JP3360473B2 - Film made of polyester composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to either <br/> Ranaru polyester film polyester compositions, and more particularly polyester oligomer is suppressed to deposit on the film surface, and the running property is improved, in particular magnetic recording medium And a biaxially oriented polyester film.

[0002]

2. Description of the Related Art Polyesters mainly composed of polyethylene terephthalate are widely used as fibers, films and other molded articles because of their excellent physical and chemical properties.

However, when polyester is used, for example, as a film for a magnetic recording medium, a ring 3 is formed on the surface of the film.
Polyester oligomers (oligomers) typified by oligomers tend to precipitate, and these oligomers cause output fluctuations when outputting magnetic signals. Therefore, methods for reducing the amount of oligomers in the polyester have been conventionally studied. For example, a method in which polyester is solid-phase polymerized at a melting point or lower (Japanese Patent Application Laid-Open No. Sho 53-101092). In this method, the degree of polymerization of the polyester is increased, so that the load on the extruder during melt extrusion is large. Further, in order to suppress an increase in the degree of polymerization, it has been proposed to heat-treat the polyester in an inert atmosphere at a temperature equal to or lower than the melting point (JP-A-2-29852).
No. 1). Although these methods can reduce the amount of the oligomer deposited on the film surface layer, they require solid-state polymerization and a heat treatment apparatus, which is not economically preferable.

[0004] A method has been proposed in which higher fatty acid esters are contained in polyester to suppress the precipitation of oligomers (Japanese Patent Application Laid-Open No. 61-126165). In this method, the effect of suppressing precipitation of the oligomer is not sufficient, and further, since the higher fatty acid ester contained in the polyester has poor affinity with the polyester, the higher fatty acid ester bleed out has a coarse crater-like shape on the film surface. Disadvantages. In the field where high recording density is required, such as a vapor deposition film for a magnetic medium, such a polyester has a crater itself as a film defect.

Further, dodecylbenzenesulfonic acid and polyalkylene glycol are used in combination for the purpose of preventing static charge (JP-A-52-47071), or lithium dodecylbenzenesulfonate is added to the polyester (Japanese Patent Laid-Open No. Hei 3-47071). 227328).

[0006] Even in these cases, it has not been possible to solve the problems that the effect of suppressing the precipitation of the oligomer is insufficient or that crater-like defects occur. Further, the film containing the polyalkylene glycol has a disadvantage that it is liable to be oxidized and deteriorated.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned disadvantages of the prior art. In particular, when a biaxially oriented film is formed, substantially no crater-like defects on the film surface are present. An object of the present invention is to provide a biaxially oriented polyester film for a magnetic recording medium or the like using a polyester composition capable of suppressing oligomers deposited on a surface layer.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide an aromatic polyester containing an aromatic dicarboxylic acid and an alkylene glycol as main components, wherein the lithium sulfonate represented by the formula (I) is added to the polyester. 0.1-1
0 consists wt% comprising a containing polyester compositions, 1
Deposits on the film surface after aging at 20 ° C for 2 hours
Number of polyester oligomers with a diameter of 0.2 μm or more
Is less than 300 pieces / mm ^2.
Lum R—X—SO ₃ —Li (I) (where R is a linear alkyl group having 5 to 30 carbon atoms, X:
(Indicating an aromatic group).

The polyester in the present invention includes aromatic dicarboxylic acids such as terephthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyldicarboxylic acid and isophthalic acid as acid components, and ethylene glycol, butanediol and cyclohexanedimethanol as glycol components. And the like. In particular,
Examples include polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate. Further, it may be a copolymerized polyester in which two or more kinds of the acid component and the diol component are used in combination,
Other components such as adipic acid, sebacic acid, alkali metal salts of 5-sulfo-isophthalate, trimellitic acid,
A polyester obtained by copolymerizing hydroxybenzoic acid or the like may be used.

