JPH1112371A - Transparent ultraviolet light-cutting polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyester film excellent in transparency and ultraviolet light-cutting. SOLUTION: This polyester constituting the subject film comprises one, two or more kinds of polyester copolymers including 3-97 mol.% naphthalene dicarboxylate as dicarboxylic acid component, based on the polyester, wherein, the content of the naphthalene dicarboxylic acid is 3-25 mol.%, based on the total dicarboxylic acid component. The subject film heat set after biaxial orientation his a mean transmittance for visible light having a wavelength of 400-700 nm of >=70% and the maximum transmittance for ultraviolet light having a wavelength of 300-360 nm of <=30%. It is preferable that there are oxygen- nonpermeable layers on at least one side of the film and the oxygen permeability of the film is <=5 cc/m<2> day atm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent polyester film having an ultraviolet ray-cutting property, and more particularly to the alteration of contents caused by ultraviolet rays, particularly the alteration of contents caused by the reaction between oxygen and contents due to the activation of ultraviolet rays. Film used for preventing food, medicine, industrial materials, parts, and the like, particularly, a film for containing oils and fats. In addition, the "film" of the present invention is intended to represent a film and a sheet.

[0002]

2. Description of the Related Art As a packaging film for foodstuffs and medicines, the content of foods and the like is deteriorated by ultraviolet rays, and in particular, the reaction between oxygen and the contents is accelerated by ultraviolet rays. To prevent deterioration,
A metal-deposited film in which a metal such as aluminum is vapor-deposited on a plastic film having a low oxygen permeability, a polyvinylidene chloride film having a low gas permeability and an excellent ultraviolet absorption property, or a film coated or laminated with polyvinylidene chloride is used. ing.

[0003] However, the metal-deposited film is not suitable as a packaging film because the metal-deposited layer makes the film opaque and makes the contents invisible. On the other hand, a polyvinylidene chloride film or a film coated or laminated with polyvinylidene chloride is transparent, but has a drawback that harmful chlorine gas is generated during incineration. In addition, polyvinylidene chloride can reduce the amount of transmitted ultraviolet light, but it still does not have sufficient UV-cutting properties, and the contents of the film react with even a small amount of oxygen due to the ultraviolet light transmitted through the film, changing the taste, etc. It's easy to do.

In recent years, a film on which a metal oxide such as aluminum oxide is deposited has been developed as a packaging film which does not impair the transparency of a plastic film as a base film.

[0005] However, although the metal oxide vapor-deposited film prevents oxygen permeation, it does not have sufficient ultraviolet ray cut-off properties, so that the transmitted ultraviolet rays cause the contents to react with a small amount of oxygen and change the taste and the like. Kneading the UV absorber into the base film on which the metal oxide is deposited,
A film has been proposed in which a metal oxide-deposited film has an improved ultraviolet-cutting property by interposing a binder layer containing an ultraviolet absorber between the base film and the vapor-deposited layer. In terms of terms, it is not yet satisfactory. Also, the film into which the UV absorber is kneaded has a problem that the UV absorber blooms on the film surface with the passage of time,
It is not suitable as a packaging film for foods and the like. Since the amount of the ultraviolet absorber that can be kneaded into contents other than foods is naturally limited from the point of blooming, it is not possible to secure sufficient ultraviolet ray cut property.

[0006] The present invention has been made in view of such circumstances, and an object of the present invention is to provide a polyester film having transparency and excellent ultraviolet-ray cutting properties.

[0007]

The present inventors have completed the present invention by paying attention to the fact that a naphthrene ring absorbs ultraviolet light having a wavelength of about 300 to 360 nm.

That is, in the transparent ultraviolet-cut polyester film of the present invention, the polyester constituting the film contains 3 to 97 mol% as a dicarboxylic acid component.
Consisting of one or more copolymerized polyesters containing naphthalenedicarboxylic acid, and wherein the content ratio of naphthalenedicarboxylic acid to all dicarboxylic acid components is 3 to 25.
Mol% of a polyester film which is heat-set after biaxial stretching and is 400 to 700 n.
m has an average transmittance of 70% or more for visible light, and 3
The maximum transmittance of ultraviolet rays of 00 to 360 nm is 30% or less.

When the polyester constituting the film consists of one kind of copolyester, it is a copolyester containing 3 to 25 mol% of naphthalenedicarboxylic acid as a dicarboxylic acid component and containing at least 75 mol% of ethylene terephthalate units. Preferably, there is.

[0010] Further, it is preferable that an oxygen barrier layer is laminated on at least one surface of the film, and the oxygen permeability of the film is 5 cc / m ² · day · atm or less. It is preferable to use a vapor deposition layer containing a metal oxide of silicon and / or aluminum as a main component.

