JP2774956B2 - Heat shrinkable film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially stretched heat-shrinkable film having at least one layer comprising a resin composition comprising a thermoplastic polyester resin, a polyester elastomer and a vinylidene chloride resin (hereinafter referred to as PVDC). .

[0002]

2. Description of the Related Art Shrink wrapping is generally the simplest method for packaging irregular and irregular foods such as fatty foods such as raw meat and processed meat products. Since these food packages require a long storage period, they have excellent oxygen gas barrier properties [200 cc / m ² · day at 30 ° C and 100% RH.
not more than atm], as well as excellent cold resistance.

[0003] PVDC films are widely used because of their excellent properties such as oxygen gas barrier properties, oil resistance and ligation properties, as well as shrinkage properties. However, ordinary PVDC may have insufficient strength under severe conditions such as the packaging of heavy objects, particularly strength at low temperatures (cold resistance), and packaging materials free of these drawbacks are desired.

[0004] US Pat. No. 4,725,651 discloses a resin composition comprising a polyester copolymer resin comprising terephthalic acid, ethylene glycol and cyclohexanedimethanol and PVDC, and the resulting molded product has an oxygen gas barrier property. It shows that the mechanical strength is excellent.

[0005] However, the above-mentioned mixed resin composition of PVDC and polyester is still not satisfactory in cold resistance.

Attempts have been made to obtain a heat-shrinkable film having good oxygen gas barrier properties and cold resistance by laminating another resin with PVDC as an oxygen gas barrier layer.
For example, an intermediate layer of PVDC containing very little or almost no additives such as plasticizers and stabilizers, and an ethylene-vinyl acetate copolymer having excellent cold resistance and adhesion to PVDC as a pair of outer layers on both sides thereof ( A three-layer film has been proposed in which the EVA) layer is co-extruded into three layers to improve cold resistance (Canada Patent No. 982923).

On the other hand, a heat-shrinkable laminated film comprising PVDC as one layer has not only an oxygen gas barrier property, a high degree of cold resistance but also melt-hole resistance, heat-resistant sealability (heat resistance of a seal portion), and transparency even after shrinkage. A film having a high function of not losing is also required especially for packaging of fatty foods such as processed meat and cheese. That is, in the heat-shrinkable film, when packaging and sterilizing fatty foods, the film softened by oil and heat is thinly stretched and torn (melt hole), due to the heat shrinkage stress generated when sterilizing, the sealing portion or It is often recognized that a tearing problem occurs in the vicinity. Therefore, not only oxygen gas barrier properties but also melt-hole resistance, and has sufficient cold resistance without pinholes or the like during heat-resistant sealing and low-temperature distribution,
There is a demand in the industry for a heat-shrinkable film having excellent transparency even after shrinkage.

As such a heat-shrinkable laminated film, a film in which the outer layer is cross-linked by an electron beam is used. For example, (1) the first layer containing an organic polymer, and (2) the oxygen permeability of the laminate (3) a PVDC-based oxygen gas barrier layer having a low oxygen permeability no greater than 70 cc / m ² · day · atm (measured according to ASTM standard D1434 at 22.8 ° C. and 0% relative humidity); In a flexible laminate suitable for use in heat shrink wraps containing an organic polymer resistant to overuse, layer 1 contains 5-20% by weight of ethylene containing units derived from vinyl acetate and It contains an oriented copolymer of vinyl acetate, and the polymer is crosslinked by irradiation, and the oxygen gas barrier layer 2 has a weight of 70 to 70%.
30 to 30% by weight and units derived from 85% vinylidene chloride
Layer 3 containing 15% of units derived from vinyl chloride and layer 3 comprising (i) a copolymer of ethylene and vinyl acetate having 5 to 20% by weight of units derived from vinyl acetate or (ii) an isotactic Laminates comprising a blend of tic polypropylene, atactic polypropylene and polybutene-1 (JP-B-58-43024) are known.

A base film layer comprising an alpha-monoolefin polymer crosslinked by irradiation.
(1) and a film layer (2) comprising a polymer crosslinkable by irradiation, irradiating the entire layer laminate of the film laminate to crosslink the polymer of the film (2) and to form a base film layer. A method for improving the delamination resistance of a stretched film laminate by further crosslinking the polymer of (1) (Japanese Patent Publication No. 61-4785).
9) or a primal or subprimal meat fillet, wherein the multilayer film contains an oxygen gas barrier layer containing a vinylidene chloride-methyl acrylate copolymer and the multilayer film has been irradiated to a dose level of about 1 to about 5 megarads. And heat-shrinkable biaxially stretched multilayer film suitable for packaging processed meat (Japanese Patent Laid-Open No. 3948/1987), and first and second layers of a composition composed of a major proportion of an ethylene / vinyl acetate copolymer And disposed between the first and second layers, the PV
Each of the compositions composed of DC was cross-linked in an amount corresponding to electron beam irradiation of 1.5 Mrad or more, and was a molecularly oriented multilayer polymer film (JP-A-62-23).
752) has been proposed.

[0010]

However, when used as a single-layer heat-shrinkable film having oxygen gas barrier properties and cold resistance, the resin composition of U.S. Pat. No. 4,725,651 has a glass transition temperature of the polyester copolymer. , The pinhole resistance at low temperatures employed in the food distribution stage is poor. In addition, there is a disadvantage that the resin is severely decomposed during extrusion molding and productivity is low. As a heat-shrinkable laminated film requiring a high-level function, for example, EVA
The / PVDC / EVA constituent film is a laminated film that can be heat-sealed, has good cold resistance, and is excellent in oxygen gas barrier properties.
Poor melt hole resistance and heat sealing.