The polyester of the present invention can be produced by a conventionally known method. For example, in the case of polyethylene terephthalate (PET), terephthalic acid (TP
A) Esterification of ethylene glycol (EG) directly, or transesterification of dimethyl terephthalate (DMT) and EG to obtain bishydroxyethyl terephthalate and its low polymer (BHT), followed by heating under reduced pressure To remove the EG. At this time, additives such as a catalyst can be optionally used as needed.

The lithium sulfonic acid salt of the present invention may be added at any stage of the polyester production process described above, but it is preferable that the intrinsic viscosity becomes 0 after the transesterification reaction or esterification reaction is substantially completed. When it is less than 0.3, it is particularly preferable because the by-product of diethylene glycol can be suppressed and the compatibility of the metal sulfonic acid salt with the polyester can be enhanced.

In the formula (I) of the present invention, it is essential that the alkyl group represented by R- is straight-chain, that is, has no branched chain. When the alkyl group has a structure having a branched chain, the effect of suppressing the precipitation of the oligomer, which is the object of the present invention, cannot be sufficiently achieved. Of course, an alkyl group having a branched chain may be mixed, but even in this case, a lithium sulfonate having a linear alkyl group as a constituent unit is 0.1 to 10%.
% By weight.

Further, in the formula (I), -X-SO ₃
Lithium aromatic sulfonic acid salt unit represented by -Li,
It may be bonded to any carbon constituting the alkyl group.

The R—X—SO ₃ —Li salt of the present invention will be described in detail by taking lithium dodecylbenzenesulfonate as an example.

A specific example in which a benzenesulfonic acid unit is bonded to the terminal of an alkyl group.

[0016]

Embedded image Specific example in the case where a benzenesulfonic acid unit is bonded to a position other than the terminal of the alkyl group.

Embedded image The alkyl group of the lithium sulfonic acid salt needs to have 5 to 30 carbon atoms. 5 carbon atoms in the alkyl group
When it is in the range of from 30 to 30, the sulfonic acid metal salt is excellent in dispersibility in polyester, and when used in a polyester film, exhibits an effect of preventing the precipitation of oligomers and suppresses crater-like defects. Further, it is preferable because the abrasion resistance of the laminated film is improved. It is particularly preferable that the alkyl group has 7 to 20 carbon atoms from the viewpoint of excellent dispersibility in the polyester and the effect of suppressing the oligomer.

Examples of such lithium sulfonic acid salts include lithium salts such as octylbenzenesulfonic acid, undecylbenzenesulfonic acid, dodecylbenzenesulfonic acid, octadecylbenzenesulfonic acid, and dodecylnaphthalenesulfonic acid. It is not limited.

The polyester composition containing such a lithium sulfonate can be suitably used as a molded article such as a polyester film or a fiber.

In this case, the composition containing the lithium sulfonate may be used as a film as it is, or may be used by blending it with a polyester not containing the lithium sulfonate to a desired concentration. Good.

Specific examples when the composition of the present invention is used as a film will be described. A single-layer film containing the polyester composition of the present invention in the entire polyester film.
A laminated film in which the polyester composition of the present invention is contained in a main layer (inner layer) of a laminated polyester film composed of a main layer and a sub-layer. A laminated film in which the polyester composition of the present invention is contained in at least one side sublayer (outer layer) of the laminated polyester film composed of the main layer and the sublayer is exemplified.

In any of the methods, the effect of suppressing the precipitation of the oligomer is exhibited. However, in the case of the laminated film shown in (1), even if the content of the lithium sulfonate in the whole film is small, it is not intended for the purpose of the present invention. It is particularly preferable because it can effectively control the precipitation of a certain oligomer and furthermore, the surface roughness of the film can be arbitrarily controlled by selecting the insoluble particles to be used together.

Will be described in more detail. A laminated film in which the polyester composition of the present invention is contained in a main layer (inner layer) of a laminated polyester film composed of a main layer and a sub-layer.

