5) The above outer layer resin, intermediate layer resin and inner layer resin were coextruded and extruded by inflation to obtain a stretch packaging film. The thickness of the obtained film for stretch packaging was 60 μm, and the thickness ratio of each layer was as shown in Table 2.

Comparative Example 4 An ethylene-vinyl acetate copolymer (vinyl acetate content: 19% by weight, density: 0.940 g / cm ³ , MFR = 2.5 g / 10 min) was used as the inner layer resin. In the same manner as in Example 5, a film for stretch packaging was obtained. The thickness of the obtained film for stretch packaging was 60 μm, and the thickness ratio of each layer was as shown in Table 2.

Comparative Example 5 A stretch wrapping film was obtained in the same manner as in Example 5, except that no volatile rust inhibitor was added to the intermediate layer. The thickness of the obtained film for stretch packaging was 60 μm, and the thickness ratio of each layer was as shown in Table 2.

(Comparative Example 6) Only the intermediate layer resin of Example 5 was extruded by an inflation method to obtain a single-layer stretch packaging film. The thickness of the obtained stretch packaging film was 60 μm.

Example 7 Outer layer resin: linear low-density polyethylene (density 0.915)
g / cm ³ , MFR = 1.4 g / 10 minutes) Intermediate layer resin: Polypropylene resin (trade name “CATAROY”, manufactured by Montelusk-Key Corporation; weight-average molecular weight 28)
The resin elution amount by cross fractionation chromatography is 0
49% by weight below 0.degree. C., 40.1% by weight above 0 to 90.degree. C. and 15% by weight or less in any 5.degree. .880 g / cm ³ , MFR = 0.8 g / 10 min) 1
00 parts by weight to which 3 parts by weight of a vaporizable rust inhibitor consisting of sodium nitrite, urea, dicyclohexylammonium nitrite and diisopropylammonium nitrite are added. Inner layer resin: ethylene-vinyl acetate copolymer (vinyl acetate content 19 Weight%, density 0.940g / cm ³ , MFR
= 2.5 g / 10 minutes) The outer layer resin, the intermediate layer resin, and the inner layer resin were co-extruded and extruded by an inflation method to obtain a stretch packaging film. The thickness of the obtained film for stretch packaging was 60 μm, and the thickness ratio of each layer was as shown in Table 2.

(Comparative Example 7) Linear low density polyethylene (density 0.915 g / cm ³ , MFR =
(1.4 g / 10 minutes), and a film for stretch packaging was obtained in the same manner as in Example 7. The thickness of the obtained film for stretch packaging was 60 μm, and the thickness ratio of each layer was as shown in Table 2.

Comparative Example 8 Except that an ethylene-vinyl acetate copolymer (vinyl acetate content: 19% by weight, density: 0.940 g / cm ³ , MFR = 2.5 g / 10 min) was used as the outer layer resin. In the same manner as in Example 7, a film for stretch packaging was obtained. The thickness of the obtained film for stretch packaging was 60 μm, and the thickness ratio of each layer was as shown in Table 2.

(Comparative Example 9) A stretch packaging film was obtained in the same manner as in Example 7, except that the intermediate layer was not mixed with a vaporizable rust inhibitor. The thickness of the obtained film for stretch packaging was 60 μm, and the thickness ratio of each layer was as shown in Table 2.

The films for stretch packaging obtained in the above Examples and Comparative Examples were evaluated as follows, and the results are shown in Table 1.
And 2. (1) Transparency: Haze was measured according to JIS K 7105. (2) Adhesive strength: The outer layer side and the inner layer side of the stretch packaging film are overlapped, and a load of 40 kg is evenly applied to an area of 150 mm × 200 mm and left at a temperature of 23 ° C. for 24 hours. It was measured. (3) Rust prevention: A bag having a size of 60 mm × 90 mm was prepared such that the inner layer of the film for stretch packaging was on the inside. Next, after polishing with a # 400 sandpaper, the steel (1.0 mm thick ×
(Width 30 mm x length 50 mm) into the bag.
1 ml of a 1% by weight saline solution was injected, the bag opening was heat-sealed, and the bag was left at a temperature of 20 ° C. for 24 hours. The state of rust generation was observed. What occurred was represented by x.

For Examples 5 to 7 and Comparative Examples 4 to 9, the tear strength according to the Elmendorf tear strength test method specified in JIS K 718.9 and JIS K 71
The tensile strength at break specified in No. 27 was measured.

[0069]

[Table 1]

[0070]

[Table 2]

[0071]

As described above, the stretch packaging film of the present invention has excellent flexibility, strength and the like, as well as excellent transparency, rust prevention and adhesiveness. Therefore, it can be suitably used for stretch packaging of steel coils and the like.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 23/06 C08L 23/06 23/10 23/10 F term (Reference) 3E086 AB02 AD17 BA04 BA15 BB22 BB58 BB90 CA40 4F100 AK03A AK06A AK06B AK07B AK46A AK63A AK63B AK63C AK68C AK69A BA03 BA07 BA10A CA13H CA14B EH17 GB15 JA13B JK08 JL01 JN01 YY00B 4J002 BB031 BB121 EG141 DF0206 EG141

Claims (5)

[Claims] 1. A stretch packaging film having at least a three-layer structure of an outer layer, an intermediate layer and an inner layer, wherein the outer layer is made of a polyamide resin and the intermediate layer has a density of 0.920.
0.935 g / cm ³ of low density polyethylene and / or
Alternatively, a film for stretch packaging, comprising a linear low-density polyethylene mixed with a vaporizable rust inhibitor, and an inner layer comprising an ethylene-vinyl acetate copolymer. 2. A stretch packaging film having at least a three-layer structure of an outer layer, an intermediate layer and an inner layer, wherein the outer layer is made of an ethylene-vinyl alcohol copolymer and the intermediate layer has a density of 0.920 to 0.935 g / cm ³ of low-density polyethylene and / or linear low-density polyethylene,
A stretch packaging film comprising a vaporizable rust inhibitor and an inner layer comprising an ethylene-vinyl acetate copolymer. 3. A stretch packaging film having at least a three-layer structure of an outer layer, an intermediate layer, and an inner layer, wherein the outer layer is made of a polyolefin resin, and the intermediate layer has a density of 0.9.
A low-density polyethylene and / or linear low-density polyethylene of 20 to 0.935 g / cm ³ containing a volatilizable rust inhibitor and having an inner layer having a single polymerization active site using a metallocene catalyst. Polymerized, molecular weight distribution Mw / Mn
(Mw; weight average molecular weight, Mn; number average molecular weight) is 1.
A stretch packaging film comprising a linear low-density polyethylene having a density of 5 to 3.0. 4. A stretch packaging film having at least a three-layer structure of an outer layer, an intermediate layer and an inner layer, wherein the outer layer has a density of 0.895 to 0.925 g / cm ³ and has a low density polyethylene and / or linear shape. The low-density polyethylene, the intermediate layer has a weight average molecular weight of 80,000 to 500,000, and the elution amount measured by the cross fractionation chromatography is 0%.
30 to 60% by weight below 0 ° C, and 30 to 90 ° C
-55% by weight and not more than 15% by weight in an optional 5 ° C range in this temperature range, and
A stretch packaging film comprising a polypropylene resin having a weight of 20 and a vaporizable rust inhibitor, and an inner layer comprising an ethylene-vinyl acetate copolymer. 5. The method according to claim 1, wherein the volatile rust inhibitor is at least one selected from the group consisting of nitrites, ammonium compounds and urea compounds.
The stretch packaging film according to any one of claims 1 to 4, wherein the film comprises a seed.