JPH03266643A - Laminated drawn film - Google Patents

Abstract

PURPOSE:To obtain a laminated drawn film with less decrease in resistance to gas permeability, especially less decrease in resistance to gas permeability under high humidity and excellent water resistance, interlaminar adhesive force etc., by incorporating a satd. polyester resin layer wherein terephthalic acid is a main ingredient and a specified copolymerized polyester resin layer and drawing it at least in one direction. CONSTITUTION:A laminated drawn film is prepd. by laminating a specified copolymerized polyester resin layer and a satd. polyester resin layer wherein terephthalic acid is a main ingredient as an acid ingredient and drawing it at least in one direction. The specified copolymerized polyester means that among dicarboxylic acids constituting the polyester, 5-95 mol% isophthalic acid or ester forming derivative thereof A and 5-95 mol% dicarboxylic acid of formula (I) or ester forming derivative thereof (B) both based on the whole acid ingredient are incorporated and the sum of the ingredients (A) and (B) are 50 mol% or more of the whole acid ingredient of the copolymerized polyester. In the formula, R<1>, R<2>, R<3> and R<4> are each hydrogen, a 1-6C alkyl, alkoxy and phenyl group or C1, Br and F.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a laminated stretched film with good gas barrier properties. In particular, the present invention relates to a laminated stretched film that has good transparency, water resistance, and interlayer adhesion, and also exhibits high gas barrier properties even under high humidity and high water content.

[Prior Art J Polyethylene terephthalate (hereinafter sometimes abbreviated as fPETJ) has a high Young's modulus, tensile strength, heat resistance,
Because it has excellent physical properties such as transparency, it has been used in films for various packaging applications, taking advantage of these characteristics.

However, in recent years, demands for high performance and high functionality for packaging materials have become increasingly strict.
At present, it is difficult to obtain fully satisfactory products using conventional PET films.

Among these required properties, there is a desire for a film that has low permeability to gases such as oxygen gas and moisture, and whose performance does not deteriorate even when subjected to freezing processing, boiling processing, retorting processing, etc. Specifically, when packaging fish, meat, shellfish, etc., a film with good gas barrier properties is used to prevent air from permeating into the packaging material, thereby preventing oxidation of proteins, oils, etc. There is a strong demand for suppressing discoloration and preserving flavor and freshness for longer.

Packaging with such a film with good gas barrier properties not only retains the unique aroma of the contents, but also prevents the permeation of moisture, which prevents the contents from discoloring or solidifying, thus preserving the original fresh flavor of the packaging. It is also possible to hold it for a period of time. For these reasons, in particular, processed foods such as kamaboko, dairy products such as butter and cheese, miso, tea, coffee, bonito flakes, furikake, ham and sausages, shellfish, pickles, instant foods, tofu or rice crackers, castella, Gas barrier properties are considered to be an extremely important property for packaging films for confectionery such as biscuits. In addition, when packaging ready-to-eat foods such as hamburgers, stews, and curries, retort treatment (processing at high temperatures of around 120-135°C for a short period of time) is used to sterilize the packaging after packaging.
, frozen storage during the distribution stage, and furthermore, boiling treatment before meals, etc., so that gas barrier properties are required to be maintained even after these treatments. These properties are also extremely important for packaging films for drugs, medical devices, etc. that must be handled under aseptic conditions.

In response to this situation, efforts are being made to develop new colorants that apply composite technologies such as resin modification, coextrusion, and lamination by blending PET resin with resins with excellent gas barrier properties. .