In this case, the content of the lithium sulfonate compound in the main layer polyester is preferably 0.05 to 2% by weight, more preferably 0.1 to 1% by weight, based on the polyester constituting the main layer. It is. When the content is in such a range, it is preferable from the viewpoint of the effect of suppressing oligomer precipitation on the film surface and the prevention of the occurrence of crater-like defects.

The sub-layer polyester does not contain a lithium sulfonate salt, or a polyester composition having a content less than that of the main layer polyester is laminated on at least one surface of the main layer. The thickness of the sublayer in this case is 0.005 to 2
μm is preferred. More preferably, it is 0.01 to 1 μm. When the thickness of the sub-layer is in this range, it is preferable from the viewpoint of the effect of suppressing the oligomer precipitation on the film surface layer and the prevention of the occurrence of crater-like defects.

Further, the sub-layer polyester preferably contains particles insoluble in polyester having an average particle diameter of 0.01 to 2 μm, preferably 0.1 to 2.0% by weight. The more preferable average particle diameter of the insoluble particles is 0.02 to 1 μm, more preferably 0.02 to 0.5 μm.
μm. Further, the shape of the insoluble particles is more preferably substantially spherical. When the average particle diameter and the content of the insoluble particles are in the above-mentioned range and the shape is substantially spherical, a large number of uniform and fine projections can be formed on the film surface. This is preferable because the electromagnetic conversion characteristics of the tape can be improved and running properties can be imparted.

A laminated film comprising the polyester composition of the present invention in at least one side sublayer (outer layer) of a laminated polyester film composed of a main layer and a sublayer.

In this case, the content of the lithium sulfonate in the polyester for the sublayer is 0.01 to 2% by weight, preferably 0.1 to 1% by weight, based on the polyester constituting the sublayer. When the content is in such a range, the effect of suppressing the oligomer precipitation on the film surface and the occurrence of crater-like defects are prevented, and furthermore, the film is preferably prevented from being scraped.

The polyester constituting the main layer is preferably a polyester composition containing no lithium sulfonate salt or containing less than the content of the sublayer polyester.
In this case, the thickness of the sublayer is preferably 0.05 to 5 μm.
More preferably, it is 0.1 to 2 μm. When the thickness of the sub-layer is within such a range, it is preferable because the effect of suppressing the oligomer precipitation on the film surface layer and the occurrence of crater-like defects are suppressed, and the film is prevented from being scraped.

Further, the sub-layer polyester contains 0.1 to 10% by weight of substantially insoluble particles which are substantially spherical with respect to the polyester having an average particle diameter of 0.01 to 2 μm so that the film surface can be uniformly formed. Since a large number of fine projections can be formed, the handleability of the film and the electromagnetic conversion characteristics as a tape for a magnetic recording medium are improved, and running properties can be imparted.

Examples of the spherical particles shown as above include inorganic particles such as colloidal silica, spherical alumina, spherical titanium, and spherical aluminum silicate, divinylbenzene-based crosslinked particles,
Examples include, but are not limited to, silicone particles, phenol resin particles, and polymethyl methacrylate resin particles.

In addition to these spherical particles, titanium oxide, silicon oxide, zinc oxide, aluminum oxide, zirconium oxide, iron oxide, aluminum hydroxide, aluminum silicate, magnesia silicate, clay, talc, calcium carbonate, lithium carbonate, Particles such as molybdenum sulfide, zinc sulfide, barium sulfate, calcium sulfate, silicon carbide, and silicon nitride can also be used in combination.

The laminated polyester film of the present invention can be manufactured by a known method. Here, the sublayer polyester is Y,
When the main layer polyester is Z, the configuration of the laminated film is Y / Z for two layers and Y / Z / Y for three layers.

In the case of three layers, the thickness of each of the Y layer constituting the surface layer when the Y _1, Y _2, Y ₁ and Y ₂ may be the same thickness, had a different thickness You may. In any case, the sublayer thickness refers to the total thickness of the Y layer.

