KR0130659B1 - Biaxial oriented polyester film - Google Patents

Abstract

The two axes orientation polyester film is characterized by including calcium carbonate of average particle-diameter of 0.05 or 3um, silica of average particle-diameter of 0.05 or 3 um and benzoguamine-melamine-formaldehyde of average particle-diameter of 0.1 or 5 um of 0.01 or 0.5 wt% as to total weight of the polyester respectively.

Description

Biaxially Oriented Polyester Film

The present invention relates to a biaxially oriented polyester film, and in particular, by adding an inorganic lubricant and an organic lubricant together with the polyester, in particular, when used as a base film of magnetic media, scratch resistance and abrasion resistance during repeated driving It relates to an improved biaxially oriented polyester film.

Among the polyesters, polyethylene terephthalate (hereinafter, abbreviated as PET) is widely used in various industrial products because of its physical and chemical stability, high mechanical strength, excellent heat resistance, weather resistance, chemical resistance, and electrical insulation. . In particular, PET film has been widely used as a base film, a capacitor, a packaging, a photo film and a label for magnetic recording media because of its excellent electrical, mechanical, thermal and chemical resistance and good processing characteristics.

The characteristics required for the polyester film used for such various purposes vary depending on the application, but particularly, the base film of the magnetic recording medium is required to have excellent scratch resistance and abrasion resistance. In magnetic recording media, the friction and abrasion between the roller and the surface of the film is very severe during the application of a high temperature magnetic layer coating process or a calendar process, and scratches easily occur on the surface of the film. In addition, the film coated with the magnetic layer is processed into a tape for video or computer, and then subjected to winding, fast forwarding, etc. in a cassette, or other friction and abrasion between the guide part and the playhead during other operations. As a result, a white powder or the like due to scratching or shaving of the surface of the film is generated, which causes a drop of the magnetic recording signal, that is, dropout.

As a method for improving scratch resistance and abrasion resistance of polyester lip, there is a method of reducing the contact area with a roller or the like by adding inorganic particles such as calcium carbonate, silica and alumina as lubricants to form irregularities on the surface of the film. . In such a method, surface properties are controlled by adding a large amount of fine particles, while scratch resistance is imparted by adding a small amount of particles having a large particle size. However, since these inorganic particles have a weak affinity with a polyester film, voids are easily formed on the surface of the film, and therefore, inorganic particles having a large particle size drop off when contacted with a roller. The problem is that dropouts occur.

Recently, a method of adding organic particles having excellent affinity with PET, a method of improving surface characteristics by improving the projection shape of the film surface by mixing two or more inorganic particles or organic particles and inorganic particles has been proposed. For example, U. S. Patent No. 4,761, 327 discloses a method for improving scratch resistance by supplementing a lack of affinity of inorganic particles by adding a mixture of organic particles such as inorganic lubricants and silicone resins.

However, in the conventional method as described above, although the affinity with the polyester film is improved by the organic particles, there is an effect of reducing the cavity, but the wear resistance and scratch resistance of the film are satisfactory due to the lack of wear resistance of the organic lubricant itself. Could not be improved.

It is an object of the present invention to provide a polyester film having improved surface properties, scratch resistance and abrasion resistance by using an inorganic particle and an organic particle having a particle size in a certain range in order to solve the above problems.

The biaxially oriented polyester film of the present invention for achieving the above object is a calcium carbonate having an average particle diameter of 0.05 to 3㎛, silica having an average particle diameter of 0.05 to 3㎛ and benzoguamine-melamine-formaldehyde having an average particle diameter of 0.1 to 5㎛ It characterized in that it comprises 0.01 to 0.5% by weight relative to the total weight of the polyester.

In the present invention, in order to improve the wear resistance of the organic lubricant while improving the lack of affinity of the inorganic lubricant to make it suitable for the base film of the magnetic recording medium, calcium carbonate and silica having a range of average particle diameters are added to the polyester as the inorganic lubricant. As the organic lubricant having a large particle size, benzoguamine-melamine-formaldehyde condensate is added together to improve the surface properties, abrasion resistance and scratch resistance of the film.

The polyester of the present invention is a crystalline polyester such as PET, polyalkylene naphthalate, and the like, although it is not particularly limited, PET is suitable. Among them, PET, in which at least 80 mol% of the repeating units are made of ethylene terephthalate, desirable. Other copolymer components include isophthalic acid, para-betaoxyethoxybenzoic acid, 2, 6-naphthalenedicarboxylic acid, 4, 4'-dicarboxydiphenyl, 4, 4'-dicarboxylbenzophenone, bis (4 Dicarboxylic acid components such as -carboxyl-diphenyl) ethane, adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid, cyclohexane-1, 4-dicarboxylic acid, and propylene glycol, butanedi, neopentyl Oxycarboxylic acid components such as glycol, diethyl glycol, cyclohexanedimethanol, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, polytetramethylgolycol component, paraoxybenzoic acid, and the like, and are optionally selected from them. Can be used.

