JPH08169965A - Oriented polyester film - Google Patents

Abstract

PURPOSE: To obtain an oriented polyester film markedly excellent in easy slidability and surface smoothness and having few coarse protrusions. CONSTITUTION: This polyester is prepared by adding 0.01-0.5wt.% calcium carbonate particles (A) having a coverage of 60 % or above based on the area of the circumscribed circle, a dispersion of particle diameters of 30% or below and a mean particle diameter of 0.5-2.0μm and 0.01-0.5wt.% calcium carbonate particles (B) having a coverage of 60% or above based on the area of the circumscribed circle, a dispersion of particle diameters of 30% or below and a mean particle diameter being 0.2-1.5μm and smaller than that of particles (A) to a polyester mainly consisting of repeating ethylene terephthalate units.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oriented polyester film, and more particularly to an oriented polyester film having excellent slipperiness and surface smoothness and having a small number of coarse projections.

[0002]

2. Description of the Related Art Polyesters such as polyethylene terephthalate are generally used for fibers, molded products, magnetic tapes, photographs, capacitors, and packaging because of their excellent physical and chemical properties. It is widely used for various purposes such as film. When used for these films, the slipperiness thereof is a major factor affecting the workability of the film manufacturing process and the processing process in each application, and further the quality of the product. In particular, when a magnetic layer is coated on the surface of a polyester film and used as a magnetic tape, friction and abrasion between the coating roll and the film surface during coating of the magnetic layer are extremely severe, and wrinkles and scratches on the film surface are likely to occur. In addition, even after slitting the film after coating the magnetic layer and processing it into audio, video or computer tape, etc., when pulling out from the reel or cassette etc. Friction and abrasion occur remarkably between them, and scratches and distortions are generated, and white powdery substances are deposited due to abrasion of the surface of the polyester film and the like, and as a result, magnetic recording signals are often lost, that is, a large cause of dropout.

Generally, in order to improve the slipperiness of a film, a method of reducing the contact area with a guide roll or the like by giving unevenness to the film surface is adopted,
As a method for forming the surface irregularities, (1) an internal particle deposition method for depositing insoluble particles from a polymer catalyst residue used as a film raw material (Japanese Patent Publication No. 49-13234 and Japanese Patent Publication No. 50-6493), (2) External particle addition method to add inert inorganic particles (Japanese Patent Publication No. 55-
2225 and Japanese Patent Publication No. 55-41648). However, the internal particle deposition method has good affinity with polyester, but it is difficult to control the amount of particles deposited in the polymer and the particle size, so the surface morphology of the film must be precisely adjusted. However, it has the drawback of being difficult to slip and having insufficient slipperiness. In addition, with the external particle addition method, the design of the film surface morphology is easier than the former, but (1) inclusion of coarse particles, (2) secondary aggregation of particles, and (3) poor affinity with polyester for surface It was difficult to satisfy all the smoothness and the slipperiness.

Generally, the larger the size of the particles in the raw material polymer, the greater the effect of improving the slidability, but the particles are large for precision applications such as magnetic tapes. Since the film itself causes defects such as dropout and the electromagnetic conversion characteristics are significantly deteriorated, the unevenness of the film surface needs to be as fine as possible. As one of means for solving these contradictory characteristics, a means for using particles of large particle size and particles of small particle size in combination is used. For example, Japanese Patent Publication No. 52-78953, Japanese Patent Publication No. 55
-40929, USP 3,821,156 and USP 3,884,870 are known. However, in the range of large particle diameters described in these documents, the surface smoothness is insufficient for application to high-grade applications such as magnetic tapes, and further causes defects such as dropout. There is a drawback that it is difficult to suppress the formation of coarse protrusions on the film surface.

[0005]

The present invention solves the above-mentioned drawbacks of the prior art particularly when an oriented polyester film is used as a base material for a magnetic tape, has a small number of coarse projections, and has a smoothness and a surface smoothness. It is intended to provide a highly excellent oriented polyester film.

