JPH10166535A - Polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packaging material having heat sealability by providing excellent flavorfulness and chemicals resistance and suitably following up a shape of its content. SOLUTION: The polyester film comprises a heat sealing layer made of polyethylenenaphthalenedicarboxylate resin having heat sealability, and a polyester elastomer layer made of polyetherester block copolymer having tetramethylenenaphthalenedicarboxylate unit as a hard segment and polyoxytetramethyleneglycol component as a soft segment in such a manner that content of the polyoxytetramethyleneglycol component is 50 to 80wt.%, and light ray permeability of 350nm is 60% or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for packaging materials having excellent flavor and weather resistance (ultraviolet absorption).

[0002]

2. Description of the Related Art Conventionally, as a packaging material for packaging foods and other articles, a packaging material composed of a laminated material mainly composed of a plastic film has been used. This layer is heat-sealed to form a bag or the like.

[0003] Polyester resins are superior to other resins, and among them, polyethylene naphthalenedicarboxylate resin has gas barrier properties, weather resistance, mechanical properties, etc., as compared with other polyester resins such as polyethylene terephthalate and polybutylene terephthalate. It is known that the material is excellent in strength and flavor.

A packaging material having a heat seal layer made of a polyethylene-2,6-naphthalenedicarboxylate resin (JP-A-8-156208) has already been proposed.

[0005]

In the above technique, polyethylene naphthalene dicarboxylate film is used after being stretched biaxially. Such a biaxially stretched polyester film has a polymer chain constituting a film having an oriented crystal. It is not suitable as a packaging material because it has no heat sealing property.

The packaging material is preferably used after being made into a bag by heat sealing, but when a film having no heat sealing property is used, it is necessary to laminate a heat sealing resin on the sealing surface. However, if a heat-sealing resin is laminated, the effects of polyethylene naphthalenedicarboxylate on chemical resistance and low adsorption cannot be exhibited.

In addition, the layer serving as the support of the sealing layer must be able to follow the shape of the content to some extent or more in order to be used as a packaging material. Conventional polyethylene terephthalate films and polyethylene naphthalenedicarboxylate films are too stiff to follow the contents.

Further, even if the film has a heat seal layer made of polyethylene naphthalenedicarboxylate resin as a seal layer for directly touching the contents, the outer layer which is a support of the heat seal layer is made of polyethylene terephthalate. Since the weather resistance is insufficient and the function as a packaging material cannot be maintained for a long period of time, or a fragrance component or a small amount of a medicinal component is adsorbed to polyethylene terephthalate in the outer layer, there is a problem in maintaining the quality of the contents.

The present invention is excellent in flavor and chemical resistance,
An object of the present invention is to provide a packaging material which can suitably follow the shape of the contents and has a heat sealing function.

[0010]

SUMMARY OF THE INVENTION The present invention provides a heat seal layer made of a polyethylene naphthalene dicarboxylate resin having heat sealability, a polyoxyethylene resin having an ethylene naphthalene dicarboxylate unit or a tetramethylene naphthalene dicarboxylate unit as a hard segment. A polyester elastomer layer comprising a polyetherester block copolymer having a tetramethylene glycol component as a soft segment and a content of the polyoxytetramethylene glycol component in the total amount of the polymer of 50 to 80% by weight. Is a polyester film having a light transmittance of 60% or less.

The polyethylene naphthalenedicarboxylate resin used for the heat seal layer is selected from any of the following resins and is 1000 g / 15 mm in the form of a film.
It is preferable to have a heat seal strength not less than the width. A homopolyester copolyester having a crystallinity of 40% or less after melt-extrusion molding. A mixed resin obtained by mixing two or more of the above polyester resins corresponding to any of the above.

More specifically, the heat-sealing layer made of the above resin is described as follows. After melt-extruding a homopolyester containing naphthalenedicarboxylic acid as an acid component and ethylene glycol as a glycol component, the roll is immediately cooled to 10 to 30 ° C. It is a non-stretched film obtained by forming a film thereon. This film has a crystallinity of 40% or less, and the polyethylene naphthalenedicarboxylate film having such a crystallinity has a thickness of 1000 g required to form a bag.
/ 15mm width or more heat seal strength. And this invention uses this film as a heat sealing layer. In addition, as said naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid,
2,7-Naphthalenedicarboxylic acid and the like are known, and any of these can be used. However, it is preferable to use 2,6-naphthalenedicarboxylic acid.

[0013] More specifically, the resin is a copolymer polyester in which at least one of an acid component and a glycol component constituting polyethylene naphthalenedicarboxylate is partially substituted with another component. The following can be exemplified as the substitution component.

