JPH0684442B2 - Polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polyester film, and more specifically,
The present invention relates to a biaxially oriented polyester film which contains inert fine particles having a specific shape and is 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 the quality of the product. If these are insufficient, for example, when a magnetic layer is applied to the surface of a polyester film and used as a magnetic tape, friction between the coating roll and the film surface during application of the magnetic layer is severe, and 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 out from the reel or cassette, winding up and other operations, many guide parts, playback heads etc. A significant amount of abrasion occurs between them, and scratches, distortions are generated, and white powdery substances are deposited due to abrasion of the surface of the polyester film. As a result, magnetic recording signals are often lost, that is, a major cause of dropout.

Conventionally, as a method of reducing the friction coefficient of polyester, many methods of generating fine particles in polyester have been proposed, but the affinity between the fine particles and polyester is not sufficient, and the transparency and abrasion resistance of the film are not sufficient. None were satisfactory. To further explain this method, as means for improving the surface properties of polyester, conventionally, a method of precipitating a part or all of a catalyst 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 (1) has a certain level of affinity with polyester because the particles are a metal salt such as a 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 fine particles and the polyester, which is the organic component, is not sufficient, peeling occurs at the boundary between the particles and the polyester during stretching, and voids are generated.

If this void is present in the polyester film, the particles easily separate from the polyester film due to damage to the polyester film due to contact between the polyester film or the polyester film and other substrate,
For example, as described above, it may cause generation of white powder or dropout in the magnetic tape 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 fine particles and polyester is a problem to be solved in terms of abrasion resistance and transparency.

In order to improve the affinity between the inorganic fine particles and the polyester, for example, surface treatment by a coupling reaction between a silane compound or a titanate compound and the inorganic particles has been proposed, but the treatment process is complicated and the 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, a polyester film containing inert fine particles having a specific shape is improved in peeling at the interface between the particles and the polyester, and has good properties. Find out,
The present invention has been reached.

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.

According to the present invention, the object of the present invention is:
This is achieved by a biaxially oriented polyester film characterized by containing cocoon-shaped inert fine particles.

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 glycols include alkylene glycols having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol, and alicyclic diols such as cyclohexanedimethanol. Etc. can be mentioned.

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

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 the total glycol component is A copolymer having 80 mol% or more of ethylene glycol is preferable. 20 mol% or less of the total acid component can be the above aromatic dicarboxylic acids other than terephthalic acid and / or naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid; cyclohexane-1 It can be an alicyclic dicarboxylic acid such as 4,4-dicarboxylic acid. Also, up to 20 mol% of the total glycol component can be the above glycols other than ethylene glycol, or, for example, hydroquinone, resorcin, 2,2-bis (4-
Aromatic diols such as hydroxyphenyl) propane; Aliphatic diols containing an aromatic ring such as 1,4-dihydroxymethylbenzene; Polyalkylene glycols (polyoxyalkylene glycols) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. And so on.

In the polyester of 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-hydroxycaproic acid, a dicarboxylic acid component and an oxycarboxylic acid component. Those which are copolymerized or bonded at 20 mol% or less based on the total amount of

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,
If necessary, additives such as dyes, ultraviolet absorbers, heat stabilizers, light stabilizers, antioxidants, light-shielding agents (for example, carbon black, titanium dioxide, etc.) can be contained.

The cocoon-shaped inert fine particles referred to in the present invention are particles having a constriction in which spherical particles are united, and are shown in FIGS.
-Figure 2 shows a typical example. In addition, as shown in FIG.
-The constricted portion in FIG. 2 may have a gentle shape. The cocoon-shaped inert fine particles are not particularly limited as long as they are insoluble in polyester and do not substantially deform during melting and stretching of polyester, and may be organic or inorganic. As the cocoon-type inert fine particles, for example, silica, titanium dioxide, silicone (polyorganosiloxane) and the like are easily available, and are preferable in terms of dispersibility in polyester.

The method for producing the cocoon-shaped inert fine particles is not limited at all, but for example, ultrafine particles of about 10 mμ or more are aggregated or grown to form primary spherical particles, and subsequently two spherical particles are combined. Then, by further growing the particles, the production method can be performed.

It should be noted that the cocoon-shaped inert fine particles may contain a small amount of aggregates of three or more spherical particles, which are by-produced during the production thereof.

The cocoon-shaped inert particles have an average major axis (D _L ) of 0.1 to 5μ.
And the ratio of the average major axis (D _L ) to the average minor axis (D _W ) (D _L
/ D _W ) is preferably 1.4 to 1.9. Furthermore, the average major axis (D _L ) is preferably in the range of 0.2 to 2 μ for applications such as magnetic tapes.

Further, the relative standard deviation of the major axis is preferably 0.7 or less, and more preferably 0.5 from the meaning of making the distribution of the film surface protrusions a sherb.
The following is more preferable.

Here, di: diameter of the individual particles (μ) D _L: number average particle diameter (mu) n: is the number of particles.

