JPH0458811B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a biaxially oriented polyester film that is smooth and highly improved in slipperiness and abrasion resistance. <Prior art and problems to be solved> Polyester, represented by polyethylene terephthalate, is used for magnetic recording, capacitors, and packaging because of its excellent mechanical properties, electrical properties, chemical resistance, and dimensional stability. , for plate making, for electrical cutting,
It is used as a base material in many fields such as photographic film. When polyester film is used in these applications, the required properties differ depending on the application, but the universally required property is workability when handling the film, and in order to improve this, the slipperiness of the film, It is necessary to reduce the coefficient of friction. In addition, when a magnetic layer is coated on the surface of a film used as a base film for audio, video, and computer applications, which have been growing rapidly in recent years, and used as a magnetic recording medium, poor slipperiness and abrasion resistance may cause problems when coating the magnetic layer. Friction and abrasion between the coating roll and the film surface are severe, and scratches are likely to occur on the film surface. Furthermore, even after the film coated with the magnetic layer is processed into products such as audio, video, and computer tapes, there are many guide parts, recording/playback heads, etc. when pulling out from a reel or cassette, winding up, or performing other operations. Significant friction and wear occur during this process, and white powdery substances are generated due to abrasion of the surface of the polyester film, which is often a major cause of missing magnetic recording signals, that is, dropouts. In order to improve these properties required of polyester films, the most commonly employed method is to add inactive fine particles to polyester in order to impart irregularities to the film surface. This method can be broadly divided into two. One of them is the precipitation method, in which one or more metal compounds soluble in ethylene glycol, such as calcium compounds and lithium compounds, are added before and after the transesterification reaction or esterification reaction, and the polyester manufacturing process, especially the polymerization This is a method in which these are precipitated as fine particles insoluble in polyester during the process. Another method that is compared to the precipitation method is the addition method, in which calcium carbonate, calcium sulfate, kaolin, silica, titanium dioxide, etc. are added as they are or after being made into fine particles during polyester synthesis or molding. Generally speaking, the larger the particle size of the particles in polyester, the greater the effect of improving slipperiness, but for precision applications such as magnetic tape, especially video, the particles themselves are large, causing dropouts and other problems. Therefore, the particles contained in polyester need to be as fine as possible. However, at present, it is extremely difficult to simultaneously satisfy these contradictory characteristics. <Means for Solving the Problems> The present inventors have discovered that as the precision of magnetic recording tapes has been further promoted in recent years, improvements in the slipperiness and abrasion resistance of base tape films have been increasingly required. In view of the circumstances, we have discovered a film for base tapes that has a smooth film surface, excellent slipperiness and abrasion resistance, and has fewer defects such as dropouts, and has arrived at the present invention. That is, the gist of the present invention is that the average particle size is 0.01 to 0.30μ.
The present invention relates to a biaxially oriented polyester film characterized by containing 0.01 to 1.0 wt% of rutile titanium dioxide having an average particle diameter of 0.31 to 1.0 μm and 0.002 to 0.5 wt% of rutile titanium dioxide having an average particle size of 0.31 to 1.0 μm. The present invention will be explained in more detail below. Polyester as used in the present invention refers to aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and naphthalene-2,6-dicarboxylic acid or esters thereof, and glycols such as ethylene glycol, diethylene glycol, tetramethylene glycol, neopentyl glycol, etc. It is a polyester that can be obtained by polycondensing. This polyester can be obtained by direct polycondensation of aromatic dicarboxylic acid and glycol, or by polycondensation after transesterification of aromatic dicarboxylic acid dialkyl ester and glycol, or by polycondensation after polycondensation of aromatic dicarboxylic acid dialkyl ester and glycol. It can also be obtained by methods such as polycondensation. Typical examples of such polymers include polyethylene terephthalate and polyethylene-2,6-
Examples include naphthalate. This polymer may be a homopolymer or may be a copolymer of a third component. In any case, in the present invention, polyesters having 80 mol% or more of ethylene terephthalate units and/or ethylene-2,6-naphthalate units are preferred. The key point of the present invention is to add specific amounts of two types of rutile titanium dioxide having different average particle sizes. The average particle size of the rutile titanium dioxide, which has a small particle size, must be 0.01 to 0.30 μm, and more preferably 0.05 to 0.27 μm. If the average particle size is less than 0.01 μm, the effect of improving slipperiness and abrasion resistance will be insufficient, which is not preferable. On the other hand, if the average particle diameter exceeds 0.30 .mu.m, the smoothness of the film surface decreases and the number of large particles that cause dropouts increases, which is not preferable.
