JPH0684443B2 - Polyester film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyester film, and more particularly to a biaxially oriented polyester film containing fine particles having a specific shape and excellent in slipperiness and abrasion resistance.

[Prior Art] Polyester film represented by polyethylene terephthalate film is widely used because of its excellent physical and chemical properties, for example, for magnetic tapes, capacitors, photography, packaging, OHP, etc. Is used for.

In a polyester film, its 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 quality of the product. If these are insufficient, for example, when a magnetic layer is applied to the polyester film surface and is used as a magnetic tape, the friction between the coating roll and the film surface during the application of the magnetic layer is severe, and the abrasion of the film surface due to this is also severe, In extreme cases, wrinkles and scratches on the film surface occur. In addition, even after slitting the film after coating the magnetic layer and processing it into audio, video or computer tape, etc., when pulling it out from the reel or cassette, winding it up, etc., many guide parts, playback heads, etc. In the meantime, abrasion occurs remarkably, scratches and distortions are generated, and white powder-like substances are deposited due to abrasion of the polyester film surface and the like, and as a result, loss of magnetic recording signals, that is, a large cause of dropout is often caused.

Conventionally, as a method for reducing the friction coefficient of polyester, many methods in which fine particles are present in polyester have been proposed, but the affinity between fine particles and polyester is not sufficient, and the transparency and abrasion resistance of the film are not sufficient. None were satisfactory. Explaining this method further, as a means for improving the surface properties of polyester, a method of precipitating a part or all of a catalyst or the like conventionally used in polyester synthesis in a reaction step (internal particle precipitation method) calcium carbonate, silicon oxide Many methods have been proposed for adding fine particles such as the above during or after the polymerization (external particle addition method).

However, the internal particle precipitation method of (3) has a good affinity to polyester to some extent because the particles are metal salts of the polyester component, but on the other hand, it is a method of generating particles during the reaction. It is difficult to control and prevent the formation of coarse particles.

In one method, if the particle size, the addition amount, etc. are appropriately selected and fine particles obtained by removing coarse particles by classification etc. are added, the slipperiness becomes excellent. However, since the affinity between the inorganic particles and the polyester, which is the organic component, is not sufficient, peeling occurs at the interface between the particles and the polyester during stretching, and voids are generated.

When the voids are present in the polyester film, the particles easily separate from the polyester film due to damage of the polyester film due to contact between the polyester film or the polyester film and other base material, and for example, for the magnetic tape as described above. It may cause white powder and dropout in the film. Further, since there are large voids around the particles, the transparency of the polyester film is impaired. Therefore, the lack of affinity between the inorganic particles and polyester is a problem to be solved in terms of abrasion resistance and transparency.

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.

[Object of the Invention] In view of the above-mentioned circumstances, the present inventors have excellent slipperiness, abrasion resistance, and the like, and are also excellent in the shape, size, distribution, and the like of the film surface protrusions, and have characteristics suitable for various applications. As a result of diligent studies to obtain a biaxially oriented polyester film having the above, it was found that the polyester film containing particles having a specific shape has improved peeling at the interface between the particles and the polyester and has good properties. Has reached the present invention.

Therefore, an object of the present invention is to provide a biaxially oriented polyester film having small voids and excellent in slipperiness and abrasion resistance.

[Constitution / Effect of Invention] According to the present invention, the purpose of the present invention is
The spherical particles (A) and the cocoon particles (B) are represented by the following formula Is achieved by a biaxially oriented polyester film.

The polyester in the present invention is a polyester having an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component. Such polyesters are substantially linear and have film forming properties, especially film formation by melt molding. Examples of aromatic dicarboxylic acids include terephthalic acid, naphthalenedicarboxylic acid, inphthalic acid, diphenylethanedicarboxylic acid,
Examples thereof include diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid and anthracene dicarboxylic acid. Examples of the aliphatic glycol include alkylene glycols having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol and decamethylene glycol, and alicyclic compounds such as cyclohexanedimethanol. Examples thereof include diols.

In the present invention, as the polyester, for example, one having alkylene terephthalate and / or alkylene naphthalate as a main constituent component is preferable.