Average major axis (D _L ) and average minor axis (D _W ) of cocoon-shaped inert particles
Uses cocoon-shaped inert fine particles with an electron microscope, for example, from 10,000 to
After taking a photograph at 50,000 times, the major axis of each cocoon-shaped particle,
The average major axis and the average minor axis can be obtained by measuring the minor axis and calculating the number average value.

The content of the cocoon-type inert fine particles is preferably 0.005 to 5% by weight, more preferably 0.01
˜3% by weight, more preferably 0.02 to 1% by weight. If the content is less than 0.005% by weight, the effect of improving the sliding property and the abrasion resistance is insufficient, whereas if it exceeds 5% by weight, the film surface is excessively roughened and the abrasion resistance is deteriorated. Absent.

In the present invention, it is preferable that the cocoon-shaped inert fine particles are subjected to a purification process to remove coarse particles before being incorporated into the 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 of incorporating the cocoon-shaped inert fine particles into the polyester is carried out at any time by any method, but it is preferable to add it as a glycol slurry before the polymerization reaction of the polyester reaction, particularly before the completion of transesterification or esterification reaction. .

The polyester film is the same as above polyester,
Alternatively, it can be obtained by diluting with another polyester (polyester which does not contain cocoon-shaped inert fine particles in a predetermined ratio). 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 any case, it is important that the finally obtained film contains the above-mentioned cocoon-type inert fine particles in the above-mentioned predetermined amount.

As the polyester film of the present invention, one having an unevenness unit formed by anisotropic projections due to cocoon-shaped inert fine particles and depressions adjacent to the projections on the surface of the film has a slipperiness and abrasion resistance of the film. From the aspect, it is more preferable. The shape of the concavo-convex unit is either one having a depression on the major axis side of the anisotropic protrusion as shown in FIG. 2-1 or 2-2, or one having a depression on the minor axis side of the anisotropic protrusion. It may be.

The method of forming the concavo-convex unit is not a concave shape by a conventional mechanical stamp such as embossing, but is generated by the deformation of the film itself in the process of stretching the film, for example, the following stretching conditions are mentioned. You can

<Formation of Concavo-convex Units Containing Dimples Adjacent to Longitudinal Side> When uniaxially stretching the unstretched polyester film containing fine cocoon-shaped inert fine particles in the machine axis direction (longitudinal direction of the film), the film before stretching By setting the preheating of the cocoon to a low temperature and setting the stretching ratio to a high value, and then performing the second axial stretching (stretching in the film width direction), anisotropic projections caused by the cocoon-shaped inert fine particles are obtained. It is possible to form a depression adjacent to the long axis side of the protrusion.

<Formation of Concavo-convex Units Containing Dimples Adjacent to Short Axis Side> When uniaxially stretching a polyester unstretched film containing fine cocoon-shaped inert fine particles in the machine axis direction (longitudinal direction of film), the film before stretching Set preheat to a higher temperature or (and) lower draw ratio,
Then, a second axial stretching (stretching in the film width direction) is performed to form an anisotropic protrusion due to the cocoon-shaped inactive fine particles and a depression adjacent to the minor axis side of the protrusion.

The film may be stretched in the usual machine axis direction (first axis direction) and width direction (second axis direction), and then further stretched in the first axis direction and / or the second axis direction. A method of performing high-stage (multi-stage) stretching to be added can also be used. Even in this case, the effect of the present invention can be maintained because the shape of the unevenness unit formed by the projections and the depressions on the film surface is slightly deformed and still exists.

The concavo-convex unit referred to in the present invention is composed of one anisotropic protrusion and a pit around it. The size and the frequency of occurrence of the uneven unit can be controlled by the cocoon-shaped inert fine particles, the amount of the cocoon-shaped inert particles present in the polymer, and the film stretching conditions.

Since the polyester film of the present invention has an anisotropic projection on the surface thereof, preferably an uneven unit consisting of the anisotropic projection and a recess adjacent to the anisotropic projection, the contact area with the film or a device in contact with the film can be reduced. It is flat and has excellent slippery effect. Further, there is an advantage that the abrasion resistance is enhanced as compared with the conventional polyester film having a large number of concave and convex units consisting of protrusions and depressions formed by simple particles on the surface of the film. In addition, as long as the effect of the present invention is not impaired, protrusions caused by externally-added particles that are insoluble in polyester and have an ordinary spherical shape, a lump shape, a plate shape, and / or internal particles precipitated during polyester synthesis or the like. It does not matter even if the concavo-convex unit having recesses having the particles as cores is mixed on the surface of the polyester film.

Here, the externally-added particles and the internally-precipitated particles each having a usual spherical, lumpy, or plate-like shape have the following volumetric shape factor φ.
, Φ is less than 0.35.

φ = V / d ³ where V = volume of the particle (μ ³ ) d = maximum diameter (μ) on the projection surface.

Further, φ _t of the whole fine particle group is represented by the number average of φ of each particle, and φ _t is less than 0.30.

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) Size and shape of cocoon-shaped inert fine particles After taking a photograph of the particles with an electron microscope at a magnification of 10,000 to 50,000, for example, the major axis and the minor axis of each cocoon-shaped particle are measured, and the number average value is calculated. Calculate 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 fine powder interference microscope (Nikon fine powder interference microscope R type)
Take a photograph at 0x magnification and count the depressions with a major axis of 2μ or more.

