JPH10168292A - Oriented polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an oriented film which is flexible, has an excellent flavor retention and low light transmittance and desirable for food packaging by uniaxially orienting a film made from a polyether ester block copolymer comprising naphthalenedicarboxylic acid, ethylene glycol and a major proportion of polyoxytetramethylene glycol. SOLUTION: The polyether ester block copolymer comprises an acid component comprising naphthalenedicarboxylic acid and a glycol component comprising at least one member selected from ethylene glycol and tetramethylene glycol and polyoxytetramethylene glycol. The polyoxytetramethylene glycol should constitute 50-80wt.% of the entire polymer. Its molecular weight is desirably 600-3,500. The oriented film is desirably one uniaxially oriented or one at least transversely clip-oriented. It has desirably a light transmittance of 60% or below, especially 20% or below to light at a wavelength of 350nm when it contains no ultraviolet absorber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretched polyester film comprising a polyetherester elastomer, and more particularly, to a stretched polyester film having excellent flexibility, good flavor and improved thickness unevenness, comprising an ultraviolet absorbent. The present invention relates to a stretched polyester film having a light transmittance at 350 nm of 60% or less without containing it and having good light resistance and light resistance.

[0002]

2. Description of the Related Art Thermoplastic polyester elastomers are:
In recent years, the amount of use has been increasing due to good moldability, and it has been used in various applications by taking advantage of features such as heat resistance and cold resistance. As a method of producing an unstretched film, for example, a method of producing an unstretched film (cast film) of a thermoplastic polyester elastomer by water application casting or the like (JP-A-4-33829) is known.

Further, a stretched elastomer comprising terephthalic acid (JP-A-7-117118) is known.

[0004] It is known that an ultraviolet absorber such as a benzophenone-based compound, a benzotriazole-based compound, or a salicylate-based compound is blended with an elastomer to improve light resistance.

[0005]

The film obtained by the conventional method is an unstretched film and has a poor thickness unevenness. Further, since a wide film cannot be obtained, productivity is low and cost is high. there were.

An object of the present invention is to provide a polyester film which is particularly suitable for packaging materials for foods and drinks, packaging materials for medicines and medical products. An object of the present invention is to provide a polyester film in which aroma components and trace amounts of medicinal components do not adsorb to a packaging material in such a use, and the taste and aroma of the ultraviolet absorber do not change due to elution.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above-mentioned objects, and as a result, have excellent flexibility, remarkably good elastic recovery, improved productivity, cost reduction, thickness unevenness, and the like. The present inventors have found that a stretched polyester film having good flavor properties and ultraviolet absorbability can be obtained, and arrived at the present invention.

That is, the present invention relates to a polyoxytetramethylene glycol, wherein naphthalenedicarboxylic acid is used as an acid component, at least one selected from the group consisting of ethylene glycol and tetramethylene glycol, and polyoxytetramethylene glycol is used as a glycol component. Consisting of a polyetherester block copolymer having a content of 50 to 80% by weight of the total amount of the polymer, and stretched in at least one direction, and having a light transmittance at 350 nm of not more than 60% at 350 nm without containing an ultraviolet absorber. Is a stretched polyester film.

In the present invention, the polyetherester block copolymer contains naphthalenedicarboxylic acid as an acid component,
A polyetherester block copolymer containing at least one selected from the group consisting of ethylene glycol and tetramethylene glycol and polyoxytetramethylene glycol as a glycol component. This copolymer is a block copolymer having an ethylene naphthalene dicarboxylate unit or a tetramethylene naphthalene dicarboxylate unit as a hard segment and a polyoxytetramethylene glycol unit as a soft segment, and has a rubber elastic property. It is a polyester elastomer.

In the above polyetherester block copolymer, the content of the polyoxytetramethylene glycol component must be 50 to 80% by weight of the total amount of the polymer, and the molecular weight of the polyoxytetramethylene glycol component is 400 to 80% by weight. 4000, especially 600-350
It is preferably 0. If the content exceeds 80% by weight, a film having flexibility and excellent elastic properties can be obtained, but the melting point of the block copolymer becomes too low, so that the elastic performance during dry heat treatment and wet heat treatment sharply decreases. To become a flexible elastic film with poor durability, while 50% by weight
If it is less than 1, a permanent set is large and the film is inferior in elastic properties, which is not preferable.

