JPH02182730A - Polyester film - Google Patents

Abstract

PURPOSE:To obtain a biaxially oriented polyester film, containing homogeneously dispersed specific calcium carbonate-based platy particles and excellent in abrasion resistance and slipperiness. CONSTITUTION:A biaxially oriented polyester film, containing calcium carbonate-based platy particles having <=1mum, preferably <=0.8mum average particle diameter and >=2.5, preferably >=3.5 average flakiness ratio (plate diameter/ plate thickness) in an amount satisfying the formula 0.0005<=WXD<=0.30 [W is the content (wt.%) of the calcium carbonate-based platy particles; D is the average particle diameter (mum) of the calcium carbonate-based platy particles] and having preferably the value of the WXD within the range of 0.001-0.22. The surface roughness (Ra) of the polyester film is 0.005-0.05mum. The above- mentioned polyester film is a base film for magnetic recording media.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a polyester film, and more specifically, the present invention relates to a polyester film containing uniformly dispersed calcium carbonate-based plate-like particles, which has excellent abrasion resistance and slipperiness. The present invention relates to a biaxially oriented polyester film.

<Prior Art> Generally, polyester, particularly polyethylene terephthalate, has excellent mechanical and chemical properties and is therefore widely used as a base film for magnetic tapes, photographs, capacitors, and the like.

In particular, there is an increasing demand for magnetic recording media for video, audio, etc. by applying magnetic powder together with a binder, or depositing or 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 a higher level of performance is required of the base film.

As the demands on the film that forms the base of such magnetic recording media become more sophisticated, it is necessary to improve the winding form and winding characteristics, which cause wrinkles in the winding of the base film. On the other hand, when the magnetic layer is made thinner, the surface irregularities of the base film itself tend to appear on the surface of the magnetic layer as well, making it impossible to avoid output fluctuations and dropouts during recording and playback due to these irregularities. As a result, it is required to improve the surface smoothness of the base film itself.

Conventionally, as a means to improve the running properties of polyester films, there has been a method of forming a film using a polyester composition containing particles obtained by precipitating part or all of the fibers used in polyester synthesis during the reaction process (internal particles). (precipitation method), ■clay, calcium phosphate, calcium carbonate,
A method of forming a film from 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 improvements to each method have been proposed. There is.

However, with the internal precipitation method, it is difficult to control the particle size per particle of the generated particles and to prevent the generation of coarse particles.For example, if coarse particles are contained in polyester, the filter If the film is made into a film, problems such as fish eyes and dropouts in magnetic tape may occur.

On the other hand, the external particle addition method has the advantage that it is easy to select the particle size and amount of particles, and if fine particles are added in which coarse particles have been classified and removed in advance, excellent slipperiness can be obtained. . However, the inorganic particles that are often used in the external particle addition method do not have sufficient affinity with polyester, so when made into a film, the l'ir# abrasion resistance is not sufficient. For example, surface treatment using a coupling reaction between a silane compound or a titanate compound and inorganic particles has been proposed, but there have been various problems such as the treatment process being complicated and the effects not being as expected.

<Purpose of the Invention> In view of the above-mentioned circumstances, the inventors of the present invention have conducted intensive studies to develop a film with a particular shape that includes fine inorganic substances in a polymer and is highly wear-resistant and easily slippery. It has been discovered that a polyester film containing calcium carbonate-based particles has improved peeling at the interface between the particles and polyester, and has good properties, and has arrived at the present invention.

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

<Configuration/Effects of the Invention> According to the present invention, an object of the present invention is to produce a calcium carbonate plate-like material 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 particles in a proportion satisfying the following formula.

0.0005<: W x D < 0.30 As is clear from the above, the main feature of the present invention is that calcium carbonate particles having a specific shape are contained in polyester under specific conditions. As a result, the polyester film has excellent abrasion resistance and slipperiness.

