JP2845249B2 - Laminated polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a laminated polyester film comprising a thermoplastic polyester composition.
More specifically, the present invention relates to a laminated polyester film using a specific thermoplastic polyester composition suitable for obtaining a film having excellent abrasion resistance, such as for a magnetic recording medium.

[0002]

2. Description of the Related Art In general, thermoplastic polyesters such as polyethylene terephthalate have excellent mechanical properties and are widely used as molded articles such as films. Usually, in order to impart lubricity to a molded article, the polyester is made to contain inert particles in the polyester, and a method of imparting irregularities to the surface of the molded article is performed. Although there are various types of such inert particles, generally, the inert particles have a problem that they lack affinity for the polyester and are inferior in abrasion resistance.

In order to solve this problem, studies have been made on surface treatment of inert particles.
JP-A-3-221158, JP-A-63-280763 (modifying the surface of colloidal silica particles with a glycol group), and JP-A-63-321345 (modifying the surface of colloidal silica particles with a coupling agent) And JP-A-62-235353 (surface treatment of calcium carbonate particles with a phosphorus compound) and the like have been proposed.

[0004] However, even in the case of using such a known method, when particles are repeatedly used by friction like a magnetic tape, particles are dropped off. For this reason, the use of special particles has recently been proposed, for example,
JP-A-62-172031 (silicon particles) and JP-A-2-129230 (delta-type aluminum oxide particles) have been proposed, but are still insufficient.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and it is particularly desirable to use a thermoplastic polyester composition containing aluminum oxide particles having a specific crystal structure. An object of the present invention is to realize excellent wear resistance as a base film of a magnetic tape or the like by forming a laminated film having a structure.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a laminate in which a thermoplastic polyester composition containing theta-type aluminum oxide particles is used as an outermost film layer constituting at least one surface. A polyester film, characterized in that the thickness of the outermost film layer containing the particles is in the range of 0.1 to 20 times the secondary particle size of the particles, which is achieved by a laminated polyester film. it can.

The crystal structure of the aluminum oxide particles can be identified by a diffraction angle 2θ value at which a diffracted X-ray appears in an X-ray diffraction method. A plurality of standard 2θ value sets are known for theta type crystal structure, but the main 2θ value is 19.
4, 31.3, 32.7, 36.7, 39.2, 44.
9, 47.4, 59.9, 62.3, 64.1, 67.
2 (degrees).

FIG. 1 shows the results of X-ray diffraction analysis of theta-type aluminum oxide particles.

The aluminum oxide particles include alpha type,
Various crystal structures such as a gamma type, a delta type and a theta type are known, and they can be determined by a method of synthesizing each particle. The theta-type aluminum oxide particles of the present invention are produced by, for example, neutralizing carbonated alum with pyrolysis.

When the theta-type aluminum oxide particles are mixed with the polyester among the aluminum oxide particles,
It is very excellent in abrasion resistance when formed into a film. The reason for this is unknown, but it is considered that the aluminum oxide particles having the crystal structure of the present invention have a high affinity for polyester.

The primary particle size of the particles is very difficult to measure because of the very fine particles, but can be measured in terms of the specific surface area. The specific surface area of the theta-type aluminum oxide of the present invention is preferably at least 10 m ² / g, more preferably at least 50 m ² / g.

Although such particles naturally cause agglomeration in the polyester, the secondary particle size can be arbitrarily selected according to the purpose of the film obtained by molding from the thermoplastic polyester composition. Can be. However, if it is too large, coarse projections are generated on the film surface, so that the thickness is preferably 2.0 μm or less, more preferably 0.5 μm or less. Further, the thickness is preferably 0.01 μm or more.

Here, the secondary particle diameter is an average diameter equivalent to a circle when 1,000 particles are observed with a transmission electron microscope.

The amount of theta-type aluminum oxide particles added is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the thermoplastic polyester in the particle-containing layer.

In order to obtain good abrasion resistance when formed into a film, the ratio of the crystal structure of theta-type aluminum oxide is preferably at least 50 wt%, particularly preferably at least 70 wt%.

The thermoplastic polyester in the present invention may be any thermoplastic polyester as long as it can form a film. For example, polyethylene terephthalate, polytetramethylene terephthalate, polycyclohexylene dimethylene terephthalate, polyethylene-2,6- There are naphthalenedicarboxylate, polyethylene-1,2-bis (2-chlorophenoxy) ethane-4,4'-dicarboxylate and the like, and polyethylene terephthalate and polyethylene-2,6-naphthalenedicarboxylate are particularly preferred.

