JP3075932B2 - Polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film, and more particularly to a polyester film having excellent abrasion resistance and scratch resistance and particularly useful as a base film of a magnetic recording medium.

[0002]

2. Description of the Related Art Biaxially oriented polyester films represented by polyethylene terephthalate films are widely used for various uses, especially for magnetic recording media, because of their excellent physical and chemical properties.

[0003] In a biaxially oriented polyester film, its slipperiness and abrasion resistance are major factors that affect the workability of the film manufacturing and processing steps and the product quality. If these are insufficient, for example, when a magnetic layer is applied to the biaxially oriented polyester film surface and used as a magnetic tape, the friction between the coating roll and the film surface is severe, and shaving powder is generated,
Scratch occurs on the film surface. Also, when used for VTRs and data cartridges, shavings and scratches are generated in the process of high-speed winding into a cassette, causing dropout.

In particular, in VTR applications, metal guides or plastic guides whose surfaces are not sufficiently finished may be used for guide posts fixed in a cassette for the purpose of cost reduction recently. rough.

In order to solve such a problem, a method of adding fine particles having a high Mohs hardness to reduce the damage (for example, Japanese Patent Application Laid-Open No. 1-306220) has been proposed. JP-A-3-6239) is known.

[0006] However, even if such a method is used, if the fine powder itself is not sufficiently dispersed in the film, such abrasion resistance and scratch resistance may not be sufficiently exhibited.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and has a good scratch resistance and abrasion resistance even for a metal guide or a plastic guide having a rough surface. It is to provide a useful polyester film.

[0008]

According to the present invention, an alkali metal salt of a divalent or trivalent polyvalent carboxylic acid having 4 to 9 carbon atoms having an alkali metal atomic weight of 0.1 to 4% is provided. Surface-treated with 0.5 to 2.0% by weight (based on alumina particles) having an average secondary particle size of 0.01 to 0.5 μm
Of alumina fine particles,
Achieved by a polyester film containing 1.0% by weight of dispersion.

Hereinafter, the present invention will be described in detail, which will clarify other objects, configurations, advantages and effects of the present invention.

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, especially film forming by melt molding.

Examples of the aromatic dicarboxylic acid include terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, diphenoxyethanedicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenylketonedicarboxylic acid, and anthracenedicarboxylic acid.

The aliphatic glycol is, for example, a polymethylene glycol having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol or the like, or cyclohexanedimethanol. Alicyclic diols and the like can be mentioned.

In the present invention, as the polyester, for example, those containing alkylene terephthalate and / or alkylene naphthalenedicarboxylate as a main repeating unit are preferably used.

Among such polyesters, in particular, polyethylene terephthalate and polyethylene-2,6-naphthalenedicarboxylate as well as, for example, terephthalic acid and / or 2,6-naphthalenedicarboxylic acid account for at least 80 mol% of all dicarboxylic acid components. A copolymer which is an acid and 80% by mole or more of the total glycol component is ethylene glycol is preferred. At that time, 20 mol% or less of the total acid component can be the above-mentioned aromatic dicarboxylic acids other than terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid. Acid; an alicyclic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid;
In addition, 20 mol% or less of the total glycol component can be the above-mentioned glycol other than ethylene glycol. For example, aromatic diols such as hydroquinone, resorcin, and 2,2-bis (4-hydroxyphenyl) propane; Aliphatic diols having an aromatic ring such as 1,4-dihydroxydimethylbenzene; and polyalkylene glycols (polyoxyalkylene glycols) such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol.

Further, the polyester in the present invention includes:
For example, aromatic oxyacids such as hydroxybenzoic acid, ω-
Also included are those in which a component derived from an oxycarboxylic acid such as an aliphatic oxyacid such as hydroxycaproic acid is copolymerized or bonded at 20 mol% or less based on the total amount of the dicarboxylic acid component and the oxycarboxylic acid component.

Further, the polyester in the present invention may be used in an amount in a range substantially linear, for example, an amount of 2 mol% or less based on the total acid components, in a polycarboxylic acid or polyhydroxy compound having three or more functional groups, for example, trimellit. Those obtained by copolymerizing an acid, pentaerthritol and the like are also included.

The above polyesters are known per se,
And it can be manufactured by a method known per se.

The above-mentioned polyester preferably has an intrinsic viscosity of about 0.4 to about 0.9 (dl / g) measured at 35 ° C. as a solution in o-chlorophenol.

In the present invention, the alumina fine particles dispersed and contained in the polyester are preferably an alkali metal salt of a divalent or trivalent polycarboxylic acid having 4 to 9 carbon atoms (hereinafter sometimes referred to as an alkali metal salt compound). It is necessary that the fine particles have a mean secondary particle diameter of 0.01 to 0.5 μm and have been surface-treated.