The laminated film in the present invention may be a laminated polyester film having four or more layers. Also in this case, the sub-layer polyester Y referred to in the present invention is laminated on the outermost layer.

The polyester film of the present invention can be formed by a conventionally known method. The three-layer Y / Z / Y will be described as an example. In the three-layer merging block having a rectangular laminated portion, in the above case, the polyester composition having a predetermined amount of the lithium sulfonate salt in the main layer and the polyester composition containing the insoluble particles in the double-sided superficial layer laminated portion come. Laminated, in the above case, a polyester composition containing substantially no lithium sulfonate salt in the main layer is laminated such that a polyester composition containing insoluble particles and lithium sulfonate salt comes to the double-sided surface layer laminated portion, After being extruded into a sheet shape from a fish tail-type die, it is cooled and solidified by a casting drum by an electrostatic application casting method to obtain an unstretched sheet. Next, the film is stretched simultaneously or successively in the biaxial direction to form a biaxially oriented film, and then thermally fixed. As the stretching method in the case of sequential stretching, a method of stretching in the longitudinal direction and then stretching in the transverse direction (longitudinal / horizontal stretching), longitudinal / horizontal / longitudinal stretching, and further longitudinal / horizontal / longitudinal / longitudinal stretching is optionally employed. You. The stretching temperature may be substantially the same as that of polyethylene terephthalate alone, but it is preferable to appropriately select the temperature depending on the blending amount of lithium sulfonate. The stretching temperature is close to or higher than the glass transition temperature of the polyester, for example, a longitudinal stretching temperature of 6.
A temperature of 0 to 100 ° C and a lateral stretching temperature of 80 to 120 ° C can be set. The stretching ratio is usually 2.5 to 5 times in the vertical direction and 2.5 to 5 times in the horizontal direction.

Heat setting is performed at a temperature higher than the final stretching temperature.
The temperature and time can be selected according to the content of the lithium sulfonate. Preferably it is 160-220 degreeC, More preferably, it is 180-210 degreeC. When the heat setting temperature is in the above-mentioned range, excellent suppression of oligomer precipitation is exhibited.

The biaxially oriented polyester film thus obtained can significantly reduce the number of oligomers deposited on the surface of the film. As a method for clarifying the effect of the present invention, the biaxially oriented polyester film of the present invention can be evaluated by the number of oligomers having a diameter of 0.2 μm or more that precipitate on the film surface after aging at 120 ° C. for 2 hours in an oven. . When the method of the present invention is not used, the number of oligomers is 1000 / mm ² or more, whereas the number of oligomers is 300 / mm 2 according to the method of the present invention.
It becomes possible to make it less than ² .

[0038] The polyester film of the present invention may further contain additives such as an antioxidant, an ultraviolet absorber, a coloring agent, a lubricant, and a pigment, if necessary.

[0039]

The present invention will be described in more detail with reference to the following examples. In addition, "part" in an Example shows a weight part. Various physical properties and characteristics in the examples were measured by the following methods.

(1) Intrinsic viscosity [η] of polymer Measured at 25 ° C. using o-chlorophenol as a solvent.

(2) Number of Surface-Deposited Oligomers and Craters
After aging in an oven at 20 ° C. for 2 hours, platinum palladium was deposited. Using an electron microscope, count the number of oligomers of 0.2 μm or more and the number of craters of 0.5 μm or more using an electron microscope, indicate the number per 1 mm ² , and evaluate them according to the following criteria. did. Number of oligomers Primary Less than 100 Secondary less than 100 to 200 Tertiary 200 to less than 300 Quaternary 300 or more Crater number Primary less than 200 Secondary 200 to less than 400 Tertiary 400 to less than 600 Quaternary 600 or more

(3) Film Average Surface Roughness (Ra) It was measured by a surface roughness meter ET-10 manufactured by Kosaka Laboratory. Using stylus type surface roughness, stylus tip radius 0.5μ
m, the stylus load was 5 mg, the measurement length was 1.2 mm, and the cutoff was 0.008 mm.

