JP3041053B2 - Oriented polyester film - Google Patents

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 suitable for magnetic tapes and the like.

[0002]

2. Description of the Related Art In general, polyesters represented by polyethylene terephthalate have excellent physical and chemical properties. Therefore, in addition to fibers and molded products, they are used for magnetic tapes, floppy disks, photographs, capacitors, and the like. for,
It is widely used in a variety of applications for packaging and for films such as radiographic films and microfilms.

[0003] When used as a film, the slipperiness and abrasion resistance are major factors that determine the workability of the film manufacturing process and the working process in each application, and the quality of the product. In particular, when a magnetic material is applied to the surface of a polyester film and used as a magnetic tape, the friction between the coating roll for applying the magnetic material and the film surface and the abrasion of the film due thereto are extremely severe, and wrinkles and wrinkles are formed on the film surface. Scratches are likely to occur.

If the speeds in the coating step and the calendering step are increased to further increase the productivity, the loss of the magnetic recording signal, that is, the dropout increases. Even after slitting the film after applying the magnetic layer and processing it into audio, video or computer tape, etc., when pulling out or winding up from reels or cassettes, etc., there is a gap between many guides and playback heads etc. Friction and abrasion are remarkably generated, and a white powder-like substance is precipitated due to generation of abrasion, distortion, and abrasion of the polyester film surface, which often causes a large dropout. Also, the formation of aggregated particles due to poor dispersion of the added particles in the polyester and the coarse protrusions caused by the large particles themselves often cause dropout and the like.

[0005] Conventionally, to improve the slipperiness and abrasion resistance of a film, the surface of the film is provided with irregularities to improve the slipperiness and abrasion resistance.
A method of reducing the contact area with a guide roll or the like has been adopted.

As a method for forming irregularities on the film surface, there are (A) an internal particle precipitation method for depositing insoluble particles from a catalyst residue of a polymer used as a film raw material (for example, JP-B-49-13234 and JP-B-50).
(B) No.-6493, etc.), and (B) a method of adding external particles by adding insoluble inorganic particles (for example, JP-A-51-34272,
A number of applications have been filed, such as Japanese Patent Publication No. 2-78953, Japanese Patent Publication No. 55-2225 and Japanese Patent Publication No. 55-41648.

[0007]

The internal particle precipitation method has an advantage that particles precipitated in a polymer have a good affinity for polyester. However, since it is difficult to control the amount and particle size of the film, there has been a defect that the surface morphology of the film cannot be precisely adjusted and the lubricity is insufficient.

[0008] On the other hand, in the external particle addition method, although the design of the film surface morphology is easier than the former, the surface smoothness is poor due to mixing of coarse particles, secondary agglomeration of particles, poor affinity with polyester, and the like. However, it was difficult to satisfy all of the slipperiness, abrasion resistance and durability.

That is, the larger the size of the particles in the raw material polymer, the greater the effect of improving the slipperiness. However, if the particles are large for precision use such as for magnetic tapes, the particles will drop. This may cause defects such as an out-of-out condition, and further, the electromagnetic conversion characteristics are significantly deteriorated. For this reason, the unevenness of the film surface needs to be as fine as possible.

As one means for solving the conflicting characteristics, a method of using both large and small particles has been proposed (for example, Japanese Patent Publication No. 52-78953).
JP-B-55-40929, U.S. Pat. No. 3,82
No. 1,156 and U.S. Pat. No. 3,884,870).

However, in the range of the particle diameter of the large-sized particles described in these documents, the surface smoothness was insufficient for application to a high-quality application such as a magnetic tape. Further, there is a disadvantage that it is difficult to suppress the formation of coarse protrusions on the film surface which cause defects such as dropout.

Further, as described above, inert inorganic particles generally have poor affinity for polyester, so that when they are blended with a polymer, they become poorly dispersible in a polymer matrix and form coarse aggregates to cause dropout. And so on. Even if the dispersibility in the polymer matrix is excellent, the affinity of the inorganic particles for the polymer is weak, so when an external force is applied when the undrawn raw material is biaxially oriented, voids (voids) are generated and the transparency is reduced. And the abrasion resistance of the film surface is reduced.

To improve the affinity between the inert inorganic particles and the polyester, a surface treatment by a coupling reaction between the silane compound or the titanate compound and the inert inorganic particles has been proposed. However, this surface treatment method has various problems such as complicated treatment steps, limited applicable particles, and the effect is not exhibited as expected.