[0006]

Means for Solving the Problems That is, in the present invention, in a polyester whose main repeating unit is ethylene terephthalate, an average particle having an area ratio to the circumscribed circle of 60% or more and a particle size variation of 30% or less. The diameter is 0.
Calcium carbonate particles (A) having a size of 5 μm or more and 2.0 μm or less, and an area ratio of 60% or more with respect to a circumscribing circle and a degree of variation in particle size of 30% or less, an average particle size of 0.2 μm or more An oriented polyester film characterized by containing 0.01 to 0.5% by weight of calcium carbonate particles (B) each having an average particle diameter of 5 μm or less and smaller than the particles (A). .

The polyester used in the present invention is a crystalline polyester with polyethylene terephthalate, polyalkylene naphthalate, etc., and is not particularly limited, but polyethylene terephthalate is particularly suitable. Above all, 80 mol% or more of its repeating units are ethylene. Other copolymerization components include terephthalate, and isophthalic acid, p-β-oxyethoxybenzoic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-dicarboxyldiphenyl, 4,4′-diene. Dicarboxylic acid components such as carboxylic benzophenone, bis (4-carboxylphenyl) ethane, adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid, cyclohexane-1,4-dicarboxylic acid, propylene glycol, butanediol, neopen Glycol, diethylene glycol, cyclohexanedimethanol, bisphenol A
The ethylene oxide adduct, a glycol component such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol or the like, an oxycarboxylic acid component such as p-oxybenzoic acid or the like can be arbitrarily selected and used. In addition, a compound containing a small amount of an amide bond, a urethane bond, an ether bond, a carbonate bond or the like may be contained as a copolymerization component.

The polyester can be produced by any method such as a so-called direct direct polymerization method in which an aromatic dicarboxylic acid and a glycol are directly reacted, a so-called transesterification method in which a dimethyl ester of an aromatic dicarboxylic acid and a glycol are transesterified. The manufacturing method can be applied. The film may be either a uniaxially oriented film or a biaxially oriented film, but a biaxially oriented film is particularly suitable.

In the present invention, the larger average particle size of calcium carbonate (A) has an average particle size of 0.5 μm or more and 2.0 or more.
It must be less than or equal to μm, and is preferably greater than or equal to 0.6 μm and less than or equal to 1.8 μm. Particularly preferably, it is 0.8 μm or more and 1.6 μm or less. If it is less than 0.5 μm, the effect of improving the slidability becomes insufficient, which is not preferable. On the contrary, 2.0μ
If it exceeds m, the surface smoothness is lowered particularly for a magnetic tape, and the number of coarse projections, which causes defects such as dropout, increases, which is not preferable. The average particle size of calcium carbonate (B) having the smaller average particle size is 0.2 μm.
It is necessary to be not less than 1.5 μm and preferably not more than 0.5 μm.
It is 25 μm or more and 1.2 μm or less. Particularly preferably, it is 0.3 μm or more and 0.8 μm or less. If it is less than 0.2 μm, the effect of improving the slidability becomes insufficient, which is not preferable. On the other hand, if it exceeds 1.5 μm, the surface smoothness is lowered especially for magnetic tapes, and the number of coarse projections, which causes defects such as dropout, increases, which is not preferable. The difference in average particle size between the calcium carbonate (A) having a larger particle diameter and the calcium carbonate (B) having a smaller particle diameter is preferably at least 0.3 μm or more for improving slipperiness.

The addition amounts of calcium carbonate (A) and calcium carbonate (B) must be 0.01% by weight or more and 0.5% by weight or less, preferably 0.0% by weight or less.
It is 3% by weight or more and 0.4% by weight or less. It is particularly preferably 0.05% by weight or more and 0.3% by weight or less. 0.01
If it is less than wt%, the effect of improving the slipperiness is insufficient, which is not preferable. If the addition amount of each of the particles exceeds 0.5% by weight, the surface smoothness is lowered particularly for magnetic tapes, and the number of coarse projections which causes defects such as dropout increases, which is not preferable. The particle shape of the calcium carbonate is one of the particularly important requirements in the present invention.
Regarding the particle shape, in consideration of the necessity of precisely adjusting the film surface morphology, the evaluation by the volume shape coefficient that has been conventionally used is not sufficient.

In order to quantitatively grasp the particle shape, the present inventors defined the ratio of the particle shape cross-sectional area of the particle and the area of the circle circumscribing the projected view of the particle as the "area ratio to the circumscribed circle".
Was defined. As the area ratio approaches 100%, it approaches a lump or a sphere. The area ratio of the calcium carbonate (A) and (B) to the circumscribed circle needs to be 60% or more, and preferably 65% or more. It is particularly preferably 70% or more. Area ratio of calcium carbonate (A) and (B) is 6
If it is less than 0%, the effect of improving the slipperiness is insufficient, which is not preferable.