When the molecular weight is less than 400, the resulting polyetherester block copolymer has poor blockability, resulting in inferior elasticity, and has a low melting point of the polymer. It is not preferable because it will occur. On the other hand, when the molecular weight exceeds 4,000, polyoxytetramethylene glycol is not easily formed into a block copolymer due to phase separation during the production of the polymer, and the rubber elasticity performance is not exhibited.

The polyetherester block copolymer will be described in more detail. More specifically, 80% by mole or more, preferably 90% by mole or more of the dicarboxylic acid component is a naphthalenedicarboxylic acid component, and the short chain glycol component is 80% by mole. 80% by weight or more, preferably 90% by weight or more of the short-chain (low-molecular-weight) glycol component and the long-chain glycol component in which at least 90% by mole is ethylene glycol component or tetramethylene glycol component. 4000, preferably 600-35
It is a copolymer obtained by a polycondensation reaction with a long-chain glycol component which is a polytetramethylene glycol component of No. 00.

Acid components other than naphthalenedicarboxylic acid used in an amount of less than 20 mol% include, for example, terephthalic acid, isophthalic acid, phthalic acid, bis (4-carboxyphenyl) methane, 4,4'-diphenyletherdicarboxylic acid Examples include aromatic dicarboxylic acids such as acids, aliphatic dicarboxylic acids such as adipic acid, sebacin, azelaic acid, and dodecane diacid, and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid.

It is also used in an amount of less than 20 mol%,
Examples of low molecular weight glycol components other than ethylene glycol or tetramethylene glycol include 1,3-propanediol, 1,5-pentadiol, 1,6-hexanediol, diethylene glycol and 1,4-
Cyclohexane dimethanol and the like.

It is also used in an amount less than 20% by weight.
Examples of the long-chain glycol component other than polyoxytetramethylene glycol include poly (oxyethylene) glycol and poly (oxypropylene) glycol. Long chain glycols including polyoxytetramethylene glycol are homopolymers, or random copolymers or block copolymers in which two or more of the repeating units constituting the homopolymer are copolymerized in a random or block form, Alternatively, two or more of the above homopolymers or copolymers can be used as a mixed polymer.

The polyetherester block copolymer has a melting point of usually 150 to 270 ° C., and is a polymer that can be melt-formed. And it is excellent in flexibility, alkali resistance, chlorine resistance, wet heat resistance, heat resistance and the like.

The polyetherester block copolymer further includes an antioxidant such as a hindered phenol compound to improve heat resistance.
Hindered amine compounds, sulfur atom-containing ester compounds and the like can be mentioned.

The stretched polyester film of the present invention comprises:
It is preferable to contain inert particles in order to impart appropriate friction and workability. Examples of the inert particles include fine particles containing elements of Periodic Tables IIA, IIB, IVA and IVB (for example, , Kaolin, alumina, titanium oxide, calcium carbonate, silicon dioxide, etc.), silicone resin,
Fine particles made of a polymer having high heat resistance such as cross-linked polystyrene can be used.

In the stretched polyester film of the present invention, the polyetherester block copolymer is melted, extruded from a die and quenched to form an unstretched film, and then the unstretched film is stretched in at least one axial direction, preferably in a transverse uniaxial direction. It can be manufactured by a method of stretching and subsequent heat setting. As a quenching method for producing an unstretched film, a method of leading the film into a water tank, a method of quenching and solidifying on a casting drum, or the like can be used. Especially in the latter case, it is preferable to apply water on the casting drum. As a stretching method, stretching by a clip is preferable. This is because the film transition temperature (Tg) of the polyetherester block copolymer is low, so that the film sticks to the roll when the film is stretched by the roll, and the stretching point of the film at the time of stretching is set on the stretching roll. This is because it is difficult to obtain a film with little unevenness and no scratches. The stretching temperature is preferably a temperature of (Tg) to (Tg + 70) ° C., and the heat setting temperature is preferably higher than the stretching temperature and lower than the melting point of the polymer. The stretching ratio is preferably set to a value that satisfies both the thickness unevenness and the breaking elongation.

That is, if the stretching ratio is large, the thickness unevenness tends to be improved, and conversely, the breaking elongation tends to be reduced.

