JPH0623262B2 - Oriented polyester film - Google Patents

Description

TECHNICAL FIELD The present invention relates to an oriented polyester film, and more particularly to an oriented polyester film having excellent slipperiness and abrasion resistance and having a small number of coarse projections.

(Prior Art) Generally, polyester such as polyethylene terephthalate has excellent physical and chemical properties, so that it is used for fibers, molded products, magnetic tapes, photographs, capacitors, and packaging. It is widely used for various purposes such as film. When used for these films, their slipperiness and abrasion resistance are major factors that affect the workability of the film manufacturing process and the processing process in each application, and further the product quality. 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. Also, 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, winding up and other operations, many guide parts, playback heads etc. Friction and wear occur remarkably between the two, and scratches and strains are generated, and white powder-like substances are deposited due to abrasion of the polyester film surface, etc. As a result, magnetic recording signals are often lost, that is, a major cause of dropout. . Generally, in order to improve the slipperiness and abrasion resistance of the film, a method of reducing the contact area between the film surface and the guide roll etc. by adopting unevenness is adopted, and as a method of forming this surface unevenness An internal particle deposition method for depositing insoluble particles from the polymer catalyst residue used as a film raw material (Japanese Patent Publication No. 49-1).
3234 and Japanese Examined Patent Publication No. 50-6493), and an external particle addition method by which inert inorganic particles are added (Japanese Examined Patent Publication No. 55-2225 and Japanese Examined Patent Publication No. 55-4).
1648). 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. With the external particle addition method, although the film surface morphology is easier to design than the former, surface smoothness, slipperiness, and abrasion resistance due to inclusion of coarse particles, secondary aggregation of particles, and poor affinity with polyester. It was difficult to satisfy all the sexual needs.

Generally, the larger the size of the particles in the raw material polymer,
Generally, the effect of improving the slidability is great, but in precision applications such as magnetic tape, the large particles themselves cause defects such as dropouts, and the electromagnetic exchange characteristics also deteriorate significantly. Therefore, 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 3,88.
4,870 and the like 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.

Further, since the inert inorganic particles generally have a poor affinity with polyester, the dispersibility in the polymer matrix becomes poor when blended with the polymer, which causes coarse aggregates to cause defects such as dropouts. Sometimes. Or, even if the dispersibility in the polymer matrix is excellent, when the unstretched original fabric is biaxially oriented, the affinity of the inorganic particles for the polymer with respect to the external force applied is weak, resulting in voids (air bubbles) and a decrease in transparency. And the abrasion resistance of the film surface is reduced.

(Problems to be Solved by the Invention) 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 slipperiness and abrasion resistance. Provides a highly excellent oriented polyester film.

(Means for Solving Problems) That is, in the present invention, the area ratio to the circumscribed circle defined by the following formula is 60% or more, and the average particle diameter is 0.5 μm in a polyester whose main repeating unit is ethylene terephthalate. Calcium carbonate particles (A) having a size of 2.0 μm or more and an area ratio to the circumscribing circle of less than 60%, an average particle size of 0.2 μm or more and 1.5 μm or less, and smaller than the particles (A) An oriented polyester film comprising 0.01 to 0.5% by weight of calcium carbonate particles (B) each having an average particle diameter.

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, and above all, 80 mol% or more of its repeating units consist of ethylene terephthalate. Other copolymerization components include isophthalic acid, p-β-oxyethoxybenzoic acid, 2,6-naphthalene dicarboxylic acid, 4,4'-dicarboxyl diphenyl, 4,4'-dicarboxylbenzo. Phenon,
Dicarboxylic acid components such as bis- (4-carboxylphenyl) ethane, adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid, cyclohexane-1,4-dicarboxylic acid, propylene glycol, butanediol,
Neopentyl glycol, diethylene glycol, cyclohexanedimethanol, ethylene oxide adduct of bisphenol A, glycol components such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and oxycarboxylic acid components such as p-oxybenzoic acid are arbitrarily selected. Can be 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.

