JP2003025424A - Ethylene/vinyl alcohol copolymer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially stretched EVOH film reduced in the generation frequency of the breaking of the film in a stretching process at the time of continuous production and maximally ensured in practical effective width at the same time. SOLUTION: The ethylene/vinyl alcohol copolymer film is characterized in that the thickness T1 (μm, 6 in Fig 1) at the center A1 in the width direction of the film and the thickness T2 at the specific point A2 in the width direction of the film satisfy a relation represented by formula (1): 0.1<=(T2-T1)/T1<=0.5. However, when a point obtained by the interior division of the area between the center A1 in the width direction of the film and the end E1 in the width direction of the film in a ratio of 95:5 is set to E2 and a point obtained by the interior division of the area between A1 and E1 in a ratio of 75:25 is set to A3, the point A2 is a point having the maximum film thickness between E2 and A3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film made of an ethylene-vinyl alcohol copolymer (hereinafter referred to as "EVOH") which has a smooth surface appearance over the entire width of the film and is beautiful.

[0002]

EVOH is widely used as a material having excellent gas barrier properties. In particular, the moisture resistance represented by a polyolefin resin, a laminate with a thermoplastic resin excellent in mechanical properties, etc. has a good balance of physical properties,
In the form of bags, tubes, cups, pouches, etc., they are widely used in various fields such as foods, cosmetics, medical chemicals, toiletries and the like. Among them, a biaxially stretched film made of EVOH (hereinafter referred to as "EVOH biaxially stretched film")
Has better gas barrier properties, mechanical properties and the like than an unstretched film, and therefore its demand is rapidly increasing, and improvement in productivity is required.

[0003]

[Problems to be Solved by the Invention] However, EVO
When it is attempted to stretch a film having a constant thickness over the entire width in order to obtain an H biaxially stretched film, the thickness unevenness becomes remarkable especially at the end portions of the film, and in extreme cases, the film breaks in the stretching process. Even if the film does not break, the portion with uneven thickness has no commercial value and has to be cut off, which lowers the film yield. Therefore, an object of the present invention is to provide an EVOH biaxially stretched film in which the frequency of breakage of the film in the stretching step during continuous production is low and at the same time the practical effective width is maximized. is there.

[0004]

DISCLOSURE OF THE INVENTION As a result of earnest studies in view of such a situation, the present inventor has found that a film made of EVOH having a specific thickness distribution in the width direction of the film (hereinafter referred to as
It was found that it is important to use "EVOH film" as a raw material, and arrived at the present invention.

That is, in the present invention, when the thickness at the center A1 in the width direction of the film is T1 (μm) and the thickness at a specific point A2 in the width direction of the film is T2 (μm), T1 and T2 are The present invention relates to an EVOH film satisfying the relationship of the following formula (1). 0.1 ≤ (T2-T1) / T1 ≤ 0.5 (1) However, the point A2 is a point that internally divides between the center A1 in the width direction of the film and the end E1 in the width direction of the film at 95: 5. E
2 and the point internally dividing 75:25 between A1 and E1 is A3, it is the point having the maximum film thickness between E2 and A3.

In the EVOH film of the present invention, when the film thickness of A3 is T3 (μm), it is preferable that T1 and T3 satisfy the relationship of the following formula (2). Further, it is preferable that T1, T2 and T3 satisfy the relationship of the following expression (3). 0.006 ≤ (T3-T1) / T1 ≤ 0.3 (2) 0.1 ≤ (T2-T3) / T1 ≤ 0.5 (3)

Further, the distance from A1 to A2 is L
When it is 12 (mm), it is preferable that T1 and L12 satisfy the relationship of the following expression (4). Further, it is preferable that T1 satisfies the following expression (5). Furthermore, it is preferable that L12 satisfies the following formula (6). 0.01 ≤ T1 / L12 ≤ 0.5 (4) 50 ≤ T1 ≤ 300 (5) 300 ≤ L12 ≤ 3000 (6)

