JP2021172678A - Polyester-based film and packaging bag using the same - Google Patents

Abstract

To provide a polyester-based film that has aroma retention capability against various organic compounds, a high fusion seal strength, and a good bag-tear resistance when a liquid is put into the content as a packaging bag.SOLUTION: A polyester-based film satisfies the following requirements (1) and (2). (1) Loss tangent (tan δ) obtained when dynamic viscoelasticity is measured at 25°C is 0.03 or more and 0.15 or less in the longitudinal direction. (2) Fusion seal strength when fusing and sealing so that the width direction is the sealing direction is 5 N/15 mm or more and 20 N/15 mm or less.SELECTED DRAWING: None

Description

The present invention relates to a polyester-based film having excellent fusing seal suitability, and a packaging bag using the same.

Film is used as a material for bags that wrap various articles such as foods, pharmaceuticals, and industrial products. The packaging bag may be made with a fusing seal. Therefore, when selecting a packaging material, not only mechanical strength and transparency but also strength and appearance of the fusing-sealed portion are taken into consideration. Films made of polyolefin resins are widely used as packaging materials because of their high versatility due to these characteristics. However, for example, a film made of a polypropylene resin as described in Patent Document 1 does not have sufficient deodorizing property (fragrance retaining property). Therefore, when the content is strongly odorous, the odorous component passes through the film. It leaks.
On the other hand, a packaging bag using a film made of a polyester resin as described in Patent Document 2 is difficult to adsorb organic compounds contained in chemical products, pharmaceuticals, foods, etc., and it is difficult to allow odorous components to permeate. , Excellent in fragrance retention.

Japanese Patent No. 4867857 JP-A-2017-210541

Masahito Matsuo, Akio Ueda, Yoshio Kondo. Study of fracture process of resin-rubber two-component polymer. Polymer chemistry. 1967, vol.24, no.264, p. 285-295.

However, in a packaging bag that is blown-sealed using a film made of a polyester resin as described in Patent Document 2, when a liquid is put into the contents, the bag is broken from the blown-sealed portion when the bag is dropped. There is a problem. Under such circumstances, there has been a demand for a material having high fragrance-retaining property to the contents and high fusing seal strength, as well as good bag-breaking resistance when a liquid is put into the contents.

The present invention has been made by paying attention to the above circumstances, and an object of the present invention is that it has a fragrance-retaining property against various organic compounds, has a high fusing seal strength, and can be used as a packaging bag as a content. It is an object of the present invention to provide a polyester-based film having good bag-breaking resistance when a liquid is put therein. Another object of the present invention is to provide a laminate containing the polyester-based film as at least one layer, and a packaging bag using the same.

That is, the present invention has the following configuration.
1. 1. A polyester-based film characterized by satisfying the following requirements (1) and (2).
(1) The loss tangent (tan δ) obtained when the dynamic viscoelasticity is measured at 25 ° C. is 0.03 or more and 0.15 or less in the longitudinal direction. (2) Fusing seal so that the film width direction is the sealing direction. The fusing seal strength at the time of this is 5N / 15mm or more and 20N / 15mm or less. The polyester-based film according to claim 1, wherein the Tg obtained by the temperature-modulated DSC measurement is −75 ° C. or higher and 25 ° C. or lower.
3. 3. The polyester-based film according to claim 1 or 2, wherein the folding holding angle is 20 degrees or more and 80 degrees or less.
4. The polyester according to any one of claims 1 to 3, wherein the heat shrinkage rate when immersed in hot water at 80 ° C. for 10 seconds is -10% or more and 10% or less in both the longitudinal direction and the width direction. System film.
5. A laminate having at least one layer of the polyester-based film according to any one of claims 1 to 4.
6. A packaging bag comprising at least a part of the polyester-based film according to any one of claims 1 to 4 or the laminate according to claim 5.

The polyester-based film of the present invention has excellent fragrance retention, high fusing seal strength, and good tear resistance when a liquid is put into the contents as a packaging bag. Therefore, according to the polyester-based film of the present invention, it is possible to provide a packaging bag which is excellent in aroma retention, has high fusing seal strength, and can use a liquid as the content.

It is a figure which shows the measuring method of the impact strength of a fusing seal part.

The polyester-based film of the present invention is composed of a resin having at least an ester bond in the skeleton of the molecular main chain, and satisfies the following requirements (1) and (2);
(1) The loss tangent (tan δ) obtained when the dynamic viscoelasticity is measured at 25 ° C. is 0.03 or more and 0.15 or less in the longitudinal direction. (2) Fusing seal so that the film width direction is the sealing direction. Fusing seal strength at the time of 5N / 15mm or more and 20N / 15mm or less

The polyester-based film of the present invention that satisfies the above requirements does not easily adsorb various organic compounds and has excellent fusing and sealing properties. Therefore, when this film is used as a bag, the odor does not leak even if food or the like is put in it, and it is suitable for a packaging bag. Further, the packaging bag having the polyester-based film of the present invention has good bag-break resistance when a liquid is put into the contents. Therefore, it can be carried with the liquid contained in the contents. Hereinafter, the polyester-based film of the present invention will be described.

1. 1. Characteristics of Polyester-based Film Next, the characteristics required for the polyester-based film of the present invention will be described.

1.1. Fusing Seal Strength First, when the polyester film of the present invention is fusing and sealed, the average value of the sealing strength needs to be 5N / 15mm or more and 20N / 15mm or less. If the fusing seal strength is less than 5N / 15mm, the fusing seal portion is easily peeled off and the bag is easily broken, so that it cannot be used. The fusing seal strength is preferably 6N / 15 mm or more, and more preferably 7N / 15 mm or more. The larger the fusing seal strength is, the more preferable it is, but the upper limit currently available is about 20 N / 15 mm, and even if it is 15 N / 15 mm, it can be said that it is practically preferable. The method of fusing and sealing will be described in Examples described later.
1.2. Impact strength of the fusing seal portion The polyester film of the present invention has a fusing seal so that the longitudinal direction is the tensile direction, and the impact strength measured by applying the impact ball of the film impact tester to the fusing seal portion is 0.4 J or more. It is preferably 8J or less. As a result of intensive research, the present inventors have found that when the bag is dropped with the liquid in the contents, the liquid gives an impact to the fusing seal portion in a short time of 0.003 seconds. I found it. In the impact strength measurement, it broke in a time close to that, so the impact strength measurement is a condition close to the actual bag drop. If the impact strength of the fusing seal portion is less than 0.4 J, it is vulnerable to momentary impact, and when the bag is dropped with the liquid contained in the contents, the bag is likely to break and cannot be used. The impact strength of the fusing seal portion is more preferably 0.45 J or more, and particularly preferably 0.5 J or more. On the other hand, if the impact strength of the fusing seal portion exceeds 0.8, the loss tangent (tan δ) at 25 ° C., which will be described later, exceeds 0.15, and there is a risk of sticking to the roll and deterioration of aroma retention. The method of measuring the impact strength of the fusing seal portion will be described in Examples.