The crystal form (crystal form) of the alumina fine particles is arbitrary, but δ-type, γ-type or θ-type is preferred.
Molds are preferred.

The alkali metal salt compound in the present invention may be any of a mono-alkali metal salt, a dialkali metal salt and a tri-alkali metal salt (in the case of a trivalent polycarboxylic acid). Sodium and potassium are preferable as the alkali metal. Aliphatic polycarboxylic acid has a carbon number 4-9, a polyvalent carboxylic acid alicyclic or aromatic, such as succinic
Acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, tartaric acid, maleic acid, fumaric acid,
1,4-cyclohexanedicarboxylic acid, terephthalic acid,
Isophthalic acid and the like can be mentioned. More specific compounds include, for example, dipotassium succinate, disodium succinate, sodium potassium succinate, potassium hydrogen succinate, sodium hydrogen succinate, dipotassium maleate, disodium maleate, sodium potassium maleate, Potassium tartrate, disodium tartrate, sodium potassium tartrate, potassium hydrogen tartrate, sodium hydrogen tartrate, potassium adipic acid, disodium adipate, potassium dihydrogen citrate, potassium dihydrogen citrate, potassium potassium citrate, potassium citrate, citric acid 2
Preferred examples include sodium hydrogen, disodium hydrogen citrate, trisodium citrate, dipotassium terephthalate, disodium terephthalate and the like. These may be hydrates. Further, the carboxyl group not forming an alkali metal base may be a free carboxyl group or may form an ester. Of these, alkali metal salts of divalent carboxylic acids are preferred, and dialkali metal salts are more preferred.

When the number of carbon atoms of the polyvalent carboxylic acid is increased, the molecular weight is increased, and the dispersing effect becomes insufficient, or the use of a large amount is not preferred. Further, when the carboxylic acid is a monovalent carboxylic acid, the dispersing effect is insufficient, and the amount of the carboxylic acid needs to be greatly increased. Is unfavorable.

In the present invention, the alkali metal salt compound is
With respect to the alumina fine particles, an alkali metal atomic weight of 0.
It is necessary to use from 0.5 to 2.0% by weight , preferably from 0.5 to 2.0% by weight .
3 to 2.0% by weight is used. When the amount is less than 0.05% by weight, the dispersing effect is insufficient. On the other hand, when the amount exceeds 2.0% by weight, phenomena such as deterioration of scratch resistance and yellowing of the film color are observed. Is not preferred.

The method of treating the surface of the alumina fine particles with the alkali metal salt compound is not particularly limited, but the surface treatment is carried out by mixing and crushing the compound and the alumina fine particles in a ball mill or the like which is frequently used in dry crushing. How and wet
When the alumina fine particles are crushed with a glycol slurry using a stirring medium type sand mill or the like which is commonly used in the formula crushing, a method of performing a surface treatment by mixing and crushing the compound is preferably used. These can be combined with purification means such as commonly used filtration or removal of coarse particles by classification or the like, and are sometimes preferable.

The average secondary particle diameter of the alumina fine particles surface-treated with an alkali metal salt compound is preferably 0.01 to 0.5 μm. If the particle size exceeds 0.5 μm, the generation of shavings increases, which is not preferable. The primary particle size of the alumina fine particles is 0.02 μm or less, and more preferably 0.005 to 0.02.
μm is preferred.

The use of alumina fine particles surface-treated with an alkali metal salt of a polycarboxylic acid according to the present invention can greatly improve the dispersibility in a film and improve the abrasion resistance and scratch resistance of the film. I can do it. The amount of the alumina fine particles is 0.05 to
The content of 1.0% by weight is preferable from the viewpoint of effects and economy.

In the present invention, if desired, inert particles having an average particle size of 0.05 to 2 μm can be blended with the polyester film in addition to the alumina fine particles.
Due to the presence of inert particles other than the alumina fine particles, more excellent results are obtained in the scratch resistance and abrasion resistance of the polyester film, the handleability in the process of manufacturing the film is improved, and the film is further subjected to magnetic recording. The runnability when used as a medium base film is improved. However, an inert particle having an excessively large average particle diameter is not preferable because the surface flatness is deteriorated and the electromagnetic conversion characteristics of the magnetic recording medium are reduced.

A preferable result is obtained when the amount of such inert particles is 0.01 to 2.0% by weight based on the polyester.

The type of the inert particles is not particularly limited, and examples thereof include inorganic inert particles such as calcium carbonate, silicon dioxide, titanium oxide, aluminum oxide, and kaolin; and organic inert materials such as silicone resin and cross-linked polystyrene. Particles and particles internally deposited by a polymerization catalyst can be used.