Acid components maleic acid, maleic anhydride, succinic acid, adipic acid,
Pimelic acid, suberic acid, azelaic acid, sebacic acid,
Aliphatic dicarboxylic acids such as dodecanoic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid; phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, diphenyl-4,4'-dicarboxylic acid, 3-sulfo acid Aromatic dicarboxylic acids such as isophthalic acid

Glycol components 1,4-butanediol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, triethylene glycol, 1,3-butylene glycol, neopentyl glycol, 1,5-pentanediol, 1,6-
Aliphatic diols such as hexanediol and polymethylene glycol; 1,4-cyclohexyl glycol, 1,4
Alicyclic diols such as cyclohexanedimethanol, 2,2-bis (4-hydroxycyclohexyl) propane and the like, and adducts of hydrogenated bisphenol A with alkylene oxides such as ethylene oxide and propylene oxide; resorcinol; Adducts of bisphenol A with alkylene oxides such as ethylene oxide and propylene oxide, such as 2-bis (4-hydroxyphenyl) propane, for example, 2,2'-bis (4-hydroxyethoxyphenyl) propane, 2,2 ' -Bis (4-hydroxydiethoxyphenyl) propane, 2,
2'-bis (4-hydroxypolyethoxyphenyl) propane, 2,2'-bis (4-hydroxypropoxylphenyl) propane, 2,2'-bis (4-hydroxydipropoxyphenyl) propane, 2,2 ' -Screw (4
-Hydroxypolypropoxyphenyl) propane and other aromatic diols These components may be used in combination of two or more.

The naphthalenedicarboxylic acid used as a main component is, for example, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,5-
Naphthalenedicarboxylic acid and 2,7-naphthalenedicarboxylic acid are used, but a plurality of kinds may be used. Preferably, it is 2,6-naphthalenedicarboxylic acid. Further, a part of the acid component and the glycol component may be substituted with a hydroxycarboxylic acid. Examples of the hydroxycarboxylic acid include aliphatic hydroxycarboxylic acids such as glycolic acid and oxypropionic acid; and aromatic hydroxycarboxylic acids such as hydroxybenzoic acid, and at least one kind can be used. This resin can be formed into a film by extrusion film formation similarly to the above resin. In the present invention, 1000 of the films made of these resins are used.
A film having a heat seal strength of at least g / 15 mm width is used.

The above resins and resins can be used as a mixture of two or more. Even in this case, it is necessary that the resin has a heat-sealing property of 1000 g / 15 mm or more in width, similarly to the above resin.

The polyester elastomer layer is a polyetherester block copolymer having an ethylene naphthalene dicarboxylate unit or a tetramethylene naphthalene dicarboxylate unit as a hard segment and a polyoxytetramethylene glycol component as a soft segment. It has properties and is a kind of thermoplastic polyester elastomer.

In the above polyetherester block copolymer, the content of the polyoxytetramethylene glycol component must be 50 to 80% by weight of the whole 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.

If the molecular weight is less than 400, the resulting polyetherester block copolymer will have poor blockability, resulting in inferior elasticity, and will have a low melting point of the polymer, resulting in insufficient durability to drying and wet heat treatment. It is not preferable because it will cause problems. On the other hand, when the molecular weight exceeds 4000, polyoxytetramethylene glycol undergoes phase separation during the production of the polymer, so that it is difficult to form a block copolymer, and rubber elasticity performance is not exhibited.

The polyetherester block copolymer will be described in more detail. More specifically, at least 50 mol%, preferably at least 80 mol%, more preferably at least 90 mol% of the dicarboxylic acid component constituting the hard segment is naphthalenedicarboxylic acid. Component. At least 50 mol%, preferably at least 80 mol%, more preferably at least 90 mol% of the short-chain glycol component constituting the hard segment is the ethylene glycol or tetramethylene glycol component. The long-chain glycol component constituting the soft segment preferably has a molecular weight of at least 80% by weight, more preferably at least 90% by weight, and has a molecular weight of 400 to 4,000, preferably 6.
It is a long-chain glycol component which is a polyoxytetramethylene glycol of 00 to 3500. The polyetherester block copolymer used in the present invention is preferably a copolymer obtained by a polycondensation reaction of such a dicarboxylic acid component and a short-chain glycol component and a long-chain glycol component.