For this purpose, research on materials with excellent gas barrier properties is active.For example, saponified ethylene-vinyl acetate copolymer (ethylene content: Saponification degree of 25 to 60 mol% vinyl acetate component is 90% or more, preferably
More than 95%. Hereinafter referred to as "rEVOH". ) has been developed and widely used. Although this EVOH resin itself shows extremely excellent gas barrier properties when completely dry, it has hydrophilic hydroxyl groups, so it has insufficient water resistance and moisture proofing properties, so it cannot be used in high humidity atmospheres or when the contents contain water. Therefore, under conditions where the moisture content of the packaging material increases, the ability to block gases such as oxygen is significantly reduced. Further, if melt molding is continued continuously for a long period of time, gel etc. may be generated, which may cause trouble. In this way, while EVOH exhibits extremely excellent gas barrier properties, EVOH itself has poor water resistance and
Because it has problems with heat resistance, and has insufficient mechanical properties and heat sealability, it is rarely used alone, but when used with PET resin or other thermoplastic resins.
OH resin is laminated and is generally used as a laminate of two or more layers by extrusion lamination, dry lamination, coextrusion lamination, etc., but it is particularly difficult to use in a retort in a high humidity atmosphere or when the contents are water-containing. In cases where it is necessary to perform high-temperature hydrothermal treatment, the gas barrier properties are still not satisfactory even when a laminate with a thermoplastic resin as described above is used.

Furthermore, instead of EVOH, polyvinylidene chloride resin (hereinafter referred to as rPVDCJ) has also been used for the same purpose. PVDC has the advantage of having good gas barrier properties and less humidity dependence. However, it is not necessarily a desirable material because of problems such as odor, discoloration, damage to incinerators when discarded, and air pollution.

On the other hand, the present inventors have discovered that a specific copolyester containing isophthalic acid and phenylenedioxydiacetic acid as the main acid components exhibits extremely excellent gas barrier properties as a new copolyester material for packaging materials. It has already been discovered (JP-A-1-167331, JP-A-1-
247422, JP-A-1-247423). However, although the copolyester has excellent gas barrier properties, it does not necessarily have sufficient toughness, and there remains the problem that it is not preferable to use it alone as a molded article.

[Problems to be Solved by the Present Invention] The object of the present invention is to provide a laminated stretched film that exhibits gas permeability, particularly less deterioration in gas permeability even under high humidity, and that has excellent water resistance, interlayer adhesion, etc. Our goal is to provide the following.

[Means for Solving the Problem] The present inventors laminated a specific copolymerized polyester resin layer that they had already discovered and a saturated polyester resin layer containing terephthalic acid as the acid component as a main component, and further stretched the layer. The inventors have discovered that a film achieves the above object, and have completed the present invention.

That is, the present invention includes a saturated polyester resin layer containing terephthalic acid as a main component, such as polyethylene terephthalate, which is commonly used in packaging films, and a specific copolymerized polyester resin layer with excellent gas barrier properties. , relates to a laminated stretched film.

The present invention will be explained in detail below.

The specific copolymerized polyester referred to in the present invention refers to (1) isophthalic acid or its ester-forming derivative (A
) is 5 to 95 mol% of the total acid components, preferably 10 to 90
mol% and ■ dicarboxylic acid represented by general formula (I) or its ester-forming derivative (B) is 5 to 95 mol% of the total acid component;
Preferably 5 to 70 mol%, more preferably 10 to 5
0 mol %, ■ A copolymerized polyester characterized in that the sum of components (A) and (B) is 50 mol % or more of the total acid components of the copolymerized polyester, or the above-mentioned (1), A copolymerized polyester which satisfies the conditions (1) and (2) and in which 5 to 50 mol% of the total acid component is naphthalene dicarboxylic acid or a derivative thereof.

R] (In the formula, R1, R2, R3, R4 are hydrogen or have 1 carbon number
~6 alkyl group, alkoxy group, phenyl group, or C1, Br, or F. ) Among R in the above general formula (I), the alkoxy group preferably has 1 to 2 carbon atoms, and particularly preferably a methoxy group. The alkyl group preferably has 1 to 3 carbon atoms, and more preferably a methyl group or an ethyl group.

