JP2003001775A - Flexible stretched polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible stretched polyester film containing a plasticizer imparting flexibility stably remaining in its polyester resin so as to be made usable as a product, keeping flexibility even under a severe condition such as a high temperature condition or the like and not substantially changed in appearance such as transparency or the like or form with the elapse of time or by heating. SOLUTION: The flexible stretched polyester film is constituted by forming thin film layers suppressing the scattering and leaching of the plasticizer on both surfaces of a plasticizer-containing polyester resin layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film softened by a plasticizer, and more particularly to a stretched polyester film having good flexibility durability and high safety, and a packaging wrap film comprising the same.

[0002]

2. Description of the Related Art Conventionally, resins such as soft polyvinyl chloride, polyvinylidene chloride, polyethylene and polypropylene have been widely used as film materials. However, in particular, among these resin films, materials containing chlorine such as soft polyvinyl chloride and polyvinylidene chloride are problematic because they may cause generation of dioxins during soil burial or incineration. Further, film materials such as polyester and polyolefin have not yet exhibited excellent flexibility such as polyvinyl chloride and polyvinylidene chloride.

[0003]

The problem to be solved by the present invention is to provide a flexible polyester film which can be used as a product. One of the problems to be solved by the problem is that a plasticizer imparting flexibility is used. It is intended to provide a polyester film which stably stays in a polyester resin and maintains flexibility even under severe conditions such as high temperature. Still another object is to provide a softened stretched polyester film which has substantially no change in appearance or morphology such as transparency due to aging or heating.

[0004]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that a thin film layer is formed on both sides of a film made of a polyester resin containing a plasticizer, By stretching the film at least uniaxially to enhance the molecular orientation and crystallinity, the flexibility is high, and the appearance and morphology do not change even after aging or heating, and it can be used as a product such as a packaging material. It has been found that a modified stretched polyester film can be provided.

That is, the softened stretched polyester film according to the present invention is characterized in that a thin film layer is formed on both sides of a polyester film containing a plasticizer.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below along with preferred embodiments.

The film according to the present invention is made of polyester containing a plasticizer for softening, and it is necessary that thin film layers are formed on both surfaces of the film. Without such a thin film layer, the flexibility durability is insufficient. Especially 7
Such a thin film layer is indispensable in order to suppress the scattering and exudation of the plasticizer when it is exposed to a high temperature of 0 ° C. or higher or hot water or oil. Generally, a method of increasing the affinity between the base resin and the plasticizer has been studied in order to suppress the scattering and leaching of the plasticizer, but it is difficult to suppress the scattering and leaching of the plasticizer even at high temperature.

The thin film layer is not particularly limited as long as the scattering and exudation of the plasticizer is suppressed. For example, the glass transition temperature is 50 ° C. or higher, preferably 65 ° C. or higher,
Polymer layer with good adhesion to the polyester used, layer containing acrylic resin as the main constituent, layer containing vinyl resin as the main constituent, layer containing epoxy resin as the main constituent, amide resin as the main constituent Examples of such layers include the components. Among these, acrylic resins and vinyl resins, which are highly effective, are particularly preferable. When used as a wrapping film for packaging, a film having a slight adhesive property is preferably used.

As the acrylic resin, various monomers can be used as its constituent components. For example, those having a basic skeleton of alkyl acrylate or alkyl methacrylate (wherein the alkyl group is an alkyl group having 1 to 25 carbon atoms) and further copolymerizing monomers having various crosslinkable functional groups can be used. Examples of such a functional group include a carboxyl group, a methylol group, an acid anhydride group, a sulfonic acid group, an amide group, a methylolated amide group, an amino group, a hydroxyl group and an epoxy group. Examples of the monomer having a functional group include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, vinylsulfonic acid, styrenesulfonic acid, acrylamide, methacrylamide, N-methylolacrylamide, methylolmethacrylamide, diethylaminoethyl. Vinyl ether, 2-aminoethyl vinyl ether, 3-aminopropyl vinyl ether, 2-aminobutyl vinyl ether, dimethylaminoethyl methacrylate, β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, polyethylene glycol monoacrylate,
Examples thereof include polyethylene glycol monomethacrylate, glycidyl acrylate, and glycidyl methacrylate. Furthermore, compounds other than the above, such as acrylonitrile, methacrylonitrile, styrene, butyl vinyl ether, vinyl acetate, vinyl pyridine, vinyl pyrrolidone, and alkoxysilanes having a vinyl group may be copolymerized. Of course, esters of the above monomers can also be used.