[0011]

Embodiments of the present invention will be described below. First, the polyester constituting the base film of the transparent ultraviolet-cut polyester film according to the present invention will be described.

Polyester is a polymer compound obtained by polycondensation of a dicarboxylic acid component and a glycol component. The polyester constituting the polyester film used in the present invention comprises 2,6-di-carboxylic acid component as a dicarboxylic acid component.
It is a copolymerized polyester containing naphthalenedicarboxylic acid such as naphthalenedicarboxylic acid and 2,7-naphthalenedicarboxylic acid. Since the naphthalene ring can absorb ultraviolet rays having a wavelength of about 300 to 360 nm, the base film can exhibit an ultraviolet ray cutting property by using naphthalenedicarboxylic acid as a dicarboxylic acid component constituting the polyester.

The copolymerized polyester containing naphthalenedicarboxylic acid may be one kind or a mixture of two or more kinds of copolymerized polyesters. The content ratio of naphthalenedicarboxylic acid to all dicarboxylic acid components is 3 to 25 mol%.
It is. If the amount is less than 3 mol%, the ultraviolet ray cut property becomes insufficient. On the other hand, when the content is 25 mol% or more, the heat resistance of the film deteriorates. Therefore, when a polyester film is composed of one type of copolymerized polyester, a copolymerized polyester containing 3 to 25 mol% of naphthalenedicarboxylic acid is used as the dicarboxylic acid component.

On the other hand, in the case of mixing two or more copolyesters, the content ratio of naphthalenedicarboxylic acid to all dicarboxylic acid components is 3 to 25 mol%, and 3 to 97 mol% as dicarboxylic acid component. A copolymerized polyester containing naphthalenedicarboxylic acid can be used. The reason why the content ratio of naphthalenedicarboxylic acid in each copolymerized polyester was 3 mol% or more was 3 mol%.
If the amount is less than mol%, the ultraviolet ray cut property becomes insufficient. The reason why the content is less than 97 mol% is that as the ratio of naphthalenedicarboxylic acid in the dicarboxylic acid component constituting the polyester increases, the ultraviolet ray cut property improves, but the transparency of the film decreases, and when it exceeds 97 mol%, This is because the desired transparency cannot be obtained.

Other dicarboxylic acid components constituting the polyester include aromatic dicarboxylic acids other than naphthalene rings such as isophthalic acid, terephthalic acid, diphenyldicarboxylic acid, and metal sulfoisophthalate; oxalic acid, succinic acid, adipic acid, and the like. Examples include aliphatic dicarboxylic acids such as sebacic acid, maleic acid, dimer acid, and indandicarboxylic acid. Of these, terephthalic acid is preferred. As the dicarboxylic acid component, a tricarboxylic acid such as trimellitic acid or an oxycarboxylic acid such as oxybenzoic acid may be used in addition to the above dicarboxylic acid.

The glycol component constituting the polyester includes aliphatic diols such as ethylene glycol, propanediol, butanediol, pentanediol, neopentyl glycol and hexanediol; alicyclic diols such as cyclohexanedimethanol; Glycol condensates such as tetramethylene glycol; aromatic diols such as ethylene oxide adducts of bisphenol derivatives; and triols such as trimethylolpropane. Of these, ethylene glycol is preferred.

Accordingly, the copolymer used in the present invention is preferably a copolymer composed of ethylene terephthalate repeating units and ethylene naphthalate repeating units. When the film is composed of one type of copolymerized polyester, it is preferable to contain 75 mol% or more of ethylene terephthalate units. In a copolymerized polyester composed of an ethylene terephthalate repeating unit and an ethylene naphthalate repeating unit, the crystallinity of the polyester generally decreases until the content of naphthalenedicarboxylic acid as a dicarboxylic acid component is less than 50 mol%. Melting point tends to be lower than that of polyethylene terephthalate. For this reason, if the content of the ethylene terephthalate unit is less than 75 mol% (the content of the ethylene naphthalate unit is 25 mol% or more), the melting point is too low, and the heat resistance is insufficient. Further, when a biaxially stretched film is obtained, the film-forming property is deteriorated.

The method for producing these polyesters is not particularly limited, and the polycondensation method can employ either a transesterification method or a direct polymerization method. Further, the stage of copolymerizing the naphthalenedicarboxylic acid is not particularly limited, the initial stage of polymerization,
Any stage such as in an extruder performed during or after polymerization may be used.

