KR19990065291A - Method for producing biaxially oriented polyester film for magnetic recording medium - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method for producing a polyester film used as a magnetic recording medium.

2. The technical problem to be solved by the invention

Compared to the conventional calcium carbonate, the present invention has an excellent effect on controlling the surface properties of polyester film, does not generate voids, has excellent dropout characteristics when manufactured with magnetic recording tape, and has excellent repeat durability and high-speed driving. It is to provide a polyester film having excellent abrasion resistance.

3. Summary of Solution to Invention

The present invention for solving the above technical problem is a method for producing a polyester film by adding a lubricant to polyethylene terephthalate, the lubricant is added to the polyester divided into A particles, B particles and C particles, but Particle A uses 0.01% to 4% of crosslinked polystyrene small particles having an average particle diameter of 0.01 µm to 0.6 µm coated with ultrafine alumina or silica within 5 nm to 50 nm on the surface of the lubricant. 0.01% to 0.1% of crosslinked polystyrene large particles having an average particle diameter of 0.7 μm to 3.0 μm coated with ultra-fine alumina or silica within 5 nm to 50 nm on the surface, and C particles are delta type or alpha having Mohs hardness of 6 or more. It is selected from type alumina or ultra-fine spherical silica, and can be solved by producing an average particle diameter of 0.005 µm to 0.15 µm and adding an amount of 0.01% to 4%.

4. Important uses of the invention

The present invention has a use as a method for producing a polyester film used as a magnetic recording medium.

Description

Method for producing biaxially oriented polyester film for magnetic recording medium

The present invention relates to a method for producing a biaxially oriented polyester film used for a magnetic recording medium, and more particularly, styrene coated with ultrafine alumina or silica of 5 nm to 50 μm in a lubricant added to a polyester film. It relates to a method for producing a biaxially oriented polyester film using particles to improve the surface properties, dropping resistance, void resistance, abrasion resistance, dropout properties and scratch resistance.

In general, polyester film has a stable chemical structure, has high mechanical strength, and is made of polyethylene terephthalate, which is excellent in heat resistance, durability, and chemical resistance, and is manufactured as a condenser, medical, industrial, packaging, photo film, and label. And magnetic recording media.

The polyester film used for the magnetic recording medium is formed by mixing inorganic films such as calcium carbonate, silica, kaolin, and alumina as a lubricant to provide runability, processability, surface characteristics, and the like to form irregularities on the surface of the polyester film. I'm making it.

However, the calcium carbonate (particularly hard calcium carbonate) used as the inorganic lubricant has an excellent effect in controlling the surface properties of the polyester film, but on the contrary, due to low affinity and low hardness with polyethylene terephthalate The film containing calcium carbonate has a problem that particles are dropped off due to wear while driving, and scratches are generated on the surface of the film, causing dropout when used as a magnetic tape.

In order to solve the above problems, Japanese Patent Laid-Open No. Hei 5-43715 uses spherical ate calcium carbonate, which is spherical in form of particles, to improve the surface resistance of a polyester film. To improve the dropping of particles.

However, when the above-mentioned calcium carbonate particles are made of polyethylene terephthalate as a raw material, when the tape produced by the generation of residual voids is repeatedly used for a long time, dropping occurs due to dropping of particles over time. Since there is a problem that the stability of the out is generated, there was a need for a lubricant having better affinity with polyethylene terephthalate.

Compared to the conventional calcium carbonate, the present invention has an excellent effect on controlling the surface properties of polyester film, does not generate voids, has excellent dropout characteristics when manufactured with magnetic recording tape, and has excellent repeat durability and high-speed driving. It is to provide a polyester film having excellent abrasion resistance.

The present invention for solving the above technical problem is a method for producing a polyester film by adding a lubricant to polyethylene terephthalate, the lubricant is added to the polyester divided into A particles, B particles and C particles, but Particle A uses 0.01% to 4% of crosslinked polystyrene small particles having an average particle diameter of 0.01 µm to 0.6 µm coated with ultrafine alumina or silica within 5 nm to 50 nm on the surface of the lubricant. 0.01% to 0.1% of crosslinked polystyrene large particles having an average particle diameter of 0.7 μm to 3.0 μm coated with ultra-fine alumina or silica within 5 nm to 50 nm on the surface, and C particles are delta type or alpha having Mohs hardness of 6 or more. It can be solved by selecting from alumina or ultra-fine spherical silica, and having an average particle diameter of 0.005 µm to 0.15 µm and an addition amount of 0.01% to 4%.