Also, the amount added to polyester is 0.01~
It needs to be 1.0wt%, and the amount added is 0.1~
0.7wt% is more preferable. If the amount added is less than 0.01 wt%, the effect of improving slipperiness and abrasion resistance will be insufficient, which is not preferable. On the other hand, if the amount added exceeds 1.0 wt%, the smoothness of the film surface will decrease and coarse particles, which may cause dropouts, will increase, which is not preferable. The average particle size of rutile titanium dioxide having a large particle size needs to be in the range of 0.31 to 1.0 μm, and more preferably, the average particle size is 0.35 to 0.70 μm. If the average particle size is less than 0.31μ, the effect of improving slipperiness and abrasion resistance will be insufficient, which is not preferable. On the other hand, if the average particle diameter exceeds 1.0 .mu.m, the smoothness of the film decreases and the number of large particles, which causes dropouts, increases, which is not preferable. The amount added to the polyester is 0.002~
It needs to be 0.5wt%, and the amount added is 0.005
~0.3wt% is more preferable. If the amount added is less than 0.002 wt%, the effect of improving slipperiness and abrasion resistance will be insufficient, which is not preferable. On the other hand, if the amount added exceeds 0.5 wt%, the smoothness of the film surface will decrease and coarse particles, which may cause dropouts, will increase, which is not preferable. In addition, in order to improve slipperiness and wear resistance, the difference in average particle size between small particle size rutile titanium dioxide and large particle size rutile type titanium dioxide must be at least
It is preferably 0.10 μm or more. The rutile type titanium dioxide used in the present invention is not limited in any way by its manufacturing method or other aspects as long as it satisfies the conditions specified above. Further, a material without surface treatment may be used, or a material with surface treatment may be used. Regarding the volume shape factor, its value is 0.1 to π/
It is preferable to use one in the range of 6. [However, the volume shape factor F is expressed by the following formula. F=V/D In ^the formula, V is the particle volume (μm ³ ), and D is the maximum diameter (μm) of the particle in the projection plane. ] The volume shape coefficient represents the degree of sphericity of the particle, and the closer it is to π/6, the closer it becomes to spherical shape. The average particle diameter used here is the value of 50% of the cumulative (weight basis) in the equivalent spherical diameter distribution measured with a centrifugal sedimentation type particle size distribution measuring device manufactured by Shimadzu Corporation. The rutile titanium dioxide used in the present invention can be added to the polyester at any stage in the polyester production process, but preferably after the transesterification or esterification reaction and before the polycondensation. Add to. The particles may be added to the polyester manufacturing process in either slurry or powder form;
When adding particles to the polyester manufacturing process, it is common to add the particles as an ethylene glycol slurry for various reasons such as automation, ease of metering, improved dispersibility, and simplification of the recovery system. When dispersing particles into a slurry,
It is necessary to disperse it in the state of primary particles with as little agglomeration as possible. In order to uniformly disperse the particles in the state of primary particles in this manner, any method such as dispersion, crushing, pulverization, classification, and sieving may be employed as necessary. Further, in order to obtain particles having a predetermined average particle size, operations such as pulverization, classification, and overtreatment of commercially available particles may be employed. When adding the particles as an ethylene glycol slurry, it is important to keep the ratio of coarse particles of 2 μm or more in the slurry to 0.5 wt% or less based on the total particles to prevent coarse protrusions on the surface of the film when it is made into a polyester film. It is particularly preferable to reduce this. In the present invention, if necessary, inert fine particles other than rutile titanium dioxide can be used as long as the average particle size and content are such that the number of coarse particles does not increase and the surface smoothness of the film is not adversely affected. may be used together. In addition to the above-mentioned inert fine particles, fine particles precipitated by a reaction between a catalyst residue and a phosphorus compound in the reaction system can be used in combination. In the present invention, known methods can be