JP2002080620A - Polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film that is excellent in cost performance and that has high hiding performance and high drawing performance. SOLUTION: This polyester film comprises 10-60 wt.% of inorganic particles with an average particle size of 1-20 μm and a specific gravity of 1.8-2.6 g/cm3. The film has a specific gravity of 0.8-1.3g/cm3 and a hiding rate of >=1.0. A polyester laminate film is prepared by having this film as a layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film which is particularly excellent in cost performance and excellent in drawing and hiding properties.

[0002]

2. Description of the Related Art Polyester films are widely used in various fields because of their excellent mechanical, thermal and electrical properties. However, in recent years, the required characteristics in various applications have become more sophisticated, and the demands have been increasingly strict, such as lowering costs and reducing the influence on the environment.

[0003] Generally, various particle compounds are added to a polyester film for the purpose of imparting functionality, production stability and high quality. For example, generally, various kinds of particles are added to improve running properties and handling properties, and in a substitute for paper, a large amount of particles are added to impart whiteness and hiding properties, In tape applications, to obtain a fine and dense surface state,
Addition of particles having good dispersibility has been carried out.

As a method for adding such particles, a method utilizing a catalyst residue in a polyester reaction system as in an internal particle method, or a method using inorganic particles or organic particles in a polyester reaction system or a kneader as in an external particle method. And the like. Among them, the method of adding external particles is most often used because of easy handling, functionalization and the like. For example, many methods have been proposed for adding a large amount of external particles to impart hiding properties and whiteness. Japanese Patent Application Laid-Open No. Hei 8-217961 and the like propose a method of adding a large amount of surface-treated calcium carbonate, but the method is not necessarily sufficient in concealing properties. Japanese Patent Application Laid-Open No. 2000-17085 proposes a method of obtaining a film having a texture like recycled paper by adding a large amount of coal ash to plastic, but this method is not necessarily sufficient in concealment properties, and furthermore, blending is not sufficient. Cost and equipment are separately required, which is disadvantageous in cost performance. Also, JP-A-8-33694
No. 1, JP-A-8-48794, etc., have proposed methods of adding spherical silica, aluminum compounds and the like having excellent dispersibility, but these particles have a good affinity for polyester. On the other hand, if the reaction activity is high and a large amount is added, phenomena such as a marked increase in viscosity and a decomposition reaction such as hydrolysis progressing even in a blend by a kneader are observed, so that it has been difficult to add a large amount.

[0005]

SUMMARY OF THE INVENTION In view of the state of the prior art, the present invention is to provide a polyester film which is excellent in cost performance and excellent in drawing and hiding.

[0006]

The present invention solves such a problem.
To solve the problem, the following means are adopted. Sand
In addition, the average particle diameter is 1 to 20 μm, and the specific gravity is 1.8 to 2.6.
g / cm^ThreeContaining 10 to 60% by weight of inorganic particles,
And the specific gravity of the film is 0.8 to 1.3 g / cm. ^Three, Hidden
Polyester having an opacity of 1.0 or more
Film.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester in the present invention is preferably a polyester in which the main constituent unit of the polyester is ethylene terephthalate, and more preferably a polyester in which 90% by weight or more of the main constituent unit is ethylene terephthalate. Can be

Further, other components may be copolymerized or blended with the polyester as long as the effects of the present invention are not impaired.

As the copolymerization component, isophthalic acid, 2,2
6-naphthalenedicarboxylic acid, adipic acid, trimethyladipic acid, sebacic acid, malonic acid, dimethylmalonic acid, succinic acid, glutaric acid, maleic acid, itaconic acid, pimelic acid, 2,2-dimethylglutaric acid, azelaic acid, Fumaric acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,4
-Cyclohexanedicarboxylic acid, 1,4-naphthalic acid, diphenic acid, 4,4'-oxybenzoic acid, 2,5
-Polyfunctional carboxylic acids such as naphthalenedicarboxylic acid, diphenylethanedicarboxylic acid, trimellitic acid and ester derivatives thereof, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propane glycol, 1,3-
Butanediol, 1,4-butanediol, 1,3 pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-
Nonanediol, 1,10-decanediol, 2,4-
Dimethyl-2-butyl-1,3-propanediol, 2
-Ethyl-2-isobutyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2,
4-trimethyl-2-hexanediol, 1,2-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 4,4′-thiodiphenol, bisphenol A, 4,4 '-Methylenediphenol, 4,4'-(2-normornylidene) diphenol, 4,4'-dihydroxybiphenol, o
-, M-, and p-dihydroxybenzene, 4,4 '
-Isopropylidenephenol, 4,4'-isopropylidenebis (2,6-dichlorophenol), 2,5-
Naphthalene diol, p-xylene diol, cyclopentane-1,2-diol, cyclohexane-1,2-
Glycol components such as diol and cyclohexane-1,4-diol can be mentioned. Among them, dicarboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid and diphenylethanedicarboxylic acid and ester derivatives thereof, propylene glycol and tetracarboxylic acid Glycol components such as methylene glycol and cyclohexanedimethanol are preferred.