The polyester film of the present invention is preferably a biaxially oriented film, for example, from Tm to (Tm + 70).
° C (where Tm is the melting point of the polyester)
Extrude the polyester with an intrinsic viscosity of 0.35 to 0.9
(Dl / g) of the unstretched film, and the unstretched film is uniaxially (longitudinal or transverse) (Tg-10) to
The film is stretched at a temperature of (Tg + 70) ° C. (here, Tg: glass transition temperature of polyester) at a magnification of 2.5 to 5.0 times, and then in a direction perpendicular to the above stretching direction (the first stage stretching is the longitudinal direction). In the case, the second stretching is in the transverse direction).
It can be manufactured by stretching at a temperature of ~ (Tg + 70) ° C at a magnification of 2.5 to 5.0 times. In this case, the area stretching ratio is preferably 9 to 22 times, more preferably 12 to 22 times. The stretching means may be either simultaneous biaxial stretching or sequential biaxial stretching.

Further, the obtained film was (Tg + 7
0) to Tm (° C.). For example, for polyethylene terephthalate film, 1
It is preferable to heat set at 90 to 230 ° C. The heat fixing time is, for example, 1 to 60 seconds.

[0032]

The present invention will be further described with reference to the following examples. In addition, each characteristic in the examples was obtained or evaluated by the following method.

(1) Average particle size of particles (i) When obtaining average particle size from granules or slurry CP-50 Centrifugal Particle Size Analyzer (Centrifugal Particle S) manufactured by Shimadzu Corporation
The particle size corresponding to 50% by mass was read from the integrated curve of the particle size calculated based on the centrifugal sedimentation curve obtained using the ize Analyzer) and the abundance of the particles having the particle size. Particle size (book “Granularity measurement technology”, published by Nikkan Kogyo Shimbun, 1975, pages 242 to 24)
7). (Ii) In the case of particles in the film A small piece of the sample film is fixed to a sample stage for a scanning electron microscope, and a sputtering device (JFC-
The film surface is subjected to ion etching under the following conditions using a 1100 type ion etching apparatus). The conditions were as follows: the sample was placed in a bell jar, the degree of vacuum was raised to a vacuum state of about 10 ⁻³ Torr, the voltage was 0.25 KV, and the current was 1
Perform ion etching at 2.5 mA for about 10 minutes. Further, the film surface was subjected to gold sputtering by the same apparatus, and 50,000 to 10,000 by a scanning electron microscope.
Observed at × 2, the equivalent spherical diameter distribution of at least 100 particles is determined by Luzex 500 manufactured by Nippon Regulator Co., Ltd., and calculated from the point of 50% by weight integration.

(2) Slurry Viscosity The viscosity of a 20% by weight alumina-containing ethylene glycol slurry is measured at 30 ° C. using a single cylindrical viscometer (Vismethron, VS-A1) manufactured by Shibaura System Co., Ltd.

(3) Abrasion resistance and scratch resistance In an apparatus used for measuring a running friction coefficient μk, a film is slit with a tape slit to a width of 1/2 inch, a winding angle is 30 degrees, and a speed of 300 m / min. Then, the vehicle is run for 200 m so that the inlet tension becomes 50 g. Evaluation is made of the shavings adhering to the fixed rod after running and the scratches of the tape after running. At this time, a 6 mmφ tape guide (surface roughness Ra = 0.15 μm) with insufficient surface finish obtained by bending a SUS sintered plate into a cylindrical shape is used as a fixing rod.

<Judgment of shavings> A: No shavings were observed at all. A: Sharpenings were slightly observed. Δ: Sharpening at a glance was recognized.

<Scratch Judgment> A: No scratches are observed. O: 1 to 5 scratches are observed. Δ: 6 to 15 scratches are observed. X: 16 or more scratches are observed.

[Examples 1 to 5] <Method for Producing Master Polymer Pellets Containing Alumina Fine Particles> The surface treatment of alumina fine particles with an alkali metal salt compound (surface treating agent) was carried out by adding an alkali metal salt compound shown in Table 1 to ethylene glycol. A primary particle size is added and mixed with aggregated particles of θ-type alumina fine particles having a diameter of 20 nm, and 0.8 mm
The average secondary particle size of the alumina fine particles is 0.2μ with a 5 liter sand glider filled with φ glass beads.
m. At this time, the concentration of the alumina fine particles in the slurry was 20% by weight, and the amount of the alkali metal compound added to the alumina fine particles (as the alkali metal atomic weight) is shown in Table 1. The obtained slurry was further filtered through a filter having a mesh size of 5 μm.