The crosslinked polystyrene particles used as A particles and B particles are coated with ultra-fine alumina or silica within 5 nm to 50 nm on the surface of the lubricant, and are excellent in heat resistance and heat-treated at a temperature of 300 ° C. for 2 hours or more. In addition, the shape of the particles does not change at all, the affinity with polyethylene terephthalate is also excellent, there is an advantage that no voids occur at all.

The crosslinked polystyrene organic particles used as lubricant A have the above heat resistance and void resistance and are spherical particles having a spherical degree (long diameter / short diameter) of 1, and an average particle diameter of 0.01 μm to 0.6 μm is used. It is preferable to use within the range of µm to 0.6 µm, and when it is added in an amount of 0.01% or less, the running friction coefficient becomes high, resulting in poor workability, and when added in an amount of 4% or more, coarse particles due to coagulation of lubricant It is preferable to add within the above range, since the drop out phenomenon appears during the production of the magnetic tape, and it is preferable to use within the range of 0.05% to 2%.

The crosslinked polystyrene organic particles used as lubricant B have the above heat resistance and void resistance and are spherical particles having a spherical degree (long diameter / short diameter) of 1, and an average particle diameter of 0.7 μm to 3.0 μm is used. It is preferable to use within the range of µm to 1.5 µm. In addition, when the amount is added at 0.01% or less, the running friction coefficient becomes high, resulting in poor workability, and when 0.1% or more is added, coarse particles due to the flocculation phenomenon of the lubricant. It is preferable to add in the above range, since the drop out phenomenon appears in the production of the magnetic tape, it is preferable to use within the range of 0.05% to 0.1%.

Organic lubricants generally form large particles due to agglomeration of particles themselves at a high temperature, so that they cannot be used as high-quality products having excellent electronic properties and dropout, and therefore, ultrafine alumina within 5 nm to 50 nm on the surface of the lubricant. Silica coated ones should be used.

In the case of using delta alumina, alpha alumina, or ultrafine silica, which is used as lubricant C, with particles having a particle size of 0.005 μm or less, the surface roughness of the film is lowered to increase the friction coefficient, resulting in poor runability. In the case of using particles having a particle diameter, the particle distribution of alumina and ultrafine silica is lowered on a certain surface during the manufacture of the magnetic tape, and the scratch resistance becomes poor during high-speed driving, so it is preferable to use within the above range. It is preferable to use within the range of 占 퐉, and when the addition amount of the lubricant is added at 0.01% or less, the running friction coefficient is increased, and when it is added more than 4%, the dispersibility is poor and the physical properties of the film are lowered there is a problem.

The manufacturing method of the polyester film in this invention is not specifically limited, After making the unstretched sheet melt-extruded the polyester containing the said additives by T-die method, etc., it is biaxially stretched so that it may have biaxial orientation. You can do it.

As the polyester which can be used in the present invention, 80 mol% or more of the repeating unit is composed of ethylene terephthalate, and other copolymerizing components are isophthalic acid, para-beta oxyethoxybenzoic acid, 2,6-naphthalenedicarboxylic acid, 4,4 ' Dicarboxylic acid components such as -dicarboxylic diphenyl, 4,4'-dicarboxylbenzophenone, bis (4-carboxydiphenyl) ethane, adipic acid, sefasin acid, 5-sodium sulfoisophthalic acid, Oxycarboxylic acid components such as propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanedimethanol, and paraoxybenzoic acid may be selected and used. May be used, and either batch or continuous may be used.

Any catalyst that can be used in the esterification reaction may be used, and alkaline earth metal compounds such as magnesium compounds, zirconium compounds, sodium compounds, potassium compounds, calcium compounds, barium compounds, germanium compounds, antimony compounds, titanium compounds, and cobalt Compounds, zinc compounds, manganese compounds and the like, any of which can be soluble in the reaction system.

The stretching of the film is the same as the usual stretching method without the process change by the additives, the stretching temperature is 60 ℃ to 150 ℃, the stretching ratio is 2.5 times to 6.0 times in the longitudinal and transverse directions, respectively, depending on the use of the film Suitable thickness design is possible, but is usually manufactured in a thickness of 2.0 μm to 200 μm.

Hereinafter, the biaxially oriented polyester film of the present invention will be prepared by the following examples and comparative examples, and the results thereof will be described.

Examples 1-4

In the polycondensation reaction of polyethylene terephthalate by a conventional method, a polymer is prepared by adding crosslinked polystyrene activator A particles and B particles coated with ultrafine alumina or silica and spherical silica lubricant C particles as shown in Table 1. Melt extrusion was carried out to make an unstretched sheet by a conventional method, and stretched 3.0 times in the transverse direction 3.0 times in the longitudinal direction at 90 ° C. to prepare a 15 μm thick film, and evaluated the performance thereof.