The present invention also includes an EVOH biaxially stretched film obtained by biaxially stretching the above EVOH film. In the EVOH biaxially stretched film, the thickness at the center A4 in the width direction of the film is T4 (μm),
The thickness at a specific point A5 in the width direction of the film is T5.
(Μm), it is preferable that T4 and T5 satisfy the relationship of the following expression (7). Further, it is preferable that T4 satisfies the following expression (8). 0.90 ≤ T5 / T4 ≤ 1.1 (7) 5 ≤ T4 ≤ 30 (8) However, the point A5 is the center A4 in the width direction of the biaxially stretched film.
Between the widthwise end E3 of the biaxially stretched film and 94: 6.
It is the point that is divided into

Further, in the present invention, when the thickness at the center A1 in the width direction of the film is T1 (μm) and the thickness at a specific point A2 in the width direction of the film is T2 (μm), T1 and T2 are E that satisfies the relationship of the following formula (1)
VOH film is biaxially stretched, E
It also includes a method for producing a VOH biaxially stretched film. In this manufacturing method, it is preferable to hold and stretch the region including the point A2. 0.1 ≤ (T2-T1) / T1 ≤ 0.5 (1) However, the point A2 is a point that internally divides between the center A1 in the width direction of the film and the end E1 in the width direction of the film at 95: 5. E
2 and the point internally dividing 75:25 between A1 and E1 is A3, it is the point having the maximum film thickness between E2 and A3.

Further, the present invention is a method for producing an EVOH biaxially stretched film, which comprises a step of biaxially stretching the film and a step of cutting out a portion including a widthwise end E3 of the biaxially stretched film. It also includes a method for producing an EVOH biaxially stretched film, characterized in that the weight of the portion is 30% by weight or less based on the weight of the entire film.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below. In the present invention, EVOH which is a raw material of the film
Can be obtained by saponifying a copolymer of ethylene and vinyl ester using an alkali catalyst or the like. As the vinyl ester, vinyl acetate can be mentioned as a typical one, but other fatty acid vinyl esters (vinyl propionate, vinyl pivalate, etc.) can also be used.

The ethylene content of EVOH is preferably 15 to 70 mol% in consideration of the film-forming property at the time of film production, the gas barrier property when the film is formed, and the like.
0 to 50 mol% is more preferable, and 25 to 45 mol% is even more preferable.

[0013] EVOH may be copolymerized with a small amount of another monomer within a range not impairing the object of the present invention. Examples of copolymerizable monomers include propylene, 1-butene, isobutene, 4-methyl-1-pentene, 1-hexene, 1-octene and other α-olefins; itaconic acid,
Unsaturated carboxylic acids such as methacrylic acid, acrylic acid and maleic acid, salts thereof, partial or complete esters thereof, nitriles thereof, amides thereof, anhydrides thereof; vinylsilane compounds such as vinyltrimethoxysilane; unsaturated sulfonic acids or salts thereof. Salts; alkyl thiols; vinylpyrrolidones and the like.

The degree of saponification of the vinyl ester component of EVOH is preferably 80 mol% or more in consideration of the thermal stability of EVOH during film production and the gas barrier property under high humidity when the film is formed. , 90 mol%
The above is more preferable, 95 mol% or more is still more preferable, and 98 mol% or more is the most preferable.

It is also possible to mix and use two or more kinds of EVOH as EVOH. In this case, each EVOH
The average value calculated by adding the blending weight ratio to the ethylene content and saponification degree of is the ethylene content and saponification degree of EVOH. Further, a heat stabilizer, an ultraviolet absorber, an antioxidant, a colorant, a filler, and other resins (polyamide, polyolefin, etc.) may be blended with EVOH within the range that does not impair the object of the present invention. Also, E
The melting point of VOH is preferably in the range of 140 to 200 ° C.