Further, in order to impart heat shrinkage to a laminate comprising a pair of polyolefins present on both sides of the PVDC layer, the laminate is generally stretched at a temperature not lower than the crystal melting point of the polyolefin by 40 ° C. or more. , The PVDC layer cannot be given a sufficient stretching orientation effect, and the thermal shrinkage of the PVDC layer is poor.
The DC layer is left out of the shrinkage behavior and bends, which tends to significantly impair the transparency of the laminate after shrinkage.

Accordingly, in the field of food packaging, there is provided a heat-shrinkable film having not only oxygen gas barrier properties and high cold resistance, but also excellent melt hole resistance and heat-resistant sealability, and excellent transparency even after shrinkage. Coveted.

An object of the present invention is to provide a heat-shrinkable film having excellent oxygen gas barrier properties and cold resistance by using a specific resin composition. Furthermore, even if it is irradiated with an electron beam, it has a layer made of this resin composition, no coloring due to decomposition, no deterioration of oxygen gas barrier property due to pinholes at low temperature is observed, and the transparency after shrinkage is further improved. It is an object to provide a heat-shrinkable laminated film.

[0014]

The resin composition of the present invention used for attaining the above-mentioned object contains 26 to 70% by weight of a thermoplastic polyester resin and 10 to 10% of a polyester elastomer.
A heat-shrinkable film having cold resistance and oxygen gas barrier properties by a biaxially stretched heat-shrinkable film having at least one layer made of the resin composition, comprising 30% by weight and 20 to 44% by weight of PVDC. Can be obtained.

An intermediate layer which is an oxygen gas barrier layer comprising the above ternary mixed resin, an outer layer of polyamide or crosslinkable polyolefin, an inner layer of the same or different crosslinkable polyolefin from the outer layer, and a low crosslinkable polyolefin. Oxygen gas barrier biaxial with a laminate comprising the innermost layer which is a heat seal layer, wherein at least the outer layer, the inner layer and the heat seal layer are cross-linked by electron beam irradiation and the heat shrinkage at 90 ° C. is 15% or more. The purpose can be achieved by a stretched heat-shrinkable film.

The resin composition used in the present invention comprises 26 to 70% by weight of a thermoplastic polyester resin, preferably 36 to 65% by weight.
And polyester elastomer 10 to 30% by weight, preferably 10
-20% by weight and PVDC 20-44% by weight, preferably 25-44% by weight.

As the thermoplastic polyester resin, terephthalic acid, isophthalic acid, orthophthalic acid, adipic acid, sebacic acid, fumaric acid, maleic acid, trimellitic acid, succinic acid, benzenedicarboxylic acid, dodecanedicarboxylic acid are used as dibasic acid components. Acid, naphthalenedicarboxylic acid,
Examples thereof include diphenyldicarboxylic acid, 2,2-bis (4-carboxyphenyl) propane, bis (4-carboxyphenyl) methane, and cyclohexanedicarboxylic acid, and their dialkyl esters (alkyl having a carbon number of C ₁ -C _{1) 4} ) Can be used.

The dialcohol component is preferably a linear dialcohol, for example, ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, hexanediol, cyclohexanediol, diethylene glycol, triethylene glycol, or the like.
Examples include tetraethylene glycol and polyethylene glycol.

In these thermoplastic polyester resins, the dibasic acid component is a mixture of terephthalic acid and isophthalic acid, and the dialcohol component is a polyester resin as described above, and 0.5 g / 100 ml of trifluoroacetic acid is used. The one having an intrinsic viscosity (IV value) of 0.5 to 0.7 dl / g at a temperature of 30 ° C. is preferably used.
The proportion of terephthalic acid and isophthalic acid is preferably a mixture of 55 mol% to 90 mol% of terephthalic acid and 45 mol% to 10 mol% of isophthalic acid.

More preferably, it is a polyester resin formed from a mixed dibasic acid component composed of terephthalic acid and isophthalic acid and a mixed dialcohol component composed of ethylene glycol and diethylene glycol, wherein the proportion of ethylene glycol and diethylene glycol is 60 to 98 mol%. And 2 to 40 mol% are particularly preferred.

The polyester resin used in the present invention is PVD
C is preferably incompatible with C, and a preferred example thereof is PIFG-40 manufactured by Kanebo Co., Ltd., which has a glass transition temperature of 68 ° C. and a terephthalic acid-isophthalic acid-ethylene glycol-diethylene glycol copolymer. It is a polymer resin.

When the polyester resin content exceeds 70% by weight,
Since the cold-resistant strength becomes unsatisfactory because the proportion of the polyester elastomer is small, the polyester component does not form a matrix at 21% by weight or less. .

As the polyester elastomer, a polyester-polyether copolymer containing (a) dicarboxylic acid (b) lower glycol (c) higher glycol as a main component is preferably used.

(A) The component is an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, phthalic acid, p-oxybenzoic acid, m-oxybenzoic acid and naphthalenedicarboxylic acid;
Oxalic acid, adipic acid, succinic acid, sebacic acid, 1,4
Selected from aliphatic dicarboxylic acids such as -cyclohexanedicarboxylic acid and 1,3-cyclohexanedicarboxylic acid, and alicyclic dicarboxylic acids.

(B) Component is 1,4 butanediol,
It can be selected from aromatic, aliphatic and alicyclic glycols such as ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, p-xylylene glycol, cyclohexane glycol and cyclohexane dimethanol.

The component (c) includes polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and copolymer glycols thereof.
Preferably is of the order of C ₈ -C ₂₀ as ethylene segments.

Preferred examples of the polyester elastomer used in the present invention are terephthalic acid-isophthalic acid-1,4
Butanediol-polytetramethylylene glycol copolymer resin [for example, Hytrel # manufactured by Du Pont-Toray Co., Ltd.]
2501].