Comparative Examples 1 to 7

In the same manner as in Examples 1 to 4, but the inorganic lubricant and uncoated crosslinked polystyrene organic particles were added to prepare a polyester film and the performance thereof is shown in Table 1 below.

Additive Preparation Conditions Performance evaluation result Lubricant Kinds Average particle size (㎛) input(%) Dropout Surface smoothness Spherical diagram Void resistance Scratch resistance Abrasion resistance after high speed driving High speed Center line average roughness (Ra: ㎛) Center Line Maximum Height (Rt) Example One Polystyrene (A-1) 0.3 0.2 ◎ 0.016 0.145 ◎ ◎ ◎ ◎ ◎ Polystyrene (B-1) 0.7 0.1 Ultra fine spiral silica 0.10 0.1 2 Polystyrene (A-1) 0.4 0.2 ◎ 0.017 0.151 ◎ ◎ ◎ ◎ ◎ Polystyrene (B-1) 0.7 0.1 Ultra fine spiral silica 0.10 0.1 3 Polystyrene (A-2) 0.3 0.2 ◎ 0.016 0.144 ◎ ◎ ◎ ◎ ◎ Polystyrene (B-2) 0.7 0.1 Ultra fine spiral silica 0.08 0.08 4 Polystyrene (A-2) 0.4 0.2 ◎ 0.017 0.159 ◎ ◎ ◎ ◎ ◎ Polystyrene (B-2) 0.7 0.1 Ultra fine spiral silica 0.05 0.06 Comparative example One Baterite Calcium Carbonate 0.3 0.3 ○ 0.014 0.135 ○ ○ △ △ △ Gamma alumina 0.2 0.1 2 Calcium carbonate 0.5 0.2 ○ 0.019 0.225 × × △ △ △ Gamma alumina 0.1 0.2 3 Baterite Calcium Carbonate 0.3 0.3 ○ 0.014 0.143 ○ ○ ○ △ △ Delta Alumina 0.09 0.3 4 Calcium carbonate 0.5 0.3 ○ 0.023 0.302 × × ○ △ △ Delta Alumina 0.12 0.2 5 Calcium carbonate 0.5 0.2 ○ 0.022 0.333 × × ○ △ △ Delta Alumina 0.15 0.2 6 Polystyrene (A) 0.4 0.3 ○ 0.016 0.132 ◎ ◎ ◎ ◎ ◎ Polystyrene (B) 0.7 0.15 Ultra fine spiral silica 0.10 0.1 7 Polystyrene (A) 0.3 0.3 ○ 0.017 0.143 ◎ ◎ ◎ ◎ ◎ Polystyrene (B) 0.9 0.1 Ultra fine spiral silica 0.10 0.1

In Table 1, the symbol -1 denoted by the polystyrene particles means ultra-fine alumina coating, and -2 means ultra-fine silica coating.

Evaluation of the performance described in Table 1 was carried out by the following method.

Average particle diameter

Yonbon Ethylene glycol slurry was measured using a centrifuge particle size analyzer manufactured by Shimadzu Corporation to obtain an average particle diameter.

Surface smoothness

Using a surface roughness meter from Kosaka Research Institute in Japan, the surface roughness was measured by contact method on a film having a thickness of 30 μm and a thickness of 20 μm having a width of 20 mm.

Center line average roughness (Ra): When the straight line is drawn parallel to the average line of the roughness curve, it is the height of the straight line where both areas of the straight line are equal.

Maximum height of the center line (Rt): The distance between the maximum height and the minimum depth in the measurement section.

The lower the average roughness and the maximum height, the better the smoothness and the better the cohesiveness.

Spherical diagram

As the ratio of the long diameter / short diameter of the particles in the particle size result obtained by measuring the ethylene glycol slurry using a centrifugal particle size measuring instrument manufactured by Shimazu, Japan.

◎: Very good ratio of long diameter / short diameter of 1.0

○: Good ratio of long diameter / short diameter to 1.0 spherical figure 1.1

(Triangle | delta): A ratio of long diameter / short diameter is 1.1 <= spherical shape 1.2,

×: ratio of long diameter to short diameter is less than 1.2

Void resistance

Polyethylene terephthalate was biaxially stretched to evaluate void resistance as the ratio (void containing length / lubrication length) of voids distributed on the surface of the film.