Furthermore, the degree of variation in particle size of calcium carbonate (A) and (B) must be 30% or less, preferably 27% or less. It is particularly preferably 20% or less. That is, if the particle size distribution is close to monodisperse,
The height and shape of the protrusions formed on the film surface are nearly uniform, which is consistent with the intention of the present invention. Calcium carbonate (A) and (B) particle size variation is 30
Above%, the morphology of the protrusions on the film surface becomes irregular, which is inconsistent with the object of the present invention, which is intended to precisely adjust the protrusions on the film surface. The calcium carbonate used in the present invention is not limited in its production method and the like as long as the above-specified conditions are satisfied, and both natural products and synthetic products can be used. For example, any of heavy calcium carbonate, light calcium carbonate and colloidal calcium carbonate may be used.

The calcium carbonate may be one which has not been surface-treated, but the calcium carbonate is not surface-treated in order to improve the dispersibility of the particles in ethylene glycol and the polymer and the affinity with the polymer. It is more preferable to use the treated one because it makes the present invention more effective. Furthermore, the presence or absence of the use of an anti-aggregation agent or a dispersion treatment agent is not particularly limited.

The method for adding the inert particles to the polyester in the present invention can be added at any stage in the polyester production process, but it is added after the completion of transesterification until the end of the initial condensation. Is particularly preferable. Further, the method for adding the inert particles to the polyester production process may be added in either a slurry state or a powder state, but it is dispersed in a slurry state from the viewpoint of preventing the particles from scattering and improving the supply accuracy and uniformity. Is preferably added as a slurry of ethylene glycol (EG). In the case of dispersion in the form of slurry, it is necessary to carry out uniform dispersion so as to reproduce the original primary particles of each particle as much as possible. Further, in order to obtain particles having a predetermined average particle diameter, commercially available fine particles may be pulverized or classified.

When the particles are added as a slurry, it is particularly preferable that the ratio of the particles having a particle size of 5 μm or more in the slurry is substantially 0% by weight or less with respect to all the particles in order to reduce the number of coarse projections. .

When the particles are added as a slurry to the polyester production process, two kinds of calcium carbonate having different average particle sizes may be added simultaneously or separately. When they are added at the same time, they may be added from separate supply ports, or the slurry may be uniformly mixed before addition to the polyester production step. In addition, it is preferable from the viewpoint of preventing aggregation of the calcium carbonate that it is added as a finely dispersed slurry in the presence of phosphoric acid and / or an alkali metal phosphite to the polyester production process.

As the alkali metal salts of phosphoric acid and phosphorous acid, orthophosphoric acid, pyrophosphoric acid, polymetaphosphoric acid, polyphosphoric acid, orthophosphorous acid, pyrophosphorous acid, polyphosphorous acid, and sodium salts of polymetaphosphorous acid. And specifically potassium salts such as sodium monophosphate, potassium monophosphate,
Dibasic sodium phosphate, dibasic potassium phosphate, tribasic sodium phosphate, tribasic potassium phosphate, sodium pyrophosphate, potassium pyrophosphate, sodium dihydrogen pyrophosphate, sodium hexametaphosphate, potassium hexametaphosphate, sodium tripolyphosphate, Potassium tripolyphosphate, sodium phosphite, sodium pyrophosphite, potassium pyrophosphite, sodium metaphosphite,
Examples thereof include potassium metaphosphite. The alkali salts may be used alone or in combination of two or more. The addition of the alkaline salt of phosphoric acid or phosphorous acid to the slurry may be performed at any stage from the start of slurry preparation to the addition to the polyester production process.

Alternatively, polyesters containing a high concentration of individual particles within the range where they do not aggregate may be separately prepared in advance, and then blended so as to have a predetermined particle concentration. Even if it contains fine particles precipitated in the polyester production process, so-called internal particles, as long as the average particle diameter and content do not increase the number of coarse particles and do not adversely affect the surface smoothness. I don't care. Incidentally, the use of the film, when the metal roll is in contact with only one surface, only the contact area contains the inert inorganic particles of the present invention, the other surface does not contain inert inorganic particles according to the purpose It may be another layer.

