JPH08217895A - Oriented polyester film - Google Patents

Abstract

PURPOSE: To obtain a film usable in many fields such as packaging materials and industrial materials, excellent especially in moldability and processability, tear resistance, heat resistance and barrier properties by blending a polyester comprising ethylene-2,6-naphthalate as a main component with a polyester comprising ethylene terephthalate containing particles as a main component so as to control a refractive index. CONSTITUTION: This oriented polyester film comprises 70-95wt.% polyester composed of at least 80mol% repeating structure unit of ethylene-2,6-naphthalene unit and 5-30wt.% polyester composed of ethylene terephthalate containing 0.001-5μm average particle diameter as a main constituent, contains 0.001-5wt.% particles in the whole polyester composition and has 1.50-1.63 refractive index in the thickness direction.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a stretched polyester film containing ethylene 2,6-naphthalate as a main constituent. More specifically, molding processability, heat resistance,
The present invention relates to a stretched polyester film having good tear resistance.

[0002]

2. Description of the Related Art Conventionally, a polyester biaxially stretched film represented by polyethylene terephthalate (hereinafter sometimes abbreviated as PET) has mechanical properties, electrical properties, chemical resistance, dimensional stability and transparency. It has excellent properties such as, and is widely used in various fields. Particularly in the field of packaging materials, it is more environmentally friendly than polymers containing halogen elements such as polyvinyl chloride, has excellent mechanical properties, is relatively inexpensive, and can be collected and used. It has come to be used as a general packaging material mainly for applications.

On the other hand, in polyethylene terephthalate,
Among the packaging materials, it is still insufficient for applications where importance is attached to the barrier property, and the barrier property has been improved by providing a metal thin film by aluminum foil, barrier resin lamination, or vapor deposition. Not only is it complicated, but the recoverability of packaging materials is poor.

In recent years, mechanical properties, heat resistance, and
Polyethylene naphthalate film has been attracting attention because of its excellent gas barrier properties. Although unstretched polyethylene naphthalate film has moldability, it has low strength and it is difficult to form a thin film. On the other hand, the biaxially stretched polyethylene naphthalate film is easy to be formed into a thin film and has high strength, but it is not easily used as a packaging material because it is easy to tear and has not been used particularly for molding.

[0005]

The object of the present invention is to solve the above-mentioned problems in the prior art and to have transparency, barrier properties, heat resistance, and tear resistance, which are suitable for packaging materials and have excellent moldability. It is to provide a good stretched polyester film.

[0006]

The stretched polyester film of the present invention for this purpose comprises 70 to 95% by weight of polyester having at least 80 mol% of repeating structural units ethylene-2,6-naphthalate units and an average particle size. Consists of 5 to 30% by weight of polyester containing ethylene terephthalate as a main constituent, and contains 0.001 to 5 μm of particles, and 0.001 to 5% by weight of the particles in the whole polyester composition, and the thickness direction It has a refractive index of 1.50 to 1.63.

The stretched polyester film of the present invention is composed essentially of ethylene-2,6-naphthalate as a main component, and the polyester having 70 to 80 mol% of repeating structural units is ethylene-2,6-naphthalate.
It is necessary to contain 95% by weight. Further, the repeating structural unit is preferably at least 85 mol%, more preferably 90 mol%. When the ethylene-2,6-naphthalate unit is less than 80 mol% of the repeating structural unit, dimensional stability and mechanical properties are poor, which is not preferable. If it is 20 mol% or less, it may be modified with the following copolymerization component.

As the copolymerization component, for example, terephthalic acid, 2,7-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenyletherdicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodium as a dibasic acid component. Aromatic dicarboxylic acids such as sulfoisophthalic acid, 5-lithium sulfoisophthalic acid, 4-sodium sulfo-2,6-naphthalenedicarboxylic acid, phthalic acid, diphenyldicarboxylic acid, diphenylthioether dicarboxylic acid, diphenylketone dicarboxylic acid and phenylindanedicarboxylic acid acid,
Aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid and fumaric acid,
Alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid,
Examples thereof include oxycarboxylic acids such as p-oxybenzoic acid, and polyether dicarboxylic acids such as polyethylene oxide dicarboxylic acid and polytetramethylene oxide dicarboxylic acid.