◎: Very good at 1.0

○: 1.0 void ratio is good at 1.2

△: 1.2≤ void ratio 1.5

×: 1.5≤ bad at void ratio

Run

After running the tape slitting the film 1/2 inch wide in a 60% RH atmosphere at 20 ° C for 45 minutes using a tape running tester of the Yokohama System Research Institute in Japan, the initial μK Obtain

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

(Circle): Good driving speed with 0.10μK0.20

△: high-speed running mode with μK = 0.20

×: High-speed running poor with μK0.20

Wear resistance

Using a tape running tester of the Yokohama System Research Institute in Japan, the film was slit 1/2 inch wide in a 20 ° C, 60% RH atmosphere, and then 200m long at a speed of 300m / min. It is evaluated by measuring the occurrence of white powder around the guide pin when observing the surface buried under a microscope.

◎: When there is no powder on guide pin

○: When one hundredth of the guide pin is 1/5 of the guide pin area.

△: When the powder is 1/2 of the guide pin

×: 100% of the guide pin is generated overall in the guide pin

Scratch resistance

Using a tape running tester of the Yokohama System Research Institute in Japan, the tape slitting the film 1/2 inch wide was run at a high speed of 300 m / min. Scratch resistance is evaluated by the presence or absence of a scratch line.

◎: excellent scratch resistance (two damaged scratch wires)

(Circle): Good scratch property (3-4 damaged scratch wires)

(Triangle | delta): Scratch-resistant ordinary (5-6 damaged scratch lines)

×: poor scratchability (more than 7 damaged scratch lines)

Dropout

Magnetic coating tapes are available from National AG's AG6200 VCR, which is commercially available.The dropout is measured using a signal generator (216/1) manufactured by Shiba Sokku Corporation and a dropout centrifuge (1DC2) manufactured by Daechang Industrial Co., Ltd. for 1 minute. Drop outs that occurred over 5㎲ × 20㏈ size were evaluated as quality criteria.

◎: 5 or less dropouts

(Circle): 6-15 dropout occurrences

△: number of dropout occurrences 16-50

×: 51 or more dropout occurrences

As can be seen from Table 1 above, in Examples 1 to 4, dropout, sphericity, void resistance, scratch resistance, wear resistance and high speed driving resistance after high speed driving were excellent. Also, the average roughness of the center line is 0.016 and 0.017, and the maximum height of the center line is 0.144 to 0.159.

However, in the case of Comparative Example 1 using 0.3% of calcium carbonate calcium carbonate having an average particle diameter of 0.3 μm and 0.1% of gamma-type alumina having an average particle diameter of 0.2 μm, the average roughness of the center line in the surface smoothness was 0.014 and the maximum of the center line. Although its height is 0.135, it maintains relatively high smoothness, but it has a good degree in dropout, sphericity, and void resistance, and appears to be moderate in scratch resistance, abrasion resistance after high-speed driving, and high-speed running resistance than the polyester according to the present invention. A somewhat falling result was obtained.

In the case of Comparative Example 2 using 0.2% calcium carbonate having an average particle diameter of 0.5 μm and gamma type alumina having an average particle diameter of 0.1 μm as a lubricant, the average roughness of the center line in the surface smoothness was 0.019 and the maximum height of the center line was It is 0.225, which maintains relatively low smoothness compared to the present invention, is good in dropout, poor in sphericity and void resistance, and normal in scratch resistance, wear resistance and high speed driving resistance. The result was much lower than the polyester according to the present invention.

In Comparative Example 3, in which 0.3% of mate calcium carbonate having an average particle diameter of 0.3 μm and 0.3% of gamma-type alumina having an average particle diameter of 0.09 μm were used as a lubricant, the average roughness of the center line in the surface smoothness was 0.014 and the maximum height of the center line was It maintains a smoothness similar to the present invention at 0.143, but is good in dropout, sphericity, void resistance and scratch resistance, and is normal in abrasion resistance and high speed driving resistance after high speed driving. The result was somewhat lower than that of the present invention.

In Comparative Example 4 using 0.3% calcium carbonate having an average particle diameter of 0.5 μm and gamma-type alumina having an average particle diameter of 0.12 μm as a lubricant, the average roughness of the center line in the surface smoothness was 0.023 and the maximum height of the center line was 0.302. It showed more irregular smoothness than the present invention, was good in dropout and scratch resistance, poor in sphericity and void resistance, and normal in abrasion resistance and fast running resistance after high speed driving. The result was much lower than polyester.

In Comparative Example 5 using 0.2% calcium carbonate having an average particle diameter of 0.5 μm and gamma-type alumina having an average particle diameter of 0.15 μm as a lubricant, the average roughness of the center line was 0.022 and the maximum height of the center line was 0.333. In addition to showing more irregular smoothness than the present invention, dropout, sphericity, void resistance, scratch resistance, wear resistance and high-speed running resistance after high-speed running is much lower than the polyester according to the present invention shown the same as in Comparative Example 4 The result was obtained.

