JPS63254134A - Polyester film - Google Patents

Abstract

PURPOSE:To obtain the titled biaxially oriented film having excellent slipperiness, chipping resistance, etc., by containing cocoon-shaped fine inert particles. CONSTITUTION:A biaxially oriented film containing cocoon-shaped fine inert particles in a polyester. The cocoon-shaped particles having 0.1-5mu average major axis (DL) and 1.4-1.9 ratio (DL/DW) of the average major axis to the average minor axis (DW) are used. The amount of the above-mentioned particles is 0.005-5wt.%. Silica, titanium dioxide or a silicone is used as the afore- mentioned particles.

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 biaxially oriented polyester film containing inert fine particles having a specific shape and having excellent slip properties, abrasion resistance, etc.

[Prior Art] Polyester films, represented by polyethylene terephthalate films, have excellent physical properties.

Because of its chemical properties, it is used in a wide range of applications, such as magnetic tape, capacitors, photography, and packaging.

It is used for OHP etc.

In polyester films, their slipperiness and cracking resistance are major factors that determine the workability of the film during the manufacturing process and various uses, as well as the quality of the product.

If these are insufficient, for example, when applying a magnetic layer to the surface of a polyester film and using it as a magnetic tape,
During application of the magnetic layer, the friction between the coating roll and the film surface is intense, and this also causes severe abrasion of the film surface.
Scratches, etc. may occur.

Furthermore, even after slitting a film coated with a magnetic layer and processing it into audio, video, or computer tape, there are many guide parts, playback heads, etc. when pulling it out from a reel or cassette, winding it, or other operations. Significant abrasion occurs between the polyester film, causing scratches and distortion, and furthermore, the surface of the polyester film is scratched and a white powdery substance is deposited, which is often a major cause of missing magnetic recording signals, that is, dropouts.

Conventionally, many methods have been proposed to reduce the coefficient of friction of polyester, including the presence of fine particles in polyester. was also not satisfactory. To further explain this method, as a means to improve the surface properties of polyester,
Traditionally, ■ A method in which part or all of the catalyst used during polyester synthesis is precipitated during the reaction process (internal particle precipitation method); ■ A method in which fine particles such as calcium carbonate or silicon oxide are added during or after polymerization (external particle addition method) Many methods have been proposed.

However, in the internal particle precipitation method (2), since the particles are metal salts of polyester components, the affinity with polyester is good to some extent, but on the other hand, the method generates particles during the reaction, so the particle amount is 1 particle. It is difficult to control the diameter and prevent the generation of coarse particles.

On the other hand, in method (2), if the particle size, amount added, etc. are appropriately selected, and fine particles from which coarse particles have been removed by classification etc. are added, excellent slipperiness can be achieved.

However, since the affinity between the inorganic fine particles and the organic component polyester is insufficient, peeling occurs at the boundary between the particles and the polyester during stretching, etc., and voids are generated.

If these voids exist in the polyester film, particles will easily detach from the polyester film due to damage to the polyester film due to contact between the polyester films or between the polyester film and other base materials.
For example, as mentioned above, it causes white powder and dropouts in magnetic tape films. Furthermore, the presence of large voids around the particles impairs the transparency of the polyester film. Therefore, the lack of affinity between @sensitive particles and polyester is a problem that must be solved in terms of abrasion resistance and transparency.

In order to improve the affinity between these inorganic fine particles and polyester, surface treatment using a coupling reaction between a silane compound or a titanate compound and steam particles has been proposed, but the treatment process is complicated and the effect is not expected. There were various problems such as not being able to cut the edges.

[Purpose of the invention] In view of the above-mentioned circumstances, the inventors of the present invention have investigated slipperiness.

Excellent abrasion resistance, etc., and the shape of the protrusions on the film surface.

As a result of intensive studies to obtain a biaxially oriented polyester film that has characteristics such as excellent size distribution and is suitable for various uses, a polyester film containing inert fine particles with a specific shape has been developed. It has been discovered that the peeling at the interface with the material is improved and the properties are good, and the present invention has been achieved.