The EVOH film of the present invention will be described with reference to FIG. The EVOH film of the present invention has a thickness T1 at the center A1 (1 in FIG. 1) in the width direction of the film.
(Μm, 6 in FIG. 1), and the thickness at a specific point A2 (5 in FIG. 1) in the width direction of the film is T2 (μm, FIG. 1).
In the case of 7), T1 and T2 satisfy the relationship of the following expression (1). 0.1 ≦ (T2-T1) / T1 ≦ 0.5 (1) However, the point A2 is 95 between the center A1 in the width direction of the film and the end E1 (2 in FIG. 1) in the width direction of the film. When the point internally dividing to 5: 5 is E2 (3 in FIG. 1) and the point internally dividing between A1 and E1 to 75:25 is A3 (4 in FIG. 1), E2 and A3 are Between them has the maximum film thickness.

The A2 is close to the edge of the film, and in the biaxial stretching of the film, the area usually containing A2 (hereinafter
The "holding region") is held and stretched by a chuck or the like. The above formula (1) represents that in the EVOH film of the present invention, the maximum thickness T2 in the holding region is larger than the thickness T1 at the center in the width direction of the film by a specific amount. (T2-T1) / T1 is preferably 0.12 or more and 0.4 or less. (T2-T1) / T1
If less than 0.1, the frequency of breakage in the stretching step increases. If (T2-T1) / T1 exceeds 0.5, a thick portion remains in the stretched film, resulting in an increase in the amount of the film to be cut off and a decrease in the yield of the biaxially stretched film.

In the EVOH film of the present invention, when the thickness of the film at A3 is T3 (μm, 8 in FIG. 1), it is preferable that T1 and T3 satisfy the relationship of the following formula (2). . In addition, the T1, T2
It is preferable that T3 and T3 satisfy the relationship of the following expression (3). 0.006 ≤ (T3-T1) / T1 ≤ 0.3 (2) 0.1 ≤ (T2-T3) / T1 ≤ 0.5 (3)

The above equation (2) indicates that in the EVOH film of the present invention, the thickness T3 at the point A3 is larger than the thickness T1 at the center 1 in the width direction of the film by a specific amount. Further, the above formula (3) is the EVOH of the present invention.
In the film, the maximum thickness T2 in the holding area
Is greater than the thickness T3 at the point A3 by a specific amount. When the thickness at the point A3 close to the holding region is adjusted so as to satisfy the above formulas (2) and / or (3), the frequency of breakage in the stretching step is further reduced, and the thickness of the film after stretching is also reduced. Of the biaxially stretched film is increased, and the yield of the biaxially stretched film is increased. (T3-T1) / T1 is preferably 0.01 or more and 0.2 or less. Also, (T2-T3) / T1 is
It is preferably 0.1 or more and 0.4 or less.

In the EVOH film of the present invention, the distance from the center A1 in the width direction of the film to the point A2 is L12.
(Mm, 9 in FIG. 1), T1 and L1
It is preferable that 2 satisfies the relationship of the following formula (4). 0.01 ≤ T1 / L12 ≤ 0.5 (4)

The above formula (4) shows that in the EVOH film of the present invention, the thickness T1 of the central portion of the film and the distance L12 related to the width of the film have a specific relationship. By using a film that satisfies this relationship, it is possible to obtain a biaxially stretched film with a high uniformity of thickness, with less frequency of breakage in the stretching step, and without imposing excessive tension on the device. T1 / L12
Is preferably 0.1 or more and 0.45 or less.

Further, in the EVOH film of the present invention, it is preferable that T1 satisfies the relation of the following formula (5). Furthermore, it is preferable that L12 satisfies the relationship of the following expression (6). 50 ≤ T1 ≤ 300 (5) 300 ≤ L12 ≤ 3000 (6)

The above formulas (5) and (6) correspond to E of the present invention.
In the VOH film, the thickness T1 in the central portion A1 of the film and the distance L12 related to the width of the film
Indicate that each is within a specific range. The thinner the film, the smaller the amount of raw material required, and the thicker the film, the lower the frequency of breakage in the stretching process. A film satisfying the above formula (5) has both advantages. Further, the shorter the width of the film, the easier the stretching,
The longer it is, the higher the productivity will be. A film satisfying the above formula (6) has both advantages. T1 is preferably 80 or more and 250 or less. Further, L12 is preferably 320 or more and 2000 or less.

