KR20000004166A - Method for fabricating diaxial orientation polyester film for magnetic record medium - Google Patents

Abstract

PURPOSE: A fabrication method of a diaxial orientation polyester film for a magnetic record medium is provided to improve an electric characteristic and a surface protrusion maintenance of a film by preventing a production of a massive grain. CONSTITUTION: The fabrication method of a diaxial orientation polyester film comprises the steps of: adding an ultra fine synthetic carbon dioxide calcium of 0.01-2 weight% having an average grain of 0.05-0.3 micrometer, a synthetic carbon dioxide calcium of 0.01-2 weight% having an average grain of 0.3-1.5 micrometer, and a calcium solvent preventive material of 0.05-10 weight% obtained by chemical functions of (R)nNX and (R)NH3X; and performing a melting extrusion and stretch by use of a well-known method.

Description

Manufacturing method of biaxially oriented polyester film for magnetic recording media (THE METHOD OF PRODUCING BIAXIALLY ORIENTED POLYESTER FILM FOR MAGNETIC RECORDING)

The present invention relates to a method for producing a biaxially oriented polyester film for a magnetic recording medium, and more particularly, to adding a suitable inorganic lubricant during the production of a polyester film to improve the surface properties of the film, and The present invention relates to a method for producing a biaxially oriented polyester film for a magnetic recording medium which improves generation of macroparticles and remarkably improves electronic characteristics after magnetic coating.

The polyester film represented by polyethylene terephthalate (PET) has a stable chemical structure, high mechanical strength, excellent heat resistance, durability, chemical resistance, and the like. It is used in many applications such as printing, labeling as well as magnetic recording media.

In particular, the magnetic recording film produced by coating a magnetic material on the surface of the polyester film, because the characteristics such as flatness and dimensional stability is superior to other types of film, it is currently used most as a substrate of the film for magnetic recording media have.

However, when the above-mentioned polyester film is manufactured with magnetic tape and a large amount of images and recordings are to be manufactured, recently, as the copy speed is gradually increased, the friction between the polyester film as a base material and the copying device during the copying process is caused. Particles are easily dropped while driving, which leads to abrasion dust, which contaminates the head of the copying device, resulting in the risk of film scratching. There was a problem.

As a method for solving the problems described above, the polyester by adding each inorganic lubricant made of calcium carbonate, silica, etc. as a lubricant in the preparation of the polyester film alone or when supplementing the effect between the inorganic lubricants is required BACKGROUND OF THE INVENTION [0002] A method of forming irregularities on the surface to impart proper runability, processability and surface characteristics as a magnetic recording medium has become common.

Among these inorganic lubricants, however, calcium carbonate and synthetic calcium carbonate are widely used because of their uniform particle size.However, when dispersed in a solvent containing a hydroxyl group, precipitation occurs after irreversible reaction with Ca (OH) ₂ . When manufactured with a tape, there is a problem that the dropout (Dorp-out) is increased.

The present invention is to solve the above problems, when the calcium carbonate is added as an inorganic lubricant during the manufacture of the polyester film, it is effective to control the surface properties of the polyester film by using a basic ammonium-based treatment agent when dispersing it in ethylene glycol It is an object of the present invention to provide a method for producing a polyester film that is excellent in remarkably improved macroparticle properties.

In the present invention, when preparing biaxially oriented polyester film for magnetic recording medium by adding alone or mixed with calcium carbonate or silica as an inorganic lubricant, ultrafine synthetic calcium carbonate having a mean particle size of 0.05 to 0.3 μm (hereinafter referred to as lubricant A) 0.01 0.01 wt% to 2 wt% of synthetic calcium carbonate (hereinafter referred to as lubricant B) having an average particle diameter of 0.3 to 1.5 μm and a compound of Formula 1 or the following Formula 2 as a calcium dissolving agent: 0.05 to 10 wt. Provided is a method for producing a biaxially oriented polyester film for a magnetic recording medium, which is added by% to melt extrusion and stretching by a conventional method.

(R) nNX

(R) NH ₃ X

In Formula 1 or Formula 2, R is an alkyl group having 1 to 10 carbon atoms, n is an integer of 3 or 4, and X is hydroxide or nitrate.