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

[Structure of the Invention] According to the invention, the object of the present invention is that in polyester,
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 containing 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, particularly by melt molding. Examples of aromatic dicarboxylic acids include terephthalic acid,
Examples include naphthalenedicarboxylic acid, isophthalic acid, diphenylethanedicarboxylic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenylgetonedicarboxylic acid, anthracenedicarboxylic acid, and the like. Examples of aliphatic glycols include ethylene glycol, trimethylene glycol, and tetramethylene glycol.

Examples include polymethylene glycols having 2 to 10 carbon atoms such as pentamethylene glycol, hexamethylene glycol and decamethylene glycol, and alicyclic diols such as cyclohexane dimetatool.

In the present invention, polyesters containing, for example, alkylene terephthalate and/or alkylene naphthalate as main constituents are preferably used.

Among such polyesters, for example, polyethylene terephthalate, polyethylene-2,6-naphthalate, etc.2, for example, 80 mol% or more of the total dicarboxylic acid component is terephthalic acid and/or 2,6-naphthalene dicarboxylic acid, and all glycol A copolymer in which 80 mol% or more of the components is ethylene glycol is preferred. In this case, up to 20 mol% of the total acid component can be the above-mentioned aromatic dicarboxylic acids other than terephthalic acid and/or naphthalene dicarboxylic acid, and also aliphatic dicarboxylic acids such as adipic acid, cepatic acid, etc.; cyclohexane-1 ,4
-Alicyclic dicarboxylic acids such as dicarboxylic acids. In addition, up to 20 mol% of the total glycol component can be the above-mentioned glycols other than ethylene glycol, or, for example, hydroquinone, resorcinol,
Aromatic diols such as 2,2-bis(4-hydroxyphenyl)propane; aliphatic diols containing an aromatic ring such as 1,4-dihydroxymethylbenzene; polyethylene glycols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. Alkylene glycol (
Polyoxyalkylene glycol) and the like can also be used.

Furthermore, 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-droxycaproic acid, a dicarboxylic acid component and an oxycarboxylic acid component. Those copolymerized or combined in an amount of 20 mol % or less based on the total amount of acid components are also included.

Furthermore, the polyester in the present invention contains a trifunctional or higher functional polycarboxylic acid or a polyhydroxy compound, such as trimellitic acid, pentaerinyl, etc., in an amount within a substantially linear range, for example, an amount of 2 mol % or less based on the total acid components. Also included are copolymerized compounds such as I--L.

Furthermore, the polyester in the present invention includes, for example, pigments,
Dyes, ultraviolet absorbers, heat stabilizers, light stabilizers, antioxidants, light shielding agents (e.g. carbon black, titanium dioxide, etc.)
It is also possible to contain additives such as the like, if necessary.

The cocoon-shaped inert fine particles referred to in the present invention are particles having a constricted shape in which spherical particles are combined.
A typical example is shown in Figure-2. In addition, as shown in Figure 1-3, the first
- The constriction in Figure 2 may have a gentle shape. There are no particular restrictions on the cocoon-shaped inert fine particles as long as they are insoluble in polyester and do not substantially deform when the polyester is melted or stretched. IIJ or an inorganic substance may be used. An example of the cocoon-shaped inert fine particles is silica.

Titanium dioxide, silicone (polyorganosiloxane)
etc. are easily available and are preferable in terms of dispersibility in polyester.

The method for producing cocoon-shaped inert fine particles is not limited in any way, but for example, ultrafine particles of about 10 mμ or more are aggregated or grown to make first spherical particles, and then two spherical particles are made. It can be produced by coalescing and further growing -10- particles.

The cocoon-shaped inert fine particles may contain a small amount of aggregates of three or more spherical particles produced as a by-product during their production.

The average length (DL) of the cocoon-shaped inert fine particles is 0.1~
5μ, and the average major axis (DL) - and the average minor axis (D
It is preferable that the ratio (DL/D, ) is between IL4 and 1.9. Further, the average length axis (DL) is preferably in the range of 0.2 to 2μ for applications such as magnetic tapes.

In addition, 1. For the purpose of sharpening the distribution of protrusions on the film surface, the relative standard deviation of the major axis is preferably 0.7 or less,
Furthermore, it is more preferably 0.5 or less.

D, number average value of two particle major diameters (μ) n: Number of particles It is.