(Operation) The present invention is constructed as described above, but the point is that two kinds of calcium carbonate having the same particle shape and the same degree of variation in particle size are used in combination in a specified amount within a specified particle size range. It is possible to obtain an oriented polyester film having extremely excellent slipperiness and surface smoothness that cannot be achieved by calcium alone. That is, the present inventors used two kinds of calcium carbonate having a particle shape close to a lump or a sphere and having a uniform particle diameter in a specific amount within a specific particle diameter range, whereby slipperiness and surface smoothness were enhanced. The inventors have found an oriented polyester film which is excellent and has few coarse particles.

(Examples) Next, examples and comparative examples of the present invention will be described. All parts in the examples mean parts by weight unless otherwise specified. The measuring method used is shown below. Average Particle Size The particle size distribution in the slurry obtained by sufficiently dispersing the calcium carbonate particles in the ethylene glycol slurry is measured by a light transmission type centrifugal sedimentation type particle size distribution measuring device (SA-CP3).
Type Shimadzu Corporation), and the integrated value of 50% was used.

Area ratio with respect to circumscribed circle Inert particles are used as a scanning electron microscope (Hitachi S-510 type)
The specimens observed and photographed in step 1 were enlarged and copied, and further traced to randomly paint 200 particles in black. Choose 20 particles arbitrarily from this trace image,
The projected cross-sectional area of each particle was measured with an image analyzer (Luzex 500 model, Nireco Corporation). In addition, the area ratio was calculated using the following formula by calculating the area of the circle circumscribing each particle.

[0022]

[Equation 1]

Degree of variation in particle size Scanning electron microscope (Hitachi S-510 type) for inactive particles
The specimens observed and photographed in step 1 were enlarged and copied, and further traced to randomly paint 200 particles in black. This image was measured for a horizontal Fere diameter using an image analyzer (Luzex 500 manufactured by Nireco Co., Ltd.), and the average value was used as the average particle diameter used in the following formula. The degree of variation in particle size was calculated by the following formula.

[0024]

[Equation 2]

Surface smoothness of film (TAR) The surface of the film was measured using a stylus-type three-dimensional surface roughness meter (SE-3AK) manufactured by Kosaka Laboratory, with a needle radius of 2 μm and a load of 30.
Under the condition of mg, a cutoff value of 0.
Measurement is performed at 25 mm over a measurement length of 1 mm, and data in the height direction is taken into the external storage device at a quantization width of 0.00312 μm at intervals of 2 μm. Such measurement is performed 150 times continuously at 2 μm intervals in the lateral direction of the film.
That is, the film is measured over a width of 0.3 mm in the lateral direction. The height data at this time is h (i, j)
When [i = 1 to 500, j = 1 to 150], the value obtained by performing the following calculation is expressed in μm.
AR [Three-Day Regional Average Roughness].

[0026]

(Equation 3)

[0027]

[Equation 4]

Sliding property of film When a film slit into a narrow width is rubbed on a metal drum and run at high speed for a long time, the magnitude of the tension after rubbing the drum is evaluated on a scale of 5 for a given supply tension. It is expressed by ranking. Grade 5: Extremely low tension (no scratches) Grade 4 ... Small tension (almost no scratches) Grade 3 ... Medium tension (slightly scratches) Grade 2 ... Slightly high tension (very many scratches) Class 1 ... High tension (a lot of scratches)

Number of Coarse Protrusions on Film Surface After thinly depositing aluminum on the film surface, coarse projections of four or more rings (number per 1 mm ^{2 of} measurement area) were counted using a ^two- beam interference microscope to determine the number of coarse projections. It is represented by the following ranking depending on the degree. Grade 5 ...... 1 / mm ² less quaternary ...... 1-3 / mm ² 3 Grade ...... 4-6 / mm ² 2 Grade ...... 7-9 pieces / mm ² 1 Grade ...... 10 or more / Mm ²

Example 1 A continuous esterification reaction apparatus comprising a two-stage complete mixing tank equipped with a stirrer, a dephlegmator, a raw material inlet and a product outlet was used to esterify the first esterification reactor. The molar ratio of EG to terephthalic acid (TPA) was adjusted to 1.7 in the system in which the reaction product was present, and 289 ppm per TPA unit was antimony trioxide as an antimony atom.
An EG slurry of TPA containing was continuously fed. At the same time, the EG solution of magnesium acetate tetrahydrate is continuously supplied from a supply port other than the EG slurry supply port of TPA so that the amount of Mg atom is 100 ppm per polyester unit unit in the reaction product passing through the reactor. Supplied at a constant pressure and an average residence time of 4.5 hours at a temperature of 255 ° C.
Was reacted.

