JPH07119292B2 - Polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polyester film,
Specifically, by including the specific inorganic fine particles, the distribution of the surface roughness and / or the friction coefficient in the film width direction is substantially uniform, and the F ₅ value in the film longitudinal direction is
The present invention relates to a high-strength polyester film having a weight of 12 kg / mm ² or more.

[Problems to be Solved by Prior Art and Invention]

The polyester film has excellent physical and chemical properties and is widely used in industry.

Above all, the biaxially stretched polyethylene terephthalate film is superior to other films in electrical characteristics, chemical resistance,
In addition to mechanical properties, it is excellent in flatness and dimensional stability, etc. and is cheap in cost. Therefore, it is used for magnetic recording media, for capacitors, for packaging, for plate making, for electric shock, for photographic films, etc. Used in the field.

On the other hand, in recent years, there is a demand for thinning in applications such as magnetic recording media and capacitors. For example, it is necessary to reduce the thickness of video / audio tapes for long-term recording, and to wind longer tapes with the same winding diameter.For capacitors, reduce the thickness in order to make the elements lighter, thinner and shorter. It is necessary to increase the capacity and make it compact.

Since the strength of a film decreases as the film becomes thinner when compared with the same film width, a film having a higher strength per unit cross-sectional area is desired.

For that reason, a method for increasing the strength by mainly improving the drawing method has been proposed. For example, as disclosed in Japanese Examined Patent Publication (Kokoku) No. 42-9270, there is a method of increasing the strength by stretching the film stretched in the longitudinal and transverse directions in the longitudinal direction.

By the way, in such a stretched polyester film,
For the purpose of improving the handling workability of the film in the film manufacturing process and the processing process, inactive inorganic or organic fine particles are usually present in the film to impart appropriate irregularities to the film surface.

This method can be roughly divided into two. One of them is a method called precipitation method, in which one or more kinds of metal compounds soluble in ethylene glycol, such as calcium compounds and lithium compounds, are added before and after the transesterification reaction or the esterification reaction, so that they are insoluble in polyester. It is a method of precipitating as fine particles.

Another method, which is compared with the precipitation method, is a method called addition method, in which inert inorganic particles such as calcium carbonate, calcium sulfate, barium sulfate, kaolin, silica, talc, graphite, carbon black, and titanium dioxide are mixed with polyester. It is known to be added at the time of synthesis or molding.

By the way, in the actual production of a stretched film, particularly in the production of a high-strength stretched film in the present invention, it is particularly difficult to obtain a film having a constant quality in the width direction. For example, the surface roughness becomes smaller toward the edges of the film, and generally has a convex distribution with the maximum in the widthwise center. On the contrary, the coefficient of friction increases toward the ends and has a concave distribution with the center in the width direction as the minimum point. This distribution of physical properties is called the so-called Boeing phenomenon. This phenomenon appears to some extent in the balance film stretched at almost equal longitudinal / horizontal ratios, but is particularly remarkable in the longitudinal tensified film stretched in the longitudinal direction. It is presumed that this is because the particles existing in the film are subjected to different stresses at the edge portions of the film than at the central portion, and the film surface morphology is different.

Therefore, since the edge portion of the film has no commercial value, it is important to suppress the bowing phenomenon as much as possible and obtain a stretched film with high yield in order to improve productivity.

In order to suppress the Boeing phenomenon, for example, Japanese Patent Publication No. 61-31526
In the publication, calcium element and phosphorus element are 1 to 15% by weight.
A method using the contained precipitated particles has been proposed. However, as shown in this publication, there is a problem that the deposited particles generally have a difficulty in control because the deposited particle diameter and the amount of particles tend to change. Further, when the direct polymerization method is carried out for cost reduction, it is difficult to adopt the precipitation method, which is a big drawback.

