JPS6347738B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an oriented polyester film that is smooth, has excellent slip properties and abrasion resistance, and has a small number of coarse particles. Due to its excellent physical and chemical properties, polyesters such as polyethylene terephthalate are generally used for textiles, molded products, and films such as magnetic tapes, photographs, capacitors, and packaging. Widely used for various purposes. When these films are used, their slipperiness and abrasion resistance are major factors that determine the workability of the film manufacturing process and processing process in each application, as well as the quality of the product. Further, the film is required to have a small number of coarse particles. If the number of coarse particles is large, breakage during the manufacturing process will increase, resulting in decreased film forming operability and electrical properties, which is not preferable. In particular, when a magnetic layer is coated on the surface of a polyester film and used as a magnetic tape, if coarse particles are present in the film, protrusions will appear on the surface of the magnetic layer even after the magnetic layer is coated, causing the magnetic head to be damaged when the magnetic tape is run. It is necessary to reduce the number of coarse particles as much as possible because a spacing loss occurs between the two and leads to a loss of magnetic signals, that is, a dropout defect. When used as a magnetic tape, slipperiness and abrasion resistance are also extremely important properties. For example, if the slipperiness and abrasion resistance are poor, the friction and abrasion between the coating roll and the film surface during application of the magnetic layer will be extremely severe, making it easy for wrinkles and scratches to occur on the film surface. In addition, even after the film is coated with a magnetic layer and slit to make audio, video, or computer tapes, there are many guide parts, playback heads, etc. when pulling it out from a reel or cassette, winding it, or other operations. Significant friction and abrasion occur between the polyester film and the polyester film, causing scratches and distortion, as well as the precipitation of white powdery substances due to abrasion of the polyester film surface, which is often a major cause of dropouts. Furthermore, when used as a magnetic tape, the surface is required to be smooth. Particularly in video applications, there is increasing demand from the market for this as an important characteristic for achieving high image quality. Generally, to improve the slipperiness and abrasion resistance of film surfaces, a method is adopted in which the surface of the film is roughened to reduce the contact area with guide rolls, etc. A method of precipitating insoluble particles from the catalyst residue, a method of adding inert inorganic particles, etc. are used. Generally, the larger the particle size of these raw material polymers, the greater the effect of improving slipperiness, but for precision applications such as magnetic tape, especially video, the large particles themselves are important. Since it can cause defects such as dropouts, the unevenness on the film surface needs to be as fine as possible, and there are currently demands to satisfy contradictory physical properties at the same time. The inventors of the present invention have taken into account the situation in which the density of magnetic recording has been further promoted in recent years, and improvements in the smoothness, slipperiness, abrasion resistance, and reduction in the number of coarse particles of base films for tapes have been increasing. The present invention was arrived at as a result of intensive studies. That is, in the present invention, in a polyester whose main repeating unit is ethylene terephthalate, the average particle size is
The following () and ( This is an oriented polyester film containing an amount that simultaneously satisfies the following formula () and an average particle diameter ratio that satisfies the following formula (). 0.2≦(A)＋(B)≦2.0 ……() 0.1≦(A)／(B)≦10 ……() 0.5≦D _A ／D _B ≦10 ……() [In the formula, (A) +(B) is the total content of components (A) and (B) expressed in weight%, (A)/(B) is the weight ratio of components (A) and (B), D _A /D _B indicates the average particle size ratio of component (A) and component (B). ] The oriented polyester film of the present invention has excellent surface smoothness, slipperiness, and abrasion resistance, and is characterized by extremely low scratches and white powder generation, as well as a small number of coarse particles. It is particularly suitable as a base film for tapes. The oriented polyester film of the present invention is characterized by comprising component (A) consisting of 0.01 to 0.5 μm kaolinite and/or talc, and at least one kind of inert fine particles selected from silica, titanium dioxide, and barium sulfate. Component (B) is used in combination with specific average particle diameters and in specific amounts. It is already known that a method of adding two types of inert inorganic particles with different particle sizes is effective in improving the slipperiness and abrasion resistance of the film surface. Among these, it is known that a method in which two types of fine particles having different particle shapes are used in combination is particularly excellent. It is true that these methods are effective as means for improving slipperiness and wear resistance, but conventionally known methods simultaneously satisfy the characteristics of highly smooth surfaces and a small number of coarse particles. That was difficult. By selecting the limited conditions in the present invention, it is possible to simultaneously satisfy the above-mentioned contradictory film characteristics for the first time. In the present invention, the polyester constituting the oriented polyester film has a main repeating unit of 80
The polyester is composed of ethylene terephthalate in an amount of at least 20 mol %, and less than 20 mol % of other components such as dicarboxylic acids, glycols, and oxycarboxylic acids that can be copolymerized with the polyester may be used. Note that a biaxially oriented film is particularly suitable as the oriented film. The average particle size of the fine particles to be added in the present invention is from 0.01 to
A range of 0.5 μm is required, and 0.05 to 0.3 μm is more preferred. If it is less than 0.01 μm, the effect of improving slipperiness and abrasion resistance will be insufficient, which is not preferable. vice versa
If it exceeds 0.5 μm, the effect of improving slipperiness and abrasion resistance reaches its peak, and furthermore, the surface smoothness deteriorates and the number of coarse particles increases, which is not preferable. As shown in equation (2), the relationship between the average particle diameters of component (A) and (B) is in the range of 0.5 to 10 as the ratio of the average particle diameter of component (A) to the average particle diameter of component (B). You need to choose. A range of 0.8 to 2.0 is particularly preferred. If it is less than 0.5, the production of coarse particles increases, which is not preferable. On the other hand, if it exceeds 10, the improvement in slipperiness and abrasion resistance will be insufficient, which is not preferable. The content of these fine particles needs to be selected in the range of 0.2 to 2.0% by weight as the total content of components (A) and (B) as shown in formula (). 0.3
A range of 1.0% by weight is particularly preferred. If it is less than 0.2% by weight, the effect of improving slipperiness and abrasion resistance will be insufficient, which is not preferable. 2.0 on the contrary
When the weight percentage is exceeded, the effect of improving slipperiness and abrasion resistance reaches a ceiling, and in addition, surface smoothness deteriorates.