An object of the present invention is to solve these conventional problems and to provide an oriented polyester film which is smooth and excellent in abrasion resistance and lubricity.

[0015]

Means for Solving the Problems The oriented polyester film according to the present invention is characterized in that the surface thereof is modified with a phosphorus compound represented by the following chemical formula and the inert inorganic particles having an average particle size of 0.1 to 2.0 μm are removed. 0.01 to 0.50% by weight.

[0016]

Embedded image

(Wherein, R represents a hydrocarbon group having 6 to 10 carbon atoms, X represents a carboxyl group or an alkoxycarbonyl group, n is 2 or 1, and m is 1
Or 0. Further, in a preferred embodiment according to the present invention, the area ratio (%) of the inert inorganic particles defined by the following formula (I) to the circumscribed circle is 60% or more, and is defined by the following formula (II). It is preferable to use inert inorganic particles having a particle size variation of 30% or less.

[0018]

(Equation 2)

[0019]

In the oriented polyester according to the present invention, the surface of the inactive inorganic particles and the terminal functional group of the polyester or ester oligomer are chemically bonded by the phosphorus compound represented by the above chemical formula, so that the polyester matrix becomes inert with the inert matrix. The adhesion at the interface with the inorganic particles is enhanced. By dispersing such a specific amount of inert inorganic particles having a specific particle size surface-modified with a specific phosphorus compound in a specific amount of a polyester film, it is smooth, excellent in slipperiness and abrasion resistance, and has drawbacks such as dropout. It is possible to obtain a polyester film in which the generation of white powder and the generation of coarse particles are extremely small.

In a preferred embodiment according to the present invention, since the inert inorganic particles having an area ratio to a circumscribed circle of 60% or more and a degree of variation in particle size of 30% or less are used, the particle shape is close to a spherical shape. In addition, since the particle diameter is relatively uniform, the height of the protrusion can be precisely adjusted, and both of the contradictory characteristics of smoothness and excellent lubricity can be satisfied.

The polyester used in the present invention is a crystalline polyester whose main repeating unit is ethylene terephthalate, and is not particularly limited. However, those in which 80 mol% or more of the repeating units are composed of ethylene terephthalate are preferred, and other copolymerizable components include isophthalic acid, p-β-oxyethoxybenzoic acid,
2,6-naphthalenedicarboxylic acid, 4,4'-dicarboxyldiphenyl, 4,4'-dicarboxylbenzophenone, bis (4-carboxylphenyl) ethane, adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid, cyclohexane- Dicarboxylic acid components such as 1,4-dicarboxylic acid, propylene glycol, butanediol, neopentyl glycol, diethylene glycol,
A cyclohexanedimethanol, an ethylene oxide adduct of bisphenol A, a glycol component such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, and an oxycarboxylic acid component such as p-oxybenzoic acid can be arbitrarily selected and used.

In addition, a small amount of a compound containing an amide bond, a urethane bond, an ether bond, a carbonate bond or the like may be contained as a copolymerization component.

In the present invention, the average particle diameter of the inert inorganic particles added to the polyester film base is 0.1.
２．０2.0 μm. Preferably it is 0.2 to 1.5 μm, more preferably 0.3 to 1.2 μm.

When the average particle size is less than 0.1 μm, the lubricity becomes insufficient. On the other hand, when the average particle size is more than 2.0 μm, the surface smoothness is insufficient especially for a magnetic tape, and defects such as drop-out may occur. The number of coarse particles causing the problem also increases.

The amount of the inert inorganic particles added is 0.0
1 to 0.50% by weight. Preferably 0.05-0.
40% by weight, more preferably 0.10 to 0.3%.
0% by weight. If the amount is less than 0.01% by weight, the lubricity becomes insufficient. On the other hand, if it exceeds 0.50% by weight, the surface smoothness becomes insufficient for a magnetic tape and coarse particles which cause defects such as dropout. The number also increases.

There is no particular limitation on the particle shape and the uniformity of the particle size of the inert inorganic particles, but these can be one of the important factors for improving the characteristics. That is, regarding the particle shape, it is not sufficient to evaluate the particle shape by using the conventionally used volume shape factor in consideration of the necessity of precisely adjusting the film surface morphology.