As the glycol component, for example,
Aliphatic glycols such as ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, neopentyl glycol, alicyclic glycols such as cyclohexanedimethanol, aromatic glycols such as bisphenol A and bisphenol S, polyethylene glycol, polypropylene glycol. , Polytetramethylene glycol, polyalkylene glycol such as polyethylene glycol-polypropylene glycol copolymer, and the like. The average molecular weight of the polyalkylene glycol or polyether dicarboxylic acid is preferably 400 to 40,000, more preferably 600 to 20,000, and even more preferably 1000.
It is from 1 to 10,000.

In particular, 2,7-naphthalenedicarboxylic acid,
It is preferable to contain the isophthalic acid component in an amount of 5 to 15 mol% because the tear resistance and the moldability are improved. Of course, a plurality of dibasic acids or a plurality of glycols may be copolymerized, and as long as the effects of the present invention are not impaired, a polyfunctional compound such as trimellitic acid, trimesic acid, and trimethylolpropane was copolymerized. You may use the thing.

Further, the average particle diameter is 0.001 to 5 μm.
By mixing a polyester containing ethylene terephthalate as a main constituent component containing the particles of the above polyester, the tear resistance of the stretched film is improved, and the moldability in the step of molding the stretched film into a container or the like, gold Excellent releasability from the mold. If the average particle size is less than 0.001 μm, the releasability from the mold is poor and the average particle size is 5 μm.
When it exceeds m, not only the transparency is deteriorated, but also particles are likely to come off. Here, the polyester having ethylene terephthalate as a main constituent component means that at least 80 mol% of repeating structural units are ethylene terephthalate,
Further, the above-mentioned copolymerization may be performed.

In the present invention, the content of particles in the total polyester composition is 0.001 to 5% by weight. If the content of the particles is less than 0.001% by weight, the particles become tacky to the mold and cause molding failure, which is not preferable. On the other hand, when the content of the particles exceeds 5% by weight, the transparency is greatly deteriorated.

After incorporating particles into the polyester having ethylene terephthalate as a main constituent, at least 80 mol% of repeating structural units are ethylene-containing.
It is presumed that by mixing with a polyester that is 2,6-naphthalate, the crystallinity and orientation around the particles will be close to that of PET, and the tear resistance and moldability will be greatly improved.

Examples of the particles include so-called internal particles generated in the polymerization system, external particles made of inorganic, organic, or a composite thereof. Known internal particles can be preferably used as the internal particles, and as the external particles, for example, wet silica, dry silica, colloidal silica, titanium oxide, calcium carbonate, calcium phosphate, calcium fluoride, lithium fluoride, barium sulfate, Examples thereof include inorganic particles such as zirconia, alumina, mica, talc, kaolin and clay, and organic particles including styrene, silicone, acrylic acid and the like as a constituent component. Of these, wet or dry silica or colloidal silica, inorganic particles such as alumina, and organic particles having styrene, silicone, acrylic acid, methacrylic acid, polyester or the like as a constituent component are preferable. Especially for packaging, calcium carbonate, silica, crosslinked polystyrene-based particles, and polyester-based particles having a refractive index relatively close to that of polyester are preferable. The shape of these particles is not particularly limited, but a shape close to a sphere is preferable. Typical examples thereof include spherical silica and crosslinked polystyrene particles. Further, these particles may be used in combination of two or more kinds.

As a method for incorporating particles into a polyester containing ethylene terephthalate as a main constituent,
There is a method by internal particles for precipitating a catalyst or the like added during the polymerization reaction of polyester, a method of adding inactive particles to the polyester synthesis reaction system, a method of melt mixing polyester chips and particles with a twin-screw extruder, etc. Either method may be used.