Specifically, the dicarboxylic acid represented by the general formula (I) includes 1,2-phenylenedioxydiacetic acid, 1,3-phenylenedioxydiacetic acid, 1,4-phenylenedioxydiacetic acid, 2-phenylenedioxydiacetic acid, -Methyl-1,3-phenylenedioxydiacetic acid, 5-methyl-1,3-phenylenedioxydiacetic acid, 6
-Methyl-1,3-phenylenedioxydiacetic acid, 5-ethyl-1,3-phenylenedioxydiacetic acid, 6-ethyl-1,3-phenylenedioxydiacetic acid, 5-methoxy-
1,3-phenylenedioxydiacetic acid, 6-medoxy 1
, 3-phenylenedioxydiacetic acid, 4-chloro-1,2
-phenylenedioxydiacetic acid, 4-chloro-1,3-phenylenedioxydiacetic acid, and the like. Among these, derivatives of 1,3-phenylenedioxydiacetic acid are preferred, and 1,3-phenylenedioxydiacetic acid is more preferred.

The dicarboxylic acid represented by the general formula (1) may be used as is in combination with isophthalic acid, or may be used as an ester-forming derivative such as an acid anhydride, an acid halide, a monoester, or a diester. Alternatively, it may be added after being quantified by reacting with glycols.

Isophthalic acid may also be used in the form of ester-forming derivatives that react with diol components, such as ester derivatives such as dimethyl isophthalate and diethyl isophthalate, and isophthalic acid halides such as isophthalic acid chloride.

The specific copolymerized polyester used in the present invention has an isophthalic acid unit (A) of 5 to 95 mol%, preferably 10 to 95 mol%.
90 mol%, dicarboxylic acid unit (B) represented by general formula (I) is 5 to 95 mol%, preferably 5 to 70 mol%
, more preferably 10 to 50 mol%.

If the main acid components shown in (A) and (B) are used in amounts exceeding the above ranges, the glass transition point (Tg) of the resulting copolyester will decrease too much, resulting in Drying becomes difficult, and the heat resistance when the obtained copolyester is made into a laminated multilayer molded product is reduced. On the other hand, when the amounts of (A) and (B) used are less than this range, the level of gas barrier properties is insufficient, so the gas barrier properties of the present invention are improved by improving the gas barrier properties of the above-mentioned resins. It is not suitable for use as an excellent laminated multilayer packaging material.

In addition, in the specific copolymerized polyester used in the present invention, the sum of isophthalic acid units and dicarboxylic acid units represented by general formula (I) is 50% of the repeating units of the total acid component.
It is necessary that it accounts for mol% or more. The sum of both is 50
If the amount is less than mol %, the copolymerized polyester will not have sufficient gas barrier properties and cannot be used as the packaging material of the present invention. Other dicarboxylic acids and oxyacids can also be used as long as the amounts of isophthalic acid and the dicarboxylic acid represented by formula (I) satisfy the above conditions.

These dicarboxylic acids include terephthalic acid, phthalic acid, 2,6-12,7-12,3-11,4-11゜5
aliphatic dicarboxylic acids such as naphthalene dicarboxylic acid, 4,4-diphenoxyethane dicarboxylic acid, 4,4-diphenylsulfone dicarboxylic acid and structural isomers thereof, malonic acid, succinic acid, adipic acid, etc. Examples of the oxyacid include hydroxybenzoic acid derivatives and glycolic acid, but naphthalene dicarboxylic acid or its ester-forming derivatives are particularly preferred, and 2,6-naphthalene dicarboxylic acid is particularly preferred. The naphthalene dicarboxylic acid component is used in an amount of 5 to 50 mol%, particularly preferably 10 to 30 mol% of the total acid component.

Diol components used in the specific copolymerized polyester used in the present invention include ethylene gelcol, 1,2-propanediol, 1,3-propanediol, 1,4-
Examples include butanediol, pentamethylenegutcol, hexamethylene glycol, neopentyl glycol, cyclohexane dimetatool, diethylene glycol, and aromatic dihydroxy compound derivatives such as bisphenol A and bisphenol S. Of these, ethylene glycol is most preferred.