1.3. Glass transition temperature (Tg)
The polyester film of the present invention preferably has a Tg of −75 ° C. or higher and 25 ° C. or lower. Tg is more preferably −70 ° C. or higher and 20 ° C. or lower, and particularly preferably −65 ° C. or higher and 15 ° C. or lower. Tg and impact strength will be described with reference to Non-Patent Document 1.

Fig. 2 of Non-Patent Document 1 shows the temperature dependence of Tg of ABS resin rubber and Charpy impact strength. In Fig. 2, when the measurement temperature of the impact strength is Tg or less of the rubber, the impact strength is almost constant and low. On the other hand, it is shown that the impact strength increases when the measured temperature of the impact strength exceeds Tg of rubber. That is, it is considered that the impact strength increases when Tg is equal to or lower than the measured temperature. When this idea is compared with the present invention, the room temperature is usually around 25 ° C. Therefore, by setting the Tg to 25 ° C. or lower, the bag tear resistance when the liquid is put into the contents at room temperature is good. It becomes. On the other hand, when Tg is lower than −75 ° C., the loss tangent (tan δ) at 25 ° C., which will be described later, exceeds 0.15 and the viscosity becomes high, so that the film may adhere to the roll during film formation or processing. There is a risk that the aroma will deteriorate.

1.4.25 ° C loss tangent (tan δ)
The polyester-based film of the present invention needs to have a tan δ at 25 ° C. in the longitudinal direction or the width direction of 0.03 or more and 0.15 or less. tan δ is represented by E'' (loss elastic modulus) / E'(storage elastic modulus), E'' indicates a viscosity term, and E'indicates an elasticity term. Above Tg, the polymer is devitrified, exhibits high viscosity, and has a large tan δ value. When tan δ at 25 ° C. is less than 0.03, E'indicating an elastic term shows a high value, and when the bag is dropped with the liquid in the contents at room temperature, the impact of the above-mentioned fusing seal portion is felt. The strength is reduced, the impact cannot be absorbed, and the bag breaks. The tan δ at 25 ° C. is preferably 0.04 or more, more preferably 0.05 or more. On the other hand, if tan δ exceeds 0.15, the viscosity becomes high and there is a risk of sticking to the roll. Further, when tan δ exceeds 0.15, the amorphous property increases, the apparent specific gravity described later becomes small, and the aroma retention property may deteriorate. It is sufficient that tan δ is within the above range in either the longitudinal direction or the width direction, but it is preferable that tan δ is within the above range in both the longitudinal direction and the width direction. The method for measuring tan δ will be described in Examples.

1.5. Folding holding angle The polyester film of the present invention preferably has a folding holding angle of 20 degrees or more and 80 degrees or less as measured by the method described later. When a bag made of a film having a folding holding angle of 80 degrees or less is twisted, the twist is held and the mouth can be sealed without binding. If the folding holding angle is 80 degrees or more, it becomes difficult to make creases at the bottom of the bag and the bag swells, so that the edges are not aligned when the bags are stacked. The upper limit of the preferable folding holding angle is 75 degrees, and it is more preferable that the upper limit is 70 degrees. Further, the smaller the folding holding angle is, the more preferable it is, but the range covered by the present invention is the lower limit of 20 degrees, and even if the folding holding angle is 25 degrees or more, it can be said that it is practically preferable.

1.6. Shrinkage rate The polyester film of the present invention preferably has a hot water heat shrinkage rate of -10% or more and 10% or less in both the longitudinal direction and the width direction when immersed in hot water at 80 ° C. for 10 seconds.
When the shrinkage rate of hot water exceeds 10% in both the longitudinal direction and the width direction, the shrinkage of the film in a high temperature environment becomes large, and it becomes difficult to maintain the original shape. In particular, when the hot water shrinkage rate in the width direction is large, the variation in the fusing seal strength becomes large. When the film is fusing, the film is melted by the heat from the fusing blade and immediately cooled and solidified to form a resin mass (so-called seal ball). When the film has heat shrinkage in the width direction, the film shrinks due to the heat from the fusing blade, so that the size of the seal balls formed after fusing varies, and as a result, the fusing seal strength varies. Will occur.

The hot water heat shrinkage rate is preferably 9% or less, more preferably 8% or less, still more preferably 7% or less in both the longitudinal direction and the width direction. On the other hand, when the thermal shrinkage of hot water is less than 0%, it means that the film is stretched, and when the stretch of the film is large, it becomes difficult for the film to maintain its original shape as in the case of high shrinkage. Tend. Therefore, the shrinkage rate of hot water in the longitudinal direction and the width direction is preferably −9% or more, more preferably −8% or more, and further preferably −7% or more. The hot water heat shrinkage in the longitudinal direction and the width direction need not be the same, and the hot water heat shrinkage in the longitudinal direction and the width direction may be different as long as they are included in the range of the hot water heat shrinkage.

1.7. Variations in Fusing Seal Strength The standard deviation of the fusing seal strength when the polyester films of the present invention are laminated and fusing sealed is preferably 0.3 or more and 2.5 or less. How to obtain the standard deviation of the fusing seal strength will be described in Examples described later. If the standard deviation of the fusing seal strength is higher than 2.5, the variation in the fusing seal strength becomes large. If there is a large variation in the fusing seal strength, even if the average value of the fusing seal strength exceeds 5N / 15mm in the entire bag, there are many places where the fusing seal strength is less than 5N / 15mm when viewed partially. This makes it difficult to use as a packaging bag because the bag is easily torn from that part. The smaller the standard deviation of the fusing seal strength is, the less the variation in the fusing seal strength is, which is preferable, but 0.3 is the lower limit at the current technical level. The standard deviation of the fusing seal strength is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1 or less. Further, even if the lower limit of the standard deviation of the fusing seal strength is about 0.4 or about 0.5, it can be used as a packaging bag without any problem.

1.8. Apparent specific gravity The apparent specific gravity of the polyester film of the present invention is preferably 1.0 g / cm ³ or more and 1.4 g / cm ³ or less. The apparent specific gravity is more preferable to be 1.02 g / cm ³ or more 1.38 g / cm ³ or less, and particularly preferably 1.04 g / cm ³ or more 1.36 g / cm ³ or less. If the apparent specific gravity is ^{less than 1.0 g / cm 3} , the crystallinity will be low and the aroma retention property may be poor. On the other hand, if the apparent specific gravity exceeds 1.4 g / cm, it becomes difficult to melt by heating, and the fusing seal strength may decrease.