On the other hand, in the addition method, there is a drawback that unnecessary coarse particles and agglomerated particles are often mixed in, and in order to avoid this, it is necessary to perform a classification operation and, if necessary, a pulverization operation as a pretreatment thereof. Therefore, the operation becomes complicated.

In addition, generally, the added particles have a poor affinity with polyester, and in the film forming step or the like, the particles are likely to come off due to contact with various rolls or other external force, causing various harmful effects. This drop-off of particles is also particularly remarkable in the tensilized film. A method of treating the particle surface with an organic compound such as organic silane or acrylic acid is used for the purpose of improving the affinity with polyester, but sufficient affinity cannot be obtained or the interaction between particles becomes stronger. It often causes agglomeration and coarse particles, which is not sufficient as an improvement method.

The improvement in the anisotropy of the physical properties such as the roughness and the coefficient of friction in the width direction and the improvement in the affinity between the particles and the polyester are particularly required in the so-called tensilized film having high strength.

[Means for solving problems]

In view of the above situation, the present inventors have made extensive studies, and as a result, there is no anisotropy in the width direction of physical properties such as roughness and friction coefficient,
In order to produce a high-strength film with good affinity between particles and polyester with high yield, it was found that certain particles may be used as a projection-forming material on the surface of the film, and the present invention was reached. It was done.

That is, the gist of the present invention is a substantially amorphous, average particle size of 0.01 to 3.0 μm, which is obtained by subjecting an alkoxysilane to a hydrolysis reaction and a condensation reaction, and is defined below [d ₁₀ / d ₉₀ ] value. 0.001 to 5 for spherical silica particles with a range of 1.1 to 2.7
A polyester film, characterized in that the polyester film contains 10% by weight and has an F ₅ value in the longitudinal direction of 12 kg / mm ² or more.

(The particle diameters d ₁₀ and d ₉₀ in the above formula are measured by an electron microscope, and the volume is integrated from the large particle side to obtain 10% and 90% of the total volume.
This is the particle size at. Hereinafter, the present invention will be described in detail.

The polyester referred to in the present invention means terephthalic acid, isophthalic acid, an aromatic dicarboxylic acid such as naphthalene-2,6-dicarboxylic acid or an ester thereof, and ethylene glycol,
It is a polyester that can be obtained by polycondensation with glycols such as diethylene glycol, tetramethylene glycol, neopentyl glycol and the like.

This polyester can be obtained by directly polycondensing an aromatic dicarboxylic acid and a glycol, or by subjecting an aromatic dicarboxylic acid dialkyl ester and a glycol to transesterification and then polycondensing, or by polycondensing an aromatic dicarboxylic acid diester. It can also be obtained by a method such as.

Typical examples of such a polymer include polyethylene terephthalate and polyethylene-2,6-naphthalate. This polymer may be a homopolymer or may be a copolymer of a third component. In any case, in the present invention, the ethylene terephthalate unit and / or the ethylene-2,6-naphthalate unit are 80 mol%.
Polymers having the above are preferable.

The spherical silica fine particles used in the present invention are obtained by a hydrolysis reaction and a condensation reaction using an alkoxysilane as a starting material and an amine catalyst.

As the alkoxysilane compound, (C _n H _{2n + 1} O) ₄ Si (n
= 1 to 8), and specific compounds include tetramethoxysilane, tetraethoxysilane,
Compounds such as tetrapropoxysilane and tetrabutoxysilane are preferably used. As the hydrolysis reaction and condensation reaction catalyst, ammonia, trimethylamine, tetraethylammonium aqueous solution, urea or the like can be used, but ammonia aqueous solution is preferable.

The method for synthesizing the spherical silica fine particles is performed as follows, for example. That is, a solution (A) in which tetramethoxysilane is dissolved in a methanol solvent is prepared, and separately, a solution (B) in which an aqueous ammonia solution is dissolved in a methanol solvent is prepared. Both solutions are stored at a predetermined temperature, for example 20 to 30 ° C., and then the solution (A) is added while vigorously stirring the solution (B). Then, after holding at a predetermined temperature for several hours, centrifuge, wash with alcohol as a solvent, and then disperse in ethylene glycol, or add ethylene glycol to the suspension of silica particles after the reaction, and then perform distillation. A method of removing excess ammonia, alcohol and water may be performed.