As a method for producing the polyester of the present invention, any of the direct polymerization method for directly reacting aromatic dicarboxylic acid and glycol and the transesterification method for transesterifying them can be applied, and the reactor may be batch or continuous. Any method may be employed.

When carried out by the transesterification method, there is no particular limitation on the transesterification catalyst and conventionally known ones can be used. For example, an alkaline earth metal compound such as a magnesium compound, a zirconium compound, a sodium compound, a potassium compound, a calcium compound and a barium compound and a cobalt compound, a zinc compound and a manganese compound can be selected and used in the reaction system.

There is no restriction | limiting in particular similarly about a polymerization catalyst, An appropriate thing can be selected and used out of an antimony compound, a germanium compound, and a titanium compound.

The inorganic particles added to the polyester film of the present invention are calcium carbonate which is a relatively large particle and silica which is a small particle. Calcium carbonate can use either hard calcium carbonate or heavy calcium carbonate, and 0.01-0.5 weight% of thing of average particle diameters 0.05-3 micrometers is added with respect to polyester total weight. When the average particle diameter of calcium carbonate is smaller than 0.05 μm and the amount of addition is less than 0.01 wt%, the surface roughness of the film is lowered, leading to abrasion during running, resulting in poor runability. On the other hand, the average particle diameter of calcium carbonate is larger than 3 μm and the amount of addition is 0.5 When the weight percentage is higher than the weight percentage, the running property of the film is improved, but the frequency of large protrusions on the surface of the film increases, which decreases the electronic characteristics and generates unnecessary coarse particles by agglomeration, which may cause dropout when manufacturing a magnetic recording tape. It is set as said range. Preferably, calcium carbonate having an average particle diameter of 0.1 to 2.0 mu m is added at 0.2 to 0.45% by weight of the total weight of the polyester.

As another inorganic particle added to the polyester film of this invention, 0.01-0.5 weight% of spherical silica is added with the average particle diameter of 0.05-3 micrometers with respect to the polyester weight. When the average particle diameter of the spherical silica is smaller than 0.05 μm and the addition amount is less than 0.01% by weight, the surface roughness of the film is lowered and the running wear is severe and the runability is reduced, whereas the average particle diameter is larger than 3 μm and the amount added is 0.5 weight. When it is more than%, the running property of the film is improved, but the frequency of large protrusions on the surface of the film is increased, which decreases the electronic properties and generates coarse particles by agglomeration, which may cause dropout in manufacturing a magnetic recording tape. It is a range. Preferably, 0.1 to 0.3% by weight of the total weight of the polyester is added to spherical silica having an average particle diameter of 0.1 to 2.0 mu m.

As for the benzoguamine-melamine-formaldehyde condensate which is organic particle | grains added to the polyester film of this invention, the thing of an average particle diameter of 0.1-5 micrometers is added 0.01-0.5 weight with respect to a polyester total weight. If the average particle diameter of the benzoguamine-melamine-formaldehyde condensate is smaller than 0.1 µm and the addition amount is less than 0.01% by weight, scratching and powdering occur on the surface of the film, whereas the average particle diameter is larger than 5 µm. If the amount is larger than 0.5% by weight, the coarse particles and the aggregated particles may cause dropout in manufacturing the magnetic recording tape. Preferably, benzoguamine-melamine-formaldehyde condensate having an average particle diameter of 0.5 to 4 mu m is added at 0.05 to 0.2% by weight of the total weight of the polyester.

The method of adding the inert inorganic and organic particles to the polyester may be added in any of a slurry form and a powder form, but it is preferable to disperse the slurry in a slurry form to prevent scattering of particles and to improve uniformity, and in particular, ethylene glycol It is preferable to add in the slurry of. In addition, these inert particles are added in the manufacturing process as a slurry undispersed by selecting a soluble in ethylene glycol from a dispersant such as an acryl-based compound such as sodium polyacrylate, sodium methacrylate or ammonium acrylate and a benzenesulfonate-based compound. It is desirable to.

In the present invention, a method for producing a polyester film is not particularly limited, and after melting a polyester having a molecular weight of about 20,000 including the above additives, extruding it into a sheet form from a die to make an uncalculated sheet, and then in a biaxial direction Stretching produces a biaxially oriented polyester film. The stretching temperature is 60 to 150 占 폚, the stretching ratio is 2.5 to 6.0 times in the longitudinal direction, preferably 3 to 5.5 times, and the horizontal direction is 2.5 to 6.0 times, preferably 3 to 5 times. The stretched film is prepared by heat setting for 1 to 200 seconds in the range of 150 to 250 ° C, preferably 170 to 240 ° C, if necessary.