In addition, the specific copolymerized polyester used in the present invention includes trimethylolethane, trimethylolpropane, pentaerythritol,
Polyfunctional compounds such as erythritol, glycerin, trimellitic acid, trimesic acid, and pyromellitic acid, and monofunctional compounds such as 0-benzoylbenzoic acid may be allowed to coexist. Such polyfunctional compounds and monofunctional compounds are used in an amount of 20 mol% or less of the diol component.

The specific copolymerized polyester used in the present invention is characterized by its intrinsic viscosity [phenol-tetrachloroethane (weight ratio 1
/1) value measured at 300C using a mixed solvent] is
It is desirable that it is in the range of 0.4 to 0.2, preferably 0.5 to 1.5. When the intrinsic viscosity is 0.4'tlh, the strength of the obtained polyester is low, and the physical properties required for practical use during molding cannot be obtained. When the intrinsic viscosity exceeds 2.0, there is a problem that the melt viscosity becomes too high, making molding such as injection and blowing difficult.

The copolymerized polyester can be produced by a conventionally known polymerization method for polyethylene terephthalate. For example, after performing a direct esterification reaction under pressure using isophthalic acid, a dicarboxylic acid represented by the general formula (I), specifically 1,3-phenylenedioxydiacetic acid, and ethylene glycol, There is a method of heating and gradually reducing the pressure to cause a polycondensation reaction.

Alternatively, an ester derivative of isophthalic acid, such as isophthalic acid dimethyl ester, is transesterified using a dicarboxylic acid derivative of general formula (I), such as 1,3-phenylenedioxydiacetic acid dimethyl ester, and ethylene glycol. It can be produced by carrying out a reaction and then further polycondensing the obtained reaction product. At that time, it is preferable to use an esterification catalyst, a transesterification catalyst, a polycondensation catalyst, a stabilizer, etc.

As the transesterification catalyst, one or more known compounds such as calcium, manganese, zinc, sodium, and lithium compounds can be used, but manganese compounds are particularly preferred from the viewpoint of transparency. As the polymerization catalyst, one or more of known antimony, germanium, titanium, and cobalt compounds can be used, and antimony, germanium, and titanium compounds are preferably used.

The saturated polyester resin containing terephthalic acid as a main component as an acid component used in the present invention is one containing 50 mol% or more of terephthalic acid as a constituent acid component, and includes polyethylene terephthalate, polybutylene terephthalate, polycyclohexylene dimethylene terephthalate. Any general saturated polyester resin that can be stretched may be used. Alternatively, saturated polyesters such as homopolymers, copolymers, and polymer mixtures for film forming, which are usually commercially available, may be used. The most suitable among these saturated polyester resins is polyethylene terephthalate (PET) resin, and the PET resin will be described in detail below as a representative.

PET resin is mainly composed of ethylene glycol and terephthalic acid, and the acid component is 70 mol% or more, preferably 80 mol% or more is terephthalic acid, and the glycol component is 70 mol% or more, preferably 80 mol% or more. The above are polyester resins that are ethylene glycol. As acid components other than terephthalic acid and diol components other than ethylene glycol, the same acids and diol components as used in the specific copolyester used in the present invention described above can be used. or more PET
The resin is manufactured by a known manufacturing method.

The thus obtained PET resin and copolymerized polyester are made into a multilayer stretched film. Methods for obtaining multilayer stretched films include extrusion lamination, dry lamination, coextrusion lamination, coextrusion sheet production (
(feed block or multi-manifold method, etc.), and both die method and tubular method are applicable.

In addition, a laminate is obtained by various solution coating methods, and then
This may be heated and stretched in a -axial or biaxial stretching machine, drawn by vacuum and pressure, etc., and is not limited to these forming methods.