The polyester elastomer has the effect of imparting flexibility to the ternary mixed resin. If it is less than 10% by weight, it is difficult to exhibit cold resistance, and if it exceeds 30% by weight, it has optical transparency and oxygen gas. It is not preferable because the barrier property deteriorates. The weight average molecular weight of the polyester elastomer used in the present invention is about 0.5 × 10 ^{4 to} 3 × 10 ⁴ , preferably 0.8 × 10 ⁴ to 2.5 × 10 ⁴ .

Since these polyester elastomers are added in an appropriate amount, a mixture of PVDC, a polyester resin and a polyester elastomer can dramatically improve cold resistance without hindering transparency.

As PVDC, a copolymer containing vinylidene chloride as a main component and a monomer copolymerizable therewith is used, and the vinylidene chloride component is preferably 65 to 95% by weight. If the vinylidene chloride content is less than 65% by weight, it becomes rubbery at room temperature, loses crystallinity, extremely deteriorates oxygen gas barrier properties, is not practical, and if it exceeds 95% by weight, the melting point becomes too high, Decomposition becomes easy, and stable melt extrusion processing becomes difficult.

The monomer copolymerizable with the vinylidene chloride monomer includes, for example, vinyl chloride, acrylonitrile, acrylic acid, methacrylic acid, and an alkyl group having 1 to 18 carbon atoms.
Acrylic acid alkyl ester, alkyl group having 1 carbon atom
-18, one or two unsaturated monomers such as methacrylic acid alkyl ester, maleic anhydride, maleic acid, maleic acid alkyl ester, itaconic acid, itaconic acid alkyl ester, vinyl acetate, ethylene, propylene, isobutylene, butadiene, etc. Those selected from more than one species are used.

A plasticizer and a stabilizer can be added to the vinylidene chloride resin as required. The added amount of the plasticizer and the stabilizer is preferably 0.1 to 3% by weight based on the PVDC. If the amount of the plasticizer and the stabilizer is less than 0.1% by weight, no effect is observed. On the other hand, if the content is more than 3% by weight, the oxygen gas barrier property is lowered, and the object of the present invention is not satisfied.

As the stabilizer, a commercially available heat stabilizer is used, and an epoxy stabilizer is particularly preferred. Specific examples of epoxy stabilizers include epoxidized vegetable oils such as soybean oil, safflower oil, sunflower oil, linseed oil, cottonseed oil, sunflower oil, and epoxidized fatty acid monoesters represented by epoxidized octyl stearate. And alicyclic epoxides typified by epoxidized fatty acid diesters obtained by epoxidizing glycol esters of unsaturated fatty acids, and epoxy hexahydrophthalic acid diesters.

The resin composition comprising such a polyester, polyester elastomer and PVDC is melt-extruded by an extruder according to a conventional method, biaxially stretched or press molded by an inflation method or the like, T-die molded, and then biaxially stretched to form a barrier. A heat-shrinkable film having excellent heat resistance and cold resistance can be formed.

The heat shrinkage at 90 ° C. is preferably 15% or more. When used as a single-layer film, the thickness is 8 to
100 μm, preferably 10 to 60 μm is desirable.

In the present invention, a known biaxial stretching means can be used in the longitudinal direction,
By stretching in the transverse direction at a stretching ratio of 2 times or more, the PVDC becomes a flat multilayered state elongated in polyester resin and polyester elastomer (microlayer state), so that the oxygen gas barrier property is lower than that of the unstretched film. And excellent.

If PVDC is less than 20% by weight, oxygen gas barrier properties are poor, and if PVDC exceeds 44% by weight, coloration due to decomposition occurs when irradiated with an electron beam, which is not preferable.

Also, P such as polyester elastomer
Mixing only with a resin compatible with VDC cannot achieve a microlayer state, so that there is no effect of improving oxygen gas barrier properties during biaxial stretching.

The heat-shrinkable film comprising the resin composition of the present invention can be used as an oxygen gas barrier layer of a biaxially stretched heat-shrinkable laminated film. As such a heat-shrinkable laminated film, as an intermediate layer, an oxygen gas barrier layer comprising the resin composition of the present invention, an outer layer of a polyamide or a crosslinkable polyolefin, an inner layer of the same or different crosslinkable polyolefin from the outer layer, and low crosslinking It is preferable to use a laminate comprising a heat seal layer made of a conductive polyolefin, wherein at least the outer layer, the inner layer, and the heat seal layer are cross-linked by electron beam irradiation and have a heat shrinkage at 90 ° C. of 15% or more.

As the polyamide resin used as the outer layer, a polyamide resin having a crystal melting point of 210 ° C. or lower, preferably 180 ° C. or lower is used. The crystal melting point of the polyamide resin is A
It is measured based on STM-D648.

As such a polyamide resin, at least one of aliphatic (C ₄ -C ₁₂ ) polyamide, alicyclic polyamide and aromatic polyamide is used. Examples of the monomer constituting the polyamide include, for example, C ₆ -C ₁₂ carbon atoms.
Linear ω-aminocarboxylic acid and its lactam, adipic acid, sebacic acid, dodecanedicarboxylic acid, heptadecanedicarboxylic acid, hexamethylene diamine, isophthalic acid, bis- (4-aminocyclohexyl) -methane,
2,2-bis- (4'-aminocyclohexyl) -propane, terephthalic acid or its dimethyl ester,
1,6-diamino-2,2,4-trimethylhexane,
Preferred are 1-amino-3-aminomethyl-3,5,5-trimethyl-cyclohexane and the like, and polymers and copolymers formed therefrom are used. Of these, nylon 6-66, nylon 6-69, nylon 6-11, nylon 12, nylon 6-12, nylon 6-66-610, nylon 6-66-610-612 and the like are preferred. Crystal melting point 2
A polyamide resin having a temperature of 10 ° C. or higher has a high processing temperature during melt extrusion of a laminate, and PVDC is easily decomposed, and good processing becomes difficult.