The thickness of the thin film layer may be a thickness sufficient to achieve the purpose, but it is preferably 1 μm or less, more preferably 0.5 μm or less. Particularly in the present invention, the rate of change in loop stiffness (ΔR) after heat treatment (135 ° C., 30 minutes) is adjusted to 20% or less, more preferably, by adjusting the type of material used for the thin film layer and the film thickness. It is preferable to increase the durability of flexibility so that it becomes 10% or less. When ΔR exceeds 20%, the durability of flexibility may be insufficient in applications that are exposed to high temperatures, for example, applications such as wrap films that are applied to heating in a microwave oven.

Further, the film of the present invention needs to be stretched in at least one direction. In so-called unstretched film or extruded sheet where crystallization or orientation has not progressed,
Due to deterioration of flexibility over time and crystallization that greatly progresses during heating, problems such as scattering and seeping out of the plasticizer and changes in appearance and morphology occur. In order to solve such a problem, the film needs to be stretched in at least one direction, and it is more preferable that the film is stretched in two directions (biaxial) and heat-fixed.

The polyester used in the present invention is a polymer containing at least 80% by weight of a polymer obtained by polycondensation of a dicarboxylic acid such as an aromatic dicarboxylic acid, an alicyclic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol. is there. Examples of the aromatic dicarboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, 1,4
-Naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-
Diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid and the like can be used, and among them, terephthalic acid, phthalic acid and 2,6-naphthalenedicarboxylic acid are preferably used. You can As the alicyclic dicarboxylic acid component, for example, cyclohexanedicarboxylic acid or the like can be used. As the aliphatic dicarboxylic acid component, for example, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, etc. can be used. These acid components may be used alone or in combination of two or more. Further, an oxy acid or the like such as hydroxyethoxybenzoic acid may be partially copolymerized.

As the diol component, for example, ethylene glycol, 1,2-propanediol, 1,3
-Propanediol, neopentyl glycol, 1,3
-Butanediol, 1,4-butanediol, 1,5-
Pentanediol, 1,6-hexanediol, 1,2
-Cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol,
Polyalkylene glycol, 2,2'-bis (4'-β
-Hydroxyethoxyphenyl) propane and the like can be used, and among them, ethylene glycol,
1,4-butanediol, 1,4-cyclohexanedimethanol, diethylene glycol and the like can be used, and particularly preferably diethylene glycol and the like can be used. These diol components may be used alone or in combination of two or more.

Further, as the polyester, other compounds such as trimellitic acid, pyromellitic acid, glycerol, pentaerythritol, monofunctional compounds such as 2,4-dioxybenzoic acid, lauryl alcohol and phenyl isocyanate can be used as the polymer. It may be copolymerized within the range of being substantially linear.

The polyester in the present invention is not particularly limited, but polyethylene terephthalate, polyethylene naphthalate (polyethylene-2,6-naphthalate), polybutylene terephthalate, polypropylene terephthalate and copolymers and modified products thereof may be used.
From the viewpoint of exhibiting the effects of the present invention, polyethylene terephthalate and polyethylene-2,6-naphthalate are preferably used from the viewpoint of heat resistance.

The plasticizer described in the present invention is not particularly limited as long as it has a plasticizing effect on polyester, but an organic plasticizer is preferable. Here, the plasticizing effect means to lower the glass transition temperature of polyester. From the viewpoint of dispersibility and compatibility, the plasticizer preferably has a number average molecular weight of 200 to 3000, more preferably 300 to 2500, and further preferably 400 to 2.
It is 000.