As the method for producing the polyester, a so-called direct polymerization method in which an aromatic dicarboxylic acid and a glycol are directly reacted,
Any manufacturing method such as a so-called transesterification method in which a dimethyl ester of an aromatic dicarboxylic acid and a glycol are transesterified 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, calcium carbonate having a larger average particle size
The average particle size of (A) must be 0.5 μm or more and 2.0 μm or less, and preferably 0.6 μm or more and 1.8 μm or less. 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 other hand, if it exceeds 2.0 μm, 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. Further, as the number of coarse projections increases, the number of rupture voids also increases, resulting in poor wear resistance, which is not preferable. Calcium carbonate with smaller average particle size
The average particle size of (B) must be 0.2 μm or more and 1.5 μm or less, and preferably 0.25 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 wear resistance 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 larger particle size calcium carbonate (A) and the smaller particle size calcium carbonate (B)
It is preferable that the difference between the average particle diameters is at least 0.3 μm or more in order to improve slidability and wear resistance.

The addition amount of calcium carbonate (A) and calcium carbonate (B) must be 0.01 wt% or more and 0.5 wt% or less, preferably 0.03 wt% or more and 0.4 wt% or less. is there. It is particularly preferably 0.05% by weight or more and 0.3% by weight or less. If it is less than 0.01% by weight, the effect of improving the slipperiness is insufficient in the case of calcium carbonate (A), and the effect of improving the wear resistance is insufficient in the case of calcium carbonate (B), 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 particle shape as the “area ratio to the circumscribing circle”, which is the ratio of the area of the circle circumscribing the projected cross-sectional area of the particle to the projected view of the particle. .
As the area ratio approaches 100%, it approaches a lump or a sphere. The area ratio of the calcium carbonate (A) to the circumscribed circle is 60
% Or more, and preferably 65% or more. It is particularly preferably 70% or more. Calcium carbonate
If the area ratio of (A) is less than 60%, the effect of improving the slidability becomes insufficient, which is not preferable. Also, the area ratio of calcium carbonate (B) to the circumscribed circle must be less than 60%,
It is preferably less than 55%. It is particularly preferably less than 50%. If the area ratio of calcium carbonate (B) is 60% or more, the effect of improving wear resistance becomes insufficient, which is not preferable. Furthermore, the degree of variation in particle size of calcium carbonate (A) is 3
It must be 0% 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 will be nearly uniform, which is consistent with the intention of the present invention. If the degree of variation in the particle size of calcium carbonate (A) exceeds 30%, the projection shape on the film surface becomes irregular, which does not meet the purpose of the present invention intended to precisely adjust the projections 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 surface-treated in order to improve the dispersibility of the particles in ethylene glycol and the polymer and to improve the affinity with the polymer. Is more preferable in order to make 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 after the transesterification is completed,
It is particularly preferable to add it before the completion of the initial condensation.
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 adding the particles as a slurry,
The proportion of particles having a size of μm or more is substantially O% by weight based on all particles
It is particularly preferable to add it as follows from the viewpoint of reducing the number of coarse projections.

When the particles are added to the polyester production process as a slurry, two types 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 alkali metal salts of phosphoric acid and phosphorous acid, orthophosphoric acid, pyrophosphoric acid, polymetaphosphoric acid, polyphosphoric acid, orthophosphorous acid, pyrophosphorous acid, polyphosphorous acid, sodium salts and potassium salts of polymetaphosphorous acid. Specifically, sodium phosphate monobasic, potassium phosphate monobasic, sodium phosphate dibasic, potassium phosphate dibasic, sodium phosphate tribasic, potassium phosphate tribasic, sodium pyrophosphate, potassium pyrophosphate, Sodium dihydrogen pyrophosphate, sodium hexametaphosphate, potassium hexametaphosphate, sodium tripolyphosphate, potassium tripolyphosphate, sodium phosphite, sodium pyrophosphite, potassium pyrophosphite, sodium metaphosphite, potassium metaphosphite Etc. The alkali salts may be used alone or in combination of two or more.