In the present invention, it is further necessary that the refractive index in the thickness direction is 1.50 to 1.63 in order to improve moldability and tear resistance. The refractive index in the thickness direction is preferably 1.52 to 1.62, more preferably 1.54 to
1.61 is desirable in terms of moldability and tear resistance.

The stretched polyester film of the present invention may have a single-layer structure or a multi-layer structure (laminated structure),
If at least one layer is made of polyester having the characteristics described above, tear resistance is improved.
Other layers include polyethylene naphthalate layer, PET
Or layers such as copolyester, or slipperiness, coloring,
It is also possible to provide a layer that imparts antistatic properties and adhesiveness.

In the present invention, the heat shrinkage ratio at 120 ° C. × 30 minutes is 0.5% or less, preferably 0, when performing molding such as drape molding, straight molding, vacuum molding, cavity molding, and drawing molding. It is preferable for the content to be 0.4% or less because the shape of the corner after molding becomes sharper.

For producing the polyester of the present invention in which at least 80 mol% of the repeating structural unit is ethylene-2,6-naphthalate, any conventionally known method can be adopted without any particular limitation. For example, directly transesterifying 2,6 naphthalenedicarboxylic acid and optionally a small amount of another dicarboxylic acid component with ethylene glycol and optionally a small amount of another glycol component, or using a dialkyl ester of the dicarboxylic acid component. In this case, a polyester can be obtained by transesterification with a glycol component and heating this under reduced pressure to remove the excess glycol component.
At this time, it is preferable to use a transesterification reaction catalyst or a polymerization reaction catalyst, or to add a stabilizer or a coloring preventing agent, if necessary. As the reaction catalyst, for example, an alkali metal compound, an alkaline earth metal compound, a zinc compound, a lead compound, a manganese compound, a cobalt compound, an aluminum compound, an antimony compound, a germanium compound, a titanium compound, among them, an antimony compound, a germanium compound is preferable, Examples of the stabilizer and the anti-coloring agent include phosphorus compounds. Examples of the antimony compound include antimony trioxide, antimony pentoxide, antimony acetate, antimony glycolate, and germanium compounds such as germanium dioxide, germanium acetate, germanium tetramethoxide, germanium tetraethoxide, germanium tetrabutoxide, and germanium ethyleneglycoxide. Germanium alkoxide compounds, water-containing germanium hydroxide, phosphorus-containing germanium compounds such as germanium phosphate,
Examples thereof include germanium phenoxide compounds such as germanium phenolate. Examples of the phosphorus compound include phosphoric acid and its ester, phosphorous acid and its ester, phosphonic acid and its ester, phosphinic acid and its ester, and those having a small reducing action such as phosphoric acid and phosphoric acid ester. Is preferred.
The polymerization temperature is preferably as low as possible so long as the molten state can be maintained. Of course, anti-coloring agent,
Antioxidants, crystal nucleating agents, lubricants, antiblocking agents, ultraviolet absorbers, defoamers, antistatic agents and the like may be added.

Further, a polyester containing ethylene terephthalate as a main constituent is also produced by a known method, but it is necessary to add external particles as necessary. When external particles are added to the reaction system, they are preferably added in the form of ethylene glycol slurry.

The stretched polyester film of the present invention is preferably produced by melt extrusion. Polyester is
During vacuum drying, a predetermined amount of a specific particle master polymer is added and mixed, and after vacuum drying, it is supplied to a melt extrusion device and discharged from a slit-shaped ordinary die. The melt is cooled and solidified on a rotating cooling drum having a mirror-finished surface or a roughened surface to obtain a substantially amorphous cast film. When cooling on a rotary cooling drum, it is preferable to employ the electrostatically applied casting method from the viewpoint of thickness uniformity.

The polyester film of the present invention may be a uniaxially stretched film, but it is preferably biaxially stretched in order to impart mechanical strength, and a general polyester biaxial stretching method can be adopted. Simultaneous biaxial stretching by the tenter method or sequential biaxial stretching method. In the case of sequential biaxial stretching, it is possible to perform stretching in the longitudinal direction or the width direction twice or more.

