JPH05202274A - Thermoplastic polyester resin composition and film made therefrom - Google Patents

Abstract

PURPOSE:To obtain the title compsn. useful for preparing an abrasion-resistant film for a magnetic recording medium, etc., by incorporating specific aluminum oxide particles into the compsn. CONSTITUTION:The title compsn. is prepd. by incorporating theta-aluminum oxide particles, pref. having a specific surface area, as a measure of the primary particle size, of 10m<2>/g or higher, still pref. 50m<2>/g or higher, and a secondary particle size of 0.01-2.0mum, still pref. 0.01-0.5mum, into the compsn.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thermoplastic polyester composition and a film comprising the same. More specifically, it relates to a thermoplastic polyester composition suitable for obtaining a film having excellent abrasion resistance for magnetic recording media and the like, and a film comprising the same.

[0002]

2. Description of the Related Art Generally, thermoplastic polyesters such as polyethylene terephthalate have excellent mechanical properties and are widely used as molded articles such as films. Usually, for the purpose of imparting slipperiness to a molded product, the polyester is made to contain inert particles in the polyester, and a method of imparting unevenness to the surface of the molded product is performed. There are various kinds of such inert particles, but in general, there is a problem that the inert particles lack affinity with the polyester and have poor abrasion resistance.

In order to solve this problem, the surface treatment of inert particles has been studied so far, for example, Japanese Patent Laid-Open Publication No. Sho-6.
3-221158, JP-A-63-280763 (the surface of colloidal silica particles is modified with a glycol group), and JP-A-63-313345 (the surface of colloidal silica particles is modified with a coupling agent). JP-A-62-235353 (wherein calcium carbonate particles are surface-treated with a phosphorus compound) has been proposed.

However, even if such a known method is used, when particles are repeatedly rubbed like a magnetic tape, particles fall off. Therefore, it has been recently proposed to use special particles, for example,
JP-A-62-172031 (silicon particles) and JP-A-2-129230 (delta-type aluminum oxide particles) have been proposed, but they are still insufficient.

[0005]

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and particularly when theta type aluminum oxide particles are blended with a thermoplastic polyester to form a film, abrasion resistance is improved. It is an object of the present invention to provide a composition capable of obtaining a film having excellent properties and a film comprising the same.

[0006]

The above-mentioned object of the present invention can be achieved by a thermoplastic polyester composition containing theta type aluminum oxide particles and a polyester film comprising the same.

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

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

Aluminum oxide particles include alpha type,
Various crystal structures such as gamma type, delta type and theta type are known, but they can be determined by the synthesis method of each particle. The theta type aluminum oxide particles of the present invention are, for example, after alum is neutralized with carbonate. It is generated by thermal decomposition.

Among the aluminum oxide particles, particularly when theta type aluminum oxide particles are blended with polyester,
It has excellent abrasion resistance when made 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 high affinity with polyester.

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

Naturally, such particles cause agglomeration in polyester, but the secondary particle diameter is arbitrarily selected according to the purpose of the film obtained by molding from the thermoplastic polyester composition. You can However, if it is too large, coarse protrusions 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, it is preferably 0.01 μm or more.

The term "secondary particle diameter" as used herein means a circle-equivalent average diameter 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.
Parts by weight are preferred.

In order to obtain good abrasion resistance when formed into a film, the proportion of the crystalline structure of theta-type aluminum oxide is preferably 50 wt% or more, particularly preferably 70 wt% or more.

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

These polyesters have, 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 of the present invention comprises
For example, theta-type aluminum oxide particles can be obtained by a manufacturing method in which glycol, which is a starting material for polyester, is mixed and stirred to form a dispersion slurry, which is added to a reaction system of thermoplastic polyester. The treatment method at this time may be, for example, ultrasonic waves or the like instead of stirring, and a medium type mill such as a sand grinder may be used.

In addition to the above-mentioned method of directly adding to the polymerization reaction system, the polyester may be blended with
A method in which theta-type aluminum oxide particles are kneaded into molten polyester is also possible. The former may be added to the polymerization reaction system at any time, but is preferably from before the transesterification reaction to before the pressure reduction of the polycondensation reaction. In the case of the latter kneading, either a method of drying the particles and kneading into the polyester or a method of directly kneading in a slurry state under reduced pressure may be used.