As the crosslinkable polyolefin used in the outer layer or the inner layer, ethylene-vinyl acetate copolymer resin (EVA, preferably having a vinyl acetate content of 5 to 20% by weight), ethylene- (meth) acrylic acid copolymer resin [A (meth) acrylic acid content of 5 to 20% by weight is preferred], an ethylene- (meth) acrylate copolymer resin [(meth) acrylate content of 5 to 20% by weight
Is preferred], ethylene-allyl (meth) acrylate copolymer resin [allyl (meth) acrylate content 0.00
5 to 2 mol%, more preferably 0.01 to 1.0 mol%], ethylene-vinyl acetate-allyl (meth) acrylate copolymer resin [vinyl acetate content 5 to 20% by weight,
(Allyl (meth) acrylate having a content of 0.005 to 2 mol%, more preferably 0.01 to 1.0 mol% is preferred), and ethylene-α-olefin-allyl (meth) acrylate copolymer resin (α-olefin is propylene , Butene-1, pentene-1, hexene-1, 4-methylpentene-1, octene-1, decene-1 and the like and mixtures thereof), ethylene-1,4 diene copolymer resin, ethylene-propylene At least one resin selected from a -1,4-diene copolymer resin, a linear low-density polyethylene obtained by vapor phase polymerization, and an ionomer resin is used. Here, (meth) acrylic acid refers to acrylic acid or methacrylic acid.

The low-crosslinkable polyolefin used for the innermost layer (the side in contact with the packaged product) as the heat sealing layer includes:
Linear low density polyethylene (LLDP) by solution polymerization
E), ethylene-propylene copolymer resin, propylene-
1 selected from butene copolymer resin and low density polyethylene
Seeds or mixtures thereof are used. The low crosslinkable polyolefin is a polyolefin that is relatively hard to crosslink when irradiated with the same electron beam as compared with the crosslinkable polyolefin. By using such a polyolefin, the sealing layer has a wider range of heat sealing suitability by irradiation, and the sealing strength is greatly improved as compared with the non-irradiated one, but the heat sealing property is lowered by excessive crosslinking. There is no.

The adhesive used for the adhesive layer may be an α-olefin polymer derivative, for example, a polymer obtained by grafting an unsaturated carboxylic acid or an anhydride thereof to polyethylene or polypropylene, or a salt thereof, α-olefin-vinyl acetate. Copolymer or derivative thereof and α-olefin-unsaturated carboxylic acid copolymer or derivative thereof, for example, ethylene- (meth) acrylic acid copolymer, ethylene-
Examples thereof include (meth) acrylic acid alkyl ester copolymers, and polymers obtained by grafting an unsaturated carboxylic acid or an anhydride thereof to any of these polymers, or salts thereof. As the unsaturated carboxylic acid or its anhydride to be graft-polymerized, acrylic acid, methacrylic acid, maleic acid, maleic anhydride and the like are used, and its amount is preferably 0.01 to 5% by weight based on the original polymer. Particularly preferred adhesive polymers include ethylene-ethyl acrylate copolymer (EEA) having an ethyl acrylate content of 5 to 25% by weight and ethylene-vinyl acetate copolymer having a vinyl acetate content of 5 to 25% by weight. Maleic anhydride is added at 0.05 to 0.
5% by weight grafted. These adhesive layers are cross-linked by electron beam irradiation and make the adhesion between the adhesive layer and an adjacent layer stronger.

The expression "crosslinked" used in the present invention means that the gel% value as a measure of the degree of crosslinking described later is 5% or more. The preferable range of the gel% value is 20 to 80% for the outer layer and the inner layer, more preferably 30 to 80%.
Is desirably within the range. If it is less than 20%, the effect of improving the melt hole resistance is small. Also, in the heat seal layer
It is desirably in the range of 10 to 40%, preferably 10 to 30%. If the degree of crosslinking of the heat sealing layer becomes too high, the sealing strength will be lost, so the gel% value of the heat sealing layer is 40%
It is desirable not to exceed.

The amount of electron beam irradiation is in the range of 1 to 12 Mrad, preferably 1 to 10 Mrad. If the irradiation dose is less than 1 megarad, the degree of crosslinking is too small to achieve the effect of crosslinking. On the other hand, when the irradiation dose exceeds 12 megarads, the sealing strength is decreased due to the coloring of the laminated film and the excessive crosslinking of the heat sealing layer, which is not preferable.

In the laminated film of the present invention, the thickness of the outer layer and the inner layer is preferably 5 to 30 μm. If the outer layer exceeds 30 μm, the stress at the time of stretching becomes too large and the film formation becomes unstable, which is not preferable. The thickness of the oxygen gas barrier layer is preferably 5 to 20 μm. If the thickness is less than 5 μm, the oxygen gas barrier effect becomes insufficient, which is not preferable. The innermost heat seal layer
30 μm is preferred. The thickness of the adhesive layer is preferably 1 to 5 μm. The thickness of all the layers of the laminate is preferably 25 to 125 μm.

The layer structure of the laminated film of the present invention can be represented by an outer layer / intermediate layer / inner layer / heat sealing layer or an outer layer / inner layer / intermediate layer / heat sealing layer. Adhesive layers can be provided on both sides.

The heat sealing layer is the side in contact with the packaged article, ie, the innermost layer, the outer layer is the other outer layer, ie, the outermost layer, and the intermediate layer and the inner layer are sandwiched between the outer layer and the heat sealing layer. . These laminated films are biaxially stretched
A heat shrinkable film having a heat shrinkage at 90 ° C. of 15% or more. The field where the laminated film is effectively used is packaging of irregular and irregular foods such as raw foods, processed meats, and fatty foods such as cheese.
When the heat shrinkage at 15 ° C. is less than 15%, the adhesion to the contents is insufficient, causing a problem of separation of the juice, which undesirably lowers the commercial value. The oxygen gas barrier property of the package requires an oxygen permeability of 200 cc / m ² · day · atm or less, and preferably 100 cc / m ² · day · atm or less. If it exceeds 200 cc / m ² · day · atm, the shelf life of the contents is shortened and the appearance is impaired, which is not preferable.