Among such polyesters, for example, polyethylene terephthalate, polyethylene-2,6-naphthalate, of course, for example, 80 mol% or more of the total dicarboxylic acid component is terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and total glycol. A copolymer in which 80 mol% or more of the component is ethylene glycol is preferable. 20 mol% or less of the total acid component can be the above-mentioned aromatic dicarboxylic acids other than terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid. An alicyclic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid, etc .; Further, 20 mol% or less of the total glycol component may be the above glycol other than ethylene glycol,
Alternatively, for example, an aromatic diol such as hydroquinone, resorcin, 2,2-bis (4-hydroxyphenyl) propane, etc .; an aliphatic diol containing an aromatic ring such as 1,4-dihydroxymethylbenzene; polyethylene glycol, polypropylene glycol, polytetra It can also be a polyalkylene glycol (polyoxyalkylene glycol) such as methylene glycol.

In the polyester used in the present invention, a component derived from an oxycarboxylic acid such as an aromatic oxyacid such as hydroxybenzoic acid; an aliphatic oxyacid such as ω-hydrocosicaproic acid, a dicarboxylic acid component and an oxycarboxylic acid. Those which are copolymerized or bonded with 20 mol% or less based on the total amount of the acid component are also included.

Further, in the polyester of the present invention, a polycarboxylic acid or polyhydroxy compound having a functionality of 3 or more, such as trimellitic acid or penta, is used in an amount in a substantially linear range, for example, an amount of 2 mol% or less based on all acid components. A copolymer of erythritol and the like is also included.

Further, the polyester in the present invention includes, for example, pigments,
Other additives such as dyes, ultraviolet absorbers, heat stabilizers, light stabilizers, antioxidants, light-shielding agents (for example, carbon black, titanium dioxide, etc.) can be contained as required.

As the true spherical particles (A) referred to in the present invention, those having a ratio of major axis to minor axis (major axis / minor axis) of 1.0 to 1.2 are preferable, and an average major axis (DAL) and an average minor axis (DAW). The particle size ratio (DAL / DAW) is also preferably 1.0 to 1.2. Also,
When the true spherical particles referred to in the present invention are defined by the following volume shape factors, those in the range of 0.36 to π / 6 are preferable.

The average diameter of the true spherical particles is preferably 0.1 to 5 µ, and more preferably 0.2 to 2 µ. From the viewpoint of sharpening the distribution of projections on the film surface, the relative standard deviation of the grain size defined below is preferably 0.7 or less, more preferably 0.5 or less.

Here, di: maximum major axis of individual particles (μ) DA: number average value of maximum major axis of particles (μ) n: number of particles.

The cocoon-shaped fine particles (B) referred to in the present invention are particles having a constriction in which spherical particles are united, and are shown in FIG.
Although a representative example is shown in FIG. 2, the constricted portion in FIG. 1-2 may have a gentle shape as shown in FIG. 1-3.

The average short diameter (DBW) and average long diameter (DBL) of these cocoon-shaped particles
The ratio (DBL / DBW) is preferably in the range of 1.4 to 1.9. The average major axis of the cocoon-shaped fine particles is preferably 0.1 to 5 μm, more preferably 0.2 to 2 μm. Furthermore, the relative standard deviation defined by the following formula of the major axis of the cocoon-shaped fine particles is preferably 0.7 or less, more preferably 0.5 or less.

Here, di: major axis of individual particles (μ) DL: number average value of major axis of particles (μ) n: number of particles.

The average major axis (DAL) and the average minor axis (DAW) of the true spherical particles, the average major axis (DBL) and the average minor axis (DBW) of the cocoon-shaped particles, and the relative standard deviation in the present invention can be measured with an electron microscope, for example. It can be determined by measuring and calculating each diameter after taking a photograph at 10,000 to 50,000 times.

The spherical fine particles and cocoon-shaped fine particles in the present invention are not particularly limited in composition as long as they are insoluble in polyester and do not substantially deform during melting or stretching of the polyester, and may be organic or inorganic. good. Specific examples of the true spherical particles or cocoon-shaped particles are preferably silica, titanium dioxide, silicone (polyorganosiloxane) and the like in view of their availability and dispersibility in polyester.

The production method of the spherical particles and the cocoon-shaped particles is not limited at all. The spherical fine particles are produced, for example, by a method of producing silica by hydrolyzing ethyl orthosilicate and then subjecting to condensation treatment; a method of producing silicone (polyorganosiloxane) by subjecting organochlorosilane to hydrolysis and then subjecting to condensation treatment. Etc. On the other hand, as a method for producing cocoon-shaped fine particles, for example, as a method similar to the conditions for producing true spherical fine particles as described below, ultrafine particles of about 1 to 10 mμ are aggregated or grown to form primary spherical particles, and then 2 A manufacturing method in which spherical particles of B are combined to further grow the particles can be mentioned. Even if a small amount of an aggregate of three or more spherical particles produced as a by-product during the production is mixed in the cocoon-shaped fine particles, it does not matter as long as the effect of the present invention is not impaired.