1.9. Thickness The thickness of the polyester film of the present invention is not particularly limited, but is preferably 3 μm or more and 200 μm or less. If the thickness of the film is thinner than 3 μm, there is a risk that the strength will be insufficient and processing such as printing will become difficult. Further, the film thickness may be thicker than 200 μm, but the fusing sealing property is inferior because a larger amount of heat is required for the fusing sealing. Not only that, if the thickness is thicker than 200 μm, the weight of the film used increases and the manufacturing cost increases, which is not preferable. The thickness of the film is more preferably 5 μm or more and 160 μm or less, and further preferably 7 μm or more and 120 μm or less.

2. Constituent materials of polyester film 2.1. Types of polyester raw materials The polyester-based resin used in the present invention contains a resin having at least an ester bond in the skeleton of the molecular main chain as a constituent component.

Further, the polyester resin used in the present invention contains 30 mol% of saturated polyvalent carboxylic acid component as a monomer capable of lowering the glass transition temperature (Tg) and increasing the value of loss tangent (tan δ) at room temperature, which will be described later. It is preferable to use more than 70 mol% or less. More preferably, it is 35 mol% or more and 65 mol% or less. If the content of the saturated polyvalent carboxylic acid component is more than 70%, there is a risk of sticking to the roll and a risk of poor aroma retention. On the other hand, when the saturated polyvalent carboxylic acid component is less than 30 mol%, the glass transition temperature becomes high, the loss sine (tan δ) at room temperature and the impact strength of the seal portion, which will be described later, decrease, and the liquid is put into the contents as a packaging bag. There is a risk that the bag will tear when dropped while it is in the bag.

Examples of the saturated polyvalent carboxylic acid include aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decandicarboxylic acid, and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid.

Among the above saturated polyvalent carboxylic acids, adipic acid and azelaic acid are preferable. By using one or more of these, it becomes easy to set the Tg of the film to 25 ° C. or lower and the tan δ at 25 ° C. to 0.03 or higher.

Further, the polyester resin used in the present invention is preferably used as an unsaturated polyvalent carboxylic acid in an amount of 30 mol% or more and 70 mol% or less. Examples of the unsaturated polyvalent carboxylic acid include aromatic polyvalent carboxylic acids, and examples thereof include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, and naphthalenedicarboxylic acid.

Among the unsaturated polyvalent carboxylic acids described above, terephthalic acid, isophthalic acid and orthophthalic acid are preferable, and terephthalic acid and isophthalic acid are more preferable. By using one or more of these, the aroma retention property becomes good.

Further, as the polyhydric alcohol component constituting the polyester resin used in the present invention, ethylene glycol is used, and in addition, 30 mol% or more of an aliphatic diol component which is a component that lowers Tg more than ethylene glycol is used. Is preferable. More preferably, it is 45 mol% or more.

Examples of the aliphatic diol component include long-chain diols such as diethylene glycol, 1,3-propanediol, 2,2-diethyl-1,3-propanediol and 1,4-butanediol, and aliphatic diols such as hexanediol. be able to.

Among these, diethylene glycol, 1,3-propanediol, and 1,4-butanediol are preferable because they have the effect of improving the above-mentioned tan δ. By using one or more of these, it becomes easy to set the Tg of the film to 25 ° C. or lower and the tan δ at 25 ° C. to 0.03 or higher.

Further, a polyester elastomer containing ε-caprolactone, tetramethylene glycol, or the like may be used as a component constituting the polyester resin. The polyester elastomer can be preferably used because it has the effect of lowering the glass transition temperature (Tg) of the film. A polyester such as polylactic acid containing a polyester containing an aliphatic hydroxycarboxylic acid component such as lactic acid also has an effect of lowering the Tg of the film, but it may lower the mechanical strength, so it is preferable not to contain it. ..

2.2. Other Ingredients In the resin constituting the polyester film of the present invention, various additives such as waxes, antioxidants, antistatic agents, crystal nucleating agents, thickeners, and heat stabilizers are included as required. Agents, color pigments, color inhibitors, UV absorbers and the like can be added. Further, fine particles may be added as a lubricant for improving the slipperiness of the film. Any fine particles can be used. For example, examples of the inorganic fine particles include silica, alumina, titanium dioxide, calcium carbonate, kaolin, and barium sulfate, and examples of the organic fine particles include acrylic resin particles, melamine resin particles, silicone resin particles, and crosslinked polystyrene. Particles and the like can be mentioned. The average particle size of the fine particles can be appropriately selected within the range of 0.05 μm to 3.0 μm (measured by a Coulter counter), if necessary. Further, the amount of fine particles added is in the range of 200 to 1200 ppm in the film, and good slipperiness (friction) and transparency can be achieved at the same time.

The method of blending the fine particles with the resin constituting the polyester-based film is not particularly limited, and examples thereof include a method of adding the fine particles at an arbitrary stage in producing the polyester-based resin. As the step of adding the fine particles, for example, the fine particles are added as a slurry dispersed in ethylene glycol or the like at the stage of esterification or the stage after the completion of the transesterification reaction and before the start of the polycondensation reaction to proceed with the polycondensation reaction. preferable. In addition, a method of blending a slurry of fine particles dispersed in ethylene glycol, water, or other solvent with a polyester resin raw material using a kneading extruder with a vent, or kneading dried fine particles and a polyester resin raw material. There is also a method of blending using an extruder.

2.3. Layer structure The layer structure may be any layer structure such as a single layer (B layer), two types and two layers (B layer / A layer), and two types and three layers (A layer / B layer / A layer). A layer structure of two or more layers is preferable, and two types and three layers are particularly preferable. In the B layer, a saturated polyvalent carboxylic acid component is used in an amount of 30 mol% or more and 70 mol% or less as a monomer capable of lowering the glass transition temperature (Tg) and increasing the value of the loss tangent (tan δ) at room temperature, which will be described later. Is preferable. By using the above-mentioned monomer capable of lowering Tg in the B layer, it is possible to improve the bag breaking resistance when the bag is dropped with the liquid contained in the content. On the other hand, if the above-mentioned monomer capable of lowering Tg is used, the viscosity becomes high and there is a risk of sticking to the roll. Therefore, ethylene terephthalate as shown in the A layer of the example is mainly used as a constituent component of the A layer ( That is, it is preferable to use a polyester resin (containing 50 mol% or more). The layer A preferably contains, as a monomer capable of reducing the folding holding angle, in a range in which the total of one or more monomer components that can be amorphous components is 12 mol% or more and 30 mol% or less. .. If the total amount of the monomer components that can be amorphous components exceeds 30 mol%, tear resistance and heat resistance tend to be insufficient, which is not very preferable. Examples of the monomer that can be an amorphous component include neopentyl glycol, 1,4-cyclohexanedimethanol, and isophthalic acid. Among these, it is particularly preferable to use neopentyl glycol.