In any case, it is preferable that the spherical silica fine particles of the present invention be finally prepared as an ethylene glycol slurry.

The concentration of spherical silica fine particles in the ethylene glycol prepared as described above is preferably less than 40 wt%. If it is less than 40 wt%, the aggregation in the ethylene glycol slurry and the formation of aggregated particles when added during the polycondensation reaction are within the practically acceptable range. More preferably less than 20 wt%, 0.5 wt%
The above is good. If the concentration of the spherical silica fine particles in ethylene glycol exceeds 40 wt%, the formation of agglomerates is severe and unfavorable when added during the agglomeration and polycondensation reaction in an ethylene glycol slurry. On the other hand, if it is less than 0.5 wt%, the amount of ethylene glycol used becomes excessive, which is economically disadvantageous and not preferable.

The characteristics of the spherical silica fine particles obtained by the hydrolysis and condensation method of the alkoxysilane in the present invention are that their spherical shape and extremely uniform particle diameter. That is, the particle size distribution of the particles is determined by an electron micrograph, and the number and volume of each particle size are integrated to obtain 10% and 90% of the integrated volume.
It is necessary that the particle diameters of the above are represented by d ₁₀ and d _90, and the value of d ₁₀ / d ₉₀ (hereinafter referred to as [d ₁₀ / d ₉₀ ]) is in the range of 1.1 to 2.7. Preferably the [d ₁₀ / d _90] good range of 1.0 to 1.6. When [d ₁₀ / d ₉₀ ] exceeds 2.7, it means that the particle size distribution is broad, which is not preferable because it becomes difficult to control the surface roughness of the film and the number of coarse particles increases.

The average particle diameter of the spherical silica fine particles used as fine particles in the present invention needs to be 0.01 to 3.0 μm. The average particle size is preferably 0.05 to 2.0 μm, particularly preferably
It is 0.1 to 1.5 μm. If it is less than 0.01 μm, the effect of improving the surface properties and the slipperiness of the film is not sufficient. 3.0 μm
If it exceeds, the surface roughness of the film becomes too large,
It is not preferable because large particles increase in mixture and the film quality deteriorates.

Further, the volumetric shape factor φ _v of the spherical silica fine particles is Is preferably satisfied.

The volume shape factor is (V: particle volume [μm ³ ], D: maximum diameter [μm] on the projection plane of the particle), which represents the degree of spherical shape of the particle. Then π
/ 6).

When φ _v becomes smaller than 0.4, the particles become closer to an ellipsoid,
When it is made into a film, the projections of the film tend to flow easily, and the variations in the projection shape increase, which causes a large change in the physical properties in the width direction of the film, and it is easy for particles to fall off and the amount of white powder generated during the process increases. Therefore, it is not preferable. If φ _v is in the above range, it can be regarded as substantially spherical.

Further, the content of the spherical silica fine particles in the polyester film needs to be 0.001 to 5% by weight, preferably
0.01 to 3.0% by weight, particularly preferably 0.05 to 2.0% by weight. When the content of the spherical silica fine particles in the polyester film is less than 0.001% by weight, the slipperiness of the obtained film is insufficient, which causes various problems in the film manufacturing process and the processing process, which is not preferable. On the other hand, if the amount exceeds 5% by weight, the surface roughness of the film becomes too large, or the production of aggregated particles increases, which is not preferable.

The spherical silica fine particles used in the present invention have an extremely sharp particle size distribution and are excellent in dispersibility in ethylene glycol, and thus do not require a special dispersion treatment or classification treatment, and further pass through a filter during slurry overtreatment. The property is also extremely excellent.