Acid components other than naphthalenedicarboxylic acid which can be used in an amount of less than 50 mol%, preferably less than 20 mol%, more preferably less than 10 mol%, include, for example, terephthalic acid, isophthalic acid, phthalic acid, bis (4- Carboxyphenyl) methane, aromatic dicarboxylic acids such as 4,4'-diphenyl ether dicarboxylic acid, adipic acid,
Examples include aliphatic dicarboxylic acids such as sebacic acid, azelaic acid, and dodecane diacid, and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, and ester-forming derivatives thereof.

The low-molecular-weight glycol component other than ethylene glycol or tetramethylene glycol which can be copolymerized in an amount of less than 50 mol%, preferably less than 20 mol%, and more preferably less than 10 mol% includes, for example,
3-propanediol, 1,5-pentadiol, 1,
Examples thereof include 6-hexanediol, diethylene glycol and 1,4-cyclohexanedimethanol.

The long-chain glycol components other than polyoxytetramethylene glycol which can be copolymerized in an amount of less than 20% by weight, preferably less than 10% by mole, include, for example, poly (oxyethylene) glycol and poly (oxypropylene) glycol. And the like. Long chain glycols including polytetramethylene 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, or Further, it can be used as a mixed polymer in which two or more of the above homopolymers or copolymers are mixed.

The polyetherester block copolymer is preferably a polymer having a melting point of 150 to 270 ° C. and capable of forming a melt film. And it is excellent in flexibility, alkali resistance, chlorine resistance, wet heat resistance, and heat resistance.

It is preferable to add an antioxidant, an ultraviolet absorber and the like to the polyetherester block copolymer in order to further improve durability such as ultraviolet light resistance and heat resistance. Such antioxidants include, for example, hindered phenol compounds, hindered amine compounds,
Examples of the sulfur atom-containing ester compound and the like and the ultraviolet absorber include, for example, benzophenone-based compounds, benzotriazole-based compounds, salicylate-based compounds, and the like.

The polyester film of the present invention preferably contains inert particles in order to impart appropriate friction and workability. Examples of the inert particles include, for example, Nos. IIA, IIB and IVA of the periodic table. And fine particles containing a high heat-resistant polymer such as fine particles containing the element IVB (eg, kaolin, alumina, titanium oxide, calcium carbonate, silicon dioxide, etc.), silicone resins, cross-linked polystyrene and the like. .

When the inert particles are contained, they may be contained in one of the heat seal layer and the polyester elastomer layer, or may be contained in both layers.

The polyester elastomer layer preferably exhibits an elongation at break of 300 to 1000%. If it is less than 300%, it cannot be used as a film for packaging because it cannot follow the inner shape, which is not preferable. In addition, the handleability of 1000% or more is poor, and there is a problem of workability such as wrinkling, which is not preferable.

The light transmittance of the film of the present invention at 350 nm is 60% or less, preferably 40% or less, more preferably 20% or less. The light transmittance at 350 nm is 6
If it is 0% or more, the light resistance is insufficient, and when used as a packaging material, there is a problem that long-term storage cannot be performed, which is not preferable.

The heat seal layer and the polyester elastomer layer are laminated to form the film of the present invention, but the lamination method is optional. A method in which a heat seal layer and a polyester elastomer layer are separately formed and laminated with an adhesive or an adhesive resin layer interposed therebetween, a method in which the heat seal layer is directly extruded and laminated on the polyester elastomer layer, and a method in which the layers are co-extruded. Known methods such as a method for obtaining a film can be employed.

The heat seal layer and the polyester elastomer layer may be non-oriented (unstretched) or may be uniaxially or biaxially stretched.

The film of the present invention obtained as described above is formed into a known bag shape or the like with the heat seal layer inside, and used as a packaging material. When paper or metal is included, it can be formed into a container having a shape such as a goebel top type, a block type, a cylindrical shape, a conical shape, or a pyramid shape. The film can also be used as a lid material for sealing the opening of a cup-shaped or tray-shaped molded container. Further, the film of the present invention can be directly formed by a method such as vacuum forming to prepare a packaging container.

[0034]

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) Elongation at break The film is cut into a sample having a width of 10 mm and a length of 150 mm, the distance between the chucks is set to 100 mm, and the film is pulled at a tensile speed of 10 mm / min and a chart speed of 500 mm / min using an universal tensile tester of Instron type. . It is calculated by the following equation from the elongation of the film at the time when the film breaks.

[0036]

(Equation 1)

(2) Light transmittance Spectrophotometer manufactured by Hitachi, Ltd.
ter) Measured with model 228A.

(3) Seal Strength The strength of the heat seal portion was measured in accordance with JIS Z-1526.