The layer ratio of the B layer in the laminated film is preferably 50% or more. When the layer ratio of the A layer is less than 50%, the value of the loss tangent (tan δ) at room temperature, which will be described later, decreases, and the packaging bag that is blown and sealed using the film is in a state where the liquid is contained in the contents. This is not preferable because the tear resistance when the bag is dropped is reduced.
In the case of a single-layer structure, a single-layer film composed of a B layer using the polyester-based resin can be used.

3. 3. Film formation conditions for polyester film 3.1. Melt-extrusion The polyester-based film of the present invention is formed by melt-extruding the polyester raw material described in "1. Polyester raw material constituting the polyester-based film" by an extruder to form an unstretched film, which is shown below. It can be obtained by the method of.
The film may be unstretched, and when it is stretched, either uniaxial stretching or biaxial stretching may be adopted, but from the viewpoint of film strength and productivity, the film obtained by biaxial stretching may be adopted. Is preferable. The polyester resin can be obtained by selecting the type and amount of the dicarboxylic acid component and the diol component and polycondensing them. Further, the chip-shaped polyester resin obtained by polycondensation in advance can be used alone or in combination of two or more as a raw material for a film.

When the raw material resin is melt-extruded, it is preferable to dry the polyester raw material using a dryer such as a hopper dryer or a paddle dryer, or a vacuum dryer. After the polyester raw material is dried in this way, it is melted at a temperature of melting point + 60 ° C. to melting point + 100 ° C. using an extruder and extruded as a film. For extrusion, any existing method such as a T-die method or a tubular method can be adopted.

Then, the unstretched film can be obtained by quenching the film melted by extrusion. As a method for rapidly cooling the molten resin, a method of casting the molten resin from a mouthpiece onto a rotary drum and quenching and solidifying the molten resin to obtain a substantially unoriented resin sheet can be preferably adopted. The film is preferably stretched in any one of the longitudinal (longitudinal) direction and the horizontal (width) direction (uniaxially stretched film, biaxially stretched film). In the following, the sequential biaxial stretching method by lateral stretching-longitudinal stretching, in which the transverse stretching is first performed and then the longitudinal stretching is performed, will be described. It doesn't matter because it only changes. Further, the simultaneous biaxial stretching method may be used.

3.2. Lateral Stretching The unstretched film obtained by quenching after melt extrusion is stretched in the lateral direction in a tenter (first tenter) with both ends in the width direction gripped by clips. The conditions for lateral stretching are preferably Tg to Tg + 30 ° C. and a magnification of about 3 to 5 times. When laminating, the temperature is set based on the layer having a high Tg. If the stretching temperature is lower than Tg, the orientation and crystallization of the film due to the transverse stretching are promoted, so that the film may be easily broken not only in the transverse stretching but also in the longitudinal stretching in the subsequent step. On the other hand, if the transverse stretching temperature is higher than Tg + 30 ° C., the thickness unevenness in the width direction may exceed 18%. Preheating is preferably performed prior to the transverse stretching, and the preheating is preferably performed until the film surface temperature reaches Tg to Tg + 30 ° C.

Further, if the lateral stretching ratio is lower than 3 times, not only the thickness unevenness in the width direction tends to exceed 18%, but also there is a possibility that breakage may occur in the final heat treatment step described later. If the lateral stretching ratio is lower than 3 times, it becomes difficult for the film to be stretched and propagated to the edge of the film (at the time of clipping), and there is a possibility that the portion not stretched to the selvage of the film (so-called stretch residue) increases. Since the molecules of the film selvage portion where the stretch residue is generated are not oriented and the elastic modulus is remarkably low as compared with the central portion of the film, the heat shrinkage stress in the width direction generated in the final heat treatment step is concentrated in the vicinity of the stretch residue. As a result, the thickness (resin volume) in the vicinity of the stretched residue moves toward the center in the film width direction, and as a result, the thickness of the end portion in the film width direction sharply decreases, the strength becomes weak, and the film breaks.

After transverse stretching, it is preferable to pass the film through an intermediate zone where no active heating operation is performed. When there is a temperature difference between the transverse heat treatment zone and the intermediate heat treatment zone of the first tenter, the heat of the intermediate heat treatment zone (hot air itself or radiant heat) flows into the transverse stretching process, the temperature of the transverse stretching zone becomes unstable, and the film quality becomes stable. It may not be possible. Therefore, it is preferable that the film after the transverse stretching and before the intermediate heat treatment is supplied to the intermediate heat treatment zone after passing through the intermediate zone over a predetermined time. In this intermediate zone, when a strip of paper is hung without passing through the film, hot air from the transverse stretching zone and the intermediate heat treatment zone is blocked so that the strip of paper hangs almost completely in the vertical direction. , Stable quality film can be obtained. It is sufficient that the transit time of the intermediate zone is about 1 second to 5 seconds. If it is shorter than 1 second, the length of the intermediate zone becomes insufficient, and the effect of blocking hot air is insufficient. Further, it is preferable that the transit time of the intermediate zone is long, but if it is too long, the equipment becomes large, so about 5 seconds is sufficient.

After passing through the intermediate zone, an intermediate heat treatment before longitudinal stretching is performed. By this intermediate heat treatment, the shrinkage rate in the width direction can be reduced. The temperature of the intermediate heat treatment is preferably in the range of ~ + 30 ° C., which is the same as the temperature of the transverse stretching. When the temperature of the intermediate heat treatment zone is lower than the transverse stretching temperature, the effect of reducing the shrinkage ratio in the transverse direction is less likely to be exhibited. On the other hand, if the transverse stretching temperature is higher than + 30 ° C., the shrinkage rate in the width direction becomes lower, but the film may crystallize too much, making it difficult to perform the subsequent stretching in the longitudinal direction. The transit time of the intermediate heat treatment zone is preferably 2 seconds to 20 seconds. If it is shorter than 2 seconds, the length of the intermediate heat treatment zone is insufficient, and it may be difficult to adjust the heat shrinkage rate in the width direction. The transit time of the intermediate heat treatment zone is preferably long, but about 20 seconds is sufficient. As a result, a laterally uniaxially stretched film is obtained.