The stretching temperature is at least 80 for the repeating structural unit.
Although any temperature can be used as long as it is in the range of not less than the glass transition temperature of the polyester whose mol% is ethylene-2,6-naphthalate and not more than the temperature rising crystallization temperature, in the present invention, in the case of stretching in the longitudinal direction. It is preferably 110 to 180 ° C, and 120 to 200 ° C in the case of stretching in the width direction. The stretching ratio in the longitudinal direction and the width direction of the film can be arbitrarily set according to the degree of orientation, strength, elastic modulus, etc. of the target film.

Further, the film is heat-treated after the biaxial stretching. This heat treatment can be performed by any conventionally known method such as in an oven or on a heated roll. The heat treatment temperature can be any temperature above the polyester crystallization temperature in which at least 80 mol% of the repeating structural units are ethylene-2,6-naphthalate and above the melting point + 20 ° C, but is preferably 150-300 ° C. . Further, the heat treatment time may be arbitrary, but is usually 0.5 to 60.
It is preferable to carry out for 2 seconds. The heat treatment may be performed while relaxing the film in the longitudinal direction and / or the width direction thereof.

The intrinsic viscosity of the polyester film of the present invention is preferably in the range of 0.4 to 1.2, more preferably 0.5 to 1.1, and particularly preferably 0.6 to 1.0.

The haze value of the film is preferably 10% or less, more preferably 5% or less. Haze value is 10%
If it exceeds, the transparency as a packaging material is lacking.

The surface state of the stretched polyester film of the present invention is such that the center line average roughness Ra is 0.030 μm or less and the maximum roughness Rt is 0.5 μm in order to maintain the transparency and to have a good handleability. The following is preferable. The center line average roughness Ra is more preferably 0.020.
It is not more than μm, and particularly preferably not more than 0.015 μm.
The maximum roughness Rt is more preferably 0.3 μm or less, and particularly preferably 0.2 μm or less.

The film thickness is 1 to 1000 μm.
m, preferably 1 to 100 μm. In producing the stretched polyester film of the present invention, if necessary, additives such as an antioxidant, a plasticizer, an antistatic agent, a weather resistance agent, an end-capping agent, and a dye can be appropriately used.

The stretched polyester film of the present invention is optionally subjected to various surface treatments such as corona discharge treatment, chemical treatment, flame treatment, ultraviolet treatment and plasma treatment in order to improve adhesion and ink adhesion. be able to.

[Characteristic Measuring Method and Evaluation Method] The characteristics of the polyester film were measured and evaluated by the following methods. (1) Intrinsic viscosity Measured at 25 ° C using o-chlorophenol as a solvent.

(2) Heat Shrinkage A film sample having a width of 10 mm and a length of 250 to 300 mm is marked at intervals of 200 mm, fixed on a sample support plate under a constant tension, and a universal projector (manufactured by Nippon Kogaku Co., Ltd.,
The original length of the marking interval was measured using V16A).
A load was applied to the measured sample using a 3 g clip, and the sample was treated while rotating in a hot air oven set to 100 ° C. for 30 minutes. The treated sample was left in an atmosphere for measuring the original length for 2 hours, and then the marking interval was measured in the same manner as the original length measuring method to obtain the shrinkage ratio.

(3) Refractive index in the thickness direction It was measured using an Abbe refractometer with sodium D line (wavelength 589 nm) as a light source.

(4) Tear propagation resistance Using a light load type tear tester (manufactured by Toyo Seiki Co., Ltd.), A
It was measured according to STM-D-1922. The sample size was 51 × 64 mm, a notch of 13 mm was made in the longitudinal direction, and the remaining 51 mm was torn, and the indicated value was read to be the smaller value in the longitudinal direction and width direction of the film.

(5) Film haze The film haze was measured according to ASTM-D1003-52.