This reaction product was continuously taken out of the system and supplied to the second esterification reaction can. 0.5 parts by weight of EG and EG solution of trimethyl phosphate are 64 ppm as P atoms based on the polyester unit in the reaction product passing through the large 2-esterification reactor, and average particle size within the range specified in the present invention. To the EG slurries of two types of calcium carbonate having a diameter, an area ratio with respect to a circumscribing circle, and a degree of variation in particle size, an aqueous solution of sodium tripolyphosphate was added so as to be 0.80 wt% as Na atoms, and the sodium tripolyphosphate was contained. The slurry was continuously supplied as calcium carbonate from separate supply ports so that the amounts were regulated under the conditions shown in Table 1, and the reaction was carried out under normal pressure at an average residence time of 5.0 hours and at a temperature of 260 ° C.

The esterification reaction product is continuously supplied to a two-stage continuous polycondensation reaction device equipped with a stirrer, a dephlegmator, a raw material charging port and a product outlet port to carry out polycondensation to obtain an intrinsic viscosity. 0.620 polyester was obtained. Melt extruding the polymer and the polymer at 290 ° C.,
Table 1 shows the film characteristics of 15 μm obtained by drawing 3.5 times in the longitudinal direction at 130 ° C. and 3.5 times in the transverse direction at 130 ° C., and then heat-treating at 220 ° C. The film obtained in this example was excellent in slipperiness and surface smoothness, and was also excellent in the number of coarse projections.

Comparative Examples 1 and 2 Films were obtained in the same manner as in Example 1 except that the large particle size calcium carbonate (A) or the small particle size calcium carbonate (B) shown in Table 1 was used alone. The obtained film properties are shown in Table 1. In any case, it was not possible to simultaneously satisfy all the contradictory properties such as smoothness, surface smoothness and the number of coarse projections.

[0034]

As described above, according to the present invention, that is, by using two kinds of calcium carbonate having a particle shape close to a lump or a sphere and having a uniform particle diameter in a specific amount within a specific particle diameter range, It has the following excellent effects. (1) Sliding property and surface smoothness can be highly improved. (2) There are very few coarse protrusions that cause defects such as dropouts.

[0035]

[Table 1]

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B29K 67:00 105: 16 B29L 7:00 (72) Inventor Yasuhiro Nishino 10 Toyo-cho, Tsuruga City, Fukui Prefecture No. 24 Toyobo Co., Ltd. Comprehensive Research Laboratory Tsuruga Branch (72) Inventor Katsuro Kuze 10-24 Toyocho, Tsuruga City, Fukui Prefecture Toyobo Co., Ltd. Comprehensive Research Laboratory Tsuruga Branch (72) Inventor Ryuichi Murashige Toyobo Co., Ltd. 10-24 Toyocho, Fukui Prefecture Toyobo Co., Ltd. Research Institute Tsuruga Branch Office (72) Inventor Osamu Makimura 10-24 Toyocho, Tsuruga City, Fukui Prefecture Toyobo Co., Ltd. Tsuruga Branch Office

Claims (2)

[Claims] 1. A polyester whose main repeating unit is ethylene terephthalate has an area ratio to the circumscribed circle of 60% or more and a particle size variation of 30%.
The following calcium carbonate particles (A) having an average particle size of 0.5 μm or more and 2.0 μm or less, and an area ratio to the circumscribing circle of 60% or more and a degree of particle size variation of 30.
0.01% to 0.5% by weight of calcium carbonate particles (B) each having an average particle size of 0.2% to 1.5 μm and having an average particle size smaller than that of the particles (A). An oriented polyester film characterized in that 2. The method according to claim 1 or 2, wherein the difference in average particle size between the calcium carbonate particles (A) and the calcium carbonate particles (B) is 0.3 μm or more. Oriented polyester film.