The molecular weight of the polyester is 0.1 in terms of reduced viscosity.
It is preferably from 4 to 1.0, and particularly preferably from 0.6 to 0.8. If the reduced viscosity is less than 0.4, the mechanical strength of the film is insufficient, and if it exceeds 1.0, the cost for polymerization and film formation becomes too high, which is not economical. Here, the reduced viscosity is a value measured at a solution concentration of 0.4 g / dl and a temperature of 30 ° C. using a mixed solvent having a mixing ratio (weight ratio) of phenol / tetrachloroethane of 6/4.

The polyester resin as a raw material of the polyester film may be added with known additives, if necessary, for example,
Lubricants, anti-blocking agents, heat stabilizers, UV absorbers,
A plasticizer, an antioxidant, an antistatic agent, a light resistance agent, an impact resistance improver and the like can be contained. However, when these additives are contained, the content needs to be within a range that does not impair the transparency of the obtained film.

The above polyester resin is formed into a film.
Axial stretching is performed to create a polyester film. As the biaxial stretching method, for example, a method in which an unstretched sheet melt-extruded from a T-die is stretched in a longitudinal direction by a roll stretching machine, and then stretched in a transverse direction by a tenter stretching machine (sequential 2
Axial stretching method), a method of simultaneously stretching the unstretched sheet in the machine direction and the transverse direction using a tenter-type simultaneous biaxial stretching machine (simultaneous 2
Axial stretching method), a method in which a sheet melt-extruded into a tube shape is expanded by gas pressure and stretched (inflation method) and the like can be employed. The thickness of the film after stretching is 8
To 50 μm, particularly preferably 10 to 20 μm. The polyester film of the present invention is biaxially stretched and then heat-fixed to fix the orientation of the polymer chains.

After stretching and heat setting, the polyester film may be subjected to a corona discharge treatment, a coating treatment, or a flame treatment, if necessary, in order to improve adhesion and wettability. In particular, when the following oxygen barrier layer is provided, it is preferable to perform the above-described treatment on the polyester film in advance in order to enhance the adhesion between the oxygen barrier layer and the polyester film.

In the ultraviolet cut film of the present invention,
When it is desired to further provide oxygen barrier properties, it is preferable to provide a transparent oxygen barrier layer. By providing a transparent oxygen barrier layer, oxidation of the content itself can be prevented without impairing the transparency. In other words, instead of tight packaging, when packaging in a state where a space is maintained, if there is a sufficient amount of oxygen even if ultraviolet rays can be cut off, alteration of the contents due to oxidation may occur, but by the oxygen barrier layer being laminated In addition, the deterioration due to such oxidation can be prevented.

The transparent oxygen barrier layer is composed of polyvinylidene chloride, ethylene vinyl alcohol copolymer, metal oxide such as silicon or aluminum. Of these, the metal oxide deposited layer is excellent in transparency and oxygen barrier properties, and since there is no generation of harmful gases and the like at the time of disposal,
It is suitable as an oxygen barrier layer.

The oxygen barrier layer may be prepared by directly depositing a metal oxide on the polyester film (in the case of a metal oxide), or the film constituting the oxygen barrier layer may be directly or easily adhered to the polyester film. It may be formed by laminating through a chemical treatment layer. still,
For the production of the vapor deposition layer, a physical vapor deposition method such as a vacuum vapor deposition method, a sputtering method, an ion plating method, or a CV
A known method such as a chemical vapor deposition method such as the D method can be used.

When the oxygen barrier layer is a metal oxide vapor-deposited layer, the thickness of the vapor-deposited layer is usually from 10 to 5000 angstroms. If the thickness is less than 10 angstroms, sufficient oxygen permeability cannot be obtained, and if it exceeds 5000 angstroms, the production cost increases, the bending resistance decreases, and cracks easily occur in the oxygen barrier layer.

The ultraviolet cut film of the present invention may further have a sealing layer laminated thereon. The sealing layer is made of polyethylene, polypropylene, chlorinated polyethylene, polyvinylidene chloride, or the like, and the lamination method includes extrusion lamination, dry lamination, and coating. The sealing layer of the film on which the oxygen barrier layer is laminated may be formed after the base film (polyester film) is formed and before the oxygen barrier layer is laminated, or may be formed after the oxygen barrier layer is laminated.

The UV-cut polyester film having the above-mentioned structure has a film thickness of 400 n.
It is necessary that the average transmittance of visible light of m to 700 nm is 70% or more. If the content is less than 70%, the contents cannot be seen clearly, which is inappropriate as a packaging film. Further, the maximum transmittance of ultraviolet rays of 300 to 360 nm is 30%.
It is as follows. If the content exceeds 30%, the contents may be deteriorated by the transmitted ultraviolet rays. Further, the haze value is preferably 10% or less. If it is less than 10%, the transparency is poor,
This is because it is unsuitable as a packaging film.