At the time of the intermediate heat treatment, the relaxing process can be performed by reducing the distance between the clips of the first tenter at an arbitrary magnification. By the relaxing treatment, the molecules oriented in the lateral direction can be relaxed without crystallizing, and the shrinkage rate in the width direction can be reduced. Relaxation after lateral stretching can be arbitrarily set in the range of 0% (relaxation rate 0% means no relaxation) to 20%. If the relaxation rate is higher than 20%, the orientation of the end portion (ear portion of the film) is too relaxed and the elastic modulus decreases, and as described above, there is a risk of breakage in the final heat treatment step.

3.3. Longitudinal stretching Subsequently, longitudinal stretching is performed. In the longitudinal stretching step, first, the horizontal uniaxially stretched film is introduced into a longitudinal stretching machine in which a plurality of roll groups are continuously arranged. In the longitudinal stretching, it is preferable to preheat the film with a preheating roll until the film temperature reaches Tg to Tg + 30 ° C. When laminating, the film temperature is set based on the layer having a high Tg. When the temperature is lower than Tg, it tends to be difficult to stretch in the vertical direction (that is, breakage is likely to occur). On the other hand, if the temperature is higher than Tg + 30 ° C., the film tends to adhere to the roll, and there is a possibility that roll stains may occur early in continuous production.
When the film temperature reaches the above range, longitudinal stretching is performed. The longitudinal stretching is performed by the speed difference of the rolls. The draw ratio is preferably 1.5 to 5 times. At this time, the rolls used for stretching are not only one-step stretching, which is two low speeds and high speeds, but also two-step stretching, which is three low speeds, medium speeds, and high speeds, and four low speeds, medium low speeds, medium high speeds, and high speeds. It is also possible to increase the number of three-stage stretching and the number of stretching stages. As the heating means, any of roll, near infrared ray, far infrared ray, hot air heater and the like can be used. Further, the relaxation in the longitudinal direction can be performed not immediately after the longitudinal stretching but also by narrowing the clip interval in the longitudinal direction by the final heat treatment as described later. Conditions such as temperature and relaxation rate will be described later.
After relaxing in the longitudinal direction (longitudinal stretching if not relaxing), it is preferable to cool the film once, and it is preferable to cool it with a cooling roll having a surface temperature of 20 ° C. to 40 ° C.

Next, the film after longitudinal stretching and cooling is introduced into the second tenter, and final heat treatment is performed, and at the same time, relaxation treatment is performed. Since the vertical and horizontal shrinkage ratios can be adjusted in the final heat treatment, it is a preferable embodiment to carry out the final heat treatment step after stretching the film. Relaxation in the second tenter can be performed at any magnification in both the vertical and horizontal directions. The relaxation rate is preferably 0% to 50% in both the vertical direction and the horizontal direction. The lower limit of the relaxation rate is 0%. If the relaxation rate is too high, there is a demerit that the production speed of the film and the product width are lowered. Therefore, the upper limit of the relaxation rate is preferably about 50%.

The heat treatment (relaxation treatment) temperature is preferably 100 ° C. to 200 ° C. If the heat treatment temperature is lower than 120 ° C., it becomes difficult to reduce the shrinkage rate of the film to 10% or less. On the other hand, the higher the heat treatment temperature, the more the shrinkage rate of the film can be reduced, which is preferable. However, if the heat treatment temperature is higher than 160 ° C., as described above, the thickness of the end portion in the film width direction decreases, which may cause fracture. Further, when the final heat treatment temperature is higher than 160 ° C., there is a risk that the film will stick when it comes into contact with the inside of the tenter.
After the final heat treatment, a polyester-based film roll can be obtained by winding while cutting and removing both ends of the film.

The polyester-based film obtained as described above may be subjected to a surface treatment step for imparting various properties to the film surface before being wound on a film roll or once wound on a film roll. Examples of such a surface treatment include a corona treatment for improving the adhesiveness of the film surface, a flame treatment, and a coating treatment for imparting antistatic performance. Adhesiveness and antistatic property can be improved by these treatments.

4. Laminated body and packaging bag using polyester-based film The polyester-based film of the present invention can be used alone, but other materials may be laminated to form a laminated body. The laminate may have at least one layer of the polyester film of the present invention, whereby the laminate has the above-mentioned characteristics such as the fusing seal strength.

Examples of other layers constituting the laminate include a non-stretched film containing polyethylene terephthalate as a constituent, a non-stretched, uniaxially stretched or biaxially stretched film containing another amorphous polyester as a constituent, and nylon as a constituent. Examples thereof include, but are not limited to, non-stretched, uniaxially stretched or biaxially stretched films, and non-stretched, uniaxially stretched or biaxially stretched films containing polypropylene as a constituent component.

The position where the polyester-based film is present in the laminated body is not particularly limited, but it is preferable that the polyester-based film of the present invention is present on the outermost layer of the laminated body. As a result, excellent fusing and sealing performance can be exhibited.
The method for producing the laminate is not particularly limited, and conventionally known methods for producing the laminate, such as a coating forming method, a coextrusion method, a laminating method, and a heat sealing method, can be used.

The polyester-based film and laminate having the above characteristics can be suitably used as a packaging bag. All of the packaging bag may be composed of the polyester film or laminate according to the present invention, but it is sufficient that the polyester film or laminate described above is present in at least a part of the packaging bag. For example, by providing the above-mentioned polyester-based film on the fusing seal portion of the packaging bag, the packaging bag has excellent fusing sealing properties, and it is possible to prevent the occurrence of waviness in the fusing sealing portion. When the packaging bag is made of the polyester film or laminate, the packaging bag has excellent fusing and sealing performance, as well as excellent fragrance retention, and when a liquid is put into the contents. Good bag resistance.

The method of having a polyester film or a laminate as a part of the packaging bag is not particularly limited, and a method similar to the method for producing a laminate such as a coating forming method, a laminating method, and a heat sealing method can be adopted. ..

The packaging bag is generally made by a fusing seal, but the packaging bag is not limited to this, and is conventionally known such as a heat seal using a heat bar (heat jaw), an adhesion using a hot melt, and a center seal using a solvent. The manufacturing method of is also available. Since the polyester-based film of the present invention has excellent fusing sealing performance, a packaging bag having a beautiful appearance can be obtained even if the fusing sealing is used to make a bag.

The packaging bag of the present invention can be suitably used as a packaging material for various articles such as foods, pharmaceuticals, and industrial products.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples as well as the present invention, and appropriate modifications are made to the extent that it can be adapted to the gist of the above and the following. Of course, it is possible to carry out, and all of them are included in the technical scope of the present invention.