The polyester used in the present invention may be any material as long as it can form a biaxially oriented film, such as polyethylene prephthalate.

Polytetramethylene terephthalate, polyethylene-ρ
-oxybenzoate, poly-1,4-cyclohexylene dimethylene terephthalate, polyethylene-2,6-
Examples include naphthalene dicarboxylate. These polyesters may be homopolyesters or copolyesters.Copolyester components include diol components such as diethylene glycol, neopentyl glycol, and dυnoalkylene glycol, adipic acid, sebacic acid, Dicarboxylic acid components such as phthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, 5-sodium sulfoisophthalic acid, trimellitic acid in an amount range such that the polymer remains substantially linear;
Examples include polyfunctional carboxylic acid components such as pyromellitic acid.

In the present invention, the calcium carbonate-based plate-like particles to be added to the polyester must satisfy specific conditions in terms of average particle diameter and average plate-like ratio. The average particle size of calcium carbonate plate-like particles is 1
The thickness is .mu.m or less, preferably 0.8 .mu.m or less. When the average particle size exceeds 1 μm, coarse particles are often mixed in, and when formed into a film, good surface flatness cannot be obtained.

The average particle size herein means the "equivalent spherical diameter" of particles at 50% by weight of all measured particles.

This "equivalent spherical diameter" means the diameter of an imaginary sphere having the same volume as the particle, and can be calculated from measurements by conventional sedimentation methods.

In addition, the average platelet ratio (plate diameter/
The plate thickness) is 2.5 or more, preferably 3.5 or more. If the average platelet ratio is less than 2.5, good abrasion resistance cannot be obtained when formed into a film. The reason for this is not clear, but when the average platelet ratio is less than 2.5, the particles act as substantially spherical or lumpy in the film.
This is thought to be because the voids around the particles become larger and the contact area between the polyester and the particles decreases.

Here, the average plate ratio is the ratio of the average value of the long axis of the particle to the average value of the thickness of the particle, and the particle is
Observe with an R mirror and measure the major axis, minor axis and thickness of one particle,
This operation can be performed on a large number of particles, and the average value can be calculated.

In addition, the plate-shaped body in the present invention is one in which the ratio of the average value of the major axis of the particles to the average value of the minor axis of the particles (average major axis of the particles)/(average minor axis of the particles) is 1.0 or more and 10.0 or less. Here, particles with a ratio of the major axis to the minor axis exceeding 10.0 act as *female particles in the film, and the orientation in the film surface direction is directional. 1ii1 also becomes directional, which is not preferable.

Such calcium carbonate-based plate-like particles are calcium carbonate or CaC0,-xCa (OH)2 ・'l
Hz O (in the formula)x! , to, 7~2.3, yha0
．． 3 to 6.0) can be exemplified. Such particles can be obtained by blowing carbon dioxide into an aqueous suspension of calcium hydroxide, separating and drying the produced calcium carbonate plate-like particles, or by subsequently contacting them with carbon dioxide gas. can.

In the present invention, it is preferable to use a refining process to adjust the size and remove coarse particles before incorporating the calcium carbonate plate-like particles into the polyester. , a ball mill, etc.; examples of the classification means include wet or dry centrifugation, passing through a filter, etc. It goes without saying that two or more of these means may be used in combination for stepwise purification.

Calcium carbonate-based platelet particles can be added to polyester at any time up to film formation6. For example, calcium carbonate particles may be added to the reaction system during the polyester synthesis reaction, or It may be added when the polyester is melted and extruded using an extruder to form a film after the synthesis reaction.

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

0.0OQ5<W x D<, 0.30
(1) When the WXD value is less than 0.0005, the slipperiness of the polyester film is insufficient. On the other hand, if the value of WXD exceeds 0.30, the slipperiness is good, but the abrasion resistance is insufficient. A more preferable value of WxD is 0.001 to 0.22.