(4) Film Coefficient of Friction (μk) Tape Run Tester SFT-70, Yokohama System Research Institute
The initial coefficient of friction with the metal guide pin (SUS27) was determined using type 0 and indicated in μk.

(5) Average Particle Diameter of Particles in Film The film is etched with plasma to ash the polyester and expose the particles. This was observed with a scanning electron microscope, and image processing was performed on 5,000 or more particles, and the average number equivalent diameter (nm) of the particles was determined as the average particle diameter.

(6) Sublayer Thickness (μm) of Laminated Film Several levels of polyester having a known particle content are prepared in advance, and an element caused by the particles (SIMS) is prepared using a secondary ion mass spectrometer (SIMS). M) and the concentration ratio (M / C) of the carbon element (C) of the polyester are determined.

Next, the M / C is measured from the polyester surface layer on the sublayer side in the depth direction of the film, and the concentration of the particles can be known.

The M / C measured as described above shows a high value on the film surface layer, but falls sharply (inflection point X) as it approaches the main layer, and then stabilizes at a constant value (inflection point Y). ). X and Y are connected by a straight line, and the distance from the value of 1/2 to the surface of the sub-layer is defined as the lamination thickness.

Reference Example The polyester used in each Example was produced as follows.

Polyester I (insoluble particles, sulfonic acid
Polyester without lithium salt) 100 parts of dimethyl terephthalate, ethylene glycol 7
To 0 parts, 0.06 parts of magnesium acetate tetrahydrate was added, and the temperature was gradually raised from 150 ° C. to 230 ° C. over 4 hours to carry out a transesterification reaction. After adding 0.03 part of germanium dioxide and 0.025 part of phosphoric acid trimethyl ester to the obtained product, the temperature of the reaction system was gradually increased and the pressure was reduced, and finally, 280 ° C. and 0.5 mmHg at 0.5 mmHg were added. Polyester I having an intrinsic viscosity of 0.625 after polycondensation reaction for 5 hours
I got

Polyester II (lithium sulfonic acid salt
Polyesters) After complete to transesterification reaction in exactly the same manner as in Experiment No1 polyester I, 10 wt% dodecylbenzenesulfonic acid lithium salt of linear silicone (Toshiba Silicone TSF4
33) Polyester having an intrinsic viscosity of 0.610 by performing a polycondensation reaction in exactly the same manner as in Example 1 except that 0.1% was added.
I got II.

Experiment Nos. 2 to 6 The addition amount of the linear lithium dodecylbenzenesulfonate used in Experiment No. 1 was 0.1% in Experiment No.
o3: 1.0%, Experiment No. 4: 5.0%, Experiment No. 5;
Except for 0.005%, Experiment No. 6; 12.0%,
A polyester was obtained in exactly the same manner as in Experiment No. 1. In experiment No. 6, the inside of the reaction system foamed remarkably from the point of time when the polycondensation reaction was started, and a trouble occurred in which the reaction product was distilled out of the reaction system. In other experiments Nos. 2 to 5, polymers could be collected without any problem.

Polyester III (containing colloidal silica)
Polyester) In polyester I, a polycondensation reaction is carried out in the same manner as polyester I except that 1% by weight of colloidal silica having a primary particle diameter of 70 nm is added after addition of trimethyl phosphate, and polyester having an intrinsic viscosity of 0.615.
I got III. The average particle size of the colloidal silica in the polyester was 70 nm.

Polyester IV (Polyester containing alumina particles )
Example of stell) In polyester I, a polycondensation reaction is carried out in the same manner as in polyester I, except that trimethyl phosphate is added and then 2% by weight of alumina is added.
615 polyester IV was obtained. The average secondary particle diameter of alumina in the polyester was 30 nm.