These polyesters include, as copolymerization components, dicarboxylic acids such as adipic acid, isophthalic acid, sebacic acid, phthalic acid, 4,4'-diphenyldicarboxylic acid, and ester-forming derivatives thereof, polyethylene glycol, diethylene glycol, Dioxy compounds such as hexamethylene glycol, neopentyl glycol, and polypropylene glycol, oxycarboxylic acids such as p- (β-oxyethoxy) benzoic acid, and ester-forming derivatives thereof may be copolymerized.

The thermoplastic polyester composition for forming the theta-type aluminum oxide particle-containing layer of the laminated polyester film of the present invention is prepared by, for example, mixing and stirring theta-type aluminum oxide particles with glycol, which is a starting material for polyester, as a solvent. And it can be obtained by a production method in which it is added to a reaction system of a thermoplastic polyester. The processing method at this time does not need to be stirring, but may be, for example, ultrasonic waves or a medium mill such as a sand grinder.

For the incorporation into the polyester, other than the above-mentioned method of directly adding to the polymerization reaction system, for example,
A method in which theta-type aluminum oxide particles are kneaded into a molten polyester is also possible. The timing of addition to the former polymerization reaction system is optional, but is preferably from before the transesterification reaction to before the start of the pressure reduction in the polycondensation reaction. In the case of the latter kneading, a method of drying and kneading the particles into polyester or a method of directly kneading while reducing the pressure in a slurry state may be used. The thermoplastic polyester composition of the present invention may contain conventionally known particles other than theta-type aluminum oxide particles, as long as the effects of the present invention are not impaired. Examples of such particles include, for example, kaolin, calcium phosphate, silicon dioxide, calcium carbonate, titanium dioxide, inorganic particles such as barium sulfate, crosslinked polystyrene, organic particles such as silicone resin particles, and at least one of alkali metals and alkaline earth metals. And particles precipitated in a polyester polymerization reaction system containing phosphorus and phosphorus as a component, that is, internal particles.

The laminated polyester film of the present invention can be manufactured by the following method.

After the polyester pellets obtained by the polymerization reaction are sufficiently dried, they are immediately supplied to an extruder. The pellet is melted at 260 to 350 ° C., extruded into a sheet from a die, cooled and solidified on a casting roll to obtain an unstretched film. As a film laminating method, a known method such as melt co-extrusion can be used. next,
Preferably, the unstretched film is biaxially stretched. As the stretching method, a sequential biaxial stretching method, a simultaneous biaxial stretching method, a method of stretching the film thus biaxially stretched again, or the like may be used. Depending on the composition of the polyester,
In order to obtain a sufficient elastic modulus as a film for a magnetic recording medium, the final stretch area ratio (longitudinal ratio × lateral ratio) is preferably 6 times or more.

In order to keep the heat shrinkage of the film small, it is preferable to perform a heat treatment at a temperature in the range of 150 to 260 ° C. for about 0.1 to 60 seconds.

In the laminated film of the present invention, the film layer constituting at least one surface is a film layer comprising the thermoplastic polyester composition containing theta-type aluminum oxide particles of the present invention. With such a laminated film configuration, the abrasion resistance, uniformity,
Good slipperiness is obtained.

The thickness of the film layer of the present invention (hereinafter also referred to as a laminated portion) constituting one surface of the laminated film is 0.1 to 20 times the secondary particle diameter of the contained aluminum oxide particles. In particular, the uniformity and smoothness of the film surface are improved.

The content of the theta-type aluminum oxide particles in the laminated portion is preferably 0.05 to 30 parts by weight, and particularly preferably 0.1 to 10 parts by weight.

[0026]

Next, the present invention will be described with reference to Examples and Comparative Examples.
This will be described in more detail.

(1) Evaluation of Specific Surface Area of Aluminum Oxide Particles B. E. FIG. T. It was measured according to the method.

(2) Evaluation of Secondary Particle Diameter of Aluminum Oxide Particles Aluminum oxide particles are mixed with polyester,
After cutting into an ultrathin section having a thickness of 0.2 μm, the section was observed with a transmission electron microscope, and evaluated by a circle-equivalent average diameter (μm) of 1000 aggregated secondary particles.

(3) Evaluation of abrasion resistance The obtained polyester composition was made into a biaxially stretched film by the method shown in the examples, and a tape-like roll slit into a narrow width was applied to a stainless steel SUS-304 guide roll at a constant tension. Rubbed at high speed for a long time and ranked according to the amount of white powder generated on the guide roll surface as follows.

