JPH0762081B2 - Polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a polyester film, and more specifically, it contains a uniformly dispersed calcium carbonate-based plate-like particle and is excellent in abrasion resistance and slipperiness. It relates to an axially oriented polyester film.

<Prior Art> Generally, polyester, especially polyethylene terephthalate, is widely used as a base film for magnetic tapes, photographs, condensers and the like because of its excellent mechanical properties and chemical properties. In particular, the demand for magnetic recording media such as video and audio is increasing by coating magnetic powder with a binder or depositing and depositing magnetic metal on a film by vapor deposition or the like. In this application, there is a tendency to make the thickness of the magnetic layer as thin as possible, and there is a tendency that higher performance is required for the base film.

As the demands on the film as the base of such a magnetic recording medium have become more sophisticated, it is necessary to improve the winding appearance and the winding characteristics that cause the wrinkling of the base film. On the other hand, if the magnetic layer is thinned, the surface irregularities of the base film itself are likely to appear on the surface of the magnetic layer as it is,
Due to the unevenness, output fluctuations and dropouts during recording and reproduction cannot be avoided, and as a result, it is required to improve the surface smoothness of the base film itself.

As a means for improving the running characteristics of a polyester film, a method of forming a particle-containing polyester composition obtained by precipitating a part or all of a catalyst or the like used during polyester synthesis in the reaction process (internal particle precipitation method) ), Clay, calcium phosphate, calcium carbonate,
A method of forming a particle-containing polyester composition obtained by adding inert particles such as silicon oxide during or after polymerization (external particle addition method) is known, and many improvement methods of each method have been proposed. There is.

However, in the internal precipitation method, it is difficult to control the amount of generated particles, the particle size, and to prevent the formation of coarse particles. For example, if coarse particles are contained in polyester, the filter may be used in the film forming process. If the film is made into a film, problems such as fisheyes and dropouts in the magnetic tape occur.

On the other hand, the external particle addition method has an advantage that it is easy to select the particle size and the particle amount, and if fine particles obtained by classifying coarse particles in advance are added, it becomes excellent in terms of slipperiness. . However, the inorganic particles, which are often used in the method of adding external particles, do not have sufficient affinity with polyester, and thus the abrasion resistance is not sufficient when formed into a film. For improving the affinity between the inorganic particles and the polyester, for example, surface treatment by a coupling reaction between a silane-based compound or a titanate-based compound and the inorganic particles has been proposed, but the treatment process is complicated and an effect is expected. There were various problems such as modest.

<Purpose of the invention> In view of the above-mentioned circumstances, the present inventors have diligently studied to develop a film excellent in abrasion resistance and slipperiness by containing a fine inorganic substance in the polymer, and as a result, it has a specific shape. It was found that the polyester film containing the calcium carbonate-based particles described above has improved peeling at the interface between the particles and the polyester, and has good properties, and has reached the present invention.

An object of the present invention is to propose a biaxially oriented polyester film excellent in abrasion resistance and slipperiness.

<Structure / Effect of Invention> According to the present invention, an object of the present invention is to provide calcium carbonate-based plate-like particles having an average particle size of 1 μm or less and an average plate-like ratio (plate diameter / plate thickness) of 2.5 or more. This is achieved by a biaxially oriented polyester film containing a ratio satisfying the following formula.

As is clear from the above, the main feature of the present invention is that calcium carbonate-based particles having a specific shape are contained in the polyester under specific conditions. As a result, the polyester film has excellent wear resistance and slipperiness.

The polyester referred to in the present invention may be any as long as it can form a biaxially oriented film, for example, polyethylene terephthalate, polytetramethylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4- Examples thereof include cyclohexylene dimethylene terephthalate and polyethylene-2,6-naphthalene dicarboxylate. These polyesters may be homopolyesters or copolyesters. Copolyester copolymer components include, for example, diol components such as diethylene glycol, neopentyl glycol, polyalkylene glycol, adipic acid, sebacic acid, phthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid. And the like, and polyfunctional carboxylic acid components such as trimellitic acid and pyromellitic acid in an amount range in which the polymer remains substantially linear.