(6) Average Particle Diameter of Particles The polyester portion of the sample is removed by a plasma low temperature ashing method (for example, PR-503 type manufactured by Daiwa Chemical Co., Ltd.) to expose the particles. The processing conditions are selected such that polyester is incinerated but particles are not damaged. This is observed by SEM, and the image of the particle is analyzed by an image analyzer (for example, QTM90 manufactured by Cambridge Instruments).
0), the frequency distribution is obtained for 500 or more observed particles, and the particle diameter showing the peak value is taken as the average particle diameter. In addition, when two or more peak values appear, it is assumed that two or more kinds of particles having different average particle diameters are added with each peak value. In the case of internal particles, a polymer cross section is cut, an ultrathin section having a thickness of about 0.1 to 1 μm is prepared, and photographs are taken using a transmission electron microscope at a magnification of about 5,000 to 20,000 times (10 sheets: 25 cm × 25 cm) was photographed, and the average particle size of the internal particles was determined by the equivalent circle diameter.

(7) Content of particles The sample is dissolved using a solvent (for example, o-chlorophenol etc.) in which the polyester is dissolved and the particles are not dissolved, and the particles are centrifuged from the solution to obtain the total weight of the sample. The particle content is defined as the weight ratio (% by weight) of the particles to. In addition, in the case where two or more kinds of particles having different average particle diameters are added, the peak height of the above frequency distribution is represented, and it is considered as the addition ratio of each particle, and the weight ratio is calculated from the average particle diameter and the specific gravity. The value converted into is the content of each particle.

(8) Center line average roughness Ra and maximum roughness Rt High precision thin film step measuring instrument ET-10 manufactured by Kosaka Laboratory Ltd.
It measured using. The conditions are as follows, and the average value of 20 measurements was taken as the value.・ Stylus tip radius: 0.5 μm ・ Stylus load: 5 mg ・ Measurement length: 1 mm ・ Cut-off value: 0.08 mm Note that Ra and Rt are defined, for example, by Jiro Nara, “Measurement / Evaluation of Surface Roughness”. Law "(Comprehensive Technology Center, 1983)
Are shown in.

(9) Formability a. Elongation The elongation at break was measured using a tensilon at a speed of 200 mm / min, and the smaller value was taken in the longitudinal direction and width direction of the film. b. Vacuum formability At 100 to 200 ° C, draw forming (forming ratio (height /
(Diameter) = 0.15) was performed and the formability was judged by the following evaluation. Grade A: Has sharp corners and a molding zone with good transparency in the temperature range of 10 ° C. or higher. Class B: In the temperature range of 5 ° C or higher and lower than 10 ° C, it has sharp corners and a molding zone with good transparency. Class C: The temperature range having a sharp corner and a molding zone with good transparency is less than 5 ° C. and the molding stability is poor. Class D: Stable molding cannot be obtained.

[0039]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Example 1 In a transesterification reactor equipped with a stirrer, a rectification column, and a condenser, 100 parts by weight of dimethyl 2,6-naphthalenedicarboxylate and ethylene glycol (hereinafter abbreviated as EG) 51
180 to 240 by adding calcium acetate 0.06 parts by weight and antimony trioxide 0.025 parts by weight to the parts by weight.
The temperature was gradually raised to 0 ° C., and simultaneously produced methanol was subjected to transesterification while continuously being distilled out of the reaction system. To the thus obtained reaction product, 0.04 parts by weight of phosphoric acid trimethyl ester was added and reacted for 5 minutes. Continuously distilling ethylene glycol continuously 28
The temperature was raised to 5 ° C. and the pressure was reduced to 0.2 mmHg at the same time to carry out a polycondensation reaction to obtain a polymer pellet having an intrinsic viscosity of 0.67.