First grade: no white powder generated Second grade: slight white powder generated Third grade: fairly much white powder generated

(4) Evaluation of Surface Roughness The obtained polyester composition was made into a biaxially stretched film by a usual method, using a Surfcom surface roughness meter according to JIS B0601, a needle diameter of 2 μm, a load of 70 mg, and a measurement reference length of 0.
The center line average roughness (Ra) was measured under the conditions of 25 mm and a cutoff of 0.08 mm.

Example 1 B. E. FIG. T. 10 parts by weight of theta-type aluminum oxide particles having a surface area of 120 m ² / g and ethylene glycol 90
The parts by weight were mixed and stirred with a dissolver at room temperature for 1 hour to obtain a theta-type aluminum oxide particle / ethylene glycol slurry (A).

On the other hand, a transesterification reaction was carried out by adding 0.06 parts by weight of magnesium acetate as a catalyst to 100 parts by weight of dimethyl terephthalate and 64 parts by weight of ethylene glycol, and then the slurry (A) 4 prepared above was added to the reaction product.
Parts by weight, 0.03 parts by weight of antimony trioxide as a catalyst, and 0.03 parts by weight of trimethyl phosphate as a heat-resistant stabilizer, and subjected to a polycondensation reaction to obtain a polyethylene terephthalate composition (Y) having an intrinsic viscosity of 0.615 Was. The secondary particle diameter measured by a transmission electron microscope was 0.15 μm.

FIG. 1 shows an X-ray diffraction pattern of the theta-type aluminum oxide particles used in Example 1.

A polyethylene terephthalate composition (X) was obtained in the same manner as above except that no aluminum oxide particles were added.

The polyethylene terephthalate composition (Y) was melt-coextruded on (X) to obtain a laminated unstretched film. The extrusion temperature at this time was 290 ° C. Thereafter, the film was stretched three times vertically and horizontally at 90 ° C., and then heat-treated at 220 ° C. for 20 seconds to obtain a laminated biaxially stretched polyester film.

Each of the layers (X) and (Y) has a thickness of 8
μm and 0.5 μm.

When this film was evaluated, as shown in Table 1, it was Ra = 0.012 μm, and the film had a first-class abrasion resistance evaluation, and was very excellent in abrasion resistance.

[0039]

[Table 1]

Example 2 A calcium carbonate-containing polyethylene terephthalate composition (Z) was prepared in the same manner as in the preparation of the composition (Y) in Example 1, except that calcium oxide having an average particle diameter of 0.8 μm was used instead of aluminum oxide. I got Example 1
In the same manner as in Example 1, except that a composition obtained by chip blending the compositions (Z) and (Y) was used instead of using only the composition (Y) in the laminated portion, theta-type aluminum oxide was used in the laminated portion. A laminated film containing 0.4% by weight and 0.5% by weight of calcium carbonate was obtained. The film had a surface roughness of 0.020 μm and a first-class abrasion resistance, and was a film with good overall evaluation.

Comparative Examples 1 to 5 Biaxially stretched polyester films were obtained in the same manner as in Example 1 except that the type of particles and the crystal structure of the aluminum oxide particles were changed. However, in Comparative Examples 1 to 5, a single-layer film was used. Table 2 shows the evaluation results of these films. These films were not films with satisfactory abrasion resistance.

[0042]

[Table 2]

[0043]

The laminated polyester film of the present invention is
Since the film contains aluminum oxide particles having a specific crystal structure and has a laminated portion having a specific ratio of thickness to the average particle diameter of the particles, the film exhibits an excellent effect of abrasion resistance. In particular, the wear resistance of the surface of the laminated film can be efficiently improved.

[Brief description of the drawings]

FIG. 1 is a chart showing an X-ray diffraction pattern of theta-type aluminum oxide particles used in Example 1.

Continuation of front page (56) References JP-A-3-172319 (JP, A) JP-A-3-43447 (JP, A) JP-A-4-216031 (JP, A) JP-A-5-16224 (JP) JP-A-4-88016 (JP, A) JP-A-5-271397 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08L 67/00-67/08 C08K 3/22 C08J 5/18 G11B 5/704 B32B 27/36

Claims (1)

(57) [Claims] 1. A thermoplastic polyester composition containing theta-type aluminum oxide particles has at least one surface.
Laminated polyester used for the outermost film layer
A steal film, wherein the outermost layer containing the particles is
The thickness of the film is 0.1 to the secondary particle diameter of the particles.
Laminated polyester characterized by being in the range of 20 times
Film.