The calcium carbonate-based plate-like particles contained in the polyester in the present invention are required to satisfy specific conditions in terms of average particle size and average plate-like ratio. The average particle size of the plate-shaped particles of calcium carbonate is 1
It is not more than μm, preferably not more than 0.8 μm. When the average particle size exceeds 1 μm, coarse particles are mixed in often, and when the film is formed, good surface flatness cannot be obtained.

Here, the average particle diameter means the “equivalent spherical diameter” of particles at a point of 50% by weight of all measured particles. The "equivalent spherical diameter" means the diameter of an imaginary sphere having the same volume as the particle, and can be calculated from the measurement by the usual sedimentation method.

Also, the average plate-like ratio of the calcium carbonate-based plate-like particles (plate diameter /
The plate thickness) is 2.5 or more, preferably 3.5 or more. If the average plate ratio is less than 2.5, good abrasion resistance cannot be obtained when the film is used. The reason for this is not clear, but when the average plate ratio is less than 2.5, the particles in the film act as substantially spherical or agglomerate, the voids around the particles become large, and the contact area between the polyester and the particles becomes large. It is thought to be due to the decrease.

Here, the average plate-like ratio is the ratio of the average value of the major axis of particles to the average value of the thickness of particles, and the major axis, minor axis and thickness of one particle are observed by observing the particle with a scanning electron microscope. Can be measured, this operation can be performed on a large number of particles, and the average value of these values can be calculated.

Incidentally, the plate-shaped body in the present invention, the ratio of the average value of the long diameter of the particles and the average value of the short diameter of the particles (average long diameter of the particles) / (average short diameter of the particles) is in the range of 1.0 or more and 10.0 or less. Refers to something. Here, if the ratio of the major axis to the minor axis of the particles exceeds 10.0, they act as fibrous particles in the film, and the orientation in the film surface direction has directionality, so the wear resistance also becomes directional. , Not preferable.

Such calcium carbonate-based plate-like particles mean calcium carbonate or CaCO ₃ · xCa (OH) ₂ · yH ₂ O (where x in the formula is 0.7
˜2.3, y is 0.3 to 6.0) can be exemplified. Such particles can be obtained by blowing carbon dioxide into an aqueous suspension of calcium hydroxide, separating the produced calcium carbonate-based plate-like particles, drying them, or thereafter further contacting them with carbon dioxide gas. .

In the present invention, it is preferable that the calcium carbonate-based plate-like particles are subjected to size adjustment and removal of coarse particles using a purification process before being incorporated into polyester. As an industrial means of the purification process, for example, a jet mill, a ball mill or the like can be used as a crushing means, and a wet or dry centrifuge, a filter, or the like can be used as a classification means. Needless to say, these means may be used in combination of two or more and purified stepwise.

The calcium carbonate-based plate-like particles may be added to the polyester at any time before film formation. For example, calcium carbonate particles may be added to the reaction system during the polyester synthesis reaction, or may be added when the polyester is melted and extruded by an extruder to form a film after the polyester synthesis reaction.

The content of the calcium carbonate-based plate-like particles in the polyester film needs to satisfy the condition of the following formula (1).

When the value of W × D is less than 0.0005, the slipperiness of the polyester film is insufficient. On the other hand, when the value of W × D exceeds 0.30, the slip property is good, but the wear resistance is insufficient. W
The more preferable value of xD is 0.001 to 0.22.

Polyester film is a method in which a polyester containing calcium carbonate-based plate-like particles is formed as it is, or a polyester containing calcium carbonate-based plate-like particles in a higher concentration is a polyester containing no calcium carbonate-based plate-like particles. It can be obtained by a method of diluting to form a film, or a method of adding calcium carbonate-based plate-like particles to a polyester containing no calcium carbonate-based plate particles at the time of film formation. In the film formation, a known method, for example, melt extrusion into a sheet at a temperature of 280 to 310 ° C., rapid solidification by quenching to form an amorphous sheet, and then, for example, in the longitudinal direction and the transverse direction, or in the longitudinal direction, the transverse direction, and the longitudinal direction are sequentially biaxial A stretching method, a simultaneous biaxial stretching method in the machine direction and the transverse direction, or the like can be adopted. The polyester film thus obtained has a surface roughness (Ra) of 0.005.
It has the property of ~ 0.05. The surface roughness (Ra) changes depending on the characteristics and amount of the calcium carbonate-based plate-like particles, and further the film forming conditions, and can be adjusted by selecting these.