Dimethyl terephthalate and ethylene glycol are subjected to a transesterification reaction by adding manganese acetate as a transesterification catalyst and antimony trioxide as a polymerization catalyst. During the reaction, a slurry of the alumina fine particles prepared as above is mixed with polyester. Fine particles were added in such an amount as to give 1% by weight. After the reaction was substantially completed, phosphorous acid was added as a stabilizer. Next, the reaction product was subjected to a polycondensation reaction by a conventional method to produce master pellets containing alumina particles having an intrinsic viscosity (orthochlorophenol: 35 ° C.) of 0.62 (dl / g).

<Method for Producing Polyester Film> A master pellet containing alumina particles produced by the above method,
Separately, polyethylene terephthalate master pellets of each lubricant type containing other lubricant particles and polyethylene terephthalate pellets containing no lubricant particles, produced by a conventional method, were mixed at a ratio such that the content shown in Table 1 was obtained. Then, after drying at 170 ° C. for 3 hours, it is supplied to an extruder hopper and melted at a melting temperature of 280 to 300 ° C.,
The molten polymer was extruded through a 1 mm slit die onto a rotating cooling drum having a surface finish of about 0.3 s and a surface temperature of 20 ° C. to obtain a 200 μm unstretched film.

The unstretched film thus obtained is preheated at 75 ° C., and is further moved between low-speed and high-speed rolls by 15 m.
m and heated by one IR heater having a surface temperature of 900 ° C. from above, stretched 3.6 times, quenched, and then supplied to a stenter and stretched 3.9 times horizontally at 105 ° C. .
The obtained biaxially oriented film was heat-set at a temperature of 205 ° C. for 5 seconds to obtain a heat-set biaxially oriented film having a thickness of 14 μm. Table 1 shows the properties of this film.

Example 6 Using an alkali metal salt compound shown in Table 1, dimethyl-2,6-naphthalenedicarboxylate in place of dimethyl terephthalate, the surface temperature of a rotary cooling drum was 60 ° C. The biaxially oriented film was obtained in the same manner as in Example 1 except that the preheating temperature was 120 ° C., the surface temperature of the infrared heater was 950 ° C., the transverse stretching temperature was 125 ° C., and the heat setting was 215 ° C. for 10 seconds. Was. Table 1 shows the properties of this film.

Comparative Examples 1 to 3 The same procedures as in Example 1 were carried out except that the types and amounts of the alkali metal compounds shown in Table 2 were used as surface treatment agents. Table 2 shows the characteristics of the obtained film.
Shown in

Comparative Example 4 Example 6 was repeated except that the kind and amount of the alkali metal compound shown in Table 2 were used as the surface treating agent.
Was performed in the same manner as described above. Table 2 shows the properties of the obtained film.

[0045]

[Table 1]

[0046]

[Table 2]

As shown in Table 1, the polyester film containing alumina particles using the surface treating agent in the examples is a polyester film having excellent abrasion resistance and scratch resistance.

On the other hand, as shown in Table 2, in the comparative examples, the alumina particles showed poor abrasion resistance and / or scratch resistance. Furthermore, the viscosity of the alumina particle-containing slurry also showed a high value except for Comparative Example 2, which also indicates that the slurry had poor dispersibility. The sodium hydroxide of Comparative Example 2 had a good slurry viscosity, but had poor scratch resistance. In all of Comparative Examples 1 to 4, satisfactory film physical properties were not obtained.

[0049]

According to the present invention, it is possible to provide a polyester film which is excellent in abrasion resistance and scratch resistance and is particularly useful as a base film of a magnetic recording medium.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08J 5/18 C08L 67/00-67/04

Claims (8)

(57) [Claims] 1. An alkali metal salt of a divalent or trivalent polycarboxylic acid having 4 to 9 carbon atoms, which is used in an amount of 0.05 to 2.0% by weight (based on alumina particles) as an alkali metal atomic weight. Surface treated, average secondary particle size is 0.01-0.5μ
m of alumina fine particles with respect to polyester is 0.05
Polyester film containing -1.0% by weight of dispersion. 2. An alkali metal salt having an alkali metal atomic weight
0.3 to 2.0% by weight (based on alumina particles)
Polyester film of claim 1, wherein there. 3. An alkali metal salt is a mono-alkali metal salt,
3. The polyester film according to claim 1, which is a dialkali metal salt or a trialkali metal salt. 4. The polyester film according to claim 1, wherein the alkali metal is sodium and / or potassium. 5. The polyester film according to claim 1, wherein the alumina has a δ-type, γ-type or θ-type crystal form. 6. The polyester film according to claim 1, further comprising 0.01 to 2% by weight (based on polyester) of inert fine particles other than alumina fine particles having an average particle size of 0.05 to 2 μm. 7. The polyester film according to claim 1, wherein the polyester is a polyester containing alkylene terephthalate or alkylene naphthalate as a main repeating component. 8. The polyester film according to claim 1, wherein the film is a biaxially oriented film.