Examples of the blend include homopolyesters other than polyethylene terephthalate, copolymerized polyesters, polycarbonates, acrylic resins, and polyolefins.

The inorganic particles in the present invention must have an average particle diameter of 1 to 20 μm from the viewpoint of drawing properties, and more preferably 1 to 15 μm from the viewpoint of film-forming properties and surface properties, and particularly preferably 1 to 15 μm. It is preferably from 10 to 10 μm from the viewpoint of film forming properties and surface properties. Examples of the type of inorganic particles include, for example, alumina, aluminum hydroxide, silica, titanium oxide, calcium carbonate, calcium phosphate, calcium oxide, magnesium oxide, magnesium hydroxide, barium sulfate, spinel, talc, zeolite, iron oxide, tin oxide, Zinc oxide, boron nitride, montmorillonite, fly ash silica fume, and the like, among which fly ash and silica fume are preferable in terms of polymerization reactivity and cost performance, and in terms of waste reduction, resource recycling, and environmental protection. Therefore, it is particularly preferable to use fly ash, which is a by-product generated when burning coal in a thermal power plant or the like. Here, fly ash is, for example, particles that can be obtained by collecting from a combustion exhaust gas of a pulverized coal combustion boiler with an electric dust collector in a coal-fired power plant or the like. Moreover, even when using two or more kinds of plural particles among these particles,
One kind of particles may be used alone, but from the viewpoint of cost performance and concealment, the specific gravity of the particles is 1.8.
２2.6 g / cm ³ .

The mixed particles in the present invention are particles obtained by mixing two or more kinds of inorganic particles, and may be mixed in advance as particles or slurry, or may be kneaded or transesterified. It may be mixed in the polymer by the supply during the esterification or polymerization reaction. As the kind of two or more kinds of inorganic particles used as the mixed particles, the above-mentioned particle groups are exemplified. Among them, mixed particles containing 50% by weight or more of silica are preferable from the viewpoint of moldability and reactivity, As other particles, iron oxide, alumina and the like are preferable from the viewpoint of moldability and reactivity. The average specific gravity of the whole mixed particles is
From the viewpoint of concealability, the average specific gravity is 1.8 to 2.6 g / cm.
Must be ³ .

The content of such inorganic particles is 10% by weight based on the weight of the polyester composition from the viewpoint of drawing properties.
It is necessary to be at least 60% by weight and not more than 60% by weight.
The following is preferred.

As a method of blending such inorganic particles with the polyester, there is a method of adding at any time of a transesterification reaction, an esterification reaction, a polymerization reaction in a polyester production process, or a method of blending with a kneader. However, from the viewpoint of cost performance, a method of adding at any time in the transesterification reaction, esterification reaction, and polymerization reaction is preferable.

The polyester film of the present invention needs to have a hiding factor of 1.0 or more, more preferably 1.2 or more, from the viewpoint of show-through. The specific gravity of the film, cost, in terms of drawability, must be a 0.8~1.3g / cm ^3, in particular, is preferably 0.8~1.2g / cm ³ .

As a method for producing a polyester film in the present invention, for example, a polyester composition containing predetermined inorganic particles is dried as required, and then supplied to a melt extruder to form a sheet from a slit die. Extrusion,
A method of obtaining an unstretched film by bringing it into contact with a casting drum and cooling and solidifying it by a method such as electrostatic application, or a method of stretching the unstretched film in the longitudinal direction or width direction of the film to obtain a uniaxially stretched film; Thereafter, there is a method in which the film is stretched again in the direction perpendicular to the uniaxial stretching direction to obtain a biaxially stretched film, but from the viewpoint of mechanical strength and surface properties of the film, it is preferable to use a biaxially stretched film.