Polyester films can be produced by directly forming polyester containing calcium carbonate-based plate-like particles, or by replacing polyester with a higher concentration of calcium carbonate-based plate-like particles with polyester that does not contain calcium carbonate-based plate-like particles. It can be obtained by diluting and forming a film, or by adding calcium carbonate plate particles to a polyester that does not contain calcium carbonate plate particles during film formation. For film formation, a known method is used, for example, usually 280 to 310°C.
A method of melt extruding into a sheet shape, rapidly cooling and solidifying it to form an amorphous sheet, and then biaxially stretching it sequentially in the longitudinal and transverse directions, or sequentially biaxially in the longitudinal and transverse directions, or simultaneous biaxial stretching in the longitudinal and transverse directions. A method such as stretching can be adopted. The polyester film thus obtained has a surface roughness (Ra
) It has a characteristic of 0.005 to 0.05. This surface roughness (Ra) varies depending on the properties and amount of the calcium carbonate-based plate-like particles, as well as the film forming dye, etc., and can be adjusted by selecting these.

The biaxially oriented polyester film of the present invention has the advantage that there is almost no detachment of particles from the film surface and the effect of imparting slipperiness is sufficiently exhibited, so that it can be used for various purposes. It can be particularly preferably used in the field of magnetic tapes, etc., which require wear resistance.

<Examples> The present invention will be specifically described below with reference to Examples. In the examples, "1 part" means part by weight.

Further, each characteristic value in the Examples was measured according to the following method.

(a) Film surface roughness (Ra) Measured according to JIS B 0601. Tokyo Seimitsusha■
A chart (film surface roughness curve) was drawn using a stylus type surface roughness tester (StlRFCOH3B) manufactured by Manufacturer Co., Ltd. under the conditions of a needle radius of 2 μm and a load of 0.07 g. A part of the measurement length is extracted in the direction of the center line, the center line of this extracted part is set as
), gi(Ra:
μm) is defined as the film surface roughness.

In the present invention, 8 measurements are taken with the reference length set as 0.25+u+, and Ra is expressed as the average value of the 5 measurements excluding 3 (II) from the largest value.

+21 I Embryonic evaluation -■ 1 part 2 inch film surface was brought into contact with a 5 opening φ stainless steel SO3304 fixing pin (surface roughness 0.58'l at an angle of 150°, at a speed of 2 m/min) Approximately 15C11 reciprocating movement and friction (at this time, the entry side tension T1
was set to 40ir).

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

At this time, select the item with almost no scratches ◎The item with only a few scratches ○The item with many scratches on the entire surface
It is judged in 4 stages as △.

(31 Palm abrasion evaluation -■ The abrasion resistance of the running surface of the base film was evaluated using a 5-stage mini super calender. The calender was a 5-stage calender consisting of a nylon roll and a steel roll. linear pressure 200 to 2/
The film was run at a film speed of 50 m/min.

The running film was run for a total length of 2000 m, and the abrasion resistance of the base film was evaluated based on the dirt that adhered to the top roller of the calendar.

4-level judgment> ◎ No stains on the nylon roll ○ Almost no stains on the nylon roll Δ Nylon roll stains × Very dirty nylon roll Example-1 Calcium carbonate-based plate-like particles were added to ethylene glycol, and a homomixer was added. was used to finely disperse the liquid while keeping the temperature at room temperature. Furthermore, it is processed in a centrifuge, and the average particle size is 0.
A slurry containing calcium carbonate-based plate-like particles of 5 μm and 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 dioxide were charged into a reactor, and a transesterification reaction was carried out while gradually raising the internal temperature from 145°C. . After the transesterification reaction was completed, 0.020 part of trimethyl phosphate was added, and then the slurry of the calcium carbonate-based plate-like particles prepared above was mixed so that the content of the calcium carbonate-based plate-like particles in the produced polyester was 1.0% by weight. Added bare.