As the organic plasticizer, ether plasticizers, ester plasticizers, phthalic acid plasticizers, phosphorus plasticizers and the like are preferable, and ether plasticizers and ester plasticizers are preferable from the viewpoint of excellent compatibility with polyester. More preferred are plasticizers. Examples of ether plasticizers include polyoxyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Examples of ester plasticizers include esters of aliphatic dicarboxylic acids and aliphatic alcohols, and examples of aliphatic dicarboxylic acids include oxalic acid, succinic acid, sebacic acid, adipic acid and the like. As the aliphatic alcohol, for example, methanol, ethanol, n-propanol, isopropanol, n-hexanol, n-octanol, 2-ethylhexanol, n-dodecanol, monohydric alcohol such as stearyl alcohol, ethylene glycol, 1,2- Propylene glycol, 1,3-propylene glycol,
1,3-butanediol, 1,5-pentanediol, 1,6-
Examples thereof include dihydric alcohols such as hexanediol, diethylene glycol, neopentyl glycol and polyethylene glycol, and polyhydric alcohols such as glycerin, trimethylolpropane and pentaerythritol.

The plasticizer used in the present invention preferably has low reactivity with the polyester in order to improve the heat resistance and solvent resistance of the polyester. Specifically, it is effective that groups having functionality with the polyester in the above-mentioned plasticizer such as a hydroxyl group and a carboxyl group are reduced, and for example, at least one of the ends of the plasticizer molecule is blocked. It is more preferable that all the ends are blocked. The end-capped plasticizer, for example, the end of polyalkylene glycol, benzoic acid, methyl benzoic acid, aromatic carboxylic acids such as naphthalene monocarboxylic acid and acetic acid, propionic acid, butyric acid, valeric acid, lauric acid, stearyl acid Examples thereof include those esterified with an aliphatic carboxylic acid such as. Further, as the ester-based plasticizer with the ends blocked,
For example, the above-mentioned ester of a dicarboxylic acid and a monohydric alcohol, or the ester of a hydroxyl group of an ester of a dihydric or higher alcohol may be esterified or etherified with a carboxylic acid or a monohydric alcohol. As the ester plasticizer, the dicarboxylic acid component has 4 to 20 carbon atoms from the viewpoint of compatibility and dispersibility with polyester.
Is more preferable, it is more preferably composed of a dicarboxylic acid having 4 to 15 carbon atoms, further preferably 4 to 12 carbon atoms, and particularly preferably 5 to 10 carbon atoms.

The addition amount of the plasticizer may be an amount capable of exerting the softening effect of the polyester, and particularly, the loop stiffness in terms of the film thickness of 10 μm is 350 μN / c.
It is advisable to adjust the type and addition amount of the plasticizer so as to be m or less. Loop stiffness of 35 in terms of thickness of 10 μm
If it exceeds 0 μN / cm, the softening effect is insufficient,
It is not easy to use when used for applications such as packaging films. The preferable amount of the plasticizer added varies depending on the type of the plasticizer and the type of polyester used, but is particularly 5 to 50% by weight.
Is preferred. If it is less than 5%, the plasticizing effect often varies, and if it exceeds 50% by weight, problems such as process troubles due to bleed-out (precipitation) on the surface may occur. From this viewpoint, the content of the plasticizer is 5 to 30.
More preferably, it is wt%.

Further, by including an adhesive on at least one side of the thin film layer of the softened stretched polyester film of the present invention, the film obtained can be provided with appropriate adhesiveness and can be suitably used as a packaging film. The pressure-sensitive adhesive may be a material that imparts appropriate tackiness, and examples thereof include fatty acid esters, aliphatic hydrocarbon resins, terpene-based resins, coumarone-indene resins, aromatic hydrocarbon resins, and rosin-based resins. Can be mentioned. Examples of the fatty acid esters include ester compounds of polyhydric alcohols such as glycerin, sorbitol, pentaerythritol, propylene glycol, polyethylene glycol, and polypropylene glycol with higher fatty acids such as oleic acid, linoleic acid, and lauric acid. , Monoglycerin oleate, polyglycerin oleate, diglycerin stearate, glycerin diricinolate, glycerin acetylricinoleate, propylene glycol oleate, propylene glycol laurate, pentaerythritol oleate, polyethylene glycol oleate, sorbitan oleate, Sorbitan laurate, polyethylene glycol sorbitan laurate, sucrose monostearate, sucrose palmitate, ® sugar oleate, sucrose laurate, sucrose behenate, one or a mixture of one or more kinds of such sucrose erucic acid ester.