In addition, in the method for producing a biaxially oriented polyester film for magnetic recording media, 0.01 to 2 wt% of ultrafine spherical silica (hereinafter referred to as lubricant C) having an average particle diameter of 0.01 to 0.15 μm together with the lubricant A and lubricant B as inorganic lubricants. Provided is a method for producing a biaxially oriented polyester film by mixing and adding%.

Synthetic calcium carbonate and ultra-fine synthetic calcium carbonate used in the present invention have an appropriate particle size distribution that can prevent the generation of large particles when prepared into a slurry through a classification treatment after milling, the average particle diameter in the case of synthetic calcium carbonate By grinding the calcium carbonate of 0.3μm or more by milling and classifying, it is prepared so that there are less than 30 particles and less than 5μm particles per 0.15mg based on the calcium carbonate concentration 15% by weight in the slurry.

When the synthetic calcium carbonate and the ultra fine calcium carbonate having the average particle diameter described above are used as the lubricant, the number of protrusions having a height of 0.1 μm formed on the surface of the film per 5 mm of the film measuring length is present in the range of 8 to 30. The smoothness of the surface is greatly improved and the electronic properties can be significantly improved.

Ultra-fine spherical silica which can be added together with the calcium carbonate is in the ratio of ionic surfactant was dissolved _{Na 2 O · nSiO 2 · mH} 2 O (1≤n≤3, 5≤m≤7) in a non-polar organic solvent After stirring at high speed, the solution was added to hydrochloric acid at 0.1 to 5N, and stirred again to prepare monodisperse fine particles with water to obtain a dispersion aqueous solution, and then substituted with an organic solvent.

The ultra-fine spherical silica produced in this way is cheaper to produce, has a better dispersibility than the fine silica prepared by the conventional flame oxidation method, and has a particle size in the range of 0.01 to 0.15 μm. When added together, the scratch resistance of the film surface is improved, and the protrusion maintenance is excellent, which can significantly improve the generation of powder due to the running at high speed and the dropping of particles.

The calcium ionization inhibitor used in the present invention suppresses calcium ionization to prevent irreversible reaction of calcium carbonate to Ca (OH) ₂ , thereby removing the calcium particles precipitated on the film, thereby improving the macroparticles of the finally prepared film. In order to greatly improve the electronic properties, at least 0.05% by weight of the weight of the calcium carbonate added as the lubricant is added, but it is not necessary to add more than 10% by weight.

The lubricant A uses an ultrafine synthetic calcium carbonate having an average particle diameter of 0.01 to 0.3 μm. When the average particle diameter is 0.01 μm or less, the surface roughness of the film is lowered, so that the coefficient of friction is increased. In manufacturing, there is a problem that the electronic properties are reduced, more preferably 0.05 to 0.2μm.

If the amount of the lubricant A is less than 0.01% by weight, the running friction coefficient is high, and the workability is poor. When 2% by weight or more of the lubricant is added, coarse particles are generated due to the coagulation of the lubricant. It is not preferable, and more preferably, it is added at 0.05-2 weight%.

When the lubricant B is added in an average particle diameter of less than 0.3μm or less than 0.01% by weight, or when the average particle diameter is added in an amount of more than 0.1% by weight of 1.5μm or more, it is difficult to obtain an appropriate range of surface roughness and number of surface projections. Problems are generated, and runability becomes worse, which causes a dropout powder.

The synthetic calcium carbonate of lubricant B having an average particle diameter in the above range is more preferably added in subdivided amounts depending on the size of the average particle diameter, that is, the synthetic calcium carbonate having an average particle diameter of less than 0.3 to 0.5 μm is 0.01 to 2 It is preferable to add the synthetic calcium carbonate having an average particle diameter of 0.5 to 1.5 탆 and added at less than 0.01% by weight.

In the case of adding the lubricant C of the ultrafine spherical silica together with the lubricant A and the lubricant B of the above-mentioned calcium carbonate, if the average particle diameter of the lubricant C is 0.01 μm or less, the size of the particles is too small and the desired scratchability is insufficient or surface roughness. It is not preferable because the friction coefficient is increased to lower the running performance is lowered, and if the average particle diameter is 0.15μm or more, it is not preferable because the shortening of the life of the neck during the slitting of the film.