The spherical silica fine particles used in the present invention can be added to the polyester at any stage in the polyester production process, but it is preferable to add them after the transesterification or esterification reaction and before the polycondensation. preferable. Further, a known method can be adopted for the polycondensation of the polyester. For example, as a catalyst for the polycondensation reaction, one or more kinds of antimony compounds, germanium compounds, titanium compounds, etc. are used and heated to about 230 to 300 ° C., and the reaction is advanced by distilling ethylene glycol under reduced pressure.

Also, for the purpose of slightly improving the surface shape and film characteristics,
Particles other than spherical silica, such as silicon dioxide, titanium dioxide, calcium carbonate, kaolin, talc, clay, inorganic zeolite, inorganic phosphate, calcium phosphate, etc. The fine particles and the like precipitated in step (3) can also be used together as long as the characteristics of the present invention are not impaired. Of course, it is also possible to use two or more types of spherical silica.

Further, in the present invention, it is essential that the F ₅ value in the longitudinal direction of the film is 12 kg / mm ² or more. It is preferably 16 kg / mm ² or more. In a film having an F ₅ value of less than 12 kg / mm ² , the bowing phenomenon is relatively small even with particles other than spherical silica, and the characteristics of spherical silica are not sufficiently produced. Furthermore, in the case of a film having high strength such as polyethylene-2,6-naphthalate, the F ₅ value in the longitudinal direction is 20 kg / mm ² or more, preferably 28 kg / m 2.
It is desirable to be m ² or more.

Moreover, the effect of the present invention are remarkably exhibited, the film longitudinal F ₅ value (F _5MD) with the direction and the in-plane direction perpendicular F ₅ value (F _5td) but Especially if you are satisfied with If the above is satisfied, the effect is more remarkable.

In the conventional high strength film within the above range, as described above, there is a problem in the anisotropy of the physical properties of the film in the width direction and the affinity between the particles and the polyester, which causes various adverse effects. By using the spherical silica of the present invention, the above problems can be solved all at once.

A well-known film forming method can be used to set the F ₅ value in the longitudinal direction to 12 kg / mm ² or more. For example, melt extrusion polyester film into a film at 270 ℃ -300 ℃,
After cooling at ~ 70 ° C, solidification to form an amorphous sheet, then biaxially stretching in the longitudinal and transverse directions or simultaneous biaxial stretching, then 110 ° C
After re-stretching 1.05 to 2.0 times in the machine direction at a temperature of up to 180 ° C, heat treatment at 160 ° C to 240 ° C may be used. On this occasion,
Techniques such as heat setting before re-longitudinal stretching, longitudinal relaxation after re-longitudinal stretching, before or after re-longitudinal stretching and micro-stretch longitudinal stretching can be appropriately adopted. In the case of polyethylene-2,6-naphthalate, a film having an F ₅ value in the longitudinal direction of the film of 20 kg / mm ² or more can be obtained by the same method except that the stretching temperature is different. For example, melt-extruded and solidified by cooling at 280 ° C to 320 ° C, a substantially non-oriented unstretched sheet of polyethylene-2,6-naphthalate is biaxially stretched longitudinally and transversely or simultaneously biaxially stretched, and then 140 1.05 times or more again at ℃ ~ 200 ℃ 4.
Re-longitudinal stretching of 0 times or more. Further, the film is heated to 180 ° C or higher 260
Heat treatment is performed at a temperature of ℃ or less. At this time, similarly, methods such as heat setting before re-longitudinal stretching, longitudinal relaxation after re-longitudinal stretching, vertical stretching before or after re-longitudinal stretching, and the like can be adopted.

The polyester film in the present invention can be used as a pace film in various fields, and since it has a good yield, it has high productivity and is extremely useful for cost reduction. or,
Since the particles are less likely to fall off, it is possible to prevent various harmful effects.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist thereof is not exceeded.