INDUSTRIAL APPLICABILITY The biaxially oriented polyester film of the present invention has the advantages that particles are hardly detached from the film surface and that the effect of imparting slipperiness is sufficiently exhibited. Therefore, it can be used for various applications. In particular, it can be preferably used in the tape field and the like when abrasion resistance is required.

<Examples> Hereinafter, the present invention will be specifically described with reference to Examples. In addition, "part" in an Example means a weight part. Further, the measurement of each characteristic value in the examples was carried out according to the following methods.

(A) Film surface roughness (Ra) It was measured according to JIS B 0601. Using a stylus type surface roughness meter (SURFCOM 3B) manufactured by Tokyo Seimitsu Co., Ltd., the radius of the needle is 2μ.
A chart (film surface roughness curve) was placed under the conditions of m and load of 0.07 g. From the film surface roughness curve, a portion of the measurement length L is extracted in the direction of its center line, the center line of this extracted portion is taken as the X axis, and the direction of longitudinal magnification is taken as the Y axis.
When the roughness curve is represented by Y = f (x), the value (Ra: μm) given by the following equation is defined as the film surface roughness.

In the present invention, 8 pieces were measured with a reference length of 0.25 mm, and Ra was expressed as an average value of 5 pieces excluding 3 pieces having the larger values.

(2) Abrasionability evaluation-I 1/2 inch width film surface is 5 mmφ stainless steel SUS
It is brought into contact with a 304 fixed pin (surface roughness 0.58) at an angle of 150 °, and reciprocates and rubs about 15 cm at a speed of 2 m / min (at this time, the entrance side tension T ₁ is 40 g).

This operation is repeated, and after 20 reciprocations, the degree of scratches on the worn surface is visually determined.

At this time, if there are almost no scratches, ◎ slight scratches are generated, ○ if many scratches are generated on the entire surface, × scratches are judged to be in the middle of the former two in four levels.

(3) Wearability Evaluation-II The abrasion resistance of the running surface of the base film was evaluated using a 5-step mini super calender. The canender was a five-stage canender consisting of a nylon roll and a styrene roll, and was run at a processing temperature of 80 ° C, a linear pressure applied to the film of 200 kg / cm, and a film speed of 50 m / min.

The running film was evaluated for the scraping property of the base film by the dirt attached to the top roller of the calendar when the running film was run for 2000 m.

<Four-stage judgment> ◎ Nylon roll was not soiled at all ○ Nylon roll was barely soiled △ Nylon roll was soiled × Nylon roll was soiled very much Example-1 Calcium carbonate based plate-like particles were added to ethylene glycol, and homomixer was added. Was used for fine dispersion while maintaining the liquid temperature at room temperature. Further processed with a centrifuge, average particle size 0.5
A slurry containing calcium carbonate plate-like particles having a particle size of μm, an average plate-like ratio of 4.0, (average major axis of particles) / (average minor axis of particles) = 3.5 was obtained.

On the other hand, 100 parts of dimethyl terephthalate, 75 parts of ethylene glycol, 0.035 parts of manganese acetate / tetrahydrate and 0.040 parts of antimony trioxide were charged into the reactor, and the transesterification reaction was carried out while gradually raising the internal temperature from 145 ° C. After completion of the transesterification reaction, 0.020 part of trimethyl phosphate was added. Then, the slurry of the calcium carbonate-based plate-like particles prepared above was added so that the content of the calcium carbonate-based plate-like particles in the produced polyester would be 1.0% by weight. Then, the reaction product was transferred to a polymerization reactor and subjected to polycondensation reaction under high temperature vacuum (final internal temperature 290 ° C.) to obtain polyethylene terephthalate (A) having an intrinsic viscosity of 0.63.