Average particle diameter (DL) and average short diameter (D) of cocoon-shaped inert fine particles
LN) is obtained by photographing cocoon-shaped inert particles using an electron microscope at a magnification of, for example, 10,000 to 50,000 times, measuring the long axis and short axis of each cocoon-shaped particle, and calculating the number average value. , the average length axis and the average particle size can be determined.

The content of the cocoon-shaped inert fine particles is preferably 0.005 to 5% by weight based on the polyester, more preferably 0.01 to 3% by weight, and even more preferably 0.02 to 1% by weight. . If this content is less than 0.005% by weight, the effect of improving slipperiness and cracking resistance is insufficient;
Exceeding this is not preferable because the film surface becomes too rough and the abrasion resistance deteriorates.

In the present invention, it is preferable to remove coarse particles from the cocoon-shaped inert fine particles using a purification process before incorporating them into the polyester. Examples of the classification means include wet or dry centrifuges, filter filtration, and the like. Two or more of these methods may be used in combination (1) or stepwise purification may be performed.

Cocoon-shaped inert fine particles can be incorporated into polyester at any time and by any method, but it is preferable to add them as a glycol slurry before the polymerization reaction of the polyester reaction, especially before the end of the transesterification or esterification reaction. . 5 Polyester film is made from the above polyester.
It can be obtained as it is or by diluting it with another polyester (polyester that does not contain a predetermined proportion of cocoon-shaped inert characteristic particles) and forming a film.

Other polyesters used for dilution include, for example, polyesters produced by conventional precipitation or addition methods or particle-free polyesters. In any case, it is necessary that the finally obtained film contains the above-mentioned predetermined amount of the above-mentioned cocoon-shaped inert fine particles.

The polyester film of the present invention has a cocoon-shaped inert feature/an uneven unit consisting of anisotropic protrusions caused by particles and depressions adjacent to the protrusions, which improves the film's slipperiness and cracking resistance. It is more preferable from the viewpoint of sex. The shape of the unevenness unit can be either one with a depression on the long axis side of the anisotropic protrusion as shown in Figure 2-1 or 2-2, or one with a depression on the short axis side of the anisotropic protrusion. It's okay to have one.

The method of forming this uneven unit is that it is not formed by conventional mechanical stamping such as embossing, but is caused by deformation of the film itself during the process of stretching the film.For example, the following stretching conditions are used. Can be done.

Formation of uneven units having depressions and depressions adjacent to the long axis side
When performing axial stretching, the film and lumen are preheated to a low temperature before stretching, the stretching ratio is set high, and then second axial stretching (stretching in the width direction of the film) is performed to form the cocoon shape. It is possible to form an anisotropic protrusion caused by the inert fine particles and a depression adjacent to the long axis side of the protrusion.

<Formation of uneven units having depressions and depressions adjacent to the short axis side> An unstretched polyester film containing fine LLI-type inert particles is stretched in the machine axis direction (film longitudinal direction).
When axially stretching, by setting the preheating of the film before stretching to a high temperature, or (and) setting the stretching ratio to the bottom, and then performing second axial stretching (stretching in the width direction of the film), An anisotropic protrusion caused by the shaped inert fine particles and a depression adjacent to the long sleeve side of this protrusion can be formed.

The film is stretched in the normal machine axis direction (first axis direction) and width direction (second axis direction), and then further stretched in the second axis direction and/or second axis direction. A method of performing high-stage (multi-stage) stretching can also be used. In this case, even if the shape of the uneven unit consisting of protrusions and depressions on the surface of the film is slightly deformed, the effect of the present invention is maintained because it remains as it is.

15. The concavo-convex unit in the present invention consists of one anisotropic protrusion and a depression around the protrusion. The size and frequency of occurrence of the uneven units can be controlled by adjusting the ageless fine particles ♀ in the preparation, the amount present in the polymer, and the stretching conditions of the film.

Since the polyester film of the present invention has on its surface an uneven unit consisting of anisotropic protrusions, preferably anisotropic protrusions and depressions adjacent to the anisotropic protrusions, the contact area between the films or with objects that come into contact with the film is reduced. It is flat, smooth, and has an excellent sliding effect, and has improved abrasion resistance compared to conventional polyester films, which have many uneven units consisting of protrusions and holes made of particles. Advantage 6 - Externally added particles insoluble in polyester and/or precipitated during synthesis of polyester having a shape of ordinary spherical, lumpy, plate-like, etc. can be used as long as the particle size does not impair the effects of the present invention. There is no problem even if uneven units having protrusions caused by internal particles and depressions having the particles as cores coexist on the surface of the polyester film.゛ -Here, externally added particles and internally precipitated particles having a normal spherical, lumpy, plate-like, etc. shape are those whose φ is less than 0.35 when defined by the volume shape factor φ below.