The amount of such an adhesive added is preferably 0.5 to 15% by weight based on the thin film layer containing the adhesive. The pressure-sensitive adhesive used is preferably biodegradable, and from this viewpoint, terpene resins, rosin resins, fatty acid esters, aliphatic hydrocarbon resins and the like are preferable.

The thickness of the softened stretched polyester film of the present invention is not particularly limited, but it is from 1 to 150 μm, particularly preferably from 5 to 100 μm, further preferably from 5 to 20 μm.
Is.

The softened stretched polyester film of the present invention can be used for various purposes by taking advantage of flexibility, heat resistance, flexibility durability, and the like. Among them, particularly when used as a packaging wrap film, its function is sufficient. It is preferable because it can be demonstrated.

Next, a method for producing the softened stretched polyester film of the present invention will be described. The softened stretched polyester film of the present invention can be obtained by an existing stretched film manufacturing method such as an inflation method, a sequential biaxial stretching method, or a simultaneous biaxial stretching method. In the case of the inflation method, a thin film layer that suppresses scattering and oozing of the plasticizer is laminated and extruded in advance, or the above thin film layer is formed offline on the stretched film. In the production of the softened polyester stretched film of the present invention by the sequential biaxial stretching method or the simultaneous biaxial stretching method, first, a predetermined amount of the above-mentioned plasticizer is contained in the polyester resin, and the film is formed from a slit-shaped die by a known method. It is melt-extruded into a shape, and it is brought into close contact with a casting drum and cooled and solidified to obtain an unstretched film. The method of adding the plasticizer to the polyester resin may be to mix the plasticizer into the resin in advance, but use a twin-screw extruder to measure the addition of the plasticizer to the molten resin in the extruder. Is preferred. The unstretched film obtained by such a method is continuously stretched in at least one direction, and then a thin film layer that suppresses scattering and seepage of the plasticizer is formed on both surfaces thereof, or a thin film layer is formed on both surfaces of the unstretched film. Stretching is carried out after the squeezing. The method for forming such a thin film layer can be carried out by various known methods such as extrusion lamination, coating and dipping of the resin used for the thin film layer. The formation of the thin film layer that suppresses the scattering and exudation of the plasticizer may be performed in-line during the film forming process before and after stretching, or may be performed offline after once obtaining the stretched film. Inline is preferred. Among these, it is preferable to form the thin film layer in-line during the film formation by the successive stretching method because of high flexibility and good stability.

That is, after stretching the unstretched film in at least one direction, a thin film layer for suppressing the scattering and exudation of the plasticizer is formed. The formation of the thin film layer can be carried out by various known methods such as extrusion lamination and coating of the resin for forming the thin film layer as described above, but especially by laminating the aqueous solution or emulsion of the resin forming the thin film layer by coating after longitudinal stretching. The in-line coating method is industrially suitable because of its low cost. Further, it is preferable that the thin film layer is laminated by in-line coating after the longitudinal stretching, then stretched in the lateral direction and heat-treated to enhance the adhesion of the thin film layer to the substrate and the toughness of the thin film layer.

[0026]

EXAMPLES The present invention will be further described below with reference to examples. In particular, polyethylene terephthalate, which has good heat resistance and is a preferable example, will be described as an example, but the present invention is not limited to this.

(Method for measuring loop stiffness) Loop stiffness (bending strength index) M in terms of film thickness of 10 μm M: sample has a length of 150 mm and a width of 1
It was cut out to 0 mm and the bending stress M1 (μN) was measured using a loop stiffener tester manufactured by Toyo Seiki Seisaku-sho, Ltd. The loop length was 50 mm and the crushing distance was 5 mm. Bending stress measurement value M1 (N), sample thickness t
From (μm), the loop stiffness M (μN / cm) with a thickness of 10 μm was calculated using the following formula.

M = M1 × (10 / t) ³ /(1.0) The measurement was carried out using 20 samples having different sampling positions in each of the longitudinal direction and the width direction, and the average value was obtained.

(Method of measuring rate of change in loop stiffness (ΔR)) The loop stiffness of the sample after heat treatment at 135 ° C. for 30 minutes in an oven is R135, the loop stiffness of the sample before heat treatment is R25, and Δ is calculated by the following equation.
Find R.