Afterwards, the reaction product was transferred to a polymerization reactor and under high temperature vacuum (
The polycondensation reaction is carried out at a final internal temperature of 290°C) and the intrinsic viscosity is 0.
．． 63 polyethylene terephthalate (^) was obtained.

Further, polyethylene terephthalate (B) having an intrinsic viscosity of 0.62 was obtained in exactly the same manner as in the production of polyethylene terephthalate (8) above, except that the slurry of calcium carbonate-based plate-like particles was not added.

These polyethylene terephthalate (^), (B)
The mixed polyethylene terephthalate (C
) The content of calcium carbonate-based plate-like particles was set at 0.20% by weight.

After drying polyethylene terephthalate (C) at 180°C, it is melt-extruded from an extruder, formed into a sheet, rapidly solidified, and then stretched at 90°C in the longitudinal direction at a stretching ratio of 4.0 times and in the transverse direction at a stretching ratio of 3.0 times. Sequential biaxial stretching at 5 times and further at 200°C
A biaxially oriented film with a thickness of 15 μm was obtained.

The properties of this film are shown in Table 1, and the resulting film had good abrasion resistance and slipperiness.

Example 2 Calcium carbonate plate-like particles were added to ethylene glycol, finely dispersed using a homomixer while keeping the liquid temperature at 80°C, and further processed with a centrifuge to reduce the average particle size to 0.
．． 5 μm, average platelet ratio 7.0° (average major axis of particles)/(
A slurry of calcium carbonate-based plate-like particles having an average minor axis of particles of -4.0 was obtained.

On the other hand, water produced by an esterification reaction of 100 parts of bis-β-hydroxyethyl ester of terephthalic acid, 65 parts of terephthalic acid, and 29 parts of ethylene glycol at a temperature of 210°C to 230°C The reaction was terminated when the distilled amount reached 13 parts, and 0.027 parts of antimony trioxide and 0.0 parts of antimony trioxide were added per 100 parts of the reaction product.
0.2 parts of trimethyl phosphate was added to the slurry of the calcium carbonate plate particles prepared above, so that the content of the calcium carbonate plate particles in the produced polyester was 0.2 parts.
It was added so that the amount was 15% by weight. Thereafter, the reaction product was transferred to a polymerization reactor and subjected to a polycondensation reaction under high-temperature vacuum (final internal temperature 290°C) to obtain polyethylene terephthalate (D) with an intrinsic viscosity of 0.60.

After drying polyethylene terephthalate (D) at 180°C, it was melt-extruded from an extruder to form a sheet, which was then rapidly cooled and solidified.

Subsequently, it was sequentially biaxially stretched at 90°C at a stretching ratio of 4.0 times in the machine direction and at a stretching ratio of 3.5 times in the horizontal direction, and further at 200°C.
A biaxially oriented film with a thickness of 15 μm was obtained.

The properties of this film are shown in Table 1, and the resulting film had good abrasion resistance and slipperiness.

Example-3 Calcium carbonate-based plate-like particles were pulverized with a jet mill,
Calcium carbonate-based plate-like particles with an average particle diameter of 0.5 μm and an average plate-like ratio of 7.0° (average major axis of particles)/(average minor axis of particles) = 5.0 were obtained.

On the other hand, polyethylene terephthalate (8) 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 ([) was adjusted to 0.18% by weight, and then the polyethylene terephthalate was added. (E) 18
After drying at 0°C, it was melt-extruded using a melt extruder to form a sheet, which was then cooled and solidified. Subsequently, the stretching ratio was 4.
0 times, and sequentially biaxially stretched at a stretching ratio of 3.5 times in the transverse direction,
Further heat treatment was performed at 200'C to obtain a biaxially oriented film with a thickness of 15 μm.

The properties of this film are shown in Table 1, and the resulting film had good 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 in the same manner as in Example 1-1.
Average plate ratio 6.0. A slurry containing calcium carbonate-based plate-like particles of (average major axis of particles)/(average minor axis of particles) -3.5 was obtained.