Various physical properties and characteristics in the examples are measured and defined as follows. In addition, "parts" and "%" in the examples are "parts by weight" unless otherwise specified.
And "% by weight".

(1) Average particle size and particle size distribution of silica particles The particles are photographed with an electron microscope and measured by a photographic method. The particle size is about 1000 particles. The average particle size is defined as the cumulative particle fraction of 50%, and the particle size distribution is 10% from the large particle side.
It is expressed as the particle size ratio at 90%.

(2) Measurement of surface roughness The center line average roughness Ra (μm) is defined as the surface roughness.

By the surface roughness measuring instrument (SE-3FK) manufactured by Kosaka Laboratory,
I asked for it as follows. That is, a portion having a reference length L (2.5 mm) is extracted from the film cross-section curve in the direction of the center line, and the center line of the extracted portion is taken as the X axis, and the direction of longitudinal magnification is taken as the Y axis. ), The value given by the following equation is expressed in μ (micron). However, the tip radius of the stylus is 2 μm, the load is 30 mg, and the cutoff value is 80 μm.
Is. Ra was an average value of 10 points, 5 points in the vertical direction and 5 points in the horizontal direction.

(3) Sliding property of film The friction coefficient, which is represented by the coefficient of friction, was measured by a method improved according to ASTM D-1894 so that a tape-shaped sample could be measured. The size of the sample at the time of measurement is 15 mm in width and 150 mm in length
And the pulling speed is 20 mm / min. The temperature is 23 ± 2 ℃,
It was carried out in an atmosphere with a humidity of 50 ± 5%.

(4) F ₅ value It was determined from the stress at 5% tension under the following conditions using Tensilon UTM-IV L type manufactured by Toyo Baldwin Co., Ltd. in an atmosphere of 23 ° C. and 50% RH.

Sample shape Strip type (length 15 cm, width 1 cm) Chuck interval 50 mm Tensile speed 100% / min (5) Number of breaks The average number of breaks per 100,000 m of film length produced was shown.

(6) White powder The white powder adhering to the feed roll in the stretcher for the stretched film was visually observed and evaluated according to the following three grades of ◯, Δ, and ×. The observation was performed when the film was wound up to 500,000 m.

○ …… No white powder generation △ …… Small white powder generation × …… Large white powder generation Example 1 (Synthesis method of spherical silica particles) 30.4 g of tetramethylsilane was melted in 400 g of methanol to obtain 2
The temperature was maintained at 0 ° C (solution A). Meanwhile, 900 g of methanol and 110 parts of water
g, add 243 g of 28% aqueous ammonia solution, mix, and 20 ° C
(B liquid). Then, a stirring device was attached to the liquid B, and the liquid A was added while stirring. Immediately after the addition, a hydrolysis reaction and a condensation reaction occurred, and the inside of the reaction system became cloudy. A
After adding the liquid and stirring for 2 hours, 103 g of ethylene glycol was added and heated under reduced pressure to remove excess water, methanol,
Ammonia was distilled off to obtain an ethylene glycol slurry containing 10% concentration of spherical silica fine particles. After drying the ethylene glycol slurry, a photograph was taken with an electron microscope to determine the average particle size and the particle size distribution B value. The average particle size is 0.27 μm, the B value is 1.5, and the particles are uniform spherical particles having a very uniform particle size. 3 of the slurry
An overtreatment was performed using a filter having an overprecision of μm cut, but the filter passability was very good.

(Production of polyester) 100 parts of dimethyl terephthalate and 60 of ethylene glycol
Parts and 0.09 parts of magnesium acetate tetrahydrate are heated in a reactor and heated, and methanol is distilled off to carry out an ester exchange reaction. It takes 4 hours from the start of the reaction to raise the temperature to 230 ° C. The exchange reaction was completed. Then, ethylene glycol slurry containing 0.3% of spherical silica particles having an average particle diameter of 0.27 μm was added, and then 0.04 part of ethyl acid phosphate and 0.035 of antimony trioxide were added.
Polyethylene terephthalate resin having an intrinsic viscosity of 0.66 was obtained by adding double the amount and conducting polycondensation for 4 hours.