<Film evaluation method>
[Average value of fusing seal strength, variation]
Fold the film in half so that the creases follow the flow direction of the film, set it in a fusing sealer (PP500 type side welder manufactured by Kyoei Printing Machinery Co., Ltd.), fusing blade angle 90 degrees, cutting edge set temperature 410 ° C, The film was blown and sealed under the condition of 140 shots / minute to prepare a side seal bag. The size of the bag is 310 mm in the direction along the fusing seal line (width direction of the film roll) x 220 mm in the direction orthogonal to the fusing seal line (flow direction of the film roll) (hereinafter, unless otherwise specified, fusing The direction along the seal line is called the "width direction", and the direction orthogonal to it is called the "flow direction").
One piece was randomly selected from the prepared bag, and a total of 40 samples (20 on each side) with a size of 15 mm in the width direction x 100 mm in the flow direction were taken from the flute-sealed part (310 mm on one side x 2 = 620 mm on both sides). Sampled. In accordance with JIS Z1707, the sample is opened 180 degrees and both ends are set in a universal tensile tester (manufactured by Shimadzu, Autograph AG-X plus) (distance between chucks: 50 mm), and the longitudinal direction (flow direction) of the sample. ) Was subjected to a tensile test at a speed of 200 mm / min, and the peel strength when the fusing seal portion was broken was measured. The maximum value of the peel strength was recorded as the strength per 15 mm (N / 15 mm) as the fusing seal strength, and the average value of 40 samples was taken as the average value of the fusing seal strength.
Further, the standard deviation calculated using the following formula 1 was used as the variation in the fusing seal strength.
Standard deviation = [{(X ₁ −X ₀ ) ² + (X ₂ −X ₀ ) ² + ・ ・ ・ + (X _n −X ₀ ) ² } / n] ^1/2 Equation 1
X _n : _{Fusing seal strength of the nth sample X 0} : Average value of fusing seal strength n: Number of samples (40)

[Folding holding angle]
The film pieces were left for 24 hours in a homeothermic environment at 20 ° C. and 65% RH. Immediately thereafter, each film was cut into 10 cm × 10 cm squares in a 20 ° C. 65% RH environment and folded in four (5 cm × 5 cm squares). When folding the film, the short side of the rectangle made by the first two folds was set to the flow direction. Then, a four-fold film was sandwiched between two pieces of glass having a size of 10 cm × 15 cm and a thickness of 2 mm, and a 5 kg weight was placed on the glass and pressed for 10 seconds. The weight was removed from the four-fold film, left for 10 seconds, and then the angle at which the film opened was measured with the last crease as the base point. The state in which the film is completely folded is 0 degrees, and the angle at which the film is completely opened is 180 degrees. In the case of the two-layer structure, the B layer was folded in a valley and measured.

[25 ° C loss tangent (tan δ)]
A sample with a size of 10 mm in the width direction x 40 mm in the flow direction is cut out according to a procedure conforming to JIS-K7244, and a dynamic viscoelastic device (Hitachi, Ltd., DMA7100) is used to raise the temperature at 10 ° C./min and the frequency at 1 Hz. The temperature was raised from −150 ° C. to 150 ° C. at a distance between chucks of 20 mm. Of the tan δ curves obtained at that time, the value of tan δ at 25 ° C. was determined.

[Measurement of impact strength of fusing seal]
A sample described by the average value of the fusing seal strength was sampled, and a film impact tester (manufactured by Toyo Seiki Seisakusho Co., Ltd., B-121402302) was used as a measuring instrument for measuring the impact strength. As shown in FIG. 1, a total of three samples having a size of 100 mm in the width direction and 100 mm in the flow direction were sampled with the fusing and sealing portion at the center. The film was fixed with a jig so that the fusing seal surface was facing down and the fusing seal portion was perpendicular to the device. As shown in FIG. 1, the impact strength at the time of breaking the fusing seal portion was measured by hitting with a hammer from the fusing seal surface. A hammer of 2J was used as a hammer for giving an impact to the test piece.

[Bag evaluation]
A bag was prepared in the same procedure as the fusing seal strength measurement.
Four sheets were randomly selected from the prepared bag, 100 mL of water was put in the bag, the mouth was tied, and a sample for evaluation of the bag drop was prepared. The bottom surface (opposite side of the opening) of this sample was dropped 10 times from a position at a height of 50 cm toward the floor, and the number of times until the bag was torn was calculated as a bag drop score as shown below. The drop bag score was calculated as the sum after four trials (maximum 10 points x 4 times = 40 points maximum, minimum 1 point x 4 times = 4 points).
1st time to break bag 1 point 2nd time to break bag 2 points 3rd time to break bag 3 points 4th time to break bag 4 points 5th time to break bag 5 points 6th time to break bag 6 points 7th time to break bag 7 points 8 8 points for broken bag at the 9th time 9 points for broken bag at the 9th time 10 points for no bag break

[Incense retention]
Two films cut into a 10 cm x 10 cm square are overlapped, and three sides are melt-sealed at 250 ° C using an impulse sealer (manufactured by Hakko Co., Ltd., NO.310-1) to open only one side. I made a three-way sticker bag. After putting 20 g each of limonene (manufactured by Nacalai Tesque Co., Ltd.) and menthol (manufactured by Nacalai Tesque Co., Ltd.) in this bag, the open side was also blown and sealed to seal the bag. The limonene used was prepared by dissolving it in ethanol to a concentration of 0.05 wt%. The menthol used was prepared by dissolving it in ethanol to a concentration of 1 g / mL. This bag was placed in a glass container having a capacity of 1000 mL and covered. One day later, a person (4 people in their 20s, 4 people in their 30s, 4 people in their 40s, 4 people in their 50s, a total of 16 people. The ratio of men and women was 50% in each age group) covered the glass container. Was opened so as to smell the air inside, and the air in the glass container was smelled, and the judgment was made as follows.
The number of people who felt the odor was 5 or less as a pass (○), and 6 or more were rejected (x).

[Appearance density]
The mass of the film cut into a 10 cm × 10 cm square was measured. The thickness of the sample was measured, and the value of the apparent specific gravity was obtained using the following formula 2.