On the other hand, as a particle master, an average particle size of 0.
A particle master A (first particles) made of polyethylene terephthalate containing 2% by weight of SiO ₂ of 5 μm and a particle master B (second particles of polyethylene terephthalate containing 1% by weight of SiO ₂ having an average particle diameter of 2 μm). ) Prepared. Then, add 1 to the above polymer pellets.
Pre-crystallized at 50 ° C. Next, the above-mentioned two types of particle master A and particle master B prepared in advance are added to the polymer pellets in an amount of 0.0 as the addition amount of the first particles.
The mixture was added and mixed so that the amount of the second particles added was 15% by weight and the amount of the second particles was 0.006% by weight, followed by vacuum drying at 180 ° C.

Then, it was supplied to an extruder, melted at 295 ° C., discharged from a usual die and cooled and solidified by a cooling drum to prepare an unstretched sheet. The obtained unstretched sheet is 1
3.5 times in the vertical direction at 35 ° C, 3.5 times in the horizontal direction at 140 ° C
After the bi-directional sequential biaxial stretching, the relaxation rate is set to 3% and 18
Heat treatment was performed at 0 ° C. for 2 seconds to obtain a biaxially stretched film having a thickness of 25 μm. The properties of the obtained film are shown in Table 1. It was excellent in tear resistance and moldability.

Example 2 A film was obtained in the same manner as in Example 1 except that the grain master was changed and the stretching ratio was 2.0 times both in the longitudinal and transverse directions. The properties of the obtained film are shown in Table 1. It was excellent in tear resistance and moldability.

Example 3 In Example 1, the particle master B was changed to an internal particle-containing master (one in which internal particles were formed by adding calcium acetate, lithium acetate, trimethyl phosphate, phosphorous acid and antimony trioxide). , Heat treatment temperature 140 ℃,
A film was obtained in the same manner as in Example 1 except that the relaxation rate was 0%. The properties of the obtained film are shown in Table 1.
Both the tear resistance and the moldability were good, but the heat shrinkage rate was large and the moldability was slightly lowered.

Example 4 In Example 1, isophthalic acid was added in an amount of 10 based on all acid components.
Mol% copolymerized polyethylene naphthalate (A), polyethylene naphthalate (B), and particle-containing polyethylene terephthalate (C) were used, and the respective resins were melted by a plurality of extruders and (B + C) ) / (A + C) / (B + C) three-layer stack (stacking ratio 1: 10: 1, the particle concentration of each layer is the same), and the heat treatment temperature was 210 ° C. The film was obtained in the same manner as in Example 1. It was The properties of the obtained film are shown in Table 2. Particularly excellent tear resistance and moldability were obtained.

Comparative Example 1 A film was obtained in the same manner as in Example 1 except that the stretching ratio was 4.9 times in length, 4.2 times in width and the heat treatment temperature was 200 ° C. The properties of the obtained film are shown in Table 2. Both tear resistance and formability were greatly reduced.

Comparative Example 2 A film was obtained in the same manner as in Example 1 except that only polyethylene naphthalate containing particles was used.
Moldability and tear resistance are greatly reduced.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

According to the present invention, ethylene-2,6-
By producing a stretched film by mixing a polyester having naphthalate as a main constituent and a polyester having particles as a main constituent with ethylene terephthalate, particularly good moldability, tear resistance, heat resistance, and good barrier properties are obtained. The stretched polyester film can be obtained and can be suitably used in many fields such as packaging materials and industrial materials.

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Claims (3)

[Claims] 1. 70 to 95% by weight of a polyester in which at least 80 mol% of repeating structural units are ethylene-2,6-naphthalate units, and an average particle size is 0.001 to 5 μm.
It is composed of 5 to 30% by weight of a polyester containing ethylene terephthalate as a main constituent component containing m particles, and 0.001 to 5% of the particles are contained in the whole polyester composition.
Contains by weight and has a refractive index in the thickness direction of 1.50 to 1.6
3. A stretched polyester film having a number of 3. 2. A stretched polyester film having a laminated structure in which at least one layer is the film layer of claim 1. 3. The heat shrinkage ratio at 120 ° C. × 30 minutes is 0.5.
% Or less, the stretched polyester film according to claim 1 or 2.