At this time, since the compatibility between the PET resin and the copolyester is extremely good, depending on the molding method such as the coextrusion lamination method, it is not necessarily necessary to use adhesive resin between the PET resin layer and the copolyester layer. You may also use Here, the adhesive resin is one that can be stretch-molded at a temperature below the melting point of the copolyester, and also bonds the copolyester composition layer and the PET resin, and does not cause any problems when actually used. Although there is no particular restriction as long as it has an adhesive strength of , ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester (eg, methyl ester, ethyl ester) copolymer, and the like.

In addition, the structure of the multilayer structure includes copolymerized polyester layer/PET resin layer, copolymerized polyester layer/adhesive resin layer/PET resin layer, PET resin layer/copolyester layer/PET resin layer, PET resin layer/ Adhesive resin layer l
Typical examples include copolymerized polyester layer l adhesive resin layer/PET resin layer, but are not limited thereto. Furthermore, each of these layers may contain a recovered product of the multilayer structure of the present invention. PET in the bisexual layer
When a resin layer is provided, the resins may be different or the same.

Although the stretching may be uniaxial or biaxial, biaxial stretching is preferred from the viewpoint of practical physical properties of the film. Regarding the biaxial stretching conditions, the stretching ratio is in the range of 1.5 times to 5 times, preferably 2.5 to 4 times in each direction, and the area ratio is 20 times or less,
Preferably it is 3 to 15 times. Also, the vertical stretch ratio/horizontal stretch ratio is 0.5 to 2, preferably 0.7 to 1.
．． It is 3. Further, as the biaxial stretching, either simultaneous stretching or sequential stretching may be employed. The appropriate temperature for stretching is 70°C ~
The temperature is 130°C. Various types of stretching equipment and heat treatment equipment can be used, but it is possible to use the stretching equipment and heat treatment equipment that are generally used in the production of biaxially stretched polyethylene terephthalate films.

If the film is unstretched, it is preferable because when used in retort applications, which is one of the main purposes of the present invention, not only will the entire film become white and the commercial value will be significantly reduced, but also the impact resistance will deteriorate. There isn't.

The unstretched original film used in the present invention has a total thickness of 5
0~20001. I, preferably 100-1000. Good. If the thickness is less than 50 μm, it will easily break during stretching, and if it exceeds 200 (h+), the quenching will become difficult and at the same time the stretching tension will become too high, making uniform stretching difficult.

In addition, the thickness of the copolymerized polyester layer of the unstretched original fabric is 2
0 to 300 μ, preferably 40 to 200 IJ. P
The thickness of the ET resin layer is 20 to 12001 J, preferably 2
0 to 800μ, and each layer of adhesive resin has a thickness of 10 to 300μ
°, preferably 10-1001. l is good. The total thickness of the laminated film after biaxial stretching is 10 to 300 IJ, preferably 15 to 150 u, the thickness of the copolyester is 2 to 50 v, preferably 2 to 20 u, and the total thickness of the PET resin phase is 4-200p, preferably 4-150p,
The thickness of the adhesive resin phase is 1 to 20 IJ, preferably 1 to 1
0. Good.

[Examples] Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

In addition, "part" in the examples means [part by weight],
Various measurement methods used in this example are shown below.

Blood clot phenol/tetrachloroethane (50150 weight ratio)
OX-TRA measured at 30°C for 1 week (PO2) under conditions of 23°C, 1100% RH
N 10/50AJ oxygen permeability measuring device (USA Mo
(manufactured by dern Controls) to measure Po2 and c
c ·mm/m2-day-atm.

Production example 1 3000 parts of isophthalic acid, 1350 parts of ethylene glycol
Place the sample in an autoclave and pressurize it in a nitrogen atmosphere (2,
The esterification reaction was carried out at 220 to 245°C for 3 hours under stirring (5 kg/cm2), and the water produced during this time was distilled out of the system.

To this esterification reaction, 460 parts of 1,3-phenylenedioxydiacetic acid and 3 parts of titanium tetrabutoxide were added, and the pressure inside the polymerization tank was gradually reduced from normal pressure, and the temperature was gradually raised to 260°C and 1 torr. A transparent polyester having an intrinsic viscosity of 0.68 was obtained in a total polymerization time of 5 hours under vacuum.