In addition, if the amount of lubricant C added is less than 0.01% by weight, the running friction coefficient is high, resulting in poor workability. When 2% or more of the lubricant is added, coarse particles are formed due to the coagulation of lubricant, which causes dropout when manufacturing magnetic tape. And more preferably 0.05 to 2% by weight.

In addition, an inorganic lubricant may use a dispersing agent in order to manufacture ethylene glycol slurry.

For example, what is necessary is just to select suitably soluble thing in ethylene glycol from dispersing agents, such as an acryl-type compound (sodium polyacrylate, sodium methacrylate, ammonium acrylate), and a benzene sulfonate type compound.

Polyester prepared by the method of the present invention is 80 mol% or more of the repeating unit is made of ethylene terephthalate, and other copolymerization components are isophthalic acid, para-beta oxyethoxy benzoic acid, 2,6-naphthalenedicarboxylic acid, 4, Dicarboxylic acid components, such as 4'- dicarboxy diphenyl and 5- sodium sulfoisophthalic acid, oxy carboxyl, such as propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexane dimethanol, and paraoxybenzoic acid It is possible to select and use an acid component etc. arbitrarily.

The present invention can be applied to any of the transesterification method and the direct polymerization method, and either batch or continuous type can be employed.

In the case of the transesterification method, there is no restriction on the transesterification catalyst, and any conventionally known one can be used.

For example, alkaline earth metal compounds such as magnesium compounds, zirconium compounds, sodium compounds, potassium compounds, calcium compounds and barium compounds, and cobalt compounds, zinc compounds and manganese compounds may be soluble in the reaction system.

The polymerization catalyst is also not limited, but may be appropriately selected from antimony compounds, germanium compounds, and titanium compounds.

Although the polyester film manufacturing method in this invention is not specifically limited, The classification process of two types of synthetic calcium carbonate among the said inorganic lubricant additives is processed by the residence time of 5 minutes and 1200-2500 rpm using the Tanabe Corporation (ZIL) classifier. One was used, and the polyester including such additives was melt-extruded by a T-die method to make an unstretched sheet, and then biaxially stretched to make the polyester film of the present invention biaxially oriented.

The stretching method is the same as that of ordinary polyester, and there is no change of the process by the above additives.

The stretching temperature is 60 to 150 占 폚, the stretching ratio is 2.5 to 6.0 times in the longitudinal direction and 2.5 to 6.0 times in the lateral direction.

The polyester film produced according to the present invention can be designed in a suitable thickness depending on the application, but is usually a film having a thickness of 2.0 to 200μm.

Hereinafter, the present invention will be described in more detail with reference to the following Experimental Examples and Comparative Examples, but the present invention is not limited to the following Examples.

<Examples 1 to 8>

In the polycondensation reaction of polyethylene terephthalate by a conventional method, a mixture of ultrafine synthetic calcium carbonate, synthetic calcium carbonate and calcium ion treatment agent or ultrafine spherical silica is added as an inorganic lubricant, and the average particle diameter and content thereof, respectively. To prepare a slurry by adding as shown in Table 1 and then prepared during the polymerization of the polymer to prepare a polymer and melt-extruded to make an unstretched sheet in a conventional manner, stretched 3.0 times longitudinally at 90 ℃ 3.0 in the transverse direction To draw twice, to prepare a biaxially stretched polyester film having a thickness of 20μm and to evaluate the performance thereof are shown in Table 1 below.

<Comparative Example 1 to Comparative Example 6>

In the same manner as in Examples 1 to 8, but the inorganic lubricant slurry prepared by mixing in a state not using the calcium ion treatment agent was prepared in the polymer production to prepare a biaxially oriented polyester film and evaluated the performance of the following table 1 is shown.

Various performance evaluation of the film manufactured in the Example and the comparative example of this invention was performed by the following method.

Experimental Example

Average particle size test of particles

The volume average average particle diameter of the ethylene glycol slurry was measured using the centrifugal particle size analyzer of Shimadzu, Japan.