The present invention will be described in more detail with reference to the following examples. However, the following examples are only examples of the present invention and the present invention is not limited thereto.

Various performance evaluations of the films produced in Examples and Comparative Examples of the present invention were carried out by the following method.

(How to measure)

1) Average diameter of particles

It is the volume average particle diameter which measured the slurry using the centrifugal particle size analyzer (SA-2CP) made by Shimadzu, Japan.

2) molecular weight

The molecular weight of the polymer was measured using a Waters Molecular Weight Measuring Device as a meta-cresule as a mobile phase, a flow rate of 1 ml / min, and a column temperature of 100 deg.

3) Surface roughness of film

Using a surface roughness meter (SURFCORDER SE-3OD) from Kosaka Institute of Japan, the surface roughness of the film was measured eight times under the conditions of measuring length 5 mm, cut-off 0.08 mm, and needle diameter 0.5 µm, and from the larger value. It was shown as five average values except three.

4) wear resistance

TBT-300F, a tape running tester of Yokohama Systems Research Institute in Japan, is used to run the tape slitting the film 1/2 inch wide at a driving speed of 3.3 cm / sec and twice the number of driving times. Was observed under a microscope to evaluate the wear resistance as follows.

Class A: When there are no powders on the guide pins, Class B: When there are about one hundred percent of the guide pins in total, Class C: More than one fifth and less than one half of the guide pins are embedded. In the case of Class D: When the amount of powder per part of the guide pin is about 1.2, Class E: When the amount of the powder is on the guide pin.

5) Scratch Resistance

TBT-300F, a tape running tester of Yokohama Systems Research Institute in Japan, is used.The tape slitting the film 1/2 inch wide is run at a driving speed of 3.3cm / sec and two runners. In the observation, the scratch resistance was evaluated as follows with or without scratch lines around the tape width.

◎: Excellent scratch property (damaged scratch wire is 2 lines or less)

●: Good scratch resistance (3-4 damaged wires)

(Triangle | delta): Scratch-resistant ordinary (damaged scratch wire is 5-6 wires)

X: poor scratch resistance (damaged scratch lines are 7 or more lines)

(Example 1-4)

According to the method of polycondensation of polyester in a conventional manner, calcium carbonate and spherical silica as inorganic lubricants and benzoguamine-melamine-formaldehyde condensates as organic lubricants are added as shown in the table to have a molecular weight of about 20,000. Polyester was prepared. The polymer thus prepared was melt-extruded at 290 ° C. to produce an unstretched sheet by a conventional method, and stretched at 3.5 ° in the longitudinal direction and 3.0 times in the transverse direction at 90 ° C. to prepare a biaxially stretched polyester film having a thickness of 50 μm. .

The performance evaluation results of the film are shown in the table.

(Comparative Example 1-9)

As in Example 1, but as shown in the table, benzoguamine-melamine-formaldehyde condensate, which is an organic lubricant, is not added, and calcium carbonate alone (Comparative Examples 1-3) and spherical silica alone are used as inorganic lubricants. (Comparative Example 4-6) and calcium carbonate and spherical silica were mixed and added (Comparative Example 7-9) to prepare a polyester film.

The performance evaluation results of the film are shown in the table.

As shown in the table, calcium carbonate and silica having an average particle diameter of 0.05 to 3 µm as inorganic particles, and benzoguamine-melamine-formaldehyde condensates having an average particle diameter of 0.1 to 5 µm as organic particles were respectively 0.1 for polyester. The polyester film of Example 1-4 prepared by adding to 5% by weight was good surface properties, in particular it can be seen that the wear resistance and scratch resistance is excellent.

On the other hand, in Comparative Example 1-9 prepared by adding only inorganic particles such as calcium carbonate and silica without adding an organic lubricant, it was found that the wear resistance and scratch resistance were particularly poor.

As described above, calcium carbonate and silica having an average particle diameter of 0.05 to 3 μm as inorganic particles, and benzoguamine-melamine-formaldehyde condensates having an average particle size of 0.1 to 5 μm as organic particles were respectively 0.1 to polyester. It can be seen that the biaxially oriented polyester film prepared by adding 5 to 5% by weight has good surface properties, excellent scratch resistance and abrasion resistance, and is particularly suitable for application to a base film of a magnetic recording medium.

[table]

Claims (1)

0.01 to 0.5% by weight of calcium carbonate having an average particle diameter of 0.05 to 3 µm, silica having an average particle diameter of 0.05 to 3 µm, and benzoguamine-melamine-formaldehyde having an average particle diameter of 0.1 to 5 µm, respectively, based on the total weight of the polyester. Biaxially oriented polyester film.