The stretching is preferably performed by a tenter method in terms of film quality. After stretching in the longitudinal direction, the film is successively biaxially stretched in the width direction. Several simultaneous biaxial stretching systems are desirable. The stretching ratio is 1.5 to 4. in each direction.
It is 0 times, preferably 1.8 to 3.5 times. Longitudinal direction,
Either of the stretching ratios in the width direction may be increased or may be the same. The stretching speed is from 1000% / min to 200%.
2,000% / min, and the stretching temperature is equal to or higher than the glass transition temperature of the polyester, [glass transition temperature + 80
° C] or lower, but can be any temperature,
[Glass transition temperature +15 to 60 ° C] is preferable. Furthermore, after biaxial stretching, the film can be heat-treated,
This heat treatment can be performed by any method such as in an oven or on a heated roll. Heat treatment temperature is 120-2
Any temperature of 50 ° C. can be used, but preferably 150 to 240 ° C. The heat treatment time can be arbitrarily set, but is preferably 0.1 to 60 seconds, more preferably 1 to 20 seconds. The heat treatment may be performed while relaxing the film in the longitudinal direction and / or the width direction. Further, re-stretching may be performed once or more in each direction, and then heat treatment may be performed.

Further, the film may be subjected to a surface treatment such as a corona discharge treatment according to the purpose.

The polyester film in the present invention may be a single-layer film or a laminated film. In the case of a laminated film, for example, a polyester film layer (hereinafter, referred to as (I) layer) of the present invention and another layer (hereinafter, referred to as (II) layer) are laminated.
It may have a layer structure, or (I) layer / (II) layer / (I)
Layer or 3 such as (II) layer / (I) layer / (II) layer
A structure in which layers are stacked may be used. When the particle content in the layer (I) is close to the upper limit of the range of the present invention, it is preferable that the layer (I) be the inner layer from the viewpoint of film forming properties, and when the particle content is close to the lower limit of the range of the present invention. It is preferable that the layer (I) is laminated on at least one of the outermost layers from the viewpoint of drawing properties.

When the polyester film of the present invention is used as a single-layer film, the thickness is preferably 30 μm or more, particularly preferably 50 μm or more, in view of the strength and workability of the film. In the case of a laminated polyester film, the thickness of the I layer is
The thickness is preferably 10 μm or more, and more preferably 20 μm or more, from the viewpoint of the strength of the film, in order to exhibit sufficient drawing and hiding properties.

In the case of a laminated polyester film, the average value of the light reflectance at a wavelength of 400 to 700 nm is 80%.
% Or more is preferable in terms of drawing properties and coloring properties, and whiteness is preferably 80% or more in terms of drawing properties and coloring properties.

The film of the present invention can be used for recording materials such as synthetic paper, for interiors such as wallpaper and floor sheets, for bonding metal plates, exterior and housing materials of electric equipment, capacitors, and electronic members. For various general industrial uses, such as carrier films for wiring, wiring boards and coatings, laminating to glass members, optical members, and heat-sensitive stencil printing.

[0023]

The present invention will be described in detail with reference to the following examples. The characteristics were measured and evaluated by the following methods. (1) Average Particle Diameter of Inorganic Particles A polyester film containing inorganic particles is subjected to plasma treatment, and the exposed inorganic particles are observed with a scanning electron microscope, at least 100 particle diameters are measured, and the longest diameter is determined as a circle. The average was determined as the equivalent diameter. (2) Film concealment ratio Using a optical densitometer TR927 (manufactured by Macbeth), the concealing ratio was determined by the optical density measured by a transmission method, and expressed as a value converted to a film thickness of 50 μm. The greater this value, the higher the concealment property. In the case of a laminated film, only a layer of the film specified in the present invention is determined using a solvent capable of dissolving and removing the laminated portion, and this is an object to be measured. In the laminated film in the following examples, the measurement was performed on the layer I obtained by dissolving and removing the layer II with o-chlorophenol. (3) Specific gravity of film A sample obtained by cutting the film into a size of 50 mm x 60 mm was measured by a float-sink method using a high-precision electronic hydrometer SD-120L (manufactured by Mirage Trading Co., Ltd.).
In the measurement, correction was made in advance by the room temperature at the time of measurement. In the case of a laminated film, the layer of the film specified in the present invention is to be measured as in the case of the above (2). In the laminated film in the following examples, the measurement was performed on the layer I obtained by dissolving and removing the layer II with o-chlorophenol. (4) Light reflectance of film Spectroscopic color difference meter SE-2000 (Nippon Denshoku Industries Co., Ltd.)
400-7 according to JIS Z-8722.
The spectral reflectance in the range of 00 nm is measured at 10 nm intervals,
Each value was determined by averaging. (5) Film whiteness Spectroscopic color difference meter SE-2000 (Nippon Denshoku Industries Co., Ltd.)
Was used to measure yz. The whiteness was calculated using the following equation. 4 × 0.847 × z−3 × y = whiteness (%)