Slurry large particle number test

A particle size of at least 2 μm and at least 5 μm was measured per 0.15 mg based on 15 wt% of the inorganic lubricant concentration in the ethylene glycol slurry using a multisizer measuring instrument (Coulter Counter, UK).

Ca ionization concentration test

Using a Beckman centrifuge (J2-21M / E) of the United States, the ethylene glycol slurry produced at 15% calcium carbonate concentration was centrifuged at 15000 rpm for 30 minutes (three times), after which the supernatant was quantitatively analyzed by an element analyzer. Was measured.

Surface smoothness and protrusion number test

The polyester film was cut to 30 mm in length and 20 mm in width, and then the surface roughness was measured by a contact method using a surface roughness meter of Kosaka Institute of Japan.

Center line average roughness (Ra): When a straight line parallel to the average line of the roughness curve is drawn, it is the height of the straight line in which both areas of the straight line become the same.

PV: Refers to the distance between the maximum height and the minimum depth in the measurement section.

Electronic characteristic test

A self-coated tape was recorded using a household VCR (Sony Japan: EVO-9500A), recording a signal superimposed on a 50% back level signal and a 100% chroma level signal, and using the reproduced signal as a signal generator (TG56B1) by Shiva Soku Corporation. The chroma-S / N ratio was measured using a noise meter (VN30A1).

◎: Chroma-S / N ratio +5 or more

○: chroma-S / N ratio +2 to 4.9

Δ: chroma-S / N ratio 0 to 1.9

×: less than 0 chroma-S / N ratio

Drop Out Test

The self-coated tape was dropped using a household VCR (Sony Japan: EVS-33), and the tape was measured for 1 minute using Shivasoku's Sigma Generator (TG7 / 1) and Noise Meter (VHO1BZ). The occurrence of error over 16dB was called dropout and the number of occurrences was evaluated by quality standard. The generated dropout sample was analyzed by electron microscope and elemental analyzer.

◎: Less than 55 dropouts

○: 56 to 80 dropout occurrences

△: 81 to 100 dropout occurrences

×: 101 or more dropout occurrences

-Drunkenness-

Using a tape running tester of the Yokohama System Research Institute in Japan, run the tape slitting the film 1/2 inch wide at 60% RH atmosphere at 20 ° C for 5 days, and then obtain the initial μK by Equation 1 below. .

μK = 0.733 log (T _out / T _in )

Where T _in is the inlet tension and T _out means the outlet tension.

(A) High speed driving

After rotating the guide pin in the running direction or the reverse direction of the film, the angle of the winding portion is measured at a running speed of 180 ° and 50 cm / sec and a running tension of 300 gr.

◎: μK≤0.1, excellent driving speed

○: Good high speed driving performance with 0.10 <μK <0.20

△: high-speed running mode with μK = 0.20

×: High-speed running poor with μK> 0.20

Surface protrusion retention after repeated driving

After 100 cycles of self-coated tape using Victor's BR6400TR tester, the surface of the film on the back side of the coating was observed 50 times at the magnification of 5000 to 10000 times with an electron microscope, and then judged whether the protrusion height was maintained. The surface protrusion retention is then evaluated.

◎: Excellent surface projection retention (PV height change less than 3nm)

○: Good surface protrusion retention (PV height change 4 to 7nm)

(Triangle | delta): Surface protrusion retention moderate (PV height change 7-15 nm)

×: Surface protrusion retention failure (PV height change 16nm or more)

