JPH0929908A - Wrapping film - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a packaging film excellent in stretchability, cutability, adhesiveness, transparency, heat resistance, water vapor barrier property, odor barrier property, non-heat shrinkability and food safety. With the goal. SOLUTION: A laminate of at least three layers in which both surface layers are made of a polypropylene resin and an intermediate layer is made of a polyamide resin containing an aromatic polyamide resin is coextrusion-molded, and then rapidly cooled to obtain a raw film. It is a biaxially stretched film obtained by stretching the film, and the thickness of the entire film is 40 μm.
The film for packaging as described below, wherein the thickness of the intermediate layer is 10 to 80% of the thickness of the entire film.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a packaging film used for food packaging and the like. Specifically, the present invention is a stretched laminated film suitable for a packaging film excellent in stretchability, cuttability, adhesiveness, transparency, heat resistance, water vapor barrier property, odor barrier property, non-heat shrinkability, and food safety. Regarding

[0002]

2. Description of the Related Art Heretofore, as a wrapping film used for packaging foods, a film containing polyvinylidene chloride, polyethylene or polyvinyl chloride as a main raw material has been known.

[0003]

However, the polyvinylidene chloride-based film has a disadvantage that it shrinks greatly when heated, and the polyethylene-based film is in contact with oily substances (for example, meat and tempura) and has high heat. In the case of the above, there is a drawback that the film is melted and holes are formed, and the polyvinyl chloride film has a problem that when it comes into contact with boiling hot water, a whitening phenomenon occurs and the contents cannot be seen.

On the other hand, an aliphatic polyamide resin is known as a resin having heat resistance as a packaging film.
Although the aliphatic polyamide resin has excellent heat resistance and mechanical strength, it is difficult to maintain its original physical properties because it has high hygroscopicity. Especially nylon-6 and nylon-6
Copolymerized nylon such as / 6,6, nylon-6 / 6,10, etc. is used for food packaging from the viewpoint of food safety because the monomer component ε-caprolactam bleeds on the film surface. It is restricted.

The film for wrapping is usually stored in a case such as a paper tube, and the film is taken up by a cutting blade called "saw blade" attached to this case and cut into an appropriate length. To use. As the "saw blade" used to cut the film, generally, a simple blade made by punching a 0.2 mm thick iron plate into a saw shape is used, and also supports this "saw blade". Also for the case, a paper box made of coated cardboard with a weight of about 350 to 700 g / m ² is used, and its rigidity is extremely low.

This type of film is required to be easily cut according to the intention of the user even by such a simple cutting mechanism, but in reality, the case and the "saw blade" are deformed. In addition to deformation, the film may be deformed or cutting may occur at a position outside the “saw blade”. More specifically, the conventional polyethylene-based film requires a considerable tensile force at the time of cutting, so that not only the case may be bent but also the film may be deformed.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to produce a packaging film in which the above-mentioned problems of conventional wrapping films have been solved. As a result, a polyamide containing an aromatic polyamide resin has been obtained. By biaxially stretching the polypropylene resin laminated on both sides of the resin by a specific co-extrusion method, the above problems are solved and the original properties (heat resistance and mechanical strength) of the polyamide resin are impaired. The present invention has been accomplished by finding that a packaging film excellent in cuttability, transparency, heat resistance, water vapor barrier property, odor barrier property, non-heat shrinkage property, and food safety can be obtained without any problems.

That is, the gist of the present invention is to co-extrude a laminate of at least three layers in which both surface layers are made of polypropylene resin and the intermediate layer is made of a polyamide resin containing an aromatic polyamide resin, and then rapidly cooled to obtain a raw film. And a biaxially stretched film obtained by stretching the raw film, wherein the thickness of the entire film is 40 μm or less, and the thickness of the intermediate layer made of a polyamide resin is 10 to 80% of the thickness of the entire film.
It exists in the film for packaging characterized by being the range of.

The packaging film of the present invention has a layered structure of at least three layers. The type of polypropylene resin that constitutes the surface layer of the packaging film is not particularly limited, and may be a propylene homopolymer or a copolymer of ethylene and propylene. Examples of the propylene homopolymer include isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene.

Further, the copolymer of propylene and other components such as ethylene may be either a random copolymer or a block copolymer. The physical properties of this polypropylene resin may be selected according to various uses, conditions, etc.
Usually, melt flow rate (MFR) 0.5 to 10 g /
A material having a density of 0.89 to 0.91 g / cm ² for 10 minutes is suitable. The melt flow rate is measured according to JIS K6758 at 230 ° C. under a load of 2.16 kg.