The method for producing the EVOH film of the present invention is not particularly limited, but for example, a method in which EVOH as described above is melt-extruded by a T-die with a screw type extruder, molded and cooled, and the like. Can be mentioned. The molding temperature is preferably in the range of 200 to 280 ° C.
If the molding temperature is lower than 200 ° C., the melt fluidity of EVOH may be insufficient and the moldability may deteriorate. If the molding temperature exceeds 280 ° C., EVOH may be thermally decomposed and the film may be colored.

The cooling temperature at this time is 0 to 40 ° C.
Is preferred. If the cooling temperature is less than 0 ° C., special equipment is required, which is disadvantageous in terms of cost. When the cooling temperature is higher than 40 ° C, the cooling time becomes long and the productivity is lowered.

The thickness distribution in the width direction of the EVOH film as described above can be easily controlled by using a lip opening adjusting bolt of a die that is usually provided in an extrusion molding machine for producing a normal film.

The EVOH film of the present invention can be made into an EVOH biaxially stretched film by simultaneous biaxial stretching or sequential biaxial stretching using a known apparatus.
As a method of simultaneous biaxial stretching, there is a stretching method in which a film is held by using a special tenter to widen the film width and the distance between adjacent clips is widened to perform longitudinal stretching at the same time. As the method of (1), a drawing method of performing lateral drawing with a tenter after longitudinal drawing is usually adopted, but the method is not limited to these methods.

The EVOH biaxially stretched film of the present invention will be described with reference to FIG. In the EVOH biaxially stretched film of the present invention, the center A4 in the width direction of the film (1 in FIG.
The thickness in 1) is T4 (μm, 14 in FIG. 2),
When the thickness at a specific point A5 (13 in FIG. 2) in the width direction of the film is T5 (μm, 15 in FIG. 2), T is
It is preferable that 4 and T5 satisfy the relationship of the following formula (7). 0.90 ≤ T5 / T4 ≤ 1.1 (7) However, the point A5 is the center A4 in the width direction of the biaxially stretched film.
And the widthwise end E3 of the biaxially stretched film (12 in FIG. 2)
It is a point that internally divides between and at 94: 6.

In the EVOH biaxially stretched film of the present invention, the above formula (7) shows that the thickness ratio between the point A5 and the center A4 in the width direction of the film is within a specific range around 1.0. It means that there is. When this ratio satisfies the above formula (7), there is an advantage that the uniformity of the thickness of the stretched film is further increased and the yield of the biaxially stretched film is increased. T5 / T4 is preferably 0.95 or more and 1.
It is less than or equal to 05.

Further, in the EVOH biaxially stretched film of the present invention, it is preferable that T4 satisfies the relationship of the following formula (8). 5 ≤ T4 ≤ 30 (8)

The above formula (8) shows that in the EVOH biaxially stretched film of the present invention, the thickness T4 at the center A4 in the width direction of the film is within a specific range. The thinner the film, the smaller the amount of raw material required, and the thicker the film, the lower the frequency of breakage in the stretching process. The biaxially stretched film satisfying the above formula (8) has both advantages. T4 is preferably 7 or more and 20 or less.

The method for producing the EVOH biaxially stretched film of the present invention will be described. The first method is a method for producing an EVOH biaxially stretched film by biaxially stretching an EVOH film in which T1 and T2 satisfy the relationship of the following formula (1). 0.1 ≤ (T2-T1) / T1 ≤ 0.5 (1)

(T2-T1) / T1 is preferably 0.
It is 12 or more and 0.4 or less. When (T2-T1) / T1 is less than 0.1, the frequency of breakage in the stretching step increases. When (T2-T1) / T1 exceeds 0.5, a thick portion remains in the film after stretching, and as a result, the amount of the widthwise end portion of the film to be cut out increases and the yield of the biaxially stretched film increases. Is reduced.