Polyester V (crosslinked polystyrene particles
Containing Polyester) The water slurry of the polyester obtained in Example 1 and the crosslinked polystyrene particles was simultaneously and continuously supplied to a vented twin-screw kneader. The generated water was continuously removed outside the kneader. The polymer after kneading contained 2% by weight of crosslinked polystyrene particles having an average particle diameter of 800 nm. The intrinsic viscosity was 0.610.

Example 1 In a three-layer merging block provided with a rectangular laminated portion adjusted to 290 ° C., 95 parts of polyester I and polyester II were used for the main layer.
(Experiment No. 1) 5 parts, polyester III on both side sublayers
Was melt-extruded from a fish-tailed die, and cooled and solidified by a rotating body by an electrostatic application casting method to obtain an unstretched sheet. Next, the film was stretched 3.5 times in the longitudinal direction at 80 ° C., and further 3.8 times in the transverse direction at 90 ° C. Then 190 ° C
For 8 seconds to obtain a biaxially oriented film having a thickness of 13 μm. This film was a 13-μm-thick biaxially oriented laminated film in which sub-layer films were laminated on both sides of the main-layer film at a thickness of 0.05 μm (total 0.1 μm). This film was good in both the occurrence of precipitated oligomers and craters. Moreover, because of its excellent surface flatness, it was a biaxially stretched film suitable as a film for vapor deposition (Tables 1 and 4).

Examples 2 to 4 and Comparative Examples 1 and 2 Experiments of Polyester II The polymers of Nos. 2 to 4 were used as the main layer polyester (adjusted with polyester I so that the lithium dodecylbenzenesulfonate salt was 0.1%). 2) A biaxially oriented laminated film in which sub-layer films were laminated on both sides of the main layer film in a thickness of 0.05 μm (total 0.1 μm) in exactly the same manner as in Example 1. This film was excellent in both generation of precipitated oligomers and craters (Tables 1 and 4).

On the other hand, the film using Experiment No. 5 (addition amount of lithium dodecylbenzenesulfonate 0.005%) was unsatisfactory in suppressing the oligomers deposited (Comparative Example 1). In Experiment No. 6, the production of the film was stopped (Comparative Example 2) because it was difficult to industrially produce the reaction product due to the problem that the reactant was distilled out of the reaction system.

Examples 5 to 9 The same procedures as in Example 1 were carried out except that the content of the linear lithium dodecylbenzenesulfonate in the main layer was changed to change the mixing ratio of polyester I and polyester II. In the same manner as in the above, a biaxially stretched laminated film having a thickness of 13 μm, in which sub-layer films were laminated on both sides of the main layer film in a thickness of 0.05 μm (a total of 0.1 μm), was obtained. The results are shown in Table 1. In each case, the generation of precipitated oligomers and craters was good, and the surface was excellent in flatness. Therefore, the biaxially oriented films were suitable as films for vapor deposition (Tables 1 and 4).

Examples 10 to 12 A biaxially oriented laminated film having a thickness of 13 μm was obtained in the same manner as in Example 1 except that the thickness of the sublayer was changed. In each case, both the precipitated oligomer and the crater were good films (Tables 2 and 4).

Examples 13 and 14 A biaxially oriented laminated film was obtained in exactly the same manner as in Example 1 except that the amount of polyester III was changed. The film had excellent flatness of the deposited oligomer, crater and film (Example 13). Further, a biaxially oriented laminated film was obtained in exactly the same manner as in Example 1 except that spherical silica of 500 nm was used instead of the colloidal silica of 70 nm used for polyester III. This film was a film having an appropriate surface roughness and excellent slipperiness (Example 1).
4) (Table 2, Table 4).