Additive Preparation Conditions Performance evaluation result Lubricant Kinds Average particle size (μm) input(%) Surface smoothness Number of large particles (more than 2μm / more than 5μm Treatment agent (0.5%) Number of protrusions (7nm / 50nm / 100nm) Slurry Ca concentration (ppm) Electronic characteristic (dB) Large particle Ca% Dropout Surface Proofability after Repeated Driving High speed Center line average roughness (Ra: μm) Center Line Maximum Height (Rt) Example 1 Ultra fine spiral silica 0.06 0.2 0.004 0.071 - TBAN 605/30/10 - ◎ 0 ◎ ◎ ◎ Ultra fine synthetic calcium carbonate 0.1 0.5 5/0 35 Synthetic Calcium Oxide 0.4 0.03 28/0 50 Synthetic Calcium Oxide 0.8 0.02 22/0 55 Example 2 Ultra fine spiral silica 0.08 0.15 0.005 0.082 - TMAH 554/29/14 - ◎ 0 ◎ ◎ ◎ Ultra fine synthetic calcium carbonate 0.2 0.4 6/0 39 Synthetic Calcium Oxide 0.4 0.02 27/0 51 Synthetic Calcium Oxide 1.2 0.01 21/0 60 Example 3 Ultra fine spiral silica 0.08 0.15 0.005 0.077 - TBAN 577/35/10 - ◎ 0 ◎ ◎ ◎ Ultra fine synthetic calcium carbonate 0.1 0.5 5/0 35 Synthetic Calcium Oxide 0.3 0.05 29/0 64 Synthetic Calcium Oxide 0.8 0.02 23/0 70 Example 4 Ultra fine spiral silica 0.06 0.2 0.005 0.085 - TEAN 533/31/22 - ◎ 0 ◎ ◎ ◎ Ultra fine synthetic calcium carbonate 0.2 0.4 6/0 40 Synthetic Calcium Oxide 0.3 0.05 30/0 62 Synthetic Calcium Oxide 1.2 0.01 22/0 51 Example 5 Ultra fine synthetic calcium carbonate 0.1 0.5 0.004 0.061 - TBAN 555/28/10 35 ◎ 0 ◎ ◎ ◎ Synthetic Calcium Oxide 0.4 0.03 47/0 50 Synthetic Calcium Oxide 0.8 0.02 42/0 55 Example 6 Ultra fine synthetic calcium carbonate 0.2 0.4 0.005 0.079 - TMAH 494/27/16 39 ◎ 3 ◎ ◎ ◎ Synthetic Calcium Oxide 0.4 0.02 47/0 51 Synthetic Calcium Oxide 1.2 0.01 40/0 60 Example 7 Ultra fine synthetic calcium carbonate 0.1 0.5 0.004 0.074 - TBAN 560/34/11 35 ◎ 0 ◎ ◎ ◎ Synthetic Calcium Oxide 0.3 0.05 48/0 64 Synthetic Calcium Oxide 0.8 0.02 42/0 70 Example 8 Ultra fine synthetic calcium carbonate 0.2 0.4 0.005 0.083 - TEAN 484/33/17 40 ◎ 2 ◎ ◎ ◎ Synthetic Calcium Oxide 0.3 0.05 47/0 62 Synthetic Calcium Oxide 1.2 0.01 39/0 51 Comparative Example 1 Globular silica 0.2 0.5 0.005 0.084 - - 415/3/0 - ◎ - ○ △ × Comparative Example 2 Globular silica 0.5 0.2 0.012 0.156 - - 270/25/3 - × - △ △ × Comparative Example 3 Globular silica 0.2 0.4 0.004 0.077 - - 370/22/0 - ◎ 36 ○ △ ◎ Synthetic Calcium Carbonate 0.4 0.02 95/7 50 Comparative Example 4 Synthetic Calcium Carbonate 0.4 0.2 0.012 0.287 95/7 SPA 261/38/25 390 × 43 ○ ◎ ◎ Synthetic Calcium Carbonate 0.8 0.1 79/10 410 Comparative Example 5 Ultra fine synthetic calcium carbonate 0.1 0.5 0.004 0.077 - - 550/30/11 45 ◎ 49 ○ ◎ ◎ Synthetic Calcium Carbonate 0.4 0.03 95/7 50 Synthetic Calcium Carbonate 0.8 0.02 79/10 53 Comparative Example 6 Ultra fine synthetic calcium carbonate 0.2 0.4 0.005 0.092 - SPA 471/35/21 305 ◎ 43 ○ ◎ ◎ Synthetic Calcium Carbonate 0.3 0.05 88/6 386 Synthetic Calcium Carbonate 1.2 0.01 82/13 423

※ In Table 1, TBAN is tetrabutylammonium nitrate, TMAH is tetramethylammonium alkoxide, TEAN is tetraethylammonium nitrate and SPA is sodium polyacrylate. Sodium polyacrylate was treated at a concentration of 1%.

