KR0168206B1 - Biaxially Oriented Polyester Film - Google Patents

Abstract

The present invention relates to a biaxially oriented polyester film, comprising: calcium carbonate having an average particle diameter of 0.05 to 3 µm, spherical silica having an average particle diameter of 0.05 to 3 µm, and benzoguamine-melamine formaldehyde having a particle size of 0.1 to 5 µm. A polyester film comprising a condensate, wherein the surface crystallinity of the first side is at least 20% higher than the crystallinity of the second side, has excellent abrasion resistance and scratch resistance and will also improve the adhesive strength with the magnetic body.

Description

Biaxially Oriented Polyester Film

The present invention relates to a biaxially oriented polyester film, and more particularly, includes an inorganic lubricant and an organic lubricant, and adjusts the degree of crystallinity of the film surface, thereby improving adhesion to the magnetic layer and abrasion resistance and scratch resistance during repeated driving. An excellent biaxially oriented polyester film.

Among polyesters, especially polyethylene terephthalate is used for magnetic tape due to its excellent physical and chemical properties. It is not only used for condensers, packaging, photographic films, medical, etc., but also for a wide range of applications such as textiles and molded products.

In a polyester film prepared by biaxially aligning such a polyester, the scratch resistance and the wear resistance act as an important factor in determining the quality state of the film. In particular, when the film is used for a magnetic recording medium, the friction and abrasion between the roller and the film surface become very severe during the high temperature magnetic layer coating process or the calendar process, and scratches easily occur on the film surface. In addition, when the film coated with the magnetic layer is cut and operated with a video or computer tape to perform winding or fast forwarding in a cassette, friction and abrasion between the guide part and the playhead are severe. Whitening, etc., may occur due to chipping, which may cause a loss of the magnetic recording signal and the kill dropout.

In order to improve wear resistance and scratch resistance of such a polyester film, an inorganic substance such as calcium carbonate, silica, or alumina is added as a lubricant to reduce the contact area with a roller or the like by forming irregularities on the surface of the film. A large amount of small particles mainly controls the surface characteristics and gives scratch resistance with a small amount of large particles. Since these inorganic particles have a weak affinity with a polyester film, they form voids on the surface of the film, There is a tendency that large inorganic particles are eliminated during contact, so that dropout occurs when manufactured with magnetic tape.

As a conventional method for improving the wear resistance, in particular the scratch resistance, of a polyester film, a method of adding a mixture of calcium carbonate and silica to a polyester film has been proposed (US Pat. No. 3,821,156). In addition, a method of improving scratch resistance by mixing and adding organic particles such as silicone resins with inorganic lubricants to compensate for the lack of affinity with polyester of inorganic particles (US Pat. No. 4,761,327) has also been proposed. However, this method has the effect of improving the affinity with the film by the organic particles to reduce the cavity, but there is a fundamental problem that the organic lubricant itself lacks wear resistance and lowers the wear resistance of the film. In addition, methods for increasing the crystallinity of the film have also been proposed in order to improve adhesion to the magnetic material, which is another property of the polyester film, but there is a problem in that the wear resistance of the film is poor when the crystallinity is increased.

Therefore, the inventors of the present invention improve the wear resistance of the film running surface while using an organic lubricant, and also increase the crystallinity of the polyester film only on the surface of the magnetic body coated surface, thereby improving the adhesion to the magnetic body without reducing the wear resistance, thereby improving magnetic recording purposes. As a result of further research to develop a film applicable to the present invention, benzoguamine-melamineformaldehyde condensate as an organic lubricant is added to a polyester film together with calcium carbonate and inorganic silica to control heat setting conditions on both sides of the film. The surface crystallinity of the magnetic coating surface was improved by 20% compared to the running surface, and the wear resistance and the scratch resistance could be improved, leading to the completion of the present invention.

It is an object of the present invention to provide a biaxially oriented polyester film having improved abrasion resistance and scratch resistance and improved adhesion to a magnetic body.