[Hot water heat shrinkage rate]
The film is cut into 10 cm × 10 cm squares, immersed in warm water at 80 ° C. ± 0.5 ° C. for 10 seconds under no load to shrink, and then immersed in water at 25 ° C. ± 0.5 ° C. for 10 seconds. , Taken out of the water. Then, the dimensions in the width direction and the flow direction of the film were measured, and the shrinkage rate in each direction was determined according to the following formula 3. The measurement was performed twice, and the average value was calculated.
Shrinkage rate (%) = {(length before contraction-length after contraction) / length before contraction} × 100 Equation 3

[Tg (glass transition temperature)]
Using a differential scanning calorimetry device (manufactured by TA Instrument, DSC250) connected to an electric cooling system (RCS120), 2 mg ± 0.2 mg of film is applied from -120 ° C to 150 ° C in a heat-only mode with temperature modulation and a modulation cycle. The temperature was raised at 2 ° C./min for 40 seconds, and the temperature was determined from the obtained reverse heat flow. The temperature on the low temperature side of the intersection of the extension line of the baseline below the glass transition temperature and the tangent line showing the maximum inclination at the transition portion was defined as the glass transition temperature (Tg). In Comparative Example 3, since the glass transition temperature could not be observed in this range, it could not be measured.
<Preparation of polyester raw material>
[Synthesis Example 1]
A stainless steel autoclave equipped with a stirrer, thermometer and partial recirculation cooler contains 100 mol% of dimethyl terephthalate (DMT) as a dicarboxylic acid component and 100 mol% of ethylene glycol (EG) as a polyhydric alcohol component. Ethylene glycol was charged so as to be 2.2 times the molar ratio of dimethyl terephthalate, and 0.05 mol% (relative to the acid component) of zinc acetate was used as a transesterification catalyst to distill off the produced methanol. While doing so, the transesterification reaction was carried out. Then, 0.225 mol% of antimony trioxide (relative to the acid component) was added as a polycondensation catalyst, and a polycondensation reaction was carried out at 280 ° C. under a reduced pressure of 26.7 Pa to obtain an intrinsic viscosity of 0.75 dl / g. Polyester (A) was obtained. This polyester (A) is polyethylene terephthalate.

[Synthesis example 2]
Polyesters (B) to (D) having different monomers were obtained in the same procedure as in Synthesis Example 1.
Polyester E is Ecofrex manufactured by BASF. The composition of each polyester is shown in Table 1. In Table 1, TPA is terephthalic acid, AA is adipic acid, BD is 1,4-butanediol, NPG is neopentyl glycol, and DEG is diethylene glycol. In the production of polyester (D), SiO ₂ (Silicia 266 manufactured by Fuji Silysia Chemical Ltd.) was added as a lubricant at a ratio of 7,000 ppm to polyester. Each polyester was appropriately formed into chips. The intrinsic viscosities of the polyesters B to D were B: 0.73 dl / g, C: 0.80 dl / g, and D: 0.75 dl / g, respectively. The number average molecular weight of polyester E was 44000 g / mol.

[Example 1]
Polyester A, polyester B, polyester C, and polyester D were mixed at a mass ratio of 25:60: 10: 5 to prepare a resin mixture for the skin layer. 100% polyester E was used for the core layer. Co-extruded at a temperature of 200 ° C. for the core layer and 280 ° C. for the skin layer using a T-die mold equipped with a multi-manifold using two twin-screw extruders, quickly cooled with a cooling roll, and the skin layer / core. An unstretched film having three layers of layers / skin layers having a thickness of 100 μm was obtained.
The unstretched film was led to a tenter (first tenter) in which a transverse stretching zone, an intermediate zone, and an intermediate heat treatment zone were continuously provided. In the intermediate zone, hot air from the transverse stretching zone and the intermediate heat treatment zone so that the strip-shaped piece of paper hangs almost completely in the vertical direction when the strip-shaped piece of paper is hung without passing through the film. Hot air is blocked.
The unstretched film led to the first tenter was transversely stretched in the transversely stretched zone at 82 ° C. under the condition of 3.8 times, passed through the intermediate zone (transit time = about 1.2 seconds), and then moved to the intermediate heat treatment zone. A laterally uniaxially stretched film was obtained by reducing the clip width of the first tenter and performing 6% relaxation while heat-treating at a temperature of 97 ° C. for 8 seconds.
The horizontally stretched film is guided to a longitudinal stretching machine in which a group of rolls including low-speed and high-speed rolls is continuously arranged, preheated on a preheating roll until the film temperature reaches 90 ° C., and then stretched on a low-speed and high-speed roll. It was stretched so that the magnification was 2.8 times. After that, the vertically stretched film was forcibly cooled by a cooling roll set to a surface temperature of 25 ° C.
Then, the cooled film is guided to a tenter (second tenter), and after being heat-treated in the second tenter in an atmosphere of 140 ° C. for 10 seconds, the film is relaxed by 17% in the lateral direction (film width direction). By cooling and cutting and removing both edges in the width direction, a polyester-based film having a thickness of about 13 μm was obtained.
Tables 2 and 3 show the production conditions and characteristics of the obtained film.

[Example 2]
A polyester-based film in which the layer ratio was changed was formed and evaluated.
Tables 2 and 3 show the film production conditions and characteristics of each example.

[Example 3]
Polyester A, polyester B, polyester C, and polyester D were mixed at a mass ratio of 25:60: 10: 5 to prepare a resin mixture for the skin layer. 100% polyester E was used for the core layer. Co-extruded at a temperature of 200 ° C. for the core layer and 280 ° C. for the skin layer using a T-die mold equipped with a multi-manifold using two twin-screw extruders, quickly cooled with a cooling roll, and the skin layer / core. An unstretched film having three layers of layers / skin layers having a thickness of 100 μm was obtained.
The unstretched film was supplied to a simultaneous biaxial stretching tenter, both ends were held by clips, and simultaneous biaxial stretching was performed under the conditions of 95 ° C. at a longitudinal stretching ratio of 2 times and a transverse stretching ratio of 3.8 times. Further, heat treatment was performed in a tenter oven at 150 ° C. for 10 seconds, and after cooling, both edges in the width direction were cut and removed to obtain a polyester film having a thickness of about 13 μm.
Tables 2 and 3 show the production conditions and characteristics of the obtained film.
[Examples 4 to 7]
A polyester-based film in which the layer composition and layer ratio of the skin layer and the core layer were variously changed was formed and evaluated. In Examples 5 to 7, a satin-finished cooling roll was used to obtain an unstretched film. When the type 2 two-layer (A / B) film was blown and sealed, the B side was set to the inner surface. Tables 2 and 3 show the film production conditions and characteristics of each example.