Examples of the biaxial stretching method include known methods such as simultaneous biaxial stretching or sequential biaxial stretching as described above. The stretching method is not particularly limited, but a method including at least a step of heating and stretching and a heat treatment is preferable.

As for the draw ratio, the machine direction (MD direction) is 2.5 to 4.5 times, and the transverse direction (TD direction) is 2.5 to 4.
5 times, and the area stretching ratio is preferably 7 to 15 times, 2.5 to 3.5 times in the longitudinal direction and 2.5 to 3.
More preferably, it is 5 times and the area stretching ratio is 8 to 12 times.

The heat stretching temperature is preferably 60 to 160 ° C, more preferably 70 to 140 ° C. When the heat-stretching temperature is in this range, a biaxially stretched film having a small thickness unevenness and being appropriately oriented and having excellent mechanical strength can be obtained. The heat stretching time is preferably in the range of 2 to 30 seconds, more preferably 3 to 10 seconds.

At this time, it is preferable from the viewpoint of production stability to carry out preheating prior to heating and stretching. The preheating temperature is preferably 60 to 160 ° C., and 70 to 140
C is more preferred. Further, the preheating temperature is preferably determined from the relationship with the heating and drawing temperature. Specifically, the preheating temperature is preferably within a range of ± 20 ° C. of the heat drawing temperature. The preheating time is preferably in the range of 2 to 30 seconds, more preferably 3 to 10 seconds.

The heat treatment temperature is preferably 150 to 190 ° C, more preferably 155 to 185 ° C. When the heat treatment temperature is within this range, the dimensional stability is high and the S
It is possible to obtain a biaxially stretched film in which the frequency of character curl is low. The heat treatment time is preferably in the range of 2 to 30 seconds, more preferably 2 to 20 seconds.

From the viewpoint of production stability, it is also preferable to add water to the film before stretching. The water content of the film is preferably 1 to 30% by weight, more preferably 1 to 20% by weight. When the water content of the film is within the above range, a biaxially stretched film having a low frequency of breakage in the stretching step and being appropriately oriented and having excellent mechanical strength can be obtained.

In the above-mentioned method for producing a biaxially stretched film, it is preferable that the region including the point A2 is held by a chuck or the like and stretched. Thereby, the frequency of breakage in the stretching step can be further reduced.

A second method for producing an EVOH biaxially stretched film of the present invention comprises a step of biaxially stretching the film and a step of cutting out a portion including the widthwise end E3 of the biaxially stretched film. A method for producing a stretched film, wherein the weight of the cut-off portion is 30% by weight or less based on the weight of the entire film.

EV used in the second manufacturing method
The OH film is not particularly limited, but the EVOH film of the present invention as described above is preferable. As the biaxial stretching method and stretching method, for example, the method and stretching method described in the description of the first manufacturing method can be adopted.

In the second manufacturing method, a step of cutting out a portion including the widthwise end E3 of the film after being biaxially stretched is essential. During biaxial stretching, the widthwise end of the film remains unstretched, so the widthwise end E3 of the film becomes thicker than the widthwise center A4 and point A5 of the film. If the step of cutting out the part including E3 is not provided, the commercial value of the film is reduced due to the uneven thickness.

In the second manufacturing method, the weight of the cut-out portion needs to be 30% by weight or less, preferably 25% by weight or less, based on the weight of the entire film. When the weight of the cut-out portion exceeds 30% by weight, the productivity of the film is reduced. In order to make the weight of the cutout portion within the above range, for example, by increasing the uniformity of the thickness of the film after stretching, the non-cutout portion, that is, the product portion is enlarged, and the end E3 in the width direction of the film is increased. Means such as reducing the weight of the portion to be cut off by reducing the thickness at is adopted.

There is no particular limitation on the method of cutting out the portion including the end E3 in the width direction of the film, and a method of using a cutter installed in a line is generally used. In order to set the weight of the cutout portion within the above range, a cutter or the like is arranged between the end portion E3 in the width direction of the film and the point A5, and E
It is preferable to cut out a portion including 3.