Further, a polyethylene terephthalate (B) having an intrinsic viscosity of 0.62 was obtained in exactly the same manner as in the production of the polyethylene terephthalate (A) except that the slurry of calcium carbonate based plate-like particles was not added.

These polyethylene terephthalates (A) and (B) were mixed so that the content of calcium carbonate-based plate-like particles in the polyethylene terephthalate (C) after mixing was 0.20% by weight.

After drying polyethylene terephthalate (C) at 180 ° C,
It was melt-extruded from an extruder, formed into a sheet, and rapidly solidified.
Subsequently, the film was sequentially biaxially stretched at 90 ° C. in the longitudinal direction at a draw ratio of 4.0 times and in the transverse direction at a draw ratio of 3.5 times, and further heat-treated at 200 ° C. to obtain a biaxially oriented film having a thickness of 15 μm.

The characteristics of this film are shown in Table 1. The obtained film was good in both abrasion resistance and slipperiness.

Example-2 Calcium carbonate based plate-like particles were added to ethylene glycol and finely dispersed using a homomixer while maintaining the liquid temperature at 80 ° C. Further processed with a centrifuge, average particle size 0.5
A slurry of calcium carbonate plate-like particles having a particle size of μm, an average plate-like ratio of 7.0, (average major axis of particles) / (average minor axis of particles) = 4.0 was obtained.

On the other hand, bis-β-hydroxyethyl ester of terephthalic acid 100 parts, terephthalic acid 65 parts and ethylene glycol 2
The esterification reaction was carried out on 9 parts of the mixture at a temperature of 210 ° C to 230 ° C. The reaction was terminated when the amount of water produced by the reaction was 13 parts, and 0.027 part of antimony trioxide and 0.002 part of trimethyl phosphate were added to 100 parts of the reaction product. Next, the slurry of the calcium carbonate-based plate-like particles prepared above was added so that the content of the calcium carbonate-based plate-like particles in the produced polyester was 0.15% by weight. After that, the reaction product was transferred to a polymerization reactor and subjected to polycondensation reaction under high temperature vacuum (final internal temperature 290 ° C.) to obtain polyethylene terephthalate (D) having an intrinsic viscosity of 0.60.

After drying polyethylene terephthalate (D) at 180 ° C,
It was melt-extruded from an extruder, formed into a sheet, and rapidly solidified. Subsequently, the film was sequentially biaxially stretched at 90 ° C. in the longitudinal direction at a draw ratio of 4.0 times and in the transverse direction at a draw ratio of 3.5 times, and further heat-treated at 200 ° C. to obtain a biaxially oriented film having a thickness of 15 μm.

The characteristics of this film are shown in Table 1. The obtained film was good in both abrasion resistance and slipperiness.

Example-3 The calcium carbonate-based plate-like particles were pulverized with a jet mill,
Average particle size 0.5 μm, average plate ratio 7.0, (average major axis of particles)
Calcium carbonate-based plate-like particles having a ratio of / (average minor axis of particles) = 5.0 were obtained.

On the other hand, polyethylene terephthalate (B) was obtained in the same manner as in Example-1. Polyethylene terephthalate (B)
The calcium carbonate-based plate-like particles obtained above were added to the mixture, and the content of the calcium carbonate-based plate-like particles in the mixed polyethylene terephthalate (E) was adjusted to 0.18% by weight. Was dried at 180 ° C., melt-extruded from a melt extruder to form a sheet, and cooled and solidified. Subsequently, the film was sequentially biaxially stretched at 90 ° C. in the longitudinal direction at a draw ratio of 4.0 times and in the transverse direction at a draw ratio of 3.5 times, and further heat-treated at 200 ° C. to obtain a biaxially oriented film having a thickness of 15 μm.

The characteristics of this film are shown in Table 1. The obtained film was good in both abrasion resistance and slipperiness.