An example of the method for producing the biaxially stretched heat-shrinkable laminated film of the present invention will be described below. As an oxygen gas barrier layer (intermediate layer), a mixture of PVDC powder and polyester elastomer and polyester resin pellets mixed at a predetermined mixing ratio, a crosslinkable polyolefin resin as an outer layer and an inner layer, and a crosslinkable polyolefin resin as a heat seal layer. If necessary, together with the adhesive resin, melt kneading is carried out by a plurality of extruders using ordinary means, and then the mixture is introduced into an annular die for lamination to form an outer layer / adhesive layer /
The layers are laminated in the order of oxygen gas barrier layer / adhesive layer / inner layer / heat sealing layer and coextruded. The obtained molten cylindrical body is 10 to 20
After quenching by cold water showering at ℃, it is made into a flat cylindrical body, introduced into an electron beam irradiation apparatus, and irradiated with a dose of 1 to 12 Mrad to all layers of the laminate, and then vertically and horizontally at 50 to 120 ° C by inflation method, respectively. It can be manufactured by simultaneous biaxial stretching at a factor of two or more. In this case, in order to make the irradiation dose in the thickness direction of the flat cylindrical body uniform, it is preferable to irradiate from both the front and back outer layers of the flat cylindrical body.

The electron beam used in the present invention includes various electron beams such as a Cockloft-Walton type, a Van de Graaff type, a resonance transformer type, an insulating core transformer type, a linear accelerator, a dynamitron type and a high frequency type cyclotron. The one with energy of 150 to 1000 KeV released from the accelerator is used.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

[0053]

Example 1 The following resin composition A was used as the resin composition.

The polyester resin has a glass transition temperature
30% by weight of terephthalic acid-isophthalic acid-ethylene glycol-diethylene glycol copolymer resin (Iv value: 0.52, PIFG-40 manufactured by Kanebo Co., Ltd.) at 68 ° C. and terephthalic acid-isophthalic acid-1,4-butanediol as a polyester elastomer. 30% by weight of a polytetramethylene glycol copolymer resin (Hytrel # 2501 manufactured by Du Pont-Toray Co., Ltd.) and 40% by weight of a vinylidene chloride-methyl acrylate copolymer resin (vinylidene chloride content: 94%) were added to the copolymer resin by 2%. A mixed resin comprising a resin to which epoxidized soybean oil is added by weight. This resin composition A was melt-kneaded with a single screw extruder (cylinder diameter 40 mm, L / D = 24), and the resin temperature 1
Extruded pellets at 80 ° C. 180 ° C using pellet press (Shinto Metal Industry Co., Ltd., AYSR5 type)
(50 kg / cm ² for 2 minutes) to obtain a sample having a thickness of 500 μm. Next, this sample was stretched at a stretching temperature of 90 ° C. using a biaxial stretching machine.
Then, the film was stretched 3.5 times in each of length and width to obtain a 40 μm film.

Example 2 A biaxially stretched film was obtained in exactly the same manner as in Example 1 except that the following K resin was used as the resin composition.

Resin K: PIFG as polyester resin
-40 45% by weight, 15% by weight of Hytrel # 2501 as polyester elastomer and vinylidene chloride-methyl acrylate copolymer resin (vinylidene chloride content 94% by weight)
A mixed resin comprising 40% by weight and 2% by weight of epoxidized soybean oil based on the copolymer resin.

Example 3 A biaxially stretched film was obtained in the same manner as in Example 1 except that the following T resin was used as the resin composition.

Resin T: PIFG as polyester resin
-40 50% by weight, 10% by weight of Hytrel # 2501 as polyester elastomer and vinylidene chloride-methyl acrylate copolymer resin (vinylidene chloride content 94% by weight)
A mixed resin comprising 40% by weight and 2% by weight of epoxidized soybean oil based on the copolymer resin.

Example 4 Example 1 was repeated except that the following resin was used as the resin composition.
A biaxially stretched film was obtained in the same manner as described above.

As a polyester resin, PI manufactured by Kanebo Co., Ltd.
65% by weight of FG-40, 13% by weight of Hytrel # 2501 as a polyester elastomer, and vinylidene chloride-methyl acrylate copolymer resin (vinylidene chloride content 94%)
A mixed resin comprising 22% by weight and 2% by weight of epoxidized soybean oil added to the copolymer resin.

Comparative Example 1 A biaxially stretched film was obtained in the same manner as in Example 1 except that the resin S was used as the resin composition.

Resin S: PIFG as polyester resin
-40 A mixed resin composed of 60% by weight of vinylidene chloride-methyl methacrylate copolymer resin (vinylidene chloride content: 94% by weight) and 40% by weight of epoxidized soybean oil added to the copolymerized resin .

Comparative Example 2 A biaxially stretched film was obtained in the same manner as in Example 1 except that the following resin compositions were used.

Resin composition: P as polyester resin
20% by weight of IFG-40, 40% by weight of Hytrel # 2501 as a polyester elastomer, 40% by weight of vinylidene chloride-methyl acrylate copolymer resin (vinylidene chloride content: 94% by weight) and 2% by weight of the epoxidized resin based on the copolymer resin A mixed resin comprising a resin to which soybean oil is added.

Comparative Example 3 A film having a thickness of 500 was prepared in the same manner as in Example 3 except that biaxial stretching was not performed.
An unstretched press sheet of μm was obtained.