By adding the following additives to the above-mentioned polypropylene resin, excellent performance as a wrap film can be obtained. Polypropylene resin 100
3 to 40 parts by weight of (A) polybutene or polyisobutylene, 0.2 to 10 parts by weight of the (B) antifogging agent, and 0.1 to 10 parts by weight of the (C) adhesive are contained with respect to parts by weight. Composition.

The component (A), polybutene or polyisobutylene, acts as a thickener and imparts excellent tackiness to the film. The compounding amount of this polybutene or polyisobutylene is 3 to 40 parts by weight, preferably 10 to 25 parts by weight, based on 100 parts by weight of the polypropylene resin. If the compounding amount is less than 3 parts by weight, sufficient tackiness is not exhibited, and conversely, if it exceeds 40 parts by weight, a large amount of bleeding causes tackiness and heat resistance is deteriorated, which is not preferable. Incidentally, the physical properties of the polybutene or polyisobutylene used here can be appropriately determined depending on the blending amount, the type of other components, the intended use of the composition, etc., but is not particularly limited, but is usually a number average molecular weight. 200-5
000, preferably 400 to 4000, more preferably 500 to 2000.

The anti-fogging agent (B) is for imparting anti-fogging property, and even if it is usually sold as an antistatic agent or the like as long as it has an anti-fogging effect, It can be said to be an antifogging agent of the invention. The antifogging agent (B) increases the tackiness of the film when used in combination with polybutene or polyisobutylene. It also has the effect of making it less likely to become cloudy even if vapor adheres.

Of the (B) antifogging agents, specifically, the valence is 3
Fatty acid esters formed from -20 polyhydric alcohols are preferred. Fatty acid ester formed from polyhydric alcohol is at least 1 of the hydroxyl groups of polyhydric alcohol.
Each is a compound obtained by esterifying a fatty acid such as a higher fatty acid having 8 to 22 carbon atoms. Here are some of the polyhydric alcohols:
Also included are condensation polymers of glycerin. The glycerin condensation polymer is a condensation polymer having a polymerization degree of usually 2 to 10, preferably 2 to 6. Among the hydroxyl groups of the glycerin condensation polymer, the number of esterified hydroxyl groups is 1 or more, preferably 1 or more and 70% or less of the number of hydroxyl groups, more preferably 1 or more and 60% of the number of hydroxyl groups. It is the following. The higher fatty acid may be saturated or unsaturated as long as it is a fatty acid having 8 to 22 carbon atoms, and is usually preferably a fatty acid having 10 to 18 carbon atoms.

Examples of the fatty acid ester formed from a polyhydric alcohol include monoglycerin oleate, glycerin triricinoleate, glycerin acetylricinoleate, pentaerythritol, sorbitan oleate, sorbitan laurate, polyethylene glycol sorbitan oleate, polyethylene glycol sorbitan laurate. Examples thereof include rate, diglycerin monolaurate, diglycerin monovalmitate, diglycerin monooleate, diglycerin monostearate, diglycerin dioleate and triglycerin monooleate.

Particularly preferred are diglycerin monolaurate and diglycerin monooleate. Of course, two or more kinds of fatty acid esters formed from these polyhydric alcohols may be used in combination. The amount of the fatty acid ester formed from this polyhydric alcohol is 0.2 to 10 parts by weight, preferably 1 to 6 parts by weight, based on 100 parts by weight of the polypropylene resin. If the blending amount is less than 0.2 parts by weight, (A)
A synergistic effect with the component polybutene or polyisobutylene does not occur. On the contrary, when it exceeds 10 parts by weight, a large amount of bleeding causes stickiness and odor, and gelling occurs frequently, which is not preferable.

The release agent (C) improves the unwinding property of the film of the wound material, and is preferably a hybrid having an acyl group having 2 to 6 carbon atoms and an acyl group having 8 to 22 carbon atoms. It is a glyceride. The mixed glyceride means that one of the three hydroxyl groups of glycerin is a lower fatty acid having 2 to 6 carbon atoms and the other one is esterified with a higher fatty acid having 8 to 22 carbon atoms. Still another one is a diacyl compound or a triacyl compound which remains a hydroxyl group or is esterified with a lower fatty acid having 2 to 6 carbon atoms or a higher fatty acid having 8 to 22 carbon atoms. The acyl groups of the triacyl compound may of course all be different. The higher fatty acid may be saturated or unsaturated as long as it has 8 to 22 carbon atoms, and usually has 10 to 1 carbon atoms.
8 fatty acids are preferred. The lower fatty acid may be any one having 2 to 6 carbon atoms.