Example-4 Calcium carbonate-based plate-like particles were added to ethylene glycol, and the average particle size was 0.6 μm, the average plate-like ratio was 6.0, (the average long diameter of the particles) / (the average shortness of the particles) in the same manner as in Example-1. Diameter) = 3.
A slurry containing the calcium carbonate-based plate-like particles of 5 was obtained.

On the other hand, a mixture of 100 parts of dimethyl 2,6-naphthalenedicarboxylate and 50 parts of ethylene glycol was added to manganese acetate / tetrahydrate.
0.018 parts was added, and the transesterification reaction was performed while gradually raising the temperature from 150 ° C to 240 ° C. During the transesterification reaction,
When the internal temperature reaches 200 ° C, a slurry containing the above-obtained calcium carbonate-based plate-like particles is formed Polyethylene-2,
6-Naphthalate (F) was added so that the content of calcium carbonate-based particles was 0.15% by weight. After the transesterification reaction, 0.013 parts of trimethyl phosphate was added, and 0.008 parts by weight of titanium acetate was added, and the reaction product was heated to 290 ° C.
The temperature was raised to 0.2 mmHg and the polycondensation reaction was performed under vacuum to obtain polyethylene-2,6-naphthalate (F) having an intrinsic viscosity of 0.57.

Polyethylene-2,6-naphthalate (F) was dried at 160 ° C., melt-extruded with a melt extruder to form a sheet, and rapidly solidified. Subsequently, the film was sequentially biaxially stretched at 130 ° C in the longitudinal direction at a draw ratio of 3.8 times and in the transverse direction at a draw ratio of 3.4 times, and further heat-treated at 200 ° C to obtain a biaxially oriented film having a thickness of 15 µm.

The characteristics of this film are shown in Table 1. The obtained film was good in both abrasion resistance and slipperiness.

Comparative Examples-1 to 4 Average particle size of calcium carbonate-based particles in Example-1,
Slurries having different average plate ratios as shown in Table 1 were obtained. The (average major axis of particles) / (average minor axis of particles) of these particles was 3.5 in Comparative Example-1, 3.0 in Comparative Example-2, and Comparative Example-3.
Was 1.1 and Comparative Example-4 was 4.5. Further, a biaxially oriented film was obtained in the same manner as in Example-1, except that the content of calcium carbonate-based particles in the film was changed as shown in Table-1.

The characteristics of these films are shown in Table 1. Those out of the conditions of the present invention had poor wear resistance and slipperiness.

Comparative Example-5 Addition of calcium carbonate-based particles to ethylene glycol,
An average particle size of 0.4 μm and an average plate ratio as in Example-1.
A slurry containing calcium carbonate-based particles of 1.5, (average major axis of particles) / (average minor axis of particles) = 20 was obtained.

On the other hand, a mixture of 100 parts of dimethyl 2,6-naphthalenedicarboxylate and 50 parts of ethylene glycol was added to manganese acetate / tetrahydrate.
0.018 parts was added, and the transesterification reaction was performed while gradually raising the temperature from 150 ° C to 240 ° C. After the completion of the transesterification reaction, 0.013 parts of trimethyl phosphate was added, and 0.008 parts by weight of titanium acetate was further added to produce a slurry containing the calcium carbonate-based particles obtained above.
6-Naphthalate (G) was added so that the content of calcium carbonate-based particles was 0.001% by weight. Then, the reaction product was heated to 290 ° C., and polycondensation reaction was performed under a vacuum of 0.2 mmHg or less to obtain polyethylene-2,6-naphthalate (G) having an intrinsic viscosity of 0.58.

Polyethylene-2,6-naphthalate (G) was dried at 160 ° C., melt-extruded from a melt extruder to form a sheet, and rapidly solidified. Subsequently, the film was sequentially biaxially stretched at 130 ° C in the longitudinal direction at a draw ratio of 3.8 times and in the transverse direction at a draw ratio of 3.4 times, and further heat-treated at 200 ° C to obtain a biaxially oriented film having a thickness of 15 µm.