Comparative Example 4 A biaxially stretched film was obtained in the same manner as in Example 1 except that only the polyester resin PIFG-40 was used instead of the resin composition.

Comparative Example 5 Instead of the resin composition, a resin obtained by adding 2% by weight of epoxidized soybean oil to the copolymerized resin to a vinylidene chloride-methyl acrylate copolymer resin (vinylidene chloride content: 94% by weight) was used. Except for the above, a biaxially stretched film was obtained in the same manner as in Example 1.

Table 1 shows the heat shrinkage, oxygen permeability (converted to a thickness of 8 μm), and impact punching energy of the films obtained in Examples 1 to 4 and Comparative Examples 1 to 5.
The physical properties are shown in Table 4.

[0069]

[Table 1]

In the present invention, as is clear from Examples 1 to 4, excellent heat-shrinkable films having both oxygen gas barrier properties and cold resistance were obtained. Generally, a single-layer heat-shrinkable film that can be practically used has a heat-shrinkage ratio of 20% or more in each of length and width and an oxygen permeability of 100 cc / m ² · day · atm
(8 µ conversion, 30 ° C, 100% RH) or less, and the impact punching energy must be 80 mj / 40 µm or more.

On the other hand, Comparative Example 1 did not contain a polyester elastomer, so that the low-temperature impact strength (indicated by impact punch-through energy) was poor. Comparative Example 2 was because the amounts of the polyester elastomer and the polyester were out of the range of the present invention. , Poor oxygen gas barrier properties. Comparative Example 3 was inferior in oxygen gas barrier properties due to unstretched, and Comparative Examples 4 and 5
Is a single film of polyester and PVDC, respectively, and thus is inferior in oxygen gas barrier properties and cold resistance.

Example 5 (1) The resin A of Example 1 was used as an intermediate layer (oxygen gas barrier layer).

(2) The following resin B was used as the outer layer.

Linear low-density polyethylene (DFDA1137, manufactured by Nippon Yunika Co., Ltd .; melt index = 1.0,
Density = 0.906 g / cm ³ ) and vinyl acetate content 7.5% by weight
EVA (NUC # 8425, manufactured by Nippon Yunika Co., Ltd .; melt index = 2.3, density = 0.93 g / cm ³ )
A resin mixed in a ratio of 70: 30% by weight.

(3) Resin B was used for the inner layer.

(4) Resin C: low-density polyethylene resin (F277-1, manufactured by Sumitomo Chemical Co., Ltd., melt index = 2.0, density = 0.924 g / cm ³ ) was used as the sealing layer. (5) Resin D as adhesive layer: Ethyl acrylate content
A 15% by weight ethylene-ethyl acrylate copolymer resin (DPDJ # 6182, manufactured by Nippon Unica Co., Ltd., melt index = 1.5, density = 0.93 g / cm ³ ) was used.

These resins A, B, B, C, and D were separately extruded by five extruders, and the molten resin was co-extruded and introduced into an annular die. As co-extruded. The resin temperature of the molten cylindrical body at the die exit is
190 ° C. The molten cylindrical body was quenched by a cold water shower ring at 10 to 30 ° C. and had a flat width of 150 mm and a thickness of about 510.
It was a flat cylindrical body of μm. The flat cylindrical body thus obtained was irradiated with an irradiation dose of 10 Mrad in an electron beam irradiation device at an acceleration voltage of 400 KeV. Next, a hot water tank at 80-95 ° C and
The film was passed through a hot-air cylinder at 110 ° C. and stretched three times in the longitudinal and transverse directions by an inflation method while being cooled by an air ring at 20 ° C. The folding width of the obtained biaxially stretched film is about 450m
m and the thickness was about 57 μm.

Example 6 Resin E as inner layer: EV with vinyl acetate content of 7.5% by weight
A biaxially stretched film was manufactured in exactly the same manner as in Example 5 except that A (manufactured by Nihon Unica Ltd., DPDJ # 8425) was used.

Example 7 A biaxially stretched film was produced in exactly the same manner as in Example 5, except that the resin E was used as the outer layer and the temperature of the hot air in the cylinder was 95 ° C.

Example 8 Resin F: Methyl acrylate content 1 as outer and inner layers
2.0% by weight of ethylene-methyl methacrylate copolymer resin (Nucrel N1202 manufactured by DuPont-Mitsui Co., Ltd.) was mixed with 10 parts of nonionic antistatic agent (Elegan S-100 manufactured by NOF Corporation).
A biaxially stretched film was manufactured in exactly the same manner as in Example 5, except that the one added with 00 ppm was used and the temperature of the hot air in the cylinder was set to 95 ° C.

Example 9 Resin G as outer and inner layers: acrylic acid content 6% by weight
Ethylene-acrylic acid copolymer resin (Esco
re # TR5001, melt index = 2.0, density = 0.93
g / cm ³ , melting temperature = 102 ° C.) and a resin in which 1000 ppm of nonionic antistatic agent (Nippon Oil & Fats Co., Ltd., Elegan S-100) is added, and the temperature of hot air in the cylinder is set to 95 ° C. Produced a biaxially stretched film in exactly the same manner as in Example 5.

Example 10 As an outer layer, resin H: nylon 6-12 copolymer (Toray Industries, Inc.)
CM6541X3, density = 1.06, melting temperature = 130 ° C.), resin I as an adhesive layer: acid-grafted EVA (Mitsubishi Yuka Corporation)
E-100H, melt index = 2.3, density = 0.9
4, melt temperature = 93 ° C.), and a biaxially stretched film was produced in exactly the same manner as in Example 5.

Example 11 Resin J: linear low density polyethylene (manufactured by Mitsui Petrochemical Co., Ltd., UZ1030L, melt index =
3.0, density = 0.910, melting temperature = 120 ° C.), and a biaxially stretched film was produced in exactly the same manner as in Example 5.