(4) Evaluation of Flavor Property A bag was prepared with the heat seal layer inside so as to have a content of 500 cc, and mineral water was put in the bag and sealed. After keeping at 37 ° C. for 4 months, the bottle was opened and the change in aroma taste was sensory-tested by 10 persons each. ：: 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.

(5) Crystallinity The density was determined and calculated according to JIS C-2151.

(6) Weather resistance test Irradiation was carried out for 300 hours with a sunshine weather meter (sunshine carbon arc lamp), and the degree of deterioration was evaluated by elongation retention (elongation after irradiation with respect to initial elongation). The evaluation criteria for the degree of deterioration are shown below. ：: elongation retention of 40% or more ×: elongation retention of less than 40% The films obtained in the following Examples and Comparative Examples were subjected to heat seal strength, flavor properties, and weather resistance tests. Table 1 shows the results.

Example 1 A heat-seal layer 30 μ of 32% crystallinity made of a homopolyester containing 2,6-naphthalenedicarboxylic acid (100 mol%) as an acid component and ethylene glycol (100 mol%) as a diol component. When,
A block copolymer comprising polytetramethylene-2,6-naphthalenedicarboxylate as a hard segment and polyoxytetramethylene glycol as a soft segment and comprising a polyetherester block copolymer having a soft segment content of 60% by weight. And a polyester elastomer layer having a thickness of 25 μm, and laminated by dry lamination (coating amount: 2.8 g / m ² ) using an aliphatic ester-based adhesive (Takelac A515, manufactured by Takeda Pharmaceutical Co., Ltd.) as an adhesive. A film was obtained.

[Example 2] 2,4-Naphthalenedicarboxylic acid (90 mol%) and 1,4-naphthalenedicarboxylic acid (10 mol%) were used as acid components and 1,4-butanediol (100 mol%) was used as a diol. Example 1 was compared with a heat-seal layer 30 μ of a 25% crystallinity composed of a copolyester as a component and a polyester elastomer layer similar to that of Example 1.
Were laminated in the same manner as described above.

Example 3 Crystallization of a copolyester containing 2,6-naphthalenedicarboxylic acid (70 mol%) and adipic acid (30 mol%) as an acid component and ethylene glycol (100 mol%) as a glycol component 18%
Was heat-sealed and the same polyester elastomer layer as in Example 1 was laminated in the same manner as in Example 1.

Comparative Example 1 The heat seal layer described in Example 1 and 2,6-naphthalenedicarboxylic acid (100 mol%) were used as an acid component, and ethylene glycol (100 mol%) was used.
Is a biaxially oriented polyethylene-2
6-naphthalene dicarboxylate film layer 25 μm
Were laminated in the same manner as in Example 1.

Comparative Example 2 The same heat seal layer as in Example 1 and a block copolymer comprising polytetramethylene terephthalate as a hard segment and polyoxytetramethylene glycol as a soft segment having a soft segment content of 60% by weight. And a 25 μm-thick polyester elastomer layer made of a polyetherester block copolymer.

Comparative Example 3 Terephthalic acid (60 mol%), adipic acid (30 mol%) and glutaric acid (10 mol%)
(Mol%) as an acid component and ethylene glycol (100 mol%) as a glycol component, a heat-seal layer 30 μ of 18% crystallinity and a polyester elastomer layer similar to that of Example 1. In the manner described above.

Comparative Example 4 Melt Flow Index 3
A heat-sealable layer of 30 μg composed of LDPE (low-density polyethylene) having a heat-sealability of g / 10 minutes and a polyester elastomer layer similar to that in Example 1 were laminated in the same manner as in Example 1. Table 1 shows the evaluation results.

[0049]

[Table 1]

As is clear from the above results, those using the polyester film of the present invention showed excellent performance in any of the tests.

[0051]

The polyester film of the present invention is excellent in weather resistance, flavor and chemical resistance, can follow the shape of the contents, can obtain sufficient heat sealing strength, and is particularly excellent as a packaging film.

Claims (2)

[Claims] 1. A heat seal layer made of a polyethylene naphthalene dicarboxylate resin having heat sealability, a hard segment comprising an ethylene naphthalene dicarboxylate unit or a tetramethylene naphthalene dicarboxylate unit and a soft segment comprising a polyoxytetramethylene glycol component. And the content of the polyoxytetramethylene glycol component in the total amount of the polymer is 50.
A polyester elastomer layer comprising a polyetherester block copolymer in an amount of about 80% by weight, and a light transmittance at 350 nm of 60% or less. 2. The polyester film according to claim 1, wherein the elongation at break of the polyester elastomer layer is 300 to 1000%.