Examples 15 to 18 and Comparative Example 3 In Example 1, polyester I was used for the main layer and polyester I, polyester II (Experiment No. 1), polyester IV, and polyester V were blended for the sub-layer to form a straight chain. Biaxially oriented films having different contents of lithium dodecylsulfonate and crosslinked polystyrene spherical particles and different sublayer thickness were obtained. Table 2 shows the content of the lithium dodecyl sulfonate, alumina, and crosslinked polystyrene spherical particles and the thickness of the sublayer in the sublayer. Even when lithium dodecylsulfonate was contained in the sub-layer, the film was excellent in both generation of precipitated oligomers and craters. Further, the biaxially oriented film was excellent in lubricity. On the other hand, when the content of the linear lithium dodecylbenzenesulfonate in the sublayer polyester was less than the range of the present invention, the precipitation of the oligomer was hardly suppressed (Comparative Example 3) (Tables 2 and 4).

Comparative Example 4 Polyester II was completely the same as Polyester II except that 10 parts of lithium dodecylbenzenesulfonate having an alkyl group having a branched chain were used instead of the linear lithium dodecylbenzenesulfonate used in Polyester II. To obtain a polyester composition. A biaxially oriented laminated film having a thickness of 13 μm was prepared by laminating sub-layer films on both surfaces of the main film in a thickness of 0.5 μm (total 1.0 μm) on both surfaces of the main film in the same manner as in Example 1 using this polymer. This film was a precipitated oligomer fourth class and a crater second class (Tables 3 and 4).

Comparative Examples 5 to 10 In the same manner as in Example 1 except that the compounds shown in Table 3 were used instead of the linear lithium dodecylbenzenesulfonate used in Polyester II, both surfaces of the main layer film were used. Sub-layer film is laminated 0.05μm each (total 0.1μm)
This was a 13 μm-thick biaxially oriented laminated film.
In each case, the preferred biaxially oriented laminated films could not be obtained due to insufficient suppression of oligomer precipitation and frequent occurrence of craters (Tables 3 and 4).

Examples 19 to 21 and Comparative Examples 11 to 12 In place of the lithium linear dodecylbenzenesulfonate (alkyl group having 12 carbon atoms) used in Example 1, the linear alkyl group had 8, 18 carbon atoms. In the same manner as in Example 1 except that the lithium sulfonate salt consisting of Nos. 26, 4, and 31 was used, sub-layer films were formed on both sides of the main-layer film.
A 13 μm-thick biaxially oriented laminated film laminated by μm (total 0.1 μm) was obtained. When the number of carbon atoms of the alkyl group is less than the range of the present invention, the effect of suppressing the organoma is not observed (Comparative Example 11). On the other hand, when the number of carbon atoms in the alkyl group exceeded the range of the present invention, craters frequently occurred and the film was a biaxially oriented laminated film that could not be used as a film for a magnetic recording medium (Comparative Example 12) (Table 3). , Table 4).

Example 22 In Example 1, the supply of the sub-layer polyester was stopped to obtain a single-layer film.

The composition of the polyester is polyester I 7
After melt extruding a composition obtained by blending 0 parts, 5 parts of polyester II, 15 parts of polyester IV, and 10 parts of polyester V, the composition was cooled and solidified by a rotating body by an electrostatic application casting method to obtain an unstretched sheet. Next, the film was stretched 3.5 times in the longitudinal direction at 80 ° C., and further 3.8 times in the transverse direction at 90 ° C. Next, the film was heat-set at 190 ° C. for 8 seconds to obtain a biaxially oriented single-layer film having a thickness of 13 μm. This film is composed of precipitated oligomer (primary), crater generation (primary), Ra20, μk
0.6, which is an excellent biaxially oriented film.

[0067]

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[0068]

The present invention is a polyester composition containing a specific lithium sulfonate. By incorporating the composition into the biaxially oriented polyester film in a specific amount, it is possible to suppress the polyester oligomer precipitated on the surface layer of the film, and since the lithium sulfonic acid salt of the present invention is preferably compatible with the polyester, the bleeding is applied to the surface layer of the film. Even when the film is out, no crater-like defects occur on the film surface.