EVO obtained by the above method
The H biaxially stretched film may be used alone as it is, or may be used by laminating a layer made of another thermoplastic resin on the biaxially stretched film. Other thermoplastic resins include polyolefins (polyethylene, polypropylene,
Poly 1-butene, poly 4-methyl-1-pentene, ethylene-propylene copolymer, copolymer of ethylene and α-olefin having 4 or more carbon atoms, copolymer of olefins and maleic anhydride, Ethylene-vinyl acetate copolymers, ethylene-acrylic acid ester copolymers, modified polyolefins obtained by graft-modifying these with unsaturated carboxylic acids or derivatives thereof, and various nylons (nylon 6,
Nylon 66, nylon 6/66 copolymer, etc.), polyvinyl chloride, polyvinylidene chloride, polyester, polystyrene, polyacrylonitrile, polyurethane, polyacetal, modified polyvinyl alcohol resin and the like. The laminating method is not particularly limited, and known methods such as an extrusion laminating method, a dry laminating method and a solution coating method can be mentioned.

The EVOH biaxially stretched film of the present invention and the laminate obtained by laminating a layer made of another thermoplastic resin on the biaxially stretched film have excellent gas barrier properties, morphological stability and transparency. Therefore, it is widely used in various fields such as foods, cosmetics, medical chemicals, and toiletries.

[0048]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Example 1 An EVOH resin having an ethylene content of 32 mol%, a saponification degree of 99.5% and a melting point of 183 ° C. was melted at a temperature of 230 ° C. and then cast from a T die onto a casting roll having a cooling surface of 15 ° C. Simultaneously with the extrusion, air was blown from an air knife at a wind speed of 30 m / sec to obtain an EVOH film. Thereafter, this film was made to contain water in an amount of 3.0% by weight, a region including a point A2 in FIG. 1 was grasped with a chuck, and a simultaneous biaxial stretching machine was used to preheat at a temperature of 120 ° C. and a stretching temperature of 120 ° C.
After stretching each laterally 3 times, heat treatment at 170 ℃,
An EVOH biaxially stretched film having a total width of 2500 mm was obtained.
Table 1 shows the parameters showing the thickness distribution of the film before and after stretching.
Shown in. In addition, Table 2 shows the number of breaks when the biaxially stretched film was continuously produced for 8 hours, the film width adopted as a product, and the weight ratio of the unnecessary portion cut off to the entire film.

Examples 2 to 4, Comparative Examples 1 to 3 Similar to Example 1 except that the lip opening adjusting bolt of the die was adjusted to change the thickness of each part of the EVOH film as shown in Table 1. To obtain an EVOH biaxially stretched film. Table 1 shows the parameters showing the thickness distribution of the film before and after stretching. In addition, Table 2 shows the number of breaks when the biaxially stretched film was continuously produced for 8 hours, the film width adopted as a product, and the weight ratio of the unnecessary portion cut off to the entire film.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

INDUSTRIAL APPLICABILITY By biaxially stretching the EVOH film of the present invention, the breakage of the film in the stretching step during continuous production is suppressed to the minimum, and at the same time, the practical effective width is ensured to the maximum. A biaxially stretched film can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an EVOH film of the present invention.

FIG. 2 is a schematic cross-sectional view of an EVOH biaxially stretched film of the present invention.

[Explanation of symbols] 1. Center A1 in the width direction of the film 2. Edge E1 in the width direction of the film 3. Point E2 that internally divides between the center A1 in the width direction of the film and the end E1 in the width direction of the film at 95: 5. Point A3 that internally divides between the center A1 in the width direction of the film and the end E1 in the width direction of the film at 75:25. Point A2 with maximum film thickness between E2 and A3 6. Thickness T1 (μm) at A1 of the film 7. Thickness T2 (μm) at A2 of the film 8. Thickness T3 (μm) at A3 of the film 9. Distance L12 (m from A1 to A2 of film
m) 11. Center A4 in width direction of biaxially stretched film 12. End E3 in the width direction of the biaxially stretched film 13. Point A5 that internally divides between the center A4 in the width direction of the biaxially stretched film and the end E3 in the width direction of the biaxially stretched film at 94: 6. Thickness of biaxially stretched film at A4 T4 (μ
m) 15. Thickness of biaxially stretched film at A5 T5 (μ
m)