Specific examples of the mixed glyceride include, for example, diacetyl monolauryl glycerin, diacetyl monopalmityl glycerin, diacetyl monooleyl glycerin, monoacetyl dilauryl glycerin, monoacetyl monopalmityl glycerin, monoacetyl dioleyl glycerin, monoacetyl monoglycerin. Lauryl glycerin, monoacetyl monooleyl glycerin, dipropionyl monolauryl glycerin, dicaproyl monolauryl glycerin, dicaproyl monopalmityl glycerin, monoacetyl monocapryl glycerin, monoacetyl monobrassyl glycerin, monopropionyl monobrassyl glycerin, Mention may be made of monoacetyl monoerucyl glycerin and the like. Particularly, diacetyl monolauryl glycerin and diacetyl monooleyl glycerin are preferable.

Of course, two or more kinds of these mixed glycerides may be used in combination. The film formed from the polypropylene-based resin composition containing the release agent (C) has good adhesiveness and can easily adhere to an object without pressure bonding. At the same time, the peeling property between the films is also improved, and the film can be easily fed out during use. The transparency is also improved.

The compounding amount of the (C) release agent of the present invention is 0.1 to 10 parts by weight, preferably 1.0 to 5.0 parts by weight, based on 100 parts by weight of the polypropylene resin. If the blending amount is less than 0.1 parts by weight, the effect of imparting tackiness or improving the peeling property is not sufficient, and conversely if it exceeds 10 parts by weight, the resulting film becomes sticky or significantly slips, and the workability is deteriorated. Becomes

On the other hand, as the polyamide resin constituting the intermediate layer of the packaging film of the present invention, one containing an aromatic polyamide resin is used. The aromatic polyamide resin preferably contains at least 2% by weight or more, and an aliphatic polyamide resin is used as the resin mixed with the aromatic polyamide resin.

The aromatic polyamide resin of the present invention is a polyamide having an aromatic ring, for example, an aromatic polyamide containing an aliphatic diamine unit and an aromatic dicarboxylic acid unit,
Aromatic polyamide comprising an aromatic diamine unit and an aliphatic dicarboxylic acid unit, or a copolyamide comprising these aromatic polyamide constituent units and a lactam or an aliphatic polyamide constituent unit comprising an aliphatic diamine unit and an aliphatic dicarboxylic acid unit Is mentioned.

In the case of copolyamide, the aromatic polyamide constituent unit must be contained in an amount of 10% by weight or more. If this amount is less than 10% by weight, the transparency of the film may be lost. When a film having a high gas barrier property is required, it is preferable that the aromatic polyamide constituent unit is contained in an amount of 85% by weight or more.

Specific examples of the monomers constituting the aromatic polyamide resin include, for example, o as the aromatic diamine unit.
, M- or p-xylylenediamine and the like, the aromatic dicarboxylic acid units include terephthalic acid, isophthalic acid,
And their methyl esters, ethyl esters, halides and the like, and these can be used as a mixture of two kinds. Examples of the aliphatic diamine unit include linear aliphatic diamines such as ethylenediamine, tetramethylenediamine, hexamethylenediamine, octamethylenediamine and decamethylenediamine. Examples of the lactam include caprolactam and lauryllactam, and examples of the aliphatic dicarboxylic acid include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and their methyl esters. , Ethyl ester, and derivatives such as halides.

The method for producing the aromatic polyamide resin is not particularly limited, and it is necessary to use a method conventionally used in the production of polyamide resins, for example, a nylon salt usually composed of a diamine unit and a dicarboxylic acid unit or an aqueous solution thereof. It is produced by a so-called melt polymerization method by adding lactam accordingly, but it can also be produced by a solution polymerization method or an interfacial polymerization method depending on the composition of the isophthalic acid unit and the terephthalic acid unit.

Of the aromatic polyamide resins, preferably
(A) A polymer comprising an aromatic polyamide constitutional unit comprising an aliphatic diamine unit and an isophthalic acid unit and / or a terephthalic acid unit, or (a) an aromatic polyamide constitutional unit and (b) a lactam or an aliphatic diamine unit. And a copolyamide composed of an aliphatic polyamide constituent unit composed of an aliphatic dicarboxylic acid unit.