Because of these properties, the effects of the polyester film of the present invention are more remarkably exhibited when used in various fields of films, particularly in the field of magnetic recording media such as magnetic tape base films.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L 67/00-67/02

Claims (12)

(57) [Claims] 1. An aromatic polyester having an aromatic dicarboxylic acid and an alkylene glycol as main components,
It consists in the polyester (I) lithium sulfonate of formula polyester composition comprising a 0.1 to 10 wt% free, off after 2 hours aging at 120 ° C.
Polyester with a diameter of 0.2μm or more deposited on the film surface
That the number of oligomers is less than 300 / mm ²
Characteristic film. R—X—SO ₃ —Li (I) (where, R: a linear alkyl group having 5 to 30 carbon atoms, X:
Represents an aromatic group). In wherein insoluble to polyester, the average particle diameter comprising 0.1 to 10.0 wt% of particles of 0.01~2μm the polyester according to claim 1, wherein the full
Film . Off of claim 2 wherein insoluble particles of the polyester is characterized by a substantially spherical
Film . 4. The method according to claim 2, wherein the lithium sulfonic acid salt according to claim 1 is contained in an amount of 0.01 to 2% by weight.
Or the film according to claim 3. 5. A laminated polyester film comprising (1) a main layer and a sub-layer, wherein (2) a sub-layer is laminated on at least one surface of the main layer, and (3) a main layer comprising the formula (I) The polyester composition according to claim 1, wherein the content of the lithium sulfonate represented by the formula (1) is 0.05 to 2% by weight, (4) the polyester constituting the sub-layer is insoluble in the polyester, and the particles having a particle size 0.01~2μm contains 0.1 to 10.0 wt% relative to polyester, moreover Ri sublayer thickness 0.005~2μm der, further
On the film surface after aging for 2 hours at 120 ° C
Precipitation of polyester oligomers with a diameter of 0.2 μm or more
A film , wherein the number is less than 300 / mm ² . R—X—SO ₃ —Li (I) (where, R: a linear alkyl group having 5 to 30 carbon atoms, X:
Represents an aromatic group). 6. The film according to claim 5 , wherein the particles insoluble in the polyester are substantially spherical. 7. A laminated polyester film composed of (1) a main layer and a sub-layer, wherein (2) a sub-layer is laminated on at least one surface of the main layer, and (3) a sub-layer of the formula (I) The content of the lithium sulfonate represented by the formula is 0.01 to 2% by weight, and the particles having an average particle diameter of 0.01 to 2 μm are insoluble in the polyester in an amount of 0.1 to 2%.
10.0 consists polyester composition of claim 1 containing by weight%, (4) sublayer thickness <br/> Oh Ri at 0.05 to 5 [mu] m, and after 2 hours aging at 120 ° C. Fill
Polyester with a diameter of 0.2μm or more
A film, wherein the number of ligomas is less than 300 / mm ² . R—X—SO ₃ —Li (I) (where, R: a linear alkyl group having 5 to 30 carbon atoms, X:
Represents an aromatic group). 8. The particles insoluble in polyester,
The film of claim 7 , wherein the film is substantially spherical. 9. biaxially oriented film for a magnetic recording medium according to any one of claims 1-8. 10. A product composed of a main layer and a sub-layer.
(2) less of the main layer
In both cases, a sublayer is laminated on one side, and (3) the main layer is represented by the formula (I).
The content of the lithium sulfonate is 0.05 to 2 times
% Of the polyester composition according to claim 1.
(4) The polyester constituting the sub-layer is polyester
Particles having an average particle diameter of 0.01 to 2 μm, which are insoluble in
0.1-10.0% by weight of polyester based on polyester
And that the sublayer thickness is 0.005 to 2 μm.
Characteristic film. RX-SO _Three -Li (I) (However, R: a linear alkyl group having 5 to 30 carbon atoms, X:
Represents an aromatic group). 11. Particles insoluble in polyester
11. The method of claim 10, wherein the shape is substantially spherical.
Film. 12. The magnetic recording device according to claim 10, wherein:
Biaxially oriented film for recording media.