ΔR = (R135−R25) / R25 * 100 (%) (polyester resin) polyethylene terephthalate (intrinsic viscosity 0.60 (dl / g), melting point 257 ° C., glass transition temperature 78 ° C., silicon oxide particles: particles Pellets having a diameter of 1.2 μm and an addition amount of 0.8% by weight) were dried by heating under vacuum at 180 ° C. for 4 hours to sufficiently remove water and used.

(Plasticizer) Plasticizer A: benzoic acid-terminated polyethylene glycol (molecular weight 600) Plasticizer B: stearyl acid-terminated polyethylene glycol (water-dispersed coating composition) acrylic resin; methyl methacrylate / butyl acrylate / acrylic acid (45 / 50/5 wt%) was prepared by diluting an acrylic resin emulsion having an average particle diameter of 0.05 μm obtained by emulsion polymerization with water so that the solid content weight ratio was 3%.

(Evaluation of Hardness) With respect to the film for packaging material, particularly the wrapping film, the hardness of the film is ◎, which is sufficiently soft to use, and the softness which is slightly hard but is not inconvenient to use, is soft. A sample with slightly inferior size was rated as Δ, and a sample with poor flexibility was rated as x.

Examples 1 to 6 Polyethylene terephthalate was melted in a twin-screw extruder at 280 ° C., and the compound shown in Table 1 was supplied as a plasticizer while being metered so that the addition amount shown in Table 1 was obtained. Add the agent to form a polymer stream, T die die temperature 250 ℃
The film was extruded into a film shape by, and cast by electrostatic application on a drum cooled to 35 ° C. to prepare an unstretched film. Continuously stretched 3 times in the longitudinal direction between heating rolls at 95 ° C,
Then, a water-dispersed coating was applied by gravure coating on each side so that the thickness of the thin film layer after biaxial stretching would be the thickness shown in Table 1 on each side. The coated uniaxially stretched film is held by a clip and guided into a tenter, and after partially drying water in a preheating step at 60 ° C, it is stretched 5.0 times in the transverse direction while being heated at a temperature of 110 ° C. Heat treatment was performed at 180 ° C. to obtain a softened stretched polyester film having a film thickness of about 10 μm. The characteristic values of the obtained softened stretched polyester film are shown in Table 1.

Comparative Examples 1 to 3 Softened stretched polyester films were obtained in the same manner as in Examples 2 and 4 except that the thin film layer was not formed of acrylic resin (Comparative Examples 1 and 2). Table 2 shows the characteristic values of the obtained polyester film. Also, without adding a plasticizer,
A polyester film having no thin film layer formed was obtained in the same manner as in Example 1. The characteristic values are also shown in Table 2 (Comparative Example 3).

[0035]

[Table 1]

[0036]

[Table 2] As is clear from comparison between Examples 1 to 6 and Comparative Example 3, addition of a plasticizer to polyester softens the film and improves the hardness as a packaging material. From the loop stiffness value before and after heating, the loop stiffness is 3
It can be seen that 50 μN / cm or less is particularly preferable. This effect increases as the amount of plasticizer added increases. Plasticizer A
Both B and B show an effect, but the addition effect is slightly different depending on the plasticizer.

Further, it can be seen from Examples 1 to 6 that by providing the coating thin film layer of the acrylic resin, the ΔR after heating can be kept small and the durability of flexibility can be improved. On the other hand, it can be seen that even if the thickness of the thin film layer is the same, if the plasticizer is changed, the effect of suppressing the scattering and exudation during heating is different and the ΔR is different. When ΔR exceeds 20%, although the effect is still present, the suppressing effect is slightly unsatisfactory (Examples 4 and 5). It can be seen from the comparison between Examples 3 and 6 that the suppression effect can be enhanced by increasing the thickness of the thin film layer. On the other hand, when such a thin film layer is not provided, the plasticizer is scattered and oozes out by heating, the flexibility cannot be kept, and it cannot be used (Example 2 and Comparative Example 1 and Example 3 and Comparative Example 2).
Contrast).