In the present invention, the preferred range of the elongation at break is 300 to 1000%. If it is less than 300%, it cannot be used as a packaging film because it cannot follow the shape of the contents, which is not preferable. On the other hand, if the content is 1000% or more, handling properties are poor, and workability problems such as wrinkles occur, which is not preferable.

The light transmittance at 350 nm is preferably 4
0% or less, more preferably 20% or less. 350n
When the light transmittance of m is 60% or more, the light resistance is insufficient, and when used for a packaging material, there is a problem that long-term storage cannot be performed, which is not preferable.

When an ultraviolet absorber is contained, the quality of the contents is adversely affected by elution and the like, and the flavor and taste are deteriorated.

The stretched polyester film of the present invention has a Young's modulus of 0.1 in both the machine axis direction and the direction perpendicular to the machine axis.
It is preferably in the range of 1 to 100 kg / mm ² ,
More preferably, it is in the range of 0.5 to 20 kg / mm ² . If the Young's modulus is less than 0.1 kg / mm ² , handling properties are poor and workability problems such as wrinkles are generated, which is not preferable. On the other hand, if it is more than 100 kg / mm ² , the film is excessively stiff and the film lacks flexibility, which is not preferable.

The stretched polyester film of the present invention preferably has a compression modulus in the thickness direction of 0.10 to 0.50 gf / μm. With this value, a stretched film having excellent flexibility, remarkably good elastic recovery, and further excellent touch can be obtained. If the compression elastic modulus in the thickness direction is less than 0.10 gf / μm, the film becomes less stiff than the characteristic of flexibility, resulting in poor handling properties and wrinkles. On the other hand, 0.50 gf / μ
If it exceeds m, flexibility and elastic recovery properties are not exhibited.

The thickness of the stretched polyester film should be set according to the intended use.
The range is 50 μm.

[0027]

The present invention will be described in more detail with reference to the following examples. In the examples, “parts” means parts by weight. Various physical property values and characteristic values in the present invention were measured by the following methods.

(1) Light transmittance Hitachi spectrophotometer (spectrophotometer)
meter) Measured with 228A type.

(2) Young's modulus A film was cut into a sample having a width of 10 mm and a length of 150 mm.
And a chart speed of 50 mm / min. With an Instron type universal tensile tester. The Young's modulus is calculated from the tangent to the rising portion of the obtained load-elongation curve.

(3) Compression modulus The film is cut into a sample having a width of 10 mm and a length of 150 mm.
A load is applied in the thickness direction of the film using a micro compression tester manufactured by Shimadzu Corporation. As an indenter, 50μ
It was measured using a plane indenter of mφ. As measurement conditions, the maximum load is 10.00 gf and the load speed is 3 mgf.
/ Sec, and presses the indenter against the film surface. The compression modulus is calculated from the tangent at the rising portion of the obtained load-strain curve.

(4) Elongation at break The film is cut into a sample having a width of 10 mm and a length of 150 mm, and the distance between the chucks is set to 100 mm. . It is calculated by the following equation from the elongation of the film at the time when the film breaks.

[0032]

(Equation 1)

(5) Evaluation of Flavor Property Mineral water was put in a 500 cc glass container, and 2 g of the film was completely immersed and sealed. After holding at 37 ° C for 4 months, open and reduce the change in fragrance for 10
A sensory test was performed on a person. ：: Eight or more evaluated when there was no change in fragrance. △: 4 to 7 people evaluated when there was no change in odor. ×: 0 to 3 people evaluated when there was no change in odor.

Example 1 A block copolymer having a hard segment of tetramethylene-2,6-naphthalenedicarboxylate unit and a soft segment of polyoxytetramethylene glycol unit, wherein the content of the soft segment is the total amount of the polymer A polyetherester block copolymer, which is 60% by weight of the above, was used.

After drying the polyetherester block copolymer, it is melted at 220 ° C., extruded from a die at 220 ° C. to a casting drum coated with water, quenched to obtain an unstretched film, and then the unstretched film. Was stretched 2.0 times in the transverse direction at a temperature of 80 ° C., and further heat-treated at 120 ° C. to obtain a transverse uniaxially stretched film. The thickness of this film was 25 μm.

The stretched film was evaluated for light transmittance, Young's modulus, compressive modulus in the thickness direction, elongation at break, thickness unevenness, and flavor properties. Table 1 shows the results.