The addition of the alkali 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 a range where they do not aggregate may be separately produced 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 contains the inert inorganic particles according to the purpose. It may be a different layer or may not be contained.

(Operation) The present invention is configured as described above, but the point is that two kinds of calcium carbonate having different particle shapes and particle size variations are used in combination in a specified amount within a specified particle size range, whereby the calcium carbonate alone or It is possible to obtain an oriented polyester film having excellent slipperiness and abrasion resistance that cannot be achieved by a combination of calcium carbonate having the same particle shape.

That is, the present invention is most characterized in that lumpy or spherical calcium carbonate and plate-like or columnar calcium carbonate are used together under specific conditions. In the present invention, particles close to lumps or spheres have extremely excellent slidability, but voids are likely to be present and abrasion resistance is insufficient. Further, calcium carbonate having a plate-like or columnar shape has a small void size and excellent wear resistance, but has insufficient slipperiness. That is, in view of the above situation, the present inventors have used two types of calcium carbonate having different particle shapes in combination in a specific amount within a specific particle size range, and thus have excellent slipperiness and abrasion resistance, and have few coarse particles. They have found an oriented polyester film.

(Example) Next, the Example and comparative example of this invention are shown. All parts in the examples mean parts by weight unless otherwise specified.

The measuring method used is shown below.

(1) Average particle size The particle size distribution in a slurry obtained by sufficiently dispersing calcium carbonate particles in an 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.

(2) Area ratio with respect to the circumscribed circle Inactive particles are scanned with an 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. Twenty particles were arbitrarily selected from this trace image, and 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.

(3) 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.

(4) 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 Ltd., the radius of the needle was 2 μm, and the load was 30.
Cutoff value 0.2 in the longitudinal direction of the film under the condition of mg.
Measurement is performed at 5 mm over a measurement length of 1 mm, and data in the height direction is taken into the external storage device with a quantization width of 0.00312 μm at intervals of 2 μm. Such measurement is continuously performed 150 times in the lateral direction of the film at intervals of 2 μm, that is, over a width of 0.3 mm in the lateral direction of the film.
When the data in the height direction at this time is h (i, j) [i = 1 to 500, j = 1 to 150], the data obtained by performing the following calculation is expressed in μm. It is TAR [Three-Day Regional Average Roughness].

(5) Abrasion resistance of film surface 7mm x 7 at 1000 times magnification using scanning electron microscope
The entire surface of the film having a size of mm was observed, and the site where the rupture void was observed was further magnified 5,000 times and photographed. Regarding the photographed burst voids, the number of those having a major axis of 5 μm or more was evaluated on a scale of 5, and the following ranking was performed.

5th grade Not recognized 4th grade 1-10 pieces 3rd grade 11-20 pieces 2nd grade 21-30 pieces 1st grade 31 pieces or more (6) Slipperyness of film Rubbing a film slit into a narrow width on a metal drum at high speed When running for a long time, the magnitude of the tension after the drum was rubbed against a constant supply tension was evaluated on a scale of 5 and represented by the following ranking.

Grade 5 ... Extremely low tension (no scratches) Grade 4 ... Low tension (almost no scratches) Grade 3 ... Medium tension (slightly scratches) Grade 2 ... Slightly high tension (very many scratches) Grade 1 ... High tension (excessive scratches) ) (7) Number of coarse protrusions on the film surface After thinly depositing aluminum on the film surface, the number of coarse protrusions of four or more rings (number per 1 mm ^{2 of} measuring area) is counted using a ^two- beam interference microscope to determine the number of coarse protrusions. It is expressed by the following ranking depending on the number.