The composition of the isophthalic acid unit and the terephthalic acid unit is not particularly limited and may be any ratio. However, when the ratio of the aliphatic polyamide structural unit in the aromatic polyamide resin is small, the ratio of the terephthalic acid unit is small. The melting point of the obtained polyamide resin is 300 ° C
As described above, since it becomes difficult to laminate with an acid-modified polyolefin, it is desirable that the terephthalic acid unit is 50% by weight or less. Usually, the isophthalic acid unit and the terephthalic acid unit are used in a weight ratio of 20:80 to 80:20. This aromatic polyamide resin may be used alone or in combination of two or more kinds.

As the aliphatic polyamide resin mixed with the aromatic polyamide resin of the polyamide resin containing the aromatic polyamide resin of the present invention, one having a relative viscosity of about 1 to 6 is usually used. Specifically, for example, hexamethylenediamine, decamethylenediamine, dodecamethylenediamine, trimethylhexamethylenediamine, 1,
Aliphatic such as 3- or 1,4-bis (aminomethyl) cyclohexane, bis (p-aminocyclohexylmethane), alicyclic diamine and aliphatic such as adipic acid, suberic acid, sebacic acid, cyclohexanedicarboxylic acid, Obtained from polyamide obtained by polycondensation with alicyclic dicarboxylic acid, polyamide obtained by condensation of aminocarboxylic acid such as ε-aminocaproic acid and 11-aminoundecanoic acid, and lactam such as ε-caprolactam and ε-laurolactam Examples thereof include polyamides and copolyamides thereof. Specifically, nylon-6, nylon-66, nylon-610, nylon-9, nylon-11, nylon-12, nylon-6 / 66, nylon-66 / 610, nylon-6 / 11 and the like can be mentioned. .

From the viewpoint of moldability, the melting point is 170 to 280.
A temperature of 0 ° C., preferably 200 to 240 ° C. is suitable. In the present invention, nylon-6 and nylon-66 are particularly preferable. By using the polyamide resin containing the aromatic polyamide resin as described above, the stretchability and the gas barrier property are improved. That is, breakage during stretching is less likely to occur than in the case of using an aliphatic polyamide alone, and stable production is possible.

Specifically, when the area stretching ratio, which is represented by the product of the longitudinal stretching ratio and the transverse stretching ratio, is 15 times or more when the aliphatic polyamide resin is used alone, breakage during stretching is likely to occur and the production is not stable. . On the other hand, if it is less than 15 times, the polypropylene of the surface layer cannot be uniformly stretched, and stretching unevenness (streaks occur due to insufficient stretching). Aromatic polyamide resin is preferably 2% by weight or more,
Particularly preferably 2 to 60% by weight, and further preferably 4 to 4
By mixing 0% by weight, the stretchability is improved, and problems such as breakage are less likely to occur.

The excellent barrier properties of the aromatic polyamide resin itself also improve the barrier properties of the film. Particularly, the barrier property under high humidity is superior to that of the aliphatic polyamide resin alone. At least three layers are essential for the layer structure of the multilayer film of the present invention, but an adhesive layer may be set if necessary. The adhesive layer is set between the intermediate layer and the surface layer. As the resin composition forming the adhesive layer, an acid-modified polyolefin resin based on polyolefin resin is suitable.

The acid-modified polyolefin resin optionally used in the present invention can be obtained by graft-reacting polypropylene and / or polyethylene with an unsaturated carboxylic acid or its derivative by any method. In addition, elastomers such as polypropylene and / or
Alternatively, a composition mixed with polyethylene may be used.

For example, a method of reacting a polyolefin and an unsaturated carboxylic acid in a molten state (for example, Japanese Examined Patent Publication No.
3-27421), a method of reacting in a solution state (for example, Japanese Examined Patent Publication No. 44-15422), a method of reacting in a slurry state (for example, Japanese Examined Patent Publication No. 43-18144), a method of reacting in a gas phase state (for example, JP-A No. 50-77493
No.). Among these methods, the melt-kneading method using an extruder is preferable because it is simple in operation.

As the raw material of the acid-modified polyolefin resin, for example, homopolymers and copolymers of polypropylene and polyethylene are used. As the copolymer, a random or block copolymer of propylene and 1 to 5% by weight of ethylene, a random or block copolymer of ethylene and 1 to 10% by weight of propylene, a propylene or ethylene and 1 to 10% by weight of C4 or higher α
-Copolymers with olefins, mixtures thereof and the like are used. Among these, particularly, a homopolypropylene and a propylene-ethylene random copolymer having a melt flow rate of 0.5 to 30 g / 10 min, particularly 5 to 15 g / 10 min and a polyethylene having an MFI of 0.3 to 30 g / 10 min and An ethylene-α-olefin copolymer is preferably used.