According to the above object, in the present invention, calcium carbonate having an average particle diameter of 0.05 to 3 µm, spherical silica having an average particle diameter of 0.05 to 3 µm, and benzoguamine-melamine formaldehyde condensate having an average particle diameter of 0.1 to 5 µm are included. And a surface crystallinity of the first side is at least 20% higher than that of the second side.

Hereinafter, the present invention will be described in more detail.

The polyester in the present invention is a crystalline polyester such as polyethylene terephthalate and polyalkylene naphthalate, and polyethylene terephthalate is particularly preferable. At least 80 mol% of the repeating units of such polyesters are composed of repeating units of ethylene terephthalate, and as other copolymerization components, isophthalic acid, 2,6-naphthalin dicarboxylic acid, 4,4'-dicarboxyl diphenyl, Dicarboxylic acids such as 4,4'-dicarboxylbenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid, cyclohexane-1,4-dicarboxylic acid Ingredients: propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanedimethanol, ethylene oxide adduct of bisphenol A, diol components such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and paraoxybenzoic acid, para Oxycarboxylic acid components such as betaoxyethoxy benzoic acid and the like can be optionally used.

Polyesters can be prepared by direct polymerization of aromatic dicarboxylic acids and glycols or by transesterification of dimethyl esters of glycols with aromatic dicarboxylic acids and glycols. Any can be used. There are no particular limitations on the catalyst in the transesterification reaction, for example, compounds of alkaline earth metals such as magnesium compounds, calcium compounds and barium compounds, compounds of alkali metals such as potassium compounds and sodium compounds, zirconium compounds, cobalt compounds and zinc compounds And manganese compounds. As the polymerization catalyst, an antimony compound, a germanium compound, a titanium compound, or the like can be used.

Calcium carbonate, which is a relatively large particle added to the polyester of the present invention, may be hard calcium carbonate or heavy calcium carbonate in a manufacturing process, and an average particle diameter of 0.05 to 3 μm, preferably 0.1 to 2.5 μm, is used in the film. 0.01 to 0.5% by weight, preferably 0.2 to 0.45% by weight is added. When the average particle diameter of calcium carbonate is larger than 3 μm or the calcium carbonate content in the film is more than 0.5% by weight, the running property of the film is improved, but the frequency of large protrusions on the surface of the film is increased, thereby decreasing the electronic properties. , There is a problem in that dropout is caused by coarse particles and aggregated particles. When the average particle diameter is smaller than 0.05 μm or when the content in the film is less than 0.01% by weight, there is a problem in that runability is poor.

Spherical silica, which is a small inorganic particle added to the polyester of the present invention, has an average particle diameter of 0.05 to 3 µm, preferably 0.1 to 2.0 µm, and is 0.01 to 0.5% by weight, preferably 0.1 to 0.3 weight in the film. % Is added. When the spherical silica average particle diameter is smaller than 0.05 μm or the spherical silica content in the film is less than 0.01% by weight, the surface roughness of the film is lowered, leading to abrasion during driving and inferior runability. If the average particle diameter is greater than 3㎛, or contains more than 0.5% by weight of the content in the film there is a problem that the electronic properties are lowered.

The benzoguamine-melamineformaldehyde condensate used as the organic lubricant in the polyester of the present invention has an average particle diameter of 0.1 to 5 탆, preferably 0.5 to 4 탆, and is preferably 0.01 to 0.5 wt% in the film. 0.05 to 0.2% by weight is added. If the average particle diameter of the benzoguamine-melamine formaldehyde condensate is smaller than 0.1 μm or the content of the film is less than 0.01% by weight, there is a problem that scratches and powders occur on the surface of the film, and the average particle size is 5 If the thickness is larger than 0.5 μm or more than 0.5 wt%, the dropout may occur due to the coarse particles and the packed particles.

The inert particles may be added in the form of slurry or powder in polyester, in order to prevent the scattering of particles and to improve the uniformity, it is preferable to add the dispersed particles in a slurry phase, and most preferably, as a slurry of ethylene glycol. .