In the present invention, true spherical particles (A) and cocoon-shaped particles (B)
The total content is preferably 0.01 to 5% by weight, more preferably 0.05 to 3% by weight, and 0.1
~ 1 wt% is particularly preferred. Further, the weight ratio (A / B) of the true spherical particles (A) and the cocoon-shaped particles (B) in the present invention
Is 0.01 to 100, preferably 0.02 to 50, 0.03 to 30
Is particularly preferable. If this weight ratio is less than 0.01,
It is substantially difficult in terms of the method of producing particles, and when it exceeds 100, it becomes substantially the same as containing only spherical particles, and there is a limit in improving the abrasion resistance.

The true spherical particles (A) and the cocoon-shaped particles (B) may be the same material or different materials, and the combination of materials is not particularly limited. For example, silica as the spherical particles, a combination of silica as the cocoon-shaped particles, silica as the spherical particles, a combination of silicone as the cocoon-shaped particles, silica and silicone as the spherical particles, a combination of silicone as the cocoon-shaped particles, etc. it can.

The true spherical particles and cocoon-shaped particles in the present invention are preferably subjected to coarse particle removal by a purification process before being incorporated into polyester. Examples of the classification means include a wet or dry centrifuge, a filter and the like. These means may be used in combination of two or more and purified stepwise.

The method for incorporating the true spherical particles and the cocoon-shaped particles into the polyester may be performed at any time by any method, but a method of adding as a glycol slurry before the polymerization reaction of the polyester reaction, particularly before the completion of transesterification or esterification reaction is preferable. preferable.

The polyester film is the same as above polyester,
Alternatively, it can be obtained by diluting with another polyester (polyester that does not contain true spherical particles and / or cocoon-shaped particles in a predetermined ratio) and perform membrane separation. Other polyesters used for dilution include, for example, polyester produced by a conventional precipitation method or addition method or a polyester containing no particles.

In the polyester film of the present invention, the film surface has an unevenness unit consisting of anisotropic projections derived from cocoon-shaped fine particles and depressions adjacent to the projections, and the film has slipperiness,
It is more preferable in terms of abrasion resistance. The shape of the uneven unit is the second
1 or FIG. 2-2, it may be either one having a depression on the major axis side of the anisotropic projection or one having a depression on the minor axis side of the anisotropic projection.

The method of forming the concave-convex unit is not a concave shape formed by a conventional mechanical stamp such as embossing, but is generated by the deformation of the film itself in the step of drawing the film, and examples thereof include the following drawing conditions. .

<Formation of Concavo-convex Units Containing Dimples Adjacent to Longitudinal Side> Preheating of the film before stretching when uniaxially stretching the unstretched film of polyester containing fine cocoon-shaped particles in the machine axis direction (longitudinal direction of the film) Is set to a low temperature, a stretching ratio is set to a high value, and then a second axial stretching (stretching in the film width direction) is performed, whereby anisotropic projections due to the cocoon-shaped fine particles and the long axis side of the projections are obtained. It is possible to form a recess adjacent to the.

<Formation of Concavo-convex Units Containing Dimples Adjacent to Minor Axis Side> When uniaxially stretching an unstretched polyester film containing fine cocoon-shaped particles in the machine axis direction (longitudinal direction of the film), preheating of the film before stretching Is set to a high temperature, or (and) the stretching ratio is set to a low temperature, and then a second axial stretching (stretching in the film width direction) is performed, whereby anisotropic projections due to the cocoon-shaped particles and the projections Can be formed adjacent to the minor axis side of the.

When stretching the film, the normal machine axis direction (first axis direction)
It is also possible to perform high-stage (multi-stage) stretching in which stretching is performed in the width direction (second axial direction) and then further stretching in the first axial stretching direction and / or the second axial stretching direction. Also in this case, the effect of the present invention is maintained because the shape of the unevenness unit formed by the projections and depressions on the film surface is slightly deformed and still exists.

Since the polyester film of the present invention has at least an anisotropic projection on the surface thereof and, in some cases, a concavo-convex unit composed of the anisotropic projection and a depression adjacent thereto, contact with a film or a device that comes into contact with the film. The area can be reduced, the surface is flat, and the sliding effect and wear resistance are excellent. Further, it has an advantage that the abrasion resistance is improved as compared with the conventional polyester film in which the surface of the film has projections formed by simple particles. In addition, as long as the effect of the present invention is not impaired, protrusions due to externally-added particles insoluble in polyester having a normal lump shape, plate shape, etc. and / or internally precipitated particles precipitated during polyester synthesis There is no problem even if unevenness units having depressions having the particles as cores are mixed on the surface of the polyester film.