Claims (12)

[Claims] 1. A thickness at a center A1 in the width direction of the film is T1 (μm), and a specific point A2 in the width direction of the film.
When the thickness at is T2 (μm), T1 and T
2 satisfies the relationship of the following formula (1),
A film made of an ethylene-vinyl alcohol copolymer. 0.1 ≤ (T2-T1) / T1 ≤ 0.5 (1) However, the point A2 is a point that internally divides between the center A1 in the width direction of the film and the end E1 in the width direction of the film at 95: 5. E
2 and the point internally dividing 75:25 between A1 and E1 is A3, it is the point having the maximum film thickness between E2 and A3. 2. The thickness of the film in A3 is T3.
The film of claim 1, wherein T1 and T3 satisfy the relationship of the following formula (2) when (μm). 0.006 ≤ (T3-T1) / T1 ≤ 0.3 (2) 3. T1, T2 and T3 are represented by the following formula (3):
The film according to claim 1 or 2, which satisfies the relationship of. 0.1 ≤ (T2-T3) / T1 ≤ 0.5 (3) 4. The distance from A1 to A2 is L12 (m
m), T1 and L12 are represented by the following formula (4):
The film according to any one of claims 1 to 3, which satisfies the relationship. 0.01 ≤ T1 / L12 ≤ 0.5 (4) 5. The film according to claim 1, wherein T1 satisfies the following formula (5). 50 ≤ T1 ≤ 300 (5) 6. The film according to claim 1, wherein L12 satisfies the following formula (6). 300 ≤ L12 ≤ 3000 (6) 7. A biaxially stretched film comprising an ethylene-vinyl alcohol copolymer, which is obtained by biaxially stretching the film according to any one of claims 1 to 6. 8. In the biaxially stretched film, the thickness at the center A4 in the width direction of the film is T4 (μm),
The thickness at a specific point A5 in the width direction of the film is T5.
The biaxially stretched film according to claim 7, wherein T4 and T5 satisfy the relationship of the following formula (7) when expressed as (μm). 0.90 ≤ T5 / T4 ≤ 1.1 (7) However, the point A5 is the center A4 in the width direction of the biaxially stretched film.
Between the widthwise end E3 of the biaxially stretched film and 94: 6.
It is the point that is divided into 9. The biaxially stretched film according to claim 7, wherein the T4 satisfies the following formula (8). 5 ≤ T4 ≤ 30 (8) 10. A specific point A in the width direction of the film, where T1 (μm) is the thickness at the center A1 in the width direction of the film.
When the thickness in 2 is T2 (μm), a film made of an ethylene-vinyl alcohol copolymer in which T1 and T2 satisfy the relationship of the following formula (1) is biaxially stretched, ethylene. -A method for producing a biaxially stretched film made of a vinyl alcohol copolymer. 0.1 ≤ (T2-T1) / T1 ≤ 0.5 (1) However, the point A2 is a point that internally divides between the center A1 in the width direction of the film and the end E1 in the width direction of the film at 95: 5. E
2 and the point internally dividing 75:25 between A1 and E1 is A3, it is the point having the maximum film thickness between E2 and A3. 11. The method for producing a biaxially stretched film made of an ethylene-vinyl alcohol copolymer according to claim 10, which stretches while holding a region including the point A2. 12. A method for producing a biaxially stretched film made of an ethylene-vinyl alcohol copolymer, which comprises a step of biaxially stretching the film and a step of cutting out a portion including a widthwise end E3 of the biaxially stretched film. The method for producing a biaxially stretched film made of an ethylene-vinyl alcohol copolymer, wherein the weight of the cut-off portion is 30% by weight or less based on the weight of the entire film.