The MFR as used herein is a value measured at 230 ° C. for polypropylene and 190 ° C. for polyethylene. The unsaturated carboxylic acids include, for example, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, and their acid anhydrides, esters, amides, imides, metal salts and the like. ,
Most preferably, maleic anhydride is used.

An organic peroxide is used to accelerate the reaction between the polyolefin and the unsaturated carboxylic acid.
Examples of the organic peroxide include benzoyl peroxide, lauroyl peroxide, azobisisobutyronitrile, dicumyl peroxide, α, α′-bis (t-butylperoxydiisopropyl) benzene,
2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, di-t-butylperoxide, Cumene hydroperoxide, t-butyl hydroperoxide and the like can be mentioned. The amount of the organic peroxide added is not particularly limited, but is usually 0.005 to 5 parts by weight, preferably 0.01 to 1 part by weight, based on 100 parts by weight of the polyolefin.

The acid-modified polyolefin resin grafted with unsaturated carboxylic acids is the polyolefin shown above,
Unsaturated carboxylic acids and organic peroxides are thoroughly mixed with a tumbler, a Henschel mixer, etc., and melt-kneaded at a temperature not lower than the melting point of the polyolefin, generally not lower than the melting point and not higher than 280 ° C. to carry out a grafting reaction. The method of melt-kneading is not particularly limited, and for example, a screw extruder, a Banbury mixer, a mixing roll or the like can be used, but a screw extruder is preferably used because of the ease of operation. The temperature and time of melt-kneading vary depending on the decomposition temperature of the organic peroxide used, but generally 160
~ 280 ° C for 0.3 to 30 minutes, preferably 170 to 2
A temperature of 50 ° C. for 1 to 10 minutes is suitable.

The graft amount of unsaturated carboxylic acids in the acid-modified polyolefin resin is 0.01 to 3% by weight, preferably 0.03 to 1% by weight. When the graft amount of unsaturated carboxylic acids is 0.01% by weight or less, the adhesiveness is lowered,
If it is 3% by weight or more, the gelled product tends to increase, which is not preferable.

In the present invention, the acid-modified polyolefin resin may be mixed with 100 parts by weight of the resin and up to 2000 parts by weight of an unmodified polyolefin resin. At this time, it is preferable to mix the unsaturated carboxylic acids in the mixture so that the graft amount of the unsaturated carboxylic acids falls within the above range. Examples of the unmodified polyolefin resin include polypropylene and polyethylene, which are raw materials of the acid-modified polyolefin resin described above.

To the acid-modified polyolefin composition of the present invention, additives such as heat stabilizers which are usually used are added in an amount of 0.0
You may contain about 005-30 weight%. By mixing the acid-modified polyolefin resin described above with the polypropylene resin for the surface layer, the adhesiveness between the intermediate layer and the surface layer can be obtained. As the layer structure, a layer having a function other than the adhesive layer may be provided. For example, it is a reproduction layer or the like that is obtained by crushing defective portions and the like generated during film forming.

The packaging film of the present invention comprises the above polypropylene resin and a polyamide resin containing an aromatic polyamide resin formed by a specific co-extrusion molding to form a layered structure of two kinds and three layers.
For example, it is formed by molding a multilayer film of [polypropylene resin / polyamide containing aromatic polyamide resin / polypropylene resin], and then biaxially stretching the film in the machine direction, the transverse direction, and both directions. The stretching may be performed in the longitudinal direction or the lateral direction first, or the longitudinal and lateral simultaneous stretching may be performed.

As the coextrusion molding, a T-die molding method or a water-cooled inflation molding method is adopted. That is, by rapidly cooling the melt-extruded resin by the above-mentioned molding method, a film having more excellent transparency and stretchability can be obtained as compared with the air-cooled inflation molding method which is usually used.

When the raw fabric is formed, the crystallinity can be suppressed to a low level by performing rapid cooling, which improves transparency and stretchability. The air-cooled inflation molding method has a small quenching effect, so that breakage occurs during stretching. In particular, in the case of the T-die molding method, the rapid cooling is liable to be broken at the time of stretching in the transverse direction. 5,
It may be cooled by bringing it into contact with cooling water having a temperature of 0 ° C. or lower, preferably 35 ° C. or lower.