(6) Show-through property The thickness is about 100 μm on 20-point alphabetical letters (black) printed on recycled paper in MS Mincho style.
m, and the degree of show-through of the characters was evaluated as follows. ：: Cannot be read at all. ○: Blurred and unreadable. Δ: Characters are blurred but readable. ×: Characters are clearly visible and readable. ◎ and ○ were accepted.

(7) Drawability The density of the pencil and the readability of the character when writing a "positive" character having a size of 20 points with an HB pencil were evaluated as follows. ◎: Write letters with almost the same density as when writing on recycled paper,
Can be read even one meter away. ：: Characters of almost the same density as when written on recycled paper can be written, but cannot be read at a distance of 1 meter. Δ: Characters can be written, but the characters are lighter than when written on recycled paper. ×: Characters cannot be written. ◎ and ○ were accepted.

(8) Repeatable drawing performance In the same manner as the drawing performance described above, the operation of writing a "positive" character with an HB pencil and erasing with an eraser is repeated 10 times, and then the state when a straight line is drawn with a ruler is evaluated. did. ：: A clean straight line can be drawn without deformation of the film. ：: The film is slightly deformed, but a straight line can be drawn without any problem. ×: The pencil was caught on the deformed portion and a straight line could not be drawn neatly. ◎ and ○ were accepted.

Example 1 After transesterification by adding calcium acetate as a catalyst to dimethyl terephthalate and ethylene glycol, fly ash having an average particle diameter of 8 μm was added to the reaction product, and the content was 30% by weight. A 50% by weight ethylene glycol slurry was added, antimony trioxide as a catalyst, and phosphoric acid as a heat stabilizer were added to carry out a polycondensation reaction, and the obtained polyethylene terephthalate composition pellets were evacuated at 160 ° C. for 4 hours. Dried.

Next, it was extruded with a single screw extruder, discharged from a usual die, cooled and solidified with a mirror-surface cooling drum while applying static electricity to obtain an unstretched film. This unstretched film is 2.5 times at 95 ° C. in the longitudinal direction and 2.times.
After stretching 5 times, heat treatment is performed at 220 ° C and the thickness is 100 μm.
Was obtained. The characteristics are shown in Table 1.

Example 2 Example 1 was repeated except that 30% by weight of silica having an average particle diameter of 1.5 μm and 3.0% by weight of α-alumina having an average particle diameter of 1.5 μm were added instead of fly ash. Polymerization was performed in the same manner as described above to obtain a polyester film. Table 1 shows the properties of the obtained polyester film.

Example 3 Example 1 was repeated except that fly ash was added in a powdery state at a rate of 50% by weight simultaneously with the supply of the raw material.
Polymerization was performed in the same manner as described above to obtain a polyester film. Table 1 shows the properties of the obtained polyester film.

Example 4 After transesterification by adding calcium acetate as a catalyst to dimethyl terephthalate and ethylene glycol, antimony trioxide as a catalyst and phosphoric acid as a heat stabilizer were added to the reaction product. Then, 10% by weight of titanium oxide having an average particle diameter of 1 μm was added as particles, and a polycondensation reaction was carried out, and the obtained pellets of the titanium oxide-containing polyethylene terephthalate composition were mixed with 1 pellet.
Vacuum dried at 60 ° C. for 4 hours.

On the other hand, a polyethylene terephthalate composition containing fly ash was obtained by polymerization in the same manner as in Example 3.