On the other hand, 100 dimethyl 2,6-naphthalene dicarboxylate
0.018 part of manganese acetate tetrahydrate was added to a mixture of 50 parts of manganese acetate and 50 parts of ethylene glycol, and
The transesterification reaction was carried out while gradually raising the temperature to °C.

During the transesterification reaction, when the internal temperature reached 200°C, a slurry containing the calcium carbonate-based plate-like particles obtained above was produced.The content of calcium carbonate-based particles in polyethylene-2,6-naphthalate ([) It was added at a concentration of 0.15% by weight. After the transesterification reaction was completed, 0.013 parts of trimethyl phosphate was added, and further 0.00 parts of titanium acetate was added.
After adding 8 parts by weight, the reaction product was heated to 290°C, and a polycondensation reaction was carried out under a vacuum of 0.2i+nH (J or less) to form polyethylene-2,6-naphthalate with an intrinsic viscosity of 0.57 ( ) was obtained.

Polyethylene-2,6-naphthalate ([) at 160℃
After drying with 7 g melt extruder;
After being rapidly cooled and solidified, the stretching ratio was 3.
8 times and sequentially biaxially stretched at a stretching ratio of 3.4 times in the transverse direction,
Further heat treatment was performed at 200°C to obtain a biaxially oriented film with a thickness of 15 μm.

The properties of this film are shown in Table 1, and the resulting film had good abrasion resistance and slipperiness.

Comparison ρJ-1 to 4 In Example-1, the average particle size of calcium carbonate particles,
Slurries with average plate ratios varied as shown in Table 1 were obtained. The average major axis of these particles/(average minor axis of particles) was 3.5° for Comparative Example-1 and 3.0° for Comparative Example-2. Comparative Example-3 is 1.1. Comparison 1-4 was 4.5. Furthermore, Table 1 shows the content of calcium carbonate particles in the film.
A biaxially oriented film was obtained in exactly the same manner as in Example 1 except for the changes shown in .

The properties of these films are shown in Table 1. Those that did not meet the requirements of the present invention had poor abrasion resistance and slipperiness.

Comparative Example-5 Adding calcium carbonate particles to ethylene glycol,
In the same manner as in Example-1, the average particle size was 0.4 μm and the average platelet ratio was 1.5. (Average major axis of particles) / (average minor axis of particles) =
A slurry containing 20 calcium carbonate particles was obtained.

On the other hand, dimethyl 2,6-naphthalene dicarboxylate 100
0.018 parts of Ltl: manganese acid tetrahydrate was added to a mixture of 50 parts of ethylene glycol and 50 parts of ethylene glycol.
The transesterification reaction was carried out while gradually raising the temperature to 40°C. After the transesterification reaction, trimethyl phosphate 0.0
After adding 13 parts of titanium acetate and further adding 0.008 parts by weight of titanium acetate, a slurry containing the calcium carbonate particles obtained above was produced using polyethylene-2,6-naphthalate (large calcium carbonate particles in GJ! was added so that the amount was 0.001% by weight.Then, the reaction product was added to 290% by weight.
The temperature was raised to ℃ and a polycondensation reaction was carried out under a vacuum of 0.211 mJl or less to obtain polyethylene-2 with an intrinsic viscosity of 0.58.
6-naphthalate CG) was obtained.

Polyethylene-2,6-naphthalate (G) at 160°
After drying at C, melt extrusion is performed using a melt extruder to form a sheet,
It solidified by rapid cooling. Subsequently, it was stretched at 130°C in the longitudinal direction at a stretching ratio of 3.
8 times, #! The film was sequentially biaxially stretched at a stretching ratio of 3.4 times in the force direction, and further heat treated at 200°C to obtain a biaxially oriented film with a thickness of 15 μm.

The properties of this film are shown in Table 1.Abrasion resistance.

The slipperiness was also insufficient.