The characteristics of this film are shown in Table 1. Both wear resistance and slipperiness were insufficient.

Example-5 Calcium carbonate-based particles were added to ethylene glycol,
Same as Example-7, average particle size 0.4 μm, average plate ratio
A slurry containing calcium carbonate plate-like particles of 3.5, (average major axis of particles) / (average minor axis of particles) = 1.5 was obtained.

On the other hand, a mixture of 100 parts of dimethyl 2,6-naphthalenedicarboxylate and 50 parts of ethylene glycol was added to manganese acetate / tetrahydrate.
0.018 parts was added, and the transesterification reaction was performed while gradually raising the temperature from 150 ° C to 240 ° C. After completion of the transesterification reaction, 0.013 parts of trimethyl phosphate was added, and 0.008 parts by weight of titanium acetate was further added, and then the slurry containing the calcium carbonate-based particles obtained above was produced.
The calcium carbonate-based plate-like particles in 2,6-naphthalate (H) were added in an amount of 0.2% by weight. Then, the reaction product was heated to 290 ° C. and polycondensed under vacuum of 0.2 mmHg or less to obtain polyethylene-2,6-naphthalate (H) having an intrinsic viscosity of 0.58.

Polyethylene-2,6-naphthalate (H) was dried at 160 ° C., melt-extruded from a melt extruder to form a sheet, and rapidly solidified. Subsequently, the film was sequentially biaxially stretched at 130 ° C in the longitudinal direction at a draw ratio of 3.8 times and in the transverse direction at a draw ratio of 3.4 times, and further heat-treated at 200 ° C to obtain a biaxially oriented film having a thickness of 15 µm.

The characteristics of this film are shown in Table 1. Both wear resistance and slipperiness were good.

Comparative Example-6 Kaolinite was added to ethylene glycol, and Example-
In the same manner as in 1, a slurry containing kaolinite particles having an average particle size of 0.6 μ, an average plate ratio of 8.5, (average major axis of particles) / (average minor axis of particles) = 1.2 was obtained.

On the other hand, a mixture of 100 parts of dimethyl 2,6-naphthalenedicarboxylate and 50 parts of ethylene glycol was added to manganese acetate / tetrahydrate.
0.018 parts was added, and the transesterification reaction was performed while gradually raising the temperature from 150 ° C to 240 ° C. After completion of the transesterification reaction, 0.013 parts of trimethyl phosphate was added, and further 0.008 parts by weight of titanium acetate was added, and then the slurry containing kaolinite obtained above was produced in polyethylene-2,6-naphthalate (I). Was added so that the kaolinite content was 0.4% by weight. Then, the reaction product is heated to 290 ° C., and polycondensation reaction is performed under a vacuum of 0.2 mmHg or less,
Polyethylene-2,6-naphthalate (I) having an intrinsic viscosity of 0.58 was obtained.

Polyethylene-2,6-naphthalate (I) was dried at 160 ° C., melt-extruded from a melt extruder to form a sheet, and suddenly solidified. Subsequently, the film was sequentially biaxially stretched at 130 ° C in the longitudinal direction at a draw ratio of 3.8 times and in the transverse direction at a draw ratio of 3.4 times, and further heat-treated at 200 ° C to obtain a biaxially oriented film having a thickness of 15 µm.

The characteristics of this film are shown in Table 1. The abrasion resistance was insufficient, and there were many coarse projections on the film surface, which was not practical.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G11B 5/704 8721-5D // B29K 67:00 B29L 7:00

Claims (3)

[Claims] 1. A biaxial orientation comprising calcium carbonate plate-like particles having an average particle size of 1 μm or less and an average plate-like ratio (plate diameter / plate thickness) of 2.5 or more in a ratio satisfying the following formula. Polyester film. 2. The surface roughness (Ra) of the polyester film is
The biaxially oriented polyester film according to claim 1, which has a thickness of 0.005 to 0.05 µm. 3. The biaxially oriented polyester film according to claim 1, wherein the polyester film is a base film for a magnetic recording medium.