200. made from the resin. Po2 of thick press sheet
is 0.45 cc-mm/m2-day-at
It showed good oxygen gas barrier properties at m.

Production Example 2 1,520 parts of dimethyl isophthalate, 1,920 parts of naphthalene dicarboxylic acid dimethyl ester, 1,920 parts of ethylene cudicol, and 1.2 parts of manganese acetate tetrahydrate were added to a reaction vessel, and the temperature was gradually raised from 160°C to 230°C. Then, the transesterification reaction was carried out until no distillate was produced.

To this system, 2360 parts of 1,3-phinidine dioxydiacetic acid, 0.8 parts of orthophosphoric acid, and 1.2 parts of germanium dioxide were added in this order, and the temperature was gradually raised from 230°C while the inside of the polymerization tank was kept constant. Gradually reduce the pressure from the pressure to 260'C10,5t
Intrinsic viscosity was 0.71 at a total polymerization time of 6 hours under a vacuum of orr.
A highly transparent polyester was obtained.

200. Po2 of thick press sheet is 0.2
It showed good oxygen gas barrier properties at 5cc-mm/m2-day-atm.

Example 1 Copolymerized polyester produced in Production Example 1 as a gas barrier resin, PET for packaging film (Diafoil ■-
H, Diafoil (manufactured by Kiki) and adhesive resin Tubatic ■-APL33E (adhesive polyolefin resin manufactured by Mitsubishi Kasei ■, melt index: 2.0 g / 10
m1n, density, 0.92, hereinafter referred to as fAPJ. ) was applied to a feed block type 3 type 5 layer coextrusion device to form an unstretched sheet under the following conditions.

Extruded sheet layer structure thickness: 100u / 40L+ / 100u /
40+, +/100u Resin: PET/AP/Copolyester/AP/PET extrusion O8 40mm
φ Extrusion temperature Copolymerized polyester (240°C) AP (2
10°C), PET (260°C) film formation 2 m
/min (electrostatic application method) Next, this extruded sheet is
Simultaneous biaxial stretching was carried out using a Long biaxial stretching machine (manufactured by Long, USA) at a tank temperature of 135° C. and a magnification of 3.3×3.3.

After stretching, heat treatment was performed at 160° C. for 110 minutes under tension. The obtained stretched film has good appearance and Po2
showed an excellent oxygen gas barrier property of 1.12 cc-mm/m2·day-atm.

This stretched film was placed in a pressure cutter (manufactured by Hirata Seisakusho) at a temperature of 120°C and a relative humidity of 100%.
After retort treatment for 1 hour, oxygen gas permeability was measured again, and Po2 was 1.15, which was almost unchanged from before retort treatment, and no change in appearance was observed.

Example 2 Except for using the copolymerized polyester prepared in Production Example 2, the same procedure as in Example 1 was carried out to obtain a three-type, five-layer biaxially stretched film with good appearance. The Po2 of the laminated film is 0.
73, indicating good oxygen gas barrier properties. In addition, Po2 after retort treatment similar to Example 1 was 0.76,
There was almost no change from before the retort treatment, and no change in appearance was observed.

Example 3 Instead of Diafoil ■H, Kodar A-150
(Bossilohexylene dimethylene terephthalate copolymer, manufactured by Eastman Chemicals, USA)
The same procedure as in Example 2 was performed except that 5 layers of 3 types of biaxially stretched films were obtained.

The laminated stretched film had a Po2 of 0.85 and exhibited good oxygen gas barrier properties. Further, Po2 after the same retort treatment as in Example 1 was 0.88, which was almost unchanged from before the treatment, and no change in appearance was observed.

Comparative Example 1 Ethylene-vinyl alcohol copolymer (EVOH) (ethylene content 38%) was used instead of copolymerized polyester.