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- of Kosaka Laboratory Ltd.) 30C). The measurement conditions are as follows.

(A) Stylus tip radius: 2μ (b) Measuring pressure: 30mg (c) Cut-off: 0.25mm (d) Measuring length: 0.5mm (e) How to collect data Repeated measurement 5 times for the same sample, the largest 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 net 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
The exit tension (T ₂ : g) when the tension controller is adjusted to 5 g is detected by the exit tension detector after the film has run 90 m, and the running wear coefficient μk is calculated by the following formula.

μk = (2.303 / θ) log (T 2 / T 1) = 0.868 log (T 2/35) 5) Wear resistance evaluation -I 1/2 inch width of the film surface 5mm stainless steel 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, ∘ indicates that there is almost no scratch, ∘ indicates that scratches are small, ○ indicates that many scratches occur on the entire surface, and × indicates that scratches occur between the former two. To do.

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
The film is run at 80 ℃, the linear pressure applied to the film is 200kg / cm, and the film speed is 50m / min. Running film length is 4000m
The abrasion property of the film is evaluated by the dirt attached to the top roller of the calendar when the film is run.

<Four-level judgment> ◎ Nylon roll is not soiled at all ○ Nylon roll is barely soiled × Nylon roll is soiled × × Nylon roll is heavily soiled Example 1 Average major axis (D _L ) 0.8 μ, average minor axis (D _L ) _W ) 0.5μ, D _L / D _W ＝
Casting drum that contains 0.2% by weight of 1.6 cocoon-shaped silica fine particles and has an intrinsic viscosity of 0.60 dl / g of polyethylene terephthalate (orthochlorophenol, 35 ° C) is dried at 160 ° C, melt-extruded at 290 ° C, and kept at 40 ° C. It was rapidly cooled and solidified to obtain an unstretched film.

Subsequently, the unstretched film was preheated to 70 ° C. with a heating roller and then stretched 3.6 times in the machine direction while being heated with an infrared heater. 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 biaxially oriented film having a thickness of 15 μ.

The characteristics of the biaxially oriented film are shown in Table 1, and the friction coefficient was low and the abrasion resistance was good.

Examples 2 and 3 In Example 1, the stretching conditions of the unstretched film were changed to the following, and the same procedure as in Example 1 was followed to obtain a biaxially oriented 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. Then, it was stretched at a temperature of 105 ° C. in the transverse direction by a factor of 3.4.

In each of these two types of biaxially oriented films, an anisotropic protrusion due to the cocoon-type silica fine particles and a dent adjacent to the protrusion were observed. In particular, in Example 2, the anisotropic protrusion was formed in the major axis direction. There was a dent, whereas in Example 3, there was a dent in the minor axis direction of the anisotropic protrusion.

The characteristics of these biaxially oriented films are shown in Table 1, and although the surface roughness Ra is low, the coefficient of friction is small and the abrasion resistance is good. there were.

Comparative Examples 1 and 2 A biaxially oriented film was prepared in the same manner as in Examples 1 and 2 except that the cocoon-shaped silica fine particles were changed to ordinary agglomerated particles of calcium carbonate (average particle size 0.7 μ, 0.30% by weight). Obtained.

The surface roughness of the obtained film was not anisotropic, and the properties of the film are shown in Table 1. All the films had inferior properties.

Examples 4 and 5 Except for changing the cocoon-type silica fine particles to cocoon-type titanium dioxide or cocoon-type silicone having an average major axis and an average minor axis shown in Table 1, the same procedure as in Example 1 was carried out to obtain a biaxially oriented film. It was The properties of the obtained films are shown in Table 1 and all were excellent.

[Brief description of drawings]

FIG. 1 shows the shape of cocoon-shaped inert fine particles, and FIGS. 1-1 and 1-2 are model diagrams when the short diameter is the same and the long diameter 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 the anisotropy caused by the cocoon-shaped inactive fine particles on the film surface and the concave and convex unit of the depression in contact with the projection. 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.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B29L 7:00 4F

Claims (5)

[Claims] 1. A biaxially oriented polyester film characterized by containing cocoon-type inert fine particles in polyester. 2. The average major axis (D _L ) of the cocoon-shaped inert fine particles is 0.
The biaxially oriented polyester film according to claim 1, wherein the biaxially oriented polyester film has a thickness of 1 to 5 µ and a ratio (D _L / D _W ) of the average major axis (D _L ) to the average minor axis (D _W ) of 1.4 to 1.9. 3. The biaxially oriented polyester film according to claim 1, wherein the amount of the cocoon-shaped inert fine particles is 0.005 to 5% by weight based on the polyester. 4. A biaxially oriented polyester film according to claim 1 or 2, wherein the cocoon-type inert fine particles are at least one of silica, titanium dioxide and silicone. 5. The invention according to claim 1, wherein the film surface has an unevenness unit composed of anisotropic projections derived from cocoon-shaped inactive fine particles and depressions adjacent to the long axis side or the short axis side of the projections. Item 8. The biaxially oriented polyester film as described in any one of items 4 to 4.