φ=■/d3　　　゛ Here, V = volume of the powder particle (μ3) d - Maximum diameter in projection plane (μ) It is.

Further, φ1 of the entire fine particle group is expressed as the number average of φ of each particle, and φ1 is less than 0.30.

The polyester film of the present invention has various advantages such as a flat surface, excellent slipperiness, and better abrasion resistance than conventional polyester films, so it can be used for various purposes. It can be particularly preferably used in the magnetic tape field, which requires wear resistance.
□ [Example] Hereinafter, the present invention will be specifically explained using examples. In addition, each characteristic value in the Examples was measured according to the following method.

1) Size and shape of shaped inert fine particles After photographing the particles with an electron microscope at a magnification of, for example, 10,000 to 50,000 times, ・Long diameter of each cocoon-shaped particle.

The average major axis and average minor axis are determined by measuring the minor axis and calculating the number average value.

2) Size of the depressions (1 number) - After depositing a thin layer of aluminum on the surface of the stretched film, a photograph was taken at a magnification of 900x using a fine powder interference microscope (R type), and the major axis of the depressions was 2μ. Count more than 6
3) Film surface roughness (Ra) Center line average roughness (Ra) is the value defined in JIS-BO601. Measure using The measurement conditions are as follows.

(a) Stylus tip radius: 2μ (b) Measurement pressure: 30+ng (C) Cutoff: 0.25IIIm (d)・Measurement length
: 0.5mm (e) How to summarize the data - Measure the sample 5 times and take the largest value as 1
This shows the average value of the remaining four cheaters.

4) Coefficient of friction of film (μk) Measured as follows using the apparatus shown in FIG. In Fig. 3, 1 is an unwinding 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 sufoon made of SUS 304 <7 ) Fixed rod (outer diameter 5III
10 is a tension detector (outlet), 12 is a guide roller, and 13 is a winding wheel.

In an environment with a temperature of 20°C and a humidity of 60%, a film cut into 1/2 inch width was held with a fixing rod of 7 (surface roughness 0.3 μm).
angle θ - (152/180) π radians (152'
) and move at a speed of 200 cm per minute (Il rubbing)
let The outlet tension when the tension controller is adjusted so that the inlet tension T1 is 35g (
T2:g) is detected by an exit tension detector after the film has traveled 90 m, and the travel wear coefficient μk is calculated using the following formula.

μk = (2,303/θ) log(T2/TI
) = 0.868 log (T2/35) 5) Abrasion evaluation - The surface of the 172-inch film was brought into contact with a 5mm diameter stainless steel fixing pin (surface roughness 0.58) at an angle of 150°, and the test was carried out every minute. It is reciprocated at a speed of 2 m for about 15 an, causing friction (at this time, the tension T1 on the entry side is 60 g).

This operation is repeated, and after 40 reciprocating measurements, the degree of scratches that have occurred on the rubbed surface is visually determined.

At this time, it is judged in four stages: ◎ if there are almost no scratches, ○ if there are only a few scratches, × if many scratches occur on the entire surface, and △ if the scratches are between the first two. do.

6] Evaluation of abrasion resistance - ■ Evaluate the abrasion resistance of the running surface of the film using a 5-stage mini super calendar. The calender is a 5-stage calender with nylon rolls and steel rolls, the processing temperature is 80℃, and the linear pressure applied to the film is 200 kg/t.
x, Film speed is 50m, 7 minutes. After running the running film for a total length of 4000 m, the abrasion resistance of the film was evaluated based on the dirt that adhered to the top roller of the calendar.