Furthermore, it is preferable because the number of coarse particles increases. Also, as shown in equation (), (A) for (B) component
The content ratio of the components should be selected in the range of 0.1 to 10. A range of 0.3 to 5 is particularly preferred. If it is less than 0.1, it is not preferable that the wear resistance decreases. On the other hand, if it exceeds 10, the slipperiness decreases, which is not preferable. Further, from the viewpoint of improving slipperiness, it is particularly preferable to select a content of component (B) of 0.1% by weight or more. The above expressions () to () must be satisfied at the same time. These fine particles may be used without surface treatment or may be surface treated. Furthermore, the presence or absence of a dispersion aid or anti-aggregation agent is not particularly limited. The average particle size referred to here is the sum of the equivalent spherical particle size distribution calculated based on Stokes' formula 50
Refers to the diameter at the % point. In the method of adding fine particles to polyester in the present invention, they can be added at any stage in the polyester manufacturing process, but it is particularly preferable to add them before the initial condensation reaction is completed. In addition, fine particles can be added to the polyester manufacturing process in either slurry or powder form, but from the viewpoint of preventing particles from scattering and improving supply accuracy and uniformity, it is preferable to disperse them in slurry form. It is preferable to add it as an EG slurry, and it is particularly preferable to add it as an EG slurry. When dispersing in slurry form, it is necessary to perform uniform dispersion so as to reproduce the original primary particles of each particle as much as possible. Furthermore, in order to obtain particles having a predetermined average particle size, pulverization treatment or classification operation of commercially available fine particles may be employed. Further, when the particles are added as a slurry to the polyester manufacturing process, the slurry of the component (A) and the slurry of the component (B) may be added simultaneously or separately. If they are added at the same time, they may be added from separate supply ports, or both slurries may be mixed uniformly before being added to the polyester manufacturing process. Alternatively, a polyester containing a high concentration of individual particles within a range that does not agglomerate may be separately produced in advance and then blended to a predetermined particle concentration. It may contain fine particles precipitated during the polyester manufacturing process, so-called internal particles, as long as the particle size and content are such that they do not increase the number of coarse particles and do not adversely affect surface smoothness. do not have. If the film is used in such a way that only one side of the film comes into contact with a metal roll, only the contacting surface may contain the inert inorganic particles of the present invention, and the other surface may contain inert inorganic particles depending on the purpose. Alternatively, it may be a separate layer that does not contain it. As mentioned above, the film of the present invention is particularly preferable as a base film for magnetic tape, but
The invention is not limited to this, and can be widely applied to other fields such as electrical applications and films for vapor deposition. Next, Examples and Comparative Examples of the present invention will be shown. All parts in the examples mean parts by weight unless otherwise specified. In addition, the measurement method used is shown below. (1) Average particle size Use the value at the cumulative 50% point of the equivalent spherical diameter distribution obtained using a Shimadzu centrifugal sedimentation particle size distribution analyzer. (2) Surface smoothness of the film Using a Surfcom 300A surface roughness tester, with a needle diameter of 1μ,
Weight 0.07g, measurement standard length 0.8mm, cutoff 0.08mm
It is expressed as center line average roughness (R _A ) measured under the following conditions. (3) Film slipperiness and abrasion resistance When a tape-like roll made by slitting a film into narrow widths is rubbed against a metal guide roll and run at high speed for a long time, the tape after being rubbed by the guide roll against a constant supply tension. The magnitude of the tension and the amount of white powder generated on the surface of the guide roll were each evaluated on a five-point scale, and expressed in the following rankings. Slipperiness Grade 1...High tension (many scratches) Grade 2...Slightly high tension (quite a lot of scratches) Grade 3...Medium tension (slightly scratches) Grade 4...Slightly low tension (almost no scratches) Grade 5...Low tension (scratches) Abrasion resistance 1st grade...very much white powder 2nd grade...a lot of white powder 3rd grade...some white powder 4th grade...almost no white powder 5th grade...no white powder (4) Coarse particles in the film Number of particles A small amount of the film was sandwiched between two cover glasses, melt-pressed at 280℃, rapidly cooled, and then observed using a phase contrast microscope. The number of particles with a maximum length of 5 μm or more is counted, and the number of particles is evaluated on a three-level scale, which is ranked as follows. 1st grade...11 or more pieces/4.8mm ² 2nd grade...4 to 10 pieces/4.8mm ² 3rd grade...0 to 3 pieces/4.8mm ^2Example 1 Stirring device, partial condenser, raw material inlet and product outlet A continuous esterification reaction device consisting of a two-stage complete mixing tank is used, and the system in which the esterification reaction product of the first esterification reaction tank is present is used.