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

The polyester pellets obtained by the polymerization reaction are sufficiently dried and then immediately fed to the extruder. The pellets are melted at 260 to 350 ° C., extruded into a sheet form from a die, cooled on a casting roll and solidified to obtain an unstretched film. Next, it is preferable to biaxially stretch this unstretched film. As the stretching method, a sequential biaxial stretching method, a simultaneous biaxial stretching method, a method of stretching the biaxially stretched film again in this manner, or the like may be used. Although it depends on the composition of the polyester, it is preferable that the final stretched area ratio (longitudinal ratio × lateral ratio) be 6 times or more in order to obtain a sufficient elastic modulus as a film for a magnetic recording medium.

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

The film of the present invention can be used as either a single layer film or a laminated film. In the case of a laminated film, it is preferable to use the film of the present invention as the film constituting at least one surface, because the film surface will have good abrasion resistance, uniformity, and slipperiness. As a film laminating method, a known method such as melt coextrusion can be used.

The thickness of the film of the present invention (hereinafter, also referred to as a laminated portion) constituting one surface of the laminated film is 0. 0 with respect to the secondary particle diameter of the aluminum oxide particles contained therein.
It is preferable that the amount is from 1 to 20 times because the film surface uniformity and slipperiness are particularly good.

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

[0026]

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

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

(2) Evaluation of secondary particle size of aluminum oxide particles Aluminum oxide particles were blended 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 the circle-equivalent average diameter (μm) of 1000 secondary particles in an aggregated state.

(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-shaped roll slit into a narrow width was applied to a stainless steel SUS-304 guide roll at a constant tension. It was rubbed at high speed for a long time and ranked as follows according to the amount of white powder generated on the surface of the guide roll, and the first grade was passed.

1st grade: No white powder generated 2nd grade: White powder slightly generated 3rd grade: White powder generated considerably

(4) Evaluation of surface irregularities The obtained polyester composition was made into a biaxially stretched film by a usual method, and a surfcom surface roughness meter according to JIS B0601 was used to measure 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. T. 10 parts by weight of theta type aluminum oxide particles having a surface area of 120 m ² / g, ethylene glycol 90
The weight parts were mixed and stirred at room temperature for 1 hour with a dissolver to obtain theta-type aluminum oxide particles / ethylene glycol slurry (A).

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

This polyethylene terephthalate composition was melted at 290 ° C., extruded, and then stretched at 90 ° C. in the length and width three times each, and then heat treated at 220 ° C. for 15 seconds to obtain a biaxially stretched polyethylene terephthalate film having a thickness of 15 μm. It was

When this film was evaluated, Ra =
The film was 0.011 μm, the abrasion resistance was rated 1 grade, and the film was very excellent in abrasion resistance.

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

Examples 2 to 4 Biaxially stretched polyester films were obtained in the same manner as in Example 1 by changing the specific surface area, secondary particle size, addition amount and the like of theta type aluminum oxide particles in the polyethylene terephthalate composition. It was The evaluation results of these films are shown in Table 1. It can be seen that these films have good abrasion resistance.

Example 5 A polyethylene terephthalate composition (X) was obtained in the same manner as in Example 1 except that aluminum oxide particles were not added.

The polyethylene terephthalate composition (Y) of Example 1 was melt-coextruded on (X) to obtain a laminated unstretched film. The extrusion temperature at this time was 290 ° C. After that, the film was stretched at 90 ° C. in the lengthwise and transverse directions three times, respectively, and further heat treated at 220 ° C. for 20 seconds to obtain a laminated biaxially stretched film.

The thickness of each of the layers (X) and (Y) is 8
μm and 0.5 μm.

When this film was evaluated, as shown in Table 1, it was Ra = 0.012 μm, and the abrasion resistance was grade 1, and the film was very excellent in abrasion resistance.

[0042]

[Table 1] 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 aluminum oxide particles were changed. The evaluation results of these films are shown in Table 2. These films were not satisfactory in abrasion resistance.

[0043]

[Table 2]

[0044]

The polyester composition of the present invention contains aluminum oxide particles having a specific crystal structure, and when it is made into a film, it exhibits an excellent abrasion resistance.

[Brief description of drawings]

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

Claims (2)

[Claims] 1. A thermoplastic polyester composition containing theta type aluminum oxide particles. 2. A thermoplastic polyester film containing theta type aluminum oxide particles.