employed for polymerizing the polyester containing rutile titanium dioxide. For example, as a catalyst for the polycondensation reaction, one or more of antimony compounds, germanium compounds, titanium compounds, etc. are used and heated to about 230 to 300°C, and the reaction is allowed to proceed by distilling off ethylene glycol under reduced pressure. In addition, when making a film, a known film forming method is used, for example, polyester chips are melted and extruded into a film at 270 to 300°C, cooled and solidified at 40 to 70°C to form an amorphous sheet, and then sequentially biaxially stretched vertically and horizontally. Alternatively, a method such as simultaneous biaxial stretching and heat treatment at 160 to 240° C. (for example, the method described in Japanese Patent Publication No. 30-5639) can be adopted. <Examples> The present invention will be explained in more detail by Examples below, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. In addition, various physical properties and characteristics were measured or defined as follows. In the examples, "parts" and "%" mean "parts by weight" and "% by weight," respectively. (1) Average particle size Centrifugal sedimentation type particle size distribution measuring device manufactured by Shimadzu Corporation
Use the integrated value (weight basis) of 50% in the equivalent sphere diameter distribution measured by the SA-CP3 type. (2) Surface smoothness of film The method described in JIS B0601-1976 was used. The measurement was performed using a surface roughness measuring machine model SE-3F (manufactured by Kosaka Institute). Stylus diameter 2μ, stylus pressure 30mm
g, the cutoff value was 0.08 mm, and the measurement length was 25 mm. Measurements were made at 12 points, the maximum and minimum values were cut out, and the average value of the 10 points was shown. (3) Sliding property Represented by the friction coefficient, which is ASTM D-
1894, using a method modified to allow measurement using tape-shaped samples. The size of the sample at the time of measurement was 15 mm in width and 150 mm in length, and the tensile speed was 20 mm/mm. Measurements were made at a temperature of 21±2℃ and humidity.
The test was carried out in an atmosphere of 65±5%. (4) Abrasion property The film was run over a length of 500 m using the running system shown in Figure 1, and the amount of wear attached to the 6mmφ hard chrome fixing pin was visually evaluated and classified into the ranks shown below. The film speed was 10 m/mm, the tension was approximately 200 g, and θ = 130°. Rank A: No adhesion at all. Rank B: Slight adhesion. Rank C: Large amount of adhesion. (5) Number of coarse protrusions Aluminum was deposited on the surface of the film and measured by the two-light velocity method using an interference microscope. The number of protrusions showing interference fringes of fourth or higher order at a measurement wavelength of 0.54μ is calculated per 25cm ² and shown. Example 1 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol, and 0.09 parts of magnesium acetate tetrahydrate were placed in a reactor, and the temperature was raised while methanol was distilled off to perform a transesterification reaction, which took 4 hours from the start of the reaction. Then, the temperature was raised to 230°C to substantially complete the transesterification reaction. Next, 0.3% by weight of small particles of rutile titanium dioxide with an average particle size of 0.25 μm, which were previously dispersed in ethylene glycol, classified and overtreated, and large particles of rutile titanium dioxide, with an average particle size of 0.45 μm, were dispersed in ethylene glycol in advance. Dispersed, classified and overtreated 0.07% by weight
After thoroughly mixing and adding, 0.04 part of ethyl acid phosphate and 0.035 part of antimony trioxide were further added and polycondensation was carried out for 4 hours to obtain a polyethylene terephthalate resin with an intrinsic viscosity of 0.66. After drying the polymer in vacuum, it is passed through an extruder to a thickness of
A 160 μm thick amorphous original film was prepared, then stretched 4 times in the machine direction and 3.9 times in the cross direction, and heat treated at 230° C. to obtain a biaxially stretched polyethylene terephthalate film with a thickness of 10 μm. Table 1 shows the properties of the obtained polyester film. As shown in Table 1, the surface smoothness, slipperiness, abrasion resistance, and number of coarse protrusions of the obtained film were very good, and were at an extremely satisfactory level as a film for magnetic tape. Example 2 Example 1 except that the average particle diameter of the small rutile titanium dioxide used in Example 1 was 0.15 μm instead of 0.25 μm, and the amount added was 0.5% by weight.