Further, in the film on which the oxygen barrier layer is laminated, the oxygen permeation amount is 5 cc / m ² · day · a.
tm or less. Oxygen permeation amount is 5cc / m ² · day ·
This is because when the content exceeds atm, the contents are easily oxidized.

The transparent ultraviolet-cut polyester film of the present invention is used in the form of bags, tubes, lids, cups and the like. Such a polyester film is mainly used for packaging foods, medicines, industrial materials, industrial parts and the like. In particular, an ultraviolet-cut polyester film having an oxygen barrier layer is suitable for packaging foods containing fats and oils.
This is because the film cuts ultraviolet rays and prevents oxygen permeation, so that oxidation of fats and oils can be suppressed and deterioration of contents during storage can be prevented.

[0031]

EXAMPLES The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited by the following examples, and may be appropriately modified without departing from the spirit of the preceding and the following. And these are all included in the technical scope of the present invention.

[Evaluation Methods] Various measurement and evaluation methods employed in the following Examples and Comparative Examples are as follows. (1) Reduced viscosity A chip or polyester film itself as a raw material of a polyester film is dissolved in a mixed solvent having a mixing ratio (weight ratio) of phenol / tetrachloroethane of 6/4,
A 0.4 g / dl solution was prepared and measured using an Ubbelohde viscometer. The temperature at the time of measurement was 30 ° C.

(2) Transparency of Film The film was evaluated by the average visible light transmittance of 400 to 700 nm and the haze of the film. Visible light average transmittance from 400 to 700 nm The spectral spectrum of the film was obtained with a Hitachi Double Beam Spectrophotometer U-2001, the light transmittance from 400 to 700 nm was recorded every 25 nm, and the average value of these was calculated. Film haze value Measured with a haze meter manufactured by Nippon Denshoku Co., Ltd. according to JIS-K6714. The lower the haze value, the better the transparency, and a film with a haze value of 10 or less is at a level at which there is no problem in quality.

(3) Ultraviolet ray cut-off property A spectral spectrum of the film was obtained with a Hitachi Double Beam Spectrophotometer U-2001, and the maximum transmittance at 300 to 360 nm was examined in the obtained spectral spectrum.

(4) Oxygen barrier property Oxygen permeability measuring device (OX-TRAN 10 / 50A:
Oxygen permeability at 0% humidity and 25 ° C. air temperature was measured using a Model Controls, Inc.).

[Synthesis of Polyester] The polyester constituting the film contains 2,6-di-carboxylic acid as a dicarboxylic acid component.
Four types of polyesters obtained by copolymerizing naphthalenedicarboxylic acid and terephthalic acid in the ratio (mol%) shown in Table 1 were used. The polymerization method and reduced viscosity of each polyester are as shown in Table 1.

[0037]

[Table 1]

[Preparation of Polyester Film] The above polyester was mixed at the ratio (% by weight) shown in Table 2, and further, a silica gel fine powder having an average particle diameter of 18 μm was added to the film to secure slipperiness and blocking resistance. 0 inside.
6% by weight was added and dispersed to prepare a polyester resin as a film raw material. The prepared polyester resin was dried under vacuum to reduce the moisture content to 0.01% by weight or less, and then melt-extruded from a T-die at 280 ° C.
The sheet was drawn on a cooling roll at 0 ° C. to obtain an unstretched sheet.
The obtained unstretched sheet is immediately stretched 3.2 times in the longitudinal direction at 90 ° C. by a roll stretching machine, and further stretched 4 times in the transverse direction at 100 ° C. by a tenter stretching machine, and then relaxed by 10%. Meanwhile, the film was heat-set at a temperature 30 ° C. lower than the melting point of the film. After heat setting, a corona discharge treatment was further performed to obtain a stretched film having a thickness of 12 μm.

Silicon dioxide and aluminum oxide were vapor-deposited on the corona-discharged surface of the obtained film using an electron beam heating type vacuum vapor deposition apparatus, and the aluminum oxide content was 200 Å and the aluminum oxide content was 40% by weight. %
Examples 1 and 2 and Comparative Examples 1 to
3 was prepared. The film of Example 3 was not subjected to vapor deposition, and remained a polyester film alone. Comparative Example 1
Is obtained by depositing a metal oxide on a normal polyester film in which naphthalenedicarboxylic acid is not copolymerized, and corresponds to a conventional example. Table 2 shows the results of the evaluation of the ultraviolet-cut polyester film produced as described above by the above evaluation method.