In order to quantitatively grasp the shape of a particle, the present inventors have determined the shape of the particle as the ratio of the projected cross-sectional area of the particle to the area of a circle circumscribed in the projected view of the particle, ie, Area ratio ". Area ratio is 10
The closer to 0%, the closer to a spherical shape.

It is desired that the area ratio of the inert inorganic particles to the circumscribed circle is 60% or more, preferably 65% or more. Particularly preferred is 70% or more. If the area ratio of the inert inorganic particles to the circumscribed circle is less than 60%, the lubricity becomes insufficient, which is not preferable.

Next, with regard to the uniformity of the particle size, the present inventors have found that if the particle size distribution is close to monodisperse, the height and shape of the projections formed on the film surface will be close to uniform. It was understood by examination of. Therefore, based on this finding, the ratio between the standard deviation of the particle size of each particle and the average particle size, that is, the “degree of particle size variation” was defined as an index indicating the uniformity of the particle size.

The degree of variation of the particle size of the inert inorganic particles is 30.
% Or less, preferably 25% or less.
Particularly preferred is 20% or less. That is, if the particle size distribution is close to monodispersion, the height and shape of the projections formed on the film surface are nearly uniform. When the degree of variation of the particle diameter of the inert inorganic particles exceeds 30%, the form of protrusions on the film surface becomes irregular, and it becomes difficult to precisely adjust the protrusions on the film surface.

In the present invention, the type of inert inorganic particles used is not particularly limited as long as the above-mentioned conditions are satisfied, but synthetic calcium carbonate and spherical silica are preferred.

In the film of the present invention, the above-mentioned inert inorganic particles are added to a polyester film substrate to improve its properties. Further, in the present invention, the surface of the inert inorganic particles is modified with a phosphorus compound represented by the following chemical formula in order to enhance the adhesion between the polyester matrix and the inert inorganic particles.

[0033]

Embedded image

In the formula, R represents a hydrocarbon group having 6 to 10 carbon atoms, and X represents a carboxyl group or an alkoxycarbonyl group. N is 2 or 1, and m is 1 or 0.

The feature of this phosphorus compound is that it has both an atomic group that chemically reacts with the inert inorganic fine particles and a functional group that can be esterified or transesterified with the polyester or its oligomer.

The addition amount of the phosphorus compound to the inert inorganic particles is 0.1 to 20% by weight, preferably 0.5 to 10% by weight. Further, two or more phosphorus compounds may be used in combination.

The method of modifying the surface of the inert inorganic particles with a phosphorus compound is not particularly limited, but includes a wet treatment method and a dry treatment method.

As a wet treatment method, inert inorganic particles are sufficiently dispersed in a dispersion medium such as water or ethylene glycol,
After adding and mixing the phosphorus compound, a method of evaporating the dispersion medium may be used.

As a dry treatment method, powders of inert inorganic particles are mixed under high-speed stirring, a solution of a phosphorus compound is sprayed onto the inorganic powders being mixed using a spray nozzle, and then dried. Spray drying method "and the like.

As a method of adding the inert inorganic particles surface-modified with the phosphorus compound to the polyester, a method of adding the particles in a slurry at the time of polymerization or a method of kneading the polymer before extrusion can be adopted.

As the solvent for the slurry of the inert inorganic particles, ethylene glycol (EG) is preferably used alone, but if it is 50% by weight or less, other solvents such as water and alcohols may be mixed. .

When the particles are dispersed in the form of a slurry, it is preferable to carry out uniform dispersion so as to reproduce the primary particles of each particle as much as possible. The method of dispersing the inert inorganic particles at the time of preparing the slurry is not particularly limited, and any method such as a rotary high-speed stirring method, a high-pressure homogenous dispersion method, and an ultrasonic dispersion method or a combination thereof may be employed. .

In order to obtain particles having a predetermined average particle size, processes such as a crushing process, a classification process, and a filtration process may be employed. In particular, when the inert inorganic particles are added as a slurry, it is particularly preferable that substantially no particles of 5 μm or more exist in the slurry from the viewpoint of reducing the number of coarse projections.

The method for producing the polyester used in the present invention includes a so-called transesterification method in which a dimethyl ester of an aromatic dicarboxylic acid and a glycol are transesterified, and a so-called direct polymerization method in which an aromatic dicarboxylic acid and a glycol are directly reacted. Either legal manufacturing method can be employed.