The unstretched multilayer film obtained by the coextrusion molding is then stretched in the machine direction, the transverse direction and both directions. Biaxial stretching is preferably performed at a draw ratio of 2 to 6 times, particularly preferably 2.5 to 5 times. The draw ratio is 2
If it is less than twice, the cuttability of the film tends to be insufficient,
On the other hand, if it is more than 6 times, the stretchability tends to decrease, and there is a tendency that the film is broken or stretched unevenly. The longitudinal stretching treatment in the case of sequential biaxial stretching is performed by stretching the unstretched film as it is or by slitting it into a predetermined width and stretching the film in the take-up direction, that is, the longitudinal direction by changing the peripheral speed of the stretching roll. It is carried out by a method of causing the like. The preheating temperature in the stretching treatment is usually [melting point of polypropylene-based resin −20 ° C.] or less, preferably 40 to 12
It is preferred to carry out at 0 ° C.

On the other hand, the transverse stretching treatment is generally carried out in a facility called a tenter stretching machine. The preheating temperature is usually [melting point of polypropylene resin −10 ° C.] or lower,
It is preferable to carry out at 50 to 140 ° C. The heat setting temperature after stretching is higher than the preheating temperature, and it is preferable that the temperature is as high as possible in order to prevent wrinkles and non-heat shrinkage of the film, and usually 10 ° C. higher than the melting point of the polypropylene resin. A low temperature is used, and specifically, it is preferably carried out at 80 to 150 ° C.

When the preheating and heat setting temperatures are higher than the proper temperature, the film melts and adheres to the stretching rolls for longitudinal stretching, and when the preheating temperature is lower than the proper temperature, the polyamide resin is insufficiently preheated for stretching. And film breakage occurs, which is not desirable. In addition to the sequential biaxial stretching method described above, the simultaneous biaxial stretching method can be applied, and there are a tenter system and a tubular system, but the preheating temperature and the heat setting temperature are the same. By carrying out this stretching step,
The cuttability of the film is greatly improved, and it can be cut to a desired length with a light force using a saw blade.

The total thickness of the packaging film of the present invention is 40 μm or less, preferably 2 to 30 μm, more preferably 5 to 20 μm, and the thickness of the intermediate layer is 10 to 80% of the total thickness of the film. . If the total thickness of the film is larger than 40 μm, the tear strength at the time of cutting the film becomes too large, which is unsuitable for use as a wrap film.

If the thickness of the intermediate layer is less than 10% of the total thickness, the heat resistance and mechanical strength inherent to the polyamide resin cannot be exhibited. On the other hand, when it is more than 80%, the thickness of the polypropylene layer becomes thin, and it becomes difficult to uniformly cover the intermediate layer by coextrusion molding. The thickness of the intermediate layer is preferably 80% or less of the total thickness. In terms of practicality when used as a stretch film or wrap film, the adhesive strength is 0.40 kg / cm for shear peel strength.
A film having a peel strength of ² or more and a 180 ° peel strength of 4.0 g / 50 mm or less can be said to be a good film.

The packaging film of the present invention is used for various packaging applications such as food packaging. Further, it is preferably used as a wrap film by imparting self-adhesiveness to both surface layers by the method described above.

[0050]

EXAMPLES Hereinafter, specific embodiments of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples as long as the gist thereof is not exceeded.
The measurements in the examples were carried out by the following methods. (1) Moisture Permeability According to JIS Z0208, it was measured under the conditions of 40 ° C. and 90% RH.

(2) Transparency The transparency was measured using a transparency measuring instrument manufactured by Murakami Color Research Laboratory. Three kinds of measured values, MAX value, MIN value, and AVE value, are obtained, but the MAX value corresponding to the visual feeling is displayed. (3) Heat-resistant temperature A strip-shaped film having a width of 30 mm and a length of 14 cm, a piece of paper is placed 25 mm above and below the sample piece, and a 10 g weight is lowered. The maximum atmospheric temperature that could not be cut in one hour was measured in steps of 10 ° C.

(4) Heat Shrinkage A film having a diameter of 10 mm was made into a sample with a punching jig,
This is dipped in an aluminum pan containing silicone oil, and this aluminum pan is placed on a hot plate at 140 ° C. Although the temperature of the hot plate once drops because the aluminum pan draws heat, the sample is taken out 45 seconds after the temperature reaches 140 ° C. and the change in size is measured.

(5) Cutability US TESTING MACHINES INC. The easiness of tearing of the film was evaluated using a PPT tear tester (trade name) manufactured by the company. In this test, a weight with a constant load equipped with a needle was dropped from a certain height on a film sample, and the easiness of tearing was quantified by the length of the film torn. The tear length is measured by setting the sample so that the tear enters the lateral direction of the film. The larger the split length, the easier it is to cut with light force. It can be said that the sample has a good cutting property. Measurement conditions: load 30g, drop height 5
0 cm.