4-step evaluation> ◎ No stains on the nylon roll ○ Almost no stains on the nylon roll × × Nylon roll gets dirty × × Example 1 in which the nylon roll gets very dirty Average major axis 1. )0.8μ, average minor axis (DL) 0.5μ,
After drying polyethylene terephthalate with an intrinsic viscosity of 0.60 dl/g at 160°C (orthochlorophenol, 35°C) containing 0.2% by weight of shaped silica fine particles of Dt/Dw -1 and 6, the polyethylene terephthalate was dried at 160°C. The mixture was melt-extruded at 40°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 stretched 3 times in the longitudinal direction while being heated with an infrared heater.
It was stretched 6 times. Subsequently, the film 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 with a thickness of 15 μm.

The properties of this biaxially oriented film are shown in Table 1, and it had a low coefficient of friction and good wear resistance.

Example 2.3 A biaxially oriented film was obtained in the same manner as in Example 1 except that the stretching conditions of the unstretched film were changed as follows.

After preheating the unstretched film to 60°C with a heating roller,
The film was stretched 4.6 times in the longitudinal direction while being heated with an infrared heater. Subsequently, it was stretched at a temperature of 90° C. in the transverse direction by a factor of 3.4.

After preheating the dog 1 × 3 O * 6 top unstretched film to 60°C with a heating roller,
The film was stretched 3.3 times in the longitudinal direction while being heated with an infrared heater. Subsequently, the film was stretched at 3.4 times in the transverse direction at a temperature of 105°C.

In both of these two types of biaxially oriented films, anisotropic protrusions caused by cocoon-shaped silica particles and depressions adjacent to the protrusions are observed, and in particular, in Example 2, the anisotropic protrusions are located in the long axis direction. On the other hand, in Example 3, there was a depression in the short axis direction of the anisotropic protrusion.

The properties of these biaxially oriented films are shown in Table 1, and although the surface roughness Ra is low, the friction coefficient is small and the abrasion resistance is also good, which is equivalent to or better than that of Example 1. there were.

Comparative Example 1.2 The same procedure as in Examples 1 and 2 was carried out, except that the cocoon-shaped silica fine particles were replaced with calcium carbonate (average particle size: 0.7μ, 0.30% by weight), which is a normal cocoon-shaped particle. An axially oriented film was obtained.

The obtained film had no anisotropy in its surface protrusions, and the properties of the film are shown in Table 1, and all of the properties were poor.

Examples 4 and 5 A biaxially oriented film was obtained in the same manner as in Example 1, except that the cocoon-shaped silica particles were changed to open titanium dioxide or cocoon-shaped silicone having the average major axis and average minor axis shown in Table 1. Ta. The properties of the obtained film are shown in Table 1, and all were excellent.

[Brief explanation of drawings]

FIG. 1 shows the shape of Ichiso's non-synthetic fine particles, and shows the shape of Ichiso's insulating particles.
Figures 1-2 are model diagrams in which the short axis is the same and the long axis is different. FIG. 1-3 is a diagram when the constriction of FIG. 1-2 is gentle. FIG. 2 is a plan view of the anisotropy caused by the cocoon-shaped inert features on the film surface and the unevenness unit of the depressions in contact with the protrusions. The shaded area indicates a depression, and Figure 2-1 shows an uneven unit having a depression in the long axis direction of the anisotropic protrusion, and Figure 2-2 shows an uneven unit having a depression in the short axis direction of the anisotropic protrusion. It is. FIG. 3 is a schematic diagram of an apparatus for measuring the coefficient of dynamic friction (μk) of a film. Procedural amendment June 2, 1986

Claims (1)

[Scope of Claims] 1. A biaxially oriented polyester film characterized by containing cocoon-shaped inert fine particles in polyester. 2. The average major axis (D_L) of cocoon-shaped inert particles is 0.1
~5μ, and the average major axis (D_L) and average minor axis (D_
The biaxially oriented polyester film according to claim 1, wherein the ratio (D_L/D_W) of W) is 1.4 to 1.9. 3. The amount of cocoon-shaped inert fine particles relative to polyester is
The biaxially oriented polyester film according to claim 1 or 2, wherein the content is 0.005 to 5% by weight. 4. The biaxially oriented polyester film according to claim 1 or 2, wherein the cocoon-shaped inert fine particles are at least one of silica, titanium dioxide, and silicone. 5. Claims 1 to 5 in which the film surface has uneven units consisting of anisotropic protrusions caused by cocoon-shaped inert fine particles and depressions adjacent to the long axis side or the short axis side of the protrusions. The biaxially oriented polyester film according to any one of Item 4.