In addition, both batch and continuous production methods can be adopted. In the case of carrying out the transesterification method, the transesterification catalyst is not particularly limited, and any conventionally known one can be used. When the reaction is carried out by a direct polymerization method, amines and quaternary compounds are used as inhibitors of DEG formation.
The use of secondary ammonium salts and the like is not restricted at all.

The film may be a uniaxially oriented film or a biaxially oriented film, but a biaxially oriented film is particularly preferred.

[0047]

Next, examples and comparative examples according to the present invention will be described. All parts used below mean parts by weight unless otherwise specified.

The measuring method used in the following experiment will be described. (1) Average particle size The particle size distribution in the slurry obtained by sufficiently dispersing the inert inorganic particles in the ethylene glycol slurry was measured using a light-transmitting centrifugal sedimentation type particle size distribution analyzer (SA-CP3 manufactured by Shimadzu Corporation). , And a value that gives an integrated value of 50% was used.

(2) The area ratio to the circumscribed circle Inert inorganic particles were observed with a scanning electron microscope (Hitachi S-510 type), the photograph was enlarged, copied, and traced to obtain 200 random particles. The particles were painted black. From this trace image, the projected cross-sectional area of each particle was measured with an image analyzer (Luzex 500, manufactured by Nireco Corporation). The area of a circle circumscribing each particle was calculated, and the area ratio was calculated based on the following equation.

[0050]

(Equation 3)

(3) Variation of Particle Size The inert inorganic particles were scanned with a scanning electron microscope (Hitachi S-51).0
Observation), copy the photographed image in an enlarged scale,
Tracing to randomly black out 200 particles
Filled. This image is converted to an image analyzer (Nireco Co., Ltd.)
Luzex 500 type)
The average particle whose diameter is measured and whose average diameter is used in the following formula
Diameter. In addition, the degree of dispersion of the particle diameter is calculated by the following equation.
Calculated.

[0052]

(Equation 4)

(4) Film Surface Smoothness (TAR) The surface of the film was measured using a stylus type three-dimensional surface roughness meter (S
E-3AK), needle radius 2 μm, load 30 mg
Condition, the cutoff value is 0.25 m in the longitudinal direction of the film.
The data in the height direction is measured every 2 μm with a quantization width of 0.00312 μm, and the data is taken into an external storage device every 2 μm.

Such measurement is carried out 150 times continuously at 2 μm intervals in the lateral direction of the film, that is, over a width of 0.3 mm in the lateral direction of the film. Assuming that the data in the height direction at this time is h (i, j) [ i = 1 to 500, j = 1 to 150], the value obtained by performing the calculation of the following equation is expressed in μm.
What is expressed in units is TAR (Three Dimensional Average Roughness).

[0055]

(Equation 5)

(5) Slippery ASTM D-1894
63, using a thread type slip tester,
The coefficient of static friction between films was measured under environmental conditions of 3 ° C. and 65 RH%.

(6) Abrasion resistance The film slit to a width of 12.5 mm was brought into contact with a commercially available razor, and evaluated by the amount of white powder adhering to the razor when the film was run for 10 m at a speed of 60 m / min. Ranked into stages.

…: Almost no white powder is generated Δ: High white powder is generated ×: White powder is generated very much

(7) Number of Coarse Particles in the Film A small amount of the film is sandwiched between
After being melt-pressed at 0 ° C., quenched, and observed using a phase contrast microscope, the image analysis processing device Luzex 500 ( Nire
And the maximum length in the particle image is 5
Number of particles of μm or more (number per measurement area 4.8 mm ² )
Is counted, and is represented by the following ranking according to the number of particles.

×: 51 or more / 4.8 mm ² × to Δ: 21 to 50 / 4.8 mm ² Δ: 11 to 20 / 4.8 mm ² Δ to ○: 4 to 10 / 4.8 mm ² ○… 0-3 / 4.8mm ²

Example 1 Esterification of the first esterification reactor using a continuous esterification reactor comprising a two-stage complete mixing tank provided with a stirrer, a decomposer, a raw material inlet and a product outlet. To the system where the reaction product is present, the terephthalic acid (TP
The molar ratio of EG to A) is 1.7 and antimony trioxide as antimony atom is 289 per TPA unit.
An EG slurry of TPA containing ppm was continuously supplied.