In addition, the inert particles described above are polyesters as undispersed slurries using acrylic compounds such as sodium polyacrylate, sodium methacrylate and ammonium acrylate as dispersants, or those soluble in ethylene glycol among benzenesulfonate compounds. It is preferred to add during the manufacturing process.

In addition to the inert particles, conventional additives such as surfactants, antioxidants, dispersants, fluorescent brighteners, and the like may be added to the polyester film of the present invention within a range that does not impair the effects of the present invention.

The production method of the polyester film of the present invention is not particularly limited and may be prepared according to a conventional biaxially oriented film production method. That is, the biaxially oriented polyester film of the present invention can be produced by melting the polyester containing the particles and extruding the sheet from the die into a sheet to make an unstretched sheet, followed by stretching in the biaxial direction. At this time, the stretching temperature is 60 to 150 ℃, the stretching ratio is 2.5 to 6.0 times in the longitudinal direction, preferably 3 to 5.5 times and the transverse direction is 2.5 to 6 times, preferably 3 to 5 times. The biaxially stretched film prepared as described above is preferably heat-fixed to the surface on which the magnetic body is to be applied at 180 to 290 ° C. for 1 to 50 seconds, preferably at 200 to 270 ° C. for 1 to 20 seconds. On the other hand, it is preferable to heat-set the surface to which the magnetic material is not applied at 150 to 250 ° C. for 1 to 200 seconds, preferably at 170 to 230 ° C. for 1 to 100 seconds according to a conventional method. Here, it is preferable that the heat setting temperature of the surface to which a magnetic substance is apply | coated is 20 degreeC higher than the heat setting temperature of the surface which is not apply | coated.

The measurement of various physical properties and properties of the polyester films produced in Examples and Comparative Examples of the present invention is measured as described below.

(1) Average particle size of particles

It is the volume average particle diameter which measured the slurry using the centrifugal particle size measuring machine (SA-2CP: Shimadzu Corporation, Japan).

(2) molecular weight

The molecular weight measuring apparatus (Waters) is used, and meta-cresol is used as a mobile phase, a flow rate is 1 ml / min, and column temperature is 100 degreeC, and the molecular weight of a polymer is measured.

(3) surface crystallinity of film

FT-IR (FTS60: DIGI Lab. (USA)) was used to measure the surface crystallinity of the film 8 times up to a depth of up to 3 µl at 60 degrees angle of incidence at KRS-5, except for the larger ones. It is represented by five average values.

(4) adhesive strength of film

It is made by a peel tester and applied to the same film surface with an acrylic adhesive to bond the films, and then the adhesive strength of the film is measured 8 times at 230cm / field speed. Represented by

(5) Running friction coefficient of film (μk)

Measured using a tape run tester (TBT-300F: Yokohama System Research Institute, Japan) .The film cut to 1/2 inch width at a temperature of 20 ° C and a humidity of 60% was contacted with a guide pin at an angle of 180 ° for 200 cm. After driving 90cm at the speed of the field, the driving friction coefficient mk is obtained as follows.

μk = 0.733 los (T ₂ / T ₁ )

Where T ₂ is the outlet tension and T ₁ is the inlet tension.

(A) low speed

After fixing the guide pin, measure the guide pin with the angle of 180 ° at the driving speed of 3.3 cm / sec and the driving tension of 50g. Μk in low-speed driving is based on 0.35, and less than that is good, and above, it is considered bad.

(B) High speed driving

After the guide pin is rotated in the tape running direction or in the reverse direction, the angle is set to 180 ° and measured at a running speed of 50 cm / sec and a running tension of 300 g. Μk in the high-speed driving is good if it is less than or equal to 0.01 and bad if it is more.

(6) wear resistance of film

Cut the film into 1/2 inch width and run it twice at the running speed of 3.3 cm in the same way as the friction coefficient measurement in (5) above, and observe the white powder on the surface of the guide pin under the microscope. Evaluate wear resistance.