Comparative Example 4 Polyethylene terephthalate was melted at 280 ° C. by a twin-screw extruder, and a plasticizer A (benzoic acid-terminated polyethylene glycol (molecular weight 600)) was used as a plasticizer to add 2
It is supplied while being weighed so as to be 5% by weight and a plasticizer is added to form a polymer stream, which is extruded into a film shape at a T die die temperature of 250 ° C. and cast on a drum cooled to 35 ° C. to have a thickness of 90 μm An unstretched film of was prepared. This unstretched film was stretched off-line, and the same water-dispersed coating as in Example 1 was used off-line to obtain a thickness of 0.2
A 5 μm thin film layer was formed.

The obtained film was soft immediately after it was formed, but when it was stored in an oven at 60 ° C. for 10 days, the film became white and turbid, and the appearance remarkably deteriorated. or,
When this unstretched film is heated at 135 ° C for 30 minutes,
The appearance of the film changed to white, the flatness deteriorated, and the flexibility greatly decreased.

Example 7 Diglycerin stearate as a pressure-sensitive adhesive was added in an amount of 3% by weight in solid content to the water-dispersed coating material applied to one surface of the thin film layer in Example 3, and the stretched film was formed under the same conditions as in Example 3. Obtained.
The obtained film had flexibility and appropriate tackiness, and was easy to use as a wrap film.

Example 8 Polyethylene terephthalate was melted at 280 ° C. by a twin-screw extruder, and a plasticizer A (benzoic acid-terminated polyethylene glycol (molecular weight 600)) was used as a plasticizer to add 2
A polymer stream was formed by feeding while being metered so as to be 5% by weight and adding a plasticizer. Also, polyethylene terephthalate was melted as a thin film layer at 280 ° C. by an extruder to form a polymer stream. These two polymer streams are joined by a die to form a laminated structure in which thin film layers are provided on both sides, and then the film is extruded into a film at a T die die temperature of 250 ° C.
An unstretched film was prepared by casting on a drum cooled to 25 ° C. Subsequently, it is stretched 3 times in the machine direction on a roller heated to 95 ° C., once cooled and then loaded into a tenter, stretched 3.5 times in the transverse direction at 110 ° C., and then heat treated at 180 ° C., Laminated film thickness 12 μm
A softened stretched polyester film (thickness of the thin film was 1 μm) was obtained. The loop stiffness of this film is 1
It was 80 μN / cm. When this stretched film was heated at 135 ° C. for 30 minutes, the scattering effect of the plasticizer was slightly inferior, but it was at a level that was somehow satisfied. At this time, ΔR was 19%.

[0042]

As described above, according to the present invention, it is possible to provide a stretched film which can keep its flexibility for a long period of time and has good flexibility durability even under severe conditions such as high temperature. Such a film is widely used for agricultural materials and packaging, and can contribute to the reduction of dust.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // B29K 67:00 B29K 67:00 B29L 7:00 B29L 7:00 9:00 9:00 F term ( reference) 3E086 AD13 BA04 BA15 BA24 BA33 BB90 DA01 4F100 AK12 AK22 AK25 AK41A AK42 AL05A BA03 BA07 BA10B BA10C CA04A CB05B CC00 EH17 EJ37A EJ38 GB15 JK06A JK17 JL00 JL13B JM02B JM02C JN01 4F210 AA21 AA24 AB07 AC03 AG01 AG03 AH54 AR06 AR20 QA02 QA03 QC02 QC03 QC06 QD05 QD08 QD13 QD34 QG01 QG15 QL02 QM02 QM03 QM06 QW07

Claims (5)

[Claims] 1. A softened stretched polyester film having thin film layers formed on both sides of a polyester film containing a plasticizer. 2. The softened stretched polyester film according to claim 1, which has a loop stiffness of 350 μN / cm or less in terms of a thickness of 10 μm. 3. The softened stretched polyester film according to claim 1, wherein the loop stiffness change rate (ΔR) after the heat treatment (135 ° C., 30 minutes) is 20% or less. 4. The softened stretched polyester film according to claim 1, wherein the thin film layer contains an adhesive on at least one surface. 5. A packaging wrap film comprising the softened stretched polyester film according to any one of claims 1 to 4.