INDUSTRIAL APPLICABILITY The polyester film of the present invention has various advantages such as a flat surface, excellent slipperiness, and excellent abrasion resistance as compared with conventional polyester films, and thus can be used for various applications. In particular, it can be preferably used in the magnetic tape field and the like where abrasion resistance is required.

[Examples] Hereinafter, specific examples will be described. In addition, the measurement of each characteristic value in the Example followed the following method.

1) Particle size and shape After taking a photograph of the particles at a magnification of 10,000 to 50,000 with an electron microscope,
The average diameter by measuring the diameter of the spherical particles, the major axis and the minor axis of the cocoon-shaped particles individually, and calculating the number average value,
Obtain the average major axis and average minor axis.

2) Size and number of recesses After thinly depositing aluminum on the surface of the stretched film,
Magnification 90 with differential interference microscope (Nikon differential interference microscope R type)
A photograph is taken at 0 times, and those having a major axis of 2 μm or more in the dent portion adjacent to the anisotropic projections of the cocoon-shaped particles are included.

3) Film surface roughness (Ra) This is a value defined by JIS-B0601 as the center line average roughness (Ra), and in the present invention, a stylus surface roughness meter (SURFCORDER SE- manufactured by Kosaka Laboratory Ltd.) 30C). The measurement conditions are as follows.

(A) Stylus tip radius: 2μ (b) Measuring pressure: 30mg (c) Cutoff: 0.25mm (d) Measuring length: 0.5mm (e) How to put together the data Value 1
Except one, the average value of the remaining four data is shown.

4) Coefficient of friction of film (μk) It is measured as follows using the apparatus shown in FIG. In Fig. 3, 1 is an unwind reel, 2 is a tension controller, 3, 5, 6, 8, 9, and 11 are free rollers, 4 is a tension detector (inlet), and 7 is a stainless steel SUS304 fixed rod ( The outer diameter is 5 mmφ, 10 is a tension detector (outlet), 12 is a guide roller, and 13 is a take-up reel.

A film cut into a width of 1/2 inch in an environment of a temperature of 20 ° C and a humidity of 60% is attached to a 7 fixing rod (surface roughness 0.3 μm) at an angle θ.
= (152/180) π radians (152 °) and contact at 20 per minute
Move (rub) at a speed of 0 cm. Inlet tension T ₁ is 3
Outlet tension when adjusting the tension controller 2 so as to 5g (T _2: g) a is film detected by the outlet tension detector into After traveling 90m, and calculates the running friction coefficient μk by the following equation.

μk = (2.303 / θ) log (T 2 / T 1) = 0.8681 log (T 2/35) 5) Wear resistance evaluation -I 1/2 inch width of the film surface 5mm Sutenren made fixing pin (surface roughness 0.58 ) At an angle of 150 °, and reciprocates about 15 cm at a speed of 2 m / min and rubs (at this time, the entrance side tension T ₁ is 60 g).

This operation is repeated, and after 40 times of reciprocation, the degree of scratches on the friction surface is visually determined.

At this time, there are almost no scratches ◎, those with few scratches ○, those with many scratches on all surfaces ×, scratches between the former two are △,
And judge in four stages.

6) Evaluation of abrasion resistance-II The abrasion resistance of the running surface of the film is evaluated using a 5-step mini super calender. The calender is a 5-stage calender consisting of nylon roll and steel roll, and the processing temperature is 80.
℃, the linear pressure applied to the film is 200kg / cm, and the film speed is 50m / min. The running film is evaluated for the sharpness of the film by the dirt attached to the top roller of the calender when the running length is 4000 m.

<Four-level judgment> ◎ Nylon roll is not soiled at all ○ Nylon roll is barely soiled △ Nylon roll is soiled × Nylon roll is soiled very much Example 1 Spherical silica with an average major axis of 0.5μ and an average minor axis of 0.45μ 0.1% by weight
And an intrinsic viscosity of 0.1% by weight of cocoon-type silica with an average major axis of 0.8μ and an average minor axis of 0.5μ (orthochlorophenol, 3
5 ° C) 0.60 dl / g polyethylene terephthalate was dried at 160 ° C, melt-extruded at 290 ° C, and rapidly solidified on a casting drum kept at 40 ° C to obtain an unstretched film.