A biaxially stretched polyester film was obtained in the same manner as above. The properties of the obtained polyester film are shown in Table 1. The properties of the obtained film were similar to those of Example 1. Comparative Example 1 Biaxial stretching was carried out in the same manner as in Example 1, except that 0.3% by weight of rutile titanium dioxide having an average particle size of 0.25 μm was previously dispersed in ethylene glycol, classified and overtreated. A polyester film was obtained. The properties of the obtained polyester film are shown in Table 1. As shown in Table 1, the obtained film had poor abrasion resistance and was insufficient in properties as a magnetic tape. Comparative Example 2 Biaxial stretching was carried out in the same manner as in Example 1, except that 0.07% by weight of rutile titanium dioxide having an average particle size of 0.45 μm was previously dispersed in ethylene glycol, classified, and overtreated. A polyester film was obtained. The properties of the obtained polyester film are shown in Table 1. As shown in Table 1, the obtained film had poor slip properties and abrasion resistance, and was insufficient as a magnetic tape characteristic. Comparative Example 3 Small particle rutile titanium dioxide with an average particle size of 0.25 μm was dispersed in ethylene glycol in advance, classified,
1.5% by weight of over-treated material and average particle size 0.45μm
A biaxially stretched polyester film was obtained in the same manner as in Example 1, except that 0.07% by weight of large-particle rutile titanium dioxide was previously dispersed in ethylene glycol, classified and filtered, and then added after thorough mixing.
The properties of the obtained polyester film are shown in Table 1. As shown in Table 1, although the obtained film has satisfactory properties in terms of slipperiness and abrasion resistance, it is inferior in the number of coarse protrusions and is insufficient for use in magnetic tapes. Comparative Example 4 Small particle rutile titanium dioxide with an average particle size of 0.25 μm was dispersed in ethylene glycol in advance, classified,
0.3% by weight of over-treated material and average particle size 0.45μm
Large-particle rutile titanium dioxide is pre-dispersed in ethylene glycol, classified and overtreated.
Example 1 except that 0.7% by weight was thoroughly mixed and added.
A biaxially stretched polyester film was obtained in the same manner as above. The properties of the obtained polyester film are shown in Table 1. As shown in Table 1, although the obtained film has satisfactory properties in terms of slipperiness and abrasion resistance, it is inferior in the number of coarse protrusions, making it unsatisfactory for use in magnetic tapes.

[Table] <Effects of the Invention> As detailed above, the film of the present invention is a film containing specific amounts of small-particle rutile titanium dioxide having a specific particle size and large-particle rutile titanium dioxide having a specific particle size. The surface smoothness required for a polyester film for magnetic tape,
It has excellent slip properties and abrasion resistance, and has the characteristic that the amount of white powder generated when running on a metal roll surface during magnetic tape production and use is extremely small. In addition, it has a characteristic of extremely low number of large protrusions that can cause dropouts when used for video tapes, so it can be used for a wide range of applications such as magnetic tapes, vapor deposition, capacitors, and packaging. be able to.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a running system for evaluating wear resistance, where I is a hard chrome fixing pin of 6 mmφ, symbol is a tension meter, and θ is 130°.

Claims (1)

[Claims] 1 0.01 to 1.0 wt% of rutile titanium dioxide with an average particle size of 0.01 to 0.30 μm and an average particle size of 0.31 to 1.0 μm
A biaxially oriented polyester film containing 0.002 to 0.5 wt% of rutile titanium dioxide.