Example 12 A biaxially stretched film was produced in exactly the same manner as in Example 5 except that the K resin of Example 2 was used as the oxygen gas barrier layer.

Example 13 Resin L: ethylene-1,4-diene copolymer resin (ROP2D manufactured by Mitsubishi Yuka Co., Ltd., melt index =
2.6, density = 0.923 g / cm ³ ) and the irradiation dose is 6
A biaxially stretched film was produced in exactly the same manner as in Example 5 except that the film was changed to Megarad.

Example 14 A biaxially stretched film was produced in the same manner as in Example 5 except that the following resin Q was used as the oxygen gas barrier layer.

Resin Q: Terephthalic acid-ethylene glycol-1,4 cyclohexane dimethanol copolymer resin (kodar manufactured by Eastman Kodak Company) as a polyester resin
PETG) 30% by weight, Hytrel # 2501 as polyester elastomer 30% by weight, vinylidene chloride-methyl methacrylate copolymer resin (vinylidene chloride content 94% by weight) 40% by weight and epoxidation of 2% by weight based on the copolymer resin A mixed resin comprising a resin to which soybean oil is added.

Table 2 collectively shows the layer constitutions and the results of physical properties tests of the films obtained in Examples 5 to 14.

[0089]

[Table 2]

[0090]

[Table 3]

Comparative Example 6 A biaxially stretched film was produced in the same manner as in Example 5, except that the following resin M was used as the oxygen gas barrier layer.

Resin M: PIFG as polyester resin
-40 80% by weight, Hytrel # 2501 15% by weight as polyester elastomer and vinylidene chloride-methyl acrylate copolymer resin (vinylidene chloride content 94% by weight)
A mixed resin comprising 5% by weight and 2% by weight of epoxidized soybean oil based on the copolymer resin.

Comparative Example 7 A biaxially stretched film was produced in exactly the same manner as in Example 5 except that resin N was used as the oxygen gas barrier layer.

Resin N: PIFG as polyester resin
-40 30% by weight, 10% by weight of Hytrel # 2501 as polyester elastomer and vinylidene chloride-methyl acrylate copolymer resin (vinylidene chloride content 94% by weight)
A mixed resin comprising 60% by weight and a resin obtained by adding 2% by weight of epoxidized soybean oil to the copolymer resin.

Comparative Example 8 A biaxially stretched film was produced in exactly the same manner as in Example 5 except that resin O was used as the oxygen gas barrier layer.

Resin O: Kodar P as a polyester resin
A mixed resin comprising 60% by weight of ETG, 40% by weight of a vinylidene chloride-methyl acrylate copolymer resin (vinylidene chloride content: 94% by weight) and 2% by weight of epoxidized soybean oil based on the copolymer resin.

Comparative Example 9 A biaxially stretched film was produced in exactly the same manner as in Example 5 except that the resin S of Comparative Example 1 was used as the oxygen gas barrier layer.

Comparative Example 10 A biaxially stretched film was produced in exactly the same manner as in Example 5 except that the resin P was used as the oxygen gas barrier layer.

Resin P: 60% by weight of Hytrel # 2501 as a polyester elastomer and 40% by weight of vinylidene chloride-methyl acrylate copolymer resin (vinylidene chloride content: 94% by weight) and 2% by weight of epoxidation based on the copolymer resin A mixed resin comprising a resin to which soybean oil is added.

Comparative Example 11 (1) As an oxygen gas barrier layer Resin R: except that a resin in which 2% by weight of epoxidized soybean oil was dispersed in a vinylidene chloride-methyl acrylate copolymer resin (vinylidene chloride content: 94% by weight) was used. Produced a biaxially stretched film in the same manner as in Example 5.

Comparative Example 12 The structure of the film was exactly the same as that of Example 5, and the film was stretched without irradiation with an electron beam. Stretching is performed in a hot water bath at 80-85 ° C and 100
The film was passed through a hot blast tube at ℃ and stretched 2.3 times in both longitudinal and transverse directions by the inflation method while being cooled by an air ring at 20 ° C. The folding width of the obtained biaxially stretched film is 345m
m and a thickness of 96 μm.

The same stretching conditions as in Example 5 (hot water tank: 80
(95 ° C, temperature in hot-air tube 110 ° C).

Table 3 collectively shows the layer constitutions and the measurement results of physical properties of the films obtained in Comparative Examples 6 to 12.

[0104]

[Table 4]

[0105]

[Table 5]

Table 4 shows physical property measuring methods. Here, the gel% value of the polyolefin layer was determined by taking out the polyolefin layer from the biaxially stretched laminated film and measuring the gel% value.

[0107]

[Table 6]

[0108]

[Table 7]

In the present invention, as is apparent from the examples,
A film excellent in heat sealability, melt hole resistance, cold resistance and transparency was obtained.

The laminated film conforming to the object of the present invention has a melt hole resistance of 0 or less in number of breakage, a cold resistance of ○, a heat shrinkage of 15% or more, a haze of 8% or less, and an oxygen permeability of 200 cc / m ^2.
・ Day ・ atm or less, coloring degree is B or more, seal strength 1.8k
g / 15 mm or more that does not cause seal fusing is required.

In Comparative Example 6, since the weight ratio of PVDC in the intermediate layer was small, sufficient oxygen gas barrier properties were not obtained.

In Comparative Example 7, since the weight ratio of PVDC in the intermediate layer was too large, PVDC became a matrix and was decomposed when irradiated with an electron beam, so that it was colored and the cold resistance was poor.

In Comparative Example 8, no improvement in cold resistance was achieved because the intermediate layer did not contain an appropriate amount of polyester elastomer. At the time of co-extrusion, the intermediate layer had already been colored by thermal decomposition.