A: If there is no powder on the guide pin

B: 1/5 per minute of guide pin body area

C: More than 1/5 and less than 1/2 of the total amount per guide pin area

D: About 1/2 of the guide pin is buried per area

E: When the guide pin is entirely powdered

(7) scratch resistance of film

Cut the film into 1/2 inch width and run it twice at the running speed of 3.3 cm / sec in the same way as the friction coefficient measurement of (3) above, and observe the damaged surface of the film under a microscope to see if there is a scratch line around the tape width. Evaluate scratch resistance.

◎: excellent scratch resistance (damaged scratch wire is 2 lines or less)

(Circle): Good scratch property (damaged scratch wire is 3-4 wire)

(Triangle | delta): Scratch-resistant normal (damage | stretched scratch line is 5 to 6 lines)

X: Scratch line defect (damaged scratch line is 7 or more lines) Hereinafter, the present invention will be described in more detail by the following examples and comparative examples. However, the following Examples and Comparative Examples are only for illustrating the present invention, but the scope of the invention is not limited to these.

[Examples 1 to 4]

To 50 parts by weight of dimethyl terephthalate and 100 parts by weight of ethylene glycol, 0.1 parts by weight of manganese acetate as a transesterification catalyst, 0.2 parts by weight of antimony trioxide as a polymerization catalyst and 0.2 parts by weight of phosphorous acid as a stabilizer, calcium carbonate, spherical as an inorganic and organic lubricant Type silica and benzoguamine-melamineformaldehyde condensate were added in the amounts shown in Table 1 and polymerized by a conventional method to prepare polyethylenetephthalate chips having a molecular weight of about 20,000.

The polymer was melt-extruded at 290 ° C. to make an unstretched sheet by a conventional method, and stretched at 3.5 ° in the longitudinal direction and 3.5 times in the transverse direction at 105 ° C., and the heat setting temperatures and times of both sides of the film are shown in Table 1 below. By adjusting, a film having a degree of crystallinity of about 20% compared to the surface crystallinity of the running surface was prepared and evaluated for performance.

The particle size and content of the lubricants, the heat setting temperature and time of the polyester film, and the surface crystallinity are as shown in Table 1 below. As shown here, it can be seen that the obtained films are of high quality with excellent wear resistance and scratch resistance.

[Comparative Examples 1 to 4]

Except for using only calcium carbonate or spherical silica alone, it was carried out in the same manner as in Examples 1 to 4, the results are shown in Table 1.

Here, it can be seen that the films obtained in Comparative Examples 1 to 4 are inferior in wear resistance and scratch resistance compared to the films obtained in Examples 1 to 4 above.

[Comparative Example 5]

Calcium carbonate, silica and the organic lubricant was added to the same as in 1 to 4, but the heat setting temperature of both sides of the film was carried out in the same manner, the results were as shown in Table 1.

Here, it can be seen that the film obtained in Comparative Example 5 has almost no difference in surface crystallinity between the magnetic coating surface and the film running surface, and is of low quality, in which the adhesive strength with the magnetic body is lower than that of the film prepared in Example.

Claims (3)

Calcium carbonate having an average particle diameter of 0.05 to 3 µm, constituent silica having an average particle diameter of 0.05 to 3 µm, and a benzoguamine-melamine formaldehyde condensate having an average particle diameter of 0.1 to 5 µm, the surface crystallinity of the first surface Is at least 20% higher than the crystallinity of the second surface. The polyester film, characterized in that the calcium carbonate, spherical silica and benzoguamine-melamineformaldehyde condensate is contained 0.01 to 0.5% by weight based on the polyester, respectively. Wherein the first surface is heat-set for 1 to 50 seconds at 180 to 290 ° C., and the second surface is at 150 to 250 ° C. for 1 to 200 seconds at a temperature of at least 20 ° C. lower than the temperature of the first surface. A polyester film characterized by phosphorus.