(6) Adhesive strength: Two films were lightly superposed, and the film was pressed three times with a linear pressure of 0.3 kg / cm by a roll having a diameter of 25 mm and a width of 150 mm. The force required for peeling the film by shearing and for peeling in the 180 ° C. direction was measured by an Instron type tensile tester.

Example 1 Using a 450 mm width three-kind five-layer coextrusion T-die molding machine, Table 1
The resin shown in 3 is simultaneously extruded from three extruders at a die temperature of 280 ° C., a chill roll temperature of 30 ° C., a take-up speed of 12 m /
A film was formed under the conditions of minutes, and three kinds of five-layer film (polypropylene resin / acid-modified polyolefin resin / polyamide resin / acid-modified polyolefin resin / polypropylene resin composition, thickness 120 μm, using the raw material resins shown in Table 1 were used. Layer ratios of 1: 1: 1: 1: 1) were molded. Then, the film was stretched by roll stretching 3 times in the machine direction at a preheating temperature of 50 ° C., then stretched 4 times in the transverse direction at a preheating temperature of 100 ° C. by a tenter stretching, and finally heat set at a heat setting temperature of 130 ° C. . The moisture permeability, transparency, heat resistant temperature, heat shrinkage ratio, cuttability, and adhesive strength of the obtained film were evaluated by the above-mentioned methods. Table 1 shows the results.

[0056]

[Table 1]

The raw material resins in Table 1 are as follows. Polypropylene resin (propylene-ethylene random copolymer): Mitsubishi Chemical Corporation, Mitsubishi Polypro 6500
J, MFR = 9g / 10min (230 ° C), ρ = 0.9g
/ Cm ³ (A) Polybutene: manufactured by Nippon Petrochemical Co., Ltd., Nisseki Polybutene LV-100, average molecular weight 500 (B) Antifogging agent = diglycerin monooleate: manufactured by Riken Vitamin Co., Ltd., Riquemal O-71- DE (C) Release agent = diacetylmonolauryl glyceride: Riken Vitamin Co., Ltd., Bohem G-002 Polyamide resin = Nylon-6: (Mitsubishi Engineering Plastics Co., Ltd., Novamid 1020) 80
Parts by weight and aromatic polyamide (hexamethylenediamine and isophthalic acid / terephthalic acid = 2/1 copolyamide): (Mitsubishi Engineering Plastics Co., Ltd.)
Made by Novamid X21) 20 parts by weight of a mixture.

Acid-modified polyolefin resin = acid-modified polypropylene resin: Mitsubishi Kagaku Co., Ltd., Modic AP19
6P, MFR = 2.7 g / 10 min (230 ° C.) Example 2 In Example 1, the layer ratio of the multilayer film was 3: 1: 2 :.
It carried out similarly except having set it to 1: 3. The results are shown in Table 2.

Example 3 The same procedure as in Example 1 was carried out except that the raw fabric molding was a water-cooled inflation molding with a cooling water temperature of 30 ° C. The results are shown in Table 2. The raw fabric molding conditions were a die diameter of 75 mmφ, a die temperature of 250 ° C., a blow-up ratio of 1.6, and a take-up speed of 10 m / min, and a film having a folding width of 190 mm and a thickness of 120 μm was molded.

Example 4 In Example 1, the raw fabric molding was water-cooled inflation molding with a cooling water temperature of 30 ° C., the stretching method was a tubular biaxial stretching method, the preheating temperature was 110 ° C., and the heat setting temperature was 130 ° C.
The same procedure was performed except that the temperature was set to ° C. The results are shown in Table 2. Example 5 The same procedure as in Example 1 was repeated except that the mixing ratio of the aliphatic polyamide resin and the aromatic polyamide resin was changed to 50% by weight: 50% by weight. The results are shown in Table 2.

Example 6 to Example 10 In Example 1 to Example 5, polybutene having an average molecular weight of 500 was replaced with 750 polybutene having an average molecular weight of 750 (manufactured by Nippon Petrochemical Co., Ltd., Nisseki Polybutene HV-35). The same procedure as in Examples 1 to 5 was performed. The results are shown in Table 2.

Examples 11 to 12 In Example 1, polybutene having an average molecular weight of 500 was replaced with polybutene having an average molecular weight of 750 (manufactured by Nippon Petrochemical Co., Ltd.,
In place of Nisseki Polybutene HV-35), the mixing ratio of the aliphatic polyamide resin and the aromatic polyamide resin was 95% by weight: 5% by weight (Example 11), 90% by weight: 10% by weight.
The same procedure as in Example 12 was repeated except that the procedure in Example 12 was changed. The results are shown in Table 2.