Example-5 426 lucium-based particles were added to ethylene glycol, and the same procedure as in Example-7 was carried out to obtain an average particle size of 0.4 μm and an average platelet ratio of 3.5. (Average major axis of particles)/(Average minor axis of particles)
A slurry containing calcium carbonate plate-like particles of -1,5 was obtained.

On the other hand, dimethyl 2,6-naphthalene dicarboxylate 100
0.018 part of #manganese acid tetrahydrate was added to a mixture of 50 parts of ethylene glycol and
The transesterification reaction was carried out while gradually increasing the temperature. 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 to produce a slurry containing the calcium carbonate particles obtained above.Polyethylene-2,6 − naphthalate group)
The content of calcium carbonate-based plate-like particles was 0.2% by weight. After that, the reaction product was heated to 290°C.
Polyethylene-2 with an intrinsic viscosity of 0.58 was heated to
6-naphthalate (obtained old).

Polyethylene-2,6-naphthalate (H) at 160°
After drying at C, melt extrusion is performed using a melt extruder to form a sheet,
It solidified by rapid cooling. Subsequently, it was stretched at 130°C in the longitudinal direction at a stretching ratio of 3.
8 times and sequentially biaxially stretched at a stretching ratio of 3.4 times in the transverse direction,
Further heat treatment was performed at 200° C. to obtain a biaxially oriented film with a thickness of 15 μm.

The properties of this film are shown in Table 1.1 Abrasion resistance.

The slipperiness was also good.

Bikyo Example-6 Adding kaolinite to ethylene glycol, Example-
In the same manner as 1, the average particle size was 0.6μ, and the average platelet ratio was 13.5.
．． A slurry containing kaolinite particles of (average major axis of particles)/average minor axis of particles) = 1.2 was obtained.

On the other hand, dimethyl 2,6-naphthalene dicarboxylate 100
0.018 part of manganese acetate tetrahydrate was added to a mixture of 50 parts of manganese acetate and 50 parts of ethylene glycol, and
The transesterification reaction was carried out while gradually raising the temperature to °C. After the transesterification reaction, trimethyl phosphate 0.01
3 parts of #titanium acid, and further adding parts by weight of #titanium acid o, ooa, a slurry containing the kaolinite obtained above was produced.Polyethylene-2,6-naphthalate (])
It was added so that the kaolinite content therein was 0.4% by weight. Then, the reaction product was heated to 290'C,
A polycondensation reaction was carried out under a vacuum of 0.2 im) I (l or less) to obtain polyethylene-2,6-naphthalate (1) having an intrinsic viscosity of 0.58.

Polyethylene-2,6-naphthalate (1) at 160℃
After drying, it was melt extruded from a 1.8 melt extruder to form a sheet
It solidified by rapid cooling. Subsequently, it was sequentially biaxially stretched at 130° C. at a stretching ratio of 3.8 times in the longitudinal direction and 3.4 times in the transverse direction.
Further heat treatment was performed at 200° C. to obtain a biaxially oriented film with a thickness of 15 μm.

The properties of this film are shown in Table 1. The abrasion resistance was insufficient, and there were many coarse protrusions on the film surface, making it impossible to put it into practical use.

Claims (1)

[Claims] 1. The average particle diameter is 1 μm or less, the average platelet ratio of the particles (plate diameter/
A biaxially oriented polyester film containing calcium carbonate plate-like particles having a plate thickness of 2.5 or more in a proportion that satisfies the following formula. 0.0005≦W×D≦0.30 [However, W: Content of calcium carbonate-based plate-like particles (wt%) D: Average particle diameter of calcium carbonate-based plate-like particles (μm)] 2. Surface roughness (Ra) is 0.0
The biaxially oriented polyester film according to claim 1, which has a thickness of 0.05 to 0.05 μm. 3. The biaxially oriented polyester film according to claim 1 or 2, wherein the polyester film is a base film for a magnetic recording medium.