Comparative Example 6 using 0.3% of polystyrene particles having an average particle diameter of 0.4 μm, 0.15% of polystyrene particles having an average particle diameter of 0.7 μm, and 0.1% of ultrafine spherical silica having an average particle diameter of 0.10 μm as a lubricant. In the case of surface smoothness, the average roughness of the centerline in the surface smoothness was 0.016 and the maximum height of the centerline was 0.132, which is similar to the present invention.The spherical shape, void resistance, scratch resistance, abrasion resistance and high speed driving resistance were found to be excellent. However, the case of dropout was shown to be favorable, and the result fell slightly compared with the polyester by this invention.

Comparative Example 7 using 0.3% of polystyrene particles having an average particle diameter of 0.3 μm, B particles of 0.1% of polystyrene particles having an average particle diameter of 0.9 μm, and 0.1% of ultrafine spherical silica having an average particle diameter of 0.10 μm as a lubricant. In the case of surface smoothness, the average roughness of the centerline in the surface smoothness was 0.017 and the maximum height of the centerline was 0.143, which is similar to the present invention.The spherical shape, the void resistance, the scratch resistance, the abrasion resistance and the high speed driving resistance were excellent. As in Comparative Example 6, the case of dropout was found to be satisfactory, resulting in a slight drop compared to the polyester according to the present invention.

As can be seen from Table 1 above, the polyester film produced by the present invention is excellent in both dropout, sphericality, void resistance, scratch resistance, wear resistance and high speed driving after high-speed driving, In the smoothness of, the average roughness of the center line is 0.016 and 0.017, and the maximum height of the center line is 0.144 to 0.159, which shows stable smoothness, which brings about the expected effect as a polyester film for magnetic recording media.

Claims (9)

In the method for producing a polyester film by adding a lubricant to polyethylene terephthalate, the lubricant is added to the polyester divided into A particles, B particles and C particles, but A particles are added to the surface of the lubricant from 5 nm to 0.01% to 4% of crosslinked polystyrene small particles having an average particle diameter of 0.01 μm to 0.6 μm coated with ultrafine alumina or silica within 50 nm is used, and B particles are extremely fine within 5 nm to 50 nm on the surface of the lubricant. 0.01% to 0.1% of crosslinked polystyrene large particles having an average particle diameter of 0.7 μm to 3.0 μm coated with alumina or silica are used, and the C particles are selected from delta type or alpha type alumina having an Mohs hardness of 6 or more, or ultrafine spherical silica. A method for producing a biaxially oriented polyester film for magnetic recording media, characterized by an average particle diameter of 0.005 µm to 0.15 µm and an addition amount of 0.01% to 4%. The method of claim 1, wherein the average particle diameter of the polystyrene A particles surface-coated from 5 nm to 50 nm by ultra-fine alumina or silica used as a lubricant is 0.1 µm to 0.6 µm, and is added within the range of 0.05% to 2%. A method for producing a biaxially oriented polyester film for a magnetic recording medium, characterized by the above-mentioned. The average particle diameter of the polystyrene B particles surface-coated from 5 nm to 50 nm by ultra-fine alumina or silica used as a lubricant is in the range of 0.01 to 0.1%. It is added in the inside, The manufacturing method of the biaxially-oriented polyester film for magnetic recording media. The biaxial for magnetic recording medium according to claim 1 or 2, wherein an average particle diameter of C particles selected from delta- or alpha-type alumina having an Mohs hardness of 6 or more, or ultra-fine spherical silica is 0.01 µm to 0.1 µm. Method for producing oriented polyester film. 4. The biaxially oriented polyester for magnetic recording medium according to claim 3, wherein the average particle diameter of C particles selected from delta- or alpha-type alumina having an Mohs hardness of 6 or more, or ultra-fine spherical silica is 0.01 µm to 0.1 µm. Method for producing a film. The method for producing a biaxially oriented polyester film for magnetic recording medium according to claim 1 or 2, wherein the sphericity of A particles and B particles used as lubricants is 1. The method for producing a biaxially oriented polyester film for magnetic recording media according to claim 3, wherein the sphericality of the A particles and the B particles used as the lubricant is one. The method for producing a biaxially oriented polyester film for magnetic recording media according to claim 4, wherein the sphericity of A particles and B particles to be used as lubricants is 1. 6. The method for producing a biaxially oriented polyester film for magnetic recording media according to claim 5, wherein the sphericality of the A particles and the B particles used as the lubricant is one.