[0037]

[Table 1]

As a result, a film having good thickness unevenness, a breaking elongation in the longitudinal direction of 700% and a breaking elongation in the transverse direction of 400% was obtained, and the compression modulus was 0.36 gf / μm.

Comparative Example 1 The same polymer as in Example 1 was melted at 220 ° C., extruded at a die temperature of 220 ° C., and quenched on a water-applied casting drum to obtain an unstretched film. The thickness of this unstretched film was 25 μm. The characteristics of this film were measured in the same manner as in Example 1. The results are shown in Table 1. As a result, the film had flexibility and good flavor, but had poor thickness unevenness.

Comparative Example 2 A block copolymer having a tetramethylene-2,6-naphthalenedicarboxylate unit as a hard segment and a polyoxytetramethylene glycol unit as a soft segment, wherein the content of the soft segment is the total amount of the polymer And a polyetherester block copolymer containing 0.2 parts by weight of a benzotriazole-based ultraviolet absorber with respect to 100 parts by weight of the block copolymer.

After drying the polyetherester block copolymer, it is melted at 220 ° C., extruded from a die at 220 ° C. to a casting drum coated with water, quenched to obtain an unstretched film, and then the unstretched film. Was stretched 2.0 times in the transverse direction at a temperature of 80 ° C., and further heat-treated at 120 ° C. to obtain a transverse uniaxially stretched film. The thickness of this film was 25 μm.

The film characteristics were evaluated in the same manner as in Example 1. The results are shown in Table 1. The film had good flexibility and uneven thickness, but was poor in flavor.

Comparative Example 3 A block copolymer having a tetramethylene terephthalate unit as a hard segment and a polyoxytetramethylene glycol unit as a soft segment, wherein the content of the soft segment is 60% by weight of the whole polymer. An ester block copolymer was used.

After drying the polyetherester block copolymer, it was melted at 200 ° C., extruded from a die at 220 ° C. to a casting drum coated with water, quenched to obtain an unstretched film, and then the unstretched film. Was stretched 2.0 times in the transverse direction at a temperature of 40 ° C., and further heat-treated at 80 ° C. to obtain a transverse uniaxially stretched film. The thickness of this film was 25 μm.

The film characteristics were evaluated in the same manner as in Example 1. The results are shown in Table 1. The film had good flexibility and uneven thickness, but was poor in flavor.

COMPARATIVE EXAMPLE 4 Tetramethylene-2,6-naphthalenedicarboxylate was melted at 300 ° C., extruded from a die and quenched to obtain an unstretched film, and then 2.0 times in the transverse direction at a preheating temperature of 140 ° C. Stretched and then 220
A heat treatment was performed at a temperature of 200 ° C. to obtain a 25 μm-thick transverse uniaxially stretched film. Although this film had good thickness unevenness and flavor, it had a compression elastic modulus of 60 gf / μm and lacked flexibility. The film characteristics were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0047]

According to the present invention, a polyetherester block copolymer containing no UV absorber has good thickness unevenness, excellent flexibility and elastic recovery, good weather resistance and flavor. It is possible to obtain a polyester film stretched in at least one uniaxial direction, preferably a polyester film stretched in a transverse uniaxial direction. This film can be particularly suitably used for packaging of foods, beverages and pharmaceuticals.

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Claims (4)

[Claims] (1) Naphthalenedicarboxylic acid as an acid component,
Polyetherester having at least one selected from the group consisting of ethylene glycol and tetramethylene glycol and polyoxytetramethylene glycol as a glycol component, and having a polyoxytetramethylene glycol component content of 50 to 80% by weight of the whole polymer. Consisting of a block copolymer, and stretched in at least one direction, with a UV absorber of 350 nm
Stretched polyester film having a light transmittance of 60% or less at 2. The naphthalenedicarboxylic acid is at least one selected from the group consisting of 2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid and 1,4-naphthalenedicarboxylic acid. The stretched polyester film according to claim 1, which is naphthalenedicarboxylic acid. 3. A Young's modulus of 0.1 to 100 kg / mm ^2.
The stretched polyester film according to claim 1 or 2, wherein 4. The film has a compression modulus in the thickness direction of 0.1.
The stretched polyester film according to claim 3, which has a thickness of 10 to 0.50 gf / μm.