The obtained polyester resin was heated and dried at 180 ° C. in a nitrogen atmosphere for 6 hours, and then extruded into a sheet by an extruder to prepare an amorphous sheet of 150 μm by an electrostatic contact cooling method. Next, this amorphous sheet was stretched 4 times in the longitudinal direction and 3.5 times in the transverse direction, and then re-stretched 1.07 times in the longitudinal direction to obtain a biaxially stretched film having a thickness of 10 μm which was reinforced in the longitudinal direction. The characteristics of the obtained film are shown in Table 1. The percentage of non-defective products of μd in the table is the percentage of films having μd within the allowable range of ± 5% with respect to the sampled film. The film is μd
The yield rate, the number of breaks, and the white powder were all acceptable levels.

Examples 2 and 3 Example 1 was repeated except that spherical silica particles obtained by changing the mixing ratio of methanol, water and aqueous ammonia solution in the solution B in Example 1 were used and the re-stretching ratio was 1.12 times. The characteristics of the stretched polyester film obtained in the same manner as
Shown in the table.

The films obtained in Examples 2 and 3 were all in the acceptable level in terms of μd non-defective rate, number of breaks, and white powder.

Example 4 A polyethylene-2,6-naphthalate pellet obtained by the same method as in Example 1 and containing 0.3% of spherical silica having an average particle size of 0.27 μm was dried at 170 ° C. under nitrogen for 6 hours.
This polyester was melt extruded in a conventional manner to give a thickness of 13
An unstretched film of 2 μm was prepared, stretched 4.5 times in the machine direction, stretched 4 times in the cross direction, and restretched 1.05 times in the machine direction to obtain a biaxially stretched film with a thickness of 7 μm reinforced in the machine direction. The characteristics of the obtained film are shown in Table 1. The film is μ
d) The rate of non-defective products, the number of breaks, and white powder were all acceptable levels.

Comparative Examples 1 and 2 Table 1 shows the properties of the film obtained by the same method as in Example 1 except that the inert particles in the polyester were calcium carbonate and titanium dioxide. Neither of the films had a satisfactory .mu.d ratio, the number of breaks, or white powder was satisfactory.

Comparative Example 3 Table 1 shows the characteristics of the film obtained by the same method as in Comparative Example 1 except that the re-stretching was not performed. The film is μd
Yield rate, although the breaking number is acceptable level, F ₅ value is low,
Also, the white powder was not satisfactory.

Comparative Example 4 The characteristics of the film obtained in the same manner as in Example 4 except that the inert particles in the polyester were changed to calcium carbonate
Shown in the table. The film was not satisfactory in terms of μd non-defective rate, number of breaks, and white powder.

[Effects of the Invention] According to the present invention described above, a polyester film having substantially the same physical properties in the width direction of the film, in particular, the surface roughness and the friction coefficient, and having high strength is provided.

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Claims (2)

[Claims] 1. A substantially amorphous, average particle size of 0, obtained by subjecting an alkoxysilane to a hydrolysis reaction and a condensation reaction.
The value of [d ₁₀ / d ₉₀ ] defined below of 01 to 3.0 μm is 1.1 to 2.7
A polyester film containing 0.001 to 5% by weight of spherical silica fine particles in the range of and having an F ₅ value in the longitudinal direction of 12 kg / mm ² or more. (The particle diameters d ₁₀ and d ₉₀ in the above formula are measured by an electron microscope, and the numbers are counted from the large particle side to obtain 10% and 90% of the total number.
This is the particle size at. ) 2. The average particle diameter of the spherical silica fine particles is 0.05 to 2.
The polyester film according to claim 1, which has a thickness of 0 μm and a content of 0.01 to 3% by weight.