[0040]

[Table 2]

From Table 2, it can be seen that the UV-cutting property is proportional to the content of naphthalenedicarboxylic acid with respect to the total amount of dicarboxylic acid in the polyester constituting the polyester film, and that the film containing less naphthalenedicarboxylic acid (Comparative Example 2) and It can be seen that the film not containing (Comparative Example 1) has insufficient UV-cutting properties.
On the other hand, in the order of Example 1, Example 2, and Comparative Example 2, 400 to 7
Since the visible light average transmittance at 00 nm is low, it is understood that the transparency is not related to the ratio of naphthalenedicarboxylic acid to the total amount of dicarboxylic acids but to the polymerization ratio of naphthalenedicarboxylic acid in the polyester. That is, when the film is made of a polyester having a high polymerization rate of naphthalenedicarboxylic acid, particularly a polyester containing a homopolymer (polyethylene naphthalate), the transparency is reduced. Therefore, without impairing the transparency, in order to obtain a film with improved ultraviolet cut properties, using a copolymerized polyester containing naphthalenedicarboxylic acid as a part of the dicarboxylic acid component, the amount of naphthalenedicarboxylic acid to the total amount of dicarboxylic acids. It can be seen that it is necessary to form the film with a higher proportion of polyester. In addition, from the comparison between Examples 1 and 2 and Comparative Examples 1 to 3 and Example 3, it can be seen that it is necessary to provide an oxygen blocking layer in order to prevent the permeation of oxygen.

[0042]

The transparent UV-cut polyester film of the present invention has excellent UV-cutting properties and transparency, so that the contents can be observed from the outside and the deterioration of the contents, such as oxidation, can be suppressed. it can. Therefore, the film of the present invention can be suitably used as a packaging film for contents in which deterioration of the contents due to ultraviolet rays becomes a problem. In particular, since the resin constituting the film itself has an ultraviolet absorbing property, there is no problem that blooming becomes a problem or an ultraviolet ray cutting effect is weakened as in the case of kneading an ultraviolet absorbing agent.

Further, by providing an oxygen-blocking layer, it is possible to prevent the permeation of oxygen in addition to cutting off ultraviolet rays, so that it is suitable for packaging of easily oxidized contents. In particular, by forming the oxygen barrier layer with a metal oxide vapor-deposited film, there is no problem of emitting harmful gas in the incineration treatment.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B32B 27/36 B32B 27/36 B65D 65/16 B65D 65/16 65/20 65/20 // C08G 63/189 C08G 63/189 C08J 7/06 CFD C08J 7/06 CFDZ B29K 67:00 B29L 7:00 9:00 (72) Inventor Seiichiro Yokoyama 2-1-1 Katada, Otsu-shi, Shiga Prefecture Toyobo Co., Ltd. Research Institute (72) Invention Person Hirohisa Fujita 17-9, Koami-cho, Nihonbashi, Chuo-ku, Tokyo Toyo Spinning Co., Ltd., Tokyo Branch Office (72) Inventor Kuriozawa Teruo 2-2-2 Dojimahama, Kita-ku, Osaka-Toyo Boseki Co., Ltd.

Claims (4)

[Claims] 1. The polyester constituting the film comprises one or more copolymerized polyesters containing 3 to 97 mol% of naphthalenedicarboxylic acid as a dicarboxylic acid component, and naphthalenedicarboxylic acid to all dicarboxylic acid components. Is a polyester having a content of 3 to 25 mol%, and the polyester film formed by heat setting after biaxial stretching has an average transmittance of visible light of 400 to 700 nm of 70% or more and 300 to 360 nm. A transparent ultraviolet-cut polyester film having a maximum ultraviolet transmittance of 30% or less. 2. The polyester constituting the film contains 3 to 25 mol% of a naphthalenedicarboxylic acid as a dicarboxylic acid component, and contains 7 ethylene terephthalate units.
A copolyester containing at least 5 mol%, wherein the polyester film formed by heat setting after biaxial stretching has an average transmittance of visible light of 400 to 700 nm of 70% or more and a maximum transmission of ultraviolet light of 300 to 360 nm. A transparent ultraviolet-cut polyester film having a ratio of 30% or less. 3. The transparent ultraviolet ray according to claim 1, wherein an oxygen barrier layer is laminated on at least one surface of the film, and the oxygen permeation amount of the film is 5 cc / m ² · day · atm or less. Cut polyester film. 4. The transparent ultraviolet-cut polyester film according to claim 3, wherein the oxygen-barrier layer is a vapor-deposited layer containing a metal oxide of silicon and / or aluminum as a main component.