Subsequently, the unstretched film was preheated to 70 ° C. with a heating roller and then heated in an infrared heater to a longitudinal direction of 3.6 ° C.
It was stretched twice. Subsequently, it was stretched 4.0 times in the transverse direction at a temperature of 90 ° C. and then heat-treated at 200 ° C. to obtain a film having a thickness of 15 μ.

The properties of the film are shown in Table 1, but the film had a low coefficient of friction and good abrasion resistance.

Examples 2 and 3 In Example 1, the stretching conditions of the unstretched film were changed to the following, and the procedure was exactly the same as in Example 1 to obtain a film.

In the case of Example 2 The unstretched film was preheated to 60 ° C. with a heating roller and then stretched 4.6 times in the machine direction while being heated with an infrared heater. Subsequently, the film was stretched in the transverse direction at a draw ratio of 3.4 times at a temperature of 90 ° C.

In the case of Example 3 The unstretched film was preheated to 90 ° C. with a heating roller and then stretched 3.3 times in the machine direction while being heated with an infrared heater. Subsequently, it was stretched at a temperature of 105 ° C. in the transverse direction by a factor of 3.4.

In both of these two types of film, anisotropic protrusions and dents adjacent to the protrusions due to the cocoon-shaped silica were observed. In the examples, there were pits in the major axis direction of the anisotropic protrusions, and in Example 3, they differed. There was a depression in the minor axis direction of the directional protrusion.

The characteristics of these films are shown in Table 1. They have a small coefficient of friction despite having a low surface roughness Ra and a good abrasion resistance, and are the same as or more than those in Example 1. .

Comparative Examples 4 to 6 and Comparative Example 1 A film was obtained in the same manner as in Example 1 except that the particle diameters and contents of spherical silica and cocoon type silica in Example 1 were changed as shown in Table 1. The characteristics of the obtained film are shown in Table 1.

Comparative Examples 2 and 3 Films were obtained in the same manner as in Examples 1 and 2, except that the cocoon-shaped silica was changed to ordinary lump particles of calcium carbonate (average particle size 0.5 μ, 0.25 wt%). The surface projections of the obtained film had no anisotropy. The properties of the obtained film are shown in Table 1, but the properties were inferior in all cases.

Examples 7 and 8 Films were obtained in the same manner as in Example 1 except that cocoon-type silica was changed to cocoon-type titanium dioxide or cocoon-type silicone having the average major axis and average minor axis shown in Table 1. The properties of the obtained film are shown in Table 1, and all of them were excellent.

[Brief description of drawings]

FIG. 1 shows the shape of cocoon-shaped fine particles, and FIGS. 1-1 and 1-2 are model diagrams when the minor axis is the same and the major axis is different. FIG. 1-3 is a diagram when the constricted portion of FIG. 1-2 is gentle. FIG. 2 is a plan view of anisotropic projections due to the cocoon-shaped fine particles on the film surface and the concave and convex units of the depressions in contact with the projections. The shaded portions indicate the depressions, FIG. 2-1 is an unevenness unit having depressions in the major axis direction of the anisotropic protrusion, and FIG. 2-2 is an unevenness unit having depressions in the minor axis direction of the anisotropic protrusion. Is. FIG. 3 is a schematic view of an apparatus for measuring the dynamic friction coefficient (μk) of the film.

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Claims (4)

[Claims] 1. A spherical spherical fine particle (A) and a cocoon fine particle (B) in a polyester are represented by the following formula: The biaxially oriented polyester film is characterized in that the content of the biaxially oriented polyester film is satisfied. 2. The average major axis (DAL) and average minor axis (DAW) of true spherical particles, and the average major axis (DBL) and average minor axis (DBW) of cocoon-shaped particles satisfy the following formulas: The biaxially oriented polyester film according to item 1. 0.1 (μ) ≤ DAL ≤ 5 (μ) 1.0 ≤ DAL / DAW ≤ 1.2 0.1 (μ) ≤ DBL ≤ 5 (μ) 1.4 ≤ DBL / DBW ≤ 1.9 3. True spherical fine particles (A) and cocoon fine particles (B)
The total content of 0.01 to 5% by weight, based on polyester
The biaxially oriented polyester film according to claim 1, wherein 4. True spherical fine particles (A) and cocoon fine particles (B)
The biaxially oriented polyester film according to any one of claims 1 to 3, wherein each is at least one of silica, titanium dioxide and silicone.