At the same time, an EG solution of magnesium acetate tetrahydrate was added through a supply port different from the TPA EG slurry supply port.
Mg atoms were continuously supplied at 100 ppm for each polyester unit in the reaction product passing through the reaction vessel, and the reaction was carried out at normal pressure and an average residence time of 4.5 hours at a temperature of 255 ° C.

The reaction product was continuously taken out of the system and supplied to the second esterification reactor. EG 0.5 parts by weight relative to the polyester units units in the reaction product passing through the second esterification reaction can, the EG solution of trimethyl phosphate as P atoms 64 ppm, and an area ratio of 75% of the circumscribed circle Synthetic calcium carbonate whose surface is modified with a phosphorus compound as shown in Table 1 having an average particle diameter of 0.88 μm having a particle diameter variation of 20% (amount of treatment: 2.0% by weight based on calcium carbonate) Was continuously supplied from separate supply ports so that the EG slurry became 0.25% by weight. Thereafter, the reaction was carried out at normal pressure and an average residence time of 5.0 hours at a temperature of 260 ° C.

The obtained esterification reaction product was converted into a mixture having a stirrer, a separator, a raw material inlet and a product outlet.
Polycondensation was carried out by continuously feeding to the continuous polycondensation reaction device of the stage to obtain a polyester having an intrinsic viscosity of 0.620. After the polyester is melt-extruded at 290 ° C., it is stretched 3.5 times in the machine direction at 90 ° C. and 3.5 times in the transverse direction at 130 ° C., and then heat-treated at 220 ° C. to obtain a 15 μm film. The results are shown in Table 1.

Comparative Example 1 A film was produced in the same manner as in Example 1, except that synthetic calcium carbonate, which was inert inorganic particles, was added without surface modification with a phosphorus compound.

Comparative Example 2 A film was prepared in the same manner as in Example 1 except that a surface treatment was performed on synthetic calcium carbonate using a phosphorus compound as shown in Table 1 which does not fall within the scope of the present invention.

Comparative Example 3 A film was produced in the same manner as in Example 1 except that the addition amount of the inert inorganic particles surface-modified with the phosphorus compound was 0.55% by weight.

Comparative Example 4 A film was produced in the same manner as in Example 1 except that 2.50 μm of synthetic calcium carbonate having an average particle size outside the range of the present invention was used.

Comparative Example 5 A film was produced in the same manner as in Example 1 except that synthetic calcium carbonate having an area ratio to a circumscribed circle of 50% was used.

Example 2 As inert inorganic particles, the area ratio to the circumscribed circle was 95%.
The surface is modified with a phosphorus compound shown in Table 1 having an average particle diameter of 0.70 μm having a particle diameter variation of 14%.
Spherical silica: using (throughput silica 2.0 wt% relative), which was added 0.10 wt%, others Example 1
A film was produced in the same manner as described above.

Comparative Example 6 A film was produced in the same manner as in Example 1 except that spherical silica similar to that of Example 2 was used, but added without surface treatment with a phosphorus compound.

[0072]

[Table 1]

As is evident from Table 1, the film according to the present invention is excellent in any of the properties of surface smoothness, lubricity, abrasion resistance, and the number of coarse particles, and is of high quality. Was.

──────────────────────────────────────────────────続 き Continued on the front page (72) Katsuro Kuze, Inventor 2-1-1 Katata, Otsu City, Shiga Prefecture Toyo Spinning Co., Ltd. (56) References JP-A-59-196359 (JP, A) JP-A-62-235353 (JP, A) JP-A-51-61594 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 5/18 C08L 67/00-67/04

Claims (2)

(57) [Claims] 1. An inert inorganic particle having a surface modified with a phosphorus compound represented by the following chemical formula and having an average particle diameter of 0.1 to 2.0 μm: 0.01 to 0.50% by weight. Characterized, oriented polyester film. Embedded image (Wherein, R represents a hydrocarbon group having 6 to 10 carbon atoms;
Represents a carboxyl group or an alkoxycarbonyl group. N is 2 or 1, and m is 1 or 0. ) 2. An inert inorganic particle defined by the following formula (I) having an area ratio (%) to a circumscribed circle of 60% or more;
And the degree of variation of the particle size defined by the following formula (II) is 3
The oriented polyester film according to claim 1, wherein the content is 0% or less. (Equation 1)