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 Examples 1 and 2 Using a continuous esterification reaction device consisting of a two-stage complete mixing tank equipped with a stirrer, a partial condenser, a raw material charging port and a product outlet, The molar ratio of EG to heterephthalic acid (TPA) in which the esterification reaction product was present was adjusted to 1.7, and EG slurry of TPA containing 289 ppm per TPA unit as antimony trioxide was continuously supplied. .

At the same time, the EG solution of magnesium acetate tetrahydrate was continuously supplied from a supply port other than the EG slurry supply port of TPA so that the amount of each Mg atom was 100 ppm per polyester unit unit in the reaction product passing through the reaction mountain. And an average residence time of 4.5 hours at a normal pressure and a temperature of 255
The reaction was carried out at ° C.

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 trimethyl phosphate EG solution are 64 ppm as P atoms with respect to the polyester unit in the reaction product passing through the second esterification reaction can, and the average particle diameter within the range specified in the present invention. , An aqueous solution of sodium tripolyphosphate was added to EG slurries of two types of calcium carbonate having an area ratio with respect to a circumscribing circle and a degree of variation in particle diameter so as to be 0.80 wt% as Na atoms, and the sodium tripolyphosphate-containing slurry carbonic acid was added. Calcium was continuously supplied from separate supply ports so that the specified amounts were obtained under the conditions shown in Table 1, and the reaction was carried out at normal pressure with an average residence time of 5.0 hours and 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 discharging port to carry out polycondensation, and an intrinsic viscosity of 0.620. Of polyester was obtained. The polymer and the polymer are melt extruded at 290 ° C. and stretched 3.5 times in the machine direction at 90 ° C. and 3.5 times in the transverse direction at 130 ° C.
The film characteristics of 15 μm obtained by heat treatment at 0 ° C. are shown in Table 1.

The film obtained in this example was excellent in slipperiness and abrasion resistance, and was also excellent in the number of coarse projections.

Comparative Examples 1 to 12 Films were obtained in the same manner as in Example 1 except that the large particle size calcium carbonate (A) and the small particle size calcium carbonate (B) shown in Table 1 were used. The obtained film properties are shown in Table 1. In any case, it was not possible to satisfy all the contradictory properties such as slipperiness, abrasion resistance and the number of coarse projections at the same time.

(Effects of the Invention) As described above, according to the present invention, that is, by using two kinds of calcium carbonate having different particle shapes together in a specific amount within a specific particle size range, the following excellent effects are obtained.

Highly improved slipperiness and wear resistance.

Very few white powder and coarse protrusions that cause defects such as dropouts.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI technical display location B29K 67:00 B29L 7:00 4F (72) Inventor Ryuichi Murashige 10 Toyo-cho, Tsuruga City, Fukui Prefecture No. 24 Toyobo Co., Ltd. Comprehensive Research Laboratory Tsuruga Branch (72) Inventor Osamu Makimura 10-24 Toyocho, Tsuruga City, Fukui Prefecture Toyobo Co., Ltd. Comprehensive Research Laboratory Tsuruga Branch Examiner Ryuichi Ide (56) References JP 63-128030 (JP, A) JP 62-164733 (JP, A)

Claims (3)

[Claims] 1. A calcium carbonate in which a polyester whose main repeating unit is ethylene terephthalate has an area ratio to the circumscribed circle defined by the following formula of 60% or more and an average particle diameter of 0.5 μm or more and 2.0 μm or less. Particles (A) and calcium carbonate particles having an area ratio of less than 60% with respect to the circumscribed circle, an average particle diameter of 0.2 μm or more and 1.5 μm or less, and an average particle diameter smaller than that of the particles (A) ( An oriented polyester film containing 0.01 to 0.5% by weight of B). 2. The oriented polyester film according to claim 1, wherein the calcium carbonate particles (A) have a particle size variation of 30% or less. 3. The method according to claim 1, 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.