As can be seen from the results of Table 1, as in Examples 1 to 8 of the present invention, the synthetic calcium carbonate, the ultra-fine synthetic carbonate, or these fine calcium silicate together with these calcium carbonates, and calcium ionization inhibitor The polyester film prepared by the addition of the ultra-low particle concentration of Ca has not found any particle having a size of 5 μm or more. Therefore, the electronic and dropout properties of the film were not only improved significantly, but the surface projection retention speed was high. The driving was also very good.

On the other hand, unlike in the embodiment of the present invention, Comparative Example 1, which is used as a lubricant added in the preparation of the polymer, a general inorganic lubricant alone or in combination with calcium carbonate and does not use a calcium ionization inhibitor as suggested in the present invention In the case of 6 to 6 it was found that the properties are very fragile in physical properties such as the electronic properties and the number of dropouts, and in Comparative Examples 4 and 6 do not use the basic ammonium compound as in the present invention as a calcium ionization inhibitor In addition, when sodium polyacrylate was used, the mechanical properties such as runability were slightly improved due to the high Ca concentration in the slurry, but the error rate was slightly higher when running due to the large number of dropouts.

In the present invention, when calcium carbonate is added as an inorganic lubricant in the production of a polyester film, it is effective in controlling surface properties of a polyester film by inhibiting calcium ionization by using a basic ammonium-based treatment agent when dispersing it in ethylene glycol. It is a useful invention to provide a method for producing a polyester film with remarkably improved particle properties.

Claims (7)

In preparing biaxially oriented polyester film for magnetic recording media by adding alone or mixed calcium carbonate or silica as an inorganic lubricant, 0.01 to 2 weight of ultra fine synthetic calcium carbonate (hereinafter referred to as lubricant A) having an average particle diameter of 0.05 to 0.3 μm. 0.01 to 2% by weight of synthetic calcium carbonate (hereinafter referred to as lubricant B) having a% and an average particle diameter of 0.3 to 1.5 μm, and a compound of the formula (1) or the following formula (2) as a calcium dissolving agent at 0.05 to 10% by weight of the weight of calcium carbonate And melt extruding and stretching by a conventional method, for producing a biaxially oriented polyester film for a magnetic recording medium. <Formula 1> (R) nNX <Formula 2> (R) NH ₃ X In Formula 1 or Formula 2, R is an alkyl group having 1 to 10 carbon atoms, n is an integer of 3 or 4, and X is hydroxide or nitrate. The magnetic recording according to claim 1, further comprising 0.01 to 2% by weight of ultrafine spherical silica (hereinafter referred to as lubricant C) having an average particle size of 0.01 to 0.15 μm as an inorganic lubricant together with the lubricant A and lubricant B. Method for producing biaxially oriented polyester film for media. The method of manufacturing a biaxially oriented polyester film for magnetic recording medium according to claim 1 or 2, wherein the lubricant A has an average particle diameter of 0.05 to 0.2 m and added at 0.05 to 2 wt%. The method of manufacturing a biaxially oriented polyester film for magnetic recording medium according to claim 1 or 2, wherein the lubricant B is added at 0.05 to 2% by weight. The method of claim 3, wherein the lubricant B is added in an amount of 0.05 to 2% by weight. The method of claim 1, wherein the lubricant B is added to the synthetic calcium carbonate having an average particle diameter of less than 0.3 to 0.5μm less than 0.01 to 2% by weight and the synthetic calcium carbonate having an average particle size of 0.5 to 1.5μm 0.01 to 1 A method for producing a biaxially oriented polyester film for a magnetic recording medium, characterized in that the addition by weight%. According to claim 3, The lubricant B is added to the composite calcium carbonate having an average particle diameter of less than 0.3 to 0.5μm less than 0.01 to 2% by weight and the synthetic calcium carbonate having an average particle diameter of 0.5 to 1.5μm is added in 0.01 to 1% by weight A method for producing a biaxially oriented polyester film for a magnetic recording medium, characterized by the above-mentioned.