Comparative Examples 1 to 4 The same procedure as in Example 1 was repeated except that the film thickness, film layer ratio and stretch ratio shown in Table 2 were used. The results are shown in Table 2. Comparative Example 5 The same procedure as in Example 1 was carried out except that the air-cooling type inflation molding was used as the raw fabric molding. The results are shown in Table 2.
Shown in In addition, the original fabric forming condition is a die diameter of 100 mm.
φ, die temperature 250 ° C., blow-up ratio 1.6, take-up speed 13 m / min, folding width 250 mm, thickness 1
A 20 μm film was molded.

Comparative Example 6 The same procedure as in Example 1 was carried out except that the intermediate layer was made of only the aliphatic polyamide resin. The results are shown in Table 2. Comparative Example 7 Comparative Example 6 was performed in the same manner as in Comparative Example 6 except that the stretching ratio shown in Table 2 was used. The results are shown in Table 2.

[0065]

[Table 2]

From Table 2, when the intermediate layer is an aliphatic polyamide resin alone, stretching unevenness occurs when biaxially stretched, or
It can be seen that there is no stretching unevenness and stable production is difficult, because breakage occurs when the transverse stretching ratio is increased to eliminate stretching unevenness.

On the other hand, it can be seen from the examples that when the aromatic polyamide resin is used in combination, stable production is possible without uneven stretching. It is considered that this is because the aromatic polyamide resin suppresses the crystallization of the aliphatic polyamide resin, the stretching is improved accordingly, and the polypropylene resin on the surface is also uniformly stretched in synchronization with the intermediate layer.

[0068]

INDUSTRIAL APPLICABILITY The packaging film of the present invention is excellent in stretchability, cuttability, transparency, heat resistance, water vapor barrier property, odor barrier property and non-heat shrinkage property, and is made of nylon-6 and its copolymerized nylon. Since the bleeding of ε-caprolactam, which is a raw material monomer, on the film surface is suppressed by laminating a polypropylene resin, it is also excellent in food safety.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinji Kawasaki 3-10-10 Shiodotsu, Kurashiki-shi, Okayama Mitsubishi Chemical Corporation Mizushima Development Laboratory

Claims (11)

[Claims] 1. A co-extrusion molding of a laminate of at least three layers, wherein both surface layers are made of polypropylene resin and the intermediate layer is made of a polyamide resin containing an aromatic polyamide resin, and the mixture is rapidly cooled to form a raw film. It is a biaxially stretched film obtained by stretching an anti-film, and the total thickness of the film is 40 μm.
The film for packaging as described below, wherein the thickness of the intermediate layer is 10 to 80% of the thickness of the entire film. 2. The packaging film according to claim 1, wherein the biaxially stretched film is stretched 2 to 6 times in the machine direction and the transverse direction, respectively. 3. The packaging film according to claim 1, wherein the intermediate layer contains at least 2% by weight of an aromatic polyamide resin. 4. The packaging film according to claim 1, wherein the intermediate layer contains 2 to 60% by weight of an aromatic polyamide resin. 5. The packaging film according to claim 1, wherein the intermediate layer contains 4 to 40% by weight of an aromatic polyamide resin. 6. A polymer in which the aromatic polyamide resin comprises (a) an aliphatic diamine unit and an isophthalic acid unit and / or a terephthalic acid unit, or (a) an aromatic polyamide constituent unit and (b) a lactam or a fat. A packaging film according to any one of claims 1 to 5, which is a copolyamide comprising a group polyamide constitutional unit. 7. A polypropylene resin 100 having a surface layer.
3 to 40 parts by weight of (A) polybutene or polyisobutylene, 0.2 to 10 parts by weight of (B) antifogging agent, and 0.1 to 10 parts by weight of (C) release agent, based on parts by weight. The packaging film according to any one of claims 1 to 6. 8. The polypropylene-based resin is a propylene-ethylene-based copolymer, which is characterized in that
The packaging film according to claim 7. 9. The packaging film according to claim 1, wherein the (B) antifogging agent is a fatty acid ester formed from a polyhydric alcohol having a valence of 3 to 20. 10. The package according to claim 1, wherein (C) the release agent is a mixed glyceride having an acyl group having 2 to 6 carbon atoms and an acyl group having 8 to 22 carbon atoms. Film. 11. The layer structure is 5 layers of polypropylene resin / acid-modified polyolefin resin / polyamide resin containing aromatic polyamide resin / acid-modified polyolefin resin / polypropylene resin.
~ The packaging film according to claim 10.