The procedure was carried out in the same manner as in Example 1, except that the degree of pycnication was 99.5%, Soarnol ■E, and Nippon Gosei Kagaku Kogyo Co., Ltd. were used.
A biaxially stretched film having the following layer structure was created.

Thickness: 10/5. / 10. / 5. / 1
0゜Cedar'' 2 PET/AP/EVOH/AP/PET
The film had a PO2 of 0.09 (0% RH) and exhibited extremely good oxygen gas barrier properties when completely dry. However, Po2 after the same retort treatment as in Example 1 was 1.
75, and the oxygen gas barrier properties were significantly deteriorated by the retort treatment.

Comparative Example 2 Soarnol ■DT (ethylene content 29%, saponification degree 99.5%, Nippon Gosei Chemical Industry ■) was used instead of Soarnol E.
A biaxially stretched film with the same layer structure was produced by the same operation as in Comparative Example 1, except that the same method was used as in Comparative Example 1.

The film had a Po2 of 0.05 and exhibited very good oxygen gas barrier properties when completely dry; however, the Po2 after retort treatment was 1.11, and as in Comparative Example 1, the retort treatment improved its oxygen gas barrier properties. sex deteriorated significantly.

In addition, this composition system had some difficulty in thermal stability during extrusion molding.

Comparative Example 3 By the same operation as in Example 1, three layers with the following layer configuration were prepared.
A five-layer extruded sheet was prepared.

Thickness: 15μ/5u/15μ/5IJ/15
μ resin: PET/AP/copolyester/AP
/ PETThe sheet had a Po2 of 1.31 and showed good oxygen gas barrier properties, but when it was subjected to the same retort treatment as in Example 1, the entire sheet turned white, significantly lowering the commercial value and causing a slight loss of oxygen gas. The bag broke due to the impact.

[Effects of the Invention] As described above, a saturated polyester resin represented by polyethylene terephthalate, polybutylene terephthalate, polycyclohexylene dimethylene terephthalate, etc. whose main component is terephthalic acid as an acid component, isophthalic acid and general formula (I) By laminating and stretching the above-mentioned copolyester resin containing phenylenedioxydiacetic acid as the main acid component, it is highly transparent, tough, and has low water permeability.
In addition, it has excellent barrier properties against gases such as oxygen, and under high humidity,
Of course, it is possible to obtain a laminated stretched film that can be used without losing any of its properties even in retort applications where high-temperature water treatment such as boiling water is applied. Therefore, the laminated stretched film of the present invention is suitable as a packaging film for various foods, medicines, medical equipment, precision instruments, etc., and is particularly useful as a packaging material for cooked foods that undergo retort processing.

Claims (4)

[Claims] (1) A saturated polyester resin layer containing terephthalic acid as a main component as an acid component, and a copolyester resin layer satisfying the following [1] to [3], and is stretched in at least one direction. Laminated stretched film. [1] Isophthalic acid or its ester-forming derivative (
A) is 5 to 95 mol% of the total acid component. [2] The dicarboxylic acid represented by the general formula (I) or its ester-forming derivative (B) accounts for 5 to 95 mol% of the total acid component. [3] The sum of components (A) and (B) is 50 mol% or more of the total acid components of the copolymerized polyester. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) (R^1, R^2, R^3, R^4 are hydrogen, alkyl groups with 1 to 6 carbon atoms, alkoxy groups, phenyl groups, or Cl, (Represents Br, F.) (2) The laminated stretched film according to claim 1, wherein 5 to 50 mol % of the total acid components of the copolymerized polyester is naphthalene dicarboxylic acid or its ester-forming derivative. (3) The laminated stretched film according to claim 1 or 2, wherein the saturated polyester resin layer is a polyethylene terephthalate resin layer. (4) The laminated stretched film according to any one of claims 1 to 3, characterized in that an adhesive resin layer is interposed between the saturated polyester resin layer and the copolyester resin layer.