In Comparative Example 9, the intermediate layer did not contain an appropriate amount of the polyester-based elastomer, so that improvement in cold resistance could not be achieved.

In Comparative Example 10, since the intermediate layer was a composition comprising two components of PVDC and a polyester elastomer, it became a compatible system and the oxygen gas barrier property was significantly deteriorated.

In Comparative Example 11, since the intermediate layer was composed only of PVDC, the cold resistance was low, and the coloration due to decomposition upon electron beam irradiation was strong.

Comparative Example 12 was a case where no electron beam irradiation was performed.
Not only can a film not be formed at a normal stretching ratio, but even if the stretching ratio is lowered, the seal strength, seal fusing property and melt hole property are poor because they are not crosslinked. Further, since the stretching temperature could not be sufficiently increased, after the heat shrinkage, the shrinkage of the intermediate layer was insufficient, and the laminate was bent and the transparency of the laminate was inferior.

[0118]

The resin composition used in the present invention is a mixture of PVDC, a thermoplastic polyester resin and a polyester elastomer in a specific ratio, so that when this resin composition is used for a heat-shrinkable film, oxygen gas barrier property and cold strength And excellent transparency. That is, since the addition amount of the polyester elastomer is appropriate, the transparency is not hindered and the cold resistance can be improved, and the weight ratio of PVDC of the mixed resin of the oxygen gas barrier layer is set to 44% by weight or less, By stretching the gas barrier layer, P
By forming the VDC particles in a flat multilayered state, oxygen gas barrier properties are maintained, and the degree of coloring due to decomposition is reduced even when irradiated with electron beams.

The biaxially stretched heat-shrinkable film of the present invention, in which the layer composed of the resin composition is used as an oxygen gas barrier layer, has at least the outer layer, the inner layer and the heat seal layer cross-linked by electron beams. In addition to the effects described above, the following effects are further obtained.

(1) The oxygen gas barrier layer can be protected from abuse.

(2) The heat resistance of the polyolefin layer is remarkably improved by electron beam irradiation, and the heat resistance of the laminated film can be improved.

(3) Since the low-crosslinkable polyolefin resin is used for the heat seal layer, the temperature range suitable for heat seal can be widened, and the seal strength can be greatly improved as compared with those without electron beam irradiation.

(4) When the adhesive layer is provided, the adhesive layer is also cross-linked, so that even if the film is boiled at a temperature close to boiling water, it is possible to prevent white turbidity due to displacement between the layers and to obtain a transparent film even after boiling. I can do things.

As a result, the oxygen permeability is preferably 200 cc.
/ M ² · day · atm or less, melt hole property [0 damage in 5 samples], haze 8% or less, seal strength
A heat-shrinkable laminated film of 1.8 kg / 15 mm or more could be obtained.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI B32B 27/36 B32B 27/36 C08L 27/08 C08L 27/08 67/02 67/02 // B29K 105: 02 105: 24 B29L 7:00 9:00 (58) Field surveyed (Int.Cl. ⁶ , DB name) C08J 5/18 CFD B29C 61/06 B32B 27/30 C B32B 27/36 B32B 25/00

Claims (8)

(57) [Claims] An oxygen gas barrier biaxially stretched heat-shrinkable film comprising a resin composition comprising 26 to 70% by weight of a thermoplastic polyester resin, 10 to 30% by weight of a polyester elastomer and 20 to 44% by weight of a vinylidene chloride resin. 2. The heat-shrinkable film according to claim 1, wherein the thermoplastic polyester resin is formed from a mixed dibasic acid component comprising terephthalic acid and isophthalic acid and a mixed dialcohol component comprising ethylene glycol and diethylene glycol. 3. A polyester elastomer comprising a mixed dibasic acid component comprising terephthalic acid and isophthalic acid;
The heat-shrinkable film according to claim 1, wherein the heat-shrinkable film is formed from a mixed dialcohol component comprising butanediol and polytetramethylene glycol. 4. An intermediate layer which is an oxygen gas barrier layer comprising the heat-shrinkable film according to claim 1.
Outer layer of polyamide or cross-linkable polyolefin, inner layer made of the same or different cross-linkable polyolefin and outer layer of heat-seal layer made of low cross-linkable polyolefin, at least outer layer, inner layer and heat seal layer by electron beam irradiation Crosslinked and has a heat shrinkage at 90 ° C
An oxygen gas barrier biaxially stretched heat-shrinkable laminated film of 15% or more. 5. The crosslinkable polyolefin is an ethylene-vinyl acetate copolymer resin, an ethylene-acrylic acid copolymer resin, an ethylene-methacrylic acid copolymer resin, an ethylene-vinyl acetate copolymer resin.
Acrylic ester copolymer resin, ethylene-methacrylic ester copolymer resin, ethylene-allyl acrylate copolymer resin, ethylene-vinyl acetate-allyl acrylate copolymer resin, ethylene-1,4 diene copolymer resin, ethylene- The heat-shrinkable laminated film according to claim 4, comprising at least one selected from a propylene-1,4 diene copolymer resin, a linear low-density polyethylene obtained by vapor phase polymerization, and an ionomer resin. 6. The low-crosslinkable polyolefin comprises at least one selected from the group consisting of a linear low-density polyethylene prepared by solution polymerization, an ethylene-propylene copolymer resin, a propylene-butene copolymer resin, and a low-density polyethylene. The heat-shrinkable laminated film according to the above. 7. The heat-shrinkable laminated film according to claim 4, wherein at least the outer layer, the inner layer and the heat sealing layer are crosslinked by irradiating the laminated film with an electron beam at a dose of 1 to 12 megarads. 8. The heat-shrinkable laminated film according to claim 4, wherein an adhesive layer is disposed between each of the outer layer, the intermediate layer, the inner layer, and the heat sealing layer.