Next, the resulting two types of polyethylene terephthalate compositions were simultaneously extruded by a single screw extruder so that the fly ash-containing layer was the inner layer and the fly ash-free layer was the outermost layer. And then solidified by cooling with a mirror-surface cooling drum while applying static electricity to obtain an unstretched laminated film. After stretching this unstretched laminated film 3.0 times at 95 ° C. in the longitudinal direction and 3.0 times at 90 ° C. in the width direction,
Heat treatment was performed at 230 ° C. to obtain a laminated polyester film having a thickness of 100 μm. The characteristics are shown in Table 1.

[0034]

[Table 1]

Example 5 Instead of adding fly ash as particles, silica having an average particle diameter of 1.5 μm was added
0% by weight, 2% by weight of α-iron oxide having an average particle size of 2.0 μm
Polymerization was performed in the same manner as in Example 3 except that the polyester composition was added to obtain a polyester composition. On the other hand, after performing transesterification by adding calcium acetate as a catalyst to dimethyl terephthalate and ethylene glycol, adding antimony trioxide as a catalyst and phosphoric acid as a heat-resistant stabilizer to the reaction product,
Calcium carbonate having an average particle size of 1.5 μm
0% by weight was added, a polycondensation reaction was performed, and the obtained pellets of the calcium carbonate-containing polyethylene terephthalate composition were vacuum-dried at 160 ° C. for 4 hours.

Next, the obtained two polyethylene terephthalate compositions were simultaneously extruded by a single screw extruder so that the silica- and α-iron oxide-containing layer became the inner layer and the calcium carbonate-containing layer became the outermost layer. After discharging from the die, it was cooled and solidified with a mirror-surface cooling drum while applying static electricity to obtain an unstretched laminated film. This unstretched laminated film is moved in the longitudinal direction by 9
After stretching 2.8 times at 5 ° C and 2.8 times at 90 ° C in the width direction, 2
Heat treatment was performed at 30 ° C. to obtain a laminated polyester film having a thickness of 100 μm. The characteristics are shown in Table 2.

[Comparative Example 1] As the particles, the average particle diameter was 1.
Polymerization and film formation were carried out in the same manner as in Example 1 except that 1% by weight of 2 μm calcium carbonate particles was added.
A 0 μm polyester film was obtained. Table 2 shows the characteristics.
Shown in

Comparative Example 2 The average particle diameter of the particles was 0.1.
Polymerization was carried out in the same manner as in Example 1, except that 50% by weight of colloidal silica having a thickness of 50 μm was added. However, a sharp increase in viscosity occurred during the reaction, and a polyester composition capable of forming a film could not be obtained.

Comparative Example 3 The average particle diameter of the particles was 1.5.
Polymerization and film formation were carried out in the same manner as in Example 1 except that 5% by weight of agglomerated silica of 5 μm was added to obtain a polyester film having a thickness of about 100 μm. The characteristics are shown in Table 2.

[0040]

[Table 2]

[0041]

According to the present invention, excellent cost performance, high concealment and drawing properties, paper replacement, wallpaper,
Interior use such as floor sheets, bonding of metal plates, exterior materials and housing materials of electrical equipment, carrier films for capacitors and electronic members, bonding to wiring boards and coatings, glass members, optics The present invention can provide a film material that can be suitably used in various general industrial uses such as a member for use in printing, heat-sensitive stencil printing, and the like.

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Claims (7)

[Claims] An average particle diameter of 1 to 20 μm and a specific gravity of 1.
It contains 10 to 60% by weight of inorganic particles of 8 to 2.6 g / cm ³ and the specific gravity of the film is 0.8 to 1.3 g / cm ^3.
A polyester film having a cm ³ and a hiding ratio of 1.0 or more. 2. The polyester film according to claim 1, wherein the inorganic particles are a mixture of two or more kinds of particles. 3. The polyester film according to claim 1, wherein the inorganic particles are coal ash (fly ash). 4. The polyester film according to claim 1, which is produced by a method of sequentially or simultaneously biaxially stretching in the machine direction and the transverse direction. 5. A laminated polyester film, wherein at least one layer is the polyester film according to claim 1. 6. The laminated polyester film according to claim 5, wherein the average value of the light reflectance at a wavelength of 400 to 700 nm is 80% or more. 7. The laminated polyester film according to claim 5, wherein whiteness is 80% or more.