The molar ratio of EG to TPA was adjusted to 1.7, and an EG slurry of TPA containing antimony trioxide as antimony atoms of 289 ppm per TPA unit was continuously supplied. At the same time, an EG solution of magnesium acetate tetrahydrate and an EG solution of sodium acetate are passed through the reactor from a supply port different from the EG slurry supply port of TPA. Na atoms were continuously supplied at concentrations of 100 ppm and 10 ppm, and the reaction was carried out at normal pressure for an average residence time of 4.5 hours and at a temperature of 255°C. This reaction product is continuously taken out of the system,
0.5 parts by weight of EG and EG solution with trimethyl phosphate were added to the polyester unit in the reaction product passing through the second esterification reactor.
An EG slurry of kaolinite with an atom size of 64 ppm and an average particle size of 0.34 μm and an EG slurry of silica with an average particle size of 0.30 μm were added from separate feed ports to give kaolinite and silica of 0.30 and 0.40% by weight, respectively. The mixture was continuously fed and reacted at normal pressure with an average residence time of 5.0 hours and a temperature of 260°C. The esterification reaction product is passed through a stirring device, a dephlegmator,
Polycondensation was carried out by continuously feeding the mixture into a two-stage continuous polycondensation reactor equipped with a raw material inlet and a product outlet to obtain a polyester having an intrinsic viscosity of 0.620.
The polymer was melt extruded at 290°C, stretched 3.5 times in the machine direction at 90°C, and 3.5 times in the transverse direction at 130°C, and then stretched at 220°C.
Table 1 shows the properties of the 15 μm film obtained by heat treatment at °C. The film obtained in this example had surface smoothness,
It can be seen that the properties of slipperiness, abrasion resistance, and number of coarse particles are all extremely good, indicating that the material is of high quality. Comparative Example 1 Table 1 shows the properties of a film obtained in the same manner as in Example 1 except that the addition of silica was stopped. The film obtained in this comparative example had extremely poor slipperiness. It also has poor wear resistance. Comparative Example 2 Table 1 shows the properties of a film obtained in the same manner as in Example 1 except that the addition of kaolinite was discontinued. The film obtained in this comparative example has poor abrasion resistance. Comparative Examples 3 to 6 Table 1 shows the results when the amount of kaolinite added, the average particle size of silica, and the amount added were variously changed in the method of Example 1. It can be seen that when the conditions of the present invention are not met, any of the properties such as surface smoothness, slipperiness, abrasion resistance, and number of coarse particles deteriorate, making it impossible to obtain a high-quality film. Example 2 and Comparative Examples 7 to 9 Table 1 shows the results when kaolinite and titanium dioxide were used in the same method as in Example 1. It can be seen that a high quality film that satisfies all the characteristics of surface smoothness, slipperiness, abrasion resistance and number of coarse particles can be obtained only when the conditions of the present invention are satisfied. Examples 3 and 4 Table 1 shows the results when kaolinite and barium sulfate were used and when talc and silica were used in the same manner as in Example 1. It can be seen that high quality films were obtained in all Examples.

【table】

【table】

Claims (1)

[Claims] 1 Polyester whose main repeating unit is ethylene terephthalate has an average particle size of 0.01 to
Component (A) consisting of kaolinite and/or talc of 0.5 μm and component (B) consisting of at least one kind of inert fine particles selected from silica, titanium dioxide and barium sulfate are combined into the following () and (). An oriented polyester film containing an amount that simultaneously satisfies the following formula and an average particle diameter ratio that satisfies the following formula (). 0.2≦(A)＋(B)≦2.0 ……() 0.1≦(A)／(B)≦10 ……() 0.5≦D _A ／D _B ≦10 ……() [In the formula, (A) +(B) is the total content of components (A) and (B) expressed in weight%, (A)/(B) is the weight ratio of components (A) and (B), D _A /D _B indicates the average particle size ratio of component (A) and component (B). ]