[Comparative Example 1]
Polyester A, polyester B, polyester D, and polyester E are mixed at a mass ratio of 25:60: 10: 5, put into a twin-screw extruder, melt-mixed at 270 ° C., extruded from a T-die, and then surface temperature. An unstretched film was obtained by cooling on a chill roll set at 30 ° C.
The unstretched film was led to a tenter (first tenter) in which a transverse stretching zone, an intermediate zone, and an intermediate heat treatment zone were continuously provided. In the intermediate zone, hot air from the transverse stretching zone and the intermediate heat treatment zone so that the strip-shaped piece of paper hangs almost completely in the vertical direction when the strip-shaped piece of paper is hung without passing through the film. Hot air is blocked.
The unstretched film led to the first tenter was transversely stretched in the transversely stretched zone at 82 ° C. under the condition of 3.8 times, passed through the intermediate zone (transit time = about 1.2 seconds), and then moved to the intermediate heat treatment zone. A laterally uniaxially stretched film was obtained by reducing the clip width of the first tenter and performing 6% relaxation while heat-treating at a temperature of 97 ° C. for 8 seconds.
The horizontally stretched film is guided to a longitudinal stretching machine in which a group of rolls including low-speed and high-speed rolls is continuously arranged, preheated on a preheating roll until the film temperature reaches 90 ° C., and then stretched on a low-speed and high-speed roll. It was stretched so that the magnification was 2.8 times. After that, the vertically stretched film was forcibly cooled by a cooling roll set to a surface temperature of 25 ° C.
Then, the cooled film is guided to a tenter (second tenter), and after being heat-treated in the second tenter in an atmosphere of 140 ° C. for 10 seconds, the film is relaxed by 17% in the lateral direction (film width direction). By cooling and cutting and removing both edges in the width direction, a polyester-based film having a thickness of about 13 μm was obtained.
Tables 2 and 3 show the production conditions and characteristics of the obtained film.

[Comparative Example 2]
Polyester A and polyester D are mixed at a mass ratio of 95: 5, put into a twin-screw screw extruder, melt-mixed at 270 ° C., extruded from a T-die, and then cooled on a chill roll whose surface temperature is set to 30 ° C. To obtain an unstretched film.
This unstretched film was led to a tenter (first tenter) in which a transverse stretching zone, an intermediate zone, and an intermediate heat treatment zone were continuously provided. In the intermediate zone, hot air from the transverse stretching zone and the intermediate heat treatment zone so that the strip-shaped piece of paper hangs almost completely in the vertical direction when the strip-shaped piece of paper is hung without passing through the film. Hot air is blocked.
Then, the unstretched film led to the first tenter is transversely stretched in the transversely stretched zone at 90 ° C. under the condition of 3.8 times, and after passing through the intermediate zone (transit time = about 1.2 seconds), the intermediate heat treatment is performed. It was guided to the zone and heat-treated at a temperature of 97 ° C. for 8 seconds to obtain a laterally uniaxially stretched film. In the intermediate heat treatment, relaxation in the width direction was not performed.
Further, the laterally stretched film is guided to a longitudinal stretching machine in which roll groups including low-speed and high-speed rolls are continuously arranged, preheated on a preheating roll until the film temperature reaches 100 ° C., and then low-speed and high-speed rolls are performed. The film was stretched so that the stretching ratio was 2.8 times. After that, the vertically stretched film was forcibly cooled by a cooling roll set to a surface temperature of 25 ° C.
Then, the cooled film is guided to a tenter (second tenter), heat-treated in the second tenter for 10 seconds in an atmosphere of 230 ° C. (relaxation rate in the film width direction is 0%), and then cooled. By cutting and removing both edges, a polyester film having a thickness of about 13 μm was obtained.
Tables 2 and 3 show the production conditions and characteristics of the obtained film.

[Comparative Example 3]
An unstretched film having a thickness of 30 μm (Toyobo Co., Ltd., Rix film (L4103-30 μm) was used for evaluation according to the above method. The evaluation results are shown in Table 3.

[Comparative Example 4]
A biaxially stretched polypropylene film having a thickness of 15 μm (Toyobo Co., Ltd., pipe wrench film-FG (P5562-15 μm) was used for evaluation according to the above method. The evaluation results are shown in Table 3.

As shown in Table 3, the films of Examples were excellent in bag-breaking resistance, aroma-retaining property, fusing and sealing performance, and the like.
On the other hand, the film of Comparative Example 1 had a bag drop score of 8 points. From this result, it can be seen that the bag formed from the film of Comparative Example 1 is liable to break when the bag is dropped, which is not preferable as a packaging bag.
Since the film of Comparative Example 2 could not be bag-made by the fusing seal, the fusing seal strength, the impact strength of the fusing seal portion, and the aroma retention property could not be measured. The film of Comparative Example 2 could not be used as a bag. In addition, Tg could not be measured because the stepped signal was unclear in the DSC measurement.

The film of Comparative Example 3 had a high folding angle of 150 degrees, and the film opened even after being folded. Therefore, when the bag was made, the crease at the bottom was not cleanly formed, and the appearance was inferior to that of the bag using the film of the example. Further, the bag using the film of Comparative Example 3 was inferior in aroma retention.
The drop bag score of the film of Comparative Example 4 was 5 points. From this result, it can be seen that the bag formed from the film of Comparative Example 4 is liable to break when the bag is dropped, which is not preferable as a packaging bag. In addition, the folding angle was as high as 180 degrees, and the film opened even after folding. Therefore, when the bag was made, the crease at the bottom was not cleanly formed, and the appearance was inferior to that of the bag using the film of the example.

The polyester-based film of the present invention has fragrance-retaining properties against various organic compounds, has high fusing and sealing strength, and has good bag-breaking resistance when a liquid is put into the contents as a packaging bag. It can be suitably used for packaging bags.

Claims (6)

A polyester-based film characterized by satisfying the following requirements (1) and (2).
(1) The loss tangent (tan δ) obtained when the dynamic viscoelasticity is measured at 25 ° C. is 0.03 or more and 0.15 or less in the longitudinal direction. (2) Fusing seal so that the film width direction is the sealing direction. Fusing seal strength at the time of 5N / 15mm or more and 20N / 15mm or less The polyester-based film according to claim 1, wherein the Tg obtained by the temperature-modulated DSC measurement is −75 ° C. or higher and 25 ° C. or lower. The polyester-based film according to claim 1 or 2, wherein the folding holding angle is 20 degrees or more and 80 degrees or less. The polyester-based film according to any one of claims 1 to 3, wherein the heat shrinkage rate when immersed in hot water at 80 ° C. for 10 seconds is -10% or more and 10% or less in both the longitudinal direction and the width direction. .. A laminate having at least one layer of the polyester-based film according to any one of claims 1 to 4. A packaging bag comprising at least a part of the polyester-based